Solving the cooling flow problem through mechanical AGN feedback

A fundamental gap in the current understanding of collapsed structures in the universe concerns the thermodynamical evolution of the ordinary, baryonic component. Unopposed radiative cooling of plasma would lead to the cooling catastrophe, a massive inflow of condensing gas toward the centre of galaxies, groups and clusters. The last generation of multiwavelength observations has radically changed our view on baryons, suggesting that the heating linked to the active galactic nucleus (AGN) may be the balancing counterpart of cooling. In this Thesis, I investigate the engine of the heating regulated by the central black hole. I argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. dramatically quenching the cooling rates for several billion years without destroying the cool-core structure. Using an upgraded version of the parallel 3D hydrodynamic code FLASH, I show that anisotropic AGN outflows can further reproduce fundamental observed features, such as buoyant bubbles, cocoon shocks, sonic ripples, metals dredge-up, and subsonic turbulence. The latter is an essential ingredient to drive nonlinear thermal instabilities, which cause cold gas condensation, a residual of the quenched cooling flow and, later, fuel for the AGN feedback engine. The self-regulated outflows are systematically tested on the scales of massive clusters, groups and isolated elliptical galaxies: in lighter less bound objects the feedback needs to be gentler and less efficient, in order to avoid drastic overheating. In this Thesis, I describe in depth the complex hydrodynamics, involving the coupling of the feedback energy to that of the surrounding hot medium. Finally, I present the merits and flaws of all the proposed models, with a critical eye toward observational concordance.

Neuroinflammation and the role of glia: relevance for neurodegenerative and neurosupportive roles

Inflammation is thought to contribute to the pathogenesis of neurodegenerative diseases. Among the resident population of cells in the brain, astroglia have been suggested to actively participate in the induction and regulation of neuroinflammation by controlling the secretion of local mediators. However, the initial cellular mechanisms by which astrocytes react to pro-inflammatory molecules are still unclear. Our study identified mitochondria as highly sensitive organelles that rapidly respond to inflammatory stimuli. Time-lapse video microscopy revealed that mitochondrial morphology, dynamics and motility are drastically altered upon inflammation, resulting in perinuclear clustering of mitochondria. These mitochondrial rearrangements are accompanied by an increased formation of reactive oxygen species and a recruitment of autophagic vacuoles. 24 to 48 hours after the acute inflammatory stimulus, however, the mitochondrial network is re-established. Strikingly, the recovery of a tubular mitochondrial network is abolished in astrocytes with a defective autophagic response, indicating that activation of autophagy is required to restore mitochondrial dynamics. By employing co-cultivation assays we observed that primary cortical neurons undergo degeneration in the presence of inflamed astrocytes. However, this effect was not observed when the primary neurons were grown in conditioned medium derived from inflamed astrocytes, suggesting that a direct contact between astrocytes and neurons mediates neuronal dysfunction upon inflammation. Our results suggest that astrocytes react to inflammatory stimuli by transiently rearranging their mitochondria, a process that involves the autophagic machinery.

Melanopsin Retinal Ganglion Cells: relevance to circadian rhythms and sleep in neurodegeneration

In this PhD thesis 3 projects were addressed focusing on the melanopsin retinal ganglion cells (mRGCs) system and its relevance for circadian rhythms and sleep in neurodegeneration. The first project was aimed at completing the characterization of mRGCs system in hereditary optic neuropathies (LHON and DOA). We confirmed that mRGCs are relatively spared also in post-mortem retinal specimens of a DOA case and pupillometric evaluation of LHON patients showed preservation of the pupillary light reflex, with attenuated responses compared to controls. Cell studies failed to indicate a protective role exerted by melanopsin itself. The second project was aimed at characterizing the possible occurrence of optic neuropathy and rest-activity circadian rhythm dysfunction in Alzheimer (AD) and Parkinson disease (PD), as well as, at histological level, the possible involvement of mRGCs in AD. OCT studies demonstrated a subclinical optic neuropathy in both AD and PD patients, with a different pattern involving the superior and nasal quadrants in AD and the temporal quadrant in PD. Actigraphic studies demonstrated a tendency towards an increased intradaily variability (IV) and reduced relative amplitude (RA) of rest-activity circadian rhythm in AD and a significant increased IV a reduced RA in PD. Immunohistochemical analysis of post-mortem retinal specimens and optic nerve cross-sections of neuropathologically confirmed AD cases demonstrated a significant loss of mRGCs and a nearly significant loss of axons in AD compared to controls. The mRGCs were affected in AD independently from age and magnitude of axonal loss. Overall these results suggest a role of the mRGCs system in the pathogenesis of circadian dysfunction in AD. The third project was aimed at evaluating the possible association between a single nucleotide polymorphism of the OPN4 gene and chronotype or SAD, failing to find any significant association with chronotype, but showing a non-significant increment of TT genotype in SAD.

Nature and relevance of inherited blueprints on business models choices and innovation: an assessment

One important metaphor, referred to biological theories, used to investigate on organizational and business strategy issues is the metaphor about heredity; an area requiring further investigation is the extent to which the characteristics of blueprints inherited from the parent, helps in explaining subsequent development of the spawned ventures. In order to shed a light on the tension between inherited patterns and the new trajectory that may characterize spawned ventures’ development we propose a model aimed at investigating which blueprints elements might exert an effect on business model design choices and to which extent their persistence (or abandonment) determines subsequent business model innovation. Under the assumption that academic and corporate institutions transmit different genes to their spin-offs, we hence expect to have heterogeneity in elements that affect business model design choices and its subsequent evolution. This is the reason why we carry on a twofold analysis in the biotech (meta)industry: under a multiple-case research design, business model and especially its fundamental design elements and themes scholars individuated to decompose the construct, have been thoroughly analysed. Our purpose is to isolate the dimensions of business model that may have been the object of legacy and the ones along which an experimentation and learning process is more likely to happen, bearing in mind that differences between academic and corporate might not be that evident as expected, especially considering that business model innovation may occur.

Riabilitazione e valutazione di pazienti con deficit neurologici mediante l'utilizzo di realtà virtuale, feedback aumentati, sensori inerziali e tecnologie video a basso costo.

La neuroriabilitazione è un processo attraverso cui individui affetti da patologie neurologiche mirano al conseguimento di un recupero completo o alla realizzazione del loro potenziale ottimale benessere fisico, mentale e sociale. Elementi essenziali per una riabilitazione efficace sono: una valutazione clinica da parte di un team multidisciplinare, un programma riabilitativo mirato e la valutazione dei risultati conseguiti mediante misure scientifiche e clinicamente appropriate. Obiettivo principale di questa tesi è stato sviluppare metodi e strumenti quantitativi per il trattamento e la valutazione motoria di pazienti neurologici. I trattamenti riabilitativi convenzionali richiedono a pazienti neurologici l’esecuzione di esercizi ripetitivi, diminuendo la loro motivazione. La realtà virtuale e i feedback sono in grado di coinvolgerli nel trattamento, permettendo ripetibilità e standardizzazione dei protocolli. È stato sviluppato e valutato uno strumento basato su feedback aumentati per il controllo del tronco. Inoltre, la realtà virtuale permette l’individualizzare il trattamento in base alle esigenze del paziente. Un’applicazione virtuale per la riabilitazione del cammino è stata sviluppata e testata durante un training su pazienti di sclerosi multipla, valutandone fattibilità e accettazione e dimostrando l'efficacia del trattamento. La valutazione quantitativa delle capacità motorie dei pazienti viene effettuata utilizzando sistemi di motion capture. Essendo il loro uso nella pratica clinica limitato, una metodologia per valutare l’oscillazione delle braccia in soggetti parkinsoniani basata su sensori inerziali è stata proposta. Questi sono piccoli, accurati e flessibili ma accumulano errori durante lunghe misurazioni. È stato affrontato questo problema e i risultati suggeriscono che, se il sensore è sul piede e le accelerazioni sono integrate iniziando dalla fase di mid stance, l’errore e le sue conseguenze nella determinazione dei parametri spaziali sono contenuti. Infine, è stata presentata una validazione del Kinect per il tracking del cammino in ambiente virtuale. Risultati preliminari consentono di definire il campo di utilizzo del sensore in riabilitazione.

Campi finiti e segnale GPS

Lo scopo della tesi è quello di studiare una delle applicazioni della teoria dei campi finiti: il segnale GPS. A questo scopo si descrivono i registri a scorrimento a retroazione lineare (linear feedback shift register, LFSR), dispositivi utili in applicazioni che richiedono la generazione molto rapida di numeri pseudo-casuali. I ricevitori GPS sfruttano il determinismo di questi dispositivi per identificare il satellite da cui proviene il segnale e per sincronizzarsi con esso. Si inizia con una breve introduzione al funzionamento del GPS, poi si studiano i campi finiti: sottocampi, estensioni di campo, gruppo moltiplicativo e costruzione attraverso la riduzione modulo un polinomio irriducibile, fattorizzazione di polinomi, formula per il numero e metodi per la determinazione di polinomi irriducibili, radici di polinomi irriducibili, coniugati, teoria di Galois (automorfismo ed orbite di Frobenius, gruppo e corrispondenza di Galois), traccia, polinomio caratteristico, formula per il numero e metodi per la determinazione di polinomi primitivi. Successivamente si introducono e si esaminano sequenze ricorrenti lineari, loro periodicità, la sequenza risposta impulsiva, il polinomio caratteristico associato ad una sequenza e la sequenza di periodo massimo. Infine, si studiano i registri a scorrimento che generano uno dei segnali GPS. In particolare si esamina la correlazione tra due sequenze. Si mostra che ogni polinomio di grado n-1 a coefficienti nel campo di Galois di ordine 2 può essere rappresentato univocamente in n bit; la somma tra polinomi può essere eseguita come XOR bit-a-bit; la moltiplicazione per piccoli coefficienti richiede al massimo uno shift ed uno XOR. Si conclude con la dimostrazione di un importante risultato: è possibile inizializzare un registro in modo tale da fargli generare una sequenza di periodo massimo poco correlata con ogni traslazione di se stessa.

The relevance of the silica metabolizing enzyme silicatein-alpha to biomineralization and the formation of biogenic silica in siliceous sponges

Die technische Silikatproduktion erfordert in der Regel hohe Temperaturen und extreme pH-Werte. In der Natur hingegen haben insbesondere Kieselschwämme die außergewöhnliche Fähigkeit, ihr Silikatskelett, das aus einzelnen sogenannten Spiculae besteht, enzymatisch mittels des Proteins Silicatein zu synthetisieren. rnIm Inneren der Spiculae, im zentralen Kanal, befindet sich das Axialfilament, welches hauptsächlich aus Silicatein-α aufgebaut ist. Mittels Antikörperfärbungen und Elektronenmikroskopischen Analysen konnte festgestellt werden, dass Silicatein in mit Kieselsäure-gefüllten Zellorganellen (silicasomes) nachzuweisen ist. Mittels dieser Vakuolen kann das Enzym und die Kieselsäure aus der Zelle zu den Spiculae im extrazellulären Raum befördert werden, wo diese ihre endgültige Länge und Dicke erreichen. Zum ersten Mal konnte nachgewiesen werden, dass rekombinant hergestelltes Silicatein-α sowohl als Siliciumdioxid-Polymerase als auch Siliciumdioxid-Esterase wirkt. Mittels Massenspektroskopie konnte die enzymatische Polymerisation von Kieselsäure nachverfolgt werden. Durch Spaltung der Esterbindung des künstlichen Substrates Bis(p-aminophenoxy)-dimethylsilan war es möglich kinetische Parameter der Siliciumdioxid-Esterase-Aktivität des rekombinanten Silicateins zu ermitteln.rnZu den größten biogenen Silikatstukuren auf der Erde gehören die Kieselnadeln der Schwammklasse Hexactinellida. Nadelextrakte aus den Schwammklassen Demospongien (S. domuncula) und Hexactinellida (M. chuni) wurden miteinander verglichen um die potentielle Existenz von Silicatein oder Silicatein-ähnliche Molekülen und die dazu gehörige proteolytischen Aktivität nachzuweisen. Biochemische Analysen zeigten, dass das 27 kDA große isolierte Polypeptid in Monoraphis mehrere gemeinsame Merkmale mit den Silicateinen der Demospongien teilt. Dazu gehören die Größe und die Proteinase-Aktivität. rnUm die Frage zu klären, ob das axiale Filament selbst zur Formbildung der Skelettelemente beiträgt, wurde ein neues mildes Extraktionsverfahren eingeführt. Dieses Verfahren ermöglichte die Solubilisierung des nativen Silicateins aus den Spiculae. Die isolierten Silicateine lagen als Monomere (24 kDa) vor, die Dimere durch nicht-kovalente Bindungen ausbildeten. Darüber hinaus konnten durch PAGE-Gelelektrophorese Tetramere (95 kDa) und Hexamere (135 kDa) nachgewiesen werden. Die Monomere zeigten eine beträchtliche proteolytische Aktivität, die sich während der Polymerisationsphase des Proteins weiter erhöhte. Mit Hilfe der Lichtmikroskopie und Elektronenmikroskopie (TEM) konnte die Assemblierung der Proteine zu filamentartigen Strukturen gezeigt werden. Die Selbstorganisation der Silicatein-α-Monomeren scheint eine Basis für Form- und Musterbildung der wachsenden Nadeln zu bilden.rn Um die Rolle des kürzlich entdeckten Proteins Silintaphin-1, ein starker Interaktionspartner des Silicatein-α, während der Biosilifizierung zu klären, wurden Assemblierungs-Experimente mit den rekombinanten Proteinen in vitro durchgeführt. Zusätzlich wurde deren Effekt auf die Biosilikatsynthese untersucht. Elektronenmikroskopische Analysen ergaben, dass rekombinantes Silicatein-α zufällig verteilte Aggregate bildet, während die Koinkubation beider Proteine (molekulares Verhältnis 4:1) über fraktal artige Strukturen zu Filamenten führt. Auch die enzymatische Aktivität der Silicatein-α-vermittelte Biosilikatsynthese erhöhte sich in Gegenwart von Silintaphin-1 um das 5,3-fache. rn

Enhancing Workers’ Well-Being. Scientific and social relevance of managing stress in the workplace

Purpose. Despite work-related stress is one of the most studied topic in organizational psychology, many aspects as for example the use of different measures (e.g. subjective and objective, qualitative and quantitative) are still under debate. According to this, in order to enhance knowledge concerning which factors and processes contribute to create healthy workplaces, this thesis is composed by four different studies aiming to understand: a) the role of relevant antecedents (e.g. leadership, job demands, work-family conflict, social support etc.) and outcomes (e.g. workplace phobia, absenteeism etc.) of work-related stress; and b) how to manage psychosocial risk factors in the workplace. The studies. The first study focused on how disagreement between supervisors and their employees on leadership style (transformational and transactional) could affect workers well-being and work team variables. The second and third study used both subjective and objective data in order to increase the quality of the reliability of the results gained. Particularly, the second study focused on job demand and its relationship with objective sickness leave. Findings showed that despite there is no direct relationship between these two variables, job demand affects work-family conflict, which in turn affect exhaustion, which leads to absenteeism. The third study analysed the role of a new concept never studied before in organizational settings (workplace phobia), as a health outcome in the JD-R model, demonstrating also its relationship with absenteeism. The last study highlighted the added value of using the mixed methods research approach in order to detect and analyse context-specific job demands which could affects workers’ health. Conclusion. The findings of this thesis answered both to open questions in the scientific literature and to the social request of managing psychosocial risk factors in the workplace in order to enhance workers well-being.

Relevance of the pig stomach for the detection of dietary factors and gut maturation and control

In this thesis two approaches were applied to achieve a double general objective. The first chapter was dedicated to the study of the distribution of the expression of genes of several bitter and fat receptor in several gastrointestinal tracts. A set of 7 genes for bitter taste and for 3 genes for fat taste was amplified with real-time PCR from mRNA extracted from 5 gastrointestinal segments of weaned pigs. The presence of gene expression for several chemosensing receptors for bitter and fat taste in different compartments of the stomach confirms that this organ should be considered a player for the early detection of bolus composition. In the second chapter we investigated in young pigs the distribution of butyrate-sensing olfactory receptor (OR51E1) receptor along the GIT, its relation with some endocrine markers, its variation with age, and after interventions affecting the gut environment and intestinal microbiota in piglets and in different tissues. Our results indicate that OR51E1 is strictly related to the normal GIT enteroendocrine activity. In the third chapter we investigated the differential gene expression between oxyntic and pyloric mucosa in seven starter pigs. The obtained data indicate that there is significant differential gene exression between oxintic of the young pig and pyloric mucosa and further functional studies are needed to confirm their physiological importance. In the last chapter, thymol, that has been proposed as an oral alternative to antibiotics in the feed of pigs and broilers, was introduced directly into the stomach of 8 weaned pigs and sampled for gastric oxyntic and pyloric mucosa. The analysis of the whole transcript expression shoes that the stimulation of gastric proliferative activity and the control of digestive activity by thymol can influence positively gastric maturation and function in the weaned pigs.