Multiple stellar populations in Globular Clusters: collection of information from the Horizontal Branch

The majority of the inhomogeneities in the chemical composition of Globular Cluster (GC) stars appear due to primordial enrichment by hot-CNO cycled material processed in stars belonging to a first stellar generation. Either massive AGB envelopes subject to hot bottom burning, or the envelopes of massive fastly rotating stars could be the progenitors. In both cases, the stars showing chemical anomalies must have also enhanced helium abundance, and we have proposed that this higher helium could be at the basis of the many different morphologies of GC horizontal branches (HB) for similar ages and metallicities. The helium variations have been beautifully confirmed by the splitting of the main sequence in the clusters omega Cen and NGC 2808, but this effect can show up only for somewhat extreme helium abundances. Therefore it is important to go on using the HB morphology to infer the number ratio of the first to the second generation in as many clusters as possible. We exemplify how it is possible to infer the presence of a He-rich stellar component in different clusters thanks to different HB features (gaps, RR Lyr periods and period distribution, ratio of blue to red stars, blue tails). In many clusters at least 50% of the stars belong to the second stellar generation, and in some cases we suspect that the stars might all belong to the second generation. We shortly examine the problem of the initial mass function required to achieve the observed number ratios and conclude that: 1) the initial cluster must have been much more massive than today's cluster, and 2) formation of the second stellar generation mainly in the central regions of the cluster may help in obtaining the desired values.Comment: to appear in the Proceedings of IAU Symposium 246 ``Dynamical Evolution of Dense Stellar Systems", E. Vesperini, M. Gierzs & A. Sills, eds., Cambridge University Pres

PROGRAMMAZIONE STRATEGICA E VALUTAZIONE GENERATIVA NELLA RIQUALIFICAZIONE DEI TESSUTI URBANI STORICI

The old town of Ragusa is undertaking a process of progressive urban enhancement in some different directions. Its differently valued parts should be covered by a general valorization strategy connecting the decision making process with functional and symbolic values that need to be adequately analyzed and represented. In such a multi-layered urban sub-system, the Architectural Unit can play the role of main information/value unit from which the valuation/decision making pattern starts. The proposed pattern includes, connects and systematizes the analysis, valuation and planning stages by coordinating quantitative appraisals and qualitative multi- criteria assessments based on a MAVT pattern. In particular, the planning stage is aimed at associating the fair Intervention Category to each Architectural Unit by generating a great number of overall intervention strategies in order to maximize different and conflicting objectives. Thus, the strategies are compared basing on their axiological profile, to lay down a trade-off scheme between them. The pattern endorses a semiotic interpretation of the urban fabric, sorting the single Architectural Units by signs, symbols and icons. DOI: http://dx.medra.org/10.19254/LaborEst.12.06            

The early evolution of Globular Clusters: the case of NGC 2808

Enhancement and spread of helium among globular cluster stars have been recently suggested as a way to explain the horizontal branch blue tails, in those clusters which show a primordial spread in the abundances of CNO and other elements involved in advanced CNO burning (D'Antona et al. 2002). In this paper we examine the implications of the hypothesis that, in many globular clusters, stars were born in two separate events: an initial burst (first generation), which gives origin to probably all high and intermediate mass stars and to a fraction of the cluster stars observed today, and a second, prolonged star formation phase (second generation) in which stars form directly from the ejecta of the intermediate mass stars of the first generation. In particular, we consider in detail the morphology of the horizontal branch in NGC 2808 and argue that it unveils the early cluster evolution, from the birth of the first star generation to the end of the second phase of star formation. This framework provides a feasible interpretation for the still unexplained dichotomy of NGC 2808 horizontal branch, attributing the lack of stars in the RR Lyr region to the gap in the helium content between the red clump, whose stars are considered to belong to the first stellar generation and have primordial helium, and the blue side of the horizontal branch, whose minimum helium content reflects the helium abundance in the smallest mass (~4Msun)contributing to the second stellar generation. This scenario provides constraints on the required Initial Mass Function, in a way that a great deal of remnant neutron stars and stellar mass black holes might have been produced.Comment: 23 pages, 7 figures, in press on The Astrophysical Journa

Oxygen Therapy during Exercise in Patients with Interstitial Lung Diseases

Introduction: ILDs are a varied group of diffuse parenchymal lung diseases associated with high morbidity and mortality. Current treatments can only slow their progression but not cure the disease. Other treatments such as oxygen therapy can also be used as support. We know very little about the effects of oxygen therapy on patients with ILDs. The aim of this study was to collect data from the literature in order to determine whether oxygen therapy can actually decrease the mortality rate or whether it is only suitable for supportive therapy for patients with ILDs. Methods: We reviewed the literature since 2010 on oxygen therapy during exercise in patients with ILDs. Studies that used cardio-pulmonary tests were excluded. We only reviewed those that used the 6 min walking test (6MWT) or the free walking test. We located 11 relevant articles. Results: All the articles except a Japanese study showed an augmentation in oxyhaemoglobin saturation during exercise when oxygen was supplied. A 2018 study called AmbOx provided important data on the effects of oxygen therapy during daily activities, showing significant improvements in quality of life. Conclusions: This review showed that the literature on the benefits of oxygen therapy in patients with ILDs does not provide sufficient evidence to draft specific guidelines. It was not possible to conclude whether oxygen therapy has an effect on mortality or can only play a supportive role. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

PAESAGGI UMANI/URBANI E PROSPETTIVE DELLA CITTÀ. UN APPROCCIO ASSIOLOGICO

This contribution deals with the issue of the representation in terms of value attributes of the municipalities characterized by complex evolutive processes involving their landscape, urban and architectural characteristics. With reference to the case study of Syracuse (Italy), an assessment pattern has been drawn with references to the two dimensions of the urban and human capital, basing on the official dataset by the Italian National Institute of Statistics (ISTAT), on a Census Sections scale. A great amount of data has been coordinated to provide the most significant indices over an observation-valuation-interpretation pattern inspired by some aspects of the evolutionary approache concerning the natural eco-systems. A GIS-based representation of the numeric results coming from a Hierarchic Multidimensional approach allowed us to identify some of the main typical urban/human profiles referable to the areas more significantly characterized by landscape-urban and socioeconomic values, in the cases of both decay and success