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When

Start: 11/16/2011 - 1:15pm

End : 11/16/2011 - 1:25pm

End : 11/16/2011 - 1:25pm

Category

Applied Math Seminar

Speaker

Erin Byrne, HMC

Abstract

Multicellular communities are a dominant, if not the predominant, form

of bacterial growth. Growing affixed to a surface, they are termed

biofilms. When growing freely suspended in aqueous environments, they

are usually referred to as flocs. Flocculated growth is important in

conditions as varied as bloodstream infections (where flocs can be

seen under the microscope) to algal blooms (where they can be seen

from low earth orbit). Understanding the distribution of floc sizes in

a disperse collection of bacterial colonies is a significant

experimental and theoretical challenge. One analytical approach is the

application of the Smoluchowski coagulation equations, a group of PDEs

that track the evolution of a particle size distribution over time.

The equations are characterized by kernels describing the result of

floc collisions as well as hydrodynamic-mediated fragmentation into

daughter aggregates. The post-fragmentation probability density of

daughter flocs is one of the least well-understood aspects of modeling

flocculation. A wide variety of functional forms have been used over

the years for describing fragmentation, and few have had experimental

data to aid in its construction. In this talk, we discuss the use of

3D positional data of Klebsiella pneumoniae bacterial flocs in

suspension, along with the knowledge of hydrodynamic properties of a

laminar flow field, to construct a probability density function of

floc volumes after a fragmentation event. Computational results are

provided which predict that the primary fragmentation mechanism for

medium to large flocs is erosion, as opposed to the binary

fragmentation mechanism (i.e. a fragmentation that results in two

similarly-sized daughter flocs) that has traditionally been assumed.

Where

Davidson, CMC

Misc. Information

TBA