Biomedical subjects

G C Sabin

Publications and source records attributed to G C Sabin.

3 recordsLinked to original sources

PubMed1993

Chaos in a periodically forced predator-prey ecosystem model.

We subject to periodic forcing the classical Volterra predator-prey ecosystem model, which in its unforced state has a globally stable focus as its equilibrium. The periodic forcing is effected by assuming a periodic variation in the intrinsic growth rate of the prey. In nondimensional form the forced system contains four control parameters, including the forcing amplitude and forcing frequency. Numerical experiments carried out over sections of the parameter space reveal an abundance of steady-state chaotic solutions. We graph Poincaré maps and calculate Lyapunov exponents and fractal dimensions for a representative selection of strange attractors. The transitions to chaos were found to be either via a Feigenbaum cascade of period-doubling bifurcations or via frequency locking.

Animals↗

PubMed1991

Disturbed nonlinear multispecies models in ecology.

We analyze a disturbed form of the general Lotka-Volterra model of an ecosystem with m interacting species. The disturbances act on the intrinsic growth rates of the species and are assumed to be bounded but otherwise unknown. We employ a Lyapunov technique and the concept of "reachable set" from control theory to estimate the set of all possible population densities that are attainable as a result of the disturbances. To calculate estimates for this reachable set, a number of numerical methods that entail the solution to one or more global optimization problems are developed. Specific examples involving two, three, and four species are solved. We also derive an explicit analytical expression that represents an estimate for the reachable set in the m-dimensional case. The estimate is conservative but can be evaluated without carrying out any optimization procedure. We show that methods developed in this paper can be applied to certain other types of nonlinear ecosystem models.

Animals↗

PubMedDate not supplied

Focus on: Northern Montana Hospital's Biomedical Services.

This paper describes the Biomedical Services of Northern Montana Hospital, a separate corporation under the parent corporation of Northern Montana Health Care Inc. Located in Havre, Montana, a rural area of north central Montana, the hospital is a 120-bed, non-profit organization. The two BMETs work as part of the Engineering Department and service almost every piece of equipment in the building (approximately 1100 items), as well as a telephone system for another facility. This paper shows that a non-urban hospital, located far from any service company outlet, can be self-supporting as far as equipment service and maintenance are concerned.

Hospital Bed Capacity, 100 to 299↗