Stephen Whitaker

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Three experiments studied timing in rats on 2-valued mixed-fixed-interval schedules, with equally probable components, Fixed-Interval S and Fixed-Interval L (FI S and FI L, respectively). When the L:S ratio was greater than 4, 2 distinct response peaks appeared close to FI S and FI L, and data could be well fitted by the sum of 2 Gaussian curves. When the(More)
Rats were trained on mixed-fixed-interval (FI) schedules, with component FIs of 30 and 60s. The probability of reinforcement according to FI 30s varied between conditions, across values of 0.1, 0.3, 0.5, 0.7 and 0.9. When response rate in the 60s intervals was measured, separate response peaks, one close to 30s, the other at 60s, could be identified when(More)
In this paper, the method of large-scale averaging is used to develop two different one-equation models describing dispersion in heterogeneous porous media. The first model represents the case of large-scale mass equilibrium, while the second represents the asymptotic behavior of a two-equation model obtained by large-scale averaging. It is shown that a(More)
In this study we describe a scheme for numerically calculating the effective diffusivity of cellular systems such as biofilms and tissues. This work extends previous studies in which we developed the macroscale representations of the transport equations for cellular systems based on the subcellular-scale transport and reaction processes. A finite-difference(More)
(Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments) 259 Crecimiento, sobrevivencia y adaptación de Bifidobacterium infantis a condiciones ácidas (Growth, survival and adaptation of Bifidobacterium infantis to acidic conditions)Espinosa 265 Statistical approach to optimization of ethanol(More)
A new type of heat exchange process is described for use in semiconductor heat sinks. It involves the use of subcooled, nucleate boiling at concave curved surfaces where radial acceleration, v/sup 2//r, can be used to develop significant and beneficial buoyancy forces. The system provides a heat transfer surface with a uniform temperature, i.e. the boiling(More)
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