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SUMMARY:Flagellar swimming in viscoelastic fluids
DTSTART;VALUE=DATE-TIME:20180709T010000Z
DTEND;VALUE=DATE-TIME:20180709T013000Z
DTSTAMP;VALUE=DATE-TIME:20190819T052618Z
UID:indico-contribution-43-115@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Robert Guy (University of California Davis)\nMany im
portant biological functions depend on microorganisms' ability to move in
viscoelastic fluids such as mucus and wet soil. The effects of fluid elast
icity on motility remain poorly understood partly because the swimmer stro
kes depend on the properties of the fluid medium\, which obfuscates the me
chanisms responsible for observed behavioural changes. We use experimental
data on the gaits of *Chlamydomonas reinhardtii* swimming in Newtonian an
d viscoelastic fluids as inputs to numerical simulations that decouple the
swimmer gait and fluid type in order to isolate the effect of fluid elast
icity on swimming. In viscoelastic fluids\, cells employing the Newtonian
gait swim faster but generate larger stresses and use more power\, and as
a result the viscoelastic gait is more efficient. Furthermore\, we show
that fundamental principles of swimming based on viscous fluid theory miss
important flow dynamics: fluid elasticity provides an elastic memory effe
ct which increases both the forward and backward speeds\, and (unlike pure
ly viscous fluids) larger fluid stress accumulates around flagella moving
tangent to the swimming direction\, compared to the normal direction.\n\nh
ttps://conferences.maths.unsw.edu.au/event/2/contributions/115/
LOCATION:University of Sydney New Law School---106
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/115/
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SUMMARY:Chemotaxis Modelling for Sperm Motility
DTSTART;VALUE=DATE-TIME:20180709T013000Z
DTEND;VALUE=DATE-TIME:20180709T020000Z
DTSTAMP;VALUE=DATE-TIME:20190819T052618Z
UID:indico-contribution-43-97@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: John LaGrone (Tulane University)\nAn important aspec
t in the study of reproduction is how sperm are guided toward an egg for f
ertilization. One such mechanism is the process of chemotaxis\, in which t
he sperm detect changes in concentration (namely of Ca+) in the fluid envi
ronment and utilize these changes to alter the waveform of their flagellar
beat. This change in beat form results in changes to the swimming path. W
e model the swimming sperm using a Kirchhoff elastic rod model coupled wit
h the method of regularized Stokeslets for the fluid motion. In order to s
imulate the effect of chemical concentrations\, we employ a stochastic dec
ision making process.\n\nhttps://conferences.maths.unsw.edu.au/event/2/con
tributions/97/
LOCATION:University of Sydney New Law School---106
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/97/
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BEGIN:VEVENT
SUMMARY:Understanding pattern formation in interacting cell populations
DTSTART;VALUE=DATE-TIME:20180709T003000Z
DTEND;VALUE=DATE-TIME:20180709T010000Z
DTSTAMP;VALUE=DATE-TIME:20190819T052618Z
UID:indico-contribution-43-44@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Edward Green (University of Adelaide)\nTissue develo
pment requires cells of different types to organise themselves into the ap
propriate patterns and structures to produce viable\, functional tissue. S
imilar processes occur in tissue repair (e.g. wound healing) or when tissu
es are grown in vitro (tissue engineering). Understanding how this organis
ation is coordinated is therefore an important basic problem in biology an
d medicine.\n\nI will present results from agent-based modelling of intera
cting cell populations\, and illustrate how different interactions between
the cells affect the patterns of cell organisation observed in tissues. I
will explain how these patterns can be quantified using pair-correlation
functions\, and discuss the extent to which we can infer cell interactions
from observed tissue-scale patterns.\n\nhttps://conferences.maths.unsw.ed
u.au/event/2/contributions/44/
LOCATION:University of Sydney New Law School---106
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/44/
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SUMMARY:Fast algorithms for the dense matrices arising from the Method of
Regularized Stokeslets
DTSTART;VALUE=DATE-TIME:20180709T060000Z
DTEND;VALUE=DATE-TIME:20180709T063000Z
DTSTAMP;VALUE=DATE-TIME:20190819T052618Z
UID:indico-contribution-43-40@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Minghao Rostami (Syracuse University)\nThe swimming
motion of microorganisms such as sperm and cilia can be modelled by severa
l methods\, all of which entail solving equations of fluid-structure inter
action. Among them\, the Method of Regularized Stokeslets (MRS) and the Ro
tne-Prager-Yamakawa tensor have the advantage of not requiring a 3D Euleri
an grid and using the fundamental solutions to the underlying equations in
stead. However\, the computations required by both methods entail the use
of dense matrices\, and they tend to be large and very costly to work with
for practical models in which the number of micro-swimmers is large. \n\n
The 'data-sparse' structure of these matrices enables the development of f
ast algorithms. To compute the matrix-vector products efficiently\, we ext
end the Kernel-Independent Fast Multipole Method (KIFMM) to the kernels as
sociated with the MRS. To solve linear systems with the same matrices eff
iciently\, we consider both a data-sparser preconditioner and a block-diag
onal preconditioner\; to expedite the application of the preconditioners\,
we employ a number of techniques such as Krylov subspace recycling. We ap
ply the proposed algorithms to study the dynamics of a large group of sper
m and the flow field induced by a carpet of cilia.\n\nhttps://conferences.
maths.unsw.edu.au/event/2/contributions/40/
LOCATION:University of Sydney New Law School---106
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/40/
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SUMMARY:Exploring the fluid dynamics of collective pulsing behaviour in xe
niid corals using the immersed boundary method
DTSTART;VALUE=DATE-TIME:20180709T063000Z
DTEND;VALUE=DATE-TIME:20180709T070000Z
DTSTAMP;VALUE=DATE-TIME:20190819T052618Z
UID:indico-contribution-43-109@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Julia Samson (University of North Carolina at Chapel
Hill)\nXeniid corals\, a family of soft corals (*Alcyonacea*)\, include s
pecies displaying a unique pulsing behaviour. Within a colony\, each indiv
idual polyp pulses by actively contracting and passively expanding eight t
entacles\, increasing the local mixing and enhancing nutrient and gas exch
ange. Using the immersed boundary method with finite elements (IBFE)\, we
constructed a 3D model of a pulsing polyp. The motion of the polyp tentacl
es is based on actual motion data tracked from videos of real polyps. We f
ind that individual polyps pull water in radially\, mix it between their t
entacles\, and expel the fluid volume in an upward jet. After validating t
his 3D IBFE model against experimentally measured flow fields\, we are now
using the model to numerically simulate small groups of polyps and to qua
ntify the effects of collective pulsing behaviour on the local fluid dynam
ics. Here\, we simulate pairs of polyps and vary the pulsing patterns (in-
phase and different degrees of out-of-phase) and distance between polyps t
o better understand how differences in collective pulsing behaviour affect
local flow and mixing.\n\nhttps://conferences.maths.unsw.edu.au/event/2/c
ontributions/109/
LOCATION:University of Sydney New Law School---106
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/109/
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