Saturday, December 31, 2011

First electronic optical fibers with hydrogenated amorphous silicon are developed

 A new chemical technique for depositing a non-crystalline form of silicon into the long, ultra-thin pores of optical fibers has been developed by an international team of scientists in the United States and the United Kingdom. The technique, which is the first of its kind to use high-pressure chemistry for making well-developed films and wires of this particular kind of silicon semiconductor, will help scientists to make more-efficient and more-flexible optical fibers.

The findings, by an international team led by John Badding, a professor of chemistry at Penn State University, will be published in a future print edition of the Journal of the American Chemical Society.

Badding explained that hydrogenated amorphous silicon -- a noncrystalline form of silicon -- is ideal for applications such as solar cells. Hydrogenated amorphous silicon also would be useful for the light-guiding cores of optical fibers; however, depositing the silicon compound into an optical fiber -- which is thinner than the width of a human hair -- presents a challenge. "Traditionally, hydrogenated amorphous silicon is created using an expensive laboratory device known as a plasma reactor," Badding explained. "Such a reactor begins with a precursor called silane -- a silicon-hydrogen compound. Our goal was not only to find a simpler way to create hydrogenated amorphous silicon using silane, but also to use it in the development of an optical fiber."

Because traditional, low-pressure chemistry techniques cannot be used for depositing hydrogenated amorphous silicon into a fiber, the team had to find another approach. "While the low-pressure plasma reactor technique works well enough for depositing hydrogenated amorphous silicon onto a surface to make solar cells, it does not allow the silane precursor molecules to be pushed into the long, thin holes in an optical fiber," said Pier J. A. Sazio of the University of Southampton in the United Kingdom and one of the team's leaders. "The trick was to develop a high-pressure technique that could force the molecules of silane all the way down into the fiber and then also convert them to amorphous hydrogenated silicon. The high-pressure chemistry technique is unique in allowing the silane to decompose into the useful hydrogenated form of amorphous silicon, rather than the much less-useful non-hydrogenated form that otherwise would form without a plasma reactor. Using pressure in this way is very practical because the optical fibers are so small."

Optical fibers with a non-crystalline form of silicon have many applications. For example, such fibers could be used in telecommunications devices, or even to change laser light into different infrared wavelengths. Infrared light could be used to improve surgical techniques, military countermeasure devices, or chemical-sensing tools, such as those that detect pollutants or environmental toxins. The team members also hope that their research will be used to improve existing solar-cell technology. "What's most exciting about our research is that, for the first time, optical fibers with hydrogenated amorphous silicon are possible; however, our technique also reduces certain production costs, so there's no reason it could not help in the manufacture of less-expensive solar cells, as well," Badding said.

In addition to Badding and Sazio, other members of the research team include Neil F. Baril, Rongrui He, Todd D. Day, Justin R. Sparks, Banafsheh Keshavarzi, Mahesh Krishna-murthi, Ali Borhan, and Venkatraman Gopalan of Penn State; and Anna C. Peacock and Noel Healy of the University of Southampton in the United Kingdom.

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The above story is reprinted from materials provided by Penn State.

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The onset of electrical resistance

Researchers at the Max-Born-Institute, Berlin, Germany, observed the extremely fast onset of electrical resistance in a semiconductor by following electron motions in real-time.

When you first learned about electric currents, you may have asked how the electrons in a solid material move from the negative to the positive terminal. In principle, they could move ballistically or 'fly' through the solid, without being affected by the atoms or other charges of the material. But this actually never happens under normal conditions because the electrons interact with the vibrating atoms or with impurities. These collisions typically occur within an extremely short time, usually about 100 femtoseconds (10 -13 seconds, or a tenth of a trillionth of a second). So the electron motion along the material, rather than being like running down an empty street, is more like trying to walk through a very dense crowd. Typically, electrons move only with a speed of 1m per hour, they are slower than snails.

Though the electrons collide with something very frequently in the material, these collisions do take a finite time to occur. Just like if you are walking through a crowd, sometimes there are small empty spaces where you can walk a little faster for a short distance. If it were possible to follow the electrons on an extremely fast (femtosecond) time scale, then you would expect to see that when the battery is first turned on, for a very short time, the electrons really do fly unperturbed through the material before they bump into anything. This is exactly what scientists at the Max-Born-Institute in Berlin recently did in a semiconductor material and report in the current issue of the journal Physical Review Letters [volume 107, 256602 (2011)]. Extremely short bursts of terahertz light (1 terahertz = 10 12 Hz, 1 trillion oscillations per second) were used instead of the battery (light has an electric field, just like a battery) to accelerate optically generated free electrons in a piece of gallium arsenide. The accelerated electrons generate another electric field, which, if measured with femtosecond time resolution, indicates exactly what they are doing. The researchers saw that the electrons travelled unperturbed in the direction of the electric field when the battery was first turned on. About 300 femtoseconds later, their velocity slowed down due to collisions.

In the attached movie, we show a cartoon of what is happening in the gallium arsenide crystal. Electrons (blue balls) and holes (red balls) show random thermal motion before the terahertz pulse hits the sample. The electric field (green arrow) accelerates electrons and holes in opposite directions. After onset of scattering this motion is slowed down and results in a heated electron-hole gas, i.e., in faster thermal motion.

The present experiments allowed the researchers to determine which type of collision is mainly responsible for the velocity loss. Interestingly, they found that the main collision partners were not atomic vibrations but positively charged particles called holes. A hole is just a missing electron in the valence band of the semiconductor, which can itself be viewed as a positively charged particle with a mass 6 times higher than the electron. Optical excitation of the semiconductor generates both free electrons and holes which the terahertz bursts, our battery, move in opposite directions. Because the holes have such a large mass, they do not move very fast, but they do get in the way of the electrons, making them slower.

Such a direct understanding of electric friction will be useful in the future for designing more efficient and faster electronics, and perhaps for finding new tricks to reduce electrical resistance.

Story Source:

The above story is reprinted from materials provided by Forschungsverbund Berlin e.V. (FVB).

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Journal Reference:

P. Bowlan, W. Kuehn, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, C. Flytzanis. High-Field Transport in an Electron-Hole Plasma: Transition from Ballistic to Drift Motion. Physical Review Letters, 2011; 107 (25) DOI: 10.1103/PhysRevLett.107.256602

Inspired by insect cuticle, scientists develop material that's tough and strong

 Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a new material that replicates the exceptional strength, toughness, and versatility of one of nature's more extraordinary substances -- insect cuticle. Also low-cost, biodegradable, and biocompatible, the new material, called "Shrilk," could one day replace plastics in consumer products and be used safely in a variety of medical applications.

The research findings appear December 13 in the online issue of Advanced Materials. The work was conducted by Wyss Institute postdoctoral fellow, Javier G. Fernandez, Ph.D., with Wyss Institute Founding Director Donald Ingber, M.D., Ph.D. Ingber is the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Children's Hospital Boston and is a Professor of Bioengineering at the Harvard School of Engineering and Applied Sciences.

Natural insect cuticle, such as that found in the rigid exoskeleton of a housefly or grasshopper, is uniquely suited to the challenge of providing protection without adding weight or bulk. As such, it can deflect external chemical and physical strains without damaging the insect's internal components, while providing structure for the insect's muscles and wings. It is so light that it doesn't inhibit flight and so thin that it allows flexibility. Also remarkable is its ability to vary its properties, from rigid along the insect's body segments and wings to elastic along its limb joints.

Insect cuticle is a composite material consisting of layers of chitin, a polysaccharide polymer, and protein organized in a laminar, plywood-like structure. Mechanical and chemical interactions between these materials provide the cuticle with its unique mechanical and chemical properties. By studying these complex interactions and recreating this unique chemistry and laminar design in the lab, Fernandez and Ingber were able to engineer a thin, clear film that has the same composition and structure as insect cuticle. The material is called Shrilk because it is composed of fibroin protein from silk and from chitin, which is commonly extracted from discarded shrimp shells.

Shrilk is similar in strength and toughness to an aluminum alloy, but it is only half the weight. It is biodegradable and can be produced at a very lost cost, since chitin is readily available as a shrimp waste product. It is also easily molded into complex shapes, such as tubes. By controlling the water content in the fabrication process, the researchers were even able to reproduce the wide variations in stiffness, from elasticity to rigidity.

These attributes could have multiple applications. As a cheap, environmentally safe alternative to plastic, Shrilk could be used to make trash bags, packaging, and diapers that degrade quickly. As an exceptionally strong, biocompatible material, it could be used to suture wounds that bear high loads, such as in hernia repair, or as a scaffold for tissue regeneration.

"When we talk about the Wyss Institute's mission to create bioinspired materials and products, Shrilk is an example of what we have in mind," said Ingber. "It has the potential to be both a solution to some of today's most critical environmental problems and a stepping stone toward significant medical advances."

Story Source:

The above story is reprinted from materials provided by Wyss Institute for Biologically Inspired Engineering at Harvard.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Javier G. Fernandez, Donald E. Ingber. Unexpected Strength and Toughness in Chitosan-Fibroin Laminates Inspired by Insect Cuticle. Advanced Materials, 2011; DOI: 10.1002/adma.201104051

New method significantly reduces production costs of fuel cells

 Researchers at Aalto University in Finland have developed a new and significantly cheaper method of manufacturing fuel cells. A noble metal nanoparticle catalyst for fuel cells is prepared using atomic layer deposition (ALD).

This ALD method for manufacturing fuel cells requires 60 per cent less of the costly catalyst than current methods.

"This is a significant discovery, because researchers have not been able to achieve savings of this magnitude before with materials that are commercially available," says Docent Tanja Kallio of Aalto University.

Fuel cells could replace polluting combustion engines that are presently in use. However, in a fuel cell, chemical processes must be sped up by using a catalyst. The high price of catalysts is one of the biggest hurdles to the wide adoption of fuel cells at the moment.

The most commonly used fuel cells cover anode with expensive noble metal powder which reacts well with the fuel. By using the Aalto University researchers' ALD method, this cover can be much thinner and more even than before which lowers costs and increases quality.

With this study, researchers are developing better alcohol fuel cells using methanol or ethanol as their fuel. It is easier to handle and store alcohols than commonly used hydrogen. In alcohol fuel cells, it is also possible to use palladium as a catalyst.

The most common catalyst for hydrogen fuel cells is platinum, which is twice as expensive as palladium. This means that alcohol fuel cells and palladium will bring a more economical product to the market.

Fuel cells can create electricity that produces very little or even no pollution. They are highly efficient, making more energy and requiring less fuel than other devices of equal size. They are also quiet and require low maintenance, because there are no moving parts.

In the future, when production costs can be lowered, fuel cells are expected to power electric vehicles and replace batteries, among other things. Despite their high price, fuel cells have already been used for a long time to produce energy in isolated environments, such as space crafts. These results are based on preliminary testing with fuel cell anodes using a palladium catalyst. Commercial production could start in 5-10 years.

This study was published in the Journal of Physical Chemistry C. The research has been funded by Aalto University's MIDE research program and the Academy of Finland.

Story Source:

The above story is reprinted from materials provided by Aalto University.

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Journal Reference:

Emma Rikkinen, Annukka Santasalo-Aarnio, Sanna Airaksinen, Maryam Borghei, Ville Viitanen, Jani Sainio, Esko I. Kauppinen, Tanja Kallio, A. Outi I. Krause. Atomic Layer Deposition Preparation of Pd Nanoparticles on a Porous Carbon Support for Alcohol Oxidation. The Journal of Physical Chemistry C, 2011; : 111103103634002 DOI: 10.1021/jp2083659

Twisting molecules by brute force: A top-down approach

Molecules that are twisted are ubiquitous in nature, and have important consequences in biology, chemistry, physics and medicine. Some molecules have unique and technologically useful optical properties; the medicinal properties of drugs depend on the direction of the twist; and within us -- think of the double helix -- twisted DNA can interact with different proteins.

This twisting is called chirality and researchers at Case Western Reserve University have found they can use a macroscopic blunt force to impose and induce a twist in an otherwise non-chiral molecule.

Their new "top-down" approach is described in the Dec. 2 issue of Physical Review Letters.

"The key is that we used a macroscopic force to create chirality down to the molecular level," said Charles Rosenblatt, professor of physics at Case Western Reserve and the senior author on the paper. Rosenblatt started the research with no application in mind. He simply wanted to see if it could be done -- essentially scientific acrobatics.

But, he points out, since antiquity chirality has played a role in health, energy, technology and more -- but until now, chirality always has been a bottom-up phenomenon. This new top-down approach, if it can be scaled up, could lead to custom designed chirality -- and therefore desired properties -- in all kinds of things.

Rosenblatt worked with post-doctoral researcher Rajratan Basu, graduate student Joel S. Pendery, and professor Rolfe G. Petschek, of the physics department at Case Western Reserve, and Chemistry Professor Robert P. Lemieux of Queen's University, Kingston, Ontario.

Chirality isn't as simple as a twist in a material. More precisely, a chiral object can't be superimposed on its mirror image. In a "thought experiment," if one's hand can pass through a mirror (like Alice Through the Looking Glass), the hand cannot be rotated so that it matches its mirror image. Therefore one's hand is chiral.

Depending on the twist, scientists define chiral objects as left-handed and right-handed. Objects that can superimpose themselves on their mirror image, such as a wine goblet, are not chiral.

In optics, chiral molecules rotate the polarization of light -- the direction depends on whether the molecules are left-handed or right-handed. Liquid crystal computer and television screen manufacturers take advantage of this property to enable you to clearly see images from an angle.

In the drug industry, chirality is crucial. Two drugs with the identical chemical formula have different uses. Dextromethorphan, which is right-handed, is a cough syrup and levomethorphan, which is lefthanded, is a narcotic painkiller.

The reason for the different effects? The drugs interact differently with biomolecules inside us, depending on the biomolecules' chirality.

After meeting with Lemieux at a conference, the researchers invented a method to create chirality in a liquid crystal at the molecular level.

They treated two glass slides so that cigar-shaped liquid crystal molecules would align along a particular direction. They then created a thin cell with the slides, but rotated the two alignment directions by approximately a 20 degree angle.

The 20-degree difference caused the molecules' orientation to undergo a right-handed helical rotation, like a standard screw, from one side to the other. This is the imposed chiral twist.

The twist, however, is like a tightened spring and costs energy to maintain. To reduce this cost, some of the naturally left-handed molecules in the crystal became right-handed. That's because, inherently, right-handed molecules give rise to a macroscopic right-handed twist, Rosenblatt explained. This shift of molecules from left-handed to right-handed is the induced chirality.

Although the law of entropy suggests there would be nearly identical numbers of left-handed and right-handed molecules, in order to keep total energy cost at a minimum, the right-handed molecules outnumbered the left, he said.

To test for chirality, the researchers applied an electrical field perpendicular to the molecules. If there were no chirality, there would be nothing to see. If there were chirality, the helical twist would rotate in proportion to the amount of right-handed excess.

They observed a modest rotation, which became larger when they increased the twist.

"The effect was occurring everywhere in the cell, but was strongest at the surface," Rosenblatt said.

Scientists have built chirality into optical materials, electrooptic devices, and more by starting at the molecular level. But the researchers are not aware of other techniques that use a macroscopic force to bring chiralty down to molecules.

The researchers are continuing to investigate ways this can be done.

Story Source:

The above story is reprinted from materials provided by Case Western Reserve University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Rajratan Basu, Joel Pendery, Rolfe Petschek, Robert Lemieux, Charles Rosenblatt. Macroscopic Torsional Strain and Induced Molecular Conformational Deracemization. Physical Review Letters, 2011; 107 (23) DOI: 10.1103/PhysRevLett.107.237804

Friday, December 30, 2011

New technique makes it easier to etch semiconductors

 Creating semiconductor structures for high-end optoelectronic devices just got easier, thanks to University of Illinois researchers.

The team developed a method to chemically etch patterned arrays in the semiconductor gallium arsenide, used in solar cells, lasers, light emitting diodes (LEDs), field effect transistors (FETs), capacitors and sensors. Led by electrical and computer engineering professor Xiuling Li, the researchers describe their technique in the journal Nano Letters.

A semiconductor's physical properties can vary depending on its structure, so semiconductor wafers are etched into structures that tune their electrical and optical properties and connectivity before they are assembled into chips.

Semiconductors are commonly etched with two techniques: "Wet" etching uses a chemical solution to erode the semiconductor in all directions, while "dry" etching uses a directed beam of ions to bombard the surface, carving out a directed pattern. Such patterns are required for high-aspect-ratio nanostructures, or tiny shapes that have a large ratio of height to width. High-aspect-ratio structures are essential to many high-end optoelectronic device applications.

While silicon is the most ubiquitous material in semiconductor devices, materials in the III-V (pronounced three-five) group are more efficient in optoelectronic applications, such as solar cells or lasers.

Unfortunately, these materials can be difficult to dry etch, as the high-energy ion blasts damage the semiconductor's surface. III-V semiconductors are especially susceptible to damage.

To address this problem, Li and her group turned to metal-assisted chemical etching (MacEtch), a wet-etching approach they had previously developed for silicon. Unlike other wet methods, MacEtch works in one direction, from the top down. It is faster and less expensive than many dry etch techniques, according to Li. Her group revisited the MacEtch technique, optimizing the chemical solution and reaction conditions for the III-V semiconductor gallium arsenide (GaAs).

The process has two steps. First, a thin film of metal is patterned on the GaAs surface. Then, the semiconductor with the metal pattern is immersed in the MacEtch chemical solution. The metal catalyzes the reaction so that only the areas touching metal are etched away, and high-aspect-ratio structures are formed as the metal sinks into the wafer. When the etching is done, the metal can be cleaned from the surface without damaging it.

"It is a big deal to be able to etch GaAs this way," Li said. "The realization of high-aspect-ratio III-V nanostructure arrays by wet etching can potentially transform the fabrication of semiconductor lasers where surface grating is currently fabricated by dry etching, which is expensive and causes surface damage."

To create metal film patterns on the GaAs surface, Li's team used a patterning technique pioneered by John Rogers, the Lee J. Flory-Founder Chair and a professor of materials science and engineering at the U. of I. Their research teams joined forces to optimize the method, called soft lithography, for chemical compatibility while protecting the GaAs surface. Soft lithography is applied to the whole semiconductor wafer, as opposed to small segments, creating patterns over large areas -- without expensive optical equipment.

"The combination of soft lithography and MacEtch make the perfect combination to produce large-area, high-aspect-ratio III-V nanostructures in a low-cost fashion," said Li, who is affiliated with the Micro and Nanotechnology Laboratory, the Frederick Seitz Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology at the U. of I.

Next, the researchers hope to further optimize conditions for GaAs etching and establish parameters for MacEtch of other III-V semiconductors. Then, they hope to demonstrate device fabrication, including distributed Bragg reflector lasers and photonic crystals.

"MacEtch is a universal method as long as the right condition for deferential etching with and without metal can be found," Li said.

The Department of Energy and the National Science Foundation supported this work.

Story Source:

The above story is reprinted from materials provided by University of Illinois at Urbana-Champaign.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Matt DeJarld, Jae Cheol Shin, Winston Chern, Debashis Chanda, Karthik Balasundaram, John A. Rogers, Xiuling Li. Formation of High Aspect Ratio GaAs Nanostructures with Metal-Assisted Chemical Etching. Nano Letters, 2011; 11 (12): 5259 DOI: 10.1021/nl202708d

Landmark discovery has magnetic appeal for scientists

The effect causes a dramatic change to how this material conducts electricity at very low temperatures. The discovery gives new insight into the mineral in which magnetism was discovered, and it may enable magnetite and similar materials to be exploited in new ways.

Ancient knowledge

"We have solved a fundamental problem in understanding the original magnetic material, upon which everything we know about magnetism is built," said Professor Paul Attfield of the Centre for Science at Extreme Conditions.

Magnetite's properties have been known for more than 2000 years and gave rise to the original concepts of magnets and magnetism.

The mineral has formed the basis for decades of research into magnetic recording and information storage materials.

The research was led by the University in collaboration with the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, where the experiments were conducted.

Their results were published in Nature.

Unexplained behaviour

In 1939, Dutch scientist Evert Verwey discovered that the electrical conductivity of magnetite decreases abruptly and dramatically at low temperatures.

At about 125 Kelvin, or minus 150 degrees Celsius, the metallic mineral turns into an insulator.

Despite many efforts, until now the reason for this transition has been debated and remained controversial.

X-ray experiment

The team of scientists fired an intense X-ray beam at a tiny crystal of magnetite at very low temperatures.

Their results enabled them to understand a subtle rearrangement of the mineral's chemical structure.

Electrons are trapped within groups of three iron atoms, where they can no longer transport an electrical current.

"This vital insight into how magnetite is constructed and how it behaves will help in the development of future electronic and magnetic technologies," Attfield said.

The research was funded by the Science and Technology Facilities Council, the Engineering and Physical Sciences Research Council, and the Leverhulme Trust.

Story Source:

The above story is reprinted from materials provided by University of Edinburgh.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal References:

Mark S. Senn, Jon P. Wright, J. Paul Attfield. Charge order and three-site distortions in the Verwey structure of magnetite. Nature, 2011; DOI: 10.1038/nature10704J. Paul Attfield. Condensed-matter physics: A fresh twist on shrinking materials. Nature, 2011; 480 (7378): 465 DOI: 10.1038/480465a

Largest ever gas mix caught in ultra-freeze trap

A team of scientists have made it easier to study atomic or subatomic-scale properties of the building blocks of matter (which also include protons, neutrons and electrons) known as fermions by slowing down the movement of a large quantity of gaseous atoms at ultra-low temperature.

This is according to a study recently published in The European Physical Journal D as part of a cold quantum matter special issue, by researchers from the Paris-based École Normale Supérieure and the Non-Linear Institute at Nice Sophia-Antipolis University in France.

Thanks to the laser cooling method for which Claude Cohen-Tannoudji, Steven Chu and William D. Phillips received the Nobel Prize in 1997, Armin Ridinger and his colleagues succeeded in creating the largest Lithium 6 (6Li) and Potassium 40 (40K) gas mixture to date. The method used involved confining gaseous atoms under an ultra-high vacuum using electromagnetic forces, in an ultra-freeze trap of sorts.

This trap enabled them to load twice as many atoms than previous attempts at studying such gas mixtures, reaching a total on the order of a few billion atoms under study at a temperature of only a few hundred microKelvins (corresponding to a temperature near the absolute zero of roughly -273 °C).

Given that the results of this study significantly increased the number of gaseous atoms under study, it will facilitate future simulation of subatomic-scale phenomena in gases. In particular, it will enable future experiments in which the gas mixture is brought to a so-called degenerate state characterised by particles of different species with very strong interactions. Following international efforts to produce the conditions to study subatomic-scale properties of matter under the quantum simulation program, this could ultimately help scientists to understand quantum mechanical phenomena occurring in neutron stars and so-called many-body problems such as high-temperature superconductivity.

Story Source:

The above story is reprinted from materials provided by Springer Science+Business Media.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

A. Ridinger, S. Chaudhuri, T. Salez, U. Eismann, D. R. Fernandes, K. Magalhaes, D. Wilkowski, C. Salomon, F. Chevy. Large atom number dual-species magneto-optical trap for fermionic 6Li and 40K atoms. The European Physical Journal D, 2011; 65 (1-2): 223 DOI: 10.1140/epjd/e2011-20069-4

Amplifier helps diamond spy on atoms

 An 'amplifier' molecule placed on the tip of a diamond could help scientists locate and identify individual atoms, Oxford University and Singapore scientists believe.

The idea builds on ongoing work towards creating a diamond nanocrystal that can be used to detect an atom's incredibly weak magnetic field. Defects within the diamond hold electrons that act rather like a compass, lining up with even the very weak magnetic field emanating from the core of an atom.

Crucially this diamond compass can be 'read' by shining a pulse of laser light into the crystal giving information about the location and type of atom -- for instance telling the difference between a carbon and hydrogen atom and giving their exact location within a structure such as a virus or new material.

'The problem with this approach is that the 'compass' only behaves well if it is buried within the diamond: this makes it very difficult to get it close enough to a structure to detect an individual atom's magnetic field,' said Dr Simon Benjamin of Oxford University's Department of Materials and National University of Singapore. 'It's a bit like trying to grasp one particular marble out of a bucket of marbles whilst wearing an oven glove.

'The new research, which the team recently report in Physical Review Letters, calculates that by attaching another 'compass' -- the amplifier molecule -- to the tip of the diamond this will pass the information about an atom along to the compass inside the diamond that can then be read.

'Our calculations show for the first time how such an amplifier could be used to make a diamond probe sensitive enough to pinpoint and identify individual atomic cores,' said Dr Benjamin. 'If this can be made to work, the additional information we would gain would be rather like moving from black and white photographs of atoms to full colour.

'Dr Erik Gauger of Oxford University's Department of Materials and National University of Singapore, an author of the paper with Dr Benjamin, said: 'The device that we propose may well represent the limit of what is possible in terms of magnetic field sensitivity and resolution; if, as we hope, it allows direct identification of atoms by their core signatures, then it will be a revolutionary tool in chemistry, biology and medicine.'

The team believe that it may only be a couple of years before diamond probes are created that will reveal the world of the atom in unprecedented detail but that the small step of adding an amplifier could make such systems many times more powerful.

Story Source:

The above story is reprinted from materials provided by University of Oxford.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Marcus Schaffry, Erik Gauger, John Morton, Simon Benjamin. Proposed Spin Amplification for Magnetic Sensors Employing Crystal Defects. Physical Review Letters, 2011; 107 (20) DOI: 10.1103/PhysRevLett.107.207210


Thursday, December 29, 2011

Functionalized graphene oxide plays part in next-generation oil-well drilling fluids

Graphene's star is rising as a material that could become essential to efficient, environmentally sound oil production. Rice University researchers are taking advantage of graphene's outstanding strength, light weight and solubility to enhance fluids used to drill oil wells.

The Rice University lab of chemist James Tour and scientists at M-I SWACO, a Texas-based supplier of drilling fluids and subsidiary of oil-services provider Schlumberger, have produced functionalized graphene oxide to alleviate the clogging of oil-producing pores in newly drilled wells.

The patented technique took a step closer to commercialization with the publication of new research this month in the American Chemical Society journal Applied Materials and Interfaces. Graphene is a one-atom-thick sheet of carbon that won its discoverers a Nobel Prize last year.

Rice's relationship with M-I SWACO began more than two years ago when the company funded the lab's follow-up to research that produced the first graphene additives for drilling fluids known as muds. These fluids are pumped downhole as part of the process to keep drill bits clean and remove cuttings. With traditional clay-enhanced muds, differential pressure forms a layer on the wellbore called a filter cake, which both keeps the oil from flowing out and drilling fluids from invading the tiny, oil-producing pores.

When the drill bit is removed and drilling fluid displaced, the formation oil forces remnants of the filter cake out of the pores as the well begins to produce. But sometimes the clay won't budge, and the well's productivity is reduced.

The Tour Group discovered that microscopic, pliable flakes of graphene can form a thinner, lighter filter cake. When they encounter a pore, the flakes fold in upon themselves and look something like starfish sucked into a hole. But when well pressure is relieved, the flakes are pushed back out by the oil.

All that was known two years ago. Since then, Tour and a research team led by Dmitry Kosynkin, a former Rice postdoctoral associate and now a petroleum engineer at Saudi Aramco, have been fine-tuning the materials.

They found a few issues that needed to be dealt with. First, pristine graphene is hard to disperse in water, so it is unsuitable for water-based muds. Graphene oxide (GO) turned out to be much more soluble in fresh water, but tended to coagulate in saltwater, the basis for many muds.

The solution was to "esterify" GO flakes with alcohol. "It's a simple, one-step reaction," said Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. "Graphene oxide functionalized with alcohol works much better because it doesn't precipitate in the presence of salts. There's nothing exotic about it."

In a series of standard American Petroleum Institute tests, the team found the best mix of functionalized GO to be a combination of large flakes and powdered GO for reinforcement. A mud with 2 percent functionalized GO formed a filter cake an average of 22 micrometers wide -- substantially smaller than the 278-micrometer cake formed by traditional muds. GO blocked pores many times smaller than the flakes' original diameter by folding.

Aside from making the filter cake much thinner, which would give a drill bit more room to turn, the Rice mud contained less than half as many suspended solids; this would also make drilling more efficient as well as more environmentally friendly. Tour and Andreas Lüttge, a Rice professor of Earth science and chemistry, reported last year that GO is reduced to graphite, the material found in pencil lead and a natural mineral, by common bacteria.

"The most exciting aspect is the ability to modify the GO nanoparticle with a variety of functionalities," said James Friedheim, corporate director of fluids research and development at M-I SWACO and a co-author of the research. "Therefore we can 'dial in' our application by picking the right organic chemistry that will suit the purpose. The trick is just choosing the right chemistry for the right purpose."

"There's still a lot to be worked out," Tour said. "We're looking at the rheological properties, the changes in viscosity under shear. In other words, we want to know how viscous this becomes as it goes through a drill head, because that also has implications for efficiency."

Muds may help graphene live up to its commercial promise, Tour said. "Everybody thinks of graphene in electronics or in composites, but this would be a use for large amounts of graphene, and it could happen soon," he said.

Friedheim agreed. "With the team we currently have assembled, Jim Tour's group and some development scientists at M-I SWACO, I am confident that we are close to both technical and commercial success."

Other authors of the paper are Rice graduate student Gabriel Ceriotti, former Rice research associates Kurt Wilson and Jay Lomeda, and M-I SWACO researchers Jason Scorsone and Arvind Patel.

Story Source:

The above story is reprinted from materials provided by Rice University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Dmitry V. Kosynkin, Gabriel Ceriotti, Kurt C. Wilson, Jay R. Lomeda, Jason T. Scorsone, Arvind D. Patel, James E. Friedheim, James M. Tour. Graphene Oxide as a High-Performance Fluid-Loss-Control Additive in Water-Based Drilling Fluids. ACS Applied Materials & Interfaces, 2011; : 111213103240001 DOI: 10.1021/am2012799

Researchers measure nanometer scale temperature

 Atomic force microscope cantilever tips with integrated heaters are widely used to characterize polymer films in electronics and optical devices, pharmaceuticals, paints, and coatings. These heated tips are also used in research labs to explore new ideas in nanolithography and data storage, and to study fundamentals of nanometer-scale heat flow. Until now, however, no one has used a heated nano-tip for electronic measurements.

"We have developed a new kind of electro-thermal nanoprobe," according to William King, a College of Engineering Bliss Professor in the Department of Mechanical Science and Engineering at Illinois. "Our electro-thermal nanoprobe can independently control voltage and temperature at a nanometer-scale point contact. It can also measure the temperature-dependent voltage at a nanometer-scale point contact."

"Our goal is to perform electro-thermal measurements at the nanometer scale," according to Patrick Fletcher, first author of the paper, "Thermoelectric voltage at a nanometer-scale heated tip point contact," published in the journal Nanotechnology. "Our electro-thermal nanoprobe can be used to measure the nanometer-scale properties of materials such as semiconductors, thermoelectrics, and ferroelectrics."

The electro-thermal probes are different than thermal nanoprobes typically used in King's group and elsewhere. They have three electrical paths to the cantilever tip. Two of the paths carry heating current, while the third allows the nanometer-scale electrical measurement. The two electrical paths are separated by a diode junction fabricated into the tip. While the cantilever design is complex, the probes can be used in any atomic force microscope.

In addition to Fletcher, co-authors of the paper include Byeonghee Lee, and William King. The research was performed in the Nanoengineering laboratory as well as the Micro and Nanotechnology Laboratory and the Materials Research Laboratory at Illinois.

Story Source:

The above story is reprinted from materials provided by University of Illinois College of Engineering.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Patrick C Fletcher, Byeonghee Lee, William P King. Thermoelectric voltage at a nanometer-scale heated tip point contact. Nanotechnology, 2012; 23 (3): 035401 DOI: 10.1088/0957-4484/23/3/035401

Shearing triggers odd behavior in microscopic particles

 Microscopic spheres form strings in surprising alignments when suspended in a viscous fluid and sheared between two plates -- a finding that will affect the way scientists think about the properties of such wide-ranging substances as shampoo and futuristic computer chips.

A team of scientists at Cornell University and the University of Chicago have imaged this behavior and have explained the forces causing it for the first time. Its findings appear in the Dec. 19-23 early edition of the Proceedings of the National Academy of Sciences.

"The experimental breakthrough revealed that these string structures were perpendicular to the shear instead of parallel to it, contrary to what many in the field were expecting," said Aaron Dinner, associate professor in chemistry at UChicago and a study co-author.

The experiment was led by Itai Cohen, associate professor of physics at Cornell, who custom-built a device that would enable him simultaneously to exert shearing forces on suspended colloids (the spheres) and image the resulting motion at 100 frames per second with a confocal microscope. Imaging speed was critical to the experiment because the string-like structures appear only at certain shear rates.

"This issue of strings has been pretty controversial. I'm not sure that we've solved all the controversies associated with them, but at least we've made a step forward," Cohen said.

Shearing forces affect the dynamic behavior of paint, shampoo and other viscous household products, but an understanding of these and related phenomena at the microscopic level has largely eluded a detailed scientific understanding until the last decade, Dinner noted.

Futuristically speaking, these forces potentially could be harnessed to produce microscopic patterns on computer chips or biosensors via special paints that flow easily when layered in one direction, but becomes hard when layered in another direction.

Cohen's objective was more scientifically immediate: to devise an experiment that would overcome the technical difficulties associated with measuring the mechanical properties of the colloidal strings while also imaging their formation. "The holy grail is to be able to understand how the structure leads to the mechanical properties and then to be able to control the mechanical properties by influencing the structure," Cohen explained.

Cohen, PhD'01, received his doctorate in physics at UChicago, as did lead author Xiang Cheng, PhD'09, a postdoctoral associate at Cornell who assembled the team; and co-author Xinliang Xu, PhD'07, a postdoctoral scholar at UChicago. The study co-authors also included Stuart Rice, the Frank P. Hixon Distinguished Service Professor Emeritus in Chemistry at UChicago and a 1999 recipient of the National Medal of Science.

As members of UChicago's Materials Research Science and Engineering Center, Rice and Dinner are part of a larger effort to determine how materials behave under the influence of various dynamic forces. Some of their physics colleagues analyze forces operating on macroscopic scales, while chemists such as Rice and Dinner attempt to assess how those findings might apply to microscopic phenomena.

Rice and his UChicago co-authors used computer simulations to develop a precise explanation for the string-like colloidal structures that formed in the Cornell experiment. "The previous simulations all left out the consequences of the flow created in the supporting fluid as the particles move, the so-called hydrodynamic forces," Rice said.

"A very large fraction of the work in the field neglects hydrodynamic forces because it's hard. You try and get away with what you can," Rice noted with amusement. "But in this case it turns out that the inclusion of those forces is the crucial element."

The simulations allowed the UChicago team to control various experimental parameters to assess their relative importance. "You can play God," Rice said. "The important finding is the overwhelming role of the lubrication forces and the anti-intuitive result that they create."

The lubrication force comes into play when two colloids come together to behave much like macroscopic ball bearings soaking in a reservoir of goopy fluid.

"Pulling them apart would be working against the fluid and so it would be very hard," Dinner said. "So actually, when you get a collision in these colloidal systems, those lubrication forces hold them together much longer, and that actually allows for some of the unique dynamics that give rise to the structure. That was specifically what the simulations showed."

Xu, the UChicago postdoctoral scholar, adapted a mathematical formula developed by John Brady at the California Institute of Technology to simplify the simulations, which ran for days and weeks at a time. "Every time you rearrange the particles, the interactions are different," Rice said. "If you were to calculate that directly, it would be extremely tedious."

But Xu's adapation of Brady's formula enabled him to generate a table of hydrodynamic interactions that listed each particle configuration. Xu found that he could accurately simplify the simulation by focusing on just two of the experiment's seven layers of colloids.

The simulations and the experiment showed that even after three centuries of study, the field of hydrodynamics continues to yield surprising discoveries. "We are still discovering novel behavior that is fundamentally determined by the hydrodynamics," Rice noted.

Story Source:

The above story is reprinted from materials provided by University of Chicago. The original article was written by Steve Koppes.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Friday, December 23, 2011

The extracellular matrix

The extracellular matrix (ECM) provides the physical and chemical conditions that enable the development of all . It is a complex nano-to-microscale structure made up of protein fibres and serves as a dynamic substrate that supports tissue repair and regeneration.

Man-made structures designed to mimic and replace the native matrix in damaged or diseased tissues are highly sought after to advance our understanding of tissue organisation and to make regenerative medicine a reality.

Self-assembling peptide fibres that have similar properties to those of the native matrices are of particular interest. However, these near-crystalline fail to arrange themselves into interconnected meshes at the , which is critical for bringing cells together and supporting .

To solve this problem, a research team at NPL designed a small protein consisting of two complementary domains (structural units) that promote the formation of highly branched networks of fibres that span microscopic dimensions. The team showed that the created matrix is very efficient in supporting cell attachment, growth and proliferation.

Provided by National Physical Laboratory

Thursday, December 22, 2011

It's elemental: Paper celebrates discovery of iodine

George Luther, Maxwell P. and Mildred H. Harrington Professor at UD, is one of 11 internationally recognized co-authors on a paper commemorating 200 years of iodine research. The paper appeared on Friday, Dec. 2, in Angewandte Chemie, one of the prime chemistry journals in the world.

Most of us think of iodine as a liquid that comes in a little brown bottle to help heal cuts or as something that gets mixed in with to prevent goiter. But the element that appears as number 53 in the periodic table was actually discovered during the Napoleonic Wars when French chemist Bernard Courtois was searching for an alternative to wood ashes as a for the production of saltpeter. Today, iodine has applications ranging from pharmaceuticals to semiconductors.

The element plays a role in a broad range of fields, including materials, medicine and physiology, , geochemistry and . The latter is where Luther's expertise was called upon for the article. His section provides an overview of iodine and its major chemical forms in the marine environment.

"Iodine is incorporated into diatoms and other algae in the ," Luther says. "Upon death, some plankton sink to the sediments, and iodine is enriched in the sediments and their porewaters. There is also some release of gaseous iodine to the atmosphere from algal and plant sources. Weathering of the continents adds some iodine to the ocean via rivers to maintain the balance of about 0.45 micromolar total iodine that is in the ocean."

Apparently, Luther doesn't have to worry about running out of research opportunities any time soon. The authors conclude that in the ocean, the iodide–iodate transformation still offers challenges to biological and chemical oceanographers. At the same time, the biogenic, evolutionary origin of the high iodine levels encountered in marine sediments requires more research efforts.

However, the man who discovered iodine two centuries ago did not fare so well. Despite the scientific significance of his discovery and the growing commercial interest in iodine, Courtois did not capitalize on his discovery. He died in poverty on Sept. 27, 1838, at the age of 62. production from seaweed quickly became a major economic activity in the coastal regions of Europe, and others went on to benefit from his finding.

More information: Commemorating Two Centuries of Iodine Research: An Interdisciplinary Overview of Current Research” appeared on Friday, Dec. 2, in Angewandte Chemie., Frithjof C. Küpper, et al.

Provided by University of Delaware (news : web)

Elusive ultrafine indoor air contaminants yield to NIST analysis

Monitoring such tiny was made possible by NIST advances in measurement capabilities. Measurements were carried out in weeks of experiments at a 340-square-meter (1,500-square-feet) test house on the NIST campus in Gaithersburg, Md. The researchers used the data to develop a model for predicting changes in the size and distribution of so-called ultrafine particles (technically, particles smaller than 100 nanometers) discharged by tools, appliances and other sources.

The measurements and model will further efforts to explain the dynamics of ultrafine particles, an area of growing interest among environmental and health researchers. They also will advance work to develop accurate and reliable methods for determining how changes in heating and cooling systems, often done to reduce energy consumption, will affect indoor environments.

"If we can understand and predict the dynamics of these extremely small indoor air contaminants, designers and equipment manufacturers can avoid potential negative impacts on the environment inside homes and buildings and may even devise ways to improve conditions and save energy at the same time," explains NIST engineer Andrew Persily.

Utrafine particles are produced naturally—by forest fires and volcanoes, for example—as well as by internal combustion engines, power plants and many other human-made sources. Although ever present in outdoor and indoor environments, ultrafine particles have eluded detection, and are not subject to federal or state air quality standards. However, particles with nanoscale dimensions have been associated with a variety of human health problems—especially heart, lung and blood disorders.

Because we spend most of our time indoors, however, the bulk of human exposure to ultrafine particles occurs in homes and buildings. Typically, releases of the tiny particles occur in periodic bursts—during cooking or hair drying, perhaps—but airborne concentrations during these episodes can greatly exceed outdoor levels, according to the NIST team.

The researchers measured the airborne concentrations of ultrafine particles at regular intervals after they were emitted by gas and electric stoves, candles, hair dryers and power tools. With their recently enhanced capabilities, the team could measure particles about four times smaller than in previous studies of indoor air contaminants.

Tests were conducted with the house central fan either on or off, which made a major difference in the behavior of ultrafine particles. With the fan off, these very small particles collide with each other and coagulate—or combine—during the first 2.5 minutes following a blast of ultrafine particles from an appliance or tool. In the process, they form successively larger particles, decreasing airborne concentrations of particles. As particles grow larger, they tend to settle on surfaces more quickly.

With the central fan recirculating air, ultrafine particles tend, in roughly equal proportions, to coagulate or settle on surfaces. Under both fan conditions, ventilation accounted for the removal of no more than about 5 percent of ultrafine particles.

Tests also revealed that for many indoor sources, such as stovetop cooking with gas, more than 90 percent of the particles emitted were smaller than 10 nanometers. In turn, emissions of smaller particles result in higher airborne concentrations that dissipate primarily through coagulation.

More information: *D. Rim, L. Wallace, A. Persily and J. Choi, Evolution of ultrafine particle size distributions following indoor episodic releases: Relative importance of coagulation, deposition and ventilation. Aerosol Science and Technology. Posted online Nov. 15, 2011. DOI 10.1080/02786826.2011.639317. Available online at

Provided by National Institute of Standards and Technology (news : web)

Scientists elevate little-studied cellular mechanism to potential drug target

The study was published December 11, 2011, in an advance online edition of the journal Nature .

"With this paper, we've elevated protein sulfenylation from a marker of oxidative stress to a bona fide reversible post translational modification that plays a key regulatory role during cell signaling," said Kate Carroll, a Scripps Research associate professor who led the study. "The sulfenyl modification is the new kid on the block."

During periods of cellular stress, caused by factors such as exposure to or chronic disease states like cancer, the level of highly reactive oxygen-containing molecules can increase, resulting in inappropriate modification of proteins and cell damage. In sulfenylation, one oxidant, , functions as a messenger that can activate through oxidation of cysteine residues in signaling proteins, producing sulfenic acid. Cysteine, an amino acid ( building block), is highly oxidant sensitive.

Conventional wisdom has long held that if hydrogen peroxide does exist in the cell at any appreciable level, it represents a disease state, not a regulatory event. The new study shows that sulfenylation is actually a positive , and that it's required for signaling through the pathway, a validation of a long-held belief in some scientific circles that hydrogen peroxide functions as a general signaling molecule, not an oxidative "bad boy" to be eliminated at all costs.

A New Chemical Probe

To explore the process, Carroll and her colleagues developed a highly selective chemical probe -- known as DYn-2 -- with the ability to detect minute differences in sulfenylation rates within the cell.

With the new probe, the team was able to show that a key signaling protein, epidermal growth factor receptor (EGFR), is directly modified by hydrogen peroxide at a critical active site cysteine, stimulating its tyrosine kinase activity.

The technology described in the new paper is unique, Carroll said, because it allows scientists to trap and detect these modifications in situ, without interfering with the redox balance of the cell. "Probing cysteine oxidation in a cell lysate is like looking for a needle in a haystack," she said, "our new approach preserves labile sulfenyl modifications and avoids protein oxidation artifacts that arise during cell homogenization."

As with phosphorylation, future studies on sulfenylation will delve into the exciting discovery of new enzymes, new signaling processes, and new mechanisms of regulation.

Another broad impact of these findings, Carroll said, is to open up an entirely new mechanism to exploit for the development of therapeutics, particularly in cancer. "It should influence the design of inhibitors that target oxidant-sensitive cysteine residues in the future," she said.

More information: "Peroxide-dependent Sulfenylation of the EGFR Catalytic Site Enhances Kinase Activity," Candice E. Paulsen et al., Nature Chemical Biology (2011).

Provided by The Scripps Research Institute (news : web)

Closing in on an ulcer- and cancer-causing bacterium

Writing in a "Paper of the Week," the scientists say the information they have obtained about the pathogen's clever employment of acid neutralizers may inform those who are designing new drugs to blunt H. pylori's effects across the globe.

H. pylori are the only bacteria known to thrive in the human stomach. It remains unclear how the pathogens are transmitted, although researchers suspect they could be spread through or water. The damage the bacteria do to the mucous coating of the gut allows to eat away at the sensitive organ lining, causing ulcers.

Although more than half of the world's population has the infection, for reasons still not quite understood most never develop ulcers. In fact, existing antibiotics can cure 80 to 90 percent of ulcers caused by the pathogen. However, H. pylori over the years have become increasingly resistant to antibiotics. Some experts have attributed that resistance to the fact that doctors are quick to prescribe antibiotics to kill it even when patients show no symptoms.

"There is a pressing need to develop new drugs and alternative strategies to fight against H. pylori infection before the prevalence of gets out of hand," says Ivan Fong, the lead author on the JBC paper and a graduate student at the Chinese University of Hong Kong whose research is focused on the biochemical makeup of protein complexes that assist in H. pylori's survival.

Ivan Fong, a graduate student at the Chinese University of Hong Kong, studies the biochemical makeup of protein complexes that assist in H. pylori's survival. Kam-Bo Wong is a professor at the institution and oversaw Fong's recent project. Credit: Chinese University of Hong Kong

It's the pathogen's ability to persist within the acid bath in the human stomach that has made it such a successful, albeit harmful, vector, says Fong. "The key is its use of an enzyme called urease to neutralize gastric acid," he explains.

H. pylori produce urease to spur the breakdown of urea, a naturally occurring chemical in the body, so that urea can release ammonia and make the gut an environment in which the pathogens can thrive. But, unlike most other enzymes, urease doesn't start doing its job immediately after being produced by the bacterium; instead, two have to be delivered to it, and then the enzyme can mature, so to speak, and thus allow H. pylori to begin their damaging work.

"As the survival of H. pylori depends on active urease, this is a life-or-death issue for the pathogen to ensure nickel ions are delivered to the urease," says Kam-Bo Wong, a professor who oversaw the project at the institution.

It's not entirely clear how H. pylori make sure that urease can mature and then neutralize the surrounding acid. But Wong's team focused on four proteins that they suspect are helpers: UreE, UreF, UreG and UreH.

Using X-ray crystallography, "which essentially performs the function of a molecular microscope to visualize proteins with atomic resolution," Fong explains, the team took snapshots of UreF and UreH. What they saw was that UreH morphs the shape of UreF to enable UreF to recruit a third player, UreG, to form the UreF-UreH-UreG complex. In other words, the three proteins hook up to collectively deliver nickel ions to the right place on urease. Once the nickel ions are in place, they serve like a flint to ignite the breakdown of urea into ammonia, which then neutralizes the stomach acids.

"So, now we have a better understanding of how the machine can assemble itself, as if a skillful mechanic were there for the job, and deliver the nickel ions," says Fong.

Importantly, the team also discovered that disrupting the formation of the crafty UreF-UreH-UreG complex does, in fact, inhibit the synthesis of active urease. They hope that the information they've obtained about the molecular structures of UreF and UreH will help in the design of drugs that will essentially muck up the works of the molecular machine.

"As active urease is the key to survival of H. pylori, designing drugs that target this complex may well be a viable strategy to eradicate the pathogen," says Wong.

More information: The abstract for the paper, titled "Assembly of the preactivation complex for urease maturation in Helicobacter pylori: Crystal Structure of the UreF/UreH complex," is available at … 830.abstract

Provided by American Society for Biochemistry and Molecular Biology

Wednesday, December 21, 2011

On the road to creating an affordable master instrument

What talented young violinist has not dreamt of playing on a Stradivarius, that non plus ultra of the violin-maker's art? Unfortunately, of course, these instruments are rare, and well beyond the budget of most musicians. "Imitations" of similar tonal quality are therefore very sought-after, and the Empa researcher Francis Schwarze has managed to achieve this feat with the help of a Swiss violin maker. By treating the with Physisporinus vitreus, a white-rot fungus which attacks and destroys certain structures in spruce, he was able to create a material with extraordinarily good tonal qualities. So good in fact that the new "fungus violin" put its own role model in the shade. At a specialist conference in 2009 two of the new instruments were compared in a blind test to a Stradivarius and both the jury of experts and the conference audience judged their sound to better than that of the violin made by the Italian Master of Cremona.

Schwarze now intends to develop a standardized biotechnological process so that sufficient fungally-treated wood can be produced to make instruments in respectable numbers. This is the only way that would allow an industrial partner interested in the technology to manufacture the violins on a quasi-"mass-produced" basis. In order to create the necessary bridge between science and industry it is vital to develop technologies which offer significant commercial advantages. In this case this means standardizing the wood treatment parameters to such an extent that a specific tonal quality can be guaranteed. This is not an easy task to accomplish with a material such as wood which is subject to natural fluctuations in quality.

Generous support from the Walter Fischli Foundation

In the Walter Fischli Foundation the Empa scientist has found financial support which will enable the "fungal violin" project continue. Explaining why he decided to provide funding for Schwarze's work, Walter Fischli, who is co-founder of the biomedical company Actelion and an enthusiastic hobby violinist, says "In my opinion it would have been unforgivable to allow such an interesting project – one that so ideally links science and the art of violin making – to wither for lack of funding." Fischli hopes that the Empa specialists will finally uncover the secret of why violin makers such as and Guarnerius managed to make instruments of such fantastic quality around 1700. Their craftsmanship is, of course, one decisive and undisputed factor but it seems that the wood they used also played a vital role. "Using modern science to explain the technical details of the material properties is something I find enormously interesting," says Fischli.

Developing a standard wood treatment process in an interdisciplinary way

The project, which commenced at the beginning of September and will run for three years, is led by Iris Brémaud, a specialist in the field of tonal woods. The French scientist is responsible for ensuring that the treatment with the white rot fungi P. vitreus and Xylaria longipes optimally "ennobles" samples of spruce and maple woods. In addition she is already in contact with Michael Baumgartner, the renowned instrument maker from Basel. Under his guidance the "fungus violins" using the treated wood will be created.

Before Empa can take delivery of the first , however, numerous tests on both treated and untreated wood samples must be carried out. Experts are currently systematically measuring the density of the wood, the speed of sound in it and its acoustic attenuation. Specialists in the field of ultrasonics are developing methods to determine where the fungus was active and where not. Other scientists expert in optical measurement techniques are using their specialist methods to create images showing how sound is radiated by the different woods and also complete instruments. The final steps should involve collaborations with specialists of psychoacoustics to understand how musicians and listeners perceive these "mushroom violins."

Provided by EMPA

Fluorescent probes increase understanding of bacterium's electron transfer

These results mark another step toward understanding the that enable a bacterial protein-in this case, the cytochrome MtrC-to transfer electrons to minerals in soil, sediment, and subsurface materials. This new information contributes to understanding protein stability and between cells and minerals, which is important for applications in synthetic biology such as biofuel production. The results were published in the journal Biochemistry.

Electron transfer by MtrC, an cytochrome on S. oneidensis, can stabilize contaminants, mitigating their impact on the population and environment. However, scientists believe that gaining insight into the electron transfer mechanisms could also play a role in directing the bacterium toward biofuel production.

"Our goal is to define the role of these cytochromes in the metabolic switching between different terminal electron acceptors," said Dr. Thomas Squier, a PNNL biochemist and senior author of the publication. "The long-term goal is to understand the stability and targeting mechanisms important to synthetic biology applications involving, for example, chemical sensing between living cells and electronic detectors as well as the development of biofuel cells."

These findings don't just relate to Shewanella, though it was in this microbe where MtrC was first seen. They also apply to many other bacteria, such as E. coli, notes Squier.

"This research ties very well into looking at and understanding as a whole," he added.

Measuring MtrC's environmental stability requires the ability to differentiate an immature protein from a mature protein after it is secreted and assembled on Shewanella's outer membrane. To do this, the scientists constructed complementary fluorescent probes to label MtrC. The highly charged carboxy-FlAsH (CrAsH) probe selectively labels mature MtrC only on the outer cell membrane, while the cell-permeable Fluorescein Arsenical Helix (FlAsH) probe labels all MtrC, including immature proteins within the cell.

More information: Xiong Y, et al. 2011. "Targeted Protein Degradation of Outer Membrane Decaheme Cytochrome MtrC Metal Reductase in Shewanella oneidensis MR-1 Measured Using Biarsenical Probe CrAsH-EDT2." Biochemistry 50(45):9738-9751 DOI: 10.1021/bi200602f

Provided by Pacific Northwest National Laboratory (news : web)

Shedding light on why it is so 'tough' to make healthier hot dogs

Anna M. Herrero and colleagues explain that some brands of sausage (frankfurters) have been reformulated with olive oil-in-water emulsion as a source of more healthful fat. With consumers gobbling up tens of billions of hot dogs annually, and the typical frankfurter packing 80 percent of its calories from fat, hot dogs have become a prime candidate for reformulation. Some hot dogs reformulated with vegetable oil develop an unpleasant chewy texture. Herrero's team set out to uncover the chemistry behind that change with an eye to guiding food companies to optimize low-fat sausage manufacture.

Using a laboratory instrument called an (IR spectrometer) they verified that sausages made with heart-healthy olive oil-in-water emulsion stabilized with casein were slightly tougher. However, when frankfurters were elaborated with an emulsion stabilized with a combination of casein and microbial transglutaminase (to help the oil blend in better) the sausage became much tougher. The IR spectrometer revealed that the proteins and fats in low-fat cooked derivates formulated with this stabilizer system as animal fat replacer showed weak lipid-protein interactions, which implies more physical entrapment of the emulsion within the meat matrix. This fact could explain why those sausages are tougher than the others.

More information: Infrared Study of Structural Characteristics of Frankfurters Formulated with Olive Oil-in-Water Emulsions Stabilized with Casein As Pork Backfat Replacer, J. Agric. Food Chem., Article ASAP. DOI: 10.1021/jf203941b

This article reports an infrared spectroscopic (FT-IR) study on lipids and protein structural characteristics in frankfurters as affected by an emulsified olive oil stabilizing system used as a pork backfat replacer. The oil-in-water emulsions were stabilized with sodium caseinate, without (F/SC) and with microbial transglutaminase (F/SC+MTG). Proximate composition and textural characteristics were also evaluated. Frankfurters F/SC+MTG showed the highest (P < 0.05) hardness and lowest (P < 0.05) adhesiveness. These products also showed the lowest (P < 0.05) half-bandwidth of the 2922 cm–1 band, which could be related to the fact that the lipid chain was more orderly than that in the frankfurters formulated with animal fat and F/SC. The spectral results revealed modifications in the amide I band profile when the olive oil-in-water emulsion replaced animal fat. This fact is indicative of a greater content of aggregated intermolecular ß-sheets. Structural characteristics in both proteins and lipids could be associated with the specific textural properties of frankfurters.

Provided by American Chemical Society (news : web)

Researchers discover a mechanism of drug resistance

However, mycophenolic acid also poisons most microbes, which has had scientists wondering how molds that produce mycophenolic acid can grow in its presence. This general problem is only understood in a few cases. Understanding how some microbes resist high concentrations of is important to designing new drugs and deciding how and when to prescribe existing drugs.

Xin Sun, a Ph.D. student in Biology Professor Liz Hedstrom’s laboratory, together with Bjarne Gram Hansen of the Technical University of Denmark, got down to the molecular level to unearth that answer for mycophenolic acid production. Their research was recently reported in The Journal of Biological Chemistry and the Biochemical Journal.

Every drug has a target — in this case a protein to which the drug binds, blocking its normal function.  In the case of mycophenolic acid, the target is the protein IMPDH, an enzyme found in every organism.  The faster an organism is growing, the more IMPDH it needs.  When an infection occurs, immune cells need to grow, so they produce more IMPDH.

Unlike most microbes, Penicillium have two copies of IMPDH.

“What Xin Sun did was to show that this second IMPDH is in fact resistant to mycophenolic acid,” says Hedstrom.  “What was puzzling is that you’d expect a change in the drug binding site, but here the drug binding site is identical in both sensitive and resistant targets. Instead, the underlying function of the second IMPDH has changed in clever and sophisticated ways so the drug is no longer effective.”

These findings also provide new insights into another scientific mystery, how antibiotic production evolved in the first place.  The team hypothesizes that Penicillium gained the second IMPDH through mutation (duplication), which allowed them to make small amounts of mycophenolic acid.  Over time, the second IMPDH evolved to become more resistant, allowing the mold to make more mycophenolic

Provided by Brandeis University (news : web)

Pharmacists crucial in plan for terrorist chemical weapons

Chemical weapons act on their victims through a number of mechanisms. They include nerve agents, chemicals that cause blistering (vesicants), choking agents, incapacitating agents, riot control agents, blood agents, and toxic industrial chemicals. With their knowledge of chemistry, , , , and therapeutics, pharmacists are a valuable asset to and planning for the unthinkable – a terrorist attack with chemical weapons.

In his article, clinical and forensic pharmacologist Peter D. Anderson details the clinical effects chemical weapons, and their treatment. work by blocking the actions of acetyl cholinesterase (the chemistry involved is similar to how many pesticides kill). These toxins include sarin, tabun, VX, cyclosarin, and soman. Vesicants like sulfur mustard and lewisite produce blisters and damage the upper airways. Choking agents, which cause fluid to build up in the lungs (pulmonary edema), include phosgene and chlorine gas.

Incapacitating agents are temporary and "non-lethal," and include fentanyl and adamsite. Mace and pepper spray are familiar riot control methods. Blood agents include cyanide, which works by blocking oxidative phosphorylation in the body. Toxic such as formaldehyde, hydrofluoric acid, and ammonia also merit consideration as terrorist weapons.

"Potential chemical weapons are in no way limited to the traditional agents that we think of as chemical weapons," Anderson explains.

The good news is that there are potential antidotes to these chemical agents, which can save lives if they are used quickly and correctly. Pharmacists need to work in their hospitals to prepare emergency plans, and with the pharmacy and therapeutic committees to stock for a potential chemical accident or terrorist attack. In the US, for example, The Centers for Disease Control and Prevention (CDC) maintains a Strategic National Stockpile of pharmaceuticals, medical equipment and supplies that can be sent in an emergency to any US state within 12 hours.

The threat from chemical agents may appear to be a symptom of our modern society, but the idea has been around since antiquity. Solon of Athens is said to have used hellebore roots (a purgative) to contaminate the water supply in the Pleistrus River during the Siege of Cirrha as long ago as 590 BC. Modern chemical warfare during World War I included the release by German soldiers of 150 tons of chlorine gas near Ypres, Belgium, and phosgene and nitrogen mustard also played a role in the conflict. Choking agents, vesicants, blood agents, and nerve gas joined the range of chemical weapons available by World War II. Even though conflicting nations produced these in large quantities, no major chemical weapon events occurred during World War II.

The Chemical Weapons Convention was finalized in 1993, prohibiting development, production, stockpiling, and use of chemical weapons. The treaty also mandated weapons destruction. 130 countries signed the convention (excluding Iraq and North Korea).

Although the article is about chemical weapons, Anderson emphasizes that pharmacists can also be a resource for biological, radiological and nuclear attacks as well as natural disasters.

More information: Emergency Management of Chemical Weapons Injuries by Peter D. Anderson is published in the Journal of Pharmacy Practice. The article is free to access here: http://jpp.sagepub … ull.pdf+html

Provided by SAGE Publications

Tuesday, December 20, 2011

Making molecular hydrogen more efficiently

Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory have developed an extraordinarily efficient two-step process that electrolyzes, or separates, from before combining them to make (H2), which can be used in any number of applications from fuel cells to industrial processing.

Easier routes to the generation of hydrogen have long been a target of scientists and engineers, principally because the process to create the gas requires a great deal of energy. Approximately 2 percent of all electric power generated in the United States is dedicated to the production of molecular hydrogen, so scientists and engineers are searching for any way to cut that figure. "People understand that once you have hydrogen you can extract a lot of energy from it, but they don't realize just how hard it is to generate that hydrogen in the first place," said Nenad Markovic, an Argonne senior who led the research.

While a great deal of hydrogen is created by reforming at , that process creates carbon-dioxide emissions. "Water electrolyzers are by far the cleanest way of ," Markovic said. "The method we've devised combines the capabilities of two of the best materials known for water-based electrolysis."

Most previous experiments in water-based electrolysis rely on special metals, like platinum, to adsorb and recombine reactive hydrogen intermediates into stable molecular hydrogen. Markovic's research focuses on the previous step, which involves improving the efficiency by which an incoming water molecule would disassociate into its fundamental components. To do this, Markovic and his colleagues added clusters of a metallic complex known as nickel-hydroxide—Ni(OH)2. Attached to a platinum framework, the clusters tore apart the water molecules, allowing for the freed hydrogen to be catalyzed by the platinum.

"One of the most important points of this experiment is that we're combining two materials with very different benefits," said Markovic. "The advantage of using both oxides and metals in conjunction dramatically improves the catalytic efficiency of the whole system."

According to Argonne materials scientist George Crabtree, who helped to initiate the establishment of Argonne's energy conversion program, the researchers' success is attributable to their ability to work on what are known as "single-crystal" systems—defect-free materials that allow scientists to accurately predict how certain materials will behave at the atomic level. "We have not only increased catalytic activity by a factor of 10, but also now understand how each part of the system works. By scaling up from the single crystal to a real-world catalyst, this work illustrates how fundamental understanding leads quickly to innovative new technologies."

This work, supported by the DOE Office of Science, is reported in the December 2 issue of Science.

Provided by Argonne National Laboratory (news : web)

Soy is on top as a high-quality plant protein

Traditional methods for determining quality have shown animal proteins such as milk and eggs to be high in quality. However, those who are interested in a plant-based diet, or diversifying their proteins, have a more difficult time determining which of their choices are high in quality. Testing methods have shown most , such as , are lower in quality than animal-based proteins.

"Accurate methods for determining protein quality are key to helping people plan a healthful diet," said Glenna Hughes, MS, research scientist at Solae. "Due to the increasing interest in including plant-based proteins in the diet, accurate information on protein quality is needed in scientific literature to help educate consumers and on this topic."

The Food and Agriculture Organization (FAO) and the (WHO) recommend using the protein digestibility-corrected amino acid score (PDCAAS) as a simple and scientific procedure for assessing protein quality. The PDCAAS methodology focuses on three different parameters: the amount of each essential amino acid the protein contains, how easily the protein can be digested, and by taking both of those parameters into account, whether the protein meets the FAO/WHO's amino acid requirements set for children aged two to five years, as they have higher needs to support growth and development than adults.

According to this study, has a PDCAAS of 1.00, meaning it is a high-quality protein that meets the needs of both children and adults. Eggs, dairy and meat proteins also have a PDCAAS score of 1.0.

However, soy protein is the only widely available high-quality plant-based protein that achieves this score.

"It's important for people to understand that a plant-based diet is healthy, but that not all proteins are created equal," said Connie Diekman, RD, LD, FADA. "If you are planning a vegetarian diet or want to incorporate plant-based proteins in your diet, understanding protein quality using the PDCAAS scale can allow you to select proteins that score higher, such as soy, to ensure that you are getting the essential amino acids you need."

More information: For more information on the study, the following is a link to the abstract: … med/22017752

Provided by Solae, LLC

Pressure prepares lobsters for long-distance delivery

The New England lobster's growing popularity has been accompanied by a drive to develop new methods to get the into hungry mouths worldwide, significantly extending its range from a once purely regional dish.

" has always been a celebration food," said John Hathaway, CEO of Shucks Maine Lobster, based in Richmond, Maine. "Outside New England it's eaten in restaurants particularly for holidays. It's huge in the European Union for Christmas. And Asia is becoming a potentially a huge market for Maine lobsters."

A machine developed by Hathaway increases the promise of selling the shellfish to markets by overcoming the array of problems associated with traditional long-distance delivery methods for New England lobsters. Transporting live lobsters involves a risk that several will die en route. The weight of their shells adds extra freight, and the infrastructure to keep them alive in restaurants before diners order them adds to their overall expense -- which is passed on to customers.

Cooking lobster meat before transporting it creates a different issue.

"The danger is overcooking a casserole or, say, lobster Newburg if the lobster's already been cooked," said Marianne LaCroix, director of marketing for the Maine Lobster Promotion Council.

Hathaway said that pre-cooked lobster "might be good enough for lobster rolls, but if you cook it again, the meat becomes very tough."

The Shucks machine uses pressurized water to remove the meat from the shellfish without cooking it. In addition to enabling the safe and relatively inexpensive transport of raw lobster meat to distant destinations around the world, the system gives chefs an easy way to prepare "lazy man's" lobster.

Unlike the whole boiled lobster beloved by New Englanders, lazy man's lobster dispenses with the shells, the bibs, and the nutcrackers and picks necessary to extract the meat from the shells. That process, known as shucking, can create a messy and embarrassing experience for customers unfamiliar with the minutiae of meat removal.

A ready supply of raw meat removed from the shell precludes the need for kitchen assistants to shuck lobsters for those meals.

The raw material for Hathaway's machine, which he calls the "Big Mother Shucker," consists of lobsters gathered from traps in the cold Atlantic Ocean off the Maine coast.

Workers load about 200 pounds of live lobsters at a time into the machine. At the turn of a switch, fresh water under pressure of 40,000 pounds per square inch floods the device.

"Within 6 seconds the water pressure will kill the animals," Hathaway said.

The high-pressure water breaks chemical bonds within the lobsters' biological cells. That causes the lobsters to die quickly but has no effect on the taste or quality of their meat. The same process also detaches the lobsters' meat from their shells' interiors. By the end of the 6-minute pressure cycle, separation is complete.

Because each part of each lobster experiences the same water pressure, the process does not deform the raw meat. When the workers crack the shell by hand, the parts of a naked lobster emerge.

The human shuckers snap off the tails to remove the tender tail meat, crack the shells with a hammer to take out the claw meat, and remove the thin legs for shucking by a machine.

Once removed, the meat is cooled on ice, packaged, and vacuum sealed. Another treatment with the water, this time at a pressure of 87,000 pounds per square inch, serves to remove any pathogens and bacteria introduced during processing. The company then ships the packages to wholesalers and distributors in North America and beyond.

"We ship the meat frozen or fresh," Hathaway said. "The fresh product has a 30-day shelf life and we offer a shelf life of 18 months to two years for the frozen product."

A more traditional method of preparing lobster meat for transportation -- blanching -- remains popular. "You boil or steam the lobster to cook it for about 2 minutes rather than 12 or 13," LaCroix explained. "This kills the lobster and allows you to extract the meat [without cooking it completely]."

Hard-shell lobsters are often shipped live, in cardboard or plastic boxes kept damp with, for example, wet newspaper. Sometimes during particularly long journeys, LaCroix said, "There are stopping points halfway where the lobsters can be put into water to recover." But not surprisingly, she added, "Mortality is higher on the way to Asia than to New York."

Hathaway learned about the pressurized water technology in 2005, when he ran a traditional lobster shack in Kennebunkport, Maine.

"I knew that it meant an opportunity to get into the Maine lobster business," Hathaway recalled. "I bought the machine, found a place to put it, but had no idea what to do with it."

That indecision didn't last long. Winning a prize for his raw lobster meat at the European Food Exposition in Brussels, Belgium in 2007 convinced Hathaway of the value of his technology.

"And each year since then,” Hathaway said, "we have grown considerably."

Source: Inside Science News Service (news : web)