  We consider the problem of determining multiple steady states for positive
real values in models of biological networks. Investigating the potential for
these in models of the mitogen-activated protein kinases (MAPK) network has
consumed considerable effort using special insights into the structure of
corresponding models. Here we apply combinations of symbolic computation
methods for mixed equality/inequality systems, specifically virtual
substitution, lazy real triangularization and cylindrical algebraic
decomposition. We determine multistationarity of an 11-dimensional MAPK network
when numeric values are known for all but potentially one parameter. More
precisely, our considered model has 11 equations in 11 variables and 19
parameters, 3 of which are of interest for symbolic treatment, and furthermore
positivity conditions on all variables and parameters.
