Classical analogue of the Unruh effect

In the Unruh effect an observer with constant acceleration perceives the quantum vacuum as thermal radiation. The Unruh effect has been believed to be a pure quantum phenomenon, but here we show theoretically how the effect arises from the classical correlation of noise. We demonstrate this idea with a simple experiment on water waves where we see the first indications of a Planck spectrum in the correlation energy

Self-organization into quantized eigenstates of a classical wave driven particle

A growing number of dynamical situations involve the coupling of particles or singularities with physical waves. In principle these situations are very far from the wave-particle duality at quantum scale where the wave is probabilistic by nature. Yet some dual characteristics were observed in a system where a macroscopic droplet is guided by a pilot-wave it generates. Here we investigate the behaviour of these entities when confined in a two-dimensional harmonic potential well. A discrete set of stable orbits is observed, in the shape of successive generalized Cassinian-like curves (circles, ovals, lemniscates, trefoils...). Along these specific trajectories, the droplet motion is characterized by a double quantization of the orbit spatial extent and of the angular momentum. We show that these trajectories are intertwined with the dynamical build-up of central wave-field modes. These dual self-organized modes form a basis of eigenstates on which more complex motions are naturally decomposed

Interaction of two walkers: Wave-mediated energy and force

A bouncing droplet, self-propelled by its interaction with the waves it generates, forms a classical wave-particle association called a "walker." Previous works have demonstrated that the dynamics of a single walker is driven by its global surface wave field that retains information on its past trajectory. Here, we investigate the energy stored in this wave field for two coupled walkers and how it conveys an interaction between them. For this purpose, we characterize experimentally the "promenade modes" where two walkers are bound, and propagate together. Their possible binding distances take discrete values, and the velocity of the pair depends on their mutual binding. The mean parallel motion can be either rectilinear or oscillating. The experimental results are recovered analytically with a simple theoretical framework. A relation between the kinetic energy of the droplets and the total energy of the standing waves is established.Comment: 11 pages, 8 figure

Prevalence of cannabis and cocaine consumption in French fishermen in South Atlantic region in 2012–2013 and its policy consequences

Background: The aim of the study was to evaluate the use of cannabis and cocaine among fishermen followed in occupational medicine in the ports of Aquitaine and Charente-Maritime (Direction interrégionale de la mer Sud-Atlantique [DIRM-SA]). Materials and methods: Thousand fishermen could be recruited during medical regulatory examination by the occupational physicians and nurses of Occupational Health Department for Seamen. Results: About 20% of fishermen were former smokers. A third of the fishermen are at risk for excessive drinking according to the AUDIT-C. The prevalence of cannabis experimentation was estimated at 58%. The prevalence of positive urine test for cannabis was 28%. The prevalence of experimentation with cocaine was about 16%. The prevalence of positive urine test for cocaine was 4.5%. Conclusions: In accordance with its objectives, this study allows objectifying cannabis and cocaine consumption among fishermen. The national rules for fitness at sea have to be modified by introducing the use of urinary tests by occupational physician

Alcohol and nicotine dependence in French seafarers

Background. To study the relationship between alcohol abuse or dependence as diagnosed by the CAGE questionnaire, and nicotine dependence as diagnosed by Fagerström Test of Nicotine Dependence (FTND) in French seamen. Materials and methods. French seamen were recruited from a stratified survey of 19 ports in France. The subjects completed a questionnaire during their annual medical check-up with occupational physicians and nurses of the Occupational Health Department (Service de santé des gens de mer). Findings. Approximately forty-four per cent of male subjects were current smokers, and approximately sixty-three per cent of these were nicotine dependent according to FTND. More than 11% of male subjects drank alcohol every day. About 16% of these were alcohol dependent according to CAGE. A strong positive relationship has been shown between alcohol dependence and nicotine dependence. There was a highly significant difference between alcohol dependent and non-alcohol dependent subjects in the FTND. Conversely, nicotine dependent and non-nicotine dependent subjects significantly differed regarding several alcohol-related variables. Conclusions. Alcohol and nicotine consumption is a major public health issue in seamen. A strong positive correlation was found between alcohol abuse or dependence and nicotine abuse or dependence. Some alcohol-related behaviours were associated with nicotine dependence, and some tobacco-related behaviours were also associated with alcohol dependence. These findings are novel for this kind of population in France. In view of these results, combined smoking cessation and alcohol consumption reduction policies should be developed in this population. Finally, future studies could analyze the work environment, which seems to be associated with consumption and dependency