Angela Stevens

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In many biological systems, movement of an organism occurs in response to a diffusible or otherwise transported signal, and in its simplest form this can be modeled by diffusion equations with advection terms of the form first derived by Patlak [Bull. of Math. Biophys., 15 (1953), pp. 311–338]. However, other systems are more accurately modeled by random(More)
The chemotaxis equations are a well-known system of partial differential equations describing aggregation phenomena in biology. In this paper they are rigorously derived from an interacting stochastic many-particle system, where the interaction between the particles is rescaled in a moderate way as population size tends to infinity. The novelty of this(More)
A widespread phenomenon in moving microorganisms and cells is their ability to reorient themselves depending on changes of concentrations of certain chemical signals. In this paper we discuss kinetic models for chemosensitive movement, which also takes into account evaluations of gradient fields of chemical stimuli which subsequently influence the motion of(More)
The myxobacteria are ubiquitous soil bacteria which aggregate under starvation conditions and build fruiting bodies to survive. Until recently the mechanisms of their social gliding, aggregation, and fruiting body formation have not been well understood. In this paper a stochastic cellular automaton model is presented to describe and provide an(More)
In this paper we study the existence of one and multidimensional traveling wave solutions for general chemotaxis or so-called Keller-Segel models without reproduction of the chemotactic species. We present a constructive approach to give modelers a choice of chemotactic sensitivity functionals, production, and degradation terms for the chemical signal at(More)
We study a kinetic model for chemotaxis introduced by Othmer, Dunbar, and Alt [22], which was motivated by earlier results of Alt, presented in [1], [2]. In two papers by Chalub, Markowich, Perthame and Schmeiser, it was rigorously shown that, in three dimensions, this kinetic model leads to the classical KellerSegel model as its drift-diffusion limit when(More)
In this paper we apply vector field topology methods to a mathematical model for the fluid dynamics of reaggregation processes in tissue engineering. The experimental background are dispersed embryonic retinal cells, which reaggregate in a rotation culture on a gyratory shaker, according to defined rotation and culture conditions. Under optimal conditions,(More)
By inserting position and time dependent "source" or "forcing" terms into the microscopic evolution equation of a lattice Boltzmann fluid and treating the generalized scheme within the usual Chapman-Enskog methodology, we show that the emergent dynamics of the lattice fluid may be usefully transformed. Our method of adjustment is demonstrated by(More)
Morphogenetic processes such as neurulation and gastrulation involve coordinated movements of cells. It is assumed that these processes happen due to long-range signaling, although the detailed mechanisms are not completely understood. Therefore, one is interested in biological “model-systems” where self-organization of cells and in particular the(More)
Cardiovascular disease is more common in schizophrenia patients than in the general population, with a hypothesized contribution from increases in adiposity produced by antipsychotic medications. We sought to test the relationship between adiposity and insulin resistance using frequently sampled intravenous glucose tolerance tests (FSIVGTTs) to quantify(More)