Understanding Hearing, Molecule By Molecule

Berkeley Lab scientists have for the first time pieced together the three-dimensional structure of one of nature’s most exquisite pieces of machinery, a gossamer-like filament of proteins in the inner ear that enables the sense of hearing and balance.

Their work opens the door for a more fundamental understanding of how hearing works. It may also lead to improved ways to treat some forms of hearing loss, which affects about ten percent of people.

The filaments help transform the mechanical vibrations of sound into electrical signals that can be interpreted by the brain. They are only four nanometers wide and 160 nanometers long (one nanometer is one-billionth of a meter), but if enough of them break, the world becomes silent. They’re part of a sensory system that operates over a range of stimuli spanning six orders of magnitude. With it, people can hear a pin drop and a jet throttle to full power. No other sensory system in biology and the electrical engineering world is capable of this feat.

“It’s one of the most beautifully deigned systems in the body,” says Manfred Auer of Berkeley Lab's Life Sciences Division. “But how it really works remains a mystery. Our goal is to determine what the system looks like, so we can determine how it functions.”

To do this, Auer and colleagues utilize electron tomography, which acquires hundreds of images of a structure at different angles, and reconstructs them into a three-dimensional composite. The technique yields highly detailed images of structures at the molecular scale.

No one had applied electron tomography to hearing research until about eight years ago, when Auer’s team set out to learn more about one of the last unmapped components of the auditory system. The inner ear is lined with hair cells that sprout hair bundles. These hair bundles bob and sway in fluid — like a wheat field bending under the wind — as the ear drum absorbs sound waves.

Zooming in even closer, each hair bundle is composed of individual hairs, also called stereocilia. Adjacent stereocilia are linked together by protein filaments, also known as tip links. When the stereocilia sway, the tip links stretch, which momentarily rips open a transduction channel that allows positively charged ions to stream into the hair cell. This initiates a neurotransmitter release that eventually reaches the nervous system. In this manner, a mechanical action — a channel prying open — is converted into an electrical signal and eventually something we hear as a chirp, beep, or voice.

“The system is incredible. But we still don’t really know what constitutes the links, and we don’t know how the hair bundle operates at the molecular level,” says Auer.

That’s beginning to change, thanks in part to Auer and colleagues’ pioneering use of electron tomography to dissect the hair bundle at the molecular level. So far, they’ve reconstructed the hair-bundle links in three dimensions, and obtained highly accurate length measurements of the links, down to the molecular scale.

“One of the holy grails in structural cell biology is obtaining a molecular inventory of complex systems, and showing how the proteins work together to achieve their marvelous function,” says Auer. “We’re striving to develop such an inventory for the hair bundle.”

Electron tomography studies of the hair bundle, in its cellular context, also enables the research team to decipher just how the hair bundle’s capabilities are unmatched in nature and the man-made world. For example, how can it adapt to an extremely loud noise, and then quickly reconfigure itself to detect a whisper? And how can it be sensitive enough to detect the whisper, but not so sensitive that it detects every molecule colliding against the ear drum?

“If the system were any more sensitive, you would hear all of the molecules in the air bumping onto your ear drum, and go crazy,” says Auer, adding that their recently obtained images are the first in a series of electron tomography explorations of hair cells.

“We know a good deal about how a hair bundle operates through clever electrophysiology experiments, but we need to know more, and for that we need to determine its molecular structure,” says Auer. “Ultimately, we will get a molecular representation of this entire bundle, with all of its machinery, which will give us a fundamental insight into how the bundle works — and how hearing really works.”

The research was funded by the National Institutes of Health, National Science Foundation, and the Department of Energy. It was reported in the June 9, 2008 issue of the Journal of the Association for Research in Otolaryngology.

One-third Of Reef-building Corals Face Extinction

A third of reef-building corals around the world are threatened with extinction, according to the first-ever comprehensive global assessment to determine their conservation status. The study findings were published today by Science Express.

Leading coral experts joined forces with the Global Marine Species Assessment (GMSA) -- a joint initiative of the International Union for Conservation of Nature (IUCN) and Conservation International (CI) -- to apply the IUCN Red List Categories and Criteria to this important group of marine species.

"The results of this study are very disconcerting," stated Kent Carpenter, lead author of the Science article, GMSA Director, IUCN Species Programme. "When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems."

Built over millions of years, coral reefs are home to more than 25 percent of marine species, making them the most biologically diverse of marine ecosystems. Corals produce reefs in shallow tropical and sub-tropical seas and have been shown to be highly sensitive to changes in their environment.

Researchers identified the main threats to corals as climate change and localized stresses resulting from destructive fishing, declining water quality from pollution, and the degradation of coastal habitats. Climate change causes rising water temperatures and more intense solar radiation, which lead to coral bleaching and disease often resulting in mass coral mortality.

Shallow water corals have a symbiotic relationship with algae called zooxanthellae, which live in their soft tissues and provide the coral with essential nutrients and energy from photosynthesis and are the reason why corals have such beautiful colors. Coral bleaching is the result of a stress response, such as increased water temperatures, whereby the algae are expelled from the tissues, hence the term "bleaching." Corals that have been bleached are weaker and more prone to attack from disease. Scientists believe that increased coral disease also is linked to higher sea temperatures and an increase in run-off pollution and sediments from the land.

Researchers predict that ocean acidification will be another serious threat facing coral reefs. As oceans absorb increasing amounts of carbon dioxide from the atmosphere, water acidity increases and pH decreases, severely impacting corals' ability to build their skeletons that form the foundation of reefs.

The 39 scientists who co-authored this study agree that if rising sea surface temperatures continue to cause increased frequency of bleaching and disease events, many corals may not have enough time to replenish themselves and this could lead to extinctions.

"These results show that as a group, reef-building corals are more at risk of extinction than all terrestrial groups, apart from amphibians, and are the most vulnerable to the effects of climate change," said Roger McManus, CI's vice president for marine programs. "The loss of the corals will have profound implications for millions of people who depend on coral reefs for their livelihoods."

Coral reefs harbor fish and other marine resources important for coastal communities. They also help protect coastal towns and other near-shore habitats from severe erosion and flooding caused by tropical storms.

Staghorn (Acroporid) corals face the highest risk of extinction, with 52 percent of species listed in a threatened category. The Caribbean region has the highest number of highly threatened corals (Endangered and Critically Endangered), including the iconic elkhorn coral (Acropora palmata) which is listed as Critically Endangered. The high biodiversity "Coral Triangle" in the western Pacific's Indo-Malay-Philippine Archipelago has the highest proportions of Vulnerable and Near-Threatened species in the Indo-Pacific, largely resulting from the high concentration of people living in many parts of the region.

Corals from the genera Favia and Porites were found to be the least threatened due to their relatively higher resistance to bleaching and disease. In addition, 141 species lacked sufficient information to be fully assessed and were therefore listed as Data Deficient. However, researchers believe that many of these species would have been listed as threatened if more information were available.

The results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. "We either reduce our CO2 emission now or many corals will be lost forever," says Julia Marton-Lefèvre, IUCN Director General. "Improving water quality, global education and the adequate funding of local conservation practices also are essential to protect the foundation of beautiful and valuable coral reef ecosystems."

Coral experts participated in three workshops to analyze data on 845 reef-building coral species, including population range and size, life history traits, susceptibility to threats, and estimates of regional coral cover loss.

The reef-building corals assessment is one group of a number of strategic global assessments of marine species the GMSA has been conducting since 2006 at Old Dominion University in Norfolk, Virginia. Other assessments are being conducted on seagrasses and mangroves that are also important habitat-forming species, all marine fishes, and other important keystone invertebrates. By 2012, the GMSA plans to complete its comprehensive first stage assessment of the threat of extinction for over 20,000 marine plants and animals, providing an essential baseline for conservation plans around the world, and tracking the extinction risk of marine species.

The results of the coral species assessment will be placed on the IUCN Red List of Threatened Species in October 2008. Currently, the assessments can be found at http://www.sci.odu.edu/gmsa/about/corals.shtml.

Brain Cells Related To Fear Identified, Paving The Way For More Effective Treatment Of Post-Traumatic Stress And Other Anxiety Disorders

The National Institute of Mental Health estimates that in any given year, about 40 million adults (18 or older) will suffer from some form of anxiety disorder, including debilitating conditions such as phobias, panic disorders and post-traumatic stress disorder (PTSD).

It is estimated that nearly 15 percent of U.S. soldiers returning from Iraq and Afghanistan develop PTSD, underscoring the urgency to develop better treatment strategies for anxiety disorders. These disorders can lead to myriad problems that hinder daily life – or ruin it altogether – such as drug abuse, alcoholism, marital problems, unemployment and suicide.

Functional imaging studies in combat veterans have revealed that the amygdala, a cerebral structure of the temporal lobe known to play a key role in fear and anxiety, is hyperactive in PTSD subjects. Potentially paving the way for more effective treatments of anxiety disorders, a recent Nature report by Denis Paré, professor at the Center for Molecular and Behavioral Neuroscience at Rutgers University in Newark, has identified a critical component of the amygdala’s neural network normally involved in the extinction, or elimination, of fear memories. Paré’s laboratory studies the amygdala and how its activity impacts behavior. His research was published online by Nature on July 9, 2008 and is scheduled to appear in the print edition later in July.

Earlier research has revealed that in animals and humans, the amygdala is involved in the expression of innate fear responses, such as the fear of snakes, along with the formation of new fear memories as a result of experience, such as learning to fear the sound of a siren that predicts an air raid.

In the laboratory, the circuits underlying learned fear are typically studied using an experimental paradigm called Pavlovian fear conditioning. In this research model on rats, a neutral stimulus such as the sound of a tone elicited a fear response in the rats after they heard it paired with an noxious or unpleasant stimulus, such as a shock to the feet. However, this conditioned fear response was diminished with repetition of the neutral stimulus in the absence of the noxious stimulus. This phenomenon is known as extinction. This approach is similar to that used to treat human phobias, where the subject is presented with the feared object in the absence of danger.

Behavioral studies have demonstrated, however, that extinction training does not completely abolish the initial fear memory, but rather leads to the formation of a new memory that inhibits conditioned fear responses at the level of the amygdala. As such, fear responses can be expressed again when the conditioned stimulus is presented in a context other than the one where extinction training took place.

For example, suppose a rat is trained for extinction in a grey box smelling of roses, and later hears the tone again in a different box, with a different smell and appearance. The rat will show no evidence of having been trained for extinction. The tone will evoke as much fear as if the rat had not been trained for extinction.

“Extinction memory will only be expressed if tested in the same environment where the extinction training occurred, implying that extinction does not erase the initial fear memory but only suppresses it in a context-specific manner,” notes Paré.

Importantly, it has been found that people with anxiety disorders exhibit an “extinction deficit,” or a failure to “forget.” However, until recently, the mechanisms of extinction have remained unknown.

As reported by Nature, Paré has found that clusters of amygdala cells, known as the intercalated (ITC) neurons, play a key role in extinction. His findings indicate that ITC cells inhibit amygdala outputs to the brain stem structures that generate fear responses. Indeed, Paré and his collaborators have shown that when ITC cells are destroyed with a targeted toxin in rats, extinction memory is impeded, mimicking the behavior seen in PTSD.

The significance of this finding derives from earlier results suggesting that PTSD reflects an extinction deficit and that the amygdala is hyperactive in this disorder. As a result, it might be possible to compensate for this abnormality and facilitate extinction with pharmacological interventions that enhance the excitability of ITC cells to inhibit amygdala outputs.

Paré’s research is supported by a $1,487,897 grant from the National Institute of Mental Health. The research project was carried out in collaboration with Rutgers graduate students Ekaterina Likhtik and John Apergis-Scoute, post-doctoral student Daniela Popa, and research assistant G. Anthony Fidacaro.

Room Temperature Superconductivity: One Step Closer To Holy Grail Of Physics

Scientists at the University of Cambridge have for the first time identified a key component to unravelling the mystery of room temperature superconductivity, according to a paper published in the journal Nature.

The quest for room temperature superconductivity has gripped physics researchers since they saw the possibility more than two decades ago. Materials that could potentially transport electricity with zero loss (resistance) at room temperature hold vast potential; some of the possible applications include a magnetically levitated superfast train, efficient magnetic resonance imaging (MRI), lossless power generators, transformers, and transmission lines, powerful supercomputers, etc.

Unfortunately, scientists have been unable to decipher how copper oxide materials superconduct at extremely cold temperatures (such as that of liquid nitrogen), much less design materials that can superconduct at higher temperatures.

Materials that are known to superconduct at the highest temperatures are, unexpectedly, ceramic insulators that behave as magnets before 'doping' (the method of introducing impurities to a semiconductor to modify its electrical properties). Upon doping charge carriers (holes or electrons) into these parent magnetic insulators, they mysteriously begin to superconduct, i.e. the doped carriers form pairs that carry electricity without loss.

The essential conundrum facing researchers in this area has been: how does a magnet that cannot transport electricity transform into a superconductor that is a perfect conductor of electricity? The Cambridge team have made a significant advance in answering this question.

The researchers have discovered where the charge 'hole' carriers that play a significant role in the superconductivity originate within the electronic structure of copper-oxide superconductors. These findings are particularly important for the next step of deciphering the glue that binds the holes together and determining what enables them to superconduct.

Dr Suchitra E. Sebastian, lead author of the study, commented, "An experimental difficulty in the past has been accessing the underlying microscopics of the system once it begins to superconduct. Superconductivity throws a manner of 'veil' over the system, hiding its inner workings from experimental probes. A major advance has been our use of high magnetic fields, which punch holes through the superconducting shroud, known as vortices - regions where superconductivity is destroyed, through which the underlying electronic structure can be probed.

"We have successfully unearthed for the first time in a high temperature superconductor the location in the electronic structure where 'pockets' of doped hole carriers aggregate. Our experiments have thus made an important advance toward understanding how superconducting pairs form out of these hole pockets."

By determining exactly where the doped holes aggregate in the electronic structure of these superconductors, the researchers have been able to advance understanding in two vital areas:

(1) A direct probe revealing the location and size of pockets of holes is an essential step to determining how these particles stick together to superconduct.

(2) Their experiments have successfully accessed the region betwixt magnetism and superconductivity: when the superconducting veil is partially lifted, their experiments suggest the existence of underlying magnetism which shapes the hole pockets. Interplay between magnetism and superconductivity is therefore indicated - leading to the next question to be addressed.

Do these forms of order compete, with magnetism appearing in the vortex regions where superconductivity is killed, as they suggest? Or do they complement each other by some more intricate mechanism? One possibility they suggest for the coexistence of two very different physical phenomena is that the non-superconducting vortex cores may behave in concert, exhibiting collective magnetism while the rest of the material superconducts.

Do We Think That Machines Can Think?

When our PC goes on strike again we tend to curse it as if it was a human. The question of why and under what circumstances we attribute human-like properties to machines and how such processes manifest on a cortical level was investigated in a project led by Dr. Sören Krach and Prof. Tilo Kircher from the RWTH Aachen University (Clinic for Psychiatry and Psychotherapy) in cooperation with the Department of "Social Robotics" (Bielefeld University) and the Neuroimage Nord (Hamburg).

Almost daily, new accomplishments in the field of human robotics are presented in the media. Constructions of increasingly elaborate and versatile humanoid robots are reported and thus human-robot interactions accumulate in daily life. However, the question of how humans perceive these "machines" and attribute capabilities and "mental qualities" to them remains largely undiscovered.

In the fMRI study, reported in PLoS ONE, Krach and colleagues investigated how the increase of human-likeness of interaction partners modulates the participants' brain activity. In this study, participants were playing an easy computer game (the prisoners' dilemma game) against four different game partners: a regular computer notebook, a functionally designed Lego-robot, the anthropomorphic robot BARTHOC Jr. and a human. All game partners played an absolutely similar sequence, which was not, however, revealed to the participants.

The results clearly demonstrated that neural activity in the medial prefrontal cortex as well as in the right temporo-parietal junction linearly increased with the degree of "human-likeness" of interaction partners, i.e. the more the respective game partners exhibited human-like features, the more the participants engaged cortical regions associated with mental state attribution/mentalizing.

Further, in a debriefing questionnaire, participants stated having increasingly enjoyed the interactions most when their respective interaction partners displayed the most human features and accordingly evaluated their opponents as being more intelligent.

This study is the first ever to investigate the neuronal basics of direct human-robot interaction on a higher cognitive level such as mentalizing. Thus, the researchers expect the results of the study to impact long-lasting psychological and philosophical debates regarding human-machine interactions and especially the question of what causes humans to be perceived as human.

Whales And Dolphins Influence New Wind Turbine Design

Sea creatures have evolved over millions of years to maximise efficiency of movement through water; humans have been trying to perfect streamlined designs for barely a century. So shouldn't we be taking more notice of the experts?

Biologists and engineers from across the US have been doing just that. By studying the flippers, fins and tails of whales and dolphins, these scientists have discovered some features of their structure that contradict long-held engineering theories. Dr Frank Fish (West Chester University) will talk about the exciting impact that these discoveries may have on traditional industrial designs on July 8th at the Society for Experimental Biology's Annual Meeting in Marseille.

Some of his observations are already being applied to real life engineering problems, a concept known as biomimetics. The shape of whale flippers with one bumpy edge has inspired the creation of a completely novel design for wind turbine blades. This design has been shown to be more efficient and also quieter, but defies traditional engineering theories.

"Engineers have previously tried to ensure steady flow patterns on rigid and simple lifting surfaces, such as wings. The lesson from biomimicry is that unsteady flow and complex shapes can increase lift, reduce drag and delay 'stall', a dramatic and abrupt loss of lift, beyond what existing engineered systems can accomplish," Dr Fish advises. "There are even possibilities that this technology could be applied to aeronautical designs such as helicopter blades in the future."

The work centres on studies of vortices, tornado-shaped water formations that develop in the wake of the animals. "In the case of the humpback whale, vortices formed from tubercles (bumps) on the front edge of flippers help to generate more lift without the occurrence of stall, as well as enhancing manoeuvrability and agility," explains Dr Fish. "In the case of the tails of dolphins, vortices are formed at the end of the up and down strokes. These vortices are involved in the production of a jet in the wake of the dolphin that produces high thrust. By regulating the production of the vortices, the dolphin can maximize its efficiency while swimming."

This work was funded by the US National Science Foundation and the US Office of Naval Research.

Simple Life Form May Have Existed 700 Million Years Earlier Than Previously Thought

The accepted timeframe for the beginnings of life on Earth is now being questioned by a Curtin University of Technology led team of scientists, after finding a key indicator to the earliest life forms in diamonds from Jack Hills in Western Australia.

The 4.2-billion-year-old diamonds found trapped inside the Jack Hills zircon crystals are the oldest-known samples of Earth’s carbon. The Curtin led team’s discovery of very high concentrations of carbon 12, or “light carbon” within these crystals is remarkable as it is a feature usually associated with organic life.

Dr Alexander Nemchin from Curtin’s Department of Applied Geology and the project leader believes the latest research will revive debate on the early evolution of life on Earth.

“We believe this find to be the oldest terrestrial light carbon reservoir discovered so far,” Dr Nemchin said.

Evidence for ancient life stretches back in time to at least 3.5 billion years ago, in the form of single-celled organisms that did not require oxygen. The discovery of light carbon in the Jack Hills crystals raises the question – did a simple life form exist on Earth 700 million years earlier than previously thought?

“We interpret the range of light carbon values observed in these inclusions as a unique chemical marker that opens up the possibility of biological activity during the period not long after the Earth’s formation,” Dr Nemchin said.

The researchers report the composition of 22 diamond and graphite inclusions from 18 Jack Hills zircon grains in the journal Nature.

“The discovery challenges our fundamental understanding of processes active in the early history of the Earth. It suggests that life may well have appeared on Earth long before the period of heavy-meteorite bombardment believed by some to have initiated the emergence of life on Earth,” Dr Nemchin said.

“Alternatively, it requires some other process to create the light carbon values, which would then question the widely held assumption that light carbon means life.”

The discovery will assist mankind in our understanding of the development of the planet and help us to better assess the conditions of the Earth up to 4,500 billion years ago.

Background

In 1983, a Curtin project team discovered extremely old zircon crystals in a collection of rocks located between Meekathara and Carnarvon. Twenty years later, the oldest diamonds were unexpectedly discovered in these rocks by many of the original team.

The recent paper in Nature is written by a team of people made up of Curtin University academic and Project Leader, Dr Alexander Nemchin, Martin Whitehouse from the Swedish Museum of Natural History, Martina Menneken and Dr Thorston Geisler a Masters student and her supervisor from the University of Munster’s Institute of Mineralogy, and Professors Pidgeon and Wilde from Curtin University’s Applied Geology Department, who originally identified the old zircons.

Rubber 'Snake' Could Help Wave Power Get A Bite Of The Energy Market

A device consisting of a giant rubber tube may hold the key to producing affordable electricity from the energy in sea waves. Invented in the UK, the 'Anaconda' is a totally innovative wave energy concept. Its ultra-simple design means it would be cheap to manufacture and maintain, enabling it to produce clean electricity at lower cost than other types of wave energy converter. Cost has been a key barrier to deployment of such converters to date.

Named after the snake of the same name because of its long thin shape, the Anaconda is closed at both ends and filled completely with water. It is designed to be anchored just below the sea's surface, with one end facing the oncoming waves.

A wave hitting the end squeezes it and causes a 'bulge wave'* to form inside the tube. As the bulge wave runs through the tube, the initial sea wave that caused it runs along the outside of the tube at the same speed, squeezing the tube more and more and causing the bulge wave to get bigger and bigger. The bulge wave then turns a turbine fitted at the far end of the device and the power produced is fed to shore via a cable.

Because it is made of rubber, the Anaconda is much lighter than other wave energy devices (which are primarily made of metal) and dispenses with the need for hydraulic rams, hinges and articulated joints. This reduces capital and maintenance costs and scope for breakdowns.

The Anaconda is, however, still at an early stage of development. The concept has only been proven at very small laboratory-scale, so important questions about its potential performance still need to be answered. Funded by the Engineering and Physical Sciences Research Council (EPSRC), and in collaboration with the Anaconda's inventors and with its developer (Checkmate SeaEnergy), engineers at the University of Southampton are now embarking on a programme of larger-scale laboratory experiments and novel mathematical studies designed to do just that.

Using tubes with diameters of 0.25 and 0.5 metres, the experiments will assess the Anaconda's behaviour in regular, irregular and extreme waves. Parameters measured will include internal pressures, changes in tube shape and the forces that mooring cables would be subjected to. As well as providing insights into the device's hydrodynamic behaviour, the data will form the basis of a mathematical model that can estimate exactly how much power a full-scale Anaconda would produce.

When built, each full-scale Anaconda device would be 200 metres long and 7 metres in diameter, and deployed in water depths of between 40 and 100 metres. Initial assessments indicate that the Anaconda would be rated at a power output of 1MW (roughly the electricity consumption of 2000 houses) and might be able to generate power at a cost of 6p per kWh or less. Although around twice as much as the cost of electricity generated from traditional coal-fired power stations, this compares very favourably with generation costs for other leading wave energy concepts.

"The Anaconda could make a valuable contribution to environmental protection by encouraging the use of wave power," says Professor John Chaplin, who is leading the EPSRC-funded project. "A one-third scale model of the Anaconda could be built next year for sea testing and we could see the first full-size device deployed off the UK coast in around five years' time."

The Anaconda was invented by Francis Farley (an experimental physicist) and Rod Rainey (of Atkins Oil and Gas). There may be advantages in making part of the tube inelastic, but this is still under assessment.

Wave-generated electricity is carbon-free and so can help the fight against global warming. Together with tidal energy, it is estimated that wave power could supply up to 20% of the UK's current electricity demand.

The two-year project 'The Hydrodynamics of a Distensible Wave Energy Converter' is receiving EPSRC funding of just over £430,000.

*A bulge wave is a wave of pressure produced when a fluid oscillates forwards and backwards inside a tube.

Music Went With Cave Art In Prehistoric Caves

Thousands of years later, we can view stone-age art on cave walls, but we can't listen to the stone-age music that would have accompanied many of the pictures. In many sites, flutes made of bone are to be found nearby.

Iegor Reznikoff of the University of Paris reports that the most acoustically resonant place in a cave -- where sounds linger or reverberate the most -- was also often the place where the pictures were densest.

And when the most-resonant spot was located in a very narrow passageway too difficult for painting, red marks are often found, as if the resonance maximum had to be signified in some way. This correlation of paintings and music, Reznikoff says, provides "the best evidence for the ritualistic meanings of the paintings and of the use of the adorned caves."

Proceeding into the direction of the best resonance (or echo) that answers to vocal sounds, one is naturally lead to panels with pictures. At the very least, in the dark caves, where hand-held light sources fall off in effectiveness, singing (and listening for resonant reactions) proved to be the best sonar-like way of exploring the caves. A significant returning sound gave some hint of a usable hall ahead in the dark.

On the 5th and 6th of July, Reznikoff will conduct a tour of a prehistoric cave where he will show some examples of the sound-picture relationship. He will also lead a visit to the Basilica of Vezelay where he will illustrate the magnificent resonance. (Talk 4pAAa1, " Sound resonance in prehistoric times: A study of Paleolithic painted caves and rocks" was presented July 3, 2008.)

'Mind's Eye' Influences Visual Perception

Letting your imagination run away with you may actually influence how you see the world. New research from Vanderbilt University has found that mental imagery—what we see with the "mind's eye"—directly impacts our visual perception.

"We found that imagery leads to a short-term memory trace that can bias future perception," says Joel Pearson, research associate in the Vanderbilt Department of Psychology. and lead author of the study. "This is the first research to definitively show that imagining something changes vision both while you are imagining it and later on."

"These findings are important because they suggest a potential mechanism by which top-down expectations or recollections of previous experiences might shape perception itself," Pearson and his co-authors write.

It is well known that a powerful perceptual experience can change the way a person sees things later. Just think of what can happen if you discover an unwanted pest in your kitchen, such as a mouse. Suddenly you see mice in every dust ball and dark corner—or think you do. Is it possible that imagining something, just once, might also change how you perceive things?

"You might think you need to imagine something 10 times or 100 times before it has an impact," says Frank Tong, associate professor of psychology and co-author of the study. "Our results show that even a single instance of imagery can tilt how you see the world one way or another, dramatically, if the conditions are right."

To test how imagery affects perception, Pearson, Tong and co-author Colin Clifford of the University of Sydney had subjects imagine simple patterns of vertical or horizontal stripes, which are strongly represented in the primary visual areas of the brain. They then presented a green horizontal grated pattern to one eye and a red vertical grated pattern to the other to induce what is called binocular rivalry. During binocular rivalry, an individual will often alternately perceive each stimulus, with the images appearing to switch back and forth before their eyes. The subjects generally reported they had seen the image they had been imagining, proving the researcher's hypothesis that imagery would influence the binocular rivalry battle.

Additional experiments found that the effect of imagery on perception was approximately the same as showing the research subject a faint representation of one of the patterns between trials. Stronger shifts in perception were found if subjects either viewed or imagined a particular pattern for longer periods of time. They found that both imagery and perception can lead to a build-up of a "perceptual trace" that influences subsequent perception.

Pearson, Clifford and Tong also discovered that changing the orientation of the image from what had been imagined greatly reduced the impact of imagery on perception. Because orientation is processed in early visual areas, this suggests that imagery's interaction with perception may occur at early stages of visual processing.

The new findings offer an objective tool to assess the often-slippery concept of imagination.

"It has been very hard to pin down in the laboratory what exactly someone is experiencing when it comes to imagery, because it is so subjective," Tong says. "We found that the imagery effect, while found in all of our subjects, could differ a lot in strength across subjects. So this might give us a metric to measure the strength of mental imagery in individuals and how that imagery may influence perception."

The findings may also help settle a longstanding debate in the research community over whether mental imagery is visual—that one imagines something just as one sees it—or more abstract.

"More recently, with advances in human brain imaging, we now know that when you imagine something parts of the visual brain do light up and you see activity there," Pearson says. "So there's more and more evidence suggesting that there is a huge overlap between mental imagery and seeing the same thing. Our work shows that not only are imagery and vision related, but imagery directly influences what we see."

The research was funded by the National Institutes of Health, an Australian Research Council Discovery Grant and an Australia National Health and Mental Research Council Martin Fellowship. Pearson is a member of the Vanderbilt Vision Research Center. Tong is a member of the Vanderbilt Vision Research Center and the Vanderbilt Center for Integrative and Cognitive Neuroscience.

New Form Of Energy-Transfer Processes: Atomic Tug Of War

A new form of energy-transfer, reported in Nature may have implications for the study of reactions going on in the atmosphere, and even for those occurring in the body.

Imagine a simple molecule consisting of two atoms as being like two balls attached together by a spring. If an incoming atom strikes one side of the molecule, the spring compresses and you would expect the molecule to jump backwards -- remember Newton's cradle?

However, research by Dr Stuart Greaves in the Chemistry department at the University of Bristol, suggests that, contrary to expectations, in certain conditions the molecule jumps forwards, not backwards.

Greaves and his colleagues studied fast hydrogen atoms colliding with supersonically cooled deuterium-deuterium molecules. On the occasions when the collision did not result in a chemical reaction, the hydrogen atoms scatter.

In these 'inelastic' processes, the scattering of the hydrogen atom is normally backwards. But in this case, the team found that the inelastic scattering process led mainly to forward scattering -- the opposite of what was expected.

Stuart Greaves said: "The reaction under study is the simplest chemical reaction possible and yet it still continues to surprise us, even after 80 years of scientific investigation. Our work provides another vital piece of the jigsaw for understanding the mechanics of chemical reactions, such as those going on in the atmosphere."

The explanation of what is happening is that even if the hydrogen atom flies past the deuterium-deuterium molecule in a 'grazing collision', this can tug on the deuterium atom nearest to it, thereby extending the bond connecting the two deuterium atoms, which causes the molecule to move forwards.

The authors suggest that this 'tug-of-war' behaviour may come into play whenever a strong attraction develops between the colliding partners, just as the gravitational effect of the Moon 'pulls' the water on Earth towards it.

This work has only been possible due to the trans-Atlantic collaboration between theory -- Stuart Greaves at Bristol University and Eckart Wrede at Durham University -- and experiments, conducted by Professor Richard Zare's group at Stanford University in California.

First Images Of Solar System's Invisible Frontier

NASA's sun-focused STEREO spacecraft unexpectedly detected particles from the edge of the solar system last year, allowing University of California, Berkeley, scientists to map for the first time the energized particles in the region where the hot solar wind slams into the cold interstellar medium.

Mapping the region by means of neutral, or uncharged, atoms instead of light "heralds a new kind of astronomy using neutral atoms," said Robert Lin, UC Berkeley professor of physics and lead for the suprathermal electron sensor aboard STEREO. "You can't get a global picture of this region, one of the last unexplored regions of the heliosphere, any other way because it is too tenuous to be seen by normal optical telescopes."

The heliosphere is a volume over which the effects of the solar wind extend, stretching from the sun to more than twice the distance of Pluto. Beyond its edge, called the heliopause, lies the relative quiet of interstellar space, at about 100 astronomical units (AU) - 100 times the Earth-sun distance.

The results, reported in the July 3 issue of the journal Nature, clear up a discrepancy in the amount of energy dumped into space by the decelerating solar wind that was discovered last year when Voyager 2 crossed the solar system's termination shock and entered the surrounding heliosheath. The termination shock is the region of the heliosphere where the supersonic solar wind slows to subsonic speed as it merges with the interstellar medium. The heliosheath is the region of roiled plasma between the shock front and the interstellar medium.

The newly discovered population of ions in the heliosheath contains about 70 percent of the energy dissipated in the termination shock, exactly the amount unaccounted for by Voyager 2's instruments, the UC Berkeley physicists concluded. The Voyager 2 results are reported in the same issue of Nature.

The twin STEREO spacecraft were launched in 2006 into Earth's orbit about the sun to obtain stereo pictures of the sun's surface and to measure magnetic fields and ion fluxes associated with solar explosions.

Between June and October 2007, however, the suprathermal electron sensor in the IMPACT (In-situ Measurements of Particles and CME Transients) suite of instruments on board each STEREO spacecraft detected neutral atoms originating from the same spot in the sky: the shock front and the heliosheath beyond, where the sun plunges through the interstellar medium.

"The suprathermal electron sensors were designed to detect charged electrons, which fluctuate in intensity depending on the magnetic field," said lead author Linghua Wang, a graduate student in UC Berkeley's Department of Physics. "We were surprised that these particle intensities didn't depend on the magnetic field, which meant they must be neutral atoms."

UC Berkeley physicists concluded that these energetic neutral atoms were originally ions heated up in the termination that lost their charge to cold atoms in the interstellar medium and, no longer hindered by magnetic fields, flowed back toward the sun and into the suprathermal electron sensors on STEREO.

"This is the first mapping of energetic neutral particles from beyond the heliosphere," Lin said. "These neutral atoms tell us about the hot ions in the heliosheath. The ions heated in the termination shock exchange charge with the cold, neutral atoms in the interstellar medium to become neutral, and then flow back in."

According to Lin, the neutral atoms are probably hydrogen, since most of the particles in the local interstellar medium are hydrogen.

The charge exchange between hot ions and neutral atoms to generate energetic neutral atoms is well known around the sun and planets, including Earth and Jupiter, and has been used by spacecraft such as IMAGE and Cassini as a means of remotely measuring the energy in ion plasmas, since neutral atoms travel much farther than ions. A new NASA mission, the Interstellar Boundary Explorer (IBEX), is planned for launch later this year to map more thoroughly the lower-energy energetic ions in the heliosheath by means of energetic neutral atoms to discover the structure of the termination shock and how hydrogen ions are accelerated there.

Lin and Wang's coauthors are IMPACT principal investigator Janet G. Luhmann and researcher Davin E. Larson. All are affiliated with UC Berkeley's Space Sciences Laboratory, which Lin directs.

Archaeologists Find Silos And Administration Center From Early Egyptian City

A University of Chicago expedition at Tell Edfu in southern Egypt has unearthed a large administration building and silos that provide fresh clues about the emergence of urban life. The discovery provides new information about a little understood aspect of ancient Egypt—the development of cities in a culture that is largely famous for its monumental architecture.

The archaeological work at Tell Edfu was initiated with the permission of the Supreme Council of Antiquities, headed by Zahi Hawass, under the direction of Nadine Moeller, Assistant Professor at the Oriental Institute, University of Chicago. Work late last year revealed details of seven silos, the largest grain bins found in ancient Egypt as well as an older columned hall that was an administration center.

Long fascinated with temples and monuments such as pyramids, scholars have traditionally spent little time exploring the residential communities of ancient Egypt. Due to intense farming and heavy settlement over the years, much of the record of urban civilization has been lost. So little archaeological evidence remains that some scholars believe Egypt did not have a highly developed urban culture, giving Mesopotamia the distinction of teaching people how to live in cities.

"The traditional view of ancient Egypt has been biased by the fact that most excavation work so far has focused on temples and tombs. The mounds which comprise the remains of Egyptian cities were either ignored, buried under modern towns, or else destroyed by modern agricultural activities. Edfu is one of the very few remaining city mounds that are accessible for scientific study," said Gil Stein, Director of the Oriental Institute.

"The work at Edfu is important and innovative in that it finally allows us to examine ancient Egypt as an urban society, whose cities and towns housed bureaucrats, craft specialists, priests, and farmers. Nadine Moeller's discovery of silos and local administrative buildings shows us how these cities actually functioned as places where the agricultural wealth of the Nile valley was mobilized for the state. Grain as currency provided the sinews of power for the pharoahs," he added.

"Ancient Egyptian administration is mainly known from texts, but the full understanding of the institutions involved and their role within towns and cities has been so far difficult to grasp because of the lack of archaeological evidence with which textual data needs to be combined," Moeller said.

At Tell Edfu, archaeologists have uncovered what amounts to a downtown area. The community, halfway between the modern cities of Aswan and Luxor, was a provincial capital an important regional center. Tell Edfu is also rare, in that almost 3,000 years of Egyptian history are preserved in the stratigraphy of a single mound.

The administrative building and silos were at the heart of the ancient community. Because grain was a form of currency, the silos functioned as a bank and a food source. The silos' size indicates the community was apparently a prosperous urban center.

The grain bins are in a large silo courtyard of the 17th Dynasty (1630-1520 B.C.) and consist of at least seven round, mud-brick silos. With a diameter between 5.5 and 6.5 meters, they are the largest examples discovered within a town center.

The team unearthed an earlier building phase for the hall that predated the silos. In that phase, a mud-brick building with 16 wooden columns stood at the site. The pottery and seal impressions found in the hall date it to the early 13th Dynasty (1773-1650 B.C.). The building layout indicates that it may have been part of the governor's palace, which was typical of provincial towns.

There is no exact parallel for such a columned hall being part of the administrative buildings. Scribes did accounting, opened and sealed containers, and received letters in the column hall. The ostraca, or inscribed pottery shards, list commodities written on them.

The administrative center was used when Egypt's political unity was lost and a small kingdom developed at Thebes (modern Luxor) and controlled most of Upper Egypt.

"During this period, we can see an increase in connections between the provincial elite, such as the family of the governor, to the royal family at Thebes, who were keen on strengthening bonds through marriage, or by awarding important offices to these people," Moeller said.

"It is exactly at this period when Edfu seems to have been very prosperous, which can now be confirmed further by archaeological discoveries such as this silo-court, a symbol for the wealth of the town," she said.

Tongue Drive System Lets Persons With Disabilities Operate Powered Wheelchairs, Computers

A new assistive technology developed by engineers at the Georgia Institute of Technology could help individuals with severe disabilities lead more independent lives.

The novel system allows individuals with disabilities to operate a computer, control a powered wheelchair and interact with their environments simply by moving their tongues.

"This device could revolutionize the field of assistive technologies by helping individuals with severe disabilities, such as those with high-level spinal cord injuries, return to rich, active, independent and productive lives," said Maysam Ghovanloo, an assistant professor in the Georgia Tech School of Electrical and Computer Engineering. Ghovanloo developed the system with graduate student Xueliang Huo.

The tongue-operated assistive technology, called the Tongue Drive system, was described on June 29 at the 2008 Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) Annual Conference in Washington, D.C. An article about this system is also scheduled to appear in an upcoming issue of the Journal of Rehabilitation Research and Development. This research was funded by the National Science Foundation and the Christopher and Dana Reeve Foundation.

To operate the Tongue Drive system, potential users only need to be able to move their tongues. Attaching a small magnet, the size of a grain of rice, to an individual's tongue by implantation, piercing or tissue adhesive allows tongue motion to direct the movement of a cursor across a computer screen or a powered wheelchair around a room.

"We chose the tongue to operate the system because unlike hands and feet, which are controlled by the brain through the spinal cord, the tongue is directly connected to the brain by a cranial nerve that generally escapes damage in severe spinal cord injuries or neuromuscular diseases," said Ghovanloo, who started working on this project about three years ago at North Carolina State University. "Tongue movements are also fast, accurate and do not require much thinking, concentration or effort."

Movement of the magnetic tracer attached to the tongue is detected by an array of magnetic field sensors mounted on a headset outside the mouth or on an orthodontic brace inside the mouth. The sensor output signals are wirelessly transmitted to a portable computer, which can be carried on the user's clothing or wheelchair.

The sensor output signals are processed to determine the relative motion of the magnet with respect to the array of sensors in real-time. This information is then used to control the movements of a cursor on the computer screen or to substitute for the joystick function in a powered wheelchair.

The system can potentially capture a large number of tongue movements, each of which can represent a different user command. A unique set of specific tongue movements can be tailored for each individual based on the user's abilities, oral anatomy, personal preferences and lifestyle.

"An individual could potentially train our system to recognize touching each tooth as a different command," explained Ghovanloo. "The ability to train our system with as many commands as an individual can comfortably remember is a significant advantage over the common sip-n-puff device that acts as a simple switch controlled by sucking or blowing through a straw."

The Tongue Drive system is also non-invasive and does not require brain surgery like some of the brain-computer interface technologies.

Ghovanloo's group recently completed trials in which six able-bodied individuals tested the Tongue Drive system. Each participant defined six tongue commands that would substitute for computer mouse tasks -- left, right, up and down pointer movements and single- and double-click. For each trial, the individual began by training the system. During the five-minute training session, the individual repeated each of the six designated tongue movements 10 times.

During the testing session, the user moved his or her tongue to one of the predefined command positions and the mouse pointer started moving in the selected direction. To move the cursor faster, users could hold their tongue in the position of the issued command to gradually accelerate the pointer until it reached a maximum velocity.

Results of the computer access test by novice users with the current Tongue Drive prototype showed a response time of less than one second with almost 100 percent accuracy for the six individual commands. This is equivalent to an information transfer rate of approximately 150 bits per minute, which is much faster than the bandwidth of most brain-computer interfaces, according to Ghovanloo.

The researchers have also tested the ability of twelve able-bodied individuals to operate an electric-powered wheelchair with the Tongue Drive system. The next step is to test and assess the usability and acceptability of the system by people with severe disabilities, said Ghovanloo. He is teaming with the Shepherd Center, an Atlanta-based catastrophic care hospital, and the Georgia Tech Center for Assistive Technology and Environmental Access, to conduct those trials.

The research team has also begun to develop software to connect the Tongue Drive system to a wide variety of readily available communication tools such as text generators, speech synthesizers and readers. In addition, the researchers plan to add control commands, such as switching the system into standby mode to permit the user to eat, sleep or engage in a conversation while extending battery life.

"We hope this technology will reduce the need of individuals with severe disabilities to receive continuous assistance from family members or caregivers, thus significantly reducing healthcare and assistance costs," noted Ghovanloo. "This system may also make it easier for them to work and communicate with others, such as friends and family."

Maize (Corn) May Have Been Domesticated In Mexico As Early As 10,000 Years Ago

The ancestors of maize originally grew wild in Mexico and were radically different from the plant that is now one of the most important crops in the world. While the evidence is clear that maize was first domesticated in Mexico, the time and location of the earliest domestication and dispersal events are still in dispute.

Now, in addition to more traditional macrobotanical and archeological remains, scientists are using new genetic and microbotanical techniques to distinguish domesticated maize from its wild relatives as well as to identify ancient sites of maize agriculture. These new analyses suggest that maize may have been domesticated in Mexico as early as 10,000 years ago.

Dr. John Jones and his colleagues, Mary Pohl, and Kevin Pope, have evaluated multiple lines of evidence, including paleobotanical remains such as pollen, phytoliths, and starch grains, as well as genetic analyses, to reconstruct the early history of maize agriculture. Dr. Jones, of the Department of Anthropology, Washington State University, Pullman, will be presenting this work at a symposium on Maize Biology at the annual meeting of the American Society of Plant Biologists in Mérida, Mexico (June 28, 2008).

While macrobotanical remains such as maize kernels, cobs, and leaves have been found in dry mountain caves, such remains are not preserved in more humid lowland areas, so the conclusions based on such remains are fragmentary. Much smaller parts of the maize plant, like cellular silica deposits, called phytoliths, and pollen and starch grains, are preserved under both humid and dry conditions. These lines of evidence, along with genetic and archeological data, are being used to reconstruct the history of agriculture to its origins around the world.

Maize is wind pollinated and sheds large amounts of pollen, which is deposited in soil and water sediments. The tough outer wall (exine) of pollen protects it from deterioration for thousands of years. While it is possible to distinguish the pollen grains of maize and its close relatives from other grasses, it is more difficult, except at the largest sizes, to differentiate the pollen of maize (Zea mays) from its presumed wild ancestor teosinte (Zea sp). Thus, while pollen can provide evidence of the presence of domesticated maize, along with that from other plants indicating agricultural activity, maize pollen alone is not definitive evidence of domesticated plants.

Phytoliths are another type of plant microfossil that is preserved for thousands of years and can be used to distinguish domesticated from wild maize. These microscopic bodies are silica or calcium oxalate deposits that accumulate in the intercellular spaces of plant stems, leaves, and roots and have characteristic shapes depending on genus and species. They are preserved even when the plant is burned or disintegrated. Scientists have found that it is possible to distinguish the microliths of teosinte from those of maize and other grasses, thus allowing them to identify the approximate dates and locations of early agricultural activity. Phytoliths are also preserved on ceramic and stone artifacts used to process food.

Jones and his co-workers analyzed the sediments from San Andrés, in the state of Tabasco on the Mexican Gulf Coast. Analysis of area sediments revealed phytoliths of domesticated varieties of maize as well as those of agricultural weeds. These data, along with evidence of burning, suggested that agriculturalists were active in that part of the Yucatan Peninsula around 7,000 years ago.

Starch grains are the most recent addition to the archeobotanical toolbox. Maize and its grass relatives produce large quantities of starch grains with unique morphological characteristics and, like phytoliths, are preserved in sediments and on cultural artifacts. Maize produces more starch than its wild relative teosinte, and the grains are much larger. The paleobotanist Dolores Piperno and her colleagues have established a number of criteria for distinguishing the starch grains of different grasses and found that those of maize and teosinte could be reliably separated on the basis of size and other morphological characters.

Maize also has a rich genetic history, which has resulted in thousands of varieties or landraces adapted to different environmental conditions. Maize scientists and geneticists have used this information to track the evolution and dispersal of maize varieties as well as to reconstruct the history of maize domestication. For example, the locus teosinte glume architecture 1 (tga1), is important in determining phytolith formation and morphology and, along with other "domestication genes" can be used to write the history of maize domestication and use by humans.

All of these methods are being used by paleobotanists, plant scientists, and archeologists like Jones and his colleagues, to reconstruct the rich history of maize domestication and evolution. Many of the ancient varieties were adaptations to different environmental conditions such as different soils, temperature, altitude, and drought. Preservation of these varieties and knowledge of their genetic and adaptive histories are of paramount importance as farmers around the world cope with changes in soil, temperature, and water availability and struggle to maintain a food supply for growing populations.

Ancient Oak Trees Help Reduce Global Warming

The battle to reduce carbon emissions is at the heart of many eco-friendly efforts, and researchers from the University of Missouri have discovered that nature has been lending a hand. Researchers at the Missouri Tree Ring Laboratory in the Department of Forestry discovered that trees submerged in freshwater aquatic systems store carbon for thousands of years, a significantly longer period of time than trees that fall in a forest, thus keeping carbon out of the atmosphere.

“If a tree is submerged in water, its carbon will be stored for an average of 2,000 years,” said Richard Guyette, director of the MU Tree Ring Lab and research associate professor of forestry in the School of Natural Resources in the College of Agriculture, Food and Natural Resources. “If a tree falls in a forest, that number is reduced to an average of 20 years, and in firewood, the carbon is only stored for one year.”

The team studied trees in northern Missouri, a geographically unique area with a high level of riparian forests (forests that have natural water flowing through them). They discovered submerged oak trees that were as old as 14,000 years, potentially some of the oldest discovered in the world. This carbon storage process is not just ancient; it continues even today as additional trees become submerged, according to Guyette.

While a tree is alive, it has a high ability to store carbon, thus keeping it out of the atmosphere. However, as it begins to decay, a tree’s carbon is released back into the atmosphere. Discovering that certain conditions slow this process reveals the importance of proper tree disposal as well as the benefits of riparian forests.

“Carbon plays a huge role in climate change and information about where it goes will be very important someday soon,” said Michael C. Stambaugh, research associate in the MU Department of Forestry. “The goal is to increase our knowledge of the carbon cycle, particularly its exchange between the biosphere (plants) and atmosphere. We need to know where it goes and for how long in order to know how to offset its effects.”

This could be a valuable find for landowners. Although it is not yet common in North America, emissions trading has been gaining popularity in parts of Europe. Also known as cap and trade, emissions trading works to reduce pollution by setting a limit on the amount of pollutants an organization can emit into the air. If they exceed that number, the group is required to obtain carbon credits. One carbon credit equals one metric ton of carbon-dioxide or other equivalent greenhouse gases.

Carbon credits can be purchased in a variety of ways. Such as: planting new trees or harvesting old wood that has stored carbon; collecting methane from landfills; or purchasing credits from other companies who have a carbon surplus by staying below their emission requirements.

This week, the California Air Resources Board announced the consideration of a large plan to fight global warming. The recommendations include reducing emissions, in part by requiring major polluters to trade carbon credits.

“Farmers can sell the carbon they have stored in their trees through a carbon credit stock market,” Guyette said. “Companies that emit excess of carbon would be able to buy carbon credits to offset their pollution.”

On The Boil: New Nano Technique Significantly Boosts Boiling Efficiency

Whoever penned the old adage “a watched pot never boils” surely never tried to heat up water in a pot lined with copper nanorods.

A new study from researchers at Rensselaer Polytechnic Institute shows that by adding an invisible layer of the nanomaterials to the bottom of a metal vessel, an order of magnitude less energy is required to bring water to boil. This increase in efficiency could have a big impact on cooling computer chips, improving heat transfer systems, and reducing costs for industrial boiling applications.

“Like so many other nanotechnology and nanomaterials breakthroughs, our discovery was completely unexpected,” said Nikhil A. Koratkar, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer, who led the project. “The increased boiling efficiency seems to be the result of an interesting interplay between the nanoscale and microscale surfaces of the treated metal. The potential applications for this discovery are vast and exciting, and we’re eager to continue our investigations into this phenomenon.”

Bringing water to a boil, and the related phase change that transforms the liquid into vapor, requires an interface between the water and air. In the example of a pot of water, two such interfaces exist: at the top where the water meets air, and at the bottom where the water meets tiny pockets of air trapped in the microscale texture and imperfections on the surface of the pot. Even though most of the water inside of the pot has reached 100 degrees Celsius and is at boiling temperature, it cannot boil because it is surrounded by other water molecules and there is no interface — i.e., no air — present to facilitate a phase change.

Bubbles are typically formed when air is trapped inside a microscale cavity on the metal surface of a vessel, and vapor pressure forces the bubble to the top of the vessel. As this bubble nucleation takes place, water floods the microscale cavity, which in turn prevents any further nucleation from occurring at that specific site.

Koratkar and his team found that by depositing a layer of copper nanorods on the surface of a copper vessel, the nanoscale pockets of air trapped within the forest of nanorods “feed” nanobubbles into the microscale cavities of the vessel surface and help to prevent them from getting flooded with water. This synergistic coupling effect promotes robust boiling and stable bubble nucleation, with large numbers of tiny, frequently occurring bubbles.

“By themselves, the nanoscale and microscale textures are not able to facilitate good boiling, as the nanoscale pockets are simply too small and the microscale cavities are quickly flooded by water and therefore single-use,” Koratkar said. “But working together, the multiscale effect allows for significantly improved boiling. We observed a 30-fold increase in active bubble nucleation site density — a fancy term for the number of bubbles created — on the surface treated with copper nanotubes, over the nontreated surface.”

Boiling is ultimately a vehicle for heat transfer, in that it moves energy from a heat source to the bottom of a vessel and into the contained liquid, which then boils, and turns into vapor that eventually releases the heat into the atmosphere. This new discovery allows this process to become significantly more efficient, which could translate into considerable efficiency gains and cost savings if incorporated into a wide range of industrial equipment that relies on boiling to create heat or steam.

“If you can boil water using 30 times less energy, that’s 30 times less energy you have to pay for,” he said.

The team’s discovery could also revolutionize the process of cooling computer chips. As the physical size of chips has shrunk significantly over the past two decades, it has become increasingly critical to develop ways to cool hot spots and transfer lingering heat away from the chip. This challenge has grown more prevalent in recent years, and threatens to bottleneck the semiconductor industry’s ability to develop smaller and more powerful chips.

Boiling is a potential heat transfer technique that can be used to cool chips, Koratkar said, so depositing copper nanorods onto the copper interconnects of chips could lead to new innovations in heat transfer and dissipation for semiconductors.

“Since computer interconnects are already made of copper, it should be easy and inexpensive to treat those components with a layer of copper nanorods,” Koratkar said, noting that his group plans to further pursue this possibility.

Along with Koratkar, co-authors of the paper include Rensselaer MANE Associate Professor Yoav Peles; Rensselaer mechanical engineering graduate student Zuankai Wang; Rensselaer Center for Integrated Electronics Research Associate Pei-I Wang; University of Colorado at Boulder Chancellor and former Rensselaer Provost G.P. “Bud” Peterson; and UC-Boulder Assistant Research Professor Chen Li.

The research was funded by the National Science Foundation.

Huge Genome-scale Phylogenetic Study Of Birds Rewrites Evolutionary Tree-of-life

The largest ever study of bird genetics has not only shaken up but completely redrawn the avian evolutionary tree. The study challenges current classifications, alters our understanding of avian evolution, and provides a valuable resource for phylogenetic and comparative studies in birds.

Birds are among the most studied and loved animals, and much of what we know about animal biology -- from natural history to ecology, speciation, reproduction, etc. -- is based on birds. Nevertheless, the avian tree-of-life has remained controversial and elusive -- until now.

For more than five years, the Early Bird Assembling the Tree-of-Life Research Project, centered at The Field Museum, has been examining DNA from all major living groups of birds. Thus far, scientists have built and analyzed a dataset of more than 32 kilobases of nuclear DNA sequences from 19 different locations on the DNA of each of 169 bird species. The results of this massive research, which is equivalent to a small genome project, will be published in Science on June 27, 2008.

"Our study and the remarkable new understanding of the evolutionary relationships of birds that it affords was possible only because of the technological advances of the last few years that have enabled us to sample larger portions of genomes," said Shannon Hackett, one of three lead authors and associate curator of birds at The Field Museum. "Our study yielded robust results and illustrates the power of collecting genome-scale data to reconstruct difficult evolutionary trees."

The results of the study are so broad that the scientific names of dozens of birds will have to be changed, and biology textbooks and birdwatchers' field guides will have to be revised. For example, we now know that:

Birds adapted to the diverse environments several distinct times because many birds that now live on water (such as flamingos, tropicbirds and grebes) did not evolve from a different waterbird group, and many birds that now live on land (such as turacos, doves, sandgrouse and cuckoos) did not evolve from a different landbird group.

Similarly, distinctive lifestyles (such as nocturnal, raptorial and pelagic, i.e., living on the ocean or open seas) evolved several times. For example, contrary to conventional thinking, colorful, daytime hummingbirds evolved from drab nocturnal nightjars; falcons are not closely related to hawks and eagles; and tropicbirds (white, swift-flying ocean birds) are not closely related to pelicans and other waterbirds.

Shorebirds are not a basal evolutionary group, which refutes the widely held view that shorebirds gave rise to all modern birds.

"With this study, we learned two major things," said Sushma Reddy, another lead author and Bucksbaum Postdoctoral Fellow at The Field Museum. "First, appearances can be deceiving. Birds that look or act similar are not necessarily related. Second, much of bird classification and conventional wisdom on the evolutionary relationships of birds is wrong."

Avian evolution

The evolution of birds has been notoriously difficult to determine. This is probably because modern birds arose relatively quickly (within a few million years) during an explosive radiation that occurred sometime between 65 million and 100 million years ago. The result of this rapid divergence early in the evolutionary history of birds is the fact that many groups of similar-looking birds (for example, owls, parrots and doves) have few, if any, living intermediary forms linking them to other well-defined groups of birds. This makes it very difficult to determine how some of these groups are evolutionarily related.

Many previous studies of avian evolution yielded conflicting results. This new study, however, is more robust because of the use of large amounts of sequence data from across the genome. The Early Bird group sequenced approximately 32 kilobases of aligned data per species, which is about five times more nuclear data than any previous study. Furthermore, the data were analyzed using several different methods and programs.

"Unlike other studies, we consistently found several well-supported, deep divisions within Neoaves (a basal division of birds that includes 95% of all living birds), and this signal was persistent across analyses," said Rebecca Kimball, the third lead author of the study and [associate professor of zoology] at the University of Florida, Gainesville.

The other co-authors of this study include scientists from the University of California, Berkeley; Smithsonian Institution; Stellenbosch University (South Africa); University of Maryland; Louisiana State University; Wayne State University; and the University of New Mexico. More than half of the people who worked on or trained in this project were women.

At The Field Museum, much of the DNA sequencing and analysis was conducted in the Pritzker Laboratory for Molecular Systematics and Evolution. The lab was established in 1974 for genetic research and to study and help preserve the world's biodiversity. Since 2000, over 190 scientists from 29 countries have trained in the lab. Today, there are more than 60 active projects in the Pritzker Lab, examining everything from sharks to plants to lichens, and from owls to flamingos.

Just last month, The Field Museum opened the Daniel F. and Ada L. Rice DNA Discovery Center, which puts a public face on the Pritzker Lab. The center opens up a working state-of-the-art laboratory to Museum visitors, who will be able to observe researchers extracting, sequencing, and analyzing DNA for several projects, including the Early Bird research. In addition, they will be able to speak with scientists at set times as they work.

In addition to the viewing area, the 1,850-square-foot DNA Discovery Center includes videos, hands-on interactives, and informative displays. The exhibition is intended for adults and students in junior high school and above. Located on the mezzanine overlooking Stanley Field Hall, the DNA Discovery Center is free with general admission.

There are an estimated 82 million birdwatchers in the United States alone, making it the country's second (to gardening) most popular hobby. Therefore, interest in the results of the Early Bird research project will be far reaching.

"We now have a robust evolutionary tree from which to study the evolution of birds and all their interesting features that have fascinated so many scientists and amateurs for centuries," Reddy said. "Birds exhibit substantial diversity (largest of the tetrapod groups), and using this 'family tree' we can begin to understand how this diversity originated as well as how different bird groups are interrelated."

Largest Crater In Solar System Revealed By NASA Spacecraft

New analysis of Mars' terrain using NASA spacecraft observations reveals what appears to be by far the largest impact crater ever found in the solar system.

NASA's Mars Reconnaissance Orbiter and Mars Global Surveyor have provided detailed information about the elevations and gravity of the Red Planet's northern and southern hemispheres. A new study using this information may solve one of the biggest remaining mysteries in the solar system: Why does Mars have two strikingly different kinds of terrain in its northern and southern hemispheres? The huge crater is creating intense scientific interest.

The mystery of the two-faced nature of Mars has perplexed scientists since the first comprehensive images of the surface were beamed home by NASA spacecraft in the 1970s. The main hypotheses have been an ancient impact or some internal process related to the planet's molten subsurface layers. The impact idea, proposed in 1984, fell into disfavor because the basin's shape didn't seem to fit the expected round shape for a crater. The newer data is convincing some experts who doubted the impact scenario.

"We haven't proved the giant-impact hypothesis, but I think we've shifted the tide," said Jeffrey Andrews-Hanna, a postdoctoral researcher at the Massachusetts Institute of Technology in Cambridge.

Andrews-Hanna and co-authors Maria Zuber of the Massachusetts Institute of Technology, and Bruce Banerdt of NASA's Jet Propulsion Laboratory in Pasadena, Calif., report the new findings in the journal Nature this week.

A giant northern basin that covers about 40 percent of Mars' surface, sometimes called the Borealis basin, is the remains of a colossal impact early in the solar system's formation, the new analysis suggests. At 8,500 kilometers (5,300 miles) across, it is about four times wider than the next-biggest impact basin known, the Hellas basin on southern Mars. An accompanying report calculates that the impacting object that produced the Borealis basin must have been about 2,000 kiolometers (1,200 miles) across. That's larger than Pluto.

"This is an impressive result that has implications not only for the evolution of early Mars, but also for early Earth's formation," said Michael Meyer, the Mars chief scientist at NASA Headquarters in Washington.

This northern-hemisphere basin on Mars is one of the smoothest surfaces found in the solar system. The southern hemisphere is high, rough, heavily cratered terrain, which ranges from 4 to 8 kilometers (2.5 to 5 miles) higher in elevation than the basin floor.

Other giant impact basins have been discovered that are elliptical rather than circular. But it took a complex analysis of the Martian surface from NASA's two Mars orbiters to reveal the clear elliptical shape of Borealis basin, which is consistent with being an impact crater.

One complicating factor in revealing the elliptical shape of the basin was that after the time of the impact, which must have been at least 3.9 billion years ago, giant volcanoes formed along one part of the basin rim and created a huge region of high, rough terrain that obscures the basin's outlines. It took a combination of gravity data, which tend to reveal underlying structure, with data on current surface elevations to reconstruct a map of Mars elevations as they existed before the volcanoes erupted.

"In addition to the elliptical boundary of the basin, there are signs of a possible second, outer ring -- a typical characteristic of large impact basins," Banerdt said.

A Plane With Wings Of Glass?

Imagine a plane that has wings made out of glass. Thanks to a major breakthrough in understanding the nature of glass by scientists at the University of Bristol, this has just become a possibility.

Despite its solid appearance, glass is actually a 'jammed' state of matter that moves very slowly. Like cars in a traffic jam, atoms in a glass can't reach their destination because the route is blocked by their neighbours, so it never quite becomes a 'proper' solid.

For more than 50 years most scientists have tried to understand just what glass is. Work so far has concentrated on trying to understand the traffic jam, but now Dr Paddy Royall from the University of Bristol, with colleagues in Canberra and Tokyo, has shown that the problem really lies with the destination, not with the traffic jam.

Publishing June 22, 2008, in Nature Materials, the team has revealed that glass 'fails' to be a solid due to the special atomic structures that form in a glass when it cools (ie, when the atoms arrive at their destination).

Royall explained: "Some materials crystallize as they cool, arranging their atoms into a highly regular pattern called a lattice. But although glass 'wants' to be a crystal, as it cools the atoms become jammed in a nearly random arrangement, preventing it from forming a regular lattice.

"Back in the 1950s, Sir Charles Frank in the Physics Department at Bristol University suggested that the arrangement of the 'jam' should form what is known as an icosahedron, but at the time he was unable to provide experimental proof. We set out to see if he was right."

The problem is you can't watch what happens to atoms as they cool because they are just too small. So using special particles called colloids that mimic atoms, but are just large enough to be visible using state-of-the-art microscopy, Royall cooled some down and watched what happened.

What he found was that the gel these particles formed also 'wants' to be a crystal, but it fails to become one due to the formation of icosahedra-like structures -- exactly as Frank had predicted 50 years ago. It is the formation of these structures that underlie jammed materials and explains why a glass is a glass and not a liquid -- or a solid.

Knowing the structure formed by atoms as a glass cools represents a major breakthrough in our understanding of meta-stable materials and will allow further development of new materials such as metallic glasses.

Metals normally crystallize when they cool, unfortunately stress builds up along the boundaries between crystals, which leads to metal failure. For example, the world's first jetliner, the British built De Havilland Comet, fell out of the sky due to metal failure. If a metal could be made to cool with the same internal structure as a glass and without crystal grain boundaries, it would be less likely to fail.

Metallic glasses could be suitable for a whole range of products that need to be flexible such as aircraft wings, golf clubs and engine parts.