Q-AIMD: A Congestion Aware Video Quality Control Mechanism

Following the constant increase of the multimedia traffic, it seems necessary to allow transport protocols to be aware of the video quality of the transmitted flows rather than the throughput. This paper proposes a novel transport mechanism adapted to video flows. Our proposal, called Q-AIMD for video quality AIMD (Additive Increase Multiplicative Decrease), enables fairness in video quality while transmitting multiple video flows. Targeting video quality fairness allows improving the overall video quality for all transmitted flows, especially when the transmitted videos provide various types of content with different spatial resolutions. In addition, Q-AIMD mitigates the occurrence of network congestion events, and dissolves the congestion whenever it occurs by decreasing the video quality and hence the bitrate. Using different video quality metrics, Q-AIMD is evaluated with different video contents and spatial resolutions. Simulation results show that Q-AIMD allows an improved overall video quality among the multiple transmitted video flows compared to a throughput-based congestion control by decreasing significantly the quality discrepancy between them

Motif pour la métamodélisation: Commentaire attribué

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A kernel transformation language for metamodel evolution and reversible model co-evolution

This report defines MicroDif, a kernel transformation language for metamodel evolution and reversible model co-evolution. To begin with, a kernel subset of Ecore is highlighted and formally defined thanks to a suitable denotational semantics. Then MicroDif is formally defined upon this subset. In a first step, the focus is put on metamodel evolution provided by a set of refactoring operators. In a second step, the focus is put on model co-evolution which is intended to be reversible thanks to a dedicated pair of transformations respectively called migration and recontextualization. Each MicroDif operator is also provided with a dedicated predicate which explains the sufficient conditions for a model to remain valid after these transformations

Relationships between sterol/phospholipid composition and xenobiotic transport in nematodes

International audienceTherapeutic failure limits prophylaxis of nematode diseases and has been mainly attributed to mutations in cellular targets of anthelmintics. Besides these specific mechanisms, alterations of drug transport also occur in parasites resistant to anthelmintics and depend on both the presence of membrane pumps such as P-glycoprotein (Pgp) and on the lipid composition of membranes. We recently showed in the nematode Haemonchus contortus, using eggs as a model, that the total cholesterol (TC) concentration alters the transport of lipophilic molecules due to membrane pumps such as P-glycoprotein and the resistance to anthelmintics. The effect of TC may depend on the presence of other lipids interacting with TC. Therefore, we analysed the lipid composition and its relationship with Pgp and resistance to anthelmintics. Better correlations were found between Pgp and free cholesterol (FC) than with TC. We also showed that the relationships between lipid composition and resistance to anthelmintics or Pgp depended on the equilibrium between FC and phospholipids (PLs), mainly PLs known to be present primarily in either the external leaflets of cell membranes or the internal leaflets. The PLs phosphatidylcholine and phosphatidylethanolamine played the most significant role, but phosphatidic acid also influenced drug resistance

Contribution of laboratory tests in the diagnosis of gastrointestinal strongylosis in ruminants and choice of treatments

The clinical diagnosis of gastrointestinal strongylosis in ruminants is often difficult because of its relatively unspecific symptomatology. Moreover, as the use of prophylactic treatments is increasingly preferred over curative treatments, quantitative and accurate tests for diagnosis are required. As the gradual development of anthelmintic resistance restricts further the choice and use of molecules, laboratory diagnostic tests become useful and even often essential. Three main categories of tests are available: traditional parasitological techniques, serological assays linked to the lesions caused by the parasites, and tests for the detection of anthelmintic resistance. The principles, conditions of use and limits of interpretation of these tests are described in this brief synthesis.Le diagnostic clinique des strongyloses gastro-intestinales des ruminants est difficile dans un grand nombre de cas en raison du manque de symptomatologie très spécifique. De plus, La tendance de plus en plus grande à traiter les animaux préventivement et non plus curativement implique de disposer de moyens de diagnostic quantitatifs sensibles. Le développement progressif de phénomènes de résistance aux anthelminthiques impose des contraintes supplémentaires quant au choix et à l'utilisation des molécules. Les tests de diagnostic de laboratoire sont utiles et même souvent indispensables, dans ces démarches. Trois grandes catégories de tests sont disponibles : les tests parasitologiques classiques, les dosages sériques en relation avec les lésions occasionnées par les parasites, les tests de détection des résistances. Les principes, les conditions d'utilisation et les limites d'interprétation sont décrits dans cette courte synthèse

Efflux pump inhibitors: a progress in parasitic nematode control

Animal and human nematode infestations are controlled primarily with anthelmintics. However, their continuous administration during outbreaks represents a significant expense for livestock farms. In humans also, their high cost limits their use in poor areas where parasitic worms are most prevalent and most pathogenic. Furthermore, nematodes have developed drug resistance mechanisms, specific or not, which reduce the efficiency of treatments. Among these mechanisms, the accelerated removal of anthelmintics by efflux pumps present in cell membranes, eggshells and cuticles is a major limiting factor. This accelerated efflux is very similar to the mechanism of multidrug resistance (MDR) observed in cancer cells and protozoa. This phenomenon is all the more worrying that it applies simultaneously to several chemical families of drugs. One solution is to block the efflux pumps in parasites with inhibitors. These pumps belong to the large family of ABC transporters, which have many characteristics in common. Some have major physiological functions or protect organs from toxic agents. As much as possible, inhibitors should not have any effect on the pumps of the host and target the parasite exclusively. The diversity of these pumps is greater in nematodes than in vertebrates, and there are differences in their protein structures. Some parts of these proteins are relatively well-conserved in the animal kingdom, while other parts show little homology from one transporter to another or from one species to another. The affinity of these pumps for the substrates can vary with the mutation of a single amino acid. These differences could be used to develop inhibitors specific of nematode pumps, which could then be combined with anthelmintics.Les anthelminthiques constituent le moyen majeur de lutte contre les nématodoses animales et humaines. Administrés de façon continue en période d'infestation, ils représentent un coût considérable pour les élevages. Chez l'homme, ce coût limite leur distribution dans les zones géographiques défavorisées où pourtant les vers parasites sont les plus nombreux et les plus pathogènes. De plus, les nématodes ont développé des mécanismes de chimiorésistance, spécifiques ou non, qui réduisent l'efficacité des anthelminthiques. Parmi ces mécanismes, le rejet accéléré des molécules thérapeutiques par des pompes d'efflux est semblable au mécanisme de multi-résistance aux médicaments (MDR) des cellules cancéreuses et des protozoaires. Ces pompes sont présentes dans les membranes cellulaires, la coque des œufs et les cuticules des nématodes. Ce rejet accéléré est d'autant plus préoccupant qu'il s'applique simultanément à plusieurs familles chimiques d'antiparasitaires. Une des solutions consiste à bloquer les pompes d'efflux des parasites à l'aide d'inhibiteurs. Ces pompes appartiennent à la grande famille des transporteurs ABC dotés de nombreuses caractéristiques communes. Certains de ces transporteurs jouent des rôles physiologiques déterminants ou protègent les organes des molécules toxiques. Les inhibiteurs doivent donc être autant que possible dépourvus d'action sur les pompes de l'hôte. La variabilité des pompes est plus importante chez les nématodes que chez les vertébrés, et il existe des différences dans leur structure protéique. Certaines parties de ces protéines sont bien conservées dans le règne animal, tandis que d'autres présentent peu d'homologie d'un transporteur à l'autre ou, pour un même transporteur, d'une espèce à l'autre. L'affinité de ces pompes pour les substrats peut varier en fonction de la mutation d'un seul acide aminé. Ces différences pourraient être mises à profit pour développer des inhibiteurs spécifiques des pompes des nématodes et les utiliser en association avec les anthelminthiques

Motif pour la métamodélisation: Flot de contrôle

National audienceDomain Specific Languages (DSL) are not necessarily purely declarative. They can have procedural features in which case their analysis implies the building of a control flow graph. The model pattern “Control Flow Graph” (CFG) describes the way to build the abstract syntax of a procedural DSL provided with branch instructions

The Steam Boiler Controller Problem in Signal-Coq

Among the various formalisms for the design of reactive systems, the SIGNAL-CO- Q formal approach, i.e. the combined use of the synchronous dataflow language SIGNAL and the proof assistant COQ, seems to be especially suited and practical. Indeed, the deterministic concurrency implied by the synchronous model on which SIGNAL is founded strongly simplifies the specification and the verification of such systems. Moreover, COQ is not limited to some kind of properties and so, its use enables to disregard what can be checked during the specification stage. In this article, we underline the various features of this SIGNAL-COQ formal approach with a large scale case study, namely the Steam Boiler problem

A comparative study of two formal semantics of the SIGNAL language

International audienceSIGNAL is a part of the synchronous languages family, which are broadly used in the design of safety-critical real-time systems such as avionics, space systems, and nuclear power plants. There exist several semantics for SIGNAL, such as denotational semantics based on traces (called trace semantics), denotational semantics based on tags (called tagged model semantics), operational semantics presented by structural style through an inductive definition of the set of possible transitions, operational semantics defined by synchronous transition systems (STS), etc. However, there is little research about the equivalence between these semantics.In this work, we would like to prove the equivalence between the trace semantics and the tagged model semantics, to get a determined and precise semantics of the SIGNAL language. These two semantics have several different definitions respectively, we select appropriate ones and mechanize them in the Coq platform, the Coq expressions of the abstract syntax of SIGNAL and the two semantics domains, i.e., the trace model and the tagged model, are also given. The distance between these two semantics discourages a direct proof of equivalence. Instead, we transformthem to an intermediate model, which mixes the features of both the trace semantics and the tagged model semantics. Finally, we get a determined and precise semantics of SIGNAL