Tracking Time-Vertex Propagation using Dynamic Graph Wavelets

Graph Signal Processing generalizes classical signal processing to signal or data indexed by the vertices of a weighted graph. So far, the research efforts have been focused on static graph signals. However numerous applications involve graph signals evolving in time, such as spreading or propagation of waves on a network. The analysis of this type of data requires a new set of methods that fully takes into account the time and graph dimensions. We propose a novel class of wavelet frames named Dynamic Graph Wavelets, whose time-vertex evolution follows a dynamic process. We demonstrate that this set of functions can be combined with sparsity based approaches such as compressive sensing to reveal information on the dynamic processes occurring on a graph. Experiments on real seismological data show the efficiency of the technique, allowing to estimate the epicenter of earthquake events recorded by a seismic network

Statistical and Graph-Based Signal Processing: Fundamental Results and Application to Cardiac Electrophysiology

The goal of cardiac electrophysiology is to obtain information about the mechanism, function, and performance of the electrical activities of the heart, the identification of deviation from normal pattern and the design of treatments. Offering a better insight into cardiac arrhythmias comprehension and management, signal processing can help the physician to enhance the treatment strategies, in particular in case of atrial fibrillation (AF), a very common atrial arrhythmia which is associated to significant morbidities, such as increased risk of mortality, heart failure, and thromboembolic events. Catheter ablation of AF is a therapeutic technique which uses radiofrequency energy to destroy atrial tissue involved in the arrhythmia sustenance, typically aiming at the electrical disconnection of the of the pulmonary veins triggers. However, recurrence rate is still very high, showing that the very complex and heterogeneous nature of AF still represents a challenging problem. Leveraging the tools of non-stationary and statistical signal processing, the first part of our work has a twofold focus: firstly, we compare the performance of two different ablation technologies, based on contact force sensing or remote magnetic controlled, using signal-based criteria as surrogates for lesion assessment. Furthermore, we investigate the role of ablation parameters in lesion formation using the late-gadolinium enhanced magnetic resonance imaging. Secondly, we hypothesized that in human atria the frequency content of the bipolar signal is directly related to the local conduction velocity (CV), a key parameter characterizing the substrate abnormality and influencing atrial arrhythmias. Comparing the degree of spectral compression among signals recorded at different points of the endocardial surface in response to decreasing pacing rate, our experimental data demonstrate a significant correlation between CV and the corresponding spectral centroids. However, complex spatio-temporal propagation pattern characterizing AF spurred the need for new signals acquisition and processing methods. Multi-electrode catheters allow whole-chamber panoramic mapping of electrical activity but produce an amount of data which need to be preprocessed and analyzed to provide clinically relevant support to the physician. Graph signal processing has shown its potential on a variety of applications involving high-dimensional data on irregular domains and complex network. Nevertheless, though state-of-the-art graph-based methods have been successful for many tasks, so far they predominantly ignore the time-dimension of data. To address this shortcoming, in the second part of this dissertation, we put forth a Time-Vertex Signal Processing Framework, as a particular case of the multi-dimensional graph signal processing. Linking together the time-domain signal processing techniques with the tools of GSP, the Time-Vertex Signal Processing facilitates the analysis of graph structured data which also evolve in time. We motivate our framework leveraging the notion of partial differential equations on graphs. We introduce joint operators, such as time-vertex localization and we present a novel approach to significantly improve the accuracy of fast joint filtering. We also illustrate how to build time-vertex dictionaries, providing conditions for efficient invertibility and examples of constructions. The experimental results on a variety of datasets suggest that the proposed tools can bring significant benefits in various signal processing and learning tasks involving time-series on graphs. We close the gap between the two parts illustrating the application of graph and time-vertex signal processing to the challenging case of multi-channels intracardiac signals

FEM Modelling of a 3D Soil-Pile System Under Earthquakes

During earthquakes seismic wave crossing through soft soil can lead to significant curvatures on pile foundations, which in turn lead to significant bending moments. These bending moments are commonly named “kinematic bending moments”, to be distinguished from the “inertial bending moments” due to horizontal forces transferred from superstructures to pile heads. Approaches to carefully evaluate inertial bending moments have been recently developed world-wide; but the evaluation of the kinematic bending moments is still questionable. In this paper a 3D soil-pile FEM system is analysed. The system is subjected to seismic input motions, applied at the base of the system, which represents the conventional bedrock. The FEM analyses lead to the evaluation of the kinematic bending moment distribution along the pile. The pile is embedded in two soil layers, characterised by three different stiffness ratio Vs2/Vs1. Moreover, five different seismic input motions recorded in Europe in the last 30 years are considered

Il Partito socialista e la pianificazione economica. Dalla ricostruzione alla nazionalizzazione dell'industria elettrica

Oggetto del presente lavoro è la politica di pianificazione economica formulata dal Partito socialista italiano tra il 1944 e il 1962. Di tale politica vengono esaminati alcuni aspetti, ritenuti di particolare significato. Il lavoro si suddivide in tre parti. La prima analizza la politica economica del PSIUP/PSI nella fase della ricostruzione (1944-48), quando il piano rappresenta dapprima – nel contesto dei governi di solidarietà nazionale – l'alternativa tecnica all'impostazione conferita al processo di ricostruzione dalle forze liberiste, per assumere poi – dopo l'estromissione delle sinistre dall'esecutivo e fino al termine del 1947 – la valenza politica di alternativa di sistema. I momenti in cui si articola questa prima fase, dominata dalla figura di Rodolfo Morandi, sono: le proposte di politica economica elaborate dal PSIUP nell’ultimo periodo della guerra; il Comitato centrale dell’ottobre 1945 ed il susseguente dibattito sui Consigli di gestione; il Congresso di Firenze dell’aprile 1946; la nascita del secondo governo De Gasperi e la definizione del suo programma economico tra il giugno ed il luglio 1946; la svolta deflazionistica einaudiana dell’estate 1947; la Conferenza economica socialista del novembre 1947. Con l’istituzione del Fronte democratico popolare, il tema della pianificazione viene progressivamente abbandonato dal PSI, che si allinea alle posizioni del PCI. La seconda parte della ricerca si apre con una disamina del percorso intellettuale, dalle originarie posizioni liberiste all'approdo planista, di Riccardo Lombardi, principale ispiratore della strategia economica del PSI a partire dagli anni Cinquanta; questa sorta di “intermezzo”, che interrompe la continuità cronologica della narrazione, è stato inserito per rintracciare, nella personale vicenda del suo uomo-simbolo, le radici profonde del planismo socialista post-morandiano. Viene quindi analizzato l’atteggiamento del PSI nei confronti di due iniziative di diversa provenienza ma convergenti nell’ampliare la portata dell’intervento pubblico in campo economico e nell’introdurre elementi più o meno accentuati di pianificazione, sia pur nel rispetto dell’economia di mercato. La prima è costituita dal Piano del lavoro della CGIL, lanciato nel 1949 e presentato, almeno fino al 1952, come alternativa alla politica economica del governo (la cosiddetta linea «stagnazionista» legata al nome del ministro del Bilancio Pella). Le vicende del Piano del lavoro, alla cui elaborazione e popolarizzazione i socialisti offrono un importante contributo, si intrecciano, a partire dal giugno del 1950, con le ripercussioni del conflitto coreano, le quali investono anche il dibattito sulla politica economica e sulla pianificazione. La seconda iniziativa è costituita dallo Schema Vanoni, la cui presentazione ufficiale, nel dicembre 1954, conferisce nuovo slancio al dibattito sulla pianificazione, coinvolgendo in esso anche settori della maggioranza governativa. La terza ed ultima parte della ricerca copre il periodo 1956-1962, gli anni cioè del «miracolo economico» e, a livello politico, della fine dell'esperienza frontista e della gestazione del centro-sinistra. Viene in questa sede rievocato il confronto interno al PSI sul tema del piano economico e delle «riforme di struttura», che vede contrapposte le diverse componenti del partito; l’attenzione si concentra necessariamente sulla corrente autonomista, che individua nel piano e nelle connesse riforme gli strumenti capaci di garantire la transizione al socialismo in un paese capitalistico dell’Occidente (secondo la strategia del «riformismo rivoluzionario»). Si passa quindi ad esaminare la genesi e l’attuazione del provvedimento qualificante di questa stagione, ossia la nazionalizzazione dell’industria elettrica – archetipo di riforma di struttura anticapitalistica e indispensabile premessa della pianificazione nell’ottica della corrente autonomista –, dalle prime compiute proposte socialiste del 1944 al complesso dibattito degli anni Cinquanta fino alla contrastata adozione del provvedimento, su impulso del governo di centro-sinistra, tra il settembre ed il novembre 1962

A functionalized enol lactone containing a protected α-amino acid

The crystal structure of N-(3,9-dimethyl-4-phenyl-2,5-dioxo-3,4-dihydro-2H,5H-pyrano[3,2-c]chromen-3-yl)-N-methylbenzamide methanol monosolvate, C28H23NO5·CH3OH, has been determined at room temperature by X-ray diffraction. Structural parameters are discussed with reference to ab initio calculations

Contribution of anthropogenic consolidation processes to subsidence phenomena from multi-temporal DInSAR: a GIS-based approach

The paper introduces an approach based on the combination of multi-temporal Differential Interferometric Synthetic Aperture Radar and geographical information systems analysis to investigate and separate several contributions to subsidence phenomena over the municipality of Ravenna (Emilia Romagna, Italy). In particular, the relationship between displacements detected over built environment and consolidation processes after construction was assessed and filtered out from the subsidence map to quantify the local overestimation of subsidence phenomena due to the mentioned processes. It requires descriptive attributes related to the age of construction and intended uses. The outcomes of the present study highlight ground consolidation processes that seem to be active over areas settled in the last 30 years with a component contributing to vertical rates up to 3 mm/yr. Such contribution represents the 20% of the cumulative displacements reported for coastal villages where different sources of subsidence increase the vulnerability to coastal erosion. We discuss the contribution of consolidation processes over a couple of recently settled areas to separate among contributions and avoid the misinterpretation of effects due to other anthropogenic sources of subsidence

Sulfurous thermal waters stimulate the osteogenic differentiation of human mesenchymal stromal cells - An in vitro study.

Strategies aimed at delaying the onset of bone tissue degeneration and the resulting skeletal fragility are key to decrease the risk of bone fracture correlated to ageing. The therapeutic properties of sulfurous thermal waters (STWs), rich in hydrogen sulfide (H2S), have been claimed for centuries. However, the direct regulation of bone cells by STWs has not been investigated yet. Here we aimed at analyzing the effect of STWs on cultured human mesenchymal stromal cells (hMSCs) derived from bone tissue. Two concentrations of STWs from 2 health spa centers in Italy (here named STW-1 and STW-2) containing, respectively, high and moderate quantities of H2S, were added to the culture media. Cytotoxicity and osteogenic differentiation were evaluated. We provided first evidence that treatment of hMSCs with STWs results in a sharp increase in intracellular H2S content, coherent with the different concentrations of H2S, thereby reveling that STWs-released H2S is internalized by cells. STWs treatment significantly induced osteogenic differentiation of hMSCs. In particular, mineral apposition was increased with a similar pattern by the two STWs, while mRNA expression of osteogenic markers (BSP, OC, RUNX-2, OPN) was differently affected. Only STW-2 induced a significant, dose-dependent increase in these gene expression. These findings support the rationale for the use of STWs as a complementary treatment of bone wasting diseases

Y-formalism and bb ghost in the Non-minimal Pure Spinor Formalism of Superstrings

We present the Y-formalism for the non-minimal pure spinor quantization of superstrings. In the framework of this formalism we compute, at the quantum level, the explicit form of the compound operators involved in the construction of the $b$ ghost, their normal-ordering contributions and the relevant relations among them. We use these results to construct the quantum-mechanical $b$ ghost in the non-minimal pure spinor formalism. Moreover we show that this non-minimal $b$ ghost is cohomologically equivalent to the non-covariant $b$ ghost.Comment: 42 pages, no figure

Partition functions of non-Lagrangian theories from the holomorphic anomaly

The computation of the partition function in certain quantum field theories, such as those of the Argyres-Douglas or Minahan-Nemeschansky type, is problematic due to the lack of a Lagrangian description. In this paper, we use the holomorphic anomaly equation to derive the gravitational corrections to the prepotential of such theories at rank one by deforming them from the conformal point. In the conformal limit, we find a general formula for the partition function as a sum of hypergeometric functions. We show explicit results for the round sphere and the Nekrasov-Shatashvili phases of the $\Omega$ background. The first case is relevant for the derivation of extremal correlators in flat space, whereas the second one has interesting applications for the study of anharmonic oscillators.Comment: 37 page