Enhancing Mobility Applications Through Bluetooth Communications

Doctoral thesis (2017)

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

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

Corporations and Human Rights: Searching for International Norms for Corporate Conduct in Domestic Case Law

Doctoral thesis (2017)

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

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

Model-Based Specification, Deployment and Adaptation of Robot Perception Systems

Doctoral thesis (2017)

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

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

Design for meaning in products and services to foster eco-sufficient user behavior: exemplified by sharing goods

Doctoral thesis (2017)

Form und Funktion des Diminutivs im luxemburgisch-moselfränkischen Übergangsgebiet

Doctoral thesis (2017)

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

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

Le mouvement-liberté. Généalogie philosophique et littéraire d'un imaginaire politique

Doctoral thesis (2017)

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

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

TESTING 21ST CENTURY SKILLS IN A CHANGING NATURE OF WORK: THE CONSTRUCT VALIDITY OF COMPLEX PROBLEM SOLVING AND ORGANIZATIONAL LEARNING

Doctoral thesis (2017)

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

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

Stem cells for modeling Parkinson's disease

Doctoral thesis (2017)

Historicizing the journey of the New Math reform from the United States to Luxembourg in the 1960s and 1970s

Doctoral thesis (2017)

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

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

Inflammatory signaling in liver cells: Cross-regulation of the IL-6/JAK/STAT3 pathway and microRNAs

Doctoral thesis (2017)

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

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

Kusuoka-Stroock type bounds for densities related to low-dimensional projections of high-dimensional SDE

Doctoral thesis (2017)

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

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

Molecular mechanisms of kinase inhibitor resistance in melanoma

Doctoral thesis (2017)

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

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

Essays on Asset Pricing Models with Jump Processes

Doctoral thesis (2017)

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

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

Automated and Effective Security Testing for XML-based Vulnerabilities

Doctoral thesis (2017)

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

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

Innovation Modes and Venturing in German Industries - An Empirical Analysis

Doctoral thesis (2017)

Automated requirements-driven testing of embedded systems based on use case specifications and timed automata

Doctoral thesis (2017)

The complexity of embedded software in safety-critical domains, such as automotive and avionics, has significantly increased over the years. For most embedded systems, standards require system testing to ... [more ▼]

The complexity of embedded software in safety-critical domains, such as automotive and avionics, has significantly increased over the years. For most embedded systems, standards require system testing to explicitly demonstrate that the software meets its functional and safety requirements. In these domains, system test cases are often manually derived from functional requirements in natural language plus other design artefacts, like UML statecharts. The definition of system test cases is therefore time-consuming and error-prone, especially given the quickly rising complexity of embedded systems. The benefits of automatic test generation are widely acknowledged today but existing approaches often require behavioural models that tend to be complex and expensive to produce, and are thus often not part of development practice. The work proposed in this dissertation focusses on the automated generation of test cases for testing the compliance between software and its functional and timing requirements. This dissertation is inspired by contexts where functional and timing requirements are expressed by means of use case specifications and timing automata, respectively. This is the development context of our industrial partner, IEE, an automotive company located in Luxembourg, who provided the case study used to validate the approach and tool described in this dissertation. This dissertation presents five main contributions: (1) A set of guidelines for the definition of functional and timing requirements to enable the automated generation of system test cases. (2) A technique for the automated generation of functional test cases from requirements elicited in the form of use case specifications following a prescribed template and natural-language restrictions. (3) A technique that reuses the automatically generated functional test cases to generate timeliness test cases from minimal models of the timing requirements of the system. (4) A technique for the automated generation of oracles for non-deterministic systems whose specifications are expressed by means of timed automata. In the context of this dissertation, automated oracles for non-deterministic systems are necessary to evaluate the results of the generated timeliness test cases. (5) The evaluation of the applicability and effectiveness of the proposed guidelines and techniques on an industrial case study, a representative automotive embedded system developed by IEE. [less ▲]

Active Learning in Cognitive Radio Networks

Doctoral thesis (2017)

In this thesis, numerous Machine Learning (ML) applications for Cognitive Radios Networks (CRNs) are developed and presented which facilitate the e cient spectral coexistence of a legacy system, the ... [more ▼]

In this thesis, numerous Machine Learning (ML) applications for Cognitive Radios Networks (CRNs) are developed and presented which facilitate the e cient spectral coexistence of a legacy system, the Primary Users (PUs), and a CRN, the Secondary Users (SUs). One way to better exploit the capacity of the legacy system frequency band is to consider a coexistence scenario using underlay Cognitive Radio (CR) techniques, where SUs may transmit in the frequency band of the PU system as long as the induced to the PU interference is under a certain limit and thus does not harmfully a ect the legacy system operability. [less ▲]

Damage detection in prestressed concrete bridges based on static load testing, sagging and modal parameters, using measurements and model updating

Doctoral thesis (2017)

Bridges are an essential part of nowadays infrastructure to cross natural and artificial obstacles like rivers, valleys or other roads and railways. Many concrete bridges were built in the last 70 years ... [more ▼]

Bridges are an essential part of nowadays infrastructure to cross natural and artificial obstacles like rivers, valleys or other roads and railways. Many concrete bridges were built in the last 70 years. The traffic density has increased immensely over the last decades and the bridges are suffering from corrosion and wear. Nevertheless, the safety of the infrastructure has to be guaranteed and therefore it is very important to find efficient methods for structural health monitoring. For this purpose, visual inspections are the most widely adopted in reality today. Considering the size of most bridge structures, it is understandable that these tests are generally very time-consuming and many personnel are needed, so they are cost-intensive. However, it is not always guaranteed that all damage can be found as only the surface is accessible. For instance, internal damage, such as corrosion of passive reinforcements or prestressed tendons, is difficult to detect. In addition, small cracks can remain undetected when covered by paints or dirt. Therefore, it is important to complement the standard methods with advanced alternatives. The aim is therefore not necessarily to replace visual inspections, but rather to find efficient methods for amendment. An idea being vigorously discussed in the scientific community is based on vibration measurements of a structure to assess its dynamic behaviour. The occurrence of damage will change the system properties, as it changes above all the stiffness distribution. So the system identification process in principle allows detection of changes of eigenfrequencies and hence stiffness. The main problem in practice on real bridges is that the robustness of a method is often insufficient, as the measured parameters are often also influenced by temperature changes. It will be shown that the impact of temperature change, e.g. between night and day, on the system properties is much higher than the influence of small damage. Furthermore, changes in soil and bearing conditions between different seasons can play a role. These environmental effects have to be taken into account while performing measurements for damage assessment. For this purpose, strategies are proposed to compensate environmental effects. Therefore, this thesis focuses on measurements under real environmental conditions, outside a laboratory. Different methods for damage assessment or stiffness tracking based on measured static and on dynamic properties of structures are deployed. Finally, the measured and analysed physical properties of the bridges in this thesis are: eigenfrequencies, mode shapes, sagging under own weight and the deflection line under a static test-loading. These quantities are tracked and artificial damage is introduced stepwise to a test-beam of a real bridge. Damage assessment and localisation is tried directly with the measured quantities but also by model-updating of a finite element model. This solid model is divided in a special way in different slices. It is possible to change the stiffness distribution along the axis of the simulated beam by varying the Young’s moduli of these slices. Furthermore, to reduce the number of free parameters for the subsequent up-dating process, an exponential damage function is introduced that describes the stiffness distribution. At first, the model was designed to fit a healthy reference state. Now measurement data from the artificially damaged test-beam are introduced and the model is updated by changing the Young’s moduli of the slices to minimise a special objective function containing the measured and simulated physical quantities. The comparison of initial and updated model allows a quantification and localisation of damage. Finally, the slice width is reduced around the identified damage region to improve the process. [less ▲]

Self-assembly of binary colloidal nanocrystals

Doctoral thesis (2017)

The synthesis of functional nanoparticles is an important step in the hierarchical construction of hybrid materials for nanotechnological applications. A useful path to build these components is to use ... [more ▼]

The synthesis of functional nanoparticles is an important step in the hierarchical construction of hybrid materials for nanotechnological applications. A useful path to build these components is to use colloidal nanocrystals that can spontaneously agglomerate into ordered structures under confinement. The focus of this thesis is to explore the diversity of superstructures that can be self-assembled using binary dispersions where the dispersed colloids have spherical or quasi-spherical shapes and interact through simple potentials with repulsive cores and short-range attractions. Using computer simulations we demonstrate that agglomeration experiments with heterogeneous binary mixtures of nanoparticles can be exploited for the synthesis of structured clusters which are proposed as potential intermediate building blocks in hierarchical self-assembly of colloidal molecules and crystals. To describe the structural properties of aggregates resulting from confined mixtures of particles with heterogeneous attractions we analyse the structure diagrams of binary Lennard-Jones clusters by means of a basin-hopping global optimisation approach for a broad range of cluster sizes, compositions and interaction energies and present a large database of minimal energy structures. We identify a variety of structures such as core-shell clusters, Janus clusters and clusters in which the minority species is located at the vertices of icosahedra. For a binary mixture with heterogeneous particle diameters we use molecular dynamics simulations to demonstrate that pressure-dependent inter-particle potentials affect the self-assembly route of the confined particles. This is in agreement with experiments where crystalline superlattices, Janus particles, and core-shell particle arrangements form in the same dispersions for moderate changes in the working pressure or the surfactant that sets the Laplace pressure inside the droplets. Comparison of experimental analysis and simulations confirms that the onset of self-assembly depends on particle size and pressure. Finally, we explore regular superlattices into which clusters can arrange by investigating the equilibrium phase behaviour for a monodisperse system of Mackay icosahedra. Monte Carlo simulations show that either a fluid phase, a crystal phase or rotator phases with different degrees of rotational correlations form. We analyse the correlations using the positional and orientational pair correlation functions and find that the densest lattice packing of hard icosahedra is stable at finite temperatures. [less ▲]

AUTOMATED DEBUGGING AND FAULT LOCALIZATION OF MATLAB/SIMULINK MODELS

Doctoral thesis (2017)

Matlab/Simulink is an advanced environment for modeling and simulating multidomain dynamic systems. It has been widely used to model advanced Cyber-Physical Systems, e.g. in the automotive or avionics ... [more ▼]

Matlab/Simulink is an advanced environment for modeling and simulating multidomain dynamic systems. It has been widely used to model advanced Cyber-Physical Systems, e.g. in the automotive or avionics industry. To ensure the reliability of Simulink models (i.e., ensuring that they are free of faults), these models are subject to extensive testing to verify the logic and behavior of software modules developed in the models. Due to the complex structure of Simulink models, finding root causes of failures (i.e., faults) is an expensive and time-consuming task. Therefore, there is a high demand for automatic fault localization techniques that can help en- gineers to locate faults in Simulink models with less human intervention. This demand leads to the proposal and development of various approaches and techniques that are able to automatically locate faults in Simulink models. Fault localization has been an active research area that focuses on developing automated tech- niques to support software debugging. Although there have been many techniques proposed to localize faults in programs, there has not been much research on fault localization for Simulink models. In this dissertation, we investigate and develop a lightweight fault localization approach to automatically and accurately locate faults in Simulink models. To enhance the usability of our approach, we also develop a stand-alone desktop application that provides engineers with a usable interface to facilitate localization of faults in their models. [less ▲]

Parkinson's disease: Evaluation of a neuroprotective target and identification of candidate biomarker signatures using murine models

Doctoral thesis (2017)

Parkinson's disease (PD) is one of the most common age-related neurologic diseases. While existing therapeutic approaches, focusing on dopamine replacement, can alleviate some of the cardinal symptoms ... [more ▼]

Parkinson's disease (PD) is one of the most common age-related neurologic diseases. While existing therapeutic approaches, focusing on dopamine replacement, can alleviate some of the cardinal symptoms, they are associated with severe adverse effects in the long-term. Therefore, identification of new therapeutic interventions to reverse, stop or slow down the progression of Parkinson’s disease is a major focus of PD research. Similarly, identifying reliable biomarkers that would enable early therapeutic intervention is another key area of current research. Here, we evaluated a recently proposed non-dopaminergic protein drug target for PD, Regulator of G-Protein Signaling 4 (RGS4), and performed preliminary studies aimed at the identification of novel biomarker signatures using two murine models of Parkinson’s disease. Recent research on new non-dopaminergic PD drug targets has indicated that inhibition of RGS4, a member of the RGS family of proteins that inactivate G-proteins, could be an effective adjuvant treatment option. However, the effectiveness of RGS4 inhibition for an array of PDlinked functional and structural neuroprotection endpoints had not yet been demonstrated. Here, we used the 6-Hydroxydopamine (6-OHDA) lesioning mouse model to address this question. We observed, using a battery of behavioral and pathological measures, that mice deficient for RGS4 are not protected from 6-OHDA induced injury, and showed enhanced susceptibility in some measures of motor function. Our results suggest that inhibition of RGS4 as a non-dopaminergic target for PD should be approached with caution. In the second part of this study, two alpha-synuclein based PD mouse models, human E46K mutated overexpressed alpha-synuclein and alpha-synuclein fibril spreading models, were used to investigate early pathological events in PD and identify novel candidate biomarker signatures for subsequent validation. Two different time points, before disease onset, and at peak disease manifestation, were analyzed in the two models. Using multiple histopathology and molecular biology techniques, we were able to identify complex changes in patterns of gene expression at early stages of the disease, well before neurodegeneration is detectable. These findings might open venues for new therapeutic strategies and provide insights on the molecular perturbations occurring during the earliest stages of the disease, paving the way for the development of a biomarker signatures for early diagnosis of Parkinson’s disease. [less ▲]

Interpretive Interactions among Legal Systems and Argumentation Schemes

Doctoral thesis (2017)

This thesis is about argumentation schemes that help to deal with interactions between national and foreign canons of interpretation in private international law cases. In fact, many legal orders, like ... [more ▼]

This thesis is about argumentation schemes that help to deal with interactions between national and foreign canons of interpretation in private international law cases. In fact, many legal orders, like Italy, require that, in conflict of laws disputes, courts apply the relevant foreign law using canons of interpretation and rules of application of the original foreign system. Our research hypothesis is that, in interpreting the foreign rule, domestic courts incur interpretive divergences of many kinds among the involved legal systems. Foreign law interpretation may result in linguistic and/or conceptual misalignments, in normative and/or interpretive gaps, and in specific incompatibilities between inner and foreign canons of interpretation. By focusing on interpretive conflicts within one legal system, legal theorists and AI and Law scholars have not yet paid sufficient attention to the issue, even if pluralist logics and argumentation have been generally applied to legal pluralism and conflict of laws. The present study fills this gap in the literature: it explores the feasibility of a theory for arguing and interpreting in private international law contexts, providing an argument-based conceptual framework that encompasses plausible interpretive interactions. To this end, and after addressing the epistemic concerns foreign law raises for domestic judges, the thesis gives a definition of cross-border interpretive incompatibilities and proposes argumentation schemes to reason with interpretive canons coming from different legal systems. An illustrative list of critical questions is used to evaluate the correctness of such interpretive reasoning. Lastly, the thesis presents the first formal developments of the study, based on the concept of meta-argumentation. It is possible to detect two main contributions to knowledge. First, this work identifies the components of foreign law interpretation, an interpretation activity with significant practical implications for legal systems today. In so doing, it also indirectly contributes to better understand interpretation at large. Secondly, its argument-based analysis paves the way for further formal applications in the domain of AI and Law. [less ▲]

Wie wird Ungleichheitsrelevanz im Bildungs- und Betreuungsalltag hergestellt? Eine qualitative Mehrebenenanalyse auf Basis ethnographischer Fallstudien in Luxemburger Kindertageseinrichtungen und Vorschulen

Doctoral thesis (2017)

Computational Aspects of Classical and Hilbert Modular Forms

Doctoral thesis (2017)

The main topic of this thesis is the study of classical and Hilbert modular forms and computational aspects of their q-expansions. The coefficients of q-expansions of eigenforms are particularly ... [more ▼]

The main topic of this thesis is the study of classical and Hilbert modular forms and computational aspects of their q-expansions. The coefficients of q-expansions of eigenforms are particularly interesting because of their arithmetic significance. Most notably, modular forms are an essential ingredient in Andrew Wiles’s proof of Fermat’s last theorem. This thesis consists of two parts: the first part concerns the distribution of the coefficients of a given classical eigenform; the second part studies computational aspects of the adelic q-expansion of Hilbert modular forms of weight 1. Part I of this thesis is an adapted version of the article On the Distribution of Frobenius of Weight 2 Eigenforms with Quadratic Coefficient Field published in Experimental Mathematics [38]. It presents a heuristic model that settles the following question related to the Sato-Tate and Lang-Trotter conjectures: given a normalised eigenform of weight 2 with quadratic coefficient field, what is the asymptotic behaviour of the number of primes p such that the p-th coefficient of this eigenform is a rational integer? Our work contributes to this problem in two ways. First, we provide an explicit heuristic model that describes the asymptotic behaviour in terms of the associated Galois representation. Secondly, we show that this model holds under reasonable assumptions and present numerical evidence that supports these assumptions. Part II concerns the study of (adelic) q-expansions of Hilbert modular forms. Our main achievements are the design, proof and implementation of several algorithms that compute the adelic q-expansions of Hilbert modular forms of weight 1 over C and over finite fields. One reason we are studying such q-expansions is that their coefficients (conjecturally) describe the arithmetic of Galois extensions of a totally real number field with Galois group in GL 2 (F p ) that are unramified at p. Using the adelic q-expansions of Hilbert modular forms of higher weight, these algorithms enable the explicit computation of Hilbert modular forms of any weight over C and the computation of Hilbert modular forms of parallel weight both over C and in positive characteristics. The main improvement to existing methods is that this algorithm can be applied in (partial) weight 1, which fills the gap left by standard computational methods. Moreover, the algorithm computes in all characteristics simultaneously. More precisely, we prove that, under certain conditions in higher weight, the output of the algorithm for given level N and quadratic character E includes a finite set of primes L such that all Hilbert modular forms of given parallel weight, level N and quadratic character E over F p are liftable for all primes p outside the set L. In particular, testing primes in the set L enabled the computation of examples of non-liftable Hilbert modular forms of weight 1. [less ▲]

Constructing Suitable Parameters for Pairing-Based Cryptography

Doctoral thesis (2017)

Arbeiten unter Hitler. NS-Sozialpolitik und Herrschaftspraxis im besetzten Luxemburg 1940-1944

Doctoral thesis (2017)

Die Arbeit untersucht Grundlagen, Konzeptionen und Auswirkungen der nationalsozialistischen Besatzungsherrschaft in Luxemburg (1940-1944) in den Bereichen der Wirtschafts- und Sozialpolitik ... [more ▼]

Die Arbeit untersucht Grundlagen, Konzeptionen und Auswirkungen der nationalsozialistischen Besatzungsherrschaft in Luxemburg (1940-1944) in den Bereichen der Wirtschafts- und Sozialpolitik. Berücksichtigung findet auch die NS-Volkstums- und Kulturpolitik. Staatliche Maßnahmen führten in der Besatzungszeit dazu, dass während einer relativ langen Phase die Auswirkungen des Krieges auf das Alltags- und Arbeitsleben wenig spürbar waren. Damit trug die Sozialpolitik zu einer politischen und psychologischen Stabilisierung des Regimes bei. Besonders betroffen von der Politik des nationalsozialistischen Gauleiters Gustav Simon waren die Luxemburger Gewerkschaften, die von den Machthabern instrumentalisiert und anschließend liquidiert wurden. An ihre Stelle trat die Deutsche Arbeitsfront, größte Massenorganisation des Regimes, die ihre vielfältigen Aktivitäten in den Bereichen der Sozial-, Wirtschafts-, Freizeit- und Kulturpolitik auch auf Luxemburg ausdehnte. Genauer untersucht wird die Institution des Stillhaltekommissars für das Organisationswesen, der die Gewerkschaften und andere Vereine liquidierte beziehungsweise nazifizierte. Damit wurden die Fundamente der Luxemburger Gesellschaft in Frage gestellt. Die Neuordnungspolitik des Regimes wird u.a. am Beispiel des Industriegebiets im Süden Luxemburgs dargestellt. Im Arbeitermilieu sahen die nationalsozialistischen Machthaber ein Experimentierfeld ihrer Politik. Krieg und Besatzung hatten letztlich auch Auswirkungen auf die großen Industriebetriebe. Gerade hier änderte sich ab der zweiten Hälfte des Krieges durch unterschiedliche Formen der Repression und Zwangsarbeit der Alltag der Menschen. Übergreifend befasst sich die Arbeit auch mit der Luxemburger Kriegsgesellschaft beziehungsweise den unterschiedlichen Reaktionen der Arbeiter und Angestellten auf Verlockung und Zwang. Kapitel: 1. Die NS-Sozialpolitik in Luxemburg 2. Die Luxemburger Gewerkschaften im Krieg. 3. Das Luxemburger Industriegebiet 4. Der Stillhaltekommissar für das Organisationswesen 5. Die Deutsche Arbeitsfront 6. Arbeiten im Krieg [less ▲]

Dissecting the crosstalk between intracellular calcium signalling and mitochondrial metabolism

Doctoral thesis (2017)

VERHALTEN AUSGEWÄHLTER NANOPARTIKEL IN KOMMUNALEN KLÄRANLAGEN UNTER BESONDERER BERÜCKSICHTIGUNG DER ANAEROBEN SCHLAMMBEHANDLUNG

Doctoral thesis (2017)

The increasing use of nanoparticles and the market to commercialize this innovative technology requires a deeper understanding of the behavior of nanoparticles (NPs) and the resulting consequences in an ... [more ▼]

The increasing use of nanoparticles and the market to commercialize this innovative technology requires a deeper understanding of the behavior of nanoparticles (NPs) and the resulting consequences in an environmentally The increasing use of nanoparticles and the market to commercialize this innovative technology requires a deeper understanding of the behavior of nanoparticles (NPs) and the resulting consequences in an environmentally relevant matrix. However, since the fate and behavior of nanoparticles is largely unknown to the environment, this study was done to investigate the key properties of nanoparticles, parameters to describe them and to discuss how these parameters can influence their fate and behavior in the natural environment. The core goal of this discussion is to relate sludge treatment to relevant properties of the nanoparticle, which may interact with a range of substances naturally present in wastewater treatment plants (WWTPs) and activated sludge. Understanding these properties is necessary for interpreting the fate of nanoparticles and predicting their effects in the actual environment. Environmentally matrix are challenging to investigate, for instance as in sludge and anaerobic sludge stabilization. According to the literature, it will be assumed that about 95% of the NPs entering the WWTP end up in the sludge. This work reports on the investigation and observation of NPs behavior in the different stages, using different experiments and metering devices. The different experiments include (i) characterization of NPs before their application (NanoSight), (ii) behavior analysis in terms of kinetic transformations (Turbiscan), (iii) long- and short-term analysis of NPs effects on anaerobic sludge stabilization (laboratory fermentation plants). The characterization represents the current size distribution of the NPs in a controlled environment (H2O). Size is one of the defining properties of NPs, which causes changes in physical and chemical properties of NPs compared to their original materials. The results show that the distribution of NPs depends on the type of particle, surface coating and dispersion concentration. These parameters are subject to permanent changes in sludge. That is why an exact allocation to the effects seems almost impossible. Characterization is indispensable for the subsequent comprehension of the effects, and for the understanding of findings, which may result from the behavioral analysis, as well as from the effect analysis. The behavioral analysis was carried out by Turbiscan technology to consider relevant sludge parameters and substances (Chemical Oxygen Demand COD, Polymers, Humic acids, digestion process) to the behavior of NPs in sludge. The initial aim was to progressively add of representative substances to approximate the experiment to natural conditions. The phase separation detection identified a clear sedimentation behavior in all samples. To explain this and the kinetic modification as well as the resultant kinetic instability, the NPs’ diameter (particle size detection) were studied. The more instable samples had often smaller diameters. The substances within the sludge seem to influence the kinetic stability of NPs. This could be caused by the dynamic corona (active interaction with environment) and hard corona (strongly bound and restrained interaction with environment) formation, as well as agglomeration or modification of surface charges. Changes in kinetic stability means changes in the behavior and fate of NPs in such an environmental media like sludge. However, since the sludge is filtered for the behavioral analysis, the microorganism’s role is neglected. In order to complete the behavioral analysis considering the microorganism’s contribution, the consequences of the NP-behavior are measured as effects under various realistic conditions. The effects of NPs’ behavior on the anaerobic microorganisms were investigated based on their potential and efficiency in anaerobic sludge stabilization for gaining additional insights. The long-term effects of NPs in sludge treatment plants (STP) were investigated using four parallel pilot reactors operated under identical conditions, with daily feeding (substrate and two different NP-concentration). There was a temporary decrease of Biogas especially at the third phase (second concentration) except for the ZnO-reactor while the proportion of methane remained stable. Based on the knowledge obtained from the characterization and behavioral analysis, this might be due to the kinetic transformation of NPs. When the particle size for instability is exceeded as a consequence of surface changes and agglomerations, rapid sedimentation occurs. After eliminating the NP-reactivity and obtaining NP-agglomerations, NPs are extracted from the digestion system (sedimentation). Due to that, the microorganisms are able to operate to their full potential and efficiency, which is an indication of extracellular inhibition and preclude probably the intracellular inhibition caused by ions release. The short-term effects of ENPs in batch experiments were investigated under identical conditions. Furthermore, oxygen was used as an inhibitor to intensify the NP’s effects on the anaerobic microorganisms and digestion process. Oxygen is toxic for anaerobic microorganisms and enhance the release of ions. NP-effects were evaluated for methane yield. It will be assumed that the corona formations created by the sludge substances, reduce the release of ions and the NP-toxicity, even after decreasing the biomass. In addition, the NPs are able to eliminate O2 as an inhibitor, as well as positively influence the production dynamics and methane yield. To sum up, the growing interest in nanoparticles and their potential has presented many challenges for science, in toxicology and innovative technologies. These challenges bring new questions related to understanding NPs and their interplay with certain circumstances. A considerable contribution has been made for understanding the behavior of nanoparticles in the environmentally relevant media. However, a partial understanding for the fate of nanoparticles in complex matrices has been gained. As the nanoparticles themselves are such a complex matter, they require more research in developing a more complete understanding of the way they function. Having this knowledge would enable to explore progressively their behavior and fate in complex matrices.. [less ▲]

Non-Monotonic Logics for Access Control: Delegation Revocation and Distributed Policies

Doctoral thesis (2017)

Second language learners’ self-initiated topic changes during book-related activities in preschool and their impact on Luxembourgish proficiency

Doctoral thesis (2017)

The present research traces the second language learning process in Luxembourgish during book related activities by 4- to 5-year old pre-schoolers with Portuguese, Cap Verdean and Brazilian origins. With ... [more ▼]

The present research traces the second language learning process in Luxembourgish during book related activities by 4- to 5-year old pre-schoolers with Portuguese, Cap Verdean and Brazilian origins. With 47,2% of the preschool population being of foreign origins, the Lusophone community forms the largest group with 24,1%. This salient fast growing multilingual and multicultural population learns Luxembourgish for integration and everyday interaction and, hence, challenges public education with its diverse and altering demands. The present study enlarges second language research in the Luxembourgish context and links to previous investigation on topics, however, by taking a pragmatic stance towards topics. Through the foregrounding of the local topic management as well as its impact on activities, which are less teacher controlled, the study pictures second language learning as a product of co-constructed interaction. The focus lies on the negotiation of story meaning through self-initiated topic changes during three book related activities: Joint reading, storytelling and play. The data consists of video recorded lessons and on stimulated recall interviews with the teachers. A multi-method framework is used to investigate pupils’ interaction and language learning processes. From a quantitative point of view, the study analyses how pupils’ utterance length varies according to the openness of the lesson by allowing self-initiated topic changes as well as the design of the book activity (1) led by teachers or (2) by the pupils. From a qualitative stance, a sequence-by-sequence analysis of the jointly constructed narrative identifies the interactional dynamics of the collaborative storytelling activities and the use of self-initiated topic changes which children draw upon to express themselves more freely. The results show that children’s utterances vary according to the activity type. Pupils produce longer utterances, when they can self-initiate a topic hereby boosting their second language proficiency – either because the teacher is withdrawing or because the participation framework is open enough for them to make creative use of the language. The children also show their capability of successfully managing topic changes without the presence of the teacher while at the same time co-constructing the meaning of the story and paying attention to lexical details. The interviews reveal the teachers’ astonishment for the degree of pupil participation as well as their pedagogical practices. Implications from the analysis are gathered in a theoretical model that links opportunities for self-initiated topic changes to language proficiency. Recommendations for a more active pupil participation during book related activities point to sense-making, joint topic negotiation and story enactment. [less ▲]

Welche Organisationsformen produzieren Wissenschaft? Expansion, Vielfalt und Kooperation im deutschen Hochschul- und Wissenschaftssystem im globalen Kontext, 1900-2010

Doctoral thesis (2017)

Overview and introduction “Which organizational forms produce science? Expansion, diversity, and cooperation in Germany's higher education and science system embedded within the global context, 1900-2010” ... [more ▼]

Overview and introduction “Which organizational forms produce science? Expansion, diversity, and cooperation in Germany's higher education and science system embedded within the global context, 1900-2010”. Already the title of my dissertation manifests an approach that examines the topic of the development of scientific productivity in the German higher education and science landscape from different perspectives: levels, dimensions, and an extensive timeframe. Deriving from and contributing to the international research project “Science Productivity, Higher Education, Research and Development, and the Knowledge Society” (SPHERE), my research focuses on the investigation of the influence of higher education development and science capacity-building on scientific knowledge production, globally, comparatively, and considerable depth for Germany, a key science producer for well over a century. Focusing mainly on the different structures and institutional settings of the German higher education and science system, the dissertations shows how these affected and contributed to the long-term development of scientific productivity worldwide. The historical, comparative, and in-depth analyses are especially important in light of advancing globalization and internationalization of science, stronger networks of scientists worldwide, and the emergence of the “knowledge society”. The research design combines macro- and meso-level analyses: the institutionalized and organizational settings in which science is produced. Since information about single authors was limited in availability, extensive micro-level analyses were not possible here, yet the research articles analyzed were all written and published by individuals working in organizations, which are in the center of analysis here. By reference to the dimensions expansion, diversity, and cooperation, I elaborated the frame of my investigation, and sorted my research questions, including country, organizational field and form, and organizational levels. The structure of this work (see outline) addresses these themes and the observed timeframe spans the years from 1900 to 2010 – more than a century (see section 1.2). My main goal was to investigate how and why scientists publish their research results in peer-reviewed journal articles. The point is to emphasize the importance of scientific findings/discoveries, because non-published results are non-existent for the scientific community. From the ways and in which formats scientists publish their work, we can deduce how science is organized (within and across disciplines). My dissertation analyzes publications in peer-reviewed journals, because they are the most important format – alongside patents in applied fields – to disseminate new knowledge in science, technology, engineering, mathematics, and health (hereafter STEM+ fields). Articles not only record new knowledge, but also contribute to the reputation of researchers and their organizations. Journal publications in reputable journals with peer-review have become the “gold standard” measure of scientific productivity. Within the last several decades, the scientization of many dimensions of societal life proceeded, and the generation of new knowledge increasingly became the focus of political, economic, and social interests – and research policymaking. Therefore, it is important to identify the institutionalized settings (organizations/organizational forms) in which science can best be produced. Here, the diverse types of organizations that produce science – mainly universities, research institutes, companies, government agencies and hospitals – were identified and differences and similarities of these organizational forms were analyzed on the basis of their character, goals, tasks, and the kinds of research their members produce. In a first step, I show why I structured my work at the interface of higher education research, science studies, and bibliometrics (see chapters 2 and 5). Analyzing publications is still the key task of bibliometrics, but the results are used by many other actors as well: higher education managers, politicians, and scientists themselves to make claims about the quality of science, to compare each other, or to influence the structure, organization, and output of the higher education and science system. While it is difficult to make direct statements about the quality of research on the basis of simply counting the number of research articles a scientist publishes, the quality of journals is used as a proxy to compare across disciplines. To measure quality, other parameters are necessary. Thus, here statements focus on the quantity of science produced, not on the intrinsic quality of the analyzed research articles, the specific research achievements of individual scholars, organizations or organizational forms, or even countries. Nevertheless, output indicators elaborated here definitely show the huge expansion of scientific production and productivity, the stability of the research university over time as the most important science producer in Germany, but also rising differentiation and diversification of the organizational forms contributing to overall scientific output. Furthermore, the start of a considerable and on-going rise in national and international collaborations can be dated to the early 1990s. The chapter about the multidisciplinary context (see chapter 2) discusses the relationship between higher education research and science studies in Germany as well as the special position of scientific knowledge in comparison to other forms of knowledge. Scientific knowledge is generated, distributed, and consumed by the scientific community. To get an overview about the most important studies in the field, and to contextualize my work within the already existing empirical studies, I describe the current state of research in chapter 3. Research questions Section 1.2 provides a detailed description of my research questions: Which organizational forms produce science? 1. How has worldwide and European scientific productivity developed between 1900 and 2010 in comparison? 2. How has the German higher education and science system been embedded in the global developments of higher education and science over time? 3. How has scientific productivity in Germany developed between 1900 and 2010? 4. Among all science-producing organizational forms, what do the key organizational forms contribute to scientific productivity? 5. Which organizational forms provide the best conditions for scientific productivity? 6. Which single organizations produce the most research in Germany? 7. What is the impact of increasing internationalization of research on national and international cooperation, measured in publications in scientific journals? Theoretical framework Theoretically (see chapter 4), I apply a neo-institutional (NI) framework to explore and explain both the tremendous expansion of higher education and science across the world and considerable differences across time and space in the institutional settings, organizational forms, and organizations that produce scientific research in Germany. Sociological NI focuses on understanding institutions as important in guiding social action and shaping processes of social development. Such an approach emphasizes the development, functioning, and principles of institutions. Milestones in NI describe the nexus of organization and society supposing that organizational structures express myths and reflect ideals institutionalized in their environment. While capturing, copying, and asserting these, structural similarity (institutional isomorphism) between organizations in society will be established. The concept of “organizational field” emphasizes relationships between organizations within an environment. Organizational fields (communities) consist of all relevant organizations. In section 4.1.2 I discuss the differences between institutions and organizations and the difficulty of a distinction of the terms, especially in German-speaking sociology, which does not distinguish clearly between these terms. Fundamentally, NI approaches differ in the dimensions or pillars and levels of analysis they privilege (see figure 5, p. 80), but they share fundamental principles and the theoretical framework. Thus NI is particularly suitable for a multi-level analysis of scientific productivity across time and space. The historical development of the German higher education and science system must analyzed considering also global developments, because on the one hand it had an enormous impact on the development of other systems worldwide, and, on the other hand, global trends affect the on-going institutionalization and organization(s) of science in Germany. Intersectoral and international cooperation is growing and becoming increasingly important, leading to diverse networks within and between higher education and science systems worldwide. The classical, national case study is hardly longer possible, because macro units like countries are highly interdependent, embedded in global, regional and local relationships, such that borders between the global and the national dimension are increasingly blurred. Nevertheless, countries are units with clearly defined boundaries and structures, thus they can be handled as units to compare. The theoretical perspectives and different levels of analysis addressed here are displayed in Figure 5. I apply the “world polity” approach as a broader lense with which to make sense of the truly global arena of higher education and science (macro level). The focus of this perspective is on global and international structures and processes, which developed over time. Through this perspective, I explore global diffusion and formal structures of formal principles and practical applications. Combining historical and sociological institutionalism helps to focus on developments and processes over time on the meso level, to explain how institutions have developed and change(d). The concepts of “critical junctures” and path dependencies are useful to explain these processes over time. To describe the transformation of knowledge production over the entire twentieth century, and to analyze different organizational forms that produce science in Germany, two prevalent theoretical concepts are discussed: Mode 1 versus Mode 2 science, and the Triple-Helix model to describe the relationship between science, industry and state. In “The New Production of Knowledge” Michael Gibbons and his colleagues describe the transformation of knowledge from an academic, disciplinary, and autonomous – “traditional” – organization of science (Mode 1) with a focus on universities as the key organizational form, to a more applied, transdisciplinary, diverse, and reflexive organization of science (Mode 2) that features a more diverse organization of science, relying on a broader set of organizations producing knowledge. Within the literature, debates center on whether this new model has replaced the old, and which of these models best describes the contemporary organization of science (here: the STEM+ fields). In turn, the Triple-Helix model preserves the historical importance of the universities. This approach assumes that future innovations emerge from a relationship between universities (production of new knowledge), industry (generation of wealth), and state (control). Data and methods In these analyses, only peer reviewed journal publications were used – as the best indicator for measuring the most legitimated, authoritative produced science. This focus enabled an investigation of publications in-depth and over a 110 year timeframe. Research articles in the most reputable, peer-reviewed, and internationally reputable journals are the gold standard of scientific output in STEM+. The data I used is based on a stratified representative sample of published research articles in journals in STEM+-fields. My measure relies on the key global source for such data, the raw data from Thomson Reuters’ Web of Science Science Citation Index Expanded (SCIE) (the other global database is Elsevier’s Scopus, which also indexes tens of thousands of journals), which was extensively recoded. Methodologically, my approach is based on a combination of comparative institutional analysis across selected countries and historically of the German higher education and science system, and the systematic global evaluation of bibliometric publication data (see chapter 6). The SCIE includes more than 90 million entries (all types of research), mainly from STEM+-fields. I focus on original research articles, because this type of publication contains certified new knowledge. The SPHERE dataset covers published research articles from 1900 to 2010. From 1900 to 1970, we selected data in 5-year-steps in the form of a stratified representative sample. From 1975 onwards full data is available for every year. Depending on the research question, either five or ten-year steps were analyzed. A detailed description of the sampling and weighting of the data can be found in chapter 6. In consideration of the criteria above, I analyzed 17,568 different journals (42,963 journals were included into the database if we count the same journals in different years), and a total of 5,089,233 research articles. To prepare the data for this research, it had to be extensively cleaned and coded. Very often our international research team found missing information on the country level and/or on the level of organizations/organizational forms. From June 2013 to December 2015, research in the archives of university libraries was necessary to manually add missing information, particularly organization location and author affiliations. In the field of bibliometrics, we find different methods to count publications. In this work, I mainly apply the “whole count” approach (see table 1, p. 126). This decision is based on the assumption that every author, organization, or country contributed equally to a publication. An overestimation of publications can’t be precluded, because research articles are counted multiple times, if a paper is produced in co-authorship, which has been rising worldwide over the past several decades. The absolute number of publications (worldwide, Europe, Germany) is based on a simple counting of research articles (without duplicates, in cases of co-authored articles). Summary of the most important results The empirical part of my work is divided into three parts. In the following sections, I will present the most important findings. The global picture – higher education and science systems in comparison The central question of my research project was “which organizational forms produce science”? For a better understanding and classification of the results of my case study, I embedded the German higher education and science system into the European and global context. I answered the questions “how did the worldwide and European scientific productivity developed between 1900 and 2010 in comparison”, and “how was/is the German higher education and science system embedded in global developments of higher education and science over time” as follows: First, I show that the worldwide scientific growth followed a pure exponential curve between 1900 and 2010 (see figures 3 and 10; pp. 50, 147) – and we can assume that this strong upward trend continues today. The massive expansion of scientific production had and still has a tremendous influence on societal developments, beyond simply economic and technical developments, but rather transforming society. I show that higher education and science systems worldwide exhibit communalities, which have led to similar developments and expansion of scientific productivity. The comparison of important European countries (Germany in comparison with Great Britain, France, Belgium and Luxembourg) uncovered the contribution of the development and spread of modern research universities and the extraordinary and continued rise in publication output (see section 7.2; Powell, Dusdal 2016, 2017a, 2017b in press). Within the global field of science, three geographical centers of scientific productivity have emerged over the twentieth century: Europe, North America, and Asia. Their relative importance fluctuates over time, but today all three centers continue to be the key regions in the production of scientific research in STEM+ journals. Especially in Asia, the growth rates have risen massively in recent years (Powell et al. 2017 in press). Second, I investigated that all countries worldwide invest more into research and development (R&D) (figure 9, p. 140). These investments have a clear impact on the scientific productivity of nations, yet there are important differences between countries in absolute production and productivity rates. Alongside direct investments in R&D or the application of patents in STEM+-fields that influence the expansion of science, the capacity for producing more knowledge fundamentally depends on rising student enrolments, a growing number of researchers, the widening of research activities into various arenas of society, the development of products, and the (re-)foundation of universities (Powell, Baker, Fernandez 2017 in press). As part of the higher education expansion and massification during the 1960s and 70s, the numbers of researchers and students rose tremendously. The growth of scientific publications thus results from the on-going institutionalization of higher education and science systems worldwide. The growth of publications is also explained by the steady growth in the number of researchers working within these growing – and increasingly interconnected – systems. Third, I could reject the argument of Derek J. de Solla Price that the pure exponential growth of scientific literature has to flatten or would slow-down several decades after the advent of “big science” (see paragraph 2.4; figure 4 and 10; p. 53, 147). Although radical historical, political, economical, and technical events (see figure 11, p. 150) led to punctual short-term decreases in publication outputs, the long-term development of universities and other organizational forms producing science led to sustained growth of scientific publications, with the numbers of publications rising unchecked over the long twentieth century. In 2010, the worldwide scientific productivity in leading STEM+ journals was about one million articles annually. Fourth, I could show that the absolute numbers have to be put into perspective and standardized in relation to the investments in R&D, the size of the higher education and science systems, the number of inhabitants (see figure 12, p. 159), and the number of researchers (table 3, p. 162; figure 13, p. 164). The initial expansion of scientific publications in STEM+-fields is based on a general growth of higher education and science systems. The different institutional settings and organizational forms that produce science have an impact on scientific productivity. The selected country case studies – Germany, Great Britain, France, Belgium and Luxembourg – demonstrate that systems with strong research universities are highly productive; they seem to provide conditions necessary for science. As a result, not only the number and quality of researchers is important, but also the institutional and organizational settings in which they are employed. Fifth, in international comparison, Germany continues to contribute significantly to scientific productivity in STEM+ fields. With an annual growth rate of 3.35%, Germany follows the United States and Japan. In 2014, German governments invested €84.5 billion in R&D – 2.9% of overall GDP. The EU-target of 3% by 2020 was barely missed. In 2010, Germany produced 55,009 research articles (see table A5). In comparison to Great Britain, France, Belgium and Luxemburg, Germany still leads in scientific output in Europe –comparing just the absolute numbers. The size of the country itself and the institutionalization of the higher education and science systems influence publication outputs, of course, with these absolute numbers in relation to other key indicators showing a different picture. Standardized by the number of inhabitants, Germany published less articles per capita than Belgium and Great Britain. The number of researchers amounted to 327,997 (FTE) in 2010. The ratio of inhabitants to scientists was 1,000:4. Among these countries studied in-depth, Luxembourg and Great Britain had more researchers per capita than did Germany. The interplay of the organizational forms of science in Germany between 1900 and 2010 On the basis of the analysis of the global and European contexts, and development of worldwide scientific productivity over time in chapter 7, I started the in-depth case study of Germany. Bridging this overview and the following in-depth analyses is a chapter on the institutionalization of the German higher education and science system (see chapter 8). Here, I described the most important institutions and organizations and the organizational field – universities, extra-university research institutes and universities of applied sciences. Furthermore, I discussed the differences between West and East Germany during their division (1945–1990). Summarizing the most important results shows that the development of publications in Germany follows global and European trends (on a lower scale) (see figure 16, p. 208). Over time, Germany experienced pure exponential growth of scientific publications and a rising diversity of organizational forms that contribute to scientific productivity (see sections 9.1 and 9.3). I answered the following three research questions: “how has the scientific productivity in Germany developed between 1900 and 2010”, “among all science producing organizational forms, what do the key organizational forms contribute to scientific productivity”, “which organizational forms provide the best conditions for scientific productivity”, and “which single organizations are the most research intense in Germany”? First, the growth curve of scientific publications in Germany turns out as expected – it shows pure exponential graph, comparable with the worldwide and European development of scientific productivity between 1900 and 2010. Here, too, cataclysmic events such as the two world wars and the Great Depression as well as reunification had only short-term (negative) impact (figure 11, p. 150) on scientific productivity, without even a medium-term slow-down or flattening of the curve. By 2010, the total number of publications in STEM+ fields by researchers in German organizations topped 55,000 in one year alone. Second, a detailed examination and comparison of the development of scientific productivity in West Germany and East Germany between 1950 and 1990 showed that the growth rate of Germany (altogether) was based mainly on steady growth of scientific publications in West Germany (see figure 17, p. 211). The growth curve of the former GDR was quite flat and proceeded on a very low level. As a result, I conclude that the GDR’s higher education and science system, based on its academy model, did not provide conditions for scientific productivity as optimally as did the BRD. Third, a detailed analysis of the “key classical” organizational forms of science – universities and extra-university research institutes – show that universities were and are the main producers of scientific publications in STEM+ from 1975 to 2010 (see figure 18, p. 217). On average, university-based researchers produced 60% of all articles and defended their status against other organizational forms, which leads to the rejection of the Mode 2 hypothesis. Non-university publications reached an average of 40%. But that does not mean that other organizational forms were not producing science as well. The percentage share of articles is ultrastable and shows only marginal variations. The thesis that the proportion of university publications should decrease over time can be rejected for the period from 1975 to 2010. This suggests that scientific productivity of universities is actually rising, since despite decreasing financial support (R&D) in favor of extra-university research institutes, the universities produced more research articles with less resources over time. Fourth, although not only scientists within universities and research institutes publish their research in scientific journals, jointly these organizational forms have produced more than three-quarters of all research articles since 1980. Already in the earlier years, they produced a large number of scientific articles. Other organizational forms also generate scientific knowledge (for an extensive description of the organizational form matrix, see table 4, pp. 222f.). Especially scientists in firms, government agencies, and hospitals publish articles in peer-reviewed journals in STEM+ (see figures 19 and 20; pp. 220, 246). Indeed, the universities have been the driving force of scientific productivity for more than a century. With their specific orientation to basic research and their linkage of research and teaching, they provide conditions that facilitate the production of science. Universities are among the oldest institutions with a high degree of institutionalization. All other organizational forms (academies, associations, infrastructures, laboratories, military, museums and non-university education) were identified in the dataset played only a minor role and were summarized in the category “further types”. Fifth, the analysis of the ten most research-intensive single organizations in Germany in the year 2010 confirmed the results. Only universities and institutes were part of this group. A summary of publications of single institutes under their umbrella organizations shows that the institutes of the Max Planck Society and of the Helmholtz Association are the leading science producers in Germany, outpacing the scientific productivity of universities, but only when aggregating the contributions of dozens of individual institutes (see table 5, p. 259f). An analysis of single institutes shows that these research institutes cannot compete with universities, because of their size and the number of researchers. The Charite – Universitätsmedizin Berlin, a hybrid organization, is another leading science producer in Germany. National and international cooperation of scientific research Finally, increasing internationalization of research has impacted on national and international cooperation. leading to collaboratively-written publications in scientific journals. Through advancing globalization, national and international scientific cooperation increased in volume and importance. International cooperation in STEM+ is facilitated by the reputation of the research organization and of the co-authors, higher visibility within the scientific community and more possibilities for interdisciplinary research as well as better or more specialized facilities. Today, more than a third of all research articles worldwide are produced in scientific collaboration; only around a quarter are single-authored articles. In contrast to Humboldt’s principle “in Einsamkeit und Freiheit” (in loneliness and freedom), research is no longer done by one scientist, but is much more likely the result of collaboration. Research networks are increasingly important, and researchers share their common interests on a research question, publishing their results in joint publications. Researchers, organizations, and indeed countries differ in the ways they organize their research and thus how they enable research and collaboration. This depends on location, size, higher education and science system, the organizational field and organizations. Here, varying patterns of scientific cooperation were presented, showing a massive increase in scientific collaboration in (inter)national co-authorships over time. Until the 1990s, researchers in all investigated countries (France, Germany, Great Britain, USA, Japan, China, Belgium, Luxembourg) published their research articles mainly as single-authored papers. Only since the 1990s have co- and multi-authored publications risen (considerably): In 2000, only a third of all publications were published by one author. In 2010, the proportion reached its lowest level with only one-fifth of all papers single-authored (see table 6, pp. 279f). Countries differ considerably in their amount of collaboratively-written research articles. References Powell, J. J. W. & Dusdal, J. (2016). Europe’s Center of Science: Science Productivity in Belgium, France, Germany, and Luxembourg. EuropeNow, 1(1). http://www.europenowjournal.org/2016/11/30/europes-center-of-science-science-productivity-in-belgium-france-germany-and-luxembourg/. Last access: 13.12.2016. Powell, J. J. W. & Dusdal, J. (2017a): Measuring Research Organizations’ Contributions to Science Productivity in Science, Technology, Engineering and Math in Germany, France, Belgium, and Luxembourg. Minerva, (). Online first. DOI: 10.1007/s11024-017-9327-z. Powell, J. J. W. & Dusdal, J. (2017b in press). The European Center of Science Productivity: Research Universities and Institutes in France, Germany, and the United Kingdom. IN Powell, J. J. W., Baker, D. P. & Fernandez, F. (Hg.) The Century of Science: The Worldwide Triumph of the Research University, International Perspectives on Education and Society Series. Bingley, UK, Emerald Publishing. Powell, J. J. W., Baker, D. P. & Fernandez, F. (2017 in press). The Century of Science: The Worldwide Triumph of the Research University, International Perspectives on Education and Society Series. Bingley, UK, Emerald Publishing. Powell, J. J. W., Fernandez, F., Crist, J. T., Dusdal, J., Zhang, L. & Baker, D. P. (2017 in press). The Worldwide Triumph of the Research University and Globalizing Science. IN Powell, J. W., Baker, D. P. & Fernandez, F. (Hg.) The Century of Science: The Worldwide Triumph of the Research University, International Perspectives on Education and Society Series. Bingley, UK, Emerald Publishing. [less ▲]

Estimation of nonlinear panel data models: an integrated likelihood based approach

Doctoral thesis (2017)

DRYING AND CONVERSION ANALYSIS OF BIOMASS BY A DEM-CFD COUPLING APPROACH

Doctoral thesis (2017)

Biomass materials as a type of renewable energy sources have attracted many attention nowadays to decrease fossil fuel usage due to ecological and economical benefits. The main objective of this PhD ... [more ▼]

Biomass materials as a type of renewable energy sources have attracted many attention nowadays to decrease fossil fuel usage due to ecological and economical benefits. The main objective of this PhD thesis is studying the drying and conversion of biomass materials with employing a hybrid four-way DEM-CFD coupling approach in which considers the solid particulates as discrete elements coupled via heat, mass and momentum transfer to the surrounding gas as continuous phase. Where a comprehensive three-dimensional numerical model is developed and applied to investigate the complex phenomena taking place during biomass drying and conversion in a reactor. That is referred to take into account the physical and chemical processes as heat-up, drying, pyrolysis, gasification and combustion including the essential heterogeneous and homogeneous reactions which is considered as an interactive solid-gas multiphase system. In the proposed model, the motion and thermodynamic state of the particles are involved with employing the relevant governing equations. Where the conductive and radiative heat transfer between particles as well as convective heat transfer between particles and gas phase are taken into account. In addition, some interfaces are extended for coupling the solid particles and the gas phase to consider the interactions in between. At first, the importance of biomass resources is discussed and then the mathematical modeling employed in the PhD thesis is explained thoroughly. To apply the model, four different cases are assessed where two chapters discuss the drying behavior of biomass particles in two different situations. Afterwards, the motion of solid particles in a bubbling fluidized bed is examined. Finally, the conversion of wood materials in a bubbling fluidized bed is determined. [less ▲]

Dynamic change of the human gastrointestinal microbiome in relation to mucosal barrier effects during chemotherapy and immune ablative intervention

Doctoral thesis (2017)

Numerous studies have demonstrated that the gastrointestinal tract (GIT) microbiota plays important roles for the human host. Since the GIT microbiota interfaces with the immune system and represents a ... [more ▼]

Numerous studies have demonstrated that the gastrointestinal tract (GIT) microbiota plays important roles for the human host. Since the GIT microbiota interfaces with the immune system and represents a first line of defense against infectious agents, interest has grown in whether the GIT microbiota may influence the outcome of different anticancer treatments. In this study, the GIT of pediatric patients with different cancer types as well as adult patients with hematologic malignancies undergoing an allogeneic hematopoietic stem cell transplantation were sampled throughout their treatment. In order to deeply profile not only the composition of the community, but also the functional capacity and expression, recently developed wet- and dry-lab methodologies for integrated multi-omic analyses were applied. The trajectories of the prokaryotic and microeukaryotic GIT communities of the patients were described in detail using 16S, 18S rRNA gene amplicon sequencing, as well as metagenomic and metatranscriptomic shotgun sequencing. Indeed, changes in the GIT microbiome in response to treatment were detected. Some changes that are generally thought to be detrimental for human health were detected during treatment, such as a decrease in alpha-diversity, a decrease in relative abundance of bacteria associated with health-promoting properties (such as Blautia spp., Roseburia spp. and Faecalibacterium spp.), as well as an increase in the relative abundance of antibiotic resistance genes. These changes were more pronounced in the adult hematology patients than in the pediatric patients, which is likely due to the more intensive treatment. Some observations need further investigation in order to explain their implication in human health. For example, in the pediatric patients, lower relative abundance of Akkermansia muciniphila was associated with mucositis and functional gene categories that are linked to bacteriophages or the bacterial defense mechanism against bacteriophages were associated with the overall status of the patient and mucositis development. Importantly, in both cohorts, high inter-individual but also high intra-individual variation in the prokaryotic communities were detected while the microeukaryotic community did not exhibit drastic changes. In conclusion, the employed integrated multi-omics analysis allowed detailed profiling of the GIT community including archaea, bacteria, eukaryotes and viruses as well as the functional potential including antibiotic resistance genes. In the future, analysis of the individual-specific processes within the GIT microbial community of patients throughout treatment might allow to adjust therapy regimens accordingly and improve the overall outcome of the therapy. [less ▲]

Spin texture of two-dimensional topological insulators

Doctoral thesis (2017)

Since the discovery of two-dimensional topological insulators a decade ago, their one-dimensional edge states have attracted significant attention due to their unique properties. For example due to time ... [more ▼]

Since the discovery of two-dimensional topological insulators a decade ago, their one-dimensional edge states have attracted significant attention due to their unique properties. For example due to time-reversal symmetry, they are protected against elastic backscattering and they propagate such that electrons with opposite spins move in opposite directions. In fact, the only necessary symmetry to sustain the edge states is time-reversal symmetry. Moreover in experimental setups, the axial spin symmetry seems to be absent. This absence allows new processes to appear such as inelastic backscattering. However, these consequences were neglected in most theoretical works where the spins are considered to be polarized in the z direction. The aim of this thesis is to provide a more realistic model taking into account a broken axial spin symmetry. In this scheme, we show that a rotation of the spin quantization axis as a function of momentum always appears. This observation leads us to develop a deeper understanding of the size of the rotation related to the material parameters and material models, using also realistic values. It also leads us to understand the implications in real space in cases where translation invariance is lost and how to quantify the rotation in such systems. The new processes which arise when the axial spin symmetry is broken have important consequences for transport in real materials. To see this, we consider a Hall bar with a hole in its middle, i.e. an antidot. This enables us to create two tunneling regions in order to probe the effect of this generic model. We also consider the effect of Coulomb interactions around the hole, as they can be important in such geometry. We discover that it is possible to probe directly the absence of axial spin symmetry. As experimental evidence is important to investigate our theoretical findings, we propose spectroscopic means to probe the spin texture. Finally, we also consider one of the experimentally-known candidate materials, namely InAs/GaSb heterostructures. From the k.p Hamiltonian, it is possible to show that their bandstructure shows some anisotropies. The latter is also reflected in the spin texture of their edge states. [less ▲]

Cross-border evidence gathering: equality of arms within the EU?

Doctoral thesis (2017)

The European Union (EU) has set the objective to develop an Area of Freedom, Security and Justice, in which on the one hand freedom of movement is promoted and on the other hand a high level of security ... [more ▼]

The European Union (EU) has set the objective to develop an Area of Freedom, Security and Justice, in which on the one hand freedom of movement is promoted and on the other hand a high level of security is ensured. The EU is therefore adopting measures to enhance international cooperation in criminal matters among the police and judicial authorities of its Member States. The adopted instruments concerning evidentiary matters, such as the gathering, freezing and/or confiscation of information and materials in another EU Member State, seem to serve the main purpose of assisting the authorities in investigating and prosecuting (cross-border) crime. This raises the question to what extent the defence is also given the possibility to gather – or to have gathered – information and materials in another EU Member State with the aim of preparing and presenting its case at trial and, in particular, whether the current (EU) legal framework on cross-border evidence gathering meets the requirements of the principle of equality of arms. This thesis addresses this question by, first of all, discussing the concept of equality of arms, as enshrined in both Article 6 ECHR and Article 47 CFR. It explains to what extent this principle is applicable to cross-border or transnational criminal proceedings and whether it has an autonomous meaning within the EU. In addition, it discusses which requirements can be deduced from the principle in relation to the possibilities of the defence to gather evidence in another EU Member State to prepare and presents its case. Subsequently, the focus is on the development of the European legislation – from both the Council of Europe and the EU – regulating the procedure of cross-border evidence gathering over the last decades. The aim is to explain the position of the defence in this development and to what extent the European legislation gives opportunities to the defence to request the assistance of foreign authorities in obtaining specific information and materials in another EU Member State. In order to understand how the European legislation is applied in practice by the EU Member States, this thesis includes a comparative study of three national jurisdictions: the Netherlands, England and Wales, and Italy. These three jurisdictions each represent a different criminal justice system, either more inquisitorial or adversarial in nature. The comparative study describes how a chosen jurisdiction interprets the principle of equality of arms. Furthermore, it examines to what extent the national jurisdiction allows the defence to carry out independent investigations abroad and how it gives the defence the opportunity to trigger the mechanism of international cooperation and to participate in the requested investigation. Finally, this thesis also includes an analysis of the criminal justice system of the International Criminal Court. In this system evidence gathering depends most of the time on State cooperation and both the Prosecutor and the defence are allowed to conduct independent investigations and seek the assistance of States. It is therefore used as a source of inspiration for potential changes of the EU legislation on cross-border evidence gathering. [less ▲]

Integration of the analysis of non-functional properties in Model-Driven Engineering for embedded systems

Doctoral thesis (2017)

The engineering of embedded systems relies on two complementary activities: modeling on the one hand enables to represent the system, analysis on the other hand makes it possible to evaluate the various ... [more ▼]

The engineering of embedded systems relies on two complementary activities: modeling on the one hand enables to represent the system, analysis on the other hand makes it possible to evaluate the various non-functional properties (for example, temporal properties with the real-time scheduling analysis). This thesis deals with the integration between these models and analyses: how to apply an analysis on a model? How to manage the analysis process? The first part of this thesis presents a comprehensive approach to answer these questions. This approach is based on four application layers: (1) models to represent the system, (2) accessors to extract data from a model, (3) analyses to compute output data and/or properties from input data (4) contracts to represent the analysis interfaces and orchestrate the analysis process. The second part of this thesis deals with the experimentation of this approach with concrete systems coming from the aerospace: a drone, an exploratory robot and a flight management system. We demonstrate that the accessors enable to apply various real-time scheduling analyses on heterogeneous architectural models, for example written with the industry standard AADL (Architecture Analysis and Design Language) or the new time-triggered language CPAL (Cyber-Physical Action Language). In addition, contracts make it possible to automate complex analysis procedures: which analysis can be applied on a given model? Which are the analyses that meet a given goal? Are there analyses to be combined? Are there interferences between analyses? Etc. [less ▲]

Entwicklung eines EDV-basierten Frühwarnsystems für die Blankaalabwanderung an der Mosel

Doctoral thesis (2017)

The eel (Anguilla anguilla L.) is a fish that is mainly found in European waters. The River Moselle is among the bodies of water inhabited by this specimen. During the downstream migration into their ... [more ▼]

The eel (Anguilla anguilla L.) is a fish that is mainly found in European waters. The River Moselle is among the bodies of water inhabited by this specimen. During the downstream migration into their Atlantic spawning ground, silver eels often experience severe to fatal injuries while passing the turbines at the barrages. This annual migration takes place in a relatively narrow timeframe. Therefore, knowing the trigger or beginning of said migration, the mortality rate of the eels could be reduced by a fish-adapted turbine control or comparable protective measures. This thesis introduces an early warning system, which predicts the periods of silver eel emigration by means of certain abiotic factors. On the basis of the information gleaned from different studies and the experience gained from many years of professional fishing, those environmental factors were identified which are connected with the migration of the silver eel. Extensive data analyses were used to substantiate these findings. The water flow, the flow differences and the lunar phase were particularly relevant. Furthermore, the season and the water temperature were taken into account. In view of the different sources of information (experience and expert knowledge, data sets and the findings derived from it), a hybrid structure of the early warning system was realized. After examining different methods from the fields of soft computing and mathematics or statistics, the fuzzy logic (knowledge-based), the case-based reasoning (casebased) and the artificial neural networks (data-based) were selected. With each of these methods, an independent prediction model was designed, tested and optimized. Special characteristics were found during the data analysis and were taken into account by the use of adequate modifiers. The models were tested on the basis of the present data sets for the Moselle. It was shown that it is possible to correctly predict most of the situations with increased catches (suggesting a migration). Threshold values for a migration were defined based on the catches. The same was done for the forecast values. Thus, for the 1963 to 1973 data record, a total of 63% (artificial neural networks), 74% (fuzzy logic), and 83% (case-based reasoning) of the events with increased catches could be detected. Since not every situation with a favorable constellation of abiotic factors also led to a migration or higher catches, a lot of "false" forecasts (up to 50%) were made as well. Good results have also been achieved when using data from recent years and most events were identified. A stand-alone program was developed for the practical application of the prognosis models. This early warning system is a software which contains a user interface for reading data and displaying prognosis values and into which the developed prognosis models are implemented. In addition, recommendations for use were compiled and presented. [less ▲]

MicroRNA regulation of hypoxia-induced tumorigenicity and metastatic potential of colon tumor-initiating cells

Doctoral thesis (2017)

The initiaton and progression of colorectal cancer (CRC), which is the second most common cause of cancer mortality in Western countries, are driven by a subpopulation of highly tumorigenic cells, known ... [more ▼]

The initiaton and progression of colorectal cancer (CRC), which is the second most common cause of cancer mortality in Western countries, are driven by a subpopulation of highly tumorigenic cells, known as cancer stem cells or tumor-initiating cells (TICs). These self-renewing TICs are, to a large extent, responsible for therapy resistance, cancer recurrence, and metastasis formation. TICs are known to extensively interact with their microenvironment and can be influenced by various extrinsic factors, such as inflammatory signaling or tumor hypoxia. Previous expression profiling studies have shown that microRNAs (miRNAs) are involved in the regulation of CRC inititation and metastatic progression. Moreover, specifc miRNAs have been identified as potential mediators of the cellular response to hypoxia. On the other hand, the molecular mechanisms that link hypoxia, miRNA expression, colon TIC regulation, and CRC progression, remain poorly understood. Thus, the main objectives of this work were to analyze the effects of hypoxia on the miRNA expression of colon TICs and to identify miRNAs that regulate metastasis initiation. In a first phase, we generated and thoroughly characterized different stable TIC-enriched spheroid cultures (SCs), both from CRC cell lines and from primary patient material. Each established SC was thereby shown to display key TIC properties, including substantial plasticity, in vitro and in vivo self-renewal capacity and, most importantly, extensive tumorigenic potential. Moreover, the individual SCs displayed increased chemoresistance capacity, compared to adherent counterpart cultures. Taken together, we could demonstrate that the spheroid system is a suitable model to study colon TICs, thereby laying the methodological foundation for the following subparts of this project. In a second step, we studied the influence of hypoxia on the miRNA expression profile of our established SCs. MiR-210-3p was thereby identified as the miRNA with the strongest response to hypoxia. Importantly, both hypoxic culture conditions and stable overexpression of miR-210 were shown to promote in vitro and in vivo self-renewal capacity of our colon TIC-enriched cultures. Moreover, by promoting lactate production and by repressing mitochondrial respiration, miR-210 was found to trigger the metabolic reprogramming of colon TICs towards a glycolytic and aggressive phenotype. Finally, we studied the role of miRNAs in the context of TIC-driven metastasis formation. By comparing primary tumor- and lymph node metastasis-derived SCs, we were able to identify the miR-371~373 cluster as an important regulator of tumorigenic and metastatic potential. Stable overexpression of the entire miR-371~373 cluster, followed by gene and protein expression analysis, enabled us to uncover the transforming growth factor beta receptor II (TGF-βRII) and the inhibitor of DNA binding 1 (Id1) as miR-371~373 cluster-responsive proteins. Most importantly, different sphere, tumor, and metastasis formation assays revealed that the miR-371~373/TGF-βRII/Id1 signaling axis regulates the self-renewal capacity and metastatic colonization potential of colon TICs. Taken together, our findings emphasize the strong plasticity of colon TICs and clearly illustrate that miRNAs can act as potent modulators of essential TIC properties. Accordingly, we could show that miR-210 and the miR-371~373 cluster are involved in metabolic reprogramming of TICs and in the regulation of metastasis formation, respectively. Altogether, our study contributes to a better understanding of the molecular mechanisms that drive TIC-induced tumor progression and may provide indications for interesting miRNA biomarker candidates and target molecules for future TIC-specific therapies. [less ▲]

Scarring effects across the life course and the transition to retirement

Doctoral thesis (2017)

This thesis investigates the long-term negative effects of unemployment, labour market inactivity and atypical employment. Within the theoretical framework of cumulative advantages and disadvantages, it ... [more ▼]

This thesis investigates the long-term negative effects of unemployment, labour market inactivity and atypical employment. Within the theoretical framework of cumulative advantages and disadvantages, it is outlined how life-course differentiation creates gaps between age peers and cohorts and how this leads to social inequality in old age. In the three separate, but linked studies, disadvantages across the career and their associations to retirement are analysed. The focus of the analyses is laid on the outcomes of career disadvantages in form of subjective and financial well-being. The three studies all use the Survey of Health, Ageing and Retirement in Europe. This large and multidimensional panel study provides not only prospective, but also retrospective data on European countries. The data base is employed in different combinations in the studies. In the first and second study, the retrospective wave SHARELIFE provides information on employment biography and is related to well-being indicators of the regular waves. In the third study, the persistence of disadvantages upon retirement is observed with a causal model. The first study investigates how disadvantages are affecting careers and subjective well-being of older Europeans. In two complementary analyses, first the employment history of older Europeans is studied with sequence analysis methods to show how non-employment and part-time work shape careers and to illustrate gender differences. In a second step, indicators of timing and duration, exemplifying the accumulation mechanisms, are related to subjective well-being in old age. The results indicate that women experience more turbulent careers with more periods of non-employment and part-time employment. However, this is not reflected in lower subjective well-being in old age. Accumulation of non-employment disadvantages is far more comprehensive for men than for women. Part-time employment has an ambiguous effect for women, but is not relevant for men. In the second study, the household level is added and it is analysed how an adverse employment history is related to wealth accumulation. The results show that cumulative non-employment and employment in lower occupations has significant disadvantages for wealth accumulation in old age. However, large differences for men and women remain. Particularly, the household composition and household factors are decisive in the effectuality of these disadvantages. The third study includes the scarring question, that means if career disadvantages continue beyond the working life. The study examines whether non-employment disadvantages are still found in retirement and the extent to which well-being levels change in the transition to retirement. Well-being scores before and after retirement are obtained and unbiased effects of the retirement transition are identified. Results indicate that being unemployed before retirement is associated with an increase in life satisfaction, but presents mainly a catching-up effect compared to employed persons transitioning to retirement. Findings are robust to selection into unemployment and country differences. [less ▲]

The spread of public-private partnerships: a political economy analysis

Doctoral thesis (2017)

Amid a general trend to redefine and reform public services, public authorities around the globe have introduced and experimented with innovative ways of involving private actors in the provision of ... [more ▼]

Amid a general trend to redefine and reform public services, public authorities around the globe have introduced and experimented with innovative ways of involving private actors in the provision of public infrastructure and services — often referred to as Public-Private Partnerships (PPPs). Infrastructure-related PPPs are, usually, a contractual arrangement for a single undertaking to build and refurbish an asset where the public authority would mandate a single company to arrange the financing of the endeavour, to design and build the project, to be in charge of the maintenance and even, on some occasions, to manage the operation of public services related to the asset. A number of European national and regional governments and the European Union institutions have showed great interest in PPPs as an alternative procurement method, whereas some governments have abstained from this trend entirely or only used PPPs sporadically. This thesis — operationalised by a mix of qualitative and quantitative methods — is an inquiry into what factors inform the decision of public authorities to engage with PPPs more frequently. It involves testing a number of specific hypotheses generated to explain differential national engagement with PPPs, notably: the efficiency and effectiveness of the state (expressed as the state of public finances and the performance of public services); and a number of institutional variables — with institutions understood in this context as the incentives and constraints imposed by the national political system and the dominant mode of capitalism. This study reconfirms findings from the PPP literature on the conditions under which public authorities are more likely to have recourse to PPPs — i.e., authorities with less than optimally performing public services and/or experiencing budgetary constraints are expected to use PPPs more frequently. This thesis, however, also argues that other institutional factors are equally important for the likelihood of countries using this alternative procurement and financing method. On the one hand, the findings suggest that the ability of governments to introduce reforms — in the form of a favourable veto point structure in the political system and the government’s relative power vis-à-vis opposition parties — is a significant predictor for the numbers of established PPPs. On the other hand, the analysis shows the relevance of the economic system; the analysis reveals that the traditional mode of coordination in the national economy — i.e., either through contracts or non-market relations — has a greater influence on PPP uptake than commonly discussed in the literature. [less ▲]

Study of Metabolite Repair in Eukaryotic Cells: Metabolic origin and fate of D-2-hydroxyglutarate in yeast and effect of NAD(P)HX repair deficiency on yeast and human cells

Doctoral thesis (2017)

Abnormal metabolites, which are useless and can even be toxic, are constantly generated inside the cell by unwanted chemical reactions or by enzymatic side reactions. Metabolite repair enzymes clean the ... [more ▼]

Abnormal metabolites, which are useless and can even be toxic, are constantly generated inside the cell by unwanted chemical reactions or by enzymatic side reactions. Metabolite repair enzymes clean the metabolite pool from these molecules. The proportion of proteins annotated as metabolite repair enzymes is currently very small but accumulating evidence suggests that a bigger part might be hidden among proteins of unknown function. The aim of this thesis was to study two of these metabolite repair systems and their physiological relevance in more detail as their importance is well illustrated through implication in disease processes. D-2-hydroxyglutaric aciduria, a severe human neurometabolic disorder, can be caused by a deficiency in the metabolite repair enzyme D-2-hydroxyglutarate (D-2HG) dehydrogenase. Higher levels of D-2HG have also been observed in cancerous cells with a mutated form of isocitrate dehydrogenase. Strikingly, in the model organism Saccharomyces cerevisiae, 2-hydroxyglutarate metabolism had remained completely unexplored. We elucidated the metabolic pathways involved in D-2HG formation and degradation in yeast using bioinformatics, metabolomics, yeast genetics, and classical biochemical tools. We discovered that Dld3, currently annotated as a D-lactate dehydrogenase, actually degrades D-2HG to α-ketoglutarate while reducing pyruvate to D-lactate, thereby acting as a transhydrogenase. We also demonstrated that the yeast phosphoglycerate dehydrogenases Ser3 and Ser33 are major sources for D-2HG formation. These findings paved the way to integrate 2HG and its associated genes into the yeast metabolic network and might help, on the long-term, to better understand underlying mechanisms in human disease as well. Other recently identified metabolite repair enzymes, NAD(P)HX dehydratase and NAD(P)HX epimerase (encoded in yeast by the YKL151C and YNL200C genes, respectively), specifically act on NADHX and NADPHX, hydrated and inactive forms of the central NADH and NADPH cofactors. Although extensively biochemically characterized, the physiological importance of these two enzymes still remains largely unclear. Only very recently, case reports were published indicating a correlation between NAD(P)HX repair deficiency and severe neuropathological symptoms starting in early childhood upon events of febrile illnesses and rapidly leading to a fatal outcome. We systematically analyzed extracts of NAD(P)HX repair deficient yeast and human cells using HPLC and LC-MS/MS methods. This enabled us to demonstrate that NADHX and NADPHX can be formed intracellularly. In the yeast system, NADHX accumulation, which could be modulated by the cultivation temperature, was accompanied by a decrease in intracellular NAD+ levels. Furthermore, we showed that NADHX interferes with serine metabolism by inhibiting the first step of the main synthesis pathway of this amino acid. In the human cell system, NAD(P)HX dehydratase deficiency led, as in yeast, to intracellular NADHX accumulation, but also to a marked decrease in cell viability after prolonged cultivation times. This is, to our knowledge, the first report about the effect of NADHX accumulation on cellular metabolism. Expanding our experimental strategy of combined transcriptomics and metabolomics approaches to the human cell model might ultimately lead to the discovery of the disease-causing cellular process. The findings in both projects led to an unexpected connection between NAD(P)HX and 2HG metabolism via the yeast homologues of 3-phoshpoglycerate dehydrogenase, Ser3 and Ser33. Both proteins catalyze the oxidation of 3-phosphoglycerate to 3-phosphohydroxypyruvate in the initial step of de novo serine biosynthesis with a concomitant reduction of α-ketoglutarate to D-2-hydroxyglutarate. By acting as transhydrogenases, they substantially, even though not exclusively, contribute to D-2HG formation in yeast. The very same enzymes were strongly inhibited in vitro and, as suggested by our findings, also in vivo by the presence of NADHX, leading to serine depletion in NAD(P)HX repair deficient cells. [less ▲]

SLA Violation Detection Model and SLA Assured Service Brokering (SLaB) in Multi-Cloud Architecture

Doctoral thesis (2017)

Cloud brokering facilitates Cloud Service Users (CSUs) to find cloud services according to their requirements. In the current practice, CSUs or Cloud Service Brokers (CSBs) select cloud services according ... [more ▼]

Cloud brokering facilitates Cloud Service Users (CSUs) to find cloud services according to their requirements. In the current practice, CSUs or Cloud Service Brokers (CSBs) select cloud services according to Service Level Agreement (SLA) committed by Cloud Service Providers (CSPs) in their website. In our observation, it is found that most of the CSPs do not fulfill the service commitment mentioned in the SLA agreement. Verified cloud service performances against their SLA commitment of CSPs provide an additional trust on CSBs to recommend services to the CSUs. In this thesis work, we propose a SLA assured service-brokering framework, which considers both committed and delivered SLA by CSPs in cloud service recommendation to the users. For the evaluation of the performance of CSPs, two evaluation techniques: Heat Map and Intuinistic Fuzzy Logic (IFL) are proposed, which include both directly measurable and non-measurable parameters in the performance evaluation CSPs. These two techniques are implemented using real data measured from CSPs. Both performance evaluation techniques rank/- sort CSPs according to their service performances. The result shows that Heat Map technique is more transparent and consistent in CSP performance evaluation than IFL technique. As cloud computing is location independent technology, CSPs should respect the current regulatory framework in delivering services to the users. In this work, regulatory compliance status of the CSPs is also analyzed and visualized in performance heat map table to provide legal status of CSPs. Moreover, missing points in their terms of service and SLA document are analyzed and recommended to add in the contract document. In the revised European data protection regulation (GPDR), data protection impact assessment (DPIA) is going to be mandatory for all organizations/tools. The decision recommendation tool developed using above mentioned evaluation techniques may cause potential harm to individuals in assessing data from multiple CSPs. So, DPIA is carried out to assess the potential harm/risks to individuals due to decision recommendation tool and necessary precaution to be taken in decision recommendation tool to minimize possible data privacy risks. To help CSUs in easy decision making to select cloud services from multi-cloud environment, service pattern analysis techniques and prediction of future performance behavior of CSPs are also proposed in the thesis work. Prediction patterns and error measurement shows that automatic prediction methods can be implemented for short time period as well as longer time period. [less ▲]

Key-Recovery Attacks Against Somewhat Homomorphic Encryption Schemes

Doctoral thesis (2017)

In 1978, Rivest, Adleman and Dertouzos introduced the concept of privacy homomorphism and asked whether it is possible to perform arbitrary operations on encrypted ciphertexts. Thirty years later, Gentry ... [more ▼]

In 1978, Rivest, Adleman and Dertouzos introduced the concept of privacy homomorphism and asked whether it is possible to perform arbitrary operations on encrypted ciphertexts. Thirty years later, Gentry gave a positive answer in his seminal paper at STOC 2009, by proposing an ingenious approach to construct fully homomorphic encryption (FHE) schemes. With this approach, one starts with a somewhat homomorphic encryption (SHE) scheme that can perform only limited number of operations on ciphertexts (i.e. it can evaluate only low-degree polynomials). Then, through the so-called bootstrapping step, it is possible to turn this SHE scheme into an FHE scheme. After Gentry's work, many SHE and FHE schemes have been proposed; in total, they can be divided into four categories, according to the hardness assumptions underlying each SHE (and hence, FHE) scheme: hard problems on lattices, the approximate common divisor problem, the (ring) learning with errors problem, and the NTRU encryption scheme. Even though SHE schemes are less powerful than FHE schemes, they can already be used in many useful real-world applications, such as medical and financial applications. It is therefore of primary concern to understand what level of security these SHE schemes provide. By default, all the SHE schemes developed so far offer IND-CPA security - i.e. resistant against a chosen-plaintext attack - but nothing is said about their IND-CCA1 security - i.e. secure against an adversary who is able to perform a non-adaptive chosen-ciphertext attack. Considering such an adversary is in fact a more realistic scenario. Gentry emphasized it as a future work to investigate SHE schemes with IND-CCA1 security, and the task to make some clarity about it was initiated by Loftus, May, Smart and Vercauteren: at SAC 2011 they showed how one family of SHE schemes is not IND-CCA1 secure, opening the doors to an interesting investigation on the IND-CCA1 security of the existing schemes in the other three families of schemes. In this work we therefore continue this line of research and show that most existing somewhat homomorphic encryption schemes are not IND-CCA1 secure. In fact, we show that these schemes suffer from key recovery attacks (stronger than a typical IND-CCA1 attack), which allow an adversary to completely recover the private keys through a number of decryption oracle queries. As a result, this dissertation shows that all known SHE schemes fail to provide IND-CCA1 security. While it is true that IND-CPA security may be enough to construct cryptographic protocols in presence of semi-honest attackers, key recovery attacks will pose serious threats for practical usage of SHE and FHE schemes: if a malicious attacker (or a compromised honest party) submits manipulated ciphertexts and observes the behavior (side channel leakage) of the decryptor, then it may be able to recover all plaintexts in the system. Therefore, it is very desirable to design SHE and FHE with IND-CCA1 security, or at least design them to prevent key recovery attacks. This raises the interesting question whether it is possible or not to develop such IND-CCA1 secure SHE scheme. Up to date, the only positive result in this direction is a SHE scheme proposed by Loftus et al. at SAC 2011 (in fact, a modification of an existing SHE scheme and IND-CCA1 insecure). However, this IND-CCA1 secure SHE scheme makes use of a non standard knowledge assumption, while it would be more interesting to only rely on standard assumptions. We propose then a variant of the SHE scheme proposed by Lopez-Alt, Tromer, and Vaikuntanathan at STOC 2012, which offers good indicators about its possible IND-CCA1 security. [less ▲]

Development of an integrated omics in silico workflow and its application for studying bacteria-phage interactions in a model microbial community

Doctoral thesis (2017)

Microbial communities are ubiquitous and dynamic systems that inhabit a multitude of environments. They underpin natural as well as biotechnological processes, and are also implicated in human health. The ... [more ▼]

Microbial communities are ubiquitous and dynamic systems that inhabit a multitude of environments. They underpin natural as well as biotechnological processes, and are also implicated in human health. The elucidation and understanding of these structurally and functionally complex microbial systems using a broad spectrum of toolkits ranging from in situ sampling, high-throughput data generation ("omics"), bioinformatic analyses, computational modelling and laboratory experiments is the aim of the emerging discipline of Eco-Systems Biology. Integrated workflows which allow the systematic investigation of microbial consortia are being developed. However, in silico methods for analysing multi-omic data sets are so far typically lab-specific, applied ad hoc, limited in terms of their reproducibility by different research groups and suboptimal in the amount of data actually being exploited. To address these limitations, the present work initially focused on the development of the Integrated Meta-omic Pipeline (IMP), a large-scale reference-independent bioinformatic analyses pipeline for the integrated analysis of coupled metagenomic and metatranscriptomic data. IMP is an elaborate pipeline that incorporates robust read preprocessing, iterative co-assembly, analyses of microbial community structure and function, automated binning as well as genomic signature-based visualizations. The IMP-based data integration strategy greatly enhances overall data usage, output volume and quality as demonstrated using relevant use-cases. Finally, IMP is encapsulated within a user-friendly implementation using Python while relying on Docker for reproducibility. The IMP pipeline was then applied to a longitudinal multi-omic dataset derived from a model microbial community from an activated sludge biological wastewater treatment plant with the explicit aim of following bacteria-phage interaction dynamics using information from the CRISPR-Cas system. This work provides a multi-omic perspective of community-level CRISPR dynamics, namely changes in CRISPR repeat and spacer complements over time, demonstrating that these are heterogeneous, dynamic and transcribed genomic regions. Population-level analysis of two lipid accumulating bacterial species associated with 158 putative bacteriophage sequences enabled the observation of phage-host population dynamics. Several putatively identified bacteriophages were found to occur at much higher abundances compared to other phages and these specific peaks usually do not overlap with other putative phages. In addition, there were several RNA-based CRISPR targets that were found to occur in high abundances. In summary, the present work describes the development of a new bioinformatic pipeline for the analysis of coupled metagenomic and metatranscriptomic datasets derived from microbial communities and its application to a study focused on the dynamics of bacteria-virus interactions. Finally, this work demonstrates the power of integrated multi-omic investigation of microbial consortia towards the conversion of high-throughput next-generation sequencing data into new insights. [less ▲]

Financial Intermediation and Macroeconomic Fluctuations

Doctoral thesis (2017)

Elucidation of new enzyme function using yeast, comparative genomics and metabolomics

Doctoral thesis (2017)

La fonction juridictionnelle au service de l’intégration sud-américaine. Regards croisés sur la contribution des juges régionaux à la construction d’un espace intégré : Europe et Amérique du Sud

Doctoral thesis (2017)

Regional integration is a global phenomenon understood in this book as “the association between sovereign States of a given geographical region, by international agreements with the aim of approximating ... [more ▼]

Regional integration is a global phenomenon understood in this book as “the association between sovereign States of a given geographical region, by international agreements with the aim of approximating national laws through a binding regional law”. In the context of South America, this definition had led to the study of six regional organizations, examined in a comparative manner to establish the degree of integration accomplished in this region. In a second step, the role of the law in an integrational organization and its control by a jurisdiction has been examined. Parallels are drawn between the role of the European Court of Justice and the EFTA Court and the regional jurisdictions in South America. Finally, the creation of a regional court through a Treaty, common to the six organizations compared is advocated. The political and legal feasibility, the precise characteristics, remedies and the character of the decisions of said regional court are discussed in depth. [less ▲]

EFFECTIVENESS OF EUROPEAN UNION LAW VERSUS PROCEDURAL PROTECTION : TRACING THE TENSION THROUGHOUT THE CASE-LAW OF THE COURT OF JUSTICE ON EX OFFICIO REVIEW BY THE NATIONAL JUDGE

Doctoral thesis (2017)

Ungleichheiten, Sexualität und Mehrsprachigkeit in der Migrationsgesellschaft. Bildungspolitische Problematisierungen und Macht in luxemburgischen Reformprojekten.

Doctoral thesis (2017)