Features

As part of efforts to understand the impact of the ash cloud from Iceland's Eyjafjallajökull volcano an Oxford team have been using LIDAR to search for airborne ash over southern England.

LIDAR sends pulses of coherent light up into the sky and measures scattered and reflected light from any particles or debris floating in the air. From timing the 'echoes' it can determine not only the presence of material but also measure its height and thickness.

Last week Adam Povey, of Oxford University's Department of Physics, was scrambled to STFC's Chilbolton Observatory in Hampshire to use a system, jointly operated by both Oxford University and Hovemere Ltd, to see if any sign could be detected of the ash cloud passing over southern England.

By last Friday his measurements could detect a thin layer of material at around 3km altitude (c10,000 feet up), part of which slowly descended over the following couple of hours before merging with echoes from other debris at the top of a convection layer (the Planetary Boundary Layer) around 3,000 feet up. Below that height, the air is full of all sorts of other debris, including human-generated pollution, so is difficult to untangle from the volcanic ash.

Since then Adam, part of Don Grainger's group at Atmospheric, Oceanic and Planetary Physics, and the team have continued to monitor the cloud and are publishing updates of the latest information and images online.

Andy Sayer, another member of the Oxford team, told me: 'From the satellites we're getting the 'big picture' of what's happened over Europe over the course of the past week or so, although because of the way the satellites sample the revisit time for any one location can be a couple of days.'

'From this we can estimate the light extinguished by the ash, and learn about the size of the particles, as well as measuring the amount of sulphur dioxide released during the eruption and where that's going.

'The lidar, on the other hand, is giving us a continuous profile of any ash at one site (Chilbolton) and we can see how distinct any layers are and how they're mixing with the rest of the atmosphere.'

Tomorrow at 2pm Susan Cheyne will be updating listeners to Radio Oxford on the progress of her conservation work in Borneo.

Susan, of Oxford University's WildCRU, is leading research into the agile gibbon and wild cat species for the OuTrop project.

We've blogged about her work before, including the amazing images and sounds of gibbons swinging through the trees and how camera traps set up in the forest have snapped photos of elusive species, such as the clouded leopard.

Above are a selection of the latest photos from her work: this year, the 8th they have been studying orangutans and the 7th agile gibbons, has seen the birth of 2 orangutans and 3 gibbons in the groups studied.

The project is hoping to make a real difference, not just to the forest apes but to the overall ecology of the rainforest: Susan has already raised over £7,000 to provide equipment to help combat forest fires and this year the team have started the first ever long-term regeneration project to re-forest the degraded peatland.

They are also offering a new training programme for the project's Indonesian staff to help pass on the skills needed to continue and expand the scientific and conservation work.

On Thursday she'll be explaining more about her research, and how members of the public can help, at an event at Science Oxford.

Dr Susan Cheyne is a member of the WildCRU, part of Oxford University's Department of Zoology.

Oxford start-up Plink Search Ltd has become the first UK company to be purchased by Google Inc.

The firm was founded in 2009 by Mark Cummins and James Philbin, two graduate students from Oxford University’s Department of Engineering Science, to commercialise technology stemming from their doctoral research.

‘Mark and I were both involved in developing visual search during our DPhils,’ James tells me. ‘Mark's research focused on visual place recognition for robot navigation, which culminated in the FabMap software. My own research looked at how visual search could be scaled robustly and efficiently to handle millions of consumer images crawled from sites such as Flickr.’

During their doctoral research, with supervisors Paul Newman and Andrew Zisserman, they realised that, although they were approaching visual search from different angles, their combined skills could reap dividends: making it possible to build a visual, rather than text, search engine that could power a mobile phone application.

James comments: ‘Our research really showed that large scale, accurate visual search was possible even with the poor imaging conditions of mobile phone cameras.’

‘By the end of our DPhils it was clear there was a great commercial opportunity,’ Mark explains. ‘The fact that there were two of us in the same lab with matching expertise and an interest in starting a company was pretty ideal.’

They decided to form a company to develop an application that could recognise art work from photos taken by mobile phones, using the FabMap code licensed from Isis Innovation as a starting point. Mark tells me: ‘It was a good baseline to start building Plink. The technology that a robot uses to recognise places versus how we do painting recognition on a mobile phone is really very similar.’

The start-up went from strength to strength with the PlinkArt application winning first prize in Google's Android Developer Competition, which identified the best applications for the Android phone operating system. It was announced today on the company blog that Plink Search is the first UK firm to be bought by Google.

‘We're both delighted with the acquisition and very pleased to be moving to Google,’ James reveals. ‘Being engineers at heart, working at Google will allow us to tackle some really interesting large scale vision problems with the computing power to back up our ambition!’

So how did their DPhil at the Department of Engineering Science prepare them for life as high-tech entrepreneurs?

Mark tells me: ‘I think doing a DPhil is actually a great route into starting a company. You get very deeply into some interesting technology, but at the same time you have the space to keep an eye on what's happening in the market.’

‘At heart we're engineers and absolutely did our DPhils for the love of it, but we were always aware of the commercial possibilities too. I think starting a company feels much more like a natural continuation of doing a DPhil than taking a job would be.’

A team, including Oxford University scientists, has achieved a new record for storing and retrieving data from an optical quantum memory, our friends PhysOrg.com report.

The researchers achieved a data rate in excess of 1GHz, 100 times what is possible with existing quantum memories, they explain in Nature Photonics. Such a speedy memory would be a key component of any future quantum computing or communications device.

The result was achieved by firing pulses of thousands of photons encoded with data into a cesium vapor cell. The vapor turns the pulses into a spin wave, and the information can be retrieved by a read pulse that converts the spin wave back into an optical signal that is picked up by a detector.

Ian Walmsley, of Oxford University's Department of Physics, told PhysOrg's Lisa Zyga: 'There are a few steps that are required [to achieve high bandwidth], but the main approach is to use atoms with a higher energy storage state, and to apply more sophisticated control pulse methods.'

'Our plans are to demonstrate the operation of the memory at the quantum limit, using an external source of nonclassical light.'

The team note that the bandwidth was limited only by the response time of the detector, so in theory the quantum memory could be capable of even larger bandwidths. Their method, based on a Raman interaction, could be applied to other storage media (such as cold gases and solid state).

Ian adds: 'Challenges for the future in general are to increase the number of bits the memory can store and the readout efficiency of the memories to the point when they can be used in applications such as quantum communications links.'

In films and books black holes capture unwary spaceships and planets, gobble up whole galaxies or offer portals to other parts of the Universe.

So the idea that, with the start of the Large Hadron Collider (LHC), physicists finally had a machine powerful enough to, potentially, create ‘mini’ black holes caused some alarm.

But what do we really know about black holes? And how would a ‘mini’ one be different from their giant cousins lurking out there in space?

‘The simplest black holes are objects with a singularity in the centre and that are surrounded by an ‘event horizon’,’ explains Cigdem Issever of Oxford University’s Department of Physics. ‘Once something comes closer to the black hole than the radius of the event horizon, it is not able to leave: even light can’t escape and so the name ‘black hole’ was given to these objects by John Archibald Wheeler back in 1967.’

A hole in the Sun
Producing black holes turns out to be about mass (energy): squeeze mass into a sphere with a radius equal to what’s known as the ‘Schwarzschild radius’ – a threshold beyond which gravity causes an object of a certain density to collapse in on itself – and a black hole will form.

‘In fact the size of the Schwarzschild radius is directly proportional to the amount of mass that is squeezed in, as well as being directly proportional to the strength of gravity,’ Cigdem tells me.

‘For example, in order to form a black hole out of our Earth, you would need to squeeze its mass into a sphere about the size of a marble (radius 8.9 mm). By comparison the Schwarzschild radius of the sun is about 3 km.’

So what would happen if we swapped our Sun for a black hole?

‘If we replaced our Sun with a black hole of the same mass, surprisingly, not much would change in our solar system. The planets’ orbits would stay the same because the gravitational field that the black hole would produce would be exactly the same as that of the Sun. Although, admittedly, the solar system would be a bit dark and cold!’

But Cigdem’s interest in black holes isn’t theoretical, as a particle physicist she will be searching for signatures of ‘mini’ black holes in the LHC collisions:

‘I became interested in them as a particle physicist back in 2003 because extra dimension models predicted that they may be produced in high-energetic cosmic rays and, if so, even in particle accelerators. If we are really able to produce them, they could give us experimental insights into quantum gravitational effects.’

She hopes that studying them may lead to a formulation of a theory of quantum gravity: marrying Einstein’s theory of general relativity (which describes gravity on large scales) with quantum mechanics (which describes physics at very small distances).

The LHC is colliding protons on protons. These protons are made up of smaller constituents, the so called ‘partons’ which are actually the particles the LHC is colliding. The Schwarzschild radius of two colliding partons – quarks and gluons for example – at the LHC is at least fifteen orders of magnitudes below the Planck length - the smallest distance or size an object can achieve in our conventional universe.

‘This means that, in conventional models of physics, there is no way a black hole could be produced in a collision of two partons. However, there are models on the market suggesting that the strength of gravity could become significantly larger at very small distances, up to 10 to the 38th [10 with 38 zeroes] times stronger,’ she comments.

‘If this is true then the Schwarzschild radius of two colliding partons becomes large enough that, at the LHC centre-of-mass energy, two partons passing each other at their Schwarzschild radius is not so unlikely anymore. So, we may be able to produce microscopic black holes after all.’

Who's afraid of a 'mini' black hole?
So what would these tiny black holes be like? Should we be worried about them?

Cigdem tells me: ‘According to Stephen Hawking, they will not be that black in fact. They will evaporate with time approximately following a black body radiation spectrum. The evaporation rate will be inversely proportional to the black hole mass.’

‘Astronomical black holes are so massive that their evaporation rate is negligible. In contrast, mini black holes are hot: unimaginably hot. The core of our Sun is at around 15,000,000 degrees Kelvin - to get close to the temperature of a mini black hole you would need to add another 42 zeroes.’

‘What this incredible temperature means is that mini black holes of tiny mass ‘evaporate’ into the far, far colder space around them almost infinitely fast. Their expected lifetime is around one octillionth of a nanosecond – so that they pop out of existence again almost as soon as they are created.’

If they do appear they will almost instantaneously burst into many particles which the ATLAS detector should pick up.

‘These particles will have very striking features. The total energy deposited in the detector will be of the order of a few TeVs [Tera electron volts] and the number of final state particles will be large. Black hole signatures can hardly be imitated by any other new physics so, if they are being produced, it will be hard to miss them,’ Cigdem adds.

So the hunt begins: on 30 March the LHC is aiming for collision energies of 7 TeV that may enable us to see some quantum gravity effects for the first time.

At the beginning of this year Dr Cigdem Issever moved to CERN to coordinate the efforts of the ATLAS Exotics physics group.

Read more about this topic in What black holes can teach us by Sabine Hossenfelder and the LHC Safety Assessment Group report.