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Incompressible limit and well-posedness of PDE models of tissue growth
Get PDFBoth compressible and incompressible porous medium models are used in the literature to describe the mechanical aspects of living tissues. Using a stiff pressure law, it is possible to build a link between these two different representations. In the incompressible limit, compressible models generate free boundary problems where saturation holds in the moving domain. Our work aims at investigating the stiff pressure limit of reaction-advection-porous medium equations motivated by tumor development. Our first study concerns the analysis and numerical simulation of a model including the effect of nutrients. A coupled system of equations describes the cell density and the nutrient concentration and the derivation of the pressure equation in the stiff limit was an open problem for which the strong compactness of the pressure gradient is needed. To establish it, we use two new ideas: an L3-version of the celebrated Aronson-Bénilan estimate, and a sharp uniform L4-bound on the pressure gradient. We further investigate the sharpness of this bound through a finite difference upwind scheme, which we prove to be stable and asymptotic preserving. Our second study is centered around porous medium equations
including convective effects. We are able to extend the techniques developed for the nutrient case, hence finding the complementarity relation on the limit pressure. Moreover, we provide an estimate of the convergence rate at the incompressible limit. Finally, we study a multi-species system. In particular, we account for phenotypic heterogeneity, including a structured variable into the problem. In this case, a cross-(degenerate)-diffusion system describes the evolution of the phenotypic distributions. Adapting methods recently developed in the context of two-species systems, we prove existence of weak solutions and we pass to the incompressible limit. Furthermore, we prove new regularity results on the total pressure, which is related to the total density by a power law of state.Tra i modelli matematici per la crescita dei tessuti, ed in particolare per la crescita tumorale, sia modelli cosiddetti comprimibili sia modelli incomprimibili sono largamente utilizzati in letteratura.
Passando al limite incomprimibile, i modelli comprimibili generano modelli a frontiera libera in cui si ha saturazione nel dominio. L’obiettivo della tesi è quello di analizzare il limite stiff pressure di equazioni del tipo reazione-convezione-diffusione degenere. Il primo lavoro riguarda l’analisi e la simulazione numerica di un modello che include la presenza di nutrienti. Un sistema di equazioni descrive l’evoluzione della densità cellulare e della concentrazione di nutrienti. In questo caso, la derivazione dell’equazione della pressione nel limite rappresentava un problema irrisolto, per il quale era necessario trovare la compattezza forte del gradiente della pressione.
Al fine di dimostrarla, sono state utilizzate due tecniche: una versione L3 della celebre stima di Aronson e Bénilan, e una stima L4 ottimale sul gradiente della pressione. Inoltre, si è investigato numericamente l’ottimalità di questa stima utilizzando uno schema upwind alle differenze
finite, che si dimostra essere stabile e asymptotic preserving. Il secondo lavoro si concentra sulle equazioni dei mezzi porosi che includono un termine di convezione. Sono state quindi estese le tecniche sviluppate nel modello con nutrienti e ricavata la relazione di complementarietà
della pressione limite. Inoltre, viene fornita una stima della velocità di convergenza del limite incomprimibile. Infine, si analizza un modello multi-specie. In particolare, è stata presa in considerazione l’eterogeneità fenotipica, includendo una variabile strutturata nel modello. In questo
caso, un sistema del tipo diffusione (degenere) incrociata descrive l’evoluzione delle distribuzioni fenotipiche. Adattando metodi recentemente sviluppati nel contesto di sistemi di due specie, si prova l’esistenza di soluzioni deboli e si passa al limite stiff. Inoltre, vengono forniti nuovi risultati di regolarità sulla pressione totale
La formación de los estados regionales italianos (siglos XIII-XV). Averiguaciones científicas y repercusiones en los libros de texto de historia, entre formación del profesorado y enfoques metodológicos
Get PDFLa ricerca intende indagare i rapporti tra le acquisizioni della ricerca scientifica nel campo della storia, con particolare riferimento al tema della formazione degli stati regionali italiani, e il suo insegnamento nella scuola secondaria di secondo grado.
Nella parte dedicata al quadro teorico si sottolinea la sempre più stringente necessità di un insegnamento e apprendimento della storia di qualità nella società attuale, basati sul senso della partecipazione democratica attiva e allo sviluppo del pensiero critico, nonostante i documenti ufficiali ministeriali non sempre dedichino al tema la giusta importanza e i recenti risultati ottenuti grazie a un questionario somministrato a studenti universitari sembrino confermare una didattica ancora legata alla pratica tradizionale. A questo proposito, quindi, occorre rifondare e ricentrare l’importanza della storia grazie all’approfondimento del lessico specifico e delle premesse epistemologiche basilari della disciplina.
A partire da queste premesse, nell’inquadramento empirico si analizza lo stato di avanzamento della ricerca scientifico-accademica recente nei confronti della formazione degli stati regionali italiani bassomedievali, si confronta il tema nei principali manuali scolatici adottati nell’area metropolitana di Bologna; e sono infine analizzate le concezioni circa la storia, la storia medievale e l’utilizzo del libro di testo degli insegnanti di storia di scuola secondaria di secondo grado grazie alle risposte derivate dalla somministrazione di un questionario sulla pratica docente.
I risultati ottenuti permetteranno di cogliere eventuali scollature tra la ricerca accademica e l’insegnamento nella scuola secondaria della storia, della storia medievale e della formazione degli stati regionali, sottolineando, talvolta, la necessità sempre più urgente di una integrata formazione continua degli insegnanti.The thesis aims to investigate the relationship between the findings of scientific research in the field of history, with particular reference to the theme of the formation of the Italian regional states in the late Middle Ages, and their teaching in secondary schools.
In the part dedicated to the theoretical framework, it underlines the increasingly pressing need for quality teaching and learning of history in today's society, based on a sense of active democratic participation and on the development of critical thinking, despite the fact that official ministerial documents do not always devote due importance to the subject. In addition, recent results obtained through a questionnaire administered to university students seem to confirm didactics still linked to traditional practice. In this sense, therefore, it is necessary to refound and refocus the importance of history by deepening the specific vocabulary and the basic epistemological premises of the discipline.
Starting from these issues, the empirical framework analyzes the state of progress of recent scientific-academic research on the formation of the Italian regional states of the late Middle Ages; compares the subject in the main school textbooks adopted in the metropolitan area of Bologna (Italy); and, finally, analyzes the conceptions on history, medieval history and the use of the textbook by secondary school history teachers thanks to the answers derived from the administration of a questionnaire on teaching practice.
The results obtained will make it possible to detect possible gaps between academic research and the secondary teaching of history, medieval history, and the formation of regional states, sometimes underlining the increasingly urgent need for an integrated in-service training of teachers.La tesis investiga las relaciones entre las averiguaciones de la investigación científica en el campo de la historia, con especial referencia al tema de la formación de los estados regionales italianos de la Baja Edad Media, y su enseñanza en los centros de secundaria.
En la parte dedicada al marco teórico, se subraya la necesidad cada vez más acuciante de una enseñanza y un aprendizaje de la historia de calidad en la sociedad actual, basados en el sentido de la participación democrática activa y en el desarrollo del pensamiento crítico, a pesar de que los documentos ministeriales oficiales no siempre dediquen la debida importancia a la asignatura y de que los recientes resultados obtenidos a través de un cuestionario administrado a los estudiantes universitarios parezcan confirmar una didáctica todavía ligada a la práctica tradicional. En este sentido, por tanto, es necesario reenfocar la importancia de la historia profundizando en el vocabulario específico y en las premisas epistemológicas básicas de la disciplina.
A partir de estos asuntos, el marco empírico analiza el estado de avance de la reciente investigación científico-académica sobre la formación de los estados regionales italianos de la baja Edad Media; compara el tema en los principales libros de texto escolares adoptados en el área metropolitana de Bolonia (Italia); y, por último, analiza las concepciones sobre la historia, la historia medieval y el uso del libro de texto de los profesores de historia de la escuela secundaria gracias a las respuestas derivadas de la administración de un cuestionario sobre la práctica docente.
Los resultados obtenidos permitirán detectar posibles lagunas entre la investigación académica y la enseñanza secundaria de la historia, la historia medieval y la formación de los estados regionales, subrayando a veces la necesidad cada vez más urgente de una formación integrada en el servicio de los profesores
About stabilization of non-minimum phase systems by output feedback
Get PDFThis thesis work has been motivated by an internal benchmark dealing with the output regulation problem
of a nonlinear non-minimum phase system in the case of full-state feedback. The system under consideration
structurally suffers from finite escape time, and this condition makes the output regulation problem very
hard even for very simple steady-state evolution or exosystem dynamics, such as a simple integrator.
This situation leads to studying the approaches developed for controlling Non-minimum phase
systems and how they affect feedback performances. Despite a lot of frequency domain results, only
a few works have been proposed for describing the performance limitations in a state space system
representation. In particular, in our opinion, the most relevant research thread exploits the so-called
Inner-Outer Decomposition. Such decomposition allows splitting the Non-minimum phase system under
consideration into a cascade of two subsystems: a minimum phase system (the outer) that contains all
poles of the original system and an all-pass Non-minimum phase system (the inner) that contains all the
unavoidable pathologies of the unstable zero dynamics.
Such a cascade decomposition was inspiring to start working on functional observers for linear and
nonlinear systems. In particular, the idea of a functional observer is to exploit only the measured
signals from the system to asymptotically reconstruct a certain function of the system states, without
necessarily reconstructing the whole state vector. The feature of asymptotically reconstructing a certain
state functional plays an important role in the design of a feedback controller able to stabilize the
Non-minimum phase system
Photochemical and photophysical processes in nanosystems: TiO2 photocatalysis and photothermal effect over motion
No full textThe integration of nanoscience and photochemistry has revealed to be a valuable and novel strategy for a wide range of applications. Light-activated nanosystems are characterized by tunable properties, high level of control and they may be easily implemented in the development of novel “green” strategies. During my PhD, I worked on different light-activated nanosystems: on one hand, I studied their photochemical and photophysical behavior upon light irradiation. On the other hand, I developed and investigated different nanosystems towards applications for water and air remediation. The prepared systems and their characterizations are briefly summarized in the next subsections. In the first part of this work, I focused my attention on the development of novel TiO2 based photocatalyst, and on their embedding and implementation in different support, such as concrete, glass and electrospun nanofibers. At the same time, TiO2 photodegradation properties were enhanced via modification with graphene and photosensitizer dyes. In the second part of this work, I focused my attention on the photophysical response of photoactive nanosystems in solution upon light excitation
Monitoring and Prediction of Thermal Emergencies in High Performance Computing Systems
Get PDFModern scientific discoveries are driven by an unsatisfiable demand for computational resources. High-Performance Computing (HPC) systems are an aggregation of computing power to deliver considerably higher performance than one typical desktop computer can provide, to solve large problems in science, engineering, or business.
An HPC room in the datacenter is a complex controlled environment that hosts thousands of computing nodes that consume electrical power in the range of megawatts, which gets completely transformed into heat.
Although a datacenter contains sophisticated cooling systems, our studies indicate quantitative evidence of thermal bottlenecks in real-life production workload, showing the presence of significant spatial and temporal thermal and power heterogeneity. Therefore minor thermal issues/anomalies can potentially start a chain of events that leads to an unbalance between the amount of heat generated by the computing nodes and the heat removed by the cooling system originating thermal hazards. Although thermal anomalies are rare events, anomaly detection/prediction in time is vital to avoid IT and facility equipment damage and outage of the datacenter, with severe societal and business losses. For this reason, automated approaches to detect thermal anomalies in datacenters have considerable potential.
This thesis analyzed and characterized the power and thermal characteristics of a Tier0 datacenter (CINECA) during production and under abnormal thermal conditions. Then, a Deep Learning (DL)-powered thermal hazard prediction framework is proposed. The proposed models are validated against real thermal hazard events reported for the studied HPC cluster while in production.
This thesis is the first empirical study of thermal anomaly detection and prediction techniques of a real large-scale HPC system to the best of my knowledge. For this thesis, I used a large-scale dataset, monitoring data of tens of thousands of sensors for around 24 months with a data collection rate of around 20 seconds
Comprehensive characterization of snowfall in terms of microphysical features, quantitative precipitation estimation and scavenging properties by in situ and remote sensing observations at an Antarctic coastal site
Get PDFSnow plays a crucial role in the Earth's hydrological cycle and energy budget, making its monitoring necessary. In this context, ground-based radars and in situ instruments are essential thanks to their spatial coverage, resolution, and temporal sampling. Deep understanding and reliable measurements of snow properties are crucial over Antarctica to assess potential future changes of the surface mass balance (SMB) and define the contribution of the Antarctic ice sheet on sea-level rise. However, despite its key role, Antarctic precipitation is poorly investigated due to the continent's inaccessibility and extreme environment. In this framework, this Thesis aims to contribute to filling this gap by in-depth characterization of Antarctic precipitation at the Mario Zucchelli station from different points of view: microphysical features, quantitative precipitation estimation (QPE), vertical structure of precipitation, and scavenging properties. For this purpose, a K-band vertically pointing radar collocated with a laser disdrometer and an optical particle counter (OPC) were used. The radar probed the lowest atmospheric layers with high vertical resolution, allowing the first trusted measurement at only 105 m height. Disdrometer and OPC provided information on the particle size distribution and aerosol concentrations. An innovative snow classification methodology was designed by comparing the radar reflectivity (Ze) and disdrometer-derived reflectivity by means of DDA simulations. Results of classification were exploited in QPE through appropriate Ze-snow rate relationships. The accuracy of the resulting QPE was benchmarked against a collocated weighing gauge. Vertical radar profiles were also investigated to highlight hydrometeors' sublimation and growth processes. Finally, OPC and disdrometer data allowed providing the first-ever estimates of scavenging properties of Antarctic snowfall. Results presented in this Thesis give rise to advances in knowledge of the characteristics of snowfall in Antarctica, contributing to a better assessment of the SMB of the Antarctic ice sheet, the major player in the global sea-level rise
Molecular simulations and modeling of pharmaceutically relevant RNA-processing enzymes
Get PDFThe two-metal-ion architecture is a structural feature found in a variety of RNA processing metalloenzymes or ribozymes (RNA-based enzymes), which control the biogenesis and the metabolism of vital RNAs, including non-coding RNAs (ncRNAs). Notably, such ncRNAs are emerging as key players for the regulation of cellular homeostasis, and their altered expression has been often linked to the development of severe human pathologies, from cancer to mental disorders. Accordingly, understanding the biological processing of ncRNAs is foundational for the development of novel therapeutic strategies and tools. Here, we use state-of the-art molecular simulations, complemented with X-ray crystallography and biochemical experiments, to characterize the RNA processing cycle as catalyzed by two two-metal-ion enzymes: the group II intron ribozymes and the RNase H1. We show that multiple and diverse cations are strategically recruited at and timely released from the enzymes’ active site during catalysis. Such a controlled cations’ trafficking leads to the recursive formation and disruption of an extended two-metal ion architecture that is functional for RNA-hydrolysis – from substrate recruitment to product release. Importantly, we found that these cations’ binding sites are conserved among other RNA-processing machineries, including the human spliceosome and CRISPR-Cas systems, suggesting that an evolutionarily-converged catalytic strategy is adopted by these enzymes to process RNA molecules. Thus, our findings corroborate and sensibly extend the current knowledge of two-metal-ion enzymes, and support the design of novel drugs targeting RNA-processing metalloenzymes or ribozymes as well as the rational engineering of novel programmable gene-therapy tools
Morphological adaptation and variation of gene expression after pneumonectomy: observations on experimental animal model
Get PDFIntroduzione
La pneumonectomia su modello animale potrebbe essere un’utile piattaforma di studio per approfondire i meccanismi della risposta compensatoria al danno polmonare. Scopo dello studio è determinare la presenza di variazioni morfologiche e di espressione del trascrittoma dopo pneumonectomia.
Materiali e metodi
Undici suini sono stati sottoposti a pneumonectomia sinistra. Sono stati eseguiti prelievi sito-specifici intraoperatori su polmone sinistro e successivamente confrontati con prelievi sito-specifici su polmone destro dopo eutanasia a 60 giorni. I prelievi degli animali con decorso regolare sono stati sottoposti a RNA-sequencing e successiva analisi computazionale per valutare il peso funzionale del singolo gene o di clusters di geni.
Risultati
Un animale è stato escluso per insorgenza di ernia diaframmatica. In 7/10 è stata riscontrata apertura della pleura mediastinica con parziale erniazione del polmone controlaterale e shift mediastinico. L’istologia ha mostrato dilatazione degli spazi aerei, rottura dei setti interalveolari, lieve infiammazione, assenza di fibrosi, stiramento radiale dei bronchi e riduzione del letto capillare. L’analisi di bulk RNA-sequencing ha identificato 553 geni espressi in modo differenziale (DEG)(P<0,001) tra pre e post-pneumonectomia. I primi 10 DEG up-regolati: Edn1, Areg, Havcr2, Gadd45g, Depp1, Cldn4, Atf3, Myc, Gadd45b, Socs3; i primi 10 geni down-regolati: Obscn, Cdkn2b, ENSSSCG00000015738, Prrt2, Amer1, Flrt3, Efnb2, Tox3, Znf793, Znf365.
Tra i DEG è stata riscontrata una predominanza di geni specifici dei macrofagi. L’analisi di gene ontology basata su DAVID ha mostrato un significativo arricchimento della "via di segnalazione apoptotica estrinseca"(FDR q=7,60x10 -3), della via di “Risposta all’insulina”(FDR q=7,60x10 -3) ed un arricchimento di geni “Regolatori negativi del segnale DDX58/IFIH1”(FDR q=7.50x10 -4).
Conclusioni
Il presente studio conferma la presenza di variazioni macroscopiche e microscopiche fenotipiche dopo pneumonectomia. L’RNA sequencing e lo studio di genomica traslazionale hanno mostrato l’esistenza di geni singoli e di network di geni disregolati dopo pneumonectomia, prevalentemente in determinate popolazioni cellulari.Introduction
Pneumonectomy on animal model could be useful to investigate mechanisms of the compensatory response to lung damage. Aim of the study is to determine the presence of morphological and transcriptome expression changes after pneumonectomy.
Materials and methods
Eleven pigs underwent left pneumonectomy. Intraoperative site-specific samples were performed on the left lung and subsequently compared with site-specific samples on the right lung after euthanasia at 60 days. The samples of the animals with a uneventful course were subjected to RNA-sequencing and subsequent computational analysis to evaluate the functional weight of the single gene or of clusters of genes.
Results
One animal was excluded for diaphragmatic hernia. In 7/10 mediastinal pleura was interrupted with partial herniation of the remaining lung and mediastinal shift. Histology showed dilation of the air spaces, rupture of the interalveolar septa, mild inflammation, absence of fibrosis, radial stretching of the bronchi and reduction of the capillary bed. Bulk RNA-sequencing analysis identified 553 differentially expressed genes (DEG) (P <0.001) between pre and post-pneumonectomy state. The top 10 up-regulated DEGs: Edn1, Areg, Havcr2, Gadd45g, Depp1, Cldn4, Atf3, Myc, Gadd45b, Socs3; the top 10 down-regulated genes: Obscn, Cdkn2b, ENSSSCG00000015738, Prrt2, Amer1, Flrt3, Efnb2, Tox3, Znf793, Znf365.
A predominance of macrophage-specific genes was found among the DEGs. The DAVID-based gene ontology analysis showed a significant enrichment of the "extrinsic apoptotic signaling pathway" (FDR q = 7.60x10 -3), of the "Insulin response" pathway (FDR q = 7.60x10 - 3) and of “DDX58 / IFIH1 negative regulators” genes (FDR q = 7.50x10 -4).
Conclusions
The present study confirms the presence of macroscopic and microscopic phenotypic variations after pneumonectomy. This translational genomics study showed the existence of individual genes and networks of genes which resulted disregulated after pneumonectomy, mainly in certain cell populations
Big data analytics and modeling for Human Mobility
Get PDFThe fast development of Information Communication Technologies (ICT) offers new opportunities to realize future smart cities. To understand, manage and forecast the city's behavior, it is necessary the analysis of different kinds of data from the most varied dataset acquisition systems. The aim of this research activity in the framework of Data Science and Complex Systems Physics is to provide stakeholders with new knowledge tools to improve the sustainability of mobility demand in future cities. Under this perspective, the governance of mobility demand generated by large tourist flows is becoming a vital issue for the quality of life in Italian cities' historical centers, which will worsen in the next future due to the continuous globalization process. Another critical theme is sustainable mobility, which aims to reduce private transportation means in the cities and improve multimodal mobility.
We analyze the statistical properties of urban mobility of Venice, Rimini, and Bologna by using different datasets provided by companies and local authorities. We develop algorithms and tools for cartography extraction, trips reconstruction, multimodality classification, and mobility simulation. We show the existence of characteristic mobility paths and statistical properties depending on transport means and user's kinds. Finally, we use our results to model and simulate the overall behavior of the cars moving in the Emilia Romagna Region and the pedestrians moving in Venice with software able to replicate in silico the demand for mobility and its dynamic
The magazine Imágenes and the documentary vision of NO-DO: image and identity of art in the national conscience
Get PDFEl objetivo principal de esta investigación es sistematizar y analizar los documentales de arte que fueron producidos por la entidad de los Noticiarios y Documentales (NO-DO), desde su surgimiento a finales de 1942, hasta su supresión oficial en 1981. Así, nos hemos centrado en examinar las diferentes actividades en las que la institución organizó su producción siempre dentro del terreno del reportaje y del documental. En este sentido, el desarrollo del documental de arte se produjo tanto en la propia sección documental que estuvo representada por las siglas “DO” de la entidad, como en la revista Imágenes, un formato periódico de producción cuya actividad se desarrolló entre 1945 y 1968.The principal aim of this investigation is to systematise and analyse the art documentaries produced by the entity called NO-DO (Noticiarios y Documentales; “News and Documentaries” in English), from its creation by the end of 1942 until its official deletion in 1981. Thus, we have focused on examining the different activities in which the institution organised its production always within the area of the report and the documentary. In this regard, the development of the art documentary flourished in the documentary section represented by the entity’s initials “DO” itself, as well as in the magazine Imágenes, a weekly production format whose activity took place between 1945 and 1968