David W. Sullivan

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The trace version of classical conditioning is used as a prototypical hippocampal-dependent task to study the recoding sequence prediction theory of hippocampal function. This theory conjectures that the hippocampus is a random recoder of sequences and that, once formed, the neuronal codes are suitable for prediction. As such, a trace conditioning paradigm,(More)
Engineering estimates of methane emissions from natural gas production have led to varied projections of national emissions. This work reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers). For well completion flowbacks,(More)
Randomness can be a useful component of computation. Using a computationally minimal, but still biologically based model of the hippocampus, we evaluate the effects of initial state randomization on learning a cognitive problem that requires this brain structure. Greater randomness of initial states leads to more robust performance in simulations of the(More)
Despite the fact that animals are not optimal, natural selection is an optimizing process that can readily control small bits and pieces of organisms. It is for this reason that we need to explain certain parameters as found in Nature (e.g., number of neurons and their average activity) to fully understand the biological basis of cognition. In this(More)
Quantal synaptic failures are random, independent events in which the arrival of an action potential fails to release transmitter. Although quantal failures destroy information, there exist conditions where such failures enhance learning by a neural network model of the hippocam-pus. In particular, we show how the appropriate failure rate can allow the(More)
Using a minimal hippocampal model, previous studies simulating trace conditioning have reproduced the empirically observed learnable trace interval and reproduced the number of training trials required for learning. However, these earlier studies did not address the effects of parameterization on performance. Here, we demonstrate a robust effect of average(More)
Methane emissions from liquid unloadings were measured at 107 wells in natural gas production regions throughout the United States. Liquid unloadings clear wells of accumulated liquids to increase production, employing a variety of liquid lifting mechanisms. In this work, wells with and without plunger lifts were sampled. Most wells without plunger lifts(More)
This paper develops two extensions of the Gupta-Santner restricted subset selection procedure. The (exact) procedure R<subscrpt>E</subscrpt> screens a set of k normal populations with unknown and unequal variances using independent random sampling within each alternative population in order to select a final subset of at most m alternatives; in the least(More)
Ambient monitoring, emission inventory development, and air quality modeling of air toxics are critical elements of human exposure and health risk assessments. The Port of Corpus Christi, Texas is among the largest in the United States with significant petroleum refining and chemical manufacturing industries. The close proximity to residential areas has(More)