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PROFESSOR: Another
part of the course

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is that I also have a
project in the course.

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And students do the
projects in pairs.

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Partly, because I just
think it's nice for them

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to have somebody to work with.

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And they've done a
huge range of projects.

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I let them do whatever
project they want.

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It has to have something
to do with cellular solids.

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And some of them
have done, sort of,

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analytical things where they've
done numerical finite element

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analysis of some
cellular structure.

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Some of them done very
experimental things.

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And some have been a lot of fun.

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So, for instance,
almost every year

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there are students who
want to work on food foams.

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And one year, for example,
there was a group made bread.

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And they looked at sort of
the processing of the bread.

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And they looked at how
if you used more yeast,

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or you let the yeast
rise, or the bread rise

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for longer, how that affected
the cellular structures.

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So they sort of
changed the chemistry

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of how they made the bread.

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And then they looked at the
micro structure of the bread

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that they got.

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I think they even did some
mechanical tests of the bread.

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So that was kind of fun.

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And I think, probably, the
most interesting project

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any student has done
was on elephants skulls.

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So you could imagine an elephant
skull is huge, and it's bony.

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So it would be very,
very heavy, if it

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didn't have some pores in it.

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And elephant skulls,
it turns out,

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have some very
large pores in them.

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I think partly to reduce
the weight of the skull,

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and the head, and the bone.

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The neck has to, kind
of, carry it all.

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So these two
students came to me.

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And they said they
had heard somewhere

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or they'd read somewhere that
these pores in the elephant

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skull had an effect on how
the elephants perceived sound

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and the acoustic transmission of
sound waves through the skull.

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And they wanted to do a
project on elephant skulls.

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So I was kind of
intrigued by this.

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I love all natural
history kinds of things.

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And I've worked
before with people

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at Harvard's Museum of
Comparative Zoology, where

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they have bones.

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They have stuffed bodies.

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They have all kinds
of animals over there.

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And I called up a
colleague over there,

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and it turned out they had
elephant skulls over there.

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So I went with one
of the students.

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And it was an attic
of the building,

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this kind of dingy place.

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And there was this huge room.

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And it was full
of elephant bones.

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And they had several
skulls, which are

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like the size of this table.

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They're huge.

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They're this big.

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And some of the
skulls were cracked.

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And you could see these
big pores in the skulls.

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And then the students
found out that University

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of Texas at Austin has CT
scans, Computed Tomography

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scans of all sorts of bones.

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And sure enough, they had
elephant skulls scanned.

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And so they got a
three-dimensional

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representation of
the elephant skull

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through this University of
Texas at Austin program.

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And then they used that as
input to a 3D printing set up.

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So they 3D printed a sort of
mimic of the elephant skull

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with some ceramic powder.

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And they made a skull
was about this big.

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And then they wanted to look at
the acoustic properties of it.

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So what they did was
they suspended the skull

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from a string.

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And they had a speaker, and
the speaker had a sound.

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And they put an
accelerometer on the skull.

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And they measured the
vibration of the skull.

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And then to compare it with the
skull that didn't have these

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pores.

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And they got the CT
image from Austin.

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And they 3D printed
this dolphin skull.

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And they did the same thing.

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They suspended the
skull from as a thread.

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And they measured the vibration.

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And they could show--
and I've forgotten

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the details of their results--
but they could show, basically,

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that the two skulls had
a different frequency

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response to the vibrations.

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And they thought maybe part
of it was because the pores.

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So these two sections
here are two sections

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of their 3D printed
elephant skull.

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I don't have the entire thing.

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But you can see this is the
orbit, where the eyes would

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have gone in here.

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And if I turn it over
and you look inside,

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you can see these pores in here.

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And also if you
look at this section

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lower down on the skull, you can
see this whole porous structure

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here, as well.

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And if we flip it over there's
a little bit more over there.

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So that was probably the
most intriguing project

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that the students did
as part of this course.

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That was quite something.