One dimensional and multiscale models for blood flow circulation

The aim of this work is to provide mathematically sound and computationally effective tools for the numerical simulation of the interaction between fluid and structures as occurring, for instance, in the simulation of the human cardiovascular system. This problem is global, in the sense that local changes can modify the solution far away. From the point of view of computing and modelling this calls for the use of multiscale methods, where simplified models are used to treat the global problem leaving to more accurate models the local description. Moreover it is characterised by the appearance of pressure waves inside the vessels. In large arteries the vessel wall dynamics can be described by a thin elastic membrane model (Navier equation) while the fluid motion can be represented by the Navier-Stokes equations for incompressible Newtonian fluids. Unfortunately, given the high levels of details furnished by this model, its computational complexity is dramatically high. Therefore reduced models have been developed. In particular, one-dimensional models, originally introduced by Euler, seem to be appropriate for the study in the time-space domain of pressure wave propagation induced by the interaction between the fluid and the vessel wall in the arterial tree. These reduced models are obtained after integrating the Navier-Stokes equations over a vessel section, supposed to be circular, and assuming an algebraic wall law to describe the relationship between pressure and wall deformation. They can be used in place of the more complex three dimensional fluid-structure models or in cooperation with them (multiscale approach). The first part of this work deals with one dimensional models. A reduced 1D model taken from literature is presented and analysed. Some extensions of the basic model, in particular with respect to vessel wall law (generalised string model) and more complex geometries (bifurcated and curved arteries), are also considered. Numerical schemes are proposed and some numerical results are presented. In the second part of this thesis we focus on a multiscale model. We consider a 55 arterial tree, described by the 1D model, coupled with lumped parameter models for heart and capillaries. In particular, specific attention has been devoted to the coupling between the left ventricle and the arterial system, whose physiopathological relevance is well known. This mathematical model gives good results in numerical tests and is able to describe the relevant features of the pressure wave propagation and reflections within the arterial system

A Comparative Study between Lycorine and Galantamine Abilities to Interact with AMYLOID β and Reduce In Vitro Neurotoxicity

Galantamine is a natural alkaloid extracted from the Amaryllidaceae plants and is used as the active ingredient of a drug approved for the treatment of the early stages of Alzheimer's disease. It mainly acts as an acetylcholinesterase (AChE) inhibitor, increasing concentrations of the acetylcholine neurotransmitter. Recent cellular studies have also shown the ability of galantamine to protect SH-SY5Y cell lines against amyloid-beta (A beta)-induced toxicity. Such investigations have supported and validated further in-depth studies for understanding the chemical and molecular features associated with galantamine-protective abilities. In addition to galantamine, other natural alkaloids are known to possess AChE inhibitory activity; among them lycorine has been extensively investigated for its antibacterial, anti-inflammatory and antitumoral activities as well. Despite its interesting biological properties, lycorine's neuroprotective functions against A beta-induced damages have not been explored so far. In this research study, the ability of galantamine and lycorine to suppress A beta-induced in vitro neuronal toxicity was evaluated by investigating the chemical interactions of the two alkaloids with A beta peptide. A multi-technique spectroscopic analysis and cellular cytotoxicity assays were applied to obtain new insights on these molecular associations. The comparison between the behaviors exhibited by the two alkaloids indicates that both compounds possess analogue abilities to interact with the amyloidogenic peptide and protect cells

«Dominus contentatur»: l’azione di Francesco Sforza nel territorio fermano e i capitoli di dedizione

Tra il 1433 e il 1446 la città di Fermo assunse un ruolo di primaria importanza nelle dinamiche dell’esperienza politica sforzesca nella Marca d’Ancona. La sottomissione a Francesco Sforza fu ufficiale dopo la stipulazione di alcuni patti che avrebbero dovuto regolare i rapporti in ambito economico, politico e giudiziario tra la comunità ed il condottiero. L’articolo, corredato da un’appendice documentaria, analizza le relazioni tra gli Sforza, la città di Fermo ed il suo contado partendo dalle condizioni poste nei patti risalenti al dicembre del 1433. Le modifiche degli accordi occorse durante il dominio, le richieste di tributi e pagamenti, il restringimento delle autonomie cittadine e la creazione di nuove cariche, l’accoglimento delle rivendicazioni avanzate dagli ambasciatori sono tutti aspetti che permettono di approfondire non soltanto la costruzione, il consolidamento e la fine della signoria di Francesco Sforza ma anche la ricezione di quest’ultima da parte delle comunità assoggettate.Between 1433 and 1446 Fermo played an important role during the Sforza’s political experience in the Marchia of Ancona. The submission to Francesco Sforza was official after the stipulation of some pacts aimed to regulate the economic, judicial and political relationships between the condottiero and the community. The paper, with an appendix of archival documents, analyzes the relations between the Sforza, the city of Fermo and its countryside, starting from the conditions set in the pacts dating back to December 1433. The changes in the agreements that occurred during his rule, the requests for taxes and payments, the limitation of the city autonomies and the creation of new offices, the acceptance of the claims made by the ambassadors are all aspects that allow to study in depth not only the construction, the consolidation and the decline of Francesco Sforza's domination, but also its reception by the subjected communities

Tra leggenda e realtà: l’incontro tra i Fraticelli di Maiolati e Braccio da Montone nel “Dialogus contra Fraticellos”

Dopo la vittoria nella battaglia di Sant’Egidio e il ridimensionamento della fazione malatestiana, la Marca d’Ancona tra il 1417 e il 1424 fu parte del processo di  costruzione statale messo in atto dal condottiero perugino Braccio da Montone. È proprio in questo ristretto arco cronologico che Fra Giacomo della Marca inserisce nel “Dialogus contra Fraticellos” un particolare incontro tra Braccio e i rappresentanti più autorevoli dei cosiddetti Fraticelli. Il presente contributo ha innanzitutto l’obiettivo analizzando il passo in questione di discernere la realtà storica dalla tradizione e in tal modo esprimere un giudizio circa l’effettiva possibilità dello svolgimento dei fatti, così come riportato nel Dialogus. Inoltre, l’articolo si pone in continuazio ne degli studi compiuti da Giovanni Annibaldi circa la sorte e la condizione degli interlocutori di Braccio, Guglielmo e Rainaldo, rispettivamente l’ imperatore e il papa della setta fraticellesca.After the victory in the battle of Sant’Egidio and the fall of the Malatesta faction, between 1417 and 1424 the Marchia of Ancona was part of the state construction process carried out by the Perugian condottiero Braccio da Montone. It is precisely in this short period that in the "Dialogus contra Fraticellos" Giacomo della Marca tells about an encounter between Braccio and the most authoritative representatives of the so called Fraticelli. The main objective of the paper is to analyze this passage to disce rn historical reality from tradition and thus express a judgment on the possibility of the development of the facts, as reported in the Dialogus. Moreover, it continues the studies carried out by Giovanni Annibaldi about the life and the condition of Bracc io’s interlocutors, Guglielmo and Rainaldo, respectively the emperor and the pope of the Fraticelli

On Parallel Computation of Blood Flow in Human Arterial Network Based on 1-D Modelling

In this study, parallel computation of blood flow in a 1-D model of human arterial network has been carried out employing a Taylor Galerkin Finite Element Method. Message passing interface libraries have been used on Origin 2000 SGI machine. A Greedy strategy for load-distribution has been devised and data-flow graphs necessary for parallelization have been generated. The performance of parallel implementation measured in terms of speedup and efficiency factors is found to be good. Further, the parallel code is used in simulating the propagation of pressure and velocity waveforms in our 1-D arterial model for two different inflow pressure pulses. Also, the influence of consideration of terminal resistance on pressure and velocity waveforms have been analyze

Demonstration of a heterogeneously integrated III-V/SOI single wavelength tunable laser

A heterogeneously integrated III-V-on-silicon laser is reported, integrating a III-V gain section, a silicon ring resonator for wavelength selection and two silicon Bragg grating reflectors as back and front mirrors. Single wavelength operation with a side mode suppression ratio higher than 45 dB is obtained. An output power up to 10 mW at 20 °C and a thermo-optic wavelength tuning range of 8 nm are achieved. The laser linewidth is found to be 1.7 MHz

Low-threshold heterogeneously integrated InP/SOI lasers with a double adiabatic taper coupler

We report on a heterogeneously integrated InP/silicon-on-insulator (SOI) laser source realized through divinylsiloxane-bis-benzocyclobutene (DVS-BCB) wafer bonding. The hybrid lasers present several new features. The III-V waveguide has a width of only 1.7 mu m, reducing the power consumption of the device. The silicon waveguide thickness is 400 nm, compatible with high-performance modulator designs and allowing efficient coupling to a standard 220-nm high index contrast silicon waveguide layer. In order to make the mode coupling efficient, both the III-V waveguide and silicon waveguide are tapered, with a tip width for the III-V waveguide of around 800 nm. These new features lead to good laser performance: a lasing threshold as low as 30 mA and an output power of more than 4 mW at room temperature in continuous-wave operation regime. Continuous wave lasing up to 70 degrees C is obtained

Optoelectronic comb generation and cross-injection locking of photonic integrated circuit for millimetre-wave generation

We demonstrate how a monolithically integrated heterodyne source was used for a 33.6 GHz signal generation using an optical solution by a combination of cross-optical injection locking inside the chip and electrical injection locking at the RF signal 7th sub-harmonic