A general framework for waves in random media with long-range correlations

We consider waves propagating in a randomly layered medium with long-range correlations. An example of such a medium is studied in \citeMS and leads, in particular, to an asymptotic travel time described in terms of a fractional Brownian motion. Here we study the asymptotic transmitted pulse under very general assumptions on the long-range correlations. In the framework that we introduce in this paper, we prove in particular that the asymptotic time-shift can be described in terms of non-Gaussian and/or multifractal processes.Comment: Published in at http://dx.doi.org/10.1214/10-AAP689 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Invariance principle, multifractional Gaussian processes and long-range dependence

This paper is devoted to establish an invariance principle where the limit process is a multifractional Gaussian process with a multifractional function which takes its values in $(1/2,1)$. Some properties, such as regularity and local self-similarity of this process are studied. Moreover the limit process is compared to the multifractional Brownian motion.Comment: Published in at http://dx.doi.org/10.1214/07-AIHP127 the Annales de l'Institut Henri Poincar\'e - Probabilit\'es et Statistiques (http://www.imstat.org/aihp/) by the Institute of Mathematical Statistics (http://www.imstat.org

Réponse optique de nanostructures plasmoniques complexes

Ce travail de thèse a porté sur l'étude de l'interaction entre une onde électromagnétique et des nanostructures plasmoniques complexes ou hybrides à différentes échelles d'espace et de temps. D'un point de vue théorique, nous nous sommes intéressés à la réponse optique de nanostructures de métaux nobles caractérisée par des résonances plasmon de surface (RPS). Nous avons montré que les interactions entre nanostructures plasmoniques modifient la localisation et l'exaltation de l'intensité et se traduisent par un décalage spectral des RPS. Nous avons alors calculé la densité de charges et identifié les modes multipolaires excités. Ensuite, nous avons utilisé les variations du champ électrique à proximité de nanostructures plasmoniques pour modifier la durée de vie, l'intensité de fluorescence ainsi que la statistique de photons de centres émetteurs. En particulier, nous avons montré que le temps moyen entre l'émission de deux photons consécutifs par un fluorophore pouvait être contrôlé. Parallèlement à ces calculs, les propriétés optiques de nanostructures plasmoniques individuelles ont été étudiées expérimentalement. Nous avons caractérisé leurs RPS en champ lointain par des mesures d'extinction. La topographie du champ électrique à leur voisinage a été réalisée par la spectroscopie de photoluminescence à deux photons. La dynamique temporelle de nanostructures lithographiées d'or a finalement été étudiée en spectroscopie femtoseconde. La forte sensibilité de la position de la RPS à la forme et à la taille des objets nous a permis de détecter les modes de vibration acoustique et de mettre en évidence l'effet de l'environnement sur l'amortissement de ces vibrations.The interaction between an electromagnetic field and complex plasmonic nanostructures has been studied at different scales of space and time. From a theoretical point of view, the optical response of noble metal nanostructures characterized by surface plasmon resonances (SPR) has been investigated. Through various examples, we have shown that electromagnetic interactions between plasmonic nanostructures change both the distribution and the exaltation of the intensity and result in a redshift of the SPR. We have then calculated the induced charge density and we have identified the multipolar modes excited. Besides, we have used the peculiar distribution of the electric field near plasmonic nanostructures to change the lifetime, the fluorescence intensity and the photon statistics of an emitter. In particular, we have demonstrated that the average time between the emission of two consecutive photons by an isolated fluorophore can be controlled by changing its environment. In addition, the optical properties of individual plasmonic nanostructures have been studied experimentally. We have characterized their SPR in the far-field by measurements of extinction. The topography of the electric field in their vicinity has been carried out by two-photon photoluminescence. The vibrational dynamics of gold nanostructures has finally been studied by femtosecond spectroscopy. The high sensitivity of the position of the SPR to the shape and size of objects has allowed us to detect acoustic vibration modes and evidenced the effect of environment on their damping

From invariance principles to a class of multifractional fields related to fractional sheets

In this paper, we study some invariance principles where the limits are Gaussian random fields sharing many properties with multifractional Brownian sheets. In particular, they satisfy the same type of self-similarity and Hölder regularity properties. We also extend the invariance principles mentioned above in a stable setting

Manipulating and squeezing the photon local density of states with plasmonic nanoparticle networks

International audienceIn this Brief Report, we show that when interconnected networks of gold particles are deposited onto a clean planar surface, they strongly modify the photonic local density of states LDOS in the immediate proximity of the self-assembled nanoparticles. They represent unique architectures for the subwavelength patterning of initially flat photonic LDOS. Moreover, we show that their local spectral signatures are well suited for the generation of sites able to enhance molecular fluorescence intensity

Unsteady Body Force Methodology for Fan Operability Assessment under Clean and Distorted Inflow Conditions

With more complex aircraft architectures, fast and cost-effective design iterations are key to improve overall fuel efficiency. This paper proposes to revisit a low-order unsteady modeling approach to replace costly full annulus URANS simulation. Unsteady Body Force Methods (UBFM) could allow a significant cost reduction for fan distortion ingestion and operability assessment. In this approach, the bladed area in the computational domain is replaced by source terms in the Navier–Stokes equations, and the cost of the simulation is reduced by a factor of 26. The operability of the fan is evaluated with and without distortion in order to assess the accuracy of the model. Previously published results of URANS simulations performed on the same fan subject to an unsteady vortex ingestion are used as reference.1 The results show that our UBFM is able to predict rotating stall cells, with patterns and rotating speed similar to the URANS data

Epidemiologic Relationship between Toscana Virus Infection and Leishmania infantum Due to Common Exposure to Phlebotomus perniciosus Sandfly Vector

Sand flies are recognised vectors of parasites in the genus Leishmania and a number of arthropod-borne viruses, in particular viruses within the genus Phlebovirus, family Bunyaviridae. In southern France, Toscana phlebovirus (TOSV) is recognized as a prominent cause of summer meningitis. Since Leishmania and TOSV have a common vector (Phlebotomus perniciosus), an epidemiologic link has been assumed for a long time. However, there is no scientific evidence of such a link between human leishmaniosis and phleboviral infections. To identify a possible link, we investigated the presence and distribution of antibodies against these two microorganisms (i) in individuals and (ii) at a spatial level in the city of Marseille (south-eastern France). Five hundred sera were selected randomly in the biobank of the Department of Parasitology of the Public Hospitals of Marseille. All sera were previously tested for IgG against Leishmania by Western Blotting, and TOSV IgG were detected by indirect immunofluorescence. The seropositivity rates were 21.4% for TOSV and 28% for Leishmania. Statistical analysis demonstrated that seropositivity for one pathogen was significantly associated with seropositivity to the other pathogen. This result provided the first robust evidence for the existence of an epidemiological relationship between Leishmania infantum and TOSV. Addresses of tested patients were geolocalized and integrated into Geographical Information System software, in order to test spatial relationship between the two pathogens. Spatial analysis did not allow to identify (i) specific patterns for the spatial distribution of positive serological results for TOSV or Leishmania, and (ii) a spatial relationship between Leishmania and TOSV positive serological results. This may reflect the fact that the sample studied was not powerful enough to demonstrate either a spatial clustering or co-location, i.e. that the actual risk exposure area is smaller than the mean of distance between patients in our study (245 m)