The TP-AGB phase. Lifetimes from C and M star counts in Magellanic Cloud clusters

Using available data for C and M giants with Mbol<-3.6 in Magellanic Cloud clusters, we derive limits to the lifetimes of the corresponding evolutionary phases, as a function of stellar mass. The C-star phase is found to have a duration between 2 and 3 Myr for stars in the mass range from 1.5 to 2.8 Msun. There is also an indication that the peak of C-star lifetime shifts to lower masses (from slightly above to slightly below 2 Msun) as we move from LMC to SMC metallicities. The M-giant lifetimes also peak at 2 Msun in the LMC, with a maximum value of about 4 Myr, whereas in the SMC their lifetimes appear much shorter but, actually, they are poorly constrained by the data. These numbers constitute useful constraints to theoretical models of the TP-AGB phase. We show that several models in the literature underestimate the duration of the C-star phase at LMC metallicities.Comment: 8 pages, to appear in Astronomy & Astrophysic

Towards simulating the photometry, chemistry, mass loss and pulsational properties of AGB star populations in resolved galaxies

Extended and updated grids of TP-AGB tracks have been implemented in the TRILEGAL population synthesis code, which generates mock stellar catalogues for a galaxy given its mass, distance, star formation history and age-metallicity relation, including also the Milky Way foreground population. Among the stellar parameters that are simulated, we now include the surface chemistry, mass-loss rates, pulsation modes and periods of LPVs. This allows us to perform a series of consistency checks between AGB model predictions and observations, that we are just starting to explore. We present a few examples of model--data comparisons, mostly regarding the near-infrared and variability data for AGB stars in the Magellanic Clouds.Comment: 5 pages, 3 figures, contributed talk to the workshop "Why galaxies care about AGB stars", Vienna, August 7-11, 200

Grand Canonical simulations of string tension in elastic surface model

We report a numerical evidence that the string tension \sigma can be viewed as an order parameter of the phase transition, which separates the smooth phase from the crumpled one, in the fluid surface model of Helfrich and Polyakov-Kleinert. The model is defined on spherical surfaces with two fixed vertices of distance L. The string tension \sigma is calculated by regarding the surface as a string connecting the two points. We find that the phase transition strengthens as L is increased, and that \sigma vanishes in the crumpled phase and non-vanishes in the smooth phase.Comment: 7 pages with 7 figure

Ranking Electoral Systems through Hierarchical Properties Ranking

Electoral systems are characterized by a wide spectrum of properties that cannot be all satisfied at the same time. We aim at examining such properties within a hierarchical framework, based on Analytic Hierarchy Process, performing pairwise comparisons at various levels of a hierarchy to get a global ranking of the electoral systems. In this way it should be possible to estimate the relative importance of each property with respect to the final ranking of every electoral formula.Electoral systems, global ranking, hierarchy, aggregations

I labirinti narrativi Di marcella cioni

In Marcella Cioni’s narrative, a competitive psychological tension prevails between the limits imposed by official culture and the desire for free and complete expression of the “I”. Her characters are all in search of their own identity and, after having discovered its coordinates, they make desperate attempts to give form to their profound feelings. Her women characters seem more able and more willing to take risks than the men, indeed they sometimes display an extreme, irrational desire for self-affirmation. The male characters are more conditioned by their socio-historical roles and their journeys are more complicated and more intellectual. Cioni’s ambitious narrative project is given germane expression by the intelligent, linguistically and structurally elaborate plots devised by this new Italian writer

Volatile compounds of essential oil Centaurea behen L. grown in Iran

      The essential oils from Compositae specie of Iran:Centaurea behen L. obtained by hydrodistillation was analyzed by GC and GC/MS.  β-Caryooyllane (24.5%), β-selinene (13.9%) and valencene (11.7%) were the main components among the sixteen constituents characterized in the oil of Centaurea behen representing  93.7% of the total components detected

Is technological change really skill biased? Evidence from the introduction of ICTs on the textile sector (1980-2000)

This paper investigates the effects of the introduction of information and communication technologies (ICTs) on the skills of a workforce. Using micro-data collected from workers in the textile sector, we analyse whether the introduction of ICTs has modified workers’ tasks, so that higher skills and longer training periods than before are necessary. Our survey has shown that ICTs i) have replaced unskilled labour in some cases and skilled labour in others; ii) have changed workers’ tasks in some cases but not in others; and finally, iii) have brought about an increase in skills for only a small number of occupations. This empirical evidence does not confirm the hypothesis that technological change, and in particular change introduced by ICTs, is necessarily skill biasedTechnological change, skill bias, textile industry

Introduzione al Neural Computing

Scopo di queste note quello di presentare alcune nozioni di base sul Neural Computing, descrivere brevemente alcuni modelli di rete neurale e illustrare i principali campi applicativi, con particolare attenzione alla Linguistica. Viene inoltre presentata una breve descrizione delle modalit di implementazione di reti neurali e viene esaminata in dettaglio l\u2019architettura sia hardware sia software di un neurocomputer, in relazione al quale vengono presentati alcuni progetti di ricerca che fanno uso di reti neurali. Il Neural Computing rappresenta il tentativo di definire modelli di calcolo che, sia pure in modo molto semplificato, simulino le funzionalit del cervello biologico. L\u2019analogia con il cervello biologico di basso livello e si basa su considerazioni architetturali e funzionali. Il neurone considerato, infatti, l\u2019elemento base del sistema. Di tale elemento base, il nucleo costituisce l\u2019elemento di elaborazione mentre dendriti ed assone sono, rispettivamente, i canali di ingresso e il canale di uscita. L\u2019assone trasmette successioni di impulsi mentre le connessioni fra neuroni avvengono mediante sinapsi la cui forza sinaptica ne determina l\u2019efficacia. Le connessioni possono essere sia di tipo eccitatorio sia di tipo inibitorio. Le sinapsi rappresentano le unit di memoria del sistema e l\u2019apprendimento si traduce in una modifica della forza sinaptica. L\u2019architettura dei sistemi neurali, d\u2019altra parte, si basa sulla definizione del concetto di neurone formale (vedi figura 1) caratterizzato da canali di ingresso e di uscita, dai pesi che simulano le sinapsi e la loro efficacia e da funzioni matematiche che ne modellizzano il comportamento. Da un punto di vista funzionale, le caratteristiche del cervello biologico che si ritrovano in parte nei sistemi neurali sono l\u2019elevata interconnettivit di elementi semplici e specializzati, l\u2019elevato parallelismo e la ridondanza Le reti neurali rappresentano pertanto modelli di calcolo che derivano alcune delle loro propriet salienti dalle teorie sul sistema nervoso centrale. Sebbene un feedback fra Neuroscienze e Neural Computing sia indubbiamente utile non strettamente necessario nella misura in cui le reti neurali sono viste come modelli astratti di calcolo e non come modelli del cervello biologico e della mente

RR Lyrae stars in the inner LMC: Where did they form?

RR Lyrae stars (RRLS) belong to population II and are generally used as a tracer of the host galaxy halo. The surface as well as vertical distribution of RRLS in the inner Large Magellanic Cloud (LMC) are studied to understand whether these stars are actually formed in the halo. RRLS identified by the OGLE III survey are used to estimate their number density distribution. The scale-height of their distribution is estimated using extinction corrected average magnitudes of ab type stars. The density distribution mimics the bar, confirming results in the literature. The distribution of their scale height indicates that there may be two populations, one with smaller scale-height, very similar to the red clump stars and the other, much larger. The distribution of the reddening-corrected magnitude along the minor axis shows variation, suggesting an inclination. The inclination is estimated to be i = 31.3 (3.5) degrees, very similar to the inclination of the disk. Thus, the RRLS in the inner LMC mimic the bar and inclination of the disk, suggesting that a major fraction of RRLS is formed in the disk of the LMC. The results indicate that the RRLS in the inner LMC trace the disk and probably the inner halo. They do not trace the extended metal-poor halo of the LMC. We suggest that a major star formation event happened in the LMC at 10-12 Gyrs ago, resulting in the formation of most of the inner RRLS, as well as probably the globular clusters, inner halo and the disk of the LMC.Comment: A&A Letters (in press