MATHEMATICS COLLOQUIUM
Speaker: Bob Guy
Title: Channeling Instabilities in Multiphase Flow Models
of True Slime Mold
Affiliation: University of California, Davis
Date: Friday, April 10, 2009
Place and Time: Room 101, Love Building, 3:35-4:30 pm
Refreshments: Room 204, Love Building, 3:00 pm
Abstract.
The true slime mold Physarum polycephalum is a single cell
organism reaching up to meters in size. The cytoplasm shows periodic
shuttle streaming through a network of tubular structures reaching
velocities up to 1 mm/s. The motion is driven by the periodic contraction
of an actin-myosin gel that is regulated by a calcium oscillation. The
tubular network and relatively fast flow are necessary for transmitting
nutrients and communicating signals over the large distances spanned by
the cell body. When the organism is small (< 100 microns) there is no
shuttle streaming and no structural organization of the cell body. As it
gets larger, flow channels develop inside the cell, streaming begins, and
the cell begins to migrate. Modeling the development of structures in
Physarum requires accounting for the flow of cytoplasm and the
rearrangement of the internal gel. We use a multiphase flow model that
treats both the sol and gel as fluids each with its own material
properties and internal forces, and we discuss instabilities of the
sol/gel mixture that produce flow channels within the gel.
|