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See detailOptimality Results on the Security of Lookup-Based Protocols
Mauw, Sjouke UL; Toro Pozo, Jorge Luis UL; Trujillo Rasua, Rolando UL

in Hancke, Gerard P.; Markantonakis, Konstantinos (Eds.) Radio Frequency Identification and IoT Security - 12th International Workshop, RFIDSec 2016, Hong Kong, China, November 30 - December 2, 2016, Revised Selected Papers (2016, December)

Distance-bounding protocols use the round-trip time of a challenge-response cycle to provide an upper-bound on the distance between prover and verifier. In order to obtain an accurate upper-bound, the ... [more ▼]

Distance-bounding protocols use the round-trip time of a challenge-response cycle to provide an upper-bound on the distance between prover and verifier. In order to obtain an accurate upper-bound, the computation time at the prover’s side should be as short as possible, which can be achieved by precomputing the responses and storing them in a lookup table. However, such lookup-based distance bounding protocols suffer from a trade-off between the achieved security level and the size of the lookup table. In this paper, we study this security-memory trade-off problem for a large class of lookup-based distance bounding protocols; called layered protocols. Relying on an automata-based security model, we provide mathematical definitions for different design decisions used in previous lookup-based protocols, and perform general security analyses for each of them. We also formalize an interpretation of optimal trade-off and find a non-trivial protocol transformation approach towards optimality. That is to say, our transformation applied to any layered protocol results in either an improved or an equal protocol with respect to the optimality criterion. This transformation allows us to provide a subclass of lookup-based protocol that cannot be improved further, which means that it contains an optimal layered protocol. [less ▲]

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See detailOptimally Combining Censored and Uncensored Datasets
Devereux, Paul J.; Tripathi, Gautam UL

in Journal of Econometrics (2009), 151

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See detailOptimierung der Wickelgüte in der Spinnvliesproduktion mit Fuzzy Control
Voos, Holger UL; Hartel, Harald; Schmitt, Peter

in Automatisierungstechnische Praxis (1999), 41(6), 48-54

This work introduces a new control concept for a re-winder in the spunweb production. The rewinder serves to cut the spunweb-rolls into several rolls of customer-specified width. High customer demands ... [more ▼]

This work introduces a new control concept for a re-winder in the spunweb production. The rewinder serves to cut the spunweb-rolls into several rolls of customer-specified width. High customer demands toward roll quality were, so far, only met unsatisfactorily with PID control of the web-tension. The newly developed control concept uses fuzzy control. It provides a modular design and is specifically adjusted to the different states of the machine that occur during production. It was proven that this concept rapidly increases roll quality. The control concept is implemented on a PLC and used in industrial spunweb production at Freudenberg Vliesstoffe KG in Kaiserslautern. [less ▲]

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See detailOptimierung und Charakterisierung einer mittels Laserstrahl gefügten Verbindung zwischen Aluminium und Polyamid 6.6
Lamberti, Christian UL

Doctoral thesis (2018)

The creation of strong joints between dissimilar materials and in particular between polymers and metals is one of the most often discussed topics in the fields of automotive, aerospace and transportation ... [more ▼]

The creation of strong joints between dissimilar materials and in particular between polymers and metals is one of the most often discussed topics in the fields of automotive, aerospace and transportation. Especially the combination of polyamide and aluminum is of highest interest, due to their market share as construction materials. New joining concepts are anticipated to deliver strong, durable and resource efficient structural components that are ideally suited for lightweight designs. However, current research activities have shown that the highly distinct material properties of these materials pose enormous challenges on the creation of hybrid structures. The cause that potentially enables the connection between the aluminum surface and the polymer is still not fully understood. The research objective of the presented work, therefore is, on the one hand, to create an optimal joint between aluminum and polyamide 6.6 using a laser beam to reach high shear strength for an industrial application. On the other hand, the presented work seeks to deliver a substantial contribution to furtherly understand the interaction between the polymer and the metal surface during the thermal joining. A laser-based joining method was developed that enables the researchers to overcome limitations of conventional processes, that is minimizing space requirements, making the application of additional gaskets obsolete, reaching high strength, saving weight and reducing processing time. The effectiveness of different surface pre-treatments has been studied, and the described optimization of this method has lead to an increase of the shear strength of the joints by more than 100 %. Laser ablation and the hydrothermal treatment of the metallic surface, before the joining operation, lead to the highest joint strength. The surface pre-treatment method of laser ablation delivered to transfer the gathered insights and experience from the laboratory to the industrial scale, due to its repeatability and reproducibility. The experiment mentioned above includes the use of production materials, such as aluminum with a higher sheet thickness of up to 1.48 mm and glass fiber reinforced polymer. Shear strength of 40 MPa was reached in quasi-static single lap shear tests. During dynamic testing, samples maintained 63 % of static breaking load after one million cycles. The hydrothermal treatment of the aluminum surface leads to a lower surface roughness of Ra = 1.58 µm in average as opposed to 4.90 µm after laser ablation. Due to the lower roughness values, the first-mentioned method was chosen to study the interaction. An XPS-analysis revealed a strong influence of the surface pre-treatment method on the chemical composition of the metal surface, which becomes noticeable by hydroxylation of the surface layer and is expressed by the oxide ratio (O/Al) and hydroxide ratio (OH/O). A high O/Al ratio of 2.36 and an OH/O ratio of 0.63 after the hydrothermal treatment is showing a strong increase of the amount of hydroxide in direct comparison to values of 35 % and 36 % of OH/O ratio after ethanol and hexane cleaning respectively. The question, as to which extent the presence of such hydroxide structures at the boundary layer of the aluminum influence the interaction between the metal surface and the polymer, was a subject matter of an additional FT-IR analysis. In case of the infrared spectra from thin polymer films on the hydrothermally treated surface, clear indications of interaction are visible. In direct comparison to the infrared spectra from polymer films on either ethanol or hexane cleaned surfaces, this interaction seems to increase nearby of the interface further. The interaction mentioned above appears at the carbonyl band and amine band as a shift of 4 cm-1 and 8 cm-1 and an increase of the full width at half maximum by 35 % respectively 40 %. Additional strong differences are visible at the molecule vibrations below 1,200 cm-1, which are typically assigned to both crystalline phases and amorphous phases of the polyamide. In case of the hydrothermal treatment, collected data indicates a polymorphous state inside the polymer films, which seems to become increasingly disordered close to the interface. On the contrary, spectra from the polymer films on ethanol and hexane pre-treated substrates show only marginal changes. Methods are proposed to build upon the results described in this work and refine distinct signs of the interaction. [less ▲]

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See detailOptimisation and validation of a high throughput screening compatible assay to identify inhibitors of the plasma membrane calcium ATPase pump--a novel therapeutic target for contraception and malaria.
Mohamed, Tamer M. A.; Zakeri, Simon A.; Baudoin, Florence et al

in Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Societe canadienne des sciences pharmaceutiques (2013), 16(2), 217-30

PURPOSE: ATPases, which constitute a major category of ion transporters in the human body, have a variety of significant biological and pathological roles. However, the lack of high throughput assays for ... [more ▼]

PURPOSE: ATPases, which constitute a major category of ion transporters in the human body, have a variety of significant biological and pathological roles. However, the lack of high throughput assays for ATPases has significantly limited drug discovery in this area. We have recently found that the genetic deletion of the ATP dependent calcium pump PMCA4 (plasma membrane calcium/calmodulin dependent ATPase, isoform 4) results in infertility in male mice due to a selective defect in sperm motility. In addition, recent discoveries in humans have indicated that a single nucleotide polymorphism (SNP) in the PMCA4 gene determines the susceptibility towards malaria plasmodium infection. Therefore, there is an urgent need to develop specific PMCA4 inhibitors. In the current study, we aim to optimise and validate a high throughput screening compatible assay using recombinantly expressed PMCA4 and the HTRF(R) Transcreener(R) ADP (TR-FRET) assay to screen a drug library. METHODS AND RESULTS: PMCA4 membrane microsomes were prepared from HEK293 cells overexpressing PMCA4. Western blot quantification revealed nearly nine-fold increased expression of PMCA4 compared to LacZ (control virus)-infected cells. Maximal PMCA4 microsomal activity was achieved in the TR-FRET assay with 15ng/mul microsomal concentration, 30-minute pre-incubation with compounds at 37 degrees C, and calcium buffering with 1mM EGTA providing 1muM free-calcium. Finally a dose-response curve for carboxyeosin (a non-specific PMCA inhibitor) under optimised conditions showed significant PMCA4 inhibition. Upon confirmation that the assay was suitable for high-throughput screening, we have screened the ChemBioNet small molecule library (~21,000 compounds) against the PMCA4 assay to identify those that are its apparent inhibitors. This screening yielded 1,494 primary hits. CONCLUSIONS: We have optimised the HTRF(R) Transcreener(R) ADP assay for high-throughput screening to identify PMCA4 inhibitors. The output of the screening campaign has provided preliminary chemical starting points that could be further developed to specific PMCA4 inhibitors for non-hormonal contraception or anti-malaria therapy. [less ▲]

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See detailOptimisation de la prise en charge médicale des patients sortant de prison au Luxembourg
Battista, Jorge; Stein, Romain; Baumann, Michèle UL

Poster (2019)

Le passage en prison peut être un gain de chance pour la santé de la population carcérale qui a généralement un faible accès au système de soins. L’élargissement de prison peut devenir une période de ... [more ▼]

Le passage en prison peut être un gain de chance pour la santé de la population carcérale qui a généralement un faible accès au système de soins. L’élargissement de prison peut devenir une période de vulnérabilité où ce gain potentiellement acquis s’annule si la transition vers la société civile n’est pas anticipée. L’objectif principal était l’identification et l’analyse des facteurs qui favorisent et s’opposent à une pratique de soins primaires chez les patients sortant du milieu carcéral au Luxembourg. L’objectif secondaire était l’élaboration de recommandations à l’égard des principaux résultats en s’appuyant sur une revue de la littérature. Méthodes : Une enquête qualitative à l’aide d’entretiens semi-dirigés a été menée auprès de médecins généralistes et de patients-détenus. Les questions des deux guides d’entretien étaient semblables afin que l’analyse permette une mise en miroir des résultats. Un recueil des caractéristiques sociodémographiques a également été effectué. A l’aide de la transcription des entretiens, une analyse de contenu thématique catégorielle de ces derniers a été réalisée au regard des objectifs. Sur base des verbatim, des items ont été formulés et regroupés en dimensions puis en thèmes. Résultats : Notre analyse a mis en lumière le manque de relais entre la prison et l’extérieur à chaque étape de la prise en charge médico-psycho-sociale du point de vue des soins et des aides proposées en prison jusqu’à l’élargissement. Des recommandations concernant des améliorations possibles ont pu être proposées, comme la création d’un réseau de médecins généralistes prenant le relais ainsi qu’une véritable coopération avec des organisations prenant en charge des toxicomanes. Conclusion : Des reformes concernant les soins en prison devraient être envisagées entre le système de l’élargissement, la création de relais socio-médicaux et des alternatives à l’incarcération, en analogie aux transitions clinics retrouvés aux États-Unis. [less ▲]

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See detailOptimisation of Terahertz Photomixer Layout
Juul, Lars UL

Doctoral thesis (2014)

This thesis examines ways to improve the output power of LT GaAs terahertz photomixer circuits, by focusing on the large impedance mismatch between photoconductor and antenna which gives rise to loss of a ... [more ▼]

This thesis examines ways to improve the output power of LT GaAs terahertz photomixer circuits, by focusing on the large impedance mismatch between photoconductor and antenna which gives rise to loss of a large fraction of power, which could potentially have been absorbed by the antenna. Impedance matching is a known problem in the microwave domain, and in this work such approaches were implemented in the terahertz domain and evaluated using a commercial numerical simulation tool with measured material properties. ?e aim was to provide cost effective design suggestions which are easily integrated into existing single layer technologies. Evaluation of high impedance antennas with integrated DC-blocking showed improvements ranging from 1.5 to 3 times the output power compared to the 3.0 µW reference case at 0.85 THz. A quarterwave transformer with an added shunt capacitance shows a 4 times improvement over the reference case. Adding a multilayer DC-block structure yields a 5 times improvement. Corrugated high impedance wire structures were evaluated for suitability in terms of radiative and transmission properties, in search for improved matching elements. Furthermore, a mechanically tunable resonant photomixer has been proposed, which yields significant improvement in output power over existing tunable broadband photomixers. Finally, a modulation scheme is proposed for binary ASK-modulation in the gigabit per second range of a terahertz photomixer, using an off the shelf 10 Gbps output driver. [less ▲]

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See detailOptimisation of the Co-Digestion of Maize and Grass Silage Influence of the Substrate Mixture on the Biogas Yield
Benito Martin, Patricia UL; Sibisi-Beierlein, Nonjabulo N.; Greger, Manfred UL

in Bilitewski, B.; Clarke, W. P.; Cossu, R. (Eds.) et al Venice 2012 Fourth International Symposium on Energy from Biomass and Waste Proceedings (2012, November)

In recent years, energy crops have been increasingly introduced as co-substrates in biogas plants due to their high biogas yield potential. The purpose of the current research was to investigate the ... [more ▼]

In recent years, energy crops have been increasingly introduced as co-substrates in biogas plants due to their high biogas yield potential. The purpose of the current research was to investigate the influence of the mixture of maize and grass silages, added as feedstock, on the specific methane production (SMP) and on the process dynamics. To this end, biological methane potential (BMP) tests were carried out in 500ml reactors with grass and maize silage in mono-digestion and 3 different co-digestion mixtures. For selected mixtures, process dynamics were further investigated in batch anaerobic experiments in 1 litre reactors by measuring different control parameters. A positive correlation was observed between the proportion of grass in the mixture and the specific methane yield due to the higher protein content (a yield up to 6% higher in comparison with mono-digestion of maize). Nevertheless, increasing amounts of grass were also related with slower degradation (lower hydrolysis rate constants) and higher instability during the first days of digestion. [less ▲]

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See detailOptimisation of the enhanced distance based broadcasting protocol for MANETs
Ruiz, Patricia UL; Dorronsoro, Bernabé UL; Valentini, Giorgio et al

in Journal of Supercomputing (2012), 62(3), 1213-1240

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See detailOptimised recovery with a coordinated checkpoint/rollback protocol for domain decomposition applications
Besseron, Xavier UL; Gautier, Thierry

in Modelling, Computation and Optimization in Information Systems and Management Sciences. MCO 2008 (2008, September)

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See detailOptimising Packet Forwarding in Multi-Tenant Networks using Rule Compilation
Hommes, Stefan UL; Valtchev, Petko; Blaiech, Khalil et al

in Optimising Packet Forwarding in Multi-Tenant Networks using Rule Compilation (2017, November)

Packet forwarding in Software-Defined Networks (SDN) relies on a centralised network controller which enforces network policies expressed as forwarding rules. Rules are deployed as sets of entries into ... [more ▼]

Packet forwarding in Software-Defined Networks (SDN) relies on a centralised network controller which enforces network policies expressed as forwarding rules. Rules are deployed as sets of entries into network device tables. With heterogeneous devices, deployment is strongly bounded by the respective table constraints (size, lookup time, etc.) and forwarding pipelines. Hence, minimising the overall number of entries is paramount in reducing resource consumption and speeding up the search. Moreover, since multiple control plane applications can deploy own rules, conflicts may occur. To avoid those and ensure overall correctness, a rule validation mechanism is required. Here, we present a compilation mechanism for rules of diverging origins that minimises the number of entries. Since it exploits the semantics of rules and entries, our compiler fits a heterogeneous landscape of network devices. We evaluated compiler implementations on both software and hardware switches using a realistic testbed. Experimental results show a reduction in both produced table entries and forwarding delay. [less ▲]

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See detailOptimising Satellite Payload Reconfiguration: An ILP Approach for Minimising Channel Interruptions
Stathakis, Apostolos UL; Danoy, Grégoire UL; Veneziano, Thomas UL et al

in 2nd ESA Workshop on Advanced Flexible Telecom Payloads (2012)

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See detailOptimising time-series experimental design for modelling of circadian rhythms: the value of transient data
Mombaerts, Laurent UL; Mauroy, Alexandre UL; Goncalves, Jorge UL

in IFAC-PapersOnLine (2016, October)

Circadian clocks consist of complex networks that coordinate the daily cycle of most organisms. In light/dark cycles, the clock is synchronized (or entrained) by the environment, which corresponds to a ... [more ▼]

Circadian clocks consist of complex networks that coordinate the daily cycle of most organisms. In light/dark cycles, the clock is synchronized (or entrained) by the environment, which corresponds to a constant rephasing of the oscillations and leads to a steady state regime. Some circadian clocks are endogenous oscillators with rhythms of about 24-hours that persist in constant light or constant darkness. This operating mechanism with and without entrainment provides flexibility and robustness to the clock against perturbations. Most of the clock-oriented experiments are performed under constant photoperiodic regime, overlooking the transitory regime that takes place between light/dark cycles and constant light or darkness. This paper provides a comparative analysis of the informative potential of the transient time-series data with the other regimes for clock modelling. Realistic data were simulated from 2 experimentally validated plant circadian clock models and sliced into several time windows. These windows represent the different regimes that take place before, meanwhile and after the switch to constant light. Then, a network inference tool was used over each window and its capability of retrieving the ground-truth of the network was compared for each window. The results suggest that including the transient data to the network inference technique significally improves its performance. [less ▲]

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See detailOptimism, self-efficacy, and perceived stress as predictors of self-reported health symptoms in college students
Schulz, Heiko; Vögele, Claus UL; Meyer, Björn

in Zeitschrift für Gesundheitspsychologie (2009), 17

Studies provide support for the notion of increased vulnerability to upper respiratory track infections (URIs) with exposure to psychological stress, but only few have examined whether optimism and self ... [more ▼]

Studies provide support for the notion of increased vulnerability to upper respiratory track infections (URIs) with exposure to psychological stress, but only few have examined whether optimism and self-efficacy might moderate this relationship. The purpose of the present study was to examine (a) the influence of academic exam stress on susceptibility to URIs and (b) the extent to which these personality characteristics buffer against stress-related vulnerability to URIs. Using a repeated-measures design, URI infection status was measured in a sample of 80 college students with self-reports both during an exam period and outside such a period. Results suggested that optimism may protect from the adverse influence of heightened stress and that pessimistic, low self-efficacious participants may be at elevated risk for the development of URIs at times of increased stress. [less ▲]

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See detailOptimization and Performance Analysis of the AEDB Broadcasting Algorithm
Ruiz, Patricia UL; Dorronsoro, Bernabé UL; Bouvry, Pascal UL

in IEEE International Workshop on Wireless Mesh and Ad Hoc Networks (2011)

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See detailOptimization and Pharmacological Validation of a Leukocyte Migration Assay in Zebrafish Larvae for the Rapid In Vivo Bioactivity Analysis of Anti-Inflammatory Secondary Metabolites
Cordero-Maldonado, M. L.; Siverio-Mota, D.; Vicet-Muro, L. et al

in PLoS ONE (2013), 8(10),

Over the past decade, zebrafish (Danio rerio) have emerged as an attractive model for in vivo drug discovery. In this study, we explore the suitability of zebrafish larvae to rapidly evaluate the anti ... [more ▼]

Over the past decade, zebrafish (Danio rerio) have emerged as an attractive model for in vivo drug discovery. In this study, we explore the suitability of zebrafish larvae to rapidly evaluate the anti-inflammatory activity of natural products (NPs) and medicinal plants used in traditional medicine for the treatment of inflammatory disorders. First, we optimized a zebrafish assay for leukocyte migration. Inflammation was induced in four days post-fertilization (dpf) zebrafish larvae by tail transection and co-incubation with bacterial lipopolysaccharides (LPS), resulting in a robust recruitment of leukocytes to the zone of injury. Migrating zebrafish leukocytes were detected in situ by myeloperoxidase (MPO) staining, and anti-inflammatory activity was semi-quantitatively scored using a standardized scale of relative leukocyte migration (RLM). Pharmacological validation of this optimized assay was performed with a panel of anti-inflammatory drugs, demonstrating a concentration-responsive inhibition of leukocyte migration for both steroidal and non-steroidal anti-inflammatory drugs (SAIDs and NSAIDs). Subsequently, we evaluated the bioactivity of structurally diverse NPs with well-documented anti-inflammatory properties. Finally, we further used this zebrafish-based assay to quantify the anti-inflammatory activity in the aqueous and methanolic extracts of several medicinal plants. Our results indicate the suitability of this LPS-enhanced leukocyte migration assay in zebrafish larvae as a front-line screening platform in NP discovery, including for the bioassay-guided isolation of anti-inflammatory secondary metabolites from complex NP extracts. © 2013 Cordero-Maldonado et al. [less ▲]

Detailed reference viewed: 74 (0 UL)