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.