Analysis of the TOF resolution: a "tomography" study of the time of flight detector of the ALICE experiment at the LHC

Questa tesi presenta uno studio dettagliato della risoluzione del rilevatore a tempo di volo TOF dell’esperimento ALICE, utilizzando dati di collisioni Pb-Pb del RUN 2 dell’acceleratore LHC del CERN. È stata effettuata un’analisi dei profili della risoluzione temporale lungo i principali assi di simmetria del rivelatore (l’asse del fascio e quelli che definiscono il piano trasverso), così da evidenziare discontinuità date dalla struttura del rivelatore. Le strutture osservate corrispondono in larga parte a effetti previsti. Le dipendenze previste sono quelle date dalla presenza di materiale, modulate dalla distanza media di traccia, che sono state confermate da una correlazione statisticamente significativa con la risoluzione. Sono anche state osservate alcune strutture impreviste, probabilmente derivanti da malfunzionamenti nell’operatività e nell’elettronica del rivelatore, che saranno oggetto di studi futuri

Analysis of the production of φ-meson pairs in pp collisions with ALICE at LHC

La mia tesi si focalizza sull'analisi della produzione di coppie di mesoni phi in collisioni protone-protone. La misura è stata fatta ad ALICE, presso l'LHC, sfruttando le sue eccellenti doti di Particle Identification. È motivata dall'osservazione di un aumento di produzione di adroni strani e multi-strani, una possibile indicazione per la formazione di QGP, in collisioni protone-protone ad alta molteplicità. Il cuore del lavoro di questa tesi riguarda lo sviluppo di una tecnica, nuova all'interno dell'esperimento di ALICE, per la misura della produzione correlata di mesoni phi. La misura proposta prende ispirazione dal modello a stringhe di Lund, che è un modello fenomenologico ispirato dalla QCD microscopica per la produzione di adroni. L'idea principale della tecnica è una generalizzazione della tecnica della massa invariante per la ricostruzione di particelle a vita media corta in due dimensioni, per estrarre il segnale dal suo fondo irriducibile. La review esaminerà prima di tutto il metodo con cui viene costruito l'istogramma bi-dimensionale, con le problematiche e assunzioni ad esso associate, come per esempio il riempimento simmetrico e le condizioni di accoppiamento dei candidati. Successivamente viene considerata l'estrazione del segnale: l'estensione del fit sull'istogramma bi-dimensionale viene descritto nelle sue componenti di fondo e segnale e come vengono estratte informazioni preziose per questo processo dagli istogrammi mono-dimensionali. Verrà poi valutata l'efficienza, comparando la naturale efficienza 2-Dimensionale con un approccio più raffinato dato dal prodotto di efficienze 1-Dimensionali. In ultimo il tema dell'estrapolazione del segnale viene considerato.Dopo lo sviluppo dell'analisi, un primo prototipo viene impiegato per produrre una misura preliminare con dati reali di ALICE per collisioni protone-protone a \sqrt{s}=7 TeV

Safety culture to improve accidental events reporting in radiotherapy

The potential for unintended and adverse radiation exposure in radiotherapy is real and should be studied because radiotherapy is a highly complex, multistep process which requires input from numerous individuals from different areas and steps of the radiotherapy workflow. The 'Incident' (I) is a consequence of which are not negligible from the point of view of protection or safety. A 'near miss' (NM) is defined as an event which is highly likely to happen but did not occur. The purpose of this work is to show that through a systematic reporting and analysis of these adverse events, their occurrence can be reduced

Pediatric Hodgkin Lymphoma: Predictive value of interim 18F-FDG PET/CT in therapy response assessment

We investigated the prognostic value of interim 18F-FDG PET/CT (PET-2) in pediatric Hodgkin lymphoma (pHL), evaluating both visual and semiquantitative analysis. Thirty pHL patients (age ⠤16) underwent serial 18F-FDG PET/CT: At baseline (PET-0), after 2 cycles of chemotherapy (PET-2) and at the end of first-line chemotherapy (PET-T). PET response assessment was carried out visually according to the Deauville Score (DS), as well as semiquantitatively by using the semiquantitative parameters reduction from PET-0 to PET-2 (ΠΣSUVmax0-2, ΠΣSUVmean0-2). Final clinical response assessment (outcome) at the end of first-line chemotherapy was the criterion standard, considering patients as responders (R) or nonresponders (NR). Disease status was followed identifying patients with absence or relapsed/progression disease (mean follow-up: 24 months, range 3-78). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of visual and semiquantitative assessment were calculated; furthermore, Fisher exact test was performed to evaluate the association between both visual and semiquantitative assessment and outcome at the end of the first-line chemotherapy. The prognostic capability of PET-2 semiquantitative parameters was calculated by ROC analysis and expressed as area under curve (AUC). Finally, progression-free survival (PFS) was analyzed according to PET-2 results based on the 5-point scale and semiquantitative criteria, using the Kaplan-Meier method. Based on the outcome at the end of first-line chemotherapy, 5 of 30 patients were NR, the remnant 25 of 30 were R. Sensitivity, specificity, PPV, NPV, and accuracy of visual analysis were 60%,72%,30%,90%,70%; conversely, sensitivity, specificity, PPV, NPV, and accuracy of semiquantitative assessment were 80%, 92%, 66.7%, 95.8%, 90%. The highest AUC resulted for ΠΣSUVmax0-2 (0.836; cut-off <12.5; sensitivity 80%; specificity 91%). The association between ΠΣSUVmax0-2 and outcome at the end of first-line chemotherapy resulted to have a strong statistical significance (P=0.0026). Both methods demonstrated to influence PFS, even if the semiquantitative assessment allowed a more accurate identification of patients with a high risk of treatment failure (P=0.005). Our preliminary results showed that PET-2 visual assessment, by using Deauville criteria, can be improved by using the semiquantitative analysis. The SUV max reduction (ΠΣSUVmax0-2) evaluation might provide a support for the interpretation of intermediate scores, predicting with good confidence those patients who will have a poor outcome and require alternative therapies

An X-ray polarimeter for hard X-ray optics

Development of multi-layer optics makes feasible the use of X-ray telescope at energy up to 60-80 keV: in this paper we discuss the extension of photoelectric polarimeter based on Micro Pattern Gas Chamber to high energy X-rays. We calculated the sensitivity with Neon and Argon based mixtures at high pressure with thick absorption gap: placing the MPGC at focus of a next generation multi-layer optics, galatic and extragalactic X-ray polarimetry can be done up till 30 keV.Comment: 12 pages, 7 figure

Multidisciplinary studies on a sick-leader syndrome-associated mass stranding of sperm whales (Physeter macrocephalus) along the Adriatic coast of Italy

Mass strandings of sperm whales (Physeter macrocephalus) are rare in the Mediterranean Sea. Nevertheless, in 2014 a pod of 7 specimens stranded alive along the Italian coast of the Central Adriatic Sea: 3 individuals died on the beach after a few hours due to internal damages induced by prolonged recumbency; the remaining 4 whales were refloated after great efforts. All the dead animals were genetically related females; one was pregnant. All the animals were infected by dolphin morbillivirus (DMV) and the pregnant whale was also affected by a severe nephropathy due to a large kidney stone. Other analyses ruled out other possible relevant factors related to weather conditions or human activities. The results of multidisciplinary post-mortem analyses revealed that the 7 sperm whales entered the Adriatic Sea encountering adverse weather conditions and then kept heading northward following the pregnant but sick leader of the pod, thereby reaching the stranding site. DMV infection most likely played a crucial role in impairing the health condition and orientation abilities of the whales. They did not steer back towards deeper waters, but eventually stranded along the Central Adriatic Sea coastline, a real trap for sperm whales

Breaking the Nanoparticle Loading-Dispersion Dichotomy in Polymer Nanocomposites with the Art of Croissant-Making

\u3cp\u3eThe intrinsic properties of nanomaterials offer promise for technological revolutions in many fields, including transportation, soft robotics, and energy. Unfortunately, the exploitation of such properties in polymer nanocomposites is extremely challenging due to the lack of viable dispersion routes when the filler content is high. We usually face a dichotomy between the degree of nanofiller loading and the degree of dispersion (and, thus, performance) because dispersion quality decreases with loading. Here, we demonstrate a potentially scalable pressing-and-folding method (P & F), inspired by the art of croissant-making, to efficiently disperse ultrahigh loadings of nanofillers in polymer matrices. A desired nanofiller dispersion can be achieved simply by selecting a sufficient number of P & F cycles. Because of the fine microstructural control enabled by P & F, mechanical reinforcements close to the theoretical maximum and independent of nanofiller loading (up to 74 vol %) were obtained. We propose a universal model for the P & F dispersion process that is parametrized on an experimentally quantifiable D factor . The model represents a general guideline for the optimization of nanocomposites with enhanced functionalities including sensing, heat management, and energy storage.\u3c/p\u3

Genetically Determined Measures of Striatal D2 Signaling Predict Prefrontal Activity during Working Memory Performance

Background: Variation of the gene coding for D2 receptors (DRD2) has been associated with risk for schizophrenia and with working memory deficits. A functional intronic SNP (rs1076560) predicts relative expression of the two D2 receptors isoforms, D2S (mainly pre-synaptic) and D2L (mainly post-synaptic). However, the effect of functional genetic variation of DRD2 on striatal dopamine D2 signaling and on its correlation with prefrontal activity during working memory in humans is not known. Methods: Thirty-seven healthy subjects were genotyped for rs1076560 (G>T) and underwent SPECT with [123I]IBZM (which binds primarily to post-synaptic D2 receptors) and with [123I]FP-CIT (which binds to pre-synaptic dopamine transporters, whose activity and density is also regulated by pre-synaptic D2 receptors), as well as BOLD fMRI during N-Back working memory. Results: Subjects carrying the T allele (previously associated with reduced D2S expression) had striatal reductions of [ 123I]IBZM and of [123I]FP-CIT binding. DRD2 genotype also differentially predicted the correlation between striatal dopamine D2 signaling (as identified with factor analysis of the two radiotracers) and activity of the prefrontal cortex during working memory as measured with BOLD fMRI, which was positive in GG subjects and negative in GT. Conclusions: Our results demonstrate that this functional SNP within DRD2 predicts striatal binding of the two radiotracers to dopamine transporters and D2 receptors as well as the correlation between striatal D2 signaling with prefrontal cortex activity during performance of a working memory task. These data are consistent with the possibility that the balance of excitatory/inhibitory modulation of striatal neurons may also affect striatal outputs in relationship with prefrontal activity during working memory performance within the cortico-striatal-thalamic- cortical pathwa

A photoelectric polarimeter for XEUS: a new window in x-ray sky

XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of Optical Astronomy in terms of collecting areas. It will be based on two satellites, locked on a formation flight, one with the optics, one with the focal plane. The present design of the focal plane foresees, as an auxiliary instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We show how such a device is capable to solve open problems on many classes of High Energy Astrophysics objects and to use X-ray sources as a laboratory for a substantial progress on Fundamental Physics.Comment: 12 pages, 7 figure