Wednesday, May 26, 2010

MYSTERIOUS QUANTUM FORCES UNRAVELED

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MIT researchers find a way to calculate the effects of Casimir forces, offering a way to keep micromachines’ parts from sticking together.

Discovered in 1948, Casimir forces are complicated quantum forces that affect only objects that are very, very close together. They’re so subtle that for most of the 60-odd years since their discovery, engineers have safely ignored them. But in the age of tiny electromechanical devices like the accelerometers in the iPhone or the micromirrors in digital projectors, Casimir forces have emerged as troublemakers, since they can cause micromachines’ tiny moving parts to stick together.

MIT researchers have developed a powerful new tool for calculating the effects of Casimir forces, with ramifications for both basic physics and the design of microelectromechanical systems (MEMS). One of the researchers’ most recent discoveries using the new tool was a way to arrange tiny objects so that the ordinarily attractive Casimir forces become repulsive. If engineers can design MEMS so that the Casimir forces actually prevent their moving parts from sticking together — rather than causing them to stick — it could cut down substantially on the failure rate of existing MEMS. It could also help enable new, affordable MEMS devices, like tiny medical or scientific sensors, or microfluidics devices that enable hundreds of chemical or biological experiments to be performed in parallel.

Quantum mechanics has bequeathed a very weird picture of the universe to modern physicists. One of its features is a cadre of new subatomic particles that are constantly flashing in and out of existence in an almost undetectably short span of time. (The Higgs boson, a theoretically predicted particle that the Large Hadron Collider in Switzerland is trying to detect for the first time, is expected to appear for only a few sextillionths of a second.) There are so many of these transient particles in space — even in a vacuum — moving in so many different directions that the forces they exert generally balance each other out. For most purposes, the particles can be ignored. But when objects get very close together, there’s little room for particles to flash into existence between them. Consequently, there are fewer transient particles in between the objects to offset the forces exerted by the transient particles around them, and the difference in pressure ends up pushing the objects toward each other.

In the 1960s, physicists developed a mathematical formula that, in principle, describes the effects of Casimir forces on any number of tiny objects, with any shape. But in the vast majority of cases, that formula remained impossibly hard to solve. “People think that if you have a formula, then you can evaluate it. That’s not true at all,” says Steven Johnson, an associate professor of applied mathematics, who helped develop the new tools. “There was a formula that was written down by Einstein that describes gravity. They still don’t know what all the consequences of this formula are.” For decades, the formula for Casimir forces was in the same boat. Physicists could solve it for only a small number of cases, such as that of two parallel plates. Then, in 2006, came a breakthrough: MIT Professor of Physics Mehran Kardar demonstrated a way to solve the formula for a plate and a cylinder.

In a paper appearing in Proceedings of the National Academy of Sciences, Johnson, physics PhD students Alexander McCauley and Alejandro Rodriguez (the paper’s lead author), and John Joannopoulos, the Francis Wright Davis Professor of Physics, describe a way to solve Casimir-force equations for any number of objects, with any conceivable shape.

The researchers’ insight is that the effects of Casimir forces on objects 100 nanometers apart can be precisely modeled using objects 100,000 times as big, 100,000 times as far apart, immersed in a fluid that conducts electricity. Instead of calculating the forces exerted by tiny particles flashing into existence around the tiny objects, the researchers calculate the strength of an electromagnetic field at various points around the much larger ones. In their paper, they prove that these computations are mathematically equivalent.

For objects with odd shapes, calculating electromagnetic-field strength in a conducting fluid is still fairly complicated. But it’s eminently feasible using off-the-shelf engineering software.

“Analytically,” says Diego Dalvit, a specialist in Casimir forces at the Los Alamos National Laboratory, “it’s almost impossible to do exact calculations of the Casimir force, unless you have some very special geometries.” With the MIT researchers’ technique, however, “in principle, you can tackle any geometry. And this is useful. Very useful.”

Since Casimir forces can cause the moving parts of MEMS to stick together, Dalvit says, “One of the holy grails in Casimir physics is to find geometries where you can get repulsion” rather than attraction. And that’s exactly what the new techniques allowed the MIT researchers to do. In a separate paper published in March, physicist Michael Levin of Harvard University’s Society of Fellows, together with the MIT researchers, described the first arrangement of materials that enable Casimir forces to cause repulsion in a vacuum.

Dalvit points out, however, that physicists using the new technique must still rely on intuition when devising systems of tiny objects with useful properties. “Once you have an intuition of what geometries will cause repulsion, then the [technique] can tell you whether there is repulsion or not,” Dalvit says. But by themselves, the tools cannot identify geometries that cause repulsion.

(Photo: Alejandro Rodriguez)

MIT

NEW PROJECT AIMS FOR FUSION IGNITION

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MIT-led Ignitor reactor could be the world’s first to reach major milestone, perhaps paving the way for eventual power production.

Russia and Italy have entered into an agreement to build a new fusion reactor outside Moscow that could become the first such reactor to achieve ignition, the point where a fusion reaction becomes self-sustaining instead of requiring a constant input of energy. The design for the reactor, called Ignitor, originated with MIT physics professor Bruno Coppi, who will be the project’s principal investigator.

The concept for the new reactor builds on decades of experience with MIT’s Alcator fusion research program, also initiated by Coppi, which in its present version (called Alcator C-Mod) has the highest magnetic field and highest plasma pressure (two of the most important measures of performance in magnetic fusion) of any fusion reactor, and is the largest university-based fusion reactor in the world.

The key ingredient in all fusion experiments is plasma, a kind of hot gas made up of charged particles such as atomic nuclei and electrons. In fusion reactors, atomic nuclei — usually of isotopes of hydrogen called deuterium and tritium — are forced together through a combination of heat and pressure to overcome their natural electrostatic repulsion. When the nuclei join together, or fuse, they release prodigious amounts of energy.

Ignitor would be about twice the size of Alcator C-Mod, with a main donut-shaped chamber 1.3 meters across, and have an even stronger magnetic field. It will be much smaller and less expensive than the major international fusion project called ITER (with a chamber 6.2 meters across), currently under construction in France. Though originally designed to achieve ignition, the ITER reactor has been scaled back and is now not expected to reach that milestone.

The Ignitor reactor, Coppi says, will be “a very compact, inexpensive type of machine,” and unlike the larger ITER could be ready to begin operations within a few years. Its design is based on a particularly effective combination of factors that researchers unexpectedly discovered during the many years of running the Alcator program, and that were later confirmed in experiments at other reactors. Together, these factors produce especially good confinement of the plasma and a high degree of purity (impurities in the hot gases can be a major source of inefficiency). The new design aims to preserve these features to produce the highest plasma current densities — the amount of electric current in a given area of plasma. The design also has additional structures needed to produce and confine burning fusion plasmas in order to create the conditions needed for ignition, Coppi says.

Coppi plans to work with the Italian ministry of research and Evgeny Velikhov, president of the Kurchatov Institute in Moscow, to finalize the distribution of tasks for the machine, the core of which is to be built in Italy and then installed in Troitsk, near Moscow, on the site of that institute’s present Triniti reactor. Velikhov, as it happens, is also the chair of the ITER council. Coppi says of these two different programs, “there’s no competition, we are complementary.”

Although seen as a possible significant contributor to the world’s energy needs because it would be free of greenhouse-gas emissions, practical fusion power remains at least two decades away, most scientists in the field agree. But the initial impetus for setting up the Alcator reactor in the 1970s had more to do with pure science: “It was set up to simulate the X-ray stars that we knew at that time,” says Coppi, whose research work has as much to do with astrophysics as with energy. Stars are themselves made of plasma and powered by fusion, and the only way to study their atomic-level behavior in detail is through experiments inside fusion reactors.

Once the reactor was in operation, he says, “we found we were producing plasmas with unusual properties,” and realized this might represent a path to the long-sought goal of fusion ignition.

Roscoe White, a distinguished research fellow at the Princeton Plasma Physics Laboratory, says that “the whole point of Ignitor is to find out how a burning plasma behaves, and there could be pleasant or unpleasant results coming from it. Whatever is learned is a gain. Nobody knows exactly how it will perform, that is the point of the experiment.” But while its exact results are unknown, White says it is important to pursue this project in addition to other approaches to fusion. “With our present knowledge it is very risky to commit the program to a single track reactor development — our knowledge is still in flux,” he says.

In addition, he says, “the completion of ITER, the only currently projected burning plasma experiment, is decades off. Experimental data concerning a burning plasma would be very welcome, and could lead to important results helping the cause of practical fusion power.” Furthermore, the Ignitor approach, if all goes well, could lead to more compact and economical future reactors: Some recent results from existing reactors, plus new information to be gained from Ignitor, “could lead to reactor designs much smaller and simpler than ITER,” he says.

Coppi remains especially interested in the potential of the new reactor to make new discoveries about fundamental physics. Quoting the late MIT physicist and Institute Professor Bruno Rossi, Coppi says, “whenever you do experiments in an unknown regime, you will find something new.” The new machine’s findings, he suggests, “will have a strong impact on astrophysics.”

(Photo: Bruno Coppi)

MIT

MARRIAGE AND LIFE EXPECTANCY

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Marriage is more beneficial for men than for women - at least for those who want a long life. Previous studies have shown that men with younger wives live longer. While it had long been assumed that women with younger husbands also live longer, in a new study Sven Drefahl from the Max Planck Institute for Demographic Research (MPIDR) in Rostock, Germany, has shown that this is not the case. Instead, the greater the age difference from the husband, the lower the wife’s life expectancy. This is the case irrespective of whether the woman is younger or older than her spouse.

Related to life expectancy choosing a wife is easy for men - the younger the better. The mortality risk of a husband who is seven to nine years older than his wife is reduced by eleven percent compared to couples where both partners are the same age. Conversely, a man dies earlier when he is younger than his spouse.

For years, researchers have thought that this data holds true for both sexes. They assumed an effect called "health selection" was in play; those who select younger partners are able to do so because they are healthier and thus already have a higher life expectancy. It was also thought that a younger spouse has a positive psychological and social effect on an older partner and can be a better caretaker in old age, thereby helping to extend the partner’s life.

"These theories now have to be reconsidered", says Sven Drefahl from MPIDR. "It appears that the reasons for mortality differences due to the age gap of the spouses remain unclear." Using data from almost two million Danish couples, Drefahl was able to eliminate the statistical shortcomings of earlier research, and showed that the best choice for a woman is to marry a man of exactly the same age; an older husband shortens her life, and a younger one even more so.

According to Drefahl’s study, published May 12th in the journal Demography, women marrying a partner seven to nine years younger increase their mortality risk by 20 percent. Hence, "health selection" can’t be true for women; healthy women apparently don’t go chasing after younger men. While many studies on mate selection show that women mostly prefer men the same age, most of them end up with an older husband. In the United States, on average a groom is 2.3 years older than his bride. "It’s not that women couldn’t find younger partners; the majority just don’t want to", says Sven Drefahl.

It is also doubtful that older wives benefit psychologically and socially from a younger husband. This effect only seems to work for men. "On average, men have fewer and lesser quality social contacts than those of women," says Sven Drefahl. Thus, unlike the benefits of a younger wife, a younger husband wouldn’t help extend the life of his older wife by taking care of her, going for a walk with her and enjoying late life together. She already has friends for that. The older man, however, doesn’t.

This means that women don’t benefit by having a younger partner, but why does he shorten their lives? "One of the few possible explanations is that couples with younger husbands violate social norms and thus suffer from social sanctions," says Sven Drefahl. Since marrying a younger husband deviates from what is regarded as normal, these couples could be regarded as outsiders and receive less social support. This could result in a less joyful and more stressful life, reduced health, and finally, increased mortality.

While the new MPIDR study shows that marriage disadvantages most women when they are not the same age as their husband, it is not true that marriage in general is unfavorable. Being married raises the life expectancy of both men and women above those that are unmarried. Women are also generally better off than men; worldwide their life expectancy exceeds that of men by a few years.

(Photo: Sven Drefahl)

Max Planck Institute

SUPERMASSIVE BLACK HOLE IS THROWN OUT OF GALAXY

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Undergraduate student Marianne Heida of the University of Utrecht has found what appears to be a supermassive black hole leaving its home galaxy at high speed. As part of an international team of astronomers, this extraordinary discovery appears in a paper in the journal Monthly Notices of the Royal Astronomical Society.

For her final year project, Marianne worked at the SRON Netherlands Institute for Space Research, used the Chandra Source Catalog (made using the orbiting Chandra X-ray Observatory) to compare hundreds of thousands of sources of X-rays with the positions of millions of galaxies. Normally each galaxy contains a supermassive black hole at its centre. The material that falls into black holes heats up dramatically on its final journey and often means that black holes are strong X-ray sources.

X-rays are also able to penetrate the dust and gas that obscures the centre of a galaxy, giving astronomers a clear view of the region around the black hole, with the bright source appearing as a starlike point. Looking at one galaxy in the Catalog, Marianne noticed that the point of light was offset from the centre and yet was so bright that it could well be associated with a supermassive black hole.

The black hole appears to be in the process of being expelled from its galaxy at high speed. Given that these objects can have masses equivalent to 1 billion Suns, it takes a special set of conditions to cause this to happen.

Marianne’s newly-discovered object is probably the result of the merger of two smaller black holes. Supercomputer models suggest that the larger black hole that results is shot out away at high speed, depending on the direction and speed in which the two black holes rotate before their collision. In any case, it provides a fascinating insight into the way in which supermassive black holes develop in the centre of galaxies.

Marianne’s research – which was carried out under the supervision of SRON researcher Peter Jonker - suggests this discovery may be only the tip of the iceberg, with others subject to future confirmation using the Chandra Observatory. She comments: "We have found many more objects in this strange class of X-ray sources. With Chandra we should be able to make the accurate measurements we need to pinpoint them more precisely and identify their nature."

Finding more recoiling black holes will provide a better understanding of the characteristics of black holes before they merge. In future, it might even be possible to observe this process with the planned LISA satellite, an instrument capable of measuring the gravity waves that the two merging black holes emit. Ultimately this information will let scientists know if supermassive black holes in the cores of galaxies really are the result of many lighter black holes merging together.

(Photo: STScI / NASA)

The Royal Astronomical Society

TEAM HARNESSING POWER OF PHOTOSYNTHESIS TO MAKE GREEN FUEL

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When people at cocktail parties used to ask Charles Schmuttenmaer what he did, he would say he was a chemistry professor who worked on transient-photo conductivity in gallium arsenide. "At that point they would generally ask me to pass the chips," the Yale chemist says with a laugh.

Now Schmuttenmaer tells them he's working on a way to harness the power of the sun to produce carbon-neutral fuel. "And then the response is, ‘Oh, that's wonderful. Way to go!'" he says.

A few years ago, Schmuttenmaer never imagined he'd be working to solve the world's energy problem. But that's exactly what he now does as one of the four founding members of the Yale Solar Group — a team of chemists trying to use sunlight to split water into its elementary components: hydrogen (a green fuel) and oxygen. In doing so, they hope to pave the way for the development of photoelectrochemical cells that could be used to generate an environmentally benign transportation fuel.

It's a challenge two of the team members — Yale chemists Gary Brudvig and Robert Crabtree — have been working on for the past 25 years, studying the process of photosynthesis and how to replicate it in artificial, "biomimetic" systems.

Four years ago another Yale scientist, theoretical chemist Victor Batista, began creating computational models of molecules that could absorb visible light and make oxygen from water. The models suggested the possibility of developing artificial photosynthetic systems based on molecules studied by Brudvig and Crabtree and on semiconductor materials that had been studied by Schmuttenmaer, an expert in laser spectroscopy.

"We decided that maybe the time was right to join forces and put everything together," Brudvig says, recalling the early days of the collaboration that has become the Yale Solar Group.

Photosynthesis is a seemingly simple process whereby plants use the sun's energy to convert carbon dioxide (CO2) into fuel — in their case, food in the form of sugars. "The equation looks deceptively simple from a chemistry point of view, but it involves hundreds of steps and many, many different components," explains Brudvig, the Eugene Higgins Professor of Chemistry and professor of molecular biophysics and biochemistry.

To tackle this complicated problem, the group began meeting in Batista's basement conference room once a week to discuss their work and the progress they were making.

Each member of the collaboration works on a different aspect of the problem. Brudvig and Crabtree work mostly on designing small chemical compounds that can make oxygen from water and figuring out how to attach those molecules to semiconductor surfaces. Schmuttenmaer uses laser spectroscopy to help understand the photochemical reactions (those involving light) and the movement of electrons within the system, while Batista provides the computational models that explain exactly what's happening at the atomic level, how different components work and how they can be improved.

All four members work closely together. Between them, they bring to the table expertise in organic, inorganic, theoretical, biophysical and synthetic chemistry. "Our expertise doesn't overlap — it's complementary," says Crabtree. "I think that's been key. All four components are essential to finding a solution."

The need to find carbon-neutral energy sources is well understood in scientific circles, and becoming more so among policymakers and the members of the general public. But the challenge is a difficult one. Current photovoltaic cells convert sunlight into electricity, but they're costly — and with commercial models operating at about 15% efficiency, they waste a lot of energy. About half of the electricity now produced is lost during transmission, and there isn't a good method to store the rest.

So instead of trying to improve on current models, the team looked to nature for inspiration. During photosynthesis, plants convert sunlight directly into fuel, rather than electricity, and all they require is water and CO2. "The reason this sort of research is gaining more interest now is because, as we think about sustainable systems, water seems to be the only practical source of electrons that is abundant and cheap enough for fuel production on a large scale," Brudvig says.

The Yale Solar Group ultimately hopes to develop the technology for commercial photoelectrochemical cells that would use sunlight to churn out oxygen on one end and transportation fuel on the other. Hydrogen, as the other component in H2O, is an obvious "green" fuel choice, but it's volatile, so the group is also looking at ways to potentially produce a liquid fuel such as methanol down the road. Whatever fuel is generated would be carbon-neutral, because the CO2 it would produce when burned would simply replace the CO2 that was taken out of the environment and used to create it in the first place.

Today the group has expanded beyond the walls of Batista's basement room. They still meet once a week, but those meetings now include upwards of 20 graduate students and postdoctoral researchers in addition to the four chemistry professors.

It's a far cry from the single postdoctoral researcher and two graduate students that the group started out with four years ago, recalls Robert Snoeberger, a fourth-year graduate student who has worked with the collaboration since the beginning. As a computational chemist, Snoeberger looks at the properties and design of light-absorbing molecules that might be useful to the group. Although he works primarily with Batista, "it's nice to get the viewpoint of the experimentalists," he says. "Usually you don't get feedback until after you publish your results."

Gary Moore, a postdoctoral fellow in the chemistry department, came to Yale last summer specifically because of the work being done by the Yale Solar Group. "It's really exciting to be able to work with a group where everyone has a different background but they are all at the forefront of their respective areas," he says. "Even though they're all chemists, they all have different approaches to the same problem."

Even more attractive to the students is the chance to work on a real-world challenge. "The energy crisis is at the forefront of the world's problems," Moore says. "It's not a problem finding sources of energy — it's a problem finding carbon-neutral energy. We're going to have to find a solution in the next 20 years."

Moore and the other members of the Yale Solar Group are big believers in the potential of the sun's energy. The 120,000 terawatts the sun constantly showers on Earth provides enough energy in one hour to power the entire planet for a full year.

But the need for alternative energy sources wasn't always recognized, even by the scientific community. When Brudvig and Crabtree started working on artificial photosynthesis in the 1980s, they were among a small number of chemists doing such research. Today, the team is happy to see alternative energy research receiving much more attention.

Recently, the various members of the group received substantial federal funding as part of three different Energy Frontier Research Centers, which were established last year to address fundamental research ranging from solar energy to electricity storage to carbon sequestration in order to find novel ways to tackle the growing energy crisis. The group is involved with three of the 46 centers that span the nation, most of them hosted by universities or national laboratories and each involving dozens of researchers from different institutions.

As for their own project, the group reached a major milestone last fall when Brudvig and Crabtree confirmed that they've found a water-splitting catalyst they expect will function in a photoelectrochemical cell, the device that splits water when exposed to sunlight.

"We've taken a big step forward to create a system that can do visible-light water-splitting. Now we have to improve its efficiency to actually make it practical," Brudvig says.

Next the team will work on creating molecular hydrogen from the ions that are present in water. Or they might focus on reducing CO2 to make methanol. Wherever the research leads, the members of the Yale Solar Group plan to continue the collaboration that has worked so well for the past several years into the — hopefully greener — future.

"I would say energy is going to be the most important scientific issue of the twenty-first century because of all the implications, from warfare to poverty to sustainability," Schmuttenmaer says. "What I find really gratifying is to be part of this project where my science is now contributing to a really important problem. It makes me feel really good to know that the work I'm doing might really help the world."

(Photo: Yale U.)

Yale University

DEATH OF A STAR IN THREE DIMENSIONS

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Researchers at the Max Planck Institute for Astrophysics in Garching have for the first time managed to reproduce the asymmetries and fast-moving iron clumps of observed supernovae by complex computer simulations in all three dimensions. To this end they successfully followed the outburst in their models consistently from milliseconds after the onset of the blast to the demise of the star several hours later.

Massive stars end their lives in gigantic explosions, so called supernovae, and can become - for a short time - brighter than a whole galaxy, which is made up of billions of stars. Although supernovae have been studied theoretically by computer models for several decades, the physical processes happening during these blasts are so complex that until now astrophysicists could only simulate parts of the process and so far only in one or two dimensions. Researchers at the Max Planck Institute for Astrophysics in Garching have now carried out the first fully three-dimensional computer simulations of a core collapse supernova over a timescale of hours after the initiation of the blast. They thus could answer the question of how initial asymmetries, which emerge deep in the dense core during the very early stages of the explosion, fold themselves into inhomogeneities observable during the supernova blast.

While the great energy of the outburst makes these stellar explosions visible far out into the Universe, they are relatively rare. In a galaxy of the size of our Milky Way, on average only one supernova will occur in 50 years. About twenty years ago, a supernova could be seen even with the naked eye: SN 1987A in the Tarantula Nebula in the Large Magellanic Cloud, our neighbouring galaxy. This relative closeness - "only" about 170,000 light years away - allowed many detailed observations in different wavelength bands over weeks and even months. SN 1987A turned out to be a core-collapse supernova, a so-called Type II event. It occurs when a massive star, which is at least nine times heavier than the sun, has burned almost all its fuel. The fusion engine in the centre of the star begins to stutter, triggering an internal collapse and thus a violent explosion of the entire star. In the case of SN 1987A the star had about 20 solar masses at its birth.

SN 1987A is probably the best studied supernova and it is still a great challenge to develop and refine models of what was happening inside the dying star to produce its emission of radiation. One of the astonishing and unexpected discoveries in SN 1987A and many subsequent supernovae was the fact that nickel and iron - heavy elements that are formed near the centre of the explosion - are mixed outward in big clumps into the hydrogen shell of the disrupted star. Nickel bullets were observed to propagate at velocities of thousands of kilometres per second, much faster than the surrounding hydrogen and much faster than predicted by simple hydrodynamic calculations in one dimension (1D), i.e., only studying the radial profile from the centre outwards.

In fact, it turned out that the brightness evolution (the so-called light curve) of SN 1987A and of similar core-collapse supernovae can only be understood if large amounts of heavy core material (in particular radioactive nickel) are mixed outwards into the stellar envelope, and light elements (hydrogen and helium from the envelope) are carried inwards to the core.

The details of supernova explosions are very difficult to simulate, not only because of the complexity of the physical processes involved but also because of the duration and range of scales - from hundreds of metres near the centre to tens of millions of kilometres near the stellar surface - that need to be resolved in ultimately three-dimensional (3D) computer models. Previously conducted simulations in two dimensions (2D, i.e., with the assumption of axial symmetry) indeed showed that the spherical shell structure of the progenitor star is destroyed during the supernova blast and large-scale mixing takes place. But the real world is three-dimensional and not all observational aspects can be reproduced by 2D models.

The new computer models of the team at the Max Planck Institute for Astrophysics can now for the first time simulate the complete burst in all three dimensions, from the first milliseconds after the explosion is triggered in the core to a time three hours later, when the shock breaks out of the progenitor star. "We found substantial deviations in our 3D models compared to previous work in 2D," says Nicolay Hammer, the lead author of the paper, "especially the growth of instabilities and the propagation of clumps differ. These are not just minor variations; this effect determines the long-time evolution and ultimately the extent of mixing and observable appearance of core-collapse supernovae."

In the 3D-simulations, metal-rich clumps have much higher velocities than in the 2D case. These "bullets" expand much more rapidly, overtaking material from the outer layers. "With a simple analytic model we could demonstrate that the different geometry of the bullets, toroidal versus quasi-spherical, can explain the differences observed in our simulations," explains co-author Thomas Janka. "While we think that the differences between the 2D- and 3D-models that we found are probably generic, many features will depend strongly on the structure of the progenitor star, the overall energy and the initial asymmetry of the blast."

"We hope that our models, in comparison to observations, will help us to understand how stellar explosions start and what causes them", adds Ewald Müller, the third author of the paper. Investigating a wider variety of progenitor stars and initial conditions will therefore be the focus of future simulation work. In particular, a detailed model that reproduces all observational features of SN 1987A still remains a challenge.

(Photo: MPA)

Max Planck Institute

EASTER ISLAND DISCOVERY SENDS ARCHAEOLOGISTS BACK TO DRAWING BOARD

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Archaeologists have disproved the fifty-year-old theory underpinning our understanding of how the famous stone statues were moved around Easter Island.

Fieldwork led by researchers at University College London and The University of Manchester, has shown the remote Pacific island’s ancient road system was primarily ceremonial and not solely built for transportation of the figures.

A complex network of roads up to 800-years-old crisscross the Island between the hat and statue quarries and the coastal areas.

Laying alongside the roads are dozens of the statues- or moai.

The find will create controversy among the many archaeologists who have dedicated years to finding out exactly how the moai were moved, ever since Norwegian adventurer Thor Heyerdahl first published his theory in 1958.

Heyerdahl and subsequent researchers believed that statues he found lying on their backs and faces near the roads were abandoned during transportation by the ancient Polynesians.

But his theory has been completely rejected by the team led by Manchester’s Dr Colin Richards and UCL’s Dr Sue Hamilton.

Instead, their discovery of stone platforms associated with each fallen moai - using specialist ‘geophysical survey’ equipment – finally confirms a little known 1914 theory of British archaeologist Katherine Routledge that the routes were primarily ceremonial avenues.

The statues, say the Manchester and UCL team just back from the island, merely toppled from the platforms with the passage of time.

“The truth of the matter is, we will never know how the statues were moved,” said Dr Richards.

“Ever since Heyerdahl, archeologists have come up with all manner of theories – based on an underlying assumption that the roads were used for transportation of the moai, from the quarry at the volcanic cone Rano Raraku.

”What we do now know is that the roads had a ceremonial function to underline their religious and cultural importance.

“They lead – from different parts of the island – to the Rano Raraku volcano where the Moai were quarried.

“Volcano cones were considered as points of entry to the underworld and mythical origin land Hawaiki.

“Hence, Rano Ranaku was not just a quarry but a sacred centre of the island.”

The previous excavation found that the roads are concave in shape –making it difficult to move heavy objects along them

And as the roads approach Rano Raraku, the statues become more frequent – which the team say, indicated an increasing grades of holiness.

“All the evidence strongly shows that these roads were ceremonial - which backs the work of Katherine Routledge from almost 100 years ago, “ said Dr Sue Hamilton.

“It all makes sense: the moai face the people walking towards the volcano.

“The statues are more frequent the closer they are to the volcano – which has to be way of signifying the increasing levels of importance.”

She added: “What is shocking is that Heyerdahl actually found some evidence to suggest there were indeed platforms.

“But like many other archaeologists, he was so swayed by his cast iron belief that the roads were for transportation – he completely ignored them.”

(Photo: U. Manchester)

The University of Manchester

CHEMICAL REMAINS OF DINOBIRD FOUND

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A 150-million-year old ‘Dinobird’ fossil, long thought to contain nothing but fossilized bone and rock, has been hiding remnants of the animal's original chemistry, according to new research.

The sensational discovery by an international team of palaeontologists, geochemists and physicists was made after carrying out state-of-the art analysis of one the world’s most important fossils - the half-dinosaur/half-bird species called Archaeopteryx.

The discovery could revolutionize the field of palaeontology say the team led by scientists at The University of Manchester and the Department of Energy's SLAC National Accelerator Laboratory in the United States.

By recording how ‘bright X-rays’ interacted with the fossil, the team have created maps showing chemical elements which were part of the living animal itself.

The maps, published today in the journal Proceedings of National Academy of Science, show that portions of the feathers are not merely impressions of long-decomposed organic material—as was previously believed.

Instead, they include fossilized fragments of actual feathers containing phosphorous and sulfur, elements that compose modern bird feathers.

Trace amounts of copper and zinc were also found in the Dinobird's bones: like birds today, the Archaeopteryx may have required those elements to stay healthy.

University of Manchester palaeontologist Dr Phil Manning said: "Archaeopteryx is to palaeontology what Tutankhamen is to archaeology. It's simply one of the icons of our field.

"You would think after 150 years of study, we'd know everything we need to know about this animal. But guess what—we were wrong."

Lead author geochemist Dr Roy Wogelius from The University of Manchester said: "We talk about the physical link between birds and dinosaurs, and now we have found a chemical link between them.

"In the fields of palaeontology and geology, people have studied bones for decades. But this whole idea of the preservation of trace metals and the chemical remains of soft tissue is quite exciting."

The researchers found significantly different concentrations of elements in the fossil than in the surrounding rock, confirming they are remnants of the Dinobird and not leached from the surrounding rock into the fossil.

SLAC physicist Uwe Bergmann, who led the X-ray scanning experiment, said: "People have never used a technique this sensitive on Archaeopteryx before.

"Because the SSRL beam is so bright, we were able to see the teeniest chemical traces that nobody thought were there."

Researcher Bob Morton said: “The discovery that certain fossils retain the detailed chemistry of the original organisms offers scientists a new avenue for learning about long-extinct creatures.

As a result, say the team, the research could change the way palaeontologists work.

Dr Wogelius added: "We're able to read so much more into these organisms now using this technology - we're literally touching ghosts.

"Chemistry is the real key in the future of palaeontology. It's a paradigm shift."

Dr Manning added: “I wouldn't be surprised if future excavations look more like CSI investigations where people look for clues at a scene of a crime.

“There's info that's still there that can't be seen with the naked eye.

“We can only see these valuable pieces of data using the x-ray vision that the synchrotron provides.”

(Photo: U. Manchester)

The University of Manchester

CAN A MOTHER'S VOICE SPUR RECOVERY FROM A COMA?

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Karen Schroeder's voice, recorded on a CD, reminded her son, Ryan, of his 4-H project when he was 10 and decided to raise pigs. "You bid on three beautiful squealing black and white piglets at the auction," she said softly. "We took them home in the trunk of our Lincoln Town Car, because we didn't have a truck."

Recordings from Ryan's mother, father or sister were played through headphones for him four times a day. They were part of a new clinical trial investigating whether repeated stimulation with familiar voices can help repair a coma victim's injured brain networks and spur his recovery.

In January 2009, Ryan, a 21-year-old college student from Huntley, Ill., was in a coma after he had been flung from his snowmobile into a tree during an ice storm. He had a traumatic brain injury; the fibers of his brain had been twisted and stretched from the impact.

He regained consciousness after nearly one month in the trial and has made steady progress during the past year. Researchers, however, won't know for certain if the therapy helped his recovery until the study is over.

The trial is being led by Theresa Pape, a research assistant professor of physical medicine and rehabilitation at Northwestern University Feinberg School of Medicine and a research health scientist at Hines VA Hospital. Funded by the U.S. Department of Veteran Affairs, the research may be useful to young people like Ryan as well as soldiers injured in combat, who have a high rate of traumatic brain injuries from roadside bombs.

"Traumatic brain injury is a huge issue in our society," Pape said. "Every 21 seconds, we have a new head injury and about one-third of those will be severe."

The most common cause of severe head injury in the civilian population is motor vehicle accidents, and the highest-risk group is 16-to-24-year-old males. In the military, the risk of traumatic brain injury is three times that of civilians, even in peacetime. While the actual number is not known, an estimated 8,470 soldiers were diagnosed with traumatic brain injury from January 2003 through September 2008. (Pape thinks that number is low, because many troops have not been evaluated for mild traumatic brain injury.)

Pape hopes the study will provide an answer to the question that families are desperate to know when a loved one is in a coma: ‘Can he hear me?' She is especially eager to know if these family voices can facilitate repair of the brain to improve the subject's ability to function and process and understand information.

Pape's hypothesis is that repeated exposure to familiar voices could help repair the brain's neural networks, some of which become sheared in traumatic brain injury. In a previous small pilot study, Pape observed that subjects in a vegetative state responded more to the voices of people who are familiar to them compared with non-familiar voices.

When those subjects heard voices of their family members, an MRI scan showed that parts of their brain were activated, appearing as bright yellow and red blobs of light scattered in an unorganized pattern. With unfamiliar voices, there was little activation.

"The question became are the familiar voices therapeutic in some way?" Pape asked. "Will they spur an improvement in behavior?"

Her background as a speech pathologist inspired the research. "I was weaned on language processing, how the brain responds to different linguistic stimuli as well as familiar or non-familiar voices, different sounds," Pape said. "This is a very speech pathology-based study."

When a subject is enrolled in the trial, Pape does a baseline functional MRI scan of his brain, examining the reaction to familiar versus unfamiliar voices. In a healthy person, she would expect to see a family member's voice activate the temporal lobe, the site of memory, and the frontal lobe, the part of the brain that pays attention when your name is called aloud. She doesn't see that in her subjects with new severe traumatic brain injury.

"As they recover, we want to see if these areas become activated in the way we'd expect in a healthy person," Pape said.

Pape also tracks the state of their axons, the thick white fibers that comprise the brain's networks and allow different parts of the brain to communicate with each other. In a traumatic brain injury, the axons can become ripped and twisted like interstate highways in a Hollywood disaster movie.

"In a healthy brain, the networks function in a very organized manner, from front to back, for example," Pape said. "The injured brain has a disorganized direction we don't understand. The axons are sheared, torqued and twisted. We're trying to figure out how and if they work after a severe brain injury. Maybe they zigzag or connect with an unexpected neuron."

For the trial, subjects are divided into three groups: high dose, who hear 10 minutes of stories daily four times a day for six weeks; low dose, who hear five minutes of stories and 35 minutes of silence four times a day; and the "sham" group who wear the head phones but don't hear any stories. After six weeks, Pape measures how the subject's behavioral condition compares to changes she sees in the brain on new MRI images.

The trial is double blinded, meaning Pape will not know whether subjects were in the high, low or sham dose group until the study, which will enroll about 45 subjects, is completed in 2011. The earlier description of Karen Schroeder's voice being played for Ryan occurred after the initial double-blinded part of the study. After this part, all subjects receive the high dose of stories for six weeks to make sure that if there is a benefit, everyone has the same advantage.

Pape's imaging data of a subject's brain before and after the voice treatment will reveal if networks are better connected as a result of the therapy, and if that is linked to improvement in the subject's functioning.

When Schroeder enrolled her son in the trial in late February 2009, about a month after his accident, he could not follow commands or make purposeful movements. His eyes were open, but he did not seem to be aware of his environment. At the time, a doctor had told Schroeder to make arrangements to place her son in a nursing home.

But after three weeks in the trial, Schroeder began to notice changes in her son. First, she said, Ryan began to notice the lights outside the window of his room in the Northwestern University Clinical Research Unit on the 10th floor of Northwestern Memorial Hospital, the location where he received the voice therapy.

"I could tell he was starting to come around," Schroeder said. "Before, he would lay in the bed and a herd of cattle could walk through and he would not be aware that they were there. Now, little by little he would start to respond.

Then, he began to slowly follow a command to push a ball out of his hand. A little more than a year later, Ryan now texts his friends, brushes his teeth and walks with a walker or a four-prong cane. He is practicing walking without a device. While he struggles with poor balance, he recently started eye therapy, which may or may not help his balance. A palate lift several months ago greatly improved his speech, according to Schroeder. Ryan continues with physical, occupational and speech therapies at the Rehabilitation Institute of Chicago in Wheeling.

"Given the extent of his injuries, Ryan has recovered well," Pape said. "But I can't draw any conclusions yet. We have to wait until we have all the study data."

In the meantime, Ryan helps at his family's asphalt paving business where he enters data into the computer. He doesn't remember his accident or hearing the tapes of his family. "He continues to make progress. It is truly a remarkable recovery," said Karen Schroeder. "The good Lord keeps throwing us ropes. We got involved in this by the grace of God."

Northwestern University

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