On the difficulty of finding spines

We prove that the set of symplectic lattices in the Siegel space $\mathfrak{h}_g$ whose systoles generate a subspace of dimension at least 3 in $\mathbb{R}^{2g}$ does not contain any $\mathrm{Sp}(2g,\mathbb{Z})$-equivariant deformation retract of $\mathfrak{h}_g$

Méthodologie et modèle d'analyse de la vulnérabilité et du risque des systèmes critiques interdépendants (regular paper)

Le travail présenté dans ce papier a pour objectif l'analyse des réseaux interdépendants, en vue de modéliser la vulnérabilité et le risque. Les concepts de Système et de composant critique sont définis. Une approche de modélisation des réseaux est présentée. Cette modélisation compatible avec la théorie des graphes, est basée sur l'analyse des interdépendances et des influences du milieu extérieur. Une démarche pour quantifier la vulnérabilité et le risque est également présentée. Celle-ci se décline en plusieurs étapes intégrant une analyse qualitative et quantitative. La méthodologie proposée inclue l'identification des systèmes à analyser, du contexte ainsi que l'évaluation des évènements redoutés

Defining a robust biological prior from Pathway Analysis to drive Network Inference

Inferring genetic networks from gene expression data is one of the most challenging work in the post-genomic era, partly due to the vast space of possible networks and the relatively small amount of data available. In this field, Gaussian Graphical Model (GGM) provides a convenient framework for the discovery of biological networks. In this paper, we propose an original approach for inferring gene regulation networks using a robust biological prior on their structure in order to limit the set of candidate networks. Pathways, that represent biological knowledge on the regulatory networks, will be used as an informative prior knowledge to drive Network Inference. This approach is based on the selection of a relevant set of genes, called the "molecular signature", associated with a condition of interest (for instance, the genes involved in disease development). In this context, differential expression analysis is a well established strategy. However outcome signatures are often not consistent and show little overlap between studies. Thus, we will dedicate the first part of our work to the improvement of the standard process of biomarker identification to guarantee the robustness and reproducibility of the molecular signature. Our approach enables to compare the networks inferred between two conditions of interest (for instance case and control networks) and help along the biological interpretation of results. Thus it allows to identify differential regulations that occur in these conditions. We illustrate the proposed approach by applying our method to a study of breast cancer's response to treatment

Auction-based Bandwidth Allocation Mechanisms for Wireless Future Internet

An important aspect of the Future Internet is the efficient utilization of (wireless) network resources. In order for the - demanding in terms of QoS - Future Internet services to be provided, the current trend is evolving towards an "integrated" wireless network access model that enables users to enjoy mobility, seamless access and high quality of service in an all-IP network on an "Anytime, Anywhere" basis. The term "integrated" is used to denote that the Future Internet wireless "last mile" is expected to comprise multiple heterogeneous geographically coexisting wireless networks, each having different capacity and coverage radius. The efficient management of the wireless access network resources is crucial due to their scarcity that renders wireless access a potential bottleneck for the provision of high quality services. In this paper we propose an auction mechanism for allocating the bandwidth of such a network so that efficiency is attained, i.e. social welfare is maximized. In particular, we propose an incentive-compatible, efficient auction-based mechanism of low computational complexity. We define a repeated game to address user utilities and incentives issues. Subsequently, we extend this mechanism so that it can also accommodate multicast sessions. We also analyze the computational complexity and message overhead of the proposed mechanism. We then show how user bids can be replaced from weights generated by the network and transform the auction to a cooperative mechanism capable of prioritizing certain classes of services and emulating DiffServ and time-of-day pricing schemes. The theoretical analysis is complemented by simulations that assess the proposed mechanisms properties and performance. We finally provide some concluding remarks and directions for future research

1-D Coordinate Based on Local Information for MAC and Routing Issues in WSNs

More and more critical Wireless Sensor Networks (WSNs) applications are emerging. Those applications need reliability and respect of time constraints. The underlying mechanisms such as MAC and routing must handle such requirements. Our approach to the time constraint problem is to bound the hop-count between a node and the sink and the time it takes to do a hop so the end-to-end delay can be bounded and the communications are thus real-time. For reliability purpose we propose to select forwarder nodes depending on how they are connected in the direction of the sink. In order to be able to do so we need a coordinate (or a metric) that gives information on hop-count, that allows to strongly differentiate nodes and gives information on the connectivity of each node keeping in mind the intrinsic constraints of WSWs such as energy consumption, autonomy, etc. Due to the efficiency and scalability of greedy routing in WSNs and the financial cost of GPS chips, Virtual Coordinate Systems (VCSs) for WSNs have been proposed. A category of VCSs is based on the hop-count from the sink, this scheme leads to many nodes having the same coordinate. The main advantage of this system is that the hops number of a packet from a source to the sink is known. Nevertheless, it does not allow to differentiate the nodes with the same hop-count. In this report we propose a novel hop-count-based VCS which aims at classifying the nodes having the same hop-count depending on their connectivity and at differentiating nodes in a 2-hop neighborhood. Those properties make the coordinates, which also can be viewed as a local identifier, a very powerful metric which can be used in WSNs mechanisms.Comment: (2011

Nouveaux instruments de paiement: une analyse du point de vue de la banque centrale

Les évolutions technologiques apportent des solutions de paiement de détail innovantes (paiements par téléphone mobile par exemple). Ce cahier d'études aborde le sujet de la qualification des nouveaux instruments de paiement. Il contient une analyse basée sur la définition des différentes formes de monnaie (dont la monnaie électronique) et des instruments de paiement, dans le cadre général des paiements et des systèmes de paiement, ainsi que dans leur contexte réglementaire national et européen. Parmi les nouvelles possibilités technologiques, les systèmes de téléphonie mobile offrent des atouts techniques et commerciaux pour le développement de solutions de paiements mobiles d'ambition ubiquitaire. Comme pour certaines solutions électroniques de paiement de détail, les paiements mobiles sont l'occasion pour des entrepreneurs non liés au secteur bancaire de devenir des prestataires de paiement de masse. L'observation des caractéristiques et des modèles de solutions de paiement électroniques et mobiles permet d'identifier si cette participation tend à être coopérative ou concurrentielle avec les banques. S'agissant des paiements, la garantie de sécurité est primordiale. L'utilisation de réseaux de télécommunication ouverts (la téléphonie mobile, Internet, etc.) génère des craintes supplémentaires liées à la fraude et à la sécurité. Une partie est consacrée aux risques associés aux paiements électroniques et à leurs composantes de sécurité. Finalement sont abordées les différentes initiatives publiques et privées qui ont pour but de promouvoir la sécurité et l'efficience des paiements électroniques. Le Système européen de banques centrales est assez entreprenant en la matière.

Etude Sur la Stratégie et le Programme D'appui à la Société Civile Burundaise

The author study's strategies and programs to build civil society in Burundi

Biodiversity in drinking water distribution systems:a brief review

In drinking water distribution systems, three groups of living organisms are usually found in the biofilm and circulating water: heterotrophic bacteria, free-living protozoa, and macro-invertebrates. Indirect evidence suggests that protozoa grazing in distribution systems can partially eliminate biomass production and accidental microbiological pollution. This paper examines the biodiversit in drinking water distribution systems