Science - USA (2021-07-09)

176 9 JULY 2021 • VOL 373 ISSUE 6551 sciencemag.org SCIENCE

RESEARCH | IN SCIENCE JOURNALS

energy into adjacent bond rota-

tions. Through careful design and

synthesis of polymer-embedded

cyclobutyl rings, the authors

showed that certain relative sub-

stituent geometries are preserved

when sonication induces ring

opening. Accompanying simula-

tions support the instigation of

“flyby” trajectories that channel

energy narrowly to cleave the

cyclic sigma bonds and then rap-

idly form acyclic pi bonds. —JSY

Science, abi7609, this issue p. 208

CATALYSIS

Hitting the limits on

propene synthesis

The greater abundance of pro-

pane from shale gas has spurred

efforts to use it as a propylene

feedstock. Direct dehydroge-

nation catalysts consisting of

platinum–tin alloy nanoparticles

supported on alumina often

must run with hydrogen dilution

to avoid carbon buildup and

excess tin to avoid alloy segrega-

tion. Motagamwala et al. report

that platinum–tin nanoparticles

interact more weakly with a silica

support and the metals thus

do not segregate. The use of

undiluted reactants allowed the

reaction to run near the thermo-

dynamically limit of about 67%

conversion with a selectivity to

propylene of more than 99%.

This catalyst also does not build

up carbon and could run up to

30 hours without deactivation.

—PDS

Science, abg7894, this issue p. 217

NEUROSCIENCE

Representing space

in past and future

As an organism moves through

space, its brain has to remem-

ber its most recent location and

anticipate its future position, not

just its current place in the world.

Earlier studies reported so-called

retrospective and prospective

place coding in rats while they

were running along linear tracks.

However, it would be advanta-

geous to study an animal that

rapidly moves through three-

dimensional space with high

IMAGING

Putting cells in

their places

Despite considerable progress

in recent years, pathological

analysis of tissues and organs

often still relies on old-fashioned

microscopic techniques.

Similarly, genomic and tran-

scriptomic analysis is commonly

applied to bulk tissue samples. To

address the limitations of these

approaches, Zhao et al. and van

Ineveld et al. have developed

methods for incorporating both

cellular location and molecular

information into the analysis of

samples from healthy organs and

tumors. By adopting a Bayesian

statistical approach, the former

identified cellular clustering in

various carcinomas, and, by using

multispectral image analysis, the

latter revealed tumor-specific cell

populations in pediatric Wilms’

tumors. Such resolution will

improve our understanding of the

biology of multiple tissue types

and the functions of cells in their

biological contexts. —YN

Nat. Biotechnol.

10.1038/s41587-021-00935-2,

10.1038/s41587-021-00926-3

(2021).

QUANTUM OPTICS

Into the valley

The topological features of band

structures provide robust propa-

gation paths for classical and

quantum states of light. Another

ingredient of band structure is

the valley degree of freedom, in

which the propagation path of

light is dependent on its polariza-

tion state. Chen et al. used both

topology and valley-dependent

transport to design and fabricate

a photonic crystal structure

capable of forming the basis of

optical quantum circuits. The

authors demonstrate the input of

left- and right-circularly polarized

states of quantum light, their

precision. Dotson and Yartsev

recorded from flying bats to inves-

tigate whether place cell activity

in hippocampus area CA1 repre-

sents local (current) or nonlocal

positions. They discovered

that the hippocampus not only

encodes the bat’s present loca-

tion but also signals its positions

in the past and future. —PRS

Science, abg1278, this issue p. 242

NETWORK DYNAMICS

How to put on a

bioluminescent light show

Synchronous swarms of flashing

fireflies are a natural wonder and

a canonical example of coor-

dinated group behavior. Using

three-dimensional reconstruc-

tions from video recordings in

Great Smoky Mountains National

Park, Sarfati et al. reveal that

incoherent individual flashes

transition to a macroscopic mar-

vel only once a critical density

of active fireflies can convey the

group pace. Flashing is syn-

chronized over a surprisingly

wide range of distances—many

meters—leading to the hypoth-

esis that the local interactions are

defined not strictly by distance

or by nearest neighbor but, for

firefly swarms, by line of sight.

The results unmask a complex

mixture of short- and long-range

interactions underlying ensemble

behavior. — JSH

Sci. Adv. 10.1126/sciadv.abg9259

(2021).

IN OTHER JOURNALS

Edited by Caroline Ash

and Jesse Smith

Synchronous fireflies in Great Smoky

Mountain National Park coordinate

light flashes locally, depending on

high density and visual connections to

establish synchrony. PHOTOS (TOP TO BOTTOM): NASA EARTH OBSERVATORY IMAGE BY LAUREN DAUPHIN; (DATA) THE U.S. GEOLOGICAL SURVEY; FLORIS VAN BREUGEL/MINDEN PICTURES

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