Characterization of a versatile and sensitive detector for gamma-ray astronomy

Il lavoro presentato in questa tesi è stato svolto presso l’Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IASF-Bologna) nell’ambito delle attività di ricerca della collaborazione ReDSoX (REsearch Drift for SOft X-rays). Il mio progetto di tesi si pone come obiettivo la realizzazione di uno spettrometro per missioni di astrofisica spaziale. Tale spettrometro si basa su una tecnologia nota e affidabile come quella dei rivelatori al Silicio, mantenendo un design compatto e la possibilità di lavorare senza la necessità di un sistema attivo di raffreddamento. Il lavoro presentato in questa tesi riguarda la caratterizzazione di un prototipo di rivelatore realizzato accoppiando un cristallo scintillatore con un rivelatore a stato solido (Silicon Drift Detector, SDD). Il fotorivelatore è costituito da una matrice di 7 SDD a geometria esagonale. Tale matrice è stata disegnata con lo specifico obiettivo di essere utilizzata come fotorivelatore per la luce di scintillazione proveniente da un cristallo scintillatore commerciale di forma cilindrica e dal diametro di 0,5”. Abbiamo utilizzato un cristallo di Bromuro di Lantanio attivato al Cerio, LaBr3(Ce). Esso é un cristallo di nuova generazione caratterizzato da un’elevata produzione di luce (light yield), un tempo di emissione molto rapido e alta linearità. In questa tesi abbiamo testato ampiamente il prototipo sia per le sue prestazioni spettroscopiche che temporali. Sono state misurate le prestazione in termini di rumore sia a temperatura ambiente che a temperature moderatamente basse

The opto-mechanical alignment procedure of the VLT Survey Telescope

The VLT Survey Telescope is a f/5.5 modified Ritchey-Chretien imaging telescope, which is being installed at the ESO-Paranal Observatory. It will provide a one square degree corrected field of view to perform survey-projects in the wavelength range from UV to I band. In this paper we describe the opto-mechanical alignment procedure of the 2.61m primary mirror, the secondary and correctors lenses onto the mechanical structure of the telescope. The alignment procedure does not rely on the mechanical precision of the mirrors. It will be achieved using ad-hoc alignment tools, described in the paper, which allows the spatial determination of optical axes (and focuses where necessary) of the optical components with respect to the axis defined by the rotation of a laser beam mounted on the instrument bearing.Comment: 10 pages, 10 figures, Proceeding 773357 of the SPIE Conference "Ground-based and Airborne Telescopes III", Sunday 27 June 2010, San Diego, California, US

Combining chemical and X-Ray microtomography investigations on crustal xenoliths at Mount Etna: evidence of volcanic gas fluxing

Crustal xenoliths embedded in lavas offer chances to provide information on the lithology of the volcano basement and the process occurring during magma ascent. In this work we studied seven xenoliths found among the scoriae ejected during several paroxysms occurred between 2011 and 2016 at the South East Crater (SEC) of Mount Etna volcano. These samples are characterized by massive presence of glass and vesicles resulting in a foam-like appearance of their texture. A detailed study of their textural and chemical features was carried out combining XRF, SEM-EDS, two-dimensional observation and Synchrotron X-ray microtomography (3D imaging). This multidisciplinary approach allowed us to identify and quantify the components of the samples, individuate the likely provenance rock, ascribable to the Numidian Flysch outcropping west of the Etnean edifice. 2D and 3D imaging were successfully applied to estimate the amount of the phases constituting the samples (grains + glass + vesicles) and the degree of partial melting that occurred during the interaction with the basaltic melt and gaseous phase. The sedimentary rocks underwent profound changes led by partial melting, gas fluxing, vesiculation and selective alkali enrichment. These processes could not be driven exclusively by the prolonged contact with the molten phase but must be considered as result of a significant contribution from the volatiles rising through the plumbing system and the sedimentary basement

Respiratory Morbidity and Exhaled Nitric Oxide in the First 2 Years of Life: the Generation R Study

Asthma is a lung disease characterized by chronic inflammation of the airways associated with bronchial hyperresponsiveness. The airflow obstruction within the lungs is responsible of recurrent episodes of wheezing, breathlessness, chest tightness and coughing. The physiopathological changes of the airways in asthma are mediated by many cells and cellular elements. It has been argued that asthma is a syndrome comprising a number of separate conditions, rather than a single disease with a broad range of severity. It has long been thought that the inappropriate response of the specific immune system to harmless antigens leading to the polarization of T‐cells toward a T‐helper 2 (Th2) phenotype was the central mechanism of asthma. However, in the last years the hypothesis of asthma as one unifying disease concept has disappeare. Novel disease and bronchial inflammation pathways, many of which are independent of adaptive immunity, have been reported. The concept of disease endotypes has been recently introduced and subtypes of asthma with different and specific pathophysiology, immunology, clinical features and response to treatment have been described. A simple categorization of the different inflammatory patterns in asthmatics based on sputum eosinophil and neutrophil proportions has been provided and four inflammatory subtypes have been identified: neutrophilic, eosinophilic, mixed granulocytic and paucigranulocytic asthma. A recent review by Haldar and Pavord suggested that non‐eosinophilic asthma represents a stable phenotype associated with distinct etiologic factors and less airway pathology. Also, it has been suggested that severe asthma should no longer be considered as the result of a progressive process, but rather as a separate pathological entity with distinct physiologic and clinical characteristics. These heterogeneous inflammatory patterns have been also reported by Brasier et al, who evaluated bronchoalveolar lavage (BAL) samples in mild to severe asthmatic patients. They showed that cytokine expression patterns in BAL could be used to identify distinct types of asthma and identify distinct subsets of methacholine hyperresponders. Despite improved understanding of pathophysiology, immunology and genetics of asthma in childhood, we still do not know the basic mechanisms underlying the development of the disease

Exhaled nitric oxide measurements in the first 2 years of life: methodological issues, clinical and epidemiological applications

Fractional exhaled nitric oxide (FeNO) is a useful tool to diagnose and monitor eosinophilic bronchial inflammation in asthmatic children and adults. In children younger than 2 years of age FeNO has been successfully measured both with the tidal breathing and with the single breath techniques. However, there are a number of methodological issues that need to be addressed in order to increase the reproducibility of the FeNO measurements within and between infants. Indeed, a standardized method to measure FeNO in the first 2 years of life would be extremely useful in order to meaningfully interpret FeNO values in this age group. Several factors related to the measurement conditions have been found to influence FeNO, such as expiratory flow, ambient NO and nasal contamination. Furthermore, the exposure to pre- and postnatal risk factors for respiratory morbidity has been shown to influence FeNO values. Therefore, these factors should always be assessed and their association with FeNO values in the specific study population should be evaluated and, eventually, controlled for

Production of large Bose-Einstein condensates in a magnetic-shield-compatible hybrid trap

We describe the production of large ${}^{23} \mathrm{Na}$ Bose-Einstein condensates in a hybrid trap characterized by a weak magnetic field quadrupole and a tightly focused infrared beam. The use of small magnetic field gradients makes the trap compatible with the state-of-the-art magnetic shields. By taking advantage of the deep cooling and high efficiency of gray molasses to improve the initial trap loading conditions, we produce condensates composed of as much as $7$ million atoms in less than $30 \; \mathrm{s}$.Comment: 8 pages, 3 figure

Effective evaluation of clustering algorithms on single-cell CNA data

Clustering methods are increasingly applied to single-cell DNA sequencing (scDNAseq) data to infer the subclonal structure of cancer. However, the complexity of these data exacerbates some data-science issues and affects clustering results. Additionally, determining whether such inferences are accurate and clusters recapitulate the real cell phylogeny is not trivial, mainly because ground truth information is not available for most experimental settings. Here, by exploiting simulated sequencing data representing known phylogenies of cancer cells, we propose a formal and systematic assessment of well-known clustering methods to study their performance and identify the approach providing the most accurate reconstruction of phylogenetic relationships