Wednesday, September 8, 2010


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The ancient "terror bird" Andalgalornis couldn't fly, but it used its unusually large, rigid skull--coupled with a hawk-like hooked beak--in a fighting strategy reminiscent of boxer Muhammad Ali.

The agile creature repeatedly attacked and retreated, landing well-targeted, hatchet-like jabs to take down its prey, according to results of a new study published this week in the journal PLoS ONE.

The study is the first detailed look at the predatory style of a member of an extinct group of large, flightless birds known scientifically as Phorusrhacids but popularly labeled "terror birds" because of their fearsome skull and often imposing size.

Terror birds evolved about 60 million years ago in isolation in South America, an island continent until the last few million years, radiating into about 18 known species ranging in size up to the 7-foot-tall (2.1 meters) Kelenken.

Because terror birds have no close analogs among modern-day birds, their life habits have been shrouded in mystery, according to William Zamer, acting deputy director of the National Science Foundation (NSF)'s Division of Integrative Organismal Systems, which funded the research.

Now, a multinational team of scientists has performed the most sophisticated study to date of the form, function and predatory behavior of a terror bird, using CT scanning and advanced engineering methods.

"No one has ever attempted such a comprehensive biomechanical analysis of a terror bird," said study lead author Federico Degrange of the Museo de La Plata/CONICET in Argentina.

"We need to figure out the ecological role these amazing birds played if we really want to understand how the unusual ecosystems of South America evolved over the past 60 million years."

The terror bird under study is called Andalgalornis and lived in northwestern Argentina about six million years ago. It was a mid-sized terror bird, standing about 4.5 feet tall (1.4 meters) and weighing in at a fleet-footed 90 pounds (40 kg).

Like all terror birds, its skull was relatively enormous (14.5 inches or 37 centimeters) with a deep narrow bill armed with a powerful, hawk-like hook.

Paper co-author Lawrence Witmer of the Ohio University College of Osteopathic Medicine ran a complete skull of Andalgalornis through a CT scanner, giving the team a glimpse into the skull's inner architecture.

The scans revealed to Witmer, Degrange and article co-author Claudia Tambussi, also from the Museo de La Plata/CONICET, that Andalgalornis was unlike other birds because it had evolved a highly rigid skull.

"Birds generally have skulls with lots of mobility between the bones, which allows them to have light but strong skulls," said Witmer.

"But we found that Andalgalornis had turned these mobile joints into rigid beams. This guy had a strong skull, particularly in the fore-aft direction, despite having a curiously hollow beak."

The evolution of this large and rigid bony weapon was presumably linked to the loss of flight in terror birds, as well as to their sometimes gigantic sizes.

From the CT scans, Stephen Wroe, director of the Computational Biomechanics Research Group at the University of New South Wales, Australia, assembled sophisticated 3-D models of the terror bird and two living species for comparison (an eagle, and the terror bird's closest living relative, the seriema).

Using computers and software supplied by Wroe, Degrange and Karen Moreno of the Université Paul Sabatier in Toulouse, France, applied an approach known as Finite Element Analysis to simulate and compare the biomechanics of biting straight down (as in a killing bite), pulling back with its neck (as in dismembering prey) and shaking the skull from side to side (as in thrashing smaller animals, or when dealing with larger struggling prey).

Color images created by the program show cool-blue areas where stresses are low and white-hot areas where stresses get dangerously high.

The simulations supported the CT-based anatomical results.

"Relative to the other birds considered in the study, the terror bird was well-adapted to drive the beak in and pull back with that wickedly recurved tip of the beak," remarked Wroe, "but when shaking its head from side to side, its skull lights up like a Christmas tree."

A key part of the analysis was determining how hard a bite Andalgalornis could deliver.

To examine bite force in birds in general, Degrange and Tambussi worked with zookeepers at the La Plata Zoo to get a seriema and an eagle to chomp down on their bite meter.

"We discovered that the bite force of Andalgalornis was a little lower than we expected, and weaker than the bite of many carnivorous mammals of about the same size," Degrange said.

"Andalgalornis may have compensated for this weaker bite by using its powerful neck muscles to drive its strong skull into prey like an axe."

The team's results give new insight into the lifestyle of a unique avian predator.

Its skull, though strong vertically, was weak from side to side; its hollow beak was in danger of catastrophic fracture if Andalgalornis grappled too vigorously with large struggling prey.

Instead, the study shows that the terror bird engaged in an elegant style more like that of Muhammad Ali--a repeated attack-and-retreat strategy with well-targeted, hatchet-like jabs.

Once killed, the prey would have been ripped into bite-sized morsels by the powerful neck pulling the head straight back or, if possible, swallowed whole.

Feeding on a diversity of now-extinct mammals and competing with the likes of saber-tooth marsupials, terror birds became top predators in their environment.

At least one gigantic terror bird, Titanis, invaded North America about two to three million years ago, but shortly afterward, the animals disappeared from Earth.

(Photo: Witmer Lab)

National Science Foundation


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An old mathematical solution proposed as a prototype of the infamous ocean rogue waves responsible for many maritime catastrophes has been observed in a continuous physical system for the first time.

The Peregrine ‘Soliton’, discovered over 25 years ago by the late Howell Peregrine (1938-2007), an internationally renowned Professor of Applied Mathematics formerly based at the University of Bristol, is a localised solution to a complex partial differential equation known as the nonlinear Schrödinger equation (NLSE).

The Peregrine solution is of great physical significance because its intense localisation has led it to be proposed as a prototype of ocean rogue waves and also represents a special mathematical limit of a wide class of periodic solutions to the NLSE.

Yet despite its central place as a defining object of nonlinear science for over 25 years, the unique characteristics of this very special nonlinear wave have never been directly observed in a continuous physical system – until now.

An international research team from France, Ireland, Australia and Finland report the first observation of highly localised waves possessing near-ideal Peregrine soliton characteristics in the prestigious journal, Nature Physics.

The researchers carried out their experiments using light rather than water, but were are able to rigorously test Peregrine’s prediction by exploiting the mathematical equivalence between the propagation of nonlinear waves on water and the evolution of intense light pulses in optical fibres.

By building on decades of advanced development in fibre-optics and ultrafast optics instrumentation, the researchers were able to explicitly measure the ultrafast temporal properties of the generated soliton wave, and carefully compare their results with Peregrine’s prediction.

Their results represent the first direct measurements of Peregrine soliton localisation in a continuous wave environment in physics. In fact, the authors are careful to remark that a mathematically perfect Peregrine solution may never actually be observable in practice, but they also show that its intense localisation appears even under non-ideal excitation conditions.

This is an especially important result for understanding how high intensity rogue waves may form in the very noisy and imperfect environment of the open ocean.

The findings also highlight the important role that experiments from optics can play in clarifying ideas from other domains of science. In particular, since related dynamics governed by the same NLSE propagation model are also observed in many other systems such as plasmas and Bose Einstein Condensates, the results are expected to stimulate new research directions in many other fields.

(Photo: Bristol U.)

University of Bristol


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Every night a battle between bats and their insect prey rages above our heads as bats call and listen for the echoes of their dinner. Many moths have developed a special anti-bat defence; unlike us, they can hear the ultrasonic calls of bats and avoid an attack with evasive flight.

Until recently, it seemed that these moths had outmanoeuvred bats in this evolutionary arms race, but researchers from Bristol’s School of Biological Sciences have discovered that one special bat species (Barbastella barbastellus) has an unexpected counterstrategy to this defence: whispering.

The barbastelle bat is a very successful hunter which eats large numbers of moths. However, the researchers did not know whether most of these moths were earless and thus unable to hear predators approaching, or whether the bats had found a way to catch moths that could hear them coming.

While previous studies could only determine the types of insects the bats had eaten (beetles, flies, moths and so on), researcher Matt Zeale developed a method using a new set of genetic markers to identify the species of those insects. This established for the first time that the barbastelle almost exclusively preys on moths that have ears.

In order to find out why the barbastelle can catch such moths when other bats cannot, the researchers then measured how well moths can detect different bat species by recording the activity of the nerve in the moth’s ear while tracking the position of flying bats at the same time. This happened in several locations around Bristol including a graveyard in Clifton.

Dr Hannah ter Hofstede said: “Recording from the ear of a moth in the field was a real challenge but it yielded some amazing results. Whereas moths can detect other bats more than 30 m away, the barbastelle gets as close as 3.5 m without being detected.”
The researchers then analysed the barbastelle’s echolocation calls and found that they are up to 100 times quieter than those of other bats.

Dr Holger Goerlitz said: “We modelled detection distances for bats and moths and found that by whispering, the barbastelle can hear the echo from an unsuspecting moth before the moth becomes aware of the approaching bat. This advantage, however, comes at the cost of reduced detection range, similar to us trying to navigate in the dark using a lighter instead of a spotlight.”

The barbastelle bats’ strategy is successful as it enables them to catch moths that would normally fly away and to avoid competition by feeding on prey that other bats find much more difficult to catch.

Such success is unusual, Dr Goerlitz said: “It’s a rare case in evolution that a predator wins the arms-race with its prey because the predator only loses its dinner, but the prey loses its life.”

(Photo: © Dietmar Nill)

University of Bristol


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Flies follow horizontal edges to regulate altitude, says a team of researchers from the California Institute of Technology (Caltech). This finding contradicts a previous model, which posited that insects adjust their height by visually measuring the motion beneath them as they fly.

This mechanism for controlling altitude—in which the insects use their eyes to track horizontal edges in their environment—is very similar to the strategy insects use to steer left and right, the researchers note. "For people interested in how the tiny brains of these creatures can control such sophisticated behaviors, it's intriguing to realize that the same circuits and mechanisms that underlie steering may also be used to control altitude," says Michael Dickinson, the Esther M. and Abe M. Zarem Professor of Bioengineering at Caltech.

Altitude control is a critical component of flight; unlike us earthbound humans, insects and other flying creatures need to control their height above the ground, or risk flying too high above it—or crashing into it.

"Insects have to make their way through three dimensions," Dickinson notes. "We wanted to know how a fly chooses a particular altitude at which to fly, and why it isn't flying at some other height."

Insects, notes Dickinson—and fruit flies in particular—have long been used as a model for understanding the basic principles of vision and how it is used to control behavior. Thus, understanding how these tiny flies use visual cues—the images, and changes in those images, that appear on their retinas as they move around—to help them maneuver through a complex landscape is an important problem. Indeed, the results of such research are being used by engineers to control small flying robots.

The Caltech team was originally trying to test a model of altitude control in insects that had been put forth by a different group of scientists a few years earlier. This model proposed the idea that insects regulate their altitude based on the movement of the ground beneath them. The lower you fly, the more quickly the world moves underneath you; the higher up you are, the more slowly the world goes by. This effect is easily observed by looking through the window of an airplane as it changes altitude during takeoff or landing.

The idea, then, was that an insect could cruise at a particular altitude by rising up if the flow beneath it was too fast and descending when the flow beneath it was too slow.

To test this, the Caltech team used an automated flight chamber developed by Andrew Straw, senior research fellow in computation and neural systems at Caltech and the paper's first author. The system employs multiple cameras to "track the position of a fly as it flies within a simple virtual-reality environment," Straw explains. In the experiments at hand, this required the projection of a pattern of stripes on the floor of a specially designed chamber through which the flies can freely travel. As the flies flew through the chamber, the researchers presented them with different speeds of visual motion on the ground beneath them, in an attempt to elicit the expected changes in altitude.

The flies, however, did not respond as expected. "We couldn't elicit any altitude changes," says Straw. "We expected them to descend in the chamber when the motion below slowed, but they didn't descend; we expected them to ascend when the forward motion was rapid, but they didn't ascend."

In other words, the insects were not behaving as predicted by the model.

After a series of experiments designed to verify these results—"We spent an enormous amount of time trying to convince ourselves that the ground-flow model did not apply to our flies," says Dickinson—they began to consider other explanations for how the insects might regulate altitude.

"We already knew that flies steer toward objects with a prominent vertical edge," says Dickinson. "They will use that vertical edge as a visual landmark for navigation, steering left and right to keep it in their sights. Our idea was that maybe they use a similar strategy in altitude by tracking horizontal edges."

To test this idea, the team projected a series of horizontal edges (a black line with black above it, white below; or vice versa) on the walls of the chamber, watching how the flies' altitude changed—or didn't change—as the height of the edge moved. Indeed, says Dickinson, "The flies would quickly adjust their altitude to match the height of the visual landmark."

But the team wasn't completely convinced. After all, the horizontal lines were the only landmarks the flies had before them; maybe they were using the lines as a guide for want of any other kind of cue.

And so the team did another experiment, in which they combined the two types of cues: they moved a horizontal edge up and down the chamber's walls while simultaneously projecting a pattern of stripes on its floor.

The results were clear: the flies oriented themselves based on the horizontal landmarks given, and ignored the pattern on the chamber floor.

The experiments were possible in part because the team could collect its data very efficiently, Straw notes. "The data size used in these experiments was very large," he says. "The system was fully automated—every time a fly flew down the tunnel, the experiment automatically started—and so could run for many hours without human supervision." This, he says, allowed them to amass an amount of data large enough to leave no doubt about the experiment's conclusions.

What's next in the study of altitude control? "We're both excited about combining this technique with genetic approaches that are available in fruit flies," says Straw. "We want to determine which parts of the brain are responsible for these and other behaviors."

(Photo: Caltech/Francisco Zabala & Michael Dickinson)

California Institute of Technology


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The smallest frog in the Old World (Asia, Africa and Europe) and one of the world's tiniest was discovered inside and around pitcher plants in the heath forests of the Southeast Asian island of Borneo. The pea-sized amphibian is a species of microhylid, which, as the name suggests, is composed of miniature frogs under 15 millimeters.

The discovery published in the taxonomy journal Zootaxa was made by Drs. Indraneil Das and Alexander Haas of the Institute of Biodiversity and Environmental Conservation at the Universiti Malaysia Sarawak, and Biozentrum Grindel und Zoologisches Museum of Hamburg, respectively, with support from the Volkswagen Foundation. Dr. Das is also leading one of the scientific teams that is searching for the world's lost amphibians, a campaign organized by Conservation International and IUCN's Amphibians Specialist Group.

"I saw some specimens in museum collections that are over 100 years old. Scientists presumably thought they were juveniles of other species, but it turns out they are adults of this newly-discovered micro species," said Dr. Das.

The mini frogs (Microhyla nepenthicola) were found on the edge of a road leading to the summit of the Gunung Serapi mountain, which lies within Kubah National Park. The new species was named after the plant on which it depends to live, the Nepenthes ampullaria, one of many species of pitcher plants in Borneo, which has a globular pitcher and grows in damp, shady forests. The frogs deposit their eggs on the sides of the pitcher, and tadpoles grow in the liquid accumulated inside the plant.

Adult males of the new species range between 10.6 and 12.8 mm – about the size of a pea. Because they are so tiny, finding them proved to be a challenge. The frogs were tracked by their call, and then made to jump onto a piece of white cloth to be examined closer. The singing normally starts at dusk, with males gathering within and around the pitcher plants. They call in a series of harsh rasping notes that last for a few minutes with brief intervals of silence. This "amphibian symphony" goes on from sundown until peaking in the early hours of the evening.

Amphibians are the most threatened group of animals, with a third of them in danger of extinction. They provide important services to humans such as controlling insects that spread disease and damage crops and helping to maintain healthy freshwater systems. Teams of scientists from Conservation International and IUCN's Amphibian Specialist Group around the world have recently launched an unprecedented search in the hope of rediscovering 100 species of "lost" amphibians – animals considered potentially extinct but that may be holding on in a few remote places.

The search, which is taking place in 20 countries on five continents, will help scientists to understand the recent amphibian extinction crisis. Dr. Das is leading a team of scientists who will search for the Sambas Stream Toad (Ansonia latidisca) in Indonesia and Malaysia in September. The toad was last seen in the 1950s. It is believed that increased sedimentation in streams after logging may have contributed to the decline of its population.

"Amphibians are quite sensitive to changes in their surroundings, so we hope the discovery of these miniature frogs will help us to understand what changes in the global environment are having an impact on these fascinating animals," said Conservation International's Dr. Robin Moore, who has organized the search on behalf of IUCN's Amphibian Specialist Group.

(Photo: Conservation I.)

Conservation Institute


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An international CSIRO-led team of astronomers has developed a new way to weigh the planets in our Solar System – using radio signals from the small spinning stars called pulsars.

“This is first time anyone has weighed entire planetary systems – planets with their moons and rings,” said team leader Dr David Champion from Germany’s Max-Planck-Institut für Radioastronomie.

“And we’ve provided an independent check on previous results, which is great for planetary science.”

Measurements of planet masses made this new way could feed into data needed for future space missions.

Until now, astronomers have weighed planets by measuring the orbits of their moons or of spacecraft flying past them. That’s because mass creates gravity, and a planet’s gravitational pull determines the orbit of anything that goes around it – both the size of the orbit and how long it takes to complete.

The new method is based on corrections astronomers make to signals from pulsars – small spinning stars that deliver regular ‘blips’ of radio waves.

The Earth is travelling around the Sun, and this movement affects exactly when pulsar signals arrive here.

To remove this effect, astronomers calculate when the pulses would have arrived at the Solar System’s centre of mass, or barycentre, around which all the planets orbit.

Because the arrangement of the planets around the Sun changes all the time, the barycentre moves around too.

To work out its position, astronomers use both a table (called an ephemeris) of where all the planets are at a given time, and the values for their masses that have already been measured.

CSIRO Astronomy and Space Science (CASS) researcher, Dr Dick Manchester, says that if these figures are slightly wrong, and the position of the barycentre is slightly wrong, then a regular, repeating pattern of timing errors appears in the pulsar data.

“For instance, if the mass of Jupiter and its moons is wrong, we see a pattern of timing errors that repeats over 12 years, the time Jupiter takes to orbit the Sun,” Dr Manchester said.

“But if the mass of Jupiter and its moons is corrected, the timing errors disappear. This is the feedback process that the astronomers have used to determine the planets’ masses.”

Data from a set of four pulsars have been used to weigh Mercury, Venus, Mars, Jupiter and Saturn with their moons and rings. Most of these data were recorded by CSIRO’s Parkes radio telescope in eastern Australia, with some contributed by the Arecibo telescope in Puerto Rico and the Effelsberg telescope in Germany.

The masses were consistent with those measured by spacecraft. The mass of the Jovian system, 9.547921(2) x 10-4 times the mass of the Sun, is significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with, but less accurate than, the value from the Galileo spacecraft.

The new measurement technique is sensitive to a mass difference of two hundred thousand million million tonnes – just 0.003 per cent of the mass of the Earth, and one ten-millionth of Jupiter’s mass.

CASS scientist Dr George Hobbs says that, in the short term, spacecraft will continue to make the most accurate measurements for individual planets.

”But the pulsar technique will be the best for planets not being visited by spacecraft, and for measuring the combined masses of planets and their moons,” Dr Hobbs said,

Repeating the measurements would improve the values even more. If astronomers observed a set of 20 pulsars over seven years they’d weigh Jupiter more accurately than spacecraft have. Doing the same for Saturn would take 13 years.

The head of the ‘Fundamental Physics in Radio Astronomy’ research group at the Max-Planck-Institut für Radioastronomie, Professor Michael Kramer, says astronomers need this accurate timing because they are using pulsars to hunt for gravitational waves predicted by Einstein’s general theory of relativity.

“Finding these waves depends on spotting minute changes in the timing of pulsar signals, and so all other sources of timing error must be accounted for, including the traces of Solar System planets,” Professor Kramer said.

(Photo: D. Champion, MPIfR)



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It's been called revolutionary -- technology that lends supercomputer-level power to any desktop. What's more, this new capability comes in the form of a readily available piece of hardware, a graphics processing unit (GPU) costing only a few hundred dollars.

Georgia Tech researchers are investigating whether this new calculating power might change the security landscape worldwide. They're concerned that these desktop marvels might soon compromise a critical part of the world’s cyber-security infrastructure -- password protection.

"We've been using a commonly available graphics processor to test the integrity of typical passwords of the kind in use here at Georgia Tech and many other places," said Richard Boyd, a senior research scientist at the Georgia Tech Research Institute (GTRI). "Right now we can confidently say that a seven-character password is hopelessly inadequate -- and as GPU power continues to go up every year, the threat will increase."

Designed to handle the ever-growing demands of computer games, today’s top GPUs can process information at the rate of nearly two teraflops (a teraflop is a trillion floating-point operations per second). To put that in perspective, in the year 2000 the world's fastest supercomputer, a cluster of linked machines costing $110 million, operated at slightly more than seven teraflops.

Graphics processing units are so fast because they're designed as parallel computers. In parallel computing, a given problem is divided among multiple processing units, called cores, and these multiple cores tackle different parts of the problem simultaneously.

Until recently, multi-core graphics processors -- which are made by either Nvidia Corp. or by AMD’s ATI unit -- were hard to use for anything except producing graphics for a monitor. To solve a non-graphics problem on a GPU, users had to couch their problems in graphical terms, a difficult task.

But that changed in February 2007, when Nvidia released an important new software-development kit. These new tools allow users to directly program a GPU using the popular C programming language.

"Once Nvidia did that, interest in GPUs really started taking off," Boyd explained. "If you can write a C program, you can program a GPU now."

This new capability puts power into many hands, he says. And it could threaten the world's ubiquitous password-protection model because it enables a low-cost password-breaking technique that engineers call "brute forcing."

In brute forcing, attackers use a fast GPU (or even a group of linked GPUs) -- combined with the right software program -- to break down passwords that are blocking them from a computer or a network. The intruders' high-speed technique basically involves trying every possible password until they find the right one.

For many common passwords, that doesn't take long, said Joshua L. Davis, a GTRI research scientist involved in this project. For one thing, attackers know that many people use passwords comprised of easy-to-remember lowercase letters. Code-breakers typically work on those combinations first.

"Length is a major factor in protecting against brute forcing a password," Davis explained. "A computer keyboard contains 95 characters, and every time you add another character, your protection goes up exponentially, by 95 times."

Complexity also adds security, he says. Adding numbers, symbols and uppercase characters significantly increases the time needed to decipher a password.

Davis believes the best password is an entire sentence, preferably one that includes numbers or symbols. That's because a sentence is both long and complex, and yet easy to remember. He says any password shorter than 12 characters could be vulnerable -- if not now, soon.

Would-be password crackers have other advantages, says Carl Mastrangelo, an undergraduate student in the Georgia Tech College of Computing who is working on the password research. A computer stores user passwords in an encrypted "hash" within the operating system. Attackers who locate a password hash can besiege it by building a rainbow table, which is essentially a database of all previous attempts to compromise that password hash.

"Generating a rainbow table takes a long time," Mastrangelo explained. "But if an attacker wants to crack many passwords quickly, once he’s built a rainbow table it might then only take about 10 minutes per password rather than several days."

Software programs designed to break passwords are freely available on the Internet, Boyd says. Such programs, combined with the availability of GPUs, mean it's only a matter of time before the password threat will be immediate.

Boyd hopes his password work will increase awareness of the GPU's potential for harm as well as benefit. One result of this research, he says, could be GPU-based workstations that would offer rapid assessments of a given password's real-world security strength.

(Photo: GIT)

Georgia Tech


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While Arctic sea ice has been diminishing in recent decades, the Antarctic sea ice extent has been increasing slightly. Researchers from the Georgia Institute of Technology provide an explanation for the seeming paradox of increasing Antarctic sea ice in a warming climate. The paper appears in the Early Edition of the Proceedings of the National Academy of Science the week of August 16, 2010.

“We wanted to understand this apparent paradox so that we can better understand what might happen to the Antarctic sea ice in the coming century with increased greenhouse warming,” said Jiping Liu, a research scientist in Georgia Tech’s School of Earth and Atmospheric Sciences.

For the last half of the 20th Century, as the atmosphere warmed, the hydrological cycle accelerated and there was more precipitation in the Southern Ocean surrounding Antarctica. This increased precipitation, mostly in the form of snow, stabilized the upper ocean and insulated it from the ocean heat below. This insulating effect reduced the amount of melting occurring below the sea ice. In addition, snow has a tendency to reflect atmospheric heat away from the sea ice, which reduced melting from above.

However, the climate models predict an accelerated warming exceeding natural variability with increased loading of greenhouse gases in the 21st century. This will likely result in the sea ice melting at a faster rate from both above and below. Here’s how it works. Increased warming of the atmosphere is expected to heat the upper ocean, which will increase the melting of the sea ice from below. In addition, increased warming will also result in a reduced level of snowfall, but more rain. Because rain doesn’t reflect heat back the way snow does, this will enhance the melting of the Antarctic sea ice from above.

“Our finding raises some interesting possibilities about what we might see in the future. We may see, on a time scale of decades, a switch in the Antarctic, where the sea ice extent begins to decrease,” said Judith A. Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech.

Georgia Tech


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Bacteria are well-known to be the cause of some of the most repugnant smells on earth, but now scientists have revealed this lowest of life forms actually has a sense of smell of its own.

A team of marine microbiologists at Newcastle University have discovered for the first time that bacteria have a molecular “nose” that is able to detect airborne, smell-producing chemicals such as ammonia.

Published in Biotechnology Journal, their study shows how bacteria are capable of ‘olfaction’ – sensing volatile chemicals in the air such as ammonia produced by rival bacteria present in the environment.

Led by Dr Reindert Nijland, the research also shows that bacteria respond to this smell by producing a biofilm – or ‘slime’ – the individual bacteria joining together to colonise an area in a bid to push out any potential competitor.

Biofilm is a major cause of infection on medical implants such as heart valves, artificial hips and even breast implants. Also known as ‘biofouling’ it costs the marine industry millions every year, slowing ships down and wasting precious fuel. But it also has its advantages. Certain biofilms thrive on petroleum oil and can be used to clean up an oil spill.

Dr Nijland, who carried out the work at Newcastle University’s Dove Marine Laboratory, said the findings would help to further our understanding of how biofilms are formed and how we might be able to manipulate them to our advantage.

“This is the first evidence of a bacterial ‘nose’ capable of detecting potential competitors,” he said.

“Slime is important in medical and industrial settings and the fact that the cells formed slime on exposure to ammonia has important implications for understanding how biofilms are formed and how we might be able to use this to our advantage. The next step will be to identify the nose or sensor that actually does the smelling.”

This latest discovery shows that bacteria are capable of at least four of the five senses; a responsiveness to light – sight – contact-dependent gene expression – touch – and a response to chemicals and toxins in their environment either through direct contact – taste – or through the air – smell.

Ammonia is one of the simplest sources of nitrogen – a key nutrient for bacterial growth. Using rival bacteria Bacillus subtilis and B.licheniformus, both commonly found in the soil, the team found that each produced a biofilm in response to airborne ammonia and that the response decreased as the distance between the two bacterial colonies increased.

Project supervisor Professor Grant Burgess, director of the Dove Marine Laboratory, said that understanding the triggers that prompt this sort of response had huge potential.

“The sense of smell has been observed in many creatures, even yeasts and slime moulds, but our work shows for the first time that a sense of smell even exists in lowly bacteria.

“From an evolutionary perspective, we believe this may be the first example of how living creatures first learned to smell other living creatures.

“It is an early observation and much work is still to be done but, nevertheless, this is an important breakthrough which also shows how complex bacteria are and how they use a growing number of ways to communicate with each other.

“Bacterial infections kill millions of people every year and discovering how your bacterial enemies communicate with each other is an important step in winning this war. This research provides clues to so far unknown ways of bacterial communication.”

(Photo: Newcastle U.)

Newcastle University




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