Light created from a vacuum

ScienceDaily (Nov. 18, 2011) — Scientists at Chalmers have succeeded in creating light from vacuum -- observing an effect first predicted over 40 years ago. In an innovative experiment, the scientists have managed to capture some of the photons that are constantly appearing and disappearing in the vacuum.

The results have been published in the journal Nature.

The experiment is based on one of the most counterintuitive, yet, one of the most important principles in quantum mechanics: that vacuum is by no means empty nothingness. In fact, the vacuum is full of various particles that are continuously fluctuating in and out of existence. They appear, exist for a brief moment and then disappear again. Since their existence is so fleeting, they are usually referred to as virtual particles.

Chalmers scientist, Christopher Wilson and his co-workers have succeeded in getting photons to leave their virtual state and become real photons, i.e. measurable light. The physicist Moore predicted way back in 1970 that this should happen if the virtual photons are allowed to bounce off a mirror that is moving at a speed that is almost as high as the speed of light. The phenomenon, known as the dynamical Casimir effect, has now been observed for the first time in a brilliant experiment conducted by the Chalmers scientists.

"Since it's not possible to get a mirror to move fast enough, we've developed another method for achieving the same effect," explains Per Delsing, Professor of Experimental Physics at Chalmers. "Instead of varying the physical distance to a mirror, we've varied the electrical distance to an electrical short circuit that acts as a mirror for microwaves."

The "mirror" consists of a quantum electronic component referred to as a SQUID (Superconducting quantum interference device), which is extremely sensitive to magnetic fields. By changing the direction of the magnetic field several billions of times a second the scientists were able to make the "mirror" vibrate at a speed of up to 25 percent of the speed of light.

"The result was that photons appeared in pairs from the vacuum, which we were able to measure in the form of microwave radiation," says Per Delsing. "We were also able to establish that the radiation had precisely the same properties that quantum theory says it should have when photons appear in pairs in this way."

What happens during the experiment is that the "mirror" transfers some of its kinetic energy to virtual photons, which helps them to materialise. According to quantum mechanics, there are many different types of virtual particles in vacuum, as mentioned earlier. Göran Johansson, Associate Professor of Theoretical Physics, explains that the reason why photons appear in the experiment is that they lack mass.

"Relatively little energy is therefore required in order to excite them out of their virtual state. In principle, one could also create other particles from vacuum, such as electrons or protons, but that would require a lot more energy."

The scientists find the photons that appear in pairs in the experiment interesting to study in closer detail. They can perhaps be of use in the research field of quantum information, which includes the development of quantum computers.

However, the main value of the experiment is that it increases our understanding of basic physical concepts, such as vacuum fluctuations -- the constant appearance and disappearance of virtual particles in vacuum. It is believed that vacuum fluctuations may have a connection with "dark energy" which drives the accelerated expansion of the universe. The discovery of this acceleration was recognised this year with the awarding of the Nobel Prize in Physics.

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A new technique makes it possible to reduce by half the amount of salt in already desalted cod

ScienceDaily (Nov. 18, 2011) — A team of researchers belonging to the Universitat Politècnica de València's CUINA group has achieved a 50% reduction in the amount of salt in already desalted cod, thus obtaining a final product that preserves all its sensory properties and is particularly suitable for persons with hypertension.

This research has been published in the Journal of Food Engineering.

The key to reducing the amount of salt in cod is to partially replace sodium with potassium after the desalting process. "Once we have desalted the cod, we introduce a piece of it in a solution containing potassium chloride. During this process, a partial exchange of sodium for potassium takes place -it is like a second desalting. Thus, we get a piece of cod containing 50% less sodium than standard desalted cod," says José Manuel Barat, a researcher at the UPV's CUINA group. The fish also retains all its properties of flavour, texture, etc., as show the results of several sensory studies that have been conducted in the UPV's laboratories. It also contains enough salt so that it can be stored under refrigeration for as long as is needed. So far, this new technique has been applied -and validated- in laboratory tests.

This new method proposed by researchers at the UPV's CUINA group responds to an increasingly important demand by the food industry for developing low-salt products. "With this technique, we open the door to offering a new product both to those consumers who, for medical reasons, must have little salt in their diet, and to the general public, who are advised to reduce their sodium intake. Furthermore, by replacing sodium chloride with potassium chloride we get an even healthier product," says José Manuel Barat.

Researchers at the UPV's CUINA group have extensive experience in the processes of salting and desalting food. They also have several patents, including a method for desalting and preserving fish.

This experience and this knowledge were applied to a collaborative project with the fishing industry company Conservas Ubago, which resulted in the commercialization of ready-to-cook refrigerated desalted cod. "Even though it was desalted cod, it still had a certain amount of salt, as it is necessary in order to store refrigerated cod. Now we have gone a step further, and have reduced even that sodium content. We have thus laid the ground for the development of a new product, with less sodium and more potassium, with all its properties unaltered, particularly suitable for diets with a low sodium content," said José Manuel Barat.

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New tool saves time, reduces risk of mistakes in diabetes care

ScienceDaily (Nov. 18, 2011) — In the fast-paced world of health care, doctors are often pressed for time during patient visits. Researchers at the University of Missouri developed a tool that allows doctors to view electronic information about patients' health conditions related to diabetes on a single computer screen. A new study shows that this tool, the diabetes dashboard, saves time, improves accuracy and enhances patient care.

The diabetes dashboard provides information about patients' vital signs, health conditions, current medications, and laboratory tests that may need to be performed. The study showed that physicians who used the dashboard were able to correctly identify data they were searching for 100 percent of the time, compared with 94 percent using traditional electronic medical records. Further, the number of mouse clicks needed to find the information was reduced from 60 to three when using the diabetes dashboard.

Richelle Koopman, associate professor of family and community medicine in the School of Medicine, says diabetes care is complex because there are so many other health conditions associated with the disease; thus coordination of treatments is required. The goal of the diabetes dashboard is to make it easier for doctors to make the right decision about treatments.

"The diabetes dashboard is so intuitive that it makes it hard for physicians not to do the right thing," Koopman said. "Doctors can see, at a glance, everything that might affect their decision. This frees up their minds and helps them make better decisions about patients' care."

According to Koopman, the research has important implications for patient safety and costs. For example, the dashboard shows doctors a list of tests that are standard for diabetes patients and indicates whether patients have recently had the tests or need to have them. This eliminates the potential for physicians to order costly tests that are not necessary.

"It is difficult to quantify how much money the dashboard saves, but in terms of time and accuracy, the savings are substantial," Koopman said. "Doctors are still going to spend 15 minutes with each patient, but instead of using a large portion of that time to search through charts for information, they can have interactive conversations with patients about lifestyle and diet changes that are important for diabetes care."

The researchers say the dashboard was well received by doctors who tested it because it was designed by physicians familiar with their needs. The study, published in Annals of Family Medicine, was a collaboration among the MU School of Medicine, The Informatics Institute, the School of Information Science and Learning Technologies in the College of Education, the Center for Health Care Quality and the Sinclair School of Nursing.

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A corny turn for biofuels from switchgrass

ScienceDaily (Nov. 18, 2011) — Many experts believe that advanced biofuels made from cellulosic biomass are the most promising alternative to petroleum-based liquid fuels for a renewable, clean, green, domestic source of transportation energy. Nature, however, does not make it easy. Unlike the starch sugars in grains, the complex polysaccharides in the cellulose of plant cell walls are locked within a tough woody material called lignin. For advanced biofuels to be economically competitive, scientists must find inexpensive ways to release these polysaccharides from their bindings and reduce them to fermentable sugars that can be synthesized into fuels.

An important step towards achieving this goal has been taken by researchers with the U.S. Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI), a DOE Bioenergy Research Center led by the Lawrence Berkeley National Laboratory (Berkeley Lab).

A team of JBEI researchers, working with researchers at the U.S. Department of Agriculture's Agricultural Research Service (ARS), has demonstrated that introducing a maize (corn) gene into switchgrass, a highly touted potential feedstock for advanced biofuels, more than doubles (250 percent) the amount of starch in the plant's cell walls and makes it much easier to extract polysaccharides and convert them into fermentable sugars. The gene, a variant of the maize gene known as Corngrass1 (Cg1), holds the switchgrass in the juvenile phase of development, preventing it from advancing to the adult phase.

"We show that Cg1 switchgrass biomass is easier for enzymes to break down and also releases more glucose during saccharification," says Blake Simmons, a chemical engineer who heads JBEI's Deconstruction Division and was one of the principal investigators for this research. "Cg1 switchgrass contains decreased amounts of lignin and increased levels of glucose and other sugars compared with wild switchgrass, which enhances the plant's potential as a feedstock for advanced biofuels."

The results of this research are described in a paper published in the Proceedings of the National Academy of Sciences (PNAS) titled "Overexpression of the maize Corngrass1 microRNA prevents flowering, improves digestibility, and increases starch content of switchgrass."

Lignocellulosic biomass is the most abundant organic material on earth. Studies have consistently shown that biofuels derived from lignocellulosic biomass could be produced in the United States in a sustainable fashion and could replace today's gasoline, diesel and jet fuels on a gallon-for-gallon basis. Unlike ethanol made from grains, such fuels could be used in today's engines and infrastructures and would be carbon-neutral, meaning the use of these fuels would not exacerbate global climate change. Among potential crop feedstocks for advanced biofuels, switchgrass offers a number of advantages. As a perennial grass that is both salt- and drought-tolerant, switchgrass can flourish on marginal cropland, does not compete with food crops, and requires little fertilization. A key to its use in biofuels is making it more digestible to fermentation microbes.

"The original Cg1 was isolated in maize about 80 years ago. We cloned the gene in 2007 and engineered it into other plants, including switchgrass, so that these plants would replicate what was found in maize," says George Chuck, lead author of the PNAS paper and a plant molecular geneticist who holds joint appointments at the Plant Gene Expression Center with ARS and the University of California (UC) Berkeley. "The natural function of Cg1 is to hold pants in the juvenile phase of development for a short time to induce more branching. Our Cg1 variant is special because it is always turned on, which means the plants always think they are juveniles."

Chuck and his colleague Sarah Hake, another co-author of the PNAS paper and director of the Plant Gene Expression Center, proposed that since juvenile biomass is less lignified, it should be easier to break down into fermentable sugars. Also, since juvenile plants don't make seed, more starch should be available for making biofuels. To test this hypothesis, they collaborated with Simmons and his colleagues at JBEI to determine the impact of introducing the Cg1 gene into switchgrass.

In addition to reducing the lignin and boosting the amount of starch in the switchgrass, the introduction and overexpression of the maize Cg1 gene also prevented the switchgrass from flowering even after more than two years of growth, an unexpected but advantageous result.

"The lack of flowering limits the risk of the genetically modified switchgrass from spreading genes into the wild population," says Chuck.

The results of this research offer a promising new approach for the improvement of dedicated bioenergy crops, but there are questions to be answered. For example, the Cg1 switchgrass biomass still required a pre-treatment to efficiently liberate fermentable sugars.

"The alteration of the switchgrass does allow us to use less energy in our pre-treatments to achieve high sugar yields as compared to the energy required to convert the wild type plants," Simmons says. "The results of this research set the stage for an expanded suite of pretreatment and saccharification approaches at JBEI and elsewhere that will be used to generate hydrolysates for characterization and fuel production."

Another question to be answered pertains to the mechanism by which Cg1 is able to keep switchgrass and other plants in the juvenile phase.

"We know that Cg1 is controlling an entire family of transcription factor genes," Chuck says, "but we have no idea how these genes function in the context of plant aging. It will probably take a few years to figure this out."

Co-authoring the PNAS paper with Chuck and Simmons were Christian Tobias, Lan Sun, Florian Kraemer, Chenlin Li, Dean Dibble, Rohit Arora, Jennifer Bragg, John Vogel, Seema Singh, Markus Pauly and Sarah Hake.

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Boosting LED Efficiency: Zinc Oxide Microwires Improve Performance of Light-Emitting Diodes (LEDs) Through the Piezo-Phototronic Effect

ScienceDaily (Oct. 31, 2011) — Researchers have used zinc oxide microwires to significantly improve the efficiency at which gallium nitride light-emitting diodes (LED) convert electricity to ultraviolet light. The devices are believed to be the first LEDs whose performance has been enhanced by the creation of an electrical charge in a piezoelectric material using the piezo-phototronic effect.
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By applying mechanical strain to the microwires, researchers at the Georgia Institute of Technology created a piezoelectric potential in the wires, and that potential was used to tune the charge transport and enhance carrier injection in the LEDs. This control of an optoelectronic device with piezoelectric potential, known as piezo-phototronics, represents another example of how materials that have both piezoelectric and semiconducting properties can be controlled mechanically.

"By utilizing this effect, we can enhance the external efficiency of these devices by a factor of more than four times, up to eight percent," said Zhong Lin Wang, a Regents professor in the Georgia Tech School of Materials Science and Engineering. "From a practical standpoint, this new effect could have many impacts for electro-optical processes -- including improvements in the energy efficiency of lighting devices."

Details of the research were reported in the Sept. 14 issue of the journal Nano Letters. The research was sponsored by the Defense Advanced Research Projects Agency (DARPA) and the U.S. Department of Energy (DOE). In addition to Wang, the research team mainly included Qing Yang, a visiting scientist at Georgia Tech from the Department of Optical Engineering at Zhejiang University in China.

Because of the polarization of ions in the crystals of piezoelectric materials such as zinc oxide, mechanically compressing or otherwise straining structures made from the materials creates a piezoelectric potential -- an electrical charge. In the gallium nitride LEDs, the researchers used the local piezoelectric potential to tune the charge transport at the p-n junction.

The effect was to increase the rate at which electrons and holes recombined to generate photons, enhancing the external efficiency of the device through improved light emission and higher injection current. "The effect of the piezo potential on the transport behavior of charge carriers is significant due to its modification of the band structure at the junction," Wang explained.

The zinc oxide wires form the "n" component of a p-n junction, with the gallium nitride thin film providing the "p" component. Free carriers were trapped at this interface region in a channel created by the piezoelectric charge formed by compressing the wires.

Traditional LED designs use structures such as quantum wells to trap electrons and holes, which must remain close together long enough to recombine. The longer that electrons and holes can be retained in proximity to one another, the higher the efficiency of the LED device will ultimately be.

The devices produced by the Georgia Tech team increased their emission intensity by a factor of 17 and boosted injection current by a factor of four when compressive strain of 0.093 percent was applied to the zinc oxide wire. That improved conversion efficiency by as much as a factor of 4.25.

The LEDs fabricated by the research team produced emissions at ultraviolet wavelengths (about 390 nanometers), but Wang believes the wavelengths can be extended into the visible light range for a variety of optoelectronic devices. "These devices are important for today's focus on green and renewable energy technology," he said.

In the experimental devices, a single zinc oxide micro/nanowire LED was fabricated by manipulating a wire on a trenched substrate. A magnesium-doped gallium nitride film was grown epitaxially on a sapphire substrate by metalorganic chemical vapor deposition, and was used to form a p-n junction with the zinc oxide wire.

A sapphire substrate was used as the cathode that was placed side-by-side with the gallium nitride substrate with a well-controlled gap. The wire was placed across the gap in close contact with the gallium nitride. Transparent polystyrene tape was used to cover the nanowire. A force was then applied to the tape by an alumina rod connected to a piezo nanopositioning stage, creating the strain in the wire.

The researchers then studied the change in light emission produced by varying the amount of strain in 20 different devices. Half of the devices showed enhanced efficiency, while the others -- fabricated with the opposite orientation of the microwires -- showed a decrease. This difference was due to the reversal in the sign of the piezo potential because of the switch of the microwire orientation from +c to -c.

High-efficiency ultraviolet emitters are needed for applications in chemical, biological, aerospace, military and medical technologies. Although the internal quantum efficiencies of these LEDs can be as high as 80 percent, the external efficiency for a conventional single p-n junction thin-film LED is currently only about three percent.

Beyond LEDs, Wang believes the approach pioneered in this study can be applied to other optical devices that are controlled by electrical fields.

"This opens up a new field of using the piezoelectric effect to tune opto-electronic devices," Wang said. "Improving the efficiency of LED lighting could ultimately be very important, bringing about significant energy savings because so much of the world's energy is used for lighting."

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World's Most Efficient Flexible Organic Light-Emitting Diodes Created On Plastic

Researchers in the University of Toronto's Department of Materials Science & Engineering have developed the world's most efficient organic light-emitting diodes (OLEDs) on plastic. This result enables a flexible form factor, not to mention a less costly, alternative to traditional OLED manufacturing, which currently relies on rigid glass.
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The results are reported online in the latest issue of Nature Photonics.

OLEDs provide high-contrast and low-energy displays that are rapidly becoming the dominant technology for advanced electronic screens. They are already used in some cell phone and other smaller-scale applications.

Current state-of-the-art OLEDs are produced using heavy-metal doped glass in order to achieve high efficiency and brightness, which makes them expensive to manufacture, heavy, rigid and fragile.

"For years, the biggest excitement behind OLED technologies has been the potential to effectively produce them on flexible plastic," says Materials Science & Engineering Professor Zheng-Hong Lu, the Canada Research Chair (Tier I) in Organic Optoelectronics.

Using plastic can substantially reduce the cost of production, while providing designers with a more durable and flexible material to use in their products.

The research, which was supervised by Professor Lu and led by PhD Candidates Zhibin Wang and Michael G. Helander, demonstrated the first high-efficiency OLED on plastic. The performance of their device is comparable with the best glass-based OLEDs, while providing the benefits offered by using plastic.

"This discovery, unlocks the full potential of OLEDs, leading the way to energy-efficient, flexible and impact-resistant displays," says Professor Lu.

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Hospital team significantly reduced risk of further vascular events after 'mini strokes'

ScienceDaily (Oct. 27, 2011) — Patients who had a transient ischaemic attack (TIA), sometimes referred to as a "mini stroke," were much less likely to experience further vascular events in the first year if their care was co-ordinated by a special hospital team. That is the key finding from a study published in the November issue of the European Journal of Neurology.

Researchers from the Department of Neurology at Aarhus University Hospital in Denmark studied 306 patients admitted to the hospital with a TIA. They found that when the patients were treated by an acute TIA team their cumulated risk of having a stroke in the first seven days was 65% lower than expected. The cumulated risk in the first 90 days fell by 74%.

"The aim of our study was to see if patients had better clinical outcomes if they were under the care of a special team, which integrated outpatient care and stroke unit facilities and provided on-going nurse-led counselling" says lead author Dr Paul von Weitzel-Mudersbach.

"TIA, which is caused by a temporary lack of blood to part of the brain, is a serious condition associated with a high short-term risk of ischaemic stroke. Previous research has shown that the cumulated stroke risk in the first three months after a TIA is ten to 12% in unselected patients and more than 30% in patients with carotid stenosis, a dangerous narrowing of the largest blood vessels that deliver blood to the brain.

"Although urgent intervention has been shown to reduce the risk of stroke, a number of previous studies have shown poor long-term drug compliance in many patients."

The patients were referred directly to the acute TIA team by their family doctor or ambulance, bypassing the emergency department. Patients who had suffered a TIA in the last 48 hours, and those with multiple TIA, faced a high risk of stroke and were admitted to the stroke unit. This offered the option for immediate preventative action, including thrombolysis drugs, to break up blood clots in the case of recurrent stroke. The other patients were seen in the outpatients department within three days of referral.

All the patients seen by the team received acute treatment with antithrombotic and cholesterol lowering drugs and were offered fast-track surgery if they had carotid stenosis. Follow-up included nurse-conducted health counselling after seven, 90 and 365 days. Each contact included the importance of secondary prevention, such as drug compliance and stopping smoking.

Key findings of the study included:

Just under two-thirds of the patients were admitted immediately after their TIA (65%) with the rest being seen as outpatients. Inpatient stays averaged one day.Over half (58%) were seen within 24 hours of their TIA and 70% within 24 hours of the call for attention. The figures at one week were 76% and 89% respectively.Just over 5% had a stroke, non-fatal heart attack or died from a vascular event within a year of their TIA.The cumulated stroke risk was calculated and compared with the ABCD2 score, an established method of identifying individuals with a high early risk of stroke after a TIA. The actual scores in the Aarhus study were 1.6% and 2% after seven and 90 days, significantly lower than the ABCD2 predicted stroke scores of 4.5% and 7.5%.Early surgery to remove the build up of plaque in the carotid blood vessels was performed in 8.5% of patients. However, the authors believe this only played a minor role in the reduced risk.The majority of the patients (95%) fulfilled at least one secondary prevention measure: reduced blood pressure, reduced cholesterol, no smoking and self-reported adherence to antithrombotic treatment. 48% achieved three out of the four targets.Most of the patients (93%) adhered to their antithrombotic treatment.More than 60% of the patients who smoked at the time of their TIA changed their smoking habits -- 31% quit and 29.5% reduced their smoking by at least 50%. Most of the changes happened in the first seven days.

"Our study shows that urgent treatment of patients with TIA is feasible and associated with a substantial reduction in stroke risk during the first three months, which is consistent with previous studies from the UK and France" says Dr von Weitzel-Mudersbach.

"We believe that early and aggressive antithrombotic treatment may play a major role in the reduction of short-term stroke risk in most patients. Meanwhile, the combination of secondary prevention efforts with a relatively high compliance rate -- including the essential telephone follow-up provided by a specially trained nurse in the first three months -- was probably responsible for the low long-term risk of adverse clinical outcome.

"Treating TIA by deploying a specialist team that can admit patients when the risk of recurrent symptoms is highest and prompt thrombolysis can be used, combined with nurse-conducted health counselling, seems to be effective."

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The above story is reprinted from materials provided by Wiley-Blackwell.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

P. v. Weitzel-Mudersbach, S. P. Johnsen, G. Andersen. Low risk of vascular events following urgent treatment of transient ischaemic attack: the Aarhus TIA study. European Journal of Neurology, 2011; 18 (11): 1285 DOI: 10.1111/j.1468-1331.2011.03452.x

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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