UNA METODOLOGIA PER LA VALUTAZIONE DI CRITICITÀ E PRIORITÀ DI INTERVENTO: IL CASO DEL LITORALE VENETO

open3nobilancio sedimentario, litorale Veneto, erosione, allagamento costiero, gestione integrata della zona costiera.openRuol, Piero; Martinelli, Luca; Favaretto, ChiaraRuol, Piero; Martinelli, Luca; Favaretto, Chiar

Population models for complex non-linear phenomena in biology: from mitochondrial dynamics to brain networks

The human brain is as much fascinating as complicated: this is the reason why it has always captured scientists’ attention in several fields of research, from biology to medicine, from psychology to engineering. In this context various non-invasive technologies have been optimized in order to allow the measure of signals, able to describe brain activities. These data, derived from measurement methods that largely differ in their nature, have opened the door to new characterizations of this organ, that highlighted the main features of its operating principles. Brain signals indeed have revealed to be fluctuating during time, both during a specific task, and when we are not carrying on any activities. Furthermore, a selective coordination among different regions of the brain has emerged. As engineers, we are particularly attracted by the description of our brain as a graph, whose nodes and edges can be representative of several different elements, at distinct spatial scales (from single neurons to large brain areas). In the last decades, wide attention has been devoted to reproduce and explain the complex dynamics of the brain elements by means of computational models. Graph theory tools, as well as the design of population models, allow the exploitation of many mathematical tools, helpful to enlarge the knowledge of healthy and damaged brains functioning, by means of brain networks. Interestingly, the incapability of human brains to work properly in case of disease, has found to be correlated with dysfunctions in the activity of mitochondria, the organelles that produce large part of the cells’ energy. In particular, specific relationships have been reported among neurological diseases and impairments in mitochondrial dynamics, which refers to the continuous change in shape of mitochondria, by means of fusion and fission processes. Although the existing link between brain and mitochondria is still ambiguous and under debate, the huge amount of energy required by our brain to work properly suggests a larger mitochondrial-dependence of the brain than of the other organs. In this thesis we report the results of our research, aimed to investigate a few aspects of this complex brain-mitochondria relationship. We focus on mitochondrial dynamics and brain network, as well as on suitable mathematical models used to describe them. Specifically, the main topics handled in this work can be summarized as follows. Population models for mitochondrial dynamics. We propose a modified preypredator non-linear population model to simulate the main processes, which take part in the mitochondrial dynamics, and the ones that are strongly related to it, without neglecting the energy production process. We present two possible setups, which differ in the inclusion of a feedback link between the available energy and the formation of new mitochondria. We discuss their dynamics, and their potential in reproducing biological behaviors. Brain signals: comparison of datasets derived through different technologies. We analyze two different datasets of brain signals, recorded with various methods (functional magnetic resonance imaging, fMRI, and magnetoencephalography, MEG), both in condition of no activity and during an attentional task. The aim of the analysis is twofold: the investigation of the spontaneous activity of the brain, and the exploration of possible relationships between the two different techniques. Brain network: a Kuramoto-based description. We analyze empirical brain data by means of their oscillatory features, with the purpose of highlighting the characteristics that a computational phase-model should be able to reproduce. Hence, we use a modified version of the classic Kuramoto model to reproduce the empirical oscillatory characteristics. Analysis and control of Kuramoto networks. Most of the theoretical contribution of this thesis refers to analytical results on Kuramoto networks. We analyze the topological and intrinsic conditions required to achieve a desired pattern of synchronization, represented by fully or clustered synchronized configuration of oscillators

Synchronization Patterns in Networks of Kuramoto Oscillators: A Geometric Approach for Analysis and Control

Synchronization is crucial for the correct functionality of many natural and man-made complex systems. In this work we characterize the formation of synchronization patterns in networks of Kuramoto oscillators. Specifically, we reveal conditions on the network weights and structure and on the oscillators' natural frequencies that allow the phases of a group of oscillators to evolve cohesively, yet independently from the phases of oscillators in different clusters. Our conditions are applicable to general directed and weighted networks of heterogeneous oscillators. Surprisingly, although the oscillators exhibit nonlinear dynamics, our approach relies entirely on tools from linear algebra and graph theory. Further, we develop a control mechanism to determine the smallest (as measured by the Frobenius norm) network perturbation to ensure the formation of a desired synchronization pattern. Our procedure allows us to constrain the set of edges that can be modified, thus enforcing the sparsity structure of the network perturbation. The results are validated through a set of numerical examples

Development of a model for the assessment of Coastal Flooding Vulnerability: an application to the Venetian littoral

In the recent years, marine flooding and its impacts have become a question of growing interest in the scientific community as well as in managing authorities, since coastal areas are the most heavily populated and developed land zones in the world. Under climate change, sea levels are rising and even storm surge intensity is possibly increasing. Therefore, it is expected that the occurrence probability of extreme coastal flooding events will increase. This major hazard requires urgent adaptations in order to increase the resistance and resilience of an area to coastal floods. The motivation of this research arises from the practical need highlighted by local managers of the Veneto region that require (possibly GIS-integrated) rapid tools to simulate the whole complexity of the problem of mapping the risk of coastal flood by wave over-topping in an urban area at large scale. The aim of this thesis is to develop a methodology in order to define flood risk maps by analysing different scenarios at a different time and spatial scales, combining both marine forcing and flood propagation in the hinterland. After an articulated theoretical study and an accurate bibliographic research, a flood propagation numerical model was implemented. In order to use GPU acceleration, i) the domain Shallow Water Equations are simplified by linearising bottom friction and neglecting advection, and ii) an appropriate vectorization method is considered. The numerical model for coastal flooding propagation was tested against four well-known benchmarks (two analytical solutions of the SWEs and two experimental tests) and applied to a real case of coastal flooding occurred at Caorle (VE) in December 2008. The methodology was finally applied to the coast of the Veneto Region, thanks to an extensive geomorphological and hydraulic knowledge of the area (Ruol et al. 2016, 2018). Combining i) a bivariate statistical analysis of marine forcing (waves and sea levels), ii) a model of wave transformation from offshore to onshore and iii) a reliability analysis, Coastal Flooding hazard maps were produced for three stretches of the Veneto littoral: Valle Vecchia, Caorle and Cavallino-Treporti

Coastal Flooding Hazard Due to Overflow Using a Level II Method: Application to the Venetian Littoral

In recent years, marine flooding and its impacts have become a question of growing interest, since coastal areas are the most heavily populated and developed land zones in the world. This paper presents a rapid tool for mapping at regional scale the hazard associated with coastal flooding due to overflow. The tool merges a recently developed numerical model that solves a simplified form of the Shallow-Water Equations and is suited for Graphic Processing Unit (GPU) acceleration, with a Level II reliability method that allows producing hazard maps of inland flooding propagation. The procedure was applied to two stretches of the Venetian littoral, i.e., Valle Vecchia and Caorle, located in the northern Adriatic Sea. The application includes the site descriptions and the resulting hazard maps that show the probability of failure in each point of the coast for a given inland inundation level

Sulla disposizione ottimale di frangiflutti galleggianti a catamarano combinati a convertitori di energia ondosa

- La ricerca in cui \ue8 inserito questo lavoro mira allo sviluppo di un dispositivo ibrido costituito da un convertitore di energia ondosa accoppiato ad un frangiflutti galleggiante. - Il frangiflutti, ancorato con pali, \ue8 costituito da elementi prefabbricati collegati rigidamente, in modo da formare una struttura a catamarano. - La configurazione migliore \ue8 la pi\uf9 stretta tra le due esaminate (8 m e 12 m di larghezza), che risulta molto efficiente pur senza essere soggetta a grosse sollecitazioni. - La struttura a catamarano \ue8 da preferire rispetto a quella tradizionale, a parit\ue0 di massa, sia in termini di trasmissione che di riflessione. - Il convertitore esaminato, idoneo ad integrare frangiflutti singoli, non \ue8 adatto ad integrare le strutture a catamarano

Hydraulic Experiments on a Small-Scale Wave Energy Converter with an Unconventional Dummy Pto

This paper investigates on a Wave Energy Converter (WEC) named Energy & Protection, 4th generation (EP4). The WEC couples the energy harvesting function with the purpose of protecting the coast from erosion. It is formed by a flap rolling with a single degree of freedom around a lower hinge. Small-scale tests were carried out in the wave flume of the maritime group of Padua University, aiming at the evaluation of the device efficiency. The test peculiarity is represented by the system used to simulate the Power Take Off (PTO). Such dummy PTO permits a free rotation of two degrees before engaging the shaft, allowing the flap to gain some inertia, and then applying a constant resistive moment. The EP4 was observed to reach a 35% efficiency, under short regular waves. The effects, in terms of coastal protection, are small but not negligible, at least for the shortest waves

Synchronization Patterns in Networks of Kuramoto Oscillators: A Geometric Approach for Analysis and Control

Synchronization is crucial for the correct functionality of many natural and man-made complex systems. In this work we characterize the formation of synchronization patterns in networks of Kuramoto oscillators. Specifically, we reveal conditions on the network weights and structure and on the oscillators’ natural frequencies that allow the phases of a group of oscillators to evolve cohesively, yet independently from the phases of oscillators in different clusters. Our conditions are applicable to general directed and weighted networks of heterogeneous oscillators. Surprisingly, although the oscillators exhibit nonlinear dynamics, our approach relies entirely on tools from linear algebra and graph theory. Further, we develop a control mechanism to determine the smallest (as measured by the Frobenius norm) network perturbation to ensure the formation of a desired synchronization pattern. Our procedure allows us to constrain the set of edges that can be modified, thus enforcing the sparsity structure of the network perturbation. The results are validated through a set of numerical example

Stroke-related alterations in inter-areal communication

Beyond causing local ischemia and cell damage at the site of injury, stroke strongly affects long-range anatomical connections, perturbing the functional organization of brain networks. Several studies reported functional connectivity abnormalities parallelling both behavioral deficits and functional recovery across different cognitive domains. FC alterations suggest that long-range communication in the brain is altered after stroke. However, standard FC analyses cannot reveal the directionality and time scale of inter-areal information transfer. We used resting-state fMRI and covariance-based Granger causality analysis to quantify network-level information transfer and its alteration in stroke. Two main large-scale anomalies were observed in stroke patients. First, inter-hemispheric information transfer was significantly decreased with respect to healthy controls. Second, stroke caused inter-hemispheric asymmetries, as information transfer within the affected hemisphere and from the affected to the intact hemisphere was significantly reduced. Both anomalies were more prominent in resting-state networks related to attention and language, and they correlated with impaired performance in several behavioral domains. Overall, our findings support the hypothesis that stroke provokes asymmetries between the affected and spared hemisphere, with different functional consequences depending on which hemisphere is lesioned