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TOP: EFREN NAVARRO-MORATALLA. BOTTOM: DAVID M. PHILLIPS/SCIENCE SOURCE
January/February 2018^ DISCOVER^41
One Magnet to Bind Them All
❯
A FRENZY FOR TWO-DIMENSIONAL MATERIALS
kicked off in 2004 with the creation of
graphene — made from just a single layer, or
monolayer, of carbon atoms. Researchers have since
made monolayers of metals, semimetals, insulators
and more, but magnetism was the final holdout. In
June, Xiaodong Xu of the University of Washington
published results of the first isolated monolayer
magnet in Nature.
The new magnet, made of chromium triiodide
(CrI 3 ), has some curious properties, just like previous
2-D materials. A single layer of CrI 3 crystals was
magnetic, but two layers were not. Yet when a third
layer was added, the magnetism reappeared. Future
applications could use this quirk to switch between
magnetic states in computers — difficult using
current technology — to improve computer memory.
It’s unlikely CrI 3 itself will end up in commercial
devices. It reacts strongly with water and oxygen,
evaporating within seconds of being exposed to air.
But Xu has high hopes the discovery will lead to new
fundamental physics. “What we’re really looking for
is anything beyond what we can imagine,” he says.
“I’m sure it’s there.” SYLVIA MORROW
Making Blood Cells in the Laboratory
❯
SCIENTISTS HAVE TAKEN
A MAJOR STEP forward
toward making artificial
blood by creating blood stem cells
in the lab.
In two studies reported in Nature
in May, teams at Harvard University
and Weill Cornell Medicine at Cornell
University created hematopoietic stem
cells (HSCs). These mature into blood’s
essential components: platelets,
white blood cells and red blood cells.
HSCs also generate a lifetime of
blood cells, which must be continually
replenished. When the body fails
to restock, life-threatening forms of
anemia, lethal infections or serious
bleeding disorders can emerge.
To make the HSCs, the Harvard
group used human skin cells to
create induced pluripotent stem
cells (iPSCs), adult cells researchers
genetically reprogram to an
embryonic-stem-cell state, where
they can grow into any kind of cell.
Adding seven transcription factors
— proteins that switch on genes —
the team then converted the IPSCs
into immature HSC-like cells.
The Weill Cornell researchers’
process was more direct: Four
transcription factors prompted
adult mouse endothelial cells,
which line the inside of blood
vessels, to turn into HSCs.
Either approach could produce
enough HSCs to transplant and —
pending further safety testing —
potentially treat leukemia, sickle
cell disease and other severe blood
disorders. Says George Daley, a stem
cell biologist who led the Harvard
study: “It’s a real scientific advance
and brings us closer to making
customized cells we can transplant
without worrying about rejection.”
LINDA MARSA
Experts created artificial blood stem cells,
the precursors to white and red blood
cells (shown here) and platelets.
A single layer of chromium
triiodide (chromium atoms
in gray, iodine in purple)