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Spectral features of matrix-sequences, GLT, symbol, and application in preconditioning Krylov methods, image deblurring, and multigrid algorithms.
Get PDFThe final purpose of any scientific discipline can be regarded as the solution of real-world problems. With this aim, a mathematical modeling of the considered phenomenon is often compulsory. Closed-form solutions of the arising functional equations are usually not available and numerical discretization techniques are required. In this setting, the discretization of an infinite-dimensional linear equation via some linear approximation method, leads to a sequence of linear systems of increasing dimension whose coefficient matrices could inherit a structure from the continuous problem. For instance, the numerical approximation by local methods of constant or nonconstant coefficients systems of Partial Differential Equations (PDEs) over multidimensional domains, gives rise to multilevel block Toeplitz or to Generalized Locally Toeplitz (GLT) sequences, respectively. In the context of structured matrices, the convergence properties of iterative methods, like multigrid or preconditioned Krylov techniques, are strictly related to the notion of symbol, a function whose role relies in describing the asymptotical distribution of the spectrum.
This thesis can be seen as a byproduct of the combined use of powerful tools like symbol, spectral distribution, and GLT, when dealing with the numerical solution of structured linear systems. We approach such an issue both from a theoretical and practical viewpoint. On the one hand, we enlarge some known spectral distribution tools by proving the eigenvalue distribution of matrix-sequences obtained as combination of some algebraic operations on multilevel block Toeplitz matrices. On the other hand, we take advantage of the obtained results for designing efficient preconditioning techniques. Moreover, we focus on the numerical solution of structured linear systems coming from the following applications: image deblurring, fractional diffusion equations, and coupled PDEs. A spectral analysis of the arising structured sequences allows us either to study the convergence and predict the behavior of preconditioned Krylov and multigrid methods applied to the coefficient matrices, or to design effective preconditioners and multigrid solvers for the associated linear systems
Developing active packaging solutions through incorporation of organic/inorganic active components in renewable materials.
Get PDFThe 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
Gene expression evaluation in patients affected by inflammatory diseases of paranasal sinuses. Valutazione dell’espressione genica in pazienti affetti da patologia infiammatoria dei seni paranasali.
Get PDFBelow the clinical observation level of chronic rhinosinusitis (CRS) there are several consistent pathophysiological mechanisms different from each other and important in the presentation of the underlying inflammation: so we could say that there are inflammatory endotypes (ET) of CRS.
These ET are subtypes of disease defined functionally and pathologically by a molecular mechanism. Each ET might be identified by specific biomarkers (BM) which originate from the encoding of specific genes.
Analysis of gene expression is the first signal of biologic modifications and leads to the identification of Expression BM.
In our study we compared the expression of selected genes between healthy patients and patients affected by CRS with nasal polyps without hypereosinophilia and/or other comorbidities.
These candidate genes were selected from literature because of their demonstrated hyper/hypo-expression at level of pathological polypoid tissue, sure that replication studies are very important for the progress of science.
In our study for the first time in the same population many genes involved in the pathogenesis of the disease were analysed at the same time and we obtained statistically significant result in 5 genes out of 9 analysed; 4 of these corroborate literature results. These 5 genes are the ones towards which future researches could address further efforts.
Collaboration between ENT and Biologist is essential both for patients endotyping and in elaborating new treatments.
Using well-defined ET in clinical studies might allow to identify patient groups that best benefit from existing as well as new treatments and this could result in personalized multidisciplinary treatments and in a substantial improvement in future patient care
Il simbolo in Pavel A. Florenskij. Genealogia di un sistema complesso.
Get PDFAccording to a hermeneutic way, the research plans to organize the most important philosophical, scientific and aesthetic essays written by Pavel A. Florenskij concerning the category of "symbol" in order to verify the requirements and identify the elements for an organic view about it, drawing its epistemic and regulative character. Through a deconstruction of leading theological comment, the work will deepen the philosophical and scientific foundation that build the layers of Florenskij’s thought. As Solov’ëv says: "before being translated in theological terms, thought is justified as a convergence of physical, magnetic and theurgic forces". Therefore the research follows the need to regulate a kind of a-theological (not atheistic) study that can decline the relationship between unity and variety, typical of the russian philosophy, through a dialectic that relates the genetic locations of the symbol (number transfinite, icon, word) in Florenskij with their respective fields of discontinuity (real numbers, space, language), establishing a constant figural type as a matrix for each one. The author's philosophical thought is discovered thus adhering to a generative complex system, whose interdisciplinary properties confirm its importance for contemporaneity
Characterization of Natural Killer cells from patients affected by pleural effusions. Caratterizzazione di cellule Natural Killer in pazienti affetti da versamento pleurico.
No full textNatural killer (NK) cells are large innate lymphocytes involved in tumor recognition and eradication. NK cell activity is impaired in cancer patients and in NSCLC these cells showed a pro-angiogenic phenotype and function. We investigated whether NK cells infiltrating inflammatory or malignant pleural effusions caused by primary or metastatic tumors of different origins (iPE, ptPE and tmPE, respectively) are able to acquire pro-tumor and pro-angiogenic features.
PE-NK cells are enriched in CD56bright CD16- NK cells expressing the decidual NK marker CD49a and the activation marker CD69, in addition to a lower expression of the CD57 maturation marker. Furthermore, NK cells derived from tmPE display pro-angiogenic properties: they are predominantly VEGF+ and they are able to induce capillary-like structures in vitro on human endothelial cells.
Moreover, NK cells from all patient samples showed lower cytotoxicity against K562 tumor target cells and lower positivity for perforin in comparison to peripheral blood of healthy donors (hPB) NK cells. After 3-day of NK culture with IL-2, PE-NK cells restored their cytotoxicity, whereas in PB-NK cells from patients did not reach a high level of killing capacity. 3-day culture using IL-2 plus TGFβ or IL-2 added with enriched pleural effusion milieu, only partially restored the cytotoxic potential. Purified hPB NK cells treated for 7 days with IL-15 and pleural effusions acquired a pro-angiogenic phenotype, showing cell polarization towards the CD56bright CD16dim IFNγlow NK cell subset, suggesting that in the PE milieu, diverse soluble factors are able to skew cytotoxic NK cells into pro-tumor, pro-angiogenic NK cells
The art of clustering bandits.
Get PDFMulti-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
Immune response induced by multi-wall carbon nanotubes: in vivo and in vitro studies on the medicinal leech. Risposta immunitatia indotta da nanotubi di carbonio a parete multipla: studi in vivo e in vitro sulla sanguisuga medicinale.
Get PDFSince the production and use of engineered nanomaterials (NMs) is steadily increasing, the development of new reliable methods to analyze NMs effects are critical.
Here we propose the medicinal leech as alternative animal model to study multi-walled carbon nanotubes (MWCNTs) effects by means of in vivo (environmental dispersion and MWCNT supplemented Matrigel injection) and in vitro studies on leeches macrophages.
Our results show that water dispersed MWCNTs evoke a massive migration of CD45+/CD68+ monocyte-macrophages cells and the production of molecules involved in innate immune response, such as the pro-inflammatory cytokine IL-18 and amyloid fibrils.
Ultrastructural analysis of MWCNTs-supplemented biomatrix revealed that in leech macrophages MWCNTs are internalized both actively (phagocytosis) and passively (membrane piercing).
Finally, MWCNT in vitro treatment cause the decrease of cell proliferation rate and the increase of both ROS production and apoptotic rate.
Moreover, in this study we identified and characterized in Hirudo two inflammatory markers striking similar to vertebrate’s MIF and GMFG, showing that these molecules are involved in macrophage response to MWCNTs.
Our combined experimental approaches, not only attest the ability of MWCNTs in inducing a potent inflammatory response, but also confirm the medicinal leech as a good alternative model that can be successfully used to study, both in vivo and in vitro, the possible harmful effects of any nanomaterial
