General Physics Thread

Researchers show commonalities in how different glassy materials fail: "Glass is mysterious. It is a broad class of materials that extends well beyond the everyday window pane, but one thing that these disparate glasses seem to have in common is that they have nothing in common when it comes to their internal structures, especially in contrast with highly ordered and patterned crystals. Glassy systems can also range in scale: from things like metallic glasses, composed of atoms, to sandcastles, composed of grains of sand.

Researchers at the University of Pennsylvania have now shown an important commonality that seems to extend through the range of glassy materials. They have demonstrated that the scaling between a glassy material's stiffness and strength remains unchanged, implying a constant critical strain that these materials can withstand before catastrophic failure, despite the extreme variation found among this class of material's physical properties."

What makes Champagne bubbly?: "Just in time for the holidays, scientists have unraveled some of the chemistry behind the diffusion of CO2 molecules in a glass of Champagne. Among their findings, they discovered that ethanol is the main molecule (along with water) responsible for the value of CO2 diffusion coefficients in Champagne, and is therefore an essential molecule to better understand the CO2 bubble formation and growth in these beverages. Besides shedding light on the bubble dynamics and subsequent tasting sensations of Champagne, the results could also have applications for evaluating the diffusion of CO2 molecules in water/alcohol mixtures that are commonly used in physical chemistry."

Defects are perfect in laser-induced graphene: "Researchers at Rice University have created flexible, patterned sheets of multilayer graphene from a cheap polymer by burning it with a computer-controlled laser. The process works in air at room temperature and eliminates the need for hot furnaces and controlled environments, and it makes graphene that may be suitable for electronics or energy storage."

New theory suggests that two parallel universes were produced by the Big Bang: "New research suggests our Universe could be moving forwards in time, while a parallel one moves backwards on the 'other side' of the Big Bang."

New 'high-entropy' alloy is as light as aluminum, as strong as titanium alloys: "Researchers have developed a new 'high-entropy' metal alloy that has a higher strength-to-weight ratio than any other existing metal material."

Physicists explain puzzling particle collisions: "An anomaly spotted at the Large Hadron Collider has prompted scientists to reconsider a mathematical description of the underlying physics. By considering two forces that are distinct in everyday life but unified under extreme conditions like those within the collider and just after the birth of the universe, they have simplified one description of the interactions of elementary particles. Their new version makes specific predictions about events that future experiments at the LHC and other colliders should observe and could help to reveal 'new physics,' particles or processes that have yet to be discovered."

Baby steps towards molecular robots: "A walking molecule, so small that it cannot be observed directly with a microscope, has been recorded taking its first nanometre-sized steps.

It's the first time that anyone has shown in real time that such a tiny object – termed a 'small molecule walker' – has taken a series of steps. The breakthrough, made by Oxford University chemists, is a significant milestone on the long road towards developing 'nanorobots'."

Researchers discover new class of stem cells: "A team of researchers in South Korea has created an ultrasensitive vibration monitor that is based on the lyriform organ in wandering spider legs. In their paper published in the journal Nature, the team describes the lyriform organ, how it works and how they applied what they learned to a new monitor that could have applications in music, speech recognition and health monitoring. Peter Frazel of the Max Planck Institute explains the work in more detail in a News & Views piece in the same journal issue."

Scientists produce new type of ice: "Researchers today unveiled a new solid phase of ice that’s the lowest density version known. Known as ice XVI, the 17th solid phase of ice discovered to date, it has a cagelike structure that can trap other molecules (green and gray above). Such ice cages, known as clathrates, are known to store enormous quantities of methane on the deep ocean floor."

edited 11th Dec '14 3:51:20 PM by rmctagg09

Nanoshaping method points to future manufacturing technology: "A new method that creates large-area patterns of three-dimensional nanoshapes from metal sheets represents a potential manufacturing system to inexpensively mass produce innovations such as "plasmonic metamaterials" for advanced technologies.

The metamaterials have engineered surfaces that contain features, patterns or elements on the scale of nanometers that enable unprecedented control of light and could bring innovations such as high-speed electronics, advanced sensors and solar cells.

The new method, called laser shock imprinting, creates shapes out of the crystalline forms of metals, potentially giving them ideal mechanical and optical properties using a bench-top system capable of mass producing the shapes inexpensively."

Scientists measure speedy electrons in silicon: "Attosecond lasers provide the shortest light pulses yet, allowing observation of nature's most short-lived events. Researchers have used these lasers for the first time to take snapshots of electrons jumping from silicon atoms into the conduction band of a semiconductor, the key event behind the transistor. They clocked the jump at 450 attoseconds and saw the rebound of the crystal lattice 60 femtoseconds later: a delay 120 times longer than the jump itself."

'Fibonacci quasiparticle' could form basis of future quantum computers: "Topological quantum computing (TQC) is a newer type of quantum computing that uses "braids" of particle tracks, rather than actual particles such as ions and electrons, as the qubits to implement computations. Using braids has one important advantage: it makes TQ Cs practically immune to the small perturbations in the environment that cause decoherence in particle-based qubits and often lead to high error rates.

Ever since TQC was first proposed in 1997, experimentally realizing the appropriate braids has been extremely difficult. For one thing, the braids are formed not by the trajectories of ordinary particles, but by the trajectories of exotic quasiparticles (particle-like excitations) called anyons. Also, movements of the anyons must be non-Abelian, a property similar to the commutative property in which changing the order of their movements must not change their final tracks. In most proposals of TQC so far, the non-Abelian statistics of the anyons has not been powerful enough, even in theory, for universal TQC.

Now in a new study published in Physical Review Letters, physicists Abolhassan Vaezi at Cornell University and Maissam Barkeshli at Microsoft's research lab Station Q have theoretically shown that anyons tunneling in a double-layer system can transition to an exotic non-Abelian state that contains 'Fibonacci' anyons that are powerful enough for universal TQC."

NIST physicists build a watt balance using LEGO blocks to measure Planck's constant: "A team of physicists at the National Institute of Standards and Technology (NIST) outside of Washington D.C. has found a way to bring physics to the masses—they've designed and built a watt balance based on LEGO blocks. They've also written a paper and uploaded it to the preprint server arXiv in which they describe their device and how it was built it, should readers wish to construct one of their own."

Future batteries: Lithium-sulfur with a graphene wrapper: "What do you get when you wrap a thin sheet of the 'wonder material' graphene around a novel multifunctional sulfur electrode that combines an energy storage unit and electron/ion transfer networks? An extremely promising electrode structure design for rechargeable lithium-sulfur batteries."

Is the Higgs boson a piece of the matter-antimatter puzzle?: "Several experiments, including the Ba Bar experiment at the Department of Energy's SLAC National Accelerator Laboratory, have helped explain some – but not all – of the imbalance between matter and antimatter in the universe. Now a SLAC theorist and his colleagues have laid out a possible method for determining if the Higgs boson is involved.

In a paper published in Physical Review D, they suggest that scientists at CERN's Large Hadron Collider (LHC), where the Higgs was discovered, look for a specific kind of Higgs decay when the collider starts up again in 2015. The details of that decay could tell them whether or not the Higgs has a say in the matter-antimatter imbalance.

'The time to plan a search strategy is now,' said Matt Dolan, a research associate in SLAC's Particle Theory group and co-author of the paper. 'That way, when the LHC begins to operate at full strength we'll be ready.'"

Scientists have found a way to make graphene magnetic: "Graphene has a lot going for it - as you've most likely heard, at just one carbon atom thick, the material is 100 times stronger than steel, light, conductive, super-flexible, and could soon be used to filter fuel straight out of thin air.

But the one property it's never had is magnetism - until now.

Researchers from Spain have now found that by inserting little 'islands' of lead, or more precisely lead atoms, into the hexagonal graphene structure, they can make the material highly magnetic."

Team opens new frontier of vast chemical 'space', makes dozens of new chemical entities: "Chemists at The Scripps Research Institute (TSRI) have invented a powerful method for joining complex organic molecules that is extraordinarily robust and can be used to make pharmaceuticals, fabrics, dyes, plastics and other materials previously inaccessible to chemists."

Electric field switching of ferromagnetism at room temperature: "In a development that holds promise for future magnetic memory and logic devices, researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and Cornell University successfully used an electric field to reverse the magnetization direction in a multiferroic spintronic device at room temperature. This demonstration, which runs counter to conventional scientific wisdom, points a new way towards spintronics and smaller, faster and cheaper ways of storing and processing data."

Spider's web weaves way to advanced networks and displays: "The next generation of light-manipulating networks may take their lead from designs inspired by spiders and leaves, according to a new report from two Boston College physicists and colleagues at South China Normal University.

Structures as commonplace as spider webs and leaf venation show they can lead to near optimal performance when copied to create flexible and durable networks that can be used in optoelectronic applications such as photovoltaic devices and display screens, the researcher team reported in a recent edition of the journal Nature Communications."

Ultrafast imaging of complex systems in 3D at near atomic resolution nears: "It is becoming possible to image complex systems in 3-D with near-atomic resolution on ultrafast timescales using extremely intense X-ray free-electron laser (XFEL) pulses.

One important step toward ultrafast imaging of samples with a single X-ray shot is understanding the interaction of extremely brilliant and intense X-ray pulses with the sample, including ionization rates.

Scientists from the U.S. Department of Energy's Argonne National Laboratory and SLAC National Accelerator Laboratory developed an extended Monte Carlo computational scheme that for the first time includes bound-bound resonant excitations that dramatically enhance ionization rates and can lead to an unexpectedly high degree of electron stripping."

A bit old but worth relinking. Feynman Lectures on Physics available for free online by CalTech

Electron spin could be the key to high-temperature superconductivity: "Cuprates are materials with great promise for achieving superconductivity at higher temperatures (-120°C). This could mean low-cost electricity without energy loss. Intense research has focused on understanding the physics of cuprates in the hope that we can develop room-temperature superconductors. EPFL scientists have now used a cutting-edge technique to uncover the way cuprates become superconductors. Their work is published in Nature Communications."

Quantum physics just got less complicated: "Here's a nice surprise: quantum physics is less complicated than we thought. An international team of researchers has proved that two peculiar features of the quantum world previously considered distinct are different manifestations of the same thing. The result is published 19 December in Nature Communications.

Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner made the breakthrough while at the Centre for Quantum Technologies at the National University of Singapore. They found that 'wave-particle duality' is simply the quantum 'uncertainty principle' in disguise, reducing two mysteries to one.

'The connection between uncertainty and wave-particle duality comes out very naturally when you consider them as questions about what information you can gain about a system. Our result highlights the power of thinking about physics from the perspective of information,' says Wehner, who is now an Associate Professor at QuTech at the Delft University of Technology in the Netherlands.

The discovery deepens our understanding of quantum physics and could prompt ideas for new applications of wave-particle duality."

edited 19th Dec '14 12:26:55 PM by rmctagg09

Scientists reveal breakthrough in optical fibre communications: "Researchers from the University of Southampton have revealed a breakthrough in optical fibre communications.

Academics from the University's Optoelectronics Research Centre (ORC) have collaborated with colleagues at Eblana Photonics Inc, in Ireland, to develop an approach that enables direct modulation of laser currents to be used to generate highly advanced modulation format signals.

The research, published in the journal Nature Communications, explores a radically new approach to the generation of spectrally-efficient advanced modulation format signals as required in modern optical communication systems.

This new technology, patented by the University of Southampton and licensed to Eblana Photonics Inc, avoids the need for costly and power-inefficient external modulator schemes that are currently used to generate such signals."

Yellowstone's thermal springs—their colors unveiled: "Researchers at Montana State University and Brandenburg University of Applied Sciences in Germany have created a simple mathematical model based on optical measurements that explains the stunning colors of Yellowstone National Park's hot springs and can visually recreate how they appeared years ago, before decades of tourists contaminated the pools with make-a-wish coins and other detritus."

Researchers open possible avenue to better electrolyte for lithium ion batteries: "'A crucial process in lithium ion batteries is the transport of lithium ions between the electrodes,' explains Saykally. 'Commercial lithium-ion batteries contain a liquid electrolyte comprising a lithium salt dissolved in an alkyl carbonate solvent system. There's disagreement in the battery industry on the nature of the local solvation environment of lithium ions in these solutions, a critical issue because the desolvation of the ions as they move through the negative electrode is believed to limit the electrical power that can be made available.'

Most previous computational simulations have predicted a tetrahedral solvation structure for the lithium ion in the electrolyte, but the new study by Saykally, Prendergast, Harris and their collaborators show this to not be the case.

'Our results indicate a solvation number of 4.5, which points to a non-tetrahedral solvation structure for the lithium ions,' says lithium-battery expert Harris. 'This contradicts numerous theoretical studies which indicated a primarily tetrahedral coordination structure with a solvation number near 2 or 3, depending on the prevalence of ion pairing. Based on our results, to design better performing electrolytes, future computational models will need to move beyond tetrahedral coordination structures.'"

Choreography of an electron pair: "Physicists are continuously advancing the control they can exert over matter. A German-Spanish team working with researchers from the Max Planck Institute for Nuclear Physics in Heidelberg has now become the first to image the motion of the two electrons in a helium atom and even to control this electronic partner dance. The scientists are succeeding in this task with the aid of different laser pulses which they timed very accurately with respect to each other. They employed a combination of visible flashes of light and extreme-ultraviolet pulses which lasted only a few hundred attoseconds. One attosecond corresponds to a billionth of a billionth of a second. Physicists aim to specifically influence the motion of electron pairs because they want to revolutionise chemistry: If lasers can steer the paired bonding electrons in molecules, they could possibly produce substances which cannot be produced using conventional chemical means."

First direct evidence that a mysterious phase of matter competes with high-temperature superconductivity: "cientists have found the first direct evidence that a mysterious phase of matter known as the 'pseudogap' competes with high-temperature superconductivity, robbing it of electrons that otherwise might pair up to carry current through a material with 100 percent efficiency.

The result, led by researchers at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, is the culmination of 20 years of research aimed at finding out whether the pseudogap helps or hinders superconductivity, which could transform society by making electrical transmission, computing and other areas much more energy efficient.

The new study definitively shows that the pseudogap is one of the things that stands in the way of getting superconductors to work at higher temperatures for everyday uses, said lead author Makoto Hashimoto, a staff scientist at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL), the DOE Office of Science User Facility where the experiments were carried out. The results were published in Nature Materials."

Halting photons could lead to miniature particle accelerators, improved data transmission: "Researchers at MIT who succeeded last year in creating a material that could trap light and stop it in its tracks have now developed a more fundamental understanding of the process. The new work—which could help explain some basic physical mechanisms—reveals that this behavior is connected to a wide range of other seemingly unrelated phenomena.

The findings are reported in a paper in the journal Physical Review Letters, co-authored by MIT physics professor Marin Soljačić; postdocs Bo Zhen, Chia Wei Hsu, and Ling Lu; and Douglas Stone, a professor of applied physics at Yale University.

Light can usually be confined only with mirrors, or with specialized materials such as photonic crystals. Both of these approaches block light beams; last year's finding demonstrated a new method in which the waves cancel out their own radiation fields. The new work shows that this light-trapping process, which involves twisting the polarization direction of the light, is based on a kind of vortex—the same phenomenon behind everything from tornadoes to water swirling down a drain."

The importance of three-way atom interactions in maintaining coherence: "Quantum computers will someday perform calculations impossible for conventional digital computers. But for that to happen, the core quantum information must be preserved against contamination from the environment. In other words, decoherence of qubits must be forestalled. Coherence, the ability of a system to retain quantum integrity—-meaning that one part of the system can be used to predict the behavior of other parts—-is an important consideration."

Piezoelectricity in 2-D semiconductor holds promise for future MEMS: "A door has been opened to low-power off/on switches in micro-electro-mechanical systems (MEMS) and nanoelectronic devices, as well as ultrasensitive bio-sensors, with the first observation of piezoelectricity in a free standing two-dimensional semiconductor by a team of researchers with the DOE's Lawrence Berkeley National Laboratory (Berkeley Lab)."

Acoustic tweezers manipulate cell-to-cell contact: "Sound waves can precisely position groups of cells for study without the danger of changing or damaging the cells, according to a team of Penn State researchers who are using surface acoustic waves to manipulate cell spacing and contact.

'Optical tweezers are the gold-standard technique in the field,' said Tony Jun Huang, professor of engineering science and mechanics. 'They can trap two cells in place, but because of their high power they tends to affect the integrity of cells, and sometimes damage them.'

Acoustic tweezers use the same low-power acoustic waves as those used in existing ultrasound machines, so they are gentle and can preserve cell integrity."

Huge electric field found in ice-cold laughing gas: "A brand new electrical phenomenon has been discovered - a huge electric field in a thin film of laughing gas. The discovery is so bizarre, the scientists who made it were convinced it was a mistake."

I guess laughter really is electrifying.

Ultrasounds dance the 'moonwalk' in new metamaterial: "Metamaterials have extraordinary properties when it comes to diverting and controlling waves, especially sound and light: for instance, they can make an object invisible, or increase the resolving power of a lens. Now, researchers have developed the first three-dimensional metamaterials by combining physico-chemical formulation and microfluidics technology. This is a new generation of soft metamaterials that are easier to shape."

World's most complex crystal simulated: "The most complicated crystal structure ever produced in a computer simulation has been achieved by researchers at the University of Michigan. They say the findings help demonstrate how complexity can emerge from simple rules.

Their 'icosahedral quasicrystal' (eye-KO-suh-HE-druhl QUAZ-eye-cris-tahl) looks ordered to the eye, but has no repeating pattern. At the same time, it's symmetric when rotated, like a soccer ball with five-fold and six-fold patches.

This property, called icosahedral symmetry, is frequently found on small scales around a single point. It's in virus shells or buckyballs – molecules of 60 carbon atoms. But it is forbidden in a conventional crystal. Like trying to tile a bathroom floor with pentagons, icosahedra do not nicely fill space, said Michael Engel, a research investigator in the Department of Chemical Engineering and first author of a paper on the findings published in Nature Materials."

How To Find Faster-Than-Light Particles: "A new paper claims to demonstrate that neutrinos not only travel faster than the speed of light, but have the brain-twisting characteristic of 'imaginary mass', a property that means they actually speed up as they lose energy.

The phrase 'extraordinary claims require extraordinary proof' has seldom been more appropriate, but Professor Robert Ehrlich, recently retired from George Mason University, believes he has that, with six different measurements from different areas of physics. All of these, Ehrlich claims in Astroparticle Physics, provide matching results that not only indicate that neutrinos have imaginary mass, but point towards the same value, making it less likely the readings are in error."

WATCH: The surprisingly complex physics of snapping spaghetti: "Spaghetti has puzzled the world's best physicists by breaking into multiple pieces when it's snapped in half. In this world-first, slow-motion footage of the phenomenon, Smarter Every Day may have finally worked out what causes the behaviour."

Simplicity will out: Novel experiment-based expression explains behavior of unconventional superconductors: "Superconductivity – perhaps the leading example of emergent quantum behavior in matter – was discovered in 1911 but lacked theoretical explanation for almost five decades. In 1957, John Bardeen, Leon Cooper, and John Robert Schrieffer (BCS) developed a microscopic theory of superconductivity1 that came to be known as the BCS theory, which describes superconductivity as a microscopic effect caused by a condensation of Cooper pairs into a boson-like state. BCS theory explains the behavior of what are now known as conventional superconductors – metals for which phonons provide the recently controversial "pairing glue" that leads to the effective attractive quasiparticle interaction responsible for their superconductivity. (Phonons are quantized lattice vibrations, and quasiparticles are mobile electrons or holes in materials; both are quantized elementary excitations.)

As it is wont to do, history is now repeating itself: Unconventional superconductors, in which pairing glue and pairing condensate symmetry differ from conventional superconductors, were discovered in the 1980s – but while it appears from both theory and experiment that electronic spin fluctuations provide the pairing glue for the unconventional superconductivity, a general model remains elusive. Recently, however, scientists at Chinese Academy of Sciences, Beijing and the Santa Fe Institute proposed such a model in the form of an experiment-based phenomenological BCS-like expression for the superconducting transition temperature Tc in heavy-electron materials that is based on a simple model for the effective range and strength of the spin-fluctuation-induced quasiparticle interaction, and reflects the unusual properties of the heavy-electron normal state – in which electrons gain mass as local electron spins lose their magnetism – from which superconductivity emerges."

A qubit candidate shines brighter: "In the race to design the world's first universal quantum computer, a special kind of diamond defect called a nitrogen vacancy (NV) center is playing a big role. NV centers consist of a nitrogen atom and a vacant site that together replace two adjacent carbon atoms in diamond crystal. The defects can record or store quantum information and transmit it in the form of light, but the weak signal is hard to identify, extract and transmit unless it is intensified.

Now a team of researchers at Harvard, the University of California, Santa Barbara and the University of Chicago has taken a major step forward in effectively enhancing the fluorescent light emission of diamond nitrogen vacancy centers - a key step to using the atom-sized defects in future quantum computers. The technique, described in the journal Applied Physics Letters, from AIP Publishing, hinges on the very precise positioning of NV centers within a structure called a photonic cavity that can boost the light signal from the defect."

Gummy bears under antiparticle fire: "Gelatin is used in the pharmaceutical industry to encapsulate active agents. It protects against oxidation and overly quick release. Tiny pores in the material have a significant influence on this, yet they are difficult to investigate. In experiments on gummy bears, researchers at Technische Universität München (TUM) have now transferred a methodology to determine the free volume of gelatin preparations."