Features

A question put to an Oxford physicist by one of his students has led to the invention of a cheap domestic wind turbine that gets the most out of variable wind power.

As this Guardian article explains John Gregg of Oxford University's Department of Physics specialises in spintronics and magnetic instrumentation but, as part of an introductory physics course, a student asked: How can an induction motor work as a generator?

In trying to find a satisfactory answer John discovered that the sort of simple induction motor used in many domestic appliances could be turned into a cheap machine for turning wind energy into power.

The real breakthrough came when he realised that the heating elements in hot water tanks aren't bothered about variable voltages or frequencies - one of the barriers to manufacturing cheap and efficient conventional wind turbines. He told The Guardian's Michael Pollitt: 'That's why we can make it cheaply and why it performs well because we are not handcuffed by the necessity to deliver 240V 50Hz.'

At the heart of the turbine is a 7.5kW induction motor that generates power continuously, feeding it into the home hot water system with any surplus energy channelled into central heating through a heat exchanger.

John explained: 'Because the generator is configured as a constant power source and acts effectively as a generator and a continuously variable electronic gearbox, the turbine aerofoils operate on the peak of their performance curves at all times, and all the power they deliver is harvested and channelled to the load. So, the diminished wind power that you get at low altitude is used to maximum effect.' 

The team who worked with John to develop and patent the new turbine through Oxford's Oxford University Innovation (they are currently setting up a spinout called RenewOx) believe that the system could generate up to 60 per cent of a household's domestic energy needs.

The turbine could be mass-produced for a very low manufacturing cost and could potentially pay for itself in between 3-7 years (a massive improvement over conventional turbines that take up to 50 years to pay for themselves).

As John comments, this just goes to show how teaching smart undergraduates can challenge tutors and inspire exciting new projects - and that those who shun undergraduate teaching to concentrate on research just might be missing out.

The turbine was developed by John Gregg and built by Reg Bendall of the Clarendon Laboratory. It uses a 10 kilowatt set of blades supplied courtesy of Eirecomposites.

New calculations suggest that the halos caused when dark matter particles collide could be frequent enough to help us detect them within a year.

The team, including Joseph Silk of Oxford University's Department of Physics, detailed their findings in a recent Science Express paper reported by PhysOrg.com.

Previous studies had suggested that such quantum collisions - termed annihilations - would be few and far between, and so the gamma rays they emit would be hard to pick up even by orbiting satellite telescopes such as NASA's Fermi.

But the team's analysis of data from previous observations picked up more collisions than expected. They theorised that this might be down to an attractive force, the Sommerfeld effect, pulling dark matter particles more closely together and so making collisions more likely.

By applying these new calculations to a model of a dark matter cloud the size of our Milky Way the researchers were able to predict that Fermi should be able to detect a few subhalos caused by these collisions in its first year of operation, and find at least ten after five years.

Such observations would give the first direct evidence for the existence of dark matter - something that would rate as one of the all-time great physics discoveries.

The work was carried out by Michael Kuhlen of the Institute for Advanced Study in Princeton, Piero Madau of the University of California, Santa Cruz, and Joseph Silk of the University of Oxford.

As BBC Online and New Scientist report methane is disappearing from Mars far faster than it vanishes on Earth, but why?

This is the big question posed by the French research behind these reports published in this week's Nature.

But, although the researchers gather the suspects - life, volcanism, an unknown natural process - in the drawing room like a scientific episode of Agatha Christie's Poirot, the findings get us no closer to knowing who the real culprit is.

Fred Taylor of Oxford's Department of Physics, for one, isn't clear what's new here: 'We have known for some time that the photochemical lifetime of methane on Mars is too long to be consistent with the recent measurements,' he tells us.

'Therefore there must be another sink for methane on Mars, probably oxidising material like peroxides and perchlorates in the soil. It would actually be surprising if this were not the case, as this new paper recognises near the end.'

He goes on to point out that it's also not news that there's little chance of life near the surface of Mars, which is why all planned missions aim to dig deep into the Martian soil to look for telltale signs of biological activity.

Fred adds: 'What is interesting is that there is methane there in the first place. Whatever its source, it is probably being vented from well below the surface, and if it isn't a biological source it still must be something interesting like geothermal activity or small cometary impacts.'

Improvements in electron microscopy have enabled scientists to see how materials made from carbon can rapidly change their structure atom by atom.

An international team led by Oxford University scientists report in this week’s Nature Nanotechnology how they used new advanced electron microscopy to image carbon atoms in graphene, a material that is of particular interest because of its remarkable electronic properties.

The new state-of-the-art electron microscopes commercially available are fitted with a special component that reduces aberrations and this produces images with higher resolution.

'It is important to be able to image carbon based molecules and nanostructures in real time in order to track their motion. Nature has constructed life based on carbon atoms and man-made synthetic carbon nanomaterials are the future of nanotechnology applications,' said Jamie Warner of Oxford University’s Department of Materials, lead author of the paper.

'However, carbon atoms are particularly hard to image because they are light and structures they are arranged in are so easy to destroy using high energy electron beams.’ 

‘We were able to use a lower energy electron beam in an electron microscope and adjust the imaging conditions to enable fast frame acquisition (12 per second) at a magnification of 2 million times. That’s about 10 times faster than anyone has managed before.’

This enabled the team to monitor a variety of shape and structural changes occurring in graphene, which is the key to some of the material’s unusual properties.

Jamie told us: ‘The way in which the low energy electrons interacted with graphene layers was unique. Normally, high energy electrons punch many holes through layered graphene sheets, however in our case the low energy electrons eroded single sheets of graphene one by one and smoothed out the edges of the material.'

'This opens new insights into the creation and modification graphene structures which may lead to improvements in their utilization in electronic devices.’ 

The research was carried out by a team including scientists from Oxford University, IFW Dresden (Germany), the STFC Rutherford Appleton Laboratory, and Imperial College London.

Technology designed by scientists at Oxford University and Leeds University can learn British Sign Language (BSL) signs from overnight TV broadcasts by matching subtitled words to the hand movements of an on-screen interpreter.

The work [detailed here] is a crucial step towards a system that can automatically recognise BSL signs and translate them into words.

A major challenge in recognising signs is to track the signer’s hands as they move on the broadcast – no mean feat as these can get lost in the background, blur or cross – and the arms can assume a vast number of configurations.

The system tackles this problem by overlaying a model of the upper body onto the video frames of the signer by looking for probable configurations, finding the large number of frames where these can be correctly identified and then ‘filling in the gaps’ to infer how the hands get from one position to another.

Another big challenge is to match a target word that appears in a subtitle to the corresponding sign – particularly difficult as words and signs often appear separated in time and words can be signed in many different ways so the corresponding sign may not appear at all.

To overcome this problem the system compares a small number of sequences in which the target word appears in the subtitles with a large number of sequences in which it does not.

Within this footage it then finds the 7-13 frames that appear often in the ‘target word’ sequences and infrequently in the ‘no target word’ ones. This enables it to learn to match over 100 target words to signs automatically.

'This is the first time that a computer system has been able to learn signs on its own and on this scale in this way - with just the information available in the broadcast’s subtitle information and video frames and without the need for humans to give it annotated examples of what each sign looks like,’ said Andrew Zisserman of Oxford University’s Department of Engineering Science who led the work with Patrick Buehler at Oxford and Mark Everingham of Leeds University’s School of Computing.

Mark Everingham said: ‘It demonstrates the sort of very tough problems which advanced image recognition technology is starting to be able to solve. These technologies have the potential to revolutionise the automated searching, classifying and analysis of moving and still images.’

This research was supported by the Engineering and Physical Sciences Research Council, Microsoft and the Royal Academy of Engineering.