Estimateurs de la cohérence pour l'analyse de signaux SEEG

Les cohérences ordinaires et partielles sont souvent considérées pour l'analyse de signaux enregistrés lors de crises épileptiques. L'objectif est de déterminer les relations statistiques entre plusieurs voies et l'organisation de l'activité épileptique. Nous étudions par simulation le biais et la variance des cohérences en module. Pour obtenir des estimateurs plus faciles à interpréter, nous calculons la cohérence moyenne. Son biais peut être plus important que l'écart-type. Un algorithme de correction du biais est proposé. Des résultats sur signaux réels sont présentés et interprétés

Relations entre les critères du module constant et de wiener

- Dans cet article nous présentons une nouvelle approche pour étudier la conjecture sur les relations entre les critères de Wiener et du module constant (CM). Notre proposition compris l'établissement d'une limite supérieure pour la fonction de coût CM, à partir d'un critère supervise, et la dérivation d'un rapport entre les minima des critères de Wiener et CM. Les résultats sont évalues par des simulations

Optimization of cw sodium laser guide star efficiency

Context: Sodium laser guide stars (LGS) are about to enter a new range of laser powers. Previous theoretical and numerical methods are inadequate for accurate computations of the return flux and hence for the design of the next-generation LGS systems. Aims: We numerically optimize the cw (continuous wave) laser format, in particular the light polarization and spectrum. Methods: Using Bloch equations, we simulate the mesospheric sodium atoms, including Doppler broadening, saturation, collisional relaxation, Larmor precession, and recoil, taking into account all 24 sodium hyperfine states and on the order of 100 velocity groups. Results: LGS return flux is limited by "three evils": Larmor precession due to the geomagnetic field, atomic recoil due to radiation pressure, and transition saturation. We study their impacts and show that the return flux can be boosted by repumping (simultaneous excitation of the sodium D2a and D2b lines with 10-20% of the laser power in the latter). Conclusions: We strongly recommend the use of circularly polarized lasers and repumping. As a rule of thumb, the bandwidth of laser radiation in MHz (at each line) should approximately equal the launched laser power in Watts divided by six, assuming a diffraction-limited spot size.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysics, AA/2009/1310

Recherche de reproductibilité dans les relations inter structures durant les crises d'épilepsie

Cet article s'inscrit dans le cadre de l'étude des signaux stéréoélectroencéphalographiques (EEG de profondeur) enregistrés lors de crises d'épilepsie. Il propose une méthode de mise en correspondance capable de quantifier, d'une crise à l'autre, les reproductibilités des relations inter-canaux estimées par la fonction de cohérence. Le travail est illustré sur des signaux construits à partir de différents scénarios décrivant un sous-type d'épilepsie (origine temporale). Les perspectives de ce travail sont liées, d'une part, à l'extraction de similarités dans l'évolution des relations qui s'établissent entre les structures cérébrales durant les crises et, d'autre part, à la mise en évidence de scénarios récurrents dans l'organisation de ces crises

Statistical characteristics of formation and evolution of structure in the universe

An approximate statistical description of the formation and evolution of structure of the universe based on the Zel'dovich theory of gravitational instability is proposed. It is found that the evolution of DM structure shows features of self-similarity and the main structure characteristics can be expressed through the parameters of initial power spectrum and cosmological model. For the CDM-like power spectrum and suitable parameters of the cosmological model the effective matter compression reaches the observed scales $R_{wall}\sim$20 -- 25$h^{-1}$Mpc with the typical mean separation of wall-like elements $D_{SLSS}\sim$50 -- 70$h^{-1}$Mpc. This description can be directly applied to the deep pencil beam galactic surveys and absorption spectra of quasars. For larger 3D catalogs and simulations it can be applied to results obtained with the core-sampling analysis. It is shown that the interaction of large and small scale perturbations modulates the creation rate of early Zel'dovich pancakes and generates bias on the SLSS scale. For suitable parameters of the cosmological model and reheating process this bias can essentially improve the characteristics of simulated structure of the universe. The models with $0.3\leq \Omega_m \leq 0.5$ give the best description of the observed structure parameters. The influence of low mass "warm" dark matter particles, such as a massive neutrino, will extend the acceptable range of $\Omega_m$ and $h$.Comment: 20pages, 7 figures, MNRAS in pres

Mathematical modelling of antimicrobial resistance in agricultural waste highlights importance of gene transfer rate

Antimicrobial resistance is of global concern. Most antimicrobial use is in agriculture; manures and slurry are especially important because they contain a mix of bacteria, including potential pathogens, antimicrobial resistance genes and antimicrobials. In many countries, manures and slurry are stored, especially over winter, before spreading onto fields as organic fertilizer. Thus these are a potential location for gene exchange and selection for resistance. We develop and analyze a mathematical model to quantify the spread of antimicrobial resistance in stored agricultural waste. We use parameters from a slurry tank on a UK dairy farm as an exemplar. We show that the spread of resistance depends in a subtle way on the rates of gene transfer and antibiotic inflow. If the gene transfer rate is high, then its reduction controls resistance, while cutting antibiotic inflow has little impact. If the gene transfer rate is low, then reducing antibiotic inflow controls resistance. Reducing length of storage can also control spread of resistance. Bacterial growth rate, fitness costs of carrying antimicrobial resistance and proportion of resistant bacteria in animal faeces have little impact on spread of resistance. Therefore effective treatment strategies depend critically on knowledge of gene transfer rates

Dihaploid Coffea arabica genome sequencing and assembly.

Coffea arabica which accounts for 70% of world coffee production is an allotetraploid with a genome size of approximately 1.3 Gb and is derived from the hybridization of C. canephora (710 Mb) and C. eugenioides (670 Mb). To elucidate the evolutionary history of C. arabica, and generate critical information for breeding programs, a sequencing project is underway to finalize a reference genome using a dihaploid line and a set of Menu Abstract: Dihaploid Coffea arabica Genome Sequencing and Assembly (Plant and Animal Genome XXIII Conference) https://pag.confex.com/pag/xxiii/webprogram/Paper16983.html [25/02/2015 15:00:12] 30 C. arabica accessions

Regulation of the Actin Cytoskeleton by an Interaction of IQGAP Related Protein GAPA with Filamin and Cortexillin I

Filamin and Cortexillin are F-actin crosslinking proteins in Dictyostelium discoideum allowing actin filaments to form three-dimensional networks. GAPA, an IQGAP related protein, is required for cytokinesis and localizes to the cleavage furrow during cytokinesis. Here we describe a novel interaction with Filamin which is required for cytokinesis and regulation of the F-actin content. The interaction occurs through the actin binding domain of Filamin and the GRD domain of GAPA. A similar interaction takes place with Cortexillin I. We further report that Filamin associates with Rac1a implying that filamin might act as a scaffold for small GTPases. Filamin and activated Rac associate with GAPA to regulate actin remodelling. Overexpression of filamin and GAPA in the various strains suggests that GAPA regulates the actin cytoskeleton through interaction with Filamin and that it controls cytokinesis through association with Filamin and Cortexillin