Science - USA (2020-09-04)

1204 4 SEPTEMBER 2020 • VOL 369 ISSUE 6508 sciencemag.org SCIENCE

RESEARCH | IN SCIENCE JOURNALS

CLIMATE RESPONSES

Accounting for heat

burdens

As climate warming becomes
more and more apparent and
influential, there is an increasing
desire to predict its long-term
impacts on species. Classically,
this has been done by extrapo-
lating lethal limits based on
those observed in the laboratory.
In the real world, however, organ-
isms do not experience a single
high temperature that then
returns to a comfortable temper-
ature, but rather a series of high
temperatures during the hot
season. Rezende et al. accounted
for these accumulative effects in
a dynamic model that accurately
predicted empirical patterns in
wild fruit fly populations, show-
ing that cumulative effects of
warming temperatures can be
included in future estimates (see
the Perspective by Huey and
Kearney). —SNV
Science, this issue p. 1242;
see also p. 1163

STELLAR ASTROPHYSICS

Ripping up a

circumstellar disk

During the process of star
formation, a disk of gas and
dust forms around the young
star, controlling the accretion
of more material. Once the star
has formed, any leftover mate-
rial in this circumstellar disk
can form planets. If a binary or

triple star forms at the center

of the disk, theoretical mod-

els predict that tidal torques

caused by their orbits can rip

the disk apart, in a process

known as disk tearing. Kraus et

al. observed the nearby young

triple-star system GW Orionis

with multiple near-infrared and

submillimeter telescopes, using

the techniques of interferome-

try and polarimetry. They found

evidence for multiple rings

with different orientations and

warping of part of the disk, both

produced by disk tearing. —KTS

Science, this issue p. 1233

ADDICTION

Opioid signaling rewards

steroid abuse

The dopamine system medi-

ates feelings of reward and

is implicated in addiction to

various drugs, including anabolic

androgenic steroids. Bontempi

and Bonci found that the neu-

rological and behavioral effects

of androgenic steroids were

indirectly mediated by opioid

receptors on dopaminergic

neurons. A single injection of

anabolic steroids in mice stimu-

lated the release of b-endorphins

in a dopaminergic neuron-rich

brain region, which activated

μ-opioid receptor signaling.

Blocking μ-opioid receptor acti-

vation prevented drug-seeking

behavior in steroid-injected

mice. —LKF

Sci. Signal. 13 , eaba1169 (2020).

NANOMATERIALS

Bending bimetallic

nanowhiskers

Metal nanocrystal wires can be

very strong, because deforma-

tion requires nucleation of new

dislocations; thus, bending

them by mechanical loading

is difficult to control and can

even break the nanowires. Qi et

al. used molecular beam epi-

taxy to grow single-crystalline

<011>-oriented gold nanowires

(~360 nanometers in diameter

and several micrometers long)

and then coated one side with

iron layers either ~50 or ~200

nanometers thick. Heating

these bimetallic nanowhis-

kers (up to 500°C) gradually

induced irreversible bending.

Diffusion of iron into the gold

nanowhiskers caused bending

through the change in lattice

parameter of the alloy as well

as a volume effect caused

by the interphase boundary

migrating toward the iron layer.

—PDS

ACS Nano 10.1021/acsnano.0c04327

(2020).

TISSUE REPAIR

Heart scars

The healing process often

involves scar formation.

However, scars display lower

elasticity than normal tissue

and can interfere with tissue

function. Such problems arise

after myocardial infarction, with

increasing scar size correlating

with higher mortality. Yokota et

al. examined gene expression

after myocardial infarction in

mice and found that collagen V

regulates scar formation. If

collagen V is absent, increased

myofibroblast formation and

expression of extracellular

Edited byCaroline Ash

andJesse Smith

IN OTHER JOURNALS

IMAGES (FROM LEFT): KRAUS

ET AL

.; ICROGRAPH OBTAINED BY GEETHA THIMMEGOWDA

Computed image of a warped circumstellar disk in a triple-star system

Pseudocolorized scanning

electron micrograph of the

wing of a giant Asian honey

bee (Apis dorsata), showing

attached particulate pollutants

below pollen grains

Published by AAAS