Science & Technology News (917)
Posted: May 22, 2015 05:21AM
Graphene is almost certainly going to be a wonder material of our time, with its amazing properties and many potential applications. Different applications pose different challenges for the material though. An example of this is polymer composites that contain graphene, but researchers at ORNL have found a solution to some of the problems.
The idea with polymer composites is to add flakes of graphene to the mix, so that they can add strength and conductivity. Graphene, despite being an atom-thick sheet of carbon, is exceedingly strong and tremendous electron mobility. When added to polymers though, the tiny flakes can clump together and not disperse correctly. The ORNL researchers' solution was to use chemical vapor deposition to create larger laminates of graphene. This resulted in the desired electrical conductance despite using only half as much graphene. Being large pieces, approximately two inches by two inches, the graphene also will not stick together.
Polymer composites with graphene could find many uses from aerospace and land vehicles to electronics and the energy sector. Before that can happen though, the researchers have to bring down costs and show the process can be scaled up, to meet manufacturing needs.
Source: Oak Ridge National Laboratory
Posted: May 21, 2015 02:37PM
Streaming and cloud services has become a popular solution for many people as a means to access media they otherwise would not be able to, at least not at the same quality or quantity. One problem with streaming content though is running into data caps, especially if someone is using a cloud gaming service. Researchers at Duke University, however, have deployed a technique that can significantly cut the data transmitted, without degrading quality.
The tool the researchers developed is named Kahawai, the Hawaiian word for stream, and what makes it special is collaborative rendering. Typical cloud gaming services work by doing all of the rendering on the remote servers, with the local client only being for display and input. Collaborative rendering splits the workload between the server and the local device, which could be a smartphone or tablet. While the finer details will still be rendered by the remote server, the local device still renders a rougher view for each frame, or a few highly detailed frames with the remote server filling in as needed. Either way, by having the local device do part of the work, the same visual quality can be achieved while cutting bandwidth down to one-sixth what current methods allow.
Another advantage over traditional streaming methods is that Kahawai can work offline by just showing the lower quality graphics the local device renders. While gaming is a logical place to start applying Kahawai, the researchers see it finding uses in other fields, such as medical imaging and CAD.
Source: Duke University
Posted: May 21, 2015 06:37AM
We may not realize it, because we cannot see it, but wireless congestion is an issue that limits rates and the number of users connecting to a single access point. It does not help matters that devices must transmit and receive on different channels. That may change soon though, thanks to researchers at the University of Bristol developing a duplexer small enough and cheap enough to integrate into phones.
The reason devices have to transmit and receive on different channels is because the emissions would interfere with each other if they were on the same frequency. A duplexer allows for the same frequency to be used by effectively removing this interference. The prototype made at Bristol suppressed the interference by a factor of over 100 million, all while using inexpensive and small components that can fit in mobile devices.
With this duplexer, filtering components could be removed from the devices, which would open up the possibility for unrestricted global roaming by allowing the devices to use any frequency band. This in turn could reduce costs as a single model could be manufactured for the entire world, and thus take advantage of the economics of scale.
Source: University of Bristol
Posted: May 20, 2015 02:29PM
Many of the devices we use every day rely on antennas, even though manufacturers have gotten quite good at hiding them. This achievement is actually not a little one as longer antennas can have desirable properties. As reported in the American Institute of Physics' Journal of Applied Physics, researchers at North Carolina State University have developed a tunable liquid antenna that may give us the best of both worlds.
The antenna in question is made of a liquid metal, which normally would require a pump to manipulate. Pumps are not exactly easy to integrate into devices like phones though, but the researchers have found an electrochemical solution that does the trick. When a voltage is applied to the liquid metal, the oxide layer on its surface is affected, which in turn impacts its surface tension. When a positive voltage is applied, the surface tensions weakens, allowing the liquid metal to flow into a capillary, lengthening the antenna, while a negative voltage does just the opposite. This allows the antenna's properties to be altered on the fly, such as increasing the range of frequencies it can operate over.
The next step for the researchers is to see what else they can do with this discovery. Potentially other tunable, liquid components could be made, such as filters, but they also want to see if more complicated shapes can be made, than one dimensional antennas.
Posted: May 20, 2015 05:22AM
Some believe that the future for some technologies will involve more directly linking them, and we already see something like this with television content that our phones can listen and react to. The trick for such a future is keeping this communication hidden from the viewer, or at least unobtrusive. Researchers at Dartmouth College have achieved just that, while still encoding information directly into the video displayed on screen.
Some attempts to encode data into video have been made before, but one does not necessarily want a QR code to appear on top of whatever they are watching. The Darthmouth researchers' solution, called HiLight, is to use the alpha channel of the image, so the information can be found in pixel translucency changes. This way the communication and screen content is separated, hiding it from the users, yet still allowing for real-time communication. Also, because it uses the visible part of the spectrum, there is not electromagnetic interference.
Source: Dartmouth College
Posted: May 19, 2015 02:43PM
For energy storage, most people think of batteries, but we may soon see some serious competition from supercapacitors. These energy storages systems are able to charge and discharge very quickly, can be flexible and cheap to make, and can even be safer to work with. Now researchers at Rice University have found a way to significantly increase the energy density of flexible microsupercapacitors made of graphene by adding boron to the mix.
Capacitors work by storing electrical charges on separated conductors, which allows them to charge up and release energy very rapidly. Supercapacitors bring with them higher energy capacities, similar to that of batteries, so one day they could see use in many applications where batteries now dominate. To create the microsupercapacitors they used, the Rice researchers used a laser to burn patterns into common polymers, resulting in the formation of a matrix of graphene flakes. From previous work they knew a commercial polyimide was the best choice, but this new study revealed that dissolving boric acid into polyamic acid, so that the polyimide sheet was boron infused, quadrupled the supercapacitor's storage capability.
With just a two-step process, the researchers are able to create microsupercapacitors with four times the storage ability and five to ten times the energy density of boron-free microsupercapacitors. Beyond that, the supercapacitors survived over 12,000 cycles while retaining 90% capacitance and after 8000 bending cycles, there was no performance loss. That flexibility could be an especially important aspect of this technique, by enabling industrial-scale roll-to-roll production.
Source: Rice University
Posted: May 19, 2015 05:49AM
Black silicon is a special form of silicon that has surface features that cause it to absorb much of the light that hits it, hence the name. Naturally there is interest in using it for solar cells and now researchers at Aalto University and Universitat Politècnica de Catalunya have set a new efficiency record of 22.1%.
To achieve this record the researchers used atomic vapor deposition to add a thin passivating film onto the black surface structures and by moving the metal contacts to the back of the cell. The film had the effect of limiting surface recombination, instead of it limiting the energized electrons that can be pulled away by the contacts for work. This is the first time the recombination issue of black silicon has been removed from such a system. Additional work may actually push the efficiency higher as the type of silicon used, p-type, is known to suffer from impurity-related degradation, so n-type silicon or more advanced cell structures could go even higher.
While the improved efficiency is definitely important and noteworthy, there is more to the operation of black solar cells than that. When tested against traditional solar cells of similar efficiency, the researchers found the black silicon cells generated more electricity because they are better at capturing light at low angles. This is important in northern areas, where the Sun shines at lower angles for a good portion of the year.
Source: Aalto University
Posted: May 18, 2015 02:28PM
Many people believe that 3D printing could lead to a revolution, as it allows for the efficient production of items, but it could also revolutionize medicine. Already we have seen 3D printers used to build a replacement windpipe for an infant, bow we could see it applied to repairing soft-tissue. Researchers at Technische Universitaet Muenchen have demonstrated that the 3D printing technique melt electrospinning writing could be used to build scaffolds that support human cartilage cells.
Attempts to build cartilage supporting scaffolds have been made before, but what makes this different is that melt electrospinning writing. It allows for filaments to be made just five micrometers in diameter. This produces the necessary stiffness while also being small enough for cells to grow around the hydrogel scaffolding.
Joint repair is one obvious use for this technology, but it could also be applied for heart tissue engineering and breast reconstruction. Naturally more study is needed before this is applied, but it is a very promising breakthrough.
Source: Technische Universitaet Muenchen
Posted: May 18, 2015 05:22AM
If you are reading this on a flatscreen display, like an LCD or OLED display, chances are you are staring through indium tin oxide (ITO) a transparent conductor. While ITO has the necessary transparency and conductivity, it is also expensive and fragile, so many are working on replacements. Among the possibilities are networks of nanowires, which are flexible and cheap as well as conductive and transparent, and now researchers at Lehigh University have made a discovery that should improve them.
The orientation of nanowires in the network is, as you would expect, very important to the network's properties. If you think that a network with strictly oriented nanowires would be the best conductor though, you would be wrong. The Lehigh researchers have built computers models of the networks and found that those with a degree of randomness are actually better conductors. The nanowires still need some restrictions on their orientation, but just the right amount will beat out heavily ordered networks.
To test the model, the researchers applied it to previously published papers, which is a common practice, and found that it accurately explains the results. This discovery could lead to improvements for many optoelectronic devices and flexible electronics.
Posted: May 15, 2015 02:28PM
Spin is a property of many particles and is at the heart of various technologies, but working with it can be challenging. Typically very powerful fields are necessary to measure it. That may be changing soon though, thanks to researchers at the Universities of Waterloo and Basel, and RWTH Aachen University.
One of the technologies that measures spin is Magnetic Resonance Imaging (MRI) or Nuclear Magnetic Resonance (NMR) and doing so takes very powerful magnets, with those in MRI machines actually being superconducting electromagnets. This is despite the fact that the spin of particles produces weak magnetic fields. Ideally weak fields could also be used to measure it, but because of the weakness and noise, this has been impossible until now. According to the researcher's work, a small ferromagnetic particle could amplify the weak field, allowing a nitrogen-vacancy qubit to detect it from 30 nm away, and at room temperature. Without the particle, the distance would have to be 1-2 nm, which is infeasible.
The hope is that this theoretical work could be used to develop superior NMR techniques for imaging biological materials, but more still needs to be done. At least this actually classical technique should be less fragile than other, quantum schemes.
Source: University of Waterloo
Posted: May 15, 2015 06:03AM
Typically when a material's temperature crosses a transition point, it will change phase, but there are ways around this, allowing a phase to persist when you would not expect it. Researchers at the University of Michigan have demonstrated this quite elegantly when they balanced two opposing crystallization mechanisms in a material. This resulted in the material staying liquid about 200 ºF below its freezing point.
The material the researchers were working with is part of a family of organic materials commonly used as pigments in electronics. They all feature a rigid core with two flexible side chains, and depending on the length of the chains, the molecules will take on one crystal structure or another. What the researchers did is balance the chains' length to cause the two modes to counter each other. Normally the material crystalizes at 273 ºF but this balance allowed it to stay liquid at 41 ºF, and cooling it further caused it to solidify into a gas. While in its supercooled state, the material was sensitive to pressure, depending on its temperature. At high temperatures even the weight of a cell would cause it to crystallize, but at room temperature and lower, a stylus was required. Even then, the crystallization was so sluggish that the researchers could write messages in the material, as the crystallized regions glowed under UV light.
This material could have some interesting uses, including as a biosensor and as an optical memory. Its ability to encode information optically could be useful, but much more work is required to develop its potential.
Source: University of Michigan
Posted: May 14, 2015 02:35PM
Researchers at MIT have managed to corral electrons in graphene in a new way that allows for tunability and high quality. Corrals have been made before, but these were always static and thus had limited potential. With this new technique though, the researchers were able to create a resonator that could have more applications than can be imagined currently.
This new method is surprisingly simple as it just places the tip of a scanning tunneling microscope over the graphene. This causes a circular barrier to form around the tip, which acts as a curved mirror and creates a whispering gallery effect. In optics, whispering gallery resonators have been used for sensing, spectroscopy, and communication, but have the issue of not being tunable. This is however, as the junction between the positive and negative regions the tip produces can be controlled. Also the tip can be moved around the graphene sheet, which opens up other possibilities. Even without that though, such a resonator could be turned into various devices, including electron lenses that could observe systems a thousand times smaller than light is able to, but without the high-energy electron beams of electron microscopy.
Using the tip of an electron microscope comes with two benefits for this and future work. One is that the tip can both create the resonator and be used to observe the system. The other is that the tips are a well-established technology already, which should make deploying this technology easier.
Posted: May 14, 2015 07:08AM
In general, simplifying a process by reducing steps is a good thing for a number of reasons, such as reducing costs and improving scalability. Researchers at Rice University have recently discovered a way to remove some steps to the production of black silicon for use as solar cells. This discovery could bring the technology closer to commercialization.
Black silicon is silicon with a special textured surface with features smaller than the wavelength of light. This makes it very efficient at capturing light at any angle. The Rice researchers have been working to fine tune the creation process for a while, but were surprised to find that the electrodes were actually able to catalyze the etching process, removing the need for other catalyst particles. Normally the metal electrodes are added last, but when the researchers had applied the electrodes earlier, and then repeated the process without the catalyst, they found black silicon formed near the electrodes.
Interestingly the etching always occurred the same distance from the electrodes, which was actually a tip-off to what was happening. An electrochemical process is causing the etching and the distance away from the electrodes is determined by the conductivity of the silicon, because after a point the charge carriers cannot move any farther. Now the trick is to optimize the process further, which the researchers suggest could be by applying a thin layer of gold on top of the silicon, with titanium sandwiched between, because it bonds well to both.
Source: Rice University
Posted: May 13, 2015 02:35PM
Despite it surrounding us and being within us, recreating Nature can be very difficult. For a long time there was no way to simulate cell membranes, but in 2010 researchers discovered how to replace a key molecule with some easier to create and work with. Now researchers at the University of Pennsylvania have succeeded in modelling how sugars on membranes can influence the behavior and interactions of cells.
Cell membranes are made of two layers of phospholipids, which are molecules with a water-loving head and water-hating tail. This allows them to self-assemble into so simple membranes just by being placed in water. In 2010 it was discovered that a class of molecules called dendrimers could replace the phospholipids, and they can be precisely tuned. On the surface of natural membranes though are sugars that are crucial for how cells interact with each other, so the question was if these artificial membranes could support sugars. The researchers have found they can by constructing a library of dendrimers that are chemically bonded to glycan sugars.
What all of this translates to is a new ability to model cell membranes, which could lead to various advances in medicine and biophysics. Some illnesses are believed to be related to mutations in proteins that interact with these sugars, such as rheumatoid arthritis, so by better understanding the processes involved, better treatments may be developed with this and much more.
Source: University of Pennsylvania
Posted: May 13, 2015 05:29AM
Bread, apples, and ducks float on water and now some metals can too. Researchers at New York University and Deep Springs Technology have created a metal matrix composite that can float on water but is still very strong. This combination could see it being used in boats and even cars, where weight can be a factor.
The material is what is called a syntactic foam, which is made by using hollow particles to reduce weight. In this case the solid material is a magnesium alloy and the hollow particles are silicon carbide spheres. These spheres can withstand pressures of 25,000 PSI before rupturing, which contributes to the metal's strength both in what they can withstand but also by absorbing energy when they do rupture. The result is a metal that has a density of just 0.92 grams per cubic centimeter, which is just under the 1.0 of water. That means a boat made of this material would still float, even after suffering serious structural damage.
A lot of work has been done over recent years to find strong and light materials, as a means to conserve energy, but being a metal, this stands apart from the plastics normally getting the attention. Metals can withstand high temperatures, which is necessary for components of engines and exhaust systems.
Source: New York University
Posted: May 12, 2015 02:38PM
There are some materials that are surprisingly prolific, thanks to their various special properties. Many believe graphene will come to be such a material, once some challenges it has are overcome. One area it may be used in is water purification, and researchers at MIT have made that more possible than ever now, by finding ways to fix the defects in graphene membranes.
Graphene is an atom-thick sheet of carbon with a variety of useful properties, including high strength and conductivity. Membranes of the material could significantly improve water purification systems, because of how much thinner the membranes would be, at one atom thick versus 200 nm thick. The problem is that the graphene membranes must first be made on a substrate like copper, which is not porous, so the graphene must be removed. This causes tears in the membrane, in addition to intrinsic defects the membrane will have. For these defects the researchers found that they could be fixed by placing the graphene in a vacuum chamber with hafnium oxide. Normally the material would not interact with graphene, but is attracted to these small defects. The larger tears can be plugged by using interfacial polymerization, which submerges the membrane between two solutions that will react together to form nylon. After the repairs are made, the researchers etch small holes into the membrane, to let water through.
With the defects and tears dealt with, and the pores etched in, the researchers found the graphene membrane could block up to 90% of larger molecules, even though it still let salt though. Additional work is needed, but graphene could become a realistic alternative to current filtration membranes, providing clean water to more places, amongst other applications.
Posted: May 12, 2015 07:01AM
Batteries are necessary for a great many systems, including micro-devices, but because of the large sizes of the energy storage devices, they must be kept off of the chips used. This could change thanks to the work of researchers at the University of Illinois, Urbana-Champaign though, as they have developed a powerful microbattery that can be easily integrated onto chips. The manufacturing processes involved can even allow for large-scale production.
To create the new battery, the researchers use 3D holographic lithography and 2D photolithography. Holographic lithography utilizes multiple light beams that interfere within a photoresist, creating the desired, interior structure. Recent work has made this process simpler to the point of making it highly scalable. The 2D photolithography is used to create the shape of the electrodes that connect to the battery, which the researchers found is particularly important. Structural parameters including size, shape, surface area, porosity, and tortuosity all impact the microbattery's performance.
As the methods used to create the microbattery are compatible with those used to create chips, the expectation is that they can be integrated directly onto chips. The fact that the miniature battery is also high-power, comparable to supercapacitors in that regard, make it very desirable for various applications from wireless sensors and transmitters and medical devices, to monitors and actuators.
Posted: May 11, 2015 07:36AM
We may not think about light very much, but in our day to day lives, we probably consider it to be somewhat simple. On the scale we live at, light is not necessarily complicated, but at the nanoscale, it can be very different from what one expects. Researchers at Aalto University have confirmed this by discovering a new way to couple light with magnetic materials that may have applications in telecommunications and more.
Normally when light strikes a material, you except it to reflect or scatter off, but on the nanoscale quantum mechanics can be involved, if the materials are ferromagnetic. Metallic nanoparticles can act like antennas for visible light, and thereby interact with the light, possibly shifting its polarization axis or intensity. The researchers applied this and built an array of ferromagnetic nanoparticles that exploits surface lattice resonances. This causes all of the particles to radiate together, creating a much more significant impact on the polarization change. By having the spacing between the particles differ, based on direction, the researchers were even able to change the frequency this effect occurs at away from the frequency the particles themselves most interact with.
This work opens new possibilities for magneto-optical effects, as previously one would not work with ferromagnetic materials, due to their high resistance. By working with the array of nanoparticles though, this issue is mitigated.
Source: Aalto University
Posted: May 8, 2015 02:01PM
There are many possibilities for the future of computing, but while the systems involved can be very different, many of them rely on optics in one way or another. Naturally this makes it important to find ways to precisely create the light being used, and researchers at the University of Rochester have made a significant discovery to achieving that. They have found how to make quantum dots in a two-dimensional semiconductor, which has never been accomplished before.
Quantum dots are occasionally referred to as artificial atoms because we are able to engineer their properties, such as the color of light they absorb and emit. Naturally there is great interest in them for photonic devices, such as those that may be used in some future computer systems. Before that can happen though we will need to find ways to integrate them into chips, which is where this discovery comes in. The Rochester researchers discovered that by layering atomically-thin sheets of tungsten disulfide on top of each other, the points where they overlap create quantum dots. By controlling the applied voltage the researchers can already tune the brightness of the quantum dot, and the next step is to adjust the frequency by manipulating the voltage.
It is an important advantage that tungsten disulfide is a 2D semiconductor, as these tend to be easier to integrate into electronics. The researchers also found that the quantum dots do not interfere with the semiconductor's electrical or optical properties, which will also prove invaluable for integration with electronics.
Source: University of Rochester
Posted: May 8, 2015 05:12AM
In my experience, people love chocolate unless they have an allergy or are actually sticking to a diet. We love it, until it has the white layer on it that looks like nothing you would want to eat. Even though these blooms are well known about, there is little understanding about them, which is why a team of researchers from DESY, the Hamburg University of Technology, and Nestle decided to study chocolate more closely.
That white layer is actually a fat bloom and, believe it or not, is completely harmless, but it still causes people to dispose of the chocolate and even file complaints. The bloom occurs when the liquid fat in the chocolate finds its way to the surface and crystallizes there. To understand the exact processes involved, the researchers pulverized samples of chocolate and shined X-rays through it to examine fat crystals and pores. Dropping sunflower oil on the samples allowed them to also watch the fat migrate, and they found the oil quickly penetrated even the smallest pores. As it dissolved into the chocolate, it affected the chocolate's structure, making it softer and easier for more fat to migrate, which could then lead to fat blooms.
Based on this study, which is the first to study the dynamics of fat blooms developing, the researchers suggest three ways to reduce the occurrence of fat blooms. One is to reduce the porosity of the chocolate, so fat migrates more slowly. The second is to keep the chocolate at a cool temperature, to limit the liquid fat. Finally the researchers suggest controlling the crystal structures of the fat in the chocolate, as this directly influences the amount of liquid fat in the chocolate. Cocoa butter has six crystal structures it can form, and some may be better than others.
Posted: May 7, 2015 02:10PM
Carbon nanotubes are an amazing material with great potential for various applications. This is thanks to their amazing strength and electrical properties, but getting them into usable forms can be difficult. Researchers at North Carolina State University and the Suzhou Institute of Nano-Science and Nano-Biotics in China have succeeded in developing a method to create large films of CNTs stronger than any that came before it.
Carbon nanotubes are a form of pure carbon and are among the strongest materials known to man, despite also being among the smallest. To utilize this strength, they have to be made into larger structures, like threads or films. The better aligned the nanotubes are within these structures, the better the properties of the final structure will be, but aligning a bunch of nanotubes a thousand times smaller than human hair tends not to be easy. Yet that is what the researchers have achieved by exploiting the imperfections of surgical blades. To the naked eye, these blades will look perfectly straight, but if one looks closer with a microscope, microscale fissures will become visible along the cutting edge. The researchers realized these fissures could be used as a kind of comb to straighten the nanotubes, just by drawing them over the blades.
The resulting films made from the microcombed nanotubes have more than double the tensile strength of regular CNT films, at over 3 gigapascals, compared to just 1.5, and some 80% better conductance. Despite that though, there is still room for improvement with this method. Right now though, the researchers are looking for an industry partner to help scale up the method for large-scale production, which, theoretically, should be easy.
Source: North Carolina State University
Posted: May 7, 2015 05:40AM
As powerful as our computers get, there are some things they will simply never be able to do because the operations involved are too complicated. For many of these problems, quantum computers may be able to provide the solutions, but we are not able to build such a computer. We are getting closer all the time though with new developments, such as a new chip architecture set to appear in the Journal of Applied Physics.
The key to quantum computers is the use of quantum bits, or qubits, which are able to represent both 0 and 1 at the same time, as opposed to electronic bits that are one or the other. There are many candidates for qubits, including ions trapped in vacuum chambers that lasers manipulate, but it is difficult to scale up the technologies involved. This is because the electrodes needed to create the trapping fields are attached to the perimeter of the chip, which has only so much room. The researchers' new solution was to switch to a ball grid array (BGA), like some computer chips use. This moves the electrodes from the perimeter to the more spacious area of the chip, significantly increasing the density of the connections.
Besides the shift to BGA, the researchers also changed the kind of capacitors commonly used from surface or edge capacitors to trench capacitors, and rewired the connections. While this is a large and valuable step forward, there is still a lot of work to be done before quantum computers can come to be.
Posted: May 6, 2015 02:27PM
There are many reasons people may need a blood transfusion, and hopefully none of us will ever experience one of those reasons. In the event someone does need a transfusion though, it is imperative the donor blood is of a useable type, which can be a problem if supplies are limited. Researchers the world over have been working to solve that problem, and those at the University of British Columbia have made a significant leap towards such a solution.
There are various types of blood that are separated by the sugars, or antigens, connected to the cells. Type O lacks these components, which is why it is known as the universal donor, as people with other types of blood can accept it. Naturally a means to convert Type A or B blood to Type O would be desirable, and this is exactly what the British Columbia researchers have been working on. An enzyme to remove the A and B antigens already exists, but the researchers applied directed evolution to make it more efficient. Directed evolution involves inserting mutations into the gene and then selecting the mutant versions with the desired effect. After just five generations the enzyme became 170 times more effective.
While the new enzyme is significantly more effective at removing the antigens, it is not perfect, and the immune system is so sensitive to blood groups that only complete removal can be used in clinical settings. That means that this research will not directly lead to results at blood banks, but to more research that hopefully will, which the researchers are confident of.
Source: University of British Columbia
Posted: May 6, 2015 05:52AM
Materials are a very important concept in many games, as changing the material of an object can dramatically affect its appearance. Still, getting the appearance right can be very difficult because of how light passes through the material, like flesh. Researchers at the Vienna University of Technology and Activision-Blizzard though have developed a means to take this into account, without resulting in a significant performance hit.
Subsurface scattering is exactly what it sounds like; the scattering of light beneath the surface. A classic example would be the red we see if we put our fingers in front of a light. To correctly emulate this in a graphics engine would require calculating the scattering for numerous light rays, which is too much to do in real-time. To simplify the process and make it useable with modern hardware, the researchers developed Separable Subsurface Scattering (SSSS). This method works by simulating a single light ray to create a filter profile. This profile can then be applied to the image repeatedly, and very quickly. On a full HD image, it would add just half a millisecond of time on standard hardware, which makes it viable for video, unlike previous methods that took too much computing time.
As you may be able to guess, Activision-Blizzard is already using SSSS, but it will not be limited to the one company. It is to be presented in the journal, Computer Graphics Forum so every developer will be free to use it.
Source: Vienna University of Technology
Posted: May 5, 2015 02:35PM
There are many possibilities for what the future of computing technology will be, from spintronics and optical computers to different kinds of quantum computers. Another possibility is valleytronics, which is a relatively new field of science. Now researchers at Berkeley Lab have discovered that graphene can contain one dimensional conducting channels that are desirable for this technology.
Valleytronics involve the movement of electrons through a 2D semiconductor as waves with two energy valleys. These valleys can then be described with a distinct momentum and quantum valley number, with the latter number being able to store information. Recent work has suggested that the domain walls in graphene could act as 1D conducting channels for electrons that would preserve electron valleys. This is in contrast to the edges of graphene that mix the valleys. The Berkeley researchers' work confirms that this is the case, at least at low temperatures.
The next step for this work is to increase the ballistic length of the channels, as this will allow for the creation of electron valley filters and other means of manipulating electron valleys. One application for valleytronics may be in quantum computers, but only time will tell.
Source: Berkeley Lab
Posted: May 5, 2015 06:21AM
Growing up, there were probably times you wished you could just vanish from your classroom, or maybe you wished someone else would. Either way, people cannot just disappear from a classroom, but some small objects now can. As reported by The Optical Society, researchers at the Karlsruhe Institute of Technology have created an invisibility cloak that can be used in classrooms to demonstrate the effect.
Invisibility is one of those powers man has been dreaming about for millennia, but only thanks to modern technology is it becoming possible. More specifically the thanks are to optical metamaterials with special properties that will bend light around objects, instead of reflecting off of them. One challenge with these cloaks is that when light is diverted around an object, it takes longer to get to the other side, like a road detour, except light as a firm speed limit. To solve this problem for the demonstration piece, the researchers used a light-scattering material, which slows down the propagation speed of the light. With all of the light moving slower inside of the material, that gives the researchers room to speed it up as it goes around an object, so every light wave has the same average speed.
The solid-state cloak the researchers build has two metal tubes coated with an acrylic paint inside of a common organic polymer that has been doped with titanium dioxide nanoparticles. With a properly bright light source, it is possible for this setup to show the principles of cloaking without any special equipment.
Source: The Optical Society
Posted: May 4, 2015 05:17AM
The future of many technologies may be flat, thanks to advances with two-dimensional materials like graphene, boron nitride (BN), and molybdenum disulfide (MoS2). The last of those three materials is of special interest to some as it is the only of the three to be a natural semiconductor, but its performance tends to be less than predicted. Researchers at Columbia University have been investigating this and found an explanation and solution for the discrepancy.
In previous work, the researchers discovered that encapsulating graphene, a plane of carbon one atom thick, in boron nitride improved its electron mobility by a factor of 50. Electron mobility is a measure of how quickly electrons can move through a material, so better mobility means better performance. The reason the encapsulated graphene performed better is because the encapsulation reduced the disorder from exposure to the environment. By encapsulating MoS2 in BN, with graphene at the ends to act as contacts, the researchers found electron mobility increased by a factor of 2 at room temperature, bringing it closer to the theoretical limit. At low temperatures the increase was on the order of 5 to 50 times better, depending on how many layers there were.
Further analysis at low temperatures revealed that contamination at the interfaces is still the main source of disorder, which means there is still room for improvement. With 2D semiconductors and other materials potentially able to push past the performance of modern technologies, you can bet this is going to be investigated more.
Source: Columbia University
Posted: May 1, 2015 02:48PM
The brain is an extraordinary organ that humanity may never fully grasp, but that does not stop us from trying. One of the fundamental functions of the human brain is to store memories, and for some the brain has difficulty forming new memories, so a better understanding of the processes involved could lead to treatments for them. Now researchers at Vanderbilt University have found a link between a signaling protein and the formation of memories.
Neurons have two types of fibers that reach out from them, dendrites and axons, with the axons sending signals that dendrites receive. Each dendrite is covered in filaments called filopodia that will develop into spines when they touch an axon, and these connections are what store memories. The Vanderbilt researchers found that the signaling protein Asef2 promotes spine formation by activating another protein, and is used by another to guide specific spines. Previously Asef2 has been linked to disorders including autism, Alzheimer's, and Down Syndrome. Autism has been associated with immature spines, which fail to form good connections, and Alzheimer's is well known for disrupting a person's memory.
The hope is to one day understand the mechanisms well enough to develop treatments to restore spine formation. Until then, we have a lot more studying to do to unravel our brains at a cellular and molecular level.
Source: Vanderbilt University
Posted: May 1, 2015 06:15AM
When X-ray photography was first discovered, it allowed us to peer into places previously impossible, and we may see a revolution like that happen again with terahertz radiation. Though at a much lower frequency, this form of light can be used to identify various illnesses and materials, at range and without damaging the subject. To best accomplish this though, a wide range of frequencies need to be created, and researchers at the University of Rochester have found a new way of doing so at a lower power than thought possible.
Specific frequencies of terahertz radiation can be made by special diodes and lasers, but these are only good for imaging work. Spectroscopy, which identifies materials by how light interacts with it, requires a broadband light source, which is made by a microplasma. To produce such a plasma requires either two powerful lasers of different frequencies, or one even more powerful laser. The Rochester researchers wondered if maybe working with special polarizations of light could improve efficiencies. It turns out this is not the case, but once the researchers learned why this did not work and the underlying physics, they found another solution. This new approach allows for the creation of the microplasma with a single laser at a much lower power than previously thought possible, and it may go even lower, by changing the gas used.
One thing interesting about this technique is that the terahertz waves go in a different direction than the laser beam, which should make it easier to couple the waves to a waveguide in a microchip.
Source: University of Rochester
Posted: April 30, 2015 02:11PM
Lithium-ion batteries are used in so many devices they practically surround us, and while most of the time this is not an issue, there are rare occasions when these batteries will explode. Obviously it is not good when a single battery explodes, but often one explosion can cause a chain reaction and neighboring batteries will explode as well. Researchers at University College London, Imperial College London, and the European Synchrotron Radiation Facility (ESRF) have now performed the first analysis of the internal structure of a battery as it explodes, in real-time.
The researchers studied two specific battery types, with one having an internal support and one not, and what occurs when thermal runaway happens. To do this they used one of the ESRF beamlines, which is capable of high speed 3D image capture. As the batteries were exposed to temperatures above 250 ºC, the researchers were able to watch the structures inside. The battery with the internal support apparently hit temperatures around 1000 ºC internally, because the copper support melted, and the heat spread out from there. In the other battery the tightly packed core collapsed, which would increase the risk of short circuits and damage to nearby objects.
While this study only worked with two types of battery, it demonstrates the feasibility of this analysis method for other types. Now the researchers are going to study a larger sample of batteries and examine the microscopic changes involved with failure.
Source: University College London