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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
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UID:UW-Physics-Event-2344
DTSTART:20120316T203000Z
DURATION:PT1H0M0S
DTSTAMP:20240329T082640Z
LAST-MODIFIED:20120312T144746Z
LOCATION:2241 Chamberlin Hall (coffee at 4:30 pm)
SUMMARY:Kelvin\, Pascal\, and mollusk shells\, Physics Department Coll
oquium\, Pupa Gilbert\, University of Wisconsin-Madison
DESCRIPTION:NacreaEuro"or mother-of-pearlaEuro"the tough\, iridescent
biomineral lining the inner side of some mollusk shells\, is composed
of aragonite (CaCO3) tablet layers alternating with organic sheets. Ne
w Polarization-dependent Imaging Contrast (PIC) maps revealed that nac
re tablets are not co-oriented\, but have a broad distribution of angu
lar orientations\, as shown by the Gilbert group (1) and subsequently
by many others. The angle spread is the full-width of this distributio
n\, and was found to vary across different species\, and different she
ll growth environments. Most interestingly\, we found strong correlati
on between nacre tablet angle spread and environmental temperature (2)
\, and this has far-reaching consequences: nacre angle spread could be
used as a thermometer. Analysis of one shell with well-established st
able oxygen isotope analysis and PIC-mapping validates the nacre therm
ometer in one modern shell. Once validated on more shells\, modern and
ancient\, nacre-paleothermometry could be established as the first en
tirely-physical\, as opposed to chemical\, proxy for temperature (3).
But the implications of this finding are more profound: if T is the te
mperature at which the nacre formed and AS is the measured angle sprea
d\, then the equation T=26.826+0.051 AS links environment and bio-stru
cture. This equation suggests that one could predict a biological stru
cture based on the environment in which the organism forms it.
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br>
\n1. RA Metzler\, M Abrecht\, RM Olabisi\, D Ariosa\, CJ Johnson\,
BH Frazer\, SN Coppersmith\, PUPA Gilbert. Architecture of columnar n
acre\, and implications for its formation mechanism. Phys. Rev. Lett.
98\, 268102\, 2007.
\n2. IC Olson\, R Kozdon\, JW Valley\, PUPA G
ilbert. Mollusk shell nacre ultrastructure correlates with environment
al temperature and pressure. J Am Chem Soc in press\, 2012.
\n3.
IC Olson\, PUPA Gilbert. Nacre as a temperature proxy. RSC Faraday Dis
cussions submitted\, 2012.
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URL:https://www.physics.wisc.edu/events/?id=2344
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