Artificial cochlea and acoustic black hole travelling waves observation: Model and experimental results

An inhomogeneous fluid structure waveguide reproducing passive behaviour of the inner ear is modelled with the help of the Wentzel–Kramers–Brillouin method. A physical setup is designed and built. Experimental results are compared with a good correlation to theoretical ones. The experimental setup is a varying width plate immersed in fluid and terminated with an acoustic black hole. The varying width plate provides a spatial repartition of the vibration depending on the excitation frequency. The acoustic black hole is made by decreasing the plate׳s thickness with a quadratic profile and by covering this region with a thin film of viscoelastic material. Such a termination attenuates the flexural wave reflection at the end of the waveguide, turning standing waves into travelling waves

Plasmidic qnrA3 Enhances Escherichia coli Fitness in Absence of Antibiotic Exposure

The widespread presence of plasmid-mediated quinolone resistance determinants, particularly qnr genes, has become a current issue. By protecting DNA-gyrase from quinolones, Qnr proteins confer a low level quinolone resistance that is not sufficient to explain their emergence. Since Qnr proteins were hypothesized to act as DNA-binding protein regulators, qnr genes could have emerged by providing a selective advantage other than antibiotic resistance. We investigated host fitness of Escherichia coli isogenic strains after acquisition of the qnrA3 gene, inserted either alone onto a small plasmid (pBR322), or harbored on a large conjugative native plasmid, pHe96(qnrA3) found in a clinical isolate. The isogenic strains were derived from the susceptible E. coli CFT073, a virulent B2 group strain known to infect bladder and kidneys in a mouse model of pyelonephritis. In vitro experiments included growth analysis by automatic spectrophotometry and flow cytometry, and competitions with CFU enumeration. In vivo experiments included infection with each strain and pairwise competitions in absence of antimicrobial exposure. As controls for our experiments we used mutations known to reduce fitness (rpsL K42N mutation) or to enhance fitness (tetA deletion in pBR322). E. coli CFT073 transformed with pBRAM(PBR322-qnrA3) had significantly higher maximal OD than E. coli CFT073 transformed with pBR322 or pBR322ΔtetA, and in vivo competitions were more often won by the qnrA3 carrying strain (24 victories vs. 9 loss among 42 competitions, p = 0.001). In contrast, when pHe96(qnrA3) was introduced by conjugation in E. coli CFT073, it exerted a fitness cost shown by an impaired growth observed in vitro and in vivo and a majority of lost competitions (33/35, p<0.0001). In conclusion, qnrA3 acquisition enhanced bacterial fitness, which may explain qnr emergence and suggests a regulation role of qnr. However, fitness was reduced when qnrA3 was inserted onto multidrug-resistant plasmids and this can slow down its dissemination without antibiotic exposure

Single InAsP/InP quantum dots as telecommunications-band photon sources

The optical properties of single InAsP/InP quantum dots are investigated by spectrally-resolved and time-resolved photoluminescence measurements as a function of excitation power. In the short-wavelength region (below 1.45 $\mu$m), the spectra display sharp distinct peaks resulting from the discrete electron-hole states in the dots, while in the long-wavelength range (above 1.45 $\mu$m), these sharp peaks lie on a broad spectral background. In both regions, cascade emission observed by time-resolved photoluminescence confirms that the quantum dots possess discrete exciton and multi-exciton states. Single photon emission is reported for the dots emitting at 1.3 $\mu$m through anti-bunching measurements

Relationship between paramacular thinning, cerebral vasculopathy, and hematological risk factors in sickle cell disease

PurposeTo identify risk factors for sickle cell maculopathy due to hematological parameters (especially anemia and hemolysis) or cerebral vasculopathy.MethodsThis retrospective study was conducted at a Referral Center. The follow-up included optical coherent tomography/optical coherent tomography angiography, neuro-radiological imaging, and a hematological assessment (hemoglobin, hemoglobin S level, reticulocytes, mean corpuscular volume, bilirubin, and lactate dehydrogenase).ResultsHundred and thirty-two sickle cell patients were included. Maculopathy was observed in 127 eyes of SS patients and 10 eyes of SC patients (p &lt; 0.001), unrelated to peripheral retinopathy. Cerebral vasculopathy was more frequent in SS patients (p &lt; 0.001) and was also associated with the presence of maculopathy (p = 0.049), and it was related to peripheral retinopathy (p &lt; 0.001). All biological parameters significantly differed according to the genotype (p &lt; 0.001) but not according to the presence of cerebral vasculopathy or maculopathy. In the multivariate analysis, reticulocytes and bilirubin were associated with the presence of cerebral vasculopathy and maculopathy.ConclusionThe data obtained were consistent with the role of anemia or hemolysis markers in cerebral vasculopathy and macular involvement. As a trend of hemolysis appears to be a risk factor for these complications, this validates the use of preventive plasmapheresis in these patients

Etude de la croissance de boîtes quantiques InAs/InP(001) par épitaxie en phase vapeur aux organométalliques pour des applications à 1,55 µm

We have studied the growth of InAs/InP(001) quantum dots by metalorganic vapor phase epitaxy for the realisation of 1.55 µm devices. The structural properties of the dots, studied by transmission electronic microscopy, and their optical properties, studied by photoluminescence, have been correlated to the growth conditions. Our study evidences on one hand thermodynamic and kinetic influences of InAs growth parameters, and on the other hand the influence of the cap-layer growth.We show that quantum dot wavelength can be tuned by varying the cap-layer growth rate or by an intentional phosphorus incorporation (InAsP dot formation). The good control of the morphology and of the emission wavelength of the dots opens the way for applications in the 1.55 µm telecommunication domain aimed by this study. The use of high cap-layer growth rate to embed the quantum dots allows to obtain an emission beyond 2 µm, and then opens the way for new applications in gas sensing. Finally, the observation at low temperature (4 K) of the exciton and biexciton of a single InAs/InP(001) quantum dot by micro-photoluminescence shows that these quantum dots could be used for the realisation of single photon sources for 1.55 µm quantum cryptography.Nous avons étudié la croissance de boîtes quantiques InAs/InP(001) par épitaxie en phase vapeur aux organométalliques en vue de la réalisation de composants à 1,55 µm. Les propriétés structurales des boîtes, étudiées par microscopie électronique en transmission, et leurs propriétés optiques, étudiées par photoluminescence, ont été corrélées aux conditions de croissance. Notre étude met en évidence d'une part les influences d'origine thermodynamique et cinétique des paramètres de croissance de l'InAs, et d'autre part une influence de l'étape de recouvrement des boîtes (encapsulation). Nous montrons que la longueur d'onde d'émission des boîtes peut être ajustée soit en modifiant la vitesse d'encapsulation, soit en incorporant volontairement du phosphore (formation de boîtes InAsP). Le bon contrôle de la morphologie et de la longueur d'onde d'émission des boîtes permet d'envisager des applications dans le domaine des télécommunications à 1,55 µm qui ont motivé ce travail. L'encapsulation des boîtes InAs/InP à forte vitesse de croissance nous a par ailleurs permis d'obtenir une émission au delà de 2 µm, ce qui ouvre de nouvelles perspectives d'applications dans la réalisation de sources pour la détection de gaz. Enfin, l'observation à basse température (4 K) de l'exciton et du biexciton d'une boîte quantique InAs/InP(001) unique en micro-photoluminescence montre que ces boîtes pourraient être utilisées pour la réalisation de sources de photons uniques pour la cryptographie quantique à 1,55 µm

Impact d' une réplication virale résiduelle sur le risque cardio-vasculaire au cours de l' infection par le VIH

Les maladies cardiovasculaires sont plus fréquentes au cours de l infection par le VIH que dans la population générale. Des études soulignent aujourd hui le rôle propre du virus dans l accélération de l athérogénèse. Malgré des traitements efficaces, un certain nombre de patients dont la virémie est inférieure au seuil de 50 copies/ml gardent en réalité une virémie résiduelle de faible niveau entre 1 et 50 copies/ml. Nous avons mesuré l épaisseur intima média carotidienne (EIMc) ainsi que la charge virale VIH avec une technique de RT-PCR ultrasensible dont le seuil de détection était de 1 copie/ml, chez 47 patients non fumeurs de sexe masculin dont l infection par le VIH était contrôlée sous traitement (charge virale <50 copies/ml).Trente trois et 14 patients avaient respectivement une virémie < 1copie/ml et entre 1 et 50 copies/ml. L EIMc globale n était pas significativement différente entre les deux groupes (0.748 mm vs 0.763mm respectivement, p=0.4), mais l EIM de l artère carotide commune était significativement plus élevée lorsqu il existait une virémie résiduelle (0.713mm vs 0.673mm, p=0.04). 17 patients avaient une virémie constamment < 1copie/ml sur un an. La moyenne de l EIMc globale de ces 17 patients était significativement inférieure à celle des autres patients (0.665mm vs 0.719mm, p<0.07). Ces différences restaient significatives après ajustement à la durée de traitement et à l ancienneté du contrôle virologique.Conclusion : La présence d une virémie VIH résiduelle entre 1 et 50 copies/ml est associée à une augmentation de l épaisseur intima média de la carotide témoignant d un risque cardiovasculaire augmentéPARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocSudocFranceF

Immersed acoustic black hole as a travelling wave absorber: understanding artificial cochlear mechanics

International audienceInner ear is constituted of fluid-filled ducts partitioned with an elastic structure, the organ of Corti. When the ear is excited by sound, travelling waves appear along the organ of Corti and stimulate the sensory cells. A peak of vibration is reached at a particular place depending on the excitation frequency. The waves are strongly attenuated after this place. Due to the complexity of in vivo experimentations, some aspects of physiological functions still need to be investigated. For this purpose, an experimental setup reproducing the passive behavior of the inner ear has been manufactured. Standing waves are usually observed on artificial cochlea devices due to wave reflection on boundaries. Acoustic black holes are known as vibration absorbers for thin structures. In this paper, an immersed acoustic black hole is used to reduce the reflected wave. Experimental results are compared with a model using the impedance matrix method. Travelling waves can be observed and this device should allow better understanding of artificial cochlear mechanics

Absorbeur de vibrations non-linéaire multi-physique

International audienceThe study of a multi-physic nonlinear vibrations absorber with an electromagnetomechanical coupling is proposed. The purpose of adding multiphysics coupling is to increase the energy dissipation of the ab-sorber by Joule effect. Two methods to etablish this coupling are presented : the coil-magnet interaction and the strongly magnetostrictive materialsL'étude d'un absorbeur de vibrations non-linéaire multi-physique avec un couplage électro-magnétomécanique est proposée. L'ajout du couplage multi-physique a pour but d'augmenter les performances de dissipa-tion d'énergie de l'absorbeur par effet Joule. Deux méthodes sont présentées pour établir ce couplage : l'interaction bobine-aimant et les matériaux fortement magnétostrictifs

Structural identification of graphene films and nanoislands on 6H-SiC(0001) by direct height measurement

International audienceAbstract By combining non-contact atomic force microscopy (nc-AFM) and Kelvin probe microscopy (KPFM) in ultra high vacuum environment (UHV), we directly measure the height and work function of graphene monolayer on the Si-face of 6H-SiC(0001) with a precision that allows us to differentiate three different types of graphene structures : zero layer graphene (ZLG), Quasi free-standing monolayer graphene (QFMLG) and bilayer graphene (BLG). The height and work function of ZLG are 2.62 ± 0.22 Å and 4.42 ± 0.05 eV respectively, when they are 4.09 ± 0.11 Å and 4.63 ± 0.05 eV for QFMLG. The work function is 4.83 ± 0.05 eV for the BLG. Unlike any other available technique, the local nc-AFM/KPFM dual probe makes it possible to directly identify the nature of nanometer-sized graphene islands that constitute the early nuclei of graphene monolayer grown on 6H-SiC(0001) by chemical vapor deposition