New method to detect quantum mechanical effects in ordinary objects

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Scanning electron micrograph of a superconducting qubit in close proximity to a nanomechanical resonator. The nanoresonator is the bilayer (silicon nitride/aluminum) beam spanning the length of the trench in the center of the image; the qubit is the aluminum island located to the left of the nanoresonator. An aluminum electrode, located adjacent to the nanoresonator on the right, is used to actuate and sense the nanoresonator's motion. Credit: Electron beam lithography was performed by Richard Muller at JPL. Nanoresonator etch was performed by Junho Suh in the Roukes Lab. Image taken by Junho Suh.
At the quantum level, the atoms that make up matter and the photons that make up light behave in a number of seemingly bizarre ways. Particles can exist in "superposition," in more than one state at the same time (as long as we don't look), a situation that permitted Schrödinger's famed cat to be simultaneously alive and dead; matter can be "entangled" -- Albert Einstein called it "spooky action at a distance" -- such that one thing influences another thing, regardless of how far apart the two are.

Previously, scientists have successfully measured entanglement and superposition in photons and in small collections of just a few atoms. But physicists have long wondered if larger collections of atoms--those that form objects with sizes closer to what we are familiar with in our day-to-day life--also exhibit quantum effects.
"Atoms and photons are intrinsically quantum mechanical, so it's no surprise if they behave in quantum mechanical ways. The question is, do these larger collections of atoms do this as well," says Matt LaHaye, a postdoctoral research scientist working in the laboratory of Michael L. Roukes, a professor of physics, applied physics, and bioengineering at the California Institute of Technology (Caltech) and codirector of Caltech's Kavli Nanoscience Institute.
"It'd be weird to think of ordinary matter behaving in a quantum way, but there's no reason it shouldn't," says Keith Schwab, an associate professor of applied physics at Caltech, and a collaborator of Roukes and LaHaye. "If single particles are quantum mechanical, then collections of particles should also be quantum mechanical. And if that's not the case--if the quantum mechanical behavior breaks down--that means there's some kind of new physics going on that we don't understand."
The tricky part, however is devising an experiment that can detect quantum mechanical behavior in such ordinary objects—without, for example, those effects being interfered with or even destroyed by the experiment itself.
Now, however, LaHaye, Schwab, Roukes, and their colleagues have developed a new tool that meets such fastidious demands and that can be used to search for quantum effects in a ordinary object. The researchers describe their work in the latest issue of the journal Nature.
In their experiment, the Caltech scientists used microfabrication techniques to create a very tiny nanoelectromechanical system (NEMS) resonator, a silicon-nitride beam—just 2 micrometers long, 0.2 micrometers wide, and weighing 40 billionths of a milligram—that can resonate, or flex back and forth, at a high frequency when a voltage is applied.
A small distance (300 nanometers, or 300 billionths of a meter) from the resonator, the scientists fabricated a second nanoscale device known as a single-Cooper-pair box, or superconducting "qubit"; a qubit is the basic unit of quantum information.
The superconducting qubit is essentially an island formed between two insulating barriers across which a set of paired electrons can travel. In the Caltech experiments, the qubit has only two quantized energy states: the ground state and an excited state. This energy state can be controlled by applying microwave radiation, which creates an electric field.
Because the NEMS resonator and the qubit are fabricated so closely together, their behavior is tightly linked; this allows the NEMS resonator to be used as a probe for the energy quantization of the qubit. "When the qubit is excited, the NEMS bridge vibrates at a higher frequency than it does when the qubit is in the ground state," LaHaye says.
One of the most exciting aspects of this work is that this same coupling should also enable measurements to observe the discrete energy levels of the vibrating resonator that are predicted by quantum mechanics, the scientists say. This will require that the present experiment be turned around (so to speak), with the qubit used to probe the NEMS resonator. This could also make possible demonstrations of nanomechanical quantum superpositions and Einstein's spooky entanglement
"Quantum jumps are, perhaps, the archetypal signature of behavior governed by quantum effects," says Roukes. "To see these requires us to engineer a special kind of interaction between our measurement apparatus and the object being measured. Matt's results establish a practical and really intriguing way to make this happen."
More information: The paper, "Nanomechanical measurements of a superconducting qubit," was published in the June 18 issue of Nature.
Source: California Institute of Technology (news : web)

Unlike Rubber Bands, Molecular Bonds May Not Break Faster When Pulled

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ScienceDaily (June 22, 2009) — From balloons to rubber bands, things always break faster when stretched. Or do they? University of Illinois scientists studying chemical bonds now have shown this isn't always the case, and their results may have profound implications for the stability of proteins to mechanical stress and the design of new high-tech polymers.

"Our findings contradict the intuitive notion that molecules are like rubber bands in that when we pull on a chemical bond, it should always break faster," said chemistry professor Roman Boulatov, who led the study. "When we stretch a sulfur-sulfur bond, for example, how fast it breaks depends on how the nearby atoms move."
The findings also contradict the conventional interpretation of experimental results obtained by other researchers studying the fragmentation rate of certain proteins containing sulfur-sulfur bonds when stretched with a microscopic force probe. In those experiments, as the force increased, the proteins fragmented faster, leading the researchers to conclude that as the sulfur-sulfur bond was stretched, it reacted faster and broke faster.
"Our experiments suggest a different conclusion," Boulatov said. "We believe the acceleration of the fragmentation was caused by a change in the protein's structure as it was stretched, and had little or nothing to do with increased reactivity of a stretched sulfur-sulfur bond."
In their experiments, the researchers use stiff stilbene as a molecular force probe to generate well-defined forces on molecules atom by atom.
The probe allows reaction rates to be measured as a function of the restoring force. Similar to the force that develops when a rubber band is stretched, the molecular restoring force contains information about how much the molecule was distorted, and in what direction.
In previous work, when Boulatov's team pulled on carbon-carbon bonds with the same force they would later apply to sulfur-sulfur bonds, they found the carbon-carbon bonds broke a million times faster than when no force was applied.
"Because the sulfur-sulfur bond is much weaker than the carbon-carbon bond, you might think it would be much more sensitive to being pulled on," Boulatov said. "We found, however, that the sulfur-sulfur bond does not break any faster when pulled."
Boulatov and his team report their findings in a paper accepted for publication in Angewandte Chemie, and posted on the journal's Web site.
"When we pulled on the sulfur-sulfur bond, the nearby methylene groups prevented the rest of the molecule from relaxing," Boulatov said, "thus eliminating the driving force for the sulfur-sulfur bond to break any faster."
Chemists must bear in mind that even in simple chemical reactions, such as a single bond dissociation, "we must take into account other structural changes in the molecule," Boulatov said. "The elongation alone, which occurs when a bond is stretched, does not represent the full picture of what happens when the reaction occurs."
The good news, Boulatov said, is that not every polymer that is stretched will break faster. "We might be able to design polymers, for example, that would resist fragmentation under modest mechanical stresses," he said, "or will not break along the stretched direction, but in some other desired direction."
With Boulatov, co-authors of the paper are graduate student and lead author Timothy Kucharski, research associate Qing-Zheng Yang, postdoctoral researcher Yancong Tian, and graduate students Zhen Huang, Nicholas Rubin and Carlos Concepcion.
Funding was provided by the National Science Foundation, the U.S. Air Force Office of Scientific Research, the American Chemical Society Petroleum Research Fund, and the U. of I.
Adapted from materials provided by University of Illinois at Urbana-Champaign.

Chemists Form World's Smallest Droplet Of Acid

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ScienceDaily (June 22, 2009) — Exactly four water molecules and one hydrogen chloride molecule are necessary to form the smallest droplet of acid. This was the result of work by the groups of Prof. Dr. Martina Havenith (physical chemistry) and Prof. Dr. Dominik Marx (theoretical chemistry) within the research group FOR 618. They have carried out experiments at ultracold temperatures close to absolute zero temperature using infrared laser spectroscopy to monitor the molecules.

This has been accompanied by theoretical ab initio simulations. According to their calculations, the reaction at these extremely cold temperatures is only possible if the molecules are aggregating one after the other.
Chemistry at ultracold temperatures in space
If you put a classical acid, for example hydrogen chloride in water, the acid molecules will preferentially lose a proton (H+). Thereby the pH-value of the solution is decreased and the solution becomes acidic. In particular, so-called hydronium ions (H3O+), are formed by protonated water molecules. This hydronium ion is an important ingredient in many chemical reactions. Despite of the fact that this is one of the most fundamental reactions, it was not clear until now how many water molecules are actually required in order to form a charge separated negative Cl- ion and a positive H3O+ ion. “Whereas we all know acids from our daily life, we have now been able to observe for the first time acid formation on a molecular level.” "We will need this knowledge in order to understant chemical processes on nanoscopic structures, on small particles and on surfaces” explains Prof. Havenith-Newen. This indicates that there is a rich chemistry even at very low temperatures; a fundamental basis for reactions within stratospheric clouds or in interstellar media. Previously, it had been unclear whether reactions with only a few water molecules can take place at theses ultracold temperatures.
Ultracold trap
For their experiments, the researchers have successively embedded hydrogen chloride as well as single water molecules in a special ultracold trap. They used nanodroplets of suprafluid helium which have a temperature of less than -272,8 °C. Molecules will first be cooled down before they have a chance to aggregate. “Suprafluid” is a special property of the helium which implies that the embedded molecules are still free to rotate before they are frozen, thereby allowing monitoring with unsurpassed precision. Captured in such a way, it is possible to obtain the chemical fingerprint of the acid – its infrared spectrum. By combining trapping with high resolution IR laser spectroscopy and theoretical calculations, the chemists demonstrated that exactly four water molecules are required to form the smallest droplet of acid: (H3O)+(H2O)3Cl-.
Important: One molecule after the other
After these results, the researchers were left with the question of how this reaction can take place at ultracold temperatures near absolute zero. “Usually, activation of chemical reactions requires the input of energy, just like for cooking at home you need a cooking plate or a gas flame” explains Prof. Marx. “However, how should this be possible at a few Kelvin (close to absolute zero)?” The calculations, in combination with experiment, showed that the reaction is only possible by a successive aggregation process. Instead of putting together 4 water molecules and an HCl molecule simultanesously at the beginning and the waiting for a dissociation process to occur, they found in their simulations that when adding the water molecules step by step, a proton is transferred exactly when adding the fourth water molecule. Then, a hydronium ion will immediately form with one of the four added water molecules. This unusual mechanism is called “aggregation induced dissociation”. “We suspect that such aggregation induced reactions, can explain chemical transformations at ultracold conditions, such as can be found at small ice particles in clouds and in interstellar media”, explains Prof. Marx.
The work which described here is part of the research unit FOR 618 “Understanding the Aggregation of Small Molecules with Precise Methods - Interplay between Experiment and Theory”( Co-ordinator: Prof. Dr. Wolfram Sander (Faculty of Chemistry and Biochemistry) which has been funded by the Germany Science Foundation and which has just been extended for three more years after successful evaluation.
Journal reference:
Anna Gutberlet, et al. Below 1 K: The Smallest Droplet of Acid Aggregation-Induced Dissociation of HCl(H2O)4. Science, 324, 1545 (2009) DOI: 10.1126/science.1171753
Adapted from materials provided by Ruhr-Universitaet-Bochum, via AlphaGalileo.

'Look Mom No Electricity': Transmitting Information with Chemistry

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Burning an infofuse transmits a sequence of pulses of light, in which information is encoded using different wavelengths (determined by various metallic salts) and the order of the pattern. Image credit: Samuel W. Thomas III, et al. ©2009 PNAS.

(PhysOrg.com) -- While information technology is generally thought to require electrons or photons for transmitting information, scientists have recently demonstrated a third method of transmission: chemical reactions. Based on a flammable “infofuse,” the new system combines information technology and chemistry into a new area the researchers call "infochemistry."

In the study, led by George Whitesides of Harvard University, with other coauthors from Harvard, Tufts University, and DARPA, the scientists explain that their system transmits information in the form of coded pulses of light generated entirely by chemical reactions, without electricity. The system is self-powered, with power being generated by combustion. The power density of the system is higher than that of electrochemical batteries, and has the advantage of not discharging over time.
As Whitesides explained to PhysOrg.com, the significance of the study is that it “demonstrates direct chemical to binary encoding, and transmission of information at a useful bit rate, without batteries.” The researchers hope that their prototype will one day make it possible to make systems that transmit useful information in circumstances in which electronics and batteries do not work, such as harsh environments and under water.
As the scientists explain, the system consists of a strip or fuse of combustible material (nitrocellulose) about 1 mm long. When ignited, a yellow-orange flame moves along the infofuse. To encode information, the scientists patterned the fuse with various metallic salts, which could be done using a desktop inkjet printer or a micropipettor. With their different emission wavelengths, the salts created distinct emission lines in different regions of the electromagnetic spectrum, similar to how the colors of fireworks are made: blue (copper), green (barium), yellow (sodium), red (lithium, strontium, calcium), or near-infrared (potassium, rubidium, cesium).
The infofuse, which burns at about 3-4 cm/sec depending on thickness and pattern spacing, is then read by a detector, such as a color CCD camera or fiber optic cable coupled to a spectrometer. The distance between the detector and burning infofuse was typically 2 m, but the detector could still detect a signal up to 30 m away in daylight.

By coding letters of the alphabet using patterns of metallic salts, the scientists transmitted the phrase, “LOOK MOM NO ELECTRICITY” on a single infofuse using the new technique. As the scientists explain, light pulses have several controllable variables that can be used to represent different letters and symbols. In addition to emission wavelength, other variables include pulse duration, time between pulses, and emission intensity. Using combinations of three alkali metals, the researchers demonstrated how to encode 40 different characters by varying some of these parameters.
“It needs a flame, but it does not need additional batteries or power, or auxiliary devices, to convert a chemical signal to a digital one,” Whitesides said. “The power needed to generate the light is produced by chemistry directly, not by drawing power from a battery.”
Although the current infofuses convert energy into light with only 1% of the efficiency of a battery-operated LED, the infofuses generate 10 times more energy per weight than an alkaline battery generates. In general, integrating information technology and chemistry could have certain advantages, possibly leading to systems that operate beyond binary schemes by using a variety of parameters that allow each information unit to carry more information than a bit. Also, since infochemistry is not bound by the principles of electronics (such as fixed circuitry), but rather the principles of chemistry, new systems could lead to novel architectures.
The scientists hope that further improvements to their system could lead to lightweight, portable, self-powered systems that can transmit information and integrate with modern information technologies. Applications could include environmental sensing and transmitting the data optically over a distance. The system could also be used for message transmission in search-and-rescue type applications.
More information: “Infochemistry and infofuses for the chemical storage and transmission of coded information.” Samuel W. Thomas III, et al. Proceedings of the National Academy of Sciences. vol. 106, no. 23, 9147-9150.

The element 112, discovered at the GSI (Centre for Heavy Ion Research in Darmstadt)

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ScienceDaily (June 12, 2009) — The element 112, discovered at the GSI Helmholtzzentrum für Schwerionenforschung (Centre for Heavy Ion Research) in Darmstadt, has been officially recognized as a new element by the International Union of Pure and Applied Chemistry (IUPAC). IUPAC confirmed the recognition of element 112 in an official letter to the head of the discovering team, Professor Sigurd Hofmann. The letter furthermore asks the discoverers to propose a name for the new element.

Their suggestion will be submitted within the next weeks. In about 6 months, after the proposed name has been thoroughly assessed by IUPAC, the element will receive its official name. The new element is approximately 277 times heavier than hydrogen, making it the heaviest element in the periodic table.
“We are delighted that now the sixth element – and thus all of the elements discovered at GSI during the past 30 years – has been officially recognized. During the next few weeks, the scientists of the discovering team will deliberate on a name for the new element”, says Sigurd Hofmann. 21 scientists from Germany, Finland, Russia and Slovakia were involved in the experiments around the discovery of the new element 112.
Already in 1996, Professor Sigurd Hofmann’s international team created the first atom of element 112 with the accelerator at GSI. In 2002, they were able to produce another atom. Subsequent accelerator experiments at the Japanese RIKEN accelerator facility produced more atoms of element 112, unequivocally confirming GSI’s discovery.
To produce element 112 atoms, scientists accelerate charged zinc atoms – zinc ions for short – with the help of the 120 m long particle accelerator at GSI and “fire” them onto a lead target. The zinc and lead nuclei merge in a nuclear fusion to form the nucleus of the new element. Its so-called atomic number 112, hence the provisional name “element 112”, is the sum of the atomic numbers of the two initial elements: zinc has the atomic number 30 and lead the atomic number 82. An element’s atomic number indicates the number of protons in its nucleus. The neutrons that are also located in the nucleus have no effect on the classification of the element. It is the 112 electrons, which orbit the nucleus, that determine the new element’s chemical properties.
Since 1981, GSI accelerator experiments have yielded the discovery of six chemical elements, which carry the atomic numbers 107 to 112. GSI has already named their officially recognized elements 107 to 111: element 107 is called Bohrium, element 108 Hassium, element 109 Meitnerium, element 110 Darmstadtium, and element 111 is named Roentgenium.
Adapted from materials provided by GSI Helmholtzzentrum für Schwerionenforschung.

Manipulating light on a chip for quantum technologies

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An artist's impression of the on-chip quantum metrology experiment (making ultraprecise measurements on chip) Photo by Will Amery, University of Bristol.

(PhysOrg.com) -- A team of physicists and engineers at Bristol University has demonstrated exquisite control of single particles of light — photons — on a silicon chip to make a major advance towards long-sought-after quantum technologies, including super-powerful quantum computers and ultra-precise measurements.

The Bristol Centre for Quantum Photonics has demonstrated precise control of four photons using a microscopic metal electrode lithographically patterned onto a silicon chip.
The photons propagate in silica waveguides — much like in optical fibres — patterned on a silicon chip, and are manipulated with the electrode, resulting in a high-performance miniaturized device.
“We have been able to generate and manipulate entangled states of photons on a silicon chip” said PhD student, Jonathan Matthews, who together with Alberto Politi performed the experiments. “These entangled states are responsible for famously ‘weird’ behaviour arising in quantum mechanics, but are also at the heart of powerful quantum technologies.”
“This precise manipulation is a very exciting development for fundamental science as well as for future quantum technologies.” said Prof Jeremy O’Brien, Director of the Centre for Quantum Photonics, who led the research.
The team reports its results in the latest issue of Nature Photonics [June 2009], a sister journal of the leading science journal Nature, and in a Postdeadline Paper at 'The International Quantum Electronics Conference (IQEC)' on June 4 in Baltimore, USA [IQEC Postdeadline Papers].
Quantum technologies with photons
Quantum technologies aim to exploit the unique properties of quantum mechanics, the physics theory that explains how the world works at microscopic scales.
For example a quantum computer relies on the fact that quantum particles, such as photons, can exist in a “superposition” of two states at the same time — in stark contrast to the transistors in a PC which can only be in the state “0” or “1”.
Photons are an excellent choice for quantum technologies because they are relatively noise-free; information can be moved around at the speed of light; and manipulating single photons is easy.
Making two photons “talk” to each other to generate the all-important entangled states is much harder, but Professor O’Brien and his colleagues at the University of Queensland demonstrated this in a quantum logic gate back in 2003 [Nature 426, 264 (2003)].

Last year, the Centre for Quantum Photonics at Bristol showed how such interactions between photons could be realised on a silicon chip, pointing the way to advanced quantum technologies based on photons [Science 320, 646 (2008)].
Photons are also required to “talk” to each other to realise the ultra-precise measurements that harness the laws of quantum mechanics. In 2007 Professor O’Brien and his Japanese collaborators reported such a quantum metrology measurement with four photons [Science 316, 726 (2007)].
Manipulating photons on a silicon chip
“Despite these impressive advances, the ability to manipulate photons on a chip has been missing,” said Mr Politi. “For the last several years the Centre for Quantum Photonics has been working towards building fully functional quantum circuits on a chip to solve these problems,” added Prof O’Brien.
The team coupled photons into and out of the chip, fabricated at CIP Technologies, using optical fibres. Application of a voltage across the metal electrode changed the temperature of the silica waveguide directly beneath it, thereby changing the path that the photons travelled. By measuring the output of the device they confirmed high-performance manipulation of photons in the chip.
The researchers proved that one of the strangest phenomena of the quantum world, namely “quantum entanglement”, was achieved on-chip with up to four photons. Quantum entanglement of two particles means that the state of either of the particles is not defined, but only their collective state, and results in an instantaneous linking of the particles.
This on-chip entanglement has important applications in quantum metrology and the team demonstrated an ultra-precise measurement in this way.
“As well as quantum computing and quantum metrology, on-chip photonic quantum circuits could have important applications in quantum communication, since they can be easily integrated with optical fibres to send photons between remote locations,” said Alberto Politi.
“The really exciting thing about this result is that it will enable the development of reconfigurable and adaptive quantum circuits for photons. This opens up all kinds of possibilities,” said Prof O’Brien.
A commentary on the work that appeared in the same issue [Nature Photonics 3, 317 (2009)] described it as “an important step in the quest for quantum computation” and concluded: “The most exciting thing about this work is its potential for scalability. The small size of the [device] means that far greater complexity is possible than with large-scale optics.”
The other co-author of the Nature Photonics paper is Dr André Stefanov, formerly a Research fellow in the Centre for Quantum Photonics, and now at the Federal Office of Metrology METAS, Switzerland.
Provided by University of Bristol (news : web)

'Colossal' Magnetic Effect Under Pressure

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The structure models for F-type and A-type magnetic ordering in manganite in response to pressure. The arrows inside orbitals indicate the spin direction of d electrons.

(PhysOrg.com) -- Millions of people today carry around pocket-sized music players capable of holding thousands of songs, thanks to the discovery 20 years ago of a phenomenon known as the “giant magnetoresistance effect,” which made it possible to pack more data onto smaller and smaller hard drives. Now scientists are on the trail of another phenomenon, called the “colossal magnetoresistance effect” (CMR) which is up to a thousand times more powerful and could trigger another revolution in computing technology.

Understanding, and ultimately controlling, this effect and the intricate coupling between electrical conductivity and magnetism in these materials remains a challenge, however, because of competing interactions in manganites, the materials in which CMR was discovered. In the June 12, 2009, issue of the journal Physical Review Letters, a team of researchers report new progress in using high pressure techniques to unravel the subtleties of this coupling.
To study the magnetic properties of manganites, a form of manganese oxide, the research team, led by Yang Ding of the Carnegie Institution’s High Pressure Synergetic Center (HPSync), applied techniques called x-ray magnetic circular dichroism (XMCD) and angular-dispersive diffraction at the Advanced Photon Source (APS) of Argonne National Laboratory in Illinois. High pressure XMCD is a newly developed technique that uses high-brilliance circularly polarized x-rays to probe the magnetic state of a material under pressures of many hundreds of thousands of atmospheres inside a diamond anvil cell.
The discovery of CMR in manganite compounds has already made manganites invaluable components in technological applications. An example is magnetic tunneling junctions in soon-to-be marketed magnetic random access memory (MRAM), where the tunneling of electrical current between two thin layers of manganite material separated by an electrical insulator depends on the relative orientation of magnetization in the manganite layers. Unlike conventional RAM, MRAM could yield instant-on computers. However, no current theories can fully explain the rich physics, including CMR effects, seen in manganites.
“The challenge is that there are competing interactions in manganites among the electrons that determine magnetic properties,” said Ding. “And the properties are also affected by external stimuli, such as, temperature, pressure, magnetic field, and chemical doping.”
“Pressure has a unique ability to tune the electron interactions in a clean and theoretically transparent manner,” he added. “It is a direct and effective means for manipulating the behavior of electrons and could provide valuable information on the magnetic and electronic properties of manganite systems. But of all the effects, pressure effects have been the least explored.”

The researchers found that when a manganite was subjected to conditions above 230,000 times atmospheric pressure it underwent a transition in which its magnetic ordering changed from a ferromagnetic type (electron spins aligned) to an antiferromagnetic type (electron spins opposed). This transition was accompanied by a non-uniform structural distortion called the Jahn-Teller effect.
“It is quite interesting to observe that uniform compression leads to a non-uniform structural change in a manganite, which was not predicted by theory,” said Ding, “Working with Michel van Veenendaal’s theoretical group at APS, we found that the predominant effect of pressure on this material is to increase the strength of an interaction known as superexchange relative to another known as the double exchange interaction. A consequence of this is that the overall ferromagnetic interactions in the system occur in a plane (two dimensions) rather than in three dimensions, which produces a non-uniform redistribution of electrons. This leads to the structural distortion.”
Another intriguing response of manganite to high pressure revealed by the experiments is that the magnetic transition did not occur throughout the sample at the same time. Instead, it spread incrementally.
“The results imply that even at ambient conditions, the manganite might already have two separate magnetic phases at the nanometer scale, with pressure favoring the growth of the antiferro-magnetic phase at the expense of the ferromagnetic phase,” said coauthor Daniel Haskel, a physicist at Argonne’s APS. “Manipulating phase separation at the nanoscale level is at the very core of nanotechnology and manganites provide an excellent playground to pursue this objective”.
“This work not only displays another interesting emergent phenomenon arising from the interplay between charge, spin, orbital and lattice in a strongly correlated electron system,” commented coauthor Dr. Ho-kwang Mao of Carnegie’s Geophysical Laboratory, Director of HPSync,” but it also manifests the role of pressure in magnetism studies of dense matter.”
More information: Pressure-induced magnetic transition in manganite (La0.75Ca0.25MnO3) Yang Ding, Daniel Haskel, Yuan-Chieh Tseng, Eiji Kaneshita, Michel van Veenendaal, John Mitchell, Stanislav V. Sinogeikin, Vitali Prakapenka, and Ho-kwang Mao, Physical Review Letters, June 2009.

Provided by Carnegie Institution

A 'cloaking device' -- it's all done with mirrors

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Scanning electron microscope images of the cloaking device. Top: Light passes through silicon posts as it bounces off a deformed reflector. Varying density of the silicon posts bends light to compensate for the distortion in the reflector. Bottom: a close-up of the array of silicon posts, each about 50 billionths of a meter in diameter. Image: Nanophotonics Group
(PhysOrg.com) -- Somewhat the way Harry Potter can cover himself with a cloak and become invisible, Cornell researchers have developed a device that can make it seem that a bump in a carpet -- or, indeed, any flat surface -- isn't there.

So far the illusion works only at the nanoscale, but the researchers suggest that the basic principle might eventually be scaled up for military and communications applications, or perhaps used in reverse to concentrate solar energy.
Devices that bend microwaves around small objects have previously been demonstrated, but this is the first cloaking device to work at optical frequencies, the researchers said.
The experimental device was built by Michal Lipson, associate professor of electrical and computer engineering, and colleagues in her Nanophotonics Research Group, based on a design by British physicists. It bends light bouncing off a reflective surface in a way that corrects for the distortion caused by a bump in the surface. Imagine controlling the light in front of a funhouse mirror so that reflections look perfectly normal, and the mirror looks flat.
A similar device has been reported by University of California-Berkeley researchers.
On a silicon wafer, Lipson's group made a tiny reflector about 30 microns (millionths of a meter) long with a 5-micron-wide bump in the middle, then placed an array of vertical silicon posts, each 50 nanometers (billionths of a meter) in diameter, in front of it. Because the posts are much smaller than the wavelength of the light, the light behaves as if it were passing through a solid whose density varies with the density of the posts. As light passes between regions of high and low density it is refracted, or bent, in the same way light is refracted as it passes from air to glass. By designing smooth transitions of the density of posts, the researchers could control the path of the light to compensate for the distortion caused by the bump.
As a result, an observer looking at light reflected from the mirror sees a flat mirror, with no sign of the bump. The device is expected to work over a range of wavelengths from infrared into visible red light, the researchers said
Of course it's still a long way to cloaking tanks on a battlefield. For starters, the thing being hidden has to hide behind a mirror, and the presence of a mirror would be a giveaway. A practical cloaking device also would have to adjust in real time to changing configurations of the object behind it.
A variation of the method might be used to bend light around an object, the researchers suggested, and a light-bending device could be made much larger by using technology that stamps or molds nanoscale patterns onto a surface.
Such refraction control might also be used in reverse, they added, to concentrate light in a small area to efficiently collect solar energy.
"At the core is the fact that we're manipulating light, telling it where to go and how to behave," said Carl Poitras, a research associate on the Cornell team.
The device was manufactured at the Cornell Nanoscale Facility, which is supported by the National Science Foundation.
Provided by Cornell University (news : web)

Ultra-dense Deuterium May Be Nuclear Fuel Of The Future

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ScienceDaily (May 12, 2009) — A material that is a hundred thousand times heavier than water and more dense than the core of the Sun is being produced at the University of Gothenburg. The scientists working with this material are aiming for an energy process that is both more sustainable and less damaging to the environment than the nuclear power used today.

Imagine a material so heavy that a cube with sides of length 10 cm weights 130 tonnes, a material whose density is significantly greater than the material in the core of the Sun. Such a material is being produced and studied by scientists in Atmospheric Science at the Department of Chemistry, the University of Gothenburg.
Towards commercial use
So far, only microscopic amounts of the new material have been produced. New measurements that have been published in two scientific journals, however, have shown that the distance between atoms in the material is much smaller than in normal matter. Leif Holmlid, Professor in the Department of Chemistry, believes that this is an important step on the road to commercial use of the material.
The material is produced from heavy hydrogen, also known as deuterium, and is therefore known as “ultra-dense deuterium”. It is believed that ultra-dense deuterium plays a role in the formation of stars, and that it is probably present in giant planets such as Jupiter.
An efficient fuel
So what can this super-heavy material be used for?
“One important justification for our research is that ultra-dense deuterium may be a very efficient fuel in laser driven nuclear fusion. It is possible to achieve nuclear fusion between deuterium nuclei using high-power lasers, releasing vast amounts of energy”, says Leif Holmlid.
The laser technology has long been tested on frozen deuterium, known as “deuterium ice”, but results have been poor. It has proved to be very difficult to compress the deuterium ice sufficiently for it to attain the high temperature required to ignite the fusion.
Energy source of the future
Ultra-dense deuterium is a million times more dense than frozen deuterium, making it relatively easy to create a nuclear fusion reaction using high-power pulses of laser light.
“If we can produce large quantities of ultra-dense deuterium, the fusion process may become the energy source of the future. And it may become available much earlier than we have thought possible”, says Leif Holmlid.
“Further, we believe that we can design the deuterium fusion such that it produces only helium and hydrogen as its products, both of which are completely non-hazardous. It will not be necessary to deal with the highly radioactive tritium that is planned for use in other types of future fusion reactors, and this means that laser-driven nuclear fusion as we envisage it will be both more sustainable and less damaging to the environment than other methods that are being developed.”
Deuterium – brief facts
Deuterium is an isotope of hydrogen that is found in large quantities in water, more than one atom per ten thousand hydrogen atoms has a deuterium nucleus. The isotope is denoted “2H” or “D”, and is normally known as “heavy hydrogen”. Deuterium is used in a number of conventional nuclear reactors in the form of heavy water (D2O), and it will probably also be used as fuel in fusion reactors in the future.
Adapted from materials provided by University of Gothenburg.

Quantum Mechanics Predicts Unusual Lattice Dynamics Of Vanadium Metal Under Pressure

Source:

http://www.sciencedaily.com/releases/2007/10/071011125338.htm

Science Daily — A Swedish research team of Dr. Wei Luo & Professor Rajeev Ahuja and US team of Dr. Y. Ding & Prof. H.K. Mao have used theoretical calculations to understand a totally new type of high-pressure structural phase transition in Vanadium. This phase was not found in earlier experiments for any element and compound. These findings are being published in the Proceedings of the National Academy of Science.
The relation between electronic structure and the crystallographic atomic arrangement is one of the fundamental questions in physics, geophysics and chemistry. Since the discovery of the atomic nature of matter and its periodic structure, this has remained as one of the main questions regarding the very foundation of solid systems.
Scientists at Carnegie's Geophysical Laboratory, USA and Uppsala University, Sweden have discovered a new type of phase transition - a change from one form to another-in vanadium, a metal that is commonly added to steel to make it harder and more durable. Under extremely high pressures, pure vanadium crystals change their shape but do not take up less space as a result, unlike most other elements that undergo phase transitions. This work was appeared in the February 23, 2007 issue of Physical Review Letters.
Trying to understand why high-pressure vanadium uniquely has the record-high superconducting temperature of all known elements inspired us to study high-pressure structure of vanadium. Usually high superconductivity is directly linked to the lattice dynamics of material.
In present paper in PNAS, again a collaboration between Uppsala University and Carnegie's Geophysical Laboratory, USA, we have looked in to the lattice dynamics of vanadium metal and it shows a very unusual behavior under pressure.
A huge change in the electronic structure is driving force behind this unusual lattice dynamics. Moreover, our findings provide a new explanation for the continuous rising of superconducting temperature in high-pressure vanadium, and could lead us to the next breakthrough in superconducting materials.
Note: This story has been adapted from material provided by Uppsala University.

Fausto Intilla
www.oloscience.com

Light Shed On Light-emitting Nanodevice

Source:

http://www.sciencedaily.com/releases/2007/10/071008130207.htm

Science Daily — An interdisciplinary team of Cornell nanotechnology researchers has unraveled some of the fundamental physics of a material that holds promise for light-emitting, flexible semiconductors.
The discovery, which involved years of perfecting a technique for building a specific type of light-emitting device, is reported in the journal Nature Materials.*
The interdisciplinary team had long studied the molecular semiconductor ruthenium tris-bipyridine. For many reasons, including its ability to allow electrons and holes (spaces where electrons were before they moved) to pass through it easily, the material has the potential to be used for flexible light-emitting devices. Sensing, microscopy and flat-panel displays are among its possible applications.
The researchers set out to understand the fundamental physics of the material -- that is, what happens when it encounters an electric field, both at the interfaces and inside the film. By fabricating a device out of the ruthenium metal complex that was spin-coated onto an insulating substrate with pre-patterned gold electrodes, the scientists were able to use electron force microscopy to measure directly the electric field of the device.
A long-standing question, according to George G. Malliaras, associate professor of materials science and engineering, director of the Cornell NanoScale Science and Technology Facility and one of the co-principal investigators, was whether an electric field, when applied to the material, is concentrated at the interfaces or in the bulk of the film.
The researchers discovered that it was at the interfaces -- two gold metal electrodes sandwiching the ruthenium complex film -- which was a huge step forward in knowing how to build and engineer future devices.
"So when you apply the electric field, ions in the material move about, and that creates the electric fields at the interfaces," Malliaras explained.
Essential to the effort was the ability to pattern the ruthenium complex using photolithography, a technique not normally used with such materials and one that took the researchers more than three years to perfect, using the knowledge of experts in nanofabrication, materials and chemistry.
The patterning worked by laying down a gold electrode and a polymer called parylene. By depositing the ruthenium complex on top of the parylene layer and filling in an etched gap between the gold electrodes, the researchers were then able to peel the parylene material off mechanically, leaving a perfect device.
Ruthenium tris-bipyridine has energy levels well suited for efficient light emission of about 600 nanometers, said Héctor D. Abruña, the E.M. Chamot Professor of Chemistry, and a principal co-investigator. The material, which has interested scientists for many years, is ideal for its stability in multiple states of oxidation, which, in turn, allows it to serve as a good electron and hole transporter. This means that a single-layer device can be made, simplifying the manufacturing process.
"It's not fabulous, but it has a reasonable emission efficiency," Abruña said. "One of the drawbacks is it has certain instabilities, but we have managed to mitigate most of them."
Among the other authors were co-principal investigators Harold G. Craighead, the C.W. Lake Jr. Professor of Engineering, and John A. Marohn, associate professor of chemistry and chemical biology.
*September 30
Note: This story has been adapted from material provided by Cornell University.

Fausto Intilla
www.oloscience.com

Unveiling The Structure Of Microcrystals

Source:

http://www.sciencedaily.com/releases/2007/10/071004092126.htm

Science Daily — Microcrystals take the form of tiny grains, so small that they resemble a powder. How can we determine their structure?
Until now, the technique of X-ray diffraction, normally used to study crystals, was not an appropriate solution. For the first time, researchers from the ESRF and the CNRS have used X-ray diffraction to determine the structure of microcrystal grains of only one cubic micrometre in size.
They gained a factor of a thousand on the size of the analysable samples thanks to new equipment created at the ESRF. This breakthrough opens up new possibilities of research to chemists, physicists and biologists.
The properties of a crystal are determined by the arrangement of its atom in space, its crystalline structure. Scientists use X-ray or neutron diffraction to study crystalline structure when the size of the crystal is more than 10 cubic micrometres. Below this limit, the solid material is considered a powder.
Scientists can apply powder diffraction to analyse such a material but this technique is not easy to exploit. Moreover, powder diffraction can only be used for materials with grain sizes of less than three millionths of a cubic micrometre. Due to these limitations, a determination of the structure of new synthetic solids in powder form is not always possible because the crystals are too small.
The teams from the ESRF and the Institute Lavoisier (CNRS/Université de Versailles Saint-Quentin) have used new set-up permitting X-ray diffraction on crystals of a size of one cubic micrometre, a volume a thousand times smaller than that ever attainable before. This new set-up consists of a focusing system for the ESRF beam, coupled with a goniometer, an instrument to position the sample with maximum precision.
The researchers studied the structure of an organic-inorganic hybrid compound (a microporous aluminium carboxylate), which could be used for gas absorption or to encapsulate various organic molecules. This study confirms that the new set-up allows pushing back the limits in crystal dimension accessible to X-ray diffraction.
“It is a revolution: what was considered a powder in the past has become a crystal today. Researchers can now bring forward samples left in their cupboards because the sizes had previously prevented their study. Now they will be able to elucidate the structures of these samples, with potentially great scientific advances on the horizon”, explains Thierry Loiseau, from the Institut Lavoisier.
Reference: A Microdiffraction Set-up for Nanoporous Metal-Organic-Framework-Type Solids. C. Volkringer, D. Popov, T. Loiseau, N. Guillou, G. Férey, M. Haouas, F. Taulelle, C. Mellot-Draznieks, M. Burghammer and C. Riekel, Nature Materials, 6 (2007) 760-4.
Note: This story has been adapted from material provided by European Synchrotron Radiation Facility.

Fausto Intilla
www.oloscience.com

New Giant Molecule Created

Source:

http://www.sciencedaily.com/releases/2007/10/071005214924.htm

Science Daily — Ulrich Kortz, Professor of Chemistry at Jacobs University, and his team successfully synthesized a polyoxometalate with 100 Tungsten and 20 Cerium atoms that has a molar mass of about 30 kilo Dalton. With a maximum diameter of 4.2 nm the inorganic molecule is comparable in size to large complex bio-molecules or even small viruses.

Polyoxometalates are anionic metal-oxygen clusters of large structural diversity with chemical properties, which make them especially interesting for applications in catalysis, but also in materials science and nanotechnology.
Ulrich Kortz and his co-workers now achieved the synthesis of the tungstogermanate*, which belongs to the polyoxometalates, by condensation of the precursors [α-GeW9O34]10- and Cerium(III) ions in aqueous solution.
With about 600 atoms in total, amongst them 100 atoms of the heavy metal Tungsten, the new compound is the third largest molecular polytungstate ever synthesized. In addition it contains the largest number of atoms of the Rare Earth Cerium ever incorporated in such a compound.
„A single molecule of our new giant tungstate has many catalytically active centers and therefore a very high catalytic potential, which normally applies only to biological catalyst molecules. Being a lot less temperature and oxidatively sensitive than bio-catalysts though and in crystalline form applicable as a heterogenic solid catalyst in liquid phase reactions our new tungstogermanate is predestined for industrial purposes,“ says Ulrich Kortz about the possible applications of the newly created molecule.
“In addition our successful synthesis allows very good inferences about the mechanism of formation by stepwise self-assembly of the simple precursors in a classic one-pot synthesis, which is vitally important for the development of other so-called ‘molecular machines’, large molecules designed to have very specific functions,“ the Jacobs chemist concludes.
*Tungstogermanate [Ce20Ge10W100O376(OH)4(H2O)30]56-
The reaction conditions and the molecular structure were published in Angewandte Chemie (doi: 10.1002/anie.200701422).
Note: This story has been adapted from material provided by Jacobs University.

Fausto Intilla

www.oloscience.com

New Particles Get A Mass Boost

Source:

http://www.sciencedaily.com/releases/2007/10/071001152838.htm

Science Daily — A sophisticated, new analysis has revealed that the next frontier in particle physics is farther away than once thought. New forms of matter not predicted by the Standard Model of particle physics are most likely twice as massive as theorists had previously calculated, according to a just-published study.
The discovery is noteworthy because experimental improvements of this magnitude rarely occur more often than once in a decade.
To see the infinitely small bits of matter that make up our universe, physicists build ever more powerful accelerators, which are the microscopes they use to see matter. But while the trend is to more powerful accelerators, the precision achieved by some less powerful ones can pinpoint the best places to look for never-before-seen particles.
Scientists at the Department of Energy's Thomas Jefferson National Accelerator Facility combined data from experiments in which electrons were used to precisely probe the nucleus of the atom. The experiments were designed to study the weak nuclear force, one of the four forces of nature. The effects of the weak force on the building blocks of the proton, up and down quarks, were determined precisely from this data and were found to be in agreement with predictions.
But when this new analysis was combined with other measurements, it raised the predicted mass scale for the discovery of new particles to about one Tera-electron-volts (1 TeV) - more than a factor of two higher than previously thought, according to Jefferson Lab scientists who published the result in Physical Review Letters.
Searches for new particles can take the form of direct production of new particles by high-energy interactions or by lower-energy, extremely precise measurements of experimental observables, which are sensitive to the existence of new particles beyond the ability of existing theories to predict.
Note: This story has been adapted from material provided by DOE/Thomas Jefferson National Accelerator Facility.

Fausto Intilla
www.oloscience.com

Magnetic Snakes Create Water Current

Source:

http://www.sciencedaily.com/releases/2007/09/070924122818.htm

Science Daily — Physicists at Argonne National Laboratory have found that magnetic particles suspended in water and subjected to an alternating magnetic field will form snake-shaped structures that can control the flow of the surrounding fluid.

Current incarnations of the magnetic snake are a few centimeters long, but the team envisions much smaller versions as pumps to manipulate liquids on microscopic scales or precursors for next-generation magnetic recording media in future computers.
The team's recent experiment shows that the speed of the water flowing along the snake depends on how quickly the magnetic field alternates.
To make a magnetic snake, the team put a water-filled beaker at the center of a magnetic coil. In the water, they suspended magnetic nickel spheres a little smaller than one tenth of a millimeter in diameter. These particles reacted to an alternating magnetic field created by the coil. The nickel spheres aligned themselves head-to-tail with nearby particles as though they contained tiny bar magnets.
The movements of the particle chain made waves on the surface of the water, encouraging the formation of parallel chains and causing a segmented pattern. The self-assembly of the snakes can take anywhere from a fraction of a second to several minutes.
This research is to be published in a forthcoming edition of Physical Review Letters. Authors are M. Belkin, A. Snezhko, I.S. Aranson, and W.-K. Kwok.
Note: This story has been adapted from material provided by American Physical Society.

Fausto Intilla

www.oloscience.com

'Hot' Ice Could Lead To Medical Device

Source:

http://www.sciencedaily.com/releases/2007/09/070926122753.htm

Science Daily — Harvard physicists have shown that specially treated diamond coatings can keep water frozen at body temperature, a finding that may have applications in future medical implants.

Doctoral student Alexander Wissner-Gross and Efthimios Kaxiras, physics professor and Gordon McKay Professor of Applied Physics, spent a year building and examining computer models that showed that a layer of diamond coated with sodium atoms will keep water frozen up to 108 degrees Fahrenheit.
In ice, water molecules are arranged in a rigid framework that gives the substance its hardness. The process of melting is somewhat like a building falling down: pieces that had been arranged into a rigid structure move and flow against one another, becoming liquid water.
The computer model shows that whenever a water molecule near the diamond-sodium surface starts to fall out of place, the surface stabilizes it and reassembles the crystalline ice structure.
Simulations show that the process works only for layers of ice so thin they’re just a few molecules wide — three nanometers at room temperature and two nanometers at body temperature. A nanometer is a billionth of a meter.
The layer should be thick enough to form a biologically compatible shield over the diamond surface and to make diamond coatings more useful in medical devices, Wissner-Gross said.
The work is not the first showing that water can freeze at high temperatures. Dutch scientists had shown previously that ice can form at room temperature if placed between a tiny tungsten tip and a graphite surface. Kaxiras and Wissner-Gross’s work shows that ice can be maintained over a large area at body temperature and pressure.
Device manufacturers have been considering using diamond coatings in medical implants because of their hardness. Concerns have been raised, however, because the coatings are difficult to get absolutely smooth, abrasion of the tissue surrounding the implant could result, and that diamond might have a higher chance of causing blood clots than other materials.
Wissner-Gross said a two-nanometer layer of ice would just fill the pits in the diamond surface, smoothing it out and discouraging clotting proteins from attaching to the surface.
“It should be just soft enough and water-friendly enough to smooth out diamond’s disadvantages,” Wissner-Gross said.
Wissner-Gross and Kaxiras are planning experiments to confirm the computerized findings in the real world. Wissner-Gross said they expect results within a year.
“We’re reasonably confident we’ll be able to realize the effect experimentally,” Wissner-Gross said.
Wissner-Gross, who has been a doctoral student at Harvard since 2003, said the research grew out of an interest in the physical interaction of nanostructured surfaces with molecules that are biologically relevant, such as water. Diamond films are growing cheaper, Wissner-Gross said, and as their cost declines the array of possible uses of the material grows wider.
“We both had this notion that it would be very interesting to combine theory with respect to diamond surfaces with what’s going on in cryobiology,” Wissner-Gross said. “We were thinking about how we could leverage this long-term trend [of declining prices] to do something interesting in the medical field.”
Note: This story has been adapted from material provided by Harvard University.

Fausto Intilla

www.oloscience.com

A New Look At The Proton

Source:

http://www.sciencedaily.com/releases/2007/09/070925092529.htm

Science Daily — Dutch researcher Paul van der Nat investigated more than three million collisions between electrons and protons. In his PhD thesis he demonstrates -for the first time– that the spin contribution of quarks to the proton can be studied by examining collisions in which two particles (hadrons) are produced.

The spin of a particle can most easily be compared to the rotating movement of a spinning top.
In the HERMES experiment at the HERA particle accelerator in Hamburg, physicists are investigating how the spin of protons can be explained by the characteristics of their building blocks: quarks and gluons.
Van der Nat investigated a method to measure the contribution of the spin of the quarks to the total spin of the proton, independent of the contribution of the spin of the gluons. For this a quark is shot out of the proton by an electron from the particle accelerator, as a result of which two hadrons are formed.
The direction and amount of motion of these two hadrons is accurately measured. This method, which Van der Nat applied for the first time, turned out to be successful.
Spin is a characteristic property of particles, just like matter and electrical charge. Spin was discovered in 1925, by the Dutch physicists Goudsmit and Uhlenbeck. In 1987, scientists at CERN in Geneva discovered that only a small fraction of the proton's spin is caused by the spin of its constituent quarks.
The HERMES experiment was subsequently set up to find this missing quantity of spin, and has been running since 1995. It is expected that spin will play an increasingly important role in many applications. The MRI scanner is a well-known example of an application in which the spin of protons plays a key role.
Note: This story has been adapted from a news release issued by Netherlands Organization for Scientific Research.

Fausto Intilla

www.oloscience.com

Portable Atomic Emission Detector Under Development

Source:

http://www.sciencedaily.com/releases/2007/09/070914172642.htm

Science Daily — Brad Jones, a professor of chemistry at Wake Forest University, is leading a team of researchers at four institutions to develop the first handheld, field instrument capable of detecting and identifying radioactive particles at the site of potential contamination.

The device will enable authorities to quickly test dust, soil, water and crops in the event of a terrorist attack such as a “dirty” bomb.
The three-year project is funded by the National Science Foundation in conjunction with the Department of Homeland Security, which asked scientists to submit proposals for radioactivity detection devices. Jones, who specializes in creating spectroscopic instruments, saw the potential to adapt a design he originally conceived years ago to permit rapid field testing for lead in blood samples.
Jones’ “Tungsten Coil Atomic Emission Spectrometer” is constructed using the metal coil filament from a standard slide projector bulb powered by a 12-volt battery, such as the type used to start boats or automobiles. Environmental samples of suspect particles are dissolved in liquid, and droplets are placed on the coil.
The samples are dried at low voltage and the residue vaporized at 3,000 degrees, producing a flash of light. Each metal displays a unique color signature, which is captured by a fiber optic sensor connected to a laptop computer. Test results are then charted on a graph showing each sample’s wavelength and intensity, allowing scientists to identify specific elements and amounts of radioactivity.
“It’s just a natural application,” Jones says, noting that the radioisotopes likely to be stolen from medical or industrial facilities and used by terrorists are also the most brightly emitting elements in atomic spectrometry. “But, the proposed device represents a new way of thinking in the field of nuclear forensics. Atomic emission spectrometry is traditionally a laboratory-based technique using very large, very expensive instruments. With immediate on-site results, residents could be given timely information about a potential threat or reassured that none existed rather than waiting for samples to be transported to laboratories for analysis.”
Portability may also lead to new applications of atomic spectrometry in the field, Jones adds, such as testing for contamination by pesticides and other pollutants.
Instrument manufacturer Teledyne Leeman Labs is interested in the production and marketing of the device once Jones’ research group perfects their prototype. Jones has collaborated with the company for more than a decade.
Other members of the research team include Clifton P. Calloway Jr., associate professor of chemistry at Winthrop University in Rock Hill, S.C.; Arthur L. Salido, assistant professor of chemistry at Western Carolina University in Cullowhee; and Joaquim A. Nobrega, professor of chemistry at the Federal University of Sao Carlos in Brazil.
Note: This story has been adapted from a news release issued by Wake Forest University.

Fausto Intilla

www.oloscience.com

Official Kilogram Losing Mass: Scientists Propose Redefining It As A Precise Number Of Carbon Atoms

Source:

http://www.sciencedaily.com/releases/2007/09/070921110735.htm

Science Daily — How much is a kilogram?

It turns out that nobody can say for sure, at least not in a way that won't change ever so slightly over time. The official kilogram -- a cylinder cast 118 years ago from platinum and iridium and known as the International Prototype Kilogram or "Le Gran K" -- has been losing mass, about 50 micrograms at last check. The change is occurring despite careful storage at a facility near Paris.
That's not so good for a standard the world depends on to define mass.
Now, two U.S. professors -- a physicist and mathematician -- say it's time to define the kilogram in a new and more elegant way that will be the same today, tomorrow and 118 years from now. They've launched a campaign aimed at redefining the kilogram as the mass of a very large -- but precisely-specified -- number of carbon-12 atoms.
"Our standard would eliminate the need for a physical artifact to define what a kilogram is," said Ronald F. Fox, a Regents' Professor Emeritus in the School of Physics at the Georgia Institute of Technology. "We want something that is logically very simple to understand."
Their proposal is that the gram -- 1/1000th of a kilogram -- would henceforth be defined as the mass of exactly 18 x 14074481 (cubed) carbon-12 atoms.
The proposal, made by Fox and Theodore P. Hill -- a Professor Emeritus in the Georgia Tech School of Mathematics -- first assigns a specific value to Avogadro's constant. Proposed in the 1800s by Italian scientist Amedeo Avogadro, the constant represents the number of atoms or molecules in one mole of a pure material -- for instance, the number of carbon-12 atoms in 12 grams of the element. However, Avogadro's constant isn't a specific number; it's a range of values that can be determined experimentally, but not with enough precision to be a single number.
Spurred by Hill's half-serious question about whether Avogadro's constant was an even or odd number, in the fall of 2006 Fox and Hill submitted a paper to Physics Archives in which they proposed assigning a specific number to the constant -- one of about 10 possible values within the experimental range. The authors pointed out that a precise Avogadro's constant could also precisely redefine the measure of mass, the kilogram.
Their proposal drew attention from the editors of American Scientist, who asked for a longer article published in March 2007. The proposal has so far drawn five letters, including one from Paul J. Karol, chair of the Committee on Nomenclature, Terminology and Symbols of the American Chemical Society. Karol added his endorsement to the proposal and suggested making the number divisible by 12 -- which Fox and Hill did in an addendum by changing their number's final digit from 8 to 6. So the new proposal for Avogadro's constant became 84446886 (cubed), still within the range of accepted values.
Fast-forward to September 2007, when Fox read an Associated Press article on the CNN.com Web site about the mass disappearing from the International Prototype Kilogram. While the AP said the missing mass amounted to no more than "the weight of a fingerprint," Fox argues that the amount could be significant in a world that is measuring time in ultra-sub-nanoseconds and length in ultra-sub-nanometers.
So Fox and Hill fired off another article to Physics Archive, this one proposing to redefine the gram as 1/12th the mass of a mole of carbon 12 -- a mole long being defined as Avogrado's number of atoms. They now hope to generate more interest in their idea for what may turn out to be a competition of standards proposals leading up to a 2011 meeting of the International Committee for Weights and Measures.
At least two other proposals for redefining the kilogram are under discussion. They include replacing the platinum-iridium cylinder with a sphere of pure silicon atoms, and using a device known as the "watt balance" to define the kilogram using electromagnetic energy. Both would offer an improvement over the existing standard -- but not be as simple as what Fox and Hill have proposed, nor be exact, they say.
"Using a perfect numerical cube to define these constants yields the same level of significance -- eight or nine digits -- as in those integers that define the second and the speed of light," Hill said. "A purely mathematical definition of the kilogram is experimentally neutral -- researchers may then use any laboratory method they want to approximate exact masses."
The kilogram is the last major standard defined by a physical artifact rather than a fundamental physical property. In 1983, for instance, the distance represented by a meter was redefined by how far light travels in 1/299,792,458 seconds -- replacing a metal stick with two marks on it.
"We suspect that there will be some public debate about this issue," Fox said. "We want scientists and science teachers and others to think about this problem because we think they can have an impact. Public discussion may play an important role in determining how one of the world's basic physical constants is defined."
How important is this issue to the world's future technological development"
"When you make physical and chemical measurements, it's important to have as high a precision as possible, and these standards really define the limits of precision," Fox said. "The lack of an accurate standard leaves some inconsistency in how you state results. Having a unique standard could eliminate that."
While the new definition would do away with the need for a physical representation of mass, Fox says people who want a physical artifact could still have one -- though carbon can't actually form a perfect cube with the right number of atoms. And building one might take some time.
"You could imagine having a lump of matter that actually had exactly the right number of atoms in it," Fox noted. "If you could build it by some kind of self-assembly process -- as opposed to building it atom-by-atom, which would take a few billion years -- you could have new kilogram artifact made of carbon. But there's really no need for that. Even if you built a perfect kilogram, it would immediately be inaccurate as soon as a single atom was sloughed off or absorbed."
Note: This story has been adapted from a news release issued by Georgia Institute of Technology.

Fausto Intilla

www.oloscience.com

'Radio Wave Cooling' Offers New Twist On Laser Cooling

Source:

http://www.sciencedaily.com/releases/2007/09/070914105600.htm

Science Daily — Visible and ultraviolet laser light has been used for years to cool trapped atoms--and more recently larger objects--by reducing the extent of their thermal motion.

Now, applying a different form of radiation for a similar purpose, physicists at the National Institute of Standards and Technology (NIST) have used radio waves to dampen the motion of a miniature mechanical oscillator containing more than a quadrillion atoms, a cooling technique that may open a new window into the quantum world using smaller and simpler equipment.
Described in a forthcoming issue of Physical Review Letters,* this demonstration of radio-frequency (RF) cooling of a relatively large object may offer a new tool for exploring the elusive boundary where the familiar rules of the everyday, macroscale world give way to the bizarre quantum behavior seen in the smallest particles of matter and light. There may be technology applications as well: the RF circuit could be made small enough to be incorporated on a chip with tiny oscillators, a focus of intensive research for use in sensors to detect, for example, molecular forces.
The NIST experiments used an RF circuit to cool a 200 x 14 x 1,500 micrometer silicon cantilever--a tiny diving board affixed at one end to a chip and similar to the tuning forks used in quartz crystal watches--vibrating at 7,000 cycles per second, its natural "resonant" frequency. Scientists cooled it from room temperature (about 23 degrees C, or 73 degrees F) to -228 C (-379 F).
Other research groups have used optical techniques to chill micro-cantilevers to lower temperatures, but the RF technique may be more practical in some cases, because the equipment is smaller and easier to fabricate and integrate into cryogenic systems. By extending the RF method to higher frequencies at cryogenic temperatures, scientists hope eventually to cool a cantilever to its "ground state" near absolute zero (-273 C or -460 F) , where it would be essentially motionless and quantum behavior should emerge.
Laser cooling is akin to using the kinetic energy of millions of ping-pong balls (particles of light) striking a rolling bowling ball (such as an atom) to slow it down. The RF cooling technique, lead author Kenton Brown says, is more like pushing a child on a swing slightly out of synch with its back-and-forth motion to reduce its arc. In the NIST experiments, the cantilever's mechanical motion is reduced by the force created between two electrically charged plates, one of which is the cantilever, which store energy like electrical capacitors.
In the absence of any movement, the force would be stable, but in this case, it is modulated by the cantilever vibrations. The stored energy takes some time to change in response to the cantilever's movement, and this delay pushes the cantilever slightly out of synch, damping its motion.
* K.R. Brown, J. Britton, R.J. Epstein, J. Chiaverini, D. Leibfried, and D.J. Wineland. 2007. Passive cooling of a micromechanical oscillator with a resonant electric circuit. Physical Review Letters. [Forthcoming].
Note: This story has been adapted from a news release issued by National Institute of Standards and Technology.

Fausto Intilla

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