A team of chemical engineers at the University of Massachusetts Amherst has discovered a small molecule that behaves the same as cellulose when it is converted to biofuel. Studying this 'mini-cellulose' molecule reveals for the first time the chemical reactions that take place in wood and prairie grasses during high-temperature conversion to biofuel. The "mini-cellulose" molecule, called α-cyclodextrin, solves one of the major roadblocks confronting high-temperature biofuels processes such as pyrolysis or gasification. The complex chemical reactions that take place as wood is rapidly heated and breaks down to vapors are unknown. And current technology doesn't allow the use of computer models to track the chemical reactions taking place, because the molecules in wood are too large and the reactions far too complicated. Paul Dauenhauer, assistant professor of chemical engineering and leader of the UMass Amherst research team, says the breakthrough achieved by studying the smaller surrogate molecule opens up the possibility of using computer simulations to study biomass. He says, "We calculated that it would take about 10,000 years to simulate the chemical reactions in real cellulose. The same biofuel reactions with 'mini-cellulose' can be done in a month!" Already his team has used insight from studying the "mini-cellulose" to make significant progress in understanding wood chemistry, Dauenhauer says. Using the faster computer simulations, they can track the conversion of wood all the way to the chemical vapor products. These reactions include creating furans, molecules that are important for the production of biofuels. The discovered reactions occurring within wood will serve as the basis for designing advanced biofuel reactors, Dauenhauer says. By creating reaction models of wood conversion, the scientists can design biomass reactors to optimize the specific reactions that are ideal for production of biofuels. For biofuels production, "We want to maximize our new pathway to produce furans and minimize the formation of gases such as CO2," says Dauenhauer. The discovery of "mini-cellulose" was enabled by a new experimental technique for studying high-temperature biomass chemistry called "thin-film pyrolysis." It involves creating sheets of cellulose, which makes up 60 percent of wood biomass, that are very thin, just a few microns thick. When the sheets are very rapidly heated at over one million degrees Celsius per minute, they create volatile chemicals which are the precursors of biofuel. »

Arizona State University researchers are finding ways to improve infrared photodetector technology that is critical to national defense and security systems, as well as used increasingly in medical diagnostics, commercial applications and consumer products. A significant advance is reported in a recent article in the journal Applied Physics Letters. It details discovery of how infrared photodetection can be done more effectively by using certain materials arranged in specific patterns in atomic-scale structures. It's being accomplished by using multiple ultrathin layers of the materials that are only several nanometers thick. Crystals are formed in each layer. These layered structures are then combined to form what are termed "superlattices." Photodetectors made of different crystals absorb different wavelengths of light and convert them into an electrical signal. The conversion efficiency achieved by these crystals determines a photodectector's sensitivity and the quality of detection it provides, explains electrical engineer Yong-Hang Zhang. The unique property of the superlattices is that their detection wavelengths can be broadly tuned by changing the design and composition of the layered structures. The precise arrangements of the nanoscale materials in superlattice structures helps to enhance the sensitivity of infrared detectors, Zhang says. Additional research in this area is being supported by a grant from the Air Force Office of Scientific Research and a new Multidisciplinary University Research Initiative (MURI) program established by the U.S. Army Research Office. ASU is a partner in the program led by the University of Illinois at Urbana-Champaign. The team is using a combination of indium arsenide and indium arsenide antimonide to build the superlattice structures. The combination allows devices to generate photo electrons necessary to provide infrared signal detection and imaging, says Elizabeth Steenbergen, an electrical engineering doctoral student who performed experiments on the supperlattice materials with collaborators at the Army Research Lab. "In a photodetector, light creates electrons. Electrons emerge from the photodetector as electrical current. We read the magnitude of this current to measure infrared light intensity," she says. "In this chain, we want all of the electrons to be collected from the detector as efficiently as possible. But sometimes these electrons get lost inside the device and are never collected," says team member Orkun Cellek, an electrical engineering postdoctoral research associate. Zhang says the team's use of the new materials is reducing this loss of optically excited electrons, which increases the electrons' carrier lifetime by more than 10 times what has been achieved by other combinations of materials traditionally used in the technology. Carrier lifetime is a key parameter that has limited detector efficiency in the past. Another advantage is that infrared photodetectors made from these superlattice materials don't need as much cooling. Such devices are cooled as a way of reducing the amount of unwanted current inside the devices that can "bury" electrical signals, Zhang says. The need for less cooling reduces the amount of power needed to operate the photodetectors, which will make the devices more reliable and the systems more cost effective. Researchers say improvements can still be made in the layering designs of the intricate superlattice structures and in developing device designs that will allow the new combinations of materials to work most effectively. The advances promise to improve everything from guided weaponry and sophisticated surveillance systems to industrial and home security systems, the use of infrared detection for medical imaging and as a road-safety tool for driving at night or during sand storms or heavy fog. "You would be able to see things ahead of you on the road much better than with any headlights," Cellek says. »

Swiss scientists have created a minor sensation in synthetic chemistry. The team of scientists from ETH Zurich and Empa, the Swiss Federal Laboratories for Materials Science and Technology, succeeded for the first time in producing regularly ordered planar polymers that form a kind of "molecular carpet" on a nanometer scale. Back in 1920 at ETH Zurich, the chemist Hermann Staudinger postulated the existence of macromolecules consisting of many identical modules strung together like a chain. His concept was initially greeted with mockery and incomprehension from his fellow chemists. But Staudinger was to be proved right (and eventually even awarded the Nobel Prize in Chemistry in 1953): today the macromolecules described as polymers are known as plastics, and by 1950 one kilogram of them was already being produced per capita worldwide. Today, more than ninety years after Staudinger's discovery about 150 million tons of plastics are manufactured every year -- a gigantic industry delivering products that our daily lives can hardly do without. A research group led by ETH Zurich scientists A. Dieter Schlüter and Junji Sakamoto has now succeeded in making a decisive breakthrough in the synthetic chemistry of polymers: they have for the first time created two-dimensional polymers. Polymers are formed when small single molecules known as monomers join together by chemical reactions like the links of a chain to form high molecular weight substances. The question remained as to whether polymers can only polymerize linearly, i.e. in one dimension. Although graphene counts as a naturally occurring representative of a two-dimensional polymer -- planar layers of carbon with a honeycomb-like pattern -- it cannot be synthesized in a controlled way. In order to develop a synthetic chemistry that generates two-dimensional molecules the ETH chemists had to first and foremost create oligofunctional monomers in such a way that they join together purely two-dimensionally instead of linearly or even three-dimensionally. Polymers of this kind must have three or more covalent bonds between the regularly repeating units. The scientists had to find out which bonding chemistry and environment was most suitable for producing this kind of "molecular carpet." »

Pulsars are among the most exotic celestial bodies known. They have diameters of about 20 kilometres, but at the same time roughly the mass of our sun. A sugar-cube sized piece of its ultra-compact matter on Earth would weigh hundreds of millions of tons. A sub-class of them, known as millisecond pulsars, spin up to several hundred times per second around their own axes. Previous studies reached the paradoxical conclusion that some millisecond pulsars are older than the universe itself. The astrophysicist Thomas Tauris from the Max Planck Institute for Radio Astronomy and the Argelander Institute for Astronomy in Bonn could resolve this paradox by computer simulations. Through numerical calculations on the base of stellar evolution and accretion torques, he demonstrated that millisecond pulsars loose about half of their rotational energy during the final stages of the mass-transfer process before the pulsar turns on its radio beam. This result is in agreement with current observations and the findings also explain why radio millisecond pulsars appear to be much older than the white dwarf remnants of their companion stars -- and perhaps why no sub-millisecond radio pulsars exist at all. The results are reported in the February 03 issue of the journal "Science." Millisecond pulsars are strongly magnetized, old neutron stars in binary systems which have been spun up to high rotational frequencies by accumulatingmass and angular momentum from a companion star. Today we know of about 200 such pulsars with spin periods between 1.4 to 10 milliseconds. These are located in both the Galactic Disk and in Globular Clusters. Since the first millisecond pulsar was detected in 1982, it has remained a challenge for theorists to explain their spin periods, magnetic fields and ages. For example, there is the "turn-off" problem, i.e. what happens to the spin of the pulsar when the donor star terminates its mass-transfer process? "We have now, for the first time, combined detailed numerical stellar evolution models with calculations of the braking torque acting on the spinning pulsar," says Thomas Tauris, the author of the present study. "The result is that the millisecond pulsars loose about half of their rotational energy in the so-called Roche-lobe decoupling phase." This phasedescribes the termination of the mass transfer in the binary system. Hence, radio-emitting millisecond pulsars should spin slightly slower than their progenitors, X-ray emitting millisecond pulsars which are still accreting material from their donor star. This is exactly what the observational data seem to suggest. Furthermore, these new findingshelp explain why some millisecond pulsars appear to have characteristic ages exceeding the age of the Universe and perhaps why no sub-millisecond radio pulsars exist. The key feature of the new results is that it has now been demonstrated how the spinning pulsar is able to break out of its so-called equilibrium spin. At this epoch the mass-transfer rate decreases which causes the magnetospheric radius of the pulsar to expand and thereby expel the collapsing matter like a propeller. This causes the pulsar to loose additional rotational energy and thus slow down its spin rate. »

Using data from NASA's Interstellar Boundary Explorer (IBEX) spacecraft, an international team of researchers has measured neutral "alien" particles entering our solar system from interstellar space. A suite of studies published in the Astrophysical Journal provides a first look at the constituents of the interstellar medium, the matter between star systems, and how they interact with our heliosphere. The heliosphere, the "bubble" in which our Sun and planets reside, is formed by the interaction between the solar wind, flowing outward from the Sun, and the interstellar medium, which presses up against it. Electrically charged, or ionized, particles cannot penetrate the boundary between these two bodies. However, neutral particles, which make up about half the material outside the heliosphere, flow freely in through the boundary. The only other spacecraft to directly detect these inflowing neutral particles was Ulysses, which more than a decade ago measured interstellar neutral helium. Although IBEX is designed primarily to map the interactions between the solar wind and ionized interstellar material, its low-energy energetic neutral atom camera has now also measured interstellar neutral particles not detected by Ulysses. From its location within Earth's orbit, IBEX has sampled interstellar hydrogen, oxygen, and neon in addition to neutral helium. Neon and oxygen reside throughout the galaxy, but researchers are unsure of their distribution. Using IBEX data, the first direct measurements of these elements in the local interstellar medium, researchers can determine how much oxygen is in the local part of the galaxy, which materials are present in what amounts and more. "Answering these questions is important for understanding the variability of the galactic soup -- the material from which stars, planets and life all form," says Dr. David J. McComas, IBEX principal investigator and an assistant vice president at Southwest Research Institute. For example, the presence of less oxygen in the local interstellar medium compared to the Sun and galactic average could indicate the Sun formed in a region with less oxygen than exists in its current location. Another possibility is that the oxygen could be preferentially tied up or "hidden" in other galactic materials, such as dust grains and ices. IBEX data reveal that interstellar neutrals enter the heliosphere at a speed of about 52,000 mph, roughly, 7,000 mph slower than inferred from Ulysses observations, and that they enter from a somewhat different direction. Magnetic forces play a major role in the interactions of the charged particles at the heliosphere's boundaries. As the overall particle speeds drop, however, the magnetic forces play an even more dominant role. "With this lower speed, the external magnetic forces cause the heliosphere to become more squished and misshapen," says McComas. "Rather than being shaped like a bullet moving through the air, the heliosphere becomes flattened, more like a beach ball being squeezed when someone sits on it." »

Researchers working at the U.S. Department of Energy's (DOE) SLAC National Accelerator Laboratory have used the world's most powerful X-ray laser to create and probe a 2-million-degree piece of matter in a controlled way for the first time. This feat, reported in Nature, takes scientists a significant step forward in understanding the most extreme matter found in the hearts of stars and giant planets, and could help experiments aimed at recreating the nuclear fusion process that powers the sun. The experiments were carried out at SLAC's Linac Coherent Light Source (LCLS), whose rapid-fire laser pulses are a billion times brighter than those of any X-ray source before it. Scientists used those pulses to flash-heat a tiny piece of aluminum foil, creating what is known as "hot dense matter," and took the temperature of this solid plasma -- about 2 million degrees Celsius. The whole process took less than a trillionth of a second. "The LCLS X-ray laser is a truly remarkable machine," said Sam Vinko, a postdoctoral researcher at Oxford University and the paper's lead author. "Making extremely hot, dense matter is important scientifically if we are ultimately to understand the conditions that exist inside stars and at the center of giant planets within our own solar system and beyond." Scientists have long been able to create plasma from gases and study it with conventional lasers, said co-author Bob Nagler of SLAC, an LCLS instrument scientist. But no tools were available for doing the same at solid densities that cannot be penetrated by conventional laser beams. "The LCLS, with its ultra-short wavelengths of X-ray laser light, is the first that can penetrate a dense solid and create a uniform patch of plasma -- in this case a cube one-thousandth of a centimeter on a side -- and probe it at the same time," Nagler said. The resulting measurements, he said, will feed back into theories and computer simulations of how hot, dense matter behaves. This could help scientists analyze and recreate the nuclear fusion process that powers the sun. "Those 60 hours when we first aimed the LCLS at a solid were the most exciting 60 hours of my entire scientific career," said Justin Wark, leader of the Oxford group. "LCLS is really going to revolutionize the field, in my view." »

Scientists have developed a new way to create electromagnetic Terahertz (THz) waves or T-rays -- the technology behind full-body security scanners. The researchers behind the study, published recently in the journal Nature Photonics, say their new stronger and more efficient continuous wave T-rays could be used to make better medical scanning gadgets and may one day lead to innovations similar to the 'tricorder' scanner used in Star Trek. In the study, researchers from the Institute of Materials Research and Engineering (IMRE), a research institute of the Agency for Science, Technology and Research (A*STAR) in Singapore, and Imperial College London in the UK have made T-rays into a much stronger directional beam than was previously thought possible, and have done so at room-temperature conditions. This is a breakthrough that should allow future T-ray systems to be smaller, more portable, easier to operate, and much cheaper than current devices. The scientists say that the T-ray scanner and detector could provide part of the functionality of a Star Trek-like medical 'tricorder' -- a portable sensing, computing and data communications device -- since the waves are capable of detecting biological phenomena such as increased blood flow around tumorous growths. Future scanners could also perform fast wireless data communication to transfer a high volume of information on the measurements it makes. T-rays are waves in the far infrared part of the electromagnetic spectrum that have a wavelength hundreds of times longer than those that make up visible light. Such waves are already in use in airport security scanners, prototype medical scanning devices and in spectroscopy systems for materials analysis. T-rays can sense molecules such as those present in cancerous tumours and living DNA, since every molecule has its unique signature in the THz range. They can also be used to detect explosives or drugs, for gas pollution monitoring or non-destructive testing of semiconductor integrated circuit chips. Current T-ray imaging devices are very expensive and operate at only a low output power, since creating the waves consumes large amounts of energy and needs to take place at very low temperatures. In the new technique, the researchers demonstrated that it is possible to produce a strong beam of T-rays by shining light of differing wavelengths on a pair of electrodes -- two pointed strips of metal separated by a 100 nanometre gap on top of a semiconductor wafer. The structure of the tip-to-tip nano-sized gap electrode greatly enhances the THz field and acts like a nano-antenna to amplify the wave generated. In this method, THz waves are produced by an interaction between the electromagnetic waves of the light pulses and a powerful current passing between the semiconductor electrodes. The scientists are able to tune the wavelength of the T-rays to create a beam that is useable in the scanning technology. Lead author Dr Jing Hua Teng, from A*STAR's IMRE, said: "The secret behind the innovation lies in the new nano-antenna that we had developed and integrated into the semiconductor chip." Arrays of these nano-antennas create much stronger THz fields that generate a power output that is 100 times higher than the power output of commonly used THz sources that have conventional interdigitated antenna structures. A stronger T-ray source renders the T-ray imaging devices more power and higher resolution. »

How liquid can a fluid be? This is a question particle physicists at the Vienna University of Technology have been working on. The "most perfect liquid" is nothing like water, but the extremely hot quark-gluon-plasma which is produced in heavy-ion collisions at the Large Hadron Collider at CERN. New theoretical results at Vienna UT show that this quark-gluon plasma could be even less viscous than was deemed possible by previous theories. Highly viscous liquids (such as honey) are thick and have strong internal friction, quantum liquids, such as super fluid helium can exhibit extremely low viscosity. In 2004, theorists claimed that quantum theory provided a lower bound for viscosity of fluids. Applying methods from string theory, the lowest possible ratio of viscosity to the entropy density was predicted to be ħ/4π (with the Planck-constant ħ). Even super fluid helium is far above this threshold. In 2005, measurements showed that quark-gluon-plasma exhibits a viscosity just barely above this limit. However, this record for low viscosity can still be broken, claims Dominik Steineder from the Institute for Theoretical Physics at Vienna UT. He obtained this remarkable result working as a PhD-student with Professor Anton Rebhan. The viscosity of a quark-gluon plasma cannot be calculated directly. Its behavior is so complicated that very sophisticated tricks have to be applied, says Anton Rebhan: "Using string theory, the quantum field theory of quark-gluon plasma can be related to the physics of black holes in higher dimensions. So we are solving equations from string theory and then transfer the results to the physics of the quark-gluon plasma." The previously established lower bound for viscosity was calculated in a very similar way. However, in these calculations the plasma was modeled to be symmetric and isotropic. "In fact, a plasma produced by a collision in a particle accelerator is not isotropic at the beginning," says Anton Rebhan. The particles are accelerated and collided along one specific direction -- so the resulting plasma shows different properties, depending on the direction from which one looks at it. The physicists at Vienna UT found a way to include this anisotropy in their equations -- and surprisingly the limit for the viscosity can be broken in this new model. "The viscosity depends on several other physical parameters, but it can be lower than the number previously considered to be the absolute lower bound," Dominik Steineder explains. The on-going quark-gluon-experiments at CERN will provide opportunities for testing the new theoretical predictions. »

KU Leuven researcher Ventsislav Valev and an international team of scientists have developed a new method for optical manipulation of matter at the nanoscale. Using 'plasmonic hotspots' -- regions with electric current that heat up very locally -- gold nanostructures can be melted and made to produce the smallest nanojets ever observed. The tiny gold nanodroplets formed in the nanojets, are perfectly spherical, which makes them interesting for applications in medicine. The 'backjet' phenomenon on which the method turns can be compared to a pebble being dropped into water. Tightly focused ultrafast laser pulses carry sufficient energy to locally melt the surface of a gold film. When a laser pulse of light hits the film, a nanoscale backjet -- a nanojet -- of molten gold surges upward. As the name suggests, nanojets on the surface of a homogeneous gold film are incredibly small, their size being determined by the distribution of energy in the light pulse. This distribution of energy is in turn dependent on the wavelength of light. Initially, scientists anticipated that nanojets could not be significantly smaller than the wavelength of light. In this study however, Ventsislav Valev and his colleagues show that nanojets can in fact be made much smaller with the help of 'plasmonic hotspots'. Plasmonic hotspots are regions on the surface of metal nanostructures where light causes very strong oscillation of the electrons. Because electron oscillations constitute an electric current and because electric currents heat up the material the same way an electric stove heats up in the kitchen, the plasmonic hotspots are extremely hot. So hot that they can melt the gold in a spot much smaller than the wavelength of light. Dr. Valev and his colleagues were successfully able to demonstrate that this tiny little pool of molten gold can give rise to the smallest nanojets ever observed. The gold nanodroplets propelled upward by the nanojets solidify in flight, producing perfectly spherical nanoparticles. These gold nanodroplets can be collected and used for medical applications including cancer treatment. The nanoparticles can be attached to molecules and injected in the blood. Once the molecules attach to cancer cells, light can be used to heat up the gold nanodroplets and destroy the cancer cells. Currently, the gold nanoparticles used in medications are chemically synthesised. These chemically synthesised gold nanoparticles have an unavoidably granular aspect. Conversely, gold nanodroplets created by the plasmonic nanojet method detailed by Dr. Valev and his colleagues are perfectly spherical, ensuring a better efficiency. »

While physicists at the Large Hadron Collider smash together thousands of protons and other particles to see what matter is made of, they're never going to hurl electrons at each other. No matter how high the energy, the little negative particles won't break apart. But that doesn't mean they are indestructible. Using several massive supercomputers, a team of physicists has split a simulated electron perfectly in half. The results, which were published in the Jan. 13 issue of Science, are another example of how tabletop experiments on ultra-cold atoms and other condensed-matter materials can provide clues about the behavior of fundamental particles. In the simulations, Duke University physicist Matthew Hastings and his colleagues, Sergei Isakov of the University of Zurich and Roger Melko of the University of Waterloo in Canada, developed a virtual crystal. Under extremely low temperatures in the computer model, the crystal turned into a quantum fluid, an exotic state of matter where electrons begin to condense. Many different types of materials, from superconductors to superfluids, can form as electrons condense and are chilled close to absolute zero, about -459 degrees Fahrenheit. That's approximately the temperature at which particles simply stop moving. It's also the temperature region where individual particles, such as electrons, can overcome their repulsion for each other and cooperate. The cooperating particles' behavior eventually becomes indistinguishable from the actions of an individual. Hastings says the phenomenon is a lot like what happens with sound. A sound is made of sound waves. Each sound wave seems to be indivisible and to act a lot like a fundamental particle. But a sound wave is actually the collective motion of many atoms, he says. Under ultra-cold conditions, electrons take on the same type of appearance. Their collective motion is just like the movement of an individual particle. But, unlike sound waves, cooperating electrons and other particles, called collective excitations or quasiparticles, can "do things that you wouldn't think possible," Hastings says. »