Entanglement from dissipative dynamics into overlapping environments

We consider two ensembles of qubit dissipating into two overlapping environments, that is with a certain number of qubit in common that dissipate into both environments. We then study the dynamics of bipartite entanglement between the two ensembles by excluding the common qubit. To get analytical solutions for an arbitrary number of qubit we consider initial states with a single excitation and show that the largest amount of entanglement can be created when excitations are initially located among side (non common) qubit. Moreover, the stationary entanglement exhibits a monotonic (resp. non-monotonic) scaling versus the number of common (resp. side) qubit

Performance Modeling in Predictable Cloud Computing

This paper deals with the problem of performance stability of software running in shared virtualized infrastructures. The focus is on the ability to build an abstract performance model of containerized application components, where real-time scheduling at the CPU level, along with traffic shaping at the networking level, are used to limit the temporal interferences among co-located workloads, so as to obtain a predictable distributed computing platform. A model for a simple client-server application running in containers is used as a case-study, where an extensive experimental validation of the model is conducted over a testbed running a modified OpenStack on top of a custom real-time CPU scheduler in the Linux kernel

Emissione di Bremsstrahlung e applicazioni astrofisiche

Questa tesi esamina la transizione free-free, in cui una particella libera e carica interagisce con il campo magnetico di un’altra particella, subendo una deviazione e perdendo velocità. La variazione di energia che ne risulta viene bilanciata dall’emissione di radiazione, un processo noto come Bremsstrahlung, termine tedesco che significa “radiazione di frenamento”. Questo meccanismo è cruciale nello studio dei plasmi astrofisici, nubi di gas molto caldo (T> 10^6 K) dove la transizione free-free è la principale sorgente di emissione perché l’idrogeno è completamente ionizzato e gli elettroni liberi hanno energie cinetiche elevate. L’elaborato è suddiviso in due parti: la prima metà offre una descrizione dei meccanismi in chiave fisico-matematica della radiazione di Bremsstrahlung. Nel capitolo 1 viene innanzitutto trattato il singolo evento, analizzando il fenomeno nella sua forma più semplice. Successivamente, viene considerato un elettrone all’interno di una nube reale, composta da un numero elevato di particelle e interazioni; vengono quindi presentate le formule necessarie per il calcolo dei principali parametri descrittivi del fenomeno. Il capitolo 2 introduce la distribuzione delle velocità per una nube reale in equilibrio termico, in cui le velocità delle particelle sono descritte dalla distribuzione di Maxwell-Boltzmann. Nei sottoparagrafi si approfondisce il tema dell’autoassorbimento e del tempo di raffreddamento nel caso di nubi dense e opache alla radiazione. Infine, viene analizzato il caso di un sistema relativistico in cui gli elettroni viaggiano a velocità prossime a quella della luce. La seconda parte dell’elaborato si concentra su temi già trattati in letteratura. In particolare, il capitolo 3 offre una panoramica su alcune applicazioni, descrivendo l’emissione nell’ISM (Mezzo Interstellare) e nell’ICM (Mezzo Intracluster), con un focus su alcuni casi reali. Gli ultimi tre paragrafi esplorano invece gli studi più recenti

Competenze olistiche e disciplinari

The theme of competence arises on the ridge of educational research, and in particular within the controversy which sees as subjects of the speech, the integral/ongoing training and the relationship between theory and practice.From this basic idea rises a school which is opened to new individual and socialneeds, capable not only of knowing how to convey information, but also to give a metacognitive mindset based on the “pestalozziane” capabilities of the human being.Hence the costant need of education, which can be expressed through teachingskills, and through the abilities to educate a person.The problem that emerges is clear and fascinating at the same time, since perpetually exposed to the cultural variables in constant turmoil. An absolute value the person, on whom it is right to invest and edify every collective development and on which we will have to capitalize on our becoming.So, if on one hand, the skill draws a legitimacy to pedagogic knowledge, on theother hand there is the dilemma on which, how much and how, it will be possible to learn skills, knowledge and competences, that make possible the accomplishment according to the indications of Ralph Waldo Emerson: “Be yourself!”Il tema della competenza si pone sul crinale della ricerca educativa, ed in particolare all’interno della querelle che vede nella formazione integrale/continua e nel rapporto tra teoria e prassi gli estremi del discorso.Proprio da questa idea di fondo nasce una “scuola aperta” alle nuove esigenze individuali e sociali, capace non solo di saper trasmettere informazioni, quanto una mentalità metacognitiva fondata sulle pestalozziane potenzialità dell’essereumano.Di qui il costante bisogno di educazione, che si esplica attraverso competenze per insegnare, così come di abilità per educare in modo paidetico la persona.Il problema che emerge è nitido ed in un certo senso affascinante, in quantoperennemente esposto alle variabili culturali in continuo fermento. Un valore assoluto, quello della persona, su cui è doveroso investire ed edificare ogni sviluppo collettivo e sui cui saremo costretti a capitalizzare il nostro divenire.Così se da un lato la competenza richiama una legittimazione al sapere pedagogico, dall’altro si pone il dilemma di quali, quante e come far apprendere abilità, conoscenze, competenze in grado di agevolare il compiersi umano secondo le indicazioni che ha lasciato Ralph Waldo Emerson: diventa chi sei

Optimal fault-tolerant placement of relay nodes in a mission critical wireless network

The operations of many critical infrastructures (e.g., airports) heavily depend on proper functioning of the radio communication network supporting operations. As a result, such a communication network is indeed a mission-critical communication network that needs adequate protection from external electromagnetic interferences. This is usually done through radiogoniometers. Basically, by using at least three suitably deployed radiogoniometers and a gateway gathering information from them, sources of electromagnetic emissions that are not supposed to be present in the monitored area can be localised. Typically, relay nodes are used to connect radiogoniometers to the gateway. As a result, some degree of fault-tolerance for the network of relay nodes is essential in order to offer a reliable monitoring. On the other hand, deployment of relay nodes is typically quite expensive. As a result, we have two conflicting requirements: minimise costs while guaranteeing a given fault-tolerance. In this paper address the problem of computing a deployment for relay nodes that minimises the relay node network cost while at the same time guaranteeing proper working of the network even when some of the relay nodes (up to a given maximum number) become faulty (fault-tolerance). We show that the above problem can be formulated as a Mixed Integer Linear Programming (MILP) as well as a Pseudo-Boolean Satisfiability (PB-SAT) optimisation problem and present experimental results com- paring the two approaches on realistic scenarios

Implementation and Deployment of a Server at the Edge Using OpenStack Components

As the 5th telecommunication Generation (5G) deployments are spreading around via various mobile operators, the capabilities behind 5G are becoming more and more understandable. Infrastructure vendors, operators, and end users now have a clear picture of the 5G potential and, for that reason, the research and the development of 5G are surely continuing. The one-to-one mapping between 5G and Software Defined Network - Network Function Virtualization (SDN-NFV) architecture is not in discussion, but the impact of porting SDN-NFV into the Radio Access Network (RAN) is still under investigation. Sometimes, the RAN requirements set strong limitations even in the basic hardware and software setup. For example, the most complete and very well integrated SDN-NFV infrastructure distributions require specific hardware capabilities in terms of available nodes, in contrast with the RAN requirement to be economic, power consumption limited and with limited overhead due to operating system and middleware cost. For that reason, this study uses only a minimal set of OpenStack components in order to evaluate what is the minimal hardware capability needed to set up a basic, but fully working environment for NFV, highlighting the pros and cons of embracing a solution solely based on standard OpenStack components

Čimbenici rizika i poslijeoperacijski prediktori za ponavljajuću herniju lumbalnog diska: dugoročno praćenje

The purpose of this study is to identify some risk factors and post-operative predictors for recurrent lumbar disc hernia (rLDH) during a long-term follow-up in patients treated with microdiscectomy. Aim of the paper: This study analyzes some risk factors and postoperative predictors for recurrent lumbar disc hernia (rLDH) during a long-term follow-up in patients treated with microdiscectomy. Material and methods. We analyzed retrospectively a consecutive series of patients who underwent lumbar spinal microdiscectomy for lumbar disc herniation (LDH) from January 2013 to June 2018 at our Institute. The rate of rLDH during long-term follow-up was analyzed and correlated with baseline and post-operative data. Results. A total of 263 patients were included with a median follow-up time of 24 months (from 13 to 43 months). Most of the patients had rLDH within the first 36 months after surgery. At multivariate analysis, recurrence of LDH was associated with higher pre-operative body mass index (BMI) and higher post-operative Oswentry disability index (ODI) with statistical significance. Conclusions. Baseline BMI and post-surgery ODI could predict rLDH after surgery during a long-term follow-up.Cilj. Ova studija analizira određene čimbenike rizika i poslijeoperacijske prediktore za ponavljajuću herniju lumbalnog diska (engl. recurrent lumbar disc hernia – rLDH) tijekom dugotrajnog praćenjaa bolesnika liječenih mikrodiskektomijom. Metode. Retrospektivno smo analizirali niz uzastopnih serija pacijenata koji su podvrgnuti lumbalnoj spinalnoj mikrodiskektomiji zbog hernije lumbalnog diska (engl. lumbar disc hernia – LDH) u razdoblju od siječnja 2013. do lipnja 2018. u našem Institutu. Stopa ponavljajuće hernije lumbalnog diska tijekom dugotrajnog praćenja analizirana je i korelirana s početnim anamnestičkim podacima i poslijeoperacijskim podacima. Rezultati. U studiju je uključeno ukupno 263 pacijenta s prosječnim vremenom praćenja od 24 mjeseca (od 13 do 43 mjeseca). Većina pacijenata imala je ponavljajuću herniju lumbalnog diska u prvih 36 mjeseci nakon operacije. Pri multivarijantnoj analizi, recidiv hernije lumbalnog diska povezan je s višim indeksom tjelesne mase (engl. body mass index – BMI) prije operacije i višim Oswestry indeksom invaliditeta nakon operacije (engl. Oswestry disability index – ODI) sa statističkom značajnošću. Zaključak. Početni indeks tjelesne mase i poslijeoperacijski Oswestry indeks invaliditeta mogu poslužiti kao prediktori ponavljajuće hernije lumbalnog diska nakon operacije tijekom dugotrajnog praćenja

iGateLink: A Gateway Library for Linking IoT, Edge, Fog and Cloud Computing Environments

In recent years, the Internet of Things (IoT) has been growing in popularity, along with the increasingly important role played by IoT gateways, mediating the interactions among a plethora of heterogeneous IoT devices and cloud services. In this paper, we present iGateLink, an open-source Android library easing the development of Android applications acting as a gateway between IoT devices and Edge/Fog/Cloud Computing environments. Thanks to its pluggable design, modules providing connectivity with a number of devices acting as data sources or Fog/Cloud frameworks can be easily reused for different applications. Using iGateLink in two case-studies replicating previous works in the healthcare and image processing domains, the library proved to be effective in adapting to different scenarios and speeding up the development of gateway applications, as compared to the use of conventional methods

Homological analysis of multi-qubit entanglement

We propose the usage of persistent homologies to characterize multipartite entanglement. On a multi-qubit data set we introduce metric-like measures defined only in terms of bipartite entanglement and then we derive barcodes. We show that they are able to provide a good classification of entangled states, at least for a small number of qubit

Self-induced consensus of Reddit users to characterise the GameStop short squeeze

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: Reddit conversation data used in this study can be retrieved from the Pushshift API at https://www.reddit.com/r/pushshift/. Stock price and traded volumes data are instead obtained by the Polygon API at https://polygon.io.The short squeeze of GameStop (GME) shares in mid-January 2021 has been primarily orchestrated by retail investors of the Reddit r/wallstreetbets community. As such, it represents a paramount example of collective coordination action on social media, resulting in large-scale consensus formation and significant market impact. In this work we characterise the structure and time evolution of Reddit conversation data, showing that the occurrence and sentiment of GME-related comments (representing how much users are engaged with GME) increased significantly much before the short squeeze actually took place. Taking inspiration from these early warnings as well as evidence from previous literature, we introduce a model of opinion dynamics where user engagement can trigger a self-reinforcing mechanism leading to the emergence of consensus, which in this particular case is associated to the success of the short squeeze operation. Analytical solutions and model simulations on interaction networks of Reddit users feature a phase transition from heterogeneous to homogeneous opinions as engagement grows, which we qualitatively compare to the sudden hike of GME stock price. Although the model cannot be validated with available data, it offers a possible and minimal interpretation for the increasingly important phenomenon of self-organized collective actions taking place on social networks.Tor Vergata University of Rom