Science - USA (2019-02-15)

IMAGES: (TOP TO BOTTOM) WILLIAMSON

ET A

L.; DUPEYROUX

ET AL

.

SCIENCE sciencemag.org

RESEARCH

Edited by Stella Hurtley

IN SCIENCE JOURNALS

IMMUNOLOGY

B1 or B2? The BCR

decides

Immunological B cells are

generally divided into two major

subsets. B2 cells generate

specific antibodies against

foreign antigens in secondary

lymphoid organs. B1 cells, found

predominantly in the peritoneal

and pleural cavities, instead

produce “natural” antibodies

as part of the innate immune

system. Two models to explain

this split exist: the “lineage

model,” wherein both subsets

have distinct progenitors, and

the “selection model,” in which

fates are directed by different B

cell antigen receptors (BCRs).

Graf et al. provide support for

the selection model using a

transgenic system in which BCR

specificities can be changed.

Mature B2 cells differentiated

into functional B1 cells when

a self-reactive B1 BCR was

swapped in, in the absence of B1

lineage precommitment. —STS

Science, this issue p. 748

CERAMICS

Elastic ceramics

Aerogels hold promise as

lightweight replacements for

thermal insulation. However,

poor mechanical stability has

hampered progress in moving

toward commercialization. Xu

et al. designed a mechanical

metamaterial that pinches in a

small amount when you com-

press it (see the Perspective by

Chhowalla and Jariwala). This

is characteristic of materials

with a negative Poisson’s ratio

and dramatically improves

mechanical stability. The trick

was using three-dimensional

graphene structures to tem-

plate the ceramic aerogels,

thus producing a superinsu-

lating material endowed with

excellent mechanical proper-

ties. —BG

Science, this issue p. 723;

see also p. 694

SURFACE SCIENCE

A path through a crowd

Catalytic reactions on surfaces

occur at pressures at which

the surfaces are completely

covered with adsorbed mol-

ecules. It would seem that this

arrangement would interfere

with reactants encountering

one another through diffusion

processes. Henß et al. used

high-speed scanning tunnel-

ing microscopy to follow the

diffusion of oxygen atoms on a

rubidium surface that was fully

covered with carbon monox-

ide (CO) molecules (see the

Perspective by Magnussen).

Oxygen-atom diffusion was

unexpectedly fast. A theoretical

model revealed that CO diffu-

sion appears to open pathways

for oxygen-atom movement.

—PDS

Science, this issue p. 715;

see also p. 695

DEVICE TECHNOLOGY

Low-power organic

transistors

For internet-of-things applica-

tions, transistors that deliver

high signal amplification (high

ROBOTIC NAVIGATION

There’s no place

like home

G

PS is not always available, let

alone perfect. Dupeyroux et al.

created the six-legged AntBot,

which integrated multiple data

sources—but not GPS—to track

its position. This was inspired by the

multisensory homing method of desert

ants, which does not use pheromones

because of the destructive desert

heat. After a random walk, AntBot

went directly back to its starting point

by combining tracked distance with

directional data from two sensors that

polarized and detected light. AntBot

is sensitive to ultraviolet light, which

means it can get home even under a

cloudy sky. —RLK

Sci. Robot. 4 , eaau0307 (2019).

Reversible isomerization in

magic-size nanoclusters

Williamson et al., p. 731

AntBot f nds its way

home without using GPS.

15 FEBRUARY 2019 • VOL 363 ISSUE 6428 703

Published by AAAS