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See detailEssays in Empirical Corporate Finance
Rolle, Gudrun UL

Doctoral thesis (2016)

The thesis comprises three independent though topically related papers that empirically investigate the relationship between corporate governance and finance. The first paper ‘Corporate Governance, Input ... [more ▼]

The thesis comprises three independent though topically related papers that empirically investigate the relationship between corporate governance and finance. The first paper ‘Corporate Governance, Input Market Regulation, and Equity Prices’ links how anti-competitive regulation in the input market impacts the effectiveness of corporate governance in terms of firm and market performance. For stock price related data, I find that governance and regulation are complements: abnormal returns of hedge portfolios based on corporate governance quality are only attainable in industries which are highly competitive. For companies in relatively competition-protected industries governance has no impact on market data. Turning to business fundamentals, the relationship reverses and governance and competition become substitutes, i.e. companies’ operating performance benefits from strong governance if the company operates in a relative anti-competitive industry. The second paper ‘Corporate Governance and Idiosyncratic Skewness: Evidence from External and Internal Provisions’ (co-authored with Thorsten Lehnert) analyzes the relationship between corporate governance and firm-specific skewness of stock returns for U.S. firms. Since firm-level skewness determinants are differences in investor opinion, information and information asymmetries, and companies with good corporate governance are more informative and transparent than their counterparts with less shareholder protection, we argue that differences in the quality of corporate governance matter to idiosyncratic skewness. We test this hypothesis by analyzing the impact of external as well as internal governance provisions, and are thus able to provide an overall understanding of the relationship between governance and firm-specific return asymmetries. The results show that better governance leads to a reduction in idiosyncratic skewness in relatively non-competitive industries. In industries that face higher levels of competition, governance has no impact on firm-specific return skewness. Especially the results of the internal governance analysis are robust and both statistically and economically significant. The third paper ‘Compensation Structure under Debt Insurance’ investigates the relevance of compensation structure as a means towards managerial incentive setting. Inside debt is designed to align managers with debt holders, and to mitigate risk-taking versus risk-avoiding conflicts of interest between shareholders and bondholders. Thus it constitutes an efficient component in the equity- and debt-like compensation structure of executives. However, under debt insurance the alignment structure should shift – towards the interests of equity holders. And it does. Exploiting first-time initiations of credit default swaps (CDS) on a reference entity, I show that companies whose debt can be insured through CDS significantly reduce their CEO’s relative debt-equity and incentive ratios, therefore shifting the incentive structure towards equity holders. The results are economically large and robust. [less ▲]

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See detailAnalysis of Bandwidth Attacks in a Bittorrent Swarm
Adamsky, Florian UL

Doctoral thesis (2016)

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See detailWissensgenerierung in Hybriden Foren: Dargestellt am Beispiel der Erstellung von Sozialindikatoren in internationalen Arbeitsgruppen
Decieux, Jean Philippe Pierre UL

Doctoral thesis (2016)

In modern knowledge societies, knowledge is increasingly co-produced in hybrid fora. Actors from heterogeneous contexts and social positions with different competences come together to discuss, negotiate ... [more ▼]

In modern knowledge societies, knowledge is increasingly co-produced in hybrid fora. Actors from heterogeneous contexts and social positions with different competences come together to discuss, negotiate and finally solve problems with real-life applications. The main goal of such a hybrid forum is to negotiate a common solution for very specific problems. <br />To date, little attention has been paid within sociology to this manner of common knowledge production in hybrid fora. Given the rise in popularity of hybrid fora, there is a need for empirical data. Addressing this need and filling this gap is a major goal of this thesis. Using the example of the construction of a specific set of quantitative Social Indicators, two case studies which illustrate how knowledge is co-produced in a hybrid forum will be presented. <br />Case Study I reconstructs the indicator production within an expert group of the European Commission. This group can structurally be characterized as a hybrid forum consisting of heterogeneous actors. The mission of this group is to create a set of indicators, namely the „European Dashboard on Youth Indicators“. This set of indicators is used as an information source for the promotion of evidence-based-policy-making for EU-Policy. This case study illustrates the structures and processes within a hybrid forum, reflecting the formative factors in the process and shows the final outcome of the indicator creation process. The analysis of this complex process highlights how the different perspectives of the stakeholders evolve and influence each other and which factors and conditions determine the decisions for the final integration of an indicator into the indicator system. This study also analyses which criteria are reflected in this hybrid context to evaluate the indicators and their consequences for practical use in different contexts of interest and application. <br />Case Study II builds on the results of Case Study I and reflects the possibilities, the potential and limitations of the practical application of the European Dashboard on Youth Indicators within the youth reporting system in Luxembourg. <br />The findings of these case studies provide a detailed and empirically grounded picture of factors influencing the indicator production within an expert group and the consequences for the alignment within a real-life application. Within the context of a rising awareness of the conditions of hybrid knowledge production, the results of these studies do not only offer a novel contribution for the perspective of the sociology of knowledge and research methodology, but also offer specific recommendations for the establishment of adequate contexts and structures for hybrid knowledge production in the context of practical applications. [less ▲]

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See detailThe role of self-regulatory capacity in the adaptation to pain
Rost, Silke UL

Doctoral thesis (2016)

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See detailELECTRODEPOSITION AND SELENIZATION OF METALLIC THIN FILMS FOR KESTERITE SOLAR CELLS APPLICATION
Crossay, Alexandre UL

Doctoral thesis (2016)

Thin films of Kesterite Cu2ZnSnSe4 (CZTSe) are prepared via a low energy cost and high material efficiency process, to be potentially used as light absorbers in solar cell devices. The fabrication process ... [more ▼]

Thin films of Kesterite Cu2ZnSnSe4 (CZTSe) are prepared via a low energy cost and high material efficiency process, to be potentially used as light absorbers in solar cell devices. The fabrication process involves two main steps: (i) formation of a metallic stack of Cu/Sn/Zn by sequential electrodeposition of Cu, Sn and Zn onto glass/Mo substrates; (ii) reactive annealing at 550°C in presence of Se and SnSe powders to form Kesterite. This thesis mainly aims at understanding the mechanisms of metal alloying and selenization occurring during step (ii), and their effects on the microstructure of the final film, the presence of secondary phases and their distribution in the thin films synthesized. The second objective is to understand their effects on the solar cells parameters. The stoichiometry of the precursor layers Cu/Sn/Zn is deliberately chosen to be Cu-poor and Zn-rich (Cu/(Zn+Sn)<1 and Zn/Sn>1), as it allows to reach the best power conversion efficiencies. Under these conditions, Kesterite, SnSe2 and ZnSe are expected. However, a study of different compositions shows that the predominant phases present are only Kesterite and ZnSe. SnSe2 is not present because this phase is unstable under the conditions of selenization, which leads to a self-regulation of tin content via gas phase exchange of SnSe during the selenization. Analyses of the selenization of Cu/Sn/Zn layers at short times and lower temperatures allow to deconstruct the mechanism of Kesterite formation into sequential steps. Because of the diffusion of metals and the formation of alloys, a reorganization of metals is observed in the thin films. The layers are then composed of Sn, Cu-Sn and Cu-Zn phases mainly, which are found to be segregating at large scales of tens of micrometers. During selenium incorporation, a tin self-regulation process is established, in which tin is depleted during the first stages of selenization, and then tin is replenished. ZnSe segregates at the surface of the absorber layer as large islands of 10-20 micrometers. By analyzing a specific position of a sample after the different process steps, it is shown that the segregation of ZnSe at this large scale is originating in the segregation of metals during alloying. Because of the presence of ZnSe on the surface of the films, part of the photocurrent generated in the absorber layer is not collected, which decrases the short circuit current of the devices. In this sense, a linear decrease of short circuit current is observed when the ZnSe molar ratio is increasing, and confirmed by external quantum efficiency (EQE) measurements showing a decrease of current collected through the whole range of photon energies. An optimal molar ratio of ZnSe/(CZTSe + ZnSe)=0.2 is found. Below this value, the short circuit current decreases, probably due to the formation of other types of harmful secondary phases such as Cu2SnSe3 or Cu2Se. A strong decrease of open circuit voltage and fill factor of the solar cells is proved to be related to the formation of blisters in the thin films, which result in the creation of pinholes due to their fragility. Formation of these blisters is supposed to originate from hydrogen evolution under the Cu layer during the electrodeposition process. Finally, a study of an additional process of prealloying between the steps of electrodeposition and selenization is presented, which demonstrates the possibility to increase the open circuit voltage of the solar cells by varying the time of this alloying step. A best power conversion efficiency of 7.2% is achieved via this method, which is close to the highest value of 9.1% reported for an electrodeposition-based process of Kesterite synthesis. [less ▲]

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See detailEvaluation of cognitive ability in heterogeneous student populations: Development of the Test of Cognitive Potential
Muller, Claire UL

Doctoral thesis (2016)

Evaluation of cognitive potential of individuals with diverse backgrounds often presents a challenge. Individuals’ imperfect mastery of the language of instruction in particular presents a major threat to ... [more ▼]

Evaluation of cognitive potential of individuals with diverse backgrounds often presents a challenge. Individuals’ imperfect mastery of the language of instruction in particular presents a major threat to validity of results and prohibits comparison to performance with better language skills. Eliminating language from test instruction may be a solution to this problem. The present thesis presents the development and validation of the innovative Test of Cognitive Potential (TCP), a language-free, tablet-based group-assessment tool designed to measure fluid intelligence within children in grade 4 (regular age between 9 and 10). Using dynamic visual instruction videos, task requirements are presented visually, without adding any verbal clarification. In order to sample a wide array of cognitive processes on different contents (domain-general, quantitative and semantic-syntactic reasoning as well as visual processing), the TCP includes a variety of subtests. Using confirmatory factor analysis, the overall structure of the test is evaluated within student samples from Luxembourg, Germany and Brazil. In a 2x2 design, measurement invariance of a latent TCP g-factor is further shown to largely hold across combinations of verbal vs. visual dynamic instruction and tablet-based vs. paper & pencil assessment. For the target TCP version (tablet and dynamic visual instruction), only one subtest is found to present increased residual variance and thus needs revision. Overall, a strong association of the TCP with criterion measures (educational achievement and a well-established test of cognitive ability) is found across samples. Measurement of a latent TCP factor could further be shown to be invariant across students with differential opportunity to learn. No strong evidence of biased measurement is found for students with different language backgrounds and socio-economic status. The Test of Cognitive Potential proofs to be a valid and reliable tool for the measurement of general cognitive ability. It will be particularly useful for the evaluation of children with limited understanding of the local language. Avoiding language bias, the TCP may contribute to the reduction of inequalities in educational opportunities that are produced by structural characteristics of many school systems. [less ▲]

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See detailCOMPOSITION AND INTERFACE STUDY OF Cu2ZnSnSe4 BASED SOLAR CELLS
Mousel, Marina UL

Doctoral thesis (2015)

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See detailGuarding the Guardians. Essays on Audit Regulation
Löhlein, Lukas UL

Doctoral thesis (2015)

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See detailEnergy-Efficient Driver Assistance System for Electric Vehicles Using Model-Predictive Control
Schwickart, Tim Klemens UL

Doctoral thesis (2015)

This thesis investigates a method to save energy and thus also extend the range of a series-production battery electric vehicle by influencing the driving style automatically with the help of a of a ... [more ▼]

This thesis investigates a method to save energy and thus also extend the range of a series-production battery electric vehicle by influencing the driving style automatically with the help of a of a cruise controller. An exploration of existing methods shows that the contextual consideration of the current and upcoming driving situation is necessary to realise safe and energy-efficient driving. This limits the appropriate approaches to online methods using updated predictions of the vehicle behaviour. It turns out that the most suitable method for the intended purpose is model-predictive control (MPC). The MPC generates controls for the accelerator pedal of the vehicle based on optimised predictions of the vehicle motion and energy consumption subject to the current and future road slope, curvature, speed limits and distance to an eventually preceding vehicle. The non-linear nature of the vehicle dynamics generally necessitates the use of a non-linear prediction model and solving a non-linear optimisation which goes along with difficulties in the online real-time implementation. However in this work - by exploiting and extending the tool sets of classical MPC - a controller based on a quadratic optimal control problem with linear constraints can be formulated that approximates the nonlinearities of the plant dynamics with equivalent accuracy as a non-linear formulation. A linear prediction model of the vehicle motion is derived by a change of the model domain from time to position and a change of variables to predict the kinetic energy of the moving vehicle instead of the driving speed. Further, a convex piece-wise linear energy consumption model is included in the inequality constraints of the problem according to the methodology of separable programming to capture the consumption characteristics of the vehicle in different operating points. In this form, real-time capability and the energy-saving potential of the presented control approach can be demonstrated by simulations of the closed loop and by implementing the controller for driving experiments. A Smart ED series-production battery electric vehicle is chosen for the practical tests and all models and parameters are identified and adapted to the characteristics of the car. In this application case, a significant energy-saving potential could be demonstrated compared to human drivers. To further reduce the computational burden and speed up the computation, the so-called move blocking method for input parameterisation of the MPC control trajectory is investigated and extended within this work to a flexible move blocking approach which enables a fast computation and at the same time high tracking performance. [less ▲]

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See detailImproved Predictions for Geotechnical Vibrations
Macijauskas, Darius UL

Doctoral thesis (2015)

In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in ... [more ▼]

In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in the soil may adversely affect surrounding buildings. These vibrations have to be predicted a priori by using currently available knowledge of the soil dynamics. Current research, conducted by Deltares research institute, showed that the reliability of methods for prediction of man-made vibrations is disappointingly low. Therefore the models for vibrations in the soil should be improved in order to get more accurate predictions. The main aim of this thesis is to increase the knowledge on dynamic soil behaviour with respect to the fundamental geotechnical aspects of the soil, like non-viscous damping, inhomogeneity, anisotropy, variable degree of saturation, etc. and to give an improved prediction method. The scientific investigations of this thesis started with the following setup: an oscillating plate on an elastic, homogeneous and isotropic half-space, where the plate oscillates harmonically in vertical direction and the soil is unsaturated. In this way, the geotechnical aspects have been left aside in order to check first whether it is possible to predict the vibration amplitudes of the oscillating plate and of the soil surface, without additional complexities. This setting allowed to compare the present analytical methods with the results, obtained from the finite element method (FEM) calculations, and showed that the analytical methods have their limitations. Therefore the wave-field near an oscillating plate had to be investigated more carefully. Unfortunately the state of the art in soil dynamics is such that only the particle vibration velocities are measured without knowing which part of the velocities/vibrations belongs to which type of basic wave (compressional, shear or Rayleigh wave). Therefore first of all, a technique to decompose the measured signal into its basic waves was developed. This new technique showed remarkably that all three basic waves have phase shifts and these phase shifts are all different from each other. The decomposition technique is an important tool for researching soil dynamics. Also a qualitative evaluation of the energy transmission between the basic waves near the vibration source was given, which showed that the R-wave energy starts at zero just at the source and grows in the near-field zone due to an energy transmission (body waves are transferring energy to the R-wave). This means that even without uncertainties in the soil body, there is a lack of understanding of the behaviour of the different waves. A real field test is performed with a shaker on a soft peaty site in the Netherlands, as an attempted to replicate the FE model experiments. It showed the limitations of the analytical methods and highlighted the indispensability of the FEM. Still, for engineering purposes, an improved analytical method is suggested, which is able to predict the geotechnical vibrations with good accuracy. Herein, one of the fundamental aspects, the material damping, was used and a hypothesis was made, that with a more correct physical model of the soil material damping, the vibration predictions with FEM can be improved. The 1D frictional damping model, first suggested by Van Baars (2011), was extended for the 3D and incorporated into the FEM software Plaxis as a User Defined Soil Material model. The results are very interesting scientifically, but do not give much better results as the already existing Rayleigh damping model. [less ▲]

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See detailDistribution Network Line Protection in the Presence of Distributed Generation
Margossian, Harag UL

Doctoral thesis (2015)

The evolution of the distribution network from a passive grid with unidirectional power flows to, in the presence of distributed generation (DGs), an active grid with bidirectional power flows can lead to ... [more ▼]

The evolution of the distribution network from a passive grid with unidirectional power flows to, in the presence of distributed generation (DGs), an active grid with bidirectional power flows can lead to some technical challenges in its operation as well as some opportunities for greater control and grid support. This dissertation studies the impact of high levels of penetration of DGs into the power system on the operation of distribution network line protection. The contribution of DGs during faults results in varying short circuit current levels that are hard to predict. This complicates the design of distribution network line protection. If the DGs are located in between the protection device and the fault, the device sees a lower current than it would see in the absence of the DGs. Conversely, if they are connected upstream of the device, the device sees a higher current than before. This means that the reliability, selectivity and speed of the protection devices can be negatively or positively affected. This dissertation analyzes what can be expected from the DGs and how the protection devices themselves can be enhanced in order to avoid these potential problems. In the planning stage, it is possible to control the outputs of DGs during faults in a way that enhances the operation of the protection devices instead of hampering it. This can be done by enforcing regulations through distribution network grid codes. There are two main grid code requirements that directly impact the fault current levels in the network: fault ride through requirements that specify how long and for what voltages the DGs need to remain connected and dynamic voltage support curves that regulate their reactive current output during faults. From these requirements, three parameters are of particular interest: the voltage threshold above which the DGs need to remain connected, the maximum current that they should be capable of producing and the maximum reactive current that they are required to produce below a certain voltage. Using these three parameters, it is possible to control the fault current levels in the network and consequently increase the maximum amount of DGs that can be connected, without endangering the operation of the protection system. In the operating stage, it is possible to enhance the protection devices themselves so that they can deal with the varying fault current levels. Here, adaptive protection is considered. By gathering information about the changes in the network, including the status of switches and DGs and changing the settings of the protection relays accordingly, the reliability, selectivity and speed of the protection system can be maintained while increasing its complexity and cost. To get the information needed from the network, a modified state estimation is proposed. The distribution network is characterized by low observability due to the low number of measurements available. For this reason, load estimates and zero injection buses are added as measurements. To account for the additional uncertainty introduced by the presence of DGs, information about the DGs and their controls are used to add additional measurements that support the state estimation. When calculating the fault current levels in the network to choose the protection relay settings, it is important to correctly account for the fault contributions of inverter based DGs that represent a significant proportion of DGs connected to the distribution network. Unlike synchronous and asynchronous generators, inverter based DGs have a controlled current output during faults. By using an iterative process where the outputs of inverter based DGs are changed based on the calculated voltage at their terminals, a more accurate calculation of the short circuit current levels can be made. Employing these methods in the planning and operating stages, it will be possible to increase the amount of DGs that can be connected to the distribution network, while avoiding cascading faults, slower operation times and the unnecessary loss of load associated with protection mal-operation. The methods should be applied in reasonable steps and whenever needed in combination with each other to ensure the practicality of their implementation and to avoid unnecessary costs. [less ▲]

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See detailAnalysis of signal transduction pathways linking L-plastin Ser5 phosphorylation to breast cancer cell invasion
Lommel, Maiti UL

Doctoral thesis (2015)

The organisation of the actin cytoskeleton is regulated by abundant actin-binding proteins. Functional alteration of these proteins contributes to pathologies such as cancer where structural and ... [more ▼]

The organisation of the actin cytoskeleton is regulated by abundant actin-binding proteins. Functional alteration of these proteins contributes to pathologies such as cancer where structural and functional modifications of the actin cytoskeleton are linked to uncontrolled cell motility and signalling. The actin-bundling protein L-plastin has initially been detected in haematopoietic cells where it plays a role in the immune response. L-plastin is also ectopically expressed in several solid tumours and is often considered as a metastatic marker. L-plastin is known to be phosphorylated in vitro and in vivo with residue serine 5 (Ser5) being the major phosphorylation site. Ser5 phosphorylation increases the F-actin-binding and -bundling activity of L-plastin and regulates actin turn-over. Recent findings demonstrate that L-plastin Ser5 phosphorylation is crucial for invasion and metastasis formation. This research work has unravelled the signalling pathways leading to L-plastin Ser5 phosphorylation in breast cancer cells. Previously, protein kinase A, protein kinase C and phosphoinositide-3-kinase have been reported to play a role in L-plastin Ser5 phosphorylation depending on the cell type and environment. This work however reveals that RSK kinases are the predominant kinases responsible for L-plastin Ser5 phosphorylation in breast cancer cells. In vitro kinase assays revealed that RSK1 and RSK2 are able to directly phosphorylate L-plastin on Ser5 and a whole genome microarray analysis pointed to an involvement of the ERK/MAPK pathway in this event. The involvement of this pathway was consolidated by activation and inhibition studies as well as by siRNA-mediated knockdowns. To our knowledge, this is the first evidence that L-plastin Ser5 phosphorylation occurs via the downstream ERK/MAPK pathway kinases, RSK1 and RSK2. Moreover, a computational modelling approach enabled us to show that RSK is the most important activator of L-plastin in breast cancer cell lines compared to other previously identified kinases. We performed migration and invasion assays which showed that RSK knockdown, besides reducing L-plastin Ser5 phosphorylation, also impaired breast cancer cell migration and invasion. The identification of a novel substrate of RSK kinases whose phosphorylation is important for cancer cell invasion underlines the importance of RSK in cancer progression and highlights RSK as a promising drug target in certain invasive carcinomas. [less ▲]

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See detailDIFFERENTIAL EFFECTS OF IL-6-TYPE CYTOKINES, THEIR INTERPLAY WITH HYPOXIA AND RESULTING EFFECTS ON THE METABOLISM
Zimmer, Andreas David UL

Doctoral thesis (2015)

IL-6-type cytokines signal mainly via the Jak/STAT pathway using the common receptor chain gp130. They are implicated in various biological processes such as differentiation, apoptosis, tissue ... [more ▼]

IL-6-type cytokines signal mainly via the Jak/STAT pathway using the common receptor chain gp130. They are implicated in various biological processes such as differentiation, apoptosis, tissue regeneration and proliferation. However, one of their main functions is the regulation of inflammatory processes, especially the initial induction of an inflammatory response. They hereby exert key steps in the onset as well as in the termination of an inflammation and in the promotion of the shift from the innate to the adaptive immune response. In hepatocellular carcinoma (HCC) IL-6 has been identified as a key factor in the onset as well as in the progression of this cancer. In this study we first investigated the effects of the IL-6-type cytokine IL-27 on hepatic cells. By evaluating IL-27 signalling in several HCC cell lines as well as hepatic cells, we could demonstrate that IL-27 does, in contrary to other IL-6-type cytokines, activate STAT1 and STAT3. A transcriptional and protein read-out of STAT3 was not found in hepatic cells. Thus, IL-27 exerts interferon γ-like functions only in the liver. Interestingly, we could further show that the IL-27 signalling can still be repressed by the canonical IL-6-type cytokine feedback regulator SOCS3, following a pre-stimulation with other IL-6-type cytokines. The second part of this thesis focused on the effects of the IL-6-type cytokine Oncostatin M (OSM) on the cellular metabolism. We hereby evaluated to which extent OSM-mediated STAT3 activation can induce a Warburg-like, highly glycolytic, metabolic phenotype under normoxia. OSM induced the expression of HIF-1α, a key factor mediating the shift to a highly glycolytic phenotype, in several HCC cell lines and immortalized hepatocytes. In the non-neoplastic hepatocyte cell line, PH5CH8, this led to the induction of a more glycolytic metabolic phenotype. The observed changes in these immortalized hepatocytes did not fully resemble the metabolic state seen under hypoxia, since mainly the observed induction of PDK1 seems to explain the effect. Overall we could not observe strong effects on glycolytic enzymes or other canonical HIF-1α target genes involved in metabolism, on a transcriptional or protein expression level in the investigated cells. Interestingly we found that HIF-1α does not seem to be mediating all the early adaptions of the cellular metabolism to hypoxia. The early inhibition of the pyruvate dehydrogenase complex could be shown to be independent of the HIF-1α-mediated up-regulation of the pyruvate dehydrogenase kinase 1, but might rather be induced by reactive oxygen species, created during the switch from normoxia to hypoxia. In summary we could show that in the liver IL-27 exerts interferon γ-like effects. Additionally, cytokine-activated STAT3 does not per se induce a glycolytic metabolic phenotype and HIF-1α is not necessary for some of the early adaptions of the cellular metabolism to hypoxia. [less ▲]

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See detailELECTRICAL CHARACTERIZATION OF KESTERITE THIN FILM ABSORBERS AND SOLAR CELLS
Weiss, Thomas UL

Doctoral thesis (2015)

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See detailKonstruktvalidität des Komplexen Problemlösens unter besonderer Berücksichtigung moderner diagnostischer Ansätze
Kretzschmar, André UL

Doctoral thesis (2015)

This thesis addresses the question whether Complex Problem Solving (CPS) could be seen as a distinct cognitive ability construct that is not considered sufficiently in the context of established theories ... [more ▼]

This thesis addresses the question whether Complex Problem Solving (CPS) could be seen as a distinct cognitive ability construct that is not considered sufficiently in the context of established theories of intelligence. For this purpose, an introduction into the research field of CPS is provided in the first part of this thesis (chapter 1). It is shown that CPS research has always been strongly influenced by the quality of the assessment tools. Therefore, to evaluate whether CPS is an independent construct requires a particular emphasis on the quality of the CPS assessment tools. Consequently, the second part of this work deals with the assessment of CPS. In chapter 2, the general challenges for CPS assessment as well as important advantages and disadvantages of contemporary CPS assessment tools (using the example of MicroDYN) are discussed. In chapter 3, the development and first empirical results of a new CPS assessment tool called MicroFIN are presented. Chapter 4 covers a particular relevant topic of computer-based CPS assessment: the influence of ICT literacy (i.e. the competence in using computers) on specific CPS assessment tools. For this purpose, the impact of ICT literacy on MicroDYN performance is examined in three different samples (N1 = 222, N2 = 341, N3 = 389). In addition, based on a sample of a pilot study (N = 91) the influence of ICT literacy on MicroFIN performance is presented. The results indicate that the impact of ICT Literacy appears neither for MicroDYN nor for MicroFIN as a threat of test validity. The third part of this work covers the central question of this thesis, that is whether CPS could be seen as a distinct cognitive ability construct that is independent of established intelligence constructs. Therefore, several criteria for an independent ability construct are discussed in chapter 5. Taking current research findings for CPS into account, open research questions for the assumption of a distinct CPS construct are examined in two empirical studies. Study 2 (chapter 6; N = 1908) focuses on the incremental validity of CPS beyond verbal reasoning in explaining the variance of school grades. For the first time in current CPS research, additional predictors for school grades (i.e. school competencies) in the mathematical and the reading domain are considered. The results indicate an incremental validity of CPS in the mathematical, but not in the reading domain. In addition, the study provides evidence that the incremental validity of CPS holds only to a small degree if relevant predictors of school grades are simultaneously taken into account. In study 3 (chapter 7; N = 227), the validity of CPS is examined with a comprehensive operationalisation of several intelligence constructs. The results indicate evidence for convergent and discriminant validity. Consequently, CPS could be seen as a specific cognitive ability that is less covered by traditional intelligence tests. With regard to the incremental validity of CPS, evidence for a statistical prediction of school grades beyond established intelligence constructs is only found for a specific, but not for a construct-representative operationalisation of intelligence. In chapter 8, an alternative interpretation of the specific CPS variance is discussed. Based on that interpretation, which has not been considered in CPS research yet, CPS can be seen as a specific content facet of cognitive tasks, but not as an independent cognitive ability. In the last part of this thesis (chapter 9), the findings and considerations concerning the assessment and construct validity of CPS are summarized. Considering current CPS assessment tools and the results for MicroFIN, research questions that are still open and the potential for future CPS assessment are presented. Furthermore, the findings from study 2 and 3 are reviewed with regard to the criteria for an independent ability construct. Finally, the assumption of a distinct CPS construct in the nomological network of intelligence is evaluated. Although further research is needed to clarify this issue, currently the assumption of a distinct CPS construct independent from established intelligence constructs does not seem justified. [less ▲]

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See detailEFFECT OF TRANSMISSION TARIFFS ON INVESTMENTS IN CONVENTIONAL AND RENEWABLE POWER GENERATION, STORAGE AND TRANSMISSION IN THE COUPLED PAN- EUROPEAN DAY-AHEAD MARKET FRAMEWORK
Bilibin, Ilya UL

Doctoral thesis (2015)

This work examines how electricity transmission tariffs influence the composition of the future power plants fleet. Transmission tariffs are classified and an optimization model of power markets and ... [more ▼]

This work examines how electricity transmission tariffs influence the composition of the future power plants fleet. Transmission tariffs are classified and an optimization model of power markets and investors profit maximization is suggested. The work finds that transmission tariffs do influence investment decisions, though this influence is not large. [less ▲]

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See detailOn the behaviour of shear stud connections in composite beams with deep decking
Nellinger, Sebastian UL

Doctoral thesis (2015)

Steel-concrete composite construction has many advantages for the construction of multistorey buildings. The use of composite beams acting compositely with the floor slab achieves longer spans and reduces ... [more ▼]

Steel-concrete composite construction has many advantages for the construction of multistorey buildings. The use of composite beams acting compositely with the floor slab achieves longer spans and reduces the weight of the beams. The weight reduction can be further improved by replacing the solid concrete slab with a steel-concrete composite slab using steel decking. However, using composite slabs reduces the shear forces that are transferred between the slab and the beam. This is because the number of studs in the span is limited by the deck geometry. In addition, the load-bearing behaviour of studs in the ribs of composite slabs is different to studs in solid slabs and shows typically a reduced resistance per stud. Currently, [DIN EN 1994-1-1, 2010] applies an empirical reduction factor to the resistance of studs in solid slabs to analyse the resistance of studs in the ribs of composite slabs. A comparison to push-out test results shows that this formulae results in an unsatisfactory correlation. Furthermore, the reduction factor is unsafe in many cases with modern decking. The latest empirical reduction factors in [Konrad, 2011] are currently discussed as alternative to the rules of [DIN EN 1994-1-1, 2010]. They show a significantly improved correlation to test results and an increased field of application. A significantly higher correlation to test results is obtained with the mechanical model by [Lungershausen, 1988]. Because of the restrictive field of application and missing parameters, like the concrete strength, it is not discussed as replacement for the reduction factors. A newly conducted series of push-out tests with modern deep steel decking shows the insufficiency of the presented analysis methods of the stud shear resistance, as the predictions were in general non-conservative. Furthermore, depending on the geometry of the shear connection, a new failure mode was observed: Rib pry-out failure. Investigation on concentric and eccentric transverse loading of push-out specimens, to consider the loading conditions of a real slab, show in general beneficial influences on the load-slip behaviour. Based on the behaviour of the studs in push-out tests, equations for the shear connector resistance based on the failure modes are developed. A combined bending failure of the shear stud and the concrete rib is assumed. The observed failure modes in the tests are considered by different yield-lines of the shear stud. The shear resistance of the pure stud gives the upper bound for the shear connector resistance. The new equations show a good correlation to test results and are safe for modern types of steel decking. In comparison to [DIN EN 1994-1-1, 2010], the field of application is extended by the stud position, as in [Konrad, 2011], and deeper decking, as in [Lungershausen, 1988]. The analysis of the bending resistance of two accompanying beam tests confirms the accuracy of the new shear stud resistance. The beam tests have very low degrees of shear connection. The end-slip at ultimate load exceeds the limiting slip of 6mm, but at 95% of ultimate load the limiting slip is satisfied. A numerical model for composite beams is verified against the test results. The model considers the shear studs as non-linear springs. A simplified load-displacement curve is presented and verified against real load-slip curves. [less ▲]

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See detailViva vox iuris - oder die juridische Stimme der Literatur. Kafkas Der Proceß und Hoffmanns Der Sandmann im Spiegel der dogmatischen Anthropologie Pierre Legendres
Becker, Katrin UL

Doctoral thesis (2015)

The doctoral dissertation “Viva vox iuris” is aimed at extending the research on law and literature by developping a new perspective, based on Pierre Legendre’s “dogmatic anthropology”. Starting with an ... [more ▼]

The doctoral dissertation “Viva vox iuris” is aimed at extending the research on law and literature by developping a new perspective, based on Pierre Legendre’s “dogmatic anthropology”. Starting with an overview of the current state of research in this field, and based on a detailed presentation of Legendre’s theory, the dissertation develops the hypothesis that the deep entanglement of law and literature confers upon literature the capacity of either reinforcing the effectivity of cultural normativity, or of influencing it in the sense of a modificatory force. The plausibility of this hypothesis is then assessed by a thorough analysis of Kafka’s The Trial and Hoffmann’s The Sandman. The Trial is presented as being a novel that stages the failure of interpretation on the diegetic, hermeneutic as well as the production level, i.e. with regard to the author (– interpretation being, from Legendre’s perspective, the fundamental cultural technique assuring a non-delusional human existence). Being confronted with this failure and the consequent lack of a regime of sense, the reader gains insight, ex negativo, into the necessity of being inscribed, by way of interpretation, into an order of Reference that needs to be mediated by literature and law. With regard to The Sandman, the dissertation undertakes to show, through a combination of the concept of testimony with the dogmatic-anthropological core concepts of alterity and representation, how the fantastical blurring of the limits between reality and fiction, as staged in the novel, provides insights into the contingency of the fundamental structure of the normative order of cultural and subjective identity. [less ▲]

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See detailAstrophysical aspects of dark matter direct detection
Magni, Stefano UL

Doctoral thesis (2015)

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See detailNON-CONTRACTUAL LIABILITIES FROM CIVILIAN VERSIONS OF GNSS: CURRENT TRENDS, LEGAL CHALLENGES AND POTENTIAL
Loukakis, Andreas UL

Doctoral thesis (2015)

Galileo is to be Europe’s own Global Navigation Satellite System (GNSS). It is expected to provide a highly accurate, guaranteed global positioning service under civilian control. It will be interoperable ... [more ▼]

Galileo is to be Europe’s own Global Navigation Satellite System (GNSS). It is expected to provide a highly accurate, guaranteed global positioning service under civilian control. It will be interoperable with the Global Positioning System (GPS), the US version of GNSS. Remarkably enough, whereas GPS was introduced as a purely military system, Galileo will be the first solely civilian GNSS, offering a great number of useful -everyday life- applications. It is expected to become fully operational by the year 2020 as part of Horizon 2020, the EU’s funding program for research and innovation. For the operation of Galileo, advanced technology will need to be employed. A number of satellites will be placed into fixed orbits in outer space; the satellites will be constantly emitting navigational signals indicating their position at any given time and in a very precise way. The navigational signals will be received by any person possessing the necessary technology, such as a GNSS receiver (the so-called navis technology). When receiving the signals from at least four satellites, the receiver can accurately pinpoint the position of persons and goods around the globe. There will be many benefits in using this technology, such as more efficient navigation of different modes of transportation (i.e. navigation of planes or ships). Besides navigational data, Galileo satellites will provide information for timing and positioning. Hence, various applications concerned with the synchronization of economic networks (i.e. at banks or financial institutions) or scientific applications related to the environment and meteorology are expected to emerge. Nonetheless, where there are advantages, there are also risks and legal challenges. Questions relating to the civil liability of the Galileo’s system operator in the event of a GNSS failure -especially liabilities connected to signal provision in space- have attracted significant interest lately. For example, a failure in signal provision (i.e. signal loss or an erroneous signal) resulting from negligence with respect to the GNSS operator may lead to damage scenarios with catastrophic consequences: an aircraft crash in a densely populated area, or a shipwreck with disastrous effects for the environment would be two examples. Following these observations, several questions must be asked from a liability law perspective. Inter alia: what are possible civil liability implications emanating from the advent of civilian versions of GNSS such as the EU’s Galileo? Can the provision of defective information from signals lead to liability implications? What would be the responses under current legal provisions? And lastly, what need may arise in the future for the initiation of a centralized approach, for instance a unified instrument, either at EU or international level, regulating liabilities for the signal in space provision? Interestingly enough, once the first GNSS structures such as the US GPS or Russian GLONASS became operational, the issue of liability from a signal failure was not of such significant concern in light of their mostly military nature. Presently, the situation has changed to an important extent: due to the advent of new non-military versions such as Galileo, the issue of liability connected to the provision of navigational signals has become topical. This research aims at examining the foregoing questions related to civil liability implications (mainly non-contractual liabilities) from the perspective of civilian versions of GNSS. The EU’s Galileo will be the most prevailing example examined in the present study. The research attempts to investigate the civil liability ramifications especially from the GNSS-Galileo operator’s perspective. Since the governance issues surrounding the operation of Galileo are still subject to debate, the research features two hypothetical case studies: on the one hand, a public governance scheme with the EU operating the system and possible liabilities against the EU, and on the other hand, a private governance scheme with a private entity operating the system and potential liabilities towards the private operator. Both case studies are examined from a de lege lata and a de lege ferenda perspective. Yet, the present research attempts to identify some future proposals. As it is argued, the issue of GNSS liability should be first regulated at regional level rather than international level. In this respect, the EU could, for example, possibly promote a future EU Regulation. Moreover, and as established by the analysis of the present study, such a Regulation should contain two elements, a substantive and procedural one. For the resolution of disputes connected to signal provision in space, the rule of strict liability and liability channeling onto the operator from a substantive viewpoint may depict the peculiarities contained within the field of satellite navigation more efficiently. Most importantly, and as far as the resolution of such disputes is concerned, this study argues that binding arbitration may be a plausible and alternative option to be considered in the foreseeable future. To this end, certain inspirations can potentially be drawn by the new PCA Rules of Arbitration on Outer Space Disputes adopted recently in December 2011. [less ▲]

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See detailLightweight Public-Key Cryptography for Wireless Sensor Nodes
Liu, Zhe UL

Doctoral thesis (2015)

This thesis studies techniques for the efficient implementation of public-key cryptography on resource-constrained computing devices such as wireless sensor nodes. We focus on three different families of ... [more ▼]

This thesis studies techniques for the efficient implementation of public-key cryptography on resource-constrained computing devices such as wireless sensor nodes. We focus on three different families of public-key cryptosystems, namely RSA, elliptic curve schemes (e.g. ECDH), as well as a lattice-based encryption algorithm using the ring variant of the Learning With Errors problem (Ring-LWE). In the context of efficient RSA implementation, this thesis first describes the Reverse Product Scanning (RPS) technique for multi-precision multiplication and squaring on 8-bit AVR processors. Then, we analyze and compare six algorithms for software implementation of Montgomery multiplication and shed some new light on the relative performance of the different variants. Finally, we present a highly-optimized 1024-bit RSA software that achieves record-setting execution times on 8-bit ATmega processors thanks to a combination of sophisticated implementation options including the Chinese Remainder Theorem (CRT), the m-ary exponentiation method, as well as the RPS multiplication technique. The main contribution of this thesis lies in the area of Elliptic Curve Cryptography (ECC), where we describe three different implementations for wireless sensor nodes equipped with 8 and 16-bit processors. First, we present several techniques to improve the performance of prime-field arithmetic operations (e.g. optimized operand caching, sliding block doubling, and Karatsuba block squaring) and report the fastest implementation of key exchange and signature generation/verification based on the NIST P-192 curve. Second, we introduce an efficient yet highly-regular library for arithmetic in Optimal Prime Fields (OPFs) and propose a novel approach for the implementation of ephemeral ECDH key exchange that exploits the birational equivalence of Montgomery and twisted Edwards curves. Third, we describe an algorithm for the generation of so-called MoTE curves that allows one to use the fastest formulae for point addition/doubling in both the Montgomery form and the twisted Edwards form. Finally, we describe efficient ECC implementations for 159 and 191-bit MoTE curves that achieve record-setting execution times for scalar multiplication on a 16-bit MSP430 processor. The third part of this thesis deals with the efficient implementation of Ring-LWE encryption and proposes novel approaches to speed up the Number Theoretic Transform (NTT) used for polynomial multiplication. Our contributions in this area include the Move-and-Add (MA) method for coefficient multiplication, the Shift-Add-Multiply-Subtract-Subtract (SAMS2) technique for modular reduction, and an optimized variant for Montgomery multiplication. Furthermore, we describe an optimized coefficient storage method to minimize the RAM footprint of NTT multiplications. Finally, we propose a special byte-scanning technique to reduce the execution time of discrete Gaussian sampling based on the Knuth-Yao random walk algorithm. [less ▲]

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See detailCollusions and Privacy in Rational-Resilient Gossip
Decouchant, Jérémie UL

Doctoral thesis (2015)

Gossip-based content dissemination protocols are a scalable and cheap alternative to centralized content sharing systems. However, it is well known that these protocols suffer from rational nodes, i.e ... [more ▼]

Gossip-based content dissemination protocols are a scalable and cheap alternative to centralized content sharing systems. However, it is well known that these protocols suffer from rational nodes, i.e., nodes that aim at downloading the content without contributing their fair share to the system. While the problem of rational nodes that act individually has been well addressed in the literature, colluding rational nodes is still an open issue. In addition, previous rational-resilient gossip-based solutions require nodes to log their interactions with others, and disclose the content of their logs, which may disclose sensitive information. Nowadays, a consensus exists on the necessity of reinforcing the control of users on their personal information. Nonetheless, to the best of our knowledge no privacy-preserving rational-resilient gossip-based content dissemination system exists. The contributions of this thesis are twofold. First, we present AcTinG, a protocol that prevents rational collusions in gossip-based content dissemination protocols, while guaranteeing zero false positive accusations. AcTing makes nodes maintain secure logs and mutually check each others’ correctness thanks to verifiable but non predictable audits. As a consequence of its design, it is shown to be a Nash-equilibrium. A performance evaluation shows that AcTinG is able to deliver all messages despite the presence of colluders, and exhibits similar scalability properties as standard gossip-based dissemination protocols. Second, we describe P AG, the first accountable and privacy-preserving gossip pro- tocol. P AG builds on a monitoring infrastructure, and homomorphic cryptographic procedures to provide privacy to nodes while making sure that nodes forward the content they receive. The theoretical evaluation of P AG shows that breaking the privacy of interactions is difficult, even in presence of a global and active opponent. We assess this protocol both in terms of privacy and performance using a deployment performed on a cluster of machines, simulations involving up to a million of nodes, and theoretical proofs. The bandwidth overhead is much lower than existing anonymous communication protocols, while still being practical in terms of CPU usage. [less ▲]

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See detailInsilico genomes for high-throughput sequencing cancer-specific analysis
Killcoyne, Sarah UL

Doctoral thesis (2015)

As a genomic disease cancer is unique in that the entire genome can be highly unstable, with new mutations accumulating at a rapid rate and massive alterations to the chromosomal structure. Structural ... [more ▼]

As a genomic disease cancer is unique in that the entire genome can be highly unstable, with new mutations accumulating at a rapid rate and massive alterations to the chromosomal structure. Structural aberrations can be highly significant to a patient’s disease, resulting in aberrant proteins that can drive a cancer to progress faster or metastasize. Such aberrations may also have more subtle effects, enabling the cellular population to more rapidly develop drug resistance or simply generate highly diverse populations within a tumor making targeted therapies less effective. In fact it is these diverse or heterogeneous cellular populations, with highly mutated and frequently structurally aberrant genomes, that make understanding the extent of a tumor genome’s variation so challenging. Large scale sequencing efforts through the Cancer Genome Atlas and the International Cancer Genome Consortium have sequenced thousands of cancer genomes, and while small-scale variants have enabled researchers to begin to trace the evolutionary history and diversity of tumor genomes, large-scale structural variations have continued to be difficult to identify.Current methods and technologies for short-read sequencing generally rely on fitting genomes to a single reference assembly that is assumed to be representative of all individuals. Tumor genomes, which consist of heterogeneous cellular populations with unique aberrations can vary significantly from a ‘normal’ genome. This means that such single references are poor representations of a cancerous cell population, and so methods that rely less directly on the reference offer better opportunities to investigate these aberrations. In this project, a new method for large-scale structural variant identification, called MultiSieve, is proposed. This method uses prior knowledge to generate and test multiple references for each patient genome. Validation using simulated data establishes the utility of the method, and a comparison with commonly used methods demonstrates that MultiSieve is capable of finding variations often missed by traditional methods and that there are likely to be more structural variants in patients than have been identified previously. [less ▲]

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See detailVISUALISATION AND BINNING OF METAGENOMIC DATA
Laczny, Cedric Christian UL

Doctoral thesis (2015)

Metagenomic sequencing and assembly have become important approaches for the in situ characterisation of mixed microbial communities. Nevertheless, the data are typically fragmented and disconnected. The ... [more ▼]

Metagenomic sequencing and assembly have become important approaches for the in situ characterisation of mixed microbial communities. Nevertheless, the data are typically fragmented and disconnected. The binning of individual sequence fragments into population-level genomic complements promotes the population-resolved synchronous study of community composition and functional potential. However, current binning approaches require a priori knowledge, scale poorly to larger datasets, or exclude human input. In this work, a reference-independent approach for the visualisation and subsequent human-augmented binning of metagenomic sequence fragments, represented by their high-dimensional, oligonucleotide frequency-based signatures, is introduced. Due to the efficient and faithful representation of high-dimensional cluster structures in low-dimensional space, the described methodology facilitates the exploration and analysis of large datasets by a human user. Subsequently, a stand-alone software implementation, VizBin, is developed and described. This graphical user interface-based tool is designed to allow a user-friendly application of the herein introduced approach without the requirement of a bioinformatical background, special training, or exceptional computing resources. Following the software development, VizBin was applied for the analysis of human gastrointestinal tract-derived metagenomic sequencing data. This allowed the recovery of six virtually complete or partial genomes of hitherto uncharacterised and deeply branching microbial populations from four taxa including a potential butyrate-producing taxon. In summary, this work illustrates how improved recovery of population-level microbial genomes is achieved by reference-independent binning of assembled metagenomic sequencing data using human input. The broad applicability and robustness of the herein introduced approach is furthermore demonstrated by using VizBin for the visualisation of state-of-the-art long read-sequencing data. Despite the increased sequence error rate of this emerging type of sequencing data, pertinent cluster structures are revealed thus motivating the development of future read-level binning approaches. Targeted wet-lab validation of in silico recovered population-level genomes and comprehensive population-resolved analysis of microbial consortia in situ are key to advancing our knowledge and understanding of microbiota in different environments. [less ▲]

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See detailInterference in Multiple-antenna Communications: From Channel Estimation to Exploitation
Alodeh, Maha UL

Doctoral thesis (2015)

Multi-antenna technologies have emerged as attractive techniques of providing efficient and reliable communications in future wireless communications. The potential gain of multiple antennas in the ... [more ▼]

Multi-antenna technologies have emerged as attractive techniques of providing efficient and reliable communications in future wireless communications. The potential gain of multiple antennas in the downlink of wireless systems is well-known: if the spatial dimension is exploited to deliver simultaneous data streams to multiple users, the total data throughput increases linearly with the number of transmit antennas. However, interference in multiple-antenna communications presents a challenging factor that should be dealt with wisely in cellular systems. This thesis is concerned with tackling the interference at two different steps in the communications process: channel estimation, and downlink data transmissions. The interference at estimation process can occur in reciprocity based channel state information (CSI) acquisition if the utilized pilots are reused in the network. On the other hand, the interference at downlink occurs when the base station serves multiple users simultaneously over the same spectrum. This first part of the thesis focuses on the channel estimation in multiple antenna multicell interference-limited networks. The channel state information (CSI) acquisition is vital for interference mitigation. Wireless networks often suffer from multicell interference, which can be mitigated by deploying beamforming to spatially direct the transmissions. The accuracy of the estimated CSI plays an important role in de-signing accurate precoders that can control the amount of interference created from simultaneous spatial transmissions to mobile users. Therefore, a new technique based on the structure of the spatial covariance matrix and the discrete cosine transform (DCT) is proposed to enhance channel estimation in the presence of interference. Bayesian estimation and Least Squares estimation frameworks are introduced by utilizing the DCT to separate the overlapping spatial paths that create the interference. The spatial domain is thus exploited to mitigate the contamination and enhance the quality of estimation. The second part of the thesis focuses on the precoding techniques in the downlink of a single cell. The constructive interference concept in the downlink of multiple-antenna systems is addressed in this paper. The concept of the joint exploitation of CSI and data information (DI) is discussed. Using symbol-level precoding, the interference between data streams is transformed under certain conditions into useful signal that can improve the signal to interference noise ratio (SINR) of the downlink transmissions. In this thesis, not only different constructive interference precoding techniques are proposed for different types of modulation, but also a transmitter architecture that can accommodate them. These schemes optimize the performance of the symbol-level precoding with respect to different objectives such as: minimizing the transmit power under per user quality of service constraint, maximizing the fairness among different users under total power constraint. Extensive simulations are performed to validate our proposed techniques and show that they outperform the conventional precoding schemes. [less ▲]

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See detailMolecular function of TRIM32 in adult neurogenesis and regulation of Parkinson's disease associated genes
Pavlou, Maria Angeliki UL

Doctoral thesis (2015)

In the adult brain, neurogenesis is restricted in two brain regions: i) the subventricular zone (SVZ) of the lateral ventricles and ii) the dentate gyrus of the hippocampus. Adult neural stem cells of the ... [more ▼]

In the adult brain, neurogenesis is restricted in two brain regions: i) the subventricular zone (SVZ) of the lateral ventricles and ii) the dentate gyrus of the hippocampus. Adult neural stem cells of the SVZ continuously generate new neurons for the olfactory bulb (OB). The fate commitment of these cells is regulated by cell fate determining proteins. Here, we aim to investigate the role of TRIM32 during the process of adult neurogenesis and understand its function in the mammalian system. In addition, we aim to identify the role of TRIM32 in transcriptional regulation of Parkinson’s disease (PD) associated genes. We focus on alpha synuclein, a gene which is also implicated in neuronal dysfunction, death and proliferation of neural stem cells. Acquiring more knowledge about the regulation of this gene may be critical for PD pathogenesis and will allow us to come to a closer understanding of the disease. [less ▲]

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See detailPositivisme juridique, relativisme axiologique et démocratie : humanisme et unité dans la pensée de Hans Kelsen
Lefort, Elisabeth UL

Doctoral thesis (2015)

The work of Hans Kelsen has been largely discussed without the unity between its different questions has been plainly revealed. This unity is what we aim to demonstrate. In our opinion, an attentive and ... [more ▼]

The work of Hans Kelsen has been largely discussed without the unity between its different questions has been plainly revealed. This unity is what we aim to demonstrate. In our opinion, an attentive and critical reading of Kelsen’s late works allows such a possibility since it is in these works that the scholar himself tries to achieve this unification. To be able to understand this try and its sense, one must read Kelsen’s late works with the perspective of the moral relativism he defends. Indeed, this relativism can be interpreted as a symptom of modernity. Moreover, it can be defined as a modern humanism. In the Kelsenian thought, what links the legal positivism, the moral relativism and the political conception of democracy is the concept of equality that underlies them implicitly. Under this perspective, the Kelsenian moral relativism reveals itself as an agnosticism that is a philosophy of perpetual questioning. This interpretation is what allows one to render explicit the systematic character of the Kelsenian work. Moreover, such a reading render also explicit the importance of this work. Kelsenian agnosticism expresses the essence of modern philosoph. Since it defines itself as a questioning, it becomes the condition of possibility of both an authentic recognition of the Other and of democracy itself. [less ▲]

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See detailEl nexo migración-desplazamiento-asilo, entre el orden fronterizo de las cosas y su desafío: políticas migratorias/fronterizas de control y gestión y prácticas emergentes de ciudadanías transfronterizas en las fronteras España (Unión Europea)-Marruecos (África) y Colombia-Venezuela (CAN-Suramérica). 1990-2010.
Naranjo Giraldo, Gloria Elena UL

Doctoral thesis (2015)

The subject of study of this doctoral thesis is addressing to the nexus configuration between asylum and intern displacement migratory processes and the identifiable response in control and management ... [more ▼]

The subject of study of this doctoral thesis is addressing to the nexus configuration between asylum and intern displacement migratory processes and the identifiable response in control and management migratory and border-crossing policies which state a “Border-crossing Order of things ”. Additionally, analyzing the potential challenge/response to that identifiable order in “Transborder Citizenship Emerging Practices” by migrants, displaced people and refugees. A comparative study is carried out about/in the frontiers Spain-Morocco (European Union) and Colombia-Venezuela (Andean Community of Nations) in the period 1990-2010. In Chapter One, it is intended to made clear the coordinates about the What and How of the research as well as the results. This is done by three subsections: the literature review and the approach to the problem; research questions, hypothesis and research objectives; research methodology. The methodological design used poses a combination between qualitative and comparative research, which allow us to analyze and compare observations and descriptions (exploratory-descriptive research) and also to analyze and compare the addresses and representations (analytical-interpretive research). Generally, the type of comparison followed was the one proposed by Skocpol and Somers called “ Contrast of Contexts ” which is essential for the interpretive comparative variant in social sciences, different to the type of comparison by “ hypothesis control ”. On the other hand, we followed Charles Ragin’s (1987) suggestions about the “Case-oriented Research ” and about the complex problems of the “ Conjunctural Causality ”, in other words, causal models that vary “ according to the context ”. In Chapter Two, Global Order of Control and Management of Migrations and Borders.. The emergence from the Migration-Displacement-Asylum nexus, the contextualization is made and the characteristics for this order are shown; in order to highlight transformation of the international migration tendencies to forced migrations and alongside with it, the emergence of the Migration-Displacement-Asylum nexus. The global order of control and migrations management as a border regime responds to a policy spin and to the policies that transform the frontiers into a mechanism for the migration control (Faist, 2003); just as shown in the detailed description of the global and regional control agendas, management and migration and border-crossing cooperation; migration and border-crossing policies, and the protection and asylum policies for refugees, asylum seeker and migrants in the frontiers Spain-Morocco and Colombia-Venezuela. In Chapter Three, emerging typologies related to the migration-displacement-asylum nexus that allowed us to make the analysis and the comparison in the specific border-crossing zones Spain-Morocco and Colombia-Venezuela; which have a big potential of being used in other case studies. These typologies correspond to: the closely related causes of forced and voluntary migration in their home countries; the diverse motivations of several migrants, displaced and asylum seekers; motivation changes during migration for many migrants, displaced and asylum seekers; motivation changes during migration for many migrants, displaced people and asylum seekers; the close relation between refugees and economic migrants in some transit countries in the Spain-Morocco frontier and the close relationship between refugees and economic migrants on the way through Colombian regions; the rising similarities in the migration process for both “ forced ” and “ voluntary ” migrants; refugees and migrant workers can have similar experiences in the host countries; the experience of return, repatriation or deportation can be similar. We have built an analytical-comparative proposal that includes theoretical contributions from anthropology and politics about frontiers and migrations, entering into conversation with political theories about frontiers, migrations and citizenship. Our proposal consists in analyzing control and migration/border-crossing management politics and the “ transborder citizenship emerging practices ” through two analytic triads “ ( IBO-1 e IBO-2 ) ”, known in critical literature about frontiers as “ IBO ( IFO in spanish ) triad: Identities, Borders, Orders “ ( Kearney, 1995; Albert, Jacobson and Lapid, 2001; Van Houtuum and Van Naerssen, 2001 ). The analytic and comparative effort allowed to integrate the two triads in three related pairs ( I-1 and I-2 ), ( B-1 and B-2 ), ( O-1 and O-2 ) between the state-built identities and their migration policies ( I-1 ) and the ways of identification-disidentification that the migrants-displaced-asylum seekers and refugees claim and negotiate ( I-2 ). Between the states border-crossing control ( B-1 ) and the unauthorized border crossing of the migrants-displaced-asylum seekers ( B-2 ). Between the states’ power and the politics orders ( O-1) and the ways of political subjectivation from the migrants-displaced-asylum seekers and refugees (O-2 ). The IBO-1 triad corresponds to the border-crossing order of things and the IBO-2 triad to the potential challenge to that order via transborder citizenship emerging practices. In Chapters Four and Five, the previous analytical-comparative framework was applied in the Spain-Morocco and Colombia-Venezuela borders. In each case, the control and management migratory and border-crossing policies were analyzed taking into account three main aspects: identities production and classification, specially the political and civic identities. This is selectivity (Filter function); the frontierization practices, not only control and regulation but also the border-permeability function (Filter function), who can or cannot enter (citizens and non-citizens production ), taking into account the role of the States as well as their regional, global and local registry. In this dimension we talk about the border-crossing order of things. On the other hand, also in each case, the practices from the migrant, displaced, refugees, asylum seeker citizenships in other border games through de-frontierization practices; it is about authorized and unauthorized border-crossing agents and they answer to the Border Crossing Control but previously, they have been qualified and some identities have been attributed such as “irregulars“, “illegals”, “undesirables” and so on, against that, they answer de facto, claiming-verifying that “Any human being is illegal”; this through active processes of disidentification and disclassification, they will be rejecting, also de facto, their imputation as non-citizens; and in this process, they act as if they were citizens, in an equality verification as human beings and as a subject of universal law (Ranciére, 1999). Summarizing, these are “transborder citizenship emerging practices “ from these migrant subjects alongside with their regional, global and local registry. In this analysis dimension, we talk about the (potential) challenge to the border-crossing order of things. Chapter Six gathers the compared analysis about the Spain-Morocco and Colombia-Venezuela borders. In this doctoral thesis, defining two case study was from the beginning the search for a comparative analysis that allowed addressing every case itself to give account of its own dynamics and evolution. From the particularities of the migration-displacement-asylum nexus in each border-crossing zone, there was an advance in a comparison, not as a migratory flows problem itself, but in its political articulations related to migration/border-crossing control and management politics and the citizenship practices. Actors and their political interactions related to their position in the face of borders. Borders are the matters of dispute that reconfigures constantly the concept of politics and the political Chapter Seven about conclusions was oriented to answer the question “How migrants, displaced people and refugees are constituted as political actors and are allowed to appeal to their community members condition? As exposed in the conclusions, in their transborder migrants condition and the democratization assertion from the borders, the transborder citizenship emerging practices take shape. Finally, we present some limitations, possible contributions from the doctoral thesis and some proposals for the future research development. The importance of contributing with studies that overcome the methodological nationalism and the internal focus was posed; also contributing to the methodological, epistemological and conceptual change in the borders, migrations and citizenship studies and strengthening a new epistemic community; and contribution to the ongoing research program about the relation between identity, borders and political orders in border-crossing zones. This analytical-comparative proposal pretends to be one step to the formation of a method or a theory about the comparative anthropology in the borders and periphery and more specifically, as the presentation of the border-crossing order of things and its challenge hypothesis. Therefore, the same questions that we have posed in this doctoral thesis could be asked concerning different borders and demarcation and policies regimes to perform compared works about how some borders are built and the migration processes that pass through it. A short-term future researching development could be addressing the migration-displacement-asylum nexus with a comparative analysis of the borders between Colombia and Venezuela and, Ecuador and Panama in the post-peace agreement transition process. [less ▲]

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See detailChallenges and Outlook in Machine Learning-based Malware Detection for Android
Allix, Kevin UL

Doctoral thesis (2015)

Just like in traditional desktop computing, one of the major security issues in mobile computing lies in malicious software. Several recent studies have shown that Android, as today’s most widespread ... [more ▼]

Just like in traditional desktop computing, one of the major security issues in mobile computing lies in malicious software. Several recent studies have shown that Android, as today’s most widespread Operating System, is the target of most of the new families of malware. Manually analysing an Android application to determine whether it is malicious or not is a time- consuming process. Furthermore, because of the complexity of analysing an application, this task can only be conducted by highly-skilled—hence hard to come by—professionals. Researchers naturally sought to transfer this process from humans to computers to lower the cost of detecting malware. Machine-Learning techniques, looking at patterns amongst known malware and inferring models of what discriminates malware from goodware, have long been summoned to build malware detectors. The vast quantity of data involved in malware detection, added to the fact that we do not know a priori how to express in technical terms the difference between malware and goodware, indeed makes the malware detection question a seemingly textbook example of a possible Machine- Learning application. Despite the vast amount of literature published on the topic of detecting malware with machine- learning, malware detection is not a solved problem. In this Thesis, we investigate issues that affect performance evaluation and that thus may render current machine learning-based mal- ware detectors for Android hardly usable in practical settings, and we propose an approach to overcome those issues. While the experiments presented in this thesis all rely on feature-sets obtained through lightweight static analysis, several of our findings could apply equally to all Machine Learning-based malware detection approaches. In the first part of this thesis, background information on machine-learning and on malware detection is provided, and the related work is described. A snapshot of the malware landscape in Android application markets is then presented. The second part discusses three pitfalls hindering the evaluation of malware detectors. We show with extensive experiments how validation methodology, History-unaware dataset construction and the choice of a ground truth can heavily interfere with the performance results of malware detectors. In a third part, we present an practical approach to detect Android Malware in real-world settings. We then propose several research paths to get closer to our long term goal of building practical, dependable and predictable Android Malware detectors. [less ▲]

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See detailAutonomie – Metaphysik – Endlichkeit: Die Endlichkeit menschlichen Denkens bei Kant
Gunkel, Alexander Jürgen UL

Doctoral thesis (2015)

It is often maintained that German Enlightenment philosophy—and especially the Enlightenment program that Immanuel Kant articulated in his famous article in the Berlinische Monatsschrift—is not able to do ... [more ▼]

It is often maintained that German Enlightenment philosophy—and especially the Enlightenment program that Immanuel Kant articulated in his famous article in the Berlinische Monatsschrift—is not able to do justice to the role of testimonial knowledge and hence is an obstacle to a down-to-earth epistemology because of its essential individualistic stance. I argue that this is a misunderstanding and that Kant like other Enlightenment thinkers actually recognizes these social factors and their impact on our knowing and thinking. I show that Kant's philosophy can be reconstructed as an attempt to show the compatibility of Enlightenment's demand for independence and the essential dependency of finite cognizers. His mature philosophy aims at developing a kind of Enlightenment Ethics of Belief that can be found in the final sections of his Critique of Pure Reason. The central task of (a Kantian conception of) Enlightenment points to intellectual independence, the thinking for oneself and the spontaneous activity of our own intellectual faculties that is not ruled by others but only by ourselves. Now this activity should consist of the actualization of the common faculty of reason and not in arbitrary decision making to believe one thing over another. Thinking for oneself thus seems to be the outcome of a competence rather than the result of a mere decision. This is an insight which was famously defended by Christian Wolff. While Wolff claims that this competence is to be understood as being able to follow some special method—the mathematical method—Kant points to the social character of thinking. Thinking for oneself means competently reasoning in accordance with rules that can only be followed and assessed through conversational practice. How is this demand for maturity affected by our finiteness? To answer this question it is necessary to give a clear concept of our finiteness. According to Kant, the core of our finiteness as human beings consists in our dependency on being passively affected: on cognizing things with our senses instead of through pure reason or by what we are told. We cannot cognize things without being affected by them; all that we know by pure reason alone are very general truths (for instance, things happen in accordance to natural laws). The terminus technicus for this concept is discursivity which is the property of concepts that distinguishes them from intuitions. A concept is a representation that is discursive which means that it is mediately related to its objects via universal marks and is hence a universal representation. Intuitions on the other hand are immediately related to their objects and are hence singular representations. Our understanding is discursive because it is a faculty of thinking which cognizes objects through concepts that are dependent on a faculty of intuitions to relate to objects. Without such intuitive, i.e., immediate relations our understanding would have no content at all. Most work on testimonial knowledge focuses on the trustworthiness and competence of the speaker. Although Kant addresses such topics, these are rather secondary reflections unsuited to be an adequate foundation for understanding of the compatibility of intellectual independence and the dependency on others. In freely following Wolff, Kant distinguishes in a first step between rational and historical cognitions. A cognition is rational if it is generated by the cognizer's own use of his pure reason, otherwise it is historical, i.e. it is given to him by his senses or the words of others. In a second step he makes a difference between rational and empirical cognitions, the latter being cognitions that can only be known historically. While the distinction between rational and empirical cognitions signifies a difference in their very character, the difference between rational and historical cognitions means a difference in our own personal access to them. (In a further step he distinguishes between discursive rational cognitions in philosophy and intuitive rational cognitions in mathematics, but this is of lesser importance than the first distinction.) The point is that different kinds of cognitions are to be treated in different ways. Having a critical stance toward testimonial knowledge means that we should not accept rational cognitions on the grounds of being told. Knowingly diverging from his predecessors, Kant defines metaphysics as the system of rational cognitions, i.e. the systematically ordered body of knowledge we gained through pure reason. Thus metaphysics is the discipline that does not allow for just historical cognitions. Now to Kant philosophy is not—as it has been for Wolff and others—the whole body of science besides mathematics, but is rather identical with metaphysics. Summarizing all these results we can assign a reason for why we should learn philosophizing rather than philosophy: It is because metaphysics is a rational discipline that we cannot learn by acquiring merely historical knowledge but only by learning to use our own faculty of reason. [less ▲]

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See detailIntersektionalität und Gouvernementalität. Die Problematisierung der Prostitution in Luxemburg um 1900 bis zum Ende der Zwischenkriegszeit
Mauer, Heike UL

Doctoral thesis (2015)

My dissertation “Intersektionalität und Gouvernementalität. Die Problematisierung der Prostitution in Luxemburg um 1900 bis zum Ende der Zwischenkriegszeit” pursues three scientific aims: first it ... [more ▼]

My dissertation “Intersektionalität und Gouvernementalität. Die Problematisierung der Prostitution in Luxemburg um 1900 bis zum Ende der Zwischenkriegszeit” pursues three scientific aims: first it advances political and feminist theory, secondly it contributes to Luxembourgian social, political and gender history by developing thirdly a fresh methodology. The object of investigation is the historical problematization of prostitution in Luxembourg – that is the perception and 'government' of prostitution as a problem of societal and individual moral conduct. My thesis is the first major historical publication, dedicated to the analysis of prostitution in Luxembourg. The main research question pursued was to identify the intersectional dimensions of this problematization of prostitution and to identify its inherent logics of power. The innovative, theory-driven method used for investigation rested on the connection of two theoretical concepts: intersectionality (a tool to understand gender as always related to other dimensions of power and inequality such as class, race, nation, citizenship, etc.) and governmentality (a distinct mode of power, which is - unlike sovereignty or discipline – characterized by the capacity to govern the conduct of others as well as by “technologies of the self” [Foucault]). By developing this methodology, my thesis also advances political and feminist theory. I highlight actual shortfalls of intersectional approaches and strengthen the tools analytical capacities to investigate power relations. I developed an understanding of intersectionality focusing on the processes and modes of how power is exercised, transcending static approaches, which perceive intersectionality solely in terms of inequalities. Empiricaly I demonstrated, that power was exercised intersectionally through the problematization of prostitution, while the problematization adressed different intersectional subjects differently: the prostitute was identified by a logic of suspicion as a poor foreign woman, who was deported in order to 'morally cleanse' the nation. Through the government of moral conduct, Luxembourgian working class women were encouraged to be good housewives in order to prevent their husbands from falling for prostitution in bars. [less ▲]

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See detailDomain-general versus Domain-specific Approach of Creativity: Arts, Science and Everyday Life
Kirsch, Christiane UL

Doctoral thesis (2015)

The investigation of domain-specificity by means of structural models is undoubtedly one of the most contemporary subjects in creativity research. Whilst the dominant approach conceives creativity as a ... [more ▼]

The investigation of domain-specificity by means of structural models is undoubtedly one of the most contemporary subjects in creativity research. Whilst the dominant approach conceives creativity as a relatively general mental capacity, a more recent, and relatively underexplored approach, conceives creativity as domain-specific. Three major domains of creative expression are often distinguished: arts, science and everyday life (Batey & Furnham, 2006). The hybrid approach reconciles to some extent the domain-general and domain-specific paradigm, by allowing for domain-general, domain-specific and even task specific features (Lubart & Guignard, 2004). The present research explored this differential approach, which raises the question, in how far the cognitive and conative creative profiles, can be generalized. These were investigated in the domains of arts, science and everyday life. The artistic creative profile of architects was compared to the scientific creative profile of psychologists and the everyday creative profile of the general population. With this in mind the three test groups (architects, psychologists, general population), were subjected to a general creativity test. One population-specific creativity test was added within every sample. The differential approach of creativity, integrating both domain-general and domain-specific features, was confirmed. This doctoral dissertation allows for different creative profiles with regard to specific domains of creative expression to be established. It became clear that architects demonstrated the expected profile for scientific creativity, whilst psychologists demonstrated the expected profile for artistic creativity. As anticipated, the everyday creative profile was presented by people of the general population. It was characterized by openness to new experiences and, to a lesser extent, by intelligence. Presently, the image of the psychologically conflicted architect, sometimes projected by the literature (Barron, 1965, 1969; MacKinnon, 1961, 1962), could not be confirmed. This image was further associated with creative psychologists. Implications and limits of these results are discussed further below. [less ▲]

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See detailBiopharm - the Influence of Macro-substrates & Conditioning on Pharmaceutical Removal Rates by Moving Bed Biofilm Reactors
Köhler, Christian UL

Doctoral thesis (2015)

Organic micropollutants with endocrine disruptive properties are present in the aquatic environment. A major part of their emission is caused by municipal wastewater treatment plants (WWTPs). For this ... [more ▼]

Organic micropollutants with endocrine disruptive properties are present in the aquatic environment. A major part of their emission is caused by municipal wastewater treatment plants (WWTPs). For this reason, a vast amount of research has been undertaken to remove xenobiotics from municipal wastewater by developing post-treatment technologies with some success. However, these technologies cause considerable environmental costs due their high demand for electrical energy implicating an increase in CO2 emissions. Consequently, existing biological treatments need first to be better understood and subsequently optimized regarding xenobiotic removal before post-treatments are employed. The study focused on the fate of xenobiotics during biological wastewater treatment. In particular, metabolic strategies of bacteria degrading pharmaceuticals were investigated within moving bed biofilm reactor (MBBR) processes. Two main objectives were tracked. On the one hand, it was to unfold the impact of macro-substrates in terms of type and molecular complexity on the activity of microorganisms and consequently pharmaceutical degradation performance. On the other hand, the study was set out to explore the adaptation of metabolic means regarding exoenzymes and consortia structure during continuous (long-term) exposure to pharmaceuticals. Accordingly, the ability to increase microbial competences during pharmaceutical short-term pulses was the general target of investigation. Both conditions continuous substance flow and short-term peak loads of xenobiotics are believed to occur in urban WWTPs. A pilot MBBR was set up next to a domestic WWTP. The pilot treated municipal sewage and served as inoculation reservoir for biofilm carriers used for in-depth laboratory experiments. The latter comprised six lab-scale MBBRs featuring flow through operation under controlled conditions regarding temperature, dissolved oxygen, pH, influent flow and influent load. The reactors were conditioned over four weeks with a synthetic sewage providing substrates and micro-nutrients in a similar manner as expected under real conditions. Biofilm was monitored by respirometry and a series of enzyme assays using fluorogenic substrates to capture esterase, phosphatase, alpha- and beta-glucosidase and aminopeptidase activity. All enzymes are essential during organic carbon metabolism. An array of macro-substrates with different molecular complexity was triggering individual enzyme activity profiles. After conditioning, 12 pharmaceuticals being subject to a range of anticipated metabolic pathways and degradation rates were spiked into the MBBRs. Their degradation kinetics were measured by liquid chromatography coupled with tandem mass spectrometry (LC MS/MS). Pseudo first-order kinetics revealed substrate related fingerprints and showed that readily biodegradable substrate leads generally to good pharmaceutical degradation performance compared to synthetic sewage with a mixture of several high molecular organic substrates. The latter was designed to induce the greatest metabolic effort of tested substrates before microbial uptake occurs. However, single substrates triggering exoenzyme activity in a more targeted manner such as maltose and cellobiose showed positive impact on the pseudo first-order rate coefficients of particular pharmaceuticals such as atenolol and diclofenac. Accordingly, alpha-glucosidase activity was found to be directly proportional to atenolol degradation kinetics. Phylogenetic characterisation of DNA and RNA involving state-of-the-art 16S ribosomal rRNA gene amplification and sequencing techniques was used to explore community structures. Prokaryote diversity in lab-scale MBBRs was in agreement to previous studies which investigated microbial consortia in full-scale systems. Multivariate analysis revealed that bacteria are adapting their active gene pool when the beta-blocker atenolol is continuously present with a concentration in ug/L range. Differential analysis unfolded that the prokaryotic genera Delftia and Lysobacter were thereby exclusively benefiting from the exposure to atenolol. Yet, compared to the influence of macro-substrates, biomass conditioning (training) with atenolol and diclofenac had no notable impact on the degradation performance of pharmaceutical short-term pulses. The outstanding comprehensive character of the study which encompassed sophisticated experimental design and powerful analytical tools from different scientific domains uncovered some interesting insights in xenobiotic degradation processes. The results finally show how biomass is reacting towards the presence of primary carbon sources and organic micro-pollutants. The outcomes highlight the importance of WWTP influent characterization being indicative of metabolic activity and therefore degradation capacity of xenobiotics. The study further suggests that xenobiotic metabolism and co-metabolism co-exist during biological treatment processes. Co-metabolism is the decisive actor when adaption time is relatively short as it was the case during the lab-scale experiments compared to real conditions. Further, the study indicates some potential of process enhancement of WWTPs ranging from straightforward implementations such as external carbon sources to more elaborated processes of bioaugmentation. [less ▲]

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See detailLa "bancabilité" des infrastructures intégratives financés par les Institutions du développement en Afrique de l'Ouest
Bassale, Wilfried UL

Doctoral thesis (2015)

Le terme « bancabilité » est l’une de ses expressions omniprésentes dans le discours des praticiens du financement des grands projets d’infrastructures sans que l’on ne sache précisément ce qu’il désigne ... [more ▼]

Le terme « bancabilité » est l’une de ses expressions omniprésentes dans le discours des praticiens du financement des grands projets d’infrastructures sans que l’on ne sache précisément ce qu’il désigne. Lorsqu’elle est présentée comme étant les prérequis à l’octroi de financements des grands projets d’infrastructures par les institutions financières, la bancabilité ou la « financiabilité » ne demeure pas moins difficile à cerner. Sa nature suscite le débat. D’aucuns doutent qu’il s’agisse d’une notion juridique, d’autres y voient une pratique essentiellement financière assimilable à l’évaluation de la situation financière des candidats à un emprunt bancaire. Son régime est tout aussi incertain. Dès lors que la bancabilité est analysée à travers le prisme de critères ou de paramètres applicables aux promoteurs des projets d’infrastructures, la formation de ces « règles » puisqu’il s’agit effectivement de règles de conduite, de prescriptions, orientant le comportement des candidats-emprunteurs, mais également les conditions de leur mise en œuvre ne peuvent échapper à un encadrement juridique. À défaut de définition textuelle, identifier les déterminants de la bancabilité, saisir sa nature, comprendre cette pratique forgée par les professionnels du crédit, la distinguer de notions similaires – telles que la rentabilité, la solvabilité ou la dignité de crédit - sont d’autant plus essentiels que la bancabilité s’apparente à un concept émergent en droit dont la gestation est en cours. A cet égard, le régime applicable aux cas de manquement lors de l’appréciation de la conformité des projets d’infrastructure eu égard aux prérequis de bancabilité reste encore à définir. La présente étude entreprend une réflexion sur la valeur des critères juridiques de bancabilité tels qu’appliqués par les principales institutions financières du développement en Afrique de l’Ouest et explore les effets de leur mise en œuvre sur les cadres juridiques nationaux et régionaux. À partir de l’analyse de projets d’infrastructure de transport d’énergie favorisant l’intégration régionale des États-membres de la Communauté Économique des États d’Afrique de l’Ouest, l’étude met en lumière les écarts entre les principaux critères juridiques de bancabilité édictés par les institutions financières de développement et la pratique observée en Afrique de l’Ouest puis, elle propose des pistes d’évolution de ces critères de bancabilité. [less ▲]

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See detailHETEROGENITÄT IM LUXEMBURGISCHEN BILDUNGSSYSTEM – SCHULLAUFBAHNEN IM VERGLEICH
Backes, Susanne UL

Doctoral thesis (2015)

This dissertation provides a detailed discussion of educational pathways through Luxembourg’s stratified school system, addressing educational inequalities in a longitudinal perspective. The link between ... [more ▼]

This dissertation provides a detailed discussion of educational pathways through Luxembourg’s stratified school system, addressing educational inequalities in a longitudinal perspective. The link between stratification and educational inequality is well documented (Van de Werfhorst & Mijs, 2010; Pfeffer 2008). However, stratified systems themselves differ in permeability and in the given opportunity structure for intragenerational social mobility through changes of school track. This dissertation focuses on the occurrence of permeability in the stratified educational system of Luxembourg by analysing secondary school students’ pathways. The study attempts to answer the following main research questions: How can the students’ pathways through Luxembourg’s educational system be characterised and systemised? Does the use of track changes rather increase or decrease educational inequalities? The author deals with these questions by carrying out a triangulated design combining secondary data analysis (administrative panel dataset of all 5,301 students born in 1990 and PISA data) and narrative interviews with (former) school students. The conceptual framework is based on Boudon’s structural-individualistic approach (1974), Bourdieu’s capital theory (1983) and concepts of the sociology of youth (e.g. Zinnecker 2003). The cluster analysis reveals different types of complete pathways of secondary school students in Luxembourg. The largest group (37%) of the students follows an immobile academic pathway, and some students in the academic track leave this track early (7%). Within the technical track, which is further subdivided, more students follow a downwardly mobile pathway (21%) than an immobile pathway (17%). A small part of students within the technical track (12%) belongs to upwardly mobile types (only 2% of all the students make the transition from the technical to the academic track). The remaining 6% of the students follow careers that were interrupted at least once. Thus, 46% of all the students experience (multiple) broken secondary school pathways. The 15 qualitative interviews illustrate that the types of educational pathways are not directly linked to particular kinds of biographies in adolescent lives: Both, moratorium-oriented and transition-oriented students can be found in different pathway types. However, different trajectories afford different degrees of agency with respect to shaping the teenage years and creating professional identities. With regard to educational inequalities, results of logistic regression analyses reveal that socioeconomic and gender-specific placement gaps tend to increase during secondary schooling. On the other hand, migrant-specific disparities decrease through upwardly mobile pathways and higher continuity rates of students with migration backgrounds, whereby in case of vulnerable migrant groups this decreasing effect does not concern the transition to the highest tracks that are required for direct university entry. Further analyses show that the mechanisms behind different transition patterns vary between branching points and student groups in terms of achievement-related and decision-related effects. Thus, this study attempts to add to the body of knowledge of the permeability of educational systems and provides useful information to support the work of policy makers and consultants in the field of education. [less ▲]

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See detailAnalysis of the Urinary Proteomes of the Participants in the “Mars 500” Flight Simulation Program Using Advanced Mass Spectrometry Techniques
Khristenko, Nina UL

Doctoral thesis (2015)

Urine is a valuable material in the clinical proteomics studies as it may contain biomarkers for diagnosis of urinary tract and renal pathologies. Nevertheless, the high variability of protein abundances ... [more ▼]

Urine is a valuable material in the clinical proteomics studies as it may contain biomarkers for diagnosis of urinary tract and renal pathologies. Nevertheless, the high variability of protein abundances in the context of normal homeostasis may mask the changes in the case of pathological protein expression and become a stumbling block in urinary proteome investigation. The main objective of this study was to define the normal (minimal) protein abundance variability in urine for a well-controlled group of healthy individuals. The analyses of urine samples collected in the frame of the “MARS 500” space flight simulation program was an unique opportunity to carry out such a study. In order to perform a reliable and systematic analysis of a large set of proteins in urine samples several challenges had to be overcome. First, a reliable sample preparation procedure had been established to address the problems associated to urine samples (e.g., the low overall protein concentration in urine). Second, a detailed map of the urinary proteome was created, including the identification of low abundant proteins in urine samples. High quality MS/MS spectra corresponding to a large set of identified peptides constituted the basis for a spectral library. The library allowed reinforcing the peptide identity confirmation by experimental spectra comparison with the reference spectra. Third, an LCMS/ MS method was devised to acquire systematically a large data set using the state-ofthe- art instrument with implemented dynamic correction of the targeted peptide monitoring time. The analysis of the urine samples collected over 100 days from six participants in the “MARS 500” program revealed unexpectedly large changes in the intra-personal protein abundances. Differences exceeding one order of magnitude between lowest and highest protein abundance measured within one individual were observed. However, some proteins exhibited a low abundance ratio, even across individuals. The proteins showing highest differences in abundance are presumably involved in the inflammatory response of the innate immune system. The present study provides a description of longitudinal protein abundance variation in urine in the context of the normal homeostasis and may be a resource for future biomarker studies. [less ▲]

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See detailDevelopment of Alternative Proteomics Methods for Lung Cancer Biomarker Evaluation
Trevisiol, Stéphane UL

Doctoral thesis (2015)

Lung cancer is a serious public health problem, killing millions of people around the world every year. It is the third most common cancer in Europe after colorectal cancer and breast cancer, but the ... [more ▼]

Lung cancer is a serious public health problem, killing millions of people around the world every year. It is the third most common cancer in Europe after colorectal cancer and breast cancer, but the deadliest since it is often detected too late. Sensitive and reliable methods for early stage detection and drug response prediction could significantly improve the therapeutic treatment and survival rate of lung cancer patients. Although tremendous efforts in biomedical research have been made over the last decades to develop novel biomarkers for cancer diagnosis and treatment response, no reliable and specific panels of biomarkers are available for early lung cancer diagnosis. During the past decade mass spectrometry (MS) based proteomics has become an important approach to biological and clinical investigations. Most MS-based protein quantification approaches generally involve trypsin digestion of the endogenous proteins in biological samples, followed by a targeted liquid chromatography-mass spectrometry (LC-MS) analysis of signature peptides indicative of the proteins of interest. Trypsin cleaves proteins C-terminal of lysine and arginine residues generating peptides that are well suited for LC-MS/MS analysis. However, despite the undeniable advantages of trypsin, the enzyme is not optimal for all types of proteomics studies due to an uneven distribution of the cleavage sites in the human proteome. During a tryptic digestion also very short non-specific peptides (< 6 amino acids) are produced resulting in a loss of sequence protein coverage. This can be problematic as the missing peptide parts could contain crucial information for disease understanding, such as specific amino acid mutations or post- translational modifications of amino acid residues. Moreover, the generation of large numbers of short peptides results in an increased background complexity which is a main limiting factor in quantification experiments as it reduces the selectivity of the measurements, which in turn affects the sensitivity of the experiments. Isotope dilution strategies are frequently employed to achieve accurate quantification of the proteins of interest using calibrated isotopically labeled peptides as internal standards. In quantitative assays, which involve the use of stable isotope-labeled standards, the reliability and the accuracy of the experiments is principally dependent on the quality of the standards. Different factors can affect the standard concentration between the synthesis and its utilization, such as incomplete solubilization, non-specific adsorption to hydrophobic surfaces or aggregation. To ensure an accurate quantification the internal standards need to be verified immediately before analysis. The purpose of this PhD thesis was to develop new proteomic approaches to remedy these limitations by using, instead of trypsin, alternative enzymes and by developing a quantification approach based on concatenated polypeptide standards containing a cleavable reporter peptide for accurate quantification. [less ▲]

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See detailExample-Dependent Cost-Sensitive Classification with Applications in Financial Risk Modeling and Marketing Analytics
Correa Bahnsen, Alejandro UL

Doctoral thesis (2015)

Several real-world binary classification problems are example-dependent cost-sensitive in nature, where the costs due to misclassification vary between examples and not only within classes. However ... [more ▼]

Several real-world binary classification problems are example-dependent cost-sensitive in nature, where the costs due to misclassification vary between examples and not only within classes. However, standard binary classification methods do not take these costs into account, and assume a constant cost of misclassification errors. This approach is not realistic in many real-world applications. For example in credit card fraud detection, failing to detect a fraudulent transaction may have an economical impact from a few to thousands of Euros, depending on the particular transaction and card holder. In churn modeling, a model is used for predicting which customers are more likely to abandon a service provider. In this context, failing to identify a profitable or unprofitable churner has a significant different economic result. Similarly, in direct marketing, wrongly predicting that a customer will not accept an offer when in fact he will, may have different financial impact, as not all customers generate the same profit. Lastly, in credit scoring, accepting loans from bad customers does not have the same economical loss, since customers have different credit lines, therefore, different profit. Accordingly, the goal of this thesis is to provide an in-depth analysis of example-dependent cost-sensitive classification. We analyze four real-world classification problems, namely, credit card fraud detection, credit scoring, churn modeling and direct marketing. For each problem, we propose an example-dependent cost-sensitive evaluation measure. We propose four example-dependent cost-sensitive methods; the first method is a cost-sensitive Bayes minimum risk classifier which consists in quantifying tradeoffs between various decisions using probabilities and the costs that accompany such decisions. Second, we propose a cost-sensitive logistic regression technique. This algorithm is based on a new logistic regression cost function; one that takes into account the real costs due to misclassification and correct classification. Subsequently, we propose a cost-sensitive decision trees algorithm which is based on incorporating the different example-dependent costs into a new cost-based impurity measure and a new cost-based pruning criteria. Lastly, we define an example-dependent cost-sensitive framework for ensembles of decision-trees. It is based on training example-dependent cost-sensitive decision trees using four different random inducer methods and then blending them using three different combination approaches. Moreover, we present the library CostCla developed as part of the thesis. This library is an open-source implementation of all the algorithms covered in this manuscript. Finally, the experimental results show the importance of using the real example-dependent financial costs associated with real-world applications. We found that there are significant differences in the results when evaluating a model using a traditional cost-insensitive measure such as accuracy or F1Score, than when using the financial savings. Moreover, the results show that the proposed algorithms have better results for all databases, in the sense of higher savings. [less ▲]

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See detailDie Herausforderung der dritten Sprache – eine Grounded-Theory-Studie zu sprachlichen Praktiken und Repräsentationen von Mehrsprachigkeit bei Studierenden dreisprachiger Masterstudiengänge an der Universität Luxemburg
Stoike-Sy, Rahel UL

Doctoral thesis (2015)

The University of Luxembourg presents itself as an international and multilingual university, two attributes that may seem at odds to those who equate internationalization with anglicization. In fact ... [more ▼]

The University of Luxembourg presents itself as an international and multilingual university, two attributes that may seem at odds to those who equate internationalization with anglicization. In fact, more than 50 % of students of this officially trilingual institution come from outside Luxembourg and the proportion of international students’ increases at the Master’s level. While the majority of Master study programs in the winter term 2012/13 were mono- or bilingual, four trilingual Masters have been offered as well. Three of them used French, English and German as languages of instruction, another one Luxembourgish, French and German. This dissertation investigates linguistic practices and representations of individual and institutional multilingualism by students and study directors in four trilingual Master study programs. The exploratory study combines an ethnographic approach with constructivist Grounded Theory. The corpus comprises around 90 hours of participant observation, 47 field notes, 19 questionnaires, and 9 interviews with students and 4 with course directors. The data has been generated in 2012 and 2013. The general research question “How do students experience individual and institutional multilingualism in trilingual Master programs?” has been split up in three specific questions: (1) How are the linguistic repertoires of the involved actors categorized? (2) Which representations of institutional multilingualism and a “multilingual study program” are constructed by students and study directors? (3) In which situations do multilingual language practices emerge in the program? The results show that the configuration of linguistic repertoires, the motivation for a Master program and their expectations, among other factors, play a role in the construction of representations of multilingualism. Students and lecturers have different linguistic resources in one, two or all three of the program languages. On the basis of the official presentation of the programs, some students expect a symmetrical form of multilingualism, but perceive an asymmetrical use of the three languages in practice. The hierarchical use of languages is accompanied by a marginalization of German in each Master and explained by the limited repertoires of students or lecturers. Receptive multilingualism is practiced in some contexts or presented as a goal and opposes the view that a multilingual study program should mean studying in three languages. The students’ expectations of support for language learning and the institutional offer of language courses diverge. While in two Masters language courses in French and German for beginners are offered, support is missing for advanced learners and for academic language. Overall, the findings suggest an influence of individual and collective linguistic repertoires on linguistic practices of teaching and studying as well as on the implementation of institutional multilingualism in practice. While students mention changes of former study practices during their Master studies, lecturers develop spontaneous strategies to deal with the linguistic heterogeneity of their groups, whereby the degree of multilingualism varies. The significance of the core category “the third language” can be explained by the fact that some students begin their studies with no or only little language resources in one of the program languages and by their tendency to hierarchize languages. The results of this qualitative study have implications for the language policy of multilingual study programs. A clear definition of a language competence profile for enrolling and finishing a multilingual study program as well as specific language learning objectives are recommended. Finally, an integration of language learning in content courses according to the CLIL-model is proposed. [less ▲]

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See detailModel-Driven Security With Modularity and Reusability For Engineering Secure Software Systems
Nguyen, Phu Hong UL

Doctoral thesis (2015)

Context: The more human beings depend on software systems, the more important role that software security engineering must play to build secure software systems. Model-Driven Security (MDS) emerged more ... [more ▼]

Context: The more human beings depend on software systems, the more important role that software security engineering must play to build secure software systems. Model-Driven Security (MDS) emerged more than a decade ago as a specialised Model-Driven Engineering (MDE) research area for engineering secure software systems. MDS is promising but not mature yet. Our recent systematic literature review (SLR) has revealed several current limitations and open issues in the state of the art of MDS research. Objectives: This PhD work aims at addressing three of the main open issues in the current state of the art of MDS research that are pointed out by the SLR. First, our SLR shows that multiple security concerns need to be handled together more systematically. Second, true Aspect-Oriented Modelling techniques for better ensuring the separation- of-concern in MDS approaches could have been leveraged more extensively. Third, complete tool chains based on integrated MDE techniques covering all the main stages of the development cycle are emerging, but still very rare. Methods: On one hand, we develop a full MDS framework with modularity based on domain-specific modelling, model transformations, and model-based security testing. This MDS framework can help us to deal with complex delegation mechanisms in access control administration, from modelling till testing. On the other hand, we propose a highly modular, reusable MDS solution based on a System of Security design Patterns (SoSPa) and reusable aspect models to tackle multiple security concerns systematically. Results: First, an extensive SLR has been conducted for revealing and analysing the current state of the art of MDS research. Second, a full MDS framework focusing on modularity has been proposed that integrates domain-specific modelling, model transformations, and model-based security testing to support all the main stages of an MDS development cycle. Third, we have developed a highly reusable, modular MDS approach based on a System of Security design Patterns for handling multiple security concerns together systematically. Finally, we have showed how our MDS approaches can be integrated in a full MDS framework, called MDS-MoRe, which could be the basis of a complete tool chain for MDS development of secure systems. Conclusion: In this thesis, integrated MDS methodologies with modularity and reusability have been proposed for engineering secure software systems. This work has tackled three main current open issues in MDS research revealed from an extensive SLR. [less ▲]

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See detailRole of Calprotectin as a Modulator of the IL27-Mediated Inflammatory Response of Endothelial Cells
Dorosz, Susann Antonia UL

Doctoral thesis (2015)

Cardiovascular diseases (CVD) are the leading causes of death with a morbidity of around 40% worldwide. Their development occur long before any symptoms are clinically evident. An underlying endothelial ... [more ▼]

Cardiovascular diseases (CVD) are the leading causes of death with a morbidity of around 40% worldwide. Their development occur long before any symptoms are clinically evident. An underlying endothelial dysfunction plays a fundamental role in the pathogenesis of cardiovascular events and is the central feature of atherosclerosis, which often appears prior to other CVD. However, the involvement of the chronic inflammatory state of the endothelium in the early mechanisms leading to the atherosclerotic phenomenon, which includes the protein-based communication between leukocytes and inflamed endothelial cells, remains to be further investigated. In this context of atherosclerosis, several key players have already been identified, but the role of the cytokines IL17D, IL27, and IL32γ is less well understood. In addition, evidence for the impact of calprotectin on promoting atherosclerosis has been reported, but its modulatory role on cytokine communication is still unclear. In this study, we first analysed the inflammatory responses of monocytes stimulated with the potent agonist TNFα to simulate a stress-induced inflammatory state. In order to characterize the monocytes as a potential cellular source of IL17D, IL27, IL32γ, and calprotectin, the regulation of gene expression was studied based on microarray data and qPCR. Highly significant up-regulations of IL27 subunit EBI3 and IL32 gene expressions were confirmed in TNFα-stimulated THP-1 cells. Furthermore, we were able to determine elevated intracellular IL27 and calprotectin protein levels in TNFα- stimulated THP-1 cells. In a second part, Human Umbilical Vein Endothelial Cells (HUVECs) were stimulated with IL17D, IL27, IL32γ, and calprotectin to characterize the induced inflammatory responses regarding gene expression. A gene-array qPCR screening demonstrated higher differential gene expression (DGE) after IL27 compared to IL17D, IL32γ, and calprotectin stimulation. Highest IL27-mediated DGEs were ob- served for CXCL10, CXCL11, IL7, and IL15. In order to highlight potential calprotectin modulatory effects on these genes, time course experiments of HUVECs stimulated with IL27+/-calprotectin were assessed by qPCR. We identified modulatory effects of cal- protectin on IL27-induced CXCL10 and IL15 gene expressions. Furthermore a mass spectrometry-based proteomic analysis of IL27+/-calprotectin-stimulated HUVECs enlightened a modulatory role of calprotectin in the late differential regulation of proteins such as the IL27 downstream effector STAT1. A literature-based pathway analysis of significant regulated proteins emphasized that calprotectin-modulated IL27 activity was able to decrease the probability of the development of atherosclerosis. Altogether, our findings suggest that calprotectin may exert a regulatory role on cytokine-mediated inflammatory responses and highlight the need of further investigations in the understanding of atherosclerosis development. [less ▲]

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See detailLes concepts d'indépendance de la justice : une analyse historique et comparée (Angleterre, Allemagne et France)
Janssen-Bennynck, Clémence UL

Doctoral thesis (2015)

Cette thèse examine les divers concepts de l’indépendance de la justice en Angleterre, en Allemagne et en France. S’inscrivant dans une approche cognitive et théorique, son objectif essentiel est de ... [more ▼]

Cette thèse examine les divers concepts de l’indépendance de la justice en Angleterre, en Allemagne et en France. S’inscrivant dans une approche cognitive et théorique, son objectif essentiel est de chercher à identifier, approfondir et suivre les évolutions du principe d’indépendance de la justice dans trois traditions nationales majeures au sein de l’Europe. Une typologie des différents sens possibles de l’indépendance de la justice est proposée au lecteur dans le chapitre préliminaire. L’analyse est, ensuite, conduite en optant pour un plan en trois parties, chaque partie étant consacrée à l’un des trois pays. Une analyse comparative transversale est, enfin, présentée dans la conclusion. [less ▲]

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See detailMultilingualism and Early Education: An Ethnography of Language Practices and Processes of Institutionalisation in Luxembourgish Early Childcare Settings
Seele, Claudia UL

Doctoral thesis (2015)

During the last twenty years, the Luxembourgish system of early childhood education and care (ECEC) has been undergoing some considerable transformations in light of growing demands by social, economic ... [more ▼]

During the last twenty years, the Luxembourgish system of early childhood education and care (ECEC) has been undergoing some considerable transformations in light of growing demands by social, economic and educational policies. In the multilingual context of Luxembourg, these demands are especially complex, ranging from language promotion and school preparation to contributing to social cohesion and to the integration of a heterogeneous society. The early educational practice today is thus confronted with multiple, at times also divergent expectations. Instead of asking how effectively educational practices might meet these demands and expectations, my research rather takes a non-normative approach by investigating how multilingualism is actually dealt with in the everyday practice of the day care centres. Drawing on praxeological and institutional perspectives as analytical tools, the thesis aims at a better understanding of the everyday accomplishment of the early educational practice in light of these societal developments. Language is thus regarded as a social practice, putting the focus on the actual doing of language and its contribution to the practical enactment of an institutional order. Institutionalisation, here, is understood as the intricate processes of referring and answering to external expectations in everyday practice in order to negotiate what ‘early childhood education and care’ actually is and means. Hence, not everything that happens in educational fields is per se ‘education’; rather it has to be performed and practically constituted as such in response to certain institutionalised norms, values and expectations. In order to investigate how language practices contribute to processes of institutionalisation in ECEC, an ethnographic research has been carried out in three state-funded Luxembourgish day care centres over the course of three years. Pertinent questions that guided my observations and analyses were for example: What different kinds of language practices can be observed in the centres? How are these language practices, on the one hand, conducive to the accomplishment of an institutional order and are, on the other hand, themselves constrained by this order? What are the respective parts of adults and children in these processes? How is early education thereby constituted but also challenged or transformed? Data analysis is based on a reflexive and constructivist Grounded Theory approach and yielded several interrelated aspects of language-mediated institutionalisation processes: First, language serves to constitute institutional boundaries and to differentiate the pedagogical social space from the ‘outside’ or ‘everyday’ world. Second, language also contributes to the creation of an institutional order ‘inside’ this pedagogical space and helps to position actors within this order. Third, language is part of processes of routinisation and incorporation that serve to stabilise the institutional practice. Finally, language is also involved in representing the early educational practice vis-à-vis its constitutive outside, such as the family and the school, thus supporting its claims to legitimacy. These processes, however, are not as straightforward as it may seem, because language also plays a part in destabilising processes of institutionalisation and bringing forward institutional changes. For example, language practices also transcend and fracture the monolingual imaginings of pedagogical space. They may not only constitute and support but also challenge and resist the institutional order as well as question its legitimacy. The study raises some important further questions that are addressed in the final chapter: How can ethnographic research contribute to processes of practice development in ECEC? How do institutional factors both enable and constrain the early educational practice? In what ways do the children themselves contribute to the practical accomplishment of early educational realities? What are the limitations of the study and further lines of inquiry for future research? [less ▲]

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See detailSuper-Resolution Approaches for Depth Video Enhancement
Al Ismaeil, Kassem UL

Doctoral thesis (2015)

Sensing using 3D technologies has seen a revolution in the past years where cost-effective depth sensors are today part of accessible consumer electronics. Their ability in directly capturing depth videos ... [more ▼]

Sensing using 3D technologies has seen a revolution in the past years where cost-effective depth sensors are today part of accessible consumer electronics. Their ability in directly capturing depth videos in real-time has opened tremendous possibilities for multiple applications in computer vision. These sensors, however, have major shortcomings due to their high noise contamination, including missing and jagged measurements, and their low spatial resolutions. In order to extract detailed 3D features from this type of data, a dedicated data enhancement is required. We propose a generic depth multi-frame super-resolution framework that addresses the limitations of state-of-the-art depth enhancement approaches. The proposed framework does not need any additional hardware or coupling with di erent modalities. It is based on a new data model that uses densely upsampled low resolution observations. This results in a robust median initial estimation, further refined by a deblurring operation using a bilateral total variation as the regularization term. The upsampling operation ensures a systematic improvement in the registration accuracy. This is explored in different scenarios based on the motions involved in the depth video. For the general and most challenging case of objects deforming non-rigidly in full 3D, we propose a recursive dynamic multi-frame super-resolution algorithm where the relative local 3D motions between consecutive frames are directly accounted for. We rely on the assumption that these 3D motions can be decoupled into lateral motions and radial displacements. This allows to perform a simple local per-pixel tracking where both depth measurements and deformations are optimized. As compared to alternative approaches, the results show a clear improvement in reconstruction accuracy and in robustness to noise, to relative large non-rigid deformations, and to topological changes. Moreover, the proposed approach, implemented on a CPU, is shown to be computationally efficient and working in real-time. [less ▲]

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See detailGeplante Bildung für die freie Welt. Die OECD und die Entstehung einer technokratischen Bildungsexpertise
Bürgi, Regula UL

Doctoral thesis (2015)

Today, national education polices are increasingly informed and affected by an international education policy space: ‘World education managers,’ equipped with standardized tests and indicators, identify ... [more ▼]

Today, national education polices are increasingly informed and affected by an international education policy space: ‘World education managers,’ equipped with standardized tests and indicators, identify ‘best practices’ that are assumed to be valid across all nation states, largely irrespective of their specific historical, cultural and educational contexts. These global experts have found many hosts and platforms for their views within international governmental organizations, foremost among them the Organization for Economic Co-operation and Development (OECD). With instruments such as the Programme for International Student Assessment (PISA), OECD has become – without having any educational mandate – a hegemonic power in the field of international education policy. The OECD is thus a significant example for a new kind of educational expertise that is characterized by a permanent, institutionalized link between policy and research. For all its ‘influence’ on contemporary policy, little is known about the emergence of this international policy space, its inner logics – its ‘managers’ and the origins of their ‘universal language’. Whereas the current research literature often associates the origins of this internationalization with the fall of the Iron Curtain, this PhD thesis argues that its roots were established and shaped during – and not after – the Cold War, with the formative period occurring during the late 1950’s and the 1960’s. By reconstructing OECD’s emerging role as an expert in education, this thesis sheds light on particular ‘actors’ or rather ‘networks’ and the ‘styles of reasoning’ that enabled, shaped, and legitimized this new international authority. More precisely, this thesis describes how, against the background of a Cold War ‘culture of control,’ a space was created for the rise of different technocratic networks. These networks were eventually characterized by the belief that education bears the ultimate means for solving the problems of societies. Within the OECD these technocratic networks found the ideal institutional platform to give their ‘styles of reasoning’ expression and to establish and to diffuse a specific goal-oriented, quantitative research culture with a strong ‘social engineering’ bent. The epistemology and methods of this specific form of research originated not the least from military war research, whereby the USA acted both as a model and as a catalyst. In the name of the ‘free world’ – as the thesis concludes – a cult of expertise was established leading less to forms of democracy than to a monarchy of ‘evidence’. By disentangling and identifying the ‘styles of reasoning’ as well as the ‘networks’ that were crucial in establishing OECD’s educational expertise, this thesis highlights that a policy phenomenon like the OECD’s PISA does not derive ‘out of the blue’ but, on the contrary, has its roots in a longer history – a decisive context that is often neglected in current explanations assembled around buzzwords like ‘globalization’ or ‘world culture’. Moreover this thesis contributes to the reconstruction of the establishment of a new institutional site that generates a specific kind of knowledge and oscillates between policy and research whilst bypassing the traditional research institutions – the universities. [less ▲]

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See detailExploiting linguistic resources for self-employment: Workplace practices and language use of Thai immigrant entrepreneurs in the German periphery
Serwe, Stefan Karl UL

Doctoral thesis (2015)

This thesis is about immigrants in self-employment in Germany. More specifically, it is about immigrants who make a culturally-endowed practice or knowledge economically available in their new home. These ... [more ▼]

This thesis is about immigrants in self-employment in Germany. More specifically, it is about immigrants who make a culturally-endowed practice or knowledge economically available in their new home. These immigrant business owners are generally referred to as ethnic entrepreneurs. Yet, according to research and widely-held public opinions in Germany, a problem that hampers the success of these businesses is the owner's lack of proficiency in the German language, which apparently impedes them from accessing institutional support and from offering their services to the majority population. However, the ways that language competence actually affects the entry of immigrants into self-employment and the execution of their daily work as business owners has received only insufficient attention, including from a sociolinguistic perspective. Hence, this thesis aspires to examine the pathways of immigrants into self-employment and how these pathways are shaped by the owners' language knowledge. Secondly, by analysing the workplace practices in close empirical detail, it aims to understand how the owners' language knowledge impacts the execution of their work and whether these practices constitute sites of language learning for the owners. Thirdly, it intends to document the challenges that the business owners face at their workplaces, in order to understand to what extent they are due to insufficient levels of language knowledge. In order to answer these research questions, this study focuses on three businesses owned and operated by first-generation female immigrants from Thailand in the federal state of Saarland in southwest Germany. Businesses by Thai immigrants are particularly interesting for the purposes of this investigation, because they have flourished in recent years and because they offer their services in markets that target the majority, primarily German-speaking population. The ventures are typical examples of ethnic small businesses created by Thai immigrants in Germany: Thai massage salons and food retails stores. The first is a large Thai massage salon run by Kanita, the second a small Thai massage salon managed by Patcharin, and the third business is a food retail store owned and operated by Wipa. The three owners (and their staff) differ in terms of their competence in German. Kanita has only minimal competence in German, Patcharin has partial competence, while Wipa has maximum competence in the language. The analysis of the pathways into self-employment of these three owners exhibits a number of similarities. In all three cases, their migration to Germany was triggered by marriage to a German national. Previously, they all had professional careers which were directly connected to their appropriation of English, a language that later enabled communication with their German husbands. While their move to Germany was generally motivated by prospects of a better future, they were unable to find work due to a lack of German proficiency. German was primarily learned informally. Informal learning was fostered by their prior experience of language learning, their individual engagement in the form of self-study and reflexivity, a deliberate exposure to German through media, and their engagement with native speakers in practices towards which that they had developed an affinity. Interestingly, these practices were either their previous professional practices or activities that they took up after migration and later on developed into their own businesses. Realising the demand for their services in the open market and among the majority population kindled Kanita's, Patcharin's and Wipa's flame to enter self-employment. They deliberately adapted their services to the requirements of their customers, but also in reaction to prejudices about their professions. The support of their husbands and other associates was also significant, as they handled tasks that were difficult to perform linguistically, as, for example, the registration of the businesses and the preparation of administrative paperwork. In sum, these findings suggest that an advanced standard level of German was no prerequisite for these owners to enter self-employment, but that the prospects of engaging in self-employed work acted as an incentive to improve their German language skills. A detailed analysis of the workplace practices at Kanita's Massage Salon shows that working with minimal competence in German is possible, but that its success depends on several factors. To complete their workplace actions, Kanita and her staff draw on both resources in their linguistic repertoires, Thai and German. In addition, all workplace actions are designed as routine actions with discursive routines that all staff members are able to master quickly. Their successful accomplishment also depends on the customers' familiarity with these actions. Therefore, formal inconsistencies in German do generally not impede the performance of work, but problems are primarily due to the staff's or the customer's inexperience with the routines. If problems occur, they tend to be solved in cooperation with colleagues or by drawing on the material resources available to the staff members. In comparison to Kanita, Patcharin and her staff have partial competence in German, which is instrumental for the performance of the key practices at their workplace. The analysis shows that their restricted competence in German is important for their work, as it provides the tools for Patcharin and her staff to perform discursive practices during the massage treatment, such as finding out about their clients' health problems, building rapport with clients, giving instructions or clarifications about the treatment, or providing assessments of their customers' health issues. Talk is an important part of the massage treatment at Patcharin's salon and it aids to construct the professional identity that Patcharin claims for herself, namely to provide a high-quality and personalised service to her customers. Thai is less relevant, but in interactions between Patcharin and her staff it serves to exchange information and coordinate work. Wipa has maximum competence in German and Thai, which allows her to manage her store and serve her customers independently and competently in line with her professional aspirations. The key practices at her store of explaining and ordering stock illustrate how Wipa relies on both the use of Thai and German to effectively perform these actions. Her maximum competence in German and in Thai permits her to make 'rational' choices about the suitability of her suppliers and to provide her customers with advice that is tuned to their linguistic and cultural background. The conclusions drawn from these findings are that an advanced competence in German in not a prerequisite for immigrant entrepreneurs to start their businesses. The owners attune their workplace actions to the level of competence in their linguistic repertoires and operate effectively. Moreover, self-employed work provides the owners with the necessary motivation and the need to appropriate German. On the other hand, the data suggest that a greater proficiency in German becomes important, if the immigrant entrepreneur wants to differentiate her business from direct competitors, as it allows them to move beyond the concrete performance of routine actions. [less ▲]

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See detailEuropean Causation in Tort Law: a Comparative Study with emphasis on Medical Law in the United Kingdom, Germany and France and Luxembourg
Hyslop, EDWARD IAN UL

Doctoral thesis (2015)

This purpose of this paper is to explore how the different jurisdictions under consideration here treat the legal notion of causation. These jurisdictions are the United Kingdom, Germany and France and ... [more ▼]

This purpose of this paper is to explore how the different jurisdictions under consideration here treat the legal notion of causation. These jurisdictions are the United Kingdom, Germany and France and Luxembourg. The problem of causation has been described as insoluble and I shall not be trying to solve it. Rather I shall consider how each of the jurisdictions here treats causation in the law, the better to ascertain whether there can be any common European idea of causation in this field. The reason for this is not only as two of the European projects aiming at codification in tort law seek to attempt if not strictly a definition of causation then recommendations in ways in which it could be refined. The European Court of Justice itself has been mandated to extract general principles common to European Union member states with regard to non-contractual obligations which can be applied when faced with a problem in tort law. I must necessarily explain the notion of causation more generally before considering causation in the law so causation itself is understood. Within the sphere of causation in the law, there are a number of theories that I examine, which can be found, to a greater or lesser extent (or sometimes not at all), in one form or another, in the jurisdictions under consideration. My conclusion is that there can be no common idea in causation from which principles in furtherance of any European codification projects may be stated. In most cases in court, a discussion of causation is not even entered into, as it is not controversial. There can be no “common sense” solutions in cases where causation is in doubt. I offer no principles. I make only one suggestion at the end with regard to experts’ reports. The originality I hope to bring to this area of law is that this will be the first work that considers French (and Luxembourg), German and British law under one cover. I conclude by what seems to be the opposite view from many jurists in that, who hold that, however courts may arrive there “the results are [or will be] just the same” in causation. [less ▲]

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See detailUnternehmertum in der Frühpädagogik - Berufsentscheidungen in Luxemburg
Ricken Geb. Weber, Kathrin Hannelore UL

Doctoral thesis (2015)

The observations, that founders of private crèches in Luxemburg possibly have a mainly non-pedagogic, but economic driven professional background, hire for the pedagogic management of their crèches ... [more ▼]

The observations, that founders of private crèches in Luxemburg possibly have a mainly non-pedagogic, but economic driven professional background, hire for the pedagogic management of their crèches qualified personnel and, compared to the gender ratio of specialized staff, are mainly male persons, cannot be confirmed with this qualitative research. The results show a certain dichotomy, but not, as suggested, concerning the job profiles ‘employed nursery nurse’ and ‘entrepreneur’. In contrast, within the group of entrepreneurs a tendency towards a dichotomy in terms of practicing tasks, early pedagogic or managerial, and size of the business, single or several crèches, appears. The assumption, that mainly male persons found private crèches cannot be confirmed. In contrary women appear to be in majority in all fields of business activity, so that there might possibly be a tendency towards a permeant feminisation of the whole private early pedagogic market. This is insofar surprising, as in this commercial part of the early pedagogic market with the new professional opportunity of being an entrepreneur due to the reflection of the literature more heterogeneity was expected. [less ▲]

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See detailINTEGRATED ANALYSIS OF TRANSCRIPT-LEVEL REGULATION OF HUMAN ADIPOGENESIS AND CELL TYPE-SELECTIVE DISEASE ASSOCIATION OF HIGH REGULATORY LOAD GENES
Galhardo, Mafalda Sofia UL

Doctoral thesis (2015)

Most diseases are characterized by altered epigenetic and metabolic states, pointing to the need of a global and combined understanding of mechanisms underlying epigenetic and metabolic changes as an ... [more ▼]

Most diseases are characterized by altered epigenetic and metabolic states, pointing to the need of a global and combined understanding of mechanisms underlying epigenetic and metabolic changes as an important piece to enable disease eradication. Adipocytes impact systemic homeostasis and their differentiation encompasses a phenotypic change whose function becomes impaired with diseases such as obesity and metabolic syndrome. Following an integrative systems biology approach, we combined different omics data from the differentiation of Simpson-Golabi-Behmel syndrome (SGBS) adipocytes with a human metabolic model to observe key metabolic changes upon differentiation, their regulation and relevance for disease. Pursuing the link to disease, we used public data from the genome-wide binding of TFs and location of active enhancers to test for disease association in function of the regulatory load, revealing a cell type-selective enrichment for disease of the high regulatory load genes. Diverse experimental data were collected, covering a gene expression time-course during adipogenesis, with identification of miR-27a, miR-29a and miR-222 target genes, the genome-wide binding profiles of PPARg, C/EBPa and LXRa , and the H3K4me3 histone modification mark for actively transcribed transcription start sites (TSSs). Metabolic genes showed a highly dynamic expression pattern during adipogenesis, most being targeted by PPARg and C/EBPa . Lipid metabolism pathways including triacylglyceride synthesis showed extensive and combinatorial regulation by TFs and miRNAs, converging on known dyslipidemia genes. For data visualization, we developed a web portal that interactively renders metabolic pathways with omics data overlaid (IDARE, http://systemsbiology.uni.lu/idare.html). Public ChIP-seq data revealed a general principle of higher disease association of genes under higher regulatory control in a cell type-selective manner. First, data from the genome-wide binding of 10 TFs in HUVEC cells showed an enrichment for vascular diseases on metabolic genes targeted by > 6 TFs. Second, data from the binding of a total of 93 TFs confirmed the enrichment for disease association of genes with the top TF load in 8 additional cell lines. Finally, active enhancer data from 139 samples spanning 96 cell types and tissues demonstrated the cell type-selective disease enrichment of the genes with the highest active enhancer load. High regulatory load genes enriched for disease association beyond genetic variation, including association types like “altered expression” and “biomarker”, among others. Additionally, high regulatory load genes appeared on average in more KEGG pathways and had higher betweenness centrality in a liver disease network than other genes, showing longer 3’UTRs harboring more binding sites for diverse microRNA families, suggesting also a higher post-transcriptional regulatory load and a role as signal integrators within biological networks. Our results point to the pertinence of including high regulatory load genes for unbiased prioritization of novel candidate genes for disease association. [less ▲]

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See detailCommunity-based vehicular networks for traffic information systems
Grzybek, Agata UL

Doctoral thesis (2015)

Traffic information systems (TIS) monitor road traffic conditions with the goal of improving the efficiency of road networks. Given the ever increasing number of cars, TIS are becoming more critical, as ... [more ▼]

Traffic information systems (TIS) monitor road traffic conditions with the goal of improving the efficiency of road networks. Given the ever increasing number of cars, TIS are becoming more critical, as they help reduce traffic congestion which have large negative social, economical, and environmental impact. Current TIS have several drawbacks. First, there are insufficient sources of traffic data, that often require either expensive sensing infrastructure or a contract with a network provider owning GPS data. Secondly, they are often limited by a centralised architecture introducing both delays in delivery of real-time data and a single-point of failure. Finally, even after collecting traffic information, they provide no easy way to effectively relay information to drivers or apply traffic management strategies. New vehicle-to-vehicle (V2V) communication technologies can potentially aid in overcoming these limitations. Using V2V, vehicles can communicate with each other and exchange traffic information within an ad hoc vehicular network (VANET). VANETs could drastically change the nature of traffic systems, moving from a centrally-controlled to a self-organised complex system covering every road segment.This thesis studies the potential of VANETs in the context of traffic data collection and traffic management using a multidisciplinary approach. We combine knowledge of networking protocols, distributed systems, and traffic theory to propose novel solutions for TIS. First, we propose a TrafficEQ system---a VANET-based TIS, that uses pure V2V communication to collect and disseminate traffic information among vehicles. Moreover, TrafficEQ provides intelligent route guidance based on a probabilistic route choice strategy. The system is evaluated using a simulation platform developed with realistic real-world scenarios. We demonstrate that TrafficEQ deals with challenging non-predictable traffic congestion better than traditional route guidance systems can. Secondly, we propose grouping vehicles into communities by similarity of their mobility patterns to improve traffic congestion detection and analysis. To facilitate this, we present the Crowdz algorithm---a community detection algorithm for VANETs. Extensive analysis on large-scale vehicular networks show that detected communities are more stable than those in a competitive algorithm. Lastly, we introduce an application which uses communities to detect and analyse traffic congestion. Simulation experiments show that identification of congested communities can help in applying appropriate control strategies. [less ▲]

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See detailInteraction in Luxembourgish as an Additional Language: An analysis of language learning as related to affordances among multilingual adult learners
Lambo Ouafo, Adrienne UL

Doctoral thesis (2015)

This study examines affordances for Luxembourgish as the ‘speak-able’ and ‘use-able’ of the target language in the learning environment. Grounded in the Sociocultural theory that assumes that active ... [more ▼]

This study examines affordances for Luxembourgish as the ‘speak-able’ and ‘use-able’ of the target language in the learning environment. Grounded in the Sociocultural theory that assumes that active verbal engagement in naturally occurring interaction enables learners to develop knowledge of target language use, the study analyses Luxembourg learners’ discourses and actions in interaction. Results show that in a context where the target language's functions are limited to "juste les petites conversations wie geet et?" [only mini-dialogues how are you?], metalinguistic awareness is crucial for the occurrence of executive affordance that allows for language learning and development to take place. Awareness of the context on the one side and of the status of the target language on the other side plays an important role in the learning and development of Luxembourgish. [less ▲]

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See detailStudying Signal Transduction Networks with a Probabilistic Boolean Network Approach
Trairatphisan, Panuwat UL

Doctoral thesis (2015)

In recent years, various modelling approaches in systems biology have been applied for the study and analysis of signal transduction networks. However, each modelling approach has its inherent advantages ... [more ▼]

In recent years, various modelling approaches in systems biology have been applied for the study and analysis of signal transduction networks. However, each modelling approach has its inherent advantages and disadvantages, so the choice has to be made based on research objectives and types of data. In this PhD dissertation, we propose probabilistic Boolean network (PBN) as one of the suitable modelling approaches for studying signal transduction networks with steady-state data. The steady-state distribution of molecular states in PBN can be correlated to the steady-state proteomic profiles generated from wet-lab experiments. In addition, the relevance of interactions within signalling networks can be assessed through the optimised selection probabilities. These features make PBNs ideal for describing the properties of signal transduction networks at steady-state with some uncertainty on network topologies. To investigate the applicability of PBNs for the study of signal transduction networks, we developed optPBN, an optimisation and analysis toolbox in the PBN framework. We demonstrated that optPBN can be applied to optimise a large-scale apoptotic network with 96 nodes and 105 interactions. Also, it allows for network contextualisation in a physiological context of primary hepatocytes through the analysis on optimised selection probabilities. Similarly, we also applied optPBN to study deregulated signal transduction networks in pathological contexts, i.e. the PDGF signalling in gastrointestinal stromal tumour (GIST) and the L-plastin signalling in breast cancer cell lines. By integrating prior information on network topology from literature with context-specific experimental data, contextualised PBNs can be derived which in turn provide additional insights into biological systems such as the importance of certain crosstalk interactions and the comparative signal flows at steady-state in non-metastatic versus metastatic cancer cell lines. In addition to the applications on fundamental research, we also explored the applications of PBNs in a pharmaceutical setting where detailed mechanistic models are usually used. Here, we applied optPBN as a tool for network ontextualisation. A proof-of-concept example on a small model demonstrated that optPBN helped to pre-select the suitable network structure according to the provided experimental data prior to the building and optimisation of detailed mechanistic models. Such application is foreseen to be applied in a pharmaceutical setting and to explore additional applications such as combinatorial drugs’ effect and toxicity screening. [less ▲]

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See detailRégulation ou règlementation des fonds islamiques en Europe?
Bouharati, Bahya UL

Doctoral thesis (2015)

Les fonds islamiques intègrent dans leur stratégie d’investissement des critères d’investissement extra-financiers fondés sur des principes directeurs issus du droit musulman. Ils répondent à une demande ... [more ▼]

Les fonds islamiques intègrent dans leur stratégie d’investissement des critères d’investissement extra-financiers fondés sur des principes directeurs issus du droit musulman. Ils répondent à une demande croissante de produits financiers religieusement orientés. Si l’industrie de la gestion d’actifs islamiques se développe sur le marché européen, les fonds islamiques, ainsi que leurs gestionnaires ne font pas l’objet d’une règlementation dédiée. Ils sont par conséquent soumis aux exigences du droit conventionnel des organismes de placement collectif, qui, selon les cas, relèvent du droit européen ou du droit interne des États membres. Pour combler l’indifférence religieuse d’un droit positif aconfessionnel, un cadre normatif spécifique complète le cadre règlementaire étatique. La régulation des fonds islamiques se fait alors par le biais de prescriptions et de recommandations issues de normes autonomes d’origines publiques et privées. Le caractère non-contraignant de ce second ensemble normatif pose la question de l’efficacité juridique de l’encadrement des fonds islamiques. Il interroge également sur l’opportunité, voire la faisabilité d’une norme étatique en la matière. Ce dernier point ne serait-il pas un pré requis nécessaire à la possible émergence d’un modèle (européen) de fonds islamiques permettant de renforcer la protection des investisseurs et l’épanouissement de ce marché ? [less ▲]

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See detailIdentification of the underlying mechanism of the c.192G>C mutation in the DJ-1 gene and functional characterisation in patient-based cellular models of Parkinson’s disease ex vivo
Obermaier, Carolin UL

Doctoral thesis (2015)

Parkinson’s disease (PD) is the second most common neurodegenerative disease and characterised by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta and in other brain ... [more ▼]

Parkinson’s disease (PD) is the second most common neurodegenerative disease and characterised by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta and in other brain regions. Homozygous loss-of-function mutations in the DJ-1 gene (PARK7) are a rare cause of familial early-onset PD. The protein encoded by PARK7 is involved in a variety of biological processes including transcriptional regulation, chaperone-like functions, oxidative stress response and mitochondrial protection. In the present study, we deciphered novel molecular mechanisms underlying the pathogenicity of the c.192G>C DJ-1 mutation previously predicted to lead to a p.E64D amino acid exchange in the DJ-1 protein. To analyse the c.192G>C DJ-1 mutation, we generated and characterised different ex vivo patient-based cellular models including patient-derived primary fibroblasts, immortalised fibroblasts, induced pluripotent stem cells (iPSCs), iPSC-derived small molecule neuronal precursor cells (smNPCs) as well as iPSC-derived midbrain-specific dopaminergic (mDA) neurons. Analyses of DJ-1 expression in these patient-derived model systems from homozygous carriers of the c.192G>C DJ-1 mutation unexpectedly revealed that this mutation leads to the loss of DJ-1 protein in these cell types. Further experiments using qPCR and an in vitro splicing assay showed a splicing defect causing complete skipping of the mutation-carrying exon 3 in the pre-mRNA. After deciphering the pathogenic mechanism, we developed a targeted genetic rescue strategy of the pathological skipping of exon 3. This was performed by using a specific U1 snRNA that specifically binds to the mutated DJ-1 pre-mRNA and allows for the re-induction of physiological splicing. In addition, we extended our strategy by first candidate approaches aiming at a pharmacological rescue that may offer novel causative treatment options in patients carrying the c.192G>C DJ-1 mutation as well as for other diseases caused by the same mutational mechanism. Beyond the molecular genetic characterisation, we developed different patient-based cellular models and addressed the functional effects of loss of DJ-1 protein in different patient-derived cells carrying the c.192G>C DJ-1 mutation (human fibroblasts, iPSC-derived mDA neurons). These analyses revealed mitochondrial impairments upon loss of DJ-1 protein in fibroblasts, including fragmentation and reduced branching of mitochondria as well as a reduced mitochondrial membrane potential compared to healthy controls. The results correlate with our observations in primary cells from DJ-1 knockout mice and support the idea of a conserved role of DJ-1 in maintaining mitochondrial function. Moreover, mDA neurons of the index patient carrying the homozygous c.192G>C DJ-1 mutation showed in-creased lesion rates of mtDNA and no increase in mtDNA copy numbers, suggesting a lack of compensatory capacity. Our data substantially contribute to the understanding of mechanisms and functions of DJ-1 mutations in PD pathogenesis, in particular focusing on mitochondrial phenotypes upon loss of DJ-1 in different human ex vivo models. This underlines the role of DJ-1 as an important key player in the response to oxidative stress and the maintenance of proper mitochondrial function and homeostasis. Overall, we show that the fibroblasts with an inherited c.192G>C DJ-1 mutation, mDA neurons differentiated from iPSCs of these human fibroblasts and the DJ-1 knockout mice constitute excellent knockout model systems to further dissect the role of DJ-1 in neurodegeneration in PD. This also offers human DJ-1 knockout models for future iso-genic control experiments with a restituted endogenous DJ-1 background. Sequentially, it is possible to test whether disease related phenotypes might be rescued by reintroducing DJ-1 or correcting the defective splicing. Finally, the discovery of the underlying mechanism of the c.192G>C DJ-1 mutation opens up novel opportunities for a first genetic and maybe even pharmacological causative treatment for PD. [less ▲]

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See detailMigranten in den Medien der europäischen Grenzregion SaarLorLux (1990-2010). Eine vergleichende Inhalts- und Diskursanalyse
Kreutzer, Elena UL

Doctoral thesis (2015)

Aufbauend auf einem aus dem Forschungsstand und seinen Defiziten abgeleiteten Mehrmethodenansatz richtet die Studie von Elena Kreutzer ihren Fokus auf die kulturwissenschaftliche Grenzgebiets-Forschung ... [more ▼]

Aufbauend auf einem aus dem Forschungsstand und seinen Defiziten abgeleiteten Mehrmethodenansatz richtet die Studie von Elena Kreutzer ihren Fokus auf die kulturwissenschaftliche Grenzgebiets-Forschung mit Blick auf Medienanalysen. Dabei liegt ihr thematischer Fokus auf der Darstellung von Migranten in den Printmedien Saarbrücker Zeitung, Républicain Lorrain und Luxemburger Wort der als hochgradig interkulturell umschriebenen europäischen Grenzregion SaarLorLux. Die inhalts- und diskursanalytischen Ergebnisse zeigten im Inter-Media-Vergleich folgende Einsichten und Erkenntnisse auf: Einerseits stellten sich über die inhaltsanalytischen Befunde heraus, dass sich die nationalen Systemkontexte in den Medieninhaltsanalysen zu journalistischen Darstellungsmerkmalen, Themenagenden sowie Handlungs- und Aussagenträgern widerspiegeln. Andererseits konnte die Arbeit über die Interdiskursanalyse übergreifende Denkmuster eruieren: Diese wurden in einem gemeinsamen Grundbestand an Kollektivsymbolen und Argumentationsmustern nachgewiesen, der von kulturenübergreifenden, aber dennoch medienspezifischen Elementen ergänzt wurde. Dabei zeigt sich in allen drei Printmedien, dass topische Muster nicht nur defensiv zur Abwehr restriktiver Bestimmungen bzw. Bestätigung vorherrschender Abwehrdiskurse verwendet wurden, sondern zeitweise auch offensiv zur Begründung zuzugs- oder integrationsfavorisierender Maßnahmen. Während auf Basis der Pro- und Contra-Tendenz in der saarländischen und lothringischen Tageszeitung jedoch ein verstärkt problem- und risikoorientierter Blick auf Migration und Migranten ermittelt wurde, richtete die luxemburgische Zeitung ihren Fokus phasenweise auf Potentiale und Ressourcen von Einwanderung und Vielfalt in Luxemburg. Die europäische Grenzregion als Ganzes in Betracht ziehende Zusammenhänge wurden weitgehend mittels grenzüberschreitender Hinweise in Sonderseiten hergestellt. Als Hinweis auf eine grenzüberschreitend kommunizierende Grenzregion genügt dieser Befund jedoch nicht [less ▲]

Detailed reference viewed: 163 (24 UL)
See detailDevelopment and Investigation of a New Dry-Stacked Wall System
Agaajani, Shahriar UL

Doctoral thesis (2015)

The present study examines the potential use of a new mortarless and modular masonry system by carrying out its development and performing experimental, numerical, analytical and practical investigations ... [more ▼]

The present study examines the potential use of a new mortarless and modular masonry system by carrying out its development and performing experimental, numerical, analytical and practical investigations. Different forms of interlocking masonry elements have been modelled and optimised. Fullscale masonry walls were assembled and tested under compressive, flexural and shear loads. The overall structural behaviour was compared to conventional masonry systems such as hollow and shuttering blocks. The investigations showed overall high structural performances for the developed dry-stacked elements. The effect of the dry joint interfaces were extensively investigated experimentally and numerically under FE analysis. Furthermore, a new numerical technique for the determination of stress-percolation in drystacked load-bearing structures has been developed under numerical computing environment, which supports the better understanding of early fissuring in dry-stacked masonry structures. Finally, based on the experimental observations, a numeric-analytical failure mechanism of the dry-stacked masonry structure is proposed under axial and flexural loading. The completion of the package of dry-stacked units, consisting of interlocking modular masonries and an accompanying array of various other precast parts, confirmed the practical issues and solutions towards the exploitation of the developed dry-stacked elements for the construction of ready-to-build, modular and load-bearing walls. [less ▲]

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See detailDNS and Semantic Analysis for Phishing Detection
Marchal, Samuel UL

Doctoral thesis (2015)

Phishing is a kind of modern swindles that targets electronic communications users and aims to persuade them to perform actions for a another’s benefit. Miscreants performing this activity are named ... [more ▼]

Phishing is a kind of modern swindles that targets electronic communications users and aims to persuade them to perform actions for a another’s benefit. Miscreants performing this activity are named phishers and employ their power of persuasion to tailor socially engineered messages able to deceive their gullible victims. A popular example of phishing activities is the stealing of web services account login information or credit card information using fake websites or spoofed emails. However, several means are used to perform phishing attacks and several goals are sought, which harden the fight against phishing. Despite the forces engaged to get rid of this threat, phishing remains a concerning problem since the financial damage it causes is increasing overtime. Moreover, the perceived fatality about being a victim of phishing erodes the trust among users and threaten the use of electronic means as way of communicating. Existing solutions to cope with phishing attacks are not adapted to their short lifetime and the variety of means used to perform them, making them inefficient. Crowd verified blacklists, emails content analysis techniques or web page content analysis techniques did not succeed to reverse the increasing trend presented by phishing consequences. None of these solutions present the essential requirements that must meet a phishing protection technique to be efficient and which are speed, coverage, reliability and usability. Stating that phishing attacks rely mostly on social engineering and that most phishing vectors leverage directing links represented by domain names and URLs, we introduce new solutions to cope with phishing. These solutions rely on the lexical and semantic analysis of the composition of domain names and URLs. Both of these resource pointers are created and obfuscated by phishers to trap their victims. Hence, we demonstrate in this document that phishing do- main names and URLs present similarities in their lexical and semantic composition that are different form legitimate domain names and URLs composition. We use this characteristic to build models representing the composition of phishing URLs and domain names using machine learning techniques and natural language processing models. The built models are used for several applications such as the identification of phishing domain names and phishing URLs, the rating of phishing URLs and the prediction of domain names used in phishing attacks. All the introduced techniques are assessed on ground truth data and show their efficiency by meeting speed, coverage and reliability requirements. This document shows that the use of lexical and semantic analysis can be applied to domain names and URLs and that this application is relevant to detect phishing attacks. [less ▲]

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See detailDeanonymisation techniques for Tor and Bitcoin
Pustogarov, Ivan UL

Doctoral thesis (2015)

This thesis is devoted to low-resource off-path deanonymisation techniques for two popular systems, Tor and Bitcoin. Tor is a software and an anonymity network which in order to confuse an observer ... [more ▼]

This thesis is devoted to low-resource off-path deanonymisation techniques for two popular systems, Tor and Bitcoin. Tor is a software and an anonymity network which in order to confuse an observer encrypts and re-routes traffic over random pathways through several relays before it reaches the destination. Bitcoin is a distributed payment system in which payers and payees can hide their identities behind pseudonyms (public keys) of their choice. The estimated number of daily Tor users is 2,000,000 which makes it arguable the most used anonymity network. Bitcoin is the most popular cryptocurrency with market capitalization about 3.5 billion USD. In the first part of the thesis we study the Tor network. At the beginning we show how to remotely find out which Tor relays are connected. This effectively allows for an attacker to reduce Tor users' anonymity by ruling out impossible paths in the network. Later we analyze the security of Tor Hidden Services. We look at them from different attack perspectives and provide a systematic picture of what information can be obtained with very inexpensive means. We expose flaws both in the design and implementation of Tor Hidden Services that allow an attacker to measure the popularity of arbitrary hidden services, efficiently collect hidden service descriptors (and thus get a global picture of all hidden services in Tor), take down hidden services and deanonymize hidden services. In the second part we study Bitcoin anonymity. We describe a generic method to deanonymize a significant fraction of Bitcoin users and correlate their pseudonyms with their public IP addresses. We discover that using Bitcoin through Tor not only provides limited level of anonymity but also exposes the user to man-in-the middle attacks in which an attacker controls which Bitcoin blocks and transactions the user is aware of. We show how to fingerprint Bitcoin users by setting an "address cookie" on their computers. This can be used to correlate the same user across different sessions, even if he uses Tor, hidden-services or multiple proxies. Finally, we describe a new anonymous decentralized micropayments scheme in which clients do not pay services with electronic cash directly but submit proof of work shares which the services can resubmit to a crypto-currency mining pool. Services credit users with tickets that can later be used to purchases enhanced services. [less ▲]

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See detailEssays on Judgment and Decision Making in Accounting
Pietsch, Christian Philipp Rafael UL

Doctoral thesis (2015)

Detailed reference viewed: 186 (44 UL)
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See detailÉtude sur la nature et le régime juridiques des accords judiciaires de coopération internationale
Segovia González, Manuel José UL

Doctoral thesis (2015)

Le visage de la coopération judiciaire internationale a depuis un certain temps été bouleversé. Il en est ainsi, par exemple, en matière civile et commerciale. L’actualité atteste l’existence de pratiques ... [more ▼]

Le visage de la coopération judiciaire internationale a depuis un certain temps été bouleversé. Il en est ainsi, par exemple, en matière civile et commerciale. L’actualité atteste l’existence de pratiques de coopération judiciaire qui étaient difficilement imaginables autrefois. La coopération entre juges de common law – notamment – va aujourd’hui au-delà des seuls aspects opérationnels des procédures. Les cas de juges coopérant pour résoudre les différends pouvant surgir au cours de leurs procédures sont de plus en plus fréquents. Pour y arriver, ils ont recours à des méthodes parfois peu orthodoxes. Ils dialoguent, communiquent par différents moyens, négocient, voire s’accordent sur la voie à suivre. Cette thèse prétend étudier des accords de coopération entre juges étatiques destinés à résoudre des conflits qui surgissent, ou qui sont susceptibles de surgir, dans le cadre de procédures données. Le phénomène, qui est au cœur de cette nouvelle réalité notamment en matière d’insolvabilité et d’enlèvement d’enfants, ne se présente cependant pas dans des formes connues ou convenues. Il ne se matérialise pas sous la forme des accords qui sont conclus au quotidien. Il relève plutôt d’un rapport qui est particulier à la situation qui engendre les accords. Néanmoins, certains d’entre eux peuvent être qualifiés de contrats. Un contrat de coopération entre juges, conclu dans le cadre d’une affaire donnée, soulève, naturellement, une multitude de questions inédites et fondamentales, les plus importantes portant, peut-être, sur son régime juridique. Sans se vouloir exhaustive, cette étude prétend répondre à certaines de ces questions. Les accords se situant aux confins de différentes branches du droit, l’une de ces questions porte sur leur appartenance à l’ordre juridique international ou à l’un des ordres juridiques des juges contractants, c’est-à-dire à un ordre juridique interne. L’ordre juridique international devant être écarté, l’étude prend de prime abord appui sur les méthodes du droit international privé pour déterminer l’ordre juridique compétent avant de se baser sur le droit administratif afin d’exclure le qualificatif de contrat administratif. Elle offre ainsi une première analyse inédite du régime juridique de ces accords de coopération judiciaire. Cette étude a un caractère résolument prospectif en ce sens qu’elle prend appui sur une pratique qui relève de tribunaux de common law et l’analyse sous l’angle de la tradition continentale. [less ▲]

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See detailOptimization of handover procedure between IEEE 802.11 access points under vehicular mobility in an urban environment.
Mouton, Maximilien UL

Doctoral thesis (2015)

This thesis presents investigations performed on the IEEE 802.11 handover process in order to optimize the exploitation of exisiting IEEE 802.11 networks in vehicular communications. As IEEE 802.11 ... [more ▼]

This thesis presents investigations performed on the IEEE 802.11 handover process in order to optimize the exploitation of exisiting IEEE 802.11 networks in vehicular communications. As IEEE 802.11 networks operate over a short range, a mobile station embedded in a vehicle faces frequent handovers leading to long disconnections. This work focused on two objectives. The first was reducing the IEEE 802.11 handover impact such that mobile users are allowed to be fully connected while they stay within the area covered by IEEE 802.11 networks. The second was optimizing the AP selection process in order to comply with the always best connected paradigm by identifying the best access points and the best handover location. These researches lead to the development of a context-based predictive handover mechanism that considers vehicle’s trajectory, road topology, and network deployment information to decide the best handover location and candidate access points. [less ▲]

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See detailUnderstanding primary-school, high-school and university students sustainable behaviours: An approach based on the theory of planned behaviour
De Leeuw, Astrid UL

Doctoral thesis (2015)

Developing a more thorough understanding of what motivates young people to adopt sustainable behaviours is an important area of concern that has practical implications for creating sound educational ... [more ▼]

Developing a more thorough understanding of what motivates young people to adopt sustainable behaviours is an important area of concern that has practical implications for creating sound educational interventions and ensuring a sustainable future. The overall purpose of this thesis was to assess and understand primary- and high-school students’ environmentally sustainable behaviours in order to inform educational interventions. Moreover, it aimed at analysing one particular socially sustainable behavioural intention among university students, notably their intention to buy fair trade products. The theory of planned behaviour (TPB) was used as the basic theoretical framework to examine these behaviours. We first conducted a pilot study for each behaviour, with the aim to identify salient beliefs of the target populations with regard to the behaviour investigated. Open-ended questionnaires were administered to a sample of 116 primary-school students, 92 high-school students, and 17 voluntary participants at the university level. A content analysis of the participants’ responses allowed the determination of the most salient beliefs, which were used as the basis for the quantitative measures of beliefs in the main studies. The first and second main studies investigated the beliefs of 812 primary-school students and 602 high-school students regarding the adoption of pro-environmental behaviours using a longitudinal approach. The gist of our results seems to be that for both age groups, educational interventions should target control beliefs especially. For instance, students insist on tools that would facilitate pro-environmental behaviours (e.g., having duplex printers or recycling bins at school and at home). However, behavioural and normative beliefs should not be neglected. The last study examined mainly differences in male and female university students’ intentions to consume fair trade products. The results indicate that for women, more emphasis should be placed on perceived behavioural control (e.g., factors that facilitate the ii purchase of fair trade products), while for men, more emphasis should be placed on attitudes towards buying fair trade products (i.e., the advantages of adopting this behaviour). Our results confirm the usefulness of the TPB as a framework for understanding young people’s sustainable intentions and behaviours, with perceived control and attitudes having considerable impacts on sustainable intentions and perceived social pressure having a rather low weight. In addition, perceived control and intentions contributed significantly to the explained variance in primary- and high-school students’ eco-friendly behaviours. This thesis makes a number of important contributions to the literature. From a practical point of view, primary- and high-school students are important populations because sustainability-related habits might be established early in life. Moreover, in their roles as potentially important future decision makers in our society (e.g., future company leaders, politicians, global citizens), university students should be sensitized to the unequal power relationships often involved in conventional trading. Offering fair trade products and encouraging their consumption should be considered a small, but important, step in universities’ duty to create awareness. Despite the positive input for interventions inspired by this thesis, some limitations have to be considered, for instance, our reliance on self-report questionnaires and the possibility that participants may have overestimated the extent to which they perform environmentally and socially desirable behaviours related to sustainability. Last, further research is needed to test the effectiveness of interventions based on the present results. [less ▲]

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See detailProvably Secure Countermeasures against Side-channel Attacks
Vadnala, Praveen Kumar UL

Doctoral thesis (2015)

Side-channel attacks exploit the fact that the implementations of cryptographic algorithms leak information about the secret key. In power analysis attacks, the observable leakage is the power consumption ... [more ▼]

Side-channel attacks exploit the fact that the implementations of cryptographic algorithms leak information about the secret key. In power analysis attacks, the observable leakage is the power consumption of the device, which is dependent on the processed data and the performed operations.\ignore{While Simple Power Analysis (SPA) attacks try to recover the secret value by directly interpreting the power measurements with the corresponding operations, Differential Power Analysis (DPA) attacks are more sophisticated and aim to recover the secret value by applying statistical techniques on multiple measurements from the same operation.} Masking is a widely used countermeasure to thwart the powerful Differential Power Analysis (DPA) attacks. It uses random variables called masks to reduce the correlation between the secret key and the obtained leakage. The advantage with masking countermeasure is that one can formally prove its security under reasonable assumptions on the device leakage model. This thesis proposes several new masking schemes along with the analysis and improvement of few existing masking schemes. The first part of the thesis addresses the problem of converting between Boolean and arithmetic masking. To protect a cryptographic algorithm which contains a mixture of Boolean and arithmetic operations, one uses both Boolean and arithmetic masking. Consequently, these masks need to be converted between the two forms based on the sequence of operations. The existing conversion schemes are secure against first-order DPA attacks only. This thesis proposes first solution to switch between Boolean and arithmetic masking that is secure against attacks of any order. Secondly, new solutions are proposed for first-order secure conversion with logarithmic complexity (${\cal O}(\log k)$ for $k$-bit operands) compared to the existing solutions with linear complexity (${\cal O}(k)$). It is shown that this new technique also improves the complexity of the higher-order conversion algorithms from ${\cal O}(n^2 k)$ to ${\cal O}(n^2 \log k)$ secure against attacks of order $d$, where $n = 2d+1$. Thirdly, for the special case of second-order masking, the running times of the algorithms are further improved by employing lookup tables. The second part of the thesis analyzes the security of two existing Boolean masking schemes. Firstly, it is shown that a higher-order masking scheme claimed to be secure against attacks of order $d$ can be broken with an attack of order $d/2+1$. An improved scheme is proposed to fix the flaw. Secondly, a new issue concerning the problem of converting the security proofs from one leakage model to another is examined. It is shown that a second-order masking scheme secure in the Hamming weight model can be broken with a first-order attack on a device leaking in the Hamming distance model. This result underlines the importance of re-evaluating the security proofs for devices leaking in different models. [less ▲]

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See detailEnabling Testing of Large Scale Highly Configurable Systems with Search-based Software Engineering: the Case of Model-based Software Product Lines
Henard, Christopher UL

Doctoral thesis (2015)

Complex situations formed by mixes of versatile environments, various user needs and time-to-market constraints led to the development of highly configurable systems. In line with the emergence of such ... [more ▼]

Complex situations formed by mixes of versatile environments, various user needs and time-to-market constraints led to the development of highly configurable systems. In line with the emergence of such systems, software development is increasingly moving from the production of a single, yet configurable software to the development of families of software products. Such families of related software are called Software Product Lines (SPLs), and they allow the automation of the configuration, deployment and management of tailored software products through the combination of software features. These features and the constraints defining their legal combinations are usually encoded in a feature model (FM), which is used to represent a SPL. One main challenge with SPLs is testing them, a task which is even more difficult as the number of features proposed is important. Ideally, all the possible products that can be configured from a SPL should be tested. This, however, is unfeasible in practice since only 270 optional features allows configuring more products than the number of atoms in the universe. Considering that realistic SPLs involve thousands of features and that testing capabilities are limited by time and budget constraints, only a subset of all the configurable products can actually be tested, introducing the needs for strategies to test such SPLs. To reduce the testing effort, techniques using combinatorial interaction testing (CIT) have been proposed and proven to be successful. However, they fail at scaling to large and heavily constrained SPLs. In addition, CIT is costly to apply due to the combinatorial explosion induced by calculating the feature combinations. Besides, existing approaches do not consider multiple and potentially conflicting testing objectives such as minimizing the number of configurations and their cost. In this respect, this dissertation introduces scalable techniques for both generating and prioritizing relevant SPL product configurations for CIT by using a similarity heuristic which avoids the combinatorial explosion. In a second step, methods for handling multiple testing objectives are presented. The following part of this thesis focuses on the quality assessment of given product configurations prior to testing. The objective here is to evaluate how good is a given set of configurations according to different testing criteria, whatever the way these configurations have been selected. This situation arises when configurations that have to be tested are already available. Since testing these software products individually is a costly and time consuming task, methodologies to evaluate them prior testing are introduced, thus allowing to discard unnecessary ones and save testing sessions. In particular, an approach based on mutation of the SPL FM which can form viable and cheaper alternative to CIT is presented. The next part of this dissertation investigates the reverse-engineering of a SPL and its FM from existing source code of software product variants. Since SPLs allows us to reduce development costs and quickly derive tailored products for specific market share, automated techniques to migrate similar product variants into a whole SPL are necessary. In particular, the challenge of reverse-engineering a SPL which is concordant with the underlying software products is tackled by a fully automated approach. In addition, since reverse-engineering approaches (whether manually or automatically performed) are inherently error-prone, a methodology for evaluating and fixing reverse-engineered SPL FM is presented. The final part of this dissertation describes the application of the introduced theoretical advances to an industrial case with the CETREL company. In this project, a credit card authorization system is tested by using credit card authorizations. The testing process is optimized by modeling credit card authorizations as a SPL, enabling the application of the above-mentioned generation and evaluation approaches. All the proposed approaches use search-based techniques combined with constraint solvers and have been validated through rigorous experiments performed on moderate to large scale SPLs. [less ▲]

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See detailIN VIVO ANALYSIS OF STEM CELLS AS A PREREQUISITE FOR AUTOLOGOUS CELL REPLACEMENT THERAPIES
Hemmer, Kathrin UL

Doctoral thesis (2015)

The seminal discovery that somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) opens new horizons for future personalised cell replacement therapies. This is particularly ... [more ▼]

The seminal discovery that somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) opens new horizons for future personalised cell replacement therapies. This is particularly interesting for neurological disorders since the central nervous system (CNS) possesses only limited regenerative potential and conventional therapies are inefficient. However, the unique feature of pluripotency bears a high risk of tumour formation and therefore restricts the direct utilisation of iPSCs for clinical applications. More recently, direct reprogramming from a somatic lineage into another e.g. into neurons, without passing through the pluripotent state, was achieved, thus circumventing the pluripotency-associated tumorigenic risk. The inability of neurons to self-renew and their restricted lineage potential, however, renders this technique inadequate for routine usage. Conversely, cardinal features of neural stem cells (NSCs) include the ability of self-renewal and trilineage differentiation potential, while their higher degree of differentiation compared to PSCs poses a lower tumorigenic risk. Thus, NSCs possess ideal requirements for neural cell based therapies. However, the features of NSCs under physiological conditions can deviate from their in vitro properties. Therefore, the in vivo features of two novel NSC lines were analysed in the present work in order to assess their relevance for therapeutic applications. The first line analysed, induced NSCs (iNSCs), were directly reprogrammed from mouse embryonic fibroblasts, without passing through the pluripotent state, by using a combination of 4 or 5 transcription factors. These iNSCs closely resemble wild-type NSCs in terms of morphology, gene expression profile, self-renewing capacity, epigenetic status, differentiation potential and functionality. Moreover, in vivo analysis revealed survival ability and multipotent differentiation capacity of the iNSCs. Thus, we proved that differentiated cells can be directly converted to acquire a true NSC identity. Remarkably, the iNSC technique overcomes some of the hurdles associated with PSCs or with induced neurons (iNs), e.g. high tumorigenic potential and inability to self-renew, respectively. In a follow-up study, we analysed the long-term in vivo properties of iNSCs and showed substantial long-term survival rates of grafted iNSCs without graft overgrowth. We further demonstrated neural multilineage differentiation potential of the iNSCs with a clear bias towards astrocytes as well as a permanent downregulation of progenitor and cell cycle markers. These data suggest that iNSCs are not predisposed to tumour formation, making them a safe source for long-term transplantations. Moreover, iNSC-derived progenies fulfil basic requirements to reconstruct damaged tissue i.e. migration, functional integration and interaction with the existing neural circuit, evidenced by the generation of synaptic connections and electrophysiological features. In addition to the murine iNSCs, we also examined multipotent neural precursor cells (NPCs) derived from human PSCs during this thesis. Noteworthy, the generation and propagation of a fully homogeneous neural culture is achieved by using only low-cost small molecules (smNPCs), without tedious manual manipulation and by robust and easy culture conditions. By this means, convenient and affordable large-scale approaches like cell replacement therapies are facilitated. Strikingly, smNPCs uniquely exhibit stable expandability while retaining a broad differentiation potential i.e. the competence to clonally and efficiently differentiate into neural tube-derived CNS lineages as well as neural crest-derived lineages. These features are, so far, only matched by PSCs. The extraordinary features of smNPCs were complemented by their in vivo capabilities: smNPCs possess the competence to survive, to differentiate into mature neurons and astrocytes and to integrate within a physiological neural network without any tumorigenic predisposition. Moreover, smNPCs did not only display a neurogenic differentiation propensity in vivo, but they were also capable of differentiating towards the midbrain dopaminergic (mDA) neuronal subtype in vivo when predifferentiated before transplantation. mDA neurons are of special interest for regenerative approaches to treat Parkinson’s disease (PD). Furthermore, we generated smNPCs from neuroectoderm- and mesoderm-derived iPSCs in order to determine if and to what extend the in vitro as well as in vivo capabilities of smNPCs are influenced by their somatic cell of origin. We found that robust and successful derivation of smNPCs as well as their differentiation potential are not affected by the donor cell type. However, transcriptomic analysis revealed that origin-dependent neural cell identies exist, to a certain degree, in smNPCs in vitro and in vivo though but only to a small extent. Remarkably, these neural cell identities provided certain advantageous features in a physiological neural environment i.e. a better survival rate and neurite outgrowth. Nevertheless, the major in vivo features that are required for the feasibility of successful cell replacement therapies are not restricted by the starting population i.e. robust neuronal differentiation efficiency as well as synapse formation. Overall, this work revealed that iNSCs and smNPCs exhibit important in vivo features that are decisive requirements for the success of future personalised cell replacement therapies. We conclude that not only the iNSC technique itself but also the long-term in vivo features of iNSC progenies render them as a highly desirable tool for glial regenerative therapies, while the multifaceted properties of smNPCs classify them as an extremely qualified tool for neuronal, and in particular mDA neuronal, cell replacement approaches. [less ▲]

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See detailThe Potential of Precipitable Water Vapour Measurements from Global Navigation Satellite Systems in Luxembourg
Ahmed, Furqan UL

Doctoral thesis (2015)

The primary objectives of this research were to investigate the potential of precipitable water vapour (PWV) estimates derived from Global Navigation Satellite Systems (GNSS) measurements, firstly, for ... [more ▼]

The primary objectives of this research were to investigate the potential of precipitable water vapour (PWV) estimates derived from Global Navigation Satellite Systems (GNSS) measurements, firstly, for short-term weather forecasting based on numerical weather prediction (NWP) in Luxembourg and its surroundings and, secondly, for monitoring climate on regional and global scales. The suitability of real-time (RT) zenith total delay (ZTD) estimates obtained from three different precise point positioning (PPP) software packages was assessed by comparing them with the state-of-the-art product from the International GNSS Service (namely the IGS Final troposphere product) as well as collocated radiosonde (RS) observations. It was found that the RT-PPP ZTD estimates from two of the three software packages meet the threshold requirements for NWP nowcasting. The biases between the RT-PPP ZTD and the reference ZTD were found to be stable over time for all the RT-PPP ZTD solutions. A millimetre-level impact on the RT-PPP ZTD estimates was also observed when integer ambiguities were resolved. The impact of assimilating GNSS-derived near real-time (NRT) ZTD in the Applications of Research to Operations at Mesoscale (AROME) NWP model using a three-dimensional, variational (3D-VAR) assimilation scheme on the quality of weather forecasts for Luxembourg was studied. It was found that the assimilation of GNSS-derived ZTD systematically improves the atmospheric humidity short-range forecasts in comparison to other water vapour observing systems (radio soundings, satellite radiances, surface networks). Examination of several case studies revealed the ability of the ZTD observations to modify the intensity and location of predicted precipitation in accordance with previous studies. The addition of ZTD from the dense GNSS network in Wallonie (Belgium) was also found to be beneficial by improving the prediction of rainfall patterns in Luxembourg. The 2D maps of IWV obtained from the hourly NRT system were compared with cloud distribution and precipitation maps from satellite and weather radar data, respectively, and a good agreement in the location of the front system was found. A rise in IWV was recorded during a precipitation event in Luxembourg and it was shown that by observing the IWV change over the ground-based GNSS stations in Luxembourg in NRT, it is possible to determine the speed and direction of the passing fronts and hence storms can also be tracked. A 5-year long global reprocessed GNSS data set containing over 400 ground-based GNSS stations and based on the double differencing strategy has been used to validate the ZTD estimates obtained from the climate reanalysis model of the European Centre for Medium-range Weather Forecasts (ECMWF) namely the ECMWF ReAnalysis-Interim (ERA-Interim) in different climate zones. It was found that the correlation coefficient between the GNSS-derived ZTD observations and the ZTD modeled by ERA-Interim ranges from 0.87 to 1.00. Higher correlation coefficients were found for the stations belonging to the climate zones with lower amount of water vapour. Furthermore, it was found that the mean, SDev and RMS of the differences depends on periodicity in the residuals, altitude of the stations in a particular zone as well as the topographic variation in the zone. Monthly and seasonal means of GNSS-derived ZTD (ZTDgnss) were computed using a global ZTDgnss dataset consisting of 19-years of data and over 400 stations to study the climate variability in different climate zones. In terms of seasonal means, it was found that the climate zones in the northern hemisphere have ZTD maxima in Boreal Summer (June-July-August) whereas those in the southern hemisphere have ZTD maxima in Austral Summer (December-January-February). Monthly and seasonal variability in ZTDgnss was also studied for the locations of 6 ground-based GNSS (SPSLux) stations in Luxembourg. It was found that all the 6 SPSLux stations experience the same monthly and seasonal variability of ZTDgnss. In terms of monthly variation, it was found that the maxima in ZTDgnss occurs around the month of July for all the 6 SPSLux stations whereas in terms of seasonal variation, the location of maxima was found to be in Summer (June-July-August). The suitability of the ZTD derived using precise point positioning (PPP) strategy for climate monitoring applications was studied through its comparison with the ZTD estimates derived using double differenced positioning (DDP) using a global network of 114 stations and duration of 1 year. The mean differences between the two were found to be ranging from -3.35 to 2.37 mm over different climate zones. Furthermore, correlation coefficients ranging from 0.90 and 1.00 were found between the ZTD obtained using the two processing strategies. It was found that use of higher elevation cut-off angles and tropospheric mapping functions based on NWP improves the agreement between the PPP and DDP solutions. [less ▲]

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See detailCredit in the Economy: Small Business Default Correlation and Firms' Co-movements
Pisa, Magdalena UL

Doctoral thesis (2015)

Small businesses play crucial part in every developed economy. They employ about 50% of the workforce and are the engine of innovation. For this reason policy makers and regulators support financing small ... [more ▼]

Small businesses play crucial part in every developed economy. They employ about 50% of the workforce and are the engine of innovation. For this reason policy makers and regulators support financing small businesses’ operations to allow them to grow and show its potential. Through a series of studies about small business credit risk, we show that small business credit risk is predominantly related to firm characteristics rather than to economy or industry wide conditions. We find evidence that a distress in a customer industry is linked to higher credit risk among the small business suppliers and that a trade credit is an important channel transmitting distress from one firm to another. [less ▲]

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See detailTowards consolidated methods for the design and evaluation of user experience
Lallemand, Carine UL

Doctoral thesis (2015)

In the “third wave” of Human-Computer Interaction (HCI), the emergence of User Experience (UX) as a key concept has opened up both exciting perspectives and hard challenges. The conceptual shift to a more ... [more ▼]

In the “third wave” of Human-Computer Interaction (HCI), the emergence of User Experience (UX) as a key concept has opened up both exciting perspectives and hard challenges. The conceptual shift to a more comprehensive and emotional view of human-computer interactions has been accompanied by the development of numerous methods and tools for the design and evaluation of interactive systems. UX research has thus been mainly driven by novelty and innovation and to date a majority of the developed tools lack validation and consolidation. UX research undoubtedly raises new concerns and challenges common conceptual and methodological practice. Thus the primary objective of this thesis is to contribute to UX consolidation. We addressed this objective by relying on a mixed-methods approach for the empirical part of this thesis, involving comparatively large and representative samples. This part encompasses six studies, representing a variety of perspectives related to UX research consolidation. More specifically, this dissertation includes a replication study (Paper A, N = 758), the translation and validation of a tool (Paper B, N = 381), the development of new design and evaluation methods (Paper C and D, N = 137 and 33), the empirical assessment of the relevance of established HCI methods for the evaluation of UX (Paper E, N = 103) and finally an investigation on how to bridge UX research and practice through a design approach (Paper F). The contributions of this thesis to UX research and practice regard both UX as a concept and its methodologies. Main findings inform about the benefits, challenges, and limitations of UX consolidation strategies as derived from our respective studies (papers A to F). Each study provides advances to both research and practice, while the combination of our studies pushes forward consolidation of UX. This is an essential step with regards to an emerging concept and informs an overarching research agenda aiming at a continuous interdisciplinary fostering of the UX field. [less ▲]

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See detailPractical Provable Security against Side-Channel Attacks
Venkatesh, Srinivas Vivek UL

Doctoral thesis (2015)

Securing cryptographic systems in the presence of side-channel leakages is still an important problem. Over recent years, the cryptography theory community has shown considerable interest in formally ... [more ▼]

Securing cryptographic systems in the presence of side-channel leakages is still an important problem. Over recent years, the cryptography theory community has shown considerable interest in formally modelling the side-channel leakages and in designing "provably" secure cryptographic primitives in these leakage models. This area is often referred to as leakage-resilient cryptography. Yet, designing a formal model that realistically captures side-channel leakages such as power consumption patterns, and designing primitives efficient enough to be deployed in practice in such a leakage model, remains a challenging research direction. In this work, we aim to bridge the above gap between the theory of provably secure cryptosystems that resist side-channel attacks and their practical relevance. Keeping this goal in mind, we analyze existing constructions and provide new ones for basic cryptographic primitives such as encryption and authentication in both public-key and symmetric-key cryptography. This dissertation consists of three parts. In the first part, we analyze existing and design new efficient leakage-resilient constructions for public-key encryption and digital signatures that tolerate continual leakage in the split-state leakage model. Our security reductions are in the generic bilinear group model. The constructions we consider are simple variants of the ElGamal key encapsulation mechanism, and the Boneh-Boyen and the Schnorr signature schemes. We also cryptanalyze a variant of the ElGamal key encapsulation mechanism that was previously conjectured to be leakage-resilient under certain conditions. The second part of this work is concerned with the protection of block ciphers in the probing adversarial leakage model. This approach, popularly known as masking in the cryptographic engineering community, is an effective countermeasure for block cipher implementations against power-analysis attacks. We improve the efficiency of a generic higher-order masking scheme recently proposed by Carlet et al. Improving the efficiency of this scheme is related to the problem of evaluating polynomials over binary finite fields in a newer cost model that counts only "non-linear" polynomial multiplications. We propose a new method for evaluating polynomials in this cost model, and argue (heuristically) that this method is asymptotically optimal. The third part deals with the construction of efficient leakage-resilient symmetric-key authentication and encryption schemes. The constructions are shown to be secure in the standard model under a recently introduced simulatable leakage assumption. This assumption offers practitioners a hope to work with a formal leakage model that allows empirical verifiability. We propose a leakage-resilient CBC-like message authentication code, and also propose a leakage-resilient PRG-based chosen-plaintext secure encryption scheme for which we quantify the leakage it tolerates during the challenge phase in terms of security of a single iteration. Our constructions tolerate continual leakage but require leak-free updates. [less ▲]

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See detailAn Event-Driven Cooperative Advanced Driver Assistance System to Mitigate Vehicular Traffic Shock Waves in Temporarily High Traffic Demand
Forster, Markus UL

Doctoral thesis (2015)

In uncoordinated vehicular traffic, available road capacity cannot be fully exploited. This often leads to the formation of traffic jams and the emergence of vehicular traffic shock waves in times of ... [more ▼]

In uncoordinated vehicular traffic, available road capacity cannot be fully exploited. This often leads to the formation of traffic jams and the emergence of vehicular traffic shock waves in times of temporarily high traffic demand. The main reason for congestion on highways is the combination of high traffic demand and small instabilities in the flow. These can be caused by bottleneck situations such as ramps, construction sites, accidents, or by small inaccuracies of human drivers. Traffic jams that are caused by the latter reason often are referred to as phantom jams. Even with modern vehicles, equipped with several sensors and driver supporting features, the drivers’ or sensors’ line of sight are already limited by the vehicle ahead. Hence, drivers or vehicles are not able to take anticipatory actions. To overcome these limitations it is necessary to investigate cooperative systems that are connected through a communication channel. In this work, we introduce a novel distributed, connectionless and event-based communication protocol that enables us to eliminate up- stream shock wave formation already with low system penetration rates. Based on traffic information ahead, we propose a Cooperative Advanced Driver Assistance System (CADAS) that recommends pre-emptive velocity reductions in order to redistribute traffic more uniformly thereby eliminating traffic peaks. Simulation results show that our proposed CADAS increases and harmonizes the average velocity, and therewith reduces the overall travel time, avoiding unnecessary slowdowns. We also demonstrate that our event-based messaging scheme uses less network resources than beaconing. Moreover, we conduct a field test on a private test track in order to validate our proposed protocol. We compare uncoordinated traffic to traffic, controlled by the proposed CADAS. With our experiments, we show that such a recommendation-based system can alleviate the formation of vehicular shock waves, thus improve vehicular traffic. Additionally, we perform simulations on the experiment scenario and compare the results to the empirical ones. With this comparison we show that our simulation results agree with the findings from the field test. [less ▲]

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See detailMathematical Modelling of Network Traffic
Li, Yu UL

Doctoral thesis (2015)

ncreasing access to the Internet is producing profound influence around the World. More and more people are taking advantage of the Internet to obtain information, communicate with each other far away and ... [more ▼]

ncreasing access to the Internet is producing profound influence around the World. More and more people are taking advantage of the Internet to obtain information, communicate with each other far away and enjoy various recreations. This largely increased demand for the Internet requires better and more effective models. During the 1990s, a number of studies show that due to a different nature from telephonic traffic, in particular a bursty nature, traditional queuing models are not applicable in modeling of modern traffic. This work presents some alternative rigorous models that can be used in studying the behavior of the Internet traffic. In the thesis, we propose several new models to explain bursty nature of network traffic. Many practical problems in computer science, natural science and insurance are highly complex, since they typically involve a huge amount of random factors. Con- ventional queuing theory cannot handle such problems and the high variance and long memory features are not yet well understood. In the first part of our research, we start with investigation of random sum as well as random product and derive a single path model of network traffic and a multiple path model of network traffic.In the second part of this thesis, we present a homotopic approach to model network traffic. [less ▲]

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See detailOn dual-polarization signalling techniques in satellite communications
Arend, Lionel Jean UL

Doctoral thesis (2015)

In satellite broadcasting and broadband communications, two orthogonal polarizations can be employed for signalling. Typically, two independent carrier signals are transmitted on the horizontal and ... [more ▼]

In satellite broadcasting and broadband communications, two orthogonal polarizations can be employed for signalling. Typically, two independent carrier signals are transmitted on the horizontal and vertical linear polarizations. In this way the available frequency spectrum is used twice. Contrary to this independent use, the present work investigates the combined use of both polarizations for signalling and the possibly associated benefits. Two different modulation techniques are investigated. The first, polarization shift keying, modulates the state of polarization of the electromagnetic wave to convey information. It is based on the phase and amplitude relationship between both carriers and is advantageous for channels strongly impaired by phase noise. The second technique defines a four-dimensional signal space for the combined modulation of amplitude and phase on both carriers. It was initially introduced as 4-quadrature signalling and permits transmission with improved power efficiency. Both techniques come from optical fibre communications, where similar propagation conditions exist. The conducted investigation is based on an analysis, simulations and the experimental verification using a specially developed demonstration transmitter and receiver. The simulations compare the power efficiency of the proposed modulation techniques with that of alternatives currently in use and analyse their behaviour upon disturbance by phase noise or non-linear distortion. The demonstrator is used to validate the findings in experimental measurements and to confirm the feasibility of both proposed techniques through a live satellite transmission. [less ▲]

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See detailHolocaust-Education in der Luxemburger Schule
Gelberg, Johanna Maria UL

Doctoral thesis (2015)

Today, the extermination of Jewish communities by the Nazi regime and its collaborators, namely the Holocaust, forms an integral part of the international political agenda. Although this dealing with the ... [more ▼]

Today, the extermination of Jewish communities by the Nazi regime and its collaborators, namely the Holocaust, forms an integral part of the international political agenda. Although this dealing with the Holocaust appears normal for us today, this was not always the case, but is the result of extensive social and political processes. In the course of this development the awareness of the special relevance of the extermination of about 6 million Jews has increased. Since the 1990s a process has emerged, that can be characterized as the universalization of Holocaust remembrance. The commemoration of the extermination of the European Jews is no longer an exclusive part of the different national cultures of remembrance, but has become an integral part of international memorial policy. An important event in this context has been the “Stockholm International Forum on the Holocaust” in the year 2000 where mainly European leaders as well as other high-ranking politicians, historians and teachers engaged with Holocaust education, Holocaust remembrance and Holocaust research. The idea was to establish an international organization that would expand Holocaust education worldwide. The aim of the present dissertation is to show how the Luxembourgian school system deals with this traumatic event that is the Holocaust and how it reacts as a system to expectations towards Holocaust and schooling, to find out how the school system works. The dissertation does not address questions as to show how the Holocaust should be taught in schools nor whether or not the Holocaust should be taught in schools at all. The dissertation analyses the particularities of teaching the Holocaust, as well as its role in the curriculum in a broader understanding of an analysis of parliamentary debates, syllabi, teaching material and the school practice. The latter includes the classroom settings and the so-called alternative teaching material like scholarly resources on the Holocaust like films, visits to museums, to concentration and extermination camps or the use of testimony from Holocaust survivors. [less ▲]

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See detailFormation of CU(IN,GA)SE2 from Solution Processed Sodium containing Metal Precursors
Berner, Ulrich Maximilian UL

Doctoral thesis (2015)

In this thesis a new chemical deposition process for the fabrication of Cu(In,Ga)Se2 absorber layers applicable as absorber material in thin film solar cells is described. Within this work a power ... [more ▼]

In this thesis a new chemical deposition process for the fabrication of Cu(In,Ga)Se2 absorber layers applicable as absorber material in thin film solar cells is described. Within this work a power conversion efficiency of up to 13.3% has been achieved which is among the highest reported values for non-vacuum based processes. The main part of this thesis is divided into 4 chapters describing the synthesis of the base materials and the ink (i), the individual process steps coating and drying together with the metal film formation (ii) as well as the selenization of the metal layer to chalcopyrites (iii). The last chapter investigates the influence of dissolved sodium salts (iv). (i) Metal formates synthesized from their respective nitrates have been chosen as starting salts due to the high reduction potential of the anion and its clean decomposition. With the reasonably toxic solvents tetramethylguanidine and methanol an ink can be produced which is highly concentrated, chemically stable and cheap. (ii) The coating and drying steps have been identified as crucial production processes to deposit homogeneous layers. In this context the solvent mixture has been shown to be responsible for unwanted material agglomerations close to the substrate boundaries. In order to minimize this effect a combined coating-drying device has been developed. The formation of metallic layers has been studied in detail. It could be shown that the respective metal ions are getting reduced consecutively at elevated temperatures between 130 and 200°C. The morphology of the resulting layers is highly dependent on the process conditions and varies from thick and porous structures to incoherent particle agglomerations. In order to overcome this issue an ink additive has been identified to densify and homogenize the metallic layer. A mechanism is proposed based on the formation of an intermediate polynuclear metal organic structure. (iii) The metallic layers could be selenized with elemental selenium in a tube oven to form dense chalcopyrites. By simulating the selenium evaporation a strong dependency of the final photovoltaic cell properties on the process temperature of the substrate layer getting in contact with evaporated selenium could be identified. (iv) Several sodium salts conveniently added to the ink have been proven to be suitable as sodium source. Compared to diffusion from the glass substrate the immediate sodium availability resulted in significantly improved cell properties. Within the evaluated sodium salts large differences have been found for example regarding the layer morphology. [less ▲]

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See detailEssays on Credit Risk: European studies in the context of the global financial crisis
Bekkour, Lamia UL

Doctoral thesis (2015)

Given the major role of credit risk in the recent financial crisis, this thesis focuses on analysing different perspectives of credit risk in Europe during the financial crisis. We consider different ... [more ▼]

Given the major role of credit risk in the recent financial crisis, this thesis focuses on analysing different perspectives of credit risk in Europe during the financial crisis. We consider different markets: Credit Default Swap (CDS), options on equities and exchange rates, and finally, the equity markets. We also look at the impact on different entities: corporates, banks and sovereigns however, we focus more on banks. [less ▲]

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See detailEssays on Sovereign and Banking Credit Risk
Rasmouki, Fanou UL

Doctoral thesis (2015)

In view of growing concerns about financial stability, this thesis revolves over two major objectives. The first objective relates to exploiting option pricing models to generate bank and sovereign credit ... [more ▼]

In view of growing concerns about financial stability, this thesis revolves over two major objectives. The first objective relates to exploiting option pricing models to generate bank and sovereign credit risk indicators and is pursued in chapters One and Two. The second objective is about determining the extent to which key institutions, namely the credit rating agencies and the ECB contributed to curing or hampering the European banking system. Chapter Three and Chapter Four address the latter theme. All through this thesis, we lay stress upon the connection between banks and sovereigns. [less ▲]

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See detailAircraft landing gear thermo-tribomechanical model development
Heirendt, Laurent UL

Doctoral thesis (2015)

A transient numerical model for studying the thermo-tribomechanical behavior of an aircraft landing gear is presented. The study reveals the major heat sources and heat sinks that impact the ... [more ▼]

A transient numerical model for studying the thermo-tribomechanical behavior of an aircraft landing gear is presented. The study reveals the major heat sources and heat sinks that impact the characteristic thermal behavior of the landing gear shock absorber. The severe in-service performance degradation and reported structural damage can be explained as a consequence of the heat generated by the high drag loads induced by rough runways on the bearings, and by the high sliding velocities of the piston. A conclusive model may lead to improved landing gear performance once the transient process of heat generation in a phase-changing grease-lubricated lower bearing is fundamentally understood. A novel tribotopological lubrication theory is derived in order to take into account all distinct physical phases of the non-Newtonian Bingham lubricant. The governing equations are solved using a hybrid numerical solver that is optimized for numerical efficiency and fast convergence. The proposed framework is validated against existing theories and results, and it demonstrates accurate predictions of the thermal performance of the landing gear. Strategies to passively optimize the lower bearing lubrication mechanism are further suggested in order to achieve optimal thermal performance of future aircraft landing gear. [less ▲]

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See detailProperty based model checking of structurally evolving Algebraic Petri nets
Khan, Yasir Imtiaz UL

Doctoral thesis (2015)

There are two important challenges in any system development life cycle, the first is to ensure the correctness of a model at the earliest stage possible and the second is to ensure its correctness once ... [more ▼]

There are two important challenges in any system development life cycle, the first is to ensure the correctness of a model at the earliest stage possible and the second is to ensure its correctness once it evolves with respect to the emergence of new requirements, performance may need to be improve, business environment is changing. Usual verification techniques such as testing and simulation are used commonly for the verification of a model. The downsides of these techniques are that there is no guarantee of the absence of errors and they need to be repeated after every evolved version. Model checking is an automatic technique for verifying finite state system models. Although, model checking is proved to be a useful technique, the typical drawback of model checking is its limits with respect to the state space explosion problem. As system gets reasonably complex, completely enumerating their states demands increasing amount of resources. Various techniques like symbolic model checking, on the fly model checking and compositional reasoning partially overcome this problem. Petri net is a well-known low-level formalism for modeling and verifying concurrent and distributed systems. The modeling of systems by low-level Petri nets is tedious and therefore various advancements have been created to raise the level of abstraction of Petri nets. Among others, Algebraic Petri nets raise the level of abstraction of Petri nets by replacing black tokens with the elements of user defined data types i.e., algebraic abstract data types. The first contribution of this thesis is to develop an approach to tackle the state space explosion problem for model checking of Algebraic Petri nets by re-using, adapting and refining state of the art techniques. The proposed approach is based on slicing and the central idea is to perform verification only on those parts that may affect the property the Algebraic Petri net model is analyzed for. We propose several slicing algorithms for Algebraic Petri nets and can be applied to Petri nets by slight modifications. The proposed slicing algorithms can alleviate the state space even for certain strongly connected nets and are proved not to increase the state space. The second contribution is an approach to improving re-verification of structurally evolving Algebraic Petri nets. The idea is to classify evolutions and properties to identify which evolutions require re-verification. We argue that for the class of evolutions that require verification, instead of verifying the whole system, only a part that is concerned by the property can be sufficient. The third contribution is the development of a stand-alone tool i.e., SLAPn. The objective of this tool is to implement proposed slicing algorithms and to show the practical usability of slicing technique. An interesting exploitation of SLAPn is that it can be added to any existing model checker as a pre-processing step. [less ▲]

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See detailAn Analysis of Legislative Assistance in the European Parliament
Pegan, ANDREJA UL

Doctoral thesis (2015)

The dissertation ‘An Analysis of Legislative Assistance in the EP’ treats the problem of unelected parliamentary officials, which assist the elected members in the EP. The main research question is how ... [more ▼]

The dissertation ‘An Analysis of Legislative Assistance in the EP’ treats the problem of unelected parliamentary officials, which assist the elected members in the EP. The main research question is how does the organisational form of legislative assistance affect the functioning of the EP. The dissertation contributes to a new area of research in legislative studies on the relationship between technocracy and democracy. To gain an insight into the research question, the dissertation is concerned with the institutional design of legislative assistance in two different ways. First, the research project explains the form of legislative assistance in the EP between 1952 and 2013. Second, the dissertation investigates the behavioural consequences (i.e. staff’s frequency of involvement in assistance) of the administrative form in the seventh term (2009-2014). Following these aims, the dissertation is divided into two empirical parts. The qualitative part explains the form of legislative assistance in the EP based on new-institutionalists approaches to organisational design and qualitative methods (content analysis of interview and secondary data). The quantitative part investigates how the form of legislative assistance affects the behaviour of staff based on organisation theory and quantitative methods (PCA/regression). A comparison with the national legislatures reveals that in most aspects the organisation of legislative assistance in the EP resembles the one in state-parliaments, while other aspects are exclusive to the EP. State-parliament characteristics were adopted already in the 1950s due to functional-ideational considerations. Changes were more dynamic in the 1960s/1970s compared to the 1980s/1990s. Until the 1980s, the administrative structures of the EP were responding to political events. Organisational structures significantly determine the frequency staff assist MEPs. To sum up, while the behaviour of staff is conditioned by the organisation of legislative assistance, the organisation itself is conditioned by the historical institutional environment and functional considerations of the EP. [less ▲]

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See detailSupporting Stress Testing in Real-Time Systems with Constraint Programming
Di Alesio, Stefano UL

Doctoral thesis (2015)

Failures in safety-critical Real-Time Embedded Systems (RTES) could result in catastrophic consequences for the system itself, its users, and the environment. Therefore, these systems are subject to ... [more ▼]

Failures in safety-critical Real-Time Embedded Systems (RTES) could result in catastrophic consequences for the system itself, its users, and the environment. Therefore, these systems are subject to strict performance requirements specifying constraints on real-time properties such as task deadlines, response time and CPU usage. Lately, RTES have been shifting towards multi-threaded application design, highly configurable operating systems, and multi-core architectures for computing platforms. The concurrent nature of their operating environment also entails that the order of external events triggering RTES tasks is often unpredictable. Such complexity in the system architecture, concurrency, and environment renders performance testing increasingly challenging. Specifically, computing input combinations that are intended to violate performance requirements, i.e., stress testing, is one of the preferred ways for verifying RTES performance. These input combinations are referred to as stress test cases, and, upon execution, are predicted to result in worst-case scenarios with respect to a performance requirement. In RTES, stress test cases are usually characterized by sequences of arrival times for aperiodic tasks in the subject system. Generating stress test cases is challenging because it is hard to predict how a particular sequence of arrival times will affect the system performance, and because the set of all arrival times for aperiodic tasks quickly grows as the system size increases. For this reason, search strategies based on Genetic Algorithms (GA) have been used to find stress test cases with high chances of violating performance requirements. For practical use, software testing has to accommodate time and budget constraints. In the context of stress testing, it is essential to investigate the trade-off between the time needed to generate test cases (efficiency), their capability to reveal scenarios that violate performance requirements (effectiveness), and to cover different scenarios where these violations arise (diversity). Even though GA are efficient, and capable of finding diverse solutions, they explore only part of the search space, and their effectiveness depends on configuration parameters. This aspect justifies considering alternative strategies, such as Constraint Programming (CP), that explore the search space completely. Furthermore, to enable effective industrial application, stress testing has to be capable of seamless integration in the development cycle of companies. Therefore, it is both important to capture specific system and contextual properties in a conceptual model, and to map such conceptual model in a standard Model Driven Engineering (MDE) language such as UML/MARTE. In this thesis, we address the challenges above by presenting a practical approach, based on CP, to support performance stress testing in RTES. Specifically, we make the following contributions: (1) a conceptual model, mapped to UML/MARTE, which captures the abstractions required to generate stress test cases, (2) a constraint optimization model to generate such test cases, and (3) a combined GA+CP stress testing strategy that achieves a practical trade-off between efficiency, effectiveness and diversity. The validation of our work shows that (1) the conceptual model can be applied with a reasonable overhead in an industrial settings, (2) CP is able to effectively identify worst-case scenarios with respect to task deadlines, response time, and CPU usage, and (3) the combined GA+CP strategy is more likely than GA and CP in isolation to scale to large and complex systems. The work in this thesis opens up the exploration of further directions, involving the use of multi-objective optimization to generate stress test cases that simultaneously exercise different performance properties of the system, and of MiniMax analysis to derive design and configuration guidelines that minimize the risk to violate performance requirements at runtime. [less ▲]

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See detailGlobalisierierung in der Zeitgenossischen Luxemburgischen Literatur - Think Global, Act Local
Lakaff, Laura UL

Doctoral thesis (2015)

As part of the research project Kulturelle Globalsierung. Kollektivsymboliken in wissenschaftlischen und medialen Globalisierungsdiskursen, initiated by IPSE at the University of Luxembourg, my ... [more ▼]

As part of the research project Kulturelle Globalsierung. Kollektivsymboliken in wissenschaftlischen und medialen Globalisierungsdiskursen, initiated by IPSE at the University of Luxembourg, my dissertation shares the opinion that globalization and its effects cannot only be understood and perceived in economics and social sciences. The phenomenon of globalization is influential and international, it has spread throughout all medias and its influences can be found everywhere, for instance in literature. The field of literature becomes the illustration and representation of the effects of globalization. Literature helps to embody abstract constructs as the one of globalization and can thereby illustrate, even explain its manifestations. Literature is a vehicle to transport new ideas, thoughts and trends as it is always a product of its time. The innovation potential of my dissertation is, that I deal specifically with contemporary Luxembourgish literature, a very small and young national literature. By putting my research focus on collective Luxembourgish, I establish an overview of national identity, seen through the eyes of mainly three different Luxembourgish authors: Roger Manderscheid, Jean Portante and Nico Helminger. These three authors have been chosen because of the language they decided to write in: Luxembourgish, German and French, but also because this project will elaborate which literature tools writers use to manifest and illustrate globalization and its features. By having three different perspectives and languages used in Luxembourg, one can show the heterogenic but yet identifying influences of globalization. The differentiated work with a specific national literature helps to capture the collective symbols that all Luxembourgish people as well non-Luxembourgish residents share and can recognize as such. By finding the unifying elements, the differences and dissociative factors can be named and analyzed. This Phd project will help to create a clearer view on Luxembourg, its literature scene and its identity in a modern and globalized world. [less ▲]

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See detailPoles Apart : Navigating the Space of Opinions in Argumentation
Podlaszewski, Mikołaj UL

Doctoral thesis (2015)

Formal argumentation is a popular reasoning method in knowledge representation for intelligent systems. For the past 20 years it has been based on Dung’s abstract argumentation theory. More recently ... [more ▼]

Formal argumentation is a popular reasoning method in knowledge representation for intelligent systems. For the past 20 years it has been based on Dung’s abstract argumentation theory. More recently several challenges have been made to this standard - for example in dynamics and aggregation of argumentation frameworks. To support these new developments in this thesis new foundations are developed based on distance measures. We introduce postulates for distance measures and we show their consistency by constructing concrete measures. In the process we develop the new notion of issue. Subsequently we use the distance measures in argumentation using distance based operators introduced by Miller and Osherson in judgment aggregation. Moreover in this thesis we also improve dialectical proof procedures for grounded semantics and study postulates of non-interference and crash resistance for Dung based non-monotonic inference. [less ▲]

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See detailStructural Relaxations in the Rotator Phase of N-Eicosane
Di Giambattista, Carlo UL

Doctoral thesis (2015)

We present relaxations of the heat capacity of the n-alkane n-eicosane (C20H42) in the metastable rotator phase. These relaxations are not connected to melting but rather to structural changes. A ... [more ▼]

We present relaxations of the heat capacity of the n-alkane n-eicosane (C20H42) in the metastable rotator phase. These relaxations are not connected to melting but rather to structural changes. A comparative study of the relaxation times with calorimetry in the time and frequency domain shows a slowing down of the dynamics on approaching the melting temperature of the rotator phase. Relaxation behaviour is also observed in the lattice structure by investigations with X-ray diffraction. It is shown that the angular position of the two most relevant X-ray lines relaxes on different time scales. One of these two relaxations can be related to the relaxations found in calorimetry. The relaxing behaviour is discussed in the framework of conformational defect formation and compared to known phenomena in literature. [less ▲]

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See detailHow does usability improve computer-based knowledge assessment?
Weinerth, Katja UL

Doctoral thesis (2015)

There has been a major shift from paper-and-pencil towards computer-based assessments (CBAs). CBA has the potential to overcome various limitations imposed by traditional assessment approaches, mostly ... [more ▼]

There has been a major shift from paper-and-pencil towards computer-based assessments (CBAs). CBA has the potential to overcome various limitations imposed by traditional assessment approaches, mostly because CBA allows for the easier and more effective measurement of complex knowledge concepts via the use of dynamic items. Innovative item formats in CBA (dynamic or interactive multimedia items) allow the assessment of complex skills (e.g., complex problem solving), but they also tend to increase the complexity of CBA instruments because of their augmented interactivity. If the CBA is not user-friendly, the test-taker might spend more time and effort trying to understand how to interact with the system instead of focusing on the assessment task itself. The research field of human-computer interaction (HCI) shows that the usability or user-friendliness of the system affects the interaction. Usability addresses how appropriate (for a particular use) or how user-friendly a CBA instrument is. Thus, to the extent that there is any detrimental technical bias in CBA affecting the user-friendliness of a CBA, it will affect the user’s interaction with the instrument and consequently the instrument’s psychometrics. There are certain guidelines (e.g., International Test Commission, 2005) that require usability testing to safeguard against the CBA instrument measuring skills or competencies other than those that are supposed to be measured by the CBA instrument. However, surprisingly little research has been conducted to investigate whether usability has been acknowledged in CBAs and whether researchers are aware of the impact usability might have on the assessment results. To answer these and further research questions, three studies were conducted within this present Ph.D. project. These studies focused on a specific CBA instrument: concept maps. A concept map is a graphical illustration of a knowledge concept and can be described as a “knowledge net.” Research has shown that the concept map is a valid and reliable instrument for measuring conceptual knowledge. Concept map instruments are a good example of the increasing popularity of CBA, as technology allows test-takers to correct and improve their concept maps with ease. Test-takers and their examiners receive immediate feedback on the correctness of the concept map. Furthermore, it is a good example of new approaches to knowledge assessment, which is currently a major trend. All of this taken together makes concept maps a good proxy for new ways of assessing knowledge. Our research builds on three studies (Study I – literature-based study, Study II – laboratory study, Study III – school study) that investigated the impact of usability on computer-based knowledge assessment using concept maps. Study I, a literature-based study, scrutinized the existing literature and answered the fundamental research question of whether and how usability has been acknowledged in CBA concept map studies. As no such literature review existed prior to the current project, a systematic literature review was conducted to shed light on the representation and relevance of usability displayed in CBA concept map studies. The literature review indicated that only 24 of 119 journal articles that assessed computer-based concept maps actually discussed the usability of the applied instrument in some way and only three of those 24 journal articles explicitly mentioned that they evaluated the usability of the applied instruments. The literature review illustrated that usability is rarely acknowledged and reported in CBA concept map studies. Our review brings to light the idea that the impact of usability, although well established in the field of HCI, has received insufficient attention in the field of educational assessment. Study II, a laboratory study, addressed the main research question of how HCI methods can be introduced to the field of educational assessment to improve the usability of a CBA concept map instrument. With a user-centered design and development approach, which makes the user the key reference, usability testing and heuristic analyses were conducted in the usability laboratory. The approved HCI methods of usability testing and heuristic analyses were combined to evaluate and further improve a CBA concept map instrument. We applied three iterative design and re-engineering cycles that were based on the results we received from the usability testing and heuristic analyses. To verify the improvements in the usability of the CBA concept map instrument, three independent and randomly assigned groups of 30 students underwent concept map assessments using the three iteratively developed instruments (baseline (V1), further developed: V2 and V3). The results of this independent design sample study showed that the HCI methods allowed us to design and develop demonstrably usability-improved concept map instruments; they furthermore revealed that the usability improvements significantly improved the assessment outcomes. Study III, a school study, empirically verified the impact that usability has on the psychometrics of the applied CBA instruments and on the satisfaction and performance of the test-takers. The experimental study was conducted at school, and 542 students were randomly assigned to one of the three CBA concept map instruments that showed consecutively improved usability. The performance of the test-takers who worked with the usability-improved instruments significantly increased in comparison with the baseline version. The test-takers indicated that they were more satisfied with the usability-improved instruments. Moreover, the internal consistency of the items from the baseline instrument in comparison with usability-improved instruments increased from a Cronbach’s alpha of .62 to .84. To summarize, Study I showed that the impact of usability is rarely evaluated and discussed in CBA concept map studies. Studies II and III clearly showed that usability has a positive impact on the test-takers’ interaction with the CBA concept map instrument. Specifically, Study II illustrated and demonstrated how HCI methods could be used to achieve usability-improved CBA instruments, which in turn allow for better assessment outcomes. In addition, Study III illustrated that the psychometrics were also affected by the usability of the instrument; specifically, the reliability (measured as the internal consistency of the applied items) increased when the usability-improved instruments were used. Thus, the continuing trend towards CBAs calls for more systematic usability research to help ensure satisfactory psychometric test properties and test-takers’ satisfaction with the instrument. The studies confirmed the hypothesis that if usability is not taken into account, the assessment results may severely compromise the quality of individual diagnostics as well as educational policies and educational decisions. [less ▲]

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