Low-Cost Carbon Capture Gets X-Rayed

Diamond Light Source is being used to improve low cost methods for carbon capture. 

Scientists from the University of Leeds are using the UK's national synchrotron to investigate the efficiency of calcium oxide (CaO) based materials as carbon dioxide (CO₂) sorbents. Their results, published in the journal of Energy & Environmental Science, provide an explanation for one of the key mechanisms involved. This new knowledge will inform efforts to improve the efficiency of this economically viable method of carbon capture and storage.

Current techniques for post-combustion carbon capture filter out CO₂ from a power plant's flue gases as they travel up a chimney. The filter is a solvent that absorbs the CO₂, before being heated, releasing water vapour and leaving behind the CO₂. In pre-combustion, the CO₂ is filtered out by use of a catalytic converter before the fossil fuel is burned and the CO₂ is diluted by other flue gases. These methods can prevent 80% to 90% of a power plant's carbon emissions from entering the atmosphere.

CaO based materials have a large range of applications including pre- and post-combustion carbon capture technologies and thermochemical fuel upgrading. They are low cost, high abundance, have a large sorption capacity and fast reaction rates during the chemical process. They capture CO₂in the temperature range 400-800 °C via the formation of calcium carbonate (CaCO3) which can be regenerated with subsequent release of CO₂, ready for compression and storage. However, after multiple capture and regeneration cycles, the materials' capacity for capture decreases due to the loss of surface area through sintering, a process that fuses powders together to create a single solid object. Although the surface area can be restored through hydration, the material suffers a reduction in mechanical strength. If these problems can be overcome, CaO based materials could provide a low cost answer for carbon capture on a very large scale.

Led by Dr Valerie Dupont and Dr Tim Comyn from the University of Leeds' Faculty of Engineering, the team carried out a series of experiments on Diamond's High resolution powder diffraction beamline, I11, using intense X-rays to study the carbon capture and hydration process in CaO based materials on the nano-scale. Their observations suggest a mechanism for the interaction between CaO and water during hydration.

Roger Molinder, an Engineering and Physical Sciences Research Council (EPSRC) funded PhD student on the project, describes, "Using the high resolution powder diffraction beamline at the Diamond synchrotron was key to this discovery; conventional X-ray sources such as those found at most Universities in the UK provide data with broad peaks, which do not make this sort of analysis possible. From a rigorous analysis of peak shapes arising from the data, we were able to determine the shape and size of the hydroxide phase, and determine the level of stress. Knowledge of these derived parameters is key to understanding the mechanism of sintering/disintegration."

Concerns about global warming have prompted both national and international efforts to curb CO₂ emissions. CaO based materials are a promising candidate for the removal of CO₂from flue gases at temperatures between 400 and 800 °C from processes such as fossil-fuel combustion. They are also being considered as a means to remove the CO₂ that is generated as a result of thermochemical fuel upgrading with biomass sources, which are growing more and more popular as an alternative to fossil fuels. Using CaO based materials for carbon capture is just one of the ways to combat global warming. Since CaO based materials are low cost, there is an economic incentive to solve the problem of surface area loss to potentially turn this into a method for large scale CO₂ capture. These recently published results are a promising step towards improving these low cost methods.

Read More

Mathematicians Solve Decade-Old Debate On Regulation of Protein Production by microRNAs in Cells

An international team of mathematicians has proposed a new solution to understanding a biological puzzle that has confounded molecular biologists.

They have applied a mathematical model to work out the functioning of small molecules known as microRNAs -- components of the body akin to the electronics in modern airplanes.

For a long time molecular biologists thought that the major role of RNA in living cells was to serve as a copy of a gene and a template for producing proteins, major cell building blocks. This belief had been changed at the end of 90s when it was found that myriads of RNA molecules are involved in regulating speeds of practically all molecular mechanisms in a cell. These abundant molecules are essential in regulating the speed of protein production- a vital function in bodily processes, including development, differentiation and cancer.

The problem to date has been that scientists have differed over interpretations of how the production of the major building blocks of a cell, proteins, is controlled by microRNAs.

Basically, there were different and sometimes conflicting theories about ways in which microRNAs regulate protein production since the results varied depending on only slightly changed experimental conditions.

Professor Alexander Gorban, who holds a Chair in Applied Mathematics at University of Leicester, said: "The old metaphor of an elephant and blind scientists trying to describe it will be always relevant to science. However, often we use it only as a metaphor, as a generic statement. In this project the elephant's metaphor can be applied literally as a working principle.

"Different biological labs or slightly changed experimental conditions meant that results were different for investigators.

"Quite dramatically, there has been a series of reports in top-ranked journals with contradictory results supporting one or another mechanism. Furthermore, researchers are puzzled by the fact that the same couple of protein and microRNA demonstrate different mechanisms of regulation in different biological labs or in slightly changed experimental conditions."

The mathematical model constructed by Professor Gorban from University of Leicester and Andrei Zinovyev from Institut Curie in Paris in collaboration with biologists Nadya Morozova and Annick Harel-Bellan from CNRS in France showed that there might be one simple mechanism which manifests itself differently in different conditions. Their findings are due to be published in the RNA Journal.

Professor Gorban said: "We have shown that what appeared to be very different mechanisms are in fact manifestations of one relatively simple biochemical reaction, but taking place in various contexts.

"Our model proposes that microRNA performs many actions simultaneously to the protein development, basically acting to get the job done (regulating the speed of protein production) in a stable and efficient way, given whatever conditions the experiment is occurring in.

"If this model is accepted, we would be able to take active steps in determining what the main mechanism of microRNA action is, as the model suggests experiments to verify the hypothesis. This in turn should lead to a resolution of a decade long debate to understand the means in which these very important molecules actually work."

Pat Heslop-Harrison, Professor of Cell Biology at the University of Leicester, said: "The discovery of miRNA and its regulatory role has completely changed our view of how genes in cells are controlled.

"Understanding all the ways the regulation is happening and interpreting experimental evidence has proved a huge challenge. In this important new paper, Alexander, Andrei, Nadya and colleagues overview the characteristic features of no less than nine different mechanisms, and then generate a unifying model of the whole system integrating the nine mechanisms.

"The multifunctional model gives dynamic predictions of gene control; it can now be tested to understand significance of the various mechanisms coexisiting under different conditions. It will be exciting to link this back the huge range of functions and responses of organisms and understanding miRNA control mechanisms is a systematic and predictive way."

Read More

Curiosity On Track: Early August Landing On Mars

Eight days before reaching Mars, NASA's Mars Science Laboratory spacecraft performed a flight-path adjustment scheduled more than nine months ago.

The trajectory correction maneuver completed late Saturday may be the last one the mission needs before landing day, though two further opportunities remain on its schedule in case they are needed.

The spacecraft is on course for delivering the mission's car-size rover, Curiosity, to a landing target beside a Martian mountain at about 10:31 p.m. PDT on Aug. 5. (1:31 a.m. on Aug. 6, EDT). After landing, the rover will spend a two-year prime mission studying whether the area has ever offered environmental conditions favorable for life.

The spacecraft used two brief thruster firings totaling about six seconds to adjust its trajectory at about 10 p.m. PDT on July 28 (1 a.m. on July 29, EDT). This maneuver had been on the mission's schedule since before launch on Nov. 26, 2011. It altered the flight path less than any of the spacecraft's three previous trajectory correction maneuvers on the way from Earth to Mars.

The Mars Science Laboratory spacecraft had been on a course in recent weeks that would have hit a point at the top of the Martian atmosphere about 13 miles (21 kilometers) east of the target entry point. On landing day, it can steer enough during its flight through the upper atmosphere to correct for missing the target entry point by a few miles and still land on the intended patch of Mars real estate. The mission's engineers and managers rated the projected 13-mile miss big enough to warrant a correction maneuver.

"The purpose of this maneuver is to move the point at which Curiosity enters the atmosphere by about 13 miles," said Tomas Martin-Mur of NASA's Jet Propulsion Laboratory, Pasadena, Calif., chief of the mission's navigation team. "The first look at telemetry and tracking data afterwards indicates the maneuver succeeded as planned."

The thruster firings altered the spacecraft's velocity by about one-fortieth of one mile per hour (one centimeter per second). Curiosity will enter Mars' atmosphere at a speed of about 13,200 mph (5,900 meters per second).

Opportunities for two further course corrections are scheduled in the final 48 hours before landing, if needed.

"I will not be surprised if this was our last trajectory correction maneuver," Martin Mur said of Saturday's event. "We will be monitoring the trajectory using the antennas of the Deep Space Network to be sure Curiosity is staying on the right path for a successful entry, descent and landing."

Descent from the top of Mars' atmosphere to the surface will employ bold techniques enabling use of a smaller target area and heavier landed payload than were possible for any previous Mars mission. These innovations, if successful, will place a well-equipped mobile laboratory into a locale especially well-suited for its mission of discovery. The same innovations advance NASA toward capabilities needed for human missions to Mars.

As of July 30, the Mars Science Laboratory spacecraft carrying the rover Curiosity will have traveled about 343 million miles (555 million kilometers) of its 352-million-mile (567-million-kilometer) flight to Mars.

JPL, a division of the California Institute of Technology in Pasadena, manages the mission for the NASA Science Mission Directorate, Washington. More information about Curiosity is online at http://www.nasa.gov/msl andhttp://mars.jpl.nasa.gov/msl/ . You can follow the mission on Facebook at: http://www.facebook.com/marscuriosity and on Twitter at: http://www.twitter.com/marscuriosity .

Read More

Eyes and Attention of Men and Women Meander in Distinctly Different Ways

In a new study published in the journal Vision Research, researchers at the University of Southern California show that the eyes and attention of men and women meander in distinctly different ways.

The article, authored by Dr. Laurent Itti and doctoral student John Shen, challenges the way scientists generally conceive of attention, or how sensory information is prioritized. While previous study of vision and attention had disregarded individual factors such as sex, race and age, Itti and Shen demonstrated that men and women pay visual attention in different ways.

Dr. Itti's lab studied 34 participants as they watched videos of people being interviewed. Behind the interview subjects, within the video frame, pedestrians, bicycles and cars passed by -- distractions included to pull attention away from the filmed conversation.

While participants watched and listened to the interview, another camera was pointed at participants' eyes, recording the movement of their pupils as they glanced across the screen.

Researchers discovered the following: • Men, when focused on the person being interviewed, parked their eyes on the speaker's mouth. They tended to be most distracted by distinctive movement behind the interview subjects • By contrast, women shift their focus between the interview subject's eyes and body. When they were distracted, it was typically by other people entering the video frame.

Dr. Laurent Itti, an associate professor of computer science at the USC Viterbi School of Engineering, runs USC's iLab, a research lab dedicated to gaining insight into biological brain function through the use of computational modeling. John Shen, also with iLab, is a Ph.D. student in the USC Neuroscience Graduate Program at the USC Dornsife College of Letters, Arts and Sciences and conducted this research as part of his doctoral thesis and USC Provost Neuroscience Fellowship.

Funding for the project came from the National Science Foundation, the U.S. Army Research Office, the U.S. Army.

Read More

Mathematicians Develop New Method for Describing Extremely Complicated Shapes

Mathematicians at the Institute for Advanced Study in New Jersey "bridged" topology and fractals and made a discovery that could lead to a new way of describing extremely complicated shapes such as the configuration of the tiniest defects in a metal or even the froth of a breaking wave.

Topology is a powerful branch of mathematics that looks at qualitative geometric properties such as the number of holes a geometric shape contains, while fractals are extremely complicated geometric shapes that appear similarly complicated even when viewed under a microscope of high magnification.

Bridging the topology and fractals, as described in the American Institute of Physics' Journal of Mathematical Physics (JMP), relies upon a recently developed mathematical theory, known as "persistent homology," which takes into account the sizes and number of holes in a geometric shape. The work described in JMP is a proof of concept based on fractals that have already been studied by other methods -- such as the shapes assumed by large polymer molecules as they twist or bend under random thermal fluctuation.

Many geometric structures with fractal-like complexity arise in nature, such as the configuration of defects in a metal or the froth of a breaking wave. Their geometry has important physical effects too, but until now we haven't had a vocabulary rich enough to adequately describe these and other complicated shapes. The mathematicians plan to use the vocabulary provided by persistent homology methods to investigate and describe complicated shapes in a whole new way.

Read More

Atomic Nucleus: Fissile Liquid or Molecule of Life?

A new view of the nucleus that unifies its liquid and molecule-like aspects has been put forward by a team from the Institut de Physique Nucléaire d'Orsay (Université Paris-Sud/CNRS) and from CEA (the French Atomic Energy Commission), in collaboration with the University of Zagreb. By making an analogy with neutron stars[1], the researchers have for the first time demonstrated one of the necessary conditions for the formation of molecule-like behavior within the atomic nucleus. Such molecule-like behavior makes it possible to understand the synthesis of elements that are key to the appearance of life.

The work is published in Nature dated 19 July 2012.

The atomic nucleus is generally described as a drop of quantum liquid with a diameter of around a million billionth of a meter. In particular, such liquid-like behavior explains nuclear fission, and applies especially to heavy nuclei, i.e. nuclei that contain a large number of nucleons (neutrons and protons). On the other hand, light nuclei[2] can behave like tiny 'molecules', or clusters, made up of neutrons and protons within the nucleus. This molecular aspect makes it possible to understand the stellar synthesis of carbon-12 and other heavier elements necessary for the appearance of life[3].

Until now, both the 'molecule-nucleus' and the 'liquid-nucleus' views coexisted. Now, a team from the Institut de Physique Nucléaire d'Orsay (Université Paris-Sud/CNRS) and from CEA (the French Atomic Energy Commission), in collaboration with the University of Zagreb, proposes a unified view of these two aspects. By solving quantum physics equations on the scale of the nucleus (in particular the Schrödinger equation), the researchers have demonstrated that, although a light nucleus can show molecule-like behavior (tending towards the crystalline state), heavier nuclei take on a liquid-like behavior.

To establish this new theory, the physicists took inspiration from neutron stars¹. The deeper you go inside a neutron star, the more you pass from a crystalline medium to a liquid medium. Thanks to this analogy, the physicists identified a mechanism of transition from the liquid to the crystalline state in the nucleus. When the interactions between neutrons and protons are not strong enough to fix them within the nucleus, the latter is in a quantum-liquid type state where protons and neutrons are delocalized. Conversely, in a crystalline state, neutrons and protons are fixed at regular intervals within the nucleus. The nuclear molecule is interpreted as being an intermediate state between a quantum liquid and a crystal. In the long term, the aim is to attain a unified understanding of the various states of the nucleus.

[1] The core of a massive star that collapses during a supernova explosion becomes so dense that protons and neutrons combine, forming neutrons. The resulting body becomes a kind of giant atomic nucleus made up mostly of neutrons, which is what gives it its name.

[2] Such as oxygen-16 (16O), which contains 8 neutrons and 8 protons.

[3] For instance, the Hoyle state of carbon-12, key to nucleosynthesis, is described as a nuclear molecule made up of three alpha particles. An alpha particle is a cluster of two neutrons and two protons.

Read More

Concussions and Head Impacts May Accelerate Brain Aging

Concussions and even lesser head impacts may speed up the brain's natural aging process by causing signaling pathways in the brain to break down more quickly than they would in someone who has never suffered a brain injury or concussion.

Researchers from the University of Michigan School of Kinesiology and the U-M Health System looked at college students with and without a history of concussion and found changes in gait, balance and in the brain's electrical activity, specifically attention and impulse control, said Steven Broglio, assistant professor of kinesiology and director of the Neurotrauma Research Laboratory.

The declines were present in the brain injury group up to six years after injury, though the differences between the study groups were very subtle, and outwardly all of the participants looked and acted the same.

Broglio, who is also affiliated with Michigan NeuroSport, stressed that the studies lay out a hypothesis where concussions and head impacts accelerate the brain's natural aging process.

The study appears in the July issue of journal Exercise and Sport Sciences Reviews.

"The last thing we want is for people to panic. Just because you've had a concussion does not mean your brain will age more quickly or you'll get Alzheimer's," Broglio said. "We are only proposing how being hit in the head may lead to these other conditions, but we don't know how it all goes together just yet."

Broglio stressed that other factors, such as lifestyle choices, smoking, alcohol consumption, physical exercise, family history and whether or not you "exercise" your brain also impact the brain's aging process. Concussion may only be one small factor.

To begin to understand how concussions might impact brain activity and its signaling pathways, researchers asked the participants to perform certain tasks in front of a computer, and took images of their brains. The brains of the nonconcussed group showed a greater area of electrical activation than the participants with a history of brain injury.

The signaling pathways in our brains are analogous to a five-lane highway. On a new highway, traffic runs smoothly and quickly as all lanes are in top shape. However, during normal aging, the asphalt deteriorates and lanes might become bumpy or even unusable. Traffic slows.

Similarly, our brains start with all pathways clear to transfer electrical signals rapidly. As we age, the brain's pathways break down and can't transfer the information as quickly. Concussive and other impacts to the head may result in a 'pothole' on the brain's highway, causing varying degrees of damage and speeding the pathway's natural deterioration.

"What we don't know is if you had a single concussion in high school, does that mean you will get dementia at age 50?" Broglio said. "Clinically, we don't see that. What we think is it will be a dose response.

"So, if you played soccer and sustained some head impacts and maybe one concussion, then you may have a little risk. If you went on and played in college and took more head balls and sustained two more concussions, you're probably at a little bigger risk. Then if you play professionally for a few years, and take more hits to the head, you increase the risk even more. We believe it's a cumulative effect."

In the next phase of study, researchers will look at people in their 20s, 40s and 60s who did and did not sustain concussions during high school sports. They hope to learn if there is an increasing effect of concussion as the study subjects age. 

Researchers from the departments of Physical Medicine and Rehabilitation, and Neurology, and the Michigan Alzheimer's Disease Center also participated in the study.

Read More

250 Years of Global Warming: Berkeley Earth Releases New Analysis

According to a new Berkeley Earth study released July 29, 2012, the average temperature of Earth's land has risen by 1.5 °C over the past 250 years. 

The temperature of the Earth’s land surface, as determined from over 36,000 temperature stations around the globe. The data is well fit by a simple model containing only known volcanic eruptions and carbon dioxide (dark line). No contribution from solar variability was necessary to make a good match. The rapid but short (decadal) variations are believed to be due to changes in ocean flows, such as El Nino and the Gulf Stream. (Credit: Image courtesy of Berkeley Earth Surface Temperature)

The good match between the new temperature record and historical carbon dioxide records suggests that the most straightforward explanation for this warming is human greenhouse gas emissions.

Together with their most recent results and papers, Berkeley Earth also released their raw data and analysis programs. They will be available online at BerkeleyEarth.orgon July 30.

The new analysis from Berkeley Earth goes all the way back to 1753, about 100 years earlier than previous groups' analyses. The limited land coverage prior to 1850 results in larger uncertainties in the behavior of the record; despite these, the behavior is significant.

Robert Rohde, Lead Scientist for Berkeley Earth and the person who carried out most of the analysis, noted that "Sudden drops in the early temperature record (1753 to 1850) correspond to known volcanic events." Volcanoes spew particles into the air, which then reflect sunlight and cool the earth for a few years. In the Berkeley Earth temperature plot, sudden dips in temperature caused by large volcanic explosions are evident back to the late 1700s.

Berkeley Earth compared the shape of the gradual rise over 250 years to simple math functions (exponentials, polynomials) and to solar activity (known through historical records of sunspot numbers), and even to rising functions such as world population.

Richard Muller, Founder and Scientific Director of Berkeley Earth, notes "Much to my surprise, by far the best match was to the record of atmospheric carbon dioxide, measured from atmospheric samples and air trapped in polar ice." He emphasizes that the match between the data and the theory doesn't prove that carbon dioxide is responsible for the warming, but the good fit makes it the strongest contender. "To be considered seriously, any alternative explanation must match the data at least as well as does carbon dioxide."

In its 2007 report the IPCC concluded only that "most" of the warming of the past 50 years could be attributed to humans. It was possible, according to the IPCC, that increased solar activity could have contributed to warming prior to 1956. Berkeley Earth analyzed about 5 times more station records than were used in previous analyses, and this expanded data base along with its new statistical approach allowed Berkeley Earth to go about 100 years farther back in time than previous studies. By doing so, the Berkeley Earth team was able to conclude that over 250 years, the contribution of solar activity to global warming is negligible.

Some of the scientists on the Berkeley Earth team admit surprise that the new analysis has shown such clear agreement between global land-­‐temperature rise and human-­‐caused greenhouse gases. "I was not expecting this," says Richard Muller, "but as a scientist, I feel it is my duty to let the evidence change my mind."

Elizabeth Muller, co-­‐Founder and Executive Director of Berkeley Earth, says that "One of our goals at Berkeley Earth is complete transparency -- we believe that everyone should be able to access raw climate data and do their own analysis. Scientists have a duty to be 'properly skeptical', and we are trying to lower the barriers to entry into the field."

Robert Rohde created an online feature that allows look up temperature records by location. "If you want to know what the temperature change has been in your city, your state, or even your country, you can now find this online atBerkeleyEarth.org" says Rohde. He adds, "We hope people will have a lot of fun interacting with the data." This feature should be available to the public by Monday, July 30.

A previous Berkeley Earth study, released in October 2011, found that the land-­‐surface temperature had risen by about 0.9 °C over the past 50 years (which was consistent with previous analyses) and directly addressed scientific concerns raised by skeptics, including the urban heat island effect, poor station quality, and the risk of data selection bias.

The Berkeley Earth team values the simplicity of its analysis, which does not depend on the large complex global climate models that have been criticized by climate skeptics for their hidden assumptions and adjustable parameters. The conclusion that the warming is due to humans is based simply on the close agreement between the shape of the observed temperature rise and the known greenhouse gas increase.

Elizabeth adds, "The current data does not include ocean temperatures; these will be added in the next phase of the Berkeley Earth studies. Another next step for our team is to think about the implications of our findings."

Read More

Record Efficiency for Next-Generation Solar Cells

Researchers from the University of Toronto (U of T) and King Abdullah University of Science & Technology (KAUST) have made a breakthrough in the development of colloidal quantum dot (CQD) films, leading to the most efficient CQD solar cell ever. Their work is featured in a letter published in Nature Nanotechnology.

The researchers, led by U of T Engineering Professor Ted Sargent, created a solar cell out of inexpensive materials that was certified at a world-record 7.0% efficiency.

"Previously, quantum dot solar cells have been limited by the large internal surface areas of the nanoparticles in the film, which made extracting electricity difficult," said Dr. Susanna Thon, a lead co-author of the paper. "Our breakthrough was to use a combination of organic and inorganic chemistry to completely cover all of the exposed surfaces."

Quantum dots are semiconductors only a few nanometres in size and can be used to harvest electricity from the entire solar spectrum -- including both visible and invisible wavelengths. Unlike current slow and expensive semiconductor growth techniques, CQD films can be created quickly and at low cost, similar to paint or ink. This research paves the way for solar cells that can be fabricated on flexible substrates in the same way newspapers are rapidly printed in mass quantities.

The U of T cell represents a 37% increase in efficiency over the previous certified record. In order to improve efficiency, the researchers needed a way to both reduce the number of "traps" for electrons associated with poor surface quality while simultaneously ensuring their films were very dense to absorb as much light as possible. The solution was a so-called "hybrid passivation" scheme.

"By introducing small chlorine atoms immediately after synthesizing the dots, we're able to patch the previously unreachable nooks and crannies that lead to electron traps," explained doctoral student and lead co-author Alex Ip. "We follow that by using short organic linkers to bind quantum dots in the film closer together."

Work led by Professor Aram Amassian of KAUST showed that the organic ligand exchange was necessary to achieve the densest film.

"The KAUST group used state-of-the-art synchrotron methods with sub-nanometer resolution to discern the structure of the films and prove that the hybrid passivation method led to the densest films with the closest-packed nanoparticles," stated Professor Amassian.

The advance opens up many avenues for further research and improvement of device efficiencies, which could contribute to a bright future with reliable, low cost solar energy.

According to Professor Sargent, "Our world urgently needs innovative, cost-effective ways to convert the sun's abundant energy into usable electricity. This work shows that the abundant materials interfaces inside colloidal quantum dots can be mastered in a robust manner, proving that low cost and steadily-improving efficiencies can be combined."

Read More

Higgs Excitations

Phase transitions between different states of matter can be associated with a specific type of excitation called the "Higgs excitation". This phenomenon has now been ob-served in a two-dimensional quantum gas at temperatures near absolute zero.

In physics spontaneous symmetry breaking is a fundamental feature of transitions between different states of matter. An example of this phenomenon is the abrupt alignment of spin orientation in a ferromagnetic substance when the material is cooled below the so-called Curie temperature. Phase transitions introduce a new degree of order into the system, which may in turn provoke a specific type of excitation that causes the ensemble of particles to behave in a coordinated fashion. If their collective motion conforms to rules akin to those of the theory of relativity, a so-called Higgs excitation may arise.

Tracking transient excitations

The Higgs excitation plays a key role in the Standard Model of Particle Physics, where it is associated with the famous Higgs boson. But Higgs excitations can also develop in solid-state-like systems. The problem is that, as in particle physics, they are difficult to detect ex-perimentally because they rapidly decay. Higgs excitations are expected to have particularly short lifetimes in low-dimensional atomic systems. Indeed, some physicists have doubted whether they could be observed in such systems at all.

An unpredictable phenomenon

A team of researchers led by Professor Immanuel Bloch, LMU physicist and a Director at the Max-Planck-Institute of Quantum Optics, in close collaboration with theorists at several American institutions, has now experimentally detected Higgs excitations in low-dimensional systems for the first time. For the experiments, they used an ultracold two-dimensional gas made up of rubidium atoms. This system is in the vicinity of a phase transition, in a state that behaves in accordance with relativistic field theories.

"We are excited to study phenomena close to absolute zero temperature that usually occur at the highest energies", says Bloch. Furthermore, the observations allow the researchers to characterize a phenomenon that is, as yet, not fully understood theoretically. This makes the new data still more valuable. (Nature, 2012) MPQ/göd

Read More

World's Smallest Semiconductor Laser Created

Physicists at The University of Texas at Austin, in collaboration with colleagues in Taiwan and China, have developed the world's smallest semiconductor laser, a breakthrough for emerging photonic technology with applications from computing to medicine.

The scientists report their efforts in this week's Science.

Miniaturization of semiconductor lasers is key for the development of faster, smaller and lower energy photon-based technologies, such as ultrafast computer chips; highly sensitive biosensors for detecting, treating and studying disease; and next-generation communication technologies.

Such photonic devices could use nanolasers to generate optical signals and transmit information, and have the potential to replace electronic circuits. But the size and performance of photonic devices have been restricted by what's known as the three-dimensional optical diffraction limit.

"We have developed a nanolaser device that operates well below the 3-D diffraction limit," said Chih-Kang "Ken" Shih, professor of physics at The University of Texas at Austin. "We believe our research could have a large impact on nanoscale technologies."

In the current paper, Shih and his colleagues report the first operation of a continuous-wave, low-threshold laser below the 3-D diffraction limit. When fired, the nanolaser emits a green light. The laser is too small to be visible to the naked eye.

The device is constructed of a gallium nitride nanorod that is partially filled with indium gallium nitride. Both alloys are semiconductors used commonly in LEDs. The nanorod is placed on top of a thin insulating layer of silicon that in turn covers a layer of silver film that is smooth at the atomic level.

It's a material that the Shih lab has been perfecting for more than 15 years. That "atomic smoothness" is key to building photonic devices that don't scatter and lose plasmons, which are waves of electrons that can be used to move large amounts of data.

"Atomically smooth plasmonic structures are highly desirable building blocks for applications with low loss of data," said Shih.

Nanolasers such as this could provide for the development of chips where all processes are contained on the chip, so-called "on-chip" communication systems. This would prevent heat gains and information loss typically associated with electronic devices that pass data between multiple chips.

"Size mismatches between electronics and photonics have been a huge barrier to realize on-chip optical communications and computing systems," said Shangjr Gwo, professor at National Tsing Hua University in Taiwain and a former doctoral student of Shih's.

Read More

New Dimension of Physics Research: Cutting the Graphene Cake

Researchers at The University of Manchester have demonstrated that graphene can be used as a building block to create new 3D crystal structures which are not confined by what nature can produce.

Sandwiching individual graphene sheets between insulating layers in order to produce electrical devices with unique new properties, the method could open up a new dimension of physics research.

Writing in Nature Materials, the scientists show that a new side-view imaging technique can be used to visualize the individual atomic layers of graphene within the devices they have built. They found that the structures were almost perfect even when more than 10 different layers were used to build the stack.

This surprising result indicates that the latest techniques of isolating graphene could be a huge leap forward for engineering at the atomic level.

This development gives more weight to graphene's suitability as a major component in the next generation of computer chips.

The researchers' side-view imaging approach works by first extracting a thin slice from the centre of the device. This is similar to cutting through a rock to reveal the geological layers or slicing into a chocolate gateaux to reveal the individual layers of icing.

The scientists used a beam of ions to cut into the surface of the graphene and dig a trench on either side of the section they wanted to isolate. They then removed a thin slice of the device.

Wonder material graphene is a two dimensional material consisting of a single layer of carbon atoms arranged in a honeycomb or chicken wire structure. It is the thinnest material in the world and yet is also one of the strongest. It conducts electricity as efficiently as copper and outperforms all other materials as a conductor of heat.

Demonstrating its remarkable properties won Professor Andre Geim and Professor Kostya Novoselov the Nobel prize for Physics in 2010. The University of Manchester is building a state-of-the-art National Graphene Institute to continue to lead the way in graphene research.

Dr Sarah Haigh, from The University of Manchester's School of Materials, said: "The difference is that our slices are only around 100 atoms thick and this allows us to visualize the individual atomic layers of graphene in projection.

"We have found that the observed roughness of the graphene is correlated with their conductivity. Of course we have to make all our electrical measurements before cutting into the device. We were also able to observe that the layers were perfectly clean and that any debris left over from production segregated into isolated pockets and so did not affect device performance.

"We plan to use this new side view imaging approach to improve the performance of our graphene devices."

Read More

Search for Higgs Boson at Large Hadron Collider Reveals New Particle

Physicists on experiments at the Large Hadron Collider announced today (July 4, 2012) that they have observed a new particle. Whether the particle has the properties of the predicted Higgs boson remains to be seen.

Hundreds of scientists and graduate students from American institutions have played important roles in the search for the Higgs at the LHC. More than 1,700 people from U.S. institutions--including 89 American universities and seven U.S. Department of Energy (DOE) national laboratories--helped design, build and operate the LHC accelerator and its four particle detectors. The United States, through DOE's Office of Science and the National Science Foundation, provides support for research and detector operations at the LHC and also supplies computing for the ATLAS and CMS experiments.

The results announced today are labeled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis. A more complete picture of today's observations will emerge later this year after the LHC provides the experiments with more data.

The new particle is in the mass region around 125-126 GeV. Publication of the analyses shown today is expected around the end of July.

"I congratulate the thousands of scientists around the globe for their outstanding work in searching for the Higgs boson," said U.S. Secretary of Energy Steven Chu. "Today's announcement on the latest results of this search shows the benefits of sustained investments in basic science by governments around the world. Scientists have been looking for the Higgs particle for more than two decades; these results help validate the Standard Model used by scientists to explain the nature of matter."

The CMS and ATLAS experiments in December announced seeing tantalizing hints of a new particle in their hunt for the Higgs, the missing piece in the Standard Model of particle physics. Since resuming data-taking in March 2012, the CMS and ATLAS experiments have more than doubled their collected data. The statistical significance of the earlier hints has grown.

"What has been announced today could not have been accomplished without the cooperation of scientists and nations throughout the world in seeking an understanding of the fundamental laws of nature," said Ed Seidel, NSF's assistant director for the Mathematical and Physical Sciences. "If the particle announced today at CERN is confirmed to be the Higgs boson, this represents a keystone in our knowledge of the elementary forces and particles that exist in our universe."

Scientists on experiments at the LHC announced their latest results at a seminar at the home of the LHC, the CERN particle physics laboratory on the border of Switzerland and France. Physicists from across the United States gathered at laboratories and universities in the middle of the night to watch a live-stream of the seminar online. The vast majority of U.S. scientists participate in the LHC experiments from their home institutions, remotely accessing and analyzing the data through high-capacity networks and grid computing.

Scientists will give more detailed presentations about the results this week at the biannual International Conference on High Energy Physics, held this year in Melbourne, Australia.

The Standard Model of particle physics has proven to explain correctly the elementary particles and forces of nature through more than four decades of experimental tests. But it cannot, without the Higgs boson, explain how most of these particles acquire their mass, a key ingredient in the formation of our universe.

Scientists proposed in 1964 the existence of a new particle, now known as the Higgs boson, whose coupling with other particles would determine their mass. Experiments at the LEP collider at CERN and the Tevatron collider at the Department of Energy's Fermilab have searched for the Higgs boson, but it has eluded discovery. Only now, after decades of developments in accelerator and detector technology and computing--not to mention advancements in the understanding of the rest of the Standard Model--are scientists approaching the moment of knowing whether the Higgs was the right solution to this problem.

"What we are observing is very likely a new particle with very large mass that would have to be a boson," said University of California Santa Barbara physicist Joe Incandela, spokesperson of the CMS experiment. "This is potentially an historic and very profound step forward in our understanding of the underlying structure of our universe. "

When protons collide in the Large Hadron Collider, their energy can convert into mass, often creating short-lived particles. These particles quickly decay into pairs of lighter, more stable particles that scientists can record with their detectors.

Theoretical physicists have predicted the rate at which the Higgs boson will be produced in high-energy proton-proton collisions at the LHC and also how it decays into certain combinations of observable particles. Experimental physicists at the ATLAS and CMS experiments have been studying the collisions and have observed a new particle. They will need to collect more data and run further analysis to determine its properties.

"If the new particle is determined to be the Higgs, attention will turn to a new set of important questions," said University of California Irvine physicist Andy Lankford, deputy spokesperson of ATLAS. "Is this a Standard Model Higgs, or is it a variant that indicates new physics and other new particles?"

Discovery of the Higgs -- or another new particle -- would represent only the first step into a new realm of understanding of the world around us.

Read More

CERN Experiments Observe Particle Consistent With Long-Sought Higgs Boson

At a seminar held at CERN today (July 4) as a curtain raiser to the year's major particle physics conference, ICHEP2012 in Melbourne, the ATLAS and CMS experiments presented their latest preliminary results in the search for the long sought Higgs particle. Both experiments observe a new particle in the mass region around 125-126 GeV.

"We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage," said ATLAS experiment spokesperson Fabiola Gianotti, "but a little more time is needed to prepare these results for publication."

"The results are preliminary but the 5 sigma signal at around 125 GeV we're seeing is dramatic. This is indeed a new particle. We know it must be a boson and it's the heaviest boson ever found," said CMS experiment spokesperson Joe Incandela. "The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."

"It's hard not to get excited by these results," said CERN Research Director Sergio Bertolucci. " We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs. With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we're seeing in the data."

The results presented today are labelled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis. Publication of the analyses shown today is expected around the end of July. A more complete picture of today's observations will emerge later this year after the LHC provides the experiments with more data.

The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure.

"We have reached a milestone in our understanding of nature," said CERN Director General Rolf Heuer. "The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe."

Positive identification of the new particle's characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.

CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a candidate for accession. Israel and Serbia are Associate Members in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.

Read More

Tevatron Scientists Announce Their Final Results On the Higgs Particle

After more than 10 years of gathering and analyzing data produced by the U.S. Department of Energy's Tevatron collider, scientists from the CDF and DZero collaborations have found their strongest indication to date for the long-sought Higgs particle. Squeezing the last bit of information out of 500 trillion collisions produced by the Tevatron for each experiment since March 2001, the final analysis of the data does not settle the question of whether the Higgs particle exists, but gets closer to an answer.

The Tevatron scientists unveiled their latest results on July 2, two days before the highly anticipated announcement of the latest Higgs-search results from the Large Hadron Collider in Europe.

"The Tevatron experiments accomplished the goals that we had set with this data sample," said Fermilab's Rob Roser, cospokesperson for the CDF experiment at DOE's Fermi National Accelerator Laboratory. "Our data strongly point toward the existence of the Higgs boson, but it will take results from the experiments at the Large Hadron Collider in Europe to establish a discovery."

Scientists of the CDF and DZero collider experiments at the Tevatron received a round of rousing applause from hundreds of colleagues when they presented their results at a scientific seminar at Fermilab. The Large Hadron Collider results will be announced at a scientific seminar at 2 a.m. CDT on July 4 at the CERN particle physics laboratory in Geneva, Switzerland.

"It is a real cliffhanger," said DZero co-spokesperson Gregorio Bernardi, physicist at the Laboratory of Nuclear and High Energy Physics, or LPNHE, at the University of Paris VI & VII. "We know exactly what signal we are looking for in our data, and we see strong indications of the production and decay of Higgs bosons in a crucial decay mode with a pair of bottom quarks, which is difficult to observe at the LHC. We are very excited about it."

The Higgs particle is named after Scottish physicist Peter Higgs, who among other physicists in the 1960s helped develop the theoretical model that explains why some particles have mass and others don't, a major step toward understanding the origin of mass. The model predicts the existence of a new particle, which has eluded experimental detection ever since. Only high-energy particle colliders such as the Tevatron, which was shut down in September 2011, and the Large Hadron Collider, which produced its first collisions in November 2009, have the chance to produce the Higgs particle. About 1,700 scientists from U.S. institutions, including Fermilab, are working on the LHC experiments.

The Tevatron results indicate that the Higgs particle, if it exists, has a mass between 115 and 135 GeV/c2, or about 130 times the mass of the proton.

"During its life, the Tevatron must have produced thousands of Higgs particles, if they actually exist, and it's up to us to try to find them in the data we have collected," said Luciano Ristori, co-spokesperson of the CDF experiment and physicist at Fermilab and the Italian Istituto Nazionale di Fisica Nucleare (INFN) . "We have developed sophisticated simulation and analysis programs to identify Higgs-like patterns. Still, it is easier to look for a friend's face in a sports stadium filled with 100,000 people than to search for a Higgs-like event among trillions of collisions."

The final Tevatron results corroborate the Higgs search results that scientists from the Tevatron and the LHC presented at physics conferences in March 2012.

The search for the Higgs particle at the Tevatron focuses on a different decay mode than the search at the LHC. According to the theoretical framework known as the Standard Model of Particles, Higgs bosons can decay in many different ways. Just as a vending machine might return the same amount of change using different combinations of coins, the Higgs can decay into different combinations of particles. At the LHC, the experiments can most easily observe the existence of a Higgs particle by searching for its decay into two energetic photons. At the Tevatron, experiments most easily see the decay of a Higgs particle into a pair of bottom quarks.

Tevatron scientists found that the observed Higgs signal in the combined CDF and DZero data in the bottom-quark decay mode has a statistical significance of 2.9 sigma. This means there is only a 1-in-550 chance that the signal is due to a statistical fluctuation.

"We achieved a critical step in the search for the Higgs boson," said Dmitri Denisov, DZero cospokesperson and physicist at Fermilab. "While 5-sigma significance is required for a discovery, it seems unlikely that the Tevatron collisions mimicked a Higgs signal. Nobody expected the Tevatron to get this far when it was built in the 1980s."

The Tevatron is one of eight particle accelerators and storage rings on the Fermilab site. The largest, operational accelerator at Fermilab now is the 2-mile-circumference Main Injector, which provides particles for the laboratory's neutrino and muon research programs.

The CDF and DZero collaborations submitted their joint Higgs search results to the electronic preprint archive arXiv.org. The paper also is available at:http://tevnphwg.fnal.gov/results/SM_Higgs_Summer_12/

Read More