Synthesis of Heteroleptic Redox-active and Spin-crossover Complexes

The following research regarding heteroleptic redox-active complexes with the potential for spin-crossover is synthetic in nature. The intent behind incorporating the Schiff base ligand N-(8-quinolyl)salicylaldimine with some redox-active species into a mixed ligand complex featuring a d4-d7 metal ion center was to prime the material for spin-crossover based on strong intermolecular interactions that would enhance cooperativity of the system. Single component systems that display spin-crossover behaviour paired with other physical properties like electrical conductivity hold significance in the field of multifunctional materials, of which there are few examples that feature mixed ligand systems. Information describing this type of chemistry and the magnetic interactions that govern these characteristics is introduced in the first chapter of this work. The synthetic strategies toward mixed ligand complexes in the form of [(Qsal)Fe(RAL)]+X- and [(Qsal)Co(RAL)]+X- have been realized from the use of mononuclear [(Qsal)FeCl2(CH3OH)] and [(Qsal)Co(OAc)]+OAc- species, respectively. The redox-active ligand (RAL) component is an arylazo ligand like 10-(8-quinolylazo)-9-phenanthrol (Qapl) or 1-(2-Pyridylazo)-2-phenanthrol (Papl), which possess a low-lying π* MO that makes them susceptible to multi-step reductions that give rise to radical intermediates. Heteroleptic complexes that were synthesized and isolated like [(Qsal)Fe(Qapl)]+BPh4-, [(Cl-Qsal)Fe(Qapl)]+BPh4-- and homoleptic [Fe(Qapl)2]+BPh4- were diffracted and measured several intermolecular π-π contacts of distances typically between 3.5-3.7 Å, often between the phenanthrene rings of adjacent Qapl ligands. Complexes In the form of [(Qsal)Fe(Qapl)]+X (X= BPh4- or SCN-) showed early onset of spin transition in solution usually beyond 298 K. These complexes were overly reduced in the glovebox which resulted in their deterioration, presumably from the cleavage of the RAL azo bond. The framework developed for the heteroleptic Fe3+ coordination chemistry was applied to cobalt, with some amendments, and afforded several heterleoptic Co3+ complexes using Qsal with the arylazo ligands Qapl and Papl. The heteroleptic cobalt complexes presented here were found to be LS Co3+ which is diamagnetic. However, there is potential under inert atmosphere to produce Co2+ and possibly a phenoxyl radical species with redox-active valence tautomers

Ottimizzazione numerico sperimentale del processo di estrusione di leghe leggere

L'estrusione a caldo di leghe leggere è un processo di formatura dove, imponendo grandi deformazioni ed elevate velocità di deformazione, è possibile ottenere profili a sezione costante di alta complessità, come profili multi-cavità e/o con spessori variabili. Negli ultimi anni, la richiesta di requisiti sempre più stringenti in termini di resistenza, qualità e precisione, combinata all’aumento della concorrenza di mercato, ha reso necessario un attento controllo e ottimizzazione del processo già in fase di progettazione per produrre componenti privi di difetti, per massimizzare la produttività e ridurre gli scarti di materiale. In questo scenario, l'obiettivo della presente tesi di dottorato è il monitoraggio e l'ottimizzazione del processo di estrusione sia in termini di identificazione e controllo dei parametri più significativi, sia in termini di progettazione degli utensili e analisi dei difetti. In particolare, il lavoro si è focalizzato sullo studio del processo di estrusione con matrice raffreddata ad azoto liquido per evitare difetti nel profilo e per migliorare la vita utile degli utensili e sull'analisi e la previsione dei difetti di charge welds e billet skin. Con riferimento alla prima tematica, anche se l'utilizzo dell'azoto nell'estrusione è una pratica industriale consolidata, lo stato dell’arte è carente di un approccio sistematico per la progettazione e l'ottimizzazione dei canali di raffreddamento. Infatti, i canali sono solitamente realizzati sulla base dell’esperienza del progettista, rendendo difficile la gestione e il controllo delle numerose variabili in gioco relative, per esempio, alla geometria e alla posizione del canale, alle proprietà del refrigerante e ai parametri di processo. In questo contesto, l'uso di modelli numerici avanzati può supportare l'implementazione di una metodologia sistematica per garantire un design efficiente in termini di raffreddamento già durante la fase di progettazione della matrice. In termini di scarto di materiale, i difetti di charge welds e billet skin riducono di molto le proprietà meccaniche ed estetiche del profilo per la presenza di zone di transizione con diversa microstruttura, alterazioni chimiche e presenza di contaminanti (ossidi, lubrificanti...). Pertanto, per la minimizzazione degli scarti risulta necessario uno studio approfondito dei difetti per poterne prevedere la comparsa e l’evoluzione durante il processo. Durante il progetto sono state eseguite diverse campagne sperimentali per monitorare sia l’evoluzione del campo termico durante il processo di estrusione con raffreddamento ad azoto sia per valutare l'influenza dei parametri di processo sull'evoluzione dei difetti. Inoltre, gran parte del lavoro è stato dedicato all’implementazione e alla validazione di modelli numerici da utilizzare come supporto mirato all'ottimizzazione di processo. Tra i risultati più significativi, il modello numerico per il raffreddamento ha evidenziato che modellando l’azoto come fluido monofase (liquido o gassoso), si ottengono buoni risultati macroscopici sull’evoluzione del campo termico, ma i limiti riscontrati hanno spinto verso un modello più complesso per tenere conto del cambiamento di fase. Il confronto numerico-sperimentale ha mostrato errori medi inferiori all'8% sia con raffreddamento sia senza. Anche in termini di estensione ed insorgenza dei difetti di charge welds e billet skin sono stati ottenuti buoni risultati numerici, soprattutto se paragonati con le attuali formulazioni teoriche ed empiriche presenti in letteratura (errori superiori al 50%). I risultati ottenuti suggeriscono l'affidabilità degli strumenti di simulazione sviluppati e la loro facile integrabilità industriale come supporto sia per l'ottimizzazione di processo che per la progettazione degli stampi.The hot extrusion of light alloys is a forming process widely used to manufacture constant cross-section profiles of any complexity, as multi-hollow and variable thicknesses profiles, by imposing high deformations rates. In the last years, requirements for high strength, quality and precision continuously increased, together with a steep increasing of the market competition, thus making mandatory an accurate setting and optimization of the extrusion process at the design stage to produce defect-free profiles, to maximize the production rates and to reduce the material scraps. In this scenario, aim of the present PhD thesis was a comprehensive monitoring and optimization of the extrusion process in terms of key-parameters identification and control, tooling design and defects assessment. More specifically, work has been focused on the investigation of the process performed with a die cooled with liquid nitrogen to avoid thermal defects in the profile and to improve the tooling set life, and on the analysis and prediction of charge welds and skin defects to reduce the material scrap. Concerning the first topic, even if the use of nitrogen in extrusion is an industrial consolidated technology, a systematic approach for the design, optimization and testing of the cooling channel is still missing in literature. Cooling channels are usually manufactured according to the designer’s experience, thus making extremely challenging the managing of the many variables involved, such as those of the channel geometry and position, of the coolant properties and of the cooling parameters. However, the use of advanced numerical tools can support the implementation of an efficient approach for the selection of an optimal cooling solution at the process-die design stage. In terms of material scrap, charge welds (front-end) and billet skin (back-end) are both defects that drastically reduce the mechanical and the esthetical properties of the final profile due to the presence of transition zones with different microstructure, altered chemical composition and contaminants (oxides, lubricants...). Then, an in-depth knowledge and an accurate predictability of these defects evolution represent a mandatory requirement for the scrap minimization. During the PhD period, different experimental campaigns have been performed to monitor the thermal field during the extrusion process with a nitrogen cooled die as well as to assess the influence of process parameters on the charge-skin defects evolution. In addition, an extensive numerical work has been accomplished by implementing and validating predictive models to be used as key support tools for process optimization. As main outcomes of the work, the proposed numerical model for nitrogen cooling showed that a discrete modelling approach (gaseous or liquid-only cooling), even if providing useful indications on the average thermal distribution, show some limitations thus pushing toward a more sophisticated mixed model to account the nitrogen phase-change. The experimental-numerical comparison showed a good matching of the results in terms of temperature prediction with average errors below 8% both in uncooled and in nitrogen cooled conditions. A good numerical prediction was found also in terms of charge welds and billet skin evolution in the investigated profiles. Numerical results evidenced a good predictability in terms of defects extend and onset, especially if data are compared with the theoretical formulas reported in literature that showed errors greater than 50% with respect to experimental data. The achieved results suggest the reliability of the developed and tested simulation tools and their easy integrability in a flexible procedure to be used for process and die-design optimization

Comment les médecins urgentologues raisonnent-ils au regard des spécificités de leur cadre et leur mode d’exercice ?

Contexte : malgré les particularités de l’environnement de pratique de la médecine d’urgence, il n’existe pas de recherches spécifiquement menées sur la thématique du raisonnement clinique dans cette spécialité. Nous avons souhaité mieux comprendre comment les médecins urgentologues raisonnent dans le cadre de la prise en charge initiale des patients. Méthode : une posture épistémologique interprétative a été adoptée à travers un devis de recherche qualitatif de type ethnographique. Des entretiens ont été réalisés auprès de médecins urgentologues experts, à l’issue de la prise en charge d’un patient réel. Ces entretiens reposaient notamment sur la visualisation de l’enregistrement vidéo en perspective subjective située, obtenu grâce à l'usage d'une microcaméra fixée sur la tempe ou la branche de lunettes des praticiens. Résultats : les hypothèses diagnostiques sont générées très précocement par les médecins, parfois même avant la rencontre avec le patient, sur la base de la prise en compte d’un nombre très limité d’informations, pour certaines contextuelles. Cinq hypothèses étaient en moyenne générées lors de la rencontre initiale et au moins une était une hypothèse de gravité. Aucune n’était formellement éliminée ou validée sans résultats d’examens complémentaires. Un jugement précoce quant à la gravité de la situation permettait également aux médecins d’orienter leurs intentions initiales vers des buts diagnostiques ou thérapeutiques. Les experts raisonnaient le plus souvent de manière intuitive. Ils prenaient en compte les spécificités de leur environnement professionnel en étant, par exemple, vigilants au temps, au caractère potentiellement évolutif de l’état clinique du malade et au devenir d’aval de celui-ci. Conclusion : l’identification du raisonnement clinique des médecins urgentologues offre des perspectives importantes en matière de pratique de la médecine d’urgence, et de formation des résidents dans cette discipline. La méthode originale de recueil des données pourrait en outre être réexploitée dans le cadre de travaux ultérieurs

An analysis of clinical reasoning through a recent and comprehensive approach: the dual-process theory

Context. Clinical reasoning plays a major role in the ability of doctors to make diagnoses and decisions. It is considered as the physician's most critical competence, and has been widely studied by physicians, educationalists, psychologists and sociologists. Since the 1970s, many theories about clinical reasoning in medicine have been put forward.Purpose. This paper aims at exploring a comprehensive approach: the “dual-process theory”, a model developed by cognitive psychologists over the last few years.Discussion. After 40 years of sometimes contradictory studies on clinical reasoning, the dual-process theory gives us many answers on how doctors think while making diagnoses and decisions. It highlights the importance of physicians’ intuition and the high level of interaction between analytical and non-analytical processes. However, it has not received much attention in the medical education literature. The implications of dual-process models of reasoning in terms of medical education will be discussed

Efficiency of Conformal Cooling Channels Inserts for Extrusion Dies

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Experimental analysis and modeling of the recrystallization behaviour of a AA6060 extruded profile

The microstructure of Al-Mg-Si alloys is gaining nowadays an increasing industrial interest because it influences the strength, crash, corrosion and esthetic properties of the extruded profiles. In order to investigate and predict the recrystallization behaviour in the extrusion of 6XXX aluminum alloys, experimental and numerical activities are still needed. In this work, the extrusion of an industrial-scale AA6060 aluminum alloy hollow profile was carried out. An innovative recrystallization model was developed and optimized by comparing the microstructural data experimentally acquired with the outputs of the simulation performed using the Finite Element commercial code Qform Extrusion. A good correlation between numerical prediction and experimental data was found, thus proving the reliability of the proposed AA6060 recrystallization model