Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. II. Statistical analysis of a sample of 67 CEMP-ss stars

Many observed CEMP stars are found in binary systems and show enhanced abundances of $s$-elements. The origin of the chemical abundances of these CEMP-$s$ stars is believed to be accretion in the past of enriched material from a primary star in the AGB phase. We investigate the mechanism of mass transfer and the process of nucleosynthesis in low-metallicity AGB stars by modelling the binary systems in which the observed CEMP-$s$ stars were formed. For this purpose we compare a sample of $67$ CEMP-$s$ stars with a grid of binary stars generated by our binary evolution and nucleosynthesis model. We classify our sample CEMP-$s$ stars in three groups based on the observed abundance of europium. In CEMP$-s/r$ stars the europium-to-iron ratio is more than ten times higher than in the Sun, whereas it is lower than this threshold in CEMP$-s/nr$ stars. No measurement of europium is currently available for CEMP-$s/ur$ stars. On average our models reproduce well the abundances observed in CEMP-$s/nr$ stars, whereas in CEMP-$s/r$ stars and CEMP-$s/ur$ stars the abundances of the light-$s$ elements are systematically overpredicted by our models and in CEMP-$s/r$ stars the abundances of the heavy-$s$ elements are underestimated. In all stars our modelled abundances of sodium overestimate the observations. This discrepancy is reduced only in models that underestimate the abundances of most of the $s$-elements. Furthermore, the abundance of lead is underpredicted in most of our model stars. These results point to the limitations of our AGB nucleosynthesis model, particularly in the predictions of the element-to-element ratios. Finally, in our models CEMP-$s$ stars are typically formed in wide systems with periods above 10000 days, while most of the observed CEMP-$s$ stars are found in relatively close orbits with periods below 5000 days.Comment: 23 pages, 8 figures, accepted for publication on Astronomy & Astrophysic

Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods

AGB stars are responsible for producing a variety of elements, including carbon, nitrogen, and the heavy elements produced in the slow neutron-capture process ($s$-elements). There are many uncertainties involved in modelling the evolution and nucleosynthesis of AGB stars, and this is especially the case at low metallicity, where most of the stars with high enough masses to enter the AGB have evolved to become white dwarfs and can no longer be observed. The stellar population in the Galactic halo is of low mass ($\lesssim 0.85M_{\odot}$) and only a few observed stars have evolved beyond the first giant branch. However, we have evidence that low-metallicity AGB stars in binary systems have interacted with their low-mass secondary companions in the past. The aim of this work is to investigate AGB nucleosynthesis at low metallicity by studying the surface abundances of chemically peculiar very metal-poor stars of the halo observed in binary systems. To this end we select a sample of 15 carbon- and $s$-element-enhanced metal-poor (CEMP-$s$) halo stars that are found in binary systems with measured orbital periods. With our model of binary evolution and AGB nucleosynthesis, we determine the binary configuration that best reproduces, at the same time, the observed orbital period and surface abundances of each star of the sample. The observed periods provide tight constraints on our model of wind mass transfer in binary stars, while the comparison with the observed abundances tests our model of AGB nucleosynthesis.Comment: 18 pages, 20 figures, accepted for publication on A&

Slowly, slowly in the wind: 3D hydrodynamical simulations of wind mass transfer and angular-momentum loss in AGB binary systems

Wind mass transfer in binary systems with AGB donor stars plays a fundamental role in the formation of a variety of objects, including barium stars and CEMP stars. We carry out a comprehensive set of SPH simulations of wind-losing AGB stars in binaries, for a variety of binary mass ratios, orbital separations, initial wind velocities and rotation rates of the donor star. The initial parameters of the simulated systems are chosen to match the expected progenitors of CEMP stars. We find that the strength of interaction between the wind and the stars depends on both the wind-velocity-to-orbital-velocity ratio ($v_\infty/v_\mathrm{orb}$) and the binary mass ratio. Strong interaction occurs for close systems and comparable mass ratios, and gives rise to a complex morphology of the outflow and substantial angular-momentum loss, which leads to a shrinking of the orbit. As the orbital separation increases and the mass of the companion star decreases, the morphology of the outflow, as well as the angular-momentum loss, become more similar to the spherically symmetric wind case. We also explore the effects of tidal interaction and find that for orbital separations up to 7-10 AU, depending on mass ratio, spin-orbit coupling of the donor star occurs at some point during the AGB phase. If the initial wind velocity is relatively low, we find that corotation of the donor star results in a modified outflow morphology that resembles wind Roche-lobe overflow. In this case the mass-accretion efficiency and angular-momentum loss differ from those found for a non-rotating donor. Finally, we provide a relation for both the mass-accretion efficiency and angular-momentum loss as a function of $v_\infty/v_\mathrm{orb}$ and the binary mass ratio that can be easily implemented in a population synthesis code to study populations of barium stars, CEMP stars and other products of interaction in AGB binaries.Comment: Accepted for publication in A&A, 20 pages, 12 figures, 4 tables. Abstract abridged due to arXiv requirement

VANTAGGI DELL’UTILIZZO DEL SISTEMA DOSIMETRICO OSL IN CASO DI EMERGENZA

VANTAGGI DELL’UTILIZZO DEL SISTEMA DOSIMETRICO OSL IN CASO DI EMERGENZA S. Abate, F. Campi, L. Garlati, O. Tambussi Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano [email protected] Il sistema dosimetrico per corpo intero OSL (Optically Stimulated Luminescence) è un tipo di dosimetria che si sta sempre più diffondendo in vari paesi. In Europa molti centri di ricerca si sono dotati di un proprio sistema dosimetrico, mentre commercialmente Landauer rappresenta il maggior fornitore di tale servizio dosimetrico, ma anche del sistema stesso (dosimetri e apparecchio di lettura). Il vantaggio di questo tipo di dosimetro consiste nella semplicità e velocità di lettura e azzeramento, anche se risulta meno affidabile dei film-badge. Inoltre, rispetto ai dosimetri a TL, risultano essere più stabili nel tempo, non dovendo subire cicli termici che ne alterano la struttura cristallina e di conseguenza le loro performance. Questo permette di utilizzare, leggere e azzerare anche il singolo dosimetro e non l’intero lotto di appartenenza. Questa caratteristica permette di utilizzare il dosimetro a OSL come un dosimetro passivo, ma col vantaggio della lettura indiretta al termine delle operazioni, proprio come per un dosimetro elettronico viene effettuata la lettura diretta su display. In questo lavoro si vogliono paragonare i vantaggi e gli svantaggi dei sistemi dosimetrici tradizionali (film-badge e TLD) con il sistema OSL. Si presentano i risultati sperimentali delle performance (dipendenza energetica, dosimetrica e angolare) del sistema dosimetrico OSL Inlight con sistema di lettura MicroStar. Infine si presentano i risultati degli irraggiamenti condotti in parallelo presso un centro LAT tra il sistema OSL e i dosimetri elettronici DMC 2000 (Mirion Technologies). Le caratteristiche di questo dosimetro permettono di concludere che questo tipo di sistema dosimetrico ha degli aspetti positivi per il suo utilizzo in caso di emergenza radiologica senza i costi di una dosimetria con strumentazione attiva

Modelling the observed properties of carbon-enhanced metal-poor stars using binary population synthesis

The stellar population in the Galactic halo is characterised by a large fraction of CEMP stars. Most CEMP stars are enriched in $s$-elements (CEMP-$s$ stars), and some of these are also enriched in $r$-elements (CEMP-$s/r$ stars). One formation scenario proposed for CEMP stars invokes wind mass transfer in the past from a TP-AGB primary star to a less massive companion star which is presently observed. We generate low-metallicity populations of binary stars to reproduce the observed CEMP-star fraction. In addition, we aim to constrain our wind mass-transfer model and investigate under which conditions our synthetic populations reproduce observed abundance distributions. We compare the CEMP fractions and the abundance distributions determined from our synthetic populations with observations. Several physical parameters of the binary stellar population of the halo are uncertain, e.g. the initial mass function, the mass-ratio and orbital-period distributions, and the binary fraction. We vary the assumptions in our model about these parameters, as well as the wind mass-transfer process, and study the consequent variations of our synthetic CEMP population. The CEMP fractions calculated in our synthetic populations vary between 7% and 17%, a range consistent with the CEMP fractions among very metal-poor stars recently derived from the SDSS/SEGUE data sample. The results of our comparison between the modelled and observed abundance distributions are different for CEMP-$s/r$ stars and for CEMP-$s$ stars. For the latter, our simulations qualitatively reproduce the observed distributions of C, Na, Sr, Ba, Eu, and Pb. Contrarily, for CEMP-$s/r$ stars our model cannot reproduce the large abundances of neutron-rich elements such as Ba, Eu, and Pb. This result is consistent with previous studies, and suggests that CEMP-$s/r$ stars experienced a different nucleosynthesis history to CEMP-$s$ stars.Comment: 17 pages, 11 figures, accepted for publication on Astronomy and Astrophysic

Integrated Care for Chronic Diseases – State of the Art

Chronic diseases represent a high cost for healthcare systems, for individuals, families, businesses and governments. The World Health Organization (WHO) estimates that an increase of 10% of chronic diseases is associated with a reduction of 0.5% of annual economic growth. Primary care has proven to ensure high levels of efficiency, effectiveness, equity, safety, timely and centrality of the patient achieving better health outcomes and lower costs. The Chronic Care Model (CCM) proposes a proactive approach in assisting the empowerment of patients and their community. The CCM contributes to improving the quality of care and health outcomes and the reduction of inequalities (e.g., ethnicity, social status) too

Litigation to Protect the Marine Environment: Parallels and Synergies with Climate Litigation

This paper reviews recent successes and obstacles in using litigation as a tool to address issues in several contexts in the marine environment. It surveys developments at the international, national, and sub-national levels and offers lessons from creative climate litigation strategies as a way to enhance litigation to protect the marine environment. It also recommends ways in which the ocean-climate nexus can provide mutual benefits in advancing the agendas of climate change regulation and ocean stewardship

Assessment of the Quality of Drinking Water Supply, and the Status of Sanitation and Hygiene in Mudulla Town, Tembaro Woreda, Southern Ethiopia

Limited access associated with poor water supply, hygiene and sanitation is widening the poverty gap, gender inequality and prevalence of water born diseases. This research work is aimed to examine the quality of existing water supply, sanitation and hygiene status of Mudula Town. To achieve this objective, the household survey and Water samples were collected from three water sources (spring), storage and taps. With the exception of Kalahiwot spring for Turbidity (7.75NTU), all others were within the standards. For bacteriological analysis, Gofore spring is within the standard. But samples tested from Bada and Kalahiwot did not meet the WHO and EPA bacteriological standards for drinking water. The correlation result of physical parameters shows that for all sources turbidity, TDS and EC has strong positive correlation with each other. With the exception of Gofere spring source, fecal coliform (E.coli) is negatively correlated with Temperature and positivity correlated with Total coliform for both spring water sources. The current average per capital water converge in the area is 68% and its consumption is strongly correlated with house hold income amount. Similarly for sanitation, from total respondents 5% use pit latrine without house, 10% pit latrine with house and remain 85% use pit latrine with wall and roof. Regarding to solid waste, 55% dispose solid waste on garden and 45% have sanitary pit. From total respondents, up to 55% do not use water after defecating. The rest also have a gap on using soap continuously. Therefore, to overcome the problems regular chlorination of water, sanitation and hygiene practicing awareness may be required. Keywords: Water Supply, Coverage, Water Quality, Sanitation and Hygiene practice

Virtual Environment for Next Generation Sequencing Analysis

Next Generation Sequencing technology, on the one hand, allows a more accurate analysis, and, on the other hand, increases the amount of data to process. A new protocol for sequencing the messenger RNA in a cell, known as RNA- Seq, generates millions of short sequence fragments in a single run. These fragments, or reads, can be used to measure levels of gene expression and to identify novel splice variants of genes. The proposed solution is a distributed architecture consisting of a Grid Environment and a Virtual Grid Environment, in order to reduce processing time by making the system scalable and flexibl

Reverse Engineering of TopHat: Splice Junction Mapper for Improving Computational Aspect

TopHat is a fast splice junction mapper for Next Generation Sequencing analysis, a technology for functional genomic research. Next Generation Sequencing technology allows more accurate analysis increasing data to elaborate, this opens to new challenges in terms of development of tools and computational infrastructures. We present a solution that cover aspects both software and hardware, the first one, after a reverse engineering phase, provides an improvement of algorithm of TopHat making it parallelizable, the second aspect is an implementation of an hybrid infrastructure: grid and virtual grid computing. Moreover the system allows to have a multi sample environment and is able to process automatically totally transparent to user