Molecules
“Most people and most scientists pay
no attention at all to mucus.” — LESLiE VoSSh ALL
The nitty-gritty of diamond polishing
By Rachel Ehrenberg
You can soften your sweetie with diamonds, but to soften a diamondtakes
some special chemistry. A liquidlike layer
of carbon at the interface between diamond-polishing wheel and gem makes
the magic that turns a grubby stone into
a girl’s best friend, new research finds.
New polishing tricks may emerge from
the research, perhaps allowing scientists
to exploit diamonds for use in optics or
semiconductors. And the computational
approach used in the study, published
online November 28 in Nature Materials,
could aid in understanding wear in materials such as metals or ceramics.
Gemstones are typically worked with
materials harder than themselves, an
approach not possible with diamond,
one of the hardest natural materials. So
polishers use diamond on diamond. The
method, which has remained unchanged
for centuries, involves coating a cast-
iron disk with olive oil and a layer of
diamond grit. The stone to be polished is
pressed against this “skeif,” and it’s up to
the skill of the polisher to find the grain
of the diamond. Polishing in the wrong
direction can damage the gemstone.
A diamond-polishing study finds that
oxygen (red) and a liquidy carbon layer
(green) help grit particles (gray, upper
left) shine the gem (gray, bottom).
strange amorphous layer of carbon, says
Michael Moseler of the Fraunhofer Institute for Mechanics of Materials IWM in
Freiburg, Germany. This liquidlike layer
between the two surfaces is very reactive,
says Moseler, who led the new work. As
the sharp edges of the grit plow by, they
scrape off some of the liquidy layer and
expose long carbon chains to the air.
Oxygen then can swoop in, snatching
off carbons to form carbon dioxide and
leaving behind a smoother surface than
scraping alone would achieve.
The research explains why polishing a
diamond in certain directions is difficult
and potentially damaging. The latticelike
arrangement of carbon atoms is such that
in some directions the carbon atoms are
so tightly bound that they resist becoming part of the amorphous layer.
“The exciting thing about this paper is
that molecular dynamics could prove to
be the most efficient way of designing new
diamond-processing technologies,” says
physicist Jonathan Hird of UCLA. The
new study describes diamond polishing
with unprecedented detail, he says.
Further research needed to validate
the modeling may be tough. “Studying
diamond polishing is experimentally
challenging and expensive,” Hird says.
“Diamond does not give up its secrets
without a fight.” s
Snot has power
to alter scents
Mice studies show sense of
smell is modified by mucus
By Laura Sanders
A rose sniffed through a snotty nose
may not smell so sweet. Enzymes in
mice’s nasal mucus transform certain
scents before the nose can detect them,
researchers report December 1 in the
would play a potential role in changing
how we perceive odors,” says neuro-
scientist Leslie Vosshall of Rockefeller
University in New York City. “Most peo-
ple and most scientists pay no attention
at all to mucus.”
But there’s more to mucus than what
meets the nose: The thick goo that serves
to lubricate the nose is teeming with pro-
teins and protein-chopping enzymes.
In the new study, Ayumi Nagashima
and Kazushige Touhara of the University
of Tokyo added odorants to tiny amounts
of mucus sucked out of a mouse’s nose
and tested the resulting chemical com-
position of the mix. After five minutes
of sitting in mucus, about 80 percent of
almond-smelling benzaldehyde was con-
verted into benzyl alcohol (a scent found
in some teas and plants) and odorless
benzoic acid. Inactive enzymes in boiled
mucus couldn’t do this odor conversion.
