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The application of chaos in communications and radar offers new and interesting possibilities. This article describes investigations on the generation of chaos in a traveling wave tube ͑TWT͒ amplifier and the experimental parameters responsible for sustaining stable chaos. Chaos is generated in a TWT amplifier when it is made to operate in a highly nonlinear regime by recirculating a fraction of the TWT output power back to the input in a delayed feedback configuration. A driver wave provides a constant external force to the system making it behave like a forced nonlinear oscillator. The effects of the feedback bandwidth, intensity, and phase are described. The study illuminates the different transitions to chaos and the effect of parameters such as the frequency and intensity of the driver wave. The detuning frequency, i.e., difference frequency between the driver wave and the natural oscillation of the system, has been identified as being an important physical parameter for controlling evolution to chaos. Among the observed routes to chaos, besides the more common period doubling, a new route called loss of frequency locking occurs when the driving frequency is adjacent to a natural oscillation mode. The feedback bandwidth controls the nonlinear dynamics of the system, particularly the number of natural oscillation modes. A computational model has been developed to simulate the experiments and reasonably good agreement is obtained between them.Experiments are described that demonstrate the feasibility of chaotic communications using two TWTs, where one is operated as a driven chaotic oscillator and the other as a time-delayed, open-loop amplifier.

Using an original automated analyzer of double bonds we determined the rate constants for oxidation of saturated and unsaturated mono- and dienoic fatty acids (in vivo substrates for beta-oxidation in the mitochondria) by the ozone titration method. The rate constant for O(3) oxidation is maximum for oleic monoenoic acid, lower for dienoic linoleic, and very low for saturated palmitic acid. The rate constant for oxidation of oleic fatty acid, which by one order of magnitude surpasses that for oxidation of essential arachidonic acid, indicates that oleic acid is a leading in vivo acceptor of active O(2) species. By the rate of trapping active oxygen species and in the quantitative aspect, endogenously produced oleic acid can be regarded as the main biological antioxidant.

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