A multifold approach to address the security issues of stateful forwarding mechanisms in Information-Centric Networks.

Doctoral thesis (2018)

Today's Internet dominant usage trends motivate research on more content-oriented future network architectures. Among the emerging future Internet proposals, the promising Information-Centric Networking ... [more ▼]

Today's Internet dominant usage trends motivate research on more content-oriented future network architectures. Among the emerging future Internet proposals, the promising Information-Centric Networking (ICN) research paradigm aims to redesign the Internet's core protocols to promote a shift in focus from hosts to contents. Among the ICN architectures, the Named-Data Networking (NDN) envisions users' named content requests to be forwarded and recorded by their names in routers along the path from one consumer to 1-or-many sources. The Pending Interest Table (PIT) is the NDN's data-plane component which temporarily records forwarded content requests in routers. On one hand, the PIT stateful mechanism enables properties like requests aggregation, multicast responses delivery and native hop-by-hop control flow. On the other hand, the PIT stateful forwarding behavior can be easily abused by malicious users to mount disruptive distributed denial of service attacks (DDoS), named Interest Flooding Attacks (IFAs). In IFAs, loosely coordinated botnets flood the network with a large amount of hard to satisfy requests with the aim to overload both the network infrastructure and the content producers. Countermeasures against IFA have been proposed since the early attack discovery. However, a fair understanding of the defense mechanisms' real efficacy is missing since those have been tested under simplistic assumptions about the evaluation scenarios. Thus, overall, the IFA security threat still appears easy to launch but hard to mitigate. This dissertation work shapes a better understanding of both the implications of IFAs and the possibilities of improving the state-of-the-art defense mechanisms against these attacks. The contributions of this work include the definition of a more complete and realistic attacker model for IFAs, the design of novel stealthy IFAs built upon the proposed attacker model, a re-assessment of the most-efficient state-of-the-art IFA countermeasures against the novel proposed attacks, the theorization and one concrete design of a novel class of IFA countermeasures to efficiently address the novel stealthy IFAs. Finally, this work also seminally proposes to leverage the latest programmable data-plane technologies to design and test alternative forwarding mechanisms for the NDN which could be less vulnerable to the IFA threat. [less ▲]

Anti-de Sitter geometry: convex domains, foliations and volume

Doctoral thesis (2018)

We study various aspects of the geometry of globally hyperbolic anti-de Sitter 3-manifolds. For manifolds with convex space-like boundaries, homeomorphic to the product of a closed, connected and oriented ... [more ▼]

We study various aspects of the geometry of globally hyperbolic anti-de Sitter 3-manifolds. For manifolds with convex space-like boundaries, homeomorphic to the product of a closed, connected and oriented surface of genus at least two with an interval, we prove that every pair of metrics with curvature less than -1 on the surface can be realised on the two boundary components. For globally hyperbolic maximal compact (GHMC) anti-de Sitter manifolds, we study various geometric quantities, such as the volume, the Hausdorff dimension of the limit set, the width of the convex core and the Holder exponent of the manifold, in terms of the parameters that describe the deformation space of GHMC anti-de Sitter structures. Moreover, we prove existence and uniqueness of a foliation by constant mean curvature surfaces of the domain of dependence of any quasi-circle in the boundary at infinity of anti-de Sitter space. [less ▲]

Speaker evaluations in multilingual contexts: The predictive role of language and nationality attitudes as distinct factors in explicit and implicit cognition

Doctoral thesis (2018)

Previous speaker evaluation models have assumed that, in social interactions, attitudes towards languages are the most salient cues that are used to form an evaluation of the person who is speaking (Giles ... [more ▼]

Previous speaker evaluation models have assumed that, in social interactions, attitudes towards languages are the most salient cues that are used to form an evaluation of the person who is speaking (Giles & Marlow, 2011). The role of attitudes towards the speaker’s national group has not been addressed because most studies have been conducted in monolingual contexts in which spoken language serves as a clear indicator of national group membership. However, the concepts of language and nationality cannot be equated in multilingual societies, which are characterized by various nationals using different languages. The present dissertation addresses the need for the development of a revised theoretical model for multilingual contexts by making a distinction between language, nationality, and speaker concepts on both an explicit and an implicit level. The adapted model applies social-cognitive theories that propose a distinction between explicit and implicit processes and further posits a differential predictive influence of explicit and implicit attitudes on explicit and implicit speaker evaluations. In the multilingual context of Luxembourg, three successive studies were conducted by adapting an audio-based Implicit Association Test (IAT) as an implicit measure of language and nationality attitudes and an evaluative priming task as implicit measure of speaker evaluations. The findings emphasized the convergent and discriminant validity of language and nationality attitudes on both an explicit and an implicit level. Furthermore, the distinctness of explicit and implicit speaker evaluations was confirmed such that explicit evaluations were influenced by explicit attitudes, and implicit evaluations were affected by implicit attitudes. In the fourth study, the model was transferred to the linguistic context of Montreal (Canada). The findings showed that implicit speaker preferences were affected by implicit nationality attitudes affirming model transferability. Overall, the dissertation shows that language is a salient factor in explicit person perception, whereas nationality plays a vital role on an implicit level, demonstrating the added value of the language-nationality and the explicit-implicit distinction in the speaker evaluation formation. Self-reports diverged from implicit measures such that an in-group bias was visible only on an implicit level, giving insight into the effect of specific socio-contextual factors in a given linguistic context as well as the practical implications for decision makers in professional domains. [less ▲]

Advanced Raman Spectroscopy of Ultrathin RNiO3 films

Doctoral thesis (2018)

The present work aims at investigating the structural properties of ultrathin rare-earth nickelate films by Raman Spectroscopy. Two remarkable cases are studied: LaNiO3 deposited epitaxially on LaAlO3 ... [more ▼]

The present work aims at investigating the structural properties of ultrathin rare-earth nickelate films by Raman Spectroscopy. Two remarkable cases are studied: LaNiO3 deposited epitaxially on LaAlO3, which shows a metal-to-insulator (MIT) transition but only in the ultrathin film regime, and NdNiO3 deposited epitaxially on NdGaO3 showing an upward shift of its MIT temperature by 130 K but only when deposited along the [111]pc direction of the substrate. The extremely small size of the films and overlap of the film and substrate signatures represent an experimental challenge and require the development of ingenious measurement and analysis strategies. To overcome these limitations, we propose the creation of a multidimensional dataset through depth profile acquisitions, in combination with multivariate analysis tools that were employed to extract the signature of the films. Different analysis strategies were used in both cases to adapt to the specificities of the respective samples. For the LNO films deposited along the [001]pc orientation of LAO, Raman depth profile measurements in combination with a Principal Component Analysis (PCA) allowed us to dissociate the signals from the film and the substrate. The evolution of the LNO peaks does not suggest any phase transition, thus, suggesting that a mechanism unrelated to the MIT of other nickelates is triggering the insulating state. This was further validated by ab initio calculations and TEM imaging. All acquired data point towards the following: as LNO becomes very thin, the surface layer (≈ 2pc u.c.), which is the most rigid part of the structure, imposes its structural and insulating characteristic. In the ultrathin regime this continues to a point where the surface of the film alters the interfacial unit cells of the substrate. For the NNO films deposited along the [111]pc orientation of NGO, depth profile measurements in combination with a Non-negative Matrix Factorisation (NMF) allowed us to dissociate the signals from the film and the substrate. The dissociation was performed at room temperature and the acquired knowledge was then utilised to fit an entire temperature series from 5 to 390 K. Comparing the tendency of the Raman signatures with other rare-earth nickelate allowed to support the proposed position of the film in the phase diagram of nickelates by a structural measurement. More generally, the methodology developed in this work is applicable to other systems and opens new perspectives for application of Raman spectroscopy on ultra-thin films. [less ▲]

The Assessment of Collaborative Problem Solving in PISA 2015: An Investigation of the Validity

Doctoral thesis (2018)

Magnetic small-angle neutron scattering on bulk metallic glasses

Doctoral thesis (2018)

The present PhD thesis is devoted to the exploration of the use of the magnetic small-angle neutron scattering (SANS) technique for analyzing the magnetic microstructure of bulk magnetic materials. More ... [more ▼]

The present PhD thesis is devoted to the exploration of the use of the magnetic small-angle neutron scattering (SANS) technique for analyzing the magnetic microstructure of bulk magnetic materials. More specifically, magnetic-field-dependent SANS has been utilized to study the magnetic microstructure of bulk metallic glasses (BMGs). The magnetic scattering is compared for soft magnetic and hard magnetic compositions in different mechanically treated states. On the basis of the continuum theory of micromagnetics, the correlation function of the spin-misalignment SANS cross section is computed and analyzed as a function of various external and material parameters. Analysis of the experimental correlation functions of the BMG reveals the existence of field-dependent anisotropic long-wavelength magnetization fluctuations on a scale of a few tens of nanometers. As a second aspect of this PhD work, we have explored the impact of the Dzyaloshinski-Moriya interaction on the elastic magnetic SANS cross section of microstructural-defect-rich materials. The effect was demonstrated by measuring polarized SANS on a nanocrystalline terbium sample and on a cold-rolled polycrystalline cobalt sample. [less ▲]

Kindheit und Fantastik. Historische Fallstudien zur Doppelcodierung in der Kinderliteratur

Doctoral thesis (2018)

Development of mass spectrometry-based assays to measure the ERCC1/XPF proteins as potential biomarkers in lung cancer

Doctoral thesis (2018)

In the last two decades, the integration of personalized medicine approaches in the management of oncology patients has led to important progress. Indeed, the use of predictive biomarkers in clinical ... [more ▼]

In the last two decades, the integration of personalized medicine approaches in the management of oncology patients has led to important progress. Indeed, the use of predictive biomarkers in clinical practice to improve treatment strategies has represented an important achievement for both patient clinical outcomes and quality of medical care. In the context of lung cancer, several studies have highlighted a potential role of the excision repair cross-complementation group 1 (ERCC1) protein as a predictive biomarker of platinum-based chemotherapy efficacy in the treatment of non-small cell lung cancer (NSCLC) patients. ERCC1 protein and its binding partner, the DNA repair endonuclease XPF, are key players in the nucleotide excision repair (NER) pathway where they repair DNA lesions caused by platinum-based drugs. However, the presence of four ERCC1 isoforms, of which only one, ERCC1-202, is functional in the NER pathway, complicates the clinical scenario. Indeed, the lack of an antibody that specifically recognizes ERCC1-202 hampers the development of a valid clinical assay to assist clinicians in therapeutic decision making. Moreover, the essential nature of the ERCC1/XPF interaction to repair DNA lesions, suggested the pivotal role of the ERCC1/XPF complex in the prediction of therapy response. Because of the need to discriminate among the four ERCC1 isoforms, to selectively quantify ERCC1-202 in an antibody-independent fashion, and because of the required contribution of the XPF protein in the DNA lesion processing, the present project aimed to develop robust mass spectrometry (MS)-based assays for the ERCC1 and XPF isoforms to provide accurate quantification of the ERCC1-202/XPF proteins as binding partners. Combining ERCC1 or XPF immunoenrichment from biological samples with targeted mass spectrometry, the selected ERCC1 and XPF proteotypic peptides (PTPs) were measured by parallel reaction monitoring (PRM) using a quadrupole-obitrap mass spectrometer. The quantification of the ERCC1-202/XPF proteins was performed using stable isotope labeled (SIL) peptides. The associated results showed that the simultaneous detection of three ERCC1 PTPs, named isoform discriminating peptides, represents a signature of ERCC1-202 and that the inclusion of control peptides allows to avoide ERCC1 isoform misclassification. The immuno-affinity studies and the evaluation of XPF stability highlighted that ERCC1-202 interacts and stabilizes XPF. Finally, a correlation between ERCC1-202/XPF protein levels was observed. In the light of the poor analytic specificity of the current immunohistochemistry (IHC) assay for the ERCC1 protein, the use of targeted MS-based assays to detect and quantify both ERCC1-202 and XPF proteins represents a more selective approach. These findings strongly suggest to assess the role of the ERCC1-202/XPF proteins as predictive biomarkers in clinical samples with the final goal to guide the clinicians’ therapeutic decisions. [less ▲]

ENFORCING EUROPEAN COMPETITION LAW THROUGH LENIENCY PROGRAMMES IN THE LIGHT OF FUNDAMENTAL RIGHTS - WITH AN OVERVIEW OF THE US LENIENCY PROGRAMME

Doctoral thesis (2018)

MULTI-GNSS ERROR CHARACTERISTICS AND BENEFITS TO LONG-TERM MONITORING APPLICATIONS IN GEOSCIENCES

Doctoral thesis (2018)

Global Navigation Satellite System (GNSS)-derived position solutions are used for crustal deformations for long-term monitoring studies such as correcting sea-level records for vertical land movements and ... [more ▼]

Global Navigation Satellite System (GNSS)-derived position solutions are used for crustal deformations for long-term monitoring studies such as correcting sea-level records for vertical land movements and to determine present-day surface-mass changes. In all these studies scientists rely heavily on precise International GNSS Service (IGS) products. In recent years the IGS products have partly been generated from a rigorous combination of GNSS, such as Global Positioning System (GPS) and Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) observations. Although combined solutions from two or more GNSS benefit from the diversity and redundancy of having more than one GNSS, the solutions are also subjected to system-specific systematic errors. Applications which demand high-accuracy products, therefore, would profit from evaluations of the benefits and error characteristics of combined GNSS solutions. In response to the increased availability of multi-GNSS observations from a truly global ground network of receivers, the goal of this thesis is to investigate their overall impacts on the derived products. Primarily, the impacts of combined GNSS data processing for stations in a constrained environment with a potential for signal obstructions, is investigated. The effects of signal obstructions on derived parameter time series and station velocity estimates are assessed. The benefits of combined solutions are evaluated for stations in constrained environments. Moreover, the study of the impacts of combined solutions on satellite orbits and station parameters contributes to the understanding of the error characteristics of combined GNSS data processing on derived products. The consistency of the parameters, noise analysis and system-specific periodic errors are assessed. Dominant system specific periodic errors and the impact of combined solutions on reducing the effects are addressed. Unmodelled or insufficiently modelled (sub-)daily errors propagate to longer periods and appear in high-end products coinciding with other longer periods, which in turn may lead to misleading interpretations of the latter. The propagation mechanism mainly depends, among other factors, on data sampling deficiencies and GNSS ground repeat periods. Here, the results of this study show that combined solutions not only reduce system-specific effects but also provide a means to identifying the sources from other compatible elements. [less ▲]

Stochastic Model Predictive Control for Eco-Driving Assistance Systems in Electric Vehicles

Doctoral thesis (2018)

Electric vehicles are expected to become one of the key elements of future sustainable transportation systems. The first generation of electric cars are already commercially available but still, suffer ... [more ▼]

Electric vehicles are expected to become one of the key elements of future sustainable transportation systems. The first generation of electric cars are already commercially available but still, suffer from problems and constraints that have to be solved before a mass market might be created. Key aspects that will play an important role in modern electric vehicles are range extension, energy efficiency, safety, comfort as well as communication. An overall solution approach to integrating all these aspects is the development of advanced driver assistance systems to make electric vehicles more intelligent. Driver assistance systems are based on the integration of suitable sensors and actuators as well as electronic devices and software-enabled control functionality to automatically support the human driver. Driver assistance for electric vehicles will differ from the already used systems in fuel-powered cars such as electronic stability programs, adaptive cruise control etc. in a way that they must support energy efficiency while the system itself must also have a low power consumption. In this work, an eco-driving functionality as the first step towards those new driver assistance systems for electric vehicles will be investigated. Using information about the internal state of the car, navigation information as well as advanced information about the environment coming from sensors and network connections, an algorithm will be developed that will adapt the speed of the vehicle automatically to minimize energy consumption. From an algorithmic point of view, a stochastic model predictive control approach will be applied and adapted to the special constraints of the problem. Finally, the solution will be tested in simulations as well as in first experiments with a commercial electric vehicle in the SnT Automation & Robotics Research Group (SnT ARG). [less ▲]

Angle and Spectral Dependence of the Internal and External Quantum Efficiency of Solar Modules

Doctoral thesis (2018)

Reviewing scientific publications in the field of photovoltaic research, it becomes apparent that most of the investigations are carried out under perpendicular light incidence even though many of the ... [more ▼]

Reviewing scientific publications in the field of photovoltaic research, it becomes apparent that most of the investigations are carried out under perpendicular light incidence even though many of the relevant processes in a solar cell or module may strongly depend on the angle of incidence. The reasons for this are most likely due to three facts. Firstly, the equipment that is available for measurements and characterization in research laboratories is mainly constructed for perpendicular incidence. Secondly, the complexity of the analysis strongly increases when the angle of incidence is considered and thirdly, there is still a lack of standardization, which makes it difficult to compare the performance of solar modules at oblique incidence. Regarding the maximization of the annual energy yield of a solar module it is crucial to be aware of operating conditions in the field. It is obvious that most of the time, light is incident on the module’s surface with an oblique angle. However, it is not sufficient to investigate the short circuit current density effects due to the variation of the angle of incidence as it is often done. The reflection and absorption properties of the materials in a solar module generally vary with the wavelength of the incident light. This is the reason why it is convenient to take the angular and the spectral performance of solar modules into account simultaneously. In this thesis a synopsis of all the relevant angle and spectral dependent effects is presented for silicon solar cells and modules. It is shown that not only optical effects are occurring, but that the internal quantum efficiency (IQE) also varies with the angle of incidence. It is also shown to which extent the implementation of textured surfaces influences the angle dependence of the external quantum efficiency (EQE) and the IQE. The analysis is performed using a newly developed analytical solar cell model that takes into account all relevant parasitic absorption processes in an untextured solar cell. Using an effective angle approach, the analysis can be extended to a textured solar cell. For more complex structures, a ray tracing tool was developed that is capable of simulating several textured layers and subsequently, of determining the corresponding EQE and IQE at all desired angles of incidence. The angle and spectral dependence of the cells and modules under investigation were determined using measurement equipment that was particularly constructed for this purpose. The angle dependence of the EQE of the samples was determined with two different systems: A filter monochromator to determine the spectral response and by transforming the electroluminescence spectrum of the samples to the EQE using the opto-electronic reciprocity relation of solar cells. To determine the angle dependence of the IQE, a measurement setup was constructed for the determination of the angular reflection spectra. Finally, the different angle and spectral dependent effects that were identified were analyzed with respect to their influence on the energy yield estimation of standard solar modules under outdoor conditions. [less ▲]

Many-Body Perturbation Theory Approach to Raman Spectroscopy and Its Application to 2D Materials

Doctoral thesis (2018)

Raman spectroscopy has become one of the most important techniques for the characterization of materials, as it allows the simultaneous probing of several properties, such as electronic and vibrational ... [more ▼]

Raman spectroscopy has become one of the most important techniques for the characterization of materials, as it allows the simultaneous probing of several properties, such as electronic and vibrational excitations, at once. This versatility, however, makes its theoretical description very challenging and, up to now, no fully satisfactory and general way for the calculation of Raman spectra from first principles exists. In this thesis, we aim to fill this gap and present a coherent theory of Raman scattering within the framework of many-body perturbation theory. We develop a novel and general, correlation function-based approach for the calculation of Raman scattering rates that can potentially also be applied to ultra-fast Raman spectroscopy out of equilibrium. Besides these theoretical developments, we present concrete computational recipes for the calculation of Raman intensities that allow the inclusion of both excitonic effects and non-adiabatic effects of lattice vibrations. The latter has so far not been possible with state-of-the-art methods, which can only take into account one of the two effects. As a first test case, we apply our theory to graphene, for which we use it to study the laser frequency and Fermi energy dependence of the Raman G-peak intensity. The flexibility of our approach also allows us to demonstrate that non-resonant processes and quantum mechanical interference effects play a significant role in Raman scattering. This applies not only to graphene but also to other two-dimensional materials of current interest, such as MoTe2 and MoS2. In addition to the development of a consistent and comprehensive description of Raman scattering, we derive a novel approach for the calculation of phonon frequencies and the screened electron-phonon coupling. It can be applied also to strongly correlated systems, for which the currently used methods are not entirely satisfactory or insufficient. Our new method goes beyond the limitations of the methods currently in use and will permit the computation of phonon-related quantities also in systems with strong correlation effects such as Kohn anomalies (e.g., graphene) or Peierls instabilities. Lastly, we present work on the application of (magneto-)Raman spectroscopy as a probe for many-body effects in graphene. Here we focus on the description of the phenomenon of magneto-phonon resonances and how it can be used to probe electronic excitation energies and to extract electron and phonon lifetimes. [less ▲]

Bewohnerorientierte Betreuung für Luxemburgs Alten- und Pflegeheimbewohner. Theoretische und empirische Analysen zur Entwicklung und Implementierung eines neuen Betreuungsmodells

Doctoral thesis (2018)

The starting point of the dissertation is the thesis that the work in Luxembourg's nursing homes is based on nursing models that are - in today's sense of gerontology - outdated in some respects. This is ... [more ▼]

The starting point of the dissertation is the thesis that the work in Luxembourg's nursing homes is based on nursing models that are - in today's sense of gerontology - outdated in some respects. This is explained in the theoretical part in (literary-) analyzes on the following topics: Aging and theories of aging, living conditions in the national homes, qualification of geriatric nursing staff, previously used nursing models, central needs of older people from the perspective of nursing models and recent research. In the second part, the author presents her support model for Luxembourg nursing homes developed in this context, which focuses on the promotion of competences, autonomy and self-determination as well as the fulfillment of the central needs of residents of care institutions. The components of the model are presented and the prerequisites for a successful implementation with regard to legal-administrative regulations, qualification of the nursing staff, sensitization of the inhabitants of residential nursing institutions and their relatives as well as the public are comprehensively elaborated and completed by considerations of quality assurance and the limits of the model. In the center of the third part is an empirical study of Luxembourg nursing staff with the aim of identifying needs and conditions for the introduction of the new support model. In a questionnaire study, with n = 155 participants of different qualification levels, their typical nursing behavior as well as caregiver-related convictions, goals and emotions were surveyed. By cluster analysis - as expected - a group of caregivers has been identified that tends to promote nursing behavior that promotes autonomy, while - contrary to expectations - no group of caregivers has shown nursing behavior that limits autonomy. Instead, there was a group with inconsistent care, characterized partly by promotion and partly by restriction on the autonomy of inhabitants of residential care institutions. A similar cluster pattern emerged for the nursing goals and beliefs. A subsequent comparison of the care behavior clusters revealed systematic differences in goals and beliefs favoring autonomy or limitation. Overall, the findings indicate a need for autonomous support and care for elderly people in Luxembourg. Finally, ways are sketched for the gradual introduction of a corresponding support model. [less ▲]

Recent developments around the Malliavin-Stein approach (Fourth moment phenomena via exchangeable pairs)

Doctoral thesis (2018)

Part I is a survey, part II is a collection of papers.

Colonization and succession of the human gastrointestinal microbiome in neonates and infants at high risk of metabolic disease in adulthood

Doctoral thesis (2018)

Recent studies have highlighted that the human gastrointestinal microbiome not only maintains important functions for the human host, but is also intimately linked to the development of the neonatal ... [more ▼]

Recent studies have highlighted that the human gastrointestinal microbiome not only maintains important functions for the human host, but is also intimately linked to the development of the neonatal immune system. Therefore, earliest perturbations to the initial colonization process of the human gastrointestinal tract have been suggested to result in adverse health effects later in life. While the rate of caesarean section deliveries is increasing worldwide, it still remains unclear to what extent a caesarean section delivery (CSD) or other perturbations affect the colonization and succession of the gastrointestinal microbiome and might eventually impact the immune development of a neonate. Although much research has been performed on bacterial colonization and succession to date, far less is known about the other two domains of life, archaea and eukaryotes. Furthermore, it remains unclear whether a delivery by caesarean section causes a disruption of mother-to-infant transmission of microbiota and whether this affects human physiology early on, with potentially persistent effects in later life. Over the course of this thesis, a multitude of objectives was tackled. First of all, the description of microbial communities and trends over time within the neonatal and infant gut microbiome, and the study of the early colonization and succession by members of the three domains of life. Second, the careful application of high-throughput approaches on earliest low biomass samples, the detection of functional repertoires and strains transferred from mothers to neonates, and the analysis of the immunostimulatory potential of neonatal gut microbiomes in relation to delivery mode with likely effects on the later health status. In a first study based on 15 infants and using a combination of 16S and 18S rRNA gene amplicon sequencing and quantitative real-time PCR, earliest differences among the three domains of life according to delivery mode were detected as early as three days postpartum. Sequences from organisms belonging to all three domains of life were detectable in all of the collected meconium samples. The findings complement previous observations of a delay in colonization and succession of CSD infants, which likely affects not only bacteria but also archaea and microeukaryotes. Based on the observation that the first 5 days postpartum showed significant differing trends between delivery modes and considering the fact that the very first days postpartum are generally under-studied, this highlighted the importance to perform more in-depth analyses of these microbiome samples. In a next step, based on 12 mother-neonate pairs, high-resolution, metagenomic analysis of the gut microbiomes of mothers and neonates was performed to resolve the earliest colonizing microbiome. After data curation and in accordance with the observed changes in community composition for both cohorts, differences with respect to encoded metabolic functions between the microbiomes of vaginally delivered (VD) or CSD neonates as early as day 3 were observed. Several functional pathways were over-represented in VD neonates, including lipopolysaccharide (LPS) biosynthesis. Genes encoding proteins involved in these functions were linked to specific strains, which were vertically transmitted from the respective mothers. Based on the candidate’s work, more follow-up work on LPS was done by a colleague with a background in immunology. Isolated LPS from faecal samples collected at day 3 had a higher immunostimulatory potential in VD neonates and cytokines measured in plasma collected at the same day presented an increased immune reaction in VD neonates. Collectively, these results suggest that vaginal delivery favours vertical transmission of specific gastrointestinal strains from mother to neonate, while caesarean section may impede this process and thereby decrease linked functional repertoires and immunostimulatory potential with potential effects on human physiology later in life. Taken together, the results obtained from both cohorts strongly indicate that maternal and neonatal factors, such as antibiotics intake or milk diet, but most importantly the delivery mode, have the potential to influence the initial neonatal bacterial, archaeal and microeukaryotic colonization of the gut microbiome shortly postpartum, with the potential to impact the neonatal immune development, which could thereby affect the later health status. [less ▲]

Tuning Self-Assembly in Liquid Crystal shells: from Interfacial- to Polymer-stabilization

Doctoral thesis (2018)

Liquid crystals form a subclass of soft materials which is easily influenced and deformed by a surface, an interface and the geometry. Of particular interest, in this thesis, is the confinement of liquid ... [more ▼]

Liquid crystals form a subclass of soft materials which is easily influenced and deformed by a surface, an interface and the geometry. Of particular interest, in this thesis, is the confinement of liquid crystals in shell geometry, imposing real or virtual defects that the liquid crystal cannot avoid. With the help of microfluidics, we prepare our research platform, liquid crystal shells, which contain and are surrounded by aqueous phases. In order to maintain such a shell structure in the aqueous phases, immiscible with the liquid crystal, appropriate stabilization is required. Here we explore two different pathways of interfacial stabilization and polymer stabilization and their impact on liquid crystal self-assembly. We primarily use either a polymeric or an ionic surfactant dissolving in water to stabilize shells and tune boundary conditions of shells. Depending on symmetrically or asymmetrically imposed boundary conditions, the nematic–isotropic phase transition appears as a single transi- tion or separated into two steps. We propose that the latter phenomenon can be understood as a result of an ordering-enhancing effect by surfactants. The nematic–smectic A phase transition is also investigated under varying boundary conditions. With a precise temperature control, we explore equilibrium smectic structures and introduce a new arrangement of focal conic arrays in shell geometry. Beyond stabilizing the shell from the shell exterior, but we also incorporate a photosensitive surface agent within the shell, enabling dynamic and reversible photoswitching of the liquid crystal alignment in real time. However, shells with interfacial stabilization cannot survive more than several weeks due to their intrinsic fluid interfaces. In particular, a liquid crystal shell can serve as a permeable mem- brane which lets the constituents of aqueous phases pass through, giving a significant influence on the liquid crystalline order. To tame liquid crystal self-assembly and make the shell struc- ture permanent, we use photopolymerization to stabilize the shells. With only 5% monomer, the entire configuration of each liquid crystal shell is locked and shell lifetime extends beyond several months. The liquid crystalline order is visualized on the nanoscale via the polymer network and we further demonstrate that the shell configurations can be a unique template for creating complex polymer networks. Finally a new experimental approach is introduced to making ultrathin shells and several issues on shell instability and alignment determination are addressed. [less ▲]

Connectivity percolation and thin film growth containing rods

Doctoral thesis (2018)

The evolution of structure in thin films is usually discussed using a kinetic description. This description, mainly developed for metallic films at low temperature, may not be applicable at higher temper ... [more ▼]

The evolution of structure in thin films is usually discussed using a kinetic description. This description, mainly developed for metallic films at low temperature, may not be applicable at higher temper- atures as the film grown is close to the equilibrium where the bulk and surface thermodynamics play an essential role, e.g. in case of deposition of organic molecules. Weaker intermolecular interactions and molecular anisotropy add to the complexity of understanding the structure of a growing film. In this thesis, we analyze simplified, coarse–grained models which have potential for addressing the interplay of equilibrium phases and structure formation using Monte Carlo (MC) simulations. Anisotropic particles are modeled by rods with steric exclusion (hard–rods), mutual attractions and interactions with a substrate. First, investigations are shown for formation of the films that con- tain rods, which have mutual attractions and substrate interaction, using MC simulations and kinetic growth model. The model de- scribed by kinetic rate equations requires microscopic quantities as input parameters such as the deposition rate, diffusion constant, and attachment and detachment rates. These parameters are extracted from MC simulations, and we compare simulated growth dynamics to predictions by rate equations. It is observed that the widely ac- cepted strategy of adopting simple kinetic rate equations to specific film growth problems fails in the case of systems with orientational degrees of freedom, such as most organic semiconductor materials. Next, by analyzing the hard–rod monolayer case, the equilibrium properties are obtained which serve as a template for growth stud- ies. Additionally, the MC simulations are compared with classical density functional theory and lattice-based simulations which allow a good methodological control in order to study more complicated and detailed models. In equilibrium, a continuous “standing–up" transition is observed with or without interactive substrate, while the equilibrium properties of the monolayer dominate growth dy- namics. Lastly, and relevant to the charge transport properties of a film, we investigated connectivity percolation in suspensions of attractive rods using the same MC simulation methods mentioned above. The simulation results are then compared with connectivity percolation theory. [less ▲]

Le rôle de la terre dans l'identité : la nouvelle appropriation foncière. Deux études de cas : Haïti et la Martinique

Doctoral thesis (2018)

DEVELOPMENT OF A COMPUTATIONAL RESOURCE FOR PERSONALIZED DIETARY RECOMMENDATIONS

Doctoral thesis (2018)

There is a global increase in the incidence of non-communicable diseases associated with unhealthy food intakes. Conditions such as diabetes, heart disease, high blood pressure, and strokes represent a ... [more ▼]

There is a global increase in the incidence of non-communicable diseases associated with unhealthy food intakes. Conditions such as diabetes, heart disease, high blood pressure, and strokes represent a high societal impact and an economic burden for health-care systems around the world. To understand these diseases, one needs to account the several factors that influence how the human body processes food, some of which are determined by the genome and patterns of gene expression that translate to the ability - or lack of - to degrade and absorb certain nutrients. Other factors, like the gut microbiota, are more volatile because its composition is highly moldable by diet and lifestyle. Multi-omics technologies can support the comprehensive collection of dietary intake data and monitoring of the health status of individuals. Also, a correct analysis of this data could lead to new insights about the complex processes involved in the digestion of dietary components and their involvement in the prevention or the appearance of health problems, but its integration and interpretation are still problematic. Thus, in this thesis, we propose the utilization of Constraint-Based Reconstruction and Analysis (COBRA) methods as a framework for the integration of this complex data. To achieve this goal, we have created a knowledge-base, the Virtual Metabolic Human (VMH), that combines information from large-scale models of metabolism from the human organism and typical gut microbes, with food composition information, and a disease compendium. VMH’s unique combination of resources leverages the exploration of metabolic pathways from different organisms, the inclusion of dietary information into in-silico experiments through its own diet designer tool, visualization and analysis of experimental and simulation data, and exploring disease mechanisms and potential treatment strategies. VMH is a step forward in providing the necessary tools to investigate the mechanisms behind the influence of diet in health and disease. Tools such as the diet designer can be used as a basis for diet optimization by predicting combinations of foods that can contribute to specific metabolic outcomes, which has the potential to be integrated and translated into treatment development and dietary recommendations in the foreseeable future. [less ▲]

Dynamical hybrid modeling of human metabolism

Doctoral thesis (2018)

Human metabolism plays a key role in disease pathogenesis and drug action. Half a century of biochemical literature leveraged by the advent of genomics allowed the emergence of computational modeling ... [more ▼]

Human metabolism plays a key role in disease pathogenesis and drug action. Half a century of biochemical literature leveraged by the advent of genomics allowed the emergence of computational modeling techniques and the in silico analysis of complex biological systems. In particular, Constraint-Based Reconstruction and Analysis (COBRA) methods address the complexity of metabolism through building tissue-specific networks in their steady state. It is known that biological systems respond to perturbations induced by pathogens, drugs or malignant processes by shifting their activity to safeguard key metabolic functions. Extending the modeling framework to consider the dynamics of these complex systems will bring simulations closer to observable human phenotypes. In this thesis, I combined physiologically-based pharmacokinetic (PBPK) models with genome-scale metabolic models (GSMMs) to form hybrid genome-scale dynamical models that provide a hypothesis-free framework to study the perturbations induced by one or more perturbagen on human tissues. On a first stage, these methodologies were applied to decipher the absorption of levodopa and amino acids by the intestinal epithelium and allowed to derive a model-based diet for Parkinson's Disease patients. In the next phase, we extended the study to 605 drugs in order to predict the occurrence of gastrointestinal side effects through a machine learning classifier, using a combination of gene expression and metabolic reactions set as features. Finally, the approach upscaled to several tissues, specifically to investigate the genesis of metabolic symptoms in type 1 diabetes and to suggest key metabolic players underlying within and between-individual variability to insulin action. Taken as whole, the integration of two modeling techniques constrained by expert biological knowledge and heterogeneous data types will be a step forward in achieving convergence in human biology. [less ▲]

The Democratic and Human Rights Transition in Sub-Saharan States since the End of the Cold War and the European Union’s Influence

Doctoral thesis (2018)

The democratic wind that first blew across the Eastern European states after the collapse of the Berlin Wall later blew across the sub-Saharan region. Authoritarian and one-party regimes were challenged ... [more ▼]

The democratic wind that first blew across the Eastern European states after the collapse of the Berlin Wall later blew across the sub-Saharan region. Authoritarian and one-party regimes were challenged across the continent. While the democratic transitions in the Eastern European states have almost been consolidated, due largely to the huge EU’s impetus or influence, the transition in the sub-Saharan states has been slow, chaotic, sporadic, violent, and unstable and in some cases, initial democratic gains have been lost. The EU has not remained indifferent to these lapses in democracy, but has in some cases follow realpolitik and in some cases, its foreign policy has gone head-to-head with some of its powerful member states, especially France. The role of France in this sub-region has been paid careful attention and results from democracy indexes show most of the former French colonies lag behind. France indeed, now uses the EU to foster its agenda in the sub-Saharan region. EU’s sanctions on Laurent Gbagbo after the disputed presidential elections of 2010 in Ivory Coast show how France can use the EU to get rid of leaders who refuse to toe the French line. The failure of the EU to speak with one voice has been a real setback to its policy of democracy and human rights promotion. French support of rigged elections in some of its ex-colonies, condemned by the EU has only gone a long way to weaken the EU’s foreign policy on democracy and human rights. This study focuses on the democratic and human rights transition currently going on in the sub-Saharan region of Africa beginning from the end of the Cold War in the 1990s. The study also pays attention to the EU’s influence, if any on the process. In order to get a good grasp of the present transition, a brief analysis on colonialism before independence and the period of the Cold War after independence have been done. Cameroon in this study has been used as a case-study of the political dynamics that occur in the transition of some of these states to democracy. To further throw light on these political dynamics, some countries across the various sub-regions of the sub-Saharan region have been analysed. However, only Cameroon did receive empirical studies. The case study and analyses show the democratic transition has or witnesses influence from internal actors and international actors. Some analysts claim internal pressure accounts most for the democratic transion while others say it is international pressure, but the majorty claims it is both. The EU’s influence has been tested in two specific cases of sanctions: Zimbabwe and Nigeria, using hypotheses for political influence. Other cases of EU’s influence are analysed from EU sanctions on Sudan, the Democratic Republic of Congo (DRC) and Guinea-Bissau. Influence in these cases has not been interpreted as a transition to an ideal form of democracy, but the compliance of these states to specific EU stated preferences. Contrary to what most political commentators erroneously refer to an African democracy, this study shows that democracy in this region is not uniform and that it varies from sub-region to sub-region with colonial heritage showing different tendencies. In addition, oil-producing and mineral-rich states lag behind in the democratic process and have long-serving leaders of whom most are corrupt. The study has relied heavily on the Freedom House and Mo Ibrahim indexes of measuring democracy. They both provided similar results, thereby giving more credibility to the analyses. This study concludes that the EU has not been a major influencer of the democratic process in the sub-Saharan region, due mostly to its internal system and can best be termed as a democracy promoter. Various factors that favour and detract the EU foreign policy on human rights and democratization in Africa have been analysed. [less ▲]

Modelling the Extensionally Driven Transitions of DNA

Doctoral thesis (2018)

Empirical measurements on DNA under tension show a jump by a factor of ≈ 1.5 − 1.7 in the relative extension at applied force of ≈ 65 − 70 pN, indi- cating a structural transition. The still ambiguously ... [more ▼]

Empirical measurements on DNA under tension show a jump by a factor of ≈ 1.5 − 1.7 in the relative extension at applied force of ≈ 65 − 70 pN, indi- cating a structural transition. The still ambiguously characterised stretched ‘phase’ is known as S-DNA. Using atomistic and coarse-grained Monte Carlo simulations we study DNA over-stretching in the presence of organic salts Ethidium Bromide (EtBr) and Arginine (an amino acid present in the RecA binding cleft). We present planar-stacked triplet disproportionated DNA as a solution phase of the double helix under tension, and dub it ‘Σ DNA’, with the three right-facing points of the Σ character serving as a mnemonic for the three grouped bases. Like unstretched Watson-Crick base paired DNA structures, the structure of the Σ phase is linked to function: the partitioning of bases into codons of three base-pairs each is the first stage of operation of recombinase enzymes such as RecA, facilitating alignment of homologous or near-homologous sequences for genetic exchange or repair. By showing that this process does not require any very sophisticated manipulation of the DNA, we position it as potentially appearing as an early step in the de- velopment of life, and correlate the postulated sequence of incorporation of amino acids (GADV then GADVESPLIT and then the full 20 residue set of canonical amino acids) into molecular biology with the ease of Σ-formation for sequences including the associated codons. To further investigate the de- pendence of stretching behaviour on the concentration of intercalating salt molecules, we present a physically motivated coarse-grained force-field for DNA under tension and use it to qualitatively reproduce regimes of force- extension behaviour which are not atomistically accessible. [less ▲]

Dynamic Network Reconstruction in Systems Biology: Methods and Algorithms

Doctoral thesis (2018)

Dynamic network reconstruction refers to a class of problems that explore causal interactions between variables operating in dynamical systems. This dissertation focuses on methods and algorithms that ... [more ▼]

Dynamic network reconstruction refers to a class of problems that explore causal interactions between variables operating in dynamical systems. This dissertation focuses on methods and algorithms that reconstruct/infer network topology or dynamics from observations of an unknown system. The essential challenges, compared to system identification, are imposing sparsity on network topology and ensuring network identifiability. This work studies the following cases: multiple experiments with heterogeneity, low sampling frequency and nonlinearity, which are generic in biology that make reconstruction problems particularly challenging. The heterogeneous data sets are measurements in multiple experiments from the underlying dynamical systems that are different in parameters, whereas the network topology is assumed to be consistent. It is particularly common in biological applications. This dissertation proposes a way to deal with multiple data sets together to increase computational robustness. Furthermore, it can also be used to enforce network identifiability by multiple experiments with input perturbations. The necessity to study low-sampling-frequency data is due to the mismatch of network topology of discrete-time and continuous-time models. It is generally assumed that the underlying physical systems are evolving over time continuously. An important concept system aliasing is introduced to manifest whether the continuous system can be uniquely determined from its associated discrete-time model with the specified sampling frequency. A Nyquist-Shannon-like sampling theorem is provided to determine the critical sampling frequency for system aliasing. The reconstruction method integrates the Expectation Maximization (EM) method with a modified Sparse Bayesian Learning (SBL) to deal with reconstruction from output measurements. A tentative study on nonlinear Boolean network reconstruction is provided. The nonlinear Boolean network is considered as a union of local networks of linearized dynamical systems. The reconstruction method extends the algorithm used for heterogeneous data sets to provide an approximated inference but improve computational robustness significantly. The reconstruction algorithms are implemented in MATLAB and wrapped as a package. With considerations on generic signal features in practice, this work contributes to practically useful network reconstruction methods in biological applications. [less ▲]

INVESTIGATION OF THE CU2(SN,GE)S3 TERNARY ALLOY FOR THIN FILM SOLAR CELLS

Doctoral thesis (2018)

This thesis examines material properties of the novel Cu2(Sn, Ge)S3 alloy, from the perspective of a solar cell scientist searching for a new light absorbing material to produce highly efficient thin-film ... [more ▼]

This thesis examines material properties of the novel Cu2(Sn, Ge)S3 alloy, from the perspective of a solar cell scientist searching for a new light absorbing material to produce highly efficient thin-film devices. [less ▲]

Computational Integrative Models for Cellular Conversion: Application to Cellular Reprogramming and Disease Modeling

Doctoral thesis (2018)

The groundbreaking identification of only four transcription factors that are able to induce pluripotency in any somatic cell upon perturbation stimulated the discovery of copious amounts of instructive ... [more ▼]

The groundbreaking identification of only four transcription factors that are able to induce pluripotency in any somatic cell upon perturbation stimulated the discovery of copious amounts of instructive factors triggering different cellular conversions. Such conversions are highly significant to regenerative medicine with its ultimate goal of replacing or regenerating damaged and lost cells. Precise directed conversion of damaged cells into healthy cells offers the tantalizing prospect of promoting regeneration in situ. In the advent of high-throughput sequencing technologies, the distinct transcriptional and accessible chromatin landscapes of several cell types have been characterized. This characterization provided clear evidences for the existence of cell type specific gene regulatory networks determined by their distinct epigenetic landscapes that control cellular phenotypes. Further, these networks are known to dynamically change during the ectopic expression of genes initiating cellular conversions and stabilize again to represent the desired phenotype. Over the years, several computational approaches have been developed to leverage the large amounts of high-throughput datasets for a systematic prediction of instructive factors that can potentially induce desired cellular conversions. To date, the most promising approaches rely on the reconstruction of gene regulatory networks for a panel of well-studied cell types relying predominantly on transcriptional data alone. Though useful, these methods are not designed for newly identified cell types as their frameworks are restricted only to the panel of cell types originally incorporated. More importantly, these approaches rely majorly on gene expression data and cannot account for the cell type specific regulations modulated by the interplay of the transcriptional and epigenetic landscape. In this thesis, a computational method for reconstructing cell type specific gene regulatory networks is proposed that aims at addressing the aforementioned limitations of current approaches. This method integrates transcriptomics, chromatin accessibility assays and available prior knowledge about gene regulatory interactions for predicting instructive factors that can potentially induce desired cellular conversions. Its application to the prioritization of drugs for reverting pathologic phenotypes and the identification of instructive factors for inducing the cellular conversion of adipocytes into osteoblasts underlines the potential to assist in the discovery of novel therapeutic interventions. [less ▲]

Mobile Network Data Analytics for Intelligent Transportation Systems

Doctoral thesis (2018)

In this dissertation, we explore how the interplay between transportation and mobile networks manifests itself in mobile network billing and signaling data, and we show how to use this data to estimate ... [more ▼]

In this dissertation, we explore how the interplay between transportation and mobile networks manifests itself in mobile network billing and signaling data, and we show how to use this data to estimate different transportation supply and demand models. To perform the necessary simulation studies for this dissertation, we present a simula- tion scenario of Luxembourg, which allows the simulation of vehicular Long-Term Evolu- tion (LTE) connectivity with realistic mobility. We first focus on modeling travel time from Cell Dwell Time (CDT), and show – on a synthetic data set– that we can achieve a prediction Mean Absolute Percentage Error (MAPE) below 12%. We also encounter proportionality between the square of the mean CDT and the number of handovers in the system, which we confirmed in the aforementioned simulation scenario. This motivated our later studies of traffic state models generated from mobile network data. We also consider mobile network data for supporting synthetic population generation and demand estimation. In a study on Call Detail Records (CDR) data from Senegal, we estimate CDT distributions to allow generating the duration of user activities, and validate them at a large scale against a data set from China. In a different study, we show how mobile network signaling data can be used for initializing the seed Origin- Destination (O-D) matrix in demand estimation schemes, and show that it increases the rate of convergence. Finally, we address the traffic state estimation problem, by showing how handovers can be used as a proxy metric for flows in the underlying urban road network. Using a traffic flow theory model, we show that clusters of mobile network cells behave characteristically, and with this model we reach a MAPE of 11.1% with respect to floating-car data as ground truth. The presented model can be used in regions without traffic counting infrastructure, or complement existing traffic state estimation systems. [less ▲]

Dependability Assessment of Android OS

Doctoral thesis (2018)

In this brave new world of smartphone-dependent society, dependability is a strong requirement and needs to be addressed properly. Assessing the dependability of these mobile systems is still an open ... [more ▼]

In this brave new world of smartphone-dependent society, dependability is a strong requirement and needs to be addressed properly. Assessing the dependability of these mobile systems is still an open issue, and companies should have the tools to improve their devices and beat the competition against other vendors. The main objective of this dissertation is to provide the methods to assess the dependability of mobile OS, fundamental for further improvements. Mobile OS are threatened mainly by traditional residual faults (when errors spread across components as failures), aging-related faults (when errors accumulate over time), and misuses by users and applications. This thesis faces these three aspects. First, it presents a qualitative method to define the fault model of a mobile OS, and an exhaustive fault model for Android. I designed and developed AndroFIT, a novel fault injection tool for Android smartphones, and performed an extensive fault injection campaign on three Android devices from different vendors to analyze the impact of component failure on the mobile OS. Second, it presents an experimental methodology to analyze the software aging phenomenon in mobile OS. I performed a software aging analysis campaign on Android devices to identify the impacting factors on performance degradation and resource consumption. Third, it presents the design and implementation of a novel fuzzing tool, namely Chizpurfle, able to automatically test Android vendor customizations by leveraging code coverage information at run-time. [less ▲]

Dynamic Origin-Destination Matrix Estimation with Interacting Demand Patterns

Doctoral thesis (2018)

It has become very fashionable to talk about Mobility as a Service, multimodal transport networks, electrified and green vehicles, and sustainable transportation in general. Nowadays, the transportation ... [more ▼]

It has become very fashionable to talk about Mobility as a Service, multimodal transport networks, electrified and green vehicles, and sustainable transportation in general. Nowadays, the transportation field is exploring new angles to solve mobility issues, applying concepts such as using machine learning techniques to profile user behaviour. While for many years “traffic pressure” and “congestion phenomena” were the most established keywords, there is now a widespread body of research pointing out how new technologies alone will solve most of these issues. One of the main reasons for this change of direction is that earlier approaches have been proven to be more “fair” than “effective” in tackling mobility issues. The main limitation was probably to rely on simple assumptions, such as in-elastic mobility travel demand (car users will stick to their choice), when modelling travel behaviour. However, while these assumptions were questionable twenty years ago, they simply do not hold in today's society. While it is still true that high-income people usually own a car, the concept of urban mobility evolved. First, new generations are likely to buy a car ten-twenty years later than their parents. Second, in many cases, users can choose options that are more effective by combining different transport modes. Wealthy people might decide to live next to their working place or to the city centre, rather than to buy a car. Thus, it becomes clear that to understand the evolution of the mobility demand we need to question some of these assumptions. While data can help in understanding this societal transformation, we argue in this dissertation that they cannot be considered as the sole source of information for the decision maker. Although data have been there for many years, congestion levels are increasing, meaning that data alone cannot solve the problem. Although successful in many case studies, data-driven approaches have the limitation of being capable of modelling only what they observed in the past. If there is no record of a specific event, then the model will simply provide a biased information. In this manuscript we point out that both elements – data and model – are equally relevant to represent the evolution of a transport system, and specifically how important is to consider the heterogeneity of the mobility demand within the modelling framework in order to fully exploit the available data. In this manuscript, we focus on the so-called Dynamic Demand Estimation Problem (DODE), which is the problem of estimating the mobility demand patterns that are more likely to best fit all the available traffic data. While this dissertation still focuses on car-users, we stress that the activity based structure of the demand needs to be explicitly represented in order to capture the evolution of a transport system. While data show a picture of the reality, such as how many people are travelling on a certain road segment or even along a certain path, this information represents a coarse aggregation of different individuals sharing a common resource (i.e. the infrastructure). However, the traffic flow is composed of different users with different trip purposes, meaning they react differently to a certain event. If we shut down a road from one day to another, commuting and not commuting demand will react in a different way. The same concept holds when dealing with different weather conditions, which also lead to a different demand pattern with respect to the typical one. This dissertation presents different frameworks to solve the DODE, which explicitly focus on the estimation of the mobility demand when dealing with typical and atypical user behaviour. Although the approach still focuses on a single mode of transport (car-users), the proposed formulation includes the generalized travel cost within the optimization framework. This key element allows accounting for the departure time choice and, in principle, it can be extended to the mode choice in future work. The methodologies presented in this thesis have been tested with a “state of the practice” dynamic traffic assignment model. Results suggest that the models can be used for real-life networks, but also that more efficient algorithm should be considered for practical implementations in order to unleash the full potential of this new approach. [less ▲]

Contributions to the asymptotic study of Hermite driven processes

Doctoral thesis (2018)

This thesis consists of two parts. Part I is an introduction to Hermite processes, Hermite random fields, Fisher information and to the papers constituting the thesis. More precisely, in Section 1 we ... [more ▼]

This thesis consists of two parts. Part I is an introduction to Hermite processes, Hermite random fields, Fisher information and to the papers constituting the thesis. More precisely, in Section 1 we introduce Hermite processes in a nutshell, as well as some of its basic properties. It is the necessary background for the articles [a] and [c]. In Section 2 we consider briefly the multiparameter Hermite random fields and we study some less elementary facts which are used in the article [b]. In section 3, we recall some terminology about Fisher information related to the article [d]. Finally, our articles [a] to [d] are summarised in Section 4. Part II consists of the articles themselves: [a] T.T. Diu Tran (2017): Non-central limit theorem for quadratic functionals of Hermite-driven long memory moving average processes. Stochastic and Dynamics, 18, no. 4. [b] T.T. Diu Tran (2016): Asymptotic behavior for quadratic variations of nonGaussian multiparameter Hermite random fields. Under revision for Probability and Mathematical Statistics. [c] I. Nourdin, T.T. Diu Tran (2017): Statistical inference for Vasicek-type model driven by Hermite processes. Submitted to Stochastic Process and their Applications. [d] T.T. Diu Tran (2017+): Fisher information and multivariate Fouth Moment Theorem. Main results have already been obtained. It should be submitted soon. [less ▲]

Integrating User- and System-Centric Perspectives into Collaborative Compound Document Authoring

Doctoral thesis (2018)

Computer-supported collaborative work is increasingly common in our professional and personal life. However, the expectations and requirements of the users are frequently neglected when addressing the ... [more ▼]

Computer-supported collaborative work is increasingly common in our professional and personal life. However, the expectations and requirements of the users are frequently neglected when addressing the technological challenges associated with the development of a distributed collaboration system. The proposed collaboration environment employs an integrative approach to distributed compound document authoring, including both a user- and system-centric perspective on collaborative work. An interruption-free, reliable, and responsive shared work environment with a near real-time representation of the work of others is a core expectation from the users. In order to provide these features, a fine-granular, graph-based data representation has been developed to serve as the basis for this approach. The data representing individual compound document elements is partitioned over sets of three distinct nodes in the graph structure. This separation of metadata and payload data enables the precise attribution of editing operations while maintaining an adaptable and extensible data representation. User-specific preferences allow for the individualization of a user's work environment to account for personal preferences, requirements from the current collaboration scenario, or limitations of the employed computer system. Support for complex, data type-specific editing commands is integrated with a concurrent command application and Layered Consistency Management model. This enables a near real-time representation of the work of others, the preservation of the users' editing intentions, and the maintenance of a globally consistent data state. Intra- and inter-document relations retain semantic connections between distinct data structure elements. Together with an element's supplemental data, this related information enables additional, autonomous conflict resolution approaches and facilitates a comprehensive representation of the conflict in case of a manual resolution process. By integrating these functionalities into one coherent system, the users are provided with an unobtrusive, yet reliable and feature-rich distributed work environment able to actively support collaborative compound document authoring. [less ▲]

Optimierung und Charakterisierung einer mittels Laserstrahl gefügten Verbindung zwischen Aluminium und Polyamid 6.6

Doctoral thesis (2018)

The creation of strong joints between dissimilar materials and in particular between polymers and metals is one of the most often discussed topics in the fields of automotive, aerospace and transportation ... [more ▼]

The creation of strong joints between dissimilar materials and in particular between polymers and metals is one of the most often discussed topics in the fields of automotive, aerospace and transportation. Especially the combination of polyamide and aluminum is of highest interest, due to their market share as construction materials. New joining concepts are anticipated to deliver strong, durable and resource efficient structural components that are ideally suited for lightweight designs. However, current research activities have shown that the highly distinct material properties of these materials pose enormous challenges on the creation of hybrid structures. The cause that potentially enables the connection between the aluminum surface and the polymer is still not fully understood. The research objective of the presented work, therefore is, on the one hand, to create an optimal joint between aluminum and polyamide 6.6 using a laser beam to reach high shear strength for an industrial application. On the other hand, the presented work seeks to deliver a substantial contribution to furtherly understand the interaction between the polymer and the metal surface during the thermal joining. A laser-based joining method was developed that enables the researchers to overcome limitations of conventional processes, that is minimizing space requirements, making the application of additional gaskets obsolete, reaching high strength, saving weight and reducing processing time. The effectiveness of different surface pre-treatments has been studied, and the described optimization of this method has lead to an increase of the shear strength of the joints by more than 100 %. Laser ablation and the hydrothermal treatment of the metallic surface, before the joining operation, lead to the highest joint strength. The surface pre-treatment method of laser ablation delivered to transfer the gathered insights and experience from the laboratory to the industrial scale, due to its repeatability and reproducibility. The experiment mentioned above includes the use of production materials, such as aluminum with a higher sheet thickness of up to 1.48 mm and glass fiber reinforced polymer. Shear strength of 40 MPa was reached in quasi-static single lap shear tests. During dynamic testing, samples maintained 63 % of static breaking load after one million cycles. The hydrothermal treatment of the aluminum surface leads to a lower surface roughness of Ra = 1.58 µm in average as opposed to 4.90 µm after laser ablation. Due to the lower roughness values, the first-mentioned method was chosen to study the interaction. An XPS-analysis revealed a strong influence of the surface pre-treatment method on the chemical composition of the metal surface, which becomes noticeable by hydroxylation of the surface layer and is expressed by the oxide ratio (O/Al) and hydroxide ratio (OH/O). A high O/Al ratio of 2.36 and an OH/O ratio of 0.63 after the hydrothermal treatment is showing a strong increase of the amount of hydroxide in direct comparison to values of 35 % and 36 % of OH/O ratio after ethanol and hexane cleaning respectively. The question, as to which extent the presence of such hydroxide structures at the boundary layer of the aluminum influence the interaction between the metal surface and the polymer, was a subject matter of an additional FT-IR analysis. In case of the infrared spectra from thin polymer films on the hydrothermally treated surface, clear indications of interaction are visible. In direct comparison to the infrared spectra from polymer films on either ethanol or hexane cleaned surfaces, this interaction seems to increase nearby of the interface further. The interaction mentioned above appears at the carbonyl band and amine band as a shift of 4 cm-1 and 8 cm-1 and an increase of the full width at half maximum by 35 % respectively 40 %. Additional strong differences are visible at the molecule vibrations below 1,200 cm-1, which are typically assigned to both crystalline phases and amorphous phases of the polyamide. In case of the hydrothermal treatment, collected data indicates a polymorphous state inside the polymer films, which seems to become increasingly disordered close to the interface. On the contrary, spectra from the polymer films on ethanol and hexane pre-treated substrates show only marginal changes. Methods are proposed to build upon the results described in this work and refine distinct signs of the interaction. [less ▲]

Transforming Time Series for Efficient and Accurate Classification

Doctoral thesis (2018)

Time series data refer to sequences of data that are ordered either temporally, spatially or in another defined order. They can be frequently found in a variety of domains, including financial data ... [more ▼]

Time series data refer to sequences of data that are ordered either temporally, spatially or in another defined order. They can be frequently found in a variety of domains, including financial data analysis, medical and health monitoring and industrial automation applications. Due to their abundance and wide application scenarios, there has been an increasing need for efficient machine learning algorithms to extract information and build knowledge from these data. One of the major tasks in time series mining is time series classification (TSC), which consists of applying a learning algorithm on labeled data to train a model that will then be used to predict the classes of samples from an unlabeled data set. Due to the sequential characteristic of time series data, state-of-the-art classification algorithms (such as SVM and Random Forest) that performs well for generic data are usually not suitable for TSC. In order to improve the performance of TSC tasks, this dissertation proposes different methods to transform time series data for a better feature extraction process as well as novel algorithms to achieve better classification performance in terms of computation efficiency and classification accuracy. In the first part of this dissertation, we conduct a large scale empirical study that takes advantage of discrete wavelet transform (DWT) for time series dimensionality reduction. We first transform real-valued time series data using different families of DWT. Then we apply dynamic time warping (DTW)-based 1NN classification on 39 datasets and find out that existing DWT-based lossy compression approaches can help to overcome the challenges of storage and computation time. Furthermore, we provide assurances to practitioners by empirically showing, with various datasets and with several DWT approaches, that TSC algorithms yield similar accuracy on both compressed (i.e., approximated) and raw time series data. We also show that, in some datasets, wavelets may actually help in reducing noisy variations which deteriorate the performance of TSC tasks. In a few cases, we note that the residual details/noises from compression are more useful for recognizing data patterns. In the second part, we propose a language model-based approach for TSC named Domain Series Corpus (DSCo), in order to take advantage of mature techniques from both time series mining and Natural Language Processing (NLP) communities. After transforming real-valued time series into texts using Symbolic Aggregate approXimation (SAX), we build per-class language models (unigrams and bigrams) from these symbolized text corpora. To classify unlabeled samples, we compute the fitness of each symbolized sample against all per-class models and choose the class represented by the model with the best fitness score. Through extensive experiments on an open dataset archive, we demonstrate that DSCo performs similarly to approaches working with original uncompressed numeric data. We further propose DSCo-NG to improve the computation efficiency and classification accuracy of DSCo. In contrast to DSCo where we try to find the best way to recursively segment time series, DSCo-NG breaks time series into smaller segments of the same size, this simplification also leads to simplified language model inference in the training phase and slightly higher classification accuracy. The third part of this dissertation presents a multiscale visibility graph representation for time series as well as feature extraction methods for TSC, so that both global and local features are fully extracted from time series data. Unlike traditional TSC approaches that seek to find global similarities in time series databases (e.g., 1NN-DTW) or methods specializing in locating local patterns/subsequences (e.g., shapelets), we extract solely statistical features from graphs that are generated from time series. Specifically, we augment time series by means of their multiscale approximations, which are further transformed into a set of visibility graphs. After extracting probability distributions of small motifs, density, assortativity, etc., these features are used for building highly accurate classification models using generic classifiers (e.g., Support Vector Machine and eXtreme Gradient Boosting). Based on extensive experiments on a large number of open datasets and comparison with five state-of-the-art TSC algorithms, our approach is shown to be both accurate and efficient: it is more accurate than Learning Shapelets and at the same time faster than Fast Shapelets. Finally, we list a few industrial applications that relevant to our research work, including Non-Intrusive Load Monitoring as well as anomaly detection and visualization by means for hierarchical clustering for time series data. In summary, this dissertation explores different possibilities to improve the efficiency and accuracy of TSC algorithms. To that end, we employ a range of techniques including wavelet transforms, symbolic approximations, language models and graph mining algorithms. We experiment and evaluate our approaches using publicly available time series datasets. Comparison with the state-of-the-art shows that the approaches developed in this dissertation perform well, and contribute to advance the field of TSC. [less ▲]

THE CAPACITY FOR COMPLIANCE WITHIN EU MULTILEVEL ADMINISTRATION: THE CASE OF THE BANKING UNION’S SINGLE SUPERVISORY MECHANISM (SSM)

Doctoral thesis (2018)

This dissertation offers a deep political science insight into the functioning of the EU new multilevel administrative system governing the micro-prudential supervision of credit institutions operating in ... [more ▼]

This dissertation offers a deep political science insight into the functioning of the EU new multilevel administrative system governing the micro-prudential supervision of credit institutions operating in the Single Market. It aims to explain the conditions affecting the formal top-bottom compliance expectation within this multilevel system. In doing so, it engages in the institutional analysis of the organisational and operational design of the Single Supervisory Mechanism (SSM). [less ▲]

AUTOMATED CALCIUM IMAGE ANALYSIS OF NEURONS DERIVED FROM PLURIPOTENT STEM CELLS

Doctoral thesis (2018)

Investigation of the Load-Bearing Behaviour of CoSFB-Dowels

Doctoral thesis (2018)

This Thesis is the first PhD thesis written about CoSFB-Dowels. Therefore, focus of the scientific work presented here, was on the identification of parameters influencing the load-bearing behaviour in ... [more ▼]

This Thesis is the first PhD thesis written about CoSFB-Dowels. Therefore, focus of the scientific work presented here, was on the identification of parameters influencing the load-bearing behaviour in general and on parameters contributing to the load-bearing capacity of CoSFB-Dowels in detail. A CoSFB-Dowel is an innovative shear connector for steel-concrete composite slim-floor beams. It consists of circular openings drilled in the web of the steel section with reinforcement bars passing through and filled with normal concrete in-situ. Push-out tests have been performed already in an earlier research project initiated by the author. In this Thesis, detailed analysis of the test results was done and a finite element model developed simulating the push-out tests, which led to an improved understanding of the overall load-bearing behaviour. Further, the numerical model was used to identify and to evaluate components contributing to the stiffness, to the linear-elastic load and to the maximum load. The findings of this research led to the formulation of a mechanical model and an analytical method to evaluate the load-bearing capacity of a CoSFB-Dowel. The analytical method was validated with the test results. This Thesis is concluded by a proposal allowing for a conservative determination of the design resistance of CoSFB-Dowels. [less ▲]

La mémoire de la "Résistance" au prisme d'une histoire comparée des associations d'anciens résistants du Luxembourg, de l'Alsace, de la Moselle et de la Belgique de l'Est (1944-2017)

Doctoral thesis (2018)

Notre thèse, qui a pu être réalisée grâce au soutien du Fonds national de la Recherche du Luxembourg et qui s’est faite dans le cadre du projet de recherche « Partizip 2 » de l’Université du Luxembourg et ... [more ▼]

Notre thèse, qui a pu être réalisée grâce au soutien du Fonds national de la Recherche du Luxembourg et qui s’est faite dans le cadre du projet de recherche « Partizip 2 » de l’Université du Luxembourg et en cotutelle avec l’Université de Lorraine, est une analyse de la mémoire de la « Résistance » depuis 1944 à 2017 par le biais d’une histoire comparée des associations d’anciens résistants du Luxembourg, de l’Alsace, de la Moselle et de la Belgique de l’Est. Il s’agit des territoires, qui, lorsque les Allemands lancent leur offensive à partir du 10 mai 1940 en Europe de l’Ouest, sont annexés (de fait) au IIIe Reich. Au cours de notre recherche, nous avons pu constater d’importantes asymétries entre ces territoires au niveau des médias mémoriels présents, comme les monuments, les musées ou les statuts juridiques en hommage aux anciens résistants. Si au Luxembourg la mémoire de la « Résistance » est plus développée par rapport aux régions françaises et belges, cela s’explique du fait qu’elle a évolué dans un contexte national « homogène ». En effet, les Alsaciens, Mosellans et Belges de l’Est doivent situer leur passé régional particulier dans un paysage mémoriel national qui s’articule autour de l’occupation et où le contexte spécifique de l’annexion (de fait) est peu connu. Or, les asymétries mémorielles n’apparaissent pas seulement entre l’Etat luxembourgeois et les régions françaises et belges, mais également entre les régions mêmes. Si l’explication de la différence entre échelles nationales et régionales est pertinente lorsque nous comparons le Luxembourg et les régions françaises et belges, elle ne permet pourtant pas de comprendre les variations mémorielles entre ces régions. Quelles sont donc les raisons de ces asymétries mémorielles ? Ou autrement formulé : quels facteurs favorisent l’intensification de la mémoire de la « Résistance » ? Afin de déterminer ces facteurs, nous avons choisi d’effectuer une histoire comparée des associations d’anciens résistants du Luxembourg, de l’Alsace, de la Moselle et de la Belgique de l’Est, qui sont des acteurs de mémoire décisifs puisque souvent à l’origine des médias mémoriels que nous venons d’évoquer. Cette démarche nous a permis de mettre en évidence des clés d’interprétation qu’une étude isolée de chaque espace en question ne rendrait pas visible. Au cours de notre recherche, nous avons déterminé plusieurs facteurs qui peuvent favoriser l’intensification de la mémoire de la « Résistance » : la coordination efficace des projets collectifs des associations d’anciens résistants par le biais d’une organisation unique ou d’un porte-parole commun, les concurrences mémorielles et la participation politique qui incitent les associations d’anciens résistants à se mobiliser, favorisant ainsi l’émergence de médias mémoriels de la « Résistance » et finalement le développement des associations d’anciens résistants et de leurs médias mémoriels dans le contexte de la globalisation de la mémoire. Ces facteurs, qui sont intrinsèquement liés et qu’il faut ainsi concevoir dans une perspective dynamique et interdépendante, sont présentés dans les chapitres de notre analyse empirique, qui est agencée en trois parties. Une première partie se consacre à l’émergence des associations d’anciens résistants et à leurs activités liées à l’immédiat après-guerre dans le contexte du rapatriement et de l’entraide, de l’épuration et de la reconstruction. Un deuxième chapitre analyse la lutte des associations d’anciens résistants pour une reconnaissance morale et matérielle ainsi que leur participation politique. Une troisième et dernière partie aborde finalement les projets mémoriels des associations d’anciens résistants entre commémoration et médiation de l’histoire dans le contexte de la globalisation de la mémoire de la Seconde Guerre mondiale. [less ▲]

Hybrid Histories: Technologies of Memory and the Cultural Dynamics of Home Movies, 1895-2005

Doctoral thesis (2018)

This dissertation analyses the cultural dynamics of home movies in the twentieth century. It investigates how various generations have recorded their family memories on film, video and digital media, and ... [more ▼]

This dissertation analyses the cultural dynamics of home movies in the twentieth century. It investigates how various generations have recorded their family memories on film, video and digital media, and, more specifically, how changes in these “technologies of memory” have shaped new forms of home movie making and screening. Covering the period from the invention of the film camera in the late nineteenth century, the introduction of 9.5mm, 16mm, 8mm small-gauges and Super 8 film technologies for amateurs, via home video to digital media technologies, this study addresses the complex interrelations between the materiality of film, video and digital media technologies, their social usages and cultural meanings from a long-term historical perspective. Focusing on specific periods of transition, it becomes clear that different media technologies, user practices and discourses not only succeed each other in time, but also increasingly interrelate, interact or even transform each other. Maintaining both a diachronic and a synchronic perspective on media transitions, this dissertation proposes an alternative form of media historiography that rethinks media histories beyond the frameworks of change and continuity by perceiving hybridity as a constant factor in media historical development. [less ▲]

Global flows, local conflicts and the challenge of urban governance: Managing the urban-airport interface in London and the South East of England

Doctoral thesis (2018)

Whilst often taken for granted, transport flows, airspace and urbanisation at ‘ground level’ are deeply intertwined. This dissertation situates London’s current controversy regarding airport expansion and ... [more ▼]

Whilst often taken for granted, transport flows, airspace and urbanisation at ‘ground level’ are deeply intertwined. This dissertation situates London’s current controversy regarding airport expansion and aircraft noise and within new understandings of urbanisation and the role of transport flows within the urban realm, analysing the contested spatial relations stretched across the three-dimensional terrain, where the urban-rural, global-local and public- private spatial divisions are polarised by the negotiation of aircraft noise. Drawing from empirical evidence related to existing noise pollution issues and the expansion of aviation infrastructure in the South East, this text interprets airspace as part of the transformation and extension of the urban fabric above the built environment of the urban region, comparable to peri-urban extension and dispersal of the urban across the earth’s surface. This study draws from empirical qualitative evidence of London Heathrow Airport, Gatwick Airport, and the local places which experience noise pollution emanating from the various, changing flight paths to and from these airports within and surrounding London’s urban boundary. Theorised in this text as the relational, interscalar urban-airport interface, the constructivist approach employed here focuses on the constellation of public and private institutions and actors who co-constitute this interface and manage aircraft noise in the context of on-going airspace modernisation, the intensification of aircraft activity and pending airport expansion. [less ▲]

Les regards experts sur l’Est en Allemagne et en Pologne : émergence, cristallisation et révision (1918-1972)

Doctoral thesis (2017)

La 1e Guerre mondiale fut le catalyseur de mutations sociales et techniques, qui suscitent de nouveaux besoins d’administration, matérialisés par l’émergence d’un nouveau groupe social: celui des experts ... [more ▼]

La 1e Guerre mondiale fut le catalyseur de mutations sociales et techniques, qui suscitent de nouveaux besoins d’administration, matérialisés par l’émergence d’un nouveau groupe social: celui des experts. Dans les États modernes allemands et polonais, un groupe particulier d’experts se détache, qui se spécialisent dans une thématique aux profondes racines culturelles : l’Est européen.Les changements de régime et de territoire entre 1918 et 1972 déstabilisent le cadre de référence des sociétés allemandes et polonaises, particulièrement entre 1939 et 1945. Cependant, l’historiographie des sciences de l’Est allemandes (Ostforschung) souligne les continuités personnelles, institutionnelles et conceptuelles fortes dans l’expertise de l’Est du « IIIe Reich » à l’Allemagne de l’Ouest. En Allemagne de l’Est et en Pologne, au contraire, le changement de régime après 1945 rend impossible toute continuité, mais la question de l’évolution de la pensée sur l’Est dans les cercles de l’expertise, qui eux se maintiennent, reste posée.En dépassant l’analyse de l’expertise en termes de subordination aux différents régimes politiques auxquels elle s’adresse, nous mettons en valeur les spécificités de l’expertise de l’Est. Elle se caractérise par un double ancrage dans l’imaginaire collectif et dans les pratiques scientifiques contemporaines, pour exprimer un but politique. Cet ancrage explique l’inertie dans les conceptions allemandes et polonaises de l’Est. L’approche comparatiste souligne tant la diversité des conceptions de l’Est, que les fonctions sociales comparables de l’Est, notamment celle d’ennemi et d’espace de projection nationale, passée et à venir [less ▲]

L’enseignement du chinois standard en tant que 3ème ou 4ème langue étrangère dans une classe de seconde en Alsace : le rôle de la notion de compétence plurilingue et pluriculturelle

Doctoral thesis (2017)

This thesis consists of a qualitative and ethnographic research. It aims to determinate the role played by the plurilingual and pluricultural competence of a teacher and her twenty-two full beginner ... [more ▼]

This thesis consists of a qualitative and ethnographic research. It aims to determinate the role played by the plurilingual and pluricultural competence of a teacher and her twenty-two full beginner students in the context of the teaching of Chinese as a foreign language. How does this teacher interpret this notion? How can this teacher take into account and make use of her students’ previously acquired languages, i.e. their plurilingual repertoire, to facilitate her teaching? This thesis concerns not only identifying the mechanisms and the frequency of the use of the plurilingual repertoire in the teaching of standard Chinese, but also interrogating the teacher and the students’ representation. This analysis intends to seize the causes of the gap between the official discourse and instructions on one hand and the empirical teaching and learning practices on the other hand. This thesis demonstrated two significant results: the “sloganization” of the notion of plurilingual and pluricultural competence in French educative language policies and the lack of awareness of the protagonists concerning their solicitation of the plurilingual and pluricultural competence in the classroom. [less ▲]

Efficient and Secure Implementations of Lightweight Symmetric Cryptographic Primitives

Doctoral thesis (2017)

This thesis is devoted to efficient and secure implementations of lightweight symmetric cryptographic primitives for resource-constrained devices such as wireless sensors and actuators that are typically ... [more ▼]

This thesis is devoted to efficient and secure implementations of lightweight symmetric cryptographic primitives for resource-constrained devices such as wireless sensors and actuators that are typically deployed in remote locations. In this setting, cryptographic algorithms must consume few computational resources and withstand a large variety of attacks, including side-channel attacks. The first part of this thesis is concerned with efficient software implementations of lightweight symmetric algorithms on 8, 16, and 32-bit microcontrollers. A first contribution of this part is the development of FELICS, an open-source benchmarking framework that facilitates the extraction of comparative performance figures from implementations of lightweight ciphers. Using FELICS, we conducted a fair evaluation of the implementation properties of 19 lightweight block ciphers in the context of two different usage scenarios, which are representatives for common security services in the Internet of Things (IoT). This study gives new insights into the link between the structure of a cryptographic algorithm and the performance it can achieve on embedded microcontrollers. Then, we present the SPARX family of lightweight ciphers and describe the impact of software efficiency in the process of shaping three instances of the family. Finally, we evaluate the cost of the main building blocks of symmetric algorithms to determine which are the most efficient ones. The contributions of this part are particularly valuable for designers of lightweight ciphers, software and security engineers, as well as standardization organizations. In the second part of this work, we focus on side-channel attacks that exploit the power consumption or the electromagnetic emanations of embedded devices executing unprotected implementations of lightweight algorithms. First, we evaluate different selection functions in the context of Correlation Power Analysis (CPA) to infer which operations are easy to attack. Second, we show that most implementations of the AES present in popular open-source cryptographic libraries are vulnerable to side-channel attacks such as CPA, even in a network protocol scenario where the attacker has limited control of the input. Moreover, we describe an optimal algorithm for recovery of the master key using CPA attacks. Third, we perform the first electromagnetic vulnerability analysis of Thread, a networking stack designed to facilitate secure communication between IoT devices. The third part of this thesis lies in the area of side-channel countermeasures against power and electromagnetic analysis attacks. We study efficient and secure expressions that compute simple bitwise functions on Boolean shares. To this end, we describe an algorithm for efficient search of expressions that have an optimal cost in number of elementary operations. Then, we introduce optimal expressions for first-order Boolean masking of bitwise AND and OR operations. Finally, we analyze the performance of three lightweight block ciphers protected using the optimal expressions. [less ▲]

Single-station monitoring of volcanoes from the cross-correlations of seismic ambient noise

Doctoral thesis (2017)

Big Data Architectures For Robust Systems

Doctoral thesis (2017)

Monitoring robustness of critical systems/infrastructures is the major use case for anomaly detection. A robust system designates a structure not only safe against intentional attacks, but also capable of ... [more ▼]

Monitoring robustness of critical systems/infrastructures is the major use case for anomaly detection. A robust system designates a structure not only safe against intentional attacks, but also capable of stemming internal failures. These systems face two primary risks: cyber attacks fall into the first category, whereas failing hardware components are part of the second category. In both cases, fast decision making is crucial. Hence, streaming data processing is the decisive asset to consider. With this background, in this thesis, we investigate two scenarios from the fields of mobile network sanity monitoring and cyber-physical security. Our contribution is threefold: We display how the real-time requirements of the two use cases push existing frameworks to their utter limits; We show which anomaly detection methods can be used to facilitate instant assessment rendering; We blueprint the extensions we contributed to big data frameworks, which are powering major silicon valley companies, to make them capable of supporting our use cases. The data-sets issued by our monitoring systems yield different properties than data from internet companies such as Google, Facebook or LinkedIn. In this work we establish our use cases, illustrate the mathematical models employed for the decision taking, and examine how big data architectures have to be altered to support our scenarios. [less ▲]

Computational ecosystems modeling and analysis of human-associated intestinal microbial communities

Doctoral thesis (2017)

Learning Finite Automata via Flexible State-Merging and Applications in Networking

Doctoral thesis (2017)

Being able to model behavior described by a linear sequence of observations (such as log files) goes a long way towards better understanding the underlying processes. This improved understanding can be ... [more ▼]

Being able to model behavior described by a linear sequence of observations (such as log files) goes a long way towards better understanding the underlying processes. This improved understanding can be very helpful in a number of activities, ranging from software (reverse) engineering to network traffic analysis. The developments in this thesis were driven by specific goals in predicting (human) behaviors captured by a software appliance observing network traffic and user requests to specific resources. Its final contributions have exceeded the original goals of the project in two important ways: I present (1) a flexible learning algorithm for finite automata accompanied by theoretical underpinning and its implementation, a contribution towards better learning algorithms, and (2) applications of the algorithm to use-cases in computer networking and beyond. The central algorithm considered in the thesis is a blue-fringe state-merging automaton learning algorithm, conducting a greedy search over feasible solutions. Its key components are a heuristic to search for consistent merges and an evaluation metric to assess the quality of a merge by assigning scores to merges. I generalize this framework by making the heuristic components explicitly parametric. While state-merging algorithms were originally defined for probabilistic and non-probabilistic finite state machines and later used to derive algorithms for more extended models such as real-time automata, the work presented here extends the scope of the algorithms to a wide range of ad-hoc defined models as well as enables the user to implement modifications to the heuristic search process. These modifications help to account for domain knowledge and richer semantics of models with a regular language core. I provide an implementation and a Python interface of the flexible state-merging framework, including stream/online and interactive variants of the algorithm based on a C++ implementation of the blue-fringe greedy search algorithm called DFASAT. The algorithm and the framework encompass and improve upon state-of-the-art approaches. The application problems considered in this thesis can be seen as classical classification and anomaly detection tasks in machine learning. The application domain is network traffic analysis with a focus on network security. I discuss the problematic properties of data from computer networks and address how using automaton models can help mitigate them. I then use the flexible state-merging approach for host profiling. I show how to efficiently learn finite state automata as behavioral profiles. These profiles can serve as digital fingerprints and help to identify malicious traffic such as botnet traffic. Moreover, I show how communication profiles can be used for sequence clustering on NetFlow data to distinguish different behaviors over time. [less ▲]

Deformation Based Curved Shape Representation

Doctoral thesis (2017)

Representation and modelling of an objects' shape is critical in object recognition, synthesis, tracking and many other applications in computer vision. As a result, there is a wide range of approaches in ... [more ▼]

Representation and modelling of an objects' shape is critical in object recognition, synthesis, tracking and many other applications in computer vision. As a result, there is a wide range of approaches in formulating representation space and quantifying the notion of similarity between shapes. A similarity metric between shapes is a basic building block in modelling shape categories, optimizing shape valued functionals, and designing a classifier. Consequently, any subsequent shape based computation is fundamentally dependent on the computational efficiency, robustness, and invariance to shape preserving transformations of the defined similarity metric. In this thesis, we propose a novel finite dimensional shape representation framework that leads to a computationally efficient, closed form solution, and noise tolerant similarity distance function. Several important characteristics of the proposed curved shape representation approach are discussed in relation to earlier works. Subsequently, two different solutions are proposed for optimal parameter estimation of curved shapes. Hence, providing two possible solutions for the point correspondence estimation problem between two curved shapes. Later in the thesis, we show that several statistical models can readily be adapted to the proposed shape representation framework for object category modelling. The thesis finalizes by exploring potential applications of the proposed curved shape representation in 3D facial surface and facial expression representation and modelling. [less ▲]

Wohnmobilität in der Großregion – eine interurbane Diskursanalyse mit Fokus auf den Städten Arlon, Thionville und Trier.

Doctoral thesis (2017)

Effects of residential mobility moulding in uneven development in border regions can be perceived very differently by city councils or planners and the local population. This dissertation focuses on the ... [more ▼]

Effects of residential mobility moulding in uneven development in border regions can be perceived very differently by city councils or planners and the local population. This dissertation focuses on the perceptions of population mobility and dwelling in a transnational cross-border polycentric region in western Europe. The economic development of the Grand Duchy of Luxembourg calls for a constant expansion of the labour market, attracting cross-border commuters and highly mobile professional elites. The concomitant rises in property prices as well as the extreme housing shortages in Luxembourg have led to an expansion of the housing market into the border regions. So far studies have mostly dealt with the socio-demographic characteristics of the transmigrants. This research aims to detect people’s perceptions of the phenomenon by applying a discourse analysis, thus aiming to trigger an increasing awareness for the emerging transnational housing market. [less ▲]

Qualitätskonstruktionen - Eine empirische Analyse zur Verarbeitung divergierender Qualitätsanforderungen am Beispiel der Offenen Jugendarbeit

Doctoral thesis (2017)

A Model-Based Framework for Legal Policy Simulation and Compliance Checking

Doctoral thesis (2017)

Information systems implementing requirements from laws and regulations, such as taxes and social benefits, need to be thoroughly verified to demonstrate their compliance. Several Verification and ... [more ▼]

Information systems implementing requirements from laws and regulations, such as taxes and social benefits, need to be thoroughly verified to demonstrate their compliance. Several Verification and Validation (V&V) techniques, such as reliability testing, and modeling and simulation, can be used for assessing that such systems meet their legal. Typically, one has to model the expected (legal) behavior of the system in a form that can be executed (simulated), subject the resulting models and the system to the same input data, and then compare the observed behavior of the model simulation and system execution. Existing V&V techniques often rely on code and complex logical expressions with no intuitive appeal to legal experts for specifying the expected behavior of a given system. Subsequently, one has no practical way to validate with legal experts that the underlying legal requirements are indeed complete and constitute a faithful representation of what needs to be implemented. Further, manually defining the expected behavior of a system and its test oracles is a tedious and error-prone task. The challenge here is to find a suitable knowledge representation that can be understood by all the involved stakeholders, e.g., software engineers and legal experts, but that remains complete and precise enough to enable automated analysis such as simulation and testing. As real data is seldom accessible in highly regulated domains, V&V requires the generation of synthetic testing data that can be used to build confidence in the reliability of the system under test. In particular, such data has to be structurally and logically well-formed to raise meaningful failures that can help reasoning about the reliability of the system under test. Further, the data should exhibit as much as possible the actual or anticipated system usage to help mimic how the system would behave under realistic circumstances. Generating such data is not a trivial task as the underlying data schemas are usually large and subject to numerous complex domain-related logical constraints. In this thesis, we investigate the use of the Unified Modeling Language (UML) and model-driven technologies, e.g., model to code transformations, to facilitate V&V activities for information systems that have to conform to laws and regulations, while tackling the above challenges. All our technical solutions have been developed and empirically evaluated in close collaboration with a government administration. Concretely, the technical solutions covered by this thesis include: - A modeling notation and methodology for formalizing legal policies. We propose a modeling notation and methodology for building abstract interpretations of the law. Models built using our methodology are simple enough to be understood by the involved stakeholders and are, at the same time, detailed enough to enable automated V&V activities. - A model-based simulation framework. We develop a model-based framework and associated tool support for simulating legal policies, when formalized using the aforementioned modeling methodology. Simulation provides a comparison baseline of how a compliant system should behave. Further, simulation is a mean to support decision-making when considering legal changes. Specifically, we report on a sizable case study where we assess the anticipated economic implications of a given policy change in Luxembourg’s tax law. - A model-based generator of test cases for reliability testing. We develop a heuristic approach for generating valid and representative test cases (data). Our generator is scalable and produces high-quality test data that is suitable for testing the reliability of data-intensive systems, e.g., a tax management system. [less ▲]