Genetic regulators of ventral midbrain gene expression and nigrostriatal circuit integrity

Doctoral thesis (2020)

Complex traits are a fundamental feature of diverse organisms. Understanding the genetic architecture of a complex trait is arduous but paramount because heterogeneity is prevalent in populations and ... [more ▼]

Complex traits are a fundamental feature of diverse organisms. Understanding the genetic architecture of a complex trait is arduous but paramount because heterogeneity is prevalent in populations and often disease-related. Genome-wide association studies have identified many genetic variants associated with complex human traits, but they can only explain a small portion of the expected heritability. This is partially because human genomes are highly diverse with large inter-personal difference. It has been estimated that every human differs from each other by at least 5 million variants. Moreover, many common variants with small effect can contribute to complex traits, but they cannot survive from stringent statistical cutoff given the currently available sample size. Mice are an ideal substitute. They are maintained in a controlled condition to minimize the variation introduced by environment. Each mouse of an inbred strain is genetically identical, but different strains bear innate genetic heterogeneity between each other, mimicking human diversity. Hence, in this work we used inbred mouse strains to study the genetic variation of complex traits. We focused on ventral midbrain, the brain region controlling motor functions and behaviors such as anxiety and fear learning that differ profoundly between inbred mouse strains. Such phenotypic diversity is directed by differences in gene expression that is controlled by cis- and trans-acting regulatory variants. Profound understanding on the genetic variation of ventral midbrain and its related phenotypic differences could pave the way to apprehend the whole genetic makeup of its associated disease phenotypes such as Parkinson’s disease and schizophrenia. Therefore, we set out to investigate the cis- and trans-acting variants affecting mouse ventral midbrain by coupling tissue-level and cell type-specific transcriptomic and epigenomic data. Transcriptomic comparison on ventral midbrains of C57BL/6J, A/J and DBA/2J, three inbred strains segregated by ~ 6 million genetic variants, pinpointed PTTG1 was the only transcription factor significantly altered at transcriptional level between the three strains. Pttg1 ablation on C57BL/6J background led to midbrain transcriptome to shift closer to A/J and DBA/2J during aging, suggesting Pttg1 is a novel regulator for ventral midbrain transcriptome. As ventral midbrain is a mixture of cells, tissue level transcriptome cannot always reveal cell type-specific regulatory variation. Therefore, we set out to generate single nuclei chromatin accessibility profiles on ¬ventral midbrains of C57BL/6J and A/J, providing a rich resource to study the transcriptional control of cellular identity and genetic diversity in this brain region. Data integration with existing single cell transcriptomes predicted the key transcription factors controlling cell identity. Putative regulatory variants showed differential accessibility across cell types, indicating genetic variation can direct cell type-specific gene expression. Comparing chromatin accessibility between mice revealed potential trans-acting variation that can affect strain-specific gene expression in a given cell type. The diverse transcriptome profiles in ventral midbrain can lead to phenotypic variation. Nigrostriatal circuit, bridging from ventral midbrain to dorsal striatum by dopaminergic neurons, is an important pathway controlling motor activity. To search for phenotypes related to dopaminergic neurons, we measured the dopamine concentration in dorsal striatum of eight inbred mouse strains. Interestingly, dopamine levels were varied among stains, suggesting it is a complex trait linked to genetic variation in ventral midbrain. To understand the genetic variation contributing to dopamine level differences, we conducted quantitative trait locus (QTL) mapping with 32 CC strains and found a QTL significantly associated with the trait on chromosome X. As expression changes are likely to be underlying the phenotypic variation, we leveraged our previous transcriptomic data from C57BL/6J and A/J to search for genes differentially expressed in the QTL locus. Col4a6 is the most likely QTL gene because of its 9-fold expression difference between C57BL/6J and A/J. Indeed, COL4A6 has been shown to regulate axogenesis during brain development. This coincides with our observation that A/J had less axon branching in dorsal striatum than C57BL/6J, prompting us to propose that Col4a6 can regulate the axon formation of dopaminergic neurons in embryonic stages. Our study provides a comprehensive overview on cis- and trans-regulatory variants affecting expression phenotypes in ventral midbrain, and how they could possibly introduce phenotypic difference associated with this brain region. In addition, our single nuclei chromatin landscapes of ventral midbrain are a rich resource for analysis on gene regulation and cell identity. Our work paves the way to apprehend full genetic makeup on the gene expression control of ventral midbrain, the result of which is important to understand the genetic background of midbrain associated phenotypes. [less ▲]

Navigating the narrow circle: Rawls and Stout on justification, discourse and institutions

Doctoral thesis (2020)

Life in political society unfolds within the bounds of a narrow circle, epistemic and moral. A person has only finite faculties and restricted moral motivation. When formulating projects, the person ought ... [more ▼]

Life in political society unfolds within the bounds of a narrow circle, epistemic and moral. A person has only finite faculties and restricted moral motivation. When formulating projects, the person ought to recognize these limits but also to check them. Accordingly, she seeks a deliberative ideal which is sensitive both to good epistemic practice and to respectful relations. How might the person best justify the shape of her society’s institutions, statutes and policies? What reflexive attitudes and dispositions ought she to adopt towards her justificatory resources? The person might work through the sequence of standpoints from John Rawls’s “political liberalism”: a first-person, action-guiding framework of deliberation and reflection. Alternatively, she might model the exploratory discourse and personal virtues characteristic of Jeffrey Stout’s “democratic traditionalism”. This work reconstructs Rawls’s and Stout’s approaches to justification, discourse and institutions and compares their differing methods in search of the most adequate deliberative ideal for democratic society. [less ▲]

L'accord exclusif d'élection de for à travers de la Convention de La Haye: une efficacité mitigée

Doctoral thesis (2020)

L'accord exclusif d'élection de for en tant que mode d'attribution de compétence dans les litiges commerciaux internationaux fait partie de l'économie du contrat international. Il constitue une composante ... [more ▼]

L'accord exclusif d'élection de for en tant que mode d'attribution de compétence dans les litiges commerciaux internationaux fait partie de l'économie du contrat international. Il constitue une composante indispensable de l'autonomie des parties en tant que principe gouvernant les rapports commerciaux internationaux. À cet égard, la promotion du commerce et des investissements internationaux nécessitent l'élaboration d'un régime international apportant la sécurité et assurant l'efficacité des accords exclusifs d'élection de for. Tel est l'objectif proclamé par les rédacteurs de la Convention de La Haye sur les accords d'élection de for. L'analyse des dispositions de la Convention révèle que cette efficacité prônée par cet instrument est mitigée. Ce constat se vérifie tant au niveau de la validité de l'accord qu'au niveau de ses effets. [less ▲]

Routing Strategies and Content Dissemination Techniques for Software-Defined Vehicular Networks

Doctoral thesis (2020)

Over the past years, vehicular networking has enabled a wide range of new applications that improve vehicular safety, efficiency, comfort, and environmental impact. Vehicular networks, however, normally ... [more ▼]

Over the past years, vehicular networking has enabled a wide range of new applications that improve vehicular safety, efficiency, comfort, and environmental impact. Vehicular networks, however, normally operate in communication-hostile environments and are characterized by dynamic topologies and volatile links, making it challenging to guarantee Quality of Service (QoS) and reliability of vehicular applications. To this end, the present work explores how the centralized coordination offered by Software-Defined Networking can improve the Quality of Service in vehicular networks, particularly for Vehicle-to-Vehicle (V2V) unicast routing and content dissemination. With regard to V2V routing, this work motivates the case for centralized network coordination by studying the performance of traditional MANET routing protocols when applied to urban VANETs, showing that they cannot provide satisfactory performance for modern vehicular applications because of their limited global network awareness, slow convergence, and high signaling. Hence, this work proposes and validates a centralized Multi-Flow Congestion-Aware Routing (MFCAR) algorithm to allocate multiple data flows on V2V routes. The first novelty of MFCAR is the SDN-based node-busyness estimation technique. The second novelty is the enhancement of the path-cost formulation as a linear combination of path length and path congestion, allowing the user application to fine-tune its QoS requirements between throughput and delay. Concerning content dissemination, this work proposes a Fairness- and Throughput-Enhanced Scheduling for Content Dissemination in VANETs (ROADNET), a centralized strategy to improve the tradeoff between data throughput and user fairness in deterministic vehicular content dissemination. ROADNET’s main novelties are the design of a graph-based multi-channel transmission scheduler and the enforcement of a transmission-priority policy that prevents user starvation. As additional contributions, the present work proposes a heuristic for the centralized selection of opportunistic content dissemination parameters and discusses the main security issues in Software-Defined Vehicular Networking (SDVN) along with possible countermeasures. The proposed techniques are evaluated in realistic scenarios (LuST), using discrete-event network simulators (OMNeT++) and microscopic vehicular-mobility simulators (SUMO). It is shown that MFCAR can improve PDR, throughput and delay for unicast V2V routing up to a five-fold gain over traditional algorithms. ROADNET can increase content dissemination throughput by 36% and user fairness by 6% compared to state-of-the-art techniques, balancing the load over multiple channels with a variance below 1%. [less ▲]

The D²Rwanda mixed-methods study including a cluster-randomised controlled clinical trial

Doctoral thesis (2020)

Diabetes mellitus prevalence has been estimated at 5.1% in Rwanda. Several factors, including an increase in screening and diagnosis programmes, the urbanization of the population, and changes in ... [more ▼]

Diabetes mellitus prevalence has been estimated at 5.1% in Rwanda. Several factors, including an increase in screening and diagnosis programmes, the urbanization of the population, and changes in lifestyle are likely to contribute to a sharp increase in the prevalence of diabetes mellitus in the next decade. Patients with low health literacy levels are often unable to recognise the signs and symptoms of diabetes mellitus, and may access their health provider late, hence presenting with more complications. The Rwandan health care system is facing a severe shortage in human resources. In response to the need for a better management of non-communicable diseases at primary health care level, a new type of community health workers was introduced: the home-based care practitioners (HBCPs). Approximately 200 HBCPs were trained and deployed in selected areas (“cells”) in nine hospitals across the country. There is growing evidence for the efficacy of interventions using mobile devices in low- and middle-income countries. In Rwanda, there is an urgent call to using mobile health interventions for the prevention and management of non-communicable diseases. The D²Rwanda (Digital Diabetes in Rwanda) research project aims at responding to this call. The overall objectives of the D²Rwanda project are: a) to determine the efficacy of an integrated programme for the management of diabetes in Rwanda, which would include monthly patient assessments by HBCPs and an educational and self-management mobile health patient tool, and; b) to qualitatively explore the ways these interventions would be enacted, their challenges and effects, and changes in the patients’ health behaviours and HBCPs’ work satisfaction. The project employed a mixed-methods sequential explanatory design consisting of a one-year cluster randomised controlled trial with two interventions and followed by focus group discussions with patients and HBCPs. The dissertation presents three studies from the D²Rwanda project. The first study aimed at describing the protocol of the research project, reporting the research questions, inclusion and exclusion criteria, primary and secondary outcomes, measurements, power calculation, randomisation methods, data collection, analysis plan, implementation fidelity and ethical considerations. The aim of the second study was to report on the translation and cultural adaptation of the Problem Areas in Diabetes (PAID) questionnaire and the evaluation of its psychometric properties. First, the questionnaire was translated following a standard protocol. Second, 29 participants were interviewed before producing a final version. Third, we examined a sample of 266 adult patients living with diabetes to determine the psychometric characteristics of the questionnaire. The full scale showed good internal reliability (Cronbach’s α = 0.88). A four-factor model with subdimensions of emotional, treatment, food-related and social-support problems was found to be an adequately approximate fit (RMSEA = 0.056; CFI = 0.951; TLI = 0.943). The mean total PAID score of the sample was high (48.21). Important cultural and contextual differences were noted, urging a more thorough examination of conceptual equivalence with other cultures. The third study aimed at reporting on the disease-related quality of life of patients living with diabetes mellitus in a non-representative sample in Rwanda and to identify potential predictors. This cross-sectional study was part of the baseline assessment of the clinical controlled trial. Between January and August 2019, 206 adult patients living with diabetes were recruited. Disease-specific quality of life was measured using the Kinyarwanda version of the Diabetes-39 (D-39) questionnaire, which was translated and cross-culturally adapted beforehand by the same group of researchers. A haemoglobin A1c (HbA1c) test was performed on all patients. Socio-demographic and clinical data were collected, including medical history, disease-related complications and comorbidities. “Anxiety and worry” and “sexual functioning” were the two most affected dimensions. Hypertension was the most frequent comorbidity (49.0% of participants). The duration of the disease and HbA1c values were not correlated with any of the D-39 dimensions. The five dimensions of quality of life were predicted differentially by gender, age, years of education, marital status, achieving a HbA1c of 7%, hypertension, presence of complications and hypoglycaemic episodes. A moderating effect was identified between use of insulin and achieving a target HbA1c of 7% in the “diabetes control” scale. Further prospective studies are needed to determine causal relationships. [less ▲]

Formal Framework for Verifying Implementations of Byzantine Fault-Tolerant Protocols Under Various Models

Doctoral thesis (2020)

The complexity of critical systems our life depends on (such as water supplies, power grids, blockchain systems, etc.) is constantly increasing. Although many different techniques can be used for proving ... [more ▼]

The complexity of critical systems our life depends on (such as water supplies, power grids, blockchain systems, etc.) is constantly increasing. Although many different techniques can be used for proving correctness of these systems errors still exist, because these techniques are either not complete or can only be applied to some parts of these systems. This is why fault and intrusion tolerance (FIT) techniques, such as those along the well-known Byzantine Fault-Tolerance paradigm (BFT), should be used. BFT is a general FIT technique of the active replication class, which enables seamless correct functioning of a system, even when some parts of that system are not working correctly or are compromised by successful attacks. Although powerful, since it systematically masks any errors, standard (i.e., ``homogeneous'') BFT protocols are expensive both in terms of the messages exchanged, the required number of replicas, and the additional burden of ensuring them to be diverse enough to enforce failure independence. For example, standard BFT protocols usually require 3f+1 replicas to tolerate up to f faults. In contrast to these standard protocols based on homogeneous system models, the so-called hybrid BFT protocols are based on architectural hybridization: well-defined and self-contained subsystems of the architecture (hybrids) follow system model and fault assumptions differentiated from the rest of the architecture (the normal part). This way, they can host one or more components trusted to provide, in a trustworthy way, stronger properties than would be possible in the normal part. For example, it is typical that whilst the normal part is asynchronous and suffers arbitrary faults, the hybrids are synchronous and fail-silent. Under these favorable conditions, they can reliably provide simple but effective services such as perfect failure detection, counters, ordering, signatures, voting, global timestamping, random numbers, etc. Thanks to the systematic assistance of these trusted-trustworthy components in protocol execution, hybrid BFT protocols dramatically reduce the cost of BFT. For example, hybrid BFT protocols require 2f+1 replicas instead of 3f +1 to tolerate up to f faults. Although hybrid BFT protocols significantly decrease message/time/space complexity vs. homogeneous ones, they also increase structural complexity and as such the probability of finding errors in these protocols increases. One other fundamental correctness issue not formally addressed previously, is ensuring that safety and liveness properties of trusted-trustworthy component services, besides being valid inside the hybrid subsystems, are made available, or lifted, to user components at the normal asynchronous and arbitrary-on-failure distributed system level. This thesis presents a theorem-prover based, general, reusable and extensible framework for implementing and proving correctness of synchronous and asynchronous homogeneous FIT protocols, as well as hybrid ones. Our framework comes with: (1) a logic to reason about homogeneous/hybrid fault-models; (2) a language to implement systems as collections of interacting homogeneous/hybrid components; and (3) a knowledge theory to reason about crash/Byzantine homogeneous and hybrid systems at a high-level of abstraction, thereby allowing reusing proofs, and capturing the high-level logic of distributed systems. In addition, our framework supports the lifting of properties of trusted-trustworthy components, first to the level of the local subsystem the trusted component belongs to, and then to the level of the distributed system. As case studies and proofs-of-concept of our findings, we verified seminal protocols from each of the relevant categories: the asynchronous PBFT protocol, two variants of the synchronous SM protocol, as well as two versions of hybrid MinBFT protocol. [less ▲]

IN PURSUIT OF OPENNESS An analysis of the legal framework of the European Union’s Copernicus’ open data policy

Doctoral thesis (2020)

The European Union (EU) civil Earth Observation (EO) programme Copernicus, has positioned itself as one of the largest EO data providers worldwide by providing an answer to strong demand for ... [more ▼]

The European Union (EU) civil Earth Observation (EO) programme Copernicus, has positioned itself as one of the largest EO data providers worldwide by providing an answer to strong demand for (environmental) data and information thanks to its open data policy mandated by its regulatory framework. Nevertheless, it has been the target of criticism by some policymakers who argue that rather benefiting Europeans, Copernicus' open data policy impacts negatively in the Union’s competitiveness and furthers the economic interests of US tech giants, such as Amazon and Google. Facing this criticism, the European Commission has evaluated possible modifications on the open data policy pillars “full, free and open” to address emerging economic and technological challenges. This dissertation contributes to this debate by answering the overarching question of whether alterations to the open data policy could be done without hampering Copernicus’ core goals, and whether such alternation would be in compliance with the EU legal framework. Specifically, this dissertation addresses the balancing of the right of access to public information against the economic public interest protection. To do so, firstly, this dissertation explains the legal meaning of the Copernicus’ open data policy pillars: 1) full, 2) free and 3) open within the context of EU law. Secondly, it explains the substantive limits of the open data policy, by examining non-contractual third party liability for the Commission, as well as the lawful exceptions to access to Copernicus data and information. These lawful exceptions are formulated by the Copernicus Regulation 377/2014 and Delegated Regulation 1159/2013 as the “protection of public security” and “international relations interests,” the “protection of privacy” and the “integrity of the Copernicus system”. However, this dissertation goes further by examining other EU law texts on the right of access to public information, such as the Regulation 1049/2001 and its Article 4 on the protection of public economic and financial interests, and the public overriding interests on access to environmental information enshrined mainly in the Regulation 1367/2006 and the Directive 2003/4/EC. Finally, it presents a proposal on how to evaluate the performance of Copernicus’ open data policy in order to determine if any substantial modification of this policy is indeed desirable. [less ▲]

Reconciling data privacy with sharing in next-generation genomic workflows

Doctoral thesis (2020)

Privacy attacks reported in the literature alerted the research community for the existing serious privacy issues in current biomedical process workflows. Since sharing biomedical data is vital for the ... [more ▼]

Privacy attacks reported in the literature alerted the research community for the existing serious privacy issues in current biomedical process workflows. Since sharing biomedical data is vital for the advancement of research and the improvement of medical healthcare, reconciling sharing with privacy assumes an overwhelming importance. In this thesis, we state the need for effective privacy-preserving measures for biomedical data processing, and study solutions for the problem in one of the harder contexts, genomics. The thesis focuses on the specific properties of the human genome that make critical parts of it privacy-sensitive and tries to prevent the leakage of such critical information throughout the several steps of the sequenced genomic data analysis and processing workflow. In order to achieve this goal, it introduces efficient and effective privacy-preserving mechanisms, namely at the level of reads filtering right upon sequencing, and alignment. Human individuals share the majority of their genome (99.5%), the remaining 0.5% being what distinguishes one individual from all others. However, that information is only revealed after two costly processing steps, alignment and variant calling, which today are typically run in clouds for performance efficiency, but with the corresponding privacy risks. Reaping the benefits of cloud processing, we set out to neutralize the privacy risks, by identifying the sensitive (i.e., discriminating) nucleotides in raw genomic data, and acting upon that. The first contribution is DNA-SeAl, a systematic classification of genomic data into different levels of sensitivity with regard to privacy, leveraging the output of a state-of-the-art automatic filter (SRF) isolating the critical sequences. The second contribution is a novel filtering approach, LRF, which undertakes the early protection of sensitive information in the raw reads right after sequencing, for sequences of arbitrary length (long reads), improving SRF, which only dealt with short reads. The last contribution proposed in this thesis is MaskAl, an SGX-based privacy-preserving alignment approach based on the filtering method developed. These contributions entailed several findings. The first finding of this thesis is the performance × privacy product improvement achieved by implementing multiple sensitivity levels. The proposed example of three sensitivity levels allows to show the benefits of mapping progressively sensitive levels to classes of alignment algorithms with progressively higher privacy protection (albeit at the cost of a performance tradeoff). In this thesis, we demonstrate the effectiveness of the proposed sensitivity levels classification, DNA-SeAl. Just by considering three levels of sensitivity and taking advantage of three existing classes of alignment algorithms, the performance of privacy-preserving alignment significantly improves when compared with state-of-the-art approaches. For reads of 100 nucleotides, 72% have low sensitivity, 23% have intermediate sensitivity, and the remaining 5% are highly sensitive. With this distribution, DNA-SeAl is 5.85× faster and it requires 5.85× less data transfers than the binary classification – two sensitivity levels. The second finding is the sensitive genomic information filtering improvement by replacing the per read classification with a per nucleotide classification. With this change, the filtering approach proposed in this thesis (LRF) allows the filtering of sequences of arbitrary length (long reads), instead of the classification limited to short reads provided by the state-of-the-art filtering approach (SRF). This thesis shows that around 10% of an individuals genome is classified as sensitive by the developed LRF approach. This improves the 60% achieved by the previous state of the art, the SRF approach. The third finding is the possibility of building a privacy-preserving alignment approach based on reads filtering. The sensitivity-adapted alignment relying on hybrid environments, in particular composed by common (e.g., public cloud) and trustworthy execution environments (e.g., SGX enclave cloud) in clouds, gets the best of both worlds: it enjoys the resource and performance optimization of cloud environments,while providing a high degree of protection to genomic data. We demonstrate that MaskAl is 87% faster than existing privacy-preserving alignment algorithms (Balaur), with similar privacy guarantees. On the other hand, Maskal is 58% slower compared to BWA, a highly efficient non-privacy preserving alignment algorithm. In addition, MaskAl requires less 95% of RAM memory and it requires between 5.7 GB and 15 GB less data transfers in comparison with Balaur. This thesis breaks new ground on the simultaneous achievement of two important goals of genomics data processing: availability of data for sharing; and privacy preservation. We hope to have shown that our work, being generalisable, gives a significant step in the direction of, and opens new avenues for, wider-scale, secure, and cooperative efforts and projects within the biomedical information processing life cycle. [less ▲]

Non-localized contact between beams with circular and elliptical cross-sections

Doctoral thesis (2020)

Numerous materials and structures are aggregates of slender bodies. We can, for example, refer to struts in metal foams, yarns in textiles, fibers in muscles or steel wires in wire ropes. To predict the ... [more ▼]

Numerous materials and structures are aggregates of slender bodies. We can, for example, refer to struts in metal foams, yarns in textiles, fibers in muscles or steel wires in wire ropes. To predict the mechanical performance of these materials and structures, it is important to understand how the mechanical load is distributed between the different bodies. If one can predict which slender body is the most likely to fail, changes in the design could be made to enhance its performance. As the aggregates of slender bodies are highly complex, simulations are required to numerically compute their mechanical behaviour. The most widely employed computational framework is the Finite Element Method in which each slender body is modeled as a series of beam elements. On top of an accurate mechanical representation of the individual slender bodies, the contact between the slender bodies must often be accurately modeled. In the past couple of decades, contact between beam elements has received wide-spread attention. However, the focus was mainly directed towards beams with circular cross-sections, whereas elliptical cross-sections are also relevant for numerous applications. Only two works have considered contact between beams with elliptical cross-sections, but they are limited to point-wise contact, which restricts their applicability. In this Ph.D. thesis, different frameworks for beams with elliptical cross-sections are proposed in case a point-wise contact treatment is insufficient. The thesis also reports a framework for contact scenarios where a beam is embedded inside another beam, which is in contrast to conventional contact frameworks for beams in which penetrating beams are actively repelled from each other. Finally, two of the three contact frameworks are enhanced with frictional sliding, where friction not only occurs due to sliding in the beams’ longitudinal directions but also in the transversal directions. [less ▲]

Condition assessment of bridge structures by damage localisation based on the DAD-method and close-range UAV photogrammetry

Doctoral thesis (2020)

The provided dissertation presents a so-called “Deformation Area Difference (DAD)” method for condition assessment of existing bridges, especially for the detection of stiffness-reducing damages. The ... [more ▼]

The provided dissertation presents a so-called “Deformation Area Difference (DAD)” method for condition assessment of existing bridges, especially for the detection of stiffness-reducing damages. The method is based on the one hand on conventional static load deflection experiments and on the other hand on a high-precision measurement of the structural deflection. The experimental load on the bridge should be generated within the serviceability limit state in order to enable a non-destructive inspection. In the course of the laboratory tests, the most innovative measuring techniques were applied, whereby the photogrammetry has delivered promising results. With the help of additional studies on the influences of camera quality and calibration, the measuring precision of photogrammetry could be brought to its limits. Both the theoretical investigations and the laboratory tests showed the successful use of the DAD method for the identification of local damages. Therefore, the first in-situ experiment was carried out on a single-span, prestressed bridge in Luxembourg. The knowledge gained from this was combined with statistical investigations based on finite element calculations and artificially generated measurement noise effect in order to determine the application limits, such as the achievable measurement precision, identifiable degree of damage, required number of measurement repetitions, influence of the damage position, optimal size of the structural deformation, etc. The development of the DAD method ready for application usefully supplements the state of the art and contributes to the reliable assessment of the bridge condition. [less ▲]

Reading in a Third Language and Grade Retention: A Longitudinal Study with Portuguese Immigrant Children in Luxembourg.

Doctoral thesis (2020)

ART LAUNDERING: PROTECTING CULTURAL HERITAGE THROUGH CRIMINAL LAW

Doctoral thesis (2020)

Improving the understanding of binge-watching behavior: An exploration of its underlying psychological processes

Doctoral thesis (2020)

The advent of the digital age with its progress in on-demand viewing technology has been associated in recent years with a dramatic increase in binge-watching (i.e., watching multiple episodes of TV ... [more ▼]

The advent of the digital age with its progress in on-demand viewing technology has been associated in recent years with a dramatic increase in binge-watching (i.e., watching multiple episodes of TV series in one session), to the point that this practice has now become the new normative way to consume TV shows. Nevertheless, along with its massive rise has come concerns about the associated mental and physical health outcomes, with initial studies even assuming its addictive nature. At a time when the psychological investigation of this behavior was only in its infancy, the current PhD thesis, therefore, aimed at improving the understanding of binge-watching, by clarifying the psychological processes involved in its development and maintenance. To this end, six empirical studies were conducted along two main research axes: 1) the conceptualization and assessment of binge-watching behaviors, and 2) the exploration of binge-watchers’ psychological characteristics. Study 1 consisted of a preliminary qualitative exploration of the phenomenological characteristics of binge-watching. Capitalizing on these pilot findings, Study 2 reported on the development and psychometric validation of two assessment instruments, measuring TV series watching motivations (“Watching TV Series Motives Questionnaire”, WTSMQ) and binge-watching engagement and symptoms (“Binge-Watching Engagement and Symptoms Questionnaire”, BWESQ). Finally, Study 3 aimed at cross-culturally validating the WTSMQ and BWESQ in nine languages (i.e., English, French, Spanish, Italian, German, Hungarian, Persian, Arabic, Chinese). Subsequent to this first line of investigation, Study 4 then explored potential binge-watchers’ subtypes by taking into consideration three key psychological factors, i.e. motivations for binge-watching, impulsivity traits, and emotional reactivity. Study 5 consisted of a pre-registered experimental study aimed at ascertaining differences on behavioral and self-reported impulsivity in non-problematic and problematic binge-watchers. Finally, Study 6 carried out the first systematic review of literature on binge-watching correlates. Beyond providing two theoretically and psychometrically sound binge-watching measures that may enable widespread expansion of international research on the topic, this doctoral research also allowed for important insights into the heterogeneous and complex nature of binge-watching, as well as into the understanding of its underlying psychological mechanisms. Centrally, by revealing that high – but healthy – and problematic engagement in binge-watching are underlined by distinct motivational and dispositional psychological processes, the overall findings of this PhD thesis bring an alternative etiological comprehension of problematic binge-watching as a maladaptive coping or emotional regulation strategy to deal with negative affect states. [less ▲]

DESIGN AND OPTIMIZATION OF SIMULTANEOUS WIRELESS INFORMATION AND POWER TRANSFER SYSTEMS

Doctoral thesis (2020)

The recent trends in the domain of wireless communications indicate severe upcoming challenges, both in terms of infrastructure as well as design of novel techniques. On the other hand, the world ... [more ▼]

The recent trends in the domain of wireless communications indicate severe upcoming challenges, both in terms of infrastructure as well as design of novel techniques. On the other hand, the world population keeps witnessing or hearing about new generations of mobile/wireless technologies within every half to one decade. It is certain the wireless communication systems have enabled the exchange of information without any physical cable(s), however, the dependence of the mobile devices on the power cables still persist. Each passing year unveils several critical challenges related to the increasing capacity and performance needs, power optimization at complex hardware circuitries, mobility of the users, and demand for even better energy efficiency algorithms at the wireless devices. Moreover, an additional issue is raised in the form of continuous battery drainage at these limited-power devices for sufficing their assertive demands. In this regard, optimal performance at any device is heavily constrained by either wired, or an inductive based wireless recharging of the equipment on a continuous basis. This process is very inconvenient and such a problem is foreseen to persist in future, irrespective of the wireless communication method used. Recently, a promising idea for simultaneous wireless radio-frequency (RF) transmission of information and energy came into spotlight during the last decade. This technique does not only guarantee a more flexible recharging alternative, but also ensures its co-existence with any of the existing (RF-based) or alternatively proposed methods of wireless communications, such as visible light communications (VLC) (e.g., Light Fidelity (Li-Fi)), optical communications (e.g., LASER-equipped communication systems), and far-envisioned quantum-based communication systems. In addition, this scheme is expected to cater to the needs of many current and future technologies like wearable devices, sensors used in hazardous areas, 5G and beyond, etc. This Thesis presents a detailed investigation of several interesting scenarios in this direction, specifically concerning design and optimization of such RF-based power transfer systems. The first chapter of this Thesis provides a detailed overview of the considered topic, which serves as the foundation step. The details include the highlights about its main contributions, discussion about the adopted mathematical (optimization) tools, and further refined minutiae about its organization. Following this, a detailed survey on the wireless power transmission (WPT) techniques is provided, which includes the discussion about historical developments of WPT comprising its present forms, consideration of WPT with wireless communications, and its compatibility with the existing techniques. Moreover, a review on various types of RF energy harvesting (EH) modules is incorporated, along with a brief and general overview on the system modeling, the modeling assumptions, and recent industrial considerations. Furthermore, this Thesis work has been divided into three main research topics, as follows. Firstly, the notion of simultaneous wireless information and power transmission (SWIPT) is investigated in conjunction with the cooperative systems framework consisting of single source, multiple relays and multiple users. In this context, several interesting aspects like relay selection, multi-carrier, and resource allocation are considered, along with problem formulations dealing with either maximization of throughput, maximization of harvested energy, or both. Secondly, this Thesis builds up on the idea of transmit precoder design for wireless multigroup multicasting systems in conjunction with SWIPT. Herein, the advantages of adopting separate multicasting and energy precoder designs are illustrated, where we investigate the benefits of multiple antenna transmitters by exploiting the similarities between broadcasting information and wirelessly transferring power. The proposed design does not only facilitates the SWIPT mechanism, but may also serve as a potential candidate to complement the separate waveform designing mechanism with exclusive RF signals meant for information and power transmissions, respectively. Lastly, a novel mechanism is developed to establish a relationship between the SWIPT and cache-enabled cooperative systems. In this direction, benefits of adopting the SWIPT-caching framework are illustrated, with special emphasis on an enhanced rate-energy (R-E) trade-off in contrast to the traditional SWIPT systems. The common notion in the context of SWIPT revolves around the transmission of information, and storage of power. In this vein, the proposed work investigates the system wherein both information and power can be transmitted and stored. The Thesis finally concludes with insights on the future directions and open research challenges associated with the considered framework. [less ▲]

Urban Green Amenity and City Structure

Doctoral thesis (2020)

One of the main components that make cities attractive to their residents is their public park and garden systems. Green urban areas from a small community garden to famous areas such as `Jardin du ... [more ▼]

One of the main components that make cities attractive to their residents is their public park and garden systems. Green urban areas from a small community garden to famous areas such as `Jardin du Luxembourg' in Paris not only shape the face of the city but are a quintessential aspect of the quality of life for local inhabitants. They offer places for local recreation, beautiful views, cleaner air and many other advantages. Recent research has validated the connection between urban parks and the well-being of the city's inhabitants. Although green urban areas might seem to be meagre in comparison with other natural ecosystems such as wetlands or forests, the value of the environmental, recreational, and other services they offer is likely to be disproportionally high due to their strategic locations. This dissertation focuses on studying the optimal provision of green urban areas and the welfare effects of a substantial change in green provision policies in the presence of other types of land uses and adverse shocks. It comprises four papers (chapters). [less ▲]

A Defence of Moral Revisionism

Doctoral thesis (2020)

This dissertation examines the implications of J. L. Mackie’s moral error theory. Rather than attempting to prove that moral error theory is true, I analyze the responses to moral error theory, in order ... [more ▼]

This dissertation examines the implications of J. L. Mackie’s moral error theory. Rather than attempting to prove that moral error theory is true, I analyze the responses to moral error theory, in order to highlight the various problems that arise when we believe that there are no moral facts. Some of the problems for moral error theorists relate to moral language, moral attitudes and moral desert. The positions that I analyze include: moral fictionalism, moral conservationism, moral negotiationism, moral conversionism, moral propagandism and various forms of weak and strong abolitionism. Ultimately, I conclude that the responses that have been offered thus far have been problematic. In addition to explaining all of the established responses to moral error theory, I offer my own response, called moral revisionism. Moral revisionism is a version of weak abolitionism that recommends abolishing moral attitudes. It also recommends reframing moral discourse into a discourse based on the satisfaction of desires. As such, it is heavily dependent on hypothetical imperatives. Even though moral error theory poses numerous challenges, I argue that these challenges are not insurmountable, if we adopt moral revisionism. Moreover, a society that adopts moral revisionism could be even more instrumentally valuable than a moral one. [less ▲]

SOCIAL CLAUSES IN OUTSOURCING PROCESSES. SOCIAL RIGHTS VERSUS ECONOMIC FREEDOMS IN THE PRISM OF THE MULTILEVEL LEGAL ORDER

Doctoral thesis (2020)

The aim of the thesis is to study the different provisions included in the notion of social clause and offer an in-depth and systematic analysis of some types of social clauses in the Italian and European ... [more ▼]

The aim of the thesis is to study the different provisions included in the notion of social clause and offer an in-depth and systematic analysis of some types of social clauses in the Italian and European Union legal order, their characteristics, their regulation, and the legal interests that are aimed at protecting, as well as their classification in the multilevel legal order. This study is preliminary for the assessment on the legitimacy of such clauses in relation to economic freedoms. Indeed, the application of social clauses is one of the fields in which the contrast between fundamental social rights and economic freedoms emerges most clearly and in relation to which some differences occur in the reconciliation of interests made by the Courts at national and EU level. The most relevant distinction for this research relies on the classification developed by Italian scholars, who, on the basis of contents and interests protected by social clauses, usually distinguish between equal treatment or first-generation social clauses and rehiring or second-generation social clauses. Also the nature of the procurement contract, public or private, may condition the judgment on the legitimacy of social clauses with regard to economic freedoms, due to the different regulations applicable in the two fields and the tension between the protection of competition and social objectives, which historically characterizes the action of the public administration in the field of public procurements. The thesis investigates the legislation and the case law concerning the first- and second-generation social clauses, both statutory and contractual, at European and Italian level, with reference to public and private procurements. From this study, it is clear that there are problems of effectiveness and applicability concerning first- and second-generation social clauses, as well as of conflicting interests: social clauses may hinder the competition, negatively condition the entrepreneur’s freedom to conduct a business, affect the entrepreneurs’ freedom of association, and, therefore, risk to contrast with the constitutional and European provisions protecting those freedoms. In this reasoning, the different levels of protection and the importance recognised to social rights and economic freedoms in the Italian and European Union legal systems, the legal framework generated by their interaction, and the type of balancing in the two legal orders must be considered. In the search for a reasonable balance between economic freedoms and social rights, the thesis explores whether the various interests protected by the different types of social clauses can fall within that notion of employment protection which constitutes an overriding reason relating to the public interest justifying a limitation of the economic freedoms and investigates to what extent the prevention of unfair competition and social dumping, the protection of workers’ rights and employment stability can justify a restriction of fundamental economic freedoms. In conclusion, the aim of the study is to investigate if it is possible to achieve a fair balance between opposing interests, social rights, on the one hand, and economic freedoms and free competition, on the other, and comprehend how the interests contrasting with them in relation to the case of social clauses can be balanced. [less ▲]

National Banking Law in the European Single Supervisory Mechanism

Doctoral thesis (2020)

In 2013, the European Central Bank acquired the competence to apply national banking law in a direct manner to banks established in the euro area, as part of its supervisory competence under the Single ... [more ▼]

In 2013, the European Central Bank acquired the competence to apply national banking law in a direct manner to banks established in the euro area, as part of its supervisory competence under the Single Supervisory Mechanism. This marks the first instance of direct administration of national law by a European institution. The thesis scrutinises the salient features as well as the strengths and weaknesses of this new administrative system in the landscape of European Union law. [less ▲]

PERFORMANCE EVALUATION AND MODELLING OF SAAS WEB SERVICES IN THE CLOUD

Doctoral thesis (2020)

This thesis studies the problem of performance evaluation and assurance of communications and services quality in cloud computing. The cloud computing paradigm has significantly changed the way of doing ... [more ▼]

This thesis studies the problem of performance evaluation and assurance of communications and services quality in cloud computing. The cloud computing paradigm has significantly changed the way of doing business. With cloud computing, companies and end-users can access the vast majority of services online through a virtualized environment. The main three services typically consumed by cloud users are Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). Cloud Services Providers (CSPs) deliver cloud services to cloud customers on a pay-per-use model while the quality of the provided services is defined using Service Level Agreements (SLAs). Unfortunately, there is no standard mechanism which exists to verify and assure that delivered services satisfy the signed SLA agreement in an automatic way, which impedes the possibility to measure accurately the Quality of Service (QoS). In this context, this thesis aims at offering an automatic framework to evaluate the QoS and SLA compliance of Web Services (WSs) offered across several CSPs. Yet unlike other approaches, the framework aims at quantifying in a fair and by stealth way the performance and scalability of the delivered WS. By stealthiness, it refers to the capacity of evaluating a given Cloud service through multiple workload patterns that makes them indistinguishable from regular user traffic from the provider point of view. This thesis work is motivated by recent scandals in the automotive sector, which demonstrate the capacity of solution providers to adapt to the behavior of their product when submitted to an evaluation campaign to improve the performance results. The framework defines a set of Common performance metrics handled by a set of agents within customized clients for measuring the behavior of cloud applications on top of a given CSP. Once modeled accurately, the agent behavior can be dynamically adapted to hide the true nature of the framework client to the CSP. In particular, the following contributions are proposed: • A new framework of performance metrics for communication systems of cloud computing SaaS. The proposed framework evaluates and classifies in a fair and stealth way the performance and scalability of the delivered WS across multiple CSPs. • Analysis of the performance metrics for the cloud SaaS Web Service (WS) by analyzing all the possible metrics which could be used to evaluate and monitor the behavior of the cloud applications. • Benchmarking the cloud SaaS applications and web services by using referenced benchmarking tools and frameworks. • Modeling the SaaS WS by providing a set of Gaussian models. These models can be used to help the other researchers to generate data representing the CSP’s behavior under a high load and under the normal usage in just a couple of minutes without any experiments. • A novel optimization model to obfuscate the testing from the CSP and to achieve stealthiness. The optimization process relies on meta-heuristic and machine learning algorithms, such as Genetic Algorithm and Gaussian Process Regression accordingly. • A virtual QoS aggregator and SLA checker which takes care of evaluating the QoS and SLA compliance of the WS offered across the considered CSPs. • Ranking multiple CSPs based on multi-criteria decision analysis. [less ▲]

Machine Learning-based Methods for Driver Identification and Behavior Assessment: Applications for CAN and Floating Car Data

Doctoral thesis (2020)

The exponential growth of car generated data, the increased connectivity, and the advances in artificial intelligence (AI), enable novel mobility applications. This dissertation focuses on two use-cases ... [more ▼]

The exponential growth of car generated data, the increased connectivity, and the advances in artificial intelligence (AI), enable novel mobility applications. This dissertation focuses on two use-cases of driving data, namely distraction detection and driver identification (ID). Low and medium-income countries account for 93% of traffic deaths; moreover, a major contributing factor to road crashes is distracted driving. Motivated by this, the first part of this thesis explores the possibility of an easy-to-deploy solution to distracted driving detection. Most of the related work uses sophisticated sensors or cameras, which raises privacy concerns and increases the cost. Therefore a machine learning (ML) approach is proposed that only uses signals from the CAN-bus and the inertial measurement unit (IMU). It is then evaluated against a hand-annotated dataset of 13 drivers and delivers reasonable accuracy. This approach is limited in detecting short-term distractions but demonstrates that a viable solution is possible. In the second part, the focus is on the effective identification of drivers using their driving behavior. The aim is to address the shortcomings of the state-of-the-art methods. First, a driver ID mechanism based on discriminative classifiers is used to find a set of suitable signals and features. It uses five signals from the CAN-bus, with hand-engineered features, which is an improvement from current state-of-the-art that mainly focused on external sensors. The second approach is based on Gaussian mixture models (GMMs), although it uses two signals and fewer features, it shows improved accuracy. In this system, the enrollment of a new driver does not require retraining of the models, which was a limitation in the previous approach. In order to reduce the amount of training data a Triplet network is used to train a deep neural network (DNN) that learns to discriminate drivers. The training of the DNN does not require any driving data from the target set of drivers. The DNN encodes pieces of driving data to an embedding space so that in this space examples of the same driver will appear closer to each other and far from examples of other drivers. This technique reduces the amount of data needed for accurate prediction to under a minute of driving data. These three solutions are validated against a real-world dataset of 57 drivers. Lastly, the possibility of a driver ID system is explored that only uses floating car data (FCD), in particular, GPS data from smartphones. A DNN architecture is then designed that encodes the routes, origin, and destination coordinates as well as various other features computed based on contextual information. The proposed model is then evaluated against a dataset of 678 drivers and shows high accuracy. In a nutshell, this work demonstrates that proper driver ID is achievable. The constraints imposed by the use-case and data availability negatively affect the performance; in such cases, the efficient use of the available data is crucial. [less ▲]

SYMBOL LEVEL PRECODING TECHNIQUES FOR HARDWARE AND POWER EFFICIENT WIRELESS TRANSCEIVERS

Doctoral thesis (2020)

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing ... [more ▼]

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing antenna arrays of few elements. However, the large number of antenna elements leads to a big increase in power consumption of conventional fully digital transceivers due to the one Radio Frequency (RF) chain / per antenna element requirement. The RF chains include a number of different components among which are the Digital-to-Analog Converters (DACs)/Analog-to-Digital Converters (ADCs) that their power consumption increases exponential with the resolution they support. Motivated by this, in this thesis, a number of different architectures are proposed with the view to reduce the power consumption and the hardware complexity of the transceiver. In order to optimize the transmission of data through them, corresponding symbol level precoding (SLP) techniques were developed for the proposed architectures. SLP is a technique that mitigates multi-user interference (MUI) by designing the transmitted signals using the Channel State Information and the information-bearing symbols. The cases of both frequency flat and frequency selective channels were considered. First, three different power efficient transmitter designs for transmission over frequency flat channels and their respective SLP schemes are considered. The considered systems tackle the high hardware complexity and power consumption of existing SLP techniques by reducing or completely eliminating fully digital RF chains. The precoding design is formulated as a constrained least squares problem and efficient algorithmic solutions are developed via the Coordinate Descent method. Next, the case of frequency selective channels is considered. To this end, Constant Envelope precoding in a Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing system (CE MIMO-OFDM) is considered. In CE MIMO-OFDM the transmitted signals for each antenna are designed to have constant amplitude regardless of the channel realization and the information symbols that must be conveyed to the users. This facilitates the use of power-efficient components, such as phase shifters and non-linear power amplifiers. The precoding problem is firstly formulated as a least-squares problem with a unit-modulus constraint and solved using an algorithm based on the coordinate descent (CCD) optimization framework and then, after reformulating the problem into an unconstrained non-linear least squares problem, a more computationally efficient solution using the Gauss-Newton algorithm is presented. Then, CE MIMO-OFDM is considered for a system with low resolution DACs. The precoding design problem is formulated as a mixed discrete- continuous least-squares optimization one which is NP-hard. An efficient low complexity solution is developed based also on the CCD optimization framework. Finally, a precoding scheme is presented for OFDM transmission in MIMO systems based on one-bit DACs and ADCs at the transmitter’s and the receiver’s end, respectively, as a way to reduce the total power consumption. The objective of the precoding design is to mitigate the effects of one-bit quantization and the problem is formulated and then is split into two NP hard least squares optimization problems. Algorithmic solutions are developed for the solution of the latter problems, based on the CCD framework. [less ▲]

Commercial Radio Stations and their Dispositif. Transnational and Intermedial Perspectives on Radio Luxembourg and Europe n°1 in the Long Sixties.

Doctoral thesis (2020)

Commercial radio stations Radio Luxembourg (French and English services) and Europe n°1 are the focal point of this work. They were popular institutions in Western Europe throughout the Long Sixties (1958 ... [more ▼]

Commercial radio stations Radio Luxembourg (French and English services) and Europe n°1 are the focal point of this work. They were popular institutions in Western Europe throughout the Long Sixties (1958-1974) working across media and broadcasting transnationally. This thesis postulates the existence of an overarching dispositif of commercial radio stations that enabled them to operate on various dimensions and differentiated them from other broadcasters. The research conducted in this thesis leans on various historical sources (i.e. institutional archives, maps, radio programmes, magazines) to analyse the dispositif through three main lenses. The first lens focuses on the appropriation and representation by the stations of a transnational broadcasting space, thanks to institutional archives and maps. The second inquires into the construction of a soundscape of commercial radio and identifies its key features by a close study and thick description of recordings as source material. Magazines - namely Salut les Copains and Fabulous 208 - are the core sources of the third lens, which studies the intermedial and intertextual entanglements of Europe n°1 and Radio Luxembourg with other media. This thesis relies on various scales and multiple dimensions of radio - such as its materiality, content, significance, and commercialism - to conduct an historical analysis on a particularly diverse source material. Building on the empirical results obtained throughout the research, this thesis shows the relevance of the dispositif concept to encompass and explains the transnational and intermedial nature of commercial radio stations. By doing so, the thesis contributes to current calls in media history to look beyond national and single-medium borders. [less ▲]

Modelling And Control Of Aerial Manipulators Considering Aerodynamic Effects

Doctoral thesis (2020)

Essays on Networks, Information Economics, and Dynamic Games of Populism and Conflict

Doctoral thesis (2020)

This thesis focuses on developing tools and models for studying strategic interaction among agents in dynamics games. This dissertation consists of one pure theory paper and two applied theory papers. The ... [more ▼]

This thesis focuses on developing tools and models for studying strategic interaction among agents in dynamics games. This dissertation consists of one pure theory paper and two applied theory papers. The first chapter develops a general result in differential games. This is an area for studying strategic interactions when agents are forward-looking and calculate their future strategic interactions. The second and third chapters deal with the problem of strategic interactions under incomplete information, in the context of networks. In the second chapter, the analytical tools for linking up strategic actions with the evolution of a network are developed. The last chapter extends the second chapter by recommending network-manager strategies that can lead to welfare-improving network evolution under incomplete information. The thesis presents the first studies to propose a search and matching mechanism of network friends in an environment of incomplete information, higher-order beliefs, and evolutionary dynamics. [less ▲]

Migration as a topic of Italian lyric poetry from Luxembourg in the second half of the 20th century and beyond

Doctoral thesis (2020)

Deep Pattern Mining for Program Repair

Doctoral thesis (2019)

Error-free software is a myth. Debugging thus accounts for a significant portion of software maintenance and absorbs a large part of software cost. In particular, the manual task of fixing bugs is tedious ... [more ▼]

Error-free software is a myth. Debugging thus accounts for a significant portion of software maintenance and absorbs a large part of software cost. In particular, the manual task of fixing bugs is tedious, error- prone and time-consuming. In the last decade, automatic bug-fixing, also referred to as automated program repair (APR) has boomed as a promising endeavor of software engineering towards alleviating developers’ burden. Several potentially promising techniques have been proposed making APR an increasingly prominent topic in both the research and practice communities. In production, APR will drastically reduce time-to-fix delays and limit downtime. In a development cycle, APR can help suggest changes to accelerate debugging. As an emergent domain, however, program repair has many open problems that the community is still exploring. Our work contributes to this momentum on two angles: the repair of programs for functionality bugs, and the repair of programs for method naming issues. The thesis starts with highlighting findings on key empirical studies that we have performed to inform future repair approaches. Then, we focus on template-based program repair scenarios and explore deep learning models for inferring accurate and relevant patterns. Finally, we integrate these patterns into APR pipelines, which yield the state of the art repair tools. The dissertation includes the following contributions: • Real-world Patch Study: Existing APR studies have shown that the state-of-the-art techniques in automated repair tend to generate patches only for a small number of bugs even with quality issues (e.g., incorrect behavior and nonsensical changes). To improve APR techniques, the community should deepen its knowledge on repair actions from real-world patches since most of the techniques rely on patches written by human developers. However, previous investigations on real-world patches are limited to statement level that is not sufficiently fine-grained to build this knowledge. This dissertation starts with deepening this knowledge via a systematic and fine-grained study of real-world Java program bug fixes. • Fault Localization Impact: Existing test-suite-based APR systems are highly dependent on the performance of the fault localization (FL) technique that is the process of the widely studied APR pipeline. However, APR systems generally focus on the patch generation, but tend to use similar but different strategies for fault localization. To assess the impact of FL on APR, we identify and investigate a practical bias caused by the FL step in a repair pipeline. We propose to highlight the different FL configurations used in the literature, and their impact on APR systems when applied to the real bugs. Then, we explore the performance variations that can be achieved by “tweaking” the FL step. • Fix Pattern Mining: Fix patterns (a.k.a. fix templates) have been studied in various APR scenarios. Particularly, fix patterns have been widely used in different APR systems. To date, fix pattern mining is mainly studied in three ways: manually summarization, transformation inferring and code change action statistics. In this dissertation, we explore mining fix patterns for static bugs leveraging deep learning and clustering algorithms. • Avatar: Fix pattern based patch generation is a promising direction in the APR community. Notably, it has been demonstrated to produce more acceptable and correct patches than the patches obtained with mutation operators through genetic programming. The performance of fix pattern based APR systems, however, depends on the fix ingredients mined from commit changes in development histories. Unfortunately, collecting a reliable set of bug fixes in repositories can be challenging. We propose to investigate the possibility in an APR scenario of leveraging code changes that address violations by static bug detection tools. To that end, we build the Avatar APR system, which exploits fix patterns of static analysis violations as ingredients for patch generation. • TBar: Fix patterns are widely used in patch generation of APR, however, the repair performance of a single fix pattern is not studied. We revisit the performance of template-based APR to build comprehensive knowledge about the effectiveness of fix patterns, and to highlight the importance of complementary steps such as fault localization or donor code retrieval. To that end, we first investigate the literature to collect, summarize and label recurrently-used fix patterns. Based on the investigation, we build TBar, a straightforward APR tool that systematically attempts to apply these fix patterns to program bugs. We thoroughly evaluate TBar on the Defects4J benchmark. In particular, we assess the actual qualitative and quantitative diversity of fix patterns, as well as their effectiveness in yielding plausible or correct patches. • Debugging Method Names: Except the issues about semantic/static bugs in programs, we note that how to debug inconsistent method names automatically is important to improve program quality. In this dissertation, we propose a deep learning based approach to spotting and refactoring inconsistent method names in programs. [less ▲]

Architectures of bureaucracy: An architectural and political history of ministerial offices in Belgium, 1915-1940

Doctoral thesis (2019)

IMPROVEMENT OF THE LOAD-BEARING CAPACITY OF DRY-STACKED MASONRY

Doctoral thesis (2019)

Mortar bonded masonry is one of the oldest construction technics traditionally used around the world. However, dry-stacked masonry (DSM) is a competitive system that confers significant assets to masonry ... [more ▼]

Mortar bonded masonry is one of the oldest construction technics traditionally used around the world. However, dry-stacked masonry (DSM) is a competitive system that confers significant assets to masonry in the sense that, concisely, it saves construction time, requires less skill labourers and ease the construction as well as the de-construction. Despite all this major benefits, the current use of DSM is hindered by the geometric imperfections of the block units and the lack of adapted design codes. Indeed, the block geometric imperfections, i.e. the bed-joint roughness and the height difference, cause a significant uneven load-distribution in DSM, which generally leads to a premature cracking and a drop of the wall compressive strength. On the other hand, the lack of adapted design codes entail significant safety hazards in the construction of such masonry walls. In view of the foregoing, through systematic numerical, experimental and analytical investigations, the present thesis aims to analyse the impacts of the block bed-joint imperfections on the mechanical response of DSM axially loaded. Furthermore, the current thesis aims to develop a strategy to overcome the block geometric imperfections and alleviate its impacts on the load-bearing capacity of DSM. Finally, the present thesis intends to develop a design model for predicting the load-bearing capacity of DSM, while taking into account the effects of the block geometric imperfections for a safe design. First of all, at the beginning of the research project, a new dry-stacked masonry block is designed and labelled ‘M-Block’. The impact of the bed-joint roughness and the block height variation on the stress distribution in a DSM is analysed through numerical modelling. It is shown that the block height difference yields five potential load cases that block units may suffer upon the axial compression of a DSM wall. Accordingly, it is also shown that a nominal DSM wall can exhibit different load percolation paths and different damages. Further, a strategy is presented to overcome the bed-joint imperfections, increase the actual contact area in the bed-joints and ultimately improve the load-bearing capacity of DSM, by adding a material layer (the ‘contact layer’) on the raw DSMb. The capacity of the contact layer to increase the actual contact and level the stress distribution was first investigated through numerical models then evidenced through experimental tests on masonry triplets. The contact layer was also investigated for improving the load-bearing capacity of dry-stacked masonry, with satisfactory results obtained on wallets tested in the lab. As the finite element modelling is cumbersome and the experimental investigations onerous and laborious, an analytical model has then been developed for predicting the load-bearing capacity of DSM. A statistical modelling has been developed for determining a factor δh, which stands for the reduction of the nominal section of a DSM generated by the block height variation. Experimental tests were also performed on masonry triplets for measuring the ultimate actual contact in the bed-joints and defining a factor δr, which stands for the reduction of the nominal contact area generated by the block bed-joint roughness. The two defined parameters were then exploited to establish the design model that takes into account the block imperfections in the prediction of the load-bearing capacity of DSM. The design model was shown quite well capable of predicting the load-bearing capacity of DSM with a mean accuracy of 93% - 106% and a standard deviation of 12% - 10%. [less ▲]

Assessment of Fundamental Motives

Doctoral thesis (2019)

Motivation, that is, the orientation of the momentary execution of life towards a positively evaluated target state (Rheinberg & Vollmeyer, 2012), is one of the most important psychological constructs ... [more ▼]

Motivation, that is, the orientation of the momentary execution of life towards a positively evaluated target state (Rheinberg & Vollmeyer, 2012), is one of the most important psychological constructs related to success in various life domains such as school, work or family life (Pellegrino & Hilton, 2013). To be able to provide guidance to people and to support them in achieving success in these life domains, it is essential to identify those motivational aspects that are relevant for the respective life domain and to make them assessable. Here, motivational aspects that are inherent in a person, such as motives or goals, are promising candidates. Both constructs can be defined as explicit cognitive representations of desirable end states (Brandstätter, Schüler, Puca, & Lozo, 2013; Karoly, 1999). However, motives and goals are distinguished at the level of abstraction, that is, goals are a concrete representation of more abstract motives (Elliot & Church, 1997). In order to broaden our understanding in the assessment of motives and goals that are of relevance for education and work as two of the most important life domains, three studies were conducted in the context of the presented dissertation. In Paper 1, we revised the theory of Fundamental Motives (Havercamp, 1998; Reiss & Havercamp, 1998) and developed a time- and cost-efficient questionnaire to assess them in research settings. Fundamental Motives are a self-contained framework of 16 motives considered to be relevant for people in their everyday lives. The framework is appealing as it provides an approach to narrow down the plethora of motives to those relevant in a variety of life domains. In addition, the framework is already used extensively in coaching for work and other areas of life (Reyss & Birkhahn, 2009). First, an initial item pool was successively refined into 16 scales with three items each (named 16 motives research scales; 16mrs) across two samples with a total sample size of N = 569 representative for the German population with respect to age, sex and education. Second, we used another representative sample (N = 999) to validate the questionnaire and explore its nomological network. Results support the reliability and validity of the 16mrs for the assessment of Fundamental Motives. Investigations of the nomological network indicate, that Fundamental Motives represent aspects of personality that are different from the Big Five personality traits (e.g., Costa & McCrae, 1992) and cover motivational aspects beyond the well-established Power, Achievement, Affiliation, Intimacy, and Fear motives (Heckhausen & Heckhausen, 2010). Paper 2 was based on the results of Study 1, since we applied the framework of Fundamental Motives, as measured by the 16mrs constructed in Study 1, to the life domain of work. In coaching in work contexts, Fundamental Motives have been used extensively, not least because of their fine-grained level of abstraction that allows for a straightforward interpretation by the client. By investigating how the satisfaction of fine-grained motives supplied by characteristics of the workplace (i.e., need-supply fit) contribute to job satisfaction, we further validated the framework itself. At the same time were able to gain more detailed insights into how need-supply fit impacts job satisfaction, compared to broader motive or value clusters. To this end, we used the representative sample from Study 1 (N = 999) and selected all working people (n = 723). We applied polynomial regression in combination with response surface analysis (e.g., Edwards & Parry, 1993), which allows to simultaneously investigate how different levels of Fundamental Motives on the one hand and different levels of supply to satisfy these motives at the workplace on the other contribute to job satisfaction. We found that job satisfaction was highest when the level of supply by the workplace exceeded the level of the motive for Social Acceptance, Status, Autonomy, Sex, and Retention motives. When a high level of the motive and a high level of supply met, job satisfaction was highest for Curiosity, Idealism, and Social Participation motives. When the supplies fell short compared to the level of the motive, job satisfaction was negatively affected by the need-supply fit of Social Acceptance, Status, Sex, Retention, Curiosity, and Idealism motives. The results can be used in coaching and career development to uncover potential causes of low job satisfaction and provide guidance to clients on how to enhance their job satisfaction. In Paper 3, we shifted the focus to education as another major life domain. Here, achievement motivation has been identified as one of the major driving forces for progression and success (Schiefele & Schaffner, 2015). On a more concrete level compared to achievement motivation, Achievement Goals have been established as students’ cognitive representations of desired and undesired end states in educational achievement contexts (Elliot & Thrash, 2002; Hulleman, Schrager, Bodmann, & Harackiewicz, 2010). These goals typically focus on mastery, that is learning as much as possible, and performance, that is outperforming others or avoiding being outperformed. So far, Achievement Goals have been mostly conceptualized as domain-specific (Bong, 2001). Although this assumption is supported by previous studies, research on the processes operating behind the domain- specificity is scarce. The dimensional comparisons theory (Möller & Marsh, 2013) has introduced dimensional comparisons as a potential process operating behind the domain- specificity. Dimensional comparisons describe intrapersonal comparisons of characteristics in a domain with characteristics in another domain for the sake of self-evaluation. Previous investigations indicated that dimensional comparison processes are involved in the formation of the domain-specificity of important educational constructs, such as Self-Concept or Test Anxiety. Consequently, our aim in study 3 was to investigate, if dimensional comparison processes operate in the formation of the domain-specificity of Achievement Goals. To this end, we used a sample of N = 381 German ninth and tenth grade students in six German highest-track schools. Results indicate that dimensional comparison processes impact the domain specificity of Achievement Goals. Thus, the results extend our understanding of the domain specificity of Achievement Goals and simultaneously add to the validity of the dimensional comparison theory. In conclusion, the presented scientific work adds to the assessment of motives and goals that are crucially important in various life domains, but especially in work and educational settings. The contributions of this dissertation to the existing literature include (1) the revision of a comprehensive motivational framework (Paper 1), (2) the development and validation of a questionnaire based on this revised framework (Papers 1 & 2), (3) important assessment related insights concerning Achievement Goals in educational settings (Paper 3), and (4) practical implications for coaching and interventions in work and educational settings as two of the most important life domains (Papers 2 & 3). [less ▲]

Graph-based Algorithms for Smart Mobility Planning and Large-scale Network Discovery

Doctoral thesis (2019)

Graph theory has become a hot topic in the past two decades as evidenced by the increasing number of citations in research. Its applications are found in many fields, e.g. database, clustering, routing ... [more ▼]

Graph theory has become a hot topic in the past two decades as evidenced by the increasing number of citations in research. Its applications are found in many fields, e.g. database, clustering, routing, etc. In this thesis, two novel graph-based algorithms are presented. The first algorithm finds itself in the thriving carsharing service, while the second algorithm is about large graph discovery to unearth the unknown graph before any analyses can be performed. In the first scenario, the automatisation of the fleet planning process in carsharing is proposed. The proposed work enhances the accuracy of the planning to the next level by taking an advantage of the open data movement such as street networks, building footprints, and demographic data. By using the street network (based on graph), it solves the questionable aspect in many previous works, feasibility as they tended to use rasterisation to simplify the map, but that comes with the price of accuracy and feasibility. A benchmark suite for further research in this problem is also provided. Along with it, two optimisation models with different sets of objectives and contexts are proposed. Through a series of experiment, a novel hybrid metaheuristic algorithm is proposed. The algorithm is called NGAP, which is based on Reference Point based Non-dominated Sorting genetic Algorithm (NSGA-III) and Pareto Local Search (PLS) and a novel problem specific local search operator designed for the fleet placement problem in carsharing called Extensible Neighbourhood Search (ENS). The designed local search operator exploits the graph structure of the street network and utilises the local knowledge to improve the exploration capability. The results show that the proposed hybrid algorithm outperforms the original NSGA-III in convergence under the same execution time. The work in smart mobility is done on city scale graphs which are considered to be medium size. However, the scale of the graphs in other fields in the real-world can be much larger than that which is why the large graph discovery algorithm is proposed as the second algorithm. To elaborate on the definition of large, some examples are required. The internet graph has over 30 billion nodes. Another one is a human brain network contains around 1011 nodes. Apart of the size, there is another aspect in real-world graph and that is the unknown. With the dynamic nature of the real-world graphs, it is almost impossible to have a complete knowledge of the graph to perform an analysis that is why graph traversal is crucial as the preparation process. I propose a novel memoryless chaos-based graph traversal algorithm called Chaotic Traversal (CHAT). CHAT is the first graph traversal algorithm that utilises the chaotic attractor directly. An experiment with two well-known chaotic attractors, Lozi map and Rössler system is conducted. The proposed algorithm is compared against the memoryless state-of-the-art algorithm, Random Walk. The results demonstrate the superior performance in coverage rate over Random Walk on five tested topologies; ring, small world, random, grid and power-law. In summary, the contribution of this research is twofold. Firstly, it contributes to the research society by introducing new study problems and novel approaches to propel the advance of the current state-of-the-art. And Secondly, it demonstrates a strong case for the conversion of research to the industrial sector to solve a real-world problem. [less ▲]

Polemik ante portas? Die Regierung "Thorn" im synchronen Spiegel von Luxemburger Wort und Tageblatt. Eine diskurslinguistische und -ethische Untersuchung

Doctoral thesis (2019)

TOWARDS A MODELLING FRAMEWORK WITH TEMPORAL AND UNCERTAIN DATA FOR ADAPTIVE SYSTEMS

Doctoral thesis (2019)

Self-Adaptive Systems (SAS) optimise their behaviours or configurations at runtime in response to a modification of their environments or their behaviours. These systems therefore need a deep ... [more ▼]

Self-Adaptive Systems (SAS) optimise their behaviours or configurations at runtime in response to a modification of their environments or their behaviours. These systems therefore need a deep understanding of the ongoing situation which enables reasoning tasks for adaptation operations. Using the model-driven engineering (MDE) methodology, one can abstract this situation. However, information concerning the system is not always known with absolute confidence. Moreover, in such systems, the monitoring frequency may differ from the delay for reconfiguration actions to have measurable effects. These characteristics come with a global challenge for software engineers: how to represent uncertain knowledge that can be efficiently queried and to represent ongoing actions in order to improve adaptation processes? To tackle this challenge, this thesis defends the need for a unified modelling framework which includes, besides all traditional elements, temporal and uncertainty as first-class concepts. Therefore, a developer will be able to abstract information related to the adaptation process, the environment as well as the system itself. Towards this vision, we present two evaluated contributions: a temporal context model and a language for uncertain data. The temporal context model allows abstracting past, ongoing and future actions with their impacts and context. The language, named Ain’tea, integrates data uncertainty as a first-class citizen. [less ▲]

Modeling Parkinson's disease using human midbrain organoids

Doctoral thesis (2019)

With increasing prevalence, neurodegenerative disorders present a major challenge for medical research and public health. Despite years of investigation, significant knowledge gaps exist, which impede the ... [more ▼]

With increasing prevalence, neurodegenerative disorders present a major challenge for medical research and public health. Despite years of investigation, significant knowledge gaps exist, which impede the development of disease-modifying therapies. The development of tools to model both physiological and pathological human brains greatly enhanced our ability to study neurological disorders. Brain organoids, derived from human induced pluripotent stem cells (iPSCs), hold unprecedented promise for biomedical research to unravel novel pathological mechanisms of a multitude of brain disorders. As brain proxies, these models bridge the gap between traditional 2D cell cultures and animal models. Owing to their human origin, hiPSC-derived organoids can recapitulate features that cannot be modeled in animals by virtue of differences in species. Parkinson’s disease (PD) is a human-specific neurodegenerative disorder. The major manifestations are the consequence of degenerating dopaminergic neurons (DANs) in the midbrain. The disease has a multifactorial etiology and a multisystemic pathogenesis and pathophysiology. In this thesis, we used state-of-the-art technologies to develop a human midbrain organoid (hMO) model with a great potential to study PD. hMOs were generated from iPSC-derived neural precursor cells, which were pre-patterned to the midbrain/hindbrain region. hMOs contain multiple midbrain-specific cell types, such as midbrain DANs, as well as astrocytes and oligodendrocytes. We could demonstrate features of neuronal maturation such as myelination, synaptic connections, spontaneous electrophysiological activity and neural network synchronicity. We further developed a neurotoxin-induced PD organoid model and set up a high-content imaging platform coupled with machine learning classification to predict neurotoxicty. Patient-derived hMOs display PD-relevant pathomechanisms, indicative of neurodevelopmental deficits. hMOs as novel in vitro models open up new avenues to unravel PD pathophysiology and are powerful tools in biomedical research. [less ▲]

Optimization assisted Designing Mechanical Elements for Direct Metal Laser Sintering

Doctoral thesis (2019)

The common question that many mechanical engineers have tried to answer is “how to maximize strength and working reliability of parts during designs while being able to minimize the parts’ weights?” The ... [more ▼]

The common question that many mechanical engineers have tried to answer is “how to maximize strength and working reliability of parts during designs while being able to minimize the parts’ weights?” The associated solutions attach the design methods, which need to be de-veloped to build up the parts. The better solutions are the more reliable and lighter parts could be built up. Hence, the fewer negative impacts on the environment could be yielded and the closer distance we could step towards the more sustainable future. Under the influences of the Fourth Industrial Revolution, many optimization methods have been being developed, aimed at supporting engineers on figuring out the above question. Despite having substantial developments in recent years, both the optimization methods and its applications in the mechanical design field are still far from being fully exploited. To evaluate the potential use of the methods, specific product developments are essentially considered and investigated. The Thesis work particularly dealt with the investigations of the optimization assisted design methods, employed to develop structures of some mechanical elements. These constructed elements were expected to have higher performance than those traditionally designed and were able to be practically produced. For gradually studying and evaluating the processes of design, it was proposed to divide the work into the five separating phases. Within the initial phase, the first scheme of the optimization assisted design was theoretically investigated. Such a scheme was relied on the combination of topology optimization and lattice optimization and was considered in association with the redesigning process of a motorcycle frame. The frame was selected for this starting phase due to the convenient definition of the design volume subjected to the optimizations. By handling the investigations in dealing with (i) the first resonance frequency, (ii) the mass, (iii) the buckling load factor, and (iv) the equivalent stress of the newly designed frame and those of the original one, the potential use of the design approach was revealed. In addition, the investigations pointed out that further studies are essentially taken place to search for more appropriate ways to apply this approach to design novel complex structures. During the next three consecutive phases, the more complicate optimization schemes were proposed and studied. The schemes were composed of three optimization steps, including free shape optimization, topology optimization, as well as lattice optimization. The studies were handled in conjunction with the processes of innovating the hydrogen valve structure, which holds the unexposed design space. Different novel configurations were developed for the valve within these phases, targeting the reduction of mass, the prolongation of fatigue life, as well as the structural compatibility of the designed valves with DMLS. In addition, the design of a test channel for the valve performed via the use of a fatigue based approach was also introduced in one of the three phases. It was aimed at providing a mean to detect multiple early valve’s damages. All of the built structures were then virtually evaluated to point out the effectiveness of the design works. Within the last phase, experimental tests were proposed to carry out. In this phase, the best possible valve structure was selected and was subjected to produce by DMLS along with post-machining afterwards. Upon completion of the fabrications, the in-house fatigue tests were tak-en place for the produced valves until damages or reaching 2E5 cycles. The obtained data of the tests provided further evidence to support the theoretical studies demonstrated in the first four phases. [less ▲]

Six regards sur la master-classe de piano : phénoménologie et sémiotique de la rencontre musicale

Doctoral thesis (2019)

In this thesis, I suggest new ways of grasping the affective dimension of musical experience that which traditional semiotics and musicology take little into account. Inspired by a dynamistic modelling ... [more ▼]

In this thesis, I suggest new ways of grasping the affective dimension of musical experience that which traditional semiotics and musicology take little into account. Inspired by a dynamistic modelling approach –which developed from the 1960s and since then has been influential in the domain of semiolinguistic disciplines–, I sketch out the fluctuating phases of semiogenesis within the field of piano masterclasses. The term ‘semiogenesis’ here, is taken in a broad sense, encompassing any deployment of sign-forms, either vague or articulated, diffused or well-defined. Such forms are conceived as being strained between expressiveness and normativity. They are also valorized in that they call the subject to participate in his or her own ‘lines of life’ which, in turn, may come to exist by those forms. A piano masterclass is given by a genuine master to highly accomplished students, both who truly testify to their own lives, to their own ways of ethical feeling, in the search for a unique musical praxis. In recent years, the field of masterclass has begun to attract the attention of the scientific community, especially in areas related to musical teaching and experience, such as psychology, aesthetics and epistemology or even sociology. Yet it is still suboptimal that most of the problems adopted in these frameworks incorporate nothing or so little in terms of the metamorphosis of sensitivity and the play of musical feeling in the characterization of their research objects. Nevertheless, the field of piano masterclass seems to be a particularly interesting and promising object of research in that the horizon of affect is preeminent in all the semiotic activities tied to it. Thus, I have attended several masterclasses in order to closely follow the praxis of the musicians (e.g., active and passive participation in masterclasses, audiovisual recordings, interviews, conversations and debates on music, etc.), in the spirit of making all its genetic depth to the semiotic activity, by approaching it under the perspective of an encountering and an orientation of musical sensibilities. One of the main tasks of my approach in the designing of the descriptions of this particular musical praxis consists in understanding the acoustic, gestural and linguistic phenomena, as giving birth to semiogenetic conditions of the constitution of a musical meaning. In this way, it is a fundamentally descriptive method, inspired by philosophical (Shaftesbury, Kierkegaard, Wittgenstein, Merleau-Ponty) and semiotic (Peirce, Saussure) minds, which joins the semiotic preoccupation from the very initial levels of a microgenesis, and by promoting it immediately into a hermeneutical and existential phenomenology. The perceptive and semiogenetic issues of musical sensitivity allow us to remodel the notion of a musical motive, understood both as a motive-of-praxis and as an existential-motive. I tried to grasp the idea of a certain listening of the musical praxis by finding there a constant passage between an ethical perception, and the search –through the playing of the music and its motives–, for a musical personality engaged in the musical praxis. Such conceptions on motive and personality proved to be fruitful to the extent that they make it possible to suggest a certain ethic of musical feeling, without reducing it to a skill, a psychology or a ritual. I have thus managed to redefine the notion of a musical ‘sign’ by playing up on the 'motival' horizon of this semiotic activity, understood – in the formal and sensitive nature of musical practices– as participation (i.e., desire and commitment to participate) to a certain regime of human existence. In this way, I believe to be paving the way for a new conception of musical praxis, which interweaves aesthetics and ethics. The thesis thus addresses these problems by casting six successive contemplations on it: Piano Masterclass; Feeling, Knowing and Doing; Field and Form; Motive and Form; Lines of Life; Enchantment. [less ▲]

The impact of macro-substrate on micropollutant degradation in activated sludge systems

Doctoral thesis (2019)

Wastewater treatment plants are designed as a first barrier to reduce xenobiotic emission into rivers. However, they are not sufficient enough to fully prevent environmental harm of emerging substances in ... [more ▼]

Wastewater treatment plants are designed as a first barrier to reduce xenobiotic emission into rivers. However, they are not sufficient enough to fully prevent environmental harm of emerging substances in the water body. Therefore, advanced treatment processes are currently being investigated but their implementation is cost-intensive. The optimisation of the activated sludge treatment to enhance biological micropollutant removal could reduce operating costs and material. Although the impact of operational parameters, such as sludge retention time and hydraulic retention time on the xenobiotic removal have been investigated, the influence of the macro-substrate composition and load on micropollutant elimination causes a high degree of uncertainty. This study focuses on the latter by analysing 15 municipal wastewater treatment plants, where variations in load and composition of the macro-substrate were expected. Assuming that macro-substrate shapes the biomass and triggers their activity, the impact of macro-substrate composition and load on xenobiotic degradation by microorganisms was analysed. It was hypothesised that on the one hand, a high dissolved organic carbon concentration might lead to enhanced xenobiotic degradation for certain substances due to a high microbial activity. The latter is assumed to be caused by a high labile dissolved organic carbon portion and the tendency for a shorter sludge retention time. On the other hand, a low dissolved organic carbon concentration, probably containing a predominant recalcitrant substrate portion, tends to a longer sludge retention time. Consequently, slow-growing and specialised microorganisms may develop, able to degrade certain xenobiotics. As a second question, the contribution of the autotrophic biomass to xenobiotic degradation was tested by inhibiting the autotrophic microorganisms during the degradation test. To additionally test the hypothesis, the impact of a readily biodegradable substrate (acetate) on the xenobiotic degradation was tested and the sensitivity of the fluorescence signal of tryptophan was used to analyse the impact of tryptophan on xenobiotic degradation. Degradation tests focusing on the removal of macro-substrate and micropollutants within 18 hours incubation in the OxiTop® system were performed. The OxiTop® system is known as fast and easy method for organic matter analysis in the wastewater. To assess the macro-substrate composition prior to and after the degradation test, three characterisation methods were applied. Firstly, to determine the labile and the rather recalcitrant portion in the dissolved organic carbon, absorbance was measured at 280 nm and further analysed. This was verified by the characterisation of both portions based on the oxygen consumption measurements. Secondly, to analyse the organic matter concerning its fluorescent properties, excitation-emission scans were run and analysed using the parallel factor analysis approach. Lastly, the chromophoric and fluorescent organic matter was separated via size-exclusion chromatography to investigate the macro-substrate composition. Micropollutant elimination efficiency was followed by measuring initial and final concentrations of the targeted substances using liquid chromatography tandem-mass spectrometry and calculating pseudo-first-order degradation rates. To distinguish between the contribution of the heterotrophic biomass and the total biomass on xenobiotic degradation, allylthiourea was added to inhibit the autotrophic biomass. No significant composition changes of the chromophoric macro-substrate were observed. A higher initial dissolved organic carbon concentration led to higher chromophoric and fluorescent properties. The same was found for the degraded dissolved organic carbon amount and the loss of signal within the chromophoric and fluorescent portions. Variations in the macro-substrate load or rather concentration were tracked. Derived from the oxygen consumption measurements, a prominent labile and non-chromophoric portion was present at higher dissolved organic carbon levels, impacting the microbial activity. However, a characterisation of the non-chromophoric macro-substrate composition was not done within the study. Regarding the micropollutant removal, varying elimination rates were observed. For 4 out of 17 substances, distinct degradation dynamics were found, suggesting a possible impact of the present macro-substrate load. However, no overall impact of the macro- substrate on xenobiotic removal was observed. Atenolol, bezafibrate and propranolol showed a negative correlation with the initial dissolved organic carbon concentration, meaning higher degradation rates at a lower substrate load. This might indicate the presence of specialised microorganisms and a higher microbial diversity. Furthermore, inhibition studies using allylthiourea suggest a contribution of the autotrophic biomass to xenobiotic degradation. Sulfamethoxazole showed a positive trend with the initial dissolved organic carbon concentration, possibly indicating co-metabolic degradation of sulfamethoxazole by the autotrophic and heterotrophic biomass. Thus, it seemed that the removal efficiencies of sulfamethoxazole benefited from higher substrate loads. With respect to the short term experiments with acetate, higher degradation efficiencies were observed for several substances in the presence of acetate. Ketoprofen and bezafibrate showed in all tested wastewaters enhanced removal efficiencies. The tryptophan test indicated the presence of tryptophan in wastewater, but no clear contribution to the xenobiotic degradation was seen. The presented findings substantially contribute to the understanding of the influencing parameters on xenobiotic degradation in activated sludge systems. By using the OxiTop® application for xenobiotic degradation tests, an easy and fast method was established. Absorbance and fluorescence measurements proved to be a sufficient method for characterisation and biodegradability estimation of organic matter, which could be further applied as online measurements on wastewater treatment plants. Thus, the current study will serve as a base for future work investigating the influencing parameters on the xenobiotic degradation pathways and focusing on the optimisation of the biological and advanced treatment process to overcome current limitations. [less ▲]

The Development and Utilization of Scenarios in European Union Energy Policy

Doctoral thesis (2019)

Scenarios are a strategic planning tool, which essentially enables decision-makers to identify future uncertainties and to devise or adjust organizational strategies. Increasingly, scenario building has ... [more ▼]

Scenarios are a strategic planning tool, which essentially enables decision-makers to identify future uncertainties and to devise or adjust organizational strategies. Increasingly, scenario building has been applied as a planning instrument by public policymakers. At the European Union (EU) level, scenarios are widely used in various policy areas and for different purposes. However, the development and utilization of scenarios in policymaking as well as their concrete impact on the decision process remain an under-explored research field. The academic literature focuses on scenarios in the business domain, where they are a well-established strategic planning component. In public policy, however, the development and use of scenarios conceivably differ from the private sector. In the case of the EU, the potential impact of its distinctive multi-stakeholder and multi-level policymaking environment on the development of scenarios is not sufficiently accounted for in the literature. Moreover, it is uncertain how scenarios are situated in the wider EU political context. This thesis seeks to explain how scenarios are developed and utilized in the EU’s policymaking process. To that end, an institutionalized scenario development exercise from the Union’s energy policy (the Ten-Year Network Development Plan, TYNDP) is investigated as a case study. Drawing from empirical evidence primarily based on elite interviews, the research applies a qualitative-interpretative research framework that combines the analytical concepts of policy networks, epistemic communities, and strategic constructivism. The combination facilitates the design of a theoretical model of inner and outer spheres in EU energy policymaking, accounting for both the role of scenarios in policymaking and the impact of political goals on their development. The research concludes that the wider EU political context of the outer sphere shapes the development of scenarios in the inner sphere and determines how they are utilized in the policymaking process. The expectations of political actors frame the technical expertise in the scenario development process. With regard to the application of scenarios in wider public policy, the research demonstrates that the closer the scenario building is to the decision-making process, the stronger the political impact on the scenarios is likely to be. This is because political actors and decision-makers seek to align the scenario outcomes to their respective preferences. [less ▲]

CONFIDENCE-BASED DECISION-MAKING SUPPORT FOR MULTI-SENSOR SYSTEMS

Doctoral thesis (2019)

We live in a world where computer systems are omnipresent and are connected to more and more sensors. Ranging from small individual electronic assistants like smartphones to complex autonomous robots ... [more ▼]

We live in a world where computer systems are omnipresent and are connected to more and more sensors. Ranging from small individual electronic assistants like smartphones to complex autonomous robots, from personal wearable health devices to professional eHealth frameworks, all these systems use the sensors’ data in order to make appropriate decisions according to the context they measure. However, in addition to complete failures leading to the lack of data delivery, these sensors can also send bad data due to influences from the environment which can sometimes be hard to detect by the computer system when checking each sensor individually. The computer system should be able to use its set of sensors as a whole in order to mitigate the influence of malfunctioning sensors, to overcome the absence of data coming from broken sensors, and to handle possible conflicting information coming from several sensors. In this thesis, we propose a computational model based on a two layer software architecture to overcome this challenge. In a first layer, classification algorithms will check for malfunctioning sensors and attribute a confidence value to each sensor. In the second layer, a rule-based proactive engine will then build a representation of the context of the system and use it along some empirical knowledge about the weaknesses of the different sensors to further tweak this confidence value. Furthermore, the system will then check for conflicting data between sensors. This can be done by having several sensors that measure the same parameters or by having multiple sensors that can be used together to calculate an estimation of a parameter given by another sensor. A confidence value will be calculated for this estimation as well, based on the confidence values of the related sensors. The successive design refinement steps of our model are shown over the course of three experiments. The first two experiments, located in the eHealth domain, have been used to better identify the challenges of such multi-sensor systems, while the third experiment, which consists of a virtual robot simulation, acts as a proof of concept for the semi-generic model proposed in this thesis. [less ▲]

Towards Optimal Real-Time Bidding Strategies for Display Advertising

Doctoral thesis (2019)

Development of an innovative U-shaped steel-concrete composite beam solution: Experimental and numerical studies on the mechanical behaviour

Doctoral thesis (2019)

An innovative solution of steel-concrete composite beam was developed taking into consideration the fire situation and the construction stage. The beam is composed of a U-shaped steel part connected to a ... [more ▼]

An innovative solution of steel-concrete composite beam was developed taking into consideration the fire situation and the construction stage. The beam is composed of a U-shaped steel part connected to a reinforced concrete part. In the construction phase, the beam is supporting the slab and constitutes a formwork for the reinforced concrete part. The U-shaped beam withstands the construction loads without any temporary propping system. When casting concrete, the steel beam is filled at the same time as the slab, this allows considerable time-saving on site. In exploitation stage, the beam behaves as a steel-concrete composite beam. The connection between the two materials is made by welded headed studs on the lower part of the U-shaped beam. In fire situations, the composite beam satisfies conventional fire stability durations due to the longitudinal reinforcements inside the concrete downstand part with sufficient covers. A literature review focuses on modern solutions that fulfils the criteria of the thesis is performed in order to develop an innovative solution optimised. In construction stage, the U-shaped steel beam without restraints is prone to lateral torsional buckling instability. In order to characterise the stability of the beam, a full-scale test is carried out at the Laboratory of the University of Luxembourg. The test clearly showed the lateral torsional buckling of the steel beam. The test results are compared to numerical simulations and analytical studies. A parametrical study, covering 200 geometrical configurations of the U-shaped beam, is carried out to validate the use of the curve "b" for the design of the steel beam for lateral torsional buckling according to Eurocodes 3. In the exploitation phase, once the concrete hardens, the beam has a steel-concrete composite behaviour provided by the shear connection between the two materials. For manufacturing reasons, the connection is located in a zone where the concrete is subjected to tension forces induced by the bending of the beam. The concrete in this zone is potentially cracked, thus the efficiency of the connection and therefore the mechanical steel-concrete composite behaviour is investigated. Another test is therefore carried out in the Laboratory of the University of Luxembourg, this time the specimen tested is made of concrete and steel. The failure mode is a shear mechanism of the composite beam at very large displacements. However, the beam specimen exhibited a real steel-concrete composite behaviour with high ductility, the connection is therefore very efficient. The test results are compared to numerical simulations in order to validate the finite element model developed. From numerical results and test results, an analytical method, based on EN 1994-1-1, is proposed to find the bending resistant of this composite beam by taking into account the partial yield of the side plates of the U-shaped steel section. A global analytical design method is proposed for the developed solution based on the Eurocodes with additional considerations and constructional guidelines. [less ▲]

Le jugement par défaut dans l'espace judiciaire européen

Doctoral thesis (2019)

French judges regularly refuse to enforce foreign judgements rendered by default against a defendant who has not appeared. This finding is also true for other Member States, as many European regulations ... [more ▼]

French judges regularly refuse to enforce foreign judgements rendered by default against a defendant who has not appeared. This finding is also true for other Member States, as many European regulations govern cross-border enforcement of decisions rendered in civil and commercial matters between Member States. The present study examines this problem in order to understand the obstacles to the circulation of default decisions and payment orders in Europe. When referring to the recognition of default judgments, it would be more accurate to refer to the recognition of decisions made as a result of default proceedings. It is indeed this (default) procedure, more than the judgment itself, which is examined by the exequatur judge to determine whether the foreign decision should be enforced. This study is therefore firstly devoted to default procedures and payment order procedures in French, English, Belgian and Luxembourgish laws. These procedures are analysed and compared in order to highlight their differences, be they conceptual or simply technical in nature. Once these discrepancies have been identified, this study turns to private international law in order to understand which elements of the default procedures are likely to hinder their circulation. The combination of these two perspectives makes it possible to envisage a gradual approximation of national default procedures in order to facilitate their potential circulation in the European area of freedom, security and justice. [less ▲]

Parliamentary involvement in EU affairs during treaty negotiations in a historical comparative perspective: the cases of the Austrian, Finnish and Luxembourgish parliaments

Doctoral thesis (2019)

Until recently, studies on the Europeanisation of national parliaments mostly tended to focus on the evolution of their institutional capacities rather than on their actual behaviour in EU affairs. This ... [more ▼]

Until recently, studies on the Europeanisation of national parliaments mostly tended to focus on the evolution of their institutional capacities rather than on their actual behaviour in EU affairs. This thesis seeks to identify variations in behavioural patterns between the Austrian, Finnish and Luxembourgish legislatures. The historical comparative perspective bases mainly on political and societal similarities between the countries. Based on historical and Sociological Institutionalism, the thesis aims to analyse the evolution and motivations of parliamentary involvement in the field of European affairs over a period running from the negotiations on the Treaty establishing a Constitution for Europe until the Treaty on Stability, Coordination and Governance in the EMU. By including both institutional and motivational indicators, the objective consists of identifying the extent to which parliamentary involvement in EU matters has been challenged in the framework of EU treaties and intergovernmental treaties on the EMU. We address the following questions: What institutional and motivational factors influenced parliamentary involvement in EU affairs? What parliamentary initiatives have been taken to improve participation in EU affairs? In which direction did institutional change happen and who triggered it? The present thesis bases primarily on qualitative data, i.e. interviews with parliamentarians, civil servants from parliamentary administrations and parliamentary group collaborators. Thereby we aim to produce empirical in-depth knowledge on actual parliamentary behaviour in each studied country. Thus, the assessment of parliamentary involvement in EU affairs through the lenses of parliamentarians’ motivations and their institutional context helps to investigate the parliamentary “black box”. [less ▲]

Investigation of the immune functions of DJ-1

Doctoral thesis (2019)

Le Luxembourg de la guerre à la paix (1918-1923). La France, actrice majeur de cette transition.

Doctoral thesis (2019)

The history of the Grand Duchy of Luxembourg between 1918 and 1923 is not fundamentally unknown. Many historians have worked on the "Luxembourg question from 1918 to 1919", or the post-war dynastic ... [more ▼]

The history of the Grand Duchy of Luxembourg between 1918 and 1923 is not fundamentally unknown. Many historians have worked on the "Luxembourg question from 1918 to 1919", or the post-war dynastic question, or the social movements emanating from this period. Three major countries are thus the protagonists of the events of this period: to begin with Luxembourg’s government and even its population. Belgium through an annexationist policy, also influenced greatly the Grand Duchy. And last but not least France. The latter's policy, which is often considered as being annexationist, cancels that of Belgium. French troops were present in Luxembourg between 1918 and 1923 on its territory. Then of a garrison. This element had never been previously studied as such, but it is the proof of the physical presence of France and of the incarnation of its political will throughout the period. The study of occupation and then of the French garrison in Luxembourg allows updating the ambiguity of the French policy but also the influence of this presence on Luxembourg’s politic, and on everyday life as well. as much as on everyday life. Finally, in order to analyze the memory consequences, of which historiography is embodied, this study is to be seen through the prism of the garrison. It thus allows us to glimpse the major role of France during this period, both in terms of multiple events (political, economic, social and diplomatic), but also it’s long-term role. [less ▲]

Assessment and Improvement of the Practical Use of Mutation for Automated Software Testing

Doctoral thesis (2019)

Software testing is the main quality assurance technique used in software engineering. In fact, companies that develop software and open-source communities alike actively integrate testing into their ... [more ▼]

Software testing is the main quality assurance technique used in software engineering. In fact, companies that develop software and open-source communities alike actively integrate testing into their software development life cycle. In order to guide and give objectives for the software testing process, researchers have designed test adequacy criteria (TAC) which, define the properties of a software that must be covered in order to constitute a thorough test suite. Many TACs have been designed in the literature, among which, the widely used statement and branch TAC, as well as the fault-based TAC named mutation. It has been shown in the literature that mutation is effective at revealing fault in software, nevertheless, mutation adoption in practice is still lagging due to its cost. Ideally, TACs that are most likely to lead to higher fault revelation are desired for testing and, the fault-revelation of test suites is expected to increase as their coverage of TACs test objectives increase. However, the question of which TAC best guides software testing towards fault revelation remains controversial and open, and, the relationship between TACs test objectives’ coverage and fault-revelation remains unknown. In order to increase knowledge and provide answers about these issues, we conducted, in this dissertation, an empirical study that evaluates the relationship between test objectives’ coverage and fault-revelation for four TACs (statement, branch coverage and, weak and strong mutation). The study showed that fault-revelation increase with coverage only beyond some coverage threshold and, strong mutation TAC has highest fault revelation. Despite the benefit of higher fault-revelation that strong mutation TAC provide for software testing, software practitioners are still reluctant to integrate strong mutation into their software testing activities. This happens mainly because of the high cost of mutation analysis, which is related to the large number of mutants and the limitation in the automation of test generation for strong mutation. Several approaches have been proposed, in the literature, to tackle the analysis’ cost issue of strong mutation. Mutant selection (reduction) approaches aim to reduce the number of mutants used for testing by selecting a small subset of mutation operator to apply during mutants generation, thus, reducing the number of analyzed mutants. Nevertheless, those approaches are not more effective, w.r.t. fault-revelation, than random mutant sampling (which leads to a high loss in fault revelation). Moreover, there is not much work in the literature that regards cost-effective automated test generation for strong mutation. This dissertation proposes two techniques, FaRM and SEMu, to reduce the cost of mutation testing. FaRM statically selects and prioritizes mutants that lead to faults (fault-revealing mutants), in order to reduce the number of mutants (fault-revealing mutants represent a very small proportion of the generated mutants). SEMu automatically generates tests that strongly kill mutants and thus, increase the mutation score and improve the test suites. First, this dissertation makes an empirical study that evaluates the fault-revelation (ability to lead to tests that have high fault-revelation) of four TACs, namely statement, branch, weak mutation and strong mutation. The outcome of the study show evidence that for all four studied TACs, the fault-revelation increases with TAC test objectives’ coverage only beyond a certain threshold of coverage. This suggests the need to attain higher coverage during testing. Moreover, the study shows that strong mutation is the only studied TAC that leads to tests that have, significantly, the highest fault-revelation. Second, in line with mutant reduction, we study the different mutant quality indicators (used to qualify "useful" mutants) proposed in the literature, including fault-revealing mutants. Our study shows that there is a large disagreement between the indicators suggesting that the fault-revealing mutant set is unique and differs from other mutant sets. Thus, given that testing aims to reveal faults, one should directly target fault-revealing mutants for mutant reduction. We also do so in this dissertation. Third, this dissertation proposes FaRM, a mutant reduction technique based on supervised machine learning. In order to automatically discriminate, before test execution, between useful (valuable) and useless mutants, FaRM build a mutants classification machine learning model. The features for the classification model are static program features of mutants categorized as mutant types and mutant context (abstract syntax tree, control flow graph and data/control dependency information). FaRM’s classification model successfully predicted fault-revealing mutants and killable mutants. Then, in order to reduce the number of analyzed mutants, FaRM selects and prioritizes fault-revealing mutants based of the aforementioned mutants classification model. An empirical evaluation shows that FaRM outperforms (w.r.t. the accuracy of fault-revealing mutant selection) random mutants sampling and existing mutation operators-based mutant selection techniques. Fourth, this dissertation proposes SEMu, an automated test input generation technique aiming to increase strong mutation coverage score of test suites. SEMu is based on symbolic execution and leverages multiple cost reduction heuristics for the symbolic execution. An empirical evaluation shows that, for limited time budget, the SEMu generates tests that successfully increase strong mutation coverage score and, kill more mutants than test generated by state-of-the-art techniques. Finally, this dissertation proposes Muteria a framework that enables the integration of FaRM and SEMu into the automated software testing process. Overall, this dissertation provides insights on how to effectively use TACs to test software, shows that strong mutation is the most effective TAC for software testing. It also provides techniques that effectively facilitate the practical use of strong mutation and, an extensive tooling to support the proposed techniques while enabling their extensions for the practical adoption of strong mutation in software testing. [less ▲]

PHENOTYPIC CHARACTERIZATION OF CELLULAR MODELS OF VPS35-ASSOCIATED MUTATION IN PARKINSON’S DISEASE

Doctoral thesis (2019)

Dynamical Modeling Techniques for Biological Time Series Data

Doctoral thesis (2019)

The present thesis is articulated over two main topics which have in common the modeling of the dynamical properties of complex biological systems from large-scale time-series data. On one hand, this ... [more ▼]

The present thesis is articulated over two main topics which have in common the modeling of the dynamical properties of complex biological systems from large-scale time-series data. On one hand, this thesis analyzes the inverse problem of reconstructing Gene Regulatory Networks (GRN) from gene expression data. This first topic seeks to reverse-engineer the transcriptional regulatory mechanisms involved in few biological systems of interest, vital to understand the specificities of their different responses. In the light of recent mathematical developments, a novel, flexible and interpretable modeling strategy is proposed to reconstruct the dynamical dependencies between genes from short-time series data. In addition, experimental trade-offs and optimal modeling strategies are investigated for given data availability. Consistent literature on these topics was previously surprisingly lacking. The proposed methodology is applied to the study of circadian rhythms, which consists in complex GRN driving most of daily biological activity across many species. On the other hand, this manuscript covers the characterization of dynamically differentiable brain states in Zebrafish in the context of epilepsy and epileptogenesis. Zebrafish larvae represent a valuable animal model for the study of epilepsy due to both their genetic and dynamical resemblance with humans. The fundamental premise of this research is the early apparition of subtle functional changes preceding the clinical symptoms of seizures. More generally, this idea, based on bifurcation theory, can be described by a progressive loss of resilience of the brain and ultimately, its transition from a healthy state to another characterizing the disease. First, the morphological signatures of seizures generated by distinct pathological mechanisms are investigated. For this purpose, a range of mathematical biomarkers that characterizes relevant dynamical aspects of the neurophysiological signals are considered. Such mathematical markers are later used to address the subtle manifestations of early epileptogenic activity. Finally, the feasibility of a probabilistic prediction model that indicates the susceptibility of seizure emergence over time is investigated. The existence of alternative stable system states and their sudden and dramatic changes have notably been observed in a wide range of complex systems such as in ecosystems, climate or financial markets. [less ▲]

Memory for Problem Solving: Comparative Studies in Attention, Working and Long-term Memory

Doctoral thesis (2019)

Living in a complex and dynamically changing environment requires accurate and timely behavioural responses that allow for adapting to such changes. Well-developed perceptual systems provide a continuous ... [more ▼]

Living in a complex and dynamically changing environment requires accurate and timely behavioural responses that allow for adapting to such changes. Well-developed perceptual systems provide a continuous flow of abundant and up-to-date information on the changes in the environment, and, thereby, allow for tailoring behavioural responses accordingly. However, issuing any behavioral response would not be possible, if it was not for information processing capacities that link one’s perception and action. Because the information processing capacities of humans and non-human animals are always limited, the available information must be sorted, selected and prioritised at all steps of information processing. The steps of information processing have different names, corresponding to their function. The processes, that support attending to and acquiring the information, belong to attention. The processes, that support working on the acquired input from the environment and comparing it with the information acquired in the past, belong to working memory. And finally, the processes, that supply and update the information acquired in the past for the use in the long term, belong to long-term memory. Attention, working and long-term memory work in concert to harness the flow of information, and to support rapid and flexible adaptation to the changes in the environment. This thesis comprises four empirical papers, in which some aspects of attention, working and long-term memory are compared across five species: the common raven (Corvus corax), the Goffin’s cockatoo (Cacatua goffiniana), the Sumatran orangutan (Pongo abelii), the common chimpanzee (Pan troglodytes) and the human (Homo sapiens sapiens). In the first two studies, chimpanzees, an orangutan, and Goffin’s cockatoos are tested in a novel experimental setup that allows for measuring long-term memory flexibility. Arguably, such flexibility allows for drawing on overlapping past experiences to solve novel problems, even when these experiences conflict with one another. The results suggest that great apes and at least some Goffin’s cockatoos can overcome such conflicts and rely on less salient yet relevant rather than more salient yet irrelevant features of overlapping experiences. In the third study, ravens and humans are tested in a series of novel working memory tasks, completed individually or with a competing partner. Ravens perform better in the social than in the individual tasks, while the opposite is true for humans. Interestingly, ravens seem to handle the increasing difficulty of the task by keeping a steady success rate, perhaps revealing a flexible adaptation to varying demands on working memory in ecological conditions. In the fourth and final study, ravens and humans are tested in another experimental setup, which requires attending to a series of objects. Ravens’ gazes to the objects are half as short as humans’, suggesting a higher speed of perception, and perhaps of cognitive processing. [less ▲]

First-Principles High-Throughput Study of Linear and Nonlinear Optical Materials

Doctoral thesis (2019)

Nonlinear optical (NLO) processes, such as second harmonic generation (SHG), play an important role in modern optics, especially in laser-related science and technology. They are at the core of a wide ... [more ▼]

Nonlinear optical (NLO) processes, such as second harmonic generation (SHG), play an important role in modern optics, especially in laser-related science and technology. They are at the core of a wide variety of applications ranging from optoelectronics to medicine. Among the various NLO materials, insulators are particularly important for second-order NLO properties. In particular, only crystals which are non-centrosymmetric can display a non-zero second-order NLO susceptibility. However, given the large number of requirements that a material needs to meet in order to be a good nonlinear optical material, the choice of compounds is drastically limited. Indeed, despite recent progress, a systematic approach to design NLO materials is still lacking. In this work, we conduct a first-principles high-throughput study on a large set of semiconductors for which we computed the linear and nonlinear susceptibility using Density Functional Perturbation Theory. For the linear optical properties, our calculations confirm the general trend that the refractive index is roughly inversely proportional to the band gap. In order to explain the large spread in the data distribution, we have found that two descriptors successfully describe materials with relatively high refraction index: (i) a narrow distribution in energy of the optical transitions which brings the average optical gap close to the direct band gap (ii) a large number of transitions around the band edge and/or high dipole matrix elements. For non-centrosymmetric crystals, we perform the calculation of the efficiency of SHG. We observe some materials with particularly high SHG, much stronger than the general relation with the linear refraction index through Miller’s rule predicts. We relate the value of Miller’s coefficient to geometric factors, i.e., how strongly the crystal deviates from a centrosymmetric one. We also identified interesting materials that show high optical responses for which it would be worth performing further analysis. [less ▲]

Une manière de dire "je" : paroles pamphlétaires dans le premier XIXe siècle (1814-1848)

Doctoral thesis (2019)

La chute de Napoléon, en 1814, marque l’entrée de la France dans un régime d’opinion. Il s’agit là du résultat d’une mutation significative de la culture politique, qui voit le discours sur la chose ... [more ▼]

La chute de Napoléon, en 1814, marque l’entrée de la France dans un régime d’opinion. Il s’agit là du résultat d’une mutation significative de la culture politique, qui voit le discours sur la chose publique gagner l’espace extra-parlementaire, donnant lieu à des formes de discours codifiées opposées à celles du débat politique officiel. Sortant de l’hémicycle pour investir la rue, la parole sur la chose publique change de nature en changeant de lieu d’exercice ; dans ce cadre, le pamphlet de la première moitié du XIXe siècle apparaît comme le catalyseur et le fruit privilégié de cet abandon progressif des formes longues de l’éloquence politique. Suivant les pas de Germaine de Staël, Benjamin Constant et surtout François-René de Chateaubriand, précurseurs de la parole pamphlétaire moderne, Paul-Louis Courier fait du pamphlet une forme de parole codifiée et stabilisée, avec sa rhétorique, ses images et ses protagonistes (le « je » pamphlétaire en particulier). Or la place centrale accordée à la figure de l’auteur pose la question de la légitimité de la pratique polémique, et notamment des stratégies mises en place par les pamphlétaires pour justifier leur entreprise de dénonciation ; c’est à ces interrogations qu’on consacrera notre propos. [less ▲]