*************** ANNOUNCEMENT **********************
* University of Utah Mathematical Biology Seminar *
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Monday, March 22 at 4:30pm in INSCC 110

Speaker: Akira Tsuda

Title: AEROSOL TRANSPORT AND DEPOSITION IN THE PULMONARY ACINUS

Abstract: 

Basic knowledge of fine aerosol transport and deposition mechanisms in
the pulmonary acinus (i.e., gas exchange region of the lung) is
fundamental to understand many physiological processes, to assess the
adverse effects of ambient particulate matter, and to improve
inhalation drug therapy.  Fine aerosol particles basically follow the
gas flow, because their inertia is not sufficient to effect crossing
of streamlines.  The characteristics of gas flow in the acinus are
therefore critical in determining particle motion.  Conventionally, it
has been assumed that the acinar flow is kinematically reversible,
consequently, there is little flow-induced mixing in the acinus.  It
follows that, for fine inhaled particles, most will be exhaled without
being mixed with residual alveolar gas and will not deposit in the
lung.  Sharply contrary to this classical prediction, we have recently
obtained direct experimental evidence of convective mixing of carrier
fluids in the lung periphery.  In ventilated excised rat lungs filled
with polymerizable silicone fluids of two colors, we demonstrated that
the acinar flow is indeed irreversible and exhibits highly convoluted
stretch-and-fold streak patterns.  These experimental observations
were followed by both computational analysis and physical model
experimentation, demonstrating the potential significance of
stretch-and-fold convective flow, when it is coupled with diffusion,
in enhancing acinar aerosol mixing and deposition.  We propose that
kinematically irreversible stretch-and-fold convection is a potent
mechanism of acinar aerosol mixing and deposition.