Monday, 30 April 2007

Solid light gains weight in future technology

The properties of light in a solid-like state as formed the basis for a new theory said to have potentials in future electronics.

By studying light with tools more commonly used to study matter, researchers have developed a theory that shows that the interactions of photons can be similar that of a solid.

"Solid light photons repel each other as electrons do. This means we can control photons, opening the door to new kinds of faster computers," said Andrew Greentree, a physicist at the University of Melbourne.

"Many real-world problems in quantum physics are too hard to solve with today’s computers. Our discovery shows how to replicate these hard problems in a system we can control and measure," he said.

While photons of light do not normally interact with each other as strongly as the electrons currently used in electronics, the researchers have shown theoretically how to engineer a 'phase transition' in photons, leading them to change their state so that they do interact with each other.

Greentree said the solid light phase transition effect ties together two very different areas of physics, optics and condensed matter 'to create a whole new way of thinking'.

More information is available from the University of Melbourne’s press release.


Thursday, 26 April 2007

Astronomers find first habitable Earth-like planet

Astronomers have discovered the most Earth-like planet outside our Solar System to date, an exoplanet with a radius only 50 percent larger than the Earth and capable of having liquid water.

This exoplanet - as astronomers call planets around a star other than the Sun – is the smallest ever found up to now and it completes a full orbit in 13 days. It is about five times the mass of the Earth that orbits a red dwarf at a distance about 14 times less than the Earth is from the Sun.

However, as the red dwarf, Gliese 581, is smaller and colder than the Sun – and thus less luminous – scientists speculate that the planet nevertheless lies in the habitable zone, the region around a star where water could be liquid!

"We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius, and water would thus be liquid," explains Stéphane Udry, from the Geneva Observatory (Switzerland) and lead-author of the paper reporting the result.

"Moreover, its radius should be only 1.5 times the Earth’s radius, and models predict that the planet should be either rocky – like our Earth – or covered with oceans," he adds.

Artist's impression of the system of three planets surrounding the red dwarf Gliese 581 - ESO

"Liquid water is critical to life as we know it," avows Xavier Delfosse, a member of the team from Grenoble University (France). "Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X."

The host star, Gliese 581, is among the 100 closest stars to us, located only 20.5 light-years away in the constellation Libra. It has a mass of only one third the mass of the Sun. Such red dwarfs are intrinsically at least 50 times fainter than the Sun and are the most common stars in our Galaxy: among the 100 closest stars to the Sun, 80 belong to this class.

"Red dwarfs are ideal targets for the search for low-mass planets where water could be liquid. Because such dwarfs emit less light, the habitable zone is much closer to them than it is around the Sun," emphasizes Xavier Bonfils, a co-worker from Lisbon University. Planets lying in this zone are then more easily detected with the radial-velocity method, the most successful in detecting exoplanets.

More information is available from the European Space Observatory’s press release.


Tuesday, 24 April 2007

Carbon fibre heralds in cars of the future

Cars and aeroplanes in the near future could be lighter, stronger, safer, and more energy efficient with the use of carbon fibre materials currently in development by material scientists in Victoria.

The development could see a new generation of cars and aeroplanes with lower energy consumption and improved safety, scientists say.

“There are enormous benefits in converting steel and aluminium parts in cars to lighter materials, especially in fuel savings,” said lead researcher Bronwyn Fox of Deakin University's Centre for Material and Fibre Innovation.

“Using carbon fibre composites produces lighter cars. Lighter cars are more fuel-efficient. Carbon fibre has a higher stiffness to weight ratio than steel, but it also absorbs more energy per kilogram, with the potential to make cars lighter and safer," he said.

More information is available from Deakin University's press release.


Friday, 20 April 2007

Shock, awe, and science journalism

Airing the views of climate change sceptics in the media only serves to keep controversy boiling, scientists have told the World Conference of Science Journalists in Melbourne, Australia.

Kevin Hennessy, Australian scientist and lead author of the Intergovernmental Panel on Climate Change (IPCC) Working Group II report, said this week that media attention on "the view of a handful of climate change sceptics" amplifies their opinions and "implies that there is little agreement about the basic facts of global warming".

Speaking in a session about climate change reporting, he said editors and journalists have a duty to ensure that facts are presented in context. Balanced reporting, he said, "perpetuates the public's perception that scientists are in disarray, which is misleading in the case of climate change".

Geoff Love, vice chair of the IPCC Working Group II, said that the IPCC assessment reports ― from 1990, 1995, 2001 and February 2007 ― are strong evidence of "the coming together of the scientific community" and that emphasis on the sceptic view does not help public understanding of climate change.

Media coverage has not always reflected the consensus of the majority of the scientific community, said Ian Lowe, president of the Australian Conservation Foundation. "That only makes the public and political discussion more difficult," he said.

More information is available from the original article at


Thursday, 19 April 2007

Hydrogen combustion engine aims to reduce greenhouse emissions

Researchers in Melbourne are developing a low-cost hydrogen combustion engine and fuel tank, in efforts to help make hydrogen a real alternative to carbon dioxide-emitting fuels.

The project is being conducted by engineers at the University of Melbourne in conjunction with industry collaborators, Ford Australia and Haskel Australia.

"Ultimately this will open up a whole new market for not previously developed low-cost fuel efficient hydrogen-powered vehicles," said project leader Michael Brear, of the University’s school of Mechanical and Manufacturing Engineering.

Brear said a goal of the $3 million project, which is supported in part by State Government funding, is to build a Victorian-manufactured engine that should achieve the world’s highest efficiency for a hydrogen-fuelled internal combustion engine.

He said hydrogen is seen as a transport fuel of the future because its reaction with air does not produce carbon dioxide, a major cause of climate change.

Many proposed hydrogen fuelled vehicles, however, are viewed as excessively expensive and impractical due to limited compression and storage capacity.

"Existing storage methods such as pressurisation of hydrogen to 350-700 atmospheres, are excessively large, very heavy or unaffordable and do not show a clear path to meeting automotive requirements," he said. "We will investigate a novel approach to high density storage of hydrogen at pressures that allow use of conventional storage equipment."

More information is available from the University of Melbourne’s press release.


Wednesday, 18 April 2007

Sleep organises memories

We have usually quite strong memories of past events like an exciting holiday or a jolly birthday party. However it is not clear how the brain keeps track of the temporal sequence in such memories: did Paul spill a glass of wine before or after Mary left the party?

Previous findings from a research group headed by Jan Born at the University of Lübeck have confirmed the widely held view that long-term memories are formed particularly during sleep, and that this process relies on the brain replaying recently encoded experiences during the night. The same research group now provides evidence that sleep not only strengthens the content of a memory but also the particular order in which they were experienced, probably by a replay of the experiences in "forward" direction.

Students were asked to learn triplets of words presented one after the other. Afterwards they slept, whereas in a control condition no sleep was allowed. Later, recall was tested by presenting one word and asking which one came before and which one came after during learning. Sleep was found to enhance word recall, but only when the students were asked to reproduce the learned words in forward direction.

This finding shows that sleep associated consolidation of memories enforces the temporal structure of the memorized episode that otherwise might be blurred to a timeless puzzle of experiences.

Findings of the study are reported in the international online journal of the Public Library of Science, PLoS ONE


Tuesday, 17 April 2007

Chill out, live longer

A psychological study has linked neuroticism and mortality, suggesting that mellowing with age could help people live longer.

In the study, researchers tracked the change in neuroticism levels of 1,663 aging men over a 12-year period.

A neurotic personality was defined as a person with the tendency to worry, feel excessive amounts of anxiety or depression and to react to stressful life events more negatively than people with low levels of the trait. Neuroticism levels were measured using a standardized personality test.

Using the data gathered in the first analysis, researchers calculated the men's mortality risk over an 18-year period using the average levels and rates of change.

By the end of the study, half of those men classified as highly neurotic with increasing levels of neuroticism had died while those whose levels decreased or were classified as less neurotic had between a 75 percent and 85 percent survival rate.

"We found that neurotic men whose levels dropped over time had a better chance at living longer," said Dan Mroczek, an associate professor of child development and family studies at Purdue University, who conducted the study. "They seemed to recover from any damage high levels of the trait may have caused. On the flip side, neurotic men whose neuroticism increased over time died much sooner than their peers."

The study will be published in the print edition of the U.S. journal Psychological Science in late May. More information is available from Purdue University’s press release.


Monday, 16 April 2007

Cannabis could provide relief to stroke patients

Some mechanisms in the brain targeted by cannabis have been found to have potentials in countering brain cell damage after a stroke.

New research by scientists at the University of Otago in New Zealand has shown that the cannabinoid CB2 receptor appears in the rat brain following a stroke. The findings have been touted as a world-first, and were published recently in the international journal Neuroscience Letters.

The CB2 receptor is a protein produced in response to stroke as part of the body's immune response system. This response causes the inflammation that leads to damage in the area of the brain around where the stroke has occurred, according to John Ashton, a medical researcher at the University’s Department of Pharmacology and Toxicology.

"If the inflammation can be stopped or reduced then it offers the hope of reducing the extent of the damage caused by stroke - and CB2 offers a potential target for such a drug,” he said.

Ashton explained that the active ingredient of cannabis, THC, targets both the CB2 and the related CB1 receptors. But while THC has been known to have some positive effects for pain management, its use is currently severely limited because of how it triggers the psychoactive CB1 receptors in the brain.

"The aim would be to develop a drug that targets the CB2 receptor without affecting CB1," Ashton said, suggesting a pharmaceutical approach similar to that that has already been taken to develop codeine from heroin.

"Heroin and codeine share common targets, but by designing codeine in such a way that it eliminated the psychoactive side-effects seen with heroin, a therapeutically useful drug was developed. There is the potential to do the same with cannabinoids," he said.

Drugs targeting CB2 could also have potential therapeutic use in other conditions involving inflammatory damage to the brain, such as Huntington's Disease and Alzheimer's Disease. There may also be scope to use them in pain management.

More information is available from the University of Otago’s press release.


Friday, 13 April 2007

Harvard study uncovers soccer referee bias

Fans of football will be relieved by the findings of a new report soon to be released at Harvard University - all those hours in the stands cheering at the team and shouting at the referee have not been in vain.

A study by Harvard University professor, Ryan Boyko, has found evidence that supports a long-held assertion by fans of the game - that playing at home gives the extra push to ensure a victory.

Boyko himself is a life-long footballer on youth and amateur level, now turned football referee in the US College divisions. Feeling the pressure from the crowd he decided, together with his brother Mark Boyko, to look into whether this could be statistically proven.

"We decided to look into what research had been done before and found a number of studies suggesting that crowd noise can bias referees toward the home team but nothing that actually demonstrated it had real effects on the game," he said.

"The obvious difficulty being that it's difficult to show that it is the referees being biased as opposed to the away players playing dirtier or worse, but our idea was that if referee psychology was the culprit different referees would respond significantly differently to crowd noise and this is exactly what we found."

A look at the final table for the A-League last season shows that winners Melbourne Victory actually won more away games than home games - according to this study a damning verdict on their fans, or perhaps the fans of their away game opponents. The Victory won six home games and eight away games in the 2006-7 season.

But perhaps more importantly, the study also shows something far more worrying, that also the referees are prone to influence from the home crowd. The team playing at home is more likely to get a penalty kick than the opposing team.

"The most interesting revelation unrelated to referee home bias that we found was that how many cards a team received in a match seem to be most determined by how many cards opponents of the other team generally get, not on any characteristic of the particular team in question," Boyko said.

"Thus it seems that certain teams are better at drawing fouls from the other team and that this effect is more important even than a team's propensity to get in trouble themselves."

Another phenomenon in big league football that also can be explained by this study is a claim by fans of smaller clubs - that referees more often take the side of the bigger team. This might be true simply because bigger teams have bigger crowds. Crunching the numbers, Boyko's studies found that ten percent more goals were scored by a home team per 10,000 spectators.

"Teams that consistently draw more spectators do seem to have a bigger home advantage and our study was unable to definitively answer whether this was due to merely having more spectators or some other variable correlated with number of spectators, such as team or player reputations."

On a stadium like Old Trafford, where famous Manchester United just this week played a stunning 7-1 win against Italian number-twos Roma, this means almost 75,000 spectators, or an output of no less than 0.75 goals per match.

In the Asian Champions League and the European Champions League, the home advantage is taken into account in the tournament regulations with the so-called away-goal rule. However, this does not officially relate to the home-bias refereeing revealed in Boyko's study, but to the pressure a team feels from playing on hostile grounds. A team in these tournaments that scores more away goals than its opponent in a knock-out game proceeds if the overall standing is a tie.

When it comes to doing something about the home-bias, Boyko says referee training and assessment could be effective. Any kind of video refereeing, meaning the game is stopped to make sure what really has happened is one of the most controversial debates in football today - some say it would make it more fair, others claim it would slow it down and take away the magic of the game. Boyko agrees that it probably wouldn't be worth it to implement full video refereeing, as is common in other forms of football.

"One relatively simple thing that could be done is installing goal line cameras such that a judge in a booth can review perhaps the most important decision of all - whether a goal has been scored or not. In this instance it could be done in a matter of seconds and probably wouldn't break up the flow of the game much. In other cases it might not be worth trying to move decisions away from the referee on the field as it might slow the game down too much and take away from the essence of the sport."

"These are questions that should be thought about intelligently and addressed by the governing bodies of professional and international soccer in light of the evidence from our study and others' studies," he said.

Reidar von Hirsch is a soccer enthusiast and freelance journalist in Sydney, Australia.


Thursday, 12 April 2007

Alien plants might not necessarily be green

Green, yellow or even red-dominant plants may live on extra-solar planets, speculate NASA scientists who believe they have found a way to predict the colour of plants on planets in other solar systems.

The scientists, whose reports appear in the March issue of U.S. journal, Astrobiology, studied light absorbed and reflected by organisms on Earth, and determined that if astronomers were to look at the light given off by planets circling distant stars, they might predict that some planets have mostly non-green plants.

Besides improving our understanding of life on Earth, the findings can potentially improve current methods of searching for life elsewhere in the universe, scientists say.

"We can identify the strongest candidate wavelengths of light for the dominant colour of photosynthesis on another planet," said Nancy Kiang, lead author of the study and a biometeorologist at NASA's Goddard Institute for Space Studies, New York.

Kiang and her colleagues calculated what the stellar light would look like at the surface of Earth-like planets whose atmospheric chemistry is consistent with the different types of stars they orbit. By looking at the changes in that light through different atmospheres, researchers identified colours that would be most favourable on other planets for photosynthesis, which is a process by which plants use energy from sunlight to produce sugar.

In the process of photosynthesis, plants convert energy from the sun into chemical energy in the form of glucose, or sugar - NASA Ames
Organisms that live in different light environments absorb the light colours that are most available. For example, there is a type of bacteria that inhabit murky waters where there is little visible light, and so they use infrared radiation during photosynthesis.

It has long been known that the chlorophyll in most plants on Earth absorbs blue and red light and less green light, so chlorophyll appears green. According to scientists, the Sun has a specific distribution of colours of light, emitting more of some colours than others. Gases in Earth's air also filter sunlight, absorbing different colours. As a result, more red light particles reach Earth's surface than blue or green light particles, so plants use red light for photosynthesis.

But not all stars have the same distribution of light colours as our Sun. Study scientists say they now realize that photosynthesis on extrasolar planets will not necessarily look the same as on Earth. Scientists expect each planet to have different dominant colours for photosynthesis, based on the planet’s atmosphere where the most light reaches the planet’s surface. The dominant photosynthesis might even be in the infrared.

"It makes one appreciate how life on Earth is so intimately adapted to the special qualities of our home planet and Sun," Kiang said.

More information is available from NASA's press release.


Wednesday, 11 April 2007

Power advancements in tiny electronics

Consumer electronics seem to be getting smaller by the day, with size becoming an increasingly poor indication of gadgets' power requirements and capabilities.

Computer scientists and engineers at the Virginia Commonwealth University are taking a new spin on data storage with the development of spin-based electronics, dubbed ‘spintronics’ for short. The technology is said to be able to supersede the limitations of Moore’s Law due to the lower energy requirements of storing information in the spin of an electron, instead of in its charge.

Electrochemists at the St Louis University are taking another approach to the issue of power. A research team is currently developing fuel cell technology that uses enzymes to extract energy from virtually any sugar source. This essentially means that any sugar solution, from soft drinks to plant sap, may soon be used to power portable electronics like cellular phones, laptops, and sensors.

Meanwhile, researchers at the Delft University of Technology are looking to make batteries smaller in order to improve their operation. A team of applied scientists are developing nanoscale batteries that are expected to deliver more usage between charges, and shorter charge/discharge times, to mobile consumers and users of electric vehicles within the next five years.


Tuesday, 10 April 2007

Maize farming found to predate Mayans by a millenium

New evidence has surfaced to suggest that ancient farmers in Mexico were cultivating an early form of maize, the forerunner of modern corn, about 7,300 years ago - 1,200 years earlier than scholars previously thought.

The findings expand on previous research that demonstrate the rapid spread of maize from southwest Mexico to the southeast and other tropical areas in the Americas, including Panama and South America.

Through an analysis of sediments in the Gulf Coast of Tabasco, Mexico, Florida State University anthropologist Mary Pohl concluded that people were planting crops in the ‘New World’ of the Americas around 5,300 B.C.

"This research expands our knowledge on the transition to agriculture in Mesoamerica," Pohl said. "These are significant new findings that fill out knowledge of the patterns of early farming.”

The shift from foraging to the cultivation of food was a significant change in lifestyle for these ancient people and laid the foundation for the later development of complex society and the rise of the Olmec civilization, Pohl said. The Olmecs predated the better known Mayans by about 1,000 years.

During her field work in Tabasco seven years ago, Pohl found traces of pollen from primitive maize and evidence of forest clearing dating to about 5,100 B.C.

Pohl's study analysed phytoliths - the silica structure of a plant - from traces of maize pollen that previous studies have found to date back to about 5,100 B.C. Her analysis puts the date of the introduction of maize in southeastern Mexico 200 years earlier than her pollen data indicated.

It also shows that maize was present at least a couple hundred years before the major onset of forest clearing. Traces of charcoal found in the soil in 2000 indicated the ancient farmers used fire to clear the fields on beach ridges to grow the crops.

"This significant environmental impact of maize cultivation was surprisingly early," she said. "Scientists are still considering the impact of tropical agriculture and forest clearing, now in connection with global warming."

The discovery of cultivated maize in Tabasco, a tropical lowland area of Mexico, challenges previously held ideas that Mesoamerican farming originated in the semi-arid highlands of Mexico and shows an early exchange of food plants.

A report on the results of the study will be published in the April 9-13 edition of the U.S. journal, Proceedings of the National Academy of Sciences. More information is available from the Florida State University’s press release.


Thursday, 5 April 2007

Brain’s breaking mechanism revealed

As wise as the counsel to ‘finish what you've started’ may be, it is also sometimes critically important to do just the opposite - stop. And according to a recent cognitive study, the ability to stop quickly, to either keep from gunning the gas when a pedestrian steps into your path or to bite your tongue mid-sentence when the subject of gossip suddenly comes into view, may depend on a few ‘cables’ in the brain.

Researchers led by cognitive neuroscientist Adam Aron, an assistant professor of psychology at the University of California, San Diego, have found white matter tracts - bundles of neurons, or 'cables', forming direct, high-speed connections, between distant regions of the brain - that appear to play a significant role in the rapid control of behaviour.

The study is the first to identify these white matter tracts in humans, confirming similar findings in monkeys, and the first to relate them to the brain's activity while people voluntarily control their movements.

"Our results provide important information about the correspondence between the anatomy and the activity of control circuits in the brain," Aron said. "We've known for some time about key brain areas involved in controlling behaviour and now we're learning how they're connected and how it is that the information can get from one place to the other really fast."

"The findings could be useful not only for understanding movement control," Aron said, "but also 'self-control' and how control functions are affected in a range of neuropsychiatric conditions such as addiction, Tourette's syndrome, stuttering and Attention Deficit Hyperactivity Disorder."

To reveal the network, Aron and a team of researchers from UCLA, Oxford University and the University of Arizona performed two types of neuroimaging scans on healthy volunteers.

They used diffusion-weighted MRI, in 10 subjects, to demonstrate the "cables" between distant regions of the brain known to be important for control, and they used functional MRI, in 15 other subjects, to show that these same regions were activated when participants stopped their responses on a simple computerized "go-stop" task.

Renderings of the brain’s "braking" network, viewed from the front and side. A cutaway of the right hemisphere reveals white matter tracts, or "cables," that connect three distant regions of the brain known to be important for controlling behaviour - David Flitney, Oxford University

One of the connected regions was the subthalamic nucleus, within the deep-seated midbrain, which is an interface with the motor system and can be considered a ‘stop button’ or the brake itself. A second region was in the right inferior frontal cortex, a region near the temple, where the control signal to put on the brakes probably comes from.

"This begs the profound question," Aron said, "of where and how the decision to execute control arises."

While this remains a mystery, Aron noted that an additional, intriguing finding of the study was that the third connected node in the network was the presupplementary motor area, which is at the top of the head, near the front. Prior research has implicated this area in sequencing and imagining movements, as well as monitoring for changes in the environment that might conflict with intended actions.

The braking network for movements may also be important for the control of our thoughts and emotions.

There is some evidence for this, Aron said, in the example of Parkinson's patients. In the advanced stages of disease, people can be completely frozen in their movements, because, it seems, their subthalamic nucleus, or stop button, is always ‘on’. While electrode treatment of the area unfreezes the patients' motor system, it can also have the curious effect of disinhibiting them in other ways. In one case, an upstanding family man became manic and hypersexual, and suddenly began stealing money from his wife to pay for prostitutes.

Examples like these motivate Aron to investigate the generality of the braking mechanism.

"The study gives us new targets for studying how the brain relates to behavior, personality and genetics," Aron said. "Variability in the density and thickness of the 'cable' connections is probably influenced by genes, and it would be intriguing if these differences explained people's differing abilities not only to control the swing of a bat but also to control their temper."

More information is available from the University of California’s press release.


Wednesday, 4 April 2007

Happy feet hit treadmills to track climate change

They may not be able to tap dance, but king penguins in the Antarctic could in fact have a role in monitoring the effects of climate change, new research suggests.

Scientists have long studied our changing environment in terms of unusual animal behaviour, such as altering patterns of fish and bird migration. Now, a research team from the University of Birmingham is finding out if the energy requirements of king penguins could be used as an alternative bio-indicator to monitor the health of the environment.

King penguins predominantly feed on a variety of fish called myctophid fish, explained bioscientist Lewis Halsey, who led the research on Possession Island in the South Indian Ocean. As the Southern Oceans warm, these fish tend to migrate further South, and away from the Islands inhabited by king penguins, he said, which makes hunting more difficult for the penguins.

“As the king penguins have to work harder to forage for the fish, their energy expenditure in doing so will increase,” Halsey said. “[This tells] us that the myctophid fish are changing location and becoming more sparse in areas of the Southern Oceans where king penguins forage.”

King Penguin - Lewis Halsey
King penguins are good candidates as bio-indicators for several reasons, the researchers say. Firstly, while at sea foraging, they cover hundreds of kilometres and are able to dive to depths of several hundred metres, so they explore a relatively large portion of the expansive Southern Oceans. Secondly, the diets of several populations of king penguins are well known. Thirdly, while foraging for food is done at sea the penguins also come ashore to breed and moult, making them accessible to researchers.

To ascertain the penguins’ energy requirements, researchers have implanted miniature heart rate data loggers into the birds. The penguins’ heart rates are then collaborated against energy expenditure under laboratory conditions, by getting the penguins to walk on a treadmill at different speeds. This data provides a correlation between heart rate and rate of energy expenditure, so any heart rate data subsequently obtained when the king penguins go to sea to forage can be used to estimate energy expenditure.

“We have deployed these loggers on birds for several years so we can look to see if the energy expended by king penguins from year to year is changing, which may give us information on the availability of myctophid fish in the Southern Oceans each year,” Halsey said.

More data is needed from the heart rate loggers during the next few years before any long term trends can be established. If the energy expended by king penguins at sea increases over time, it is likely that myctophid fish are getting harder to come by, which could be due to the warming of the Southern Oceans, Helsey said.


Tuesday, 3 April 2007

Hello, Hogwarts: invisibility cloak created

Researchers using nanotechnology have taken a step toward creating an ‘optical cloaking’ device that could render objects invisible by guiding light around anything placed inside the cloaked area.

The theoretical design uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked.

Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, a professor of electrical and computer engineering at Purdue University and one of the researchers developing the cloak.

The design does, however, have a major limitation: It works only for any single wavelength, and not for the entire frequency range of the visible spectrum, Shalaev said.

"But this is a first design step toward creating an optical cloaking device that might work for all wavelengths of visible light," he said.

Calculations indicate the device would make an object invisible in a wavelength of 632.8 nanometers, which corresponds to the colour red. The same design, however, could be used to create a cloak for any other single wavelength in the visible spectrum, Shalaev said, and could potentially cloak an area as large as a person or an aircraft.

"What we propose is the cloaking of objects of any shape and size," Shalaev said.

Images depicting scientific simulations (Cloak off, top. Cloak on, bottom) to show how objects might be "cloaked" to render them invisible - Birck Nanotechnology Center, Purdue University
Two requirements are needed to render an object invisible: Light must not reflect off of the object, and the light must bend around the object so that people would see only the background and not the cloaked object itself.

"If you satisfied only the first requirement of preventing light from reflecting off of the object, you would still see the dark shadowlike shape of the object, so you would know something was there," Shalaev said. "The most difficult requirement is to bend light around the cloaked object so that the background is visible but not the object being cloaked. The viewer would, in effect, be seeing around, or through, the object."

The device would be made of so-called ‘non-magnetic metamaterials’, which are synthetic materials that have no magnetic properties. Having no magnetic properties makes it much easier to cloak objects in the visible range but also causes a small amount of light to reflect off of the cloaked object, researchers say.

A key factor in the design is the ability to reduce the amount by which the material refracts light, so that its index of refraction is less than one. Refraction occurs as electromagnetic waves, including light, bend when passing from one material into another.

Natural materials typically have refractive indices greater than one. The new design reduces a refractive index to values gradually varying from zero at the inner surface of the cloak, to one at the outer surface of the cloak, which is required to guide light around the cloaked object.

Creating the tiny needles would require the same sort of equipment already used to fabricate nanotech devices. The needles in the theoretical design are about as wide as ten nanometers, or billionths of a meter, and as long as hundreds of nanometers. They would be arranged in layers emanating from a central spoke in a cylindrical shape.

Although the design would work only for one frequency, it still might have applications, such as producing a cloaking system to make soldiers invisible to night-vision goggles.

"Because night-imaging systems detect only a specific wavelength, you could, in theory, design something that cloaks in that narrow band of light," Shalaev said. Another possible application is to cloak objects from "laser designators" used by the military to illuminate a target, he said.

Researchers say that creating a cloak for rendering total invisibility in the entire visible spectrum would be a bigger challenge, requiring further advances in optical metamaterials and new combinations of nanotechnology with highly abstract ideas.

More information is available from Purdue University's press release.


Monday, 2 April 2007

Male circumcision to control HIV infection

The World Health Organization (WHO) and the joint United Nations Program on HIV/AIDS, UNAIDS, have recommended that male circumcision be added to approved interventions to reduce the risk of heterosexually acquired HIV infection in men.

The recommendation follows what was found to be compelling evidence of the benefits of male circumcision, as presented by three trials carried out on African men between the ages of 18 and 24.

One study was held in Kisumu, Kenya where an estimated 26 percent of uncircumcised men are HIV infected by age 25. The majority of the 2,784 HIV negative, uncircumcised men who participated in the study were Luo, an ethnic group that does not traditionally practice circumcision.

Half the men were randomly assigned to circumcision and half the men remained uncircumcised for two years. Participants received free HIV testing and counselling, medical care, tests and treatment for sexually transmitted infections, condoms and behavioural risk counselling during periodic assessments throughout the study.

The clinical trial, which was led by Robert Bailey, a professor of epidemiology at the University of Illinois, found that 47 of the 1,391 uncircumcised men contracted HIV, compared to 22 of the 1,393 circumcised men.

"Our study shows that circumcised men had 53 percent fewer HIV infections than uncircumcised men," said Bailey. "We now have very concrete evidence that a relatively simple surgical procedure can have a very large impact on HIV."

Two other trials, held in Uganda and South Africa, yielded similar results, indicating that circumcision effectively reduced the rate of new HIV infections by 48 to 60 percent.

But experts warn that countries should consider male circumcision as part of a wider HIV prevention package, including HIV testing and counselling services to prevent men developing a false sense of security.

Circumcised men may feel they are protected from becoming HIV infected, Bailey said, and may be more likely to engage in risky behaviour. However, he said, ‘circumcision is by no means a natural condom’, concluding that circumcision will be most effective if it is integrated with other prevention and reproductive health services.

Kenya's director of Medical Services, James Nyikal, cautiously welcomed the recommendation from the WHO and UNAIDS.

"Although male circumcision considerably reduces the risk of HIV/AIDS transmission, there is a high risk of circumcised men becoming complacent and engaging in risky sexual behaviour," he said.

But while Kevin De Cock, director of HIV/AIDS at the WHO, acknowledges that it will be a number of years before the impact of the research is evident on the HIV epidemic, he said that the joint recommendations of the WHO and UNAIDS represent ‘a significant step forward in HIV prevention’.

"Countries with high rates of heterosexual HIV infection and low rates of male circumcision now have an additional intervention which can reduce the risk of HIV infection in heterosexual men," he said.

More information is available from the University of Illinois’ press release and from’s article announcing the WHO/UNAIDS recommendation.