23 March 2013 | NewScientist | 17

World’s thinnest scope revealed

THIN as a human hair and with a resolution four times that of similar devices, the world’s slimmest endoscope could soon visualise the parts other scopes cannot reach.

Endoscopes are used to look inside the body, and usually consist of a bundle of fibres that transmit light and images. Joseph Kahn at Stanford University, California, and colleagues have now created one out of just a single optical fibre. Usually, single fibres scramble the light signal, so the team developed an algorithm to reconstruct images.

Currently, the prototype can show objects 2.5 micrometres in size – a third of the diameter of a red blood cell – but the team reckons it will be able to improve the resolution to 0.3 micrometres.

The endoscope could be used to observe brain activity in minute detail or to detect cancer cells (Optics Express, doi.org/ktc).

“Just as the telecoms industry has devised ways to squeeze more information content through optical fibres, this team have done the same for medical endoscopy,” says Stephen Boppart at the University of Illinois at Urbana-Champaign.

Mid-sized quantum computer could solve mystery of primesA MILLION-DOLLAR puzzle relating to prime numbers could be tackled using only a mid-sized quantum computer.

There is a race to find ever bigger primes, but no one can predict when the next one will pop up. One way to measure their distribution is via a formula that calculates how many exist below a number, X. The Riemann hypothesis says this is possible for every X. But though a proof is worth $1 million in prize money from the Clay Mathematics Institute, no one has yet managed

to produce one. Mathematicians instead find ways to count primes below ever bigger values of X and compare these to the Riemann prediction to see if any disagree. The record so far has been to count the primes below a septillion. It took three months to crunch the sums; for a number with an extra zero, it would take nine months.

Now a team led by José Latorre of the University of Barcelona in Spain has devised the first quantum algorithm to count primes (arxiv.org/abs/1302.6245). Quantum computers should be

HOLLYWOOD director James Cameron found little evidence of life when he descended 11,000 metres to the deepest point in the oceans last year. If only he had taken a microscope.

Ronnie Glud at the University of Southern Denmark in Odense and his colleagues dispatched autonomous sensors and sample collectors into the Mariana trench in the western Pacific. Every cubic centimetre of mud they brought back contained, on average, 10 million microbes – about 10 times more than mud collected from a plateau at the top of the trench. The Mariana microbes

were also twice as active (Nature Geoscience, doi.org/kts).

At first glance, that is surprising. Life in the deep mostly relies on leftovers from the surface for food: detritus that slowly drops into the abyss. Just 1 per cent reaches the abyssal plateaus, so you might expect even less to get to the trench’s deepest point. In fact, says Glud, ocean trenches are particularly good at capturing this food. Their broad, steep slopes act as a funnel channelling it right down to the bottom – where it fertilises the bacterial zoo that Cameron missed.

Not dead! The abyss is a bacterial zoo

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faster than ordinary ones because their bits occupy multiple states at once, not just a 1 or a 0. But the largest ones built have just a handful of “qubits”, so this speed gain has not been practically realised.

Using the Latorre algorithm, smashing the record for primes would require an 80 qubit computer. That’s bigger than any that exist today but much smaller than the 1000-bit beast required for the famous quantum algorithm, Shor’s, to beat the record for factorisation.

Swallows evolve anti-vehicle wings

NATURE, red in wheel and fender. Birds in Nebraska have evolved shorter wings, which may help them avoid dying on roads by taking off quickly and darting away from cars.

Eighty million US birds are killed by traffic each year. Cliff swallows (Petrochelidon pyrrhonota) have taken to nesting on road bridges, so may be especially vulnerable.

Charles Brown of the University of Tulsa in Oklahoma has been picking up dead swallows for 30 years. Roadkill numbers have steadily declined since the 1980s, even as the number of roadside nests has risen. The killed birds have longer wings than birds caught in mist nets for research, and on average the caught birds’ wings have got shorter (Current Biology, doi.org/ktv).

It makes sense: shorter wings are better for a quick vertical take-off, and improve manoeuvrability.

“Everything fits with the idea that it’s vehicular selection,” says Ronald Mumme of Allegheny College in Meadville, Pennsylvania.

The swallows are the latest case of humans influencing evolution. Fish are maturing more quickly because of commercial fishing, and two formerly diverging populations of Darwin’s Galapagos finches seem to be collapsing back into one now that food from bird feeders is replacing their natural diets.

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