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Home » Page 1473

Giant Faraday rotation spotted in graphene

The polarization of light can be rotated by almost 6° as it passes through a single sheet of graphene in a magnetic field, according to an international team of physicists. This latest property of graphene – a sheet of carbon just one atom thick – was unexpected because large rotations normally occur only in much thicker materials. The scientists believe that this newly discovered property of graphene could be exploited in new devices that switch light using electric and magnetic fields.

The fact that the polarization of light can rotate as it travels through a material exposed to a magnetic field is, of course, nothing new. Physicists have long known that it is to do with that fact that right- and left-circularly polarized light can propagate at different speeds. It means that when linearly polarized light passes through such a material, the right and left components of the light interfere such that the polarization is rotated by a certain angle when it emerges.

But because the size of this “Faraday angle” is proportional to the thickness of the material, graphene – being just one atomic layer thick – was not expected to generate a large rotation. However, Alexey Kuzmenko and colleagues at the University of Geneva have found that the material can twist the polarization of light by 0.1 radians, or about 6°. Researchers at the Fritz Haber Institute in Berlin and the University of Erlangen-Nueremberg – both in Germany – and the Lawrence Berkeley Laboratory in the US were also involved in the work.

A big surprise

According to Kuzmenko, the team made its discovery while using infrared light to study aspects of the quantum Hall effect in graphene. “We didn’t expect to see a large [rotation] in graphene,” he says “We expected to see a rotation of about 0.01 radians and instead we saw 0.1 radians.” The result means that graphene has a bigger Faraday rotation per atomic layer than any other material – beating out its nearest semiconductor rivals in the infrared by a factor of 10.

The team measured the Faraday rotation by passing infrared light through a polarizing filter to create a linearly polarized beam. This beam was then sent through a graphene sample with a magnetic field perpendicular to its surface. After the light emerged, it was passed through a second polarizing filter and on to a detector. If the polarizations of the two filters are exactly 90° apart, no light should be detected. But if the polarization of the light is rotated as it passes through the graphene, the angle at which no light is detected will be shifted by the Faraday angle.

Unusual orbits

The physicists believe that the large rotation is a result of graphene’s electrons behaving as if they have no mass. When subjected to a magnetic field, the electrons occupy a spectrum of circular “cyclotron” orbits that is very different to that found in other materials. Transitions between these orbits affect the circular polarization of the transmitted light and result in a much enhanced Faraday angle.

According to Kuzmenko, the effect could be used to create switches in which light can travel in one direction, but not in the opposite direction. These optical diodes, known as “Faraday isolators”, are not currently available for infrared light.

One important benefit of making such magneto-optical devices from graphene is that the direction of the Faraday rotation can be reversed by simply applying an electric field to the graphene. In other materials, in contrast, this is only possible by reversing the applied magnetic field, which is a slower and more complicated process. The reason, according to Kuzmenko, is graphene’s unique ability to change the sign of its charge carriers from negative to positive by simply applying an electric field.

Future photonics and optoelectronics

Andrea Ferrari of the University of Cambridge in the UK believes that this newly discovered optical property of graphene is yet more evidence that the material’s future lies in photonics and optoelectronics. “The Faraday effect and the associated magneto-optical Kerr effect are widely used in optical communications, data storage and computing,” he told physicsworld.com. “These, combined with the [other known] properties of graphene, could lead to uniquely performing devices.”

There are, however, several challenges involved in making practical devices. One is that about 10 independent layers of graphene would be needed to achieve a rotation of about 45° – which would be required in practical devices. Another problem is that graphene absorbs infrared light, which would lead to significant signal loss in devices.

The research is published in Nature Physics doi: 10.1038/NPHYS1816.

US loses status as a ‘colossus of science’

The US is no longer a “colossus of science” according to a new report looking into the country’s scientific output. Written by information-services provider Thomson Reuters, it says that although the US still holds a “commanding” lead in terms of its research impact, its forerunner status is being eroded. The report blames this on a rapid rise in scientific publishing from countries in Asia and Europe.

The report, released yesterday, notes that the Asia-Pacific region has now overtaken the US in terms of published papers and spending on research. In 2008 the US invested $384bn while Asian countries invested $387bn in total, and while researchers in the US published around 310,000 papers in 2009, over 330,000 were published by scientists in the Asia-Pacific region.

In the physical sciences, the report notes that investment in physics and engineering in the US has “taken a back seat” compared to the biological science at a time when countries in Asia are increasing their spending on research in the physical sciences. “In physics, the trend for the US in terms of world share is distinctly downward,” says the report.

Materials decline

The report also warns that while some counties, such as the UK, have maintained their share of the world’s scientific output while faced with growing global competition that fraction in the US has fallen. Indeed, the report highlights research into materials science as one particular area of decline. In 1994 the US published nearly a third of all papers in materials research but this has now reduced to 15%, while China now publishes 23% of papers, and the 27 nations that make up the European Union (EU) publish around 30%.

“Considering the recent rapid acceleration of physics output in China the data in the report is no surprise,” says Werner Marx, an information scientist from the Max Planck Institute for Solid State Research in Stuttgart, Germany. “Europe is already beginning to match the US’s performance in terms of citation impact and the question now is how rapidly countries in Asia will catch up”.

However, it is not all gloomy news. The report says that the current state of scientific research in the US remains strong, with “excellent academic institutions that are a magnet for the best minds worldwide” and that the US provides “significant” funding in research and development, which stood at 2.8% of Gross Domestic Product in 2009.

The Thomson Reuters report into the impact of US research comes days after the United Nations Educational, Scientific and Cultural Organization released its Science Report 2010. The report, which is published every five years, says that China is now “a hair’s breadth” away from having more researchers than the US and the EU and that it now publishes more scientific articles than Japan.

‘Super-twisted’ light swirls into view

Researchers at the University of Glasgow in the UK are the first to have created “super-twisted light” in the lab. The light is so-called because it has a high degree of circular polarization and could be used to detect minute quantities of biological molecules in solution. Indeed, super-twisted light could help scientists study the proteins responsible for neurodegenerative diseases such as Alzheimer’s or Parkinson’s.

Most biological molecules have a certain chirality (right- or left-handedness) and this intrinsic property can be used to detect biomolecules in “chiroptical” spectroscopic techniques such as circular dichroism, optical rotatory dispersion and Raman optical activity. Here, scientists typically measure the small differences when left- and right-circularly polarized light interacts with a chiral sample. In circularly polarized light, the electric field vector rotates around the direction of propagation creating a right- or left-handed helix.

Although widely employed, these techniques are not all that sensitive because chiroptical effects are inherently weak. As a result, the techniques can only be used to study samples containing relatively high concentrations of target molecules. Recently, researchers put forward the idea of using “super-twisted” light in such techniques to increase sensitivity. This light has a greater level of chirality than that of ordinary circularly polarized light because it is twisted much “tighter”. However, the problem was that, until now, no-one knew how to create it in the lab.

Gammadions of gold

Malcolm Kadodwala and colleagues produced their super-twisted light by shining ordinary light through a specially designed metamaterial made up of chiral gold nanoparticles. The metamaterial comprises left- or right-handed gold gammadions 400 nm long and 100 nm thick deposited on a glass substrate and arranged in a square lattice with a periodicity of 800 nm.

The light produced allowed the team to detect certain proteins at picogram levels, a sensitivity a million times greater than that possible with current chiroptical techniques. “We are very excited about the research,” says Kadodwala. “This light, which does not occur naturally, allows us to detect biological molecules at unprecedented low concentrations.”

The light seems to be particularly effective at detecting amyloid proteins – insoluble molecules that stick together to form plaques. These plaques are thought be responsible for certain neurodegenerative diseases. “In fact, super-twisted light is highly sensitive to the secondary, or beta, structure of a protein,” Kadodwala told physicsworld.com. “Beta structure is found in the coat proteins of certain viruses and in amyloid fibrils.”

The researchers reported their work in Nature Nanotechnology doi:10.1038/nnano.2010.209.

Galaxy Zoo paper goes supernova

By Hamish Johnston

In 2007 a group of astronomers launched Galaxy Zoo with the aim of harnessing people power to classify galaxies.

The idea is that the general public would scan telescope images of galaxies and classify their shapes. Astronomers simply don’t have the time to analyse the hundreds of thousands of galaxy images that are gathered robotically and Galaxy Zoo was a great success.

The Galaxy Zoo team launched several more projects including Galaxy Zoo: The Hunt for Supernovae, which enlists the public in the search for exploding stars.

Now, Galaxy Zoo has published its first scientific paper on supernovae. Nearly 14,000 supernova candidates were classified by more than 2500 individuals within a few hours of data collection.

You can read all about the results here.

LHC sees its first ZZ event

The Large Hadron Collider (LHC) at CERN in Geneva has produced its first pair of Z bosons, based on data released by the compact muon solenoid (CMS) collaboration. Seeing this first pair is an important step in the giant collider’s hunt for the Higgs boson because the generation and analysis of many more such events could provide one of the key signatures of the elusive Higgs.

Believed to provide all particles with mass, the Higgs boson is the last missing piece of the Standard Model of particle physics. The LHC, designed to collide protons into one another at energies of up to 14 TeV, is expected to find the elusive boson – assuming that the Higgs does indeed exist.

Evidence for the Higgs will not come as a single observation. Instead, physicists must accumulate data related to the energy distribution of the particles that the Higgs decays into. One of the cleanest such decay signatures is the transformation of the Higgs into two Z bosons – particles that are one of the carriers of the weak nuclear force. The Z bosons then decay into pairs of heavy charged particles known as muons, which leave an unmistakable footprint in a detector such as CMS.

Layers of particle sensors

Now, the first such event at the LHC has been seen by CMS – one of the collider’s two enormous general-purpose detectors. CMS consists of concentric layers of particle sensors placed inside and around the bore of a 4 T superconducting magnet. Any Z bosons produced by the proton–proton collisions at the centre of the bore are too short-lived to be detected by the surrounding instrumentation. However, the muons last for long enough to travel out from the collision point and traverse all of the detector’s inner sensors. They then travel through a number of gas-filled layers revealing their trajectory via the ionization of this gas. Moving charged particles are bent by a magnetic field such that the curvature of the muons’ paths reveals their momentum.

The CMS data, obtained in the early hours of 24 September, clearly reveal the tracks of four muons (see figure). And the masses of these muons, grouped into two pairs, result in values for the mass of the Z of just over 92 GeV, which is very close to the known Z mass. CMS collaboration member Tommaso Dorigo of the University of Padova in Italy is delighted with the result, describing it on his blog as “as beautiful as they get, or even more so”.

No Higgs required

But Dorigo says that this result on its own provides no evidence that the Higgs boson exists. He points out that pairs of Z bosons can be produced directly by the proton collisions and do not require the intermediate creation of the Higgs. Indeed, he says that this is likely to be the reaction that took place in this case. Showing that the Higgs exists will involve observing many such ZZ pairs and then plotting the distribution of the mass of the pairs. If the pairs are produced in only the direct reaction, then this distribution should be fairly flat; but if instead the Higgs is involved, then the distribution should instead show a peak at a particular value – the mass of the Higgs.

Predicting how many data are likely to be needed to prove that this peak exists, and therefore how long the machine will have to run for before the Higgs is found, is difficult because the fraction of ZZ events that would result from the decay of the Higgs depends on its mass, which is not known from theory. Above about 180 GeV – the combined mass of two Zs – the Higgs can readily decay into a Z-pair, but at lower masses it would be far more likely to decay into other particles that are not so easy to detect.

“For a given Higgs mass we know how many Z pairs, and therefore how many muon quadruplets, we should produce,” says Dorigo. “But since we don’t know the mass, the fraction of muon events that is due to a Higgs could be lower than a tenth or as high as a few tenths.”

Don’t speculate, accumulate

Dorigo is reluctant to speculate on when he and his colleagues might finally bag the Higgs. But in very round terms, he says that about 100 pairs of Zs are likely to be needed, which, he believes, means about 100 times the amount of collision data collected so far. This would be about five times the amount of data that would be accumulated before the collider is due to be switched off for an upgrade to full energy at the end of 2011, meaning that conclusive evidence of a Higgs decay to ZZ pairs before then is unlikely (although other decay signatures might enable a discovery with fewer data).

However, ATLAS team member Andy Parker of Cambridge University in the UK points out that the Fermilab’s Tevatron accelerator in the US could have its lifespan extended to 2014, which might prompt CERN to delay the upgrade for a year. He says that any decision on whether to extend the current run will depend on how well the accelerator performs next year, but he believes that “this year has gone exceptionally well” and that CERN “could still decide to run in 2012”. Either way, he says, the latest CMS result shows that the LHC’s experiments “now have enough data to begin the Higgs search in earnest”.

The work is described in this presentation from the CMS collaboration

Honeycomb windows that could harvest the Sun

A materials science breakthrough in the US and Taiwan could lead to a new type of window that can harness the power of the Sun. The newly created transparent material can efficiently capture photons to generate electricity thanks to its honeycomb structure, which blends the properties of a semiconductor polymer with those of a carbon-rich fullerene.

The chosen polymer, P1, is efficient at absorbing photons, which causes electrons and holes within the material to combine into bound states known as excitons. The role of the fullerene – which is a compound formed when a large number of carbon atoms form ball-shaped molecules – is to then undo this process by dissociating the electrons and holes. Suitably placed electrodes can then extract the charges to produce photocurrents.

Mircea Cotlet, one of the researchers based at Brookhaven National Laboratory near New York City, told physicsworld.com that the biggest challenge was finding a way to merge the polymer and fullerene into a honeycomb lattice. His team achieved this by creating a flow of micron-sized water droplets across a thin layer of the polymer/fullerene solution. Water droplets then self-assemble into large arrays within the solution. Once the newly formed solution has evaporated it leaves behind a hexagonal honeycomb pattern over a large area of the polymer, which the researchers observed using scanning probe and electron microscopy.

“Though such honeycomb-patterned thin films have previously been made using conventional polymers like polystyrene, this is the first report of such a material that blends semiconductors and fullerenes to absorb light and efficiently generate charge and charge separation,” says Cotlet.

A window of opportunity

Cotlet is keen to stress that the idea behind the study was to explore the basic science and to develop self-assembly methods that do not require intense laboratory infrastructure. He reveals, however, that his team now intends to develop the work by implementing the honeycomb into devices and carrying out a number of tests. Among the applications that could spring from the work are optical displays and devices, including transparent solar cells.

Another possibility is to incorporate the honeycomb films into windows. As the polymer chains gather mostly at the edges of hexagons, the films would remain mostly transparent with remaining chains spread thinly across the hexagon centres. “Imagine a house with windows made of this kind of material, which, combined with a solar roof, would cut its electricity costs significantly. This is pretty exciting,” says Cotlet.

It is not yet clear how much electricity these windows could generate but it will not be enough to keep a building self-sustained. “At the end, you have a window in any house, why not get some electricity out of it?” says Cotlet.

The research is described in a research paper in Chemistry of Materials.

Hubble successor hit by budget setback

NASA boss Charles Bolden has announced sweeping changes to the management of the $5bn James Webb Space Telescope (JWST) after an independent report called for the space agency to tackle budget overruns and delays to what is one of NASA’s flagship missions. The report by the seven-member JWST review panel, chaired by John Casani from NASA’s Jet Propulsion Laboratory, also says that the telescope will require an additional funding boost of $1.5bn if it is to launch by late 2015.

The JWST, which was due to be launched in 2014, is designed to study the formation of stars and galaxies and examine the physical and chemical properties of solar systems. It will do this by using four onboard instruments – consisting of cameras and spectrometers – that are cooled to only a few degrees above absolute zero by liquid nitrogen.

JWST is mainly a NASA project with collaboration from the European Space Agency and the Canadian Space Agency. But since its conception in the late 1990s the telescope has increasingly eaten into NASA’s resources, consuming around 40% of the agency’s $1bn astrophysics budget in 2010. The review into the JWST was initiated in June by Democrat senator Barbara Mikulski from Maryland over concerns about schedule delays and cost overruns.

Management changes

In its report, the panel notes that the JWST is in “very good technical shape”, saying that cost increases and schedule delays have been caused by “budgeting and program management, not technical performance”. But in a separate letter sent by Casani to Bolden, Casani suggested that the project’s organization needed to be restructured and called for the way the JWST programme is independently assessed to be improved.

The organizational changes to the JWST’s management, announced by Bolden, will involve assigning a new senior manager at NASA headquarters as well as a programme director who will have both technical and cost staff working alongside them. “No-one is more concerned about the situation we find ourselves in than I am,” Bolden states. “I am disappointed we have not maintained the level of cost control we strive to achieve.”

To enable the telescope to launch by September 2015 at the earliest, the panel has called for an extra $1.5bn on JWST’s budget, requiring $250m to be added in 2011 and 2012 and the remainder at a later date. The report notes that the additional funding must go “hand-in-hand” with management changes.

The JWST will have a 6.5 m diameter mirror, consisting of 18 hexagonal folding mirror segments that are each 1.3 m in diameter, giving the telescope a total collecting area of 24 m2. The telescope will operate for around 10 years in an orbit 1.5 million km away from Earth, at a point in space called Lagrange Point 2.

Nanoribbons make good memories

A new memory cell made of an extremely narrow graphene “nanoribbon” has been unveiled by researchers in Germany, Switzerland and Italy. An important benefit of the new cell is that it can be made much smaller than a conventional silicon cell, resulting in memory chips with much greater storage density than silicon-based devices.

The most important property of a memory chip is its capacity, that is, the amount of information it can store. To satisfy the demand for more powerful computers, the capacity of memory chips per chip area (also known as their storage density) has been increasing exponentially over the last 20 years – so obeying Moore’s law.

Storage density ultimately depends on the size of a unit memory cell (the smaller the better), which stores one bit of information, 0 or 1. Preserving Moore’s law will thus depend on how good scientists are at fabricating ever smaller unit memory cells. Graphene – a 2D sheet of carbon just one atom thick – is a promising material in this respect thanks to its exceptional electronic and mechanical properties because it could allow devices smaller than 10 nm to be made. 10 nm is around the dimension at which devices based on silicon reach their limits.

Reaching the 10 nm scale

Roman Sordan of the Politecnico di Milano and colleagues in Stuttgart and Lausanne have now reached the 10 nm scale by making a memory cell based on graphene nanoribbons – the form of graphene that has the smallest possible area. “Indeed, the area of our new memory cell is so small that it allows for a very high storage density,” Sordan said. “We thus expect that graphene nanoribbon memory chips will allow Moore’s law to continue for the foreseeable future.”

The team fabricated graphene nanoribbons by depositing V2O5 nanofibres atop graphene and then etching the sample using an argon ion beam. The ion beam removes any graphene not protected by the nanofibres. This simple method forms graphene nanoribbons underneath the nanofibres, which are subsequently removed.

Very narrow nanoribbons

The advantage of using nanofibres as etching masks is that the technique can produce very narrow nanoribbons that are less than 20 nm wide. The ribbons also have smoother edges that those made by standard lithography. Rough edges usually degrade the characteristics of a device.

Another advantage of using V2O5 fibres is that they can easily be removed once the ribbons have been patterned – you just need to flush the sample with water, which is a simple and environmentally friendly process, said Sordan.

The researchers found that gate voltage pulses of opposite signs can switch the device between digital on (bit 1) and off (bit 0) states. After the device flips, it remains in the new state even after the gate voltage is reset – that is, it can “remember” its state. “This memory effect probably originates from charges surrounding the nanoribbons, which are trapped by water molecules adsorbed on the SiO2 substrate on which the devices were made,” explained Sordan. “The nanoribbons possess a memory effect most likely due to a simple mechanism by which water vapour from the air attaches to the hydrophilic substrate and then traps charges in the vicinity of the nanoribbons.”

Small and very fast

The device has a transition time (the time a device needs to flip its memory state once triggered) that is three orders of magnitude shorter than that of previously reported memory devices made from either graphene or carbon nanotubes. The transition time is directly related to the highest frequency at which the device can be clocked. This means that the shorter the transition, the higher the clock rate – an important point because memory devices not only need to be small but also very fast, says Sordan.

“Our memory cells are also very robust and versatile,” he added. “They can be used as both static random access memories and nonvolatile flash memories cell for ultrahigh storage density applications.”

The researchers, who have published their work in Small, will now try to develop digital logic gates based on graphene nanoribbons – the other important class of devices needed to realize all-graphene computers. “We have already made graphene logic gates but think that those made from nanoribbons will be better.”

LHC now fully fledged heavy metal collider

  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
  • Courtesy: CERN
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  • Detlef Kuchler, a physicist in CERN's beams department, holds a piece of the lead source material used to create heavy ions for the LHC. (Courtesy: M Brice/CERN)

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In the early hours of Sunday morning, the first collisions between lead ions were recorded at the Large Hadron Collider (LHC) at CERN. The complete transition from protons to lead took just four days, after the final proton beams of 2010 were extracted from the LHC last Thursday.

“The speed of the transition to lead ions is a sign of the maturity of the LHC,” says Rolf-Dieter Heuer, CERN’s director-general. “The machine is running like clockwork after just a few months of routine operation.”

The development marks the beginning of the main physics programme for the ALICE experiment, which has been designed specifically for heavy-ion collisions and is seeking to recreate the conditions that existed just 10–11 s after the Big Bang. At this time, the energy in the universe was so concentrated that protons and neutrons could not hold together – instead, space began to be filled with a dense soup of subatomic particles known as quark–gluon plasma.

Strong but mysterious

One of ALICE’s main scientific goals is to characterize the quark–qluon plasma in an attempt to find out more about the nature of the strong force, one of the four fundamental forces in nature. Despite being responsible for generating 98% of the mass of atoms, the strong force is still the most poorly understood of the forces.

To do this, the detector was specifically designed to track large numbers of particles. It can detect up to 15,000 particles per event, which may be produced from the collisions between lead nuclei occurring in the centre of the detector.

These images show the first collisions, recorded yesterday by ALICE’s innermost detector, the Inner Tracking System. The shaded structures represent a perspective view of the detector elements; and the lines are the reconstructed particle trajectories with the colour scale indicating the energy of the particles. As expected such collisions produce an unprecedented number of particles, reaching 2500–3000 charged particles per collision.

Mini Big Bangs

“We are thrilled with the achievement!” says David Evans, leader of the UK team at the ALICE experiment. “The collisions generated mini Big Bangs and the highest temperatures and densities ever achieved in an experiment.”

Lead ions within the LHC are colliding with a centre-of-mass energy of 2.76 TeV per colliding nucleon pair, which generates temperatures in the region of 10 trillion degrees. The temperatures and densities are an order of magnitude larger than the previous record held by the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory in the US.

CERN engineers will now spend up to a week tuning the beamlines in preparation for the scientific programme. Evans and his fellow researchers will then record data until 6 December when CERN will shut down for maintenance work over Christmas. Operation of the collider will start again with protons in February and physics runs will continue through 2011.

Listening to the sounds of slippery slopes

Transport networks and vulnerable communities at the bottom of slopes could benefit from a landslide early warning system that monitors the noise levels within soil. Claimed to be the first of its kind in the world, it works by monitoring sound to establish whether a large-scale slip is imminent so that measures can be taken.

Worldwide, many thousands of people die each year as a result of slope failures and many others are left homeless without access to basic supplies. In more developed countries, the risk to people’s lives tends to be smaller but the impact on the built environment costs billions of dollars to repair each year, and it can be highly disruptive to transport networks. In an attempt to limit this global hazard, the United Nations has drawn up a strategy, which includes a plan to promote the development of early warning systems.

One way to monitor the risk in real-time is to equip a slope with an array of microphones and to “listen” for increased noise levels as soils begin to move. The trouble with this method is that the relatively low frequencies associated with large-scale slope movements can also be produced by a number of other environmental sources – leading to an unacceptable number of false alarms.

But researchers in the UK believe they can offer a more reliable acoustic monitoring system through an interesting spin on the technique. Instead of positioning acoustic sensors directly onto the slope, they place their microphones within steel tubes that are then in-filled with granular material. Then, if slopes do begin to slip, the sounds produced by the jostling granular material are at higher frequencies than those generated by the surrounding soil. The steel tubes act as a waveguide to amplify the sound.

Field trials

To test its device, the team led by Neil Dixon at Loughborough University carried out a series of tests at Hollin Hill, an active landslide in northern England. By comparing its measurements with traditional slope measurements taken using an inclinometer, Dixon’s team says it found strong correlation between acoustic emission and slope displacement. “Hollin Hill provided us with a controlled environment to test our device, the next stage is to trial this on different types of slope and eventually use it as a means of predicting landslides,” explains Dixon.

Vulnerable people are often more exposed to the risk of landslides and other hazards, due to a lack of knowledge or lack of choice 

Ed Phillips, Practical Action

In the short term, Dixon’s team is seeking to work with railways, buses and other transport companies, which currently account for more than half of the purchases of landslide monitoring systems in the UK. “At present, most systems require a person to go out into the field to check a monitoring device – we are offering a system that can relay information in real-time, for example a text message,” says Dixon.

If the technique can become established, Dixon hopes that the technology can be transferred to developing countries, particularly to tropical regions where heavy rainfall and earthquake activity can leave slopes vulnerable to failure. Dixon envisages a simplified version of the system where the acoustic microsensors are connected to an audible alarm system rather than an electronic communications network.

The development is welcomed Ed Phillips, a spokesperson at Practical Action, a charity that promotes technology for development, who points out that people in the developing world are often more vulnerable to landslides. “Vulnerable people are often more exposed to the risk of landslides and other hazards, due to a lack of knowledge or lack of choice – for example building their homes on steep slopes.”

More landslides to come

According to many climate researchers, the frequency and extent of landslides could increase dramatically in certain parts of the world in the coming years. “It is fair to say that a changing climate could include more extreme rainfall events, and those in turn could lead to more landslides,” says Tim Lenton, an earth systems researcher at the University of East Anglia, UK.

This is a view shared by Richard Jardine, a geomechanics researcher at Imperial College London. “It will probably be greatest in degrading permafrost regions. The impact may be greatest in high mountain areas – Alps, Andes, Himalayas etc – or in regions with weak rocks and soils, such as parts of Siberia, Alaska or Canada. And also in warmer areas where we have steep slopes and high rainfall already such as Central America, Brazil, or China,” he says.

This research is part of an ongoing project involving Loughborough University and the British geological Survey called: assessment of landslides using an acoustic real-time monitoring system (ALARMS).

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