ABSTRACT
We present a way of coupling two nonautonomous, periodically forced, chaotic C O2 lasers in a master-slave configuration in order to achieve complete synchronization. The method consists of modulating the forcing of the slave laser by means of the difference between the intensities of the two lasers, and lends itself to a simple physical implementation. Experimental evidence of complete synchronization induced by a suitable coupling strength is shown, and a numerical model is used to achieve further insight of the synchronization phenomena. Finally, we describe a possible application of the investigated technique to the design of a digital communication system.
ABSTRACT
We present a simple method for real-time encoding of information in the interspike intervals of a homoclinic chaotic system. The method has been experimentally tested on a CO2 laser with feedback displaying Sil'nikov chaos and synchronized with an external pulsed signal. Information is encoded by the length of the temporal intervals between consecutive pulses of the external signal. This length is varied each time a new pulse is generated.
Subject(s)
Lasers , Nonlinear Dynamics , Carbon Dioxide , Statistics as Topic , Time FactorsABSTRACT
Soman, an anticholinesterasic neurotoxic drug, induces epileptic seizures during severe intoxication. The neuropathological lesions then observed are linked to the appearance of these seizures, but their trigger conditions still remain unknown and a great variability between animals is observed. We have developed a technique allowing, in freely moving rats, the in vivo determination of three sets of neurophysiological data, before and during a soman intoxication. For the same rat, we associated cortical acetylcholinesterase (AChE) activity by microdialysis with both the assay of extracellular acetylcholine (ACh) concentrations and electroencephalographic (EEG) recording and power spectrum analysis (gamma band). Data have been analyzed to define the critical parameters which lead to the epileptic fit. Although we found thresholds for seizure occurrence, AChE inhibition having to be over 65% and ACh over 200-fold the baseline, these two criteria are not sufficient to predict the appearance of seizures. Only animals with no increase of energy in the gamma band early after soman poisoning will then exhibit an epileptic fit. Gamma band energy is modulated by noradrenergic activity and might be related to the sympathetic response to stress. So we can hypothesize, that the variation of energy in gamma band after intoxication, which might be related to stress adaptation strategy, may determine whether or not the animal will exhibit an epileptic fit.