1731 research outputs found
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Privacy Preserving Enforcement of Sensitive Policies in Outsourced and Distributed Environments
No full textThe enforcement of sensitive policies in untrusted environments is still an open challenge for policy-based systems. On the one hand, taking any appropriate security decision requires access to these policies. On the other hand, if such access is allowed in an untrusted environment then confidential information might be leaked by the policies. The key challenge is how to enforce sensitive policies and protect content in untrusted environments. In the context of untrusted environments, we mainly distinguish between outsourced and distributed environments. The most attractive paradigms concerning outsourced and distributed environments are cloud computing and opportunistic networks, respectively.
In this dissertation, we present the design, technical and implementation details of our proposed policy-based access control mechanisms for untrusted environments. First of all, we provide full confidentiality of access policies in outsourced environments, where service providers do not learn private information about policies during the policy deployment and evaluation phases. Our proposed architecture is such that we are able to support expressive policies and take into account contextual information before making any access decision. The system entities do not share any encryption keys and even if a user is deleted, the system is still able to perform its operations without requiring any action. For complex user management, we have implemented a policy-based Role-Based Access Control (RBAC) mechanism, where users are assigned roles, roles are assigned permissions and users execute permissions if their roles are active in the session maintained by service providers. Finally, we offer the full-fledged RBAC policies by incorporating role hierarchies and dynamic security constraints.
In opportunistic networks, we protect content by specifying expressive access control policies. In our proposed approach, brokers match subscriptions against policies associated with content without compromising privacy of subscribers. As a result, an unauthorised broker neither gains access to content nor learns policies and authorised nodes gain access only if they satisfy fine-grained policies specified by publishers. Our proposed system provides scalable key management in which loosely-coupled publishers and subscribers communicate without any prior contact. Finally, we have developed a prototype of the system that runs on real smartphones and analysed its performance
The sub Saharan Africa Cotton Sector. Selected Features
No full textThough cotton only represents a very small share in world merchandise trade, it is an indispensable commodity in sub-Saharan Africa (SSA). Productivity and profitability of cotton production and processing are key determinants of growth in cotton producing countries. This study analyses the SSA cotton sector. The first section will use value chain analysis to trace the value creation process from the raw material stage to final retail products. The second section analyses the sector from an industrial organizational perspective, highlighting how the sector’s specific features have influenced reforms outcomes and comparing experiences to other reformed SSA crop sectors. The purpose of section three is to shed light on Research and Development in cotton in SSA, framed in a broader picture of agricultural research in SSA. The final section analyses the issue of quality in cotton and tests the assertion that fully implemented reforms have undermined quality performance of the cotton sector in SSA.
Keywords sub-Saharan Africa Cotton Sector, Cotton Liberalization, Cotton R&D, Cotton Qualit
Analysis of the PC algorithm as a tool for the inference of gene regulatory networks: evaluation of the performance, modification and application to selected case studies.
No full textThe expansion of a Gene Regulatory Network (GRN) by finding additional causally-related genes, is of great importance for our knowledge of biological systems and therefore relevant for its biomedical and biotechnological applications.
Aim of the thesis work is the development and evaluation of a bioinformatic method for GRN expansion. The method, named PC-IM, is based on the PC algorithm that discovers causal relationships starting from purely observational data. PC-IM adopts an iterative approach that overcomes the limitations of previous applications of PC to GRN discovery.
PC-IM takes in input the prior knowledge of a GRN (represented by nodes and re-
lationships) and gene expression data. The output is a list of genes which expands the known GRN. Each gene in the list is ranked depending on the frequency it appears causally
relevant, normalized to the number of times it was possible to find it. Since each frequency value is associated with precision and sensitivity values calculated using the prior knowledge of the GRN, the method provides in output those genes that are above the value of frequency that optimize precision and sensitivity (cut-off frequency).
In order to investigate the characteristics and the performances of PC-IM, in this thesis work several parameters have been evaluated such as the influence of the type and size of input gene expression data, of the number of iterations and of the type of GRN.
A comparative analysis of PC-IM versus another recent expansion method (GENIES) has been also performed.
Finally, PC-IM has been applied to expand two real GRNs of the model plant Arabidopsis thaliana
Jean Hotman (1552-1636)- Irenik im Spannungsfeld von späthumanistischer Gelehrsamkeit, Theologie und Religionspolitik in Frankreich um 1600
No full textIn der Reformationsgeschichtsschreibung wurde der Blick in den letzten Jahrzehnten zunehmend über gängige Schematismen der Konfessionsgrenzen hinweg auf Phänomene individualisierter religiöser Sensibilität gerichtet, die sich "weder Rom noch Genf" eindeutig zuordnen lassen und erst unter der Prämisse von religiöser Pluralität greifbar werden. Unter solchen Prämissen sind auch die vielfältigen religiösen Reunionsprojekten des 16. und frühen 17. Jahrhunderts zu untersuchen, die von religiös moderaten Kräften beider Lager entworfen wurden. Diese Phänomene werden in meinem Dissertationsprojekt an französischen Fallbeispielen untersucht. Insbesondere die Regierungszeit Heinrichs IV. gab Friedensansätzen ungeheuren Aufwind. Es geht in diesem Zusammenhang auch um eine differenzierte Vermessung der vertretenen Ideen sowie um ihre Zuordnung zu verschiedenen Gelehrtenkreisen, die in der Forschung immer noch häufig unter dem einheitlichen Etikett der "Politiques" firmieren. Exemplarisch wird dies an den Werken und der Korrespondenz von Jean Hotman (1552-1636) unternommen. Dieser stand in der Forschung bisher - obwohl an seiner überragenden Bedeutung für die Initiativen zur Stiftung religiösen Friedens kein Zweifel herrschen kann - meist im Schatten seines Vaters François Hotman. Dies mag nicht zuletzt daran liegen, dass Jean Hotman hauptsächlich als Sammler und Herausgeber anderer Autoren bekannt wurde, statt mit eigenen Werken groß in Erscheinung zu treten. Allerdings schmälerte dies keineswegs seinen Einfluss auf die tagespolitischen Geschehnisse, da solche Kompilationen oft substantiell auf die Weltbilder und Argumentationsmuster der Zeitgenossen wirken konnten. Bibliographien, wie der von Hotman 1607 verfasste Syllabus (weitere Ausgaben 1628, 1629), sind deshalb für den Reunionsdiskurs des 16. und frühen 17. Jahrhunderts von höchstem Erkenntnisinteresse. Die internationale Ausrichtung dieser Textsammlung bietet auf der einen Seite die Möglichkeit, den Unions- und Toleranzdiskurs in Frankreich in seine prägenden europäischen Kontexte einzuordnen, und ermöglicht auf der anderen Seite, Verbindungslinien aufzuzeigen, welche die frühen Texte der Reformation mit solchen des 17. Jahrhunderts verbinden. Vielfach wird hierbei deutlich, dass verschiedene Denkansätze über die Regierungszeit Heinrichs IV. hinaus ihre Aktualität behielten und Zäsuren wie "1598" und "1610" hinterfragt werden müssen
New Maps for Africa? Contextualising the 'Chinese Model' within Ethiopian and Kenyan Paradigms of Development
No full textSince the early 2000s, there has been a sharp increase in speculations that China’s development trajectory may provide a model for other developing countries—particularly those in Africa—to follow, and that this poses a profound challenge to the dominant global development paradigm. A highly-charged media and policy debate has increasingly made its way into the academic literature, with central questions focusing around the lessons that African and developing countries are drawing from China and around the desirability of such emulation. Due to the exploratory and recent nature of this growing literature, however, very few studies have been sufficiently grounded in empirical or theoretical analysis.
This dissertation seeks to remedy this situation by examining the ideational influence of China’s development on those ultimately charged with evaluating and implementing these purported ‘models’: developing country elites. Drawing on the theories of cross-societal emulation (Westney 1987) and lesson-drawing (Rose 1991), it finds that elites in two countries cases—Ethiopia and Kenya-indeed seek to emulate countries in East Asia. China, however, is viewed as only one source of potential ‘lessons’, and its elites often embed its experiences within a wider East Asian development trajectory.
In both country cases, this emulation challenges many of the assumptions that have driven development since the 1970s. Unlike the Washington Consensus, the development paradigm prompted by this lesson-drawing is historically-contingent and views nation-building by a strong, visionary political leadership as the country’s single most important priority. Because it favours large physical infrastructure projects, rapid economic growth, technologically-optimistic solutions and a civilisatory discourse, its divergence from the more recent ‘Augmented’ Washington Consensus is even more striking. In these and in other central lessons drawn, the development approach it most resembles, in fact, is the modernisation theory of the 1950s and 1960s.
Despite the fact that both Kenya and Ethiopia thus possess modernising elites that seek to emulate aspects of the East Asian experience, different dynamics drive the process in each national context. In Ethiopia, a country slowly emerging from a history of communism and isolationism, a strong and ideologically unified ruling party looks to China, South Korea and other countries with a history of strong state intervention. In Kenya, by contrast, a coalition of business leaders, technocrats and planners view Singapore and Malaysia as potential models by virtue of a shared colonial history and divergent post-colonial path. Kenya’s vision, whilst more moderate, is also more constrained due to the relative lack of influence its modernisers wield in the political process. In both cases, historical factors bound and condition elites’ choice of model.
The emerging literature on the ‘Chinese Model’ of development deserves credit for beginning to theoretically and empirically substantiate an important current policy debate, but it also vastly underestimates the importance of its predecessors. Given the extent to which Ethiopian and Kenyan elites root their emulation in the region as a whole, the East Asian ‘developmental state’ model is one such fore-runner. Most importantly, however, this emulation illustrates the enduring topicality of many of the assumptions of modernisation theory—assumptions that are likely to play a central role in informing African and even global development paradigms in the future
Large-scale Structural Reranking for Hierarchical Text Categorization
No full textCurrent hierarchical text categorization (HTC) methods mainly fall into three directions: (1) Flat one-vs.-all approach, which flattens the hierarchy into independent nodes and trains a binary one-vs.-all classifier for each node. (2) Top-down method, which uses the hierarchical structure to decompose the entire problem into a set of smaller sub-problems, and deals with such sub-problems in top-down fashion along the hierarchy. (3) Big-bang approach, which learns a single (but generally complex) global model for the class hierarchy as a whole with a single run of the learning algorithm.
These methods were shown to provide relatively high performance in previous evaluations. However, they still suffer from two main drawbacks: (1) relatively low accuracy as they disregard category dependencies, or (2) low computational efficiency when considering such dependencies.
In order to build an accurate and efficient model we adopted the following strategy: first, we design advanced global reranking models (GR) that exploit structural dependencies in hierarchical multi-label text classification (TC). They are based on two algorithms: (1) to generate the k-best classification of hypotheses based on decision probabilities of the flat one-vs.-all and top-down methods; and (2) to encode dependencies in the reranker by: (i) modeling hypotheses as trees derived by the hierarchy itself and (ii) applying tree kernels (TK) to them. Such TK-based reranker selects the best hierarchical test hypothesis, which is naturally represented as a labeled tree. Additionally, to better investigate the role of category relationships, we consider two interesting cases: (i) traditional schemes in which node-fathers include all the documents of their child-categories; and (ii) more general schemes, in which children can include documents not belonging to their fathers.
Second, we propose an efficient local incremental reranking model (LIR), which combines a top-down method with a local reranking model for each sub-problem. These local rerankers improve the accuracy by absorbing the local category dependencies of sub-problems, which alleviate the errors of top-down method in the higher levels of the hierarchy. The application of LIR recursively deals with the sub-problems by applying the corresponding local rerankers in top-down fashion, resulting in high efficiency.
In addition, we further optimize LIR by (i) improving the top-down method by creating local dictionaries for each sub-problem; (ii) using LIBLINEAR instead of LIBSVM; and (iii) adopting the compact representation of hypotheses for learning the local reranking model. This makes LIR applicable for large-scale hierarchical text categorization.
The experimentation on different hierarchical datasets has shown promising enhancements by exploiting the structural dependencies in large-scale hierarchical text categorization
Contextual effects on the educational ambition of immigrants' children and natives in Italy and Belgium
No full textThe new wave of global immigration to Europe has increased the urgency to discern which aspects of school context and of social interactions within the educational system need to be strengthened in order to create an environment where both immigrant and native students can perform at their best. Looking at educational ambitions allows studying educational performance, in order to estimate the gap between students of migrant backgrounds and natives, and to measure the social integration of immigrants’ children.
My presentation aims to identify which resources and interactions within the school environment need to be strengthened with the purpose of improving educational expectations and aspirations of immigrants’ children and natives.
First, I explore to what extent school resources, parental involvement in school and family environment shape educational expectations of migrants and natives in two European countries: Belgium and Italy. After delineating this international perspective, I deepen the analysis of the Italian case. I investigate to what extent the expectations and aspirations of the children of immigrants are influenced by the educational expectations of their native schoolmates using data on children of immigrants living in Italy and attending their final year of middle school (8th grade). In the final part of my presentation, I tackle the challenging issue of the impact of the presence of immigrants’ children on the educational aspirations of natives
I Sonetti delle Opere Toscane di Luigi Alamanni: edizione critica
No full textIl mio lavoro ha portato all’allestimento dell’edizione critica delle tre sezioni dei Sonetti delle Opere Toscane di Luigi Alamanni. Le Opere Toscane, edite in due volumi tra il 1532 e 1533 a Lione, presentano un’architettura complessa ed estremamente articolata. Contengono quindici diverse sezioni: [volume primo] Elegie, Egloghe, Sonetti (prima sezione), Sonetti (seconda sezione), Favola di Narcisso, Diluvio Romano, Favola di Athlante, Satire, Salmi; [volume secondo] Selve, Favola di Phetonte, Tragedia di Antigone, Inni, Stanze, Sonetti (terza sezione).
Le tre sezioni dei Sonetti constano di un totale di 257 componimenti.
Questa tesi preliminarmente illustra la struttura generale dei due volumi delle Opere Toscane sottolineando le ragioni che hanno persuaso l’autore a far convivere sezioni così numerose, diverse per genere e metro: Alamanni dà alle stampe un libro di poesia unico tra le raccolte coeve spinto da un’ indubbia volontà di sperimentazione letteraria.
A seguito dell’edizione vera e propria, che è scandita secondo le fasi classiche dei lavori d’edizione (censimento della tradizione manoscritta, censimento della tradizione a stampa, nota al testo, edizione dei Sonetti e apparato), mi sono concentrato sull’analisi e sull’edizione di un gruppo delimitato della tradizione manoscritta, i 38 componimenti tràditi dal manoscritto Magliabechiano 676 della Biblioteca Nazionale di Firenze. Questo gruppo di Sonetti presenta le caratteristiche di un piccolo Canzoniere, con dei tratti e un’organizzazione strutturale differenti rispetto alle fisionomie finali che le tre sezioni assumeranno nella princeps
From Hypernuclei to Hypermatter: a Quantum Monte Carlo Study of Strangeness in Nuclear Structure and Nuclear Astrophysics
No full textThe work presents the recent developments in Quantum Monte Carlo calculations for nuclear systems including strange degrees of freedom. The Auxiliary Field Diffusion Monte Carlo algorithm has been extended to the strange sector by the inclusion of the lightest among the hyperons, the Λ particle. This allows to perform detailed calculations for Λ hypernuclei, providing a microscopic framework for the study of the hyperon-nucleon interaction in connection with the available experimental information. The extension of the method for strange neutron matter, put the basis for the first Diffusion Monte Carlo analysis of the hypernuclear medium, with the derivation of neutron star observables of great astrophysical interest
Advances in the modelling of in-situ powder diffraction data
No full textX-ray powder diffraction is a well-established technique to analyse structural and microstructural properties of materials. The possibility to record in-situ powder diffraction data allows studying changes within the structure and microstructure of a sample that occur in dependence on the applied external conditions (e.g. temperature, pressure). In the present thesis, in-situ X-ray powder diffraction was used to study structural and microstructural changes of different samples occurring at elevated temperature or upon UV illumination.
Several structural phase transitions were studied using the approach of parametric Rietveld refinement. In parametric Rietveld refinement a set of powder diffraction pattern is refined simultaneously, constraining the evolution of some parameters using mathematical models, so that only the variables of the model need to be refined. In order to model and analyse the behaviour of structural parameters, Landau theory and its corresponding equations were used, owing to the fact that structural parameters (e.g. lattice strain, changes in atomic positions or occupancy) comprise an order parameter as defined in Landau theory. For description of the crystal structure of materials, several different approaches were tested, e.g. atomic coordinates, symmetry modes, rigid body rotations or rigid body symmetry modes.
The dependence of preparation conditions on the properties of nanomaterials and their growth kinetics was studied using Whole Powder Pattern Modelling. This method allows modelling X-ray powder diffraction pattern using the microstructure of the sample without the use of arbitrary profile functions. The Fourier transforms of frequently observed effects as crystallite shape and size distribution or density of various defects, like dislocations and stacking faults, are utilised in order to get the resulting diffraction profile. Two different systems with industrial application, CeO2 and Cu2ZnSnS4, which were produced using a sol-gel approach, were investigated