Image enhancement for a Bose-Einstein condensate interferometer

The atom, thanks to its wave behaviour, can manifest phenomena which are, usually, associated to light: interference is one of them. The possibility of cooling atomic clouds and manipulating the states of the atoms contained in them opened many new opportunities to exploit these states in many ways; one of them is measuring various kinds of physical observables with high precision, thanks to the aforementioned interference phenomena: this is atom interferometry. Since the first Bose-Einstein condensates in atomic gases were obtained, there has been a keen interest in interference between them, as it would mean to observe coherent quantum phenomena between macroscopic objects. Nevertheless, the high atomic density of condensates with respect to non condensed, thermal atomic clouds makes it difficult to ignore the effects of interactions within them. For the applications, understanding the role of interactions in the formation of interference figures is crucial. In this thesis, an algorithm for the enhancement of absorption images of a condensate has been developed. This algorithm computes an image basis for the noise and then remove the projection of the starting image from this basis, thus obtaining a clean image. This algorithm has then been applied to the enhancement of images obtained from atom interferometry. These images have then been analyzed using two techniques, and the obtained results have been compared to those for an ideal condensate. The results have been found not compatible with the ideal case, and are then due to atom-atom interactions

Generazione e caratterizzazione dinamica di potenziali ottici mediante un dispositivo a microspecchi

In questa tesi si tratta della caratterizzazione dinamica dei potenziali ottici che possono essere ottenuti mediante un dispositivo a microspecchi (DMD), che sarà utilizzato in esperimenti con atomi freddi. Lo studio della superfluidità nei condensati di Bose-Einstein, e del fenomeno ad essa strettamente collegato della formazione di vortici, è uno filoni di ricerca più sviluppati nell'ambito della fisica degli atomi freddi. Gli apparati sperimentali fanno uso di complessi sistemi di generazione di potenziali ottici variabili nel tempo. Un dispositivo a microspecchi consiste di una matrice di specchi, ciascuno dei quali può essere controllato da un attuatore elettromeccanico; questo dispositivo consente quindi di modulare la radiazione luminosa che esso riflette, variandola anche nel tempo. È possibile quindi utilizzare tale dispositivo per produrre un potenziale ottico variabile nel tempo. Il lavoro sperimentale svolto per questa tesi comprende misure di tempi di commutazione e fedeltà delle immagini generate utilizzando un dispositivo a microspecchi, e lo sviluppo di un codice di controllo che, mediante un algoritmo PID, consenta di ridurre le distorsioni indotte dal sistema ottico

Neurobiological Dysfunctional Substrates for the Self-Medication Hypothesis in Adult Individuals with Attention-Deficit Hyperactivity Disorder and Cocaine Use Disorder:A Fluorine-18-Fluorodeoxyglucose Positron Emission Tomography Study

Objectives: Attention-deficit hyperactivity disorder (ADHD) in adulthood shows high co-occurrence rates with cocaine use disorder (CoUD). The self-medication hypothesis (SMH) provides a theoretical explanation for this comorbidity. This study investigates the neurobiological mechanisms that could support SMH in adult patients with attention-deficit hyperactivity disorder with cocaine use disorder (ADHD–CoUD).Materials and Methods: We included 19 ADHD–CoUD patients (84.2% male; age: 32.11 years [7.18]) and 16 CoUD patients (68.7% male; age: 36.63 years [8.12]). All subjects underwent a fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG PET) brain scan. We tested brain metabolism differences between ADHD–CoUD and CoUD patients using voxel-based and regions of interest (ROIs)-based analyses. The correlation between dependence/abstinence duration and regional brain metabolism was also assessed in the two groups. Lastly, we investigated the integrity of brain metabolic connectivity of mesocorticolimbic and nigrostriatal dopaminergic systems, and large-scale brain networks involved in ADHD and addictions.Results: The voxel-wise and ROIs-based approaches showed that ADHD–CoUD patients had a lower metabolism in the thalamus and increased metabolism in the amygdala and parahippocampus, bilaterally, than CoUD subjects and healthy controls (HCs). Metabolism in the thalamus negatively correlated with years of dependence in ADHD–CoUD patients. Moreover, connectivity analyses revealed that ADHD–CoUD patients had a more preserved metabolic connectivity than CoUD patients in the dopaminergic networks and large-scale networks involved in self-regulation mechanisms of attention and behaviors (i.e., anterior default mode network [ADMN], executive network [ECN], and anterior salience network [aSAN]).Conclusions: We demonstrated distinct neuropathological substrates underlying substance-use behaviors in ADHD–CoUD and CoUD patients. Furthermore, we provided neurobiological evidence in support of SMH, demonstrating that ADHD–CoUD patients might experience short-term advantages of cocaine assumption (i.e., compensation of dopaminergic deficiency and related cognitive-behavioral deficits).</p

Should We Cry over the Spilt Milk? Market Power and Structural Change along Dairy Supply Chains in EU Countries

A &ldquo;first-pass&rdquo; test on a set of monthly prices index series from 2000 to 2015 was applied to detect market power exertion in the dairy value chain of 25 EU countries. Due to econometric and theoretical restrictions, the test yielded conclusive findings only in 11 over 25 EU Countries. Such results show that in Austria, Portugal, Slovakia, Hungary and Croatia, the downstream sector exerts market power. Other EU countries (Spain, UK, Denmark, Czech Republic, Bulgaria and Sweden) are characterised by perfectly competitive dairy chains. These results were consistent with the findings of previous studies based on structural and mark-up models. Results of the market power test in the subsample of 11 countries have been related to various structural characteristics of the dairy chains. Market power exertion is negatively related to the average farm size. Such variable may be seen as a proxy of the degree of supply concentration provided by Producers Organizations (POs) to increase the bargaining power of the farm sector along the food chain. To test such a hypothesis, comparable data on supply concentration by POs across EU Countries are necessary. On the other hand, the structural change, represented by the increase of average farm size over time and the concentration rate in higher classes (above 250,000 &euro; of Standard Output) is almost unrelated to the perfectly competitive conduct along EU dairy chains