Thursday, March 3, 2011

One step closer to chemotherapy with reduced side-effects

 Researchers have created a tiny device that triggers reactions in cells.

The technology could enable to be activated at the site of a .

Targeting drug treatment where it is needed could safeguard the rest of the patient’s body.

This approach could help curb side-effects associated with such as hair loss, sickness and weakened immunity.

The device delivers tiny quantities of palladium.

This metal is not naturally found in human cells, but helps to trigger reactions in the cell.

The palladium works without altering everyday cell functions, such as producing proteins and metabolizing energy.

Researchers encased tiny particles of palladium in a harmless coating that is able to enter live cells.

They found that, in the lab, the metal was able to trigger specific reactions in the cell without having any effect elsewhere.

Although the research is at an early stage, scientists believe the technique will allow the therapeutic use of to manipulate cell activity.

This could produce substances, such as drugs, without affecting the rest of the body.

The discovery could pave the way for delivering therapies to where they are needed in the body, scientists say, and could also be used to deliver dyes to organs for diagnostic tests

More information: The study, published in Nature Chemistry, was carried out in collaboration with the Universiti Kebangsaan Malaysia.

New material provides 25 percent greater thermoelectric conversion efficiency

February 15, 2011 New material provides 25 percent greater thermoelectric conversion efficiency


Thermoelectric materials and technology have powered spacecraft for decades. But, thanks to advances in efficiency discovered at the Ames Laboratory, thermoelectric materials may have new, broader ?green? energy applications. Credit: U.S. Dept. of Energy's Ames Laboratory

Automobiles, military vehicles, even large-scale power generating facilities may someday operate far more efficiently thanks to a new alloy developed at the U.S. Department of Energy's Ames Laboratory. A team of researchers at the Lab that is jointly funded by the DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering and the Defense Advanced Research Projects Agency, achieved a 25 percent improvement in the ability of a key material to convert heat into electrical energy.

"What happened here has not happened anywhere else," said Evgenii Levin, associate scientist at Ames Laboratory and co-principal investigator on the effort, speaking of the significant boost in efficiency documented by the research. Along with Levin, the Ames Lab-based team included: Bruce Cook, scientist and co-principal investigator; Joel Harringa, assistant scientist II; Sergey Bud'ko, scientist; and Klaus Schmidt-Rohr, faculty scientist. Also taking part in the research was Rama Venkatasubramanian, who is director of the Center for Solid State Energetics at RTI International, located in North Carolina.

So-called that convert heat into electricity have been known since the early 1800s. One well-established group of thermoelectric materials is composed of tellurium, antimony, germanium and silver, and thus is known by the acronym "TAGS." Thermoelectricity is based on the movement of charge carriers from their heated side to their cooler side, just as electrons travel along a wire.

The process, known as the Seebeck effect, was discovered in 1821 by Thomas Johann Seebeck, a physicist who lived in what is now Estonia. A related phenomenon observed in all thermoelectric materials is known as the Peltier effect, named after French physicist Jean-Charles Peltier, who discovered it in 1834. The Peltier effect can be utilized for solid-state heating or cooling with no moving parts.

In the nearly two centuries since the discovery of the Seebeck and Peltier effects, practical applications have been limited due to the low efficiency with which the materials performed either conversion. Significant work to improve that efficiency took place during the 1950s, when thermoelectric conversion was viewed as an ideal power source for deep-space probes, explained team member Cook. "Thermoelectric conversion was successfully used to power the Voyager, Pioneer, Galileo, Cassini, and Viking spacecrafts," he said.

Despite its use by NASA, the low efficiency of thermoelectric conversion still kept it from being harnessed for more down-to-earth applications – even as research around the world continued in earnest. "Occasionally, you would hear about a large increase in efficiency," Levin explained. But the claims did not hold up to closer scrutiny.

All that changed in 2010, when the Ames Laboratory researchers found that adding just one percent of the rare-earth elements cerium or ytterbium to a TAGS material was sufficient to boost its performance.

The results of the group's work appeared in the article, "Analysis of Ce- and Yb-Doped TAGS-85 Materials with Enhanced Thermoelectric Figure of Merit," published online in November 2010 in the journal .

The team has yet to understand exactly why such a small compositional change in the material is able to profoundly affect its properties. However, they theorize that doping the TAGS material with either of the two rare-earth elements could affect several possible mechanisms that influence thermoelectric properties.

Team member Schmidt-Rohr studied the materials using Ames Laboratory's solid-state nuclear magnetic resonance spectroscopy instruments. This enabled the researchers to verify that the one percent doping of cerium or ytterbium affected the structure of the thermoelectric material. In order to understand effect of magnetism of rare earths, team member Bud'ko studied magnetic properties of the materials. "Rare-earth elements modified the lattice," said Levin, referring to the crystal structure of the thermoelectric materials.

The group plans to test the material in order to better understand why the pronounced change took place and, hopefully, to boost its performance further.

The durable and relatively easy-to-produce material has innumerable applications, including recycling waste heat from industrial refineries or using auto exhaust heat to help recharge the battery in an electric car. "It's a very amazing area," Levin said, particularly since many years of prior research into TAGS materials enables researchers to understand their nature. Better understanding of the thermoelectric and their improvement can immediately result in applications at larger scale than now.

Additionally, the Ames Laboratory results – dependent as they were on doping TAGS with small amounts of cerium or ytterbium – provide yet more evidence of rare-earth elements' strategic importance. Cerium or ytterbium are members of a group of 15 lanthanides, deemed essential to just about every new technology from consumer electronics and cell phones to hybrid car batteries and generator motors in wind turbines. The Ames Laboratory has been a leader in rare-earth research going back to the closing days of World War II. Fears of shortages of rare-earth elements have caused these little-known materials to be a much-talked-about subject in the news lately.

More information: E.M. Levin, B.A. Cook, J.L. Harringa, S. L. Bud'ko, R. Venkatasubramanian, K. Schmidt-Rohr, "Analysis of Ce- and Yb-Doped TAGS-85 Materials with Enhanced Thermoelectric Figure of Merit," Advanced Functional Materials, 2010, in press. DOI:10.1002/adfm.201001307

Provided by Ames Laboratory (news : web)

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Oxygen levels in the air do not limit plant productivity

 There have been concerns that present oxygen levels may limit plant productivity. Swedish researchers at Umea University show that this is not the case in a new study published in the journal The Proceedings of the National Academy of Sciences (PNAS). The results are encouraging since they demonstrate that plans for future biomass and solar fuels production are not limited by this effect.

Do increased oxygen levels limit by ? Is this unique process adapted to the low oxygen levels that existed when photosynthesis evolved nearly three billion years ago? These questions have generated vivid discussions in the academic world. Now Umea researchers together with colleagues at the University of Osnabrueck, Germany, can settle the debate. Increased levels of oxygen in the air do not directly inhibit photosynthesis.

“If photosynthetic productivity was directly inhibited by increased oxygen levels it would have severe consequences. It would limit the plans to use and artificial photosynthesis as future means to produce fuel in a sustainable way, since more photosynthesis by plants, photosynthetic bacteria and artificial catalysts would lead to more oxygen, especially locally within bioreactors or artificial devices” says Johannes Messinger, professor at the Department of Chemistry at Umea University.

In the present study, the researchers employed a mass spectrometric technique together with isotopic water (H218O) to probe the effect of increased concentrations of oxygen on the mechanism of water splitting. Water splitting is a complicated reaction which takes place in a large protein complex, called photosystem 2. The absorbed light energy is used to split two water molecules at a time into one molecule of molecular oxygen and four protons.

“We increased the oxygen pressure up to 50 times over ambient conditions. This did not lead to a block of oxygen evolution from water by photosystem 2,” says Johannes Messinger.

Researchers at Umea University’s Solar Fuels Environment as well as other researchers worldwide are trying to unravel all required details from the photosynthesis. Their goal is to be able to build manmade devices that, by employing the same principles as photosynthesis, are able to store solar energy in fuels such as hydrogen or ethanol.

Photosynthesis by plants and certain bacteria uses the energy of sunlight to split water into molecular oxygen, and to reduce carbon dioxide to the carbohydrates we eat. This process evolved about 2-3 billion years ago, and has been the basis for life as we know it. Basically all the oxygen in the Earth’s atmosphere was generated in this way and also most of the biomass, from which parts converted by geological processes into coal, oil and natural gas.

More information: Membrane-inlet mass spectrometry reveals a high driving force for oxygen production by photosystem II
Authors: Dmitriy Shevela, Katrin Beckmann, Juergen Clausen, Wolfgang Junge, and Johannes Messinger
http://www.pnas.or … 108.abstract

Green chemistry offers route towards zero-waste production

Novel green chemical technologies will play a key role helping society move towards the elimination of waste while offering a wider range of products from biorefineries, according to a University of York scientist.

Professor James Clark, Director of the University's Green Chemistry Centre of Excellence, will tell a symposium at the Annual meeting of the American Association for the Advancement of Science (AAAS) that the use of low environmental impact green chemical technologies will help ensure that products are genuinely and verifiably green and sustainable.

He says the extraction of valuable chemicals from biomass could form the initial processing step of many future biorefineries.

"We have shown that wax products with numerous applications, can be extracted from crop and other by-products including wheat and barley straws, timber residues and grasses, using supercritical carbon dioxide -- a green chemical technology that allows the production of products with no solvent residues," he says.

"The extracted residues can be used in applications including construction as well as in bioprocessing."

Low-temperature microwaves can also be used to pyrolyse biomass, allowing greater control over the heating process. The process results in significant energy savings and produces high quality oils, and oils and solids with useful chemical properties.

Professor Clark says that combining continuous extraction with microwave irradiation, it is possible separate an aqueous phase leaving the oils cleaner, less acidic and with lower quantities of other contaminants such as alkali metals. The oils have significant potential as feedstocks for making chemical products as well as for blending into transport fuels.

"Our microwave technology can also be tuned to produce bio-chars with calorific values and physical properties that make them suitable for co-firing with coal in power-stations," he adds.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of York, via EurekAlert!, a service of AAAS.

GRIN plasmonics: A practical path to superfast computing, ultrapowerful optical microscopy and invisibility carpet-cloaking devices

They said it could be done and now they've done it. What's more, they did it with a GRIN. A team of researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley, have carried out the first experimental demonstration of GRIN -- for gradient index -- plasmonics, a hybrid technology that opens the door to a wide range of exotic optics, including superfast computers based on light rather than electronic signals, ultra-powerful optical microscopes able to resolve DNA molecules with visible light, and "invisibility" carpet-cloaking devices.

Working with composites featuring a dielectric (non-conducting) material on a metal substrate, and "grey-scale" electron beam lithography, a standard method in the computer chip industry for patterning 3-D surface topographies, the researchers have fabricated highly efficient plasmonic versions of Luneburg and Eaton lenses. A Luneburg lens focuses light from all directions equally well, and an Eaton lens bends light 90 degrees from all incoming directions.

"This past year, we used computer simulations to demonstrate that with only moderate modifications of an isotropic dielectric material in a dielectric-metal composite, it would be possible to achieve practical transformation optics results," says Xiang Zhang, who led this research. "Our GRIN plasmonics technique provides a practical way for routing light at very small scales and producing efficient functional plasmonic devices."

Zhang, a principal investigator with Berkeley Lab's Materials Sciences Division and director of UC Berkeley's Nano-scale Science and Engineering Center (SINAM), is the corresponding author of a paper in the journal Nature Nanotechnology, describing this work titled, "Plasmonic Luneburg and Eaton Lenses." Co-authoring the paper were Thomas Zentgraf, Yongmin Liu, Maiken Mikkelsen and Jason Valentine.

GRIN plasmonics combines methodologies from transformation optics and plasmonics, two rising new fields of science that could revolutionize what we are able to do with light. In transformation optics, the physical space through which light travels is warped to control the light's trajectory, similar to the way in which outer space is warped by a massive object under Einstein's relativity theory. In plasmonics, light is confined in dimensions smaller than the wavelength of photons in free space, making it possible to match the different length-scales associated with photonics and electronics in a single nanoscale device.

"Applying transformation optics to plasmonics allows for precise control of strongly confined light waves in the context of two-dimensional optics," Zhang says. "Our technique is analogous to the well-known GRIN optics technique, whereas previous plasmonic techniques were realized by discrete structuring of the metal surface in a metal-dielectric composite."

Like all plasmonic technologies, GRIN plasmonics starts with an electronic surface wave that rolls through the conduction electrons on a metal. Just as the energy in a wave of light is carried in a quantized particle-like unit called a photon, so, too, is plasmonic energy carried in a quasi-particle called a plasmon. Plasmons will interact with photons at the interface of a metal and dielectric to form yet another quasi-particle, a surface plasmon polariton (SPP).

The Luneburg and Eaton lenses fabricated by Zhang and his co-authors interacted with SPPs rather than photons. To make these lenses, the researchers worked with a thin dielectric film (a thermplastic called PMMA) on top of a gold surface. When applying grey-scale electron beam lithography, the researchers exposed the dielectric film to an electron beam that was varied in dosage (charge per unit area) as it moved across the film's surface. This resulted in highly controlled differences in film thickness across the length of the dielectric that altered the local propagation of SPPs. In turn, the "mode index," which determines how fast the SPPs will propagate, is altered so that the direction of the SPPs can be influenced.

"By adiabatically tailoring the topology of the dielectric layer adjacent to the metal surface, we're able to continuously modify the mode index of SPPs," says Zentgraf. "As a result, we can manipulate the flow of SPPs with a greater degree of freedom in the context of two-dimensional optics."

Says Liu, "The practicality of working only with the purely dielectric material to transform SPPs is a big selling point for GRIN plasmonics. Controlling the physical properties of metals on the nanometer length-scale, which is the penetration depth of electromagnetic waves associated with SPPs extending below the metal surfaces, is beyond the reach of existing nanofabrication techniques."

Adds Zentgraf, "Our approach has the potential to achieve low-loss functional plasmonic elements with a standard fabrication technology that is fully compatible with active plasmonics."

In the Nature Nanotechnology paper, the researchers say that inefficiencies in plasmonic devices due to SPPs lost through scattering could be reduced even further by incorporating various SPP gain materials, such as fluorescent dye molecules, directly into the dielectric. This, they say, would lead to an increased propagation distance that is highly desired for optical and plasmonic devices. It should also enable the realization of two-dimensional plasmonic elements beyond the Luneburg and Eaton lenses.

Says Mikkelsen, "GRIN plasmonics can be immediately applied to the design and production of various plasmonic elements, such as waveguides and beam splitters, to improve the performance of integrated plasmonics. Currently we are working on more complex, transformational plasmonic devices, such as plasmonic collimators, single plasmonic elements with multiple functions, and plasmonic lenses with enhanced performance."

This research was supported by the U.S. Army Research Office and the National Science Foundation's Nano-scale Science and Engineering Center.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Thomas Zentgraf, Yongmin Liu, Maiken H. Mikkelsen, Jason Valentine, Xiang Zhang. Plasmonic Luneburg and Eaton lenses. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2010.282

How Safe Is Nano? Nanotoxicology: An interdisciplinary challenge

The rapid development of nanotechnology has increased fears about the health risks of nano-objects. Are these fears justified? Do we need a new discipline, nanotoxicology, to evaluate the risks? Empa scientists Harald F. Krug and Peter Wick discuss these questions in the new edition of the journal Angewandte Chemie.

"Research into the safety of nanotechnology combines biology, chemistry, and physics with workplace hygiene, materials science, and engineering to create a truly interdisciplinary research field," explain Krug and Wick. "There are several factors to take into account in the interaction of nano-objects with organisms," they add. The term nanotoxicology is fully justified. "Nanoscale particles can enter into cells by other means of transport than larger particles."

Another critical feature is the large surface area of nano-objects relative to their volume. If a similar amount of substance is absorbed, an organism comes into contact with a significantly larger number of molecules with nanoparticles than with larger particles. Dose-effect relationships cannot therefore be assumed to be the same. Furthermore, chemical and physical effects that do not occur with larger particles may arise. "Whether the larger or smaller particle is more toxic in any given case cannot be predicted," according to the authors. "Clearly, the type of chemical compound involved and its conformation in a specific case can also not be ignored." Carbon in the form of diamond nanoparticles is harmless, whereas in the form of nanotubes -- depending on length and degree of aggregation -- it may cause health problems. It is also thus impossible to avoid considering each nanomaterial in turn.

For a risk assessment, it is also necessary to keep in mind what dosage would be considered realistic and that not every observed biological effect automatically equates to a health risk.

Krug and Wick indicate that a large amount of data about the biological effects of nanomaterials is available, but not all studies are reliable. Sometimes it is not possible to reproduce the specific material tested or the conditions. "By pointing out methodological inadequacies and making concrete recommendations for avoiding them, we are hoping to contribute to a lasting improvement in the data," state Krug and Wick.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Empa.

Journal Reference:

Harald F. Krug, Peter Wick. Nanotoxikologie - eine interdisziplinäre Herausforderung. Angewandte Chemie, 2011; DOI: 10.1002/ange.201001037