Attempting return: Iraqis' re-migration from Iraq

The voluntary repatriation of refugees and internally displaced persons is interpreted as evidence of restored security and political stability, improved civil-state relations and public confidence in reconstruction efforts in war-torn countries. Iraqi refugees' decision to return is less driven by improvements in Iraq than by their desire to rebuild their lives back home and to overcome the difficult legal and socio-economic conditions in neighbouring countries. The article explores Iraqi returnees' experiences based on accounts of their repatriation and subsequent re-migration to Syria and Jordan. The micro and macro transformations occurring in post-Saddam Iraq have a strong bearing on refugees' return and reintegration in their home communities. In the absence of permanent solutions to protracted displacement, the Iraqis resort to transnational mobility and networks as alternative livelihood strategies and participate in the socio-economic developments in home and host countries through the constant multi-directional flow of economic, social and human capita

Seeing faces: evidence suggesting cortical disinhibition in the genesis of visual hallucinations.

The neural mechanisms responsible for triggering visual hallucinations are poorly understood. Here, we report a unique patient whose hallucinations consist exclusively of faces, and which could be reliably precipitated by looking at trees. Using functional Magnetic Resonance Imaging (fMRI), we found that, while face hallucinations was associated with increased neural activity in a number of cortical regions, including low-level visual areas, there was significant decreased activity in the right fusiform face area, a region that is empirically defined by increase activity during veridical perception of faces. These findings indicate key differences in how hallucinatory and veridical perceptions lead to the same phenomenological experience of seeing faces, and are consistent with the hypothesis that hallucinations may be generated by decreased inhibitory inputs to key cortical regions, in contrast to the excitatory synaptic inputs underlying veridical perception

The return of the bursts: Thermonuclear flashes from Circinus X-1

We report the detection of 15 X-ray bursts with RXTE and Swift observations of the peculiar X-ray binary Circinus X-1 during its May 2010 X-ray re-brightening. These are the first X-ray bursts observed from the source after the initial discovery by Tennant and collaborators, twenty-five years ago. By studying their spectral evolution, we firmly identify nine of the bursts as type I (thermonuclear) X-ray bursts. We obtain an arcsecond location of the bursts that confirms once and for all the identification of Cir X-1 as a type I X-ray burst source, and therefore as a low magnetic field accreting neutron star. The first five bursts observed by RXTE are weak and show approximately symmetric light curves, without detectable signs of cooling along the burst decay. We discuss their possible nature. Finally, we explore a scenario to explain why Cir X-1 shows thermonuclear bursts now but not in the past, when it was extensively observed and accreting at a similar rate.Comment: Accepted for publication in The Astrophysical Journal Letters. Tables 1 & 2 merged. Minor changes after referee's comments. 5 pages, 4 Figure

Quantum clock: A critical discussion on spacetime

We critically discuss the measure of very short time intervals. By means of a Gedankenexperiment, we describe an ideal clock based on the occurrence of completely random events. Many previous thought experiments have suggested fundamental Planck-scale limits on measurements of distance and time. Here we present a new type of thought experiment, based on a different type of clock, that provide further support for the existence of such limits. We show that the minimum time interval $\Delta t$ that this clock can measure scales as the inverse of its size $\Delta r$. This implies an uncertainty relation between space and time: $\Delta r$ $\Delta t$ $> G \hbar / c^4$; where G, $\hbar$ and c are the gravitational constant, the reduced Planck constant, and the speed of light, respectively. We outline and briefly discuss the implications of this uncertainty conjecture.Comment: 10 pages, published in Physical Review

Progettazione ed implementazione dell'infrastruttura server per un sistema distribuito di scansione e mappatura della rete Internet

L'obiettivo della tesi è la realizzazione di un infrastruttura Server all'interno di un sistema distribuito che permetta la raccolta di informazioni sulla rete e di generarne una mappa completa. Fra le mansioni del Server, le principali sono la scelta dei Job da assegnare ad ognuno dei Client, in modo da assicurare una copertura efficiente della rete, e la raccolta dei dati generati dai Client; inoltre il Server si occupa dell'integrazione dei dati, dell'isolamento dei casi anomali e della risoluzione delle ambiguità che si possono riscontrare durante le analisi. La scelta dei Job viene effettuata in base a condizioni opportunistiche come la posizione geografica del Client o la rete a cui esso è connesso. The thesis main goal is to realize the Server infrastructure for a distributed system with the aim to collect information about the Internet and to generate a detailed map of it. Amongst the duties of the Server, the main ones are the correct choosing of a Job to assign to each Client, so to ensure an efficient covering of the Internet, and the collecting of the data generated from the Clients; the Server's due to merge these data, to identify anomalities within it and to solve ambigous cases which can be found during the analysis. Each Job is chosen considering opportunistic conditions like the Client's geographic location or the network he's connected to

Iraqi refugees' assisted and spontaneous return from Syria and Jordan

The thesis investigates the causes and nature of return in the context of the Iraqis displaced to Syria and Jordan after the 2003 US-led war in Iraq. It combines critical International Relations theories with transnational approaches in Migration Studies to investigate: (1) how regional and international geopolitics have shaped asylum and migration regimes in the Middle East; (2) how Iraqi forced migrants have interacted with such regimes in order to reach safety, sustainable livelihoods and personal development opportunities and; (3) the decision-making processes and transnational migration practices of Iraqi individuals and families. It finds that Iraqis’ returns result from the uneasy interaction between international and national asylum and migration regimes and the lack of agreement on a common legal framework for durable solutions to the Iraqi displacement. The presence and mobility of the Iraqis in Syria and Jordan are regulated within national immigration systems. The immigration and residency policies of the home and host governments confirm the historical importance of voluntary and involuntary population movements as a nation-building and governance tool in the Middle East. Regional governments and international agencies manage the Iraqi displaced and steer their return through the provision, or the lack thereof, of assistance and information. The Iraqis respond to the limited institutional assistance and information by developing independent coping strategies and informal information and communication systems based on the use of information and communication technologies and on their transnational mobility and social networks. Transnational mobility and livelihoods therefore constitute a precondition for Iraqis’ sustainable return and reintegration in home societies undergoing political and socio-economic transition. In this context, return is a complex process that takes time and entails various degrees and modalities of transnational mobility, social networks and livelihoods connecting host and home societies

A complete X-ray spectral coverage of the 2010 May-June outbursts of Circinus X-1

Circinus X-1 is a neutron-star-accreting X-ray binary in a wide (P$_{\rm orb}$ = 16.6 d), eccentric orbit. After two years of relatively low X-ray luminosity, in May 2010 Circinus X-1 went into outburst, reaching 0.4 Crab flux. This outburst lasted for about two orbital cycles and was followed by another shorter and fainter outburst in June. We focus here on the broadband X-ray spectral evolution of the source as it spans about three order of magnitudes in flux. We attempt to relate luminosity, spectral shape, local absorption, and orbital phase. We use multiple Rossi-XTE/PCA (3.0--25 keV) and Swift/XRT (1.0--9.0 keV) observations and a 20 ks long Chandra/HETGS observation (1.0--9.0 keV), to comprehensively track the spectral evolution of the source during all the outbursting phases. These observations were taken every two/three days and cover about four orbital cycles. The PCA data mostly cover the major outburst, the XRT data monitor the declining phase of the major outburst and all the phases of the minor outburst, and Chandra data provide an essential snapshot of the end of this overall outbursting phase. The X-ray spectrum can be satisfactorily described by a thermal Comptonization model with variable neutral local absorption in all phases of the outburst. No other additive component is statistically required. The first outburst decays linearly, with an ankle in the light curve as the flux decreases below $\sim$\,5 $\times$ 10$^{-10}$ erg cm$^{-2}$ s$^{-1}$. At the same time, the source shows a clear spectral state transition from an optically thick to an optically thin state. While the characteristics of the first, bright, outburst can be interpreted within the disk-instability scenario, the following, minor, outburst shows peculiarities that cannot be easily reconciled in this framework.Comment: Accepted for publication in Astronomy and Astrophysic

The Broad Band Spectrum of MXB 1728-34 Observed by BeppoSAX

We report on the results of a broad band (0.1-100 keV) spectral analysis of the bursting atoll source MXB 1728-34 observed by the BeppoSAX satellite. Three bursts were present during this observation. The spectrum during the bursts can be fitted by a blackbody with a temperature of 2 keV. From the bursts we also estimate a distance to the source of 5.1 kpc. MXB 1728-34 was in a rather soft state during the BeppoSAX observation. The persistent spectrum is well fitted by a continuum consisting of a soft blackbody emission and a comptonized spectrum. We interpreted the soft component as the emission from the accretion disk. Taking into account a spectral hardening factor of 1.7, we estimated that the inner disk radius is $R_{\rm in} \sqrt{\cos i} \sim 20$ km, where i is the inclination angle. The comptonized component could originate in a spherical corona, with temperature of 10 keV and optical depth of 5, surrounding the neutron star. A broad gaussian emission line at 6.7 keV is observed in the spectrum, probably emitted in the ionized corona or in the inner part of the disk. Another emission line is present at 1.66 keV.Comment: 12 pages, accepted by Ap

Development and Validation of a Thermo-Economic Model for Design Optimisation and Off-Design Performance Evaluation of a Pure Solar Microturbine

The aim of this paper is to present a thermo-economic model of a microturbine for solar dish applications, which demonstrates the applicability and accuracy of the model for off-design performance evaluation and techno-economic optimisation purposes. The model is built using an object-oriented programming approach. Each component is represented using a class made of functions that perform a one-dimensional physical design, off-design performance analysis and the component cost evaluation. Compressor, recuperator, receiver and turbine models are presented and validated against experimental data available in literature, and each demonstrated good accuracy for a wide range of operating conditions. A 7-kWe microturbine and solar irradiation data available for Rome between 2004 and 2005 were considered as a case study, and the thermo-economic analysis of the plant was performed to estimate the levelised cost of electricity based on the annual performance of the plant. The overall energy produced by the plant is 10,682 kWh, the capital cost has been estimated to be EUR 27,051 and, consequently, the specific cost of the plant, defined as the ratio between the cost of components and output power in design condition, has been estimated to be around EUR 3980/kWe. Results from the levelised cost of electricity (LCOE) analysis demonstrate a levelised cost of electricity of EUR 22.81/kWh considering a plant lifetime of 25 years. The results of the present case study have been compared with the results from IPSEpro 7 where the same component characteristic maps and operational strategy were considered. This comparison was aimed to verify the component matching procedure adopted for the present model. A plant sizing optimisation was then performed to determine the plant size which minimises the levelised cost of electricity. The design space of the optimisation variable is limited to the values 0.07–0.16 kg/s. Results of the optimisation demonstrate a minimum LCOE of 21.5 [EUR/kWh] for a design point mass flow rate of about 0.11 kg/s. This corresponds to an overall cost of the plant of around EUR 32,600, with a dish diameter of 9.4 m and an annual electricity production of 13,700 [kWh]