France in the Contemporary Scene

In order to better understand France\u27s stand in the great international issues of the hour, it is well, first of all, to survey briefly the internal situation of my country. Our attitude toward the world cannot but reflect the forces and values that we represent

Link Quality Metrics in Large Scale Indoor Wireless Sensor Networks

International audiencePouvoir estimer la qualité d'un lien sur la base d'un minimum de paquets est essentiel pour un réseau de capteur sans fil multisaut en environnement "indoor" compte tenu du coût énergétique de cette estimation et de ses conséquences sur la stabilité des routes construites sur ces liens. Notre étude s'appuie ainsi sur des expérimentations intensives menées sur une plateforme Senslab (\cite{www_senslab}) qui nous ont permis de trouver des lois de distribution suivies par les métriques physiques (RSSI, LQI) pour 3 catégories de liens (bons, mauvais, intermédiaires) regroupés par plage de PRR (Packet Reception Ratio). Sur la base de ces distributions, nous observons comment elles peuvent nous aider à discriminer les différents liens et ainsi les utiliser dans de futures expérimentations pour améliorer l'efficacité de protocoles de routage de réseaux de capteurs dans le choix des liens

Topology Construction in RPL Networks over Beacon-Enabled 802.15.4

In this paper, we propose a new scheme that allows coupling beacon-enabled IEEE 802.15.4 with the RPL routing protocol while keeping full compliance with both standards. We provide a means for RPL to pass the routing information to Layer 2 before the 802.15.4 topology is created by encapsulating RPL DIO messages in beacon frames. The scheme takes advantage of 802.15.4 command frames to solicit RPL DIO messages. The effect of the command frames is to reset the Trickle timer that governs sending DIO messages. We provide a detailed analysis of the overhead incurred by the proposed scheme to understand topology construction costs. We have evaluated the scheme using Contiki and the instruction-level Cooja simulator and compared our results against the most common scheme used for dissemination of the upper-layer information in beacon-enabled PANs. The results show energy savings during the topology construction phase and in the steady state

Architecture à qualité de service pour systèmes satellites DVB-S/RCS dans un contexte NGN

L'objet de cette thèse est de doter les réseaux satellites d'accès géostationnaires d'une architecture de QoS compatible avec l'infrastructure NGN (Next Generation Network) qui entend réaliser la convergence des réseaux et services de communication existants et à venir. Dans une première étape, nous établissons un modèle de QoS NGN s'inspirant principalement de l'évolution des architectures de QoS dans les réseaux IP. Dans une deuxième étape, nous démontrons que les réseaux satellites ne disposent pas, en l'état actuel, d'une architecture de QoS suffisamment mature pour assurer un accès large bande aux futurs services IP multimédias. Afin d'y remédier, nous spécifions une architecture de QoS NGN unifiée assurant une étroite collaboration entre les mécanismes de QoS déployés à différents niveaux de communication (Application, Session, Réseau et MAC). Elle assure à la fois une différenciation de la QoS adaptée aux besoins des différentes classes d'applications au niveau IP tout en optimisant l'utilisation des ressources satellites via des mécanismes de bande passante à la demande au niveau MAC. Deux solutions applicatives assurant la corrélation dynamique entre les applications et les services réseaux différenciés sont également spécifiées et implémentées. Enfin un émulateur satellite de niveau réseau a été implémenté et nous a permis d'évaluer les garanties de QoS offertes par notre architecture et de valider leur conformité avec les besoins d'applications multimédias réelles. ABSTRACT : This thesis deals with the integration of geostationary access satellite networks in the NGN (Next Generation Network) infrastructure, a global QoS-enabled communication network based on IP. The first part depicts this multiservice ubiquitous infrastructure anchored on a clean separation between a transport/network domain and a service/application domain. Then a unified NGN control and management architecture, mainly inspired by the past and current IP QoS architectures, is proposed. In a second part, starting from this model and through a critical analysis of current DVB-S/RCS satellite systems, we demonstrate that satellite QoS architectures are not mature enough to support broadband access to future multimedia services and to integrate into the emerging NGN infrastructure. In order to cope with these issues, a NGNcompliant QoS architecture for DVB-S/RCS systems is defined. It relies on a cross-layer approach based on a tight interaction between QoS mechanisms available at different communication layers (Application, Session, Network and MAC). It aims at maximizing satellite capacity utilization at different granularity levels through a relevant configuration of DiffServ services using session/application signalling information and the use of optimized bandwidth on demand allocation schemes at the MAC layer. Application solutions (QoS Agent and QoS SIP Proxy) were developed while the satellite network with its associated QoS architecture was implemented through a network emulator. This latter enables us to evaluate the QoS guarantees provided by this architecture and to validate its appropriateness with real multimedia applications needs

Sustainable Traffic Aware Duty-Cycle Adaptation in Harvested Multi-Hop Wireless Sensor Networks

International audienceSustainable power management techniques in energy harvesting wireless sensors currently adapt the consumption of sensors to their harvesting rate within the limits of their battery residual energy, but regardless of the traffic profile. To provide a fairer distribution of the energy according to application needs, we propose a new sustainable traffic aware duty-cycle adaptation scheme (STADA) that takes into account the traffic load in addition to previous factors. We evaluate our protocol in the specific context of multi-hop IEEE 802.15.4 beacon-enabled wireless sensor networks powered by solar energy. Simulations show that our solution outperforms traffic-unaware adaptation schemes while minimizing the variance of the quality of service provided to applications

Energy Consumption and Performance of IEEE 802.15.4e TSCH and DSME

International audienceThe recent IEEE 802.15.4e standard has introduced two interesting modes of operation: Time Slotted Channel Hopping (TSCH) and Deterministic and Synchronous Multi-channel Extension (DSME). Both provide a mix of time and frequency division to improve the performance of the previously available synchronized MAC mode (beacon-enabled 802.15.4). In this paper, we compare the performance of DSME and TSCH with respect to the energy consumption, throughput, and delay through an analysis of their respective ways of operation. We use an energy consumption model coming from our previous experience on the design of recent energy harvesting motes for the GreenNet platform. Our results show that DSME performs slightly better in terms of the energy consumption spent in data transfers. Both protocols exhibit similar delays for a given duty cycle, nevertheless, TSCH obtains shorter delay and higher throughput for low duty cycles. For higher duty cycles, TSCH results in lower throughput—for applications that send little data, the fixed slot configuration of TSCH results in wasted bandwidth. DSME can allocate shorter slots, which is beneficial for applications that transmit short packets

Hybrid catalysis for enantioselective Baeyer-Villiger oxidation and stereoselective epoxidation: a Cp*Ir complex to fuel FMN and FAD reduction for flavoprotein monooxygenase modules

Taking advantage of the unique properties of two-component flavo-monooxygenases and the ability of [Cp*Ir(bpy-OMe)H]+ to transfer hydrides to reduce flavins, we extended the scope of the pH- and oxygen-robust iridium(iii)-complex to drive the enzymatic reaction of a FMN-dependent Baeyer-Villiger monooxygenase and a FAD-dependent styrene monooxygenase (respectively FPMO Group C and E), using formic acid as H-donor for NADH recycling

Cultural flies:Conformist social learning in fruitflies predicts long-lasting mate-choice traditions

Despite theoretical justification for the evolution of animal culture, empirical evidence for it beyond mammals and birds remains scant, and we still know little about the process of cultural inheritance. In this study, we propose a mechanism-driven definition of animal culture and test it in the fruitfly. We found that fruitflies have five cognitive capacities that enable them to transmit mating preferences culturally across generations, potentially fostering persistent traditions (the main marker of culture) in mating preference. A transmission chain experiment validates a model of the emergence of local traditions, indicating that such social transmission may lead initially neutral traits to become adaptive, hence strongly selecting for copying and conformity. Although this situation was suggested decades ago, it previously had little empirical support.</p

Enzymatic Baeyer-Villiger Oxidation of Benzo-Fused Ketones:Formation of Regiocomplementary Lactones

Baeyer-Villiger monooxygenases (BVMOs) are enzymes that are known to catalyse the Baeyer-Villiger oxidation of ketones in aqueous media using O(2) as oxidant. Herein, we describe the oxidation of a set of diverse benzo-fused ketones by three different BVMOs in both aqueous and non-conventional reaction media. Most of the tested ketones, for example, 1-tetralone and 1- and 2-indanone, were converted by one of the employed biocatalysts. The catalytic efficiency could be improved by performing the oxidation reactions at a relatively high pH and by adding organic cosolvents. One striking observation is that absolute and complementary regioselectivities were obtained when oxidizing a range of 1-indanones using two different BVMOs. The conversion of 1-indanone by 4-hydroxyacetophenone monooxygenase (HAPMO) results in the formation of the expected lactone, 3,4-dihydrocoumarin. In contrast, by using a phenylacetone monooxygenase mutein (M-PAMO), conversion of 1-indanone leads to the formation of only the unexpected lactone, 1-isochromanone. This illustrates that by the appropriate choice of BVMO as biocatalyst, the effective and regioselective conversion of a wide range of benzo-fused ketones is feasible. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

Photobiocatalytic Oxyfunctionalization with High Reaction Rate using a Baeyer-Villiger Monooxygenase from Burkholderia xenovorans in Metabolically Engineered Cyanobacteria

Baeyer-Villiger monooxygenases (BVMOs) catalyze the oxidation of ketones to lactones under very mild reaction conditions. This enzymatic route is hindered by the requirement of a stoichiometric supply of auxiliary substrates for cofactor recycling and difficulties with supplying the necessary oxygen. The recombinant production of BVMO in cyanobacteria allows the substitution of auxiliary organic cosubstrates with water as an electron donor and the utilization of oxygen generated by photosynthetic water splitting. Herein, we report the identification of a BVMO from Burkholderia xenovorans (BVMOXeno) that exhibits higher reaction rates in comparison to currently identified BVMOs. We report a 10-fold increase in specific activity in comparison to cyclohexanone monooxygenase (CHMOAcineto) in Synechocystis sp. PCC 6803 (25 vs 2.3 U g(DCW)(-1) at an optical density of OD750 = 10) and an initial rate of 3.7 +/- 0.2 mM h(-1). While the cells containing CHMOAcineto showed a considerable reduction of cyclohexanone to cyclohexanol, this unwanted side reaction was almost completely suppressed for BVMOXeno, which was attributed to the much faster lactone formation and a 10-fold lower KM value of BVMOXeno toward cyclohexanone. Furthermore, the whole-cell catalyst showed outstanding stereoselectivity. These results show that, despite the self-shading of the cells, high specific activities can be obtained at elevated cell densities and even further increased through manipulation of the photosynthetic electron transport chain (PETC). The obtained rates of up to 3.7 mM h-1 underline the usefulness of oxygenic cyanobacteria as a chassis for enzymatic oxidation reactions. The photosynthetic oxygen evolution can contribute to alleviating the highly problematic oxygen mass-transfer limitation of oxygendependent enzymatic processes