18 | NewScientist | 15 June 2013

EVERY one of us has a superpower. Shave off the very tip of your finger or toe and it should grow back. Now we know how.

Like amphibians, humans can regenerate skin and bone, but unfortunately our powers of regeneration are limited to the ends of our fingers. It’s a trick we share with mice, so to find out how we do it, Mayumi Ito at New York University and her

colleagues took a closer look at mouse digits.

Using a cell-labelling technique, the team identified a previously unknown population of stem cells at the base of each toenail. Tests showed that these “nail stem cells” help with ordinary nail growth, but can also rebuild the entire digit tip after amputation.

We already know that the skin

Comet Lovejoy’s magnetic message

AS DEATH-DEFYING comet Lovejoy plunged into the sun’s corona, it wagged its tail – a sign that such “sungrazers” can act as probes of this unexplored region.

The magnetic field in the sun’s atmosphere, or corona, controls the solar wind and solar eruptions but the region is too hot for spacecraft to enter. Luckily, there’s a family of comets that isn’t afraid to plunge in. In 2011, Lovejoy became the first to dive through the corona and emerge intact.

Now a team led by Cooper Downs of Predictive Science in San Diego, California, reveals that Lovejoy’s tail, which turned from ice to plasma as the comet passed through, moved erratically compared with the comet’s path. That suggests the wiggling is caused by the corona’s magnetic field (Science, doi.org/msk). By applying the wiggle to competing models of the field, the team hopes to find the most accurate one.

Under starter’s orders – cheetahs versus Usain Bolt

IT TURNS out cheetahs aren’t that fast after all. It’s their acceleration that leaves everything else in the dust.

“Everyone thinks cheetahs run at incredibly high top speeds, over 60 miles (97 kilometres) per hour, but these measurements were made with imprecise speedometers,” says Alan Wilson of The Royal Veterinary College at the University of London. Plus, they were made on animals raised in captivity, unaccustomed to hunting.

In the quest for better data, Wilson designed solar-powered collars with GPS trackers, accelerometers, gyroscopes and other bits of kit to get a snapshot of life

Win

frie

d S

chä

fer

/im

ageb

roke

r/f

LPa

in brief

Regeneration is at our fingertips plays a pivotal role in triggering amphibian limb regrowth. The new results suggest the same is true of our ability to regrow fingertips (Nature, DOI: 10.1038/nature12214).

“We at least partly retain the mechanisms that operate limb regeneration in amphibians,” says Ito. “Knowing more about how nail epidermal cells induce digit-tip regeneration may provide direct clues to extend our ability for regeneration.”

on the savannah, and fitted them on three females and two males. The fastest speed recorded was 93 kph, but the team was surprised to find their cheetahs tended to run at a more moderate 54 kph. What made them such good hunters was their ability to accelerate up to 3 metres per second and decelerate by 4 mps in a single stride (Nature, DOI: 10.1038/nature12295). The muscle power required to generate this acceleration was four times what Usain Bolt used for his 100-metre world record.

“Cheetahs don’t run particularly quickly,” says Wilson. “Their success is more a matter of the manoeuvring and acceleration.” The impala, gazelles and other animals they prey on are agile, and the final moments of a hunt are often played out with an intricate to-and-fro of footwork, rather than a flat-out race.

PASTA helps marathon runners keep the pace – and maybe some spinning stars too.

Rapidly rotating neutron stars called pulsars should slow down over time as they radiate energy. But lone pulsars appear to settle at a rate of about 12 seconds per spin.

José Pons at the University of Alicante in Spain and colleagues ran simulations of pulsars with different crust configurations. Those with lumpy crusts slowed to between 10 and 20 seconds and stayed steady at that rate (Nature Physics, DOI: 10.1038/nphys2640).

Pons says the lumps could help the stars retain energy. They may be made of a jumble of “nuclear pasta” – nuclei in the dense crust that are forced into exotic shapes like spaghetti and macaroni.

‘Nuclear pasta’ lets pulsars twirl

130615_N_In Brief.indd 18 11/6/13 09:38:59