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|  | Re: New Millenium Technology VIII
« Reply #30 on Nov 13, 2011, 1:16am » | |
Researchers Ink Nanostructures With Tiny 'Soldering Iron'
![[image]](http://img707.imageshack.us/img707/603/111107160241large485749.jpg "[image]")
Thermal dip-pen nanolithography turns the tip of a scanning probe microscope into a tiny soldering iron that can be used to draw chemical patterns as small as 20 nanometers on surfaces. (Credit: Image courtesy of DeYoreo, et. al)
ScienceDaily (Nov. 7, 2011) — Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have shed light on the role of temperature in controlling a fabrication technique for drawing chemical patterns as small as 20 nanometers. This technique could provide an inexpensive, fast route to growing and patterning a wide variety of materials on surfaces to build electrical circuits and chemical sensors, or study how pharmaceuticals bind to proteins and viruses.
One way of directly writing nanoscale structures onto a substrate is to use an atomic force microscope (AFM) tip as a pen to deposit ink molecules through molecular diffusion onto the surface. Unlike conventional nanofabrication techniques that are expensive, require specialized environments and usually work with only a few materials, this technique, called dip-pen nanolithography, can be used in almost any environment to write many different chemical compounds. A cousin of this technique -- called thermal dip-pen nanolithography -- extends this technique to solid materials by turning an AFM tip into a tiny soldering iron.
Dip-pen nanolithography can be used to pattern features as small as 20 nanometers, more than forty thousand times smaller than the width of a human hair. What's more, the writing tip also performs as a surface profiler, allowing a freshly-writ surface to be imaged with nanoscale precision immediately after patterning.
"Tip-based manufacturing holds real promise for precise fabrication of nanoscale devices," says Jim DeYoreo, interim director of Berkeley Lab's Molecular Foundry, a DOE nanoscience research center. "However, a robust technology requires a scientific foundation built on an understanding of material transfer during this process. Our study is the first to provide this fundamental understanding of thermal dip-pen nanolithography."
In this study, DeYoreo and coworkers systematically investigated the effect of temperature on feature size. Using their results, the team developed a new model to deconstruct how ink molecules travel from the writing tip to the substrate, assemble into an ordered layer and grow into a nanoscale feature.
"By carefully considering the role of temperature in thermal dip-pen nanolithography, we may be able to design and fabricate nanoscale patterns of materials ranging from small molecules to polymers with better control over feature sizes and shapes on a variety of substrates," says Sungwook Chung, a staff scientist in Berkeley Lab's Physical Biosciences Division, and Foundry user working with DeYoreo. "This technique helps overcome fundamental length scale limitations without the need for complex growth methods."
DeYoreo and Chung collaborated with a research team from the University of Illinois at Urbana-Champaign that specializes in fabricating specialized tips for AFMs. Here, these collaborators developed a silicon-based AFM tip with a gradient of charge-carrying atoms sprinkled into the silicon such that a higher number reside at the base while fewer sit at the tip. This makes the tip heat up when electricity flows through it, much like the burner on an electric stove.
This 'nanoheater' can then be used to heat up inks applied to the tip, causing them to flow to the surface for fabricating microscale and nanoscale features. The group demonstrated this by drawing dots and lines of the organic molecule mercaptohexadecanoic acid on gold surfaces. The hotter the tip, the larger the feature size the team could draw.
"We are excited about this collaboration with Berkeley Lab, which combines their remarkable nanoscience capabilities with our technology to control temperature and heat flow on the nanometer scale," says co-author William P. King, a University of Illinois professor of mechanical sciences and engineering. "Our ability to control the temperature within a nanometer-scale spot enabled this study of molecular-scale transport. By tuning the hotspot temperature, we can probe how molecules flow to a surface."
"This thermal control over tip-to-surface transfer developed by Professor King's group adds versatility by enabling on-the-fly variations in feature size and patterning of both liquid and solid materials," DeYoreo adds.
Chung is the lead author and DeYoreo the corresponding author of a paper reporting this research in the journal Applied Physics Letters. The paper is titled "Temperature-dependence of ink transport during thermal dip-pen nanolithography." Co-authoring the paper with Chung, DeYoreo and King were Jonathan Felts and Debin Wang.
This work at the Molecular Foundry was supported by DOE's Office of Science and the Defense Advanced Research Projects Agency.
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The above story is reprinted from materials provided by DOE/Lawrence Berkeley National Laboratory.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
http://www.sciencedaily.com/releases/2011/11/111107160241.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #31 on Nov 14, 2011, 12:15am » | |
Could graphene be the new silicon?
It started with a few experiments with Scotch tape and a pencil. Then graphene, stronger than steel, one atom thick and a super-conductor, was born, a wonder material that could be as revolutionary as silicon, say its Nobel prize-winning creators. Now with £50m from the UK government, they're out to prove it
o Tim Adams
o The Observer, Sunday 13 November 2011
![[image]](http://img268.imageshack.us/img268/2482/graphenesheetmodel3d006.jpg "[image]")
A 3D model of graphene's chicken wire structure. Photograph: nobeastsofierce/Alamy
Somehow it seems appropriate that the government might be basing some of its hopes for the economy's recovery on a substance that is one atom thick. The substance in question – graphene – 200 times as strong as steel, seems to some designed to carry the weight of almost anything – but George Osborne's Plan A? That would indeed make it a miracle material.
Nevertheless the chancellor made a detour from the Tory conference in Blackpool in September to visit Manchester University, graphene's spiritual home, and to announce a £50m investment. Graphene is claimed by some as an innovation that will prove as revolutionary as the silicon chip, or even plastics, both of which it may supersede. A poster campaign around Manchester currently reminds you that the industrial revolution was born in the city at the beginning of the 19th century. Two hundred years on the challenge is to keep the "graphene revolution" in the north west, too.
Sitting in his lab at the university, Konstantin Novoselov one half of the 2010 physics Nobel prize-winning team that "discovered" graphene, runs through the superlatives of his material – uniquely strong and flexible and the best conductor of electricity yet found – with a kind of amused pride before explaining its genesis. Graphene wasn't so much of a eureka moment as a eureka year or two, but since it was first identified the exclamation marks have kept coming. What they began with, however, was some pencil lead and a roll of Scotch tape.
In 2004 Novoselov, a 37-year old from the Ural mountains with a deadpan wit, was a post-doctorate researcher in conductivity in a department run by fellow Russian émigré Andre Geim. "It was always the style in our lab to have side projects going on," he recalls. "We were working on issues of microscopic electromagnetism during the day, but we had a few after-hours projects on the go mainly for fun."
At the time, Andre Geim was probably best known for his "frog levitation" experiment. This showed that if you placed small amphibians between two large electromagnets they would defy gravity and swim in the air. The experiment won him an Ig-Nobel prize (awarded for the most enjoyably pointless research of the year; Geim remains the only recipient both of an Ig-Nobel and the real thing).
It was in the same spirit of airborne pond-dwellers that Geim and his team began to think about creating a 2D or one atom thick substance. One Friday night, as you do, they were talking about the possibilities of creating a transformer made of metal rather than a semi-conductor such as silicon. The obvious material to test that hypothesis was graphite, so they spent a while trying to find the thinnest possible slice of graphite, to see if it would work.
Over a few weeks they had several attempts at it. On one occasion Geim bought a very expensive chunk of graphite and asked a Chinese research student to polish it on a machine. The student came back the following day with a very expensive bag full of dust.
At around the same time the lab had received a microscope that allowed you to see atomic structures, and Geim's team wanted a very clear structure to look at. Graphite again was the obvious choice and, Novoselov recalls, they discovered that the best way to prepare a smooth surface on the graphite "was to use a piece of Scotch tape and just use it to peel away any residue or dust or crap that was on it".
At some point, thinking again about the metal transistor hypothesis, someone said, "Why don't we have a look at the stuff that is left on the tape", which they were throwing away. "So," Novoselov recalls, "we tested that and the very first sample worked, just about, as a transistor." Over the course of a year, now working mostly full-time, the team improved the conductivity of the graphite by making it thinner and thinner until they got to the point where they could see the ultimate goal was to get something one atom thick, a previously unthinkable goal. "We had worked a lot in micro-electronics but it seemed very unlikely that anything one atom thick could be stable," Novoselov says.
Graphene graphic A closer look at graphene and its uses. Click here to see a readable image of the graphic.
Still using a refinement of the Scotch tape technique, what followed was another "long and quite enjoyable process, testing the properties, making calculations, studying the physics"; and eventually the 2D graphite was produced. Novoselov and Geim were surprised to see that it not only maintained a bonded structure like chicken wire, but also had an apparently uniquely symmetrical arrangement of electrons that enhanced conductivity. Graphene's properties were announced in 2004.
Geim and Novoselov knew they were on to something but were surprised to discover the storm that the discovery made. "We were not aware that there had been a huge community of people already working worldwide on the problem we had solved," Novoselov suggests. "We were just newcomers. But almost immediately papers started to pile up."
Novoselov and Geim, the Crick and Watson of graphene, quickly began to see the possibilities of the material. "It was a new physics for us and for everybody," Novoselov says. There was quickly talk of it creating everything from super-strong aircraft to paper-thin and foldable touch screens, to graphene replacing glass – it is perfectly transparent – and improving plastic, and revolutionising everything from nanosurgery to homebuilding.
None of these possibilities has been overturned by subsequent experiments with graphene but the technology remains so new very few practical applications are in even prototype stage (at one point Novoselov shows me a little square of graphene layered about as thick as cellophane, which switches from opaque to transparent with the application of electricity through a pair of bulldog clips – but that is about as far as it goes).
Graphene may be formed of unique bonds, but the synergy between research and application, between university and industry is still nowhere near as tight as it might be. I imagine, universities and corporations are throwing money at graphene research in other parts of the world?
"Yes," Novoselov says, "but money is not the only thing. Before the £50m we had no more than any other lab, but we still kept at the front of this. It's more time than money." If you think that you can make a new kind of transistor and put it into your computer straight away, he suggests, then you are wrong. How to integrate this into existing technology let alone allow it to begin to shape new technology will take years if not decades. He points to the example of silicon. "The first transistor was maybe 1947, silicon appeared six or seven years later and then it was another 10 or 20 years before integrated circuits." 2D technology may take even longer to become properly commercial, but he has no doubt that eventually it will.
One of the intentions of the £50m investment is to create a "graphene hub" around the Manchester lab, to integrate the research into cutting-edge British industry. Currently the team's findings do not extend too far beyond the university in the north-west. Novoselov and Geim run a regular seminar to discuss issues; it started with just the two of them, but now perhaps 50 people from different scientific disciplines take part, share knowledge and raise questions. The TV astrophysicist Professor Brian Cox, who is based at the university, is alive to the excitement of this group: "Graphene will revolutionise the world, there's not a doubt in my mind," he says. "And this will be the best place in the world to do research into that and commercialise it, if that investment is used properly…"
Exactly how the investment will be used is currently being debated. Novoselov would love in the first instance to open his seminar up to a more commercial audience. "We are going from first principles to prototyping, but if you threw industry people into that room you might get to production quite quickly."
They are, of course, not alone in trying to get graphene to market. To begin with they thought about trying to patent or trademark the material or at least some of their techniques. Geim was disabused of the notion by the CEO of "a world-leading phone company", Novoselov recalls. "Andre was at a conference in the US quite early on. He met this guy and mentioned the idea of intellectual property. He was told, 'We know this material exists and we are doing our own research into it. Of course you can patent it if you want, but if graphene is half the material we think it is we will place 100 patent lawyers on it and you will spend the rest of your life and the GDP of your small island trying to fight for it.'"
Novoselov anyway doubts that protection of knowledge would properly accelerate the technology. To a degree, it has to be open source. If they are going to create a graphene hub, he suggests, then the hub itself needs to be something of a prototype – for the effective sharing of knowledge in a competitive market. It is no secret that European universities do not tend to be as good at such partnerships as American universities and those in the far east; moreover, Britain lacks the commercial scientific expertise in these fields to develop products quickly, compared, say, to Silicon Valley. "We are in the position still where we don't know exactly what they need and they don't know exactly what we have got," Novoselov says. "It is frustrating. We don't want industry to come to us and just say tell us what you know, we want to work in partnership."
The Nobel prize worked quite well as a profile-raiser, Novoselov suggests, but the £50m has worked better: "We have had more contacts from big companies in the last few weeks since that was announced than in all the years before that." Since 2004, he reckons, the lab has spent around £6m on research in total, about half raised from European grants and the rest from projects with South Korean and American corporations. Novoselov hopes the government money will attract more leading-edge scientists to the project, reversing what has been "a bit of a brain drain" to the far east.
Does he feel a weight of responsibility, as a potential saviour of the British economy?
He laughs. "To a degree. Remember that £50m on a global scale is not a vast amount of money. For us it is good money, but the government spends that in a blink of an eye on quantitative easing, or a few miles of a new road or whatever. Still in terms of graphene I am certain we will have something…"
It is that faith which keeps Novoselov working the long hours (though with twin two-year-old daughters at home, sleep is not always easy to come by). And graphene itself is the gift that keeps on giving. Every month, he suggests, there are new possibilities. "The real excitement at the moment is the way we can now layer graphene with different 2D materials," he says, "with each layer having different properties." The stacking means that in theory it will be possible to design materials with the properties to meet any needs. "You tell me 'I want blue and highly conductive and bendy' and we can make it." To a certain degree, he suggests, the only limits to graphene may be those of imagination. "We still tend to think of how this material might be used in the form of current objects. We can imagine, say, a 2D layered photodetective material, with a solar cell and transistor combined which would allow you to make a very thin plastic touchscreen that generated its own power." He smiles.
"We are still thinking inside the box but trying to enlarge the box slightly." The possibility though, he suggests, is that the pencil-lead and Scotch tape miracle will one day create different boxes altogether. Whether they will be made in Britain may yet be the ultimate £50m question.
http://www.guardian.co.uk/science/2011/n....geim-manchester
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #32 on Nov 14, 2011, 1:55am » | |
Researching Graphene Nanoelectronics for a Post-Silicon World
![[image]](http://img713.imageshack.us/img713/9388/111110094844large358861.jpg "[image]")
A new study from researchers at Rensselaer Polytechnic Institute details how stacking nanoribbons of graphene can boost the material’s ability to transmit electrical charges. The discovery further supports the idea that graphene could one day replace traditional copper as the best material for interconnects that transmit data and power around computer chips. (Credit: Rensselaer/Nayak)
ScienceDaily (Nov. 10, 2011) — Copper's days are numbered, and a new study at Rensselaer Polytechnic Institute could hasten the downfall of the ubiquitous metal in smart phones, tablet computers, and nearly all electronics. This is good news for technophiles who are seeking smaller, faster devices.
As new generations of computer chips continue to shrink in size, so do the copper pathways that transport electricity and information around the labyrinth of transistors and components. When these pathways -- called interconnects -- grow smaller, they become less efficient, consume more power, and are more prone to permanent failure.
To overcome this hurdle, industry and academia are vigorously researching new candidates to succeed traditional copper as the material of choice for interconnects on computer chips. One promising candidate is graphene, an atom-thick sheet of carbon atoms arranged like a nanoscale chicken-wire fence. Prized by researchers for its unique properties, graphene is essentially a single layer of the graphite found commonly in our pencils or the charcoal we burn on our barbeques.
Led by Rensselaer Professor Saroj Nayak, a team of researchers discovered they could enhance the ability of graphene to transmit electricity by stacking several thin graphene ribbons on top of one another. The study, published in the journal ACS Nano, brings industry closer to realizing graphene nanoelectronics and naming graphene as the heir apparent to copper.
"Graphene shows enormous potential for use in interconnects, and stacking up graphene shows a viable way to mass produce these structures," said Nayak, a professor in the Department of Physics, Applied Physics, and Astronomy at Rensselaer. "Copper's limitations are apparent, as increasingly smaller copper interconnects suffer from sluggish electron flows that results in hotter, less reliable devices. Our new study makes a case for the possibility that stacks of graphene ribbons could have what it takes to be used as interconnects in integrated circuits."
The study, based on large-scale quantum simulations, was conducted using the Rensselaer Computational Center for Nanotechnology Innovations (CCNI), one of the world's most powerful university-based supercomputers.
Copper interconnects suffer from a variety of unwanted problems, which grow more prominent as the size of the interconnects shrink. Electrons travel through the copper nanowires sluggishly and generate intense heat. As a result, the electrons "drag" atoms of copper around with them. These misplaced atoms increase the copper wire's electrical resistance, and degrade the wire's ability to transport electrons. This means fewer electrons are able to pass through the copper successfully, and any lingering electrons are expressed as heat. This heat can have negative effects on both a computer chip's speed and performance.
It is generally accepted that a quality replacement for traditional copper must be discovered and perfected in the next five to 10 years in order to further perpetuate Moore's Law -- ;an industry mantra that states the number of transistors on a computer chip, and thus the chip's speed, should double every 18 to 24 months.
Nayak's recent work, published in the journal ACS Nano, is titled "Effect of Layer Stacking on the Electronic Structure of Graphene Nanoribbons." When cut into nanoribbons, graphene is known to exhibit a band gap -- an energy gap between the valence and conduction bands -- which is an unattractive property for interconnects. The new study shows that stacking the graphene nanoribbons on top of each other, however, could significantly shrink this band gap.
"The optimal thickness is a stack of four to six layers of graphene," said Neerav Kharche, first author of the study and a computational scientist at CCNI. "Stacking more layers beyond this thickness doesn't reduce the band gap any further."
The end destination, Nayak said, is to one day manufacture microprocessors -- both the interconnects and the transistors -- entirely out of graphene. This game-changing goal, called monolithic integration, would mean the end of the long era of copper interconnects and silicon transistors.
"Such an advance is likely still many years into the future, but it will certainly revolutionize the way nearly all computers and electronics are designed and manufactured," Nayak said.
Along with Nayak and Kharche, contributors to this study were: former Rensselaer physics graduate student Yu Zhou; Swastik Kar, former Rensselaer physics research assistant professor; and Kevin P. O'Brien of Intel Corporation.
Story Source:
The above story is reprinted from materials provided by Rensselaer Polytechnic Institute.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
1. Neerav Kharche, Yu Zhou, Kevin P. O’Brien, Swastik Kar, Saroj K. Nayak. Effect of Layer Stacking on the Electronic Structure of Graphene Nanoribbons. ACS Nano, 2011; 5 (8): 6096 DOI: 10.1021/nn200941u
http://www.sciencedaily.com/releases/2011/11/111110094844.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #33 on Nov 14, 2011, 2:50am » | |
Chemistry: New Insight Into 100-Year-Old Haber-Bbosch Process of Converting Nitrogen to Ammonia
ScienceDaily (Nov. 11, 2011) — For the past 100 years, the Haber-Bosch process has been used to convert atmospheric nitrogen into ammonia, which is essential in the manufacture of fertilizer. Despite the longstanding reliability of the process, scientists have had little understanding of how it actually works. But now a team of chemists, led by Patrick Holland of the University of Rochester, has new insight into how the ammonia is formed. Their findings are published in the latest issue of Science.
Holland calls nitrogen molecules "challenging." While they're abundant in the air around us, which makes them desirable for research and manufacturing, their strong triple bonds are difficult to break, making them highly unreactive. For the last century, the Haber-Bosch process has made use of an iron catalyst at extremely high pressures and high temperatures to break those bonds and produce ammonia, one drop at a time. The question of how this works, though, has not been answered to this day.
"The Haber-Bosch process is efficient, but it is hard to understand because the reaction occurs only on a solid catalyst, which is difficult to study directly," said Holland. "That's why we attempted to break the nitrogen using soluble forms of iron."
Holland and his team, which included Meghan Rodriguez and William Brennessel at the University of Rochester and Eckhard Bill of the Max Planck Institute for Bioinorganic Chemistry in Germany, succeeded in mimicking the process in solution. They discovered that an iron complex combined with potassium was capable of breaking the strong bonds between the nitrogen (N) atoms and forming a complex with an Fe3N2 core, which indicates that three iron (Fe) atoms work together in order to break the N-N bonds. The new complex then reacts with hydrogen (H2) and acid to form ammonia (NH3) -- something that had never been done by iron in solution before.
Despite the breakthrough, the Haber-Bosch process is not likely to be replaced anytime soon. While there are risks in producing ammonia at extremely high temperatures and pressures, Holland points out that the catalyst used in Haber-Bosch is considerably less expensive than what was used by his team. But Holland says it is possible that his team's research could eventually help in coming up with a better catalyst for the Haber-Bosch process -- one that would allow ammonia to be produced at lower temperatures and pressures.
At the same time, the findings could have a benefit far removed from the world of ammonia and fertilizer. When the iron-potassium complex breaks apart the nitrogen molecules, negatively charged nitrogen ions -- called nitrides -- are formed. Holland says the nitrides formed in solution could be useful in making pharmaceuticals and other products.
Story Source:
The above story is reprinted from materials provided by University of Rochester.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
1. M. M. Rodriguez, E. Bill, W. W. Brennessel, P. L. Holland. N2 Reduction and Hydrogenation to Ammonia by a Molecular Iron-Potassium Complex. Science, 2011; 334 (6057): 780 DOI: 10.1126/science.1211906
http://www.sciencedaily.com/releases/2011/11/111111152240.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #34 on Nov 15, 2011, 3:11pm » | |
Engineers Solve Energy Puzzle: How Energy Levels Align in a Critical Group of Advanced Materials
ScienceDaily (Nov. 6, 2011) — University of Toronto materials science and engineering (MSE) researchers have demonstrated for the first time the key mechanism behind how energy levels align in a critical group of advanced materials. This discovery is a significant breakthrough in the development of sustainable technologies such as dye-sensitized solar cells and organic light-emitting diodes (OLEDs).
Transition metal oxides, which are best-known for their application as super-conductors, have made possible many sustainable technologies developed over the last two decades, including organic photovoltaics and organic light-emitting diodes. While it is known that these materials make excellent electrical contacts in organic-based devices, it wasn't known why -- until now.
In research published in Nature Materials, MSE PhD Candidate Mark T. Greiner and Professor Zheng-Hong Lu, Canada Research Chair (Tier I) in Organic Optoelectronics, lay out the blueprint that conclusively establishes the principle of energy alignment at the interface between transition metal oxides and organic molecules.
"The energy-level of molecules on materials surfaces is like a massive jigsaw puzzle that has challenged the scientific community for a very long time," says Professor Lu. "There have been a number of suggested theories with many critical links missing. We have been fortunate to successfully build these links to finally solve this decades-old puzzle."
With this piece of the puzzle solved, this discovery could enable scientists and engineers to design simpler and more efficient organic solar cells and OLEDs to further enhance sustainable technologies and help secure our energy future.
Story Source:
The above story is reprinted from materials provided by University of Toronto Faculty of Applied Science & Engineering.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
1. Mark T. Greiner, Michael G. Helander, Wing-Man Tang, Zhi-Bin Wang, Jacky Qiu, Zheng-Hong Lu. Universal energy-level alignment of molecules on metal oxides. Nature Materials, 2011; DOI: 10.1038/nmat3159
http://www.sciencedaily.com/releases/2011/11/111106151019.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #35 on Nov 15, 2011, 3:13pm » | |
Not One, Not Two, Not Three, but Four Clones: First Quantum Cloning Machine to Produce Four Copies
ScienceDaily (Nov. 6, 2011) — Xi-Jun Ren and Yang Xiang from Henan Universities in China, in collaboration with Heng Fan at the Institute of Physics of the Chinese Academy of Sciences, have produced a theory for a quantum cloning machine able to produce several copies of the state of a particle at atomic or sub-atomic scale, or quantum state, in an article about to be published in The European Physical Journal D. The advance could have implications for quantum information processing methods used, for example, in message encryption systems.
Quantum cloning is difficult because quantum mechanics laws only allow for an approximate copy—not an exact copy—of an original quantum state to be made, as measuring such a state prior to its cloning would alter it.
In this study, researchers have demonstrated that it is theoretically possible to create four approximate copies of an initial quantum state, in a process called asymmetric cloning. The authors have extended previous work that was limited to quantum cloning providing only two or three copies of the original state. One key challenge was that the quality of the approximate copy decreases as the number of copies increases.
The authors were able to optimise the quality of the cloned copies, thus yielding four good approximations of the initial quantum state. They have also demonstrated that their quantum cloning machine has the advantage of being universal and therefore is able to work with any quantum state, ranging from a photon to an atom.
Assymetric quantum cloning has applications in analysing the security of messages encryption systems, based on shared secret quantum keys. Two people will know whether their communication is secure by analysing the quality of each copy of their secret key. Any third party trying to gain knowledge of that key would be detected as measuring it would disturb the state of that key.
Story Source:
The above story is reprinted from materials provided by Springer Science+Business Media.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
1. X. J. Ren, Y. Xiang, H. Fan. Optimal asymmetric 1 → 4 quantum cloning in arbitrary dimension. The European Physical Journal D, 2011; DOI: 10.1140/epjd/e2011-20370-2
http://www.sciencedaily.com/releases/2011/11/111106150759.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: New Millenium Technology VIII
« Reply #36 on Nov 15, 2011, 3:17pm » | |
2-D Electron Liquid Solidifies in a Magnetic Field
![[image]](http://img338.imageshack.us/img338/8314/111105153311large805412.jpg "[image]")
Electron densities for the ground state of N=7 electrons in a magntic field, at: (a) fractional filling ν =1/3, corresponding to the angular momentum L2 = 63, shown in red on the left hand side (α = 0, β = 1). The total wave function is Ψ= Φ63 whose density is seen to exhibit a uniform circular amplitude characteristic of a liquid state, and (b) a mixed state in the neighborhood of ν =1/3, obtained by disorder-induced coupling between the ground state Φ63 and the adjacent excited state with L1 = 57. The density of the broken-symmetry mixed state Ψ= α Φ57 + β Φ63 (with α = 1/ 2, β =1/ 2) , shown in blue on the right, exhibits a non-uniform crystalline pattern, portraying formation of a disorder-pinned wigner crystallite. The results were obtained through exact diagonalization of the hamiltonian, with the parameters corresponding to GaAs, i.e. a dielectric constant κ = 13.1 and an effective mass m* =0.0067 me, and a confining potential of 3.6 meV. Lengths are given in units of the magnetic lengthlB, and the units of the vertical axes are 10âˆ'2lB-2. The electron density is normalized to the number of particles, N. (Credit: Image courtesy of Georgia Institute of Technology)
ScienceDaily (Nov. 5, 2011) — Physicists from the Georgia Institute of Technology have developed a theory that describes, in a unified manner, the coexistence of liquid and pinned solid phases of electrons in two dimensions under the influence of a magnetic field. The theory also describes the transition between these phases as the field is varied. The theoretical predictions by Constantine Yannouleas and Uzi Landman, from Georgia Tech's School of Physics, aim to explain and provide insights into the origins of experimental findings published last year by a team of researchers from Princeton, Florida State and Purdue universities.
The research appears in the Oct. 27 edition of the journal Physical Review B.
The experimental discovery in 1982 of a new Hall conductance step at a fraction ν=1/m with m=3, that is at (1/3)e2/h (with more conductance steps, at other m, found later) -- where h is the Planck constant and e is the electron charge -- was made for two-dimensional electrons at low temperatures and strong magnetic fields and was greeted with great surprise. The theoretical explanation of this finding a year later by Robert Laughlin in terms of a new form of a quantum fluid, earned him and the experimentalists Horst Störmer and Daniel Tsui the 1998 Nobel Prize with the citation "for the discovery of a new form of quantum fluid with fractionally charged excitations." These discoveries represent conceptual breakthroughs in the understanding of matter, and the fractional quantum Hall effect (FQHE) liquid states, originating from the highly correlated nature of the electrons in these systems, have been termed as new states of matter.
"The quantum fluid state at the 1/3 primary fraction is the hallmark of the FQHE, whose theoretical understanding has been formulated around the antithesis between a new form of quantum fluid and the pinned Wigner crystal," said Landman, Regents' and Institute Professor in the School of Physics, F.E. Callaway Chair and director of the Center for Computational Materials Science (CCMS) at Georgia Tech. "Therefore, the discovery of pinned crystalline signatures in the neighborhood of the 1/3 FQHE fraction, measured as resonances in the microwave spectrum of the two-dimensional electron gas and reported in the Physical Review Letters in September 2010 by a group of researchers headed by Daniel Tsui, was rather surprising," he added.
Indeed, formation of a hexagonally ordered two-dimensional electron solid phase, a so called Wigner crystal (WC) named after the Nobel laureate physicist Eugene Wigner who predicted its existence in 1934, has been anticipated for smaller quantum Hall fractional fillings, ν, of the lowest Landau level populated by the electrons at high magnetic fields, for example ν = 1/9, 1/7 and even 1/5. However, the electrons in the ν=1/3 fraction were believed to resist crystallization and remain liquid.
The Georgia Tech physicists developed a theoretical formalism that, in conjunction with exact numerical solutions, provides a unified microscopic approach to the interplay between FQHE liquid and Wigner solid states in the neighborhood of the 1/3 fractional filling. A major advantage of their approach is the use of a single class of variational wave functions for description of both the quantum liquid and solid phases.
"Liquid characteristics of the fractional quantum Hall effect states are associated with symmetry-conserving vibrations and rotations of the strongly interacting electrons and they coexist with intrinsic correlations that are crystalline in nature," Senior Research Scientist Yannouleas and Landman wrote in the opening section of their paper. "While the electron densities of the fractional quantum Hall effect liquid state do not exhibit crystalline patterns, the intrinsic crystalline correlations which they possess are reflected in the emergence of a sequence of liquid states of enhanced stability, called cusp states, that correspond in the thermodynamic limit to the fractional quantum Hall effect filling fractions observed in Hall conductance measurements," they added.
The key to their explanation of the recent experimental observations pertaining to the appearance of solid characteristics for magnetic fields in the neighborhood of the 1/3 filling fraction is their finding that "away from the exact fractional fillings, for example near ν=1/3, weak pinning perturbations, due to weak disorder, may overcome the energy gaps between adjacent good angular momentum symmetry-conserving states. The coupling between these states generates broken-symmetry ground states whose densities exhibit spatial crystalline patterns. At the same time, however, the energy gap between the ground state at ν=1/3 and adjacent states is found to be sufficiently large to prevent disorder-induced mixing, thus preserving its quantum fluid nature."
Furthermore, the work shows that the emergence of the crystalline features, via the pinning perturbations, is a consequence of the aforementioned presence of crystalline correlations in the symmetry-conserving states. Consequently, mixing rules that govern the nature of the disorder-pinned crystalline states have been formulated and tested. Extrapolation of the calculated results to the thermodynamic limit shows development of a hexagonal Wigner crystal with enhanced stability due to quantum correlations.
"In closing, the nature of electrons in the fractional quantum Hall regime continues now for close to three decades to be a subject of great fascination, a research field that raises questions whose investigations can lead to deeper conceptual understanding of matter and many-body phenomena, and a rich source of surprise and discovery," said Landman.
This work was supported by the Office of Basic Energy Sciences of the US Department of Energy.
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The above story is reprinted from materials provided by Georgia Institute of Technology.
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Journal Reference:
1. Constantine Yannouleas, Uzi Landman. Unified microscopic approach to the interplay of pinned-Wigner-solid and liquid behavior of the lowest Landau-level states in the neighborhood of ν=1/3. Physical Review B, 2011; 84 (16) DOI: 10.1103/PhysRevB.84.165327
http://www.sciencedaily.com/releases/2011/11/111105153311.htm
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« Reply #37 on Nov 15, 2011, 3:21pm » | |
Simulating Real-World Surfaces for Automotive Design
ScienceDaily (Nov. 7, 2011) — Today, cars are designed on computers, and to assist with this, designers want processes which generate realistic surfaces such as seat covers. Researchers have now developed high-resolution scanners which copy objects and fabric samples in a few minutes, converting them into virtual models. The light effects are startlingly realistic.
When buying a car, customers are not just interested in its fuel consumption. They rather turn their attention to the car's appearance. The interior fittings should have a quality look, the pattern on the seat covers should be subtle and understated and the leather-look dashboard should add a sense of luxury. That is why designers want to know at an early stage how a piece of fabric or imitation leather will look in the new car cockpit. Models used to be manufactured by hand, but that was time-consuming. And although computer simulation is faster, it takes time as well: real-world objects must first be scanned at high resolution and then translated to the virtual world. Researchers at the Fraunhofer Institute for Computer Graphics Research IGD in Darmstadt are now hoping to accelerate this process.
They have developed two scanners which capture images of real objects with micrometer precision and use the data to generate deceptively lifelike virtual images. The first device, the HDR-ABTF scanner, is specifically designed to capture images of materials such as textiles and leather, lit from different directions, precisely and especially quickly. Computers can then be used to simulate how an object -- for instance a car seat -- covered in that material will look in changing light conditions. The second device, the meso scanner, captures high-resolution images of three-dimensional objects. Unlike conventional systems, it even records finest surface details with yet unmatched precision.
Both scanners have been developed from established processes which are more expensive or which take longer. "For industrial applications, though, we need fast and affordable devices with high resolution," explains Martin Ritz, a developer at Fraunhofer IGD. This is what the HDR-ABTF scanner delivers. A single-lens reflex camera installed in the device looks down on the object from above. The material is lit successively by several LEDs arranged in a quadrant arc, so that the surface is lit from various different angles and photographed in varying light conditions. The end result is a series of exposures for each light direction, which can then be integrated on a PC to produce high-resolution HDR images. A vehicle designer can then combine the image data with the computer model of a car seat and observe the material's behavior when lit from any angle. There are already similar processes that use multiple cameras and considerably more light sources, but working with the equipment developed by Fraunhofer IGD is both simpler and faster. Within the period of just ten minutes, a new material can be scanned and translated to a virtual model.
The meso scanner captures images of small three-dimensional objects. Conventional 3-D scanners project a relatively coarse pattern of stripes onto an object and the software infers the three-dimensional shape from the distortion of the stripes. This innovative new scanner instead projects a much more detailed pattern of black and white stripes onto the object, each of which is just about a third of a millimeter or so across. Using a special lens in front of the projector, this pattern is moved across the object with sub-pixel accuracy, which is to say it is shifted in individual steps of 1/25 of a pixel or less. This means that the object is scanned in much greater detail than before, achieving high resolution. Any hollows or wrinkles can be recorded with a depth measurement which has an accuracy of around 30 micrometers -- which is two to three times more accurate than without the lens-shifting system.
As Ritz points out, "The meso scanner isn't just interesting for car development. There's also scope for museums to use it to scan rare exhibits such as jewelry or coins with high precision." Another possible application for the device would be in the computer gaming industry. Researchers will be showcasing the initial prototypes of the new scanners at the booth of the Fraunhofer Additive Manufacturing Alliance at the Euromold trade fair from November 29 to December 2, 2011 in Frankfurt am Main.
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The above story is reprinted from materials provided by Fraunhofer-Gesellschaft.
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http://www.sciencedaily.com/releases/2011/11/111107121442.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
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« Reply #38 on Nov 15, 2011, 3:23pm » | |
Secrets of Tunneling Through Energy Barriers: How Massless Electrons Tunnel Through Energy Barriers in a Carbon Sheet Called Graphene
ScienceDaily (Nov. 7, 2011) — Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics Andre Geim and Konstantin Novoselov, who performed transport experiments on this one-carbon-atom-thick material. A review article, just published in The European Physical Journal B, explores the theoretical and experimental results to date of electrons tunneling through energy barriers in graphene.
As good an electrical conductor at room temperature as copper graphene is, it also outperforms all other known materials as a heat conductor. It is both very dense due to its honeycomb lattice structure and almost completely transparent, making it suitable, among other applications, for touch screens and light panels.
What could partly explain graphene's properties is that electrons travelling inside the material behave as if they were massless. Their behavior is described by the so-called massless Dirac equation that is normally used for high-energy particles such as neutrinos nearing the speed of light. However, electrons in graphene move at a constant speed 300 times smaller than that of light.
In this review, P.E. Allain and J.N. Fuchs, both from the Université Paris-Sud, focus on the tunneling effect occurring when Dirac electrons found in graphene are transmitted through different types of energy barriers. Contrary to the laws of classical mechanics, which govern larger scale particles that cannot cross energy barriers, electron tunneling is possible in quantum mechanics -- though only under restricted conditions, depending on the width and energy height of the barrier.
However, the Dirac electrons found in graphene can tunnel through energy barriers regardless of their width and energy height; a phenomenon called Klein tunneling, described theoretically for 3D massive Dirac electrons by the Swedish physicist Oskar Klein in 1929. Graphene was the first material in which Klein tunneling was observed experimentally, as massive Dirac electrons required energy barriers too large to be observed.
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The above story is reprinted from materials provided by Springer Science+Business Media.
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Journal Reference:
1. P. E. Allain, J. N. Fuchs. Klein tunneling in graphene: optics with massless electrons. The European Physical Journal B, 2011; 83 (3): 301 DOI: 10.1140/epjb/e2011-20351-3
http://www.sciencedaily.com/releases/2011/11/111107155410.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #39 on Nov 15, 2011, 3:28pm » | |
Incredible Shrinking Material: Engineers Reveal How Scandium Trifluoride Contracts With Heat
![[image]](http://img192.imageshack.us/img192/9431/1111071619558645302.jpg "[image]")
Heat causes the atoms in ScF3 to vibrate, as captured in this snapshot from a simulation. Fluorine atoms are in green while scandium atoms are in yellow. Click here for the video of the simulation: http://www.youtube.com/user/caltech#p/u/0/l46Kgm5u3Nw (Credit: Caltech/C. Li et al.)
ScienceDaily (Nov. 7, 2011) — They shrink when you heat 'em. Most materials expand when heated, but a few contract. Now engineers at the California Institute of Technology (Caltech) have figured out how one of these curious materials, scandium trifluoride (ScF3), does the trick -- a finding, they say, that will lead to a deeper understanding of all kinds of materials.
The researchers, led by graduate student Chen Li, published their results in the November 4 issue of Physical Review Letters (PRL).
Materials that don't expand under heat aren't just an oddity. They're useful in a variety of applications -- in mechanical machines such as clocks, for example, that have to be extremely precise. Materials that contract could counteract the expansion of more conventional ones, helping devices remain stable even when the heat is on.
"When you heat a solid, most of the heat goes into the vibrations of the atoms," explains Brent Fultz, professor of materials science and applied physics and a coauthor of the paper. In normal materials, this vibration causes atoms to move apart and the material to expand. A few of the known shrinking materials, however, have unique crystal structures that cause them to contract when heated, a property called negative thermal expansion. But because these crystal structures are complicated, scientists have not been able to clearly see how heat -- in the form of atomic vibrations -- could lead to contraction.
But in 2010 researchers discovered negative thermal expansion in ScF3, a powdery substance with a relatively simple crystal structure. To figure out how its atoms vibrated under heat, Li, Fultz, and their colleagues used a computer to simulate each atom's quantum behavior. The team also probed the material's properties by blasting it with neutrons at the Spallation Neutron Source at Oak Ridge National Laboratory (ORNL) in Tennessee; by measuring the angles and speeds with which the neutrons scattered off the atoms in the crystal lattice, the team could study the atoms' vibrations. The more the material is heated the more it contracts, so by doing this scattering experiment at increasing temperatures, the team learned how the vibrations changed as the material shrank.
The results paint a clear picture of how the material shrinks, the researchers say. You can imagine the bound scandium and fluorine atoms as balls attached to one another with springs. The lighter fluorine atom is linked to two heavier scandium atoms on opposite sides. As the temperature is cranked up, all the atoms jiggle in many directions. But because of the linear arrangement of the fluorine and two scandiums, the fluorine vibrates more in directions perpendicular to the springs. With every shake, the fluorine pulls the scandium atoms toward each other. Since this happens throughout the material, the entire structure shrinks.
The surprise, the researchers say, was that in the large fluorine vibrations, the energy in the springs is proportional to the atom's displacement -- how far the atom moves while shaking -- raised to the fourth power, a behavior known as a quartic oscillation. Most materials are dominated by quadratic (or harmonic) oscillations -- characteristic of the typical back-and-forth motion of springs and pendulums -- in which the stored energy is proportional to the square of the displacement.
"A nearly pure quantum quartic oscillator has never been seen in atom vibrations in crystals," Fultz says. Many materials have a little bit of quartic behavior, he explains, but their quartic tendencies are pretty small. In the case of ScF3, however, the team observed the quartic behavior very clearly. "A pure quartic oscillator is a lot of fun," he says. "Now that we've found a case that's very pure, I think we know where to look for it in many other materials." Understanding quartic oscillator behavior will help engineers design materials with unusual thermal properties. "In my opinion," Fultz says, "that will be the biggest long-term impact of this work."
The other authors of the PRL paper, "The structural relationship between negative thermal expansion and quartic anharmonicity of cubic ScF3," are former Caltech postdoctoral scholars Xiaoli Tang and J. Brandon Keith; Caltech graduate students Jorge Muñoz and Sally Tracy; and Doug Abernathy of ORNL. The research was supported by the Department of Energy.
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The above story is reprinted from materials provided by California Institute of Technology. The original article was written by Marcus Woo.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
http://www.sciencedaily.com/releases/2011/11/111107161955.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #40 on Nov 15, 2011, 3:30pm » | |
Chemists Develop Compounds Capable of Forming Heat-Resistant, Economic and Biocompatible Gels
ScienceDaily (Nov. 9, 2011) — Eating a yogurt or a jelly, using a pharmaceutical or cosmetic cream or shampoo... are just some of the numerous everyday actions in which we use gels developed through a process of gelation. Researchers from Universitat Jaume I have patented a new family of compounds that enables to develop gels more resistant to high temperatures with a higher level of biocompatibility and able to work with a variety of organic solvents, and all this with an easy synthesis, scalable and low cost.
This family of compounds has significant applications in industries such as pharmaceuticals and cosmetics or food industry, among others.
A jellifying agent is a substance that when is added to a liquid, transforms it into ice. When the liquid used is water, it is called hydrogel. But if the solvents used are organic compounds, they use organojellifying compounds such as the developed by the group Sustainable chemistry: supported reactants and catalysts. Supramolecular chemistry from the UJI, led by the chair professor Santiago Luis. 'Normally, when we develop a compound or family compounds able to form organogels, they only act in such a way in a very small number of solvents. The fundamental difference is that our group of compounds is capable of forming gels with a very high range of solvents', the researcher explains.
Another contribution of the compound is its ability to maintain stability at temperatures up to 100° C, thus allowing the products to keep their properties. In addition, the basic chemical structures that form compounds are amino acids, which provide products that are in most cases biocompatible. 'As they have units easily acceptable by the biological world, they don't have incompatibility, allergies or toxicities problems," Santiago Luis stresses.
To all these advantages, we have to add the fact that these compounds with a jellifying action at low concentrations are cheap.
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http://www.sciencedaily.com/releases/2011/11/111109093727.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #41 on Nov 15, 2011, 3:41pm » | |
New Hybrid Detector Monitors Alpha, Beta, and Gamma Radiation Simultaneously
ScienceDaily (Nov. 8, 2011) — By combining three layers of detection into one new device, a team of researchers from Japan has proposed a new way to monitor radiation levels at power plant accident sites. The device would be more economical that using different devices to measure different types of radiation, and could limit the exposure times of clean-up workers by taking three measurements simultaneously.
Radioactive decay produces three flavors of emissions: alpha, beta, and gamma. Alpha particles comprise 2 neutrons and 2 protons. Because of their large mass and relatively slow speed, alpha particles are the least penetrating of the three types of radiation, and can be stopped by a sheet of paper. Beta particles are electrons that can travel farther than alpha particles, but not as far as high-energy gamma photons, the third type of radiation.
The researchers took advantage of the different penetrating properties of the three types of radiation to design their device. Their new radiation detector has three scintillators, which are sheets of material that light up when hit by radiation. Alpha particles strike only the first scintillator, beta particles travel on to the second scintillator, and gamma photons make it all the way through to the third scintillator. The scintillators were then coupled to a photomultiplier tube, a device that converts the light pulses into electrical current.
Because the shape of a light pulse differs depending on which type of radiation produced it (alpha particles produce sharp peaks, gamma particles more broad pulses), the device could distinguish between the different radiation types and produce counts for all three simultaneously. The new device could be used for a range of applications in which scientists might need to determine the types of radioactive material present, the researchers write.
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Journal Reference:
1. Seiichi Yamamoto, Jun Hatazawa. Development of an alpha/beta/gamma detector for radiation monitoring. Review of Scientific Instruments, 2011; (accepted)
http://www.sciencedaily.com/releases/2011/11/111108201548.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #42 on Nov 15, 2011, 3:48pm » | |
Can Metals Remember Their Shape at Nanoscale, Too?
ScienceDaily (Nov. 8, 2011) — University of Constance physicists Daniel Mutter and Peter Nielaba have visualised changes in shape memory materials down to the nanometric scale in an article about to be published in the European Physical Journal B.
Metallic alloys can be stretched or compressed in such a way that they stay deformed once the strain on the material has been released. Only shape memory alloys, however, can return to their original shape after being heated above a specific temperature.
For the first time, the authors determine the absolute values of temperatures at which shape memory nanospheres start changing back to their memorised shape -- undergoing so-called structural phase transition, which depends on the size of particles studied. To achieve this result, they performed a computer simulation using nanoparticles with diameters between 4 and 17 nm made of an alloy of equal proportions of nickel and titanium.
To date, research efforts to establish structural phase transition temperature have mainly been experimental. Thanks to a computerised method known as molecular dynamics simulation, the authors were able to visualise the transformation process of the material during the transition. As the temperature increased, they showed that the material's atomic-scale crystal structure shifted from a lower to a higher level of symmetry. They found that the strong influence of the energy difference between the low- and high-symmetry structure at the surface of the nanoparticle, which differed from that in its interior, could explain the transition.
Most of the prior work on shape memory materials was in macroscopic scale systems and used for applications such as dental braces, stents or oil temperature-regulating devices for bullet trains. Potential new applications include the creation of nanoswitches, where laser irradiation could heat up such shape memory material, triggering a change in its length that would, in turn, function as a switch.
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Journal Reference:
1. D. Mutter, P. Nielaba. Simulation of the thermally induced austenitic phase transition in NiTi nanoparticles. The European Physical Journal B, 2011; DOI: 10.1140/epjb/e2011-20661-4
http://www.sciencedaily.com/releases/2011/11/111108104623.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #43 on Nov 15, 2011, 3:50pm » | |
Fundamental Discovery Casts Enzymes in New Light
ScienceDaily (Nov. 9, 2011) — A tree outside Oak Ridge National Laboratory researcher Pratul Agarwal's office window provided the inspiration for a discovery that may ultimately lead to drugs with fewer side effects, less expensive biofuels and more.
Just as a breeze causes leaves, branches and ultimately the tree to move, enzymes moving at the molecular level perform hundreds of chemical processes that have a ripple effect necessary for life. Previously, protein complexes were viewed as static entities with biological function understood in terms of direct interactions, but that isn't the case. This finding, recently published in PLoS Biology, may have enormous implications.
"Our discovery is allowing us to perhaps find the knobs that we can use to improve the catalytic rate of enzymes and perform a host of functions more efficiently," said Agarwal, a member of the Department of Energy laboratory's Computer Science and Mathematics Division.
Making this discovery possible was ORNL's supercomputer, Jaguar, which allowed Agarwal and co-author Arvind Ramanathan to investigate a large number of enzymes at the atomistic scale.
The researchers found that enzymes have similar features that are entirely preserved from the smallest living organism -- bacteria -- to complex life forms, including humans.
"If something is important for function, then it will be present in the protein performing the same function across different species," Agarwal said. "For example, regardless of which company makes a car, they all have wheels and brakes."
Similarly, scientists have known for decades that certain structural features of the enzyme are also preserved because of their important function. Agarwal and Ramanathan believe the same is true for enzyme flexibility.
"The importance of the structure of enzymes has been known for more than 100 years, but only recently have we started to understand that the internal motions may be the missing piece of the puzzle to understand how enzymes work," Agarwal said. "If we think of the tree as the model, the protein move at the molecular level with the side-chain and residues being the leaves and the protein backbone being the entire stem."
This research builds on previous work in which Agarwal identified a network of protein vibrations in the enzyme Cyclphilin A, which is involved in many biological reactions, including AIDS-causing HIV-1.
While Agarwal sees this research perhaps leading to medicines able to target hard to cure diseases such as AIDS, he is also excited about its energy applications, specifically in the area of cellulosic ethanol. Highly efficient enzymes could bring down the cost of biofuels, making them a more attractive option.
Funding for this research was provided by ORNL's Laboratory Directed Research and Development program. Ramanathan was a graduate student at Carnegie Mellon University when this work began and now also works at ORNL. The paper is titled "Evolutionarily conserved linkage between enzyme fold, flexibility and catalysis."
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The above story is reprinted from materials provided by DOE/Oak Ridge National Laboratory.
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Journal Reference:
1. Arvind Ramanathan, Pratul K. Agarwal. Evolutionarily Conserved Linkage between Enzyme Fold, Flexibility, and Catalysis. PLoS Biology, 2011; 9 (11): e1001193 DOI: 10.1371/journal.pbio.1001193
http://www.sciencedaily.com/releases/2011/11/111109093941.htm
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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| | Re: New Millenium Technology VIII
« Reply #44 on Nov 15, 2011, 3:52pm » | |
New Process for Making Non-Sticky, Biodegradable Chewing Gum Developed
ScienceDaily (Nov. 8, 2011) — We find it on chairs, stuck under desks, on pavements or stuck to our shoes. Chewing gum is sticky -- and it does not degrade easily. This leads to increased cleaning costs for our local authorities. However, Professor Elke Arendt of University College Cork has developed a novel process for creating biodegradable chewing gum. She is looking for companies who might be interested in commercialising the product.
Chewing gum is made from synthetic rubber, softeners, sweeteners and flavourings. Synthetic rubbers are stretchy, have strong adhesive properties and are resistant to many chemicals used for cleaning. Reducing the stickiness of chewing gum requires a change in the chemical structure of its rubber base. However, the rubber base also determines commercially important features such as flavour, chewiness and shelf- life. The challenge for the food industry is to develop a non-sticky, chewy biodegradable gum with all the flavour of conventional gum.
Professor Arendt and her research team at the School of Food and Nutritional Sciences, University College Cork have responded to this challenge by providing the industry with a novel process for the development of biodegradable chewing gum, using cereal proteins as the main ingredients. These natural proteins are modified using technologies and ingredients that increase the elasticity of the cereal proteins so that they can be used as a base material for the production of chewing gum. The technology has been patented and UCC is looking for companies to commercialise the product. The work for this project was funded by the Department of Agriculture, Food and Forestry under the FIRM program.
The original idea came from other research work of Professor Arendt in the area of gluten-free cereal products, where the wheat needs to be replaced by other proteins with visco-elastic properties.
Professor Arendt is a senior member of staff in the School of Food and Nutritional Sciences at UCC and her research is in the area of cereal and brewing science. She has been leading the field of gluten free research worldwide for the last 10 years. Currently Professor Arendt has a research team of 20 researchers and PhD students.
Story Source:
The above story is reprinted from materials provided by University College Cork, via AlphaGalileo.
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http://www.sciencedaily.com/releases/2011/11/111108125407.htm
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