Search for pulsations at high radio frequencies from accreting millisecond X-ray pulsars in quiescence

It is commonly believed that millisecond radio pulsars have been spun up by transfer of matter and angular momentum from a low-mass companion during an X-ray active mass transfer phase. A subclass of low-mass X-ray binaries is that of the accreting millisecond X-ray pulsars, transient systems that show periods of X-ray quiescence during which radio emission could switch on. The aim of this work is to search for millisecond pulsations from three accreting millisecond X-ray pulsars, XTE J1751-305, XTE J1814-338, and SAX J1808.4-3658, observed during their quiescent X-ray phases at high radio frequencies (5 - 8 GHz) in order to overcome the problem of the free-free absorption due to the matter engulfing the system. A positive result would provide definite proof of the recycling model, providing the direct link between the progenitors and their evolutionary products. The data analysis methodology has been chosen on the basis of the precise knowledge of orbital and spin parameters from X-ray observations. It is subdivided in three steps: we corrected the time series for the effects of (I) the dispersion due to interstellar medium and (II) of the orbital motions, and finally (III) folded modulo the spin period to increase the signal-to-noise ratio. No radio signal with spin and orbital characteristics matching those of the X-ray sources has been found in our search, down to very low flux density upper limits. We analysed several mechanisms that could have prevented the detection of the signal, concluding that the low luminosity of the sources and the geometric factor are the most likely reasons for this negative result.Comment: 5 pages, 3 figures. Accepted for publication by A&

The Use of genetic markers in the study of social structure in mammals: wolf and wild boar as case studies

Questa tesi mostra l’utilità dei marcatori molecolari nello studio di alcuni aspetti cruciali della popolazione e della struttura sociale dei mammiferi. In particolare sono stati investigati il cinghiale (Sus scrofa) ed il lupo (Canis lupus). In primo luogo si è definito il quadro dello stato genetico del cinghiale in Europa. In seguito la struttura genetica è stata analizzata ad una scala più fine, concentrandosi in particola modo sulle relazioni di parentela all’interno dei gruppi sociali e delle cucciolate. Lo studio della struttura sociale del cinghiale è stato condotto integrando I dati genetici con i dati spaziali della popolazione toscana oggetto di studio. La previsione di una struttura sociale matriarcale non è stata confermata dai dati, infatti, si è riscontrato un basso grado di parentela fra gli individui appartenenti alla stessa unità sociale. L’alto ricambio osservato all’interno della popolazione, principalmente dovuto ad un’alta mortalità dovuta a caccia e bracconaggio, sembra essere la causa principale dello scostamento dall’atteso. Nella stessa popolazione è stata testata la presenza di multipaternità all’interno delle cucciolate. Sono state analizzate dodici famiglie, costituite da scrofe incinte, abbattute durante la stagione venatoria, e dai rispettivi feti. La multipaternità, precedentemente riscontrata in popolazioni di cinghiale europeo, è stata rilevata anche nella popolazione in esame, rivelando come la poliandria possa diventare comune in alcune popolazioni. Dopodichè, una volta definito un protocollo d’analisi che permettesse l’utilizzo affidabile di campioni noninvasivi, si è proceduto a ricostruire la struttura genetica di una popolazione di lupo appenninico in un arco di tempo di sei anni. Tale analisi è stata condotta mediante l’utilizzo di microsatelliti autosomici e localizzati sul cromosoma sessuale Y, in modo da ottenere un quadro storico delle relazioni tra branchi, o all’interno di un branco, che non fosse influenzato dai meccanismi di trasmissione parentale e da possibili diversi pattern di dispersione fra sessi. Si è dunque osservato un basso flusso genico tra branchi adiacenti con conseguente strutturazione genetica ed una variabilità all’interno della linea maschile che si discosta dal monomorfismo riportato per la linea materna nella specie

Evaluation of User Gestures in Multi-touch Interaction: a Case Study in Pair-programming

Natural User Interfaces are often described as familiar, evocative and intuitive, predictable, based on common skills. Though unquestionable in principle, such definitions don't provide the designer with effective means to design a natural interface or evaluate a design choice vs another. Two main issues in particular are open: (i) how do we evaluate a natural interface, is there a way to measure 'naturalness'; (ii) do natural user interfaces provide a concrete advantage in terms of efficiency, with respect to more traditional interface paradigms? In this paper we discuss and compare observations of user behavior in the task of pair programming, performed at a traditional desktop versus a multi-touch table. We show how the adoption of a multi-touch user interface fosters a significant, observable and measurable, increase of nonverbal communication in general and of gestures in particular, that in turn appears related to the overall performance of the users in the task of algorithm understanding and debugging

A multi-wavelength pipeline for pulsar searches

Pulsar studies in the recent years have shown, more than others, to have benefited from a multi-wavelength approach. The INAF - Astronomical Observatory in Cagliari (INAF-OAC) is a growing facility with a young group devoted to pulsar and fast transients studies across the electromagnetic spectrum. Taking advantage of this expertise we have worked to provide a suite of multi-wavelength software and databases for the observations of pulsars and compact Galactic objects at the Sardinia Radio Telescope (SRT). In turn, radio pulsar observations at SRT will be made available, in a processed format, to gamma-ray searches using AGILE and Fermi gamma-ray satellite and, in a near future, they will be complementary to polarimetric X-ray observations with IXPE.Comment: Accepted for publications in Rendiconti Lincei as Proceedings of "A Decade of AGILE: Results, Challenges and Prospects of Gamma-Ray Astrophysics

Interactive Spaces Natural interfaces supporting gestures and manipulations in interactive spaces

This doctoral dissertation focuses on the development of interactive spaces through the use of natural interfaces based on gestures and manipulative actions. In the real world people use their senses to perceive the external environment and they use manipulations and gestures to explore the world around them, communicate and interact with other individuals. From this perspective the use of natural interfaces that exploit the human sensorial and explorative abilities helps filling the gap between physical and digital world. In the first part of this thesis we describe the work made for improving interfaces and devices for tangible, multi touch and free hand interactions. The idea is to design devices able to work also in uncontrolled environments, and in situations where control is mostly of the physical type where even the less experienced users can express their manipulative exploration and gesture communication abilities. We also analyze how it can be possible to mix these techniques to create an interactive space, specifically designed for teamwork where the natural interfaces are distributed in order to encourage collaboration. We then give some examples of how these interactive scenarios can host various types of applications facilitating, for instance, the exploration of 3D models, the enjoyment of multimedia contents and social interaction. Finally we discuss our results and put them in a wider context, focusing our attention particularly on how the proposed interfaces actually improve people’s lives and activities and the interactive spaces become a place of aggregation where we can pursue objectives that are both personal and shared with others

Traces of past reintroduction in genetic diversity:The case of the Balkan chamois (Mammalia, Artiodactyla)

The translocation of wild animal species became a common practice worldwide to re-establish local populations threatened with extinction. Archaeological data confirm that chamois once lived in the Biokovo Mountain but, prior to their reintroduction in the 1960s, there was no written evidence of their recent existence in the area. The population was reintroduced in the period 1964–1969, when 48 individuals of Balkan chamois from the neighbouring mountains in Bosnia and Herzegovina were released. The main objective of this study was to determine the accuracy of the existing historical data on the origin of the Balkan chamois population from the Biokovo Mountain and to assess the genetic diversity and population structure of the source and translocated populations 56 years after reintroduction. Sixteen microsatellite loci were used to analyse the genetic structure of three source chamois populations from Prenj, Čvrsnica and Čabulja Mountains and from Biokovo Mountain. Both STRUCTURE and GENELAND analyses showed a clear separation of the reintroduced population on Biokovo from Prenj's chamois and considerable genetic similarity between the Biokovo population and the Čvrsnica-Čabulja population. This suggests that the current genetic composition of the Biokovo population does not derive exclusively from Prenj, as suggested by the available literature and personal interviews, but also from Čvrsnica and Čabulja. GENELAND analysis recognised the Balkan chamois from Prenj as a separate cluster, distinct from the populations of Čvrsnica and Čabulja. Our results thus highlight the need to implement genetic monitoring of both reintroduced and source populations of endangered Balkan chamois to inform sustainable management and conservation strategies in order to maximise the chances of population persistence

Long Term Study of the Double Pulsar J0737-3039 with XMM-Newton: pulsar timing

The relativistic double neutron star binary PSR J0737-3039 shows clear evidence of orbital phase-dependent wind-companion interaction, both in radio and X-rays. In this paper we present the results of timing analysis of PSR J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that collected ~20,000 X-ray counts from the system. We detected pulsations from PSR J0737-3039A (PSR A) through the most accurate timing measurement obtained by XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR A's pulse profile in X-rays is very stable despite significant relativistic spin precession that occurred within the time span of observations. This yields a constraint on the misalignment between the spin axis and the orbital momentum axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even after its disappearance in radio. The unusual phenomenology of PSR B's X-ray emission includes orbital pulsed flux and profile variations as well as a loss of pulsar phase coherence on time scales of years. We hypothesize that this is due to the interaction of PSR A's wind with PSR B's magnetosphere and orbital-dependent penetration of the wind plasma onto PSR B closed field lines. Finally, the analysis of the full XMM-Newton dataset provided evidences of orbital flux variability (~7%) for the first time, involving a bow-shock scenario between PSR A's wind and PSR B's magnetosphere.Comment: Comments: 16 Pages, 6 Figures. Accepted for publication in Astrophysical Journal (Draft Version