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Design and evolution of sociotechnical systems. A requirements engineering perspective
Get PDFSociotechnical systems are systems of systems where social, technical, and organizational systems interact with each other to satisfy their requirements. The interplay of social and technical systems blurs the borders in between them, and the constant change within and outside the sociotechncial systems create difficulties to manage the overall evolution.
This thesis explores the methods to model, analyse, and evolve the requirements of sociotechnical systems. We propose a systematic design process and a formal language
to aid social systems refine their requirements into not other requirements but also social interactions to generate system as well as interaction specifications. Although such specifications are useful to generate interaction protocols among systems, they haven’t
been investigated in detail by the requirements engineering community. We then explore the design space created during the design process with artificial intelligence planing to discover sequence of actions to satisfy requirements with minimal cost.
We adopt an iterative approach for handling requirements evolution and focus on the problem of selecting the optimal set of requirements for the next release. We capture synergies among requirements in goal-oriented requirements models and transform the next release problem into a multi-objective satisfiability modulo theories/optimization modulo theories problem and solve it using an external reasoner. We apply a similar approach for risk analysis using goal models. We model goals, risks, and treatments in three layers and solve multi-objective risk analysis problem with SMT/OMT reasoning. We evaluate our proposal with self-evaluation studies, a case study and scalability experiments and report results. The novelty of these two approaches is the combination of satisfiability analysis with multi-objective optimization for goal models
Linear, nonlinear and quantum optics in Silicon Photonics
No full textThis thesis work covers both classical and quantum aspects of nonlinear propagation of photons in nanophotonic Silicon waveguides. The work has been carried out within the framework of the project SIQURO, which aims to bring the quantum world into integrated photonics by using
the Silicon platform and, therefore, permitting in a natural way the integration of quantum photonics with electronics. The research towards on chip bright quantum sources of photon pairs has been done by investigating Multi Modal Four Wave Mixing in micrometer-size waveguides, thus exploiting the large third order nonlinearity of Silicon. The possibility to induce second order nonlinearities by straining its unit cell has been also analyzed through the study of the electro-optic effect. This has been done with the aim to promote Silicon as a platform for the integration of quantum sources of entangled photons based on
Spontaneous Parametric Down Conversion. New quantum interference effects have been reported in a free space
unbalanced Mach Zehnder interferometer asymmetrically excited by colour entangled photon pairs.
Innovative designs of integrated quantum circuits have been proposed, which extend the capabilities of the quantum
circuits demonstrated so far and provide additional functionalities. This work represents a step forward to the
realization of self subsistent integrated devices for quantum enhanced measurement, quantum computation and quantum crypthography
Biomimetic and Bioinspired Biologically Active Materials
No full textTissue engineering is an interdisciplinary field aimed to design and engineer an efficient system for tissue and organ regeneration, for instance, for bone healing, based on the combined use of scaffolds, cells, bioactive or signalling molecules. An optimal tissue engineering procedure requires materials and scaffolds fulfilling several requirements, one of those being the ability to trigger and control the crosstalk with the biological environment both in vitro and in vivo, and to induce and control the extracellular matrix production and assembling. Diatomite is one of the most abundant natural sources of hydrated amorphous silica resulting from the accumulation of diatom skeletons. Diatoms possess particular features in structure, morphology as well as composition. Interestingly, it has been recognized that the formation process of diatom skeleton is possibly related to that of human bone. In this study, we wanted to utilize diatoms as silicon donor additives in scaffolds for bone tissue engineering, having been demonstrated the important role of silicon in bone formation. In this first part of the project, we used several methods to eliminate impurities in the raw diatomite. Diatom microparticles (DMPs) and nanoparticles (DNPs) were successfully produced by fragmentation of purified diatoms under alkaline condition. Our result showed that both DMPs and DNPs were able to release silicon, as detected in-vitro by inductively coupled plasma optical emission spectrometry (ICP/OES). In addition, diatom microparticles and nanoparticles - derived from diatom skeletons - showed minimal or non-cytotoxic effects in-vitro as determined by lactate dehydrogenase assays on cell cultures. These findings suggest that diatom particles derived from diatom skeleton as a silicon donor might have potential use for bone tissue engineering. In the second part of this thesis, we studied the effect of diatom particles on some properties of silk fibroin/diatom particles scaffolds. To handle this task, a series of fibroin scaffolds loaded with different amounts and size of diatom particles (microparticles, nanoparticles and their combination) were fabricated by using the salt leaching method. Diatom particles addition influenced scaffold morphology and mechanical properties, and its biological behaviour as assessed on human osteosarcoma cell line MG63 cultures. Scaffolds loaded with diatom particles strongly enhanced cell adhesion, metabolic activity and proliferation. Moreover, the possible beneficial effect of the addition of diatoms particles to silk fibroin on early bone formation was determined through collagen type I synthesis evaluation, osterix expression and alkaline phosphatase induction. Cultures with human mesenchymal stem cells (hMSCs) demonstrated the silk/diatom particles scaffolds were able to induce the differentiation of progenitor cells. In conclusion, our findings provided strong evidence for a potential use of diatom particles- derived from natural diatom skeleton in biological applications, in particular for bone tissue regeneration
Polysiloxane based neutron detectors
No full textIn the last decade, neutron detection has been attracting the attention of the scientific community for different reasons. On one side, the increase in the price of 3He, employed in the most efficient and the most widely used neutron detectors. On the other side, the harmfulness of traditional xylene based liquid scintillators, used in extremely large volumes for the detection of fast neutrons. Finally, the demand for most compact and rough systems pushed by the increased popularity of neutron imaging, neutron scattering and neutron diffraction techniques.
Polysiloxanes could help addressing some of the existing issues regarding neutron detection thanks to their unique properties. For this reason, in this work, polysiloxane scintillators have been developed and characterized, with a special attention to their optical properties and their time response. In particular, this thesis describes the investigation of the scintillation performances of several different polysiloxane liquids. The results have been connected with the optical properties of the material, in turns linked to its molecular structure, allowing to select the most suitable polysiloxane solvent for liquid scintillators. The timing properties of scintillating mixtures employing the best performing polysiloxane solvent were consequently analyzed as a function of the primary dye concentration, with a special focus to the pulse shape discrimination (PSD) capability of the material. PSD is indeed one of the most important characteristic of liquid scintillators, and one of the factors determining their large use. Beside polysiloxane liquids, time response of polysiloxane plastic scintillators was also investigated with the aim of studying their PSD capability. At the moment, indeed, only few examples of plastic scintillators capable of PSD exist, and also in those cases some criticalities emerged connected with stability issues and efficiency. Production of red emitting polysiloxane plastic scintillators is also described in this work, analyzing the energy transfer process between dyes in order to optimize the readout with an avalanche photodiode. This would allow overcoming some issues connected with the use of photomultiplier tubes, in more compact and rugged systems.
Finally some preliminary results about the HYDE experiment are presented. This project aims at the development of a hybrid detector for neutrons, combining a 3D silicon diode with a suitable neutron converter, in order to produce a compact efficient neutron detector with good spatial resolution. With this goal different types of converters for fast and thermal neutrons were tested and the performances of 3D and planar devices were compared
Seismic Performance Analysis of Bridges with Isolation Devices Enhanced by Hybrid Dynamic Substructuring
Get PDFThe Seismic Performance Analysis of Bridges (SPAB) constitutes one of the biggest challenges for structural and civil engineers. In fact, the handling of these design problems requires a deep knowledge of structural behavior and a huge expertise with numerical and analytical tools necessary to perform advanced Finite Element (FE) simulations including dynamic and probabilistic aspects. Within the scope of SPAB, this thesis proposes the analysis of complex bridges assisted by the profitable well-known method of Dynamic ubstructuring (DS), advanced model updating strategies, fully probabilistic approaches and innovative time integration algorithms. SPAB includes the evaluation of several nonlinear behaviors inside the structural components and the quantification of benefits generated by safety systems such as isolation devices. As a result, in order to highlight the main advantages of a well designed isolation system, most of the cases analyzed include the comparison between non isolated and isolated configurations. In greater detail, four different bridges have been analyzed and will be presented in this thesis. First, the Rio Torto highway viaduct, an existing Reinforced Concrete (RC) viaduct on the A1 Italian highway between Florence and Bologna. The structure has been investigated at the laboratory of the Joint Research Center in Ispra (VA) by means of Hybrid Simulations (HSs). The set of 1 : 2.5 scaled substructures included two RC frame piers and the isolation system. The critical issues of the structure due to the complexity of the geometry and the awfulness was the presence of poor seismic details characterized by plain steel rebars. Owing to lack in knowledge for this type of rebars, tests were needed to analyze the seismic response in the as built configuration and to evaluate the effectiveness of a seismic retrofitting designed with a traditional Concave Sliding Bearings (CSBs) system. Then, a typical RC bridge with an innovative prototype of Concave Sliding Bearing (CSB) has been tested at the EUCENTRE Tress Laboratory in Pavia (PV) through HSs. The set of Physical Substructures (PSs) included a 1 : 2 scaled RC box section pier and a full-scale CSB. The prototype was characterized by an asymptotic relation between friction coefficient and load rate. All the benefits of the DS were exhibited during the test; in fact, to exploit the actual potentiality of the isolation system, even with the low speed of the test, the restoring force coming from the CSB was numerically corrected at each time step. Furthermore, a short-medium span Steel Concrete Composite Bridge made with Hot rolled I-girders (SCCBH) has been investigated. The SCCBH is an example of structural optimization; in fact, it combines both economic and functional benefits deriving from the reduction of in site works, e.g. welding, and short construction time. In particular, The novelties were threefold: i) the testing of a novel connection between a steel I-girder and a Concrete Cross Beam (CCB); ii) the development of a novel mechanical model for this connections; iii) the application of the Performance Based Earthquake Engineering (PBEE) to SCCBH. The experimental campaign has been performed on six 1 : 2 scaled substructures, representing a deck subassembly, tested in both longitudinal and transverse loading directions. Finally, a simulation-based reliability assessment of a complex cable-stayed foot/cyclic bridge located close to the sea and equipped with dynamic viscous dampers was performed. The scope was to investigate the benefits of Circular Hollow Section (CHS) structural members for this type of structure when erected in an aggressive environment. A FE model of the structure has been validated, and then used to perform a probabilistic time dependent analysis. Therefore, two corrosion models, i.e. general and localized, capable of evaluating the reduced load bearing section were implemented; and appropriate probability distribution functions were assigned to input model parameters to evaluate the response of the facility during its service life. As a result, the time dependent probabilities of failure have been evaluated and compared with the codes prescriptions
Novel Methods based on the Fusion of Multisensor Remote Sensing Data for Accurate Forest Parameter Estimation
No full textIn the last decade the increasing availability of high resolution remote sensing data enabled precision forestry, which aims to obtain a precise reconstruction of the forest at stand, sub-stand or individual tree level. This calls for the need of developing techniques tailored on such new data that can achieve accurate forest parameters estimations. Moreover, in this context the integration of multiple remote sensing data brings to a more comprehensive representation of the forest structure. Accordingly, the goal of this thesis is the development of novel methods for the automatic estimation of forest parameters that can exploit the different properties of multiple remote sensing data sources. The thesis provides five main novel contributions to the state-of-the-art. The first contribution of the thesis addresses the problem of the single tree crowns segmentation in multilayered forest by using very high-density multireturn LiDAR data. The aim of the proposed method is to fully exploit the potential of these data to detect and delineate the single tree crowns of both dominant and sub-dominant trees by a hierarchical 3-D segmentation technique applied directly in the point cloud space. The second contribution of the thesis regards the estimation of the diameter at breast height (DBH) of each individual tree by using high-density LiDAR data. The proposed data-driven method extensively exploits the information provided by the high resolution data to model the main environmental variables that can affect the stems growth in terms of crown structure, topography and forest density. The third contribution of the thesis proposes a 3-D model based approach to the reconstruction of the tree top height by fusing low-density LiDAR data and high resolution optical images. The geometrical structure of the tree is reconstructed via a properly defined parametric model which drives the fusion of the data. Indeed, when high resolution LiDAR data is not available, the integration of different remote sensing data sources represents a valid solution to improve the parameter estimation. In this context, the fourth contribution of the thesis addresses the fusion of low-density airborne LiDAR data and terrestrial LiDAR data to perform localized forest analysis. The proposed technique automatically registers the two LiDAR point clouds by using the spatial pattern of the forest in order to integrate the data and to automatically estimate the crown parameters. The fusion of the LiDAR point clouds leads to a more comprehensive representation of the 3-D structure of the crowns. Finally, we introduce a sensor-driven domain adaptation method for the classification of forest areas sharing similar properties but located in different areas. The proposed method takes advantage from the availability of multiple remote sensing data to detect features subspaces where data manifolds are partially (or completely) aligned.
Qualitative and quantitative experimental results obtained on large forest areas confirm the effectiveness of the methods developed in this thesis, which allow an improvement in terms of accuracy when compared to other state-of-the-art methods
Cis and Trans, p53 and NF-kB rules of transactivation
Get PDFp53 and NF-kB families of Transcription Factors (TFs) are among the most studied proteins in tumour biology, typically known to function as antagonists, although recent studies identified example of positive, even cooperative interactions. p53 and NF-kB act as dimer or dimer of dimers, bind cis regulatory elements (referred herein as Response Elements REs) of which multiple versions exist in the genome, and coordinate very large networks of target genes, through highly regulated transactivation specificities. TAp53 is a tumour suppressor activated upon genotoxic and physiological stress and involved primarily in deciding senescence, cell cycle arrest or apoptosis as cell fate; the NF-kB proteins are involved in cell survival, proliferation and innate immunity responses. In our study we tried to elucidate in detail the intrinsic nucleotide preferences of p53 and NF-kB as sequence specific TFs and their impact on transactivation specificity. Selecting various in vivo validated cognate REs and testing various ad-hoc sequence permutations, we evaluated the role of identity and positioning of nucleotides in transactivation potential and specificity. To this aim different transcription assays were used, starting from a defined assay in yeast where p53 or NF-kB protein levels and the sequence of the RE are the only variables. With human wild type p53, I tested various REs used in co-crystallization studies probing nucleotide positions that are not directly contacted by the p53 DNA binding domain, to explore the effect of DNA conformational shifts on transactivation. Also, we investigated the effect on strength and direction of p53-induced transcription of changes in the nucleotides flanking an RE, selected based on torsional flexibility measurements. For the NF-kB family, relA/p65 and NFkB1/p50 were tested as single proteins or when co-expressed using a panel of REs selected based on different DNA binding affinities. The correlation between DNA binding and transactivation potential was examined. Further, the negative modulator IkB-alpha was co-expressed and its impact measured as a function of NF-kB protein type, expression level, or RE being tested. Both for p53 and NF-kB studies, we confirmed that the hierarchical organization of nucleotides within REs observed with yeast was reasonably well conserved in A549, H1299 or MCF7 human cells using transient transfection and/or treatments to activate endogenous p53 or NF-kB. Finally, I contributed to an ongoing study focusing on the interplay between p53 and NF-kB at the transcriptional level. Using microarrays and quantitative PCR we had observed highly synergistic expression of a group of genes involved potentially in metastasis, cell growth and proliferation upon combined treatment of MCF7 cells with doxorubicin, a chemotherapeutic agent, and TNF-alpha, an inflammatory cytokine. I have studied regions of the promoters of several such synergistic genes carrying putative p53 and NF-kB binding sites to study cis-mediated regulation of gene expression. This led to the investigation of cell type specific effects and the contribution of cofactors in the transcriptional synergy.
Thus the main goals of my thesis work have been:
1. To evaluate the hierarchy of nucleotides in the DNA code read by p53 and NF-kB as sequence-specific transcription factors.
2. Investigate the conservation of transactivation capacity and specificity between yeast and mammalian systems for the tested panel of REs.
3. Estimate the contribution of physical properties of DNA (torsional rigidity or flexibility) contiguous to a p53 RE in influencing the strength and the direction of transcription.
4. Explore the molecular mechanisms underlying transcriptional synergy in response to Doxorubicin and TNF alpha treatment
Marine organisms as sources of materials for instructive scaffolds design
Get PDFDuring the last years, there has been an even increasing interest for natural derived materials and for the study of the biophysical processes involved in their formation.
In fact, despite the possibility to fabricate home-made materials in reproducible way to meet specific performance demands, the complexity of biological systems suggested to consider nature as an inspiration for the design and synthesis of new types of materials. In this context, marine biomaterials are a area of research with significant applications. In fact, the marine environment represents a unique resource of natural inorganic and organic materials with peculiar properties such as chemical and structural complexity, multifunctionality and miniaturization that are not possible to obtain in the laboratory. Therefore, the isolation, characterization and processability of marine materials are crucial aspects for the development of the marine biotechnologies industry. The aim of this study was to to isolate and synthesize naturally-derived materials from marine organisms for biomedical use and namely for tissue engineering applications. The study has been divided into two main parts. The first part concerned the isolation and characterization of an important natural biopolymer: collagen. In particular, Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were isolated from Loligo Vulgaris squid mantle and comparatively characterized.
In the second part of the work a novel method to process cuttlefish bone powders for the production of highly bioactive ceramics formulations has been developed
Frame-Based Ontology Population from Text: Models, Systems, and Applications
No full textOntology Population from text is an interdisciplinary task that integrates Natural Language Processing (NLP), Knowledge Representation, and Semantic Web techniques to extract assertional knowledge from texts according to specific ontologies. As most information on the Web is available as unstructured text, Ontology Population plays an important role in bridging the gap between structured and unstructured data, thus helping realizing the vision of a (Semantic) Web where contents are equally consumable by humans and machines. In this thesis we move beyond Ontology Population of instances and binary relations, and focus on (what we call) Frame-based Ontology Population, whose target is the extraction of semantic frames from text. Semantic frames are defined by RDFS/OWL ontologies, such as FrameBase and the Event Situation Ontology derived from FrameNet, and consist in events, situations and other structured entities reified as ontological instances (e.g., a sell event) and connected to related instances via properties specifying their semantic roles in the frame (e.g., seller, buyer). This representation (called neo-Davidsonian) supports expressing n-ary and arbitrarily qualified relations, and permits leveraging complex NLP tasks such as Semantic Role Labeling (SRL), which annotates frame-like structures in text consisting of predicates and their semantic arguments as defined by domain-general predicate models.
We contribute to the task of Frame-based Ontology Population from multiple directions. We start with developing an extension of the Lemon lexicon model for ontologies (PreMOn) to represent predicate models --- PropBank, NombBank, VerbNet, and FrameNet --- and their mappings to FrameBase. Based on this, our core contribution is a Frame-based Ontology Population approach (PIKES) where processing is decoupled in two phases: first, an English text is processed by a SRL-based NLP pipeline to extract mentions, i.e., snippets of text denoting entities or facts; then, mentions are processed by mapping rules to extract ontological instances aligned to DBpedia and Yago, and semantic frames aligned to FrameBase. We represent all the contents involved in this process in RDF with named graphs, according to an ontological model (KEM) built on top of the semiotic notions of meaning and reference, aligned to DOLCE and the NLP Interchange Format (NIF) ontologies. The model allows navigating from any piece of extracted knowledge to its mentions and back, and allows representing all the generated intermediate information (e.g., NLP annotations) and associated metadata (e.g., confidence, provenance). Based on this model, we propose a scalable system (KnowledgeStore) for storing and querying all the text, mentions, and RDF data involved in the population process, together with relevant RDF background knowledge, so that they can be jointly accessed by applications. Finally, to support the necessary RDF processing tasks, such as rule evaluation, RDFS and owl:sameAs inference, and data filtering and integration, we propose a tool (RDFpro) implementing a simple, non-distributed processing model combining streaming and sorting techniques in complex pipelines, capable of processing billions of RDF triples on a commodity machine.
We describe the application of these solutions for processing differently scoped/sized datasets within and outside the NewsReader EU Project, and for improving search performances in Information Retrieval, through an approach (KE4IR) that enriches the term vectors of documents and queries with semantic terms obtained from extracted knowledge. All the proposed solutions were implemented and released open-source with demonstrators, and ontological models were published online according to Linked Data best practices. The results obtained were validated via empirical performance evaluations and case studies
Shaping economic inequality: the starring role of the household in the 'welfare triad'
No full textThe present thesis analyses the role of household in producing and reproducing inequality in contemporary societies. While individual and macro level factors influencing economic inequality have been widely investigated, meso level factors have received much less attention so far. This thesis, thus, investigates how the employment behaviour of individuals and their sorting into households, and their dynamics in time and space contribute to deepen inequality. Firstly, it contributes to the still open debate on the consequences of changes in households for economic inequality focusing on four European countries and the United States over two decades. Increases in single-headed households, in female labour market participation, and in the employment and earnings similarity of partners are changes of primary interests for economic inequality. In addition, the thesis investigates how market, state, and family produce and redistribute economic resources and shape the distribution of income and its stratification across household types. Secondly, the thesis moves then towards a dynamic perspective and merges three different lines of research: the life course research, stratification research, and comparative research. It does so studying how life course events affect income trajectories of different social groups in different countries/contexts. Specifically, this thesis investigates the consequences of job loss across different social strata. The idea is that social risks may strengthen or weaken social stratification if risks, and their consequences, are unevenly distributed across social groups. Finally, these aspects are investigated for two countries, Germany and the United States, characterized by relevant variations in those institutions – the market, family and welfare state – which have the capacity to affect the risk of experiencing job loss, and to buffer its economic consequences