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See detailBackreaction and the Covariant Formalism of General Relativity
Magni, Stefano UL

Bachelor/master dissertation (2012)

This thesis is a review of backreaction, which is a possible alternative to dark energy and modified gravity. We describe in detail the 3+1 covariant formalism and Frobenius' theorem. We present the ... [more ▼]

This thesis is a review of backreaction, which is a possible alternative to dark energy and modified gravity. We describe in detail the 3+1 covariant formalism and Frobenius' theorem. We present the averaging procedure developed by Buchert, the Buchert equations and the generalization of these equations to the case of general matter. We then generalize to arbitrary number of spatial dimensions. We focus on the case of 2+1 dimensions, where the relation between the topology and the geometry of a surface imposes a global constraint on backreaction. [less ▲]

Detailed reference viewed: 38 (8 UL)
See detailBacteria online - University of Cambridge iGEM 2007 project
Han, Yutao UL; Hengrung, N.; Liew, Y. et al

Scientific Conference (2008)

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See detailBad irreducible subgroups and singular locus for character varieties in PSL(p,C)
Guerin, Clément UL

in Geometriae Dedicata (2017)

We give the centralizers of irreducible representations from a finitely generated group $\Gamma$ to $PSL(p,\mathbb{C})$ where p is a prime number. This leads to a description of the singular locus (te ... [more ▼]

We give the centralizers of irreducible representations from a finitely generated group $\Gamma$ to $PSL(p,\mathbb{C})$ where p is a prime number. This leads to a description of the singular locus (te (the set of conjugacy classes of representations whose centralizer strictly contains the center of the ambient group) of the irreducible part of the character variety $\chi^i(\Gamma,PSL(p,\mathbb{C}))$. When $\Gamma$ is a free group of rank $l\geq 2$ or the fundamental group of a closed Riemann surface of genus $g\geq 2$, we give a complete description of this locus and prove that this locus is exactly the set of algebraic singularities of the irreducible part of the character variety. [less ▲]

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See detailBad representations and homotopy groups of Character Varieties
Guerin, Clément UL; Lawton, Sean; Ramras, Daniel

E-print/Working paper (2019)

Let G be a connected, reductive, complex affine algebraic group, and let Xr denote the moduli space of G-valued representations of a rank r free group. We first characterize the singularities in Xr ... [more ▼]

Let G be a connected, reductive, complex affine algebraic group, and let Xr denote the moduli space of G-valued representations of a rank r free group. We first characterize the singularities in Xr resolving conjectures of Florentino-Lawton. In particular, we compute the codimension of the orbifold singular locus using facts about Borel-de Siebenthal groups. We then use this codimension to calculate some higher homotopy groups of the smooth locus of Xr, proving conjectures of Florentino-Lawton-Ramras. Lastly, using the earlier analysis of Borel-de Siebenthal groups, we prove a conjecture of Sikora about CI Lie groups. [less ▲]

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See detailThe BAFin's decision in Continental AG v. Schaeffler - Matter of Law, or Enforcement?
Zetzsche, Dirk Andreas UL

in European Business Organization Law Review (EBOR)(10/1) (2009)

Detailed reference viewed: 99 (1 UL)
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See detailLa BAGROI (Banque des donnés des Auteurs de la Grande Région d’Origine Italienne) comme témoin d’intégration
Cicotti, Claudio UL

in Boesen, Elisabeth; Lentz, Fabienne (Eds.) Migration et mémoire: concepts et méthodes de recherche (2010)

Detailed reference viewed: 30 (0 UL)
See detailLa BAGROI e la testualità della migrazione in Lussemburgo e nella Grande Regione
Cicotti, Claudio UL

in Rêves d'Italie. Italies de rêve. (2008)

Detailed reference viewed: 33 (0 UL)
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See detailBahnbrechende Leistungen. "Nobelpreis in Mathematik": Abelpreis an Thompson und Tits
Mortini, Raymond; Schlichenmaier, Martin UL

Article for general public (2008)

Detailed reference viewed: 78 (2 UL)
See detailLa baie de Portland : un paysage qui se (dé)voile
Thiltges, Sébastian UL

in Freyermuth, Sylvie; Halen, Pierre; Wittmann, Jean-Michel (Eds.) Échappées littéraires en francophonie (2016)

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See detailLa baignoire, le lit et la porte. La vie sociale des objets de la psychiatrie
Majerus, Benoît UL

in Geneses (2011), 82(1), 95--119

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See detailDie bakterielle Signalverarbeitung am Beispiel des Sucrose Phosphotransferasesystems in Escherichia coli : Modellierung und experimentelle Überprüfung
Sauter, Thomas UL

Doctoral thesis (2003)

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase ... [more ▼]

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase systems (PTSs) of the cell fulfil besides the transport of various carbohydrates, also the function of one signal processing system. Extra- and intracellular signals are converted within the PTS protein chain to important regulatory signals affecting e.g. carbon metabolism and chemotaxis. A detailed dynamical model of the sucrose PTS was developed describing transport and signal processing function. It was formulated using a detailed description of complex formation and phosphate transfer between the chain proteins. Model parameters were taken from literature or were identified with own experiments. Using a formal algorithm including cluster analysis, PTS and glycolysis could be identified as biological functional units with limited autonomy. Simulation studies together with experimental hints showed that the dynamic behaviour of phosphate transfer in the PTS runs within one second. Therefore a description of steady state characteristics is sufficient for describing the signaling properties of the sucrose PTS. A steady state characteristic field describes the degree of phosphorylation of the PTS protein EIIACrr as a function of the input variables extracellular sucrose concentration and intracellular PEP:pyruvate ratio. The model has been validated with different experiments performed in a CSTR using an sucrose positive Escherichia coli W3110 derivative. A method for determining intracellular metabolite concentrations has been developed. A sample preparation technique using a boiling ethanol buffer solution was successfully applied. The PTS output signal degree of phosphorylation of EIIACrr was also measured. Steady state conditions with varying dilution rate and dissolved oxygen concentration and dynamical variations applying different stimuli to the culture were considered. Pulse, and stop feeding experiments with limiting sucrose concentrations were performed. Simulation and experimental results matched well. The same holds for the expanded sucrose PTS and glycolysis model. [less ▲]

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See detailBalance is the challenge--the impact of mitochondrial dynamics in Parkinson's disease.
Burbulla, Lena F.; Krebiehl, Guido; Krüger, Rejko UL

in European journal of clinical investigation (2010), 40(11), 1048-60

Impaired mitochondrial function has been implicated in neurodegeneration in Parkinson's disease (PD) based on biochemical and pathoanatomical studies in brains of PD patients. This observation was further ... [more ▼]

Impaired mitochondrial function has been implicated in neurodegeneration in Parkinson's disease (PD) based on biochemical and pathoanatomical studies in brains of PD patients. This observation was further substantiated by the identification of exogenic toxins, i.e. complex I inhibitors that directly affect mitochondrial energy metabolism and cause Parkinsonism in humans and various animal models. Recently, insights into the underlying molecular signalling pathways leading to alterations in mitochondrial homeostasis were gained based on the functional characterization of mitoprotective genes identified in rare forms of inherited PD. Using in vitro and in vivo loss of function models of the Parkin, PINK1, DJ-1 and Omi/HtrA2 gene, the emerging field of mitochondrial dynamics in PD was established as being critical for the maintenance of mitochondrial function in neurons. This underscored the concept that mitochondria are highly dynamic organelles, which are tightly regulated to continuously adapt shape to functional and anatomical requirements during axonal transport, synaptic signalling, organelle degradation and cellular energy supply. The dissection of pathways involved in mitochondrial quality control clearly established the PINK1/Parkin-pathway in the clearance of dysfunctional mitochondria by autophagy and hints to a complex interplay between PD-associated proteins acting at the mitochondrial interface. The elucidation of this mitoprotective signalling network may help to define novel therapeutic targets for PD via molecular modelling of mitochondria and/or pharmacological modulation of mitochondrial dynamics. [less ▲]

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See detailThe balance model : Hindrance or support for the solving of linear equations with one unknown
Vlassis, Joëlle UL

in Educational Studies in Mathematics (2002)

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See detailA Balanced Scorecard for Managing the Aging Workforce
VOELPEL, S. C.; Streb, Christoph Klaus UL

in Organizational Dynamics (2010), 39(1), 84-90

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See detailA balancing act: Parameter estimation for biological models with steady-state measurements
Mizera, Andrzej UL; Pang, Jun UL; Sauter, Thomas UL et al

in Proceedings of 11th Conference on Computational Methods in Systems Biology (CMSB'13) (2013)

Detailed reference viewed: 83 (8 UL)
See detailBalancing competitiveness and social fairness
Muñoz, Susana UL

Scientific Conference (2017, March 29)

This contribution provides a preliminary analysis of the first outline of the European Pillar of Social Rights launched in Mach 2016, pending the European Commission's final proposal expected in early ... [more ▼]

This contribution provides a preliminary analysis of the first outline of the European Pillar of Social Rights launched in Mach 2016, pending the European Commission's final proposal expected in early 2017. [less ▲]

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See detailBALANCING NON-FUNCTIONAL REQUIREMENTS IN CLOUD-BASED SOFTWARE: AN APPROACH BASED ON SECURITY-AWARE DESIGN AND MULTI-OBJECTIVE SOFTWARE DYNAMIC MANAGEMENT
El Kateb, Donia UL

Doctoral thesis (2015)

Beyond its functional requirements, architectural design, the quality of a software system is also defined by the degree to which it meets its non-functional requirements. The complexity of managing these ... [more ▼]

Beyond its functional requirements, architectural design, the quality of a software system is also defined by the degree to which it meets its non-functional requirements. The complexity of managing these non-functional requirements is exacerbated by the fact that they are potentially conflicting with one another. For cloud-based software, i.e., software whose service is delivered through a cloud infrastructure, other constraints related to the features of the hosting data center, such as cost, security and performance, have to be considered by system and software designers. For instance, the evaluation of requests to access sensitive resources results in performance overhead introduced by policy rules evaluation and message exchange between the different geographically distributed components of the authorization system. Duplicating policy rule evaluation engines traditionally solves such performance issues, however such a decision has an impact on security since it introduces additional potential private data leakage points. Taking into account all the aforementioned features is a key factor to enhance the perceived quality of service (QoS) of the cloud as a whole. Maximizing users and software developers satisfaction with cloud-based software is a challenging task since trade-off decisions have to be dynamically taken between these conflicting quality attributes to adapt to system requirements evolution. In this thesis, we tackle the challenges of building a decision support method to optimize software deployment in a cloud environment. Our proposed holistic method operates both at the level of 1) Platform as a service (PaaS) by handling software components deployment to achieve an efficient runtime optimization to satisfy cloud providers and customers objectives 2) Guest applications by making inroads into the design of applications to enable the design of secure systems that also meet flexibility, performance and cost requirements. To thoroughly investigate these challenges, we identify three main objectives that we address as follows: The first objective is to achieve a runtime optimization of cloud-based software deployment at the Platform as a service (PaaS) layer, by considering both cloud customers and providers constraints. To fulfill this objective, we leverage the models@run.time paradigm to build an abstraction layer to model a cloud infrastructure. In a second step, we model the software placement problem as a multi-objective optimization problem and we use multi-objective evolutionary algorithms (MOEAs) to identify a set of possible cloud optimal configurations that exhibit best trade-offs between conflicting objectives. The approach is validated through a case study that we defined with EBRC1, a cloud provider in Luxembourg, as a representative of a software component placement problem in heterogeneous distributed cloud nodes. The second objective is to ameliorate the convergence speed of MOEAs that we have used to achieve a run-time optimization of cloud-based software. To cope with elasticity requirements of cloud-based applications, we improve the way the search strategy operates by proposing a hyper-heuristic that operates on top of MOEAs. Our hyper-heuristic uses the history of mutation effect on fitness functions to select the most relevant mutation operators. Our evaluation shows that MOEAs in conjunction with our hyper-heuristic has a significant performance improvement in terms of resolution time over the original MOEAs. The third objective aims at optimizing cloud-based software trade-offs by exploring applications design as a complementary step to the optimization at the level of the cloud infrastructure, tackled in the first and second objectives. We aimed at achieving security trade-offs at the level of guest applications by revisiting current practices in software methods. We focus on access control as a main security concern and we opt for guest applications that manage resources regulated by access control policies specified in XACML2. This focus is mainly motivated by two key factors: 1) Access control is the pillar of computer security as it allows to protect sensitive resources in a given system from unauthorized accesses 2) XACML is the de facto standard language to specify access control policies and proposes an access control architectural model that supports several advanced access requirements such as interoperability and portability. To attain this objective, we advocate the design of applications based on XACML architectural model to achieve a trade-off between security and flexibility and we adopt a three-step approach: First, we identify a lack in the literature in XACML with obligation handling support. Obligations enable to specify user actions that have to be performed before/during/after the access to resources. We propose an extension of the XACML reference model and language to use the history of obligations states at the decision making time. In this step, we extend XACML access control architecture to support a wider range of usage control scenarios. Second, in order to avoid degrading performance while using a secure architecture based on XACML, we propose a refactoring technique applied on access control policies to enhance request evaluation time. Our approach, evaluated on three Java policy-based systems, enables to substantially reduce request evaluation time. Finally, to achieve a trade-off between a safe security policy evolution and regression testing costs, we develop a regression-test-selection approach for selecting test cases that reveal faults caused by policy changes. To sum up, in all aforementioned objectives, we pursue the goal of analysing and improving the current landscape in the development of cloud-based software. Our focus on security quality attributes is driven by its crucial role in widening the adoption of cloud computing. Our approach brings to light a security-aware design of guest applications that is based on XACML architecture. We provide useful guidelines, methods with underlying algorithms and tools for developers and cloud solution designers to enhance tomorrow’s cloud-based software design. Keywords: XACML-policy based systems, Cloud Computing, Trade-offs, Multi-Objective Optimization [less ▲]

Detailed reference viewed: 267 (51 UL)
See detailBalancing the core activities of universities: For a university that teaches.
Biesta, Gert UL

in Sugden, R; Wilson, J; Valania, M (Eds.) Leadership and cooperation in academia: Reflecting on the roles and responsibilities of university faculty and management (2013)

Detailed reference viewed: 100 (0 UL)