Levitation At Microscopic Scale Could Lead To Nanomechanical Devices Based On Quantum Levitation

Magicians have long created the illusion of levitating objects in the air. Now researchers have actually levitated an object, suspending it without the need for external support. Working at the molecular level, the researchers relied on the tendency of certain combinations of molecules to repel each other at close contact, effectively suspending one surface above another by a microscopic distance.

This is an artist's rendition of how the repulsive Casimir-Lifshitz force between suitable materials in a fluid can be used to quantum mechanically levitate a small object of density greater than the liquid. Figures are not drawn to scale. In the foreground a gold sphere, immersed in Bromobenzene, levitates above a silica plate. Background: when the plate is replaced by one of gold levitation is impossible because the Casimir-Lifshitz force is always attractive between identical materials. (Credit: Courtesy of the lab of Federico Capasso, Harvard School of Engineering and Applied Sciences)

Researchers from Harvard University and the National Institutes of Health (NIH) have measured, for the first time, a repulsive quantum mechanical force that could be harnessed and tailored for a wide range of new nanotechnology applications.

The study, led by Federico Capasso, Robert L. Wallace Professor of Applied Physics at Harvard's School of Engineering and Applied Science (SEAS), will be published as the January 8 cover story of Nature.

The discovery builds on previous work related to what is called the Casimir force. While long considered only of theoretical interest, physicists discovered that this attractive force, caused by quantum fluctuations of the energy associated with Heisenberg's uncertainty principle, becomes significant when the space between two metallic surfaces, such as two mirrors facing one another, measures less than about 100 nanometers.

"When two surfaces of the same material, such as gold, are separated by vacuum, air, or a fluid, the resulting force is always attractive," explained Capasso.

Remarkably, but in keeping with quantum theory, when the scientists replaced one of the two metallic surfaces immersed in a fluid with one made of silica, the force between them switched from attractive to repulsive. As a result, for the first time, Capasso and his colleagues measured what they have deemed a repulsive Casimir.

To measure the repulsive force, the team immersed a gold coated microsphere attached to a mechanical cantilever in a liquid (bromobenzene) and measured its deflection as the distance from a nearby silica plate was varied.

"Repulsive Casimir forces are of great interest since they can be used in new ultra-sensitive force and torque sensors to levitate an object immersed in a fluid at nanometric distances above a surface. Further, these objects are free to rotate or translate relative to each other with minimal static friction because their surfaces never come into direct contact," said Capasso.

By contrast, attractive Casimir forces can limit the ultimate miniaturization of small-scale devices known as Micro Electromechanical Systems (MEMS), a technology widely used to trigger the release of airbags in cars, as the attractive forces may push together moving parts and render them inoperable, an effect known as stiction.

Potential applications of the team's finding include the development of nanoscale-bearings based on quantum levitation suitable for situations when ultra-low static friction among micro- or nano-fabricated mechanical parts is necessary. Specifically, the researchers envision new types of nanoscale compasses, accelerometers, and gyroscopes.

Capasso's coauthors are Jeremy Munday, formerly a graduate student in Harvard's Department of Physics and presently a postdoctoral researcher at the California Institute of Technology, and Dr. V. Adrian Parsegian, Senior Investigator at the National Institutes of Health in Bethesda, Maryland. The Harvard researchers have filed for a U.S. patent covering nanodevices based on quantum levitation.

The authors acknowledge the support of the Center for Nanoscale Systems at Harvard University, a member of the National Nanotechnology Infrastructure Network; the National Science Foundation; the Intramural Research Program of the NIH; and the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

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Two-Dimensional High-Temperature Superconductor Discovered

Scientists at Brookhaven Lab have discovered a state of two-dimensional (2D) fluctuating superconductivity in a high-temperature superconductor with a particular arrangement of electrical charges known as "stripes."

A superconductor, like the one shown above, conducts electricity with no resistance.
(Credit: Image courtesy of DOE/Brookhaven National Laboratory)

The finding was uncovered during studies of directional dependence in the material's electron-transport and magnetic properties. In the 2D plane, the material acts as a superconductor - conducts electricity with no resistance - at a significantly higher temperature than in the 3D state.

"The results provide many insights into the interplay between the stripe order and superconductivity, which may shed light on the mechanism underlying high-temperature superconductivity," said Brookhaven physicist Qiang Li.

Understanding the mechanism of high-temperature superconductivity is one of the outstanding scientific issues in condensed matter physics, Li said. Understanding this mechanism could lead to new strategies for increasing the superconducting transition temperature of other superconductors to make them more practical for applications such as electrical transmission lines.

"As electricity demand increases, the challenge to the national electricity grid to provide reliable power will soon grow to crisis levels," Li said. "Superconductors offer powerful opportunities for restoring the reliability of the power grid and increasing its capacity and efficiency by providing reactive power reserves against blackouts, and by generating and transmitting electricity."

This research was presented at The March 2008 American Physical Society Meeting in New Orleans, La., March 10 -14.

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Superconducting State Can Be Induced By High Pressure In So-called High-temperature Superconductors

Superconductors can convey more than 150 times more electricity than copper wires because they don't restrict electron movement, the essence of electricity. But to do this, the materials have to be cooled below a very low, so-called, transition temperature, which often makes them impractical for widespread use. Now for the first time, scientists have found that in addition to chemical manipulation, the superconducting state can be induced by high pressure in so-called high-temperature superconductors. The discovery, published in the May 30, 2008, issue of Physical Review Letters, opens a new window on understanding and harnessing these miracle materials.

This graph is a 3D phase diagram which compares conditions under which the
superconducting state in a bismuth-based high-temperature
be induced. The graph shows changes by “doping” (x)—the removal of an electron
equivalent to addition of a “hole” or positive charge (x)—pressure (P), and temperature (T).
The onset of superconductivity (pink area) and the “insulator-to-metal” transition occurs
at higher doping and at higher pressure. The line at 21GPa (207,000 atmospheres) is nearly
vertical, which indicates a similarity in the behaviour of electrons’ coupled spins (magnons)
and units of vibration (phonons) at low and high temperatures.
(Credit: Image courtesy Tanja Cuk)

The early superconductors had to be cooled to extremely low (below 20 K or -423° F) temperatures. But in the 1980s scientists discovered a class of what they call high-temperature superconductors made of ceramic copper oxides, called cuprates. They found that at temperatures as high as about 135 K, or -216º F, these materials transition into superconductors. Understanding how they work and thus how they can be manipulated to operate at even higher temperatures is currently one of the most important unsolved problems in physics--a holy grail for many.

"In cuprate superconductors the atoms are arranged in a layered structure," explained co-author of the study, Viktor Struzhkin at the Carnegie Institution's Geophysical Laboratory. "When the material goes into the superconducting state, changes occur in the copper-oxide planes, the electron spins behave differently, the vibrational energy is altered, the charges move differently, and more."

Another co-author of the study, Alexander Goncharov, elaborated: "Over the years scientists have found that the transition temperature can be increased with a specific amount of 'doping,' which is the addition of charged particles--either negatively charged electrons or positively charged holes. We wanted to see the effects of high pressure on one bismuth-based high-temperature cuprate (Bi1.98.Sr2.06Y0.68Cu2O8+´). Pressure has the added bonus that it can be applied gradually, like tuning a radio. We gradually tuned in to the superconductivity and could watch what happened over a broad range of pressures."

The scientists observed the subatomic effects on the material of pressures close to 350,000 times the atmospheric pressure at sea level (35 GPa) using a diamond anvil cell to squeeze the sample and specialized techniques, Raman spectroscopy and X-ray diffraction, to measure the changes.

"21 GPa was the magic number, or critical pressure," remarked Tanja Cuk, the lead author and a student at Stanford University, who carried out this work as part of her Ph.D. thesis research. "By compressing the structure, we were able to observe changes in six different physical properties. But even more exciting, the changes were similar to those observed when the material has been doped to its optimal level. This means that the critical pressure is likely related to doping. Plus, by finding that pressure can be used instead of temperature and doping, we've found an entirely new approach to studying what's behind superconducting properties of high-Tc superconductors."

According to Struzhkin: "This study brings us one step closer to understanding the mechanism of high-temperature superconductivity by giving a completely new perspective of the superconducting state driven by a continuous variable--pressure. It appears that superconductivity is favored on the borderline between insulating and metallic states. By applying these high pressures, we may be able to discover the missing clues to the mechanism of the high-temperature superconductivity and move a few steps closer to using superconductors in daily life. This could change our whole energy system."

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Vibrations In Crystal Lattice Play Big Role In High Temperature Superconductors

An elegant experiment conducted by University of California, Berkeley, and Lawrence Berkeley National Laboratory (LBNL) scientists, in collaboration with a group of scientists at Tokyo University, shows clearly that in high temperature superconductors, vibrations in the crystal lattice play a significant though unconventional role.

A ceramic high temperature superconductor is actually
a very poor metal, almost an insulator, at room temperature
because electrons interact only slightly with the solid lattice (top),
as represented by a slight depression in the crystal lattice.
As the ceramic is cooled below a critical temperature, however,
electrons pair up and are able to 'dance' with the vibrating lattice,
stabilizing one another, as represented by a deep impression in the lattice.
(Graphic by Gey-Hong Gweon/LBNL)

The results, reported in the July 8 issue of Nature, shed much-needed light on the enigmatic superconductors which, 18 years after their discovery, still puzzle theoreticians and experimentalists. The findings also could point scientists to new materials to explore as possible superconductors.

"We know that there are in nature different materials that might be superconductors, but up to now these new superconductors have not been found," said lead researcher Alessandra Lanzara, assistant professor of physics at UC Berkeley and faculty scientist at LBNL. "In a way, these results will put the finger on some classes of material that are a potentially important system for superconductivity."

High temperature superconductors are almost always some type of copper oxide (cuprate) ceramic doped with a variety of elements, from bismuth, yttrium and lanthanum to strontium and calcium. For unknown reasons, this mélange of atoms conducts electricity without resistance at temperatures as high as 130 degrees above absolute zero (130 K or -143 degrees Celsius), unlike the conventional metallic superconductors that must be cooled below 20 K to become superconducting.

While conventional superconductors are explained by the seminal Nobel-Prize winning Bardeen-Cooper-Schrieffer (BCS) theory, high temperature superconductivity is still in search of a theoretical explanation. In the BCS theory, each electron pairs with an electron of opposite spin to form a new entity, a Cooper pair, that can move without resistance through the material. The pairing is made possible by interactions between the electrons and the metal atoms vibrating in place in the crystal lattice. The lattice is the ordered three-dimensional arrangement of atoms in a solid, like the scaffolding of a crystal.

Most researchers studying high temperature superconductors have disregarded these lattice vibrations, called phonons, under the assumption that they play no role in the high temperature superconductors. According to many of these theories, high temperature superconductivity arises from quantum voids or "holes," which are created by depleting electrons from the sample, moving on top of a background of magnetic moments. In these theories, phonons are not at all important. Nonetheless, there remains a group of physicists who are more reluctant to abandon phonons because of a lack of hard evidence that they are not involved in the phenomena.

"There is this ongoing debate whether phonons play any role in superconductivity and whether magnetism is the important clue that determines the properties of cuprates," Lanzara said. "We thought, 'This debate is going to go on forever unless we come up with some new experiment.' The collaboration with the group of Professor Hide Takagi and Dr. Takao Sasagawa in Tokyo University, who have provided unique high-quality single crystals, has made this experiment possible".

The experiment, which involved tweaking the material's crystal lattice by substituting heavier oxygen-18 for some of the normal oxygen-16, showed that a heavier and thus stiffer lattice affected the electron cloud that permeates the superconductor.

"We are able with ARPES to extract information regarding the influence of the lattice on the single electron dynamics in the cuprates, directly and unambiguously," Gweon said, referring to angle-resolved photoemission spectroscopy (ARPES), which is used to measure the velocity of the electrons in a material.

"The results we found provide the first direct evidence for a significant and unconventional role of phonons in the high temperature superconductivity, meaning that all the reasons that have been used so far to disregard the importance of phonons are not valid anymore," Lanzara said.

"Our experiment doesn't say one way or another whether phonons are the only component, but it does say that phonons play a very important role," added Gey-Hong Gweon, the first author and a postdoctoral physicist at LBNL. "But our results definitely show that there is a strong interaction between the lattice and the electrons, in a way that cannot be disregarded as is done in many theories."

Lanzara, Gweon and theorist Dung-Hai Lee, UC Berkeley professor of physics, agree with many of their colleagues that in high temperature superconductors, the repulsive electron-electron interaction is very strong, and that the tendency for electrons of opposite spins to pair up into a "singlet'' has a lot to do with the antiferromagnetic interaction that's responsible for making the undoped ceramic materials antiferromagnets. However, they also believe that this tendency to form spin singlets enhances the interaction between the electrons and the phonons.

Such an electronically enhanced electron-phonon coupling is similar to what happens in the so-called spin-Peierls systems, where alternating electrons in a solid lattice adopt opposite spins and, as a result, pair up into an ordered system similar to Cooper pairing, though these pairs do not roam the solid but stay near their lattice electrons. The alternating spin arrangement that characterizes spin-Peiels behavior is identical to the antiferromagnetic situation in high temperature superconductors.

The team believes, then, that the mutual feedback of the magnetic and electron-phonon interaction is critical to the high temperature superconducting state. There is pairing in the two populations of electrons, one "localized" and the other "free," both perhaps enhanced by the electrons' interactions with the crystal lattice. According to Lee, if the localized electron pairs are bound lightly enough to the lattice atoms, they can resonate with the coherent motion of the Cooper pairs of free conducting electrons, leading to superconductivity.

"There are materials where the electron-phonon interaction enhances a spin type of ordering and vice versa. This has not been observed before in high temperature superconductors," Lanzara said. "The formation of the electron pair, the Cooper pair, is mediated through the phonons, and at the same time there is a feedback from the magnetic interaction. So, the two enhance one another."

The team worked with a material called Bi-2212, which is a copper oxide doped with bismuth, strontium and calcium that becomes superconducting at 92 K (-181 degrees Celsius). The crystal structure is basically comprised of two alternating layers: one a plane of copper and oxygen molecules interspersed with strontium and calcium atoms, the other a lattice of bismuth and oxygen. The team replaced some of the oxygen with a heavier isotope, O-18, and used the ARPES technique to measure the energy or velocity of the electrons in the material.

"These data provide the first direct evidence for a significant role that phonons play in the high temperature superconductivity," Gweon said.

The work was supported by the Department of Energy.

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New Insights Into High-temperature Superconductors

Scientists at the Carnegie Institution's Geophysical Laboratory in collaboration with a physicist at the Chinese University of Hong Kong have discovered that two different physical parameters --pressure and the substitution of different isotopes of oxygen (isotopes are different forms of an element) --have a similar effect on electronic properties of mysterious materials called high-temperature superconductors. The results also suggest that vibrations (called phonons), within the lattice structure of these materials, are essential to their superconductivity by binding electrons in pairs. The research is published in the February 26 - March 2 on-line edition of the Proceedings of the National Academy of Sciences.

Superconductors are substances that conduct electricity -- the flow of electrons -- without any resistance. Electrical resistance disappears in superconductors at specific, so-called, transition temperatures, Tc's. The early conventional superconductors had to be cooled to extremely low (below 20 K or --253ºC) temperatures for electricity to flow freely. In 1986 scientists discovered a class of high-temperature superconductors made of ceramic copper oxides that have much higher transition temperatures. But understanding how they work and thus how they can be manipulated has been surprisingly hard.

As Carnegie's Xiao-Jia Chen, lead author of the study explains: "High-temperature superconductors consist of copper and oxygen atoms in a layered structure. Scientists have been trying hard to determine the properties that affect their transition temperatures since 1987. In this study, we found that by substituting oxygen-16 with its heavier sibling oxygen-18, the transition temperature changes; such a substitution is known as the isotope effect. The different masses of the isotopes cause a change in lattice vibrations and hence the binding force that enables pairs of electrons to travel through the material without resistance. Even more exciting is our discovery that manipulating the compression of the crystalline lattice of the high-Tc material has a similar effect on the superconducting transition temperature. Our study revealed that pressure and the isotope effect have equivalent roles on the transition temperature in cuprate superconductors."

Superconducting materials can achieve their maximum transition temperatures at a specific amount of "doping," which is simply the addition of charged particles (negatively charged electrons or positively charged holes). Both the transition temperature and isotope effect critically depend on the doping level. For optimally doped materials, the higher the maximum transition temperature is, the smaller the isotope effect is.

Understanding this behavior is very challenging. The Carnegie / Hong Kong collaboration found that if phonons are at work, they would account both for the magnitude of the isotope effect, as a function of the doping level, and the variation among different types of cuprate superconductors. The study also revealed what might be happening to modify the electronic structures among various optimally doped materials to cause the variation of the superconducting properties. The suite of results presents a unified picture for the oxygen isotope effect in cuprates at ambient condition and under high pressure.

"Although we've known for some time that vibrations of the atoms, or phonons, propel electrons through conventional superconductors, they have just recently been suspected to be at work in high-temperature superconductors," commented coauthor Viktor Struzhkin. "This research suggests that lattice vibrations are important to the way the high-Tc materials function as well. We are very excited by the possibilities arising from these findings."

This work was supported by the Office of Basic Energy Science and National Nuclear Security Administration of the US Department of Energy and the Hong Kong Research Grants Council. This research was conducted by X. J. Chen, V. V. Struzhkin, Z. G. Wu, R. J. Hemley, and H. K. Mao (Carnegie Institution); and H. Q. Lin (The Chinese University of Hong Kong).

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New High-Temperature Superconductors Are Iron-based With Unusual Magnetic Properties

In the initial studies of a new class of high-temperature superconductors discovered earlier this year, research at the Commerce Department's National Institute of Standards and Technology (NIST) has revealed that new iron-based superconductors share similar unusual magnetic properties with previously known superconducting copper-oxide materials.

The magnetic structure of the new iron-based superconductors
was determined at the thermal triple-axis spectrometer at the
NIST Center for Neutron Research. Physicists Jeff Lynn
and Ying Chen prepare the instrument for use.
(Credit: Copyright Robert Rathe)

These superconductors may one day enable energy and environmental gains because they could significantly heighten the efficiency of transferring electricity over the electric grid or storing electricity in off-peak hours for later use.

"While we still do not understand how magnetism and superconductivity are related in copper-oxide superconductors," explains NIST Fellow Jeffrey Lynn at the NIST Center for Neutron Research (NCNR), "our measurements show that the new iron-based materials share what seems to be a critical interplay between magnetism and superconductivity."

The importance of magnetism to high-temperature superconductors is remarkable because magnetism strongly interferes with conventional low-temperature superconductors. "Only a few magnetic impurities in the low-temperature superconductors sap the superconducting properties away," says Lynn.

By contrast, copper-oxide superconductors, discovered in 1986, tolerate higher magnetic fields at higher temperatures. The highest performance copper-oxide superconductors conduct electricity without resistance when cooled to "transition temperatures" below 140 Kelvin (-133 Celsius) and can simply and cheaply be cooled by liquid nitrogen to 77 Kelvin or (-196 Celsius).

Japanese researchers discovered earlier this year that a new class of iron-based superconducting materials also had much higher transition temperatures than the conventional low-temperature superconductors. The discovery sent physicists and materials scientists into a renewed frenzy of activity reminiscent of the excitement brought on by the discovery of the first high-temperature superconductors over 20 years ago.

Earlier work on the copper-oxide superconductors revealed that they consist of magnetically active copper-oxygen layers, separated by layers of non-magnetic materials. By "doping," or adding different elements to the non-magnetic layers of this normally insulating material, researchers can manipulate the magnetism to achieve electrical conduction and then superconductivity.

The group of scientists studying the iron-based superconductors used the NCNR, a facility that uses intense beams of neutral particles called neutrons to probe the atomic and magnetic structure of the new material.

As neutrons probed the iron-based sample supplied by materials scientists in Beijing, they revealed a magnetism that is similar to that found in copper-oxide superconductors, that is, layers of magnetic moments--like many individual bar magnets--interspersed with layers of nonmagnetic material. Lynn notes that the layered atomic structure of the iron-based systems, like the copper-oxide materials, makes it unlikely that these similarities are an accident.

One of the exciting aspects of these new superconductors is that they belong to a comprehensive class of materials where many chemical substitutions are possible. This versatility is already opening up new research avenues to understand the origin of the superconductivity, and should also enable the superconducting properties to be tailored for commercial technologies.

Researchers from the following institutions partnered with NIST in these studies: University of Tennessee, Knoxville; Oak Ridge National Laboratory; University of Maryland; Ames Laboratory; Iowa State University and the Chinese Academy of Sciences' Beijing National Laboratory for Condensed Matter Physics.

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Iron-based Materials May Unlock Superconductivity’s Secrets

Researchers at the National Institute of Standards and Technology (NIST) are decoding the mysterious mechanisms behind the high-temperature superconductors that industry hopes will find wide use in next-generation systems for storing, distributing and using electricity.

NIST researchers have found that new iron-based high-temperature
superconductors subtly change their molecular shape as temperatures decrease.
This graphic shows a superconductor transitioning from tetragonal (at top) to
orthorhombic at about 220 Kelvin (-53 Celsius). Such physical changes
appear to be a precursor to superconductivity, in which electric
current can flow without resistance. (Credit: NIST)

In two new papers on a recently discovered class of high-temperature superconductors, they report that the already complicated relationship between magnetism and superconductivity may be more involved than previously thought, or that a whole new mechanism may drive some types of superconductors.

At temperatures approaching absolute zero, many materials become superconductors, capable of carrying vast amounts of electrical current with no resistance. In such low-temperature superconductors, magnetism is a villain whose appearance shatters the fragile superconductive state. But in 1986, scientists discovered "high temperature" (HTc) superconductors capable of operating much warmer than the previous limit of 30 degrees above absolute zero.

In fact, today's copper-oxide materials are superconductive in liquid nitrogen, a bargain-priced coolant that goes up to a balmy 77 degrees above absolute zero. Such materials have enabled applications as diverse as high-speed maglev trains, magnetic-resonance imagers and highly sensitive astronomical detectors. Still, no one really understands how HTc superconductivity works, although scientists have long suspected that in this case, magnetism boosts rather than suppresses the effect.

The beginnings of what could be a breakthrough came in early 2008 when Japanese researchers announced discovery of a new class of iron-based HTc superconductors. In addition to being easier to shape into wires and otherwise commercialize than today's copper-oxides, such materials provide scientists fresh new subjects with which to develop and test theories about HTc superconductivity's origins.

Scientists at NIST's Center for Neutron Research and a team including researchers from the University of Tennessee at Knoxville, Oak Ridge National Laboratory, the University of Maryland, Ames Laboratory and Iowa State University used beams of neutrons to peek into a superconductor's atomic structure. They first found iron-based superconductors to be similar to copper-oxide materials in how "doping" (adding specific elements to insulators in or around a HTc superconductor) influences their magnetic properties and superconductivity.

Then the team tested the iron-based material without doping it. Under moderate pressure, the volume of the material's crystal structure compressed an unusually high 5 percent. Intriguingly, it also became superconductive without a hint of magnetism.

The iron-based material's behavior under pressure may suggest the remarkable possibility of an entirely different mechanism behind superconductivity than with copper oxide materials, NIST Fellow Jeffrey Lynn said. Or it could be that magnetism is simply an ancillary part of HTc superconductivity in general, he said—and that a similar, deeper mechanism underlies the superconductivity in both. Understanding the origin of the superconductivity will help engineers tailor materials to specific applications, guide materials scientists in the search for new materials with improved properties and, scientists hope, usher in higher-temperature superconductors.

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Quest For A New Class Of Superconductors

Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.

This photo shows a magnet levitating above a high-temperature
superconductor, cooled with liquid nitrogen. A persistent electric
current flows on the surface of the superconductor, effectively
forming an electromagnet that repels the magnet. The expulsion
of an electric field from a superconductor is known as the Meissner Effect.
(Credit: Image courtesy of DOE/Los Alamos National Laboratory)

In a review published December 20 in Nature, researchers David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material's structure.

The review, "Superconductivity without phonons," explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, usually at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)--the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.

A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen--minus 321 degrees Fahrenheit (minus 196 degrees Celsius)--are known as "high-temperature superconductors."

A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972.

The net attraction between electrons, which formed the basis for the BCS theory, comes from their coupling to phonons, the quantized vibrations of the crystal lattice of a superconducting material; this coupling leads to the formation of a macroscopically occupied quantum state containing pairs of electrons--a state that can flow without encountering any resistance, that is, a superconducting state.

"Much like the vibrations in a water bed that eventually compel the occupants to move together in the center, phonons can compel electrons of opposite spin to attract one another, says Pines, who with Bardeen in 1954, showed that this attraction could win out over the apparently much stronger repulsion between electrons, paving the way for the BCS theory developed a few years later.

However, according to Pines, Monthoux and Lonzarich, electron attraction leading to superconductivity can occur without phonons in materials that are on the verge of exhibiting magnetic order--in which electrons align themselves in a regular pattern of alternating spins.

In their Review, Pines, Monthoux and Lonzarich examine the material characteristics that make possible a large effective attraction that originates in the coupling of a given electron to the internal magnetic fields produced by the other electrons in the material. The resulting magnetic electron pairing can give rise to superconductivity, sometimes at substantially higher temperatures than are found in the materials for which phonons provide the pairing glue.

Among the classes of materials that appear capable of superconductivity without phonons are the so-called heavy electron superconductors that have been studied extensively at Los Alamos since the early 1980's, certain organic materials, and the copper oxide materials that superconduct at up to twice the temperature at which nitrogen liquefies.

"If we ever find a material that superconducts at room temperature--the 'Holy Grail' of superconductivity--it will be within this class of materials," says Pines. "This research shows you the lamp post under which to look for new classes of superconducting materials."

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New Family Of Superconductors Discovered

University of Saskatchewan Canada Research Chair John Tse and colleagues in Germany have identified a new family of superconductors – research that could eventually lead to the design of better superconducting materials for a wide variety of industrial uses.

Dr. John Tse and colleagues in Germany have identified
a new family of superconductors -- research that could
eventually lead to the design of better superconducting
materials for a wide variety of industrial uses.
(Credit: Image courtesy of University of Saskatchewan)

In an article published in the journal Science, the team has produced the first experimental proof that superconductivity can occur in hydrogen compounds known as molecular hydrides.

“We can show that if you put hydrogen in a molecular compound and apply high pressure, you can get superconductivity,” said Tse. “Validation of this hypothesis and understanding of the mechanism are initial steps for design of better super-conducting materials.”

Superconductors conduct electricity without creating friction or heat loss. An electric current can therefore flow in a loop of superconducting wire indefinitely with no power source. Examples of existing superconducting materials include magnets used in MRI machines and the magnets that enable high-speed trains to float above the track without friction or energy loss as heat.

Team member Mikhail Eremets of the Max Plank Institute in Germany did the laboratory work in detecting superconductivity in the hydrogen compound silane, while Tse and his graduate student Yansun Yao provided the theoretical basis for understanding the mechanism involved and identified the key chemical structures.

Most commercial superconducting materials have to operate at very low temperatures which requires expensive super-cooling equipment.

“Our research in this area is aimed at improving the critical temperature for superconductivity so that new superconductors can be operated at higher temperatures, perhaps without a refrigerant,” said Tse.

It has long been hypothesized that hydrogen, the simplest of the elements, may be able to conduct electricity without creating friction or heat loss (superconductive behavior) if it’s compressed into a very dense solid form. Though many researchers have tried using pure hydrogen, they have not been able to achieve the necessary hydrogen density to produce superconductivity.

Instead of using pure hydrogen, the Germany-Canada team, following an earlier suggestion by Prof. Neil Ashcroft at Cornell University, compressed hydrogen-rich molecules (hydrides). They were able to reach the necessary density for superconductivity at much lower pressure than with pure hydrogen – an achievement that will shed greater understanding on the fundamental nature of superconductivity.

The U of S work, funded by NSERC and the Canada Research Chairs program, involved extensive calculations – some taking as long as a month – at the WestGrid computing facility and with the Canada Foundation for Innovation-funded high-performance computing facility at the U of S.

In related research, Tse’s team is using the Canadian Light Source synchrotron to study high pressure structures of other hydrides systems on potential superconductivity and making use of them to store hydrogen for fuel cells.

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Why the universe may be teeming with aliens

Rocky planet outside of our solar system. Must not be too hot or too cold, but just the right temperature to support life.

It sounds like a simple enough wish list, but finding a planet that fulfils all of these criteria has kept astronomers busy for decades. Until recently, it meant finding a planet in the “Goldilocks zone” - orbiting its star at just the right distance to keep surface water liquid rather than being boiled off or frozen solid.

Now, though, it’s becoming increasingly clear that the question of what makes a planet habitable is not as simple as finding it in just the right spot. Many other factors, including a planet’s mass, atmosphere, composition and the way it orbits its nearest star, can all influence whether it can sustain liquid water, an essential ingredient for life as we know it. As astronomers explore newly discovered planets and create computer simulations of virtual worlds, they are discovering that water, and life, might exist on all manner of weird worlds where conditions are very different from those on Earth. And that means there could be vastly more habitable planets out there than we thought possible. “It’s like science fiction, only better,” says Raymond Pierrehumbert, a climate scientist at the University of Chicago, who studies planets inside and outside of our solar system.

Distance from the nearest star is, of course, important. In our own solar system, Venus has long served as an example of what can happen if a planet gets too close to its star. Venus is only 28 per cent closer to the sun than Earth is, but its surface is a sweltering 460 °C, hot enough to melt lead, and it chokes under a thick carbon dioxide atmosphere 90 times the density of Earth’s.

Put Earth where Venus is and it would probably end up looking rather similar. The extra solar radiation would increase evaporation from the oceans, boosting the amount of water vapour in the atmosphere. As water vapour is a greenhouse gas, this increase would set off a vicious cycle, with higher temperatures triggering more evaporation, until the planet’s surface was hot enough to boil away the oceans. At the other extreme, water on a planet that is too far from its star will simply freeze, like on Mars.

However, in 1993 a study by James Kasting of Pennsylvania State University, University Park, demonstrated that even in our own solar system, the habitable zone is not based on distance alone. In a calculation based onthe sun’s current brightness,

Kasting worked out that while moving Earth just 5 per cent closer to the sun would doom it to the same fate as Venus, it could move almost 1.7 times its current distance from the sun before it would freeze (Icarus, vol 101, p 108). This outer limit is interesting because it is beyond the orbit of Mars, whose orbit has a radius about 1.5 times that of Earth.

So if Mars is in our solar system’s Goldilocks zone, why isn’t it teeming with life? The answer lies in how a planet’s mass affects its ability to hold on to a habitable atmosphere. On Earth, the carbon cycle works as a kind of thermostat that keeps the climate liveable. Volcanic activity releases CO₂, which warms the Earth’s surface via the greenhouse effect, increasing evaporation and rain. The rain erodes carbon-containing minerals from rocks, washing them into the sea. Eventually, these minerals are pulled deep into the Earth in subduction zones.

This balance between emitting and sequestering CO₂ has helped keep the Earth’s climate stable for the past 4 billion years. Mars, though, is only half the size of Earth, so its interior cooled quickly, shutting down the volcanic activity needed to supply CO₂ to the atmosphere. Its weaker gravity also allows its atmosphere to drift away into space. As a result, there is too little CO₂ in the Martian atmosphere to warm its surface enough to sustain liquid water. This has probably been the case for much of the past few billion years.

Goldilocks not required

Mass, however, is not the only factor. In a series of computer simulations published earlier this year, David Spiegel of Princeton University explored whether factors such as a planet’s spin axis or speed of rotation could allow a planet outside of the habitable zone to hold onto liquid water long enough to sustain life (The Astrophysical Journal, vol 681, p 1609). “I’ve been kind of twisting the ***** so that they’re different from Earth, but they all have the same mass as Earth,” says Spiegel, who was at Columbia University in New York when he carried out the work.

In some simulations, the team altered the tilt of the planet’s spin axis. Earth’s axis is tilted 23.5 degrees relative to the plane of its orbit, which is why each hemisphere has longer periods of sunlight during summer and shorter ones during winter. When they gave planets a tilt of 90 degrees, similar to that of the gas giant Uranus in our own solar system, the much larger variations in illumination led to more extreme seasons.

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U.S. hopes to develop bug-sized, flying spies

This photo, taken from computer animation video and released by the U.S. Air Force, shows the next generation of drones, called Micro Aerial Vehicles, or MAVs. The MAVs could be as tiny as bumblebees and capable of flying undetected into buildings, where they could photograph,
record, and even attack insurgents and terrorists.

DAYTON, Ohio - If only we could be a fly on the wall when our enemies are plotting to attack us. Better yet, what if that fly could record voices, transmit video and even fire tiny
weapons?

That kind of James Bond-style fantasy is actually on the drawing board. U.S. military engineers are trying to design flying robots disguised as insects that could one day spy on enemies and conduct dangerous missions without risking lives.

“The way we envision it is, there would be a bunch of these sent out in a swarm,” said Greg Parker, who helps lead the research project at Wright-Patterson Air Force Base in Dayton. “If we know there’s apossibility of bad guys in a certain building, how do we find out? We
think this would fill that void.”

In essence, the research seeks to miniaturize the Unmanned Aerial Vehicle drones used in Iraq and Afghanistan for surveillance and reconnaissance.

The next generation of drones, called Micro Aerial Vehicles, or MAVs, could be as tiny as bumblebees and capable of flying undetected into buildings, where they could photograph, record, and even attack insurgents and terrorists.

By identifying and assaulting adversaries more precisely, the robots would also help reduce or avoid civilian casualties, the military says. Parker and his colleagues plan to start by developing a bird-sized robot as soon as 2015, followed by the insect-sized models by 2030.

The vehicles could be useful on battlefields where the biggest challenge is collecting reliable intelligence about enemies.

“If we could get inside the buildings and inside the rooms where their activities are unfolding, we would be able to get the kind of intelligence we need to shut them down,” said Loren Thompson, a defense analyst with the Lexington Institute in Arlington, Va.

Philip Coyle, senior adviser with the Center for Defense Information in Washington D.C., said a major hurdle would be enabling the vehicles to carry the weight of cameras and microphones.

“If you make the robot so small that it’s like a bumblebee and then you ask the bumblebee to carry a video camera and everything else, it may not be able to get off the ground,” Coyle said.

Parker envisions the bird-sized vehicles as being able to spy on adversaries by flying into cities and perching on building ledges or power lines.
The vehicles would have flappable wings as a disguise but use a separate propulsion system to fly. “We think the flapping is more so people don’t notice it,” he said. “They think it’s a bird.”

Unlike the bird-sized vehicles, the insect-sized ones would actually use flappable wings to fly, Parker said. He said engineers want to build a vehicle with a 1-inch wingspan, possibly made of an elastic material. The vehicle would have sensors to help avoid slamming into buildings or other objects.

Existing airborne robots are flown by a ground-based pilot, but the smaller versions would fly independently, relying on preprogrammed instructions. Parker said the tiny vehicles should also be able to withstand bumps. “If you look at insects, they can bounce off of walls and keep flying,” he said. “You can’t do that with a big airplane, but I don’t see any reason we can’t do that with a small one.”

An Air Force video describing the vehicles said they could possibly carry chemicals or explosives for use in attacks.

Once prototypes are developed, they will be flight-tested in a new building at Wright-Patterson dubbed the “micro aviary” for Micro Air Vehicle Integration Application Research Institute.

“This type of technology is really the wave of the future,” Thompson said. “More and more military research is going into things that are small, that are precise and that are extremely focused on particular types of missions or activities.”

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How a camra can steal your keys?

Hide those keys. A quick camera phone picture could unlock your doors.

Scientists in California have developed a software algorithm that automatically creates a physical key based solely on a picture of one, regardless of angle or distance. The project, called Sneakey, was meant to warn people about the dangers of haphazardly placing keys in the open or posting images of them online.

“People will post pictures with their credit cards but with the name and number greyed out,” said Stefan Savage, a professor at the University of California, San Diego who helped develop the software. “They should have the same sensitivity with their keys.”

When Savage and his students searched online photo sharing Web sites, like Flickr, they easily found thousands of photos of keys with enough definition to replicate. A more social person could simply use their cell phone camera to snap a quick picture of stray keys on a table top.

For a more dramatic demonstration, the researchers set up a camera with a zoom lens 200 feet away. Using those photos, they created a working key 80 percent on their first try. Within three attempts they opened every lock.

Three attempts could take less than five minutes. The replication process is very easy. Once the researchers have the image it takes the software roughly 30 seconds to decode the ridges and grooves on the key. If the angle is off or the lighting is tricky it takes the computer take a little longer.

The longest part of the process, about one whole minute, is cutting the key.

“I think that this work would be really easy for someone else to reproduce,” said Savage of his work. “Someone familiar with signal processing, mat lab, and image transformation could do it in two days if they are good.”

Keys, as the researchers demonstrated, are actually fairly easy to decode. A majority of keys marketed to consumers are basically just four to six different numbers. Each number corresponds to a ridge or valley in the key. When inserted into a lock, the ridges and valleys lines up a series of small pins that lets the lock turn.

“The premise is that a key holds some kind of secret that lets you unlock something,” said Savage. “But it’s a very funny secret, its a secret that can easily be seen.”

Creating a new key is easy enough that some locksmiths and security experts do it by sight alone. The locks the UCSD team broke were some of the most common in the country.

Marc Weber Tobias, an attorney and security expert who has been picking locks since he was a boy, says the UCSD project does a good job of underscoring the insecurity of conventional cylinder locks. But the idea of someone standing up to a mile away with high resolution camera and stealing keys with a shutter is small compared to the next generation of video cameras being installed.

“The real issue is the new digital video cameras shooting at 30 frames a second,” said Tobias. “There are millions and millions of these cameras everywhere.” If someone got their hands on sensitive parts of the video they could easily duplicate key sets.

Locksmiths, and the UCSD scientists won’t use their talents or technology for ill-gotten gains. But not everyone is so ethical, and experts urge people to take physical security more seriously.

“This isn’t the biggest security threat that you might face,” said Savage. “But you should only take your keys out when you are going to use them.”

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Ancient flying reptile bigger than a car

An artist’s representation of Lacusovagus, which scientists say represents a new genus of pterosaurs, flying reptiles that dominated the skies 115 million years ago.

A fossil of a toothless flying pterosaur, with a body bigger than some family cars, represents the largest of these extinct reptiles ever to be found and has forced the creation of a new genus, scientists announced Thursday.

Pterosaurs ruled the skies 115 million years ago during the dinosaur age. They are often mistaken for dinosaurs.

Mark Witton of the University of Portsmouth identified the creature from a partial skull fossil. Witton estimates the beast would have had a 5.5-yard (5-meter) wingspan. It stood more than a yard (about 1 meter) tall at the shoulder.

“Some of the previous examples we have from this family in China are just 60 centimeters [about 2 feet] long — as big as the skull of the new species. Put simply, it dwarfs any chaoyangopterid we’ve seen before by miles,” Witton said.

The finding also is significant because it originated in Brazil and is the only example of the Chaoyangopteridae, a group of toothless pterosaurs, to be found outside China.

Witton has christened the new species Lacusovagus, meaning “lake wanderer,” after the large body of water in which the remains were buried. The findings are detailed in the November issue of the journal Palaeontology.

He was asked to examine the specimen which had lain in a German museum for several years after its discovery in the Crato Formation of the Araripe Basin in North East Brazil, an area well known for the its fossils and their excellent state of preservation. However, he said that this fossil was preserved in an unusual way, making its interpretation difficult.

“Usually fossils like this are found lying on their sides but this one was lying on the roof of its mouth and had been rather squashed which made even figuring out whether it had teeth difficult,” Witton said.

“Still, it’s clear to see that Lacusovagus had an unusually wide skull which has implications for its feeding habits — maybe it liked particularly large prey. The remains are very fragmentary, however, so we need more specimens before we can draw any conclusions.”

The discovery of this pterosaur fossil in Brazil, so far away from its closest relatives in China, demonstrates how little scientists still know about the distribution and evolutionary history of this group of creatures, Witton said.

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Head-banging hammers the brain

Researchers concluded that head-banging to a typical heavy metal tempo could cause mild traumatic brain injury or concussion (Source: Monica Quesada/Rueters)

Led Zeppelin's immortal song 'Dazed and Confused' might well have been a clinical observation on the state of their audience's brains, say Australian researchers who have found over-enthusiastic head-banging can cause mild brain injury.In a study published in the British Medical Journal this week, two University of New South Wales (UNSW) researchers concluded that head-banging to a typical heavy metal tempo could cause mild traumatic brain injury or concussion, and neck injury, particularly as the tempo of the music and angle of movement increased.

"Clearly it's a serious issue," says Associate Professor Andrew McIntosh, co-author and professor of biomechanics at UNSW."If you observe people after concerts they clearly look dazed, confused and incoherent, so something must be going on and we wanted to look into it."

Beats per minute

After careful observation of the behaviour of heavy metal concert-goers, McIntosh and honours student Declan Patton constructed a theoretical head-banging model to better understand the mechanics of the practice.They also spoke to a focus group of local musicians to identify ten popular songs to head-bang to.

"These songs had an average tempo of 146 beats per minute, and at this tempo we predict that head banging can cause headaches and dizziness if the range of movement of the head and neck is greater than 75°," the researchers wrote.

Several songs were selected as controls against which to compare the risk of heavy metal head-banging, including Whitney Houston's 'I Will Always Love You'.

But McIntosh says attempts to find control cases of head-banging at alternative venues, such as Andre Rieu concerts, were unsuccessful.

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Scientist calls for robot ethics

Ethics guidelines are urgently needed to control the growing use of robots in caring for children and the elderly, says one UK robotics expert.Professor Noel Sharkey, of the Department of Computer Science at the University of Sheffield, makes his case in today's issue of the journal Science.

Sharkey argues that the steady increase in the use of robots in day-to-day life poses unanticipated risks and ethical problems.In particular he worries about the impact of long-term exposure of "vulnerable" groups such as children and the elderly to "personal care" robots.

"There are already at least 14 companies in Japan and South Korea that have developed child care robots," says Sharkey.

"The question here is, will this lead to neglect and social exclusion?"

Robots make teddy bears redundant

Sharkey says studies have shown that children prefer robots to a teddy bear and develop attachment to the machines.He says short-term exposure "can provide an enjoyable and entertaining experience that creates interest and curiosity".

But Sharkey says children cared for by robots may, over the long-term, suffer psychological impacts from lack of human contact.Animal experiments suggest young monkeys left in the care of robots "became unable to deal with other monkeys and to breed," says Sharkey.He says there are also already many "elder-care" robots in wide use, such as the Japanese "My Spoon", which can automatically feed older people, and an electric bathtub robot that can automatically wash and rinse them.

Sharkey also expresses concern about plans to develop military robots that can autonomously locate targets and destroy them without human intervention."The ethical problems arise because no computational system can discriminate between combatants and innocents in a close-contact encounter," he says.

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Tunneling Effect In Strong Laser Field

Physicists have worked on the quantum physics description of the tunnelling effect for 60 years. The group led by Ursula Keller has now for the first time succeeded in measuring time intervals that enable the direct measurement of the tunnelling time of electrons in laser-induced ionisation. No corresponding delay was measured in the experiment: something that astonished many physicists. An established but perhaps over-simplified explanatory model begins to look shaky.

Ionization of a helium atom as a "proof of principle"
of the attosecond clock: a circularly polarized laser beam
inside an electromagnetic field strikes the atom, whose
electron is split off (i.e. ionized) andis captured by a detector.
(Credit: Image courtesy of ETH Zurich)

When new technologies allow theoretical models to be tested experimentally, scientists must be prepared to say goodbye to accepted thought patterns. The current publication by Professor Ursula Keller and her team at the Institute of Quantum Electronics of ETH Zurich could bring about just such a break with accepted wisdom. The group succeeded for the first time ever in measuring experimentally the tunnelling delay times of electrons ionized in strong laser fields.

The tunnelling effect is responsible for the ability of bound electrons in atoms to pass through an energy barrier even though the barrier’s energy is higher than the electron’s binding energy. According to classical physics, overcoming this barrier is impossible, hence the assumption of a quantum-mechanical process.

A popular way of illustrating this is to imagine a ball that does not have enough momentum to surmount a hump, so simply “tunnels through” it instead. Keller says “Contrary to some accepted theories, our measurement has shown that this so-called tunnelling ionisation takes place with almost no delay. The results of her most recent experiments appear in a recent issue of the scientific journal “Science”.

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Reproductive Spores Are Remarkably Aerodynamic

The reproductive spores of many species of fungi have evolved remarkably drag-minimizing shapes, according to new research by mycologists and applied mathematicians at Harvard University.

In many cases, the scientists report in the Proceedings of the National Academy of Sciences, the drag experienced by these fungal spores is within one percent of the absolute minimum possible drag for their size. But these sleek shapes are seen only among spores distributed by air flow, not those which are borne by animals.

Morel fungus. The reproductive spores of many
species of fungi have evolved remarkably drag-minimizing
shapes, according to new research by mycologists and applied
mathematicians at Harvard University.
(Credit: Wikimedia commons, public domain photo)

"We set out to answer a very simple question: Why do fungal spores have the shapes that they do?" says co-author Marcus Roper, who contributed to the research as an applied mathematics graduate student in Harvard's School of Engineering and Applied Sciences. "It turns out that for forcibly ejected spores, the shape can be explained by simple physical principles: The spores need to have a close to minimum possible air resistance for their size. As projectiles, they are close to perfect."

Roper is now a postdoctoral researcher at the University of California, Berkeley.

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Mobiles to take a great leap forward

Moore's Law dictates that chips will shrink and get more powerful

Technology legend Gordon Moore may have been working at Intel when he thought up the law that bears his name, but it applies to any and every microprocessor.

Be the chip inside a PC, or mobile phone, the logic of Moore's Law dictates that they will get progressively more powerful thanks to the inexorable progress of the semiconductor industry.

This has led the PC through successive generations - 286, 386, 486, Pentium - and now mobile handsets are about to embark on a generational shift of their own.

More than 80% of the chips inside mobile phones are designed by UK firm Advanced Risc Machines (Arm) and the most versatile phones of 2008, such as Apple's iPhone 3G, have one or more Arm 11 processing cores onboard.

The Arm 11 series debuted in 2003 and now, five years later, the phones and the applications they run are starting to stretch it to the limit.

Rob Coombs, a spokesman for Arm, said the Arm 11 was roughly 11 times the processing power of the Arm 7 chip that debuted in 1993 and is still used today in the most basic phones.

But now, said Mr Coombs, the Arm 11 family is starting to make way for the Cortex range of processors. He claims the Cortex A9 series will have 30-100 times the processing power of those 1993 era chips.

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Can Microsoft sustain in Mobile Market

You want a phone that can do it all? Internet, music, photos, films, documents, texting, instant messaging, diary, contacts and ... err ... phone calls?

Then a smartphone is right for you. But as the market for high-end mobiles gets ever more crowded, which should you pick?

The global market leader, Symbian, makes the software that runs most of Nokia's smart phones (and a few others).

Research in Motion with its e-mail friendly Blackberry devices has cornered the corporate market and is pushing into the consumer space.

Apple is minting it with its sleek but expensive iPhone. And only a few months ago internet search giant Google entered the field with its Linux-based Android software, designed to power internet-savvy mobile phones.

Sony Ericsson's Xperia X1 is at the high
end of Windows Mobile phones

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Temporary bans on the use of USB Drive

Fears of infection by a virus led the US DoD to ban the use of flash drives.

To most people the USB stick is a humble, innocuous device that does nothing more than help them tote around their most important files.

But to the US Department of Defense (DoD), the USB stick has a dark side - one that criminally-minded hackers are only too eager to exploit.

In late November, the US DoD imposed a temporary ban on the use of flash drives and other removable, recordable media such as CDs, DVDs and floppy disks. The ban applied to users of both the classified and unclassified networks the US military operates.

The order was sent out to help the security staff at the DoD combat the spread of a Windows worm - a self-propagating program. In this case the malicious program was a variant of the SillyFDC worm known as Agent.btz.

This lurks unseen on USB drives and only springs to life when an infected flash drive is inserted into an uninfected PC.

Once installed, the worm does not sit dormant. Instead, it downloads code from elsewhere on the net and stays in touch with its creators.

To scupper the chance that criminals could be using its network resources, the DoD slapped a ban on the use of USB sticks.

But, said Tim Ellsmore, chief executive of security firm 3ami, those restrictions could make it harder for people to get their jobs done.

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Is Einstein's theory of relativity abnormal

Physicists at Indiana University have developed a promising new way to identify a possible abnormality in a fundamental building block of Einstein's theory of relativity known as "Lorentz invariance." If confirmed, the abnormality would disprove the basic tenet that the laws of physics remain the same for any two objects traveling at a constant speed or rotated relative to one another.
IU distinguished physics professor Alan Kostelecky and graduate student Jay Tasson take on the long-held notion of the exact symmetry promulgated in Einstein's 1905 theory and show in a paper to be published in Physical Review Letters that there may be unexpected violations of Lorentz invariance that can be detected in specialized experiments.

An image taken from an animation using Kostelecky's
Standard Model Extenstion to predict how apples might
fall differently. (Credit: Image courtesy of Indiana University)

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