An experimental and theoretical approach to correct for the scattered radiation in an X-ray computer tomography system for industrial applications

The main problem connected to cone beam computed tomography (CT) systems for industrial applications employing 450 kV X-ray tubes is the high amount of scattered radiation which is added to the primary radiation (signal). This stray radiation leads to a significant degradation of the image quality. A better understanding of the scattering and methods to reduce its effects are therefore necessary to improve the image quality. Several studies have been carried out in the medical field at lower energies, whereas studies in industrial CT, especially for energies up to 450 kV, are lacking. Moreover, the studies reported in literature do not consider the scattered radiation generated by the CT system structure and the walls of the X-ray room (environmental scatter). In order to investigate the scattering on CT projections a GEANT4-based Monte Carlo (MC) model was developed. The model, which has been validated against experimental data, has enabled the calculation of the scattering including the environmental scatter, the optimization of an anti-scatter grid suitable for the CT system, and the optimization of the hardware components of the CT system. The investigation of multiple scattering in the CT projections showed that its contribution is 2.3 times the one of primary radiation for certain objects. The results of the environmental scatter showed that it is the major component of the scattering for aluminum box objects of front size 70 x 70 mm2 and that it strongly depends on the thickness of the object and therefore on the projection. For that reason, its correction is one of the key factors for achieving high quality images. The anti-scatter grid optimized by means of the developed MC model was found to reduce the scatter-toprimary ratio in the reconstructed images by 20 %. The object and environmental scatter calculated by means of the simulation were used to improve the scatter correction algorithm which could be patented by Empa. The results showed that the cupping effect in the corrected image is strongly reduced. The developed CT simulation is a powerful tool to optimize the design of the CT system and to evaluate the contribution of the scattered radiation to the image. Besides, it has offered a basis for a new scatter correction approach by which it has been possible to achieve images with the same spatial resolution as state-of-the-art well collimated fan-beam CT with a gain in the reconstruction time of a factor 10. This result has a high economic impact in non-destructive testing and evaluation, and reverse engineering.

Influence of Electromagnetic Fields On Biological Signalling: An Experimental and Theoretical Approach

The primary goals of this study were to develop a cell-free in vitro assay for the assessment of nonthermal electromagnetic (EMF) bioeffects and to develop theoretical models in accord with current experimental observations. Based upon the hypothesis that EMF effects operate by modulating Ca2+/CaM binding, an in vitro nitric oxide (NO) synthesis assay was developed to assess the effects of a pulsed radiofrequency (PRF) signal used for treatment of postoperative pain and edema. No effects of PRF on NO synthesis were observed. Effects of PRF on Ca2+/CaM binding were also assessed using a Ca2+-selective electrode, also yielding no EMF Ca2+/CaM binding. However, a PRF effect was observed on the interaction of hemoglobin (Hb) with tetrahydrobiopterin, leading to the development of an in vitro Hb deoxygenation assay, showing a reduction in the rate of Hb deoxygenation for exposures to both PRF and a static magnetic field (SMF). Structural studies using pyranine fluorescence, Gd3+ vibronic sideband luminescence and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were conducted in order to ascertain the mechanism of this EMF effect on Hb. Also, the effect of SMF on Hb oxygen saturation (SO2) was assessed under gas-controlled conditions. These studies showed no definitive changes in protein/solvation structure or SO2 under equilibrium conditions, suggesting the need for real-time instrumentation or other means of observing out-of-equilibrium Hb dynamics. Theoretical models were developed for EMF transduction, effects on ion binding, neuronal spike timing, and dynamics of Hb deoxygenation. The EMF sensitivity and simplicity of the Hb deoxygenation assay suggest a new tool to further establish basic biophysical EMF transduction mechanisms. If an EMF-induced increase in the rate of deoxygenation can be demonstrated in vivo, then enhancement of oxygen delivery may be a new therapeutic method by which clinically relevant EMF-mediated enhancement of growth and repair processes can occur.

Reconstruction and analysis of the NF-kB pathway interactome: a systems biology approach

Background. One of the phenomena observed in human aging is the progressive increase of a systemic inflammatory state, a condition referred to as “inflammaging”, negatively correlated with longevity. A prominent mediator of inflammation is the transcription factor NF-kB, that acts as key transcriptional regulator of many genes coding for pro-inflammatory cytokines. Many different signaling pathways activated by very diverse stimuli converge on NF-kB, resulting in a regulatory network characterized by high complexity. NF-kB signaling has been proposed to be responsible of inflammaging. Scope of this analysis is to provide a wider, systemic picture of such intricate signaling and interaction network: the NF-kB pathway interactome. Methods. The study has been carried out following a workflow for gathering information from literature as well as from several pathway and protein interactions databases, and for integrating and analyzing existing data and the relative reconstructed representations by using the available computational tools. Strong manual intervention has been necessarily used to integrate data from multiple sources into mathematically analyzable networks. The reconstruction of the NF-kB interactome pursued with this approach provides a starting point for a general view of the architecture and for a deeper analysis and understanding of this complex regulatory system. Results. A “core” and a “wider” NF-kB pathway interactome, consisting of 140 and 3146 proteins respectively, were reconstructed and analyzed through a mathematical, graph-theoretical approach. Among other interesting features, the topological characterization of the interactomes shows that a relevant number of interacting proteins are in turn products of genes that are controlled and regulated in their expression exactly by NF-kB transcription factors. These “feedback loops”, not always well-known, deserve deeper investigation since they may have a role in tuning the response and the output consequent to NF-kB pathway initiation, in regulating the intensity of the response, or its homeostasis and balance in order to make the functioning of such critical system more robust and reliable. This integrated view allows to shed light on the functional structure and on some of the crucial nodes of thet NF-kB transcription factors interactome. Conclusion. Framing structure and dynamics of the NF-kB interactome into a wider, systemic picture would be a significant step toward a better understanding of how NF-kB globally regulates diverse gene programs and phenotypes. This study represents a step towards a more complete and integrated view of the NF-kB signaling system.

Mixed Mode Fracture Behaviour of Piezoelectric Materials

Piezoelectrics present an interactive electromechanical behaviour that, especially in recent years, has generated much interest since it renders these materials adapt for use in a variety of electronic and industrial applications like sensors, actuators, transducers, smart structures. Both mechanical and electric loads are generally applied on these devices and can cause high concentrations of stress, particularly in proximity of defects or inhomogeneities, such as flaws, cavities or included particles. A thorough understanding of their fracture behaviour is crucial in order to improve their performances and avoid unexpected failures. Therefore, a considerable number of research works have addressed this topic in the last decades. Most of the theoretical studies on this subject find their analytical background in the complex variable formulation of plane anisotropic elasticity. This theoretical approach bases its main origins in the pioneering works of Muskelishvili and Lekhnitskii who obtained the solution of the elastic problem in terms of independent analytic functions of complex variables. In the present work, the expressions of stresses and elastic and electric displacements are obtained as functions of complex potentials through an analytical formulation which is the application to the piezoelectric static case of an approach introduced for orthotropic materials to solve elastodynamics problems. This method can be considered an alternative to other formalisms currently used, like the Stroh’s formalism. The equilibrium equations are reduced to a first order system involving a six-dimensional vector field. After that, a similarity transformation is induced to reach three independent Cauchy-Riemann systems, so justifying the introduction of the complex variable notation. Closed form expressions of near tip stress and displacement fields are therefore obtained. In the theoretical study of cracked piezoelectric bodies, the issue of assigning consistent electric boundary conditions on the crack faces is of central importance and has been addressed by many researchers. Three different boundary conditions are commonly accepted in literature: the permeable, the impermeable and the semipermeable (“exact”) crack model. This thesis takes into considerations all the three models, comparing the results obtained and analysing the effects of the boundary condition choice on the solution. The influence of load biaxiality and of the application of a remote electric field has been studied, pointing out that both can affect to a various extent the stress fields and the angle of initial crack extension, especially when non-singular terms are retained in the expressions of the electro-elastic solution. Furthermore, two different fracture criteria are applied to the piezoelectric case, and their outcomes are compared and discussed. The work is organized as follows: Chapter 1 briefly introduces the fundamental concepts of Fracture Mechanics. Chapter 2 describes plane elasticity formalisms for an anisotropic continuum (Eshelby-Read-Shockley and Stroh) and introduces for the simplified orthotropic case the alternative formalism we want to propose. Chapter 3 outlines the Linear Theory of Piezoelectricity, its basic relations and electro-elastic equations. Chapter 4 introduces the proposed method for obtaining the expressions of stresses and elastic and electric displacements, given as functions of complex potentials. The solution is obtained in close form and non-singular terms are retained as well. Chapter 5 presents several numerical applications aimed at estimating the effect of load biaxiality, electric field, considered permittivity of the crack. Through the application of fracture criteria the influence of the above listed conditions on the response of the system and in particular on the direction of crack branching is thoroughly discussed.

Ab initio quantum mechanical investigation of structural and chemical-physical properties of selected minerals for minero-petrological, structural ceramic and biomaterial applications

The purpose of this thesis is the atomic-scale simulation of the crystal-chemical and physical (phonon, energetic) properties of some strategically important minerals for structural ceramics, biomedical and petrological applications. These properties affect the thermodynamic stability and rule the mineral-environment interface phenomena, with important economical, (bio)technological, petrological and environmental implications. The minerals of interest belong to the family of phyllosilicates (talc, pyrophyllite and muscovite) and apatite (OHAp), chosen for their importance in industrial and biomedical applications (structural ceramics) and petrophysics. In this thesis work we have applicated quantum mechanics methods, formulas and knowledge to the resolution of mineralogical problems ("Quantum Mineralogy”). The chosen theoretical approach is the Density Functional Theory (DFT), along with periodic boundary conditions to limit the portion of the mineral in analysis to the crystallographic cell and the hybrid functional B3LYP. The crystalline orbitals were simulated by linear combination of Gaussian functions (GTO). The dispersive forces, which are important for the structural determination of phyllosilicates and not properly con-sidered in pure DFT method, have been included by means of a semi-empirical correction. The phonon and the mechanical properties were also calculated. The equation of state, both in athermal conditions and in a wide temperature range, has been obtained by means of variations in the volume of the cell and quasi-harmonic approximation. Some thermo-chemical properties of the minerals (isochoric and isobaric thermal capacity) were calculated, because of their considerable applicative importance. For the first time three-dimensional charts related to these properties at different pressures and temperatures were provided. The hydroxylapatite has been studied from the standpoint of structural and phonon properties for its biotechnological role. In fact, biological apatite represents the inorganic phase of vertebrate hard tissues. Numerous carbonated (hydroxyl)apatite structures were modelled by QM to cover the broadest spectrum of possible biological structural variations to fulfil bioceramics applications.

El principio de neutralidad interna en el IVA

La tesis estudia el principio de neutralidad en su vertiente interna y su aplicación efectiva en el IVA. Se centra en los principales aspectos de la configuración jurídica del impuesto: derecho de deducción, exenciones y tipos reducidos. Se realiza en primer lugar una aproximación teórica al principio desde un punto de vista jurídico y también económico. Una vez construido el principio se acomete una comparación de las distintas clases de impuestos indirectos que pueden establecerse y se analiza su cumplimiento del principio de neutralidad fiscal. El énfasis es mayor en los impuestos en cascada, impuestos monofásicos minoristas y en el IVA. El objetivo de la tesis es, por tanto, concretar el contenido del principio, desarrollar sus implicaciones económicas principales y analizar el grado de cumplimiento real de la Directiva IVA. Desde el punto de vista del derecho de deducción y de las exenciones el estudio se apoya en el análisis de la jurisprudencia del Tribunal de Justicia de la Unión Europea, donde se profundizará en cuestiones como la utilización de bienes de uso mixto, la consideración de costes como directos o generales y las formas de ejercicio del exceso de deducción (devolución y compensación). Además, la tesis muestra las principales excepciones al principio de neutralidad establecidas en la Directiva IVA: prohibiciones al derecho de deducción, exenciones y tipos reducidos. En esta parte también se apoyará el estudio en la jurisprudencia del TJUE, que ha construido en gran medida los criterios de interpretación de estas excepciones. En conclusión, el objetivo de la tesis es medir si la directiva IVA cumple con el principio de neutralidad fiscal, para lo que deberá haberse especificado primero su significado concreto y se habrá debido diferenciar entre sus dos dimensiones: interna y externa.

L’espace urbain indien dans la littérature européenne au XXème siecle. Pour une perspective post-orientaliste.

L'affermarsi della teoria della « imaginative geography » di Edward Saïd (Orientalism, 1978), nell'arco degli ultimi trent'anni, ha imposto un orientamento prettamente sociopolitico, gramsciano e foucaultiano alla critica del testo, proponendo un'unica soluzione interpretativa per un corpus eterogeneo di testi (scientifici e artistici, antichi e moderni) accomunati dal fatto di « rappresentare l'Oriente ». La costruzione europea dello spazio orientale, dice Saïd, non rappresenta solo un misconoscimento dell'Altro, ma una sua rappresentazione tendenziosa e finalizzata a sostenere la macchina dell'imperialismo occidentale. In particolare, la rappresentazione « femminilizzata » della geografia orientale (come luogo dell'exploit del maschio bianco) preparebbe e accompagnerebbe l'impresa di assoggettamento politico e di sfruttamento economico dei paesi ad Est dell'Europa. Se Orientalism ha conosciuto fortune alterne dall'anno della sua apparizione, negli ultimi anni una vera e propria corrente anti-saidiana ha preso forza, soprattutto in ambito francese. Attraverso l'analisi di circa trenta opere francesi, belga, inglesi e italiane del Novecento, questa tesi cerca di visualizzare i limiti teorici della prospettiva saidiana rivolgendosi a un esame della rappresentazione dello spazio urbano indiano nella letteratura europea contemporanea. Nello specifico, uno studio delle nuove strutture e dei nuovi modelli della femminilizzazione dello spazio orientale indiano cercherà di completare – superandolo in direzione di un « post-orientalismo » – il riduzionismo della prospettiva saidiana.

Studi per una operante storia del territorio. Il libro incompiuto di Saverio Muratori

Muratori concepisce Studi per una operante storia del territorio come una lettura del territorio, una sua interpretazione. E’ una raccolta di disegni (255 disegni a mano e 18 prove di stampa), in cui sono riportati soltanto i tratti rilevanti dei territori considerati al fine dello studio. La tesi ha come obiettivo quello di compiere un’analisi filologica dei documenti e cercare di cogliere le finalità, valutando la sua attendibilità ai giorni nostri. Nella scelta del titolo, Studi per una operante storia del territorio. Il libro incompiuto di Saverio Muratori,inserendo nel titolo quello originale dell'opera, si rende esplicita l’intenzione filologica di base da cui si sviluppano le considerazioni fatte nello svolgimento di questa ricerca, costantemente attenta alla coerenza con i disegni analizzati. Questa coerenza è dettata dalla volontà di perseguire le logiche di confronto che hanno caratterizzato il lavoro di Muratori. Il titolo che descrive il corpus dei disegni mette in primo piano il sistema uomo-natura, che il territorio rappresenta nella sua totalità di unicum. La tesi è suddivisa in due parti. La prima verte sullo studio dei materiali d’archivio relativi agli Studi sul territorio, in cui è spiegato il metodo di catalogazione utilizzato. Fondamentale, ai fini di un primo approccio alla ricerca, è il contributo dato dall’architetto Alessandro Giannini attraverso la preliminare schedatura del materiale ed dell'analisi riportata in Leggendo le minute dell’Atlante del territorio di Saverio Muratori. La seconda parte della tesi verte su un percorso dialettico tra la filosofia, la teoria, la didattica e la pratica progettuale di Muratori, ambiti da tenere in considerazione per una interpretazione critica alla sua metodologia, che ha come fine ultimo il reale, quindi il territorio, in cui trova, prima attraverso la trattazione teorica esposta in Civiltà e territorio, la concreta conclusione nei disegni degli Studi per una operante storia del territorio.

Nuove pratiche turistiche e sostenibilita'. I profili del turista lento in Valnerina

Il presente lavoro intende analizzare il tema del turista lento che nell’ultimo decennio si è diffuso nel dibattito scientifico e culturale connesso al tema della sostenibilità e della qualità della vita e nel contesto dell’approccio teorico strutturato intorno alle nuove tendenze dello Slow Tourism. In una prima parte la tesi delinea il framework della sostenibilità con particolare attenzione al recente dibattito in corso sulla “decrescita” e l’“a-crescita” come concetti alternativi al paradigma della crescita. Successivamente viene evidenziato il modo in cui le idee di base ed i principi dello sviluppo sostenibile sono stati applicati al turismo e indagato il legame tra sostenibilità e responsabilità e come questo configura l’emergere di un turismo “responsustable”. In tale contesto viene analizzata la relazione tra turismo e lentezza in cui a filosofia slow non deve essere interpretata come un fenomeno del momento o un innovativo prodotto turistico, ma come una filosofia di vita, un movimento sociale e globale che negli ultimi anni ha caratterizzato i diversi ambiti socio-economici delle comunità locali. Successivamente attraverso una review della letteratura nazionale ed internazionale sul tema, la pluralità di prospettive teoriche vengono sistematizzate in tre ipotesi di lettura riconducibili a tre paradigmi: sostenibilità- slow tourism- territorio; benessere – slow tourism – qualità della vita; esperienza – slow tourism – consumo. Nella seconda parte del lavoro viene presentata l’indagine empirica a partire dall’analisi di contesto del territorio in cui si è svolta l’attività di ricerca, i nove comuni del Comprensorio Turistico della Valnerina in Umbria, con particolare riferimento all’analisi dell’offerta e della domanda turistica. Successivamente sono presentati i risultati di un questionario somministrato a 620 turisti attraverso il quale viene analizzato il profilo motivazionale, le esperienze di fruizione turistica e la percezione della qualità territoriale da parte del turista e delineato il profilo del turista slow in Valnerina.