Chemical and kinematical properties of Blue Straggler stars in Galactic globular clusters

Blue straggler stars (BSSs) are brighter and bluer (hotter) than the main-sequence (MS) turnoff and they are known to be more massive than MS stars.Two main scenarios for their formation have been proposed:collision-induced stellar mergers (COL-BSSs),or mass-transfer in binary systems (MT-BSSs).Depleted surface abundances of C and O are expected for MT-BSSs,whereas no chemical anomalies are predicted for COL-BSSs.Both MT- and COL-BSSs should rotate fast, but braking mechanisms may intervene with efficiencies and time-scales not well known yet,thus preventing a clear prediction of the expected rotational velocities.Within this context,an extensive survey is ongoing by using the multi-object spectrograph FLAMES@VLT,with the aim to obtain abundance patterns and rotational velocities for representative samples of BSSs in several Galactic GCs.A sub-population of CO-depleted BSSs has been identified in 47 Tuc,with only one fast rotating star detected.For this PhD Thesis work I analyzed FLAMES spectra of more than 130 BSSs in four GCs:M4,NGC 6397,M30 and ω Centauri.This is the largest sample of BSSs spectroscopically investigated so far.Hints of CO depletion have been observed in only 4-5 cases (in M30 and ω Centauri),suggesting either that the majority of BSSs have a collisional origin,or that the CO-depletion is a transient phenomenon.Unfortunately,no conclusions in terms of formation mechanism could be drawn in a large number of cases,because of the effects of radiative levitation. Remarkably,however,this is the first time that evidence of radiative levitation is found in BSSs hotter than 8200 K.Finally, we also discovered the largest fractions of fast rotating BSSs ever observed in any GCs:40% in M4 and 30% in ω Centauri.While not solving the problem of BSS formation,these results provide invaluable information about the BSS physical properties,which is crucial to build realistic models of their evolution.

Progettazione, modellazione e integrazione di risorse rinnovabili per promuovere lo sfruttamento dell'energia da moto ondoso e la Blue Growth.

L’energia da onda potrebbe assumere un ruolo fondamentale per la transizione energetica durante i prossimi decenni, grazie alla sua continuità nel tempo molto superiore rispetto ad altre risorse rinnovabili e alla sua vasta distribuzione nello spazio. Tuttavia, l’energia da onda è ancora lontana dall’essere economicamente sostenibile, a causa di diverse problematiche tecnologiche e alle difficoltà finanziarie associate. In questa ricerca, si è innanzitutto affrontata una delle maggiori sfide tecniche, nello specifico la progettazione e modellazione di sistemi di ancoraggio per i dispositivi galleggianti, proponendo possibili soluzioni per la modellazione numerica di sistemi di ancoraggio complessi e per l’ottimizzazione dei dispositivi stessi. Successivamente sono state analizzate le possibili sinergie strategiche di installazioni per lo sfruttamento della energia da onda con altre risorse rinnovabili e la loro applicazione nel contesto di aree marine multiuso. In particolare, una metodologia per la valutazione della combinazione ottimale delle risorse rinnovabili è stata sviluppata e verificata in due diversi casi studio: un’isola e una piattaforma offshore. Si è così potuto evidenziare l’importante contributo della risorsa ondosa per la continuità energetica e per la riduzione della necessità di accumulo. Inoltre, è stato concepito un metodo di supporto decisionale multicriteriale per la valutazione delle opzioni di riuso delle piattaforme offshore alla fine della loro vita operativa, come alternativa al decommissionamento, nell’ottica di una gestione sostenibile e della ottimizzazione dell’uso dello spazio marino. Sulla base dei criteri selezionati, l’inclusione di attività innovative come la produzione di energia da onda si è dimostrata essere rilevante per rendere vantaggioso il riuso rispetto al decommissionamento. Numerosi studi recenti hanno infatti sottolineato che, nell’ambito della “crescita blu”, i mercati come l’oil&gas, le attività offshore e le isole stimoleranno lo sviluppo di tecnologie innovative come lo sfruttamento dell’energia da onda, promuovendo la sperimentazione e fornendo un importante contributo all’avanzamento tecnico e alla commercializzazione.

The blue side of diabetes: assessing the impact of depression in people with type 2 diabetes using real-world data

The aim of the thesis is to assess the impact of depression in people with type 2 diabetes. Using Healthcare Utilization Databases, I estimated in a large population-based cohort with type 2 diabetes the incidence of depression over 10 year-period, identified the demographic and clinical predictors of depression, and determined the extent to which depression is a risk factor for acute and long-term complications and mortality. In the context of COVID-19 pandemic, I evaluated whether the presence of a history of depression in type 2 diabetes increased the Emergency Department (ED) access rate for diabetes-related complications, and I investigated changes in the incidence of depression during the first year of the pandemic. Findings from the first study indicated that developing depression was associated with being a woman, being over 65 years, living in rural areas, having insulin as initial diabetes medication and having comorbid conditions; the study also confirmed that depression was associated with an increased risk for acute and long-term diabetes complications and all-cause mortality. The second observational study showed a higher rate of ED access for diabetes-related complications during the pandemic in people with type 2 diabetes and a history of depression than in those without a history of depression, similar to what was observed in a pre-pandemic period. As shown in the third population-based study, the incidence of depression decreased in 2020 compared to 2019, mainly during the first and the second waves of the COVID-19 pandemic, when people probably had difficulty reaching healthcare services. This new real-world evidence will help healthcare professionals identify timely patients at high risk of developing depression. Lastly, policymakers and physicians will benefit from new evidence of the effects of the COVID-19 pandemic on depression in people with type 2 diabetes to ensure a high level of care during crisis periods.

Synthesis and characterization of prussian blue analogue materials for post-Li ion batteries

Energy issues have always been a subject of concern to people. During the past 30 years, rechargeable Li-ion batteries (LIBs) have been widely used in portable electronic devices and power tools because of their high energy density and efficiency among practical secondary batteries. While the unevenly distribution of Lithium sources and the increasing cost of lithium-raw material can not satisfy the requirement for further cost reduction, especially for the grid-scale energy storage. Post-lithium ion batteries as promising replacement for LIBs have attracted wide attention, owing to their high abundant resources and adequate insertion potential. Similar with Li-ion batteries, finding a suitable electrode material is the key for the research and application of the post-Li ion batteries. In our project, we focus our study on Prussian blue analogues (PBAs), with formula AxM[M’(CN)6]1-y□y•zH2O (0≤x≤2, 0

Advanced X-ray techniques for the structural characterisation of Prussian Blue Analogue cathode materials

The thesis is dedicated to the implementation of advanced x-ray-based techniques for the investigation of the battery systems, more predominantly, the cathode materials. The implemented characterisation methods include synchrotron based x-ray absorption spectroscopy, powder x-ray diffraction, 2-dimensional x-ray fluorescence, full field transmission soft x-ray microscopy, and laboratory x-ray photoelectron spectroscopy. The research highlights the different areas of expertise for each described method, in terms of material characterisation, exploring their complementarities and intersections. The results are focused over manganese hexacyanoferrate and partially Ni substituted manganese hexacyanoferrate, through both organic and aqueous battery systems. In aqueous system, the modification of cathode composition has been observed with various techniques, indicating to the processes occurring in bulk, surface, locally or in long-range, including with the speciation by 2-dimensional scanning, and the time-resolution, by the implementation of the operando measurements. In organic media, the inhomogenisation of the cathode material during the aging process was investigated by the development of the special image treatment procedure for the maps, obtained from the transmission soft x-ray microscopy. It worth mentioning, that apart from the combination of the outcomes from the various x-ray measurements, the exploration of the new capabilities was also conducted, namely, probing the oxidation state of the element with the synchrotron-based 2-dimensional x-ray fluorescence technique, which, generally, with conventional set up, is not possible to achieve. The results and methodology from this thesis can, of course, be generalised on the characterisation of the other battery systems, and not only, as the x-ray techniques are one of the most informative and sophisticated methods for advanced structural investigation of the materials.