The amplitude death phenomenon has been experimentally observed with a pair of thermo-optical oscillators linearly coupled by heat transfer. A parametric analysis has been done and compared with numerical simulations of a time delayed model. The role of the coupling strength is also discussed from experimental and numerical results. [1] are some of the observed behaviors that can be described by phase models considering a weak coupling. On the other hand, effects associated with the amplitude of the different units are expected for strong couplings. One of the most intriguing effects is the so-called amplitude death, dealing with the absence of oscillations for the coupled system while each subsystem oscillates when isolated. Two kinds of amplitude death have been considered. In one of the types the coupling creates a saddle-node pair of fixed points on the limit cycle of the entrained oscillations [5], while the second one is associated with a more common bifurcation-the Hopf bifurcation-in which the oscillation amplitudes are damped out up to reach a steady state [6]. The relevance of the second kind of amplitude death and the important role assumed by the time delay in the coupling of oscillators have been recently noted due to its possible application in physics, chemistry, medicine, and biology [7]. The effect has been predicted to occur for two or more identical or different coupled oscillators [6,[8][9][10], but it has not been experimentally observed until now [7].Here, we present the experimental observation of the amplitude death phenomenon with two optothermal oscillators, located on the same interferometric device and thermally coupled. The relation with the coupling effects on the Hopf bifurcation of the whole system is clearly stated by means of a parametric analysis as a function of the coupling strength and the relative light irradiation of the coupled units. The experimental results are compared with simulations of a time delayed model. The nonlinear system is based on the so-called optothermal bistability with localized absorption (BOITAL) and consists of a Fabry-Pérot cavity where the input mirror is a partially absorbing film, the rear mirror is a high reflection dielectric coating, and the spacer is made of two transparent layers with opposite thermo-optic effects [11]. Such a kind of system presents a multiple steady-state solution associated with the periodic interferometric function and can experience a supercritical Hopf bifurcation due to the competition and time delay between the contributions of the two layers to the light phase shift [11]. With this configuration and increasing the input power, the system destabilizes at the first stable branch yielding a limit cycle, which grows by approaching the neighboring saddle point and a homoclinic connection may occur. After the connection the limit cycle is destroyed and the flow escapes towards an upper node branch where a similar behavior takes place.For a transversally extended optical device, different oscillators separated by a distan...

We show how certain N-dimensional dynamical systems are able to exploit the full instability capabilities of their fixed points to do Hopf bifurcations and how such a behavior produces complex time evolutions based on the nonlinear combination of the oscillation modes that emerged from these bifurcations. For really different oscillation frequencies, the evolutions describe robust wave form structures, usually periodic, in which selfsimilarity with respect to both the time scale and system dimension is clearly appreciated. For closer frequencies, the evolution signals usually appear irregular but are still based on the repetition of complex wave form structures. The study is developed by considering vector fields with a scalar-valued nonlinear function of a single variable that is a linear combination of the N dynamical variables. In this case, the linear stability analysis can be used to design N-dimensional systems in which the fixed points of a saddle-node pair experience up to NϪ1 Hopf bifurcations with preselected oscillation frequencies. The secondary processes occurring in the phase region where the variety of limit cycles appear may be rather complex and difficult to characterize, but they produce the nonlinear mixing of oscillation modes with relatively generic features.

No abstract

No abstract

We have grown thin film libraries of the Mg-Al system using a high-throughput synthesis methodology that combines the sequential deposition of pure elements (Mg and Al) by an electron-beam (e-beam) evaporation technique and the use of a special set of moving shadow masks. This novel mask has been designed to simultaneously prepare four identical arrays of different compositions that will permit the characterization of the same library after several treatments. Wavelength dispersive spectroscopy (WDS) and micro-X-ray diffraction have been used as high-throughput screening techniques for the determination of the composition and structure of every member of the library in the as-deposited state and after hydrogenation at 1 atm of H2 during 24 h at three different temperatures: 60, 80, and 110 degrees C. We have analyzed the influence of the Mg-Al ratio on the hydrogenation of magnesium, as well as on the appearance of complex hydride phases. We have also found that aluminum can act as a catalyzer for the hydrogenation reaction of magnesium.