Bound Bogoliubov quasiparticles in photon superfluids

Bogoliubov's description of Bose gases relies on the linear dynamics of noninteracting quasiparticles on top of a homogeneous condensate. Here, we theoretically explore the weakly-nonlinear regime of a one-dimensional photon superfluid in which phonon-like elementary excitations interact via their backreaction on the background flow. The generalized dispersion relation extracted from spatiotemporal intensity spectra reveals additional branches that correspond to bound Bogoliubov quasiparticles -- phase-locked collective excitations originating from nonresonant harmonic-generation and wave-mixing processes. These mechanisms are inherent to fluctuation dynamics and highlight non-trivial scattering channels other than resonant interactions that could be relevant in the emergence of dissipative and turbulent phenomena in superfluids.Comment: 6 pages, 4 figure

Anticipating the response of excitable systems driven by random forcing

We study the regime of anticipated synchronization in unidirectionally coupled model neurons subject to a common external aperiodic forcing that makes their behavior unpredictable. We show numerically and by implementation in analog hardware electronic circuits that, under appropriate coupling conditions, the pulses fired by the slave neuron anticipate (i.e. predict) the pulses fired by the master neuron. This anticipated synchronization occurs even when the common external forcing is white noise.Comment: 12 pages (RevTex format

Electrochemical microsensors for cutaneous surface analysis: Application to the determination of pH and the antioxidant properties of stratum corneum

Potentiometry and cyclic voltammetry were proposed as simple, reliable and non invasive methods for the simultaneous determination of pH and antioxidant properties of skin. Experiments were performed with microelectrodes just deposited on skin surface without any gel or water added. pH was measured by means of the zero current potential of a tungsten W/WO3 sensor. A nerstian response was recorded in pH range 4 to 6 corresponding to the normal skin pH values. The global antioxidant capacity was deduced from the anodic charge passed during the plotting of cyclic voltammograms on platinum or gold microelectrodes. Comparing the half wave or peak potentials of these curves with those recorded for experiments performed in aqueous solution, the main hydrophilic antioxidants species were detected, i.e. ascorbic acid, uric acid and glutathione. This relatively easy-to-use analytical method made it possible to follow in real time the efficiency of topic treatment as well as to study the influence of oxidative stres

Predict-prevent control method for perturbed excitable systems

We present a control method based on two steps: prediction and prevention. For prediction we use the anticipated synchronization scheme, considering unidirectional coupling between excitable systems in a master-slave configuration. The master is the perturbed system to be controlled, meanwhile the slave is an auxiliary system which is used to predict the master's behavior. We demonstrate theoretically and experimentally that an efficient control may be achieved.Comment: 4 pages, 5 figure