Science & Technology News (733)
Posted: December 19, 2014 02:27PM
Hydrogen is the simplest and most common element in the Universe, as it consists of one proton surrounded by one electron. This simplicity has made it invaluable for testing theories that involve extreme situations. Now it has been discovered by researchers at the Carnegie Institution that under extreme pressure, hydrogen behaves unlike previous theories suggested.
At extreme pressures between 2 and 3.5 million times normal air pressure, it was believed that hydrogen would resemble a conductive metal, with atoms packed closely together. Instead, hydrogen has been observed to form layered sheets similar to graphene at these high pressures. Graphene is an atom-thick sheet of carbon atoms, where the atoms are arranged in a hexagonal structure, like chicken wire. This structure for hydrogen was actually theorized thirty years ago, but most were expecting the metal-like structure predict in the 1930s.
The hydrogen atoms bonded this way because the rings of hydrogen actually possess intrinsic stability. This indicates that chemical bonding still occurs under more conditions than most believed, though of course the effects of these bonds can be very different from what we normally observe.
Source: Carnegie Institution
Posted: December 19, 2014 06:52AM
It is possible that within our lifetimes we will see electronics replaced by another technology field, and one possible replacement is spintronics. Instead of using the charge of electrons, spintronics would utilize their innate magnetic properties, which is not simple. Researchers at Berkeley Lab and Cornell University however, have recently succeeded in flipping the magnetization of a spintronic device at room temperature, using an electric field.
While electrons do represent a single electrical pole, they still have two magnetic poles thanks to their spin. By manipulating the orientation of their spin, it should be possible to store and process information, which is the idea behind spintronics. Because spin is a characteristic of electrons, this could be done with far less energy than conventional electronics. Of course none of that will matter if spintronics cannot be brought out of laboratories. The researchers were working with a multiferroic material, which means it has a combination of electric and magnetic properties coexisting, and found they could switch its magnetism using an electric field, instead of an electric current. The field requires about a tenth the energy needed for a current to achieve the same.
The multiferroic material used was bismuth ferrite, which is the only one known to be thermodynamically at room temperature. It had been thought there were barriers to prevent the switching achieved, but the two-step process the researchers found made it possible.
Source: Berkeley Lab
Posted: December 18, 2014 02:11PM
Right now, medical labs are very important because they can be the only places with the technology needed to identify a patient's disease. This can be problematic though, as it restricts access to these tests, which is why many are working on advanced devices to brings these tests out of labs. Now researchers at the University of California, Los Angeles have created a lens-free microscope that can be used to identify cell-level abnormalities, while being smaller and cheaper.
Traditional microscopes use occasionally large lenses and bright lights to enlarge images for examination. This lens-free microscope however, uses a sensor array, like those in digital cameras, with an LED or laser to record the specimen's patterns of shadows. These patterns are then processed as holograms, building a 3D image of the specimen, for a pathologist to study. This design matches the accuracy of traditional bright-field optical microscopes, but also provides a much larger field of view.
The researchers tested their lens-free microscope by imaging multiple specimens, and providing those images to a board-certified pathologist. The pathologist's diagnoses, based on those images, proved to be accurate 99% of the time.
Posted: December 18, 2014 08:04AM
Some day we will see superconductors being used to carry electricity with almost no loss. When that day will come though is hard to guess, because so much is still not known about superconductivity. Researchers at MIT have recently made a discovery that could enable a deeper understanding of superconductors than previously possible.
Superconductivity arises in certain materials at specific critical temperatures, depending on the behavior of the material's electrons. That temperature tends to decrease when working with thin films though, which are used to examine the superconducting-to-insulating transition. Exactly how the temperature changes has not been mathematically described though, so the researchers ran a series of experiments, controlling thin film thickness and resistance per unit area, or sheet resistance. Doing this they discovered that the product of thickness and critical temperature equaled a constant (A) divided by sheet resistance raised to a specific power (B). The researchers, now armed with this equation and its two constants, A and B, searched through superconductor literature, to see if it applied for more than the material they were working with, and found it did, though the values of A and B varied. Not liking that two constants are involved, the researchers plotted them against each other and found that they fell along a straight line. That means that only one constant is needed for the equation's general form.
The relationship between A and B is more interesting than that though, as the pairs at the bottom of the line came from more ordered superconductors, while those at the top had more disordered, amorphous structures. There is no theoretical explanation for this relationship currently, but the equation is still going to prove invaluable by predicting what films will make good superconductors, without having to actually make them.
Posted: December 17, 2014 02:20PM
Central to our myriad of devices are semiconductor junctions that transfer charge between materials. To do so efficiently, only certain pairs of materials can be used and their crystalline structures must be properly aligned. At least that is what we thought was the case, but researchers at North Carolina State University have found an exception to this rule that could have powerful implications.
What the researchers found is that the crystalline-structure restrictions do not appear to apply to 2D semiconducting materials. When they stacked a layer of molybdenum sulfide and a layer of tungsten sulfide, they found that the stack was as efficient at transferring charge when the layers were randomly stacked as when they were precisely aligned. Though only these two materials were worked with, the researchers believe this may apply to all 2D semiconductors.
Considering how expensive and difficult it is to precisely stack these layers, finding it is not necessary could drop the cost of many technologies.
Source: North Carolina State University
Posted: December 17, 2014 05:37AM
Some of the best things in life do not come easily, and that is also true of materials science. Every now and then though, new discoveries can make things easy. Researchers at Rice University have recently found a way to very efficiently produce graphene using a laser and an inexpensive plastic.
Graphene is an atom-thick sheet of carbon that looks like chicken-wire, because of how the atoms arrange themselves into hexagons. At least that is the case for pure graphene. The laser-induced graphene (LIG) the Rice researchers created is actually a 20 micron-thick foam comprised of graphene flakes, filled with defects. These defects though, rings made of five and seven carbon atoms, are actually good in this instance because they can hold electrons. This makes it an ideal material for use in microsupercapacitors, which could one day come to replace batteries with high energy densities and great charge and discharge rates. Even after 9000 charge cycles, the prototype supercapacitors did not suffer significant degradation.
Making the LIG was as simple as firing a laser at polyimide flexible plastic sheets, which is called Kapton and can purchased in huge rolls. The laser writing process itself can be done in air and at room temperature, so the process could be easily scaled up for mass production and even integrated into a roll-to-roll manufacturing.
Source: Rice University
Posted: December 16, 2014 02:39PM
Metal alloys are crucial to our daily lives as so much is dependent on the various properties, from corrosion protection to improved strength, of those composite materials. Currently many are investigating high-entropy alloys, which are comprised of five or more metals, with roughly equally distributions. These materials can have very desirable properties, and researchers at North Carolina State University and Qatar University have recently found one with the highest known strength-to-weight ratio of all metals.
This new alloy is made of lithium, magnesium, titanium, aluminum, and scandium. It has a low density, comparable to aluminum, but its strength comes in above that of titanium alloys. Such a combination is obviously very powerful, with its strength-to-weight ratio matching that of some ceramics, without the brittleness. We could potentially see this alloy being used in vehicles and prosthetics.
More work still needs to be done to understand the alloy's characteristics, and how to best process it. The researchers also want to see if the scandium could be replaced or removed, as it is a very expensive metal.
Source: North Carolina State University
Posted: December 16, 2014 06:28AM
Protecting our identities and credit cards has become ever more important over the years, especially as we hear about large-scale security breaches. There are many new technologies that offer improved protection, like smart cards, but they still have flaws. As reported in Optica researchers in the Netherlands have developed Quantum-Secure Authentication, which leverages quantum mechanics to protect credit cards, and could be tamper proof.
Instead of relying on a magnetic strip or chip to store information, QSA uses nanoparticles painted onto a card. These nanoparticles will scatter any light that strikes them, creating a pattern, but it is not just any, normal light source used here. The photons have to be quantum in nature, so that they can enter a superposition as a result of the nanoparticles. Superposition is a quantum mechanical phenomenon whereby one object can exist in multiple, mutually exclusives states at the same time, such as being in multiple places at the same time. If the superposition is observed, such as to copy it, the pattern collapses, making it impossible to learn what the pattern was, and later reproduce it. Also, because superposition is used, fewer the photons can be used to scan the card, potentially just one, which lends to the method's security.
Another advantage to Quantum-Secure Authentication is that it is already realistic, because the technology it uses is simple and cheap. This could help it be adopted in credit cards and much more, such as ID cards for entering buildings and even cars.
Source: The Optical Society
Posted: December 15, 2014 10:07AM
One of the many uses of modern, mobile electronics is for fitness tracking, like measuring steps and how far someone has run. What has not quite made it to mobile devices is pulse and blood-oxygen saturation levels, because the technology needed for measuring the latter is both rigid and expensive. Researchers at the University of California, Berkeley however have developed a new device that uses flexible organic electronics, which can be significantly cheaper.
The conventional monitoring devices work by measuring the amount of red and infrared light that passes through a finger or earlobe. Oxygen-rich blood cells absorb infrared light, while oxygen-poor cells absorb red light. By measuring the variances over time, it is possible to get the person's pulse. Instead of using infrared light, the Berkeley device uses green light, from a green OLED deposited on a piece of plastic, along with a red OLED and light sensors. It turns out that the absorption difference between red and green light is comparable to that of red and infrared light, so this approach is still viable.
One of the advantages to organic electronics is their flexible nature, which enables this monitoring device to conform to the user's body. Also they are so cheap that they could be disposable, like adhesive bandages are, after use.
Posted: December 15, 2014 06:14AM
Sometimes when humans talk to each other, we miss a word or two, but that is okay because we can often still interpret the meaning. Computers however lack that ability, so a single bit being off can destroy the meaning of a message. Researchers at MIT however, have developed a theory that could protect against just that.
Part of the reason human communication can miss some words is because we are good at figuring out the minimum amount of information required for meaningful communication, given the context. For computers this would be compression, and it can be achieved with the sender and receiver sharing a codebook, in which possible messages are assigned a unique code. While the complete code is needed to be certain of what the message is, there is a minimum number of symbols needed to accurately guess at the complete message, using probabilities. This new theory allows for the sender and receiver to still communicate even if they disagree on these probabilities, and even if their codebooks are slightly different.
With this theory, it may be possible to devise new communication protocols that are more flexible and reliable than modern ones.
Posted: December 12, 2014 10:12AM
Many people would tell you that a distraction makes it harder to study, as your attention is split. While that makes sense, it is only half the story as one must also recall what is learned. Researchers at Brown University decided to investigate how distractions influence learning and recalling, and an interesting discovery.
For their study, the researchers had 48 volunteers reach for targets on a computer screen, while the virtual world would bend by 45º. Some of the volunteers were also asked to count symbols as they move across the screen, while others were told to just ignore them. When asked to demonstrate the reaching skills they learned, some were also asked to count the symbols again. This experiment found that the group that never experienced the symbols recalled the task the best, as did those that experienced the highest number of symbols at both the learning and recalling stages. Those who experienced any other combination, such as seeing the symbols at one stage but not the other, did worse. A second study with 50 subjects indicated that the distractions do not need to be identical, but just to the same degree.
More work is now being done to better understand how attention can influence learning, but already some applications are being predicted. The researchers believe rehabilitation techniques could benefit from this, as patients learning to walk will one day be walking in areas full of distractions.
Source: Brown University
Posted: December 12, 2014 06:46AM
Size does matter for many technologies, and fairly often, smaller is better, especially when you can do more with it. One example of this would be computers, which have gone from filling floors of buildings to fitting in our pockets, and in the future we may have particle accelerators sitting on desks, instead of spanning miles underground. One of those compact particle accelerators has now set a new record at Berkeley Lab by pushing electrons up to 4.25 giga-electron volts, over just nine centimeters.
The record-setting device is a laser-plasma accelerator, which works by having the laser cut a channel through the plasma, for the electrons to travel, and waves to carry the electrons to tremendous energy levels. The laser in this case was the Berkeley Lab Laser Accelerator, or BELLA, which is a new petawatt laser that is among the most powerful in the world. It also has impressive pointing stability as the researchers were able to aim the laser pulse onto a 500 micrometer hole from 14 meters away. Traditional accelerators, like the LHC, use electric fields to accelerate particles, and that one in particular has a limit of 100 mega-electron volts per meter, before the metal breaks down.
The researchers plan to continue refining their approach and computer models to achieve 10 giga-electron volts, which will in part require tuning the density of the plasma. Compact accelerators could have an amazing impact on science by at least reducing the need for 17-mile long accelerators, like the LHC.
Source: Berkeley Lab
Posted: December 11, 2014 02:24PM
Skin is an amazing organ in part because of the sense of touch it gives us, allowing us to feel pressure and movement. Artificial skin has been developed to give prosthetics pressure sensitivity, but they lack the ability to detect the direction the pressure is being applied. As reported in ACS Nano, researchers have created an artificial skin with a new design to it that enables it to sense the direction of stress.
To give the artificial skin this ability, the researchers looked to human skin, whereas others have considered microstructures found in beetles and dragonflies. This new focus led them to develop a structure of tiny domes that interlock and deform in response to forces, and even when air is blown across it. Location, direction, and intensity were all sensed by the new skin, which is information that we naturally use to know how to best grip an object.
The natural applications for the artificial skin are prosthetics, rehabilitation devices, and robots. Anywhere it would be useful to have a sense of touch that does not already, could potentially benefit from this.
Source: American Chemical Society
Posted: December 11, 2014 06:46AM
For a long time, lasers as destructive weapons have been confined to science fiction, but that is changing as the technology has great offensive and defensive potential. Researchers at the Office of Naval Research and their partners have been working on the Laser Weapon System (LaWS) for some time now, and have recently tested it on a deployed ship in the Persian Gulf.
For the tests, LaWS was deployed on the USS Ponce, where sailors worked with it for several months, reporting that it operated flawlessly, even in adverse weather conditions. The system is operated by a video-game like controller and has a range of capabilities, from non-lethal dazzling, to lethal destruction. It was tested against targets mounted on small, moving boats and even shot down a Scan Eagle UAV, and passed the tests as it locked on and destroyed targets with "near-instantaneous lethality."
Besides the impressive capabilities of LaWS, there are other benefits to laser weapons, including lower costs and improved safety. Being electrical in nature, laser weapons do not need any potentially dangerous propellant and can be fired for less than a dollar per shot, compared to missiles that can cost millions.
Source: Office of Naval Research
Posted: December 10, 2014 02:14PM
Piston engines are quite common in the world, in part because these are what power most cars and other machines. One alternative design is the Wankel engine, which is a simpler and smaller design, rotating a rounded triangle in an oval chamber, that has its own advantages and disadvantages. An MIT startup called LiquidPiston has created a new engine design that can be even smaller, but is also more efficient and solves some of the Wankel's problems.
The differences between the two engines are apparent immediately as the X Mini by LiquidPiston actually uses a rotating oval in a rounded triangle chamber. This allows it to use the high-efficiency hybrid cycle (HEHC) that increases combustion efficiency by maintaining a constant volume during combustion and uses overexpansion. Keeping a constant volume ensures all of the fuel is burned, which is a problem for Wankel engines, and increases the expansion pressure. Overexpansion means that the gases are allowed to expand until the pressure is gone; extending the time spent pulling out the energy.
At 10,000 RPM, the 70-cubic-centimeter, four pound engine puts out 3.5 horsepower, as it is now, but in the future a three pound version could potentially put out five horsepower at 15,000 RPM. The researchers envision the engine being used to replace small piston engines, like those in chainsaws and lawnmowers, but could be scaled for use in significantly lighter generators and for military applications.
Posted: December 10, 2014 07:57AM
Silicon is approaching the end of its reign as the dominant semiconductor for technology as we approach sizes the material just cannot support. Other semiconductors however, can go smaller, and the work by researchers at Purdue University has improved one material's chances. Germanium was used to create the world's first transistor and now it may become the basis for future circuits.
On the Periodic Table, germanium is directly beneath silicon, which means the two materials share many properties, including being semiconductors. Germanium as a higher electron and hole mobility though, which makes it a better candidate for ultra-fast circuits. Previously it had only been made into P-type transistors, but N-type transistors are also needed for CMOS devices.
By doping germanium, and etching away the top later, the Purdue researchers have found a way to create N-type transistors from germanium, opening up the possibility of germanium CMOS circuits. Already they have created an inverter from germanium, and it is the best-performing non-silicon inverter to date.
Source: Purdue University
Posted: December 9, 2014 02:35PM
Even though many people only associate solar power with dark, silicon cells, the technology will likely have altogether different appearances in the future. For example, some solar power technologies come in a liquid form that can be sprayed onto arbitrary surfaces. Colloidal quantum dots (CQDs) could be applied this way, but the actual spraying process is complicated, but researchers at the University of Toronto are changing that.
Traditionally batch processing is used to apply CQDs to a surface, but this is a somewhat slow and inefficient process, as it requires multiple stages. What the Toronto researchers built with airbrushes and a spray nozzle used in steel mills is able to do the same job, but very rapidly and efficiently, in a roll-to-roll method. This would also make adding these solar cells to other manufacturing processes much simpler.
The researchers ultimately want to see backups capable of spraying solar cells onto roofs, but that is still a ways off. As that is developed though, CQDs will also see their own performance improved, making for a more powerful combination.
Source: University of Toronto
Posted: December 9, 2014 06:40AM
The ability of geckos to adhere to just about any surface has inspired a number of technologies, such as special gloves. There has been a question though, about whether geckos must apply some force for the adhesion to work. Researchers at the University of California, Riverside put this question to the test by measuring the adhesion strength of living and dead geckos.
The reason geckos are able to stick to almost any surfaces has to do with what are call van der Waals forces. These are the very small forces between molecules that can actually pull them together. To take advantage of them, gecko toes are covered with hair-like structures called setae that can actually require an electron microscope to see in detail. While these setae provide the clinging forces, some have believed that some active component is also required, such as using muscles to push the toes against the surface. By using a device to measure shear forces, the Riverside researchers found no difference in strength between living and recently-dead geckos. However, living geckos will hyperextend their toes to reduce adhesion, to prevent injury.
What this research translates to is that geckos use no energy when clinging to a surface, such as when they are sleeping. That adhesion can be entirely passive could influence many technologies.
Posted: December 8, 2014 07:10AM
Even in this digital age, filled with displays, paper is still used with potentially 90% of all business information still being recorded on it. Typically this paper is discarded after one use, which makes some sense as you can only print on a page once, right? Researchers at the University of California, Riverside have created a rewriteable paper that could obviously reduce waste quite efficiently.
This new paper is made out of glass or plastic and contains a redox dye, a catalyst, and a thickening agent. Redox dyes are chemicals that are colored when oxidized, but when reduced, meaning they gain electrons, become transparent. Combined with the catalyst and thickening agent, it is possible to use ultraviolet light to cause this reduction, so the colored, opaque sheet will become transparent where the light reaches. By heating the paper to 115 ºC, the dyes are oxidized and return to their original coloring, removing what was printed on them. Considering laser printers can already heat paper up to 200 ºC, this erasing processing is quite feasible.
Currently the paper is only able to be rewritten 20 times before there is a significant loss in contrast or resolution and the printing will fade after three days. The researchers are working towards the paper surviving 100 cycles and extending the legibility beyond three days. They are also confident that it will be possible to print on the paper in multiple colors, though currently they have only worked with single colors.
Posted: December 5, 2014 10:02AM
Everybody is likely familiar with lithium batteries because they are such a ubiquitous energy storage system. What fewer people may know though is that they are very hard to improve and that one method to do so presents serious issues. Researchers at the Pacific Northwest National Laboratory however, have recently found out why a specific coating can improve that method's effectiveness.
Normally lithium batteries rely on graphite electrodes to absorb and release the lithium ions, thereby storing and releasing electricity. Silicon electrodes can potentially hold ten times as many lithium ions though, and could allow for batteries with many times the life we have today. The problem is that silicon is so fragile that the swelling it undergoes when taking in the lithium ions breaks the electrodes. Silicon nanoparticles can help, and also offer even better performance, but still suffer the fracturing problem. Researchers at the National Renewable Energy Laboratory and University of Colorado, Boulder have found that a rubber-like coating of aluminum glycerol protects can let the nanoparticle electrodes survive five times longer. Now, thanks to PNNL, we know why.
Uncoated silicon nanoparticles will have an oxide layer on their surface, which restricts their ability to swell, but the aluminum glycerol, or alucone, actually removes that oxide layer is allows for the swelling. The researchers also observed the alucone preventing the nanoparticles from merging, which was another issue that would damage the electrodes.
Posted: December 5, 2014 06:22AM
In the future we may have advanced quantum computers capable of running algorithms that modern electronic computers could never hope to. There is still a lot of work to be done before these devices can become reality though, including finding ways to store and read quantum information. Now researchers at the Technische Universitaet Muenchen have found a way to access the information stored in nitrogen vacancies electronically, which has never been accomplished before.
Nitrogen vacancies are a defect found in diamonds where carbon atoms have been replaced by nitrogen atoms. When the nitrogen atoms are hit by a laser, an electron is popped up to a higher energy state, creating an electron-hole pair that can store quantum information. To access this information, the researchers used nanodiamonds and a layer of graphene. When the electron-hole pair, which acts as a dipole, formed in the diamond, another dipole formed in the graphene, which is highly conductive. Gold electrodes are then able to record the induced charge, thereby measuring the information electronically.
As the electron-hole pairs will disappear in a matter of nanoseconds, the researchers had to use a laser that reaches into picoseconds and use very sensitive equipment. Such a combination should allow it to future quantum computers to achieve clock speeds in the terahertz domain, if this system is used.
Source: Technische Universitaet Muenchen
Posted: December 4, 2014 10:03AM
Metamaterials are a special class of materials with unnatural properties. For example, a metamaterial can be made to bend light backwards, opening up the possibility for invisibility cloaks and flat lenses. Actually designing and building them is rather complicated though, but researchers at the University of Pennsylvania have made a recent discovery that may make it all much simpler.
Inspired by digital electronics that can sample analog signals to create a digital signal; the researchers found they could create metamaterial bits based on electromagnetic properties. Specifically it is a material's permittivity they look at, which is a measure of how it reacts to an electric field inside of it. When you place two materials with different and opposite permittivity values against each other, you can get some very odd results like a new permittivity value far outside what the two original materials had. By controlling the geometry of the bits though, the permittivity of the metamaterial byte can be controlled. All it takes is that the two materials have opposite permittivity values; one must be positive and the other negative.
Obviously this discovery could dramatically simplify the design of bulk metamaterials, especially as it opens up so many material combinations. The researchers did their simulations with silver and glass, but if these materials do not have the necessary physical properties to be used as a hyperlens, another combination could be found and the lens made from that.
Source: University of Pennsylvania
Posted: December 3, 2014 02:15PM
Since the first rumble pack was developed, people have been trying to developer better and more advanced haptic systems to provide users with tactile information. In some cases haptics have even been used for rehabilitation and surgical training. Researchers at the University of Bristol have recently described a way to create 3D haptic shapes, which users can feel in mid-air.
To create these floating 3D shapes, the researchers use ultrasound patterns that combine and cancel out to create air disturbances. These disturbances are invisible but can be felt by a hand entering the projected, haptic shape. To visualize the effect, the researchers aimed the patterns at a layer of oil, showing off the technologies ability to project moving objects and multiple objects at the same time.
Last year some of the same researchers also developed UltraHaptics technology, which could similarly provide haptic feedback in the air, though in that case to identify buttons on a display. This new technology could be used to let surgeons feel diseases, like tumors, by touching haptic recreations from CT scans.
Source: University of Bristol
Posted: December 3, 2014 06:09AM
At times I wonder if we will ever stop finding new uses for graphene. It has previously been found that graphene is impermeable to gases and most liquids, so many expected protons to be blocked, just as hydrogen is. Researchers at the University of Manchester though have found that protons can slip through, which may lead to applications in fuel cells.
Graphene is an atom-thick sheet of carbon with a hexagonal structure to it, like chicken wire. This structure, it turns out is able to block every gas, including hydrogen and helium, and all liquids but water. Protons, which are hydrogen atoms without an electron, were expected to also be blocked, but when the researchers tested it, they found the protons slipped through easily, especially if the temperature was elevated or catalytic nanoparticles covered the graphene film. This ability to let protons but not hydrogen through could also be present in boron nitride, which is also called white graphene, as it has the same structure.
This discovery could have valuable applications with fuel cells, as a replacement to existing proton membranes. These membranes are meant to only allow protons through, but some of the fuel can slip through too, degrading the cell's performance. As graphene even a thin film of graphene would block the fuel, that degradation would be prevented. The researchers point out that graphene could be used to harvest hydrogen from the air, by applying a current to it.
Source: University of Manchester
Posted: December 2, 2014 05:47AM
With as much as 15% of energy in the United States going toward air conditioning, technologies that can keep things cool efficiently are always of interest. Researchers at Stanford University have devised a novel approach that reflects and radiates heat into space with a passive and advanced mirror.
The mirror is a multilayered material just 1.8 microns thick, making it thinner than aluminum foil. It contains seven layers of silicon dioxide and hafnium oxide atop a layer of silver that have had their thicknesses tuned to best radiate infrared light into space, while also reflecting Sunlight. Radiating infrared light is one of the ways a warm body can give off heat, and at the frequency this light will be at, it will not warm the air it passes through. When the researchers tested their photonic radiative cooling mirror, as they are calling it, the mirror was almost 9 ºF cooler than the air surrounding it as it prevented some 97% of Sunlight from actually reaching the building.
Before we can see these mirrors deployed to reduce cooling costs, two issues must be addressed. Naturally, one is how to mass produce the mirrors, but the other is the daunting task of finding ways to effectively shuttle heat from inside a building to the radiator, so it can be sent to space.
Source: Stanford University
Posted: December 1, 2014 02:06PM
On the surface of the Earth we are not exposed to much radiation, but surrounding the planet are belts of very high energy radiation, such as electrons traveling at nearly the speed of light. For years now we have observed at these ultrarelativistic electrons do not come to close to the Earth, but have not understood why. Using data from NASA's Van Allen Probes, researchers at MIT have devised an explanation that could be of great use for future satellites.
These ultrarelativistic electrons move so fast that they can complete an orbit of the Earth in just five minutes. With so much energy, they pose a serious risk to satellites and astronauts, but for conveniently they do not come within 11,000 Km of the Earth's surface. To explain this limit, the researchers looked at a few possibilities, including the Earth's magnetic field and ground-based radios. The magnetic field could not be the answer, because the limit is not affected by weak spots in it, and terrestrial radio waves would not affect the high energy electrons. What the researchers eventually determined was that the solution has to do with the plasmapheric hiss. This is a phenomenon of very low frequency electromagnetic waves in the Earth's upper atmosphere. The researchers determined that when the electrons encounter it, they are made to move parallel to the Earth's magnetic field, which causes them to collide with neutral gas atoms, which absorb them.
This explanations means there is a very firm barrier that will prevent any of these ultrarelativistic electrons from coming below 11,000 Km. Such information will be very important to future satellites, as it effectively gives them a safe zone where they will be free of this ionizing radiation, allowing for much longer lifespans.
Posted: December 1, 2014 05:52AM
One of the reasons so many materials are made from petrochemicals is because oil contains long chains of hydrocarbons. Synthesizing similar hydrocarbon chains has traditionally been all but impossible, but that has been changing of late. Now researchers at KU Leuven have found a way to convert cellulose into these materials, and with one more step, into gasoline.
Cellulose is a very common chemical on Earth because of its role in plant life, and it is already made of long chains of hydrocarbons. The catch is that it also has a lot of oxygen bonded to it, which has to be removed before being converted into petrochemicals. The researchers found a way to remove the oxygen though, such that waste materials like sawdust could be thrown into a chemical reactor with a catalyst, and at the right temperature and pressure, the desired hydrocarbons will be produced half a day later.
While using this method to produce gasoline is one application, it could also be used to create ethylene, propylene, and benzene, which can become rubber, plastic, nylon, insulating foam, and more.
Source: KU Leuven
Posted: November 28, 2014 06:04AM
Some scientific discoveries are the results of weird confluence of concepts, and this would likely be an example of such. For some time researchers have known that adding a pattern to the surface of a solar cell can improve its efficiency. Those at Northwestern University though, have found that the data-storage patterns on Blu-Ray discs, any disc, are nearly optimal at improving efficiency.
The reason patterns improve efficiency is because they more effectively scatter light into the cell. As it turns out, the nanoscale patterns that store data on Blu-Ray discs are nearly the ideal texture, and it does not matter what the data is. Why the data did not matter puzzled the researchers, but then one of their wives, who is also a database engineer at IBM, suggested that data compression could be involved, and this turned out to be correct. The data compression methods used on Blu-Ray discs ensure the pattern reduced is a quasi-random sequence of pits and island and that there are no longer strings of consecutive pits or islands, for error tolerance.
The resulting quasi-random patterns have feature sizes between 150 nm and 525 nm, which actually works well for trapping light across the solar spectrum. So far the researchers have tested it on polymer solar cells, but it should have applications with other kinds of solar cells as well.
Source: Northwestern University
Posted: November 26, 2014 02:15PM
Data storage is a big deal as all computers require it and in the case of RAM, it can also be one of the significant power sinks. This is because RAM has to continually refresh the information stored within it. High speed, nonvolatile memory would address this issue as it would not need the constant rewriting, and researchers at the University of Nebraska-Lincoln have recently found a way to improve a potential replacement for RAM.
Ferroelectric tunnel junctions contain a very thin ferroelectric layer between two electrodes. The layer is thin enough that electrons can tunnel through it, but only if its polarization allows. This polarization can be changed by applying a voltage. What the Nebraska-Lincoln researchers have done is created such a junction using graphene electrodes and ammonia. Graphene is an atom-thick sheet of carbon atoms that is highly conductive. The ammonia is placed between the graphene and the ferroelectric layer, and the key here was how the graphene interacted with the ammonia. The combination resulted in a greater difference between the on and off states of the junction, making it clearer which state it was in.
A larger gap between states will make it easier to quickly read the stored data. The researchers also found indications that the graphene-ammonia combination may increase the stability of the ferroelectric layer, which will tend to relax over time, losing its polarization.
Source: University of Nebraska-Lincoln
Posted: November 26, 2014 06:58AM
Electricity and magnetism are two fairly different phenomena and at times, technologies based on them compete with each other, as they both have advantages and disadvantages. Many are working to develop technologies that employ both though, to tap the advantages of both, without the disadvantages. Researchers at MIT have recently made a discovery that could enable just that in computer memory and likely more.
The researchers were working with a device that looks similar to a capacitor, in that it has two conductive layers separated by an insulating layer. In this device though, both conducting layers are magnetic, but one has a fixed magnetic orientation while the other can be switched between orientations. When the two layers have the same orientation, more electricity can get through the insulating layer than if the orientations were different. The switching is achieved by applying a voltage. What the researchers discovered is that if the insulating material is an oxide, the voltage is 100 times more powerful at altering the magnetic properties. This is because the oxygen ions in the insulating layer would move in response to the voltage.
This discovery could one day be used to create a nonvolatile magnetic memory system and already the researchers have achieved a switching rate of a megahertz. Of course it will have to be faster than that to compete with modern, electrical memory, but this discovery could also open doors to controlling other properties, such as reflectivity and thermal conductance.