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

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

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

Essai sur la corde vibrante et ses non-linéarités.

As soon as its elasticity is sollicitated, the Melde vibrating string exhibits a strong nonlinear behaviour even though it is made of a perfectly elastic material. When sinusoidally excited by means of an electric vibrator, the string's motion may become bistable, yielding hysteresis cycles. We propose a simple model accounting for these cycles, and bringing in a unique adjustable parameter gathering the wealth of dissipative processes that limit the string's oscillation amplitude

An Alarm Pheromone Modulates Appetitive Olfactory Learning in the Honeybee (Apis Mellifera)

In honeybees, associative learning is embedded in a social context as bees possess a highly complex social organization in which communication among individuals is mediated by dance behavior informing about food sources, and by a high variety of pheromones that maintain the social links between individuals of a hive. Proboscis extension response conditioning is a case of appetitive learning, in which harnessed bees learn to associate odor stimuli with sucrose reward in the laboratory. Despite its recurrent use as a tool for uncovering the behavioral, cellular, and molecular bases underlying associative learning, the question of whether social signals (pheromones) affect appetitive learning has not been addressed in this experimental framework. This situation contrasts with reports underlining that foraging activity of bees is modulated by alarm pheromones released in the presence of a potential danger. Here, we show that appetitive learning is impaired by the sting alarm pheromone (SAP) which, when released by guards, recruits foragers to defend the hive. This effect is mimicked by the main component of SAP, isopentyl acetate, is dose-dependent and lasts up to 24 h. Learning impairment is specific to alarm signal exposure and is independent of the odorant used for conditioning. Our results suggest that learning impairment may be a response to the biological significance of SAP as an alarm signal, which would detract bees from responding to any appetitive stimuli in a situation in which such responses would be of secondary importance

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