Towards Unstructured Knowledge Integration in Natural Language Processing

In the last decades, Artificial Intelligence has witnessed multiple breakthroughs in deep learning. In particular, purely data-driven approaches have opened to a wide variety of successful applications due to the large availability of data. Nonetheless, the integration of prior knowledge is still required to compensate for specific issues like lack of generalization from limited data, fairness, robustness, and biases. In this thesis, we analyze the methodology of integrating knowledge into deep learning models in the field of Natural Language Processing (NLP). We start by remarking on the importance of knowledge integration. We highlight the possible shortcomings of these approaches and investigate the implications of integrating unstructured textual knowledge. We introduce Unstructured Knowledge Integration (UKI) as the process of integrating unstructured knowledge into machine learning models. We discuss UKI in the field of NLP, where knowledge is represented in a natural language format. We identify UKI as a complex process comprised of multiple sub-processes, different knowledge types, and knowledge integration properties to guarantee. We remark on the challenges of integrating unstructured textual knowledge and bridge connections with well-known research areas in NLP. We provide a unified vision of structured knowledge extraction (KE) and UKI by identifying KE as a sub-process of UKI. We investigate some challenging scenarios where structured knowledge is not a feasible prior assumption and formulate each task from the point of view of UKI. We adopt simple yet effective neural architectures and discuss the challenges of such an approach. Finally, we identify KE as a form of symbolic representation. From this perspective, we remark on the need of defining sophisticated UKI processes to verify the validity of knowledge integration. To this end, we foresee frameworks capable of combining symbolic and sub-symbolic representations for learning as a solution.

Use of sub-lethal high pressure homogenization (HPH) treatments to enhance functional properties of lactic acid bacteria probiotic strains

The aim of this PhD thesis was to evaluate the effect of a sub-lethal HPH treatment on some probiotic properties and on cell response mechanisms of already-known functional strains, isolated from Argentinean dairy products. The results achieved showed that HPH treatments, performed at a sub-lethal level of 50 MPa, increased some important functional and technological characteristics of the considered non intestinal probiotic strains. In particular, HPH could modify cell hydrophobicity, autoaggregation and resistance to acid gastric conditions (tested in in vitro model), cell viability and cell production of positive aroma compounds, during a refrigerate storage in a simulated dairy product. In addition, HPH process was able to increase also some probiotic properties exerted in vivo and tested for two of the considered strains. In fact, HPH-treated cells were able to enhance the number of IgA+ cells more than other not treated cells, although this capacity was time dependent. On the other hand, HPH treatment was able to modify some important characteristics that are linked to the cell wall and, consequently, could alter the adhesion capacity in vivo and the interaction with the intestinal cells. These modifications, involving cell outermost structures, were highlighted also by Trasmission Electron Microscopy (TEM) analysis. In fact, the micrographs obtained showed a significant effect of the pressure treatment on the cell morphology and particularly on the cell wall. Moreover, the results achieved showed that composition of plasma membranes and their level of unsaturation are involved in response mechanisms adopted by cells exposed to the sub-lethal HPH treatment. Although the response to the treatment varied according to the characteristics of individual strains, time of storage and suspension media employed, the results of present study, could be exploited to enhance the quality of functional products and to improve their organoleptic properties.

Who can (not) be Greek? Citizenship, Identity and Belonging among youth of sub-Saharan African background in Athens

‘Who can be Greek?’ This was the question posed to the Greek society for the first time before the implementation of the Act 3838 in March 2010 which gave the right to access the Greek citizenship -under specific preconditions- to all children of legal migrants born or schooled in Greece. This change of the Nationality Code in order to include all those children was coincided by the economic crisis resulting into the rise of xenophobia, racism and extreme-right rhetoric. The outcome was the cancellation of the Act 3838 by the State Council in February 2013. Under this particular framework, the notions of identity and belonging formed among the youth of African background in Athens are explored. The ways those youngsters perceive not only themselves but also their peers, their countries of origin and the country they live in, are crucial elements of their self-identification. Researches have shown that the integration of the second generation is highly connected to their legal and social status. However, integration is a rather complex process, influenced and shaped by many variables and multiple factors. It is not linear; therefore, its outcomes are difficult to be predicted. Yet, I argue that citizenship acquisition facilitates the process as it transforms those children from ‘aliens’ to ‘citizens’. How these youngsters are perceived by the majority society and the State is one of the core questions of the research, focusing on the imposed dual ‘otherness’ they are subject to. On the one hand, they have to deal with the ‘otherness’ originating from the migrant status inherited to them by their parents, and on the other with the ‘otherness’ deriving from their different phenotypic characteristics. Race matters and becomes a means of discrimination against youth of African background who are perceived as inassimilable and ‘forever others’.