10 bizarre gadgets from CES 2013

UPDATED Formation helicopters, mind-controlled cat ears and much more

By Mary Branscombe

1. Swiveling cat ears

With the power of your mind! Neurosky's brainwave scanning band really works, but are cat ears showing your feelings really the best use?

2. Parrot AR Drone

Parrot's gyroscopic AR Drone quadcopters flying in formation; the real Top Guns fly some 100 miles west of Vegas at China Lake

3. HAPIfork

Slow down and chew your food properly, or the HAPIfork will start buzzing; it doesn't check if your elbows are on the table though.

4. Dhama Pursuit business shirt

Stay cool, or warm, or just right. Dhama's Pursuit business shirt has built-in heating and cooling from 73 to 122 degrees – but no Jackie Chan moves.

5. TrackingPoint guns

Bringing a whole new meaning to point and click, TrackingPoint's Linux-powered guns have head-up displays for choosing your target.

6. Lifeproof Kitchen iPad case

It's not a chopping board, but if you use your iPad for recipes this hermetically sealed Lifeproof case will keep it clean in the kitchen.

7. Acase Black Diamond IIIs

There's no shortage of Bluetooth speakers at CES but the Black Diamond IIIs from Acase are the only ones you're likely to mistake for disco lights.

8. Apple Juice cleaner

This screen cleaner really does smell of fresh apples; especially if you press too hard and spray it all over your shirt…

9. Tylt Energi

Tylt's Energi backpack with a hefty battery can charge your iPad but it might also turn you bright green

10. Pinlo stands

These adorable stands from Pinlo customise your iPhone power supply and cuddle your phone while it charges

11. Aaaaah

What everyone who goes to CES really wants: the time to lie back and rest weary feet in a massage chair!

'Taxels' Convert Mechanical Motion to Electronic Signals

Apr. 25, 2013 — Using bundles of vertical zinc oxide nanowires, researchers have fabricated arrays of piezotronic transistors capable of converting mechanical motion directly into electronic controlling signals. The arrays could help give robots a more adaptive sense of touch, provide better security in handwritten signatures and offer new ways for humans to interact with electronic devices.

Georgia Tech researcher Wenzhuo Wu holds an array of piezotronic transistors capable of converting mechanical motion directly into electronic controlling signals. The arrays are fabricated on flexible substrates. (Credit: Image courtesy of Georgia Institute of Technology, Research Communications)

The arrays include more than 8,000 functioning piezotronic transistors, each of which can independently produce an electronic controlling signal when placed under mechanical strain. These touch-sensitive transistors -- dubbed "taxels" -- could provide significant improvements in resolution, sensitivity and active/adaptive operations compared to existing techniques for tactile sensing. Their sensitivity is comparable to that of a human fingertip.

The vertically-aligned taxels operate with two-terminal transistors. Instead of a third gate terminal used by conventional transistors to control the flow of current passing through them, taxels control the current with a technique called "strain-gating." Strain-gating based on the piezotronic effect uses the electrical charges generated at the Schottky contact interface by the piezoelectric effect when the nanowires are placed under strain by the application of mechanical force.

The research will be reported on April 25 in the journal Science online, at the Science Express website, and will be published in a later version of the print journal Science. The research has been sponsored by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF), the U.S. Air Force (USAF), the U.S. Department of Energy (DOE) and the Knowledge Innovation Program of the Chinese Academy of Sciences.

"Any mechanical motion, such as the movement of arms or the fingers of a robot, could be translated to control signals," explained Zhong Lin Wang, a Regents' professor and Hightower Chair in the School of Materials Science and Engineering at the Georgia Institute of Technology. "This could make artificial skin smarter and more like the human skin. It would allow the skin to feel activity on the surface."

Mimicking the sense of touch electronically has been challenging, and is now done by measuring changes in resistance prompted by mechanical touch. The devices developed by the Georgia Tech researchers rely on a different physical phenomenon -- tiny polarization charges formed when piezoelectric materials such as zinc oxide are moved or placed under strain. In the piezotronic transistors, the piezoelectric charges control the flow of current through the wires just as gate voltages do in conventional three-terminal transistors.

The technique only works in materials that have both piezoelectric and semiconducting properties. These properties are seen in nanowires and thin films created from the wurtzite and zinc blend families of materials, which includes zinc oxide, gallium nitride and cadmium sulfide.

In their laboratory, Wang and his co-authors -- postdoctoral fellow Wenzhuo Wu and graduate research assistant Xiaonan Wen -- fabricated arrays of 92 by 92 transistors. The researchers used a chemical growth technique at approximately 85 to 90 degrees Celsius, which allowed them to fabricate arrays of strain-gated vertical piezotronic transistors on substrates that are suitable for microelectronics applications. The transistors are made up of bundles of approximately 1,500 individual nanowires, each nanowire between 500 and 600 nanometers in diameter.

In the array devices, the active strain-gated vertical piezotronic transistors are sandwiched between top and bottom electrodes made of indium tin oxide aligned in orthogonal cross-bar configurations. A thin layer of gold is deposited between the top and bottom surfaces of the zinc oxide nanowires and the top and bottom electrodes, forming Schottky contacts. A thin layer of the polymer Parylene is then coated onto the device as a moisture and corrosion barrier.

The array density is 234 pixels per inch, the resolution is better than 100 microns, and the sensors are capable of detecting pressure changes as low as 10 kilopascals -- resolution comparable to that of the human skin, Wang said. The Georgia Tech researchers fabricated several hundred of the arrays during a research project that lasted nearly three years. The arrays are transparent, which could allow them to be used on touch-pads or other devices for fingerprinting. They are also flexible and foldable, expanding the range of potential uses.

Among the potential applications:

• Multidimensional signature recording, in which not only the graphics of the signature would be included, but also the pressure exerted at each location during the creation of the signature, and the speed at which the signature is created.

• Shape-adaptive sensing in which a change in the shape of the device is measured. This would be useful in applications such as artificial/prosthetic skin, smart biomedical treatments and intelligent robotics in which the arrays would sense what was in contact with them.

• Active tactile sensing in which the physiological operations of mechanoreceptors of biological entities such as hair follicles or the hairs in the cochlea are emulated. Because the arrays would be used in real-world applications, the researchers evaluated their durability. The devices still operated after 24 hours immersed in both saline and distilled water.

Future work will include producing the taxel arrays from single nanowires instead of bundles, and integrating the arrays onto CMOS silicon devices. Using single wires could improve the sensitivity of the arrays by at least three orders of magnitude, Wang said. "This is a fundamentally new technology that allows us to control electronic devices directly using mechanical agitation," Wang added. "This could be used in a broad range of areas, including robotics, MEMS, human-computer interfaces and other areas that involve mechanical deformation."

This research was supported by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF) under grant CMMI-0946418, the U.S. Air Force (USAF) under grant FA2386-10-1-4070, the U.S. Department of Energy (DOE) Office of Basic Energy Sciences under award DE-FG02-07ER46394 and the Knowledge Innovation Program of the Chinese Academy of Sciences under grant KJCX2-YW-M13. The content is solely the responsibility of the authors and does not necessarily represent the official views of DARPA, the NSF, the USAF or the DOE.

Bold Move Forward in Molecular Analyses

Apr. 25, 2013 — A dramatic leap forward in the ability of scientists to study the structural states of macromolecules such as proteins and nanoparticles in solution has been achieved by a pair of researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab). The researchers have developed a new set of metrics for analyzing data acquired via small angle scattering (SAS) experiments with X-rays (SAXS) or neutrons (SANS). Among other advantages, this will reduce the time required to collect data by up to 20 times.

Small angle scattering (SAS) with X-rays (pictured here) or neutrons is the only imaging technique that provides a complete snapshot of the thermodynamic state of macromolecules in a single image. (Credit: Image courtesy of DOE/Lawrence Berkeley National Laboratory)

"SAS is the only technique that provides a complete snapshot of the thermodynamic state of macromolecules in a single image," says Robert Rambo, a scientist with Berkeley Lab's Physical Biosciences Division, who developed the new SAS metrics along with John Tainer of Berkeley Lab's Life Sciences Division and the Scripps Research Institute.

"In the past, SAS analyses have focused on particles that were well-behaved in the sense that they assume discrete structural states," Rambo says. "But in biology, many proteins and protein complexes are not well-behaved, they can be highly flexible, creating diffuse structural states. Our new set of metrics fully extends SAS to all particle types, well-behaved and not well-behaved."

Rambo and Tainer describe their new SAS metrics in a paper titled "Accurate assessment of mass, models and resolution by small-angle scattering." The paper has been published in the journal Nature.

Says co-author Tainer, "The SAS metrics reported in our Nature paper should have game-changing impacts on accurate high-throughput and objective analyses of the flexible molecular machines that control cell biology."

In SAS imaging, beams of X-rays or neutrons sent through a sample produce tiny collisions between the X-rays or neutrons and nano- or subnano-sized particles within the sample. How these collisions scatter are unique for each particle and can be measured to determine the particle's shape and size. The analytic metrics developed by Rambo and Tainer are predicated on the discovery by Rambo of an SAS invariant, meaning its value does not change no matter how or where the measurement was performed. This invariant has been dubbed the "volume-of-correlation" and its value is derived from the scattered intensities of X-rays or neutrons that are specific to the structural states of particles, yet are independent of their concentrations and compositions.

"The volume-of-correlation can be used for following the shape changes of a protein or nanoparticle, or as a quality metric for seeing if the data collection was corrupted," Rambo says. "This SAS invariant applies equally well to compact and flexible particles, and utilizes the entire dataset, which makes it more reliable than traditional SAS analytics, which utilize less than 10-percent of the data."

The volume-of-correlation was shown to also define a ratio that determines the molecular mass of a particle. Accurate determination of molecular mass has been a major difficulty in SAS analysis because previous methods required an accurate particle concentration, the assumption of a compact near-spherical shape, or measurements on an absolute scale.

"Such requirements hinder both accuracy and throughput of mass estimates by SAS," Rambo says. "We've established a SAS-based statistic suitable for determining the molecular mass of proteins, nucleic acids or mixed complexes in solution without concentration or shape assumptions."

The combination of the volume-of-correlation with other metrics developed by Rambo and Tainer can provide error-free recovery of SAS data with a signal-to-noise ratio below background levels. This holds profound implications for high-throughput SAS data collection strategies not only for current synchrotron-based X-ray sources, such as Berkeley Lab's Advanced Light Source, but also for the next-generation light sources based on free-electron lasers that are now being designed.

"With our metrics, it should be possible to collect and analyze SAS data at the theoretical limit," Rambo says. "This means we can reduce data collection times so that a 90- minute exposure time used by commercial instruments could be cut to nine minutes."

Adds Tainer, "The discovery of the first x-ray scattering invariant coincided with the genesis of the Berkeley Lab some 75 years ago. This new discovery of the volume-of-correlation invariant unlocks doors for future analyses of flexible biological samples on the envisioned powerful next-generation light sources.

This research was funded through DOE's Office of Science and the National Institutes of Health.

Supertough, Strong Nanofibers Developed

Apr. 24, 2013 — University of Nebraska-Lincoln materials engineers have developed a structural nanofiber that is both strong and tough, a discovery that could transform everything from airplanes and bridges to body armor and bicycles. Their findings are featured on the cover of this week's April issue of the American Chemical Society's journal, ACS Nano.

This high-resolution scanning electron microscopy image shows ultra-tough and strong continuous nanofibers developed by University of Nebraska-Lincoln engineers that can be easily aligned and bundled for handing and processing into various applications. (Credit: Joel Brehm, Dimitry Papkov, Yuris Dzenis)

"Whatever is made of composites can benefit from our nanofibers," said the team's leader, Yuris Dzenis, McBroom Professor of Mechanical and Materials Engineering and a member of UNL's Nebraska Center for Materials and Nanoscience.

"Our discovery adds a new material class to the very select current family of materials with demonstrated simultaneously high strength and toughness."

In structural materials, conventional wisdom holds that strength comes at the expense of toughness. Strength refers to a material's ability to carry a load. A material's toughness is the amount of energy needed to break it; so the more a material dents, or deforms in some way, the less likely it is to break. A ceramic plate, for example, can carry dinner to the table, but shatters if dropped, because it lacks toughness. A rubber ball, on the other hand, is easily squished out of shape, but doesn't break because it's tough, not strong. Typically, strength and toughness are mutually exclusive.

Dzenis and colleagues developed an exceptionally thin polyacrilonitrile nanofiber, a type of synthetic polymer related to acrylic, using a technique called electrospinning. The process involves applying high voltage to a polymer solution until a small jet of liquid ejects, resulting in a continuous length of nanofiber.

They discovered that by making the nanofiber thinner than had been done before, it became not only stronger, as was expected, but also tougher.

Dzenis suggested that toughness comes from the nanofibers' low crystallinity. In other words, it has many areas that are structurally unorganized. These amorphous regions allow the molecular chains to slip around more, giving them the ability to absorb more energy.

Most advanced fibers have fewer amorphous regions, so they break relatively easily. In an airplane, which uses many composite materials, an abrupt break could cause a catastrophic crash. To compensate, engineers use more material, which makes airplanes, and other products, heavier.

"If structural materials were tougher, one could make products more lightweight and still be very safe," Dzenis said.

Body armor, such as bulletproof vests, also requires a material that's both strong and tough. "To stop the bullet, you need the material to be able to absorb energy before failure, and that's what our nanofibers will do," he said.

Dzenis' co-authors are mechanical and materials engineering colleagues Dimitry Papkov, Yan Zou, Mohammad Nahid Andalib and Alexander Goponenko in UNL's Department of Mechanical and Materials Engineering, and Stephen Z.D. Cheng of the University of Akron, Ohio.

This research was funded by the National Science Foundation, the Air Force Office of Scientific Research and a U.S. Army Research Office Multidisciplinary University Research Initiative grant.

Recipe for Low-Cost, Biomass-Derived Catalyst for Hydrogen Production

Apr. 24, 2013 — In a paper to be published in an upcoming issue of Energy & Environmental Science, researchers at the U.S. Department of Energy's Brookhaven National Laboratory describe details of a low-cost, stable, effective catalyst that could replace costly platinum in the production of hydrogen. The catalyst, made from renewable soybeans and abundant molybdenum metal, produces hydrogen in an environmentally friendly, cost-effective manner, potentially increasing the use of this clean energy source.

Splitting hydrogen from water: This illustration depicts the synthesis of a new hydrogen-production catalyst from soybean proteins and ammonium molybdate. Mixing and heating the ingredients leads to a solid-state reaction and the formation of nanostructured molybdenum carbide and molybdenum nitride crystals. The hybrid material effectively catalyzes the conversion of liquid water to hydrogen gas while remaining stable in an acidic environment. (Credit: Image courtesy of DOE/Brookhaven National Laboratory)

The research has already garnered widespread recognition for Shilpa and Shweta Iyer, twin-sister high school students who contributed to the research as part of an internship under the guidance of Brookhaven chemist Wei-Fu Chen, supported by projects led by James Muckerman, Etsuko Fujita, and Kotaro Sasaki.

"This paper reports the 'hard science' from what started as the Iyer twins' research project and has resulted in the best-performing, non-noble-metal-containing hydrogen evolution catalyst yet known -- even better than bulk platinum metal," Muckerman said.

The project branches off from the Brookhaven group's research into using sunlight to develop alternative fuels. Their ultimate goal is to find ways to use solar energy -- either directly or via electricity generated by solar cells -- to convert the end products of hydrocarbon combustion, water and carbon dioxide, back into a carbon-based fuel. Dubbed "artificial photosynthesis," this process mimics how plants convert those same ingredients to energy in the form of sugars. One key step is splitting water, or water electrolysis.

"By splitting liquid water (H₂O) into hydrogen and oxygen, the hydrogen can be regenerated as a gas (H₂) and used directly as fuel," Sasaki explained. "We sought to fabricate a commercially viable catalyst from earth-abundant materials for application in water electrolysis, and the outcome is indeed superb."

." ..the best-performing, non-noble-metal-containing hydrogen evolution catalyst yet known..."

This form of hydrogen production could help the scientists achieve their ultimate goal.

"A very promising route to making a carbon-containing fuel is to hydrogenate carbon dioxide (or carbon monoxide) using solar-produced hydrogen," said Fujita, who leads the artificial photosynthesis group in the Brookhaven Chemistry Department.

But with platinum as the main ingredient in the most effective water-splitting catalysts, the process is currently too costly to be economically viable.

Comsewogue High School students Shweta and Shilpa Iyer entered the lab as the search for a cost-effective replacement was on.

The Brookhaven team had already identified some promising leads with experiments demonstrating the potential effectiveness of low-cost molybdenum paired with carbon, as well as the use of nitrogen to confer some resistance to the corrosive, acidic environment required in proton exchange membrane water electrolysis cells. But these two approaches had not yet been tried together.

The students set out to identify plentiful and inexpensive sources of carbon and nitrogen, and test ways to combine them with a molybdenum salt.

"The students became excited about using familiar materials from their everyday lives to meet a real-world energy challenge," Chen recounted. The team tested a wide variety of sources of biomass -- leaves, stems, flowers, seeds, and legumes -- with particular interest in those with high protein content because the amino acids that make up proteins are a rich source of nitrogen. High-protein soybeans turned out to be the best.

To make the catalyst the team ground the soybeans into a powder, mixed the powder with ammonium molybdate in water, then dried and heated the samples in the presence of inert argon gas. "A subsequent high temperature treatment (carburization) induced a reaction between molybdenum and the carbon and nitrogen components of the soybeans to produce molybdenum carbides and molybdenum nitrides," Chen explained. "The process is simple, economical, and environmentally friendly."

Electrochemical tests of the separate ingredients showed that molybdenum carbide is effective for converting H₂O to H₂, but not stable in acidic solution, while molybdenum nitride is corrosion-resistant but not efficient for hydrogen production. A nanostructured hybrid of these two materials, however, remained active and stable even after 500 hours of testing in a highly acidic environment.

"We attribute the high activity of the molybdenum-soy catalyst (MoSoy) to the synergistic effect between the molybdenum-carbide phase and the molybdenum-nitride phase in the composite material," Chen said.

Structural and chemical studies of the new catalyst conducted at Brookhaven's National Synchrotron Light Source (NSLS) and the Center for Functional Nanomaterials (CFN) are also reported in the paper, and provide further details underlying the high performance of this new catalyst.

"The presence of nitrogen and carbon atoms in the vicinity of the catalytic molybdenum center facilitates the production of hydrogen from water," Muckerman said.

The scientists also tested the MoSoy catalyst anchored on sheets of graphene -- an approach that has proven effective for enhancing catalyst performance in electrochemical devices such as batteries, supercapacitors, fuel cells, and water electrolyzers. Using a high-resolution transmission microscope in Brookhven's Condensed Matter Physics and Materials Science Department, the scientists were able to observe the anchored MoSoy nanocrystals on 2D graphene sheets.

The graphene-anchored MoSoy catalyst surpassed the performance of pure platinum metal. Though not quite as active as commercially available platinum catalysts, the high performance of graphene-anchored MoSoy was extremely encouraging to the scientific team.

"The direct growth of anchored MoSoy nanocrystals on graphene sheets may enhance the formation of strongly coupled hybrid materials with intimate, seamless electron transfer pathways, thus accelerating the electron transfer rate for the chemical desorption of hydrogen from the catalyst, further reducing the energy required for the reaction to take place," Sasaki said.

The scientists are conducting additional studies to gain a deeper understanding of the nature of the interaction at the catalyst-graphene interface, and exploring ways to further improve its performance.

In the paper, the authors -- including the two high-school students -- conclude: "This study unambiguously provides evidence that a cheap and earth-abundant transition metal such as molybdenum can be turned into an active catalyst by the controlled solid-state reaction with soybeans…The preparation of the MoSoy catalyst is simple and can be easily scaled up. Its long-term durability and ultra-low capital cost satisfy the prerequisites for its application in the construction of large-scale devices. These findings thus open up new prospects for combining inexpensive biomass and transition metals…to produce catalysts for electro-catalytic reactions."

Additional collaborators in this research were Chiu-Hui Wang and Yimei Zhu of Brookhaven Lab.

Nanowires Grown On Graphene Have Surprising Structure

Apr. 23, 2013 — When a team of University of Illinois engineers set out to grow nanowires of a compound semiconductor on top of a sheet of graphene, they did not expect to discover a new paradigm of epitaxy.

Schematic representation of phase segregated InGaAs/InAs nanowires grown on graphene and single phase InGaAs nanowires grown on a different substrate. (Credit: Parsian Mohseni)

The self-assembled wires have a core of one composition and an outer layer of another, a desired trait for many advanced electronics applications. Led by professor Xiuling Li, in collaboration with professors Eric Pop and Joseph Lyding, all professors of electrical and computer engineering, the team published its findings in the journal Nano Letters.

Nanowires, tiny strings of semiconductor material, have great potential for applications in transistors, solar cells, lasers, sensors and more.

"Nanowires are really the major building blocks of future nano-devices," said postdoctoral researcher Parsian Mohseni, first author of the study. "Nanowires are components that can be used, based on what material you grow them out of, for any functional electronics application."

Li's group uses a method called van der Waals epitaxy to grow nanowires from the bottom up on a flat substrate of semiconductor materials, such as silicon. The nanowires are made of a class of materials called III-V (three-five), compound semiconductors that hold particular promise for applications involving light, such as solar cells or lasers.

The group previously reported growing III-V nanowires on silicon. While silicon is the most widely used material in devices, it has a number of shortcomings. Now, the group has grown nanowires of the material indium gallium arsenide (InGaAs) on a sheet of graphene, a 1-atom-thick sheet of carbon with exceptional physical and conductive properties.

Thanks to its thinness, graphene is flexible, while silicon is rigid and brittle. It also conducts like a metal, allowing for direct electrical contact to the nanowires. Furthermore, it is inexpensive, flaked off from a block of graphite or grown from carbon gases.

"One of the reasons we want to grow on graphene is to stay away from thick and expensive substrates," Mohseni said. "About 80 percent of the manufacturing cost of a conventional solar cell comes from the substrate itself. We've done away with that by just using graphene. Not only are there inherent cost benefits, we're also introducing functionality that a typical substrate doesn't have."

The researchers pump gases containing gallium, indium and arsenic into a chamber with a graphene sheet. The nanowires self-assemble, growing by themselves into a dense carpet of vertical wires across the surface of the graphene. Other groups have grown nanowires on graphene with compound semiconductors that only have two elements, but by using three elements, the Illinois group made a unique finding: The InGaAs wires grown on graphene spontaneously segregate into an indium arsenide (InAs) core with an InGaAs shell around the outside of the wire.

"This is unexpected," Li said. "A lot of devices require a core-shell architecture. Normally you grow the core in one growth condition and change conditions to grow the shell on the outside. This is spontaneous, done in one step. The other good thing is that since it's a spontaneous segregation, it produces a perfect interface."

So what causes this spontaneous core-shell structure? By coincidence, the distance between atoms in a crystal of InAs is nearly the same as the distance between whole numbers of carbon atoms in a sheet of graphene. So, when the gases are piped into the chamber and the material begins to crystallize, InAs settles into place on the graphene, a near-perfect fit, while the gallium compound settles on the outside of the wires. This was unexpected, because normally, with van der Waals epitaxy, the respective crystal structures of the material and the substrate are not supposed to matter.

"We didn't expect it, but once we saw it, it made sense," Mohseni said.

In addition, by tuning the ratio of gallium to indium in the semiconductor cocktail, the researchers can tune the optical and conductive properties of the nanowires.

Next, Li's group plans to make solar cells and other optoelectronic devices with their graphene-grown nanowires. Thanks to both the wires' ternary composition and graphene's flexibility and conductivity, Li hopes to integrate the wires in a broad spectrum of applications.

"We basically discovered a new phenomenon that confirms that registry does count in van der Waals epitaxy," Li said.

This work was supported in part by the Department of Energy and the National Science Foundation. Postdoctoral researcher Ashkan Behnam and graduate students Joshua Wood and Christopher English also were co-authors of the paper. Li also is affiliated with the Beckman Institute for Advanced Science and Technology, the Micro and Nanotechnology Lab, and the Frederick Seitz Materials Research Lab, all at the U. of I.

The Crystal's Corners: New Nanowire Structure Has Potential to Increase Semiconductor Applications

Apr. 23, 2013 — There's big news in the world of tiny things. New research led by University of Cincinnati physics professors Howard Jackson and Leigh Smith could contribute to better ways of harnessing solar energy, more effective air quality sensors or even stronger security measures against biological weapons such as anthrax. And it all starts with something that's 1,000 times thinner than the typical human hair -- a semiconductor nanowire.

These cross-sectional electron microscope images show a quantum well tube nanowire’s hexagonal facets and crystal quality (left), and electron concentration in its corners. (Credit: Image courtesy of University of Cincinnati)

UC's Jackson, Smith, recently graduated PhD student Melodie Fickenscher and physics doctoral student Teng Shi, as well as several colleagues from across the US and around the world recently have published the research paper "Optical, Structural and Numerical Investigations of GaAs/AlGaAs Core-Multishell Nanowire Quantum Well Tubes" in Nano Letters, a journal on nanoscience and nanotechnology published by the American Chemical Society. In the paper, the team reports that they've discovered a new structure in a semiconductor nanowire with unique properties.

"This kind of structure in the gallium arsenide/aluminum gallium arsenide system had not been achieved before," Jackson says. "It's new in terms of where you find the electrons and holes, and spatially it's a new structure."

EYES ON SIZE AND CORNERING ELECTRONS

These little structures could have a big effect on a variety of technologies. Semiconductors are at the center of modern electronics. Computers, TVs and cellphones have them. They're made from the crystalline form of elements that have scientifically beneficial electrical conductivity properties. Many semiconductors are made of silicon, but in this case they are made of gallium arsenide. And while widespread use of these thin nanowires in new devices might still be around the corner, the key to making that outcome a reality in the coming years is what's in the corner.

By using a thin shell called a quantum well tube and growing it -- to about 4 nanometers thick -- around the nanowire core, the researchers found electrons within the nanowire were distributed in an unusual way in relation to the facets of the hexagonal tube. A close look at the corners of the tube's facets revealed something unexpected -- a high concentration of ground state electrons and holes.

"Having the faceting really matters. It changes the ballgame," Jackson says. "Adjusting the quantum well tube width allows you to control the energy -- which would have been expected -- but in addition we have found that there's a highly localized ground state at the corners which then can give rise to true quantum nanowires."

The nanowires the team uses for its research are grown at the Australian National University in Canberra, Australia -- one partner in this project that extends to disparate parts of the globe.

AFFECTING THE SCIENCE OF SMALL IN A BIG WAY

The team's discovery opens a new door to further study of the fundamental physics of semiconductor nanowires. As for leading to advances in technology such as photovoltaic cells, Jackson says it's too soon to tell because quantum nanowires are just now being explored. But in a world where hundreds of dollars' worth of technology is packed into a 5-by-2.5 inch iPhone, it's not hard to see how small but powerful science comes at a premium.

The team at UC is one of only about a half dozen in the US conducting competitive research in the field. It's a relatively young discipline, too, Jackson says, and one that's moving fast. For such innovative science, he says it's important to have a collaborative effort. The team includes scientists from research centers in the Midwest, the West Coast and all the way Down Under: UC, Miami University of Ohio and Sandia National Laboratories in California here in the US; and Monash University and the Australian National University in Australia.

The team's efforts are another example of how UC not only stands out as a leader in top-notch science, but also in shaping the future of the discipline by providing its students with high-quality educational and research opportunities.

"We're training students in state-of-the-art techniques on state-of-the-art materials doing state-of-the-art physics," Jackson says. "Upon completing their education here, they're positioned to go out and make contributions of their own."

Additional contributors to the paper are Jan Yarrison-Rice of Miami University, Oxford, Ohio; Bryan Wong of Sandia National Laboratories, Livermore, Calif.; Changlin Zheng, Peter Miller and Joanne Etheridge of Monash University, Victoria, Australia; and Qiang Gao, Shriniwas Deshpande, Hark Hoe Tan and Chennupati Jagadish of the Australian National University, Canberra, Australia.

Einstein's Gravity Theory Passes Toughest Test Yet

Apr. 25, 2013 — A strange stellar pair nearly 7,000 light-years from Earth has provided physicists with a unique cosmic laboratory for studying the nature of gravity. The extremely strong gravity of a massive neutron star in orbit with a companion white dwarf star puts competing theories of gravity to a test more stringent than any available before.

Superdense neutron star, emitting beams of radio waves as a pulsar, center, is closely paired with a compact white-dwarf star. Together, the two provide physicists with an unprecedented natural, cosmic "laboratory" for studying the nature of gravity. The grid background illustrates the distortions of spacetime caused by the gravitational effect of the two objects. (Credit: Antoniadis, et al.)

Once again, Albert Einstein's General Theory of Relativity, published in 1915, comes out on top.

At some point, however, scientists expect Einstein's model to be invalid under extreme conditions. General Relativity, for example, is incompatible with quantum theory. Physicists hope to find an alternate description of gravity that would eliminate that incompatibility.

A newly-discovered pulsar -- a spinning neutron star with twice the mass of the Sun -- and its white-dwarf companion, orbiting each other once every two and a half hours, has put gravitational theories to the most extreme test yet. Observations of the system, dubbed PSR J0348+0432, produced results consistent with the predictions of General Relativity.

The tightly-orbiting pair was discovered with the National Science Foundation's Green Bank Telescope (GBT), and subsequently studied in visible light with the Apache Point telescope in New Mexico, the Very Large Telescope in Chile, and the William Herschel Telescope in the Canary Islands. Extensive radio observations with the Arecibo telescope in Puerto Rico and the Effelsberg telescope in Germany yielded vital data on subtle changes in the pair's orbit.

In such a system, the orbits decay and gravitational waves are emitted, carrying energy from the system. By very precisely measuring the time of arrival of the pulsar's radio pulses over a long period of time, astronomers can determine the rate of decay and the amount of gravitational radiation emitted. The large mass of the neutron star in PSR J0348+0432, the closeness of its orbit with its companion, and the fact that the companion white dwarf is compact but not another neutron star, all make the system an unprecedented opportunity for testing alternative theories of gravity.

Under the extreme conditions of this system, some scientists thought that the equations of General Relativity might not accurately predict the amount of gravitational radiation emitted, and thus change the rate of orbital decay. Competing gravitational theories, they thought, might prove more accurate in this system.

"We thought this system might be extreme enough to show a breakdown in General Relativity, but instead, Einstein's predictions held up quite well," said Paulo Freire, of the Max Planck Institute for Radioastronomy in Germany.

That's good news, the scientists say, for researchers hoping to make the first direct detection of gravitational waves with advanced instruments. Researchers using such instruments hope to detect the gravitational waves emitted as such dense pairs as neutron stars and black holes spiral inward toward violent collisions.

Gravitational waves are extremely difficult to detect and even with the best instruments, physicists expect they will need to know the characteristics of the waves they seek, which will be buried in "noise" from their detectors. Knowing the characteristics of the waves they seek will allow them to extract the signal they seek from that noise.

"Our results indicate that the filtering techniques planned for these advanced instruments remain valid," said Ryan Lynch, of McGill University.

Freire and Lynch worked with a large international team of researchers. They reported their results in the journal Science.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

'Taxels' Convert Mechanical Motion to Electronic Signals

Apr. 25, 2013 — Using bundles of vertical zinc oxide nanowires, researchers have fabricated arrays of piezotronic transistors capable of converting mechanical motion directly into electronic controlling signals. The arrays could help give robots a more adaptive sense of touch, provide better security in handwritten signatures and offer new ways for humans to interact with electronic devices.

Georgia Tech researcher Wenzhuo Wu holds an array of piezotronic transistors capable of converting mechanical motion directly into electronic controlling signals. The arrays are fabricated on flexible substrates. (Credit: Image courtesy of Georgia Institute of Technology, Research Communications)

The arrays include more than 8,000 functioning piezotronic transistors, each of which can independently produce an electronic controlling signal when placed under mechanical strain. These touch-sensitive transistors -- dubbed "taxels" -- could provide significant improvements in resolution, sensitivity and active/adaptive operations compared to existing techniques for tactile sensing. Their sensitivity is comparable to that of a human fingertip.

The vertically-aligned taxels operate with two-terminal transistors. Instead of a third gate terminal used by conventional transistors to control the flow of current passing through them, taxels control the current with a technique called "strain-gating." Strain-gating based on the piezotronic effect uses the electrical charges generated at the Schottky contact interface by the piezoelectric effect when the nanowires are placed under strain by the application of mechanical force.

The research will be reported on April 25 in the journal Science online, at the Science Express website, and will be published in a later version of the print journal Science. The research has been sponsored by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF), the U.S. Air Force (USAF), the U.S. Department of Energy (DOE) and the Knowledge Innovation Program of the Chinese Academy of Sciences.

"Any mechanical motion, such as the movement of arms or the fingers of a robot, could be translated to control signals," explained Zhong Lin Wang, a Regents' professor and Hightower Chair in the School of Materials Science and Engineering at the Georgia Institute of Technology. "This could make artificial skin smarter and more like the human skin. It would allow the skin to feel activity on the surface."

Mimicking the sense of touch electronically has been challenging, and is now done by measuring changes in resistance prompted by mechanical touch. The devices developed by the Georgia Tech researchers rely on a different physical phenomenon -- tiny polarization charges formed when piezoelectric materials such as zinc oxide are moved or placed under strain. In the piezotronic transistors, the piezoelectric charges control the flow of current through the wires just as gate voltages do in conventional three-terminal transistors.

The technique only works in materials that have both piezoelectric and semiconducting properties. These properties are seen in nanowires and thin films created from the wurtzite and zinc blend families of materials, which includes zinc oxide, gallium nitride and cadmium sulfide.

In their laboratory, Wang and his co-authors -- postdoctoral fellow Wenzhuo Wu and graduate research assistant Xiaonan Wen -- fabricated arrays of 92 by 92 transistors. The researchers used a chemical growth technique at approximately 85 to 90 degrees Celsius, which allowed them to fabricate arrays of strain-gated vertical piezotronic transistors on substrates that are suitable for microelectronics applications. The transistors are made up of bundles of approximately 1,500 individual nanowires, each nanowire between 500 and 600 nanometers in diameter.

In the array devices, the active strain-gated vertical piezotronic transistors are sandwiched between top and bottom electrodes made of indium tin oxide aligned in orthogonal cross-bar configurations. A thin layer of gold is deposited between the top and bottom surfaces of the zinc oxide nanowires and the top and bottom electrodes, forming Schottky contacts. A thin layer of the polymer Parylene is then coated onto the device as a moisture and corrosion barrier.

The array density is 234 pixels per inch, the resolution is better than 100 microns, and the sensors are capable of detecting pressure changes as low as 10 kilopascals -- resolution comparable to that of the human skin, Wang said. The Georgia Tech researchers fabricated several hundred of the arrays during a research project that lasted nearly three years. The arrays are transparent, which could allow them to be used on touch-pads or other devices for fingerprinting. They are also flexible and foldable, expanding the range of potential uses.

Among the potential applications:

• Multidimensional signature recording, in which not only the graphics of the signature would be included, but also the pressure exerted at each location during the creation of the signature, and the speed at which the signature is created.

• Shape-adaptive sensing in which a change in the shape of the device is measured. This would be useful in applications such as artificial/prosthetic skin, smart biomedical treatments and intelligent robotics in which the arrays would sense what was in contact with them.

• Active tactile sensing in which the physiological operations of mechanoreceptors of biological entities such as hair follicles or the hairs in the cochlea are emulated. Because the arrays would be used in real-world applications, the researchers evaluated their durability. The devices still operated after 24 hours immersed in both saline and distilled water.

Future work will include producing the taxel arrays from single nanowires instead of bundles, and integrating the arrays onto CMOS silicon devices. Using single wires could improve the sensitivity of the arrays by at least three orders of magnitude, Wang said. "This is a fundamentally new technology that allows us to control electronic devices directly using mechanical agitation," Wang added. "This could be used in a broad range of areas, including robotics, MEMS, human-computer interfaces and other areas that involve mechanical deformation."

This research was supported by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF) under grant CMMI-0946418, the U.S. Air Force (USAF) under grant FA2386-10-1-4070, the U.S. Department of Energy (DOE) Office of Basic Energy Sciences under award DE-FG02-07ER46394 and the Knowledge Innovation Program of the Chinese Academy of Sciences under grant KJCX2-YW-M13. The content is solely the responsibility of the authors and does not necessarily represent the official views of DARPA, the NSF, the USAF or the DOE.

Near-Field Behavior of Semiconductor Plasmonic Microparticles Measured

Apr. 22, 2013 — Recent progress in the engineering of plasmonic structures has enabled new kinds of nanometer-scale optoelectronic devices as well as high-resolution optical sensing. But until now, there has been a lack of tools for measuring nanometer-scale behavior in plasmonic structures which are needed to understand device performance and to confirm theoretical models.

Atomic force microscope image of plasmonic semiconductor microparticles. (Credit: Image courtesy of University of Illinois College of Engineering)

"For the first time, we have measured nanometer-scale infrared absorption in semiconductor plasmonic microparticles using a technique that combines atomic force microscopy with infrared spectroscopy," explained William P. King, an Abel Bliss Professor in the Department of Mechanical Science and Engineering (MechSE) at Illinois. "Atomic force microscope infrared spectroscopy allows us to directly observe the plasmonic behavior within microparticle infrared antennas."

The article describing the research, "Near-field infrared absorption of plasmonic semiconductor microparticles studied using atomic force microscope infrared spectroscopy," appears in Applied Physics Letters.

"Highly doped semiconductors can serve as wavelength flexible plasmonic metals in the infrared," noted Daniel M. Wasserman, assistant professor of electrical and computer engineering at Illinois. "However, without the ability to visualize the optical response in the vicinity of the plasmonic particles, we can only infer the near-field behavior of the structures from their far-field response. What this work gives us is a clear window into the optical behavior of this new class of materials on a length scale much smaller than the wavelength of light."

The article compares near-field and far-field measurements with electromagnetic simulations to confirm the presence of localized plasmonic resonance. The article further reports high resolution maps of the spatial distribution of absorption within single plasmonic structures and variation across plasmonic arrays.

"The ability to measure near field behavior in plasmonic structures allows us to begin expanding our design parameters for plasmonic materials," commented Jonathan Felts, a MechSE graduate student. "Now that we can measure the optical behavior of individual features, we can start to think about designing and testing more complex optical materials."

The authors on the research are Jonathan Felts, Stephanie Law, Daniel M. Wasserman, and William P. King of the University of Illinois at Urbana-Champaign, along with Christopher M. Roberts and Viktor Podolskiy of the University of Massachusetts. The article is available online. This research was supported by the National Science Foundation.

Germanium Is Now Laser Compatible

Apr. 22, 2013 — Good news for the computer industry: a team of researchers has managed to make germanium suitable for lasers. This could enable microprocessor components to communicate using light in future, which will make the computers of the future faster and more efficient.

Light emitting bridges of germanium can be used for communication between microprocessors. (Credit: Hans Sigg, PSI)

Researchers from ETH Zurich, the Paul Scherrer Institute (PSI) and the Politecnico di Milano have jointly developed a manufacturing technique to render the semiconductor germanium laser-compatible through high tensile strain. In their paper recently published in Nature Photonics, they reveal how they can generate the necessary tensile strain efficiently. The scientists demonstrate that they can use their method to effectively alter the optical properties of germanium, which is unsuitable for lasers as such: "With a strain of three per cent, the material emits around twenty-five times more photons than in a relaxed state," explains Martin Süess, a doctoral student at the Laboratory for Nanometallurgy headed by Ralph Spolenak and the EMEZ at ETH Zurich. "That's enough to build lasers with," adds his colleague Richard Geiger, a doctoral student at the Laboratory for Micro- and Nanotechnology at the PSI and the Institute for Quantum Electronics at ETH Zurich under Jérôme Faist.

High tension through microbridges

In order to bring the germanium into a laser-compatible, stretched form with the new method, the researchers use the slight tension generated in germanium when it evaporates on silicon, strengthening this prestrain with so-called microbridges: they score exposed germanium strips, which remain attached to the silicon layer at both ends, in the middle on both sides. The two halves of the strip thus remain connected solely by an extremely narrow bridge, which is precisely where, for physical reasons, the strain of the germanium grows so intense that it becomes laser-compatible.

"The tensile strain exerted on the germanium is comparable to the force exerted on a pencil as two lorries pull upon it in opposite directions," says Hans Sigg, the project manager at the PSI, explaining the feat on a micrometre scale in everyday proportions. The material properties change because the individual atoms move apart a little through the expansion of the material, which enables the electrons to reach energy levels that are favourable for the generation of light particles, so-called photons.

Germanium laser for the computer of the future

The interdisciplinary research team's method could increase the performance of future computer generations considerably. After all, in order to improve computer performance, computer chips have constantly been made smaller and more densely packed. However, this approach will eventually hit a brick wall in the foreseeable future. "In order to increase performance and speed further, the individual components need to be linked more closely and communicate with each other more efficiently," explains Süess. This requires new transmission paths that are faster than today, where the signals are still transmitted via electricity and copper cables.

"The way to go in future is light," says Geiger. In order to be able to use this to transfer data, however, first of all light sources are needed that are so small as to fit onto a chip and react well to silicon, the base material of all computer chips. Silicon itself is not suitable for the construction of laser light, which is also the reason why it is so important for the researchers to make germanium laser-compatible: "Germanium is perfectly compatible with silicon and already used in the computer industry in the production of silicon chips," explains Geiger. If it is possible to build tiny lasers out of germanium using the new method, a system change is within reach. "We're on the right track," says Süess. The international team of researchers is currently in the process of actually constructing a germanium laser with the new method.

Research Harnesses Solar-Powered Proteins to Filter Harmful Antibiotics from Water

Apr. 19, 2013 — New research, just published, details how University of Cincinnati researchers have developed and tested a solar-powered nano filter that is able to remove harmful carcinogens and antibiotics from water sources -- lakes and rivers -- at a significantly higher rate than the currently used filtering technology made of activated carbon.

These spheres represent solar-powered antibotic filters. Each sphere is smaller than the diamter of a human hair. One day, a collection of such filters could float downstream from urban or farming areas to capture harmful compounds in water. (Credit: Image courtesy of University of Cincinnati)

In the journal Nano Letters, Vikram Kapoor, environmental engineering doctoral student, and David Wendell, assistant professor of environmental engineering, report on their development and testing of the new filter made of two bacterial proteins that was able to absorb 64 percent of antibiotics in surface waters vs. about 40 percent absorbed by the currently used filtering technology made of activated carbon. One of the more exciting aspects of their filter is the ability to reuse the antibiotics that are captured.

Kapoor and Wendell began development of their new nano filter in 2010 and testing in 2012, with the results reported in a paper titled "Engineering Bacterial Efflux Pumps for Solar-Powered Bioremediation of Surface Waters."

The presence of antibiotics in surface waters is harmful in that it breeds resistant bacteria and kills helpful microorganisms, which can degrade aquatic environments and food chains. In other words, infectious agents like viruses and illness-causing bacteria become more numerous while the health of streams and lakes degrades.

So, according to Wendell, the newly developed nano filters, each much smaller in diameter than a human hair, could potentially have a big impact on both human health and on the health of the aquatic environment (since the presence of antibiotics in surface waters can also affect the endocrine systems of fish, birds and other wildlife).

Surprisingly, this filter employs one of the very elements that enable drug-resistant bacteria to be so harmful, a protein pump called AcrB. Wendell explained, "These pumps are an amazing product of evolution. They are essentially selective garbage disposals for the bacteria. Our innovation was turning the disposal system around. So, instead of pumping out, we pump the compounds into the proteovesicles." (The new filtering technology is called a proteovesicle system.)

One other important innovation was the power source, a light-driven bacterial protein called Delta-rhodopsin which supplies AcrB with the pumping power to move the antibiotics.

The bacterial protein system has a number of advantages over present filtration technology:

• The operation of the new filtering technology is powered by direct sunlight vs. the energy-intensive needs for the operation of the standard activated carbon filter.

• The filtering technology also allows for antibiotic recycling. After these new nano filters have absorbed antibiotics from surface waters, the filters could be extracted from the water and processed to release the drugs, allowing them to be reused. On the other hand, carbon filters are regenerated by heating to several hundred degrees, which burns off the antibiotics.

• The new protein filters are highly selective. Currently used activated carbon filters serve as "catch alls," filtering a wide variety of contaminants. That means that they become clogged more quickly with natural organic matter found in rivers and lakes.

Said Wendell, "So far, our innovation promises to be an environmentally friendly means for extracting antibiotics from the surface waters that we all rely on. It also has potential to provide for cost-effective antibiotic recovery and reuse. Next, we want to test our system for selectively filtering out hormones and heavy metals from surface waters."

In relation to the work published in this paper, Wendell and Kapoor tested their solar-powered nano filter against activated carbon, the present treatment technology standard outside the lab. They tested their innovation in water collected from the Little Miami River. Using only sunlight as the power source, they were able to selectively remove the antibiotics ampicillin and vancomycin, commonly used human and veterinary antibiotics, and the nucleic acid stain, ethidium bromide, which is a potent carcinogen to humans and aquatic animals.

Antibody Transforms Stem Cells Directly Into Brain Cells

Apr. 22, 2013 — In a serendipitous discovery, scientists at The Scripps Research Institute (TSRI) have found a way to turn bone marrow stem cells directly into brain cells.

Scientists at The Scripps Research Institute have found a simple way to turn bone marrow stem cells directly into brain precursor cells, such as those shown here. (Credit: Image courtesy of the Lerner lab, The Scripps Research Institute)

Current techniques for turning patients' marrow cells into cells of some other desired type are relatively cumbersome, risky and effectively confined to the lab dish. The new finding points to the possibility of simpler and safer techniques. Cell therapies derived from patients' own cells are widely expected to be useful in treating spinal cord injuries, strokes and other conditions throughout the body, with little or no risk of immune rejection.

"These results highlight the potential of antibodies as versatile manipulators of cellular functions," said Richard A. Lerner, the Lita Annenberg Hazen Professor of Immunochemistry and institute professor in the Department of Cell and Molecular Biology at TSRI, and principal investigator for the new study. "This is a far cry from the way antibodies used to be thought of -- as molecules that were selected simply for binding and not function."

The researchers discovered the method, reported in the online Early Edition of the Proceedings of the National Academy of Sciences the week of April 22, 2013, while looking for lab-grown antibodies that can activate a growth-stimulating receptor on marrow cells. One antibody turned out to activate the receptor in a way that induces marrow stem cells -- which normally develop into white blood cells -- to become neural progenitor cells, a type of almost-mature brain cell.

Nature's Toolkit

Natural antibodies are large, Y-shaped proteins produced by immune cells. Collectively, they are diverse enough to recognize about 100 billion distinct shapes on viruses, bacteria and other targets. Since the 1980s, molecular biologists have known how to produce antibodies in cell cultures in the laboratory. That has allowed them to start using this vast, target-gripping toolkit to make scientific probes, as well as diagnostics and therapies for cancer, arthritis, transplant rejection, viral infections and other diseases.

In the late 1980s, Lerner and his TSRI colleagues helped invent the first techniques for generating large "libraries" of distinct antibodies and swiftly determining which of these could bind to a desired target. The anti-inflammatory antibody Humira®, now one of the world's top-selling drugs, was discovered with the benefit of this technology.

Last year, in a study spearheaded by TSRI Research Associate Hongkai Zhang, Lerner's laboratory devised a new antibody-discovery technique -- in which antibodies are produced in mammalian cells along with receptors or other target molecules of interest. The technique enables researchers to determine rapidly not just which antibodies in a library bind to a given receptor, for example, but also which ones activate the receptor and thereby alter cell function.

Lab Dish in a Cell

For the new study, Lerner laboratory Research Associate Jia Xie and colleagues modified the new technique so that antibody proteins produced in a given cell are physically anchored to the cell's outer membrane, near its target receptors. "Confining an antibody's activity to the cell in which it is produced effectively allows us to use larger antibody libraries and to screen these antibodies more quickly for a specific activity," said Xie. With the improved technique, scientists can sift through a library of tens of millions of antibodies in a few days.

In an early test, Xie used the new method to screen for antibodies that could activate the GCSF receptor, a growth-factor receptor found on bone marrow cells and other cell types. GCSF-mimicking drugs were among the first biotech bestsellers because of their ability to stimulate white blood cell growth -- which counteracts the marrow-suppressing side effect of cancer chemotherapy.

The team soon isolated one antibody type or "clone" that could activate the GCSF receptor and stimulate growth in test cells. The researchers then tested an unanchored, soluble version of this antibody on cultures of bone marrow stem cells from human volunteers. Whereas the GCSF protein, as expected, stimulated such stem cells to proliferate and start maturing towards adult white blood cells, the GCSF-mimicking antibody had a markedly different effect.

"The cells proliferated, but also started becoming long and thin and attaching to the bottom of the dish," remembered Xie.

To Lerner, the cells were reminiscent of neural progenitor cells -- which further tests for neural cell markers confirmed they were.

A New Direction

Changing cells of marrow lineage into cells of neural lineage -- a direct identity switch termed "transdifferentiation" -- just by activating a single receptor is a noteworthy achievement. Scientists do have methods for turning marrow stem cells into other adult cell types, but these methods typically require a radical and risky deprogramming of marrow cells to an embryonic-like stem-cell state, followed by a complex series of molecular nudges toward a given adult cell fate. Relatively few laboratories have reported direct transdifferentiation techniques.

"As far as I know, no one has ever achieved transdifferentiation by using a single protein -- a protein that potentially could be used as a therapeutic," said Lerner.

Current cell-therapy methods typically assume that a patient's cells will be harvested, then reprogrammed and multiplied in a lab dish before being re-introduced into the patient. In principle, according to Lerner, an antibody such as the one they have discovered could be injected directly into the bloodstream of a sick patient. From the bloodstream it would find its way to the marrow, and, for example, convert some marrow stem cells into neural progenitor cells. "Those neural progenitors would infiltrate the brain, find areas of damage and help repair them," he said.

While the researchers still aren't sure why the new antibody has such an odd effect on the GCSF receptor, they suspect it binds the receptor for longer than the natural GCSF protein can achieve, and this lengthier interaction alters the receptor's signaling pattern. Drug-development researchers are increasingly recognizing that subtle differences in the way a cell-surface receptor is bound and activated can result in very different biological effects. That adds complexity to their task, but in principle expands the scope of what they can achieve. "If you can use the same receptor in different ways, then the potential of the genome is bigger," said Lerner.

In addition to Lerner and Xie, contributors to the study, "Autocrine Signaling Based Selection of Combinatorial Antibodies That Transdifferentiate Human Stem Cells," were Hongkai Zhang of the Lerner Laboratory, and Kyungmoo Yea of The Scripps Korea Antibody Institute, Chuncheon-si, Korea.

Funding for the study was provided by The Scripps Korea Antibody Institute and Hongye Innovative Antibody Technologies (HIAT).

Ancient DNA Reveals Europe's Dynamic Genetic History

Apr. 23, 2013 — Ancient DNA recovered from a series of skeletons in central Germany up to 7,500 years old has been used to reconstruct the first detailed genetic history of modern Europe.

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Ancient DNA recovered from a series of skeletons in central Germany up to 7,500 years old has been used to reconstruct the first detailed genetic history of modern Europe. (Credit: © lily / Fotolia)

The study, published today in Nature Communications, reveals a dramatic series of events including major migrations from both Western Europe and Eurasia, and signs of an unexplained genetic turnover about 4,000 to 5,000 years ago.

The research was performed at the University of Adelaide's Australian Centre for Ancient DNA (ACAD). Researchers used DNA extracted from bone and teeth samples from prehistoric human skeletons to sequence a group of maternal genetic lineages that are now carried by up to 45% of Europeans.

The international team also included the University of Mainz in Germany and the National Geographic Society's Genographic Project.

"This is the first high-resolution genetic record of these lineages through time, and it is fascinating that we can directly observe both human DNA evolving in 'real-time', and the dramatic population changes that have taken place in Europe," says joint lead author Dr Wolfgang Haak of ACAD.

"We can follow over 4,000 years of prehistory, from the earliest farmers through the early Bronze Age to modern times."

"The record of this maternally inherited genetic group, called Haplogroup H, shows that the first farmers in Central Europe resulted from a wholesale cultural and genetic input via migration, beginning in Turkey and the Near East where farming originated and arriving in Germany around 7,500 years ago," says joint lead author Dr Paul Brotherton, formerly at ACAD and now at the University of Huddersfield, UK.

ACAD Director Professor Alan Cooper says: "What is intriguing is that the genetic markers of this first pan-European culture, which was clearly very successful, were then suddenly replaced around 4,500 years ago, and we don't know why. Something major happened, and the hunt is now on to find out what that was."

The team developed new advances in molecular biology to sequence entire mitochondrial genomes from the ancient skeletons. This is the first ancient population study using a large number of mitochondrial genomes.

"We have established that the genetic foundations for modern Europe were only established in the Mid-Neolithic, after this major genetic transition around 4,000 years ago," says Dr Haak. "This genetic diversity was then modified further by a series of incoming and expanding cultures from Iberia and Eastern Europe through the Late Neolithic."

"The expansion of the Bell Beaker culture (named after their pots) appears to have been a key event, emerging in Iberia around 2800 BC and arriving in Germany several centuries later," says Dr Brotherton. "This is a very interesting group as they have been linked to the expansion of Celtic languages along the Atlantic coast and into central Europe."

"These well-dated ancient genetic sequences provide a unique opportunity to investigate the demographic history of Europe," says Professor Cooper.

"We can not only estimate population sizes but also accurately determine the evolutionary rate of the sequences, providing a far more accurate timescale of significant events in recent human evolution."

The team has been working closely on the genetic prehistory of Europeans for the past 7-8 years.

Professor Kurt Alt (University of Mainz) says: "This work shows the power of archaeology and ancient DNA working together to reconstruct human evolutionary history through time. We are currently expanding this approach to other transects across Europe."

Genographic Project director Spencer Wells says: "Studies such as this on ancient remains serve as a valuable adjunct to the work we are doing with modern populations in the Genographic Project. While the DNA of people alive today can reveal the end result of their ancestors' ancient movements, to really understand the dynamics of how modern genetic patterns were created we need to study ancient material as well."