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Development of an enzymatic tool-box for lignin oxidation/degradation. Sviluppo di un tool-box enzimatico per l’ossidazione e la degradazione della lignina.
No full textLignin is an amorphous polymer characterized by a wide range of molecular mass components, a disordered and branched three-dimensional structure, insoluble in water and in most common solvents. In order to perform lignin degradation, enzymatic treatment could represent an environmentally friendly alternative to chemical methods.
The main purpose of this PhD project was to develop an "enzymatic tool-box" for an efficient oxidation and degradation of lignin into aromatic monomers. Biochemical properties of available commercial and recombinant ligninolytic enzymes (laccase, Mn peroxidase and lignin peroxidase) were evaluated under identical experimental conditions, with the final goal to identify interesting biocatalysts for lignin degradation. The effect of pH, temperature, NaCl, DMSO and Tween-80 on the enzymatic activity has been investigated. The activity of novel enzymes, such as the membrane-bound polyphenol oxidase from the marine bacterium Marinomonas mediterranea (MmPPOA) and a peroxidase produced by Nonomuraea gerenzanensis, was also evaluated.
A new high-throughput colorimetric screening to assay the oxidation/degradation of lignin by different enzymes was developed: this method facilitates the identification of optimal conditions for a lignin treatment based on the combined use of various laccases and peroxidases. On this side, coupling the colorimetric assay with a size-exclusion chromatography analysis allows to identify changes in lignin molecular mass distribution due to enzymatic treatment.
Finally, based on recent literature, a chemo-enzymatic process to depolymerise lignin was carried out on two lignin linkage model compounds and on four technical lignins. This could represent an innovative and feasible way for valorisation of lignin under mild conditions
Role of robotic-assisted surgery for endometrial cancer staging. Comparison with open abdominal operations
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Ruthenium and rhodium catalyzed C-N bond formation reactions in the synthesis of nitrogen containing heterocyclic compounds
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Ethylene or propylene based copolymers with higher 1-olefins by metallocene catalysts: correlation between microstrusture and properties.
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Developing active packaging solutions through incorporation of organic/inorganic active components in renewable materials.
No full textThe development of new antimicrobial active packaging systems have been gaining a raising interest due to its potential to increase product shelf-life and provide food quality and safety benefits allied to society demands on food-related health risks, multi-drug resistance and environmental problems. A great variety of organic substances such as phenolic compounds and essential oils as well as inorganic metal oxide nanoparticles such as Ag+, ZnO and TiO2 have been intensively studied for having antimicrobial properties, although their efficiency is highly dependent on the target microorganisms, the material or media where they act as well as the surrounding environment are relevant (Burt, 2004; Suppakul et al., 2003; Visai et al., 2011). Recent research in active packaging is mostly focused on the use of natural renewable material resources including preservatives to develop biodegradable and recyclable packaging products. Accordingly, the NEWGENPAK project was funded within ITN-Marie Skłodowska-Curie EU program with the aim “to take wood cellulose based material a significant step forward by replacing petroleum-based additives used in paper and board packaging materials in order to achieve the barrier and other crucial properties needed for competitive, low carbon footprint, packaging materials”.
NEWGENPAK, the acronym for New Generation of Cellulose Fibre Based Packaging Materials for Sustainability, just finished in December 2015, was an interdisciplinary research training network (ITN) constituted by 8 European universities, 3 research institutes and 6 enterprises from all over Europe, with13 researchers working full time developing their own individual researcher projects, making collaborations and receiving training on the field. This PhD thesis was carried out within this project and developed mainly at Innovhub SSI – Paper Division, Milan, Italy.
The main target of this work was to attain antibacterial cellulose-based materials for food packaging applications, following two approaches based in the incorporation of active organic components or active nanoparticles as active agents. Besides, it was studied the possibility to develop an antibacterial packaging for medical applications, in order to prevent medical cross contamination. The fate of the nanoparticles in the recycling process and their effect on the biodegradability of the packaging was initially assessed as an important part of environmental aspects related to the end of life of packaging products.
The first approach, described in the chapter 2, aimed to explore the possibilities to extract polyphenols from black tea brewing residues and use them as active compounds for the development of active cellulosic-based surfaces. Therefore, the chemical characterization of black tea residues as well as the antioxidant and antimicrobial properties of their extracts were addressed. The best infusion conditions, considering the yield of extraction, the antioxidant activity and the total phenolic content, were found to be at 80ºC for 7.5 minutes for an infusion of 2.5 g of tea residue in 100 mL of water, and just 1.1 mg of these extract where enough to provide a bactericidal effect. The resulting paper coated with 3.8 g/m2 of polyphenols-based coating formulation attained a complete killing effect against S. aureus.
In the second approach, several papers were functionalized with formulations based on photo-active TiO2 NPs by dip-coating and compared regarding their antibacterial activity. The results presented in the chapter 3 have shown that both handsheets of bleached Kraft pulp (BK) and chemithermomechanical pulp (CTMP) displayed a bactericidal effect against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa, even after three weeks of storage either in light and dark conditions, while pre-coated recycled paper (PCR) and bleached pre-coated Kraft (BPK) paper samples did not shown any antibacterial activity. The effect of TiO2 NPs against S. aureus was inhibited in: i) PCR samples due to the presence of considerable amounts of inorganic compounds, such as calcium carbonate, that shielded the effect of active nanoparticles; and ii) BPK samples, most likely due to their high hydrophobicity that did not permit a good retention of the NPs and homogenous coating distribution. Accordingly, different preparation methods and deposition techniques were considered for hydrophobic surfaces and compared regarding the amount of TiO2 incorporated in nanofibrillated cellulose (NFC) loaded and finally retained on the BPK paper surfaces. Under the best conditions with the polyelectrolyte-assisted deposition 90% of nanoparticles retention was attained against only 25% for the direct-mixture formulations. The antibacterial activity of the paper samples reached approximately 2 log bacterial reduction of S. aureus showing the possibility to achieve a contact active surface based on layer-by layer assembly NFC-TiO2 formulation. Moreover a scale-up pilot demonstration of an over-print varnish based on ZnO nanoparticles was performed to be loaded by flexographic printing at industrial scale for medical packaging applications. The SAFEBOX packaging demonstrator produced was loaded with only 5.6 mg/m2 of ZnO NPs based varnish, due to some technical production constraints and restrictions, therefore it presented a slightly bacteriostatic effect with less than one log reduction. However, with the possibility to increase the amount of NPs loaded on the paper surface, promising results can be achieved. Preliminary results obtained at lab scale showed a bactericidal effect, up to 4 log reduction, for papers with about 1,5g/m2 of ZnO NPs on the surface. Regarding the preliminary studies on environmental impact of NPs, towards packaging end-of-life options presented also in the chapter 3, laboratory tests have shown only marginal effect of active ingredients on biodegradability performance whereas recyclability tests have shown a reasonable good retention of TiO2 nanoparticles (approximately 90%) in the recycled fibres after one recycling loop
Lager e Gulag. Riflessioni sulla società concentrazionaria.
No full textLager e Gulag. Riflessioni sulla società concentrazionaria is about Nazi and Soviet Concentration Camps. It tries to show that this subject is still relevant, not only because Concentration Camp as an institution has never disappeared, but also because what happened in Germany and Russia in the first part of the XX century concerns Contemporary Age, so every human being today and in the future: that's why Lager e Gulag intends to be more than a descriptive monograph about the most impressive tragedy of the history. We could say that this work investigates a representative set of factors involved in the matter of totalitarian camps, from a philosophical, anthropological and theological perspective. It is divided in two parts: the first one deals with Concentration Camps in general (chapter I) and Nazi and Soviet Camps in particular (chapters II and III), seen as spaces where time, bodies and minds are brutally controlled by the authorities in order to dominate prisoners. The second one deals with disciplines and topics strictly connected with life and thinking inside Concentration Camps: biopolitics (chapter IV), behaviours (chapter V), faith (chapter VI); the quest for God after Auschwitz and Kolyma, the problem of evil and human nature (chapter VII). This Ph.D. thesis is therefore an attempt to focus on two different forms of the same “world apart”
Performaatività del linguaggio e risignificazione dei termini nella costruzione delle identità di genere.
No full textThis thesis aims to investigate the concept of performativity in the meaning given to it by the American philosopher Judith Butler. This means that this research refers to the Gender Studies' and Queer Theory's ambit of which the aforementioned scholar is one of the major representatives. In particular we chose to deepen the concept of performativity of language (beginning from the “speech act theory” analysis by philosopher John Austin) and its relation with gender. Thus we try to clarify in which sense gender is performative, to investigate which are its relations with the body and finally to evaluate if a resignification of the terms is possible, always referring to Butler's theories.
The structure of the thesis in its first half remains without doubt within the field of theoretic and critical treatment, in the second half instead it searches for confirmation of the theories in question by analysing some case studies.
What emerged is that the subjects always establish themselves in a double dynamic of subjection and subjectivity, they're vulnerable bodies but also capable of “agency” and these gendered bodies can be constructed by words in a performative manner, at the same time though the individuals themselves can speak and change the order of that discourse
Oral fluids and auxiliary diagnostic techniques in autoimmune and neuropathic disorders of the oral cavity. Local and systemic implications. Fluidi orali e tecniche ausiliarie diagnostiche nei disordini autoimmuni e neuropatici del cavo orale. Implicazioni locali e sistemiche.
No full textIn this dissertation different features of oral fluids were analyzed in order to verify whether saliva and/or the crevicular fluid may be helpful in diagnosing underlying pathologies, monitorizing systemic diseases activity or contributing to a better understanding of idiopathic oral pathologies.
- In the first study, saliva was quantitatively analyzed through the spitting method in a group of patients affected by the most common idiopathic psychosomatic disorder of the oral cavity, known as Burning Mouth Syndrome. This study showed how saliva is a complex fluid, and that the central nervous system and emotional attitudes are very strong influencing agents on the oral health.
- In the second study, 35 patients affected by Oral Lichen Planus, an autoimmune disorder, were recruite. Salivary fluid and crevicular fluid samples were collected to measure the presence of Human ß2-defensin, an antimicrobial peptide involved in immunomodulatory functions. It was observed that HBD-2 could become a very important index to measure the disease’s activity and its evolution in the future.
- In the third study it was demonstrated that periodontal pockets and saliva contain Helicobacter pylori and that oral hygiene is useful in preventing the formation of a reservoir of microorganisms involved in gastritis and gastric cancer.
- In the fourth study, a total group of 34 patients affected by Rheumatoid Arthritis were examined and several links between rheumatic factors and periodontal indices were found.
In the end, a total number of 240 patients were recruited in this experimental work and each study contributed to new topics in the research on saliva and crevicular fluid as potential diagnostic tools for oral pathologies and systemic diseases
The art of clustering bandits.
No full textMulti-armed bandit problems are receiving a great deal of attention because they adequately formalize the exploration-exploitation trade-offs arising in several industrially relevant applications, such as online advertisement and, more generally, recommendation systems. In many cases, however, these applications have a strong social component, whose integration in the bandit algorithms could lead to a dramatic performance increase. For instance, we may want to serve content to a group of users by taking advantage of an underlying network of social relationships among them. The purpose of this thesis is to introduce novel and principled algorithmic approaches to the solution of such networked bandit problems. Starting from a global (Laplacian-based) strategy which allocates a bandit algorithm to each network node (user), and allows it to "share" signals (contexts and payoffs) with the neghboring nodes, our goal is to derive and experimentally test more scalable approaches based on different ways of clustering the graph nodes. More importantly, we shall investigate the case when the graph structure is not given ahead of time, and has to be inferred based on past user behavior. A general difficulty arising in such practical scenarios is that data sequences are typically nonstationary, implying that traditional statistical inference methods should be used cautiously, possibly replacing them with by more robust nonstochastic (e.g., game-theoretic) inference methods.
In this thesis, we will firstly introduce the centralized clustering bandits. Then, we propose the corresponding solution in decentralized scenario. After that, we explain the generic collaborative clustering bandits. Finally, we extend and showcase the state-of-the-art clustering bandits that we developed in the quantification problem
Equivalence relations and operators on ordered algebraic structures with difference.
No full textThis work concerns algebraic models of fuzzy and many-valued propositional logics, in particular Boolean Algebras, Heyting algebras, GBL-algebras and their dual structures, and partial algebras.
The central idea is the representation of complex structures through simpler structures and equivalence relations on them: in order to achieve this, a structure is often considered under two points of view, as total algebra and partial algebra. The equivalence relations which allow the representation are congruences of partial algebras.
The first chapter introduces D-posets, the partial algebraic structures used for this representation, which generalize Boolean algebras and MV-algebras.
The second chapter is a study of congruences on D-posets and the structure of the quotients, in particular for congruences induced by some kinds of idempotent operators, here called S-operators. The case of Boolean algebras and MV-algebras is studied more in detail.
The third chapter introduces GBL-algebras and their dual, and shows how the interplay of an S-operator with a closure operator gives rise to a dual GBL-algebra. Other results about the representation of finite GBL-algebras and GBL*algebras (GBL-algebras with monoidal sum), part of two papers previously published, are summarized and put in relation with the other results of this work