MATH & TECHNOLOGY
Design based on exotic materials is also energy-efficient
New laser offers a more stable beam
LIFE & EVOLUTION
Toads will regret
eating this beetle
Small prey without any sting
possess a surprising defense
BY MARIA TEMMING
A new type of laser is modeled after an
exotic class of materials called topological
insulators. And it’s proving more reliable
and energy-efficient than its conventional counterparts, paving the way for
possible use in quantum communication
and next-generation electronics.
Described online February 1 in Science,
the device is composed of a grid of semiconductor rings that convert energy into
particles of light. The device channels
these photons in one direction around
the grid until they are emitted as a beam.
The design borrows from the concept
behind topological insulators — a kind
of material that blocks electric current
through its interior but let electrons surf
along its surface (SN: 5/22/10, p. 22).
Scientists have engineered devices
BY SUSAN MILIUS
Toad versus bombardier beetle is almost
a fair fight. Toads are much bigger, can
tongue-strike in an eyeblink and swallow
all kinds of nasty stuff. But bombardier
beetles can shoot hot steam and noxious
chemicals from their back ends.
In lab face-offs, more than 40 percent
of Pheropsophus jessoensis bombardiers
escaped alive after being swallowed by
toads, researchers at Kobe University
in Japan report February 7 in Biology
Letters. These lucky beetles were vomited up — in one case, 107 minutes after
being gulped — covered with goo, but
still able to pull themselves together and
walk away. Fifteen of 16 beetles coughed
up into daylight lived for at least 17 days,
with one still going 562 days later.
that similarly steer sound waves, but
researchers had debated whether that
same kind of control could be exerted
over the light particles generated inside
lasers (SN: 5/2/15, p. 9).
To turn on the laser, the researchers
feed light or electrical energy into the
grid’s outer rings, which convert that
Scalding internal beetle blasts proved
vital in persuading the toads to spit up
the bugs, ecologists Shinji Sugiura and
Takuya Sato report. After prodding some
beetles into spraying until no more defensive chemicals remained, the team fed the
defenseless beetles to toads. The toads
kept almost all of these beetles down.
The bombardier group of more than
600 beetle species has become a textbook example of chemical defense (SN
Online: 4/30/15). When provoked, the
beetles mix two substances inside their
abdomens that react explosively, and
shoot out a noxious stream that can reach
around 100° Celsius. Yet the defenses are
understudied, Sugiura says.
P. jessoensis beetles are common in
East Asia. In the lab, wild-caught toads
(Bufo japonicus and B. torrenticola) willingly swallowed these beetles. With each
big gulp, the researchers listened for the
sound of a beetle blast inside the toad.
“Not easy to hear,” Sugiura says, but it’s
possible to catch a slight bu or vu sound.
Surviving beetles spent from 12 to
107 minutes in a toad stomach, averag-
In a new type of laser (illustrated), energy
injected into the outer rings of a lattice (red)
generates light particles that travel around the
outer edge of the grid to a corner, where they
escape as a single beam (top left).
A bombardier beetle regurgitated by a toad
comes out covered in slime, but later manages
to get up and walk away.
energy into the laser’s light. The rings
are linked together by racetrack-shaped
loops precisely positioned to steer those
light particles along a one-way path.
While only the outer rings transmit the
laser light, the whole grid is needed to
guide the photons, says Boubacar Kante,
an electrical and computer engineer at
the University of California, San Diego,
who wasn’t involved in the work.
Ferrying light along the grid’s outer
edge in a single direction makes the
laser more immune to manufacturing
errors or malfunctions that can cripple
lasers, says study coauthor Mordechai
Segev, a scientist at the Israel Institute of
Technology in Haifa. If photons encounter a defect, like a missing ring, they can’t
bounce back or scatter, which would
waste energy. Instead, the photons are
forced to go around the rough patch and
Such reliable lasers could be used for
sending information in a quantum network or to build better optical circuits. s
ing in the 40-minute range. To vomit, a
toad has to sort of turn its stomach inside
out, which isn’t a quick process. So far,
researchers don’t know if beetles have
tricks for coping with toad stomach acid.
Making a toad give back its lunch is an
accomplishment. “Toads are tough,” says
evolutionary ecologist Rick Shine of the
University of Sydney, who has studied
Gregory Brown, also at the University
of Sydney, says the hot chemical blast
would be like “having a small bomb go
off” in the stomach. “What does surprise
me,” he says, “is that the defense only
worked around 50 percent of the time.” s