Megan Olsen

Bio: Megan Olsen is an academic researcher from Loyola University Maryland. The author has contributed to research in topics: Verification and validation of computer simulation models & Metamorphic testing. The author has an hindex of 8, co-authored 26 publications receiving 178 citations. Previous affiliations of Megan Olsen include Loyola University Chicago & University of Massachusetts Amherst.

Multiscale Agent-based Model of Tumor Angiogenesis

Abstract: Computational models of cancer complement the biological study of tumor growth. However, existing modeling approaches can be both inefficient and inaccurate due to the difficulties of representing the complex interactions between cells and tissues. We present a three-dimensional multiscale agent-based model of tumor growth with angiogenesis. The model is designed to easily adapt to various cancer types, although we focus on breast cancer. It includes cellular (genetic control), tissue (cells, blood vessels, angiogenesis), and molecular (VEGF, diffusion) levels of representation. Unlike in most cancer models, both normally functioning tissue cells and tumor cells are included in the model. Tumors grow following the expected spheroid cluster pattern, with growth limited by available oxygen. Angiogenesis, the process by which tumors may encourage new vessel growth for nutrient diffusion, is modeled with a new discrete approach that we propose will decrease computational cost. Our results show that despite proposing these new abstractions, we see similar results to previously accepted angiogenesis models. This may indicate that a more discrete approach should be considered by modelers in the future.

Increasing Validity of Simulation Models Through Metamorphic Testing

Abstract: Simulation validation, demonstrating that a simulation accurately represents the system it studies, poses a particularly potent form of the oracle problem. A simulation must be validated for its results to be reliable, but often no oracle exists due to the nature of simulations. We propose taking the metamorphic testing (MT) approach from the realm of software verification and applying it for validating executable simulation models. By establishing pseudo-oracles based on metamorphic relations between parameters and behaviors within an executable model, we can create a methodical approach for validating simulation models. We propose an overall framework and guidelines to apply MT for simulation validation, with details for two prevalent simulation approaches: agent-based simulation models (ABM), and discrete-event simulation (DES) modeling. Through three case studies, we demonstrate the successful application of MT toward validating three different simulation models: an ABM of gossip propagation, an ABM of cancer, and a DES of airport check-in and security.

Conspecific Emotional Cooperation Biases Population Dynamics: A Cellular Automata Approach

Abstract: In this paper, the authors evaluate the benefit of emotions in population dynamics and evolution. The authors enhance cellular automata (CA) simulating the interactions of competing populations with emotionally inspired rules in communication, interpretation, and action. While CAs have been investigated in studies of population dynamics due to their ability to capture spatial interactions, emotion-like interactions have yet to be considered. Our cellular stochastic system describes interacting foxes that feed on rabbits that feed on carrots. Emotions enable foxes and rabbits to improve their decisions and share their experiences with neighboring conspecifics. To improve the system’s biological relevance, it includes inter-species disease transmission, and emotions encode data pertaining to both survival and epidemic reduction. Results indicate that emotions increase adaptability, help control disease, and improve survival for the species that utilizes them. Simulations support the hypothesis that the acquisition of emotion may be an evolutionary result of competitive species interactions.

Evolution and the Theory of Games

Abstract: In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

The Symbolic Species: The Co-Evolution of Language and the Brain

Abstract: A review of The Symbolic Species: The Co-Evolution of Language and the Brain, by Terrance Deacon, 1997. New York: W.W. Norton, 527pp. ISBN 0393317544. $29.95 USD. Hardcover.