Christopher Duffy

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The differentiation of granule cell dendrites in the dentate gyrus of the hippocampal region was studied in a series of developing fetal and postnatal rhesus monkeys whose brains were processed by the rapid Golgi method. The total combined lengths of dendrites, the total number of dendritic spines, and their density on the proximal, middle, and distal(More)
The physiological development of potentiating processes in the rat dentate gyrus were compared to morphological development. Rapid Golgi techniques were coupled with in vitro studies of dentate granule cell frequency potentiation, post-tetanic potentiation and long-term potentiation. Frequency potentiation and long-term potentiation exhibited a(More)
Long-term potentiation of the hippocampal slice preparation results in an increase in the incorporation of labeled valine into the proteins destined for secretion into the extracellular medium. Double-labeling methods established that the increased secretion of the labeled proteins was limited to the potentiated region of a slice; incorporation of labeled(More)
The physiological development of monosynaptic response habituation in the rat dentate gyrus was compared to morphological development. Rapid Golgi techniques were coupled with in vitro studies of dentate granule cell habituation to several frequencies and intensities of monosynaptic excitation. Except for the youngest group, the degree of habituation(More)
The Critical Zone (CZ) incorporates all aspects of the earth's environment from the vegetation canopy to the bottom of groundwater. CZ researchers target processes that cross timescales from that of water fluxes (milliseconds to decades) to that of the evolution of landforms (thousands to tens of millions of years). Conceptual and numerical models are used(More)
We examine t-colourings of oriented graphs in which, for a fixed integer k ≥ 1, vertices joined by a directed path of length at most k must be assigned different colours. A homomorphism model that extends the ideas of Sherk for the case k = 2 is described. Dichotomy theorems for the complexity of the problem of deciding, for fixed k and t, whether there(More)
The Prisoner's Dilemma Process on a graph G is an iterative process where each vertex, with a fixed strategy (cooperate or defect), plays the game with each of its neighbours. At the end of a round each vertex may change its strategy to that of its neighbour with the highest pay-off. Here we study the spread of cooperative and selfish behaviours on a(More)
A (m, n)-colored mixed graph is a graph having arcs of m different colors and edges of n different colors. A graph homomorphism of a (m, n)-colored mixed graph G to a (m, n)-colored mixed graph H is a vertex mapping such that if uv is an arc (edge) of color c in G, then f (u)f (v) is also an arc (edge) of color c. The (m, n)-colored mixed chromatic number χ(More)