  We investigate the influence of aperiodic modulations of the exchange
interactions between nearest-neighbour rows on the phase transition of the
two-dimensional eight-state Potts model. The systems are studied numerically
through intensive Monte Carlo simulations using the Swendsen-Wang cluster
algorithm for different aperiodic sequences. The transition point is located
through duality relations, and the critical behaviour is investigated using FSS
techniques at criticality. While the pure system exhibits a first-order
transition, we show that the deterministic fluctuations resulting from the
aperiodic coupling distribution are liable to modify drastically the physical
properties in the neighbourhood of the transition point. For strong enough
fluctuations of the sequence under consideration, a second-order phase
transition is induced. The exponents $\beta/\nu$, $\gamma /\nu$ and
$(1-\alpha)/\nu$ are obtained at the new fixed point and crossover effects are
discussed. Surface properties are also studied.
