Showing papers by "University of Patras published in 1973"

A frequency entrainment model with relevance to systems displaying adaptive behaviour

Abstract: This paper considers a non-conservative pendulum-type non-linear oscillator which emulates some behavioural features of systems displaying adaptive response, or biological rhythms, under the influence of an environmental excitation (‘ Zeitgeber ’) of electromagnetic origin, for instance. Of special interest are : (a) The entraining or locking-in process of the oscillation under a sudden change Δω of the Zeitgeber frequency ; (b) the time interval within which locking-in is achieved, and (c) the evolution of the oscillation under constant excitation of varying amplitude It is shown that the range of entertainment (pull-in region) increases with the amplitude of excitation and depends on the sign of Δω, and the oscillation damps out for constant excitation beyond a certain critical amplitude The above results are deduced on a quantitative basis by introducing a method of following up the entrainment process in the plane ‘ phase-error—instantaneous frequency offset ’.

Studies of a homologous gene-enzyme system, esterase C, in Drosophila melanogaster and Drosophila simulans.

Abstract: Electrophoretic variants of nonspecific esterases (Est-6 and Est-C) of various populations of Drosophila melanogaster and Drosophila simulans from Northern Greece were studied by means of starch gel electrophoresis, and the results are compared with those obtained from standard stocks. Two new alleles of the Est-6 locus of D. melanogaster and two new alleles of the Est-6 locus of D. simulans are described. The position of the Est-C locus in D. simulans is estimated. Evidence is presented for the genetic homology of the Est-C locus of D. melanogaster and the Est-C locus of D. simulans.

Planar Periodic Orbits Using Second and Third Variations

Abstract: The techniques applied in the calculation of closed solutions of the planar restricted problem of three bodies are presented Use of second and third variational equations is made by means of which both orbits and entire families of orbits can be computed by straight forward expansion of the sufficient conditions for periodicity into Taylor series

Second and Third Order Variations of the Three Dimensional Restricted Problem

Abstract: The numerical techniques, along with the analytic details and justification used, in computing periodic orbits and families of periodic orgits of double symmetry in the three-dimensional restricted three-body problem are described. Two distinct methods are applied in this endeavor, namely the predictor-corrector method and the method of direct expansion of the family into Taylor series. The latter is applied here for the first time.

On a Conjecture by Poincaré

Abstract: The conjecture of Poincare (1892) on the ‘density’ of periodic orbits of the restricted 3-body problem is discussed and generalized for dynamical system with stable closed solutions. It is shown that under certain conditions the above conjecture is valid for certain domains of the phase space. Under the same conditions the ‘branching’ of a family of periodic orbits is shown to be ‘dense’.