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Cell Invasion Models: How Complex do They Need to Be?
No full textThe invasion of the extracellular matrix (ECM) by cancer cells is a highly complex process, but many mathematical models describing it are quite simple. This raises the question how these simpler models differ from the more complex ones regarding their dependence on the input parameters and their qualitative results, and whether simpler models are able to capture and reproduce the results of complex models.
To investigate these questions, three cell invasion models are examined: two simple to intermediate partial differential equation (PDE) models with six and eight parameters, respectively, and a complex hybrid model with 17 parameters. The hybrid model was originally developed for angiogenesis, featuring a Cellular Potts model and a finite element formulation, and is extended in this work to describe cell invasion as travelling waves.
The models’ parameter sensitivity with respect to initial ECM density, the ECM degradation rate and the cell proliferation probability, is examined using a variance-based method at various points in time. At first, the PDE models exhibit mainly first-order effects from the initial ECM density, and later in time from the ECM degradation rate. At all points in time, the hybrid model is affected the most by the proliferation probability, and by interaction effects between all three parameters.
The data fitting abilities are tested by generating data using the hybrid model and estimating the corresponding PDE model parameters. This is done under consideration of various phenomena of the hybrid model, and with different numbers of parameters to be estimated. Using the fitted parameters, the shape approximations and the velocities of the travelling invading waves are compared between the models. The best approximations in shape are performed by the PDE model with eight parameters, the best approximations in wave speed are obtained using the model with six parameters.
Overall, the main finding is that even though the model outputs are relatively similar and can be approximated adequately by the PDE models, the dependence of the hybrid model on its input parameters differs substantially from the one of the PDE models
Automated Classification of Physiologic, Glaucomatous, and Glaucoma-Suspected Optic Discs Using Machine Learning
No full textBus Priority Procedure for Signalized Intersections Based on Bus Occupancy and Delay
No full textThis study proposes a bus prioritisation strategy at signalised intersections to enhance public transport reliability and attractiveness. Nowadays, bus prioritisation at intersections is con-ducted according to a first-come, first-served principle, lacking compatibility with future vehi-cle-to-infrastructure communication. A framework for prioritising buses based on their delay and occupancy was developed and tested in a SUMO microscopic traffic simulation subnet-work of the city of Ingolstadt. Buses are prioritised using a 25-level hierarchy. Four degrees of prioritisation interventions are implemented based on bus priority levels with signal cycles ad-justed to advance preferred green phases. The timing of the prioritisation is based on an Esti-mated Time of Arrival (ETA) prediction that considers past speed and travel time data as well as bus stops that are on the way to the intersection. The prioritisation logic was tested in simu-lation scenarios with on- and off-peak conditions and with several buses requesting priority and varying degrees of priority. The results show that the developed prioritization concept works, and prioritised buses benefit from a strong reduction in their travel times (up to 87 %) and number of stops. Buses with lower priority levels may experience deterioration in their travel time (up to 126 %) when arriving at the same time as a high-priority bus, but consider-ing the fewer affected passengers and smaller delay, this seems acceptable. The study high-lighted the influence of neighbouring intersections on traffic flows and identified critical factors for successful prioritisation such as the timing and route of the bus suggesting areas for fur-ther research
Determining Excited-State Absorption Properties of a Quinoid Flavin by Polarization-Resolved Transient Spectroscopy
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