PHOTO: ALAN MURPHY/MINDEN PICTURESsciencemag.org SCIENCEby trapping external medium into
membrane-bound vesicles or
vacuoles. These structures are
promptly resolved, thus avoiding
accumulation of endomem-
branes and volume expansion.
In a variety of cultured cells,
Freeman et al. found that this
resolution entails conversion
of spherical vacuoles into thin
tubules, a process that involves
marked changes in surface-to-
volume ratio (see the Perspective
by King and Smythe). Shrinkage
of membrane-bound struc-
tures is driven by ion fluxes and
subsequent osmotic transfer of
water. Shriveled vacuoles attract
curvature-sensing proteins that
promote the extension of fine
tubules. Ion channels thereby
control membrane remodeling,MASS EXTINCTION
An impact with a
dash of volcanism
Around the time of the end-
Cretaceous mass extinction that
wiped out dinosaurs, there was
both a bolide impact and a large
amount of volcanism. Hull et al.
ran several temperature simula-
tions based on different volcanic
outgassing scenarios and com-
pared them with temperature
records across the extinction
event. The best model fits to
the data required most outgas-
sing to occur before the impact.
When combined with other lines
of evidence, these models sup-
port an impact-driven extinction.
However, volcanic gases may
have played a role in shaping therise of different species after the
extinction event. —BG
Science, this issue p. 266QUANTUM CRITICALITY
Spin-charge
entanglement
Many physical properties fol-
low characteristic scaling laws
near quantum critical points,
which are associated with phase
transitions at absolute zero tem-
perature. The material YbRh 2 Si 2
has an antiferromagnetic
quantum critical point, where
spin-related properties are
expected to follow such a scal-
ing. Unexpectedly, Prochaska et
al. found that charge fluctuations
follow a critical scaling as well.The researchers fabricated high-
quality thin films of YbRh 2 Si 2
and used transmission spec-
troscopy to measure the optical
conductivity of the film and infer
the scaling. Their findings point
to a highly entangled state of
charge and spin, which may also
be responsible for the strange-
metal phase in this material.
—JS
Science, this issue p. 285CELL BIOLOGY
Ion fluxes resolve
organellar volume
Animal cells continuously sample
the surrounding medium, a
feature accentuated in immune
cells. Sampling is accomplishedBIOMECHANICSWing shapes take flight
B
irds can dynamically alter the shape of their wings during
flight, although how this is accomplished is poorly understood.
Matloff et al. found that two mechanisms control the move-
ment of the individual feathers. Whenever the skeleton moves,
the feathers are redistributed passively through compliance
of the elastic connective tissue at the feather base. To prevent the
feathers from spreading too far apart, hook-shaped microstructures
on adjacent feathers form a directional fastener that locks adjacent
feathers. These features are found across a range of bird sizes; how-
ever, because the detachment of the hooks is noisy, they are notably
absent in silent fliers, such as barn owls. —MSL
Science, this issue p. 293RESEARCH
IN SCIENCE JOURNALS
Edited by Michael FunkAn acrobatic midair altercation between
male Baltimore orioles, Icterus galbula260 17 JANUARY 2020 • VOL 367 ISSUE 6475
Published by AAAS