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Cell-laden hydrogels for biofabrication: matrices processing and cryopreservation
Get PDFIn this dissertation, a report of my PhD research activity is provided. The activity was carried out in Biotech Research Center, part of the Industrial Engineering Department, of the University of Trento (Italy), under the supervision of Prof. Claudio Migliaresi and Dr. Devid Maniglio. Biofabrication, an approach to the bottom-up paradigm of tissue engineering, represents the research topic. This technology is defined as the production of complex biological constructs using cells, components of the ECM, biomolecules, and biomaterials that are assembled with different techniques in an engineered tissue fragment. The general aim of the work was to address some of the problems that currently limited the development and applicability of biofabrication. In particular, two issues were considered in the experimental part: the cryopreservation of cell-laden hydrogel constructs and the development of novel building blocks containing cells using alginate-based hydrogels. Alginate was the material of choice for investigation, as an accepted support for different tissue engineering applications that can sustain several modification and fabrication methods.
In the first chapter, the concepts of bottom-up tissue engineering and biofabrication are introduced. The role and state of the art of hydrogels to manufacture cell-laden building blocks, the techniques for cell encapsulation and the commonly used fabrication strategies for biofabrication and bioprinting are reviewed together with their applications. Moreover, the limitations that currently restrict the applicability of hydrogel-based tissue engineering are discussed.
In chapter two, the role of alginate hydrogels in tissue engineering and biofabrication is described. In particular, its chemical content, crosslinking behavior, manufacturing capacity, and applications are reviewed with emphasis on the possible modification of alginate hydrogels in order to enhance biocompatibility and functionality of encapsulated cells.
The experimental part is described in the following chapters. Chapter three introduces the concept of cryopreservation and in particular the issues concerning the preservation of cell-laden building blocks. Subsequently, the impact of cryopreservation on the viability and functionality of cells encapsulated in alginate matrices is evaluated comparing different cryoprotective agents. The experimental methods for manufacturing and preserving cell-laden alginate fibers and for performing the biological and structural tests are reported. The results are presented, discussed and compared with the state of the art.
In chapter four, a novel method for encapsulating cells within alginate-based hydrogel films with micrometer thickness is described. The procedure for immobilizing cells within hydrogel films with different composition is described, together with the performed biological assays aimed at selecting the best matrix composition. The results are reported and discussed, emphasizing the potential applications and future developments of the proposed method
The Singularity Problem in Gravitational Theory. The Spherically Symmetric Case
Get PDFIn this work we discuss some specific features related to the concept of singularity in the gravitational theory. We give a brief review of some various definitions for singularity, then we explore some "negative" results, in the sense they are not able to reproduce, in general, a regular solution. We present some of these approaches, namely the non-commutative geometry; the Non-Linear Electrodynamics; and the conformal approach. We later generalize these results into a no-go theorem, which is actually a fully original result. In the second part of this work, we discuss some working examples of regular solutions: we present three of them already present in literature (non-minimal Yang-Mills coupling, mimetic field approach and non-polynomial gravity), then we use such results to build up a model of a regular cosmological solution. Its generating mechanism and its main features are described, replacing the Big Bang with a bounce; the inflationary behavior at large time is also recovered. In the following two chapters, we present some different schemes to build regular solutions from the coupling between gravity and a scalar field. In particular, in chapter 7, we use a minimal coupling, while in chapter 8 we find some sufficient (though not necessary) conditions to build a regular solution, within the framework of the Horndeski theory. In both cases we are not able to find explicit results. In the ninth chapter we discuss a model of a regular black hole, coupling gravity with some fluid: in this case, an exact solution is found. We prove it is regular and we show some of its general features; we also discuss the time-dependent case, although we are only able to discuss its asymptotic behavior. We also discuss some of its problems, mainly due to instability. In the appendices we try to extend the no-go theorem to theories and try to solve the instabilities of the fluid approach respectively
Il concorso apparente di norme nel diritto penale internazionale
Get PDFLa commissione sistematica o su larga scala dei crimini internazionali non sembra lasciare molto spazio a singole ed isolate violazioni. Il diritto penale internazionale costituisce, per sue caratteristiche intrinseche, luogo del molteplice e della pluralità, in cui il concorso di norme e di reati trova la sua più naturale e logica manifestazione. La ricerca ha ad oggetto il concorso apparente di norme nel diritto penale internazionale e, in particolare, le ipotesi di convergenze normative che si instaurano tra il crimine di genocidio, i crimini contro l’umanità e i crimini di guerra così come definiti dallo Statuto di Roma e applicati dalla Corte penale internazionale.
Rilevata l’assenza, negli Statuti dei tribunali internazionali, di disposizioni dedicate al concorso di norme, e viste le criticità e insufficienze che emergono dalle soluzioni adottate dalla giurisprudenza, lo studio privilegia un approccio di diritto comparato volto a individuare – se esistono – principi e criteri di soluzione da applicarsi alle ipotesi di convergenza che si verificano tra i crimini codificati all’interno dello Statuto di Roma. L’analisi tiene distinte i casi di concorso intra-categoriale, che ricomprendono le convergenze che si verificano all’interno della stessa categoria di crimine, e le ipotesi di concorso inter-categoriale, avente ad oggetto le convergenze che si verificano tra le diverse categorie di crimini. Sullo sfondo la consapevolezza che qualsiasi strada intrapresa verso la razionalizzazione e semplificazione del concorso di norme deve fare i conti con l’impossibilità di eliminare o annientare a priori il fenomeno della convergenza, in quanto esso è inevitabile
Commento testuale ai frammenti di Epicarmo
Get PDFQuesto lavoro di tesi contribuisce allo studio della commedia dorica di V secolo a.C. attraverso l’analisi dei testi del suo maggior esponente, Epicarmo di Siracusa. Vengono presi in esame i frammenti autentici che è possibile attribuire con certezza ad un determinato dramma e, per ciascun brano, si provvede ad un commento dettagliato delle peculiarità linguistiche, drammaturgiche e contenutistiche. Il proposito della ricerca è stato capire come Epicarmo si collocasse nel panorama culturale siciliano in cui visse, indagare l’uso della variazione linguistica e ricercare le peculiarità dei suoi drammi.
Per trovare risposta a questi interrogativi, è stato necessario adottare un approccio di tipo interdisciplinare, poiché non è possibile racchiudere tali tematiche nella sola letteratura greca di V secolo. Un contributo fondamentale proviene dagli studi di storia della lingua greca e dalla dialettologia, che hanno permesso di definire le peculiarità linguistiche del dorico in uso a Siracusa e di evidenziare eventuali discrepanze presenti nei testi del commediografo. Nel commento ai brani, infatti, è costante il confronto tra la forma linguistica adottata da Epicarmo e quella corrispondente nello ionico-attico. Importante si rivela anche il contributo della sociolinguistica, una teoria che dà importanza al condizionamento esercitato dai parlanti su una lingua. Lo studio dei testi epicarmei indaga anche se esistano elementi linguistici tali da caratterizzare un determinato personaggio in base al suo status sociale, alla sua provenienza e al suo genere sessuale.
I risultati ottenuti dallo studio linguistico e testuale sono notevoli. Innanzitutto, Epicarmo porta in scena argomenti mitologici, storici e scene riprese dalla vita quotidiana, mescolandovi parodia e travestimento. Due personaggi in particolare, Eracle ed Odisseo, compaiono frequentemente nelle opere del commediografo e diventano protagonisti delle azioni più diverse. Rilevante è anche la quantità e la lunghezza dei cataloghi che caratterizzano i frammenti epicarmei e che rispondono a determinati scopi comici. La forma ad elenco, ripresa probabilmente dalla letteratura epica, sembra essere stata particolarmente cara ad Epicarmo, che la impiega in molti testi. Inoltre, è probabile che, almeno in alcuni drammi, fosse previsto un coro comico, anche se non è chiaro quanti individui lo componessero e quale fosse la sua funzione.
Dal punto di vista linguistico, i testi del commediografo sono composti nel dialetto dorico di Siracusa, anche se compaiono talvolta alcune espressioni peculiari di altri dialetti. In qualche occasione, inoltre, i frammenti sembrano testimoniare la variazione sincronica in atto nella lingua parlata.
In conclusione, la produzione comica di Epicarmo mostra un forte carattere regionale, evidente sia dalla scelta di scrivere in dorico sia dai numerosi riferimenti a prodotti tradizionali e ad argomenti locali. Tuttavia, la lingua e i contenuti del poeta risentono in larga misura anche dell’ambiente culturale e politico della Sicilia di V secolo a.C. e attestano relazioni tra il commediografo siracusano e gli intellettuali contemporanei, fra i quali spicca Eschilo
Numerical Cognition in Zebrafish (Danio rerio)
Get PDFThe use of numerical information is widespread throughout the animal kingdom, providing adaptive benefits in several ecological contexts, including foraging, anti-predatory strategies and mating. Given the importance to possess numerical abilities, it is plausible that similar selective pressures in favor of processing numerical information would have acted in different species, even in those more distantly related to humans, such as fish. The aim of this work was to investigate several aspects of numerical abilities in zebrafish (Danio rerio).
In the first part, discrimination of quantity (magnitude) was investigated. Zebrafish were tested in free-choice experiments for their preference for different numerosities of conspecifics, taking advantage of shoaling behavior. Zebrafish chose to approach the location previously occupied by the larger in number between two groups of conspecifics (no longer visible at test) in sets of 1 versus 2 items and 2 versus 3 items, but failed at 3 versus 4 items. Similarly, when tested with larger numbers, zebrafish succeeded with 2 versus 4, 4 versus 6 and 4 versus 8 items, but failed with 6 versus 8 items. The results suggest that zebrafish rely on an approximate number system to discriminate memorized sets of conspecifics of different magnitudes and the degree of precision in recall is mainly dependent on the ratio between the sets to be discriminated.
The aim of the second part was to investigate, for the first time, the use of proto-arithmetic addition abilities in zebrafish. Fish were tested in a spontaneous choice-test paradigm in which sets of conspecifics disappeared one-by-one behind one of two opaque screens, forming two groups that differed in number. Fish preferred to inspect the screen occluding the larger group of fish in sets of 1 versus 2 items and 2 versus 4 items, but failed at 2 versus 3 items. When tested under controlled conditions for continuous variables (overall time of the stimuli presentation in the two groups equalized) zebrafish were affected by the motion of the stimuli, showing a preference for the group of conspecifics that moved faster. Although results suggest that fish possess proto-arithmetic addition capacities, further studies seem to be needed to clarify in which circumstances zebrafish use numerical or non-numerical features.
In the third part, ordinal numerical competencies were investigated. Fish learned to identify the second element in a series of five identical elements arranged sequentially. To assess whether zebrafish used ordinal information rather than non-numerical information, such as spatial distances, fish underwent a series of tests. When the length of the apparatus (exp. 1) and the inter-element distance (exp. 2) varied at test, creating a potential conflict with ordinal information, fish selected the correct ordinal position over spatial distance. Fish showed however difficulty when the set of elements changed, such as when the number of elements almost doubled (from 5 to 9 elements, exp.3).
The aim of the fourth part was to study the possible link between number and space in the mapping of numerosities. Such an ability has been observed in primates and in birds, resembling a human mental number line. Zebrafish learned to associate a target number with a reward and then were tested in a preference choice test between two identical numerosities, but different to the training one, placed on the right and the left side of the experimental apparatus. Results suggested that zebrafish spontaneously associated smaller numbers with the left space and larger numbers with the right space, although a potential limitation of the use of mapping strategies is probably related to the ratio between the numerosities presented during training and testing. Control conditions confirmed that the overall perimeter and the overall area did not strongly influence the orientation of the supposed mental line. However, zebrafish were not completely unaffected by changes in surface areas of the stimuli.
Given its widespread use in the field of genomics, zebrafish may provide a useful model organism in the study of the genetic bases of numerical cognition
Monitoring of reading and spelling in glioma patients undergoing awake surgery
Get PDFOne of the main aims of awake surgery for glioma patients is to preserve quality of life, while maximizing tumor resection. Focusing on an important yet understudied aspect of quality of life, this thesis investigates to what extent written language may be affected by a glioma or glioma surgery. By reviewing current assessments of reading and spelling in awake surgery studies, we aimed to provide a better understanding of how neuroanatomical theories may guide neurosurgical practice, and to evaluate how examinations of written language in glioma patients can be improved. To provide a direct clinical application for this knowledge, we developed a theory-driven written language battery specifically for glioma patients. Lastly, we tested its efficacy and evaluated reading and spelling performance in neurosurgical practice. The studies in this thesis have provided a better understanding of written language in neurosurgical practice. In particular, it has contributed to prediction and prevention of written language disorders in glioma patients undergoing awake surgery, and it has resulted in a valid examination tool to carefully monitor reading and spelling in this patient group
Study of the aging hereditariness of concrete through a novel viscoelastic formulation
Get PDFThis thesis focuses on the study of the creep deformations exhibited by concrete structures, with a particular attention to long-span prestressed box girders. During their service life, such structures can experience excessive multidecade deflections mainly due to the creep phenomenon and the large difference in shrinkage between the top and bottom slabs, sometimes causing damages of structural elements and huge economic losses. In order to prevent such consequences, the multidecade deflections of this class of structures need to be carefully predicted; therefore, very refined creep constitutive laws are required for relevant creep analyses. The most widely used creep model for the prediction of the time-dependent behavior of highly creep-sensitive structures is Model B3, which was calibrated through a data bank comprising results coming from different laboratories spread throughout the world. In this thesis, an already existing viscoelastic formulation, conceived for any viscous kernel, is integrated with Model B3 and the resulting finite element scheme is successfully applied to study the long-term behavior of a realistic structure, the Colle Isarco viaduct in Italy. Another contribution to this research work concerns the prediction of multidecade deflections exhibited by concrete structures through a novel creep constitutive law based on variable-order fractional calculus, resulting in an excellent feature with respect to classical creep models. Indeed, the creep deformations obtained through the proposed model are very close to the deformations evaluated by means of Model B3. Moreover, the suggested creep law is characterized by less aging terms than Model B3, with the consequent advantage to exactly derive the relevant relaxation function from the fundamental relationship of linear viscoelasticity. In order to perform creep analyses with the suggested fractional-order law, a numerical integration scheme characterized by a fractional-order viscous kernel is also developed and verified on realistic concrete structures subjected to multiple load histories.
To the best of the author's knowledge, this research work presents the first creep constitutive lawavailable in literature that, through fractional operators, explores the time-dependent behavior of aging materials. Furthermore, a suitable numerical integration
scheme is introduced and successfully applied to representative concrete structures
Integrating Ecosystem Services in urban planning
Get PDFWhile ecosystem service knowledge has demonstrated to enhance decision-making at different levels, successfully managing the interface between science and policies is still a challenge. The thesis focuses on cities, and aims to explore the integration of ecosystem services in urban planning processes and tools. A preliminary review of recent urban plans reveals shortcomings in current practices and the potential benefits of a further integration. At the conceptual level, the problem of integration is addressed by building a framework that shows the entry points and pathways through which planning actions affect the supply and demand of urban ecosystem services. The framework is applied to systematise a fragmented scientific evidence, and to select a set of indicators that planners can use to assess the impacts of planning decisions.
At the operational level, the integration of ecosystem service knowledge is tested in a real-life planning context dealing with the prioritization of brownfield regeneration scenarios in the city of Trento (Italy). Alternative scenarios are assessed based on the beneficiaries of two key ecosystem services, namely microclimate regulation and nature-based recreation, hence compared through a multi-criteria analysis that allows exploring multiple perspectives and balancing competing interests.
The last part of the thesis frames the integration of ecosystem services in urban planning in the wider context of spatial strategies for sustainable urban development. The six main spatial strategies agreed-upon at the European level, including the 'green city' strategy supported by the ecosystem service approach, are compared with the recent development trends of 175 European cities. The results reveal factors that may hinder the implementation of the strategies, as well as potential conflicts and trade-offs that should be carefully considered when aiming at a truly-sustainable urban development
A new apparatus to simulate fundamental interactions with ultracold atoms
Get PDFIn this thesis I present the construction of a new apparatus aimed at studying two-component Bose-Einstein condensates (BECs) in the presence of a Rabi coupling, where the two components correspond to internal states of sodium atoms. The coherent mixture, in the miscible regime, also exhibits a metastable excitation consisting in a domain wall of relative phase connecting vortices of different components. Due to the peculiar energy dependence of such a configuration, an attractive force, independent of the vortex distance, is expected, making this system a candidate for mimicking features of quark confinement in QCD. The surface tension of the domain wall structure can be experimentally controlled via the strength of the coupling, allowing to study the system dynamics in different regimes. These include a predicted regime in which, for sufficient high coupling strength, the domain wall breaks and new vortex couples nucleate, providing by itself an interesting experimental realization of spin counterflow dynamical instabilities in a superfluid system, as well as a phenomenon analogous to string breaking in QCD. The choice of sodium as atomic species is motivated by its collisional properties that allow to obtain a perfect spatial superposition between the two miscible components |F = ±1⟩ if trapped by a spin-independent potential, avoiding the known phenomenon of ’buoyancy’. Studying the dynamics of such systems for sufficiently long times, with a mixture subject to Zeeman differential energy shifts, requires a specific effort to remove magnetic field fluctuations: a rough estimate suggests that in order to maintain the system coherence for a sufficiently long time to study its dynamics, magnetic field fluctuations should be reduced by at least three orders of magnitude compared to typical values observed in laboratory environment. Such attenuations can be obtained by means of multiple layers of μ-metal, that is incompatible with the use of ordinary magnetic traps, characterized by large magnetic field gradients on the atoms, due to residual magnetization and saturation of the shielding material. To avoid such effects it is required to either evaporatively cool atoms into an optical dipole trap loaded from a molasses stage, or a hybrid approach by means of which atoms are transferred to a low-gradient quadrupole trap superimposed to the optical trap. Producing BECs with such protocols greatly benefits from an efficient optical molasses cooling stage to prepare the sample in the best conditions of temperature and density before loading atoms into the trap. With this regard, the main limitation of ordinary laser cooling techniques is their reliance on absorption and spontaneous emission cycles, which limits the lowest temperature and highest density that can be reached as a consequence of residual heating effects and photon-reabsorption. An important resource to cope with these limits are dark states. In a broader sense a dark state is a state which does not interact with the exciting light field, and an atom in such a state would be neither subject to the beneficial cooling effects nor to the detrimental effects of light scattering. It is possible, however, to exploit the phenomenon of electromagnetically induced transparency (EIT) to induce a velocity-selective cooling mechanism for which slower atoms, that do not need further cooling, are trapped in a dark state corresponding to a coherent superposition of atomic levels whose excitation probabilities interfere destructively, while the cooling mechanism still applies to the fastest atoms. Among these techniques, gray molasses cooling allows to reach temperatures as low as a few recoil temperatures, while retaining atomic densities useful to reach quantum degeneracy in the subsequent stages of the experiment. In order to exploit this technique, an additional laser source had to be implemented during my thesis. To realize a gray molasses on the sample only |F⟩ → |F − 1⟩ or |F⟩ → |F⟩ transitions can be chosen, requiring blue-detuned laser, in contrast to ordinary (sub)Doppler laser cooling techniques. Both these requirements rule out the
use of the D2 transition used for ordinary laser cooling techniques, due to its finely-spaced hyperfine structure. On the other hand, the D1 transition is characterized by a broader level spacing in the hyperfine structure and the absence of higher energy states on the blue side of the |F = 2⟩ → |F' = 2⟩ transition. As part of the work for this thesis, I successfully implemented and characterized gray molasses cooling on the D1 optical line of sodium. The buildup of the new apparatus includes the assembly of a new laser source for laser trapping and cooling on the D2 line, the assembly of the optical table devoted to the frequency and amplitude control of all the laser beams involved in the optical laser cooling procedures as well as the electronic control system. Design and assembly of the UHV and baking procedures for the stainless steel vacuum chamber are also described as well as the laser cooling techniques employed to load the atoms in a Dark-Spot MOT. Regarding the production of BEC, various strategies were attempted for different dipole beam configurations. Dipole traps typically suffer from the tradeoff between capture volume and trap depth at a given power, while hybrid traps usually take advantage of a magnetic trap stage that would not be compatible with the μ-metal shielding. Preliminary attempts to reach quantum degeneracy after directly loading the dipole trap from molasses were unsuccessful due to spurious effects. An alternative approach based on a magnetic-shield compatible hybrid trap protocol, in the absence of magnetic trap compression, was successfully implemented
Diversity Aware Visualization
Get PDFThis thesis aims to address a significant issue related with the consumption of diversified data in the field of semantics and knowledge representation by using a framework which allows the data consumption in a generic, scalable and pleasing manner. The work proposes a mixed solution by splitting the issue into four subproblems: how to preserve the richness associated with the data; how to present information about an object in a single or multiple visualization contexts; and to provide a seamless exploration of interconnected entities; and how to design a tool that offers a better user experience.
A real-world object can have various representations which lead to data diversity. However, each representation captures a view (mostly partial) of an object. To preserve the richness associated with the data, we follow an entity-centric design approach. In this approach, we represent multiple datasets related to an object as an entity with various properties. An entity is then further categorized in a group according to its similarities or differences.
Our contextual model not only considers the transformation of objects as entities but also adapts to various visualization contexts. These contexts are space, list, timeline, and network. We design a multiview visualization framework that allows simultaneous presentation of entities according to these four defined visualization contexts.
To allow seamless interaction of data with the users, we emphasized on using a multilayered architecture where: 1)datasets are aggregated and stored using an entity-centric approach, 2) visualized in various contexts and viewpoints simultaneously according to the entity types and users' need. This adaptation is capable enough to facilitate presentation and exploration of diversified data according to users need.
To prove the feasibility of our framework, we applied it to visualize diversified data in various settings. Continuous interaction with the end users produced valuable feedback and essential design suggestions. Finally, multiple prototypes were evaluated with the end users to verify their usability. The results obtained were highly favorable