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See detailA decision support system for energy saving in Waste Water Treatment Plants
Torregrossa, Dario UL

Doctoral thesis (2018)

Waste Water Treatment Plants (WWTPs) are complex facilities, in which an efficient energy management can produce relevant benefits for the environment and the economy. Today, big data can be used for a ... [more ▼]

Waste Water Treatment Plants (WWTPs) are complex facilities, in which an efficient energy management can produce relevant benefits for the environment and the economy. Today, big data can be used for a more efficient plant management, enabling high-frequency assessment and ultimately a more efficient use of resources. In order to achieve this, a computer-based support is necessary to analyse the enormous amount of data that WWTP sensors can produce. When this PhD project started, the literature review showed that, in the WWTP domain, the few available decision support systems (DSSs) were promising but still with large room for improvements; in fact, these tools were plant-specific, focussed mainly on process parameters and (most of them) working with low-frequency aggregated data (yearly data). This thesis instead proposes a cooperative decision support system called Shared Knowledge Decision Support System (SK-DSS). SK-DSS is plant generic, i.e. able to simultaneously work with many WWTPs and based on key performance indicators. SK-DSS analyses the processes occurring in the plants and provide case-based solutions. Moreover, this DSS provides a platform to enable the plant managers to exchange information and cooperate. This thesis proposes the model of SK-DSS, a web-application, and applications to improve the energy performance of pump, blowers and biogas. [less ▲]

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See detailAdvanced Symbol-level Precoding Schemes for Interference Exploitation in Multi-antenna Multi-user Wireless Communications
Spano, Danilo UL

Doctoral thesis (2018)

The utilization of multi-antenna transmitters relying on full frequency reuse has proven to be an effective strategy towards fulfilling the constantly increasing throughput requirements of wireless ... [more ▼]

The utilization of multi-antenna transmitters relying on full frequency reuse has proven to be an effective strategy towards fulfilling the constantly increasing throughput requirements of wireless communication systems. As a consequence, in the last two decades precoding has been a prolific research area, due to its ability to handle the interference arising among simultaneous transmissions addressed to different co-channel users. The conventional precoding strategies aim at mitigating the multi-user interference (MUI) by exploiting the knowledge of the channel state information (CSI). More recently, novel approaches have been proposed where the aim is not to eliminate the interference, but rather to control it so as to achieve a constructive interference effect at each receiver. In these schemes, referred to as symbol-level precoding (SLP), the data information (data symbols) is used together with the CSI in the precoding design, which can be addressed following several optimization strategies. In the context of SLP, the work carried out in this thesis is mainly focused on developing more advanced optimization strategies suitable to non-linear systems, where the per-antenna high-power amplifiers introduce an amplitude and phase distortion on the transmitted signals. More specifically, the main objective is to exploit the potential of SLP not only to achieve the constructive interference at the receivers, but also to control the per-antenna instantaneous transmit power, improving the power dynamics of the transmitted waveforms. In fact, a reduction of the power variation of the signals, both in the spatial dimension (across the different antennas) and in the temporal dimension, is particularly important for mitigating the non-linear effects. After a detailed review of the state of the art of SLP, the first part of the thesis is focused on improving the power dynamics of the transmitted signals in the spatial dimension, by reducing the instantaneous power imbalances across the different antennas. First, a SLP per-antenna power minimization scheme is presented, followed by a related max-min fair formulation with per-antenna power constraints. These approaches allow to reduce the power peaks of the signals across the antennas. Next, more advanced SLP schemes are formulated and solved, with the objective of further improving the spatial dynamics of the signals. Specifically, a first approach performs a peak power minimization under a lower bound constraint on the per-antenna transmit power, while a second strategy minimizes the spatial peak-to-average power ratio. The second part of this thesis is devoted to developing a novel SLP method, referred to as spatio-temporal SLP, where the temporal variation of the transmit power is also considered in the SLP optimization. This new model allows to minimize the peak-to-average power ratio of the transmitted waveforms both in the spatial and in the temporal dimensions, thus further improving the robustness of the signals to non-linear effects. Then, this thesis takes one step further, by exploiting the developed spatio-temporal SLP model in a different context. In particular, a spatio-temporal SLP scheme is proposed which enables faster-than-Nyquist (FTN) signaling over multi-user systems, by constructively handling at the transmitter side not only the MUI but also the inter-symbol interference (ISI). This strategy allows to benefit from the increased throughput provided by FTN signaling without imposing additional complexity at the user terminals. Extensive numerical results are presented throughout the thesis, in order to assess the performance of the proposed schemes with respect to the state of the art in SLP. The thesis concludes summarizing the main research findings and identifying the open problems, which will constitute the basis for the future work. [less ▲]

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See detailRisk Monitoring and Intrusion Detection for Industrial Control Systems
Muller, Steve UL

Doctoral thesis (2018)

Cyber-attacks on critical infrastructure such as electricity, gas, and water distribution, or power plants, are more and more considered to be a relevant and realistic threat to the European society ... [more ▼]

Cyber-attacks on critical infrastructure such as electricity, gas, and water distribution, or power plants, are more and more considered to be a relevant and realistic threat to the European society. Whereas mature solutions like anti-malware applications, intrusion detection systems (IDS) and even intrusion prevention or self-healing systems have been designed for classic computer systems, these techniques have only been partially adapted to the world of Industrial Control Systems (ICS). As a consequence, organisations and nations fall back upon risk management to understand the risks that they are facing. Today's trend is to combine risk management with real-time monitoring to enable prompt reactions in case of attacks. This thesis aims at providing techniques that assist security managers in migrating from a static risk analysis to a real-time and dynamic risk monitoring platform. Risk monitoring encompasses three steps, each being addressed in detail in this thesis: the collection of risk-related information, the reporting of security events, and finally the inclusion of this real-time information into a risk analysis. The first step consists in designing agents that detect incidents in the system. In this thesis, an intrusion detection system is developed to this end, which focuses on an advanced persistent threat (APT) that particularly targets critical infrastructures. The second step copes with the translation of the obtained technical information in more abstract notions of risk, which can then be used in the context of a risk analysis. In the final step, the information collected from the various sources is correlated so as to obtain the risk faced by the entire system. Since industrial environments are characterised by many interdependencies, a dependency model is elaborated which takes dependencies into account when the risk is estimated. [less ▲]

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See detailWorkplace bullying: Validation of a measurement and the role of competition, passive avoidant leadership style, psychological contract violation and basic need frustration.
Sischka, Philipp UL

Doctoral thesis (2018)

Workplace bullying, mobbing or harassment describe a situation where an employee is the target of systematic mistreatment by other organizational members (i.e., colleagues, supervisors, subordinates) that ... [more ▼]

Workplace bullying, mobbing or harassment describe a situation where an employee is the target of systematic mistreatment by other organizational members (i.e., colleagues, supervisors, subordinates) that may cause severe social, psychological and psychosomatic problems in the targeted employee. Since the appearance of the book “The harassed worker” by Brodsky (1976) and initial studies by Heinz Leymann (1986, 1990), workplace bullying research has developed into a huge and still massively growing research area that is conducted all over the globe. Especially, when related concepts are considered, a vast amount of studies have researched prevalence, risk factors, consequences, and, very recently, psychological mechanisms of workplace bullying exposure. A literature review revealed that existing workplace bullying exposure self-report inventories exhibit some weaknesses. Therefore, the first study (Chapter 2) aimed to develop a new short scale, the Luxembourg Workplace Mobbing Scale (LWMS) in three different language versions (i.e., Luxembourgish, French, German). Furthermore, it investigated the psychometric properties and the validity of this scale and examined if the three language versions exhibit measurement invariance. The LWMS revealed good psychometric properties in terms of its internal consistency and its factor structure. Furthermore, metric and partial scalar invariance across the three language versions could be established. Initial validation tests revealed high criterion validity of the LWMS. In line with recent workplace bullying exposure research, the LWMS was meaningfully linked with other working factors and measures of psychological health. The second study (Chapter 3) aimed to test the LWMS’s factor structure and measurement invariance across possible risk groups of bullying exposure (i.e., gender, age, and occupational groups). Moreover, based on recent theories and findings on workplace bullying the study aimed to further elucidate the LWMS’s nomological net with relevant psychological (i.e., psychological well-being, work engagement, sleeping hours, suicidal thoughts) and physiological health measures (i.e., physiological health problems, alcohol and smoking consumption, body mass index) as well as with important organizational criteria (i.e., work performance, turnover intention, absenteeism) and with self-labeling victim status. Evaluation of different measurement invariance models confirm metric and (partial) scalar invariance across all compared groups. Neither age, gender, nor the most frequent areas of occupation in Luxembourg represent important risk factors for workplace bullying exposure. Regarding criterion validity, with the exceptions of alcohol and smoking consumption, all proposed psychological and physiological health measures as well as organizational criteria are meaningfully associated with the LWMS. In summary, the LWMS is especially useful, when the identification of workplace bullying exposure risk groups or cross-cultural research is of concern. The third study (Chapter 4) aimed to test specific organizational risk factors of the occurrence of workplace bullying. Specifically, competition and passive avoidant leadership style were tested as risk factors of workplace bullying (exposure and perpetration) assessed with two assessment methods (behavioral experience and self-labeling method). Consistent with theoretical reasoning and prior research, results demonstrated that competition as well as passive avoidant leadership style are important risk factors of workplace bullying exposure. Moreover, results showed that the same effects showed up for perpetration. Even more interesting, passive avoidant leadership style acted as a moderator on the effect of competition on workplace bullying exposure. In line with theory, competition is stronger related to workplace bullying exposure, when passive avoidant leadership is high. Thus, passive avoidant leadership style can be considered a disruptive factor reinforcing the negative association with competition. Regarding workplace bullying perpetration the same moderation effect was only found for the self-labeled assessment method. The fourth study (Chapter 5) aimed to identify different psychological mechanisms (i.e., psychological contract violation and frustration of basic needs) that link being target of workplace bullying and health, attitudinal and behavioral outcomes. Furthermore, their relative impact and importance on different outcomes were highlighted. Psychological contract violation was an important mediator for decreased job satisfaction and higher turnover intentions, whereas frustration of autonomy mediated the effect between workplace bullying exposure and increased levels of burnout, frustration of competence mediated the effect of bullying exposure on decreased work performance and frustration of relatedness was strongly associated with decreased well-being and vigor. Results showed that feelings of psychological contract violation and frustration of basic needs accounted for unique variation in many outcome variables, pointing to the individual contribution of both psychological mechanisms. The present thesis deepens our understanding of the organizational circumstances under which workplace bullying is more likely and the psychological mechanisms that link the bullying exposure with several outcomes. These results can guide possible prevention and intervention strategies. [less ▲]

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See detailAnti-de Sitter geometry: convex domains, foliations and volume
Tamburelli, Andrea UL

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 ▲]

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See detailSpeaker evaluations in multilingual contexts: The predictive role of language and nationality attitudes as distinct factors in explicit and implicit cognition
Lehnert, Tessa Elisabeth UL

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 ▲]

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See detailAdvanced Raman Spectroscopy of Ultrathin RNiO3 films
Schober, Alexander UL

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 ▲]

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See detailSTUDY OF THE INCORPORATION MECHANISMS OF ORGANIC CHEMICALS INTO HAIR
Chata, Caroline Georgette Samia UL

Doctoral thesis (2018)

Hair presents several advantages for biomonitoring the exposure to pollutants. For instance, this matrix is representative of the mid to long term exposure depending on the length of the sample. However ... [more ▼]

Hair presents several advantages for biomonitoring the exposure to pollutants. For instance, this matrix is representative of the mid to long term exposure depending on the length of the sample. However the question concerning the hair incorporation mechanism of chemicals remain partially unravelled. The subject of the present PhD was the “study of the incorporation mechanisms of organic chemicals into hair” (StICHa). Therefore we focused on the influence of biological and physicochemical parameters on the incorporation of pesticides into hair. The results presented in the project were obtained from three experiments whose two animal experiments conducted on rats. The first one allowed to link levels of exposure of pesticides to the corresponding concentrations in plasma and in hair. This also allowed to study the accumulation of pesticides in the rat body over time and to investigate the influence of the pesticide physicochemical properties on their incorporation into hair. The second one provided pharmacokinetic (PK) parameters of pesticides in blood after a single exposure and highlighted the concept of background exposure corresponding to the detectable chemicals concentration in the animals before exposure due to environmental contamination. An in vitro test was also conducted to investigate bonds between pesticides and blood components and their influence on hair incorporation. [less ▲]

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See detailUNRAVELING THE COMPLEX GENETICS OF NEUROLOGICAL DISORDERS
Bobbili, Dheeraj Reddy UL

Doctoral thesis (2018)

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See detailMagnetic small-angle neutron scattering on bulk metallic glasses
Mettus, Denis UL

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 ▲]

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See detailDevelopment of mass spectrometry-based assays to measure the ERCC1/XPF proteins as potential biomarkers in lung cancer
Antonelli, Daniela UL

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 ▲]

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See detailStochastic Model Predictive Control for Eco-Driving Assistance Systems in Electric Vehicles
Sajadi Alamdari, Seyed Amin UL

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 ▲]

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See detailTraditions in Tension: An Ethnographic Inquiry of Luxembourg’s Family-Run Hotels
Adiguna, Rocky UL

Doctoral thesis (2018)

The suggestion that tradition plays a role in family business is a long-acknowledged but often presumed notion in family business research. As a result, studies that attempt to conceptualise tradition as ... [more ▼]

The suggestion that tradition plays a role in family business is a long-acknowledged but often presumed notion in family business research. As a result, studies that attempt to conceptualise tradition as a focal point remain scarce. This dissertation addresses this vacuum by examining the properties and processes that are involved in the tradition-making and tradition-maintaining of hospitality-based family businesses. Based on an ethnographic inquiry of five hotel-running families in Luxembourg, this dissertation inquires into the meanings and tensions of tradition. Drawing from a process perspective, it explores how family owner-managers receive, enact, and perpetuate the continuity of the family businesses as traditions. Theoretically, this study contributes to two streams of literature: to the family business literature by providing a conceptual foundation for understanding tradition as process, and to the process organisation studies literature by proposing family business as an exemplar of tradition where the past is immanent in the present. Methodologically, this study attends to discourses and narratives at the national level, the industry level, and the organisational level to contextualise the family-run hotels in a wider discursive space. These multi-level analyses constitute the basis for the application of a field ethnography which attempts to explore the relationality between different modes of discourse in a chosen field: texts, talks, actions, and images. As a result, the lived narratives of five hotel-running families are produced. This dissertation advances tradition as a root metaphor for family business and proposes three different angles of seeing the family business as tradition: family business as received tradition, family business as enacted tradition, and family business as tradition to be transmitted. In alignment with the process perspective, four dualities in the enactment of the family businesses as traditions are discussed: repetition and novelty, preservation and abandonment, being and appearing, and certainty and possibility. Ultimately, this dissertation puts into question the predominant understanding of tradition as a fixed construct argues instead that tradition's apparent unity, fixity, and stability is a result of a reflexive process which is enacted by owner-managers on a daily basis. [less ▲]

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See detailAngle and Spectral Dependence of the Internal and External Quantum Efficiency of Solar Modules
Reiners, Nils UL

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 ▲]

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See detailCharacterization and Multi-Physical Analysis of RF-Driven Microwave Plasma Applications from 1.3 GHz to 3.5 GHz
Schopp, Christoph UL

Doctoral thesis (2018)

This thesis presents the analysis of microwave plasma frequency-dependence based on the investigation of multi-physical parameters. Fundamentals of a microwave plasma and high-frequency technology are ... [more ▼]

This thesis presents the analysis of microwave plasma frequency-dependence based on the investigation of multi-physical parameters. Fundamentals of a microwave plasma and high-frequency technology are explained. Frequency-dependent effects on the base point impedance are presented in combination with the description of the used measuring hardware. Development of a bi-static network for the main plasma states (ignition and operation) is presented on the example of two high-pressure lamps at 2.45 GHz. Networks of both lamps are custom-built during the course of this thesis. An efficacy of 135 lm/W is achieved exceeding the efficacy of most LEDs. Frequency-dependent electrical properties are analyzed by reflection measurements of three different prototypes (argon plasma jet, phosphor-coated lamp and hollow glass cylinder filled with xenon) for the first time. A novel and simple lumped element and 3D-model are developed for the fitting of the plasma. A series resonance circuit substitutes the frequency-dependency of the capacitive plasma. The models are extended for S21 measurements by a novel developed transmission prototype. A simple frequency-dependent capacitor lumped element model fits the transmission parameters of the plasma. The novel core/cone3D-model is capable of fitting the plasma in an FEM simulator by only using the conductivity. A significant influence of the frequency on the spatial properties of all prototypes is measured for the first time by a simple CMOS camera and a custom image registration routine. The spatial extension is inversely proportional to the frequency. Optical measurements identify the participating ion species. Influence of the frequency on single spectral bands are presented in an in-depth analysis using optical emission spectroscopy. A proportionality of the frequency and the energy density in the microwave plasma is revealed. This is supported by the thermal measurements. The plasma jet rotational temperature is determined by the hydroxyl band at 310nm and shows a maximum values of 1350 K at only 15 W. [less ▲]

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See detailMany-Body Perturbation Theory Approach to Raman Spectroscopy and Its Application to 2D Materials
Reichardt, Sven UL

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 ▲]

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See detailBewohnerorientierte Betreuung für Luxemburgs Alten- und Pflegeheimbewohner. Theoretische und empirische Analysen zur Entwicklung und Implementierung eines neuen Betreuungsmodells
Pax, Nadine UL

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 ▲]

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See detailA Scalable and Accurate Hybrid Vulnerability Analysis Framework
Thome, Julian UL

Doctoral thesis (2018)

As the Internet has become an integral part of our everyday life for activities such as e-mail, online-banking, shopping, entertainment, etc., vulnerabilities in Web software arguably have greater impact ... [more ▼]

As the Internet has become an integral part of our everyday life for activities such as e-mail, online-banking, shopping, entertainment, etc., vulnerabilities in Web software arguably have greater impact than vulnerabilities in other types of software. Vulnerabilities in Web applications may lead to serious issues such as disclosure of confidential data, integrity violation, denial of service, loss of commercial confidence/customer trust, and threats to the continuity of business operations. For companies these issues can result in significant financial losses. The most common and serious threats for Web applications include injection vulnerabilities, where malicious input can be “injected” into the program to alter its intended behavior or the one of another system. These vulnerabilities can cause serious damage to a system and its users. For example, an attacker could compromise the systems underlying the application or gain access to a database containing sensitive information. The goal of this thesis is to provide a scalable approach, based on symbolic execution and constraint solving, which aims to effectively find injection vulnerabilities in the server-side code of Java Web applications and which generates no or few false alarms, minimizes false negatives, overcomes the path explosion problem and enables the solving of complex constraints. [less ▲]

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See detailRecent developments around the Malliavin-Stein approach (Fourth moment phenomena via exchangeable pairs)
Zheng, Guangqu UL

Doctoral thesis (2018)

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

Detailed reference viewed: 47 (11 UL)
See detailColonization and succession of the human gastrointestinal microbiome in neonates and infants at high risk of metabolic disease in adulthood
Wampach, Linda UL

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 ▲]

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See detailLarge-scale and Flexible Nanogenerator based on ZnO conical nanostructures by Nano-Imprint Lithography and Atomic Layer Deposition
Spirito, David Mario André UL

Doctoral thesis (2018)

The present work stands in the context of the rapid growth of portable electronics and wireless sensors. This growth drives the request for advances in materials science and technology to harvest energy ... [more ▼]

The present work stands in the context of the rapid growth of portable electronics and wireless sensors. This growth drives the request for advances in materials science and technology to harvest energy from ambient sources. Piezoelectric nanogenerators, which convert vibrations into electrical energy, are considered as one of the promising building blocks for the design of low-cost and performant energy harvesting devices. Several demonstrations of PENGs have been reported throughout the last decade, many of them based on Zinc Oxide –ZnO– nanowires. Despite interesting performances, literature also suggests that the classical bottom-up approach of optimized ZnO-based PENGs performance approaches its limits and that top-down approaches merit further attention. This has motivated the present work, with the aim to conceptualize by models, to fabricate and to investigate a new type of piezoelectric nanogenerator based on ZnO nanostructures to overcome current limitations. To achieve this goal, we have used a top-down approach that allows an accurate control of the aspect ratio and density of tailored ZnO nanowires by using Nano-Imprint Lithography and Atomic Layer Deposition. In our work, we demonstrate that this approach enables the fabrication of large flexible piezoelectric nanogenerators with interesting properties. In the first part of this work, we have optimized the synthesis of crystalline N-doped ZnO films by ALD at a deposition temperature as low as T = 80 °C. We have particularly investigated the role of the time of purge with nitrogen as purge gas in each cycle of a ZnO monolayer of the ALD process. A thorough chemical and structural analysis illustrates that the time of purge allows tuning the N-doping-level which, despite being low, affects both the long-range and short-range structure. Raman and luminescence spectroscopy suggest a complex defect structure, characterized by nitrogen ions which substitute oxygen ions and by Zn cations on interstitial sites. Importantly, even the low level of nitrogen doping allows tuning the sheet resistivity of ZnO films by several orders of magnitude. The ability to obtain crystallized and tunable N-doped ZnO films down to 80 °C by ALD provides a critical building block to tune structural, optic and electric properties for a variety of applications. In the second part, we have designed, fabricated and characterized a new type of PENGs based on patterned nanostructures made of conical-shape ZnO pillars. First, we have used a finite element modeling to identify the optimization for the electromechanical performances of the ZnO nanowires, namely in terms of their aspect ratio and pitch. This has defined the stamps of the nano-imprint, which has then be combined with a low temperature conformal ALD to provide ZnO conical nanostructures. A thorough structural analysis of such nanostructures attests a high crystallinity, a polycrystalline growth and piezoelectric properties. This has been the necessary technological achievement for addressing in a next step functional patterned piezoelectric nanogenerators. We have produced small flexible devices with an active area of 4 x 4 mm2, using either a blocking electronic barrier with alumina, either a p-n junction with a conductive polymer (PEDOT:PSS). The different devices and architectures have then been characterized at matching impedance. The electric characterization of a device with a p-n junction exhibits a maximum output voltage of 0.2 V and a power density of 0.3 µW cm-2. An effective transverse piezoelectric coefficient value e31eff of -0.45 C m-2 is determined, which corresponds to the order of magnitude reported in literature. As a proof of concept for potential industrialization, we scaled the P-PENGs up to 20 cm² for large flexible substrates. The 3.7 billion pillars, sandwiched between electrodes, evidence the robustness of our process. The analysis of the constitutive piezoelectric equations has prompted us to pay a particular attention to an accurate setup for P-PENGs characterization, which turns out to be mandatory to compare accurately devices. For this, we setup an electromechanical actuator. Two devices with the same architecture but with different levels of N-doping are compared. Using an equivalent electrical model, the performance of the P-PENG with the higher N-doped ZnO shows a larger output voltage and power density than the device with a lower N-doping level. This comparison shows that the higher N-doping-level leads to an increase of 150 % of the power output. From this we calculate that the effective piezoelectric coefficient increases by about 60 % for a P-PENG based on higher N-doped ZnO. This latter demonstrates an energy conversion efficiency of 10 %, on top of PENG based on ZnO. [less ▲]

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See detailTuning Self-Assembly in Liquid Crystal shells: from Interfacial- to Polymer-stabilization
Noh, Junghyun UL

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 ▲]

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See detailStructural properties of steel-concrete composite joints
Duarte da Costa, Job UL

Doctoral thesis (2018)

The performance of steel and concrete composite frames is influenced by the structural properties of beam-to-column composite joints. The accurate assessment of these properties constitutes therefore an ... [more ▼]

The performance of steel and concrete composite frames is influenced by the structural properties of beam-to-column composite joints. The accurate assessment of these properties constitutes therefore an important element for a realistic representation of the structural behaviour at serviceability and ultimate limit state. However, the structural joint properties are not equally covered by current design standards; analytical guidance is provided to assess the resistance and stiffness of composite joints, whereas for the rotation capacity an experimental proof is required. Due to the additional effort required to determine the rotation capacity, the global plastic analysis finds little application in the design of composite frames, resulting in a lack of efficiency and material optimization in the final design. In the present work, an analytical model to calculate the rotation capacity of composite joints is derived. Based on the knowledge developed in this research, an improvement of the current design rules for the joint stiffness is proposed. This model is based on an experimental test campaign comprising eight full-scale beamto- column joints with composite slim-floor beams. Besides, a finite element model was developed with the software Abaqus, which has been validated by the experimental tests. Numerical simulations were performed to investigate in-depth the conducted experiments and to analyse the behaviour of additional composite joints with different reinforcement properties. This research has resulted in new analytical design rules for the joint stiffness and rotation capacity. The reliability of these new design rules has been demonstrated for different joint typologies using experimental and numerical data. The development of an analytical method for the rotation capacity of composite joints allows composite beams with composite beam-to-column joints to be designed according to the global plastic analysis without need of experimental evidence. Furthermore, the improvement of the current design rules for the stiffness of composite joints induces a more accurate assessment of the action effects at serviceability and ultimate limit state. This thesis provides therefore a complete methodology to design beam-to-column composite joints. [less ▲]

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See detailDEVELOPMENT OF A COMPUTATIONAL RESOURCE FOR PERSONALIZED DIETARY RECOMMENDATIONS
Noronha, Alberto UL

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 ▲]

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See detailSpectrum Monitoring Algorithms for Wireless and Satellite Communications
Politis, Christos UL

Doctoral thesis (2018)

Nowadays, there is an increasing demand for more efficient utilization of the radio frequency spectrum as new terrestrial and space services are deployed resulting in the congestion of the already crowded ... [more ▼]

Nowadays, there is an increasing demand for more efficient utilization of the radio frequency spectrum as new terrestrial and space services are deployed resulting in the congestion of the already crowded frequency bands. In this context, spectrum monitoring is a necessity. Spectrum monitoring techniques can be applied in a cognitive radio network, exploiting the spectrum holes and allowing the secondary users to have access in an unlicensed frequency band for them, when it is not occupied by the primary user. Furthermore, spectrum monitoring techniques can be used for interference detection in wireless and satellite communications. These two topics are addressed in this thesis. In the beginning, a detailed survey of the existing spectrum monitoring techniques according to the way that cognitive radio users 1) can detect the presence or absence of the primary user; and 2) can access the licensed spectrum is provided. Subsequently, an overview of the problem of satellite interference and existing methods for its detection are discussed, while the contributions of this thesis are presented as well. Moreover, this thesis discusses some issues in a cognitive radio system such as the reduction of the secondary user's throughput of the conventional \listen before talk" access method in the spectrum. Then, the idea of simultaneous spectrum sensing and data transmission through the collaboration of the secondary transmitter with receiver is proposed to address these concerns. First, the secondary receiver decodes the signal from the secondary transmitter, then, removes it from the total received signal and finally, applies spectrum sensing in the remaining signal in order to decide if the primary user is active or idle. The effects of the imperfect signal cancellation due to decoding errors, which are ignored in the existing literature, are considered in our analysis. The analytical expressions for the probabilities of false alarm and detection are derived and numerical results through simulations are also presented to validate the proposed study. Furthermore, the threat of interference for the satellite communications services is studied in this thesis. It proposes the detection of interference on-board the satellite by introducing a spectrum monitoring unit within the satellite transponder. This development will bring several benefits such as faster reaction time and simplification of the ground stations in multi-beam satellite systems. Then, two algorithms for the detection of interference are provided. The first detection scheme is based on energy detector with signal cancellation exploiting the pilot symbols. The second detection scheme considers a two-stage detector, where first, the energy detector with signal cancellation in the pilot domain is performed, and if required, an energy detector with signal cancellation in the data domain is carried out in the second stage. Moreover, the analytical expressions for the probabilities of false alarm and detection are derived and numerical results through simulations are provided to verify the accuracy of the proposed analysis. Finally, this thesis goes one step further and the developed algorithms are evaluated experimentally using software defined radios, particularly universal software radio peripherals (USRPs), while it concludes discussing some open research topics. [less ▲]

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See detailDynamical hybrid modeling of human metabolism
Ben Guebila, Marouen UL

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 ▲]

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See detailLuxemburgische Intonation: System und Sprachkontakt
Manzoni, Judith Maria UL

Doctoral thesis (2018)

Intonation is usually one of the latest linguistic fields to be investigated in a language, which explains why no systematic approach of the tonal inventory can be found of Luxembourgish, itself a very ... [more ▼]

Intonation is usually one of the latest linguistic fields to be investigated in a language, which explains why no systematic approach of the tonal inventory can be found of Luxembourgish, itself a very young and little researched Germanic language. The main goal of this thesis is therefore to analyze the intonation of Luxembourgish in order to compile a tonal inventory by working on the characteristics of the different intonational patterns used by Luxembourgish native speakers. For this, a formal as well as a functional analysis is carried out, which is used to describe (within the autosegmental-metrical framework) the characteristics of the intonational system. This study establishes six different nuclear patterns, four of which are used in more than one conversational situation, meaning that these situations are not differentiated on the level of intonation. A thorough acoustic analysis depicts the different intonation patterns phonetically, which allows for the comparison of the same conversational situation in different speaking styles (scripted vs. unscripted speech). These findings form the basis for a comparison between the Luxembourgish intonation and the intonation of other languages, which leads to the questions whether the Luxembourgish intonation inventory differs from the ones of the two other official languages in Luxembourg, German and French. This also brings up the question about intonational transfer in the French or German speech of Luxembourgish native speakers. Results show that the German and French intonation systems differ quite strongly from the Luxembourgish system which leads to intonational interferences, even though these interferences are of a different nature in both languages. In brief, this study provides a systematic approach to Luxembourgish intonation and for the first time combines the tonal patterns with their function in discourse while also giving insights into intonational interferences produced by Luxembourgish native speakers in French and German. [less ▲]

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See detailModelling the Extensionally Driven Transitions of DNA
Taghavi, Amirhossein UL

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 ▲]

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See detailLe contrôle juridictionnel de conventionnalité et de constitutionnalité des lois au Grand-Duché de Luxembourg
Sauer, Carola UL

Doctoral thesis (2018)

The thesis analyses the judicial review of laws, more precisely their compatibility with "higher law" in the Grand Duchy of Luxembourg. Since the 19th century, general courts have authority to review laws ... [more ▼]

The thesis analyses the judicial review of laws, more precisely their compatibility with "higher law" in the Grand Duchy of Luxembourg. Since the 19th century, general courts have authority to review laws as to international law. In 1996/1997, the Constitutional Court was established and empowered to examine ordinary statute law as to their compatibility with the Constitution. As a result, the rule of law might be considered realized. However, the powers of this special court and the legal effects of its judgements are considerably limited. What is more, the analysis of constitutional jurisprudence reveals clear self-limiting tendancies of the constitutional judges themselves. Moreover, it is general wisdom that the Constitutional Court has no authority to review the compatibility of any law with international law. The latter competence is exclusively with the ordinary judge. This situation causes legal uncertainty, bearing the risk of contradictory jurisprudence of high courts. The judicial separation of constitutionality and conventionality review also lacks coherence with respect to the primacy of public international in the Grand-Duchy, and it ignores the existing overlapping of international law and Constitution. [less ▲]

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See detailDynamic Network Reconstruction in Systems Biology: Methods and Algorithms
Yue, Zuogong UL

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 ▲]

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See detailINVESTIGATION OF THE CU2(SN,GE)S3 TERNARY ALLOY FOR THIN FILM SOLAR CELLS
Robert, Erika UL

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 ▲]

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See detailThe institution of linguistic dissidence in the Balearic Islands: ideological dynamics of Catalan standardisation
Duane Bernedo, Lucas John UL

Doctoral thesis (2018)

This thesis describes ethnographically the recent institution of linguistic dissidence in the Balearic Islands, understood as the establishment of a belief in the archipelago’s socio-political field that ... [more ▼]

This thesis describes ethnographically the recent institution of linguistic dissidence in the Balearic Islands, understood as the establishment of a belief in the archipelago’s socio-political field that claims ‘Balearic’, and not the current Catalan, must share official status with Castilian as its authentic autochthonous language. Three associations of language activists created in 2013 are responsible for this development. This thesis analyses two years of social media activity of the three language activist associations, together with other materials. Findings show how activists engaged in a struggle for the legitimisation of an alternative standard that revolved around authenticity ideologies, while they simultaneously secured and advanced the anonymity value of Castilian. Social media was instrumental for these purposes, as it provided activists representational control to articulate discourses about language and to police language practices. This thesis also examines the implications that this development represented for Catalan standardisation. I interviewed 11 language planners working at different institutions in the Balearic Islands and two Catalan language advocates. The interviews provided accounts on the ways institutional actors police the standard variety. After finding a vertical distribution of standard practices among institutional actors, the analysis focuses on a local planner’s social media practices. In all, this thesis advances three arguments about the activists’ strategic adoption of the standard language regime, the existence of an identification need in the Balearic linguistic market, and the role of minoritisation on standardisation. [less ▲]

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See detailComputational Integrative Models for Cellular Conversion: Application to Cellular Reprogramming and Disease Modeling
Zickenrott, Sascha UL

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 ▲]

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See detailComputational Integrative Models for Cellular Conversion: Application to Cellular Reprogramming and Disease Modeling
Jung Geb. Zickenrott, Sascha UL

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 ▲]

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See detailActive Harmonics Compensation in Smart Grids
Kobou Ngani, Patrick UL

Doctoral thesis (2018)

The quality of electric power is a key factor for the electricity supply service. It defines how good the characteristics of the supplied power meet the standard ones. Among several other power quality ... [more ▼]

The quality of electric power is a key factor for the electricity supply service. It defines how good the characteristics of the supplied power meet the standard ones. Among several other power quality issues, the harmonics are of more and more concern over the last decades. This is essentially due to the widespread use of electronic components. This thesis focuses on the development of a voltage active power filter implementing a new selective harmonics compensation algorithm. The first design is described as following: band-pass filters decompose the measured voltage signal as a sum of different harmonics voltages; PLLs (frequency-tuned) transform of the oscillating signals into two orthogonal and rotating components (dq-transform). The dq-components of each harmonic are controlled to zero using standard PI-controllers and the compensating harmonics waves are generated via the inverse PLL. All the harmonics compensating waves are superimposed and added to the fundamental reference signal. This represents the final control signal of the inverter. Implemented in the MATLAB-SIMULINK simulation environment, this foreseen methodology depicted as major issue the control stability especially when the system frequency differs from the rated 50-Hertz frequency. This is the reason why a second design has been proposed. The major improvement is done on the harmonics detection stability by replacing the PLLs frames by the well-known internal frame of the fundamental voltage of the controlled inverter. After the convincing theoretical results from the simulations, the method is implemented and validated experimentally on a test rig in the lab. The two key features of the developed active power filter (APF) are: 1)Its ability to be used as a standalone power unit that compensates by itself the harmonics that could appear in the system while generating the fundamental voltage necessary to build up the micro-grid. 2)Its ability to serve as a full grid-tied power element that not only mitigates the voltages harmonics on the coupled grid but also supports the grid by controlling the exchanged active and reactive powers between the inverter and the grid. In addition to the developed harmonic mitigation technique, a new grid synchronization method has been proposed along with a new power control algorithm combined with a grid impedance estimator for grid-tied inverter. Further investigations and development are required for three-phase unbalance voltage systems as well as for single-phase voltage power system for low power grids. [less ▲]

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See detailScience learning in an early childhood classroom in Luxembourg: A journey from sociocultural and cultural historical theories to post-humanism
Haus Geb. Hilgers, Jana Maria UL

Doctoral thesis (2018)

In this dissertation, I map the journey I went on; from applying cultural-historical theory to the application of posthumanist perspectives on science learning and researching science learning in an early ... [more ▼]

In this dissertation, I map the journey I went on; from applying cultural-historical theory to the application of posthumanist perspectives on science learning and researching science learning in an early childhood classroom in Luxembourg. Within this work, I show the process of realizing that the theories I applied for a certain amount of time at the beginning of the Ph.D. revealed a gap to me concerning what I wanted to achieve in the field of researching science learning. I draw on posthumanist perspectives to elaborate broader views of the research process to show how each (human and non-human) participant contributes to the context of science education with young children in Luxembourg. I also I present findings that changed my perspective on research and data analysis with young children in the field of science education. In sharing my reflexive journey, I contribute to ongoing methodological and ethical discussions about the research process with – rather than on – young children, as well as working to increase awareness of the importance of the researcher's stance and positioning towards both human and non-human research participants in Luxembourg classrooms. In the chapters that follow, I show the trajectory of how I applied sociocultural and later posthumanist theory and ethnographic video analysis to data I collected in one Kindergarten science classroom in Luxembourg. Findings of this journey show how human and non-human beings work together, and provide impulses for researchers to situate themselves reflexively to consider why and how they are doing research and what they hope to gain from it. This is not to promote a narcissistic and self-indulgent view of the researcher, but to point out what might be missing from some research reports that claim to be participatory when in fact they reproduce the researcher's perspectives of the children's view and "sell" it as their own, instead of listening and including participants’ voices. In order to link this to posthumanist theory and agential realism (e.g., Barad, 2007), this thesis theorizes research processes in ways that not only take into account who is researching whom, but that draw attention to the surrounding entanglements that constitute research, and how the research itself changes and is changed by the participating human and non-human beings. The papers assembled below show how all participating (human and non-human) beings are entangled and together become through and for one another. [less ▲]

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See detailContributions to the asymptotic study of Hermite driven processes
Tran, Thi Thanh Diu UL

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 ▲]

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See detailIntegrating User- and System-Centric Perspectives into Collaborative Compound Document Authoring
Klein, Johannes UL

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 ▲]

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See detailAdaptive capacities of cancer cells in Glioblastoma
Dirkse, Anne Marie Elisabeth UL

Doctoral thesis (2018)

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See detailAnalysis of cancer related protein isoforms by mass spectrometry
Ancheva, Lina UL

Doctoral thesis (2018)

Detailed reference viewed: 74 (8 UL)
See detailOptimierung und Charakterisierung einer mittels Laserstrahl gefügten Verbindung zwischen Aluminium und Polyamid 6.6
Lamberti, Christian UL

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 ▲]

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See detailSustainable Building Transitions in Luxembourg and Freiburg: Local Meanings, Circumstances and Rationales
Preller Geb. Jung, Bérénice Cynthia UL

Doctoral thesis (2018)

Sustainable building has become a subject of high policy emulation to address sustainability challenges. Publications and interventions from international organisations concord in outlining the high share ... [more ▼]

Sustainable building has become a subject of high policy emulation to address sustainability challenges. Publications and interventions from international organisations concord in outlining the high share of greenhouse gas emissions produced by the building sector, while at the same time pointing towards the important leverage for sustainability interventions on the built environment. The realisation of sustainable building crosses serval functional domains: regulatory, economic, cultural, social, natural etc. It requires also to consider buildings in a comprehensive manner from their inception, construction, up to their use and eventual retrofit or demolition but also in relationship with their wider (urban) settings. And last but not least, it requires close interactions with a wide range of stakeholders with different interests and disciplinary perspectives. As a result, sustainable building transformations are a widely diversified agenda. Hence the primary interest, as well as objective of this work, has been to try to better grasp the causes and mechanisms that explain such large differentiation of sustainable building. Drawing on critical sustainable urban literature, I posit sustainable building as diversified because it is a situated and socially mediated object. Conceptually, the work engages with two approaches. First the literature on sustainable socio-technical transitions, in particular the Multi-Level Perspective. Its grounding in co-evolutionary and institutional thinking helps to comprehend the socio-material complexity of sustainable building across a broad range of dimensions and connections. In complementing, and following the adopted socially constructed stance, the work further looks at the discursive constructs used to argue in favour of the transformation towards sustainable building, as the performativity of discourse helps to explain why that change occurs. The operationalisation of the research inquires sustainable building transformations in two European urban areas, Luxembourg (LU) and Freiburg (D), that both focus on sustainable building transformations in their urban policy agenda. Using a mix of qualitative research methods (interviews, cooperative research workshops, and the discourse analysis of a text corpus), I look into detail at how sustainable building policies are played out and how their content varies in relation to the geographical context in which they are situated. Of particular interest to my research is to understand why the transitions towards sustainable building in Luxembourg and Freiburg is a certain way, following the ideologies and interpretations that underlay it. This focus allows to uncover similarities in both Luxembourg and Freiburg where sustainable building is dominantly addressed via technicalities, energy efficiency and green growth, thus tying onto the mainstreamed socio-economic paradigm, despite locally differentiated circumstances. [less ▲]

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See detailTransforming Time Series for Efficient and Accurate Classification
Li, Daoyuan UL

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 ▲]

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See detailCONSEQUENCES OF EARLY LIFE STRESS FOR PAIN PROCESSING AND COPING WITH STRESS IN LATER LIFE: BEHAVIOURAL AND BIOCHEMICAL STUDIES IN THE RAT
Genty, Julien UL

Doctoral thesis (2018)

Stress is commonly defined as the response to a non-specific situation presenting a psychological and/or physical challenge. In order to react in an appropriate manner to environmental threats the body ... [more ▼]

Stress is commonly defined as the response to a non-specific situation presenting a psychological and/or physical challenge. In order to react in an appropriate manner to environmental threats the body will trigger a wide range of defence mechanisms. However cases where challenges are sustained and the individual does not have the ability to cope with the stress are nowadays believed to be a main factor for the onset and exacerbation of a broad range of disorders. Among these are psychiatric disorders such as depression but also pain affections. Pain is described by the International Association for the study of Pain (IASP) as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. As for stress, this system aiming at preserving the body integrity can become defective and enhance pain sensitivity or foster the development of chronic pain. These two health problems categories each represent a considerable issue of public health. Indeed the World Health Organization (WHO) estimates that 27% of the European adult population had experienced at least one episode of mental disorder and the IASP reported that 19% of the pan-European population experienced chronic pain (Macfarlane, Pain 2016). Furthermore, chronic pain and stress-related disorders are greatly comorbid, having deleterious effects on the efficacy of treatments. Despite the raising awareness of clinical and pre-clinical research on their overlapping pathways, common mediators and interactions, the nature of the relationship between chronic pain conditions and stress-related disorders is not yet elucidated. The studies I undertook during my Ph.D. aimed to understand how chronic stress, with an emphasis on early-life stress, is linked to altered nociceptive transmission and to modified chronic pain vulnerability. Early life stress (ELS) was of particular interest as this period of life is subjected to an intense neuronal plasticity of notably stress and pain systems. Furthermore it is increasingly accepted that early life factors are linked to the susceptibility to develop chronic pain conditions in adulthood. As pain is a multidimensional system, I had to restrict my studies to one of the relay stations for the transmission of pain. In the context of chronic stress, most of the work was done on the brain circuits underlying the affective part of pain but little is known about the effect of chronic pain on spinal nociceptive processes. Since chronic stress is a broad phenomenon altering not only processing at the brain level, I focused my studies on spinal dorsal horn noxious transmission. The first stage of my work was to assess the impact of ELS on neuropathic pain, a type of chronic pain arising from nerve lesions. In a second step, I sought to determine if the results obtained in this first study were specific to the type of pain (neuropathic) or also were valid for another type of chronic pain, e.g. chronic inflammatory pain. The third study aimed to determine if ELS would predispose to enhanced vulnerability to stress exposure later in life and to concomitant alterations of chronic pain. To finish, during the last year of my Ph.D. I investigated the possible mechanisms underlying the behavioural results using pharmacological manipulations and initiated a separate project devoted to in vivo electrophysiological characterization of the response behaviour of nociceptive spinal dorsal horn neurons. In the following introduction, I will give an overview of the stress systems, focusing on the hypothalamo-pituitary adrenal (HPA) axis and early life stress. Then I will outline the different part of the pain system and concepts of central sensitization involved in chronic pain. [less ▲]

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See detailEmployment Dynamics, Firm Performance and Innovation Persistence in the Context of Differentiated Innovation Types: Evidence from Luxembourg
Zhen, Ni UL

Doctoral thesis (2018)

This doctoral dissertation examines the essential topics of employment dynamics, firm performance and innovation persistence comprehensively. In particular, this doctoral dissertation provides an ... [more ▼]

This doctoral dissertation examines the essential topics of employment dynamics, firm performance and innovation persistence comprehensively. In particular, this doctoral dissertation provides an assessment of the differentiated role of innovation strategies in employment, firm performance and innovation persistence. Chapter 2 studies the dynamic relationship between technological innovation and employment using Luxembourgish firm level data pertaining to the non-financial corporate sector during the period 2003-2012. A simple theoretical model that distinguishes the employment effect of product innovation from that of process innovation is developed. The model is then estimated by two-step generalised method of moments using an unbalanced panel data stemming from the annual structural business survey merged with the biennial innovation survey. The results show that the semi-elasticity of employment with respect to product innovation lies between 0.2% and 0.5%. The differential in the employment effects between radical and incremental innovation is estimated to be 50%. Similarly, the employment level differential between product innovators and firms with unchanged products lies between 4% and 11%. Unlike product innovation, however, process innovation does not have any significant effect on the firm level of employment. Chapter 3 investigates the two-way relationship between technological innovation and firm performance at the firm level. In the framework of evolutionary economics, innovation is regarded as a highly cumulative process which exhibits positive feedback. This chapter aims at capturing the interdependent relationship and possible bidirectional causality between innovation and firm performance. Superior firm performance facilitates the emergence of innovations, innovation contributes to firm performance by gaining successful and sustainable competitive advantage, which forms a virtuous circle. A fully recursive simultaneous model is established where product and process innovation are explicitly distinguished. The system of simultaneous equations with mixed structure is estimated by full information maximum likelihood methods. The longitudinal firm-level data is applied over the 2003-2012 period by merging five waves of the Luxembourgish innovation survey with structural business surveys. This chapter discovers that enhanced firm performance facilitates process innovation and process innovation improves firm performance, which forms a self-reinforcing virtuous circle. An opposite pattern is identified for the product innovation on the ground of cannibalization effect and inherent market risks associated with new products. Chapter 4 explores innovation persistence at the firm level by means of dynamic nonlinear random effects models based on the estimator proposed by Albarrán et al. [2015]. It aims at capturing the true state dependence which indicates the causal relationship between innovation in one period and decision to innovate in the subsequent period. The Albarrán et al. [2015] method accounts for unobserved individual effects that are correlated with the initial conditions as well as the unbalanced structure of panel. Using five questionnaire waves of Luxembourgish Community Innovation Surveys (CIS) for the years 2002-2012, this study provides new insights on the differentiated patterns of persistence among product and process innovation. Results highlight the relevance of innovation persistence for all types of innovation, particularly the highest level of persistence is found for product innovation. In addition, the state dependence of product innovation is mainly associated with sunk costs relevant to R&D expenditures, whereas the state dependence of process innovation can be attributed to other factors such as dynamic increasing returns and learning effect. The further differentiation of product innovator category reveals that the state dependence of incremental product innovation can be mainly attributed to sunk costs relevant to R&D expenditures. In contrast, the joint significance of average R&D intensity, intramural R&D share as well as the past realization of radical product innovation suggests the role of other factors such as dynamic increasing returns and learning effect in fostering state dependence for radical innovations. [less ▲]

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See detailHybrid Histories: Technologies of Memory and the Cultural Dynamics of Home Movies, 1895-2005
van der Heijden, Tim UL

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 ▲]

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See detailTHE PARKINSON’S DISEASE ASSOCIATED PINK1-PARKIN PATHWAY IN PATHOLOGY AND DEVELOPMENT
Jarazo, Javier UL

Doctoral thesis (2018)

Parkinson’s disease (PD) has an aetiology not completely understood. One of the hypothesis in the field is that many neurodegenerative diseases are influenced by developmental disorders. The underlying ... [more ▼]

Parkinson’s disease (PD) has an aetiology not completely understood. One of the hypothesis in the field is that many neurodegenerative diseases are influenced by developmental disorders. The underlying concept is that already during brain development some processes are deregulated producing a higher degree of susceptibility for neurodegeneration during aging. Two hereditary early onset forms of PD are caused by recessive mutations in PTEN-induced putative kinase 1 (PINK1) and Parkin genes that regulate mitochondrial function and morphology, quarantining damaged mitochondria before their degradation as well as triggering the process of mitophagy. Our hypothesis is that alterations of the Pink1-Parkin pathway have an impact in mitochondrial physiology tempering the differentiation ability of neuroepithelial stem cells into dopaminergic neurons. For evaluating this hypothesis we reprogramed patients’ fibroblasts carrying PINK1 mutations, as well as from healthy individuals, to human induced pluripotent stem cells. We developed a streamlined technique of gene editing (FACE) by using the CRISPR/Cas9 system combined with a composite of fluorescent proteins in the donor template for biallelic gene targeting. Isogenic controls were generated using this technique that allowed us to analyze the contribution of corrected patients’ mutations in the cellular defects observed. Human iPSCs were differentiated into a neuroepithelial stem cell state (NESC) from where the cells were further differentiated into neurons. We established different algorithms for pattern recognition and applied them for image analysis of different features such as mitochondrial morphology, proliferation capacity, apoptosis and differentiation. Patient’s derived cells presented an impaired differentiation efficiency into dopaminergic neurons as well as an imbalanced cell renewal that can be linked to the mitochondrial differences. Using 3D cultures, such as microfluidics and organoids, we were able to recapitulate this differentiation impairment in a system that mimics better the context of an in vivo environment. We evaluated the energetic capabilities of the NESCs and the firing activity of differentiated neurons, which also showed a dysregulation in patient cells. We introduced a new system for large-scale analysis of the autophagy and mitophagy pathways by the combination of stably integrated Rosella constructs in different patients’ lines and an image analysis script for classification of the different subcellular structures involved in these pathways activities. This revealed that the basal activity as well as the response against stressors of these pathways are altered in cells derived from patients having different mutations causative of PD. We performed a screen of repurposed drugs as well as of novel compounds to evaluate their impact in this altered developmental transition identifying a potential candidate to be further analysed in an in vivo context. [less ▲]

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See detailLa mémoire de la "Résistance" au prisme d'une histoire croisée des associations d'anciens résistants du Luxembourg, de l'Alsace, de la Moselle et de la Belgique de l'Est (1944-2017)
Hoffmann, Elisabeth Jeanne Suzette UL

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 ▲]

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See detailGlobal flows, local conflicts and the challenge of urban governance: Managing the urban-airport interface in London and the South East of England
Mcdonough, Evan UL

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 ▲]

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See detailL’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
Chen, Yan-Zhen UL

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 ▲]

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See detailInvestigation of crack development in a fairfaced replacement screed based on fiber-reinforced concrete
Weiler, Michael UL

Doctoral thesis (2017)

In the present study, a design concept for unreinforced, cement-bound concrete floors is presented. The work concentrates on cracking caused by shrinkage of the concrete used. The central components of ... [more ▼]

In the present study, a design concept for unreinforced, cement-bound concrete floors is presented. The work concentrates on cracking caused by shrinkage of the concrete used. The central components of the work are a numerical model (Finite element model) which, taking into account all time-dependent material parameters and with the aid of a simple calculation approach, is able to predict crack paths on sharp edges. In addition, with the help of the model, it is possible to simulate the curling of the corners of a float mounted concrete floor. For this purpose, the required material parameters (static elastic modulus, uniaxial tensile strength) were investigated under laboratory conditions and compared with prognosis values of an available prognosis software and with the analytical prognosis approach of DIN EN 1992-1-1: 2011-01. In a first step, the crack formation and crack development on a small, H-shaped concrete sample were examined and a crack path was calculated using a first numerical approach. This first numerical approach was subsequently validated on large-scale surfaces. On the basis of the large-scale experiments, the numerical model was further developed with regard to curling of concrete floors. All experiments were calculated with the approach of element failure method (EFM) using the commercial finite element software ANSYS. The design concept is completed by a parameter study. By means of this parameter study, it is possible to identify the parameters which decisively influences cracking. The present work thus makes an important contribution to the numerical modelling of damage in unreinforced concrete structures. [less ▲]

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See detailComputational Methods for Analysing Long-run Dynamics of Large Biological Networks
Yuan, Qixia UL

Doctoral thesis (2017)

Systems biology combines developments in the fields of computer science, mathematics, engineering, statistics, and biology to study biological networks from a holistic point of view in order to provide a ... [more ▼]

Systems biology combines developments in the fields of computer science, mathematics, engineering, statistics, and biology to study biological networks from a holistic point of view in order to provide a comprehensive, system level understanding of the underlying system. Recent developments in biological laboratory techniques have led to a slew of increasingly complex and large biological networks. This poses a challenge for formal representation and analysis of those large networks efficiently. To understand biology at the system level, the focus should be on understanding the structure and dynamics of cellular and organismal function, rather than on the characteristics of isolated parts of a cell or organism. One of the most important focuses is the long-run dynamics of a network, as they often correspond to the functional states, such as proliferation, apoptosis, and differentiation. In this thesis, we concentrate on how to analyse long-run dynamics of biological networks. In particular, we examine situations where the networks in question are very large. In the literature, quite a few mathematical models, such as ordinary differential equations, Petri nets, and Boolean networks (BNs), have been proposed for representing biological networks. These models provide different levels of details and have different advantages. Since we are interested in large networks and their long-run dynamics, we need to use ``coarse-grained" level models that focus on the system behaviour of the network while neglecting molecular details. In particular, we use probabilistic Boolean networks (PBNs) to describe biological networks. By focusing on the wiring of a network, a PBN not only simplifies the representation of the network, but it also captures the important characteristics of the dynamics of the network. Within the framework of PBNs, the analysis of long-run dynamics of a biological network can be performed with regard to two aspects. The first aspect lies in the identification of the so-called attractors of the constituent BNs of a PBN. An attractor of a BN is a set of states, inside which the network will stay forever once it goes in; thus capturing the network's long-term behaviour. A few methods have been discussed for computing attractors in the literature. For example, the binary decision diagram based approach and the satisfiability based approach. These methods, however, are either restricted by the network size, or can only be applied to synchronous networks where all the elements in the network are updated synchronously at each time step. To overcome these issues, we propose a decomposition-based method. The method works in three steps: we decompose a large network into small sub-networks, detect attractors in sub-networks, and recover the attractors of the original network using the attractors of the sub-networks. Our methods can be applied to both asynchronous networks, where only one element in the network is updated at each time step, and synchronous networks. Experimental results show that our proposed method is significantly faster than the state-of-the-art methods. The second aspect lies in the computation of steady-state probabilities of a PBN with perturbations. The perturbations of a PBN allow for a random, with a small probability, alteration of the current state of the PBN. In a PBN with perturbations, the long-run dynamics is characterised by the steady-state probability of being in a certain set of states. Various methods for computing steady-state probabilities can be applied to small networks. However, for large networks, the simulation-based statistical methods remain the only viable choice. A crucial issue for such methods is the efficiency. The long-run analysis of large networks requires the computation of steady-state probabilities to be finished as soon as possible. To reach this goal, we apply various techniques. First, we revive an efficient Monte Carlo simulation method called the two-state Markov chain approach for making the computations. We identify an initialisation problem, which may lead to biased results of this method, and propose several heuristics to avoid this problem. Secondly, we develop several techniques to speed up the simulation of PBNs. These techniques include the multiple central processing unit based parallelisation, the multiple graphic processing unit based parallelisation, and the structure-based parallelisation. Experimental results show that these techniques can lead to speedups from ten times to several hundreds of times. Lastly, we have implemented the above mentioned techniques for identification of attractors and the computation of steady-state probabilities in a tool called ASSA-PBN. A case-study for analysing an apoptosis network with this tool is provided. [less ▲]

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See detailEfficient and Secure Implementations of Lightweight Symmetric Cryptographic Primitives
Dinu, Dumitru Daniel UL

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 ▲]

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See detailProposal of a Failure Criterion of Adhesively Bonded Connections with Silicone
Staudt, Yves Nico Louis UL

Doctoral thesis (2017)

In the field of façade engineering, structural silicone sealants have been used in adhesively bonded connections since the 1960s. The low strength and stiffness of silicone rubber compared to other types ... [more ▼]

In the field of façade engineering, structural silicone sealants have been used in adhesively bonded connections since the 1960s. The low strength and stiffness of silicone rubber compared to other types of adhesives are compensated by the excellent adhesion properties and the good resistance against ageing and environmental influences, like UV radiation. Silicone sealants show a pronounced nonlinear material behaviour. The applicable design concepts in civil engineering propose simplified design equations, which are based on the assumption of a linear material law. Due to the current state of knowledge and to compensate the simplified model assumptions in the design concept, high reduction factors on the material strength and many restrictions on applications are defined. In order to overcome these drawbacks, the stress state within the sealant is increasingly described using the Finite Element Method. Considering the results of these analysis, the assessment of both the complex stress states with a suitable failure criterion and the influence of stress singularities on the failure behaviour constitute inevitable questions. The present work addresses these two questions. In the first step, the strain magnitude has been determined as a suitable failure criterion for the defect-free bulk material of the considered Dow Corning® 993 structural silicone sealant, subjected to a quasi-static loading. The failure criterion has been calibrated using the results of uniaxial tension as well as circular shear tests and validated with the results of compression tests. The strain magnitude is a strain-based failure criterion, which can be seen as a measure for the distortion of the molecular chains. In a second step, the stress distribution of the single-lap shear joint has been investigated in detail. For the assessment of the singular stresses and strains at the edge area of the interface between the adhesive and the substrate, referred to as two-material wedge, the so-called coupled stress and energy criterion, a concept of Finite Fracture Mechanics, was extended to nonlinear elastic material behaviour. Based on results of conduced simple shear tests on small bonded connections with varying adhesive thicknesses and overlap lengths, the coupled criterion was used to predict the crack initiation loads and a good agreement with the experimentally recorded values was obtained. Knowing the strength and the critical energy release rate of the material, the crack initiation load and the corresponding crack length are determined in the coupled criterion by solving an optimisation problem based on a Finite Element Analysis. The stress partial criterion has been modified to consider the strain magnitude as a failure criterion. In order to analyse the energy partial criterion, the critical energy release rate of Dow Corning® 993 structural silicone sealant has been determined in Double Cantilever Beam tests using the evaluation method based on the J-integral approach. Furthermore, concepts of the Theory of Critical Distances were used to determine the failure loads of the small scale tests. Unlike as for the notched circular shear tests and the tension tests on small scale bonded connections, good predictions were found in the Finite Element Analysis for the simple shear specimens, when a constant element size and formulation at the vicinity of the two-material wedge were used. Similar results were obtained with the point method and the control volume approach. These findings indicate that the characteristic material length for silicone rubber is not constant. [less ▲]

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See detailBig Data Architectures For Robust Systems
Falk, Eric UL

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 ▲]

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See detailCONTRIBUTIONS TO THE STATISTICS OF RANDOM PROCESSES USING MALLIAVIN CALCULUS
Krein, Christian Yves Léopold UL

Doctoral thesis (2017)

In this dissertation we present several applications of Malliavin calculus, both to the statistical analysis of continuous time stochastic processes and to limit theorems for non-linear functionals of ... [more ▼]

In this dissertation we present several applications of Malliavin calculus, both to the statistical analysis of continuous time stochastic processes and to limit theorems for non-linear functionals of Gaussian Fields. Malliavin calculus extends techniques of classical calculus of variations from deterministic functions to random variables. In Malliavin calculus, the so called Malliavin derivative and its adjoint, the divergence operator, are combined with the theory of Hilbert spaces. Just as classical calculus, this theory has proved to be a powerful tool and its applications vary from the existence of densities, to the construction of estimators and the study of weak convergence of sequences of random variables and random vectors, with a special focus on normal approximations. The first part of the present document is essentially a generalization of a result of Privault and Réveillac (2008), which extends a seminal paper of Stein (1956). Stein has shown that, under certain conditions, there are biased estimators which perform better than the standard estimator for the mean of a multivariate normal vector. It has been shown by Privault and Réveillac that a similar statement holds for Gaussian processes and we shall present a generalization of their work to continuous time models, where the noise is either a chaotic Brownian martingale or a non-martingale noise living in the second Wiener chaos. This first part of the work corresponds to the paper "Drift estimation with non-gaussian noise using Malliavin Calculus" (2015) which has been published by the Electronic Journal of Statistics. In the second part of the work we give necessary and sufficient criteria for the convergence of sequences of random variables, living in a fixed sum of Wiener chaoses, to a limit which lives in the sum of the first two Wiener chaoses. Our results extend the important findings of Nualart and Peccati (2005), the so-called Fourth Moment Theorem, and a recent finding of Azmoodeh, Peccati and Poly (2014). Our criteria make use of the so-called Gamma-operators which are derived from scalar products of Malliavin derivatives and the infinitesimal generator of the Ornstein-Uhlenbeck semi-group, see for instance Azmoodeh, Peccati and Poly (2014). This part corresponds to the paper "Weak convergence on Wiener space: targeting the first two chaoses" (2017) which has been submitted to the Latin American Journal of Probability and Mathematical Statistics (ALEA). In the last part of the present work we consider a sequence living in a fixed Wiener chaos and converging in law to a normal variable. A second sequence is supposed to converge in law to a target variable which is the sum of a linear combination of independent chi-square distributed random variables and an independent normal variable. We derive conditions under which the sequence of random vectors, formed by both sequences of random variables, converges in law. We use again Gamma-operators and cumulants to derive necessary and sufficient conditions which can be seen as generalization of results of Peccati and Tudor (2005) for Gaussian limits in the case of sequences of random vectors which converge componentwise. We apply methods developed by Nourdin and Peccati (2009) to examine the rate of convergence of a sequence of double Wiener integrals towards a normal variable. [less ▲]

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See detailLearning Finite Automata via Flexible State-Merging and Applications in Networking
Hammerschmidt, Christian UL

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 ▲]

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See detailAPPROACHES FOR IDENTIFICATION OF TRANSCRIPTIONAL AND POST-TRANSCRIPTIONAL REGULATORS OF MESENCHYMAL STEM CELL DIFFERENTIATION USING TIME-SERIES EPIGENOMIC DATA
Gerard, Déborah UL

Doctoral thesis (2017)

Gene regulatory networks (GRNs) control cellular differentiation and development and recapitulate the physical interactions between transcription factors (TFs) and their influence on their target genes ... [more ▼]

Gene regulatory networks (GRNs) control cellular differentiation and development and recapitulate the physical interactions between transcription factors (TFs) and their influence on their target genes that ultimately results into a defined cell phenotype. In addition, cellular differentiation represents the path a cell undergoes through multiple stages before reaching a terminally differentiated state and is by nature dynamic. Moreover, epigenetic regulation as well as post-transcriptional control of gene expression are critical for faithful cellular phenotype. Cellular differentiation of progenitor cells into their daughter cells provide a dynamic controllable system to study the epigenetic mechanisms as well as the transcriptional output that take place towards cellular specifications, and the TFs and non-coding RNAs that dictate their differentiation. Here, we have generated time-series transcriptomic and epigenomic data during the differentiation of bone marrow stromal cells towards adipocytes and osteoblasts and characterized a novel approach called EPIC-DREM to construct dynamic GRNs of adipocytes and osteoblasts. In order to focus on shared transcriptional regulators of early commitment of bone marrow stromal cells towards adipocytes and osteoblasts, we have concentrated our analysis on dynamic super-enhancers to prioritize the identified TFs and discovered aryl hydrocarbon receptor (AHR) as a transcriptional regulator of the multipotent state. In addition, the generated of time-series epigenomic data were used as input for linear regression analysis that allowed to predict genes that are dynamically controlled by post-transcriptional regulators such as microRNAs (miRs). Indeed, genes that differ from their predicted expression level as assessed by the residuals of the linear regression model can be informative about their mRNA stability. In order to decipher genes that are under dynamic post-transcriptional control, the standard deviation of gene’s residuals was taken as a dynamic measure of changes in mRNA stability and clustering analysis coupled to microRNA motifs enrichment analysis allowed to identify post-transcriptionally co-regulated mRNAs. Based on the linear regressions analysis, miR-204 was identified as a potential regulator of adipogenesis. Integration of these types of data can contribute to the understanding of transcriptional and post-transcriptional control of cell differentiation and the here established approaches for key regulators identification can be widely applied to study other cell states transitions. [less ▲]

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See detailDeformation Based Curved Shape Representation
Demisse, Girum UL

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 ▲]

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See detailWohnmobilität in der Großregion – eine interurbane Diskursanalyse mit Fokus auf den Städten Arlon, Thionville und Trier.
Christmann, Nathalie UL

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 ▲]

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See detailArt as an Investment
Nasser Eddine, Ali UL

Doctoral thesis (2017)

During the 1970s and 1980s, the art markets gave abnormal returns. Individuals started speculating on art prices, and institutional investors soon entered the scene. Economists then began evaluating this ... [more ▼]

During the 1970s and 1980s, the art markets gave abnormal returns. Individuals started speculating on art prices, and institutional investors soon entered the scene. Economists then began evaluating this new alternative asset class. In this thesis, we review global art markets, analyze the methodologies employed for studying art as an investment, and seek answers to some fundamental questions. To build solid conclusions, we developed the largest up-to-date dataset of repeat sales of art objects. Our main additional contributions to the literature can be summarized as follows. First, we review and explain the growth in international art markets. Second, we show that it is unreasonable to make a comparison between the two main methodologies used for studying the investment perspective of art: the repeat-sales and hedonic regression frameworks. The returns estimated using the hedonic approach depend greatly on the specifications of the model. Thus, we find that of the two, the repeat-sales models are the most robust. Third, we study the returns on art after accounting for transaction costs. Importantly, we show that taking this fair view renders impractical the widely used art-investment measurement methodologies. Fourth, we revisit the “masterpiece effect”, and find strong evidence supporting its existence. Fifth, we investigate the potential of art investment. We find that the inclusion of art in an optimal portfolio depends significantly on the abnormal returns seen in the 1980s. Omitting these years leads to its exclusion. However, art may add a diversification benefit to an investment portfolio due to its low-to-negative correlation with other asset classes. Sixth, we analyze the optimal holding period of art and find that, in general, the returns increase with the length of the holding period. Nevertheless, we observe significant returns, accompanied with high levels of volatility, for trades made over very short time horizons. We notice that this “flipping” practice has been increasing in recent decades. Finally, we consider the effect some special cases have on art investment returns. We find that artworks that trade frequently tend not to outperform the market. Moreover, the nature of an artwork’s ownership history doesn’t alter returns. We also examine the returns on artworks selected by experts, and find that, surprisingly, they underperform. [less ▲]

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See detailA Model-Based Framework for Legal Policy Simulation and Compliance Checking
Soltana, Ghanem UL

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 ▲]

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See detailLa compétence d'incrimination de l'Union européenne. Recherche sur le pouvoir pénal européen
Simon, Perrine UL

Doctoral thesis (2017)

The allocation by the Lisbon Treaty of a genuine criminalisation competence to the Union – article 83 TFEU – prompts the analysis of the existence and the exercice of European criminal law power. It ... [more ▼]

The allocation by the Lisbon Treaty of a genuine criminalisation competence to the Union – article 83 TFEU – prompts the analysis of the existence and the exercice of European criminal law power. It raises the question of the promotion, through criminalisation choices, of essential values to the community. Analysing the criminal law power is interconnected to the question about the nature of the European project as a whole, true existential space of society (ethos) or simple functional space comprised of objectives (telos). Despite the aspiration to clarify the delimitation of European penal power within the new treaty, its ambit remains unclear. An implicit criminalisation competence – an implied criminal law power – could still exist, allowing to overcome the minimum harmonisation provided for by article 83 TFEU. To admit such an implied power would mean revive competence creep. The exercice of the criminalisation competence is progressively framed, beyond the classical principles of subsidiarity and proportionality, by the criminal law principles of ultima ratio as well as the principles of legality and proportionality of criminal offences and penalties expressed in the Charter of fundamental rights. However, these principles have not been taken into account according to the actions of the legislator who appear to follow a securitarian trend. It is to the Court, through an in-depth proportionality check, to determine if the Charter can become the marker of criminal law policy characterised by its moderation and liberalism, and henceforth contribute to a European criminal law identity. [less ▲]

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See detailOn the Use of Alloy in Engineering Domain Specific Modeling Languages
Gammaitoni, Loïc UL

Doctoral thesis (2017)

Domain Specific Modeling Languages (DSMLs) tend to play a central role in modern design processes as they enable the effective involvement of domain experts by focusing on a particular problem domain ... [more ▼]

Domain Specific Modeling Languages (DSMLs) tend to play a central role in modern design processes as they enable the effective involvement of domain experts by focusing on a particular problem domain while abstracting away technical details. In this thesis, we investigate the specification of DSMLs with a particular focus on domain expert driven validation. Mainly, we are interested in developing Alloy-based approaches, allowing the definition of specifications from which instances can be generated and given to the domain experts for the sake of validation. The work we present in this thesis can be divided into three parts: The first part concerns the definition and execution of model transformations defined in Alloy. While Alloy analysis can be used as an execution engine for model transformations, the analysis process is time consuming. Model transformations playing a central role in DSML definitions, the development of a new model transformation language, named F-Alloy, retaining the benefits of Alloy with the added property of being efficiently computable was necessary. The second part focuses on validation. In that domain, our first contribution is a novel approach to the validation of model transformations called Visualization-Based Validation (VBV). VBV relies on the review by domain experts of intuitive depictions of model transformation traces to validate model transformation specifications. The whole process is made efficient by the usage of hybrid analysis, a combination of Alloy analysis and F-Alloy interpretation, allowing to reduce the time needed to analyze model transformations to the time needed to analyze its source. Our second contribution in the validation area is the definition of an Alloy-based approach to the specification and validation of DSMLs and of a design process defining how DSMLs can be validated using Alloy analysis at each iteration of the process. More precisely, we present how the abstract syntax, concrete syntax and operational semantics of a DSML can be defined using Alloy and F-Alloy, and show that the validation of a DSML' s abstract syntax and semantics benefits from the application of its concrete syntax. The third and last part aims at bringing those contributions to the practical world. To achieve this we developed a tool named Lightning implementing the aforementioned contributions. This tool, which belongs to the category of language workbenches, has been successfully used in an inter-disciplinary collaboration to define the Robot Perception System Language (RPSL). Based on this definition of RPSL, a framework has been developed to allow the execution of so called design space explorations. This framework represents a successful application of our approach to the real world problem of having RPSL specifications validated by experts in robotics. [less ▲]

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See detailEnhancing Mobility Applications Through Bluetooth Communications
Bronzi, Walter UL

Doctoral thesis (2017)

In the world of short and medium-range wireless technologies, Bluetooth has recently come to the forefront of innovation. Within the next five years its market presence, especially in its Low Energy ... [more ▼]

In the world of short and medium-range wireless technologies, Bluetooth has recently come to the forefront of innovation. Within the next five years its market presence, especially in its Low Energy variation, is expected to nearly double across all market segments. The technology is quickly and steadily gaining importance for a wide range of applications with a specific focus on Internet of Things (IoT) devices. The growing availability and variety of such devices constitute an untapped potential that we plan on exploiting. Our focus in this thesis is to understand Bluetooth’s capabilities and explore its potential in mobile contexts. One specific field where this technology remains unexplored is Vehicular Ad Hoc Networks (VANETs). Because of the need to implement and moderate vehicular communications, the topic of Intelligent Transportation Systems (ITSs) is now trending more than ever. In this thesis we propose two ways we can benefit from Bluetooth in a mobile environment. Firstly, we consider the technology as a communication medium to investigate how di↵erent mobilities a↵ect the link performance between two devices. To do this, we define a set of communication experiments, in our case between two vehicles, to analyse how Bluetooth Low Energy (BLE) is a↵ected by varying speed, distance and traffic conditions. We find that the maximum communication range between two devices can go beyond 100m and that a robust connection, capable of handling sudden signal losses or interference, can be achieved up to a distance of 50m. The experiments were conducted using a proof-of-concept mobile application for o↵-the-shelf smartphones that can be used to transmit data over multiple hops in various Vehicle-to-Everything (V2X) scenarios. Secondly, we consider Bluetooth discovery capabilities as an information medium by using a connectionless approach to analyse di↵erent mobility frameworks. As there is an increasing need for vehicles and objects to become aware of their context, we implement Bluetooth as a sensing system to provide contextual information about its surroundings. Our challenge is to find out to what extent we can exploit the Bluetooth discovery and beaconing scheme for this purpose. We collect and analyse a dataset of Bluetooth Classic and BLE discoveries and evaluate their respective characteristics and ability to provide context-aware information from a vehicular perspective. By examining data recorded about encountered devices, such as quantity, quality of signal and device class information, we infer distinctive Bluetooth behaviours related to context and application. For this purpose, we propose a set a features to train a classification model to recognize di↵erent driving environments (i.e. road classes). Investigating the performance of our classifier, we were able to predict up to three classes (highway, city, extra-urban) by using only Bluetooth discovery data and no geographical information. This outcome gives promising results targeted at low energy and privacy-friendly applications and can open up a wide range of research directions. In conclusion, in this thesis we present two ways of applying Bluetooth to mobile contexts for deploying novel human mobility applications. [less ▲]

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See detailManaging the City-Region Like a Startup: Entrepreneurialism and Shifting Local Economic Governance in Developing Countries
Fegue, Jean Cyril UL

Doctoral thesis (2017)

The emerging experience of cities in the Global South regarding the complexity of their response to territorial competition's pressures requires the rethinking of the very concept of urban competitiveness ... [more ▼]

The emerging experience of cities in the Global South regarding the complexity of their response to territorial competition's pressures requires the rethinking of the very concept of urban competitiveness. This study proposes the distributionally-sensitive modeling of urban competitiveness (DS-MUC) in a perspective that is driven by the norm of Equity. The DS-MUC is posited as a critical theory to neoliberalism and as a contribution to the social sustainability and to the normative investigation of post-capitalist urban transformations in the Global South.The application of the DS-MUC in the investigation of Da Nang in Vietnam and Cebu City in the Philippines reveals that an interactive, relational and network-based entrepreneurial governance's capacity has a much greater proclivity to deliver Equity and therefore to achieve a 'high-quality competitiveness' than a city's organizing capacity embedded in illiberal, state-paternalistic and public-sector monopolistic arrangements. [less ▲]

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See detailCorporations and Human Rights: Searching for International Norms for Corporate Conduct in Domestic Case Law
Baglayan Ceyhan, Basak UL

Doctoral thesis (2017)

Recent years have seen much debate concerning the interplay between human rights and corporations. Part of that debate has focused on corporate violations of human rights norms and possible legal ... [more ▼]

Recent years have seen much debate concerning the interplay between human rights and corporations. Part of that debate has focused on corporate violations of human rights norms and possible legal accountability mechanisms for such breaches. The present research is concerned with one such accountability mechanism, namely litigation before domestic courts seeking to enforce corporations’ international obligations and the complaints before the OECD National Contact Points (‘NCPs’). The thesis analyses how domestic courts and the OECD NCPs have conceptualised and implemented corporations’ human rights obligations. It is premised on the assumption that, through their application of international norms in their particular national context, these institutions act to crystallize and clarify the ambit of such norms. [less ▲]

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See detailReiten van der stede wegen. Dienstliche Mobilität und städtische Kommunikation im Spiegel der Rechnungsbücher der Stadt Luxemburg (1388-1500) mit besonderer Betonung des Reitverkehrs
Meiers, Fabienne UL

Doctoral thesis (2017)

The aim of the doctoral thesis was to give an answer to the question of how important equestrian traffic was for official communication in and out of urban areas, as well as to identify mobility ... [more ▼]

The aim of the doctoral thesis was to give an answer to the question of how important equestrian traffic was for official communication in and out of urban areas, as well as to identify mobility behaviours of municipal administrative staff acting on behalf of the city. In order to conduct the following study the account books of the city of Luxembourg were used as source base; they encompass the period between 1388 and 1500. [less ▲]

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See detailModel-Based Specification, Deployment and Adaptation of Robot Perception Systems
Hochgeschwender, Nico UL

Doctoral thesis (2017)

As robots are becoming ubiquitous and more capable, the need for introducing solid robot software development methods is pressing to increase robots' task spectrum. This thesis is concerned with improving ... [more ▼]

As robots are becoming ubiquitous and more capable, the need for introducing solid robot software development methods is pressing to increase robots' task spectrum. This thesis is concerned with improving software engineering of robot perception systems. The presented research employs a model-based approach to provide the means to represent knowledge about robotics software. The thesis is divided into three parts, namely research on the specification, deployment and adaptation of robot perception systems. The first part contributes the design and development of two domain-specific languages, namely RPSL and DepSL. Those languages provide suitable notations and abstractions to enable domain experts to express, compose and explore functional, architectural and deployment design decisions of robot perception systems. The resulting models are interpretable, thus they can be used not only to communicate design decisions to stakeholders, but also to verify them in an early development stage. The second part contributes means for deploying perception systems on real robot systems even in the presence of varying resource conditions. To this end, functional, architectural and deployment models are composed in a graph-structure. Such a graph enables not only humans, but also robots to derive implicitly defined information about their software both at design time and run time. The second part also contributes a reference architecture for deploying robot perception systems. The architecture provides a template solution for integrating not only the models required for deployment, but also all the other means required to carry out deployment. The third part utilizes both RPSL, DepSL and the reference architecture to specify, implement and evaluate three different robot perception systems. Those are capable to satisfy changing requirements induced, for example, by the robot's tasks or environment. This is achieved by proposing algorithms which derive adaptation actions based on models and varying requirements. [less ▲]

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See detailContextual Integrity and Tie Strength in Online Social Networks: Social Theory, User Study, Ontology, and Validation
Ahmed, Javed UL

Doctoral thesis (2017)

Online Social Networks (OSNs) have become an important part of daily digital interactions for more than half billion users around the world. Unconstrained by physical spaces, OSNs offer to social web ... [more ▼]

Online Social Networks (OSNs) have become an important part of daily digital interactions for more than half billion users around the world. Unconstrained by physical spaces, OSNs offer to social web users new means to communicate, interact, and socialize. Online social networks exhibit many of the characteristics of human societies in terms of forming relationships and sharing personal information. However, current OSNs mainly assume binary, static, and symmetric relationship of equal value between the connected users. In human societies, social relationships are of varying tie strength, dynamic, and asymmetric in nature. The lack of an effective mechanism to represent diversity in social relationships leads to undesirable consequences of users personal information leakage to the unwanted audience and raises privacy concerns. The issue of privacy has received significant attention in both the research literature and the mainstream media. In this dissertation, we conduct a user study to analyze users' attitude towards personal information disclosure in online social networks. The study gives insight into user's information sharing behavior and interaction patterns in online social networks. The findings reveal that personal information disclosure depends on the quality of relationship among the users and it can be easily inferred from user interaction pattern in online social networks. We propose a theoretical framework that addresses the aforementioned issue from a social science perspective and exploits existing social theories of Goffman, Granovetter, and Nissenbaum to model social privacy for OSNs users. Based on this theoretical framework, we developed SOCPRI (SOCial PRIvacy) ontology to represent diversity in social relationships in online social networks. This model regulates personal information disclosure on the basis of the social role and the relationship quality between the OSNs users. The model is evaluated by translating competency questions into description logic (DL) queries to demonstrate the applicability of our approach. The results of ontology evaluation demonstrate the appropriateness of our ontology against proposed requirements. Based on this model a privacy-friendly online social networking environment can be developed to address some of the existing issues such as context collapse and user control. [less ▲]

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See detailForm und Funktion des Diminutivs im luxemburgisch-moselfränkischen Übergangsgebiet
Edelhoff, Maike UL

Doctoral thesis (2017)

Diminutive formation is a common word formation process of the Luxembourgish (Lux.) lan-guage and the neighbouring Moselle-Franconian (MsFrc) dialects. The aim of this thesis is to collect and to analyse ... [more ▼]

Diminutive formation is a common word formation process of the Luxembourgish (Lux.) lan-guage and the neighbouring Moselle-Franconian (MsFrc) dialects. The aim of this thesis is to collect and to analyse the characteristics of this process, integrate them into common morpho-logical theories and to establish their geolinguistic properties. On a functional level, the diminutives show the same characteristics in both varieties although the loss of the evaluative meaning is further developed in Lux. than in MsFrc. How-ever, the most apparent differences can be seen on the level of the fomal execution of the di-minutive rule: While the diminutives in MsFrc share many similarities, such as grammatical gender, the singular suffix and to an extent also the plural marking with Standard German, the Lux. language differs greatly from the others. In Lux. the singular formation is quite similar to the one in the other varieties, however, the plural suffix is triggered by the syllabic and prosodic properties of the base noun. Additionally, the grammatical gender of the diminutive is in con-cordance with the gender of the base noun and hence, not influenced by the suffix. The reasons for these peculiar attributes are to be found both in the historical development of the language and its current structural form as well as in its sociolinguistic context. The consequences of the differing structural properties are clearly displayed on a geo-linguistic level. Although the varieties are historically closely related the differing formal ex-pressions of the diminutive meaning lead to the emergence of groups of isoglosses coinciding with the state border. In brief, the history and the present situation of the diminutive serve as evidence that the dialect continuum that once crossed the state border has been falling apart and that it has been replaced by a solid linguistic border that separates the closely related varieties from each other. [less ▲]

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See detailIndividual rights under Union law. A study on the relation between rights, obligations and interests in the case law of the Court of Justice
Warin, Catherine UL

Doctoral thesis (2017)

In the increasingly rights-centred legal system of the Union, the concept of individual rights is the source of growing confusion, and is more than ever in need of clarification. This thesis addresses the ... [more ▼]

In the increasingly rights-centred legal system of the Union, the concept of individual rights is the source of growing confusion, and is more than ever in need of clarification. This thesis addresses the following questions. Firstly, how does the relation between rights, obligations and interests define the nature and function of individual rights in the Union’s legal order? Secondly, to what extent is the evolution of the Union’s constitutional framework challenging the original concept of individual rights? These questions are addressed essentially by tracing the development of the CJEU’s method for identifying individual rights and by mapping the relation between rights, obligations and interests that emerges from the case law. The basic characteristics of the concept of individual rights are inferred from this relation. The case law on individual rights is examined through the lens of the basic concept of individual rights, i.e. in the light of the relation between rights, obligations and interests. The study scrutinises cases in which this relation took shape and is still developing, looking in turn at the protection of economic, non-economic, and collective interests. Special attention is paid to the impact of the introduction of the Charter of Fundamental Rights in the EU legal order as well as to the implications of the EU concept of rights for the requirement of an effective remedy. [less ▲]

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See detailIn Luxemburg mit Portugal verbunden : Eine Verflechtungsgeschichte portugiesischer Migrantenvereine in Luxemburg und Portugals Emigrationspolitik (1974-1997).
Hinger, Thierry Pierre UL

Doctoral thesis (2017)

The thesis is a contribution to the migration history of Luxembourg and Portugal for the period between 1974 and the end of the 20th century. It analyses the entangled history of the Portuguese migrant ... [more ▼]

The thesis is a contribution to the migration history of Luxembourg and Portugal for the period between 1974 and the end of the 20th century. It analyses the entangled history of the Portuguese migrant organizations in Luxembourg and the emigration policy of Portugal in the context of the Portuguese nation (re-)building process that took place after the end of dictatorship and the loss of the empire, in Portugal and abroad. No more an imperial nation, Portugal became after April 25 1974 what Dufoix calls a trans-territorial nation. It emphasized the role of the Portuguese living abroad as a part of the nation and adopted an emigration policy that aimed at protecting the Portuguese migrants and strengthening their ties with Portugal. The entanglement of the two actors, the migrant organizations and the Portuguese state, in Luxembourg reveals their interrelation in the fields of political participation across borders, economics, and culture and education. They offered the Portuguese migrants in Luxembourg ways and means to maintain cross-border connections with Portugal, and must therefore be considered as two actors in the Portuguese nation (re-)building process that took place in Luxembourg. The thesis offers a historical account of the institutional role of the state of origin with its emigration policy and the migrant’s organizations in the country of destination in maintaining cross-border connections with the country of origin. [less ▲]

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See detailLe mouvement-liberté. Généalogie philosophique et littéraire d'un imaginaire politique
Jeusette, Julien UL

Doctoral thesis (2017)

Cette thèse, qui se situe au croisement de trois champs de recherche (la littérature, la philosophie, l’histoire des idées), a pour ambition de retracer la manière dont le déracinement, le nomadisme et ... [more ▼]

Cette thèse, qui se situe au croisement de trois champs de recherche (la littérature, la philosophie, l’histoire des idées), a pour ambition de retracer la manière dont le déracinement, le nomadisme et l’errance ont été investis, à un moment donné de notre Histoire, d’une appréciation positive, au moment même où la sédentarité et l’enracinement se sont vus taxés de conservatisme ennuyeux. Nous postulons que cet imaginaire politique, que nous appelons « mouvement-liberté » (tout discours axiologique valorisant le mouvement libre et infini, et dévalorisant toute forme d’immobilité), émerge dans Les Nourritures terrestres d’André Gide et dans Ainsi parlait Zarathoustra de Nietzsche à la fin du XIXe siècle. Nous montrons ensuite que ce discours s’amplifie au cours des années 1920-1930, notamment au sein des textes que nous avons qualifiés de « romans de fuite » ; la troisième partie de la thèse porte sur les années 1960-1970 et met en évidence la redondance discursive du « mouvement-liberté » au sein de la « French theory ». La dernière partie met en lumière la façon dont le « mouvement-liberté », qui était politiquement critique et explicitement de l’ordre du contre-pouvoir de la fin du XIXe siècle jusqu’aux années 1970, est aujourd’hui récupéré par le néolibéralisme, qui le revendique pour son propre compte et le travestit en « idéologie nomade ». [less ▲]

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See detailAb initio approaches to Resonant Raman Spectroscopy of Transition Metal Dichalcogenides
Pereira Coutada Miranda, Henrique UL

Doctoral thesis (2017)

This thesis deals with the theory and simulation of resonant Raman spectroscopy in two-dimensional transition metal dichalcogenides. We present two different ab initio approaches. In the first, we ... [more ▼]

This thesis deals with the theory and simulation of resonant Raman spectroscopy in two-dimensional transition metal dichalcogenides. We present two different ab initio approaches. In the first, we calculate the Raman susceptibility tensor as a function of laser energy from the change of the dielectric susceptibility with atomic displacements. In the second, we formulate the Raman tensor in terms of time-dependent perturbation theory and calculate it using electron-light and electron-phonon coupling matrix elements obtained from density functional theory. We investigate the role of resonance, quantum interference and excitonic effects in the Raman spectra of single and triple-layer MoTe2. We compare our simulations with experimental results, explaining the dependence of the Raman intensities on the excitation energy. We demonstrate that the two approaches are formally and numerically equivalent in the adiabatic limit. In addition, the second approach allows to include the dynamical effects and captures a shift of the intensities with respect to the adiabatic case. This method is also more computationally efficient and is extended to include temperature effects using many-body perturbation theory. We have implemented both of these methods in a software package with interfaces to open source ab initio codes. Furthermore, we have developed web based tools to visualize excitonic states and phonon modes. [less ▲]

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See detailTESTING 21ST CENTURY SKILLS IN A CHANGING NATURE OF WORK: THE CONSTRUCT VALIDITY OF COMPLEX PROBLEM SOLVING AND ORGANIZATIONAL LEARNING
Mainert, Jakob Simon UL

Doctoral thesis (2017)

This thesis investigates the empirical assessment and construct validity of complex problem-solving (CPS) skills and organizational learning (OL) in a changing nature of work. Technological and ... [more ▼]

This thesis investigates the empirical assessment and construct validity of complex problem-solving (CPS) skills and organizational learning (OL) in a changing nature of work. Technological and organizational change enlarge the gap between the type of employee required by the market and the employees who are actually being provided by higher education as human capital to the market. Two constructs, CPS and OL, might strengthen human capital to close the emerging gap in a changing nature of work. [less ▲]

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See detailL'intégration des élèves nouvellement arrivés en France dans l'espace scolaire français. Langues, représentations, identités en contexte.
Kadas, Timea UL

Doctoral thesis (2017)

Our thesis focuses on newcomer students in France and aims at understanding how these students integrate into French schools and exploring the educational paths they tread. Thus, this study is based ... [more ▼]

Our thesis focuses on newcomer students in France and aims at understanding how these students integrate into French schools and exploring the educational paths they tread. Thus, this study is based mainly on the analysis of the discourse of thirteen students concerning their learning and their school experiences. It is also based on the representations that these students have of themselves, others (French students, teachers), their learning in general, their learning of the French language in particular and the context in which this learning takes place. Our thesis also focuses on the students’ first languages and their role in the learning process. The link between language and identity has long been established by researchers from different disciplines. Therefore, we have tried to understand, through an autobiographical project based on the notions of multiliteracy and multimodality, how the first languages of the students can be taken into consideration in order to help them progress in both the learning of French and learning in general. We also considered the significance of such an approach in the reconstruction of these students' identities. Furthermore, in response to our initial question regarding how these students integrate into the French education system, we investigated two complementary perspectives: that of the institution through interviews with three teachers, three heads of school and two inspectors and that of the students’ families through questioning nine parents. The aim of this study is to contribute to the body of research on the role of migration in the French educational context and to provide a better understanding of the current educational challenges facing our globalized society. [less ▲]

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See detailANALYSIS OF NEURONAL DIFFERENTIATION IN GENETIC FORMS OF PARKINSON’S DISEASE REVEALS A NEURODEVELOPMENTAL CONTRIBUTION
Walter, Jonas UL

Doctoral thesis (2017)

During the mammalian embryonic neurodevelopment, all neurons descend from neuroepithelial stem cells. Accumulating evidences indicate a contribution of neurodevelopmental processes to the vulnerability to ... [more ▼]

During the mammalian embryonic neurodevelopment, all neurons descend from neuroepithelial stem cells. Accumulating evidences indicate a contribution of neurodevelopmental processes to the vulnerability to diseases. Here, we elucidate such developmental contribution in the context of Parkinson’s disease by combining high content imaging approaches, single-cell RNA sequencing, 3D image analysis, and multifactorial functional mitochondrial readouts. We found that the prominent PD-associated LRRK2-G2019S mutation accelerates dopaminergic neuron differentiation, accompanied by a reduced viability, resulting in indistinguishable dopaminergic neuron quantities. Our data indicate that the unexpected dynamics is driven by LRRK2-G2019S-dependent aberrations in gene expression as well as mitochondrial health and biogenesis of the neuroepithelial stem cell population. We conclude that LRRK2-G2019S modifies the dynamics of dopaminergic neuron fate specification during development, what may constitute a predisposition to parts of the PD-associated clinical manifestations. [less ▲]

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See detailStem cells for modeling Parkinson's disease
Nickels, Sarah Louise UL

Doctoral thesis (2017)

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See detailHistoricizing the journey of the New Math reform from the United States to Luxembourg in the 1960s and 1970s
Nadimi Amiri, Shaghayegh UL

Doctoral thesis (2017)

This research investigates the process of the New Math, an internationally disseminated reform of school mathematics in the Grand Duchy of Luxembourg, during the 1960s and 1970s. This mathematics reform ... [more ▼]

This research investigates the process of the New Math, an internationally disseminated reform of school mathematics in the Grand Duchy of Luxembourg, during the 1960s and 1970s. This mathematics reform was propagated in the Western side of the Cold War to promote the mathematical and scientific power of Western countries. With this initial objective as a core of the study, the research then expands the area of the research to look at the mathematics education in the western countries. Timewise also, this expansion goes beyond the 1960s and 1970s, the era of the New Math reform. Thus, in a broader perspective, the research attempts to study what school policymakers expect from school mathematics historically in Western countries. It studies how the background idea and reasoning of the New Math reform through the journey of the reform from the United States to Europe and Luxembourg was changed and adapted to be applicable in the educational context of Luxembourg. The three main questions of the research are: 1 How was the New Math reform received and advanced in Luxembourg? 2 What did Luxembourgers expect from their school mathematics? Or Why students in Luxembourg should learn mathematics? 3 What was the reasoning behind mathematics education in Western countries through the history of schooling? The research began by exploratory methods to clear the property of the research and to determine the data collection method and other features that research needed to improve its design. This approach led to a collection of data including documents related to the context of Luxembourg, and context outside Luxembourg. This collection included both primary and secondary sources. The research studied texts of laws, regulations, newspapers, conference proceedings of the era, mathematics textbooks, teacher journals and other officially published sources as well as unpublished sources such as correspondences between different actors related to the school system and math education. For reading and analyzing data, the research was inspired by Foucault’s archaeological approach in historical research and the study of different layers, which shape the discourse. In addition to Foucault, Popkewitz (e.g., 1997, 2009; Popkewitz & Lindblad, 2004) and Hacking (2012) inspired the work in developing the historical study of the reasoning. The research indicated two paradigms, which shaped the answers to the questions “why students should learn mathematics.” The first paradigm supports the reasoning, which argues that mathematics education should improve thinking ability, mental power and intellectuality. The second paradigm was based on the idea that mathematics offers a tool to learners to solve the problems of everyday life such as economics, engineering, etc. The research showed that these two paradigms shaped the discourse before and during the New Math reform and in different contexts and culture. [less ▲]

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See detailSelective vulnerability in Parkinson's disease: contributions from neuronal connectivity, lineage and functional identity
Oliveira, Miguel UL

Doctoral thesis (2017)

In Parkinson's disease (PD) patients, a specific set of neuronal populations are known to present Lewy pathology, cell death or both. This selective distribution of vulnerability is observed during ... [more ▼]

In Parkinson's disease (PD) patients, a specific set of neuronal populations are known to present Lewy pathology, cell death or both. This selective distribution of vulnerability is observed during disease progression and it has been hypothesised to result from both brain connectivity and shared cell-autonomous characteristics. Herein we simulate the contribution of the connectome alone to the spread of arbitrary aggregates using a computational model of temporal spread within an abstract representation of the mouse mesoscale connectome. Our simulations are compared with the spread of alpha-synuclein aggregation within in vivo mouse models. This comparison highlights that neuronal connectivity appears to be required for the presence of alpha-synuclein aggregation, however, it is insufficient to fully describe the pattern of distribution of pathology throughout the mouse brain. Therefore, we further investigate the role of the shared cell-autonomous characteristics by analysing the developmental lineages, mature transcriptomic profiles and metabolic capabilities of a subset of 28 synaptically connected neuronal populations that are vulnerable to PD, to varying degrees. We highlight a set of developmental transcription factors that are commonly required for specification of many vulnerable brainstem neurons, e.g. Ascl1 and Lmx1b, and transcription factors that are able to distinguish between differently vulnerable neuronal populations, e.g. Pitx3. Using genome-wide microarray data from six brains of healthy donors, we further investigate the existence of a shared transcriptomic profile between vulnerable neuronal populations. We highlight a list of genes whose expression levels seem to selectivity identify the set of vulnerable neuronal populations. Interestingly, many of these genes are involved in biological processes previously implicated in PD, some of which have also variants previously highlighted in genome-wide association studies of PD. Since the vulnerable set of neurons are known to have a high metabolic burden, we used a constraint-based modelling approach to generate metabolic models and further investigate their ability to generate mitochondrial ATP. Interestingly, most of the metabolic models of vulnerable brain structures seem to specifically require the same set of metabolic reactions in order to generate mitochondrial ATP. This thesis, therefore, highlights the importance of a multidisciplinary approach to understanding the pathogenesis of PD. [less ▲]

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See detailInflammatory signaling in liver cells: Cross-regulation of the IL-6/JAK/STAT3 pathway and microRNAs
Servais, Florence UL

Doctoral thesis (2017)

Interleukin-6 (IL-6) plays important roles in the regulation of liver functions and promotes the development of hepatocellular carcinoma (HCC), the most common primary liver cancer. Whereas protein ... [more ▼]

Interleukin-6 (IL-6) plays important roles in the regulation of liver functions and promotes the development of hepatocellular carcinoma (HCC), the most common primary liver cancer. Whereas protein-encoding genes are well-studied, the contribution of IL-6-regulated microRNAs (miRNAs) to its effects is largely unexplored. Similarly, little is known about miRNAs regulating key molecules of the IL-6/JAK/STAT3 signaling pathway. In the main part of this thesis, cell-based high-throughput screenings systems were developed, allowing the identification of miRNAs interfering with the IL-6/JAK/STAT3 signaling. Out of 538 miRNA mimics, this dual screening approach followed by various validation steps (luciferase-3’UTR-reporter assays, western blot and flow cytometry analyses) allowed us to identify twelve miRNAs targeting STAT3, JAK1, SOCS3, IL6R and/or gp130, ten of them had not yet been reported as regulators of this pathway before. In the second part of this work, microarray analyses revealed that primary hepatocytes are considerably more responsive to IL-6 stimulation regarding changes in their miRNomes than liver-derived cell lines. Despite their weaker response, one of the top regulated miRNA found in the primary hepatocytes, miR-146b-5p, could also be induced by IL-6-type cytokines (IL-6 and Oncostatin M) in cell lines. Its functional role(s) in hepatocytes are currently investigated. A larger, comparative study included additionally Interferon gamma and IL-27, cytokines with a STAT1-dominated response, and supplementary cell lines originating not only from the liver but also from other tissues. While all cytokines had profound effects on the mRNA transcriptomes, only very small to moderate changes were observed at the miRNome level, suggesting that the regulation mediated by cytokines mainly happens through the modulation of protein-coding genes rather than by fine-tuning via miRNAs. Additionally, we analyzed expression of a broad panel of cytokines in sera of 125 patients with liver diseases (steatosis, non-alcoholic steatohepatitis, HCC) by bead-based multiplex immunoassays. We observed that, for example, serum HGF, IL-6 and IL-8 levels increased in relation with the severeness of liver pathology while PDGF-BB and RANTES decreased. When investigating the impact of the patatin-like phospholipase domain-containing protein 3 variant I148M (PNPLA3 I148M), known to be a risk factor for the development of liver diseases, on the serum levels of cytokines, no significant differences could be observed between the different genotypes. In this PhD thesis, we identified and characterized miRNAs relevant for the IL-6/JAK/STAT3 signaling pathway, including miR-146b-5p as an IL-6-inducible miRNA. Others like miR-194-5p, miR-4473 and miR-548k were demonstrated to be negative regulators of this pathway and may be of potential therapeutic significance. In addition, we showed that, while miRNAs can modulate this pathway, IL-6 seems to rather regulate the mRNA transcriptome than the miRNome. [less ▲]

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See detailKusuoka-Stroock type bounds for densities related to low-dimensional projections of high-dimensional SDE
Ledent, Antoine Patrick Isabelle Eric UL

Doctoral thesis (2017)

One of the purposes of this thesis is to use Malliavin calculus and Stochastic Taylor expansions to study the densities of interacting systems of stochastic differential equations (SDE), seen as ... [more ▼]

One of the purposes of this thesis is to use Malliavin calculus and Stochastic Taylor expansions to study the densities of interacting systems of stochastic differential equations (SDE), seen as projections of SDE onto a low-dimensional space, and to control the dependence of the constants on the dimension of the background space. The setting includes time-dependent SDE and a relatively large class of path-dependent SDE. Several results also shed light on the classical theory of SDE, independently of the control on the constants. In Part 1, assuming the system satisfies suitably defined projected equivalents of the classic ellipticity or weak Hörmander conditions, we prove Gaussian estimates in terms of the Euclidean distance where, provided natural assumptions, for a fixed target-space dimension, the constants depend polynomially on the background dimension, and, in the elliptic case, on the number of driving Brownian motions. In Part 2, we first define suitable generalisations of (time-dependent) control distances and prove Kusuoka-Stroock type results without control on the constants. In particular, we obtain a time-dependent extension of a result of Léandre about SDE with non-trivial drifts, i.e., drifts which are not uniformly contained in the span of the other vector fields. Then, we introduce a condition which we call the `Progressive Hörmander condition' and prove similar control-type estimates valid under this assumption, with polynomial control on the growth of the constants with background space dimension. The condition is of independent interest in the study of SDE, and shows the connection between the classic works of Ben Arous, Kusuoka, Léandre and Stroock, and the more recent works of Bally, Caramellino, Delarue, Menozzi and Pigato. To main technique required is the study of density and scaling properties of some careful choice of linear combinations of terms of the signature of the driving path. In Part 3, we introduce a stricter condition called the `separated progressive Hörmander condition', and prove lower bounds and local strict positivity under this assumption. (By `local' we mean local around the solution of the deterministic ODE driven by a null control, rather than local round the initial point.) The main technical difficulty is the identification of points contained in the interior of the support of the log-signature of the path in the d dimensional Euclidean space composed of d Brownian motions and a deterministic linear component. The purpose of Part 4 is to use some results and techniques of the rest of the thesis to prove extensions of a theorem of Löcherbach about uniformly elliptic interacting branching diffusions. [less ▲]

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See detailIdentification of DNA damage response genes as targets for personalized treatment of Glioblastoma through RNA interference screens
Erasimus, Hélène Claudine Pascale UL

Doctoral thesis (2017)

Despite surgical resection and genotoxic treatment with ionizing radiation and the DNA alkylating agent temozolomide (TMZ), glioblastoma (GBM) remains one of the most lethal cancers, due in part to the ... [more ▼]

Despite surgical resection and genotoxic treatment with ionizing radiation and the DNA alkylating agent temozolomide (TMZ), glioblastoma (GBM) remains one of the most lethal cancers, due in part to the action of DNA repair factors that drive resistance and lead to tumor relapse. Important features of these mechanisms include the inherent redundancy and complexity of the many DNA repair pathways activated as part of the DNA damage response (DDR). One important DDR factor is encoded by the O-6-methylguanine-DNA methyltransferase (MGMT) gene whose epigenetic silencing is a strong predictive marker for favorable outcome in GBM patients treated with TMZ. However, even patients displaying MGMT promoter methylation succumb to tumor relapse, indicating that other DNA repair mechanisms promote resistance to the treatment. The main aim of this work was to identify essential DDR factors that support GBM cell survival under TMZ treatment in order to provide novel targets and thus, novel insights into drug combinations that could overcome GBM chemoresistance. The strategy to achieve this goal was to use well-characterized GBM cell lines in focused loss of function shRNA screens performed under different conditions. Indeed, screens were designed to uncover DDR genes that are essential for GBM cells i) under normal conditions, ii) under TMZ treatment, iii) and under TMZ treatment in MGMT negative contexts. Pooled shRNAs targeting more than 500 DDR genes were introduced into GBM cells reflecting two clinically-relevant GBM contexts: a MGMT-positive context using MGMT-expressing cells and a negative one, using cell lines in which MGMT was depleted hrough pharmacological inhibition or RNA interference. Potential DDR targets that could sensitize GBM cells to TMZ have been identified and some of them validated. Surprisingly, some of these targets are not only involved in pathways that are commonly known to drive TMZ resistance (i.e. Double strand break repair, Direct repair), but also in repair pathways such as transcription-coupled nucleotide excision repair (TC-NER) or the early steps of the Fanconi Anemia pathway (FA). While components of the early FA pathway might be attractive targets especially in MGMT-negative contexts, it may be interesting to target factors involved in the early steps of the TC-NER to sensitize MGMTpositive cells to TMZ. So in addition to its predictive and prognostic value, MGMT might be a relevant stratification marker to treat patients in a personalized way. Supporting this hypothesis, the screen analyses revealed that the curative inhibition of some genes in combination with TMZ treatment might turn to be deleterious depending on MGMT expression level. One of the promising target will be further investigated in vitro as well as in vivo to elucidate the molecular mechanisms by which this gene operates to confer cellular resistance to TMZ. This study opens up new horizons for combinatorial therapies and hopefully, will be used to improve therapeutical approaches, particularly for MGMT-positive GBM patients, who currently do not benefit at all from chemotherapy. [less ▲]

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See detailMolecular mechanisms of kinase inhibitor resistance in melanoma
Cesi, Giulia UL

Doctoral thesis (2017)

In my thesis, I elucidated several aspects of melanoma biology, all related to the influence of targeted therapies in both responding and resistant melanoma cells. To better understand the MAPK signalling ... [more ▼]

In my thesis, I elucidated several aspects of melanoma biology, all related to the influence of targeted therapies in both responding and resistant melanoma cells. To better understand the MAPK signalling pathway, the impact of BRAF inhibitors on metabolic alterations as well as the connection between BRAF inhibitors and the onset of drug resistance was investigated. This introduction is focused on four topics: i) melanoma, ii) cancer metabolism, iii) miRNAs and iv) extracellular vesicles. First, melanoma biology including incidence rates, etiology, canonical and altered signalling pathways, therapies and resistance mechanisms will be introduced. The second part of the introduction will concentrate on metabolic alterations in the context of cancer and their implication on proliferation and survival. Thirdly, miRNAs and extracellular vesicles will be illustrated providing insights into their role in cancer development and especially drug resistance [less ▲]

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See detailCHARACTERIZATION OF PARKINSON’S DISEASE GENE DJ-1/PARK7 IN CD4+CD25+FOXP3+ REGULATORY T-CELLS
Danileviciute, Egle UL

Doctoral thesis (2017)

DJ-1, also known as PARK7, as its name suggests, is one of the familial Parkinson’s disease (PD) genes. Defects in human DJ-1 are the cause of autosomal recessive early-onset PD. DJ-1 is a redox ... [more ▼]

DJ-1, also known as PARK7, as its name suggests, is one of the familial Parkinson’s disease (PD) genes. Defects in human DJ-1 are the cause of autosomal recessive early-onset PD. DJ-1 is a redox-responsive protein and is long thought to mainly play an essential protective role in neurons. DJ-1 is ubiquitously expressed throughout the body rather than only in brain and is involved in several biological functions. We here seek to characterize a novel role of DJ-1 in regulatory T cells, currently recognized as CD4+CD25+FOXP3+ regulatory T-cells (Tregs), which are well-known immune suppressor cells in many peripheral diseases and emerging to play a role in several neurodegenerative diseases. [less ▲]

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See detailEssays on Asset Pricing Models with Jump Processes
Cui, Xuecan UL

Doctoral thesis (2017)

This dissertation contains four autonomous academic papers on asset pricing models with jump processes, including the studies of equilibrium asset pricing model, option pricing model, and empirical test ... [more ▼]

This dissertation contains four autonomous academic papers on asset pricing models with jump processes, including the studies of equilibrium asset pricing model, option pricing model, and empirical test. The common thread between them is the application of jump processes that links them in asset price modeling. The first three papers study Lévy process and its inhomogeneous extensions, while the last one studies contagious Hawkes processes. The first essay proposes a novel equilibrium asset pricing model under the semiparametric jump diffusion framework, including drift, volatility and jump intensity in a general time-varying form. The corresponding pricing kernel provides insights on option pricing, and equity premium puzzle [Mehra & Prescott (1985)]. The analytical solutions of equity premium and European call option are given as well. The second essay introduces a new econometric method/procedure to disentangle the three time-varying components of drift, volatility and jump in asset prices. By combining Hodrick-Prescott filter and particle filters, I decomposed the three timevarying components in the S&P500 index, and observed the clustering of volatility and jumps, though the clustering effects are more pronounced when the time-varying drift is negative. Empirical results support the proposed time-varying jump diffusion asset pricing model in Chapter 2. The third essay studies the (un)importance of small jumps in option pricing models. The option pricing literature argues that the behavior of small jumps in a Geometric Lévy model is of paramount importance [Carr et al. (2002)]. This is evidently true for very short time horizons and very deep in- and out-of-the-money options. In this paper, we took the complementary view and asked what values of time to maturity and option moneyness in a Geometric Lévy model lead to option prices, which are practically indistinguishable from the price of plain vanilla options in the BlackScholes model. In other words, in what situation that the Lévy model in question can be replaced with a Brownian motion with minimal pricing error. We produced explicit tight bounds in the case of a Poisson jump process, and related heuristic bounds for arbitrary Lévy process with exponentially decaying jump intensity. The fourth essay models and tests contagious jumps in bull/bear market regimes, in which I developed the regime switching Hawkes processes to model the contagious asset jumps in the international stock market. This new model allows serial and regional contagion in international asset prices, in which contagious impact can be flexible to accommodate different market conditions. [less ▲]

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See detailAutomated and Effective Security Testing for XML-based Vulnerabilities
Jan, Sadeeq UL

Doctoral thesis (2017)

Nowadays, the External Markup Language (XML) is the most commonly used technology in web services for enabling service providers and consumers to exchange data. XML is also widely used to store data and ... [more ▼]

Nowadays, the External Markup Language (XML) is the most commonly used technology in web services for enabling service providers and consumers to exchange data. XML is also widely used to store data and configuration files that control the operation of software systems. Nevertheless, XML suffers from several well-known vulnerabilities such as XML Injections (XMLi). Any exploitation of these vulnerabilities might cause serious and undesirable consequences, e.g., denial of service and accessing or modifying highly-confidential data. Fuzz testing techniques have been investigated in the literature to detect XMLi vulnerabilities. However, their success rate tends to be very low since they cannot generate complex test inputs required for the detection of these vulnerabilities. Furthermore, these approaches are not effective for real-world complex XML-based enterprise systems, which are composed of several components including front-end web applications, XML gateway/firewall, and back-end web services. In this dissertation, we propose several automated security testing strategies for detecting XML-based vulnerabilities. In particular, we tackle the challenges of security testing in an industrial context. Our proposed strategies, target various and complementary aspects of security testing for XML-based systems, e.g., test case generation for XML gateway/firewall. The development and evaluation of these strategies have been done in close collaboration with a leading financial service provider in Luxembourg/Switzerland, namely SIX Payment Services (formerly known as CETREL S.A.). SIX Payment Services processes several thousand financial transactions daily, providing a range of financial services, e.g., online payments, issuing of credit and debit cards. The main research contributions of this dissertation are: -A large-scale and systematic experimental assessment for detecting vulnerabilities in numerous widely-used XML parsers and the underlying systems using them. In particular, we targeted two common XML parser’s vulnerabilities: (i) XML Billion Laughs (BIL), and (ii) XML External Entities (XXE). - A novel automated testing approach, that is based on constraint-solving and input mutation techniques, to detect XMLi vulnerabilities in XML gateway/firewall and back-end web services. - A black-box search-based testing approach to detect XMLi vulnerabilities in front-end web applications. Genetic algorithms are used to search for inputs that can manipulate the application to generate malicious XML messages. - An in-depth analysis of various search algorithms and fitness functions, to improve the search-based testing approach for front-end web applications. - Extensive evaluations of our proposed testing strategies on numerous real-world industrial web services, XML gateway/firewall, and web applications as well as several open-source systems. [less ▲]

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