Friday, September 25, 2009

SECRETS OF INSECT FLIGHT REVEALED

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Researchers are one step closer to creating a micro-aircraft that flies with the manoeuvrability and energy efficiency of an insect after decoding the aerodynamic secrets of insect flight.

Dr John Young, from the University of New South Wales (UNSW) in Australia, and a team of animal flight researchers from Oxford University's Department of Zoology, used high-speed digital video cameras to film locusts in action in a wind tunnel, capturing how the shape of a locust's wing changes in flight. They used that information to create a computer model which recreates the airflow and thrust generated by the complex flapping movement.

The breakthrough result, published in the journal Science, means engineers understand for the first time the aerodynamic secrets of one of Nature's most efficient flyers – information vital to the creation of miniature robot flyers for use in situations such as search and rescue, military applications and inspecting hazardous environments.

"The so-called `bumblebee paradox' claiming that insects defy the laws of aerodynamics, is dead. Modern aerodynamics really can accurately model insect flight," said Dr Young, a lecturer in the School of Aerospace, Civil and Mechanical Engineering at the Australian Defence Force Academy (UNSW@ADFA).

"Biological systems have been optimised through evolutionary pressures over millions of years, and offer many examples of performance that far outstrips what we can achieve artificially.

"An insect's delicately structured wings, with their twists and curves, and ridged and wrinkled surfaces, are about as far away as you can get from the streamlined wing of an aircraft," Dr Young said.

"Until very recently it hasn't been possible to measure the actual shape of an insect's wings in flight – partly because their wings flap so fast, and partly because their shape is so complicated.

"Locusts are an interesting insect for engineers to study because of their ability to fly extremely long distances on very limited energy reserves."

Once the computer model of the locust wing movement was perfected, the researchers ran modified simulations to find out why the wing structure was so complex.

In one test they removed the wrinkles and curves but left the twist, while in the second test they replaced the wings with rigid flat plates. The results showed that the simplified models produced lift but were much less efficient, requiring much more power for flight.

"The message for engineers working to build insect-like micro-air vehicles is that the high lift of insect wings may be relatively easy to achieve, but that if the aim is to achieve efficiency of the sort that enables inter-continental flight in locusts, then the details of deforming wing design are critical," Dr Young said.

(Photo: Animal Flight Group, Oxford University/John Young, UNSW@ADFA)

University of New South Wales

RESEARCHERS MAKE RARE METEORITE FIND USING NEW CAMERA NETWORK IN AUSTRALIAN DESERT

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Researchers have discovered an unusual kind of meteorite in the Western Australian desert and have uncovered where in the Solar System it came from, in a very rare finding published in the journal Science.

Meteorites are the only surviving physical record of the formation of our Solar System and by analysing them researchers can glean valuable information about the conditions that existed when the early Solar System was being formed. However, information about where individual meteorites originated, and how they were moving around the Solar System prior to falling to Earth, is available for only a dozen of around 1100 documented meteorite falls over the past two hundred years.

Dr Phil Bland, the lead author of today's study from the Department of Earth Science and Engineering at Imperial College London, said: "We are incredibly excited about our new finding. Meteorites are the most analysed rocks on Earth but it's really rare for us to be able to tell where they came from. Trying to interpret what happened in the early Solar System without knowing where meteorites are from is like trying to interpret the geology of Britain from random rocks dumped in your back yard."

The new meteorite, which is about the size of cricket ball, is the first to be retrieved since researchers from Imperial College London, Ondrejov Observatory in the Czech Republic, and the Western Australian Museum, set up a trial network of cameras in the Nullarbor Desert in Western Australia in 2006.

The researchers aim to use these cameras to find new meteorites, and work out where in the Solar System they came from, by tracking the fireballs that they form in the sky. The new meteorite was found on the first day of searching using the new network, by the first search expedition, within 100m of the predicted site of the fall. This is the first time a meteorite fall has been predicted using only the data from dedicated instruments.

The meteorite appears to have been following an unusual orbit, or path around the Sun, prior to falling to Earth in July 2007, according to the researchers' calculations. The team believes that it started out as part of an asteroid in the innermost main asteroid belt between Mars and Jupiter. It then gradually evolved into an orbit around the Sun that was very similar to Earth's. The other meteorites that researchers have data for follow orbits that take them back, deep into the main asteroid belt.

The new meteorite is also unusual because it is composed of a rare type of basaltic igneous rock. The researchers say that its composition, together with the data about where the meteorite comes from, fits with a recent theory about how the building blocks for the terrestrial planets were formed. This theory suggests that the igneous parent asteroids for meteorites like today's formed deep in the inner Solar System, before being scattered out into the main asteroid belt. Asteroids are widely believed to be the building blocks for planets like the Earth so today's finding provides another clue about the origins of the Solar System.

The researchers are hopeful that their new desert network could yield many more findings, following the success of their first meteorite search.

Dr Bland added: "We're not the first team to set up a network of cameras to track fireballs, but other teams have encountered problems because meteorites are small rocks and they're hard to find in vegetated areas. Our solution was quite simple - build a fireball network in a place where it's easy to find them. The Nullarbour Desert is ideal because there's very little vegetation and dark rocks show up really easily on the light desert plain.

"It was amazing to find a meteorite that we could track back to its origin in the asteroid belt on our first expedition using our small trial network. We're cautiously optimistic that this find could be the first of many and if that happens, each find may give us more clues about how the Solar System began," said Dr Bland.

The researchers' network of cameras takes a single time-lapse picture every night to record any fireballs in the sky. When a meteorite falls, researchers can then use complex calculations to uncover what orbit the meteorite was following and where the meteorite is likely to have landed, so that they can retrieve it.

(Photo: ICL)

Imperial College London

A TINY TYRANNOSAUR

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When you think of Tyrannosaurus rex, a small set of striking physical traits comes to mind: an oversized skull with powerful jaws, tiny forearms, and the muscular hind legs of a runner. But, researchers have just unearthed a much smaller tyrannosauroid in China, no more than three meters long, that displays all the same features – and it predates the T. rex by tens of millions of years.

This finding, published online by the journal Science at the Science Express website on September 17, means that such specialized physical features did not evolve as the prehistoric predators grew in size. Instead, they were present for feeding efficiency at all sizes of the dinosaurs during their reign in the Cretaceous Period.

Paul Sereno from the University of Chicago and National Geographic explorer-in-residence, along with colleagues, studied the new, small-bodied fossil, naming it Raptorex kriegsteini, and estimated that it was a young adult when it died. They examined the skull, teeth, nose, spine, shoulders, forearms, pelvis, and hind legs of the new fossil, comparing the features to larger evolutionary versions of tyrannosauroid dinosaurs.

"First, we used the best mechanical preparation of the specimen possible, which entails the finest needles and air abrasives under a microscope," Sereno said in an email interview. "Then we made molds and casts of the cranial bones, assembled a cast skull, and sent that skull through a CT scanner at the University of Chicago hospital to get the snout cross-section… We used silicone on the skull roof to cast the forebrain of R. kriegsteini… Finally, I made a thin-section from one femur, or thigh bone, for microscopic examination, and determined that the individual had lived to be five or six years old."

The researchers conclude that the "predatory skeletal design" of R. kriegsteini was simply scaled up with little modification in its carnivorous descendants, whose body masses eventually grew 90 times greater.

Sereno and his colleagues also use this new fossil to propose and describe three major morphological stages in the evolutionary history of tyrannosauroid dinosaurs.

(Photo: Todd Marshall)

FOR CARNIVOROUS PLANTS, SLOW BUT STEADY WINS THE RACE

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Like the man-eating plant in Little Shop of Horrors, carnivorous plants rely on animal prey for sustenance. Fortunately for humans, carnivorous plants found in nature are not dependent on a diet of human blood but rather are satisfied with the occasional fly or other insect. The existence of carnivorous plants has fascinated botanists and non-botanists alike for centuries and raises the question, "Why are some plants carnivorous?"

A recent article by Drs. Jim Karagatzides and Aaron Ellison in the September issue of the American Journal of Botany (www.amjbot.org/cgi/content/full/96/9/1612) addresses this question. As Ellison stated, "The general answer to this is that in environments that have few nutrients (such as bogs, where we study carnivorous plants), carnivory allows these plants to capture nutrients 'on the wing'. But if it's so good to be a carnivorous plant in these kinds of environments, why aren't there more carnivorous plants? Knowing how much it 'costs' a carnivorous plant to make a trap is a key piece of information needed to understand why there aren't more carnivorous plants."

Elllison and Karagatzides simultaneously measured both costs and benefits for traps, leaves, roots, and rhizomes of 15 different carnivorous plant species, including pitcher plants and the Venus fly trap. By measuring the construction cost of carbon needed to create these plant structures and comparing it to the payback time—the amount of time the structure takes to photosynthesize to recoup the carbon used in its construction—Ellison and Karagatzides were able to determine how beneficial a trap might be to a plant.

Contrary to expectations, the average cost to create a trap was actually significantly lower than the cost to create a leaf. Ellison said, "The most interesting result is that carnivorous traps are 'cheap' to make (at least compared with leaves). Models of the evolution of carnivory in plants have suggested that traps should be 'expensive' structures—they take a lot of carbon and nutrients to make, and so only when they can't recover these costs in any other way should carnivory be adaptive (or evolutionarily favored). But because carnivorous plants have very low rates of photosynthesis, it still takes a very long time for the plants to 'pay' for them (by accumulating new carbon through photosynthesis)."

Understanding how carbon and mineral nutrients are allocated among different plant organs, different species, and vegetation of different biomes is one of the major goals of the field of plant ecology. Carnivorous plants are a model organism to study these carbon and mineral nutrient tradeoffs because the plants inhabit open environments where light and water are not limiting but nutrients are in extremely short supply, and therefore it is relatively easy to separate out experimentally the effects of nutrient limitation from effects of limitation of light or water.

Ellison and Karagatzides's findings advance our understanding of how complete food webs function. Ellison stated, "Nicholas Gotelli [from the University of Vermont] and I, along with our students and colleagues, have spent more than 10 years developing this micro-ecosystem as a model for how complete food webs—including the plant as both producer and habitat, and the aquatic food web that lives in the pitchers as both detritivore and mutualist—and aquatic ecosystems actually work. These studies have provided new insights into population dynamics and extinction, the importance of food webs for persistence of top predators, and now how organisms allocate nutrients to better control and modulate energy and nutrient fluxes across ecosystem boundaries."

American Journal of Botany

FAKE VIDEO DRAMATICALLY ALTERS EYEWITNESS ACCOUNTS

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Associate Professor Dr Kimberley Wade from the Department of Psychology led an experiment to see whether exposure to fabricated footage of an event could induce individuals to accuse another person of doing something they never did.

In the study, published in Applied Cognitive Psychology, Dr Wade found that almost 50% of people shown fake footage of an event they witnessed first hand were prepared to believe the video version rather than what they actually saw.

Dr Wade’s research team filmed 60 subjects as they took part in a computerised gambling task. The subjects were unknowingly seated next to a member of the research team as they both separately answered a series of multiple-choice general knowledge questions.

All subjects were given a pile of fake money to gamble with and they shared a pile of money that represented the bank. Their task was to earn as much money as possible by typing in an amount of money to gamble on the chances of them answering each question correctly. They were told the person who made the highest profit would win a prize.

When they answered each question, subjects saw either a green tick on their computer monitor to show their answer was correct, or a red cross to show it was incorrect. If the answer was wrong, they would be told to return the money to the bank.

After the session, the video footage was doctored to make it look as if the member of the research team sat next to the subject was cheating by not putting money back into the bank.

One third of the subjects were told that the person sat next to them was suspected of cheating. Another third were told the person had been caught on camera cheating, and the remaining group were actually shown the fake video footage. All subjects were then asked to sign a statement only if they had seen the cheating take place.

Nearly 40% of the participants who had seen the doctored video complied. Another 10% of the group signed when asked a second time by the researchers. Only 10% of those who were told the incident had been caught on film but were not shown the video agreed to sign, and about 5% of the control group who were just told about the cheating signed the statement.

Dr Wade said: “Over the previous decade we have seen rapid advances in digital-manipulation technology. As a result, almost anyone can create convincing, yet fake, images or video footage. Our research shows that if fake footage is extremely compelling, it can induce people to testify about something they never witnessed.”

University of Warwick

BIOLOGISTS DISCOVER 'DEATH STENCH' IS A UNIVERSAL ANCIENT WARNING SIGNAL

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The smell of recent death or injury that repels living relatives of insects has been identified as a truly ancient signal that functions to avoid disease or predators, biologists have discovered.

David Rollo, professor of biology at McMaster University, found that corpses of animals, from insects to crustaceans, all emit the same death stench produced by a blend of specific fatty acids.

The findings have been published in the journal Evolutionary Biology.

Rollo and his team made the discovery while they were studying the social behavior of cockroaches. When a cockroach finds a good place to live it marks the site with pheromone odours that attract others. In trying to identify the precise chemicals involved, Rollo extracted body juices from dead cockroaches.

"It was amazing to find that the cockroaches avoided places treated with these extracts like the plague," says Rollo. "Naturally, we wanted to identify what chemical was making them all go away."

The team eventually identified the specific chemicals that signaled death. Furthermore, they found that the same fatty acids not only signaled death in ants, caterpillars, and cockroaches, they were equally effective in terrestrial woodlice and pill bugs that are actually not insects but crustaceans related to crayfish and lobsters.

Because insects and crustaceans diverged more than 400-million years ago it is likely that most subsequent species recognize their dead in a similar way, that the origin of such signals was likely even older, and that such behaviour initially occurred in aquatic environments (few crustaceans are terrestrial).

"Recognizing and avoiding the dead could reduce the chances of catching the disease, or allow you to get away with just enough exposure to activate your immunity," says Rollo. Likewise, he adds, release of fatty acids from dismembered body parts could provide a strong warning that a nasty predator was nearby.

"As explained in our study, fatty acids—oleic or linoleic acids—are reliably and quickly released from the cells following death. Evolution appears to have favoured such clues because they were reliably associated with demise, and avoiding contagion and predation are rather critical to survival."

The generality and strength of the phenomenon, coupled with the fact that the fatty acids are essential nutrients rather than pesticides, holds real promise for applications such as plant and stored product protection or exclusion of household pests.

McMaster University

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