27 October 2012 | NewScientist | 15

Immunity down to a sense of good taste

NEVER mind the bitter end – it is the bitter beginning of an infection that triggers an immune response.

We know that taste receptors on the tongue detect bitter foods, but there are also identical taste receptors in the upper airway. Noam Cohen at the University of Pennsylvania in Philadelphia and his team think they know why.

They grew cell cultures from sinus tissue samples collected from surgical patients, and found that bitter taste receptors in the tissue picked up the presence of Pseudomonas aeruginosa, a bacterium that can cause pneumonia. The sinus tissue responded by producing nitric oxide to kill the invading microbes (Journal of Clinical Investigation, doi.org/jj4).

“Certain people have strong innate defences against these bacteria, which is based on their ability to detect bitterness,” says Cohen. “Others who don’t really ‘taste’ these bitter compounds have a weakened defence.”

The research could lead to nasal sprays designed to activate the taste receptors and boost people’s natural defences against sinus infections.

Recycled quantum bits break algorithmic recordREUSING old computer parts sounds like a terrible way to boost processing power, but it has enabled a quantum computer to smash an algorithmic record.

Anthony Laing and colleagues at the University of Bristol, UK, have used recycled quantum bits, or qubits, to carry out a quantum calculation known as Shor’s algorithm on a larger number than ever before. The algorithm exploits quantum mechanics to simplify the factorisation of numbers into their prime components – a hard task for

ordinary, classical computers when the numbers get really large. However, until now, the largest number factorised using Shor’s algorithm was 15.

Part of the difficulty in reaching higher numbers is creating enough qubits to do the job. Laing used a photon as the qubit – he realised it was possible to split the algorithm into parts and run one part at a time on a single photon. Reusing the photon like this slows things down, but for huge numbers it should still be much faster than a classical computer.

SQUIDGY would describe most frogs, but male Otton frogs have a spiky side. They get into vicious scuffles that leave them badly scarred, thanks to retractable claws stashed in their pseudothumbs.

While most frogs have only four toes on their forelimbs, the Otton frog (Babina subaspera) has evolved pseudothumbs on its front feet. When Noriko Iwai of the University of Tokyo, Japan, captured wild frogs, she found that males have longer and thicker pseudothumbs than females.

Each pseudothumb conceals a bony spine which can be pushed out the

front, puncturing the skin. Males are more likely to do this than females, which prefer not to use them.

The males use them to fight and mate, says Iwai. Competing males leap on each other and wrestle face to face. As they do so they jam their spines into each other, ripping flesh. Mating males also use the spines to keep a tight grip on females, wounding them in the process (Journal of Zoology, doi.org/jj6).

Iwai thinks the spines evolved to help males mate with females – which are much smaller than them – and were later co-opted for fighting.

‘Wolverine frog’ makes its point

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The team factorised the number 21, a record for Shor’s algorithm but far from the large numbers needed if quantum computers are to become more useful than their classical counterparts (Nature Photonics, doi.org/jkf ). Laing hopes the technique will help quantum computers reach this point.

However, the ability to factorise numbers with more than about 300 decimal digits would be deadly for cryptography methods that depend on the difficulty of factorising large numbers.

Titan created by giant moon clash

LURKING among the icy moons of Saturn, the giant moon Titan is like a monstrous copy of Earth. Frigid lakes and black dunes made of hydrocarbons lie under a choking atmosphere of organic smog. Now it seems that, like Earth, Titan was built from several smaller bodies smacking together and merging to become a planetary chimera.

The discovery also hints that the creation of Titan spawned icy minions – a family of mid-sized moons unlike anything else in the solar system. The work was presented on 17 October at the annual meeting of the American Astronomical Society’s Division of Planetary Sciences in Reno, Nevada.

Erik Asphaug of the University of California, Santa Cruz, and colleagues think the Saturn system evolved like a planetary nursery, with proto-moons emerging from a disc of ice-rich, orbiting material.

In their model, Saturn starts out with a family of four large moons, similar to Jupiter’s four biggest moons. Computer simulations show that, as these young moons settle into stable orbits, their gravity pulls them towards each other and they go through a series of collisions.

As the final two big moons merge to create Titan, they liberate some icy material from their mantles, which spins outwards and congeals into the mid-size moons seen today.

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