Science - USA (2022-04-15)

258 15 APRIL 2022 • VOL 376 ISSUE 6590 science.org SCIENCE

and other applications.

Fine-scale features and

good transparency are often

required. Toombs et al.

combined microscale com-

puted axial lithography with a

photopolymer-silica nanocom-

posite to synthesize fine glass

parts. They were able to create

optical components, truss and

lattice structures, and three-

dimensional microfluidics

structures. This method should

be flexible enough to provide

a wide variety of high-quality

glass parts for many different

applications. —BG

Science, abm6459, this issue p. 308

Edited by Michael Funk

IN SCIENCE JOURNALS

ARCHAEOLOGY

Dating an ancient Maya calendar

A

260-day divinatory calendar known as the
tzolkin was used across much of Mesoamerica in
antiquity, but dating its origins has proven to be
difficult. Stuart et al. report on the discovery of a
painted mural fragment bearing the hieroglyphic
date “7 Deer,” a day in the calendric cycle, at the Late
Preclassic period Maya site of San Bartolo, Guatemala.
The fragment with the glyph, along with 10 other
examples of text on other fragments, was obtained
from a secure archaeological context dated between
300 and 200 BCE. This is the earliest evidence of the
260-day calendar known from the Maya region and
is at least 150 years older than previous estimates of
its age. —MSA Sci. Adv. 10.1126/sciadv.abl9290 (2022).

Mural fragment from a Late Preclassical Maya site
with a hieroglyph corresponding to a calendar date

RESEARCH

PHOTOS (LEFT TO RIGHT: STUART

ET AL

.; NA

ET AL.

Hydrogel actuators

with a semipermeable

membrane move quickly

and withstand loads.

HYDROGELS

Wrap it up
Conventional stimuli-responsive
hydrogel actuators generally
suffer from weak actuation
force and slow response speed
because of the osmotic-driven
actuation mechanism. They
are also limited in how much
pressure they can endure and
will collapse or shatter if pushed
too hard. Na et al. signifi-
cantly increased the actuation
stress of a hydrogel by wrap-
ping the gel in a relatively stiff
but flexible semipermeable
membrane, which confined the

transverse deformation (see the

Perspective by Jiang and Song).

This effect is similar to the turgor

pressure seen in biological cells.

The actuation speed can also be

enhanced by adding the electro-

lyte into the water solution and

applying an electric field, which

reduces the actuation time from

hours to minutes. —MSL

Science, abm7862, this issue p. 301

see also abo4603, p. 245

3D PRINTING

Fabulous fabrication

Glass is an important material

for micro-optics, microfluidics,

ORGANIC CHEMISTRY

Controlled release

of amine reactants

The formation of carbon–

nitrogen bonds is a key step

in the synthesis of numerous

pharmaceuticals and related

compounds. However, it is often

not feasible to use the most

direct nitrogen-bearing precur-

sors because they inhibit metal

catalysts at high concentration

through strong coordination.

Ali et al. report a creative way

around this problem for allylic

amination reactions. Most of the

nitrogen reactants are protected