Acoustic coupling between two air bubbles in water

The acoustic coupling between two air bubbles immersed in water is clearly demonstrated. The system is acoustically forced, and its response is detected. The experimental results confirm that both theoretically predicted eigenmodes, respectively symmetrical and antisymmetrical, do exist. Their frequencies, measured as a function of the bubbles spacing, follow theoretical estimations within a 10% accuracy.Comment: 14 pages, 6 figures, submitted to European Physical Journal E (2nd version

Acoustics at an interface : promoting the Lagrange picture

In Fluid Mechanics, the Euler description is widely taught and used at the undergraduate level, and the Lagrange description is rather presented as an alternative peculiarity. In this paper, it is argued that, as far as acoustics is envisaged, the Lagrange description occurs to offer a more suitable approach as well from a pedagogical viewpoint as from a technical one. Sound generation by a pulsating source and reflection/transmission at an interface are discussed in this respect

Lagrangian Sound

At least at the undergraduate level, most lectures and textbooks about hydrodynamics make use of the so-called Eulerian picture, where pressure, temperature, velocity of the fluid are treated as continuous fields defined by the value they take at each geometrical point of the reference frame the fluid moves in. There nevertheless exists another possible description of the movement which consists in labelling the fluid element themselves, and keep this labelling in the course of the motion. This so-called Lagrangian picture is scarcely taught for it often brings in somehow involved mathematics, although it occurs to be more intuitive than the Eulerian picture. In this paper, we try to illustrate the latter feature on the exemple of the otherwise cumbersome problem of the Rayleigh acoustic radiation pressure, and we argue that dealing with the mathematical difficulties implied by the Lagrangian picture may be a good pedagogical opportunity to familiarize with tensorial calculus

G2MARS a collaborative approach to improve fodder quality of European sorghum germplasm

The ability of sorghum to maintain a high level of biomass production in stressful environments makes it an interesting crop for animal feed as fodder, and for biomaterials and bioenergy production. Sorghum hybrids with improved agronomical behavior and high biomass quality are being developed for the European market. However the development of such hybrids requires a lot of field testing and biomass analyses. The current marker assisted breeding strategies offer the possibilities to better understand the genetic architecture of biomass quality and accelerate the creation of improved varieties. The G2MARS design developed in the frame of the “Biomass For the Future” project is gathering the know-how of both private companies and publics institutes to deliver new genetic marker and improved germplasm for the European biomass market. Seven biparental connected populations were developed in both genetic pools (3 in the male, 3 in the female and one male-female populations). These populations involved elite commercial cultivars and high biomass quality sorghum landraces. A total of 964 hybrids from these 7 populations were characterized in 2016 and 2017 in 2 locations. Agronomical traits and biomass quality related traits were measured. A QTL detection taking advantage of the connected design was performed with MCQTL and allowed the detection of 17 and 6 QTL respectively in the male and female pools. For each QTL the parental alleles were ranked allowing to define 2 target molecular ideotypes. The crossing strategy aiming to combine the most efficiently the favorable alleles was defined using Optimas. The G2MARS project offered the opportunity to take advantage of the specific skills of both private and public partners and develop a joint breeding action do develop hybrids suitable to fit the expectations of the biomass value chains. IN addition, this design improved the understanding of the genetic architecture of biomass quality traits that was mobilized to optimize the recombination strategy. This work was supported by the Biomass For the Future project (ANR-11-BTBR-0006-BFF) funded by the French National Research Agency (ANR)

The adiabatic invariant of any harmonic oscillator : an unexpected application of Glauber's formalism

In this theoretical paper, we propose a general derivation of the adiabatic invariant of the n-degree-of-freedom harmonic oscillator, available whichever the physical nature of the oscillator and of the parametrical excitation it undergoes. This derivation is founded on the use of the classical Glauber variables and ends up with this simplest result: the oscillator's adiabatic invariant is just the sum of all the semiclassical quanta numbers associated with its different eigenmodes

De Montréal à la région d’Yverdon-les-Bains, comment les influenceurs nous font voyager

Ce travail consiste à étudier théoriquement, puis plus concrètement, comment la collaboration avec des influenceurs peut être intégrée dans une stratégie de marketing d’une destination touristique. L’objectif final est d’élaborer des recommandations et de proposer un plan d’action à la région d’Yverdon-les-Bains qui souhaite initier une telle démarche. Pour ce faire, j’ai procédé en trois étapes. Dans un premier temps, une recherche minutieuse a été menée dans la littérature et sur internet afin de comprendre comment interagir avec ces nouveaux prescripteurs de tendances dans le domaine du tourisme. Il a ensuite été question d’interroger la ville de Montréal pour recueillir un avis concret sur les bonnes pratiques de la collaboration avec ces leaders d’opinion digitaux. Enfin, sur la base des recherches effectuées et des enseignements livrés par l’expérience de Montréal, des recommandations ont été proposées à la région d’Yverdon-les-Bains dans le but d’intégrer les influenceurs dans sa stratégie de marketing. Si la ville de Montréal est très avancée dans ce domaine et attire un public jeune, Yverdon-les-Bains région, au contraire, mise actuellement son offre touristique sur son patrimoine et attire un public plus âgé. La région possède un bon potentiel pour implanter cette nouvelle méthode de communication. Il sera cependant fondamental qu’elle suive rigoureusement les étapes proposées dans ce travail afin de créer les conditions nécessaires à une collaboration avec des influenceurs. Plus généralement, aucune destination ne devrait négliger l’impact potentiel de ce type de collaboration dans sa stratégie marketing

Latent inhibition in an insect: the role of aminergic signaling

Latent inhibition (LI) is a decrement in learning performance that results from the nonreinforced pre-exposure of the to-beconditioned stimulus, in both vertebrates and invertebrates. In vertebrates, LI development involves dopamine and serotonin; in invertebrates there is yet no information. We studied differential olfactory conditioning of the proboscis extension response in the honeybee Apis mellifera, and we compared LI in individuals treated with antagonists of biogenic amines (dopamine, octopamine, and serotonin). An antagonist of octopamine receptors and two antagonists of serotonin receptors showed LI disruption. We thus provide evidence that serotonin would participate in the regulation of LI in honeybees.Fil: Fernandez, Vanesa Maribel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Giurfa, Martín. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Devaud, Jean Marc. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Farina, Walter Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin

Radiative Lifetimes of Single Excitons in Semiconductor Quantum Dots- Manifestation of the Spatial Coherence Effect

Using time correlated single photon counting combined with temperature dependent diffraction limited confocal photoluminescence spectroscopy we accurately determine, for the first time, the intrinsic radiative lifetime of single excitons confined within semiconductor quantum dots. Their lifetime is one (two) orders of magnitude longer than the intrinsic radiative lifetime of single excitons confined in semiconductor quantum wires (wells) of comparable confining dimensions. We quantitatively explain this long radiative time in terms of the reduced spatial coherence between the confined exciton dipole moment and the radiation electromagnetic field.Comment: 4 pages, 3 figure

Relationship between brain plasticity, learning and foraging performance in honey bees.

Brain structure and learning capacities both vary with experience, but the mechanistic link between them is unclear. Here, we investigated whether experience-dependent variability in learning performance can be explained by neuroplasticity in foraging honey bees. The mushroom bodies (MBs) are a brain center necessary for ambiguous olfactory learning tasks such as reversal learning. Using radio frequency identification technology, we assessed the effects of natural variation in foraging activity, and the age when first foraging, on both performance in reversal learning and on synaptic connectivity in the MBs. We found that reversal learning performance improved at foraging onset and could decline with greater foraging experience. If bees started foraging before the normal age, as a result of a stress applied to the colony, the decline in learning performance with foraging experience was more severe. Analyses of brain structure in the same bees showed that the total number of synaptic boutons at the MB input decreased when bees started foraging, and then increased with greater foraging intensity. At foraging onset MB structure is therefore optimized for bees to update learned information, but optimization of MB connectivity deteriorates with foraging effort. In a computational model of the MBs sparser coding of information at the MB input improved reversal learning performance. We propose, therefore, a plausible mechanistic relationship between experience, neuroplasticity, and cognitive performance in a natural and ecological context