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Approximation and spectral analysis for large structured linear systems.
No full textIn this work we are interested in standard and less standard structured linear systems coming from applications in various _elds of computational mathematics and often modeled by integral and/or di_erential equations. Starting from classical Toeplitz and Circulant structures, we consider some extensions as g-Toeplitz and g-Circulants matrices appearing in several contexts in numerical analysis and applications. Then we consider special matrices arising from collocation methods for di_erential equations: also in this case, under suitable assumptions we observe a Toeplitz structure. More in detail we _rst propose a detailed study of singular values and eigenvalues of g-circulant matrices and then we provide an analysis of distribution of g-Toeplitz sequences. Furthermore, when possible, we consider Krylov space methods with special attention to the minimization of the computational work. When the involved dimensions are large, the Preconditioned Conjugate Gradient (PCG) method is recommended because of the much stronger robustness with respect to the propagation of errors. In that case, crucial issues are the convergence speed of this iterative solver, the use of special techniques (preconditioning, multilevel techniques) for accelerating the convergence, and a careful study of the spectral properties of such matrices. Finally, the use of radial basis functions allow of determining and studying the asymptotic behavior of the spectral radii of collocation matrices approximating elliptic boundary value problems
La Bisanzio dei lumi. L'impero romano d'oriente nella storiografia e nella cultura.
No full textIn the 17th and 18th centuries, especially (but not exclusively) starting from the reign of Louis XIV, the interest in Byzantine Empire has seen in France – and also in Italy although in a more marginal way – a new flowering.
In this period of time, almost a century and a half, going from the reign of the Sun King (1638-1715) until the French Revolution (1789), the revival of Byzantine studies is determined from different factors – religious, political, emotional, philosophical – which cannot be reduced only to the discreditable image provided by the Enlightenment (however, not by “all” Enlightenment).
The Byzantine Empire with its Greek orthodox faith becomes from a catholic point of view the emblem of the betrayal of the “true” Roman Catholic faith and, for this reason, connected with the more recent Protestant Reformation. From another one, Byzantium is meant to glorify Louis XIV, whose lineage went back to the Latin emperors of Constantinople (1204-1261), as well as to support his pretensions to the Constantinopolitan throne against Habsburg’s one. At the same time, if from one side Byzantine history is aimed at the celebration of French monarchy, on the other one, with the rise of the Ottoman Empire threatening Europe, the Byzantine Empire conquered by the Turks in 1453 is raised as a negative model to avoid. In the end, with the rise of Enlightenment thought in the 18th century, Byzantium is taken as example of the despotism and the violence of despotic power against an absolutism more “enlightened”.
However, contemporary, a positive, although not predominant, view of the Byzantine Empire can be found. In particular that is concerning the crusades involving the Byzantine Empire between the 11th and 13th centuries, seen and condemned as an attack of the Latins against the Byzantines.
The aim of this work is hence to shed light on the complexity of the “Byzantium problem” in the 17th-18th centuries, showing how the history of Byzantine Empire has been subject to a different and sometimes controversial, interpretations which it is not possible to ascribe to a coherent and uniform thought
Essays on development economics.
No full textThis thesis consists of four essays in empirical development economics. The first three essays focus on macroeconomic topics, examining issues related to the business cycle, fiscal and monetary policy, whereas the last one is focusing on a microeconomic topic, namely the relationship between schooling and child labor.
The first contribution investigates the effectiveness of macroeconomic policies in the recoveries periods in the Middle East, North Africa and Pakistan (MENAP). It is found that fiscal policy played a key role during the recoveries to potential output, although with weaker effects for the countries in the region that are more open to trade; monetary policy is found to have been less effective. The second essay explores the effects of the Medium-Term Expenditure Framework (MTEF) adoption on the main fiscal performance indicators, finding a positive and encouraging impact on fiscal discipline, allocative efficiency and technical efficiency, although the last one is not always robust. The third essay aims at identify the nexus between the excess of liquidity and commodity prices; in particular, it assesses whether the commodity prices react more powerfully than the consumer goods’ prices to changes in real money balances. The results show a positive relationship between real money and real commodity prices and provide empirical evidence for a stronger response of commodity prices with respect to consumer goods’ prices.
The last essay investigates the determinants of primary school enrollment, attendance and child labor in Bolivia, with a special attention at identifying the substitution and complementary relationships between schooling and working. The empirical findings reveal that the increase in enrollment is led by indigenous children and those living in urban areas. Moreover, contrary to common belief, being extremely poor and indigenous are the main determinants of school attendance; while extremely poor children increased their school attendance, they were not able to reduce child labor. On the other hand, indigenous children made them substitutes increasing schooling and reducing child labor.
Different econometric techniques have been used, among which Ordinary Least Squares, Fixed Effects, Instrumental Variables, Generalized Methods of Moments estimations, Stochastic Frontier Analysis, Cointegrated Vector Autoregression and Multivariate Probit models
Six-transmembrane epithelial antigen of the postate (STREAP): a potential target of immunotherapy of prostate cancer.
No full textImmunotherapy has been proposed as a complementary or alternative therapy for the treatment of advanced prostate cancer (PC), one of the leading causes of tumor-related mortality in men. From different approaches that have been tested in recent years, it is now becoming more evident that the choice of the appropriate antigen to target is crucial for the best outcome.
Generally tumor-associated antigens (TAAs) undergo peripheral tolerance during tumor progression, which dampens the efficacy of vaccination protocols. It can be hypothesized that the kinetic and depth of immune tolerance varies depending on the timing and relative expression of the TAA.
These differences may represent a key for successful immunotherapy approaches even in patients with advanced disease.
Aim of my thesis was to investigate the dynamics of CD8+ T cells specific for normal tissue antigens over-expressed during the spontaneous tumor development and progression in the transgenic adenocarcinoma of the mouse prostate (TRAMP) mice, a primary model of human PC.
We have found that Prostate Stem Cell Antigen (PSCA) and Six-Transmembrane Epithelial Antigen of the Prostate (STEAP), two well known PC-associated antigens, behave differently in term of immunological response when compared with the transgenic Tag IV antigen, which drives oncogenesis in TRAMP mice. While a dendritic cells (DC)-based immunization was able to elicit measurable immune responses for all three antigens in young males affected by mouse prostate intraepithelial neoplasia (mPIN), aged mice affected by PC progressively lost immunity against Tag IV and in part for PSCA, but not against STEAP. The findings correlated with the amount of antigens expressed in the prostate, therefore suggesting that tolerance against this type of TAA follows the same rule of that induced for tissue-associated antigens in peripheral tissues: the more the antigen is expressed the more tolerance is profound.
Finally, a combined therapy of allotransplantation and DC-STEAP vaccination effectively reduced tumor burden in TRAMP mice, underlying how this therapeutic strategy when targeted to a reliable antigen is able to restore cancer immunosurveillance
Spectral distributions of structured matrix-sequences: tools and applications.
No full textThis Ph.D. thesis provides a systematic and unifying treatment of the spectral analysis of matrix sequences collecting the state of the art of the research in this field and providing new advanced results which are interesting both from the theoretical and from the algorithmic point of view.
The first part, made up by Chapters 1–5 concerns the description and analysis of the available tools, together with their generalization including the development of new effective tools of analysis. The basic concept of “approximating class of sequences” is introduced and analyzed in depth. Some new results of great interest have been obtained. It is worth citing an extension of a perturbation result concerning the eigenvalues of Hermitian matrix sequences which are perturbed with non-Hermitian perturbations. These results have been applied to Toeplitz sequences, and to the Tilli class. The classes of g-circulant and g-Toeplitz matrix sequences are introduced as well, and their spectral analysis is carried out.
The second part, formed by Chapters 6–8 is addressed to applications. It contains several new and interesting results. A relevant role is played by the preconditioning of g-Toeplitz matrix sequences by means of g-circulant matrices with a specific attention to the regularizing properties which take their importance in the applications concerning image processing, filtering and restoration. Another interesting application concerns two-grid and multi-grid techniques.
A third application concerns the saddle point problem where once again the spectral approximation of a suitable matrix plays a fundamental role
Desarrollo endógeno en una región de frontera: Los Llanos Orientales, departamentos de Casanare y Meta (Colombia)
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The E-ELT adptive mirror: prototype and optical test
No full textGround-based optical-infrared 10m-class telescopes, such as Keck, Gemini, and Very Large Telescopes (VLT), are currently leading many of the astronomical research fields due to their unprecedented collecting areas. However, many new astrophysical quests arose from recent observations, justifying the need for even larger telescopes, with diameters > 30 m.
The European scientific community, led by the European Southern Observatory (ESO), takes part in this challenging competition whit the "European-Extremely Large Telescope" (E-ELT), a revolutionary project for a 40m-class telescope that will allow us addressing many of the most pressing unsolved questions about our Universe.
Building Extremely Large Telescopes asked for innovative technologies, from larger and repeatable optical manufacturing techniques to produce hundredths of aspherical off-axis hexagonal segments and large monolithic mirrors, or large thin optical shell mirrors, to better and faster controls (active and adaptive optics), together with more specialized focal plane instrumentations devoted to address specific astrophysical questions, more likely to large particle physics experiments.
Moreover the challenge of building extremely large telescope pushes forward the parallel ability to measure and test optical components of large sizes.
Adaptive Optics (AO) techniques allow to obtain enhanced ground-based astronomical observations, partially restoring diffraction-limited spatial resolutions, by compensating the degrading effects of the atmospheric turbulence. The delivered image quality of an AO-assisted telescope depends on the level of the correction of the wavefront error due to the atmosphere.
This work focuses on the adaptive deformable mirror unit (M4AU) of the E-ELT. During my Ph.D. study, I took part in the competitive "EELT-M4 project" study, led by an Italian-French consortium (Microgate, ADS, SAGEM, INAF-O.A.Brera).
Optical measurements were conceived, designed and performed on a similar, scaled-down, fully-representative prototype of the final system, to fully validate the proposed concept. Due to very stringent requirements in term of wavefront correction (10-100 nm rms), only interferometric optical setups were able to provide enough accuracy and sensitivity to carry out the work.
A set of three devices has been designed for the tests:
- a Ritchey-Common test setup (RCT), able to cover the full area of the M4AU DP optical surface with a single measurement, taken with a phase-shifting Fizeau interferometer;
- a Stitching Interferometric Setup (SIS), where a scanning smaller optical beam is able to reconstruct the same optical surface with increased capture range and spatial resolution, useful in the first steps of the calibration procedures;
- a piston sensing unit (PSU), which exploits the optical path difference between adjacent optical shells, after careful analysis of diffraction patterns.
Those devices, together with purposely designed control softwares and data reduction softwares,
were used during a 6-months measurement campaign, demonstrating the full compliance of the prototype system with the requirements to be obtained in the final system (flattening of each optical shell, co-phasing of the optical shells, optical stroke calibration, stability of calibration under time and changing environmental conditions).
Results have been positively reviewed by the EELT project office, and were used as feedback on the design of final optical test system, to be operated on the 2.5m M4AU unit
Effetti cardiovascolari dei farmaci antipsicotici di seconda generazione (SGA).
No full textIntroduction: The QTc prolongation by antipsychotic drugs is of major concern, especially in light of the data indicating an increased risk of sudden death in psychiatric patients taking these drugs. Sudden death in psychiatric patients could be partially attributed to drug-induced torsades de pointes and for this reason careful evaluation of QTc prolonging properties of antipsychotic drugs is needed.
Objectives: This study aims to evaluate QTc prolungation effects of second generation antipsychotic drugs
Methods: Subjects treated with atypical antipsychotic drugs since October 2008 were enrolled in the study. Patients have been evaluated in two steps with ECG before taking drugs (T0) and after 2 months of therapy. Patients drug-naive or after a pharmachological switch were enrolled.
Results: 49 patients (27 men; 22 women) accepted to join the research.
63 % of subjects were drug-naïve, 37 % had been treated before with typical or atypical antipsychotic drugs.
Prescribed drugs were Risperidone, Paliperidone, Aripiprazolo, Olanzapine, Ziprasidone and Quetiapine.
No significant difference occurred between T0 and T1 in QTc lenght in the whole examined group.
Ziprasidone and Olanzapine produced a non-significant drug-induced prolongation of QTc
