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When you typically think of
beetles you don't think of things
that can hurt you, or that are
particularly interesting. They
just crawl around and you might
step on them occasionally, but
there are certain types of
beetles that have a really famous
defense mechanism that actually
can hurt you. They are called
bombardier beetles and they
defend themselves by detonating
explosions inside of their bodies
and spraying out hot, nasty
chemicals; so hot it is the
temperature of boiling water.
And so I study these beetles to
understand a) how they have these
explosions happen inside their
bodies, and b) are there things
we can learn from that.
Previously people have looked at
this by taking images of the
outside of the beetle using
high-speed photography to watch
the pulses fly through the air.
Whereas we are looking at the
inside of the beetle using
cutting-edge synchrotron
radiation to visualize the spray
being formed inside the beetle.
So that allows us to see how
these pulses, instead of coming
out as a continuous stream, comes
out as a series of pulses.
And what we find is a part of
the explosion chamber actually
deforms during the explosion
and when it does so it cuts off
the flow of reactants into the
explosion chamber. And so, that
causing the explosion to
temporarily start, or stop.
Bombardier beetles are one of
the most famous examples of
chemical defense in nature and
people have been trying to
understand how they produce these
hot sprays for a very long time,
and they've been trying to
understand how these beetles
have evolved. And our work really
shows that something as
complicated as a pulse jet spray
can emerge from very simple
modifications. You know, these
softening of a particular part of
the reaction chamber can produce
a huge change in the type of
spray. If you look at these
beetles relatives it comes out
as a gentle mist whereas in this
case it comes out as a pulsed jet.