The Enhanced Single-dish Control System and wide surveys of compact sources

The Italian radio telescopes currently undergo a major upgrade period in response to the growing demand for deep radio observations, such as surveys on large sky areas or observations of vast samples of compact radio sources. The optimised employment of the Italian antennas, at first constructed mainly for VLBI activities and provided with a control system (FS – Field System) not tailored to single-dish observations, required important modifications in particular of the guiding software and data acquisition system. The production of a completely new control system called ESCS (Enhanced Single-dish Control System) for the Medicina dish started in 2007, in synergy with the software development for the forthcoming Sardinia Radio Telescope (SRT). The aim is to produce a system optimised for single-dish observations in continuum, spectrometry and polarimetry. ESCS is also planned to be installed at the Noto site. A substantial part of this thesis work consisted in designing and developing subsystems within ESCS, in order to provide this software with tools to carry out large maps, spanning from the implementation of On-The-Fly fast scans (following both conventional and innovative observing strategies) to the production of single-dish standard output files and the realisation of tools for the quick-look of the acquired data. The test period coincided with the commissioning phase for two devices temporarily installed – while waiting for the SRT to be completed – on the Medicina antenna: a 18-26 GHz 7-feed receiver and the 14-channel analogue backend developed for its use. It is worth stressing that it is the only K-band multi-feed receiver at present available worldwide. The commissioning of the overall hardware/software system constituted a considerable section of the thesis work. Tests were led in order to verify the system stability and its capabilities, down to sensitivity levels which had never been reached in Medicina using the previous observing techniques and hardware devices. The aim was also to assess the scientific potential of the multi-feed receiver for the production of wide maps, exploiting its temporary availability on a mid-sized antenna. Dishes like the 32-m antennas at Medicina and Noto, in fact, offer the best conditions for large-area surveys, especially at high frequencies, as they provide a suited compromise between sufficiently large beam sizes to cover quickly large areas of the sky (typical of small-sized telescopes) and sensitivity (typical of large-sized telescopes). The KNoWS (K-band Northern Wide Survey) project is aimed at the realisation of a full-northern-sky survey at 21 GHz; its pilot observations, performed using the new ESCS tools and a peculiar observing strategy, constituted an ideal test-bed for ESCS itself and for the multi-feed/backend system. The KNoWS group, which I am part of, supported the commissioning activities also providing map-making and source-extraction tools, in order to complete the necessary data reduction pipeline and assess the general system scientific capabilities. The K-band observations, which were carried out in several sessions along the December 2008-March 2010 period, were accompanied by the realisation of a 5 GHz test survey during the summertime, which is not suitable for high-frequency observations. This activity was conceived in order to check the new analogue backend separately from the multi-feed receiver, and to simultaneously produce original scientific data (the 6-cm Medicina Survey, 6MS, a polar cap survey to complete PMN-GB6 and provide an all-sky coverage at 5 GHz).

Ion implantation of organic thin films and electronic devices

Organic semiconductors have great promise in the field of electronics due to their low cost in term of fabrication on large areas and their versatility to new devices, for these reasons they are becoming a great chance in the actual technologic scenery. Some of the most important open issues related to these materials are the effects of surfaces and interfaces between semiconductor and metals, the changes caused by different deposition methods and temperature, the difficulty related to the charge transport modeling and finally a fast aging with time, bias, air and light, that can change the properties very easily. In order to find out some important features of organic semiconductors I fabricated Organic Field Effect Transistors (OFETs), using them as characterization tools. The focus of my research is to investigate the effects of ion implantation on organic semiconductors and on OFETs. Ion implantation is a technique widely used on inorganic semiconductors to modify their electrical properties through the controlled introduction of foreign atomic species in the semiconductor matrix. I pointed my attention on three major novel and interesting effects, that I observed for the first time following ion implantation of OFETs: 1) modification of the electrical conductivity; 2) introduction of stable charged species, electrically active with organic thin films; 3) stabilization of transport parameters (mobility and threshold voltage). I examined 3 different semiconductors: Pentacene, a small molecule constituted by 5 aromatic rings, Pentacene-TIPS, a more complex by-product of the first one, and finally an organic material called Pedot PSS, that belongs to the branch of the conductive polymers. My research started with the analysis of ion implantation of Pentacene films and Pentacene OFETs. Then, I studied totally inkjet printed OFETs made of Pentacene-TIPS or PEDOT-PSS, and the research will continue with the ion implantation on these promising organic devices.

Solutions to common issues in widefield microscopy: vignetting, mosaicing and depth of focus

In this thesis we have developed solutions to common issues regarding widefield microscopes, facing the problem of the intensity inhomogeneity of an image and dealing with two strong limitations: the impossibility of acquiring either high detailed images representative of whole samples or deep 3D objects. First, we cope with the problem of the non-uniform distribution of the light signal inside a single image, named vignetting. In particular we proposed, for both light and fluorescent microscopy, non-parametric multi-image based methods, where the vignetting function is estimated directly from the sample without requiring any prior information. After getting flat-field corrected images, we studied how to fix the problem related to the limitation of the field of view of the camera, so to be able to acquire large areas at high magnification. To this purpose, we developed mosaicing techniques capable to work on-line. Starting from a set of overlapping images manually acquired, we validated a fast registration approach to accurately stitch together the images. Finally, we worked to virtually extend the field of view of the camera in the third dimension, with the purpose of reconstructing a single image completely in focus, stemming from objects having a relevant depth or being displaced in different focus planes. After studying the existing approaches for extending the depth of focus of the microscope, we proposed a general method that does not require any prior information. In order to compare the outcome of existing methods, different standard metrics are commonly used in literature. However, no metric is available to compare different methods in real cases. First, we validated a metric able to rank the methods as the Universal Quality Index does, but without needing any reference ground truth. Second, we proved that the approach we developed performs better in both synthetic and real cases.

Strategie per la pianificazione metropolitana

La finalità della ricerca è l'individuazione di uno strumento urbanistico per governare il territorio metropolitano che garantisca la successione efficace ed efficiente delle azioni nelle quali si articola il processo di pianificazione strategica. All'interno della ricerca, da un lato si indaga lo sviluppo storico-culturale che ha caratterizzato in Italia il concetto di area metropolitana, individuandone i contenuti e le operazioni che portano alla perimetrazione del suo territorio. Dall'altro lato si approfondisce il tema della pianificazione strategica come strumento fondamentale per il governo delle città metropolitane intermedie. Si è proceduto all'approfondimento del dibattito culturale e scientifico sul tema delle aree metropolitane, nell'esperienza di pianificazione strategica sviluppata in ambito internazionale e successivamente il dibattito politico che si è sviluppato nella realtà italiana sul concetto di area metropolitana, evidenziandone gli aspetti condivisi e le diverse tipologie di approccio per ottenere una perimetrazione utile al piano di governo del territorio. Ovviamente, nel processo di analisi, un ruolo dominante è stato assunto dal quadro istituzionale e normativo che si è sviluppato ed è tuttora in corso sul tema delle aree metropolitane. Alla tematica relativa alla definizione delle aree, si è sviluppato un consistente approfondimento sui requisiti che devono essere posseduti da un piano strategico costruito sulle esigenze di un'area metropolitana. E' stata individuata l'area metropolitana di Bologna quale area oggetto di studio approfondito, ripercorrendo le vicende che hanno animato il dibattito sulla nascita della Città metropolitana delimitata dalla Provincia. A tal proposito, si è sviluppata una riflessione sui contenuti innovativi e promozionali del piano strategico, valutando gli effetti che il Piano Strategico Metropolitano in corso di elaborazione sarà in grado di produrre sulle dinamiche territoriali e socio-economiche dell'area bolognese.

Mappatura dell'impervious e consumo di suolo tramite analisi di change detection in telerilevamento

Il telerilevamento rappresenta un efficace strumento per il monitoraggio dell’ambiente e del territorio, grazie alla disponibilità di sensori che riprendono con cadenza temporale fissa porzioni della superficie terrestre. Le immagini multi/iperspettrali acquisite sono in grado di fornire informazioni per differenti campi di applicazione. In questo studio è stato affrontato il tema del consumo di suolo che rappresenta un’importante sfida per una corretta gestione del territorio, poiché direttamente connesso con i fenomeni del runoff urbano, della frammentazione ecosistemica e con la sottrazione di importanti territori agricoli. Ancora non esiste una definizione unica, ed anche una metodologia di misura, del consumo di suolo; in questo studio è stato definito come tale quello che provoca impermeabilizzazione del terreno. L’area scelta è quella della Provincia di Bologna che si estende per 3.702 km2 ed è caratterizzata a nord dalla Pianura Padana e a sud dalla catena appenninica; secondo i dati forniti dall’ISTAT, nel periodo 2001-2011 è stata la quarta provincia in Italia con più consumo di suolo. Tramite classificazione pixel-based è stata fatta una mappatura del fenomeno per cinque immagini Landsat. Anche se a media risoluzione, e quindi non in grado di mappare tutti i dettagli, esse sono particolarmente idonee per aree estese come quella scelta ed inoltre garantiscono una più ampia copertura temporale. Il periodo considerato va dal 1987 al 2013 e, tramite procedure di change detection applicate alle mappe prodotte, si è cercato di quantificare il fenomeno, confrontarlo con i dati esistenti e analizzare la sua distribuzione spaziale.

Detailed study of the seismotectonic setting in the Lucanian Apennines and surrounding areas (Southern Italy)

In this research work I analyzed the instrumental seismicity of Southern Italy in the area including the Lucanian Apennines and Bradano foredeep, making use of the most recent seismological database available so far. I examined the seismicity occurred during the period between 2001 and 2006, considering 514 events with magnitudes M ≥ 2.0. In the first part of the work, P- and S-wave arrival times, recorded by the Italian National Seismic Network (RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were re-picked along with those of the SAPTEX temporary array (2001–2004). For some events located in the Upper Val d'Agri, I also used data from the Eni-Agip oil company seismic network. I computed the VP/VS ratio obtaining a value of 1.83 and I carried out an analysis for the one-dimensional (1D) velocity model that approximates the seismic structure of the study area. After this preliminary analysis, making use of the records obtained in the SeSCAL experiment, I incremented the database by handpicking new arrival times. My final dataset consists of 15,666 P- and 9228 S-arrival times associated to 1047 earthquakes with magnitude ML ≥ 1.5. I computed 162 fault-plane solutions and composite focal mechanisms for closely located events. I investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by more concentrated background seismicity. Moreover, I applied the double difference technique (DD) to improve the earthquake locations. Considering these results and different datasets available in the literature, I carried out a detailed analysis of single sub-areas and of a swarm (November 2008) recorded by SeSCAL array. The relocated seismicity appears more concentrated within the upper crust and it is mostly clustered along the Lucanian Apennine chain. In particular, two well-defined clusters were located in the Potentino and in the Abriola-Pietrapertosa sector (central Lucanian region). Their hypocentral depths are slightly deeper than those observed beneath the chain. I suggest that these two seismic features are representative of the transition from the inner portion of the chain with NE-SW extension to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, the seismicity is generally deeper and more scattered and is associated to the Murge uplift and to the small structures present in the area. I also observed a small structure NE-SW oriented in the Abriola-Pietrapertosa area (activated with a swarm in November 2008) that could be considered to act as a barrier to the propagation of a potential rupture of an active NW-SE striking faults system. Focal mechanisms computed in this study are in large part normal and strike-slip solutions and their tensional axes (T-axes) have a generalized NE-SW orientation. Thanks to denser coverage of seismic stations and the detailed analysis, this study is a further contribution to the comprehension of the seismogenesis and state of stress of the Southern Apennines region, giving important contributions to seismotectonic zoning and seismic hazard assessment.

Marine biodiversity survey in the Northern Red Sea: a large-scale monitoring carried out in collaboration with volunteer divers

Concerns over global change and its effect on coral reef survivorship have highlighted the need for long-term datasets and proxy records, to interpret environmental trends and inform policymakers. Citizen science programs have showed to be a valid method for collecting data, reducing financial and time costs for institutions. This study is based on the elaboration of data collected by recreational divers and its main purpose is to evaluate changes in the state of coral reef biodiversity in the Red Sea over a long term period and validate the volunteer-based monitoring method. Volunteers recreational divers completed a questionnaire after each dive, recording the presence of 72 animal taxa and negative reef conditions. Comparisons were made between records from volunteers and independent records from a marine biologist who performed the same dive at the same time. A total of 500 volunteers were tested in 78 validation trials. Relative values of accuracy, reliability and similarity seem to be comparable to those performed by volunteer divers on precise transects in other projects, or in community-based terrestrial monitoring. 9301 recreational divers participated in the monitoring program, completing 23,059 survey questionnaires in a 5-year period. The volunteer-sightings-based index showed significant differences between the geographical areas. The area of Hurghada is distinguished by a medium-low biodiversity index, heavily damaged by a not controlled anthropic exploitation. Coral reefs along the Ras Mohammed National Park at Sharm el Sheikh, conversely showed high biodiversity index. The detected pattern seems to be correlated with the conservation measures adopted. In our experience and that of other research institutes, citizen science can integrate conventional methods and significantly reduce costs and time. Involving recreational divers we were able to build a large data set, covering a wide geographic area. The main limitation remains the difficulty of obtaining an homogeneous spatial sampling distribution.