Self-healing surfaces

[ScienceNology] - The engineers‘ dream of self-healing surfaces has taken another step towards becoming reality – researchers have produced a electroplated layer that contains tiny nanometer-sized capsules. If the layer is damaged, the capsules release fluid and repair the scratch.

Human skin is a phenomenon – small scratches and cuts heal quickly, leaving no trace of a scar after just a few days. It’s a different matter with materials, such as metals – if the electroplated layer protecting the metals from corrosion is scratched, rust protection is lost. Engineers are working on transferring the self-healing effect of skin to materials. The idea behind this is to introduce evenly distributed fluid-filled capsules into the electroplated layer – rather like raisins in a cake. If the layer is damaged, the pellets at the point of damage burst, the fluid runs out and ‘repairs’ the scratch. Until now, these plans have failed due to the size of the capsules – at 10 to 15 micrometers they were too large for the electroplated layer, which is around 20 micrometers thick. The capsules altered the mechanical properties of the layer.

Researchers from the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, together with colleagues from Duisburg-Essen University, have developed a process for producing electroplated layers with nano-capsules, in a project being financed by the Volkswagen Foundation. At only a few hundred nanometers in diameter, the capsules are measured on another scale entirely, compared with previous results. “The challenge lies in not damaging the capsules when producing the electroplated layer”, says Dr. Martin Metzner, Head of Department at IPA. “The smaller the capsules, the thinner and more sensitive their casing. The electrolytes used for these electroplated-technical processes are extremely aggressive chemically and can easily destroy the capsules”. The researchers therefore had to find a compatible material for the capsule casing depending on the electrolytes used.

Mechanical bearings are one example of possible applications – the materials of the bearings usually have a electroplated coating, in which the capsules can be embedded. If there is a temporary shortage of lubricant, part of the bearing’s coating is lost, the capsules at the top of the layer burst and release lubricant. The bearing is not therefore damaged if it temporarily runs dry. The researchers have produced the first copper, nickel and zinc coatings with the new capsules, although surface coverage does not extend beyond the centimeter scale. Experts estimate that it will be another one and a half to two years before whole components can be coated. In a further step the team worked on more complex systems – involving differently filled capsules, for example, whose fluids react with one another like a two component adhesive.



A Research News from Fraunhofer , August 2009

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The perfect cut

[ScienceNology] - You need the right tool to slice silicon blocks into paper-thin wafers: a several-kilometer-long wire wetted with a type of grinding paste. And all the parameters must be optimally adjusted – only then can significant material losses be avoided during the cutting process.

The ability to cut onions into thin slices isn’t just a matter of practice – choosing the right implement also helps make good onion rings. The same principle applies when cutting silicon blocks to make wafers for solar cells. You need a special slicing tool to produce paper-thin wafers from silicon blocks (“ingots”): reminiscent of an egg slicer, a filigree wire is used to cut through the ingot at a speed of up to 60 km/h. This wire is several hundred kilometers long and arranged in such a way that the ingot is sliced into hundreds of wafers simultaneously. The process takes around six hours and the resultant slices are approximately 180 µm thick.

Dr. Rainer Kübler, business unit manager at the Fraunhofer Institute for Mechanics of Materials IWM, explains: “When slicing the wafers, the challenge is to reduce the saw gap width.” The space between two wafers is governed by the thickness of the wire. The steel wire is wetted with a type of paste (“slurry”), a mixture of silicon carbide and polyethylene glycol. This is harder than silicon and cuts through the ingot. The gap arises where the silicon is reduced to powder during cutting. “Gap widths are currently around 180 µm,” says Kübler, “which means that given a wafer thickness of 180 µm, we generate the same amount of waste for each silicon slice. That’s inefficient.”

The researchers “want to achieve smaller saw gap widths of around 100 µm, which are also suitable for industrial applications.” In a project funded by the federal ministry for the environment (BMU), they are currently studying the abrasion process and contact regimes using a single-wire saw and are principally interested in the interactions between the wire, the slurry and the silicon. They are also using computer modeling to simulate different configurations. What forces are at work when sawing with thin wires? How can one ensure the wire is well wetted? What is the best grain size for the slurry and how must the particles be distributed?

“We want to answer all these questions and ultimately arrive at optimal wire and slurry systems that are suitable for industrial applications,” says Kübler. The researchers are currently striving to achieve gap widths of 90 µm, which would represent a huge increase in efficiency as waste would be halved.



A Research News from Fraunhofer , August 2009

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Chinese culture at the crossroads

[ScienceNology] - Recent archaeological discoveries from far-flung corners of China are forcing scientists to reconsider the origins of ancient Chinese civilization – and a new crop of young archaeologists are delving into the modern nation's roots. In the August 21 issue of the journal Science, a group of articles by Science news writer Andrew Lawler explore how, over several millennia, the most populous and economically vibrant nation in the world evolved from a much wider array of peoples and cultures than once imagined.

Lawler crisscrossed China recently for three weeks, traveling from the country's steamy southeastern plains to the rugged westernmost province of Xinjiang, interviewing dozens of archaeologists at a host of sites. This special news package puts a spotlight on how the various archaeological findings of the past decade are challenging what the Chinese people once thought about their country and themselves. As a construction boom continues to alter the physical face of the country – inadvertently uncovering vital clues to China's past, illuminating ancient trade routes and long-lost cultures – a new and more complex history of the Chinese people is emerging right before their very eyes.

The wealth of these recent archaeological discoveries demands a re-write of some history books – and young scholars are even now questioning the existence of a legendary Chinese dynasty, the Xia. Less willing to take ancient texts at face value than their predecessors, this new generation of Chinese researchers is relying on physical data – and more "Western" methods – in their attempts to accurately retrace Chinese history.

But looting and development threaten to destroy the country's heritage. In a land full of wealthy tombs and poor farmers, grave robbing has been an ancient tradition. China's current construction boom poses yet another threat to archaeological sites, though new laws are attempting to halt such damage. Those who destroy evidence of the country's rich history now face jail time and even the death penalty (though no one appears to have been executed for looting yet). Meanwhile, archaeologists are finding novel ways to work with developers and provincial governments to rescue at least some ancient sites from the destruction that comes with the country's economic growth.

"The exciting discoveries made recently across China, coupled with the country's fast-paced development, make this an opportune time to dig into new questions about China's origins, the state of its threatened ancient sites, and the increasing expertise of its archaeologists," says Andrew Lawler, author of the Science news package.

Lawler's special news package on Chinese archaeology covers the accidental discovery and later excavation of Jinsha, an ancient site located near downtown Chengdu in Sichuan, and about 600 miles (1000 kilometers) from the traditional center of Chinese civilization along the Yellow River. Long assumed to have been a cultural backwater, researchers have only recently gleaned the real history of Sichuan's surprisingly ancient and rich culture, which is thousands of years older than they had once believed. Now, thanks to a group of savvy archaeologists and their allies in the city government, Jinsha has become a museum, protected from looters and complete with adjacent land reserved for further archaeological digs in the future.

Another article by Lawler illuminates the earliest Silk Road which brought valued goods like bronze from the west and possibly the staple grain of ancient China, millet, to the west. These recent discoveries have led Chinese researchers to acknowledge significant outside influence on their ancient culture, breaking an old taboo put in place when China was largely closed to the outside world.

Contact: Natasha Pinol
npinol@aaas.org
202-326-7088
American Association for the Advancement of Science



An Archeology News from EurekAlert! , 20 August 2009

Photo credit to : http://www.chinaexpress.ca

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Cornell synchrotron unveils long-hidden Wyeth painting

[ScienceNology] - Stubborn layers of paint had kept them hidden for several decades, but the bluish, purplish and reddish hues of a 1919 painting by 20th-century artist N.C. Wyeth have finally come to light, thanks to cutting-edge technologies developed at the Cornell High Energy Synchrotron Source (CHESS).

The careful visualization of a Wyeth magazine illustration depicting two men engaged in a brawl, only known previously in black and white, was publicly unveiled Aug. 19 at an American Chemical Society symposium by chemist and art conservation expert Jennifer L. Mass, M.S. '92, Ph.D. '95.

Mass, who collaborated on the Wyeth project with CHESS senior research associate Arthur Woll and art conservators Christina Bisulca, Noelle Ocon and Matt Cushman, described the powerful X-ray technology used to unveil the old painting, which Wyeth had painted over in about 1923 with his work "Family Portrait."

CHESS scientists, led by Woll, developed a technique called confocal X-ray fluorescence that harnesses the brilliant X-rays from the National Science Foundation-supported CHESS to deal specifically with the problem of painted-over paintings. They teamed with Mass, senior scientist at Delaware's Winterthur Museum and Country Estate, to study "Family Portrait" after it was discovered 12 years ago that a second work, the scene of a dramatic struggle from a 1919 Everybody's Magazine article titled "The Mildest Mannered Man," lay underneath it.

Christina Bisulca/University of Delaware

Scientists at CHESS used confocal X-ray fluorescence to extract the colors of a painting by N.C. Wyeth that had been hidden under another painting.

Brandywine River Museum

The magazine illustration of Wyeth's painting, previously known only in black and white.

Their device focuses an X-ray beam onto a painting and collects the fluorescent X-rays given off by the chemicals in the various layers of paint. Each color of paint produces a unique fluorescence spectrum, like a chemical fingerprint, which can then be mapped to reconstruct the original color schemes in the hidden painting.

Confocal X-ray microscopy isn't new; it had been tried in Europe several years ago, but mostly on scientific specimens, said Sol Gruner, CHESS director and professor of physics.

"We built a setup specifically to look at large works of art," Gruner said.

The result of the CHESS project was the discovery of a painting once thought to be lost, two scientific papers describing the new confocal X-ray techniques -- and a few surprises.

For example, one might expect the burning furnace plume depicted in the rightmost part of the painting to glow a brilliant orange, Gruner said. As it turns out, Wyeth used a more subtle tone.

"The colors are quite pale, something that was surprising to us, and there were much more muted yellows and oranges, and more prevalent pinks and violets then we were expecting," Mass said.

The collaboration between art conservators and CHESS scientists is growing, Gruner said, with several other projects in the pipeline that involve specific works of art as well as old manuscripts.

Confocal X-ray fluorescence is a slow, arduous technique; scanning a portion of a painting the size of a quarter takes nine hours. A project at CHESS is also ongoing to look at ways to speed up this process, which would allow more art historians to access the technology, already applied in such disciplines as biology, archaeology and dendrochronology, said Ernie Fontes, CHESS assistant director.

"Confocal X-rays on paintings is still a very specialist niche," Fontes said.

Even so, Gruner expects that other synchrotron facilities will soon begin operating instruments for art conservation, given that the confocal technology is well known and accessible to synchrotron scientists.

"Our primary role in this, which is common for CHESS, is to lead by example," Gruner said.


By : Anne Ju , (607) 255-9735 , amj8@cornell.edu


A News from Cornell University , 20 August 2009

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Camera Flash Turns an Insulating Material Into a Conductor

An insulator can now be transformed to conduct electricity by an ordinary camera flash.

A Northwestern University professor and his students have found a new way of turning graphite oxide -- a low-cost insulator made by oxidizing graphite powder -- into graphene, a hotly studied material that conducts electricity. Scientists believe graphene could be used to produce low-cost carbon-based transparent and flexible electronics.

Previous processes to reduce graphite oxide relied on toxic chemicals or high-temperature treatment. The idea for a simple new process came in a burst of inspiration: Can a camera flash instantly heat up the graphite oxide and turn it into graphene?

The process, invented by Jiaxing Huang, assistant professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science, his graduate student Laura J. Cote and postdoctoral fellow Rodolfo Cruz-Silva, was published in the Aug. 12 issue of the Journal of the American Chemical Society.

Materials scientists previously have used high-temperature heating or chemical reduction to produce graphene from graphite oxide. But these techniques could be problematic when graphite oxide is mixed with something else, such as a polymer, because the polymer component may not survive the high-temperature treatment or could block the reducing chemical from reacting with graphite oxide.

In Huang’s flash reduction process, researchers simply hold a consumer camera flash over the graphite oxide and, a flash later, the material is now a piece of fluffy graphene.

”The light pulse offers very efficient heating through the photothermal process, which is rapid, energy efficient and chemical-free,” Huang said.

When using a light pulse, photothermal heating not only reduces the graphite oxide, it also fuses the insulating polymer with the graphene sheets, resulting in a welded conducting composite.

Using patterns printed on a simple overhead transparency film as a photo-mask, flash reduction creates patterned graphene films. This process creates electronically conducting patterns on the insulating graphite oxide film -- essentially a flexible circuit.

The research group hopes to next create smaller circuits on a single graphite-oxide sheet at the single-atom layer level. (The current process has been performed only on thicker films.)

“If we can make a nano circuit on a single piece of graphite oxide,” Huang said, “it will hold great promise for patterning electronic devices.”

The National Science Foundation supported this research.


By: Megan Fellman


A News from NorthWestern University , 18 August 2009

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New research supports model for nuclear pore complex

To protect their DNA, cells in higher organisms are very choosy about what they allow in and out of their nuclei, where the genes reside. Guarding access is the job of transport machines called nuclear pore complexes, which stud the nuclear membrane. Despite these gatekeepers’ conspicuously large size (they are made of 30 different proteins), they have proved largely inscrutable to researchers over the years. But bit by bit, scientists are learning how these machines work.

Now a new study reveals the structure of one of the proteins that makes up this molecule-trafficking complex. Researchers have also shown how that protein interacts with a partner, supporting a model that calls for a flexible “ring” around the opening of each pore. The work could offer a key insight into an important design feature of this little-understood and evolutionarily ancient structure, an innovation fundamental to the development of nearly all multicellular life on Earth.

<-- Paring the pore. A new model of how the nuclear pore complex might work suggests that an interaction between two proteins — key elements of the yellow ring pictured above — link together, forming a flexible fence around the pore’s opening.

The research, performed by Hyuk-Soo Seo, a postdoctoral associate, and André Hoelz, a research associate, both in Rockefeller University’s Laboratory of Cell Biology, determined the molecular structure of the only remaining unsolved protein in an important piece of the nuclear pore called the Nup84 complex. Nup84 is a Y-shaped element that was recently imaged in three dimensions by Martin Kampmann, also a member of the lab headed by Howard Hughes Medical Institute Investigator Günter Blobel. In experiments published online last week in the Proceedings of the National Academy of Sciences, Seo, Hoelz and colleagues focused on the behavior of this newly solved protein — or nucleoporin — called Nup120, one of seven comprising the Nup84 complex. They determined that one end of Nup120, the N-terminal domain, is attached by a stretchable tether to one other protein in the complex, Nup133.

Furthermore, the researchers showed in living cells that mutations to a critical region of the tether interfered with the export of messenger RNA, one of the nuclear pore’s chief responsibilities, confirming the functional importance of this loose linkage between the two proteins.

“It’s a very nice correlation from the structure to the function,” Hoelz says. “It’s the first example where we can really pin down how the [Nup84] complexes arrange with each other, and what we believe we see is a flexible ring that could expand and contract to import and export large molecules.”



A research from Rockefeller University , 18 August 2009

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Electrifying ideas to market

<-- Fluoreszenzmikroskopische recordings of E. coli - culture. Live / Dead - staining with BacLight - kit (Molecular Probes): green = live, red = dead (Source: Institute for Materials Science, TU Dresden)

The project BIOMINT research scientist at the TU Dresden in a new laboratory for innovation, the pyroelectric properties of crystals. Ein Wirtschaftswissenschaftler überprüft, ob die jeweiligen Ergebnisse vermarktbar sind An economist checked whether the results are marketable

Pyroelektrizität - that is the property of certain materials such as quartz or complex silicates, such as tourmaline, if you change the temperature with the formation of a surface charge to respond. As a result, formed by the material around an electrical box. As this effect in bioprocess could be used, examines the research and creation project BIOMINT under the direction of Jun.-Prof. Dirk Meyer at the Technical University of Dresden. On the thematically complex projects are employees of the Institute for Structure Physics, Material Science, Genetics and Food Engineering and Biotechnology involved.

In a two-year project to the researchers, with financial support from the "Format" - the initiative of the Federal Ministry for Education and Research (BMBF) fathom how intelligent materials with the demand for resource-saving, environmental and health-oriented technologies can be satisfied. In the center of the project will exploit the special characteristics of pyroelectric crystalline materials in connection with biotechnology and physico-chemical processes.

"Depending on the structure and the specific shape of the crystals can be as field strengths of several millimeters per kilovolt occur," said Dirk Meyer. "With this change could, for example, cell, switch ', that is permeable to certain molecules or impermeable make." The application of filter processes in, for example in the disinfection or the production of chemicals, food substances or drugs, which is on the hand.

"Conceivably would also be harmful micro-organisms, which they, for example, in washing machines proliferate, with the help of Pyroelektrizität instantaneously, without the harsh chemicals used to be," says Professor Meyer. One goal of the project was also a new technology platform for the use of pyroelectric materials in the bioprocessing, environmental and life sciences market.

To view the projects in addition to all the technological challenges and relevance to market orientation, is for the entire duration of the project, a graduate in Economics Dresden University of Technology has its place - a novelty in this field, such as project staff Robert Schmid stresses. And adds: "The projects in this laboratory for innovation should be established in addition to subsequent projects at the TU Dresden practically proven framework to enable long-term success in the above sense possible."



Source : Technical University of Dresden , Germany, 17 August 2009

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The world's tiniest laser - 'Cornell dots'

<-- Schematic (not to scale) of the modified Cornell dot used to create the world's smallest laser. The particle, 44 nanometers in diameter, consists of a silica shell surrounding a 14-nanometer gold core. Energy bouncing between dye molecules and a plasmon oscillation in electrons in the gold amplifies the light output.

By Bill Steele

Researchers have modified nanoparticles known as "Cornell dots" to make the world's tiniest laser -- so small it could be incorporated into microchips to serve as a light source for photonic circuits. The device may also have applications for sensors, solar collectors and in biomedicine.

The original Cornell dots, created by Ulrich Wiesner, the Spencer T. Olin Professor of Engineering at Cornell, consist of a core of dye molecules enclosed in a silica shell to create an unusually luminous particle. The new work by researchers at Norfolk (Virginia) State University (NSU), Purdue University and Cornell uses what Wiesner calls "hybrid Cornell dots," which have a gold core surrounded by a silica shell in which dye molecules are embedded.

The research is reported in the Aug. 16 online issue of the journal Nature and will appear in a coming print issue.

Using nanoparticles 44 nanometers (nm -- one billionth of a meter or about three atoms in a row) wide, the device is the smallest nanolaser reported to date, and the first operating in visible light wavelengths, the researchers said.

"This opens an interesting playground in terms of miniaturization," said Wiesner. "For the first time we have a building block a factor of 10 smaller than the wavelength of light."

False color simulation of the intensity distribution of light emission in a nanoparticle in "spaser" mode, with the highest intensity shown in red. -->

An optical laser this small is impossible because a laser develops its power by bouncing light back and forth in a tuned cavity whose length must be at least half the wavelength of the light to be emitted. In the first tests of the new device, the light emitted had a wavelength of 531 nm, in the green portion of the visible spectrum.

In a conventional laser, molecules are excited by an outside source of energy, which may be light, electricity or a chemical reaction. Some molecules spontaneously release their energy as photons of light, which bounce back and forth between two reflectors, in turn triggering more molecules to emit photons.

In the new device, dye molecules in the nanoparticle are excited by a pumping laser. A few molecules spontaneously release their added energy to generate a plasmon -- a wave motion of free electrons at an optical frequency -- in the gold core. In the tiny space, the dye molecules and the gold core are coupled by electric fields, explains Purdue co-author Vladimir Shalaev.

Oscillations of the plasmon in turn trigger more dye molecules to release their energy, which further pumps up the plasmon, creating a "spaser" (surface plasmon amplification by stimulated emission of radiation). When the energy of the system reaches a threshold the electric field collapses, releasing its energy as a photon. The size of the core -- 14 nm in diameter -- is chosen to set up a resonance that reinforces a wave corresponding to the desired 531 nm light output.

Tests at NSU indicate that the lasing effect occurs within each Cornell dot and is not a phenomenon of a collection of the nanoparticles working together, making this unquestionably the world's smallest laser.

"Some people argue that the ability to produce a surface plasmon in this way will be even more useful," added NSU professor and lead author Mikhail Noginov. It has been suggested that plasmons could be used to send signals across a microchip at the speed of light -- much faster than electrons in wires -- but in less space than photonic circuits need.

The idea of a spaser was first proposed in 2003 by physicists Mark Stockman at Georgia State University and David Bergman at Tel Aviv University. The theory behind the new approach was developed by Evgenii Narimanov at Purdue.


The work is funded by the National Science Foundation, with additional funding from the U.S. Army Research Office.


A news from Cornell University Chronicle Online , 17 August 2009

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Archaeologists find cache of cuneiform tablets in 2,700-year old Turkish temple

Excavations led by a University of Toronto archaeologist at the site of a recently discovered temple in southeastern Turkey have uncovered a cache of cuneiform tablets dating back to the Iron Age period between 1200 and 600 BCE. Found in the temple's cella, or 'holy of holies', the tablets are part of a possible archive. The cella also contained gold, bronze and iron implements, libation vessels and ornately decorated ritual objects.

"The assemblage appears to represent a Neo-Assyrian renovation of an older Neo-Hittite temple complex, providing a rare glimpse into the religious dimension of Assyrian imperial ideology," said Timothy Harrison, professor of near eastern archeology in the Department of Near and Middle Eastern Civilizations and director of U of T's Tayinat Archaeological Project (TAP). "The tablets, and the information they contain, may possibly highlight the imperial ambitions of one of the great powers of the ancient world, and its lasting influence on the political culture of the Middle East."

Partially uncovered in 2008 at Tell Tayinat, capital of the Neo-Hittite Kingdom of Palastin, the structure of the building where the tablets were found preserves the classic plan of a Neo-Hittite temple. It formed part of a sacred precinct that once included monumental stelae carved in Luwian (an extinct Anatolian language once spoken in Turkey) hieroglyphic script, but which were found by the expedition smashed into tiny shard-like fragments.

"Tayinat was destroyed by the Assyrian king Tiglath-pileser III in 738 BCE, and then transformed into an Assyrian provincial capital, equipped with its own governor and imperial administration," said Harrison. "Scholars have long speculated that the reference to Calneh in Isaiah's oracle against Assyria alludes to Tiglath-pileser's devastation of Kunulua - i.e., Tayinat. The destruction of the Luwian monuments and conversion of the sacred precinct into an Assyrian religious complex may represent the physical manifestation of this historic event."

The temple was later burned in an intense fire and found filled with heavily charred brick and wood which, ironically, contributed to the preservation of the finds recovered from its inner chambers. "While those responsible for this later destruction are not yet known, the remarkable discoveries preserved in the Tayinat temple clearly record a pivotal moment in its history," said Harrison. "They promise a richly textured view of the cultural and ethnic contest that has long characterized the turbulent history of this region."

TAP is an international project, involving researchers from a dozen countries, and more than 20 universities and research institutes. It operates in close collaboration with the Ministry of Culture of Turkey, and provides research opportunities and training for both graduate and undergraduate students. The project is funded by the Social Sciences and Humanities Research Council of Canada and the Institute for Aegean Prehistory (INSTAP), and receives support from the University of Toronto.



A News from the University of Toronto , 07 August 2009

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