Numerical methods for all-speed flows in fluid-dynamics and non-linear elasticity

In this thesis we are concerned with the numerical simulation of compressible materials flows, including gases, liquids and elastic solids. These materials are described by a monolithic Eulerian model of conservation laws, closed by an hyperelastic state law that includes the different behaviours of the considered materials. A novel implicit relaxation scheme to solve compressible flows at all speeds is proposed, with Mach numbers ranging from very small to the order of unity. The scheme is general and has the same formulation for all the considered materials, since a direct dependence on the state law is avoided via the relaxation. It is based on a fully implicit time discretization, easily implemented thanks to the linearity of the transport operator in the relaxation system. The spatial discretization is obtained by a combination of upwind and centered schemes in order to recover the correct numerical viscosity in different Mach regimes. The scheme is validated with one and two dimensional simulations of fluid flows and of deformations of compressible solids. We exploit the domain discretization through Cartesian grids, allowing for massively parallel computations (HPC) that drastically reduce the computational times on 2D test cases. Moreover, the scheme is adapted to the resolution on adaptive grids based on quadtrees, implementing adaptive mesh refinement techinques. The last part of the thesis is devoted to the numerical simulation of heterogeneous multi-material flows. A novel sharp interface method is proposed, with the derivation of implicit equilibrium conditions. The aim of the implicit framework is the solution of weakly compressible and low Mach flows, thus the proposed multi-material conditions are coupled with the implicit relaxation scheme that is solved in the bulk of the flow. Dans cette thèse on s’intéresse à la simulation numérique d’écoulements des matériaux compressibles, voir fluides et solides élastiques. Les matériaux considérés sont décrits avec un modèle monolithique eulérian, fermé avec une loi d’état hyperélastique qui considère les différents comportéments des matériaux. On propose un nouveau schéma de relaxation qui résout les écoulements compressibles dans des différents régimes, avec des nombres de Mach très petits jusqu’à l’ordre 1. Le schéma a une formulation générale qui est la même pour tous le matériaux considérés, parce que il ne dépend pas directement de la loi d’état. Il se base sur une discrétization complétement implicite, facile à implémenter grâce à la linearité de l’opérateur de transport du système de relaxation. La discrétization en éspace est donnée par la combinaison de flux upwind et centrés, pour retrouver la correcte viscosité numérique dans les différents régimes. L’utilisation de mailles cartésiennes pour les cas 2D s’adapte bien à une parallélisation massive, qui permet de réduire drastiquement le temps de calcul. De plus, le schéma a été adapté pour la résolution sur des mailles quadtree, pour implémenter l’adaptivité de la maille avec des critères entropiques. La dernière partie de la thèse concerne la simulation numérique d’écoulements multi-matériaux. On a proposé une nouvelle méthode d’interface “sharp”, en dérivant les conditions d’équilibre en implicite. L’objectif est la résolution d’interfaces physiques dans des régimes faiblement compressibles et avec un nombre de Mach faible, donc les conditions multi-matériaux sont couplées au schéma implicite de relaxation

Characterization of new synthetic or natural compounds with broad spectrum or dual antiviral activity in HIV-1 treatment

In recent years many advances have been made in the fight against HIV-1 infection. However, the lack of a vaccine, together with the increasing resistance to the highly active anti-retroviral therapy (HAART), make HIV-1 infection still a serious global emergency. Development of inhibitors that operate by a novel mechanism of action could expand the options for clinicians to address these unmet medical needs for the HIV-1-infected patient population or could represent novel options for an effective prevention. In this contest, one possibility is the development of single drug with multiple targets binding, such as the natural compound kuwanon-L. Derived from the computational identification of novel potential allosteric inhibitors of HIV integrase, in this thesis kuwanon-L has been further characterised in enzymatic assays to evaluate its activity in vitro. Moreover, kuwanon-L was tested in cellular-based assays to confirm its antiviral activity also on viral strains. Finally, its mechanism of action was further investigated through a time-of-addition (TOA) experiment and its innovative dual mode of action on both HIV integrase and reverse transcriptase was confirmed in enzymatic assays. On the other hand, compounds with novel mechanisms of action and targeting very early steps of viral life cycle, as the novel series of rhodanine derivatives investigated in the second part of this work, may represent potent anti-HIV-1 agents suitable for prevention approaches. Their activity not only on HIV but also on other sexually transmitted infections such as HSV-1/2 viruses, and their favourable pharmacokinetic profile further emphasize their usage as topical microbicides in pre-exposure prophylaxis (PrEP) approaches

La risicoltura italiana oltre la PAC: nuove opportunità e possibili strategie

Rice is the staple food of more than half of the world population and its availability is crucial to food security in a context of continuous demographic growth. Rice production also represents a fundamental economic activity: more than 110 countries are involved, generating a global paddy production of 759.6 million tonnes and an estimated international exchange of about 24.5 billion dollars. Likewise, rice production is strictly linked to social and environmental sustainability, as it is based on a complex ecological system, which has crucial influence on climate, biodiversity and landscape challenges. Despite of its worldwide nature, rice market is highly concentrated. Italy has a key role since rice fields in the Po valley cover half of total EU28 production. Thanks to the agricultural self-sufficiency policy, Italian rice sector grew rapidly after the Second World War, highlighting the competitiveness of national producers and varieties. Nevertheless, in recent decades, the sector is wobbeling under the pressure of internal structural problems, combined with a global economic downturn and a critical evolution of the international commerce. A partial reduction of the number of farms as well as of the extension of cultivations, frequent price fluctuations and the fall of revenues, emphasise the presence of serious weaknesses and threats. In such a context, the revision of the Common Agricultural Policy (CAP) is considered to be the main responsible of this crisis. Nevertheless, a critical overview underlines that it is only one of multiple interacting factors influencing rice market development, whereas lacks in business strategies and entrepreneurial culture determine a poor performance in this sector, at large. Moreover, CAP not only creates obstacles and limits to farmers’ activity, but also support innovative strategies for the renewal of this sector

Monitoring air pollution effects on sleep-disordered breathing in children for supporting Public Health Policy

The so called “Sleep Disordered Breathing” (SDB) are breathing disorders which appear while the baby is sleeping. They rappresent a variety of pathologics mainly characterized by an airways change with snooring and/or a breathing effort caused by an increased resistance of the high airways and pharingeal collapse. Ethipatogenetic has been mainly understood and there are some risk factors like adenotonsillar hypertrophy, obesity and cranium-facial anomalies. There are also some other factors which can determine pathology like e.g. enviromental and genetic factors. In literature there are some studies that show how environmental pollution (outdoor and indoor) represents the main cause of SDB in a child. The aim of this ecological study is to analize the geografical distribution of SDB in the italian province of Varese, by using the data collected in the Pediatrics. In order to put in evidence the possible associations between SDB and the enriromental pollution, we have compared these results with NO2 distribution spatial scheme. NO2 can be considered the most important marker of enviromental pollution because it is the main component of gas emission and it’s correlated with other combustion products. Data were collected from 2010–2014 and focused on children who resided in Varese, were over 1 year of age, with SDB. The total number of children analyzed was 754: 476 males (63,13%) and 278 females (36,87%). Snooring occurs in 284 cases ((37,67%), mild OSAS in 259 (34,35%), moderate OSAS in 150 (19,89%) and severe OSAS in 61 (8,09%). For each patient, we gathered information about the child’s municipality of residence, sex, and the value of the apnea-hypopnea index (AHI). AHI is based on polysomnographic recordings conducted overnight by means of Embla’s Embletta Gold sleep system, a recording system that can discriminate the SDB severity level. All of the children were diagnosed with respect to SDB based on their AHI index. AHI mean is 3,48, value that doesn’t differ from the AHI in F and M (3,58 vs 3,42) With the available data was made a map representing the geography of the SDB. The results reported have to be considered preliminary and exploratory note abouve. The positive association we observed between SDB in children and the fact that they were living in an area characterized by a high density of traffic-related pollutants should be more carefully examined, as airway inflammation is a potential mechanism connected with the effect of air pollution and SDB exacerbations—such effect can be due to the oxidative stress related to the incomplete combustion of fossil fuels that produces high levels of polyaromatic hydrocarbons. Further research is necessary to clarify the role of air pollutants on SDB and on respiratory diseases in children. This additional work would allow the wider acquisition of knowledge about potentially modifiable contributors to the risk of developing SDB during childhood, which could then be the basis for improving children’s pulmonary health

Enhancing data privacy and security related process through machine learning

In this thesis, we exploit the advantages of Machine learning (ML) in the domains of data security and data privacy. ML is one of the most exciting technologies being developed in the world today. The major advantages of ML technology are its prediction capability and its ability to reduce the need for human activities to perform tasks. These benefits motivated us to exploit ML to improve users' data privacy and security. Firstly, we use ML technology to try to predict the best privacy settings for users, since ML has a strong prediction ability and the average user might find it difficult to properly set up privacy settings due to a lack of knowledge and subsequent lack of decision-making abilities regarding the privacy of their data. Besides, since the ML approach has the potential to considerably cut down on manual efforts by humans, our second task in this thesis is to exploit ML technology to redesign security mechanisms of social media environments that rely on human participation for providing such services. In particular, we use ML to train spam filters for identifying and removing violent, insulting, aggressive, and harassing content creators (a.k.a. spammers) from a social media platform. It helps to solve violent and aggressive issues that have been growing on social media environments. The experimental results show that our proposals are efficient and effective

The prototype phase of the ENUBET positron tagger

Understanding the interaction of neutrinos with the other particles of the Standard Model is a fundamental activity in particle physics. The uncertainties on the initial neutrino flux limit the sensitivity on the neutrino cross section measurement in the GeV range to a precision of 10-20%. The scientific goal of the ENUBET project is to improve this sensitivity up to 1% by developing an active decay tunnel, as opposed to traditional neutrino beams, which have a passive decay region. By tagging the positrons emitted in the Ke3 decay (K+ -> π0 + e+ + νe) it is possible to infer the initial neutrino flux. If the tunnel is short enough (about 50 m) the Ke3 decay is the only source of neutrinos. Shashlik calorimeters are suitable to instrument such a tunnel, because they are cost effective, have a good geometrical adaptability and their energy resolution can be tuned with the proper absorbing/scintillator tiles thickness and fiber frequency. To separate the positrons from the pion background these calorimeters are longitudinally segmented with a compact readout based on Silicon PhotoMultipliers embedded in the bulk of the calorimeter itself. This thesis describes the prototyping activity of the ENUBET Collaboration for the positron tagger and the tests performed at the CERN PS-T9 beamline from July 2016 to October 2017. The details of each prototype design and the results in terms of linearity and energy resolution are presented

Il pensiero filosofico e politico di Vito D'Ondes Reggio

My thesis focuses on the philosophical and political thought of Baron Vito D’Ondes Reggio (Palermo, 1811 - Florence, 1885). The first chapter is about the baron's life, with special emphasis on his intellectual formation, the sources of his thought, and his specific contribution to the pivotal events in Italian history of the 19th century in which he took part: from the Sicilian Revolution of 1848 to his work as a deputy of the Kingdom of Italy; from his parliamentary resignation after the "capture of Rome" (20 September 1870) to the foundation of the "Work of the Congress" (1874). The second chapter analyses his philosophical thought concerning the relationship between the individual, society, and the State. Finally, the third and last chapter introduces D’Ondes Reggio’s theories concerning the “natural” origin of property and his arguments against the “convenitionalist” position

Migration and innovation: An analysis based on patent data. Migration et innovation : Une analyse basée sur des données de brevet.

This thesis investigates the migration of inventors by studying their contribution to the innovation at both destination and in their home country, after controlling for individual characteristics such as gender, education, experience, company mobility and others. In addition, we decompose the flows of migrants by entry channel in the destination country, such as the education channel, the multinational channel or when the inventors change of company and investigate the selection of migrants and the productivity gap between natives and migrants. Also, in the analysis, we decompose the cohort of entry in the destination country to compare the productivity differences among migrants themselves. Finally, we study whether return migrants are more productive than their non-migrants’ colleagues in origin countries, as a function of their experiences abroad. Cette thèse a pour but d’analyser la migration des inventeurs en étudiant leur contribution à l’innovation de leur pays de destination ainsi que leur pays d’origine, en contrôlant par leurs caractéristiques individuelles telles que leur genre, éducation, expérience, mobilité interentreprise et d’autres. De plus, nous décomposons les flux de migrants par canaux d’entrer dans le pays de destination, tel que le canal de l’éducation, multinational ou si l’inventeur change d’entreprise, et analysons la sélection des migrants et le gap de productivité entre les natifs et les migrants. Aussi, dans cette analyse, nous décomposons les cohortes d’entrées dans le pays de destination en comparant la productivité entre les migrants eux-mêmes. Finalement, nous étudions si les migrants de retour sont plus productifs que leurs collègues non migrants dans leur pays d’origine en fonction de leur expérience acquise à l’étranger

QSAR models for the screening, prediction and refinement of PBT Properties of Contaminants of Emerging Concern.

The prompt identification of the adverse effects of Contaminant of Emerging Concern (CEC) is fundamental to ensure high protection level for human health and the environment. Persistent, Bioaccumulative and Toxic (PBT) compounds are chemicals of high concern and should be readily identified. The aim of this thesis is to propose an approach based on Quantitative Structure Activity Relationship (QSAR) models for the evaluation of the intrinsic environmental hazard of CECs. First, a screening of the potential PBT behavior of pharmaceuticals is performed by consensus approach. Results demonstrate a high agreement (i.e.86%) between the different QSAR models. Then, QSARs are developed to estimate acute toxicity of pharmaceuticals in aquatic species. All models have good fitting (R2>0.75) and predictivity (Q2EXT>0.68). An Aquatic Toxicity Index is proposed and modelled. Moreover, interspecies correlation models are also developed. Finally, QSARs for the prediction of whole-body human biotransformation Half-Lives are developed for organic chemicals. Predictions for the biotransformation potential are integrated in a mechanistic mass-balance multimedia environmental fate food-web model to estimate the Biomagnification Factor (BMF) in human in a tiered approach. The introduction of biotransformation strongly affects the calculation of BMF and the elimination processes related to biotransformation are predominant in the overall bioaccumulation

Analogue Hawking radiation in Bose-Einstein condensates

This Thesis develops in the field of analogue gravity, a branch of physics which relies on a specific correspondence that exists between fluid dynamics and curved spacetimes; thanks to that, effects which are hard to study in the gravitational context are investigated in the realm of hydrodynamics with the hope that the consequent results could be transferred back to the cosmological domain and give us better insights in the gravitational context. In this Thesis, I try to introduce the reader to the realm of analogue gravity and to the concepts of Bose-Einstein condensation, Hawking radiation and its analogue counterpart (Chapter 1 and 2); then in Chapter 3 and 4 I describe the details of our work. In the past years, we have developed two directions of research, both aimed at the characterization of the analogue Hawking radiation in Bose-Einstein condensates. One side of our work had the purpose of investigating the results obtained in recent experiments apt to the detection of the analogue Hawking radiation in a quantum gas. Our results are very important in the description of the phenomena and give insights on how to develop future experiments (Chapter 3). The other side of our work aimed at the characterization of this effect from a theoretical point of view by means of an innovative approach, which allows for a much deeper and more detailed description of the radiation and helps shine new light on this effect (Chapter 4). In Chapter 5 we briefly discuss the possible developments of our studying, highlighting the missing pieces of this field and suggesting possible ways to approach the existing problems