X-Ray studies of the physics of matter around super-massive black-holes in nearby Seyfert galaxies

Seyfert galaxies are the closest active galactic nuclei. As such, we can use them to test the physical properties of the entire class of objects. To investigate their general properties, I took advantage of different methods of data analysis. In particular I used three different samples of objects, that, despite frequent overlaps, have been chosen to best tackle different topics: the heterogeneous BeppoS AX sample was thought to be optimized to test the average hard X-ray (E above 10 keV) properties of nearby Seyfert galaxies; the X-CfA was thought the be optimized to compare the properties of low-luminosity sources to the ones of higher luminosity and, thus, it was also used to test the emission mechanism models; finally, the XMM–Newton sample was extracted from the X-CfA sample so as to ensure a truly unbiased and well defined sample of objects to define the average properties of Seyfert galaxies. Taking advantage of the broad-band coverage of the BeppoS AX MECS and PDS instruments (between ~2-100 keV), I infer the average X-ray spectral propertiesof nearby Seyfert galaxies and in particular the photon index (~1.8), the high-energy cut-off (~290 keV), and the relative amount of cold reflection (~1.0). Moreover the unified scheme for active galactic nuclei was positively tested. The distribution of isotropic indicators used here (photon index, relative amount of reflection, high-energy cut-off and narrow FeK energy centroid) are similar in type I and type II objects while the absorbing column and the iron line equivalent width significantly differ between the two classes of sources with type II objects displaying larger absorbing columns. Taking advantage of the XMM–Newton and X–CfA samples I also deduced from measurements that 30 to 50% of type II Seyfert galaxies are Compton thick. Confirming previous results, the narrow FeK line is consistent, in Seyfert 2 galaxies, with being produced in the same matter responsible for the observed obscuration. These results support the basic picture of the unified model. Moreover, the presence of a X-ray Baldwin effect in type I sources has been measured using for the first time the 20-100 keV luminosity (EW proportional to L(20-100)^(−0.22±0.05)). This finding suggests that the torus covering factor may be a function of source luminosity, thereby suggesting a refinement of the baseline version of the unifed model itself. Using the BeppoSAX sample, it has been also recorded a possible correlation between the photon index and the amount of cold reflection in both type I and II sources. At a first glance this confirms the thermal Comptonization as the most likely origin of the high energy emission for the active galactic nuclei. This relation, in fact, naturally emerges supposing that the accretion disk penetrates, depending to the accretion rate, the central corona at different depths (Merloni et al. 2006): the higher accreting systems hosting disks down to the last stable orbit while the lower accreting systems hosting truncated disks. On the contrary, the study of the well defined X–C f A sample of Seyfert galaxies has proved that the intrinsic X-ray luminosity of nearby Seyfert galaxies can span values between 10^(38−43) erg s^−1, i.e. covering a huge range of accretion rates. The less efficient systems have been supposed to host ADAF systems without accretion disk. However, the study of the X–CfA sample has also proved the existence of correlations between optical emission lines and X-ray luminosity in the entire range of L_(X) covered by the sample. These relations are similar to the ones obtained if high-L objects are considered. Thus the emission mechanism must be similar in luminous and weak systems. A possible scenario to reconcile these somehow opposite indications is assuming that the ADAF and the two phase mechanism co-exist with different relative importance moving from low-to-high accretion systems (as suggested by the Gamma vs. R relation). The present data require that no abrupt transition between the two regimes is present. As mentioned above, the possible presence of an accretion disk has been tested using samples of nearby Seyfert galaxies. Here, to deeply investigate the flow patterns close to super-massive black-holes, three case study objects for which enough counts statistics is available have been analysed using deep X-ray observations taken with XMM–Newton. The obtained results have shown that the accretion flow can significantly differ between the objects when it is analyzed with the appropriate detail. For instance the accretion disk is well established down to the last stable orbit in a Kerr system for IRAS 13197-1627 where strong light bending effect have been measured. The accretion disk seems to be formed spiraling in the inner ~10-30 gravitational radii in NGC 3783 where time dependent and recursive modulation have been measured both in the continuum emission and in the broad emission line component. Finally, the accretion disk seems to be only weakly detectable in rk 509, with its weak broad emission line component. Finally, blueshifted resonant absorption lines have been detected in all three objects. This seems to demonstrate that, around super-massive black-holes, there is matter which is not confined in the accretion disk and moves along the line of sight with velocities as large as v~0.01-0.4c (whre c is the speed of light). Wether this matter forms winds or blobs is still matter of debate together with the assessment of the real statistical significance of the measured absorption lines. Nonetheless, if confirmed, these phenomena are of outstanding interest because they offer new potential probes for the dynamics of the innermost regions of accretion flows, to tackle the formation of ejecta/jets and to place constraints on the rate of kinetic energy injected by AGNs into the ISM and IGM. Future high energy missions (such as the planned Simbol-X and IXO) will likely allow an exciting step forward in our understanding of the flow dynamics around black holes and the formation of the highest velocity outflows.

Precision horticulture: application on apple orchards

Precision horticulture and spatial analysis applied to orchards are a growing and evolving part of precision agriculture technology. The aim of this discipline is to reduce production costs by monitoring and analysing orchard-derived information to improve crop performance in an environmentally sound manner. Georeferencing and geostatistical analysis coupled to point-specific data mining allow to devise and implement management decisions tailored within the single orchard. Potential applications range from the opportunity to verify in real time along the season the effectiveness of cultural practices to achieve the production targets in terms of fruit size, number, yield and, in a near future, fruit quality traits. These data will impact not only the pre-harvest but their effect will extend to the post-harvest sector of the fruit chain. Chapter 1 provides an updated overview on precision horticulture , while in Chapter 2 a preliminary spatial statistic analysis of the variability in apple orchards is provided before and after manual thinning; an interpretation of this variability and how it can be managed to maximize orchard performance is offered. Then in Chapter 3 a stratification of spatial data into management classes to interpret and manage spatial variation on the orchard is undertaken. An inverse model approach is also applied to verify whether the crop production explains environmental variation. In Chapter 4 an integration of the techniques adopted before is presented. A new key for reading the information gathered within the field is offered. The overall goal of this Dissertation was to probe into the feasibility, the desirability and the effectiveness of a precision approach to fruit growing, following the lines of other areas of agriculture that already adopt this management tool. As existing applications of precision horticulture already had shown, crop specificity is an important factor to be accounted for. This work focused on apple because of its importance in the area where the work was carried out, and worldwide.

Una implementazione della Logica Defeasible Temporale per il ragionamento giuridico

La presente tesi descrive l’implementazione in Java di un algoritmo per il ragionamento giuridico che cattura due sue importanti peculiarità: la defeasibility del ragionamento normativo e il concetto di tempo. “Defeasible” significa “ritrattabile” e sta ad indicare, appunto, quegli schemi di ragionamento nei quali è possibile rivedere o ritrattare le conclusioni tratte precedentemente. Il tempo è essenziale per un’accurata rappresentazione degli scenari presenti nel mondo reale e in particolare per gli scenari giuridici. I profili temporali delle norme sono essenzialmente due: (i) tempo esterno della norma, cioè il periodo durante il quale la norma è valida cioè appartiene al sistema giuridico; (ii) tempo interno della norma che fa riferimento al periodo in cui la norma si applica. In particolare quest’ultimo periodo di tempo coincide con il periodo in cui le condizioni presenti nella norma devono presentarsi affinché essa produca i suoi effetti. Inoltre, nella tesi viene presentata un’estensione della logica defeasible in grado di distinguere tra regole con effetti persistenti, che valgono non solo per l’istante in cui si verificano le premesse ma anche per ogni istante successivo, e regole con effetti transitori, che valgono per un singolo istante. L’algoritmo presentato in questa tesi presenta una complessità lineare nelle dimensioni della teoria in ingresso e può interagire con le applicazioni del web semantico poiché elabora teorie scritte in Rule-ML, un linguaggio basato su XML per la rappresentazione di regole.

Libro, diaspora e ri-costruzioni identitarie. Per una storia della tipografia sefardita portoghese nell'Italia del Cinquecento

Il lavoro ripercorre le tracce che gli ebrei portoghesi, esuli dopo il biennio 1496-97, lasciarono nel loro cammino attraverso l'Europa. In particolare, l'interesse si concentra sulla breve parentesi italiana, che grazie all'apertura e alla disponibilità  di alcuni Signori, come i Gonzaga di Mantova, i Medici, i Dogi della Serenissima e gli Este, risulta ricchissima di avvenimenti e personaggi, decisivi anche per la storia culturale del Portogallo. L'analisi parte evidenziando l'importanza che ebbe la tipografia ebraica in Portogallo all'epoca della sua introduzione nel Paese; in secondo luogo ripercorre la strada che, dal biennio del primo decreto di espulsione e del conseguente battesimo di massa, porta alla nascita dell'€™Inquisizione in Portogallo. Il secondo capitolo tenta di fare una ricostruzione, il più possibile completa e coerente, dei movimenti degli esuli, bollati come marrani e legati alle due maggiori famiglie, i Mendes e i Bemveniste, delineando poi il primo nucleo di quella che diventerà  nel Seicento la comunità  sefardita portoghese di Amsterdam, dove nasceranno le personalità  dissidenti di Uriel da Costa e del suo allievo Spinoza. Il terzo capitolo introduce il tema delle opere letterarie, effettuando una rassegna dei maggiori volumi editi dalle officine tipografiche ebraiche stanziatesi in Italia fra il 1551 e il 1558, in modo particolare concentrando l'attenzione sull'€™attività  della tipografia Usque, da cui usciranno numerosi testi di precettistica in lingua ebraica, ma soprattutto opere cruciali come la famosa «Bibbia Ferrarese» in castigliano, la «Consolação às Tribulações de Israel», di Samuel Usque e la raccolta composta dal romanzo cavalleresco «Menina e Moça» di Bernardim Ribeiro e dall'ecloga «Crisfal», di un autore ancora non accertato. L'ultimo capitolo, infine, si propone di operare una disamina di queste ultime tre opere, ritenute fondamentali per ricostruire il contesto letterario e culturale in cui la comunità  giudaica in esilio agiva e proiettava le proprie speranze di futuro. Per quanto le opere appartengano a generi diversi e mostrino diverso carattere, l'€™ipotesi è che siano parte di un unicum filosofico e spirituale, che intendeva sostanzialmente indicare ai confratelli sparsi per l'Europa la direzione da prendere, fornendo un sostegno teoretico, psicologico ed emotivo nelle difficili condizioni di sopravvivenza, soprattutto dell'integrità religiosa, di ciascun membro della comunità.