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See detailCo-evaporation and Scanning Probe Microscopy Characterizations of Hybrid Halide Perovskite Thin Films for Solar Cells
Gallet, Thibaut UL

Doctoral thesis (2021)

Hybrid organic-inorganic perovskites (HOIPs) are the trending materials when discussing solar cells. Their power conversion efficiency went from 3.8% to 25.5% in twelve years, making them extremely ... [more ▼]

Hybrid organic-inorganic perovskites (HOIPs) are the trending materials when discussing solar cells. Their power conversion efficiency went from 3.8% to 25.5% in twelve years, making them extremely promising, especially when combined with silicon in a tandem configuration. This improvement has been achieved by finding the best candidates for charge extraction and by interface engineering, compositional engineering and surface passivation. However, the surface of the HOIPs is still not well understood, and the role of grains boundaries for example is still highly debated. Determining the intrinsic surface properties of HOIPs is therefore crucial to find the best passivation strategies or fabrication designs to limit the surface and interfacial losses, and further improve solar cell efficiencies. Currently, solution-based processes are the most used techniques for fabrication, even though their upscalability towards commercialization is highly unlikely, and the use of solvents, sometimes toxic, considerably alters the perovskite surface, which makes the interpretation of their characterization challenging and sometimes misleading. The aim of this thesis is to clarify the intrinsic surface properties of HOIPs, and mainly CH3NH3PbI3 (or MAPbI3), by using surface-sensitive techniques such as scanning tunneling microscopy and spectroscopy (STM and STS) and Kelvin probe force microscopy (KPFM). To that end, HOIP thin films are mainly fabricated by thermal co-evaporation to achieve pristine surfaces, and inert-gas transfer is used to avoid contamination before their characterization. The lateral variations of the local density of states of MAPbI3 and mixed halide HOIPs are investigated. The grain-to-grain and facet variations are linked to different density of surface states that pin the Fermi level at the surface, and different workfunctions (WF), which are both attributed for MAPbI3 to different surface terminations, and for the mixed HOIPs to an additional degradation of the perovskites. The effect of varying the methylammonium iodide (MAI) content, via the partial pressure, in co-evaporated MAPbI3 is studied and the excess of MAI proves to be detrimental, as it introduces low-dimensional perovskites and stacked perovskite sheets that considerably reduce its intrinsic stability. Therefore near-stoichiometric conditions are preferred and yield films more stable to light and heat and without photostriction. Nevertheless this intrinsic stability is still not optimal, and the continuous variations of the WF measured by KPFM upon prolonged illumination is investigated. Combined with X-ray photoelectron spectroscopy (XPS), the photo-induced degradation of MAPbI3, and evaporation of I2 are revealed as the causes of these variations. Besides, by combining KPFM and photoluminescence (PL) techniques for different thicknesses and substrates, energy band diagrams can be drawn and unveil a bending of the bands in the bulk. Lastly, the surface sensitivity of HOIPs is investigated when they are intentionally put in contact with extrinsic factors such as oxygen and solvents, and the surface properties are shown to be considerably altered. In addition, passivation strategies are used to demonstrate how surfaces can be improved. [less ▲]

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See detailDétection des vulnérabilités dans la procédure de protection internationale
Petry, Ralph UL; Osburg, Mathis UL; Nienaber, Birte UL

Article for general public (2021)

La vulnérabilité des demandeurs de protection internationale est un élément clé de l’acquis communautaire en matière d’asile. La directive relative aux procédures d’asile (2013/32/UE – refonte) et la ... [more ▼]

La vulnérabilité des demandeurs de protection internationale est un élément clé de l’acquis communautaire en matière d’asile. La directive relative aux procédures d’asile (2013/32/UE – refonte) et la directive sur les conditions d’accueil (2013/33/UE – refonte) prévoient des dispositions particulières pour les personnes vulnérables en ce qui concerne, respectivement, la procédure de protection internationale (c’est-à-dire des garanties procédurales spéciales) et l’accueil (c’est-à-dire des besoins particuliers en matière d’accueil). Par conséquent, pour que les États membres soient en mesure de prévoir et de garantir ces dispositions particulières pour les demandeurs vulnérables, il est essentiel qu’une vulnérabilité potentielle soit détectée et identifiée à un stade précoce de la procédure de protection internationale. C’est dans ce contexte que EMN Luxembourg a décidé, en consultation avec les autorités luxembourgeoises et des acteurs nationaux, de lancer une demande d’information aux Etats membres. L’objectif de cette note de synthèse est de déterminer comment les vulnérabilités des demandeurs de protection internationale sont détectées dans le cadre de la procédure de protection internationale dans les Etats membres de l’UE et comment le suivi de cette détection est garanti par les autorités et les acteurs impliqués, y compris les garanties procédurales spéciales. [less ▲]

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See detailNowe technologie w sprawach karnych
Wisniewska, Katarzyna UL

Scientific Conference (2021, November 25)

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See detailWissenschaft heißt, Unsicherheit erzeugen, nicht Bekanntes zu reproduzieren… Ein Interview mit Andreas Fickers, Direktor des Centre for Contemporary and Digital History (C2DH) in Luxemburg
Fickers, Andreas UL

Article for general public (2021)

Seit 2016 ist Andreas Fickers Direktor des Luxemburg Centre for Contemporary and Digital History (C2DH) an dessen Konzeption, Aufbau und Organisation er maßgeblich beteiligt war. Das C2DH hat in den ... [more ▼]

Seit 2016 ist Andreas Fickers Direktor des Luxemburg Centre for Contemporary and Digital History (C2DH) an dessen Konzeption, Aufbau und Organisation er maßgeblich beteiligt war. Das C2DH hat in den wenigen Jahren seiner Existenz eine ungeheure Strahlkraft weit über den europäischen Raum hinaus erreicht und gilt hinsichtlich seiner Forschungsleistung und -kompetenz im Bereich der Digital- und der Public History als sogenannte Leuchtturm-Institution. Sowohl die Arbeit des Direktors, als auch die Forschungsleistung des gesamten Instituts werden alle fünf Jahre von einer international besetzten Fachkommission evaluiert. Im September diesen Jahres wurde der Vertrag Andreas Fickers um weitere fünf Jahre verlängert [less ▲]

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See detailA Reusable Structural System Fit for Geometrical Standardisation and Serial Production
Odenbreit, Christoph UL; Yang, Jie UL; Romero, Alfredo UL et al

in Proceedings of the XII Steel and Composite Construction Conference (2021, November 25)

A series of demountable connections for reusable composite flooring systems and a standardized adjustable steel connection have been developed and tested, to facilitate circular economy as well as the ... [more ▼]

A series of demountable connections for reusable composite flooring systems and a standardized adjustable steel connection have been developed and tested, to facilitate circular economy as well as the serial production of structural elements and the suitability to be added into BIM or other digital tools. Demountable beam and floor elements and adjustable steel connections form the basis of a Lego-liked ‘plug and play’ circular framed structural system. This paper presents the proposed circular system, the results from experiments and finite element analyses and indicates the analysing methods for structural engineers to open a path way for fully implementation of the structures ‘as built’ into digital tools, fabrication and construction. [less ▲]

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See detailNumerical Investigation of Steel-LVL Timber Composite Beams
Romero, Alfredo UL; Yang, Jie UL; Hanus, François et al

in Proceedings of the XII Steel and Composite Construction Conference (2021, November 25)

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies ... [more ▼]

In the last years, new connectors of steel-concrete composite flooring systems have been developed and investigated to enhance the circularity and standardisation of building components. Recent studies showed that timber can be used as an alternative to the concrete slab in hybrid structures. However, the knowledge in steel-timber composite flooring systems is still very limited. This contribution presents numerical investigations of steel-LVL timber composite beams. The load deformation behaviour was determined through 3D finite element models. The design resistance of the composite beams was estimated analytically through a strain-controlled approach. The results of this study show that the resistances obtained in the numerical models and the strain-controlled approach are in good agreement. Moreover, obtained deflections and slip values were given at ultimate load. [less ▲]

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See detailNeurotoxic Amyloidogenic Peptides Identified in the Proteome of SARS-COV2: Potential Implications for Neurological Symptoms in COVID-19
Islam, Saba; Charnley, Mirren; Bindra, Guneet et al

E-print/Working paper (2021)

COVID-19 is primarily known as a respiratory disease caused by the virus SARS-CoV-2. However, neurological symptoms such as memory loss, sensory confusion, cognitive and psychiatric issues, severe ... [more ▼]

COVID-19 is primarily known as a respiratory disease caused by the virus SARS-CoV-2. However, neurological symptoms such as memory loss, sensory confusion, cognitive and psychiatric issues, severe headaches, and even stroke are reported in as many as 30% of cases and can persist even after the infection is over (so-called ‘long COVID’). These neurological symptoms are thought to be caused by brain inflammation, triggered by the virus infecting the central nervous system of COVID-19 patients, however we still don’t fully understand the mechanisms for these symptoms. The neurological effects of COVID-19 share many similarities to neurodegenerative diseases such as Alzheimer’s and Parkinson’s in which the presence of cytotoxic protein-based amyloid aggregates is a common etiological feature. Following the hypothesis that some neurological symptoms of COVID-19 may also follow an amyloid etiology we performed a bioinformatic scan of the SARS-CoV-2 proteome, detecting peptide fragments that were predicted to be highly amyloidogenic. We selected two of these peptides and discovered that they do rapidly self-assemble into amyloid. Furthermore, these amyloid assemblies were shown to be highly toxic to a neuronal cell line. We introduce and support the idea that cytotoxic amyloid aggregates of SARS-CoV-2 proteins are causing some of the neurological symptoms commonly found in COVID-19 and contributing to long COVID, especially those symptoms which are novel to long COVID in contrast to other post-viral syndromes. [less ▲]

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See detailWhy is Everyone Training Very Deep Neural Network with Skip Connections?
Oyedotun, Oyebade UL; Al Ismaeil, Kassem; Aouada, Djamila UL

in IEEE Transactions on Neural Networks and Learning Systems (2021)

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See detailFactors Affecting the Implementation of Computational Thinking in the Curriculum
Hennico, Jeff; Reuter, Robert UL; Weinberger, Armin

Scientific Conference (2021, November 24)

Computational thinking (CT) in fundamental education is an emerging topic in research about educational policies and practices around the globe. In Luxembourg, CT was introduced as a learning topic in ... [more ▼]

Computational thinking (CT) in fundamental education is an emerging topic in research about educational policies and practices around the globe. In Luxembourg, CT was introduced as a learning topic in fundamental schools in 2020. This situation offers a unique opportunity to investigate how various factors influence emerging CT teaching practices. Based on a revised version of the Technology Acceptance Model (Inan & Lowther, 2010), a research-based path model of CT teaching was developed, emphasising the influence of teachers’ beliefs and readiness on CT teaching practices. It investigated the effects of demographic factors, teaching approaches, ICT proficiency, previous CT experience, and overall support for technology integration on readiness, beliefs, and CT teaching practices. The current study reveals that teachers are interested in teaching CT. However, they hold a widespread misconception (Fessakis & Prantsoudi, 2019), confusing CT with programming or technology use. ICT proficiency is indeed associated with beliefs about CT and readiness for teaching CT. Readiness for teaching CT, beliefs about CT, and previous CT experience are the strongest predictors for CT teaching practices. In line with Cuny et al. (2010), the current study highlights the importance of training teachers to accurately define CT and to identify good practices. [less ▲]

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See detail5G AND BEYOND NETWORKS WITH UAV: TRAJECTORY DESIGN AND RESOURCE ALLOCATION
Tran Dinh, Hieu UL

Doctoral thesis (2021)

Over the past few years, unmanned aerial vehicle (UAV)-enabled wireless communications have attracted considerable attention from both academia and industry due to their high mobility, low cost, strong ... [more ▼]

Over the past few years, unmanned aerial vehicle (UAV)-enabled wireless communications have attracted considerable attention from both academia and industry due to their high mobility, low cost, strong light-of-sight communication links, and ease of deployment. Specifically, UAVs can be deployed to serve as aerial base stations (BSs), relays, power sources, etc., to support ground users (GUs) in various scenarios such as surveillance missions, search and rescue, crop monitoring, delivery of goods, data collection, emergency communications, secrecy communications, space-air-ground communications, etc. Despite many advantages, UAV-enabled communications are not without limitations. The limitations of UAVs have imposed technical restrictions on weight, size, and energy capability, thereby affecting the durability and performance of UAVs. The key goal of this dissertation is to propose and develop new frameworks and efficient optimization algorithms to solve novel challenging problems, facilitate the design and deployment of UAV-enabled communications. Consequently, these proposed algorithms can become one of the foundations for deploying UAVs in future wireless systems. Specifically, this dissertation investigates different UAV communication systems by addressing several important research problems through four emerging scenarios: 1) Design UAV trajectory based on traveling salesman problem with time window (TSPTW); 2) Full-duplex (FD) UAV relay-assisted emergency communications in Internet of Things (IoT) networks; 3) Backscatter- and cache-assisted UAV communications; and 4) Satellite- and cache-assisted UAV communications in 6G aerial networks. In the first scenario, we provide the coarse trajectory for the UAV based on TSPTW, which has not been investigated in UAV communications yet. Concretely, we propose two trajectory design algorithms based on TSPTW, namely heuristic algorithm and dynamic programming (DP)-based algorithm, and they are compared with exhaustive search and traveling salesman problem (TSP)-based methods. Based on the feasible path obtained from proposed algorithms, we minimize the total UAV’s energy consumption for each given path via a joint optimization of the UAV velocities in all hops. Simulation results show that the energy consumption value of DP is very close to that of the exhaustive algorithm with greatly reduced complexity. Based on this work, an efficient TSPTW-based algorithm can be used as an initialized trajectory for designing a joint problem of UAV trajectory and other communications factors (e.g., communication scheduling, transmit power allocation, time allocation), which are challenges. We then study the case of a FD UAV relaying system in IoT networks. Specifically, a UAV can be deployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer it to a ground gateway (GW). Especially, the impact of latency constraint for the uplink (UL) and downlink (DL) transmission utilizing FD or half-duplex (HD) mode is investigated. Using the proposed system model, we aim to maximize the total number of served IoT devices subject to the maximum speed constraint of the UAV, total traveling time constant, UAV trajectory, maximum transmit power at the devices/UAV, limited cache size of the UAV, and latency constraints for both UL and DL. Next, we attempt to maximize the total throughput subject to the number of served IoT devices. The outcome of this work will motivate a new framework for UAV-aided communications in disaster or emergency communications. Next, a novel system model that considers SWIPT, backscatter and caching in UAV wireless networks is developed. Based on this model, we aim to maximize the system throughput by jointly optimizing the dynamic time splitting (DTS) ratio and the UAV’s trajectory with caching capability at the UAV. This is the first work that jointly considers wireless power transfer (WPT), caching, and BackCom in UAV communications, which provides a potential solution for a battery-free drone system that can fly for a long period in the sky to support the terrestrial communication systems. Finally, a novel system model for effective use of LEO satellite- and cache-assisted UAV communication is proposed and studied. Specifically, caching is provided by the UAV to reduce backhaul congestion, and the LEO satellite assists the UAV’s backhaul link. In this context, we aim to maximize the minimum achievable throughput per ground user (GU) by jointly optimizing cache placement, the UAV’s transmit power, bandwidth allocation, and trajectory with a limited cache capacity and operation time. The outcomes of this work can provide a new design framework for Satellite-UAV-terrestrial communications that includes two tiers, i.e., the backhaul link from satellite to UAV and the access link from UAV to ground users, which imposes new challenges and was not investigated before. [less ▲]

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See detailNon-Standard Errors
Wolff, Christian UL; Zhang, Lu UL; Holzmeister, Felix

E-print/Working paper (2021)

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See detailCopper-Carbon Nanotube Composites for Lightning Strike Protection
Duhain, Antoine Edmond UL

Doctoral thesis (2021)

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See detailThe antioxidant glutathione as a regulator of natural killer cell immunity
Frias Guerra, Luana UL

Doctoral thesis (2021)

Natural killer (NK) cells are cytotoxic lymphocytes that belong to the innate branch of the immune system. Regulation of NK cell activity relies on the expression and engagement of a wide range of ... [more ▼]

Natural killer (NK) cells are cytotoxic lymphocytes that belong to the innate branch of the immune system. Regulation of NK cell activity relies on the expression and engagement of a wide range of inhibitory and activating receptors that detect signals arising from cells in distress. Besides their cytotoxic function, NK cells are effective producers of cytokines that participate in the regulation of other immune cells, such as dendritic cells and T cells. These innate lymphocytes control microbial infections and malignant cell growth, which are pathological conditions where reactive oxygen species (ROS) play a crucial role. ROS participate in cell signaling events and constitute important secondary messengers for immune cell proliferation and growth. However, when accumulated, their presence leads to oxidative stress due to their high reactivity against biomolecules. In order to ensure coordinated levels of ROS, cells are endowed of antioxidant systems that allow for ROS detoxification. One of the most important intracellular antioxidants is glutathione (GSH). Given the subset specificity of GSH regulation in immunity, we aimed to investigate the role of this antioxidant in NK cells. Using a genetic-based approach, through a flox-Cre system, we specifically abrogated GSH production in NK cells. Mutant mice had a reduced abundance of NK cells, when compared to controls. Furthermore, in vitro stimulation of NK cells with IL-15, showed that ablation of GSH production renders NK cells unable to proliferate and these cells were less cytotoxic. NK cells lacking GSH accumulated mitochondrial ROS, resulting in reduced mitochondrial fitness. This was paralleled by a general metabolic shutdown, and reduced mTOR and STAT5 signaling. In vivo, GSH and redox regulation were demonstrated to be key for NK cell-mediated regulation of T cells, in a viral model of lymphocytic choriomeningitis virus (LCMV). Moreover, in an experimental tumor model, deletion of GSH resulted in an NK cell intrinsic impairment of tumor dissemination and increased exhaustion. Taken together, our results indicate GSH as a key checkpoint for NK cell homeostasis and function. [less ▲]

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See detailLe dernier chant du Paradis de Dante
Cicotti, Claudio UL

Presentation (2021, November 22)

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See detailLa cuisine italienne dans le contexte du Street food global
Cicotti, Claudio UL

Conference given outside the academic context (2021)

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See detailDeep Learning for Safe Human-Robot Collaboration
Duque, Nicolas; Mejia, Lina; Martinez Luna, Carol UL et al

in Advances in Automation and Robotics Research (2021, November 21)

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See detailDeterminants of Self-Stigma in People with Parkinson's Disease: A Mixed Methods Scoping Review
Hanff, Anne-Marie UL; Leist, Anja UL; Fritz, Joëlle UL et al

in Journal of Parkinson's Disease (2021)

Background: Self-stigma in people with Parkinson's disease (PD) can substantially impact quality of life and possibilities for social participation. An integrative analysis of determinants of self-stigma ... [more ▼]

Background: Self-stigma in people with Parkinson's disease (PD) can substantially impact quality of life and possibilities for social participation. An integrative analysis of determinants of self-stigma has been lacking. Objective: We sought to explore which complementary insights from qualitative and quantitative studies, as well as from expert consultation, could be gained. Methods: An established mixed methods study design was employed to first conduct a mixed methods scoping review of published qualitative and quantitative literature, and then consult with experts to arrive at an exhaustive list of determinants of self-stigma after a thematic synthesis. Results: A total of 87 unique determinants of self-stigma were identified. Quantitative studies and expert consultations mainly identified personal determinants of people with self-stigma (e.g., age, anxiety, or apathy). In contrast, qualitative studies identified social situations associated with self-stigma (e.g., joint meals of people with typical PD with others). Notably, self-stigma of people with PD was found to be particularly salient in unfamiliar places, at the working place or in contact with people without PD. Across methods, cognitive impairment, tremor, and abnormal walk and unsteady gait, respectively, were associated with self-stigma. Conclusion: The mixed method study design yielded complementary insights, but also factors commonly associated with self-stigma across methods. Future prioritization exercises may gain further insights into self-stigma of people with PD. Facilitating social encounters by both addressing needs of affected people and raising knowledge and public awareness may improve quality of life in people with PD [less ▲]

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