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A little disorder goes a long way, especially when it comes to harnessing the sun's energy. Scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) jumbled the atomic structure of the surface layer of titanium dioxide nanocrystals, creating a catalyst that is both long lasting and more efficient than all other materials in using the sun's energy to extract hydrogen from water.

Their photocatalyst, which accelerates light-driven chemical reactions, is the first to combine durability and record-breaking efficiency, making it a contender for use in several clean-energy technologies.

It could offer a pollution-free way to produce hydrogen for use as an energy carrier in fuel cells. Fuel cells have been eyed as an alternative to combustion engines in vehicles. Molecular hydrogen, however, exists naturally on Earth only in very low concentrations. It must be extracted from feedstocks such as natural gas or water, an energy-intensive process that is one of the barriers to the widespread implementation of the technology.

"We are trying to find better ways to generate hydrogen from water using sunshine," says Samuel Mao, a scientist in Berkeley Lab's Environmental Energy Technologies Division who led the research. "In this work, we introduced disorder in titanium dioxide nanocrystals, which greatly improves its light absorption ability and efficiency in producing hydrogen from water."

Mao is the corresponding author of a paper on this research that was published online Jan. 20, 2011 in Science Express with the title "Increasing Solar Absorption for Photocatalysis with Black, Hydrogenated Titanium Dioxide Nanocrystals." Co-authoring the paper with Mao are fellow Berkeley Lab researchers Xiaobo Chen, Lei Liu, and Peter Yu.

Mao and his research group started with nanocrystals of titanium dioxide, which is a semiconductor material that is used as a photocatalyst to accelerate chemical reactions, such as harnessing energy from the sun to supply electrons that split water into oxygen and hydrogen. Although durable, titanium dioxide isn't a very efficient photocatlayst. Scientists have worked to increase its efficiency by adding impurities and making other modifications.

The Berkeley Lab scientists tried a new approach. In addition to adding impurities, they engineered disorder into the ordinarily perfect atom-by-atom lattice structure of the surface layer of titanium dioxide nanocrystals. This disorder was introduced via hydrogenation.

The result is the first disorder-engineered nanocrystal. One transformation was obvious: the usually white titanium dioxide nanocrystals turned black, a sign that engineered disorder yielded infrared absorption.

The scientists also surmised disorder boosted the photocatalyst's performance. To find out if their hunch was correct, they immersed disorder-engineered nanocrystals in water and exposed them to simulated sunlight. They found that 24 percent of the sunlight absorbed by the photocatalyst was converted into hydrogen, a production rate that is about 100 times greater than the yields of most semiconductor photocatalysts.

In addition, their photocatalyst did not show any signs of degradation during a 22-day testing period, meaning it is potentially durable enough for real-world use.

Its landmark efficiency stems largely from the photocatalyst's ability to absorb infrared light, making it the first titanium dioxide photocatalyst to absorb light in this wavelength. It also absorbs visible and ultraviolet light. In contrast, most titanium dioxide photocatalysts only absorbs ultraviolet light, and those containing defects may absorb visible light. Ultraviolet light accounts for less than ten percent of solar energy.

"The more energy from the sun that can be absorbed by a photocatalyst, the more electrons can be supplied to a chemical reaction, which makes black titanium dioxide a very attractive material," says Mao, who is also an adjunct engineering professor in the University of California at Berkeley.

The team's intriguing experimental findings were further elucidated by theoretical physicists Peter Yu and Lei Liu, who explored how jumbling the latticework of atoms on the nanocrystal's surface via hydrogenation changes its electronic properties. Their calculations revealed that disorder, in the form of lattice defects and hydrogen, makes it possible for incoming photons to excite electrons, which then jump across a gap where no electron states can exist. Once across this gap, the electrons are free to energize the chemical reaction that splits water into hydrogen and oxygen.

"By introducing a specific kind of disorder, mid-gap electronic states are created accompanied by a reduced band gap," says Yu, who is also a professor in the University of California at Berkeley's Physics Department. "This makes it possible for the infrared part of the solar spectrum to be absorbed and contribute to the photocatalysis."

This research was supported by the Department of Energy's Office of Energy Efficiency and Renewable Energy. Transmission electron microscopy imaging used to study the nanocrystals at the atomic scale was performed at the National Center for Electron Microscopy, a national user facility located at Berkeley Lab.

Source: ScienceDaily

 
By Admin (from 14/03/2011 @ 14:00:47, in en - Science and Society, read 1694 times)

Light-emitting diodes (LEDs) are an increasingly popular technology for use in energy-efficient lighting. Researchers from North Carolina State University have now developed a new technique that reduces defects in the gallium nitride (GaN) films used to create LEDs, making them more efficient.

LED lighting relies on GaN thin films to create the diode structure that produces light. The new technique reduces the number of defects in those films by two to three orders of magnitude. “This improves the quality of the material that emits light,” says Dr. Salah Bedair, a professor of electrical and computer engineering at NC State and co-author, with NC State materials science professor Nadia El-Masry, of a paper describing the research. “So, for a given input of electrical power, the output of light can be increased by a factor of two – which is very big.” This is particularly true for low electrical power input and for LEDs emitting in the ultraviolet range.

The researchers started with a GaN film that was two microns, or two millionths of a meter, thick and embedded half of that thickness with large voids – empty spaces that were one to two microns long and 0.25 microns in diameter. The researchers found that defects in the film were drawn to the voids and became trapped – leaving the portions of the film above the voids with far fewer defects.

Defects are slight dislocations in the crystalline structure of the GaN films. These dislocations run through the material until they reach the surface. By placing voids in the film, the researchers effectively placed a “surface” in the middle of the material, preventing the defects from traveling through the rest of the film.

The voids make an impressive difference.

“Without voids, the GaN films have approximately 10[to the 10th power] defects per square centimeter,” Bedair says. “With the voids, they have 10[to the 7th power] defects. This technique would add an extra step to the manufacturing process for LEDs,  but it would result in higher quality, more efficient LEDs.”

The paper, “Embedded voids approach for low defect density in epitaxial GaN films,” was published online Jan. 17 by Applied Physics Letters. The paper was co-authored by Bedair; Pavel Frajtag, a Ph.D. student at NC State; Dr. Nadia El-Masry, a professor of material science and engineering at NC State; and Dr. N. Nepal, a former post-doctoral researcher at NC State now working at the Naval Research Laboratory. The research was funded by the U.S. Army Research Office.

Source: NCSU News

 
By Admin (from 13/03/2011 @ 11:00:22, in en - Science and Society, read 1985 times)

An ant colony is the last place you'd expect to find a maths whiz, but University of Sydney researchers have shown that the humble ant is capable of solving difficult mathematical problems.

These findings, published in the Journal of Experimental Biology, deepen our understanding of how even simple animals can overcome complex and dynamic problems in nature, and will help computer scientists develop even better software to solve logistical problems and maximise efficiency in many human industries.

Using a novel technique, Chris Reid and Associate Professor Madeleine Beekman from the School of Biological Sciences, working with Professor David Sumpter of Uppsala University, Sweden, tested whether Argentine ants (Linepithema humile) could solve a dynamic optimisation problem by converting the classic Towers of Hanoi maths puzzle into a maze.

Finding the most efficient path through a busy network is a common challenge faced by delivery drivers, telephone routers and engineers. To solve these optimisation problems using software, computer scientists have often sought inspiration from ant colonies in nature - creating algorithms that simulate the behaviour of ants who find the most efficient routes from their nests to food sources by following each other's volatile pheromone trails. The most widely used of these ant-inspired algorithms is known as Ant Colony Optimisation (ACO).

"Although inspired by nature, these computer algorithms often do not represent the real world because they are static and designed to solve a single, unchanging problem," says lead author Chris Reid, a doctoral student from the Behaviour and Genetics of Social Insects Laboratory.

"But nature is full of unpredictability and one solution does not fit all. So we turned to ants to see how well their problem solving skills respond to change. Are they fixed to a single solution or can they adapt?"

The researchers tested the ants using the three-rod, three-disk version of the Towers of Hanoi problem - a toy puzzle that requires players to move disks between rods while obeying certain rules and using the fewest possible moves. But since ants cannot move disks, the researchers converted the puzzle into a maze where the shortest path corresponds to the solution with fewest moves in the toy puzzle. The ants at the entry point of the maze could chose between 32,768 possible paths to get to the food source on the other side, with only two of the paths being the shortest path and thus the optimal solution.

The ants were given one hour to solve the maze by creating a high traffic path between their nest and the food source, after which time the researchers blocked off paths and opened up new areas of the maze to test the ants' dynamic problem solving ability.

After an hour, the ants solved the Towers of Hanoi by finding the shortest path around the edge of the maze. But when that path was blocked off, the ants responded first by curving their original path around the obstacle and establishing a longer, suboptimal, route. But after a further hour, the ants had successfully resolved the maze by abandoning their suboptimal route and establishing a path that traversed through the centre of the maze on the new optimal route.

But not all the colonies' problem solving skills were equal: ants that were allowed to explore the maze without food for an hour prior to the test made fewer mistakes and were faster at resolving the maze compared to the ants that were naive. This result suggests that the "exploratory pheromone" laid down by ants searching a new territory is key in helping them adapt to changing conditions.

"Even simple mass-recruiting ants have much more complex and labile problem solving skills than we ever thought. Contrary to previous belief, the pheromone system of ants does not mean they get stuck in a particular path and can't adapt. Having at least two separate pheromones gives them much more flexibility and helps them to find good solutions in a changing environment. Discovering how ants are able to solve dynamic problems can provide new inspiration for optimisation algorithms, which in turn can lead to better problem-solving software and hence more efficiency for human industries."

Source: PhysOrg

 
By Admin (from 12/03/2011 @ 11:00:27, in en - Science and Society, read 1611 times)

Physicists are closer than ever to finding the source of the Universe's mysterious dark matter, following a better than expected year of research at the Compact Muon Solenoid (CMS) particle detector, part of the Large Hadron Collider (LHC) at CERN in Geneva.

The scientists have now carried out the first full run of experiments that smash protons together at almost the speed of light. When these sub-atomic particles collide at the heart of the CMS detector, the resultant energies and densities are similar to those that were present in the first instants of the Universe, immediately after the Big Bang some 13.7 billion years ago. The unique conditions created by these collisions can lead to the production of new particles that would have existed in those early instants and have since disappeared.

The researchers say they are well on their way to being able to either confirm or rule out one of the primary theories that could solve many of the outstanding questions of particle physics, known as Supersymmetry (SUSY). Many hope it could be a valid extension for the Standard Model of particle physics, which describes the interactions of known subatomic particles with astonishing precision but fails to incorporate general relativity, dark matter and dark energy.

Dark matter is an invisible substance that we cannot detect directly but whose presence is inferred from the rotation of galaxies. Physicists believe that it makes up about a quarter of the mass of the Universe whilst the ordinary and visible matter only makes up about 5% of the mass of the Universe. Its composition is a mystery, leading to intriguing possibilities of hitherto undiscovered physics.

Professor Geoff Hall from the Department of Physics at Imperial College London, who works on the CMS experiment, said: "We have made an important step forward in the hunt for dark matter, although no discovery has yet been made. These results have come faster than we expected because the LHC and CMS ran better last year than we dared hope and we are now very optimistic about the prospects of pinning down Supersymmetry in the next few years."

The energy released in proton-proton collisions in CMS manifests itself as particles that fly away in all directions. Most collisions produce known particles but, on rare occasions, new ones may be produced, including those predicted by SUSY – known as supersymmetric particles, or 'sparticles'. The lightest sparticle is a natural candidate for dark matter as it is stable and CMS would only 'see' these objects through an absence of their signal in the detector, leading to an imbalance of energy and momentum.

In order to search for sparticles, CMS looks for collisions that produce two or more high-energy 'jets' (bunches of particles travelling in approximately the same direction) and significant missing energy.

Dr Oliver Buchmueller, also from the Department of Physics at Imperial College London, but who is based at CERN, explained: "We need a good understanding of the ordinary collisions so that we can recognise the unusual ones when they happen. Such collisions are rare but can be produced by known physics. We examined some 3 trillion proton-proton collisions and found 13 'SUSY-like' ones, around the number that we expected. Although no evidence for sparticles was found, this measurement narrows down the area for the search for dark matter significantly."

The physicists are now looking forward to the 2011 run of the LHC and CMS, which is expected to bring in data that could confirm Supersymmetry as an explanation for dark matter.

The CMS experiment is one of two general purpose experiments designed to collect data from the LHC, along with ATLAS (A Toroidal LHC ApparatuS). Imperial’s High Energy Physics Group has played a major role in the design and construction of CMS and now many of the members are working on the mission to find new particles, including the elusive Higgs boson particle (if it exists), and solve some of the mysteries of nature, such as where mass comes from, why there is no anti-matter in our Universe and whether there are more than three spatial dimensions.

Source: PhysOrg - More Info at: CMS

 

The mechanism that controls the internal 24-hour clock of all forms of life from human cells to algae has been identified by scientists.

Not only does the research provide important insight into health-related problems linked to individuals with disrupted clocks – such as pilots and shift workers – it also indicates that the 24-hour circadian clock found in human cells is the same as that found in algae and dates back millions of years to early life on Earth.

Two new studies out today in the journal Nature from the Universities of Cambridge and Edinburgh give insight into the circadian clock which controls patterns of daily and seasonal activity, from sleep cycles to butterfly migrations to flower opening.

One study, from the University of Cambridge's Institute of Metabolic Science, has for the first time identified 24-hour rhythms in red blood cells. This is significant because circadian rhythms have always been assumed to be linked to DNA and gene activity, but – unlike most of the other cells in the body – red blood cells do not have DNA.

Akhilesh Reddy, from the University of Cambridge and lead author of the study, said: "We know that clocks exist in all our cells; they're hard-wired into the cell. Imagine what we'd be like without a clock to guide us through our days. The cell would be in the same position if it didn't have a clock to coordinate its daily activities.

"The implications of this for health are manifold. We already know that disrupted clocks – for example, caused by shift-work and jet-lag – are associated with metabolic disorders such as diabetes, mental health problems and even cancer. By furthering our knowledge of how the 24-hour clock in cells works, we hope that the links to these disorders – and others – will be made clearer. This will, in the longer term, lead to new therapies that we couldn't even have thought about a couple of years ago."

For the study, the scientists, funded by the Wellcome Trust, incubated purified red blood cells from healthy volunteers in the dark and at body temperature, and sampled them at regular intervals for several days. They then examined the levels of biochemical markers – proteins called peroxiredoxins – that are produced in high levels in blood and found that they underwent a 24-hour cycle. Peroxiredoxins are found in virtually all known organisms.

A further study, by scientists working together at the Universities of Edinburgh and Cambridge, and the Observatoire Oceanologique in Banyuls, France, found a similar 24-hour cycle in marine algae, indicating that internal body clocks have always been important, even for ancient forms of life.

The researchers in this study found the rhythms by sampling the peroxiredoxins in algae at regular intervals over several days. When the algae were kept in darkness, their DNA was no longer active, but the algae kept their circadian clocks ticking without active genes. Scientists had thought that the circadian clock was driven by gene activity, but both the algae and the red blood cells kept time without it.

Andrew Millar of the University of Edinburgh's School of Biological Sciences, who led the study, said: "This groundbreaking research shows that body clocks are ancient mechanisms that have stayed with us through a billion years of evolution. They must be far more important and sophisticated than we previously realised. More work is needed to determine how and why these clocks developed in people – and most likely all other living things on earth – and what role they play in controlling our bodies."

Source: PhysOrg

 
By Admin (from 10/03/2011 @ 08:00:14, in en - Science and Society, read 1611 times)

We have seen some beautifull new designs for future cities over the last few years.And these images from Russian architectural firm Remistudio are nothing less than amazing. Remistudio has designed a massive hotel concept that can be erected at land or sea, is completely self sustaining and is able to endure extreme floods.

The arch-shaped building, dubbed the Ark, has a structure that enables it to float and exist autonomously on the surface of the water. The Ark was also designed to be a bioclimatic house with independent life-support systems, including elements ensuring a closed-functioning cycle.

The Ark concept, which Remistudio designed in connection with the International Union of Architects’ program “Architecture for Disaster Relief,” can be built in various climates and in seismically dangerous regions because its basement is a shell structure, devoid of ledges or angles. A load-bearing system of arches and cables allows weight redistribution along the entire corpus in case of an earthquake. The building’s clever design enables an optimal relationship between its volume and its outer surface, significantly saving materials and providing energy efficiency. Its prefabricated frame also allows for fast construction.

The Ark constitutes a single energy system. Its shape is convenient for installing photovoltaic cells at an optimal angle toward the sun. The cupola, in the upper part, collects warm air which is gathered in seasonal heat accumulators to provide an uninterrupted energy supply for the whole complex independently from outer environmental conditions. The heat from the surrounding environment — the outer air, water or ground — is also used.

Alexander Remizov, of Remistudio, said: 'For architecture there are two major concerns.  "The first is maintenance of security and precautions against extreme environmental conditions and climate changes. The second one is protection of natural environment from human activities. The Ark is an attempt to answer the challenges of our time. Provision is made for an independent life support system. 'All the plants are chosen according to compatibility, illumination and efficiency of oxygen producing, and with the aim of creating an attractive and comfort space. Through the transparent roof there is enough light for plants and for illuminating the inner rooms."

Source: Inhabitat

 

Scientists from the University of Amsterdam (UvA) have developed a process for making fully biodegradable, non-toxic and non-hazardous thermoset resins from readily available, low-cost plant materials.

It's hoped that this new range of plastics could be used for panels such as MDF in the construction industry and replace polyurethane and polystyrene packaging... all without increasing cost or production times.

Most of the plastic products used in domestic products and the construction industry are thermosetting plastics; polymer materials that irreversibly cure.

They are made of three-dimensional networks of cross-linked polymers. Bakelite resin, produced from the reaction of phenol with formaldehyde, is one example, and the material is still used to bind wood fibers in pressed wood such as medium density fiberboard (MDF) and formica. Synthetic resins are also widely used in the construction industry for example in Medium Density Overlay (MDO), a combination of concrete and plywood, used in concrete molds.

Modern synthetic resins have a lot of negatives: they are made from diminishing fossil sources, are not biodegradable and can only be burned under strict conditions because they release toxic substances.

However, by combining plant materials and specific process conditions Professor Gadi Rothenberg and Dr. Albert Alberts of the University of Amsterdam's (UvA) Heterogeneous Catalysis and Sustainable Chemistry research group, have created a selection of bio-plastics ranging from hard foam material to flexible thin sheet materials.

Production time is comparable to current thermosetting processes, and the research team believe they can compete with existing plastics on price, but will need to manufacture on a larger scale to be certain.

A major plus is the availability and affordability of raw materials. Any plant materials can be used, for example grass, hay and trees.

Follow-up research will focus on new applications and process development and upscaling.

Source: GizMag

 
By Admin (from 07/03/2011 @ 14:00:35, in en - Science and Society, read 2085 times)

How do you use a scientific method to measure the intelligence of a human being, an animal, a machine or an extra-terrestrial? So far this has not been possible, but a team of Spanish and Australian researchers have taken a first step towards this by presenting the foundations to be used as a basis for this method in the journal Artificial Intelligence, and have also put forward a new intelligence test.

"We have developed an 'anytime' intelligence test, in other words a test that can be interrupted at any time, but that gives a more accurate idea of the intelligence of the test subject if there is a longer time available in which to carry it out", José Hernández-Orallo, a researcher at the Polytechnic University of Valencia (UPV), tells SINC.

This is just one of the many determining factors of the universal intelligence test. "The others are that it can be applied to any subject – whether biological or not – at any point in its development (child or adult, for example), for any system now or in the future, and with any level of intelligence or speed", points out Hernández-Orallo.

The researcher, along with his colleague David L. Dowe of the Monash University, Clayton (Australia), have suggested the use of mathematical and computational concepts in order to encompass all these conditions. The study has been published in the journal Artificial Intelligence and forms part of the "Anytime Universal Intelligence" project, in which other scientists from the UPV and the Complutense University of Madrid are taking part.

The authors have used interactive exercises in settings with a difficulty level estimated by calculating the so-called 'Kolmogorov complexity' (they measure the number of computational resources needed to describe an object or a piece of information). This makes them different from traditional psychometric tests and artificial intelligence tests (Turing test).

Use in artificial intelligence

The most direct application of this study is in the field of artificial intelligence. Until now there has not been any way of checking whether current systems are more intelligent than the ones in use 20 years ago, "but the existence of tests with these characteristics may make it possible to systematically evaluate the progress of this discipline", says Hernández-Orallo.

And what is even "more important" is that there were no theories or tools to evaluate and compare future intelligent systems that could demonstrate intelligence greater than human intelligence.

The implications of a universal intelligence test also impact on many other disciplines. This could have a significant impact on most cognitive sciences, since any discipline depends largely on the specific techniques and systems used in it and the mathematical basis that underpins it.

"The universal and unified evaluation of intelligence, be it human, non-human animal, artificial or extraterrestrial, has not been approached from a scientific viewpoint before, and this is a first step", the researcher concludes.

Source: PhysOrg

 
By Admin (from 03/03/2011 @ 10:00:31, in en - Science and Society, read 2295 times)

Southwest Windpower, maker of the Skystream 3.7, unveiled a new version of the popular turbine at CES 2011 called Skystream 600.  The turbine features an improved design with larger blades, enhanced software, and an improved integrated inverter.  And, according to a press release, Skystream 600 will be the “first fully smart grid-enabled wind turbine” on the market when available in April 2011.

With the improvements, Skystream 600 is estimated to produce about 74% more energy than Skystream 3.7.  The small wind turbine can provide an average of 7,400 kWh of energy per year in 12 mph average annual wind speeds.

These numbers are pretty good — about 60% of an average American’s home energy needs — but everything depends on siting, wind conditions, tower height, and several other factors.

Skystream 600 comes with the internet-accessible Skyview system showing users how much energy is produced in real time.  Southwest Windpower told Jetson Green in an email that the company has not yet decided on a price for the new turbine.

Source: JetsonGreen

 

Researchers have created a new aerogel that boasts amazing strength and an incredibly large surface area. Nicknamed ‘frozen smoke’ due to its translucent appearance, aerogels are manufactured materials derived from a gel in which the liquid component of the gel has been replaced with a gas, resulting in a material renowned as the world’s lightest solid material. The new so-called “multiwalled carbon nanotube (MCNT) aerogel” could be used in sensors to detect pollutants and toxic substances, chemical reactors, and electronics components.

Although aerogels have been fabricated from silica, metal oxides, polymers, and carbon-based materials and are already used in thermal insulation in windows and buildings, tennis racquets, sponges to clean up oil spills, and other products, few scientists have succeeded in making aerogels from carbon nanotubes.

The researchers were able to succeed where so many before them had failed using a wet gel of well-dispersed pristine MWCNTs. After removing the liquid component from the MWCNT wet gel, they were able to create the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm3.

MWCNT aerogels infused with a plastic material are flexible, like a spring that can be stretched thousands of times, and if the nanotubes in a one-ounce cube were unraveled and placed side-to-side and end-to-end, they would carpet three football fields. The MWCNT aerogels are also excellent conductors of electricity, which is what makes them ideal for sensing applications and offers great potential for their use in electronics components.

A report describing the process for making MWCNT aerogels and tests to determine their properties appears in ACS Nano.

Source: zeitnews

 
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