Sviluppo e applicazione di nuovi criteri per la verifica a fatica multiassiale di componenti strutturali in leghe di acciaio e alluminio

La presente Tesi ha per oggetto lo sviluppo e la validazione di nuovi criteri per la verifica a fatica multiassiale di componenti strutturali metallici . In particolare, i nuovi criteri formulati risultano applicabili a componenti metallici, soggetti ad un’ampia gamma di configurazioni di carico: carichi multiassiali variabili nel tempo, in modo ciclico e random, per alto e basso/medio numero di cicli di carico. Tali criteri costituiscono un utile strumento nell’ambito della valutazione della resistenza/vita a fatica di elementi strutturali metallici, essendo di semplice implementazione, e richiedendo tempi di calcolo piuttosto modesti. Nel primo Capitolo vengono presentate le problematiche relative alla fatica multiassiale, introducendo alcuni aspetti teorici utili a descrivere il meccanismo di danneggiamento a fatica (propagazione della fessura e frattura finale) di componenti strutturali metallici soggetti a carichi variabili nel tempo. Vengono poi presentati i diversi approcci disponibili in letteratura per la verifica a fatica multiassiale di tali componenti, con particolare attenzione all'approccio del piano critico. Infine, vengono definite le grandezze ingegneristiche correlate al piano critico, utilizzate nella progettazione a fatica in presenza di carichi multiassiali ciclici per alto e basso/medio numero di cicli di carico. Il secondo Capitolo è dedicato allo sviluppo di un nuovo criterio per la valutazione della resistenza a fatica di elementi strutturali metallici soggetti a carichi multiassiali ciclici e alto numero di cicli. Il criterio risulta basato sull'approccio del piano critico ed è formulato in termini di tensioni. Lo sviluppo del criterio viene affrontato intervenendo in modo significativo su una precedente formulazione proposta da Carpinteri e collaboratori nel 2011. In particolare, il primo intervento riguarda la determinazione della giacitura del piano critico: nuove espressioni dell'angolo che lega la giacitura del piano critico a quella del piano di frattura vengono implementate nell'algoritmo del criterio. Il secondo intervento è relativo alla definizione dell'ampiezza della tensione tangenziale e un nuovo metodo, noto come Prismatic Hull (PH) method (di Araújo e collaboratori), viene implementato nell'algoritmo. L'affidabilità del criterio viene poi verificata impiegando numerosi dati di prove sperimentali disponibili in letteratura. Nel terzo Capitolo viene proposto un criterio di nuova formulazione per la valutazione della vita a fatica di elementi strutturali metallici soggetti a carichi multiassiali ciclici e basso/medio numero di cicli. Il criterio risulta basato sull'approccio del piano critico, ed è formulato in termini di deformazioni. In particolare, la formulazione proposta trae spunto, come impostazione generale, dal criterio di fatica multiassiale in regime di alto numero di cicli discusso nel secondo Capitolo. Poiché in presenza di deformazioni plastiche significative (come quelle caratterizzanti la fatica per basso/medio numero di cicli di carico) è necessario conoscere il valore del coefficiente efficace di Poisson del materiale, vengono impiegate tre differenti strategie. In particolare, tale coefficiente viene calcolato sia per via analitica, che per via numerica, che impiegando un valore costante frequentemente adottato in letteratura. Successivamente, per validarne l'affidabilità vengono impiegati numerosi dati di prove sperimentali disponibili in letteratura; i risultati numerici sono ottenuti al variare del valore del coefficiente efficace di Poisson. Inoltre, al fine di considerare i significativi gradienti tensionali che si verificano in presenza di discontinuità geometriche, come gli intagli, il criterio viene anche esteso al caso dei componenti strutturali intagliati. Il criterio, riformulato implementando il concetto del volume di controllo proposto da Lazzarin e collaboratori, viene utilizzato per stimare la vita a fatica di provini con un severo intaglio a V, realizzati in lega di titanio grado 5. Il quarto Capitolo è rivolto allo sviluppo di un nuovo criterio per la valutazione del danno a fatica di elementi strutturali metallici soggetti a carichi multiassiali random e alto numero di cicli. Il criterio risulta basato sull'approccio del piano critico ed è formulato nel dominio della frequenza. Lo sviluppo del criterio viene affrontato intervenendo in modo significativo su una precedente formulazione proposta da Carpinteri e collaboratori nel 2014. In particolare, l’intervento riguarda la determinazione della giacitura del piano critico, e nuove espressioni dell'angolo che lega la giacitura del piano critico con quella del piano di frattura vengono implementate nell'algoritmo del criterio. Infine, l’affidabilità del criterio viene verificata impiegando numerosi dati di prove sperimentali disponibili in letteratura.

Studies of the cationic polymerisation of vinylic and energetic cyclic ether monomers

The cationic polymerisation of various monomers, including cyclic ethers bearing energetic nitrate ester (-ON02) groups, substituted styrenes and isobutylene has been investigated. The main reaction studied has been the ring-opening polymerisation of 3- (nitratomethyl)-3-methyl oxetane (NIMMO) using the alcohol/BF3.0Et2 binary initiator system. A series of di-, tri- and tetrafunctional telechelic polymers has been synthesised. In order to optimise the system, achieve controlled molecular weight polymers and understand the mechanism of polymerisation the effects of certain parameters on the molecular weight distribution, as determined by Size Exclusion Chromatography, have been examined. This shows the molecular weight achieved depends on a combination of factors including -OH concentration, addition rate of monomer and, most importantly, temperature. A lower temperature and OH concentration tends to produce higher molecular weight, whereas, slower addition rates of monomer, either have no significant effect or produce a lower molecular weight polymer. These factors were used to increase the formation of a cyclic oligomer, by a side reaction, and suggest, that the polymerisation of NIMMO is complicated with endbiting and back biting reactions, along with other transfer/termination processes. These observations appear to fit the model of an active-chain end mechanism. Another cyclic monomer, glycidyl nitrate (GLYN), has been polymerised by the activated monomer mechanism. Various other monomers have been used to end-cap the polymer chains to produce hydroxy ends which are expected to form more stable urethane links, than the glycidyl nitrate ends, when cured with isocyanates. A novel monomer, butadiene oxide dinitrate (BODN), has been prepared and its homopolymerisation and copolymerisation with GL YN studied. In concurrent work the carbocationic polymerisations of isobutylene or substituted styrenes have been studied. Materials with narrow molecular weight distributions have been prepared using the diphenyl phosphate/BCl3 initiator. These systems and monomers are expected to be used in the synthesis of thermoplastic elastomers.

Navigazione di articoli scientifici e citazioni: un ambiente scalabile e flessibile

Questo lavoro di tesi si concentra sulle estensioni apportate a BEX (Bibliographic Explorer), una web app finalizzata alla navigazione di pubblicazioni scientifiche attraverso le loro citazioni. Il settore in cui si colloca è il Semantic Publishing, un nuovo ambito di ricerca derivato dall'applicazione delle tecnologie del Semantic Web allo Scholarly Publishing, che ha come scopo la pubblicazione di articoli accademici a cui vengono associati metadati semantici. BEX nasce all'interno del Semantic Lancet Project del Dipartimento di Informatica dell'Università di Bologna, il cui obiettivo è costruire un Linked Open Dataset di pubblicazioni accademiche, il Semantic Lancet Triplestore (SLT), e fornire strumenti per la navigazione ad alto livello e l'uso approfondito dei dati in esso contenuti. Gli scholarly Linked Open Data elaborati da BEX sono insiemi di triple RDF conformi alle ontologie SPAR. Originariamente BEX ha come backend il dataset SLT che contiene metadati relativi alle pubblicazioni del Journal Of Web Semantics di Elsevier. BEX offre viste avanzate tramite un'interfaccia interattiva e una buona user-experience. L'utente di BEX è principalmente il ricercatore universitario, che per compiere le sue attività quotidiane fa largo uso delle Digital Library (DL) e dei servizi che esse offrono. Dato il fermento dei ricercatori nel campo del Semantic Publishing e la veloce diffusione della pubblicazione di scholarly Linked Open Data è ragionevole pensare di ampliare e mantenere un progetto che possa provvedere al sense making di dati altrimenti interrogabili solo in modo diretto con queries SPARQL. Le principali integrazioni a BEX sono state fatte in termini di scalabilità e flessibilità: si è implementata la paginazione dei risultati di ricerca, l'indipendenza da SLT per poter gestire datasets diversi per struttura e volume, e la creazione di viste author centric tramite aggregazione di dati e comparazione tra autori.

PARLEN: uno strumento modulare per l’analisi di articoli e il riconoscimento di entità

La tesi descrive PARLEN, uno strumento che permette l'analisi di articoli, l'estrazione e il riconoscimento delle entità - ad esempio persone, istituzioni, città - e il collegamento delle stesse a risorse online. PARLEN è inoltre in grado di pubblicare i dati estratti in un dataset basato su principi e tecnologie del Semantic Web.

Characterisation of an ubiquitin binding CUE domain in presenilin-1

The presenilins are the catalytic component of the gamma-secretase protease complex, involved in the regulated intramembrane proteolysis of numerous type-1 transmembrane proteins, including Amyloid precursor protein (APP) and Notch. In addition to their role in the γ-secretase complex the presenilins are involved in a number of γ-secretase independent functions such as calcium homeostasis, apoptosis, inflammation and protein trafficking. Presenilin function is known to be regulated through posttranslational modifications like endoproteolysis, phosphorylation and ubiquitination. Using a bioinformatics and protein sequence analysis approach this lab has identified a putative ubiquitin binding CUE domain in the presenilins. The aim of this project was to characterise the function of the presenilin CUE domains. Firstly, the presenilins are shown to contain a functional ubiquitin-binding CUE domain that preferentially binds to K63-linked polyubiquitin chains. The PS1 CUE domain is shown to be dispensable for PS1 endoproteolysis and γ-secretase mediated cleavage of APP, Notch and IL-1R1. This suggests the PS1 CUE domain is involved in a γ-secretase independent PS1 function. Our hypothesis is that the PS1 CUE domain is involved in regulating PS1’s intermolecular protein-protein interactions or intramolecular PS1:PS1 interactions. Here the PS1 CUE domain is shown to be dispensable for the interaction of PS1 and the K63-linked polyubiquitinated PS1 interacting proteins P75NTR, IL-1R1, TRAF6, TRAF2 and RIP1. To further investigate PS1 CUE domain function a mass spectrometry proteomics based approach is used to identify PS1 CUE domain interacting proteins. This proteomics approach demonstrated that the PS1 CUE domain is not required for PS1 dimerization. Instead a number of proteins thatinteract with the PS1 CUE domain are identified as well as proteins whose interaction with PS1 is downregulated by the presence of the PS1 CUE domain. Bioinformatic analysis of these proteins suggests possible roles for the PS1 CUE domain in regulating cell signalling, ubiquitination or cellular trafficking.

La generazione di modelli tridimensionali densi in ambito architettonico mediante la fotogrammetria digitale

The Italian territory offers a wide range of treasures in the field of Cultural Assets. This is a highly relevant property, which needs an accurate management and preservation performed by appropriate tools, also giving attention to the maintenance and safeguard from risk factors. Nowadays the increasing development of new digital technologies, added by remarkable steps forward got by the subject of Geomatic makes possible an efficient integration among different techniques, helped also by spread of solutions to improve the data import-export and transmission between different devices. The main objective of this thesis is to experience the photogrammetric restitution implemented in a commercial software of digital photogrammetry, in order to generate a dense 3D model of the facade of the Basilica Sant'Apollinare Nuovo in Ravenna. The 1st Chapter, after a general introduction regarding the 3D survey of Cultural Heritage and some considerations linked to the use of digital photogrammetry in this field, is focused to analyze the case of stereoscopic and the monoscopic approach. In particular, it develops the theme of close-range photogrammetry. The 2nd Chapter, exposes the theme of digital images, from color theory until their appearing on the monitor. The 3rd Chapter, develops the case study of the Basilica di Sant'Apollinare Nuovo, the historical, architectural and religious of the same. Also, it is examined the issue of photogrammetry and laser scanning of the case study. The final part of the same chapter, treats the processing of data processing the software Agisoft PhotoScan, in order to generate, by means of Structure from Motion technique, a digital geometric 3D model of the Basilica Facade. The digital model has been scaled on the basis of measurements made on the field. With the software it was possible to accomplish the three phases of the photogrammetric data processing: internal orientation, exterior orientation and restitution.

Sintesi e Caratterizzazione di Elettrodi Modificati Chimicamente con nuovi complessi Carbenici del Ferro

The Chemically Modified Electrodes (CME) are widely used in electroanalytical chemistry as chemical sensors. The interest in the covalent anchoring of a redox mediator on the electrode surface is increasing, because it allows the sensibility and the selectivity of this kind of systems to improve. My work is situated in this field of research and involves the synthesis of new Iron(0) complexes that contain cyclopentadienone, N-heterocyclic carbene (NHC) and carbonyl ancillary ligands. These complexes have shown electrochemical properties similar to those of ferrocene (organometallic compound widely used as electrochemical sensor). These complexes have been properly functionalized with a EDOT group in the NHC ligand side chain that it was after used for the realization of Electrochemically Modified PEDOT thanks to copolymerization reaction between the functionalized complex and the EDOT in different amounts. All the synthetic steps were assisted by suitable characterizations (NMR, IR, ESI-MS, cyclic voltammetry and X-ray for the monomeric compound as imidazolium salt and NHC functionalized complexes; cyclic voltammetry, IR e SEM for the copolymers). The properties of the polymer as a selective sensor was preliminarily investigated for dopamine and 2-propanol.

Time-resolved fluorescence observation of di-tyrosine formation in horseradish peroxidase upon ultrasound treatment leading to enzyme inactivation

The application of ultrasound to a solution can induce cavitional phenomena and generate high localised temperatures and pressures. These are dependent of the frequency used and have enabled ultrasound application in areas such as synthetic, green and food chemistry. High frequency (100 kHz to 1 MHz) in particular is promising in food chemistry as a means to inactivate enzymes, replacing the need to use periods of high temperature. A plant enzyme, horseradish peroxidase, was studied using time-resolved fluorescence techniques as a means to assess the effect of high frequency (378 kHz and 583 kHz) ultrasound treatment at equivalent acoustic powers. This uncovered the fluorescence emission from a newly formed species, attributed to the formation of di-tyrosine within the horseradish peroxidase structure caused by auto-oxidation, and linked to enzyme inactivation.

Copio (Baschi-Montecchio, Terni). Un avamposto etrusco sulla sinistra del Tevere Presentazione dei risultati delle indagini di superficie (maggio - giugno 2015)

This paper attempts to demonstrate the importance of the archaeological area of Copio, in province of Terni (Italy). Discovered for the first time in the 1980 by the local historian then mentioned in 2001 and in 2003 in two different archaeological publications, the site of Copio started to arouse interest for its position, lying on a hilltop above one of the most interesting pre-Roman necropolis of Umbria (Vallone di San Lorenzo). The link between the well-known necropolis and Copio is today well-accepted. The aim of this paper, based on a field-walking survey and the analisys of the archaeological finds, is to demonstrate the importance of this area during the pre-Roman period as a commercial bridgehead linked to Volsinii. Strategically lying only one km to east from the Tiber, it should have enjoyed this important and commercial path for the local trade moving goods in incoming and outcoming.

Covalent/crystallite cross-linked co-network hydrogels : an efficient and simple strategy for mechanically strong and tough hydrogels

Covalent/crystallite cross-linked co-network hydrogels have been prepared using epoxy and PVA through a cyclic freezing-thawing process. The PVA/epoxy hydrogels show enhanced mechanical strength and toughness. PVA/epoxy hydrogels with 4 wt% epoxy loading display maximum tensile strength and toughness of 1.1 MPa and 2838 kJ/m3 respectively. The fracture toughness of PVA/epoxy hydrogels ranges from 160 to 450 J/m2. Radius of gyration and fractal information of the hydrogels were obtained by fitting the SAXS data to the Guinier and power law models. The enhanced mechanical properties are attributed to the increase in covalent bonding and decrease in crystallite distribution with an increase in epoxy content. However a larger hysteresis is shown for PVA/epoxy hydrogels due to irreversible destruction of covalent bonds between epoxy and PVA.

Sulfur transfer and activation by ubiquitin-like modifier system Uba4•Urm1 link protein urmylation and tRNA thiolation in yeast

Urm1 is a unique dual-function member of the ubiquitin protein family and conserved from yeast to man. It acts both as a protein modifier in ubiquitin-like urmylation and as a sulfur donor for tRNA thiolation, which in concert with the Elongator pathway forms 5-methoxy-carbonyl-methyl-2-thio (mcm5s2) modified wobble uridines (U34) in anticodons. Using Saccharomyces cerevisiae as a model to study a relationship between these two functions, we examined whether cultivation temperature and sulfur supply previously implicated in the tRNA thiolation branch of the URM1 pathway also contribute to proper urmylation. Monitoring Urm1 conjugation, we found urmylation of the peroxiredoxin Ahp1 is suppressed either at elevated cultivation temperatures or under sulfur starvation. In line with this, mutants with sulfur transfer defects that are linked to enzymes (Tum1, Uba4) required for Urm1 activation by thiocarboxylation (Urm1-COSH) were found to maintain drastically reduced levels of Ahp1 urmylation and mcm5s2U34 modification. Moreover, as revealed by site specific mutagenesis, the Stransfer rhodanese domain (RHD) in the E1-like activator (Uba4) crucial for Urm1-COSH formation is critical but not essential for protein urmylation and tRNA thiolation. In sum, sulfur supply, transfer and activation chemically link protein urmylation and tRNA thiolation. These are features that distinguish the ubiquitin-like modifier system Uba4•Urm1 from canonical ubiquitin family members and will help elucidate whether, in addition to their mechanistic links, the protein and tRNA modification branches of the URM1 pathway may also relate in function to one another.

Time-Dependent Density Functional Molecular Orbital and Excited State Calculations on Bis(porphyrinyl)butadiynes in the Monocationic, Neutral, Monoanionic, and Dianionic Oxidation States

We report a theoretical study of the multiple oxidation states (1+, 0, 1−, and 2−) of a meso,meso-linked diporphyrin, namely bis[10,15,20-triphenylporphyrinatozinc(II)-5-yl]butadiyne (4), using Time-Dependent Density Functional Theory (TDDFT). The origin of electronic transitions of singlet excited states is discussed in comparison to experimental spectra for the corresponding oxidation states of the close analogue bis{10,15,20-tris[3‘,5‘-di-tert-butylphenyl]porphyrinatozinc(II)-5-yl}butadiyne (3). The latter were measured in previous work under in situ spectroelectrochemical conditions. Excitation energies and orbital compositions of the excited states were obtained for these large delocalized aromatic radicals, which are unique examples of organic mixed-valence systems. The radical cations and anions of butadiyne-bridged diporphyrins such as 3 display characteristic electronic absorption bands in the near-IR region, which have been successfully predicted with use of these computational methods. The radicals are clearly of the “fully delocalized” or Class III type. The key spectral features of the neutral and dianionic states were also reproduced, although due to the large size of these molecules, quantitative agreement of energies with observations is not as good in the blue end of the visible region. The TDDFT calculations are largely in accord with a previous empirical model for the spectra, which was based simplistically on one-electron transitions among the eight key frontier orbitals of the C4 (1,4-butadiyne) linked diporphyrins.