Physics Today Daily Edition

Subscribe to Physics Today Daily Edition feed
Please follow the links to view the content.
Updated: 1 day 10 hours ago

Wearable electronic skin allows for thought-controlled devices

24 April 2015

New Scientist: An electroencephalogram (EEG) is a common device for measuring brain activity. The technology has also been used to allow a wearer to remotely control a variety of devices. However, the electrodes and wires of a normal EEG make it unwieldy in any but the most controlled conditions. Now, John Rogers of the University of Illinois at Urbana-Champaign and his colleagues have built an EEG into a thin wearable skin that adheres to the body via the van der Waals force and stays in place for up to two weeks. The small patch is worn just behind the ear, and test subjects used it to spell words on a screen in front of them. During the testing, the EEG was still connected to the screen by wires. Rogers's team is working to incorporate wireless connectivity into the device. The researchers' primary goal is to use the device for remote monitoring of medical conditions such as seizures, but they think it could also be used to control a variety of simple devices.

New algorithm improves 3D imaging of complex biomolecules

24 April 2015

MIT Technology Review: Determining the three-dimensional structure of large proteins and other biomolecules has proven difficult. X-ray crystallography works well for molecules that form crystals, but many proteins do not. Now, Marcus Brubaker of the University of Toronto and his colleagues have developed an algorithm that improves a different, previously less effective, imaging technique called electron cryomicroscopy. The technique involves freezing molecules in a thin film and imaging them with transmission electron microscopy. A 3D composite of multiple 2D images of the same molecule can then be constructed. However, the process is time-consuming due to the amount of noise in the images and uncertainty concerning the molecules' orientations when they were imaged. Thanks to two algorithmic innovations, Brubaker's team was able to reduce the imaging time from 2 weeks to just 24 hours. The key improvements were using a machine learning process to sift through the noise in the images to glean the useful information and incorporating importance sampling. The latter relies on the fact that molecules in thin films are usually positioned on their sides, so the algorithm can skip evaluating potential head-on structural orientations.

Electrode implants reveal tinnitus’s manifestation in the brain

24 April 2015
BBC: Tinnitus, the hearing of phantom sounds, may affect a larger area of the human brain than previously thought. The condition is often caused by noise-induced hearing loss or neurological damage. Until now, it was thought that only the hearing pathway was affected. Recently Phillip Gander of the University of Iowa and colleagues were able to gather much more extensive data on the condition by studying a man who had had electrodes planted on his brain to monitor his epilepsy. Through the use of those electrodes, the researchers were able to compare his brain activity when his tinnitus was loud with when it was quiet. They found that brain wave oscillations associated with tinnitus extended far beyond the sections of the brain involved with just hearing. The results are based on only one subject, but the researchers hope to be able to expand their study by gaining access to other patients undergoing similar electrode monitoring.

Radio telescope probes the relationship between cosmic rays and lightning

24 April 2015
Nature: The connection between cosmic rays and thunderstorms is one of many phenomena being investigated by researchers using the Low-Frequency Array (LOFAR), a network of radio antennas and particle detectors spread across five European countries. When cosmic rays hit Earth’s atmosphere, they collide with air molecules and create a shower of electrically charged particles that fall toward the ground. The particles emit radio waves, which can be detected by LOFAR. The researchers noticed that the radio waves fall in orderly patterns with their polarizations neatly aligned when the weather is fair, but they get scrambled when passing near thunderclouds, which consist of layers of positively and negatively charged particles. Although lightning strikes have long been known to provide a form of electrostatic discharge between electrically charged layers in a cloud or between clouds and the ground, what triggers a lightning strike has remained a mystery. Now the LOFAR researchers propose that it may be those cosmic rays raining in from distant space that push the clouds’ electric fields past the tipping point.

A good name rather than great riches

24 April 2015
When and why did solid-state physics become condensed-matter physics?

Thomas A. O’Halloran

24 April 2015

Introducing GSOFT

24 April 2015
A new topical group within the American Physical Society is devoted to the science of soft condensed matter.

Canadian budget proposal emphasizes industry connections

23 April 2015

Nature: Prime Minister Stephen Harper's Conservative government released its budget proposal on 21 April. With modest increases in scientific spending in some areas, the budget continues the Conservative Party's push for more applied research and connections between government, universities, and industry. The budget includes Can$1.33 billion (US$1.09 billion) for new university and hospital research facilities. The money is to be spread out over 6 years beginning in 2017. Many of the increased areas of funding have language specifically related to business and industry. The budget also includes Can$243 million to support Canada's involvement over the next 10 years in the international Thirty Meter Telescope project in Hawaii.

Blocking a certain protein may help prevent blindness

23 April 2015
New Scientist: Age-related macular degeneration, which can eventually lead to blindness, is caused by the abnormal growth of blood vessels in the retina. The weakened vessels can then leak blood, resulting in a hemorrhage. To better understand the processes involved, researchers led by Alain Chédotal of the Institute of Vision in Paris studied the effect of a certain protein, Slit2, on angiogenesis. In experiments conducted on mice, the researchers found that suppressing production of that protein severely reduced the growth of retinal blood vessels. Thus controlling Slit2 might also "block the chaotic development of blood vessels in ocular diseases," according to Chédotal.

Young crust in subduction zone under Cascades produces unusual magma

23 April 2015

Ars Technica: Subduction zones occur where oceanic crust is forced down under continental crust. As the subducted material is pushed toward the mantle, it melts into magma. The amount of water present in the different layers of the rock affects how quickly pockets of magma form. Rock that formed more recently is still warm, which means that it doesn't have to descend as far down into the mantle to start heating up and become dehydrated. Kristina Walowski of the University of Oregon and her colleagues, who have collected minerals from volcanos in the southern region of the Cascades, have confirmed that the subducted plate there is quite young. However, a simulation based on the isotopes in the minerals suggests that the water escaped the rock well before it reached the depth at which magma forms. That led Walowski's team to adjust the model to incorporate water trapped at the bottom layer of the crust. That reservoir of water leads to the formation of magma, and the ratios of other elements in the minerals in the Cascades support the idea that a young oceanic plate is being turned into magma there.

Diving bird runs on water to attract a mate

23 April 2015
Science: Few vertebrates have the ability to defy gravity by running across the surface of water. One species that has managed the feat is the grebe, a type of freshwater diving bird that lives in western North America. For both the western and Clark’s grebes, “rushing” for brief periods of up to seven seconds is used as a courting display. But until recently, researchers did not know exactly how grebes, which can weigh up to about 2 kg, manage to skim across the water. In May 2012 Glenna Clifton of Harvard University and her colleagues spent a month in the field, where they managed to capture high-speed video of the novel display. From that footage, the researchers have determined that the grebes are able to slap their feet rapidly against the water’s surface, as many as 20 times per second. However, the force generated is just half that needed to keep them up. To determine how they generate the rest of the force may require filming under the water.

Measuring ionization potential one atom at a time

23 April 2015
Researchers in Japan have begun probing the atomic physics of elements that can be produced only in minute quantities.

Wisconsin state agency hit with official Florida-like climate-change taboo

23 April 2015
Chicago Tribune headline says, “Daughter of Earth Day founder banned from global warming work in Wisconsin.”

Radio waves detected from individual electrons

22 April 2015
Science: Charged particles traveling through magnetic fields are deflected from their linear paths and instead follow curved trajectories. In doing so, they release radiation. For the first time, researchers have detected the radio waves of a single electron trapped in a spiral in a strong magnetic field. To achieve this, a team of scientists at the University of Washington in Seattle trapped krypton-83 gas produced by the decay of rubidium-83. When trapped, each krypton atom ejected a single electron with a known energy. The electrons were piped into a waveguide cell in the presence of a superconducting magnet. The waveguide was designed to detect electromagnetic radiation between 25 GHz and 27 GHz and transmit the radiation to amplifiers. That allowed the researchers to track the change in frequency of the emissions of individual electrons as they lost energy and spiraled inward. The technique provides researchers with a new method for measuring the energy of electrons in a nondestructive manner. It may also be useful for calculating the mass of neutrinos by using electrons emitted from tritium atoms via beta decay.

<em>Hubble</em> spots mysterious exploding star

22 April 2015
Nature: A mysterious stellar outburst has been captured by NASA’s Hubble Space Telescope. Images taken in January and August 2014 reveal what appears to be an exploding star in the constellation Eridanus. The explosion's brightness was 100 times greater than that of an ordinary nova yet 10 times fainter than that of a supernova. One possible explanation is that the outburst was a kilonova, which occurs when two neutron stars collide. However, none of the high-energy radiation that is typically emitted by such events was observed. Another possibility is that the explosion represents an entirely new class of celestial objects. If so, it is hoped that future telescopes with much wider fields of view, such as the Large Synoptic Survey Telescope and the Wide-Field Infrared Survey Telescope, may find more of them.

New atomic clock sensitive to altitude change of just 2 cm

22 April 2015
Los Angeles Times: The connection between time and gravity was made 100 years ago by Albert Einstein. As ever more precise clocks have been developed, researchers have been able to demonstrate the effects of time dilation by comparing the speed of clocks located at different altitudes—in satellites separated by miles, in an airplane and on the ground, on top of a mountain and at sea level, and even just one foot apart. Now, Jun Ye of JILA and his colleagues have developed an atomic clock sensitive enough to show the effect of gravity when the clock is moved just 2 cm up or down. The new clock, which is a version of an optical lattice, uses a laser to measure the movement of an electron in orbit around a strontium nucleus. To improve on previous optical lattice clocks, Ye's team used highly sensitive thermometers and one of the most stable lasers available. They also were able to reduce the disruptive effects of the laser on the electron. The result is a clock three times more sensitive than the previous best clock and several orders of magnitude more sensitive than the world's official time-keeping atomic clock.

Japanese maglev train sets another world speed record

22 April 2015
BBC: In a recent test, Japan’s magnetic levitation, or maglev, train attained a record speed of 603 km/h. The test lasted 10.8 seconds, during which the train traveled 1.8 km along an experimental track. It broke its own record from last week of 590 km/h. Maglev trains use electromagnets to provide both levitation above and propulsion along a special guideway. Japan plans for the trains to begin commercial service in 2027. The first line would connect Tokyo and Nagoya, a distance of about 280 km. The maglev trains will cut the travel time in half of that attained by Japan’s Shinkansen, a high-speed train that has been providing service for the past half century. During a visit to the US later this month, Japanese prime minister Shinzo Abe is expected to promote building a maglev system between New York and Washington, DC.

Cyclonic circulation development during extreme precipitation

21 April 2015
A numerical study reveals that vortex formation played a crucial role in the floods that devastated towns on Colorado’s Front Range.

Cold spot in cosmic microwave background was caused by "supervoid"

21 April 2015
Wired: Several of the maps of the cosmic microwave background (CMB) radiation have revealed a spot that is unusually large and cold. Its size and coldness have posed a challenge to theories of the universe's early history. Now Istvan Szapudi of the University of Hawaii and his colleagues believe they have an explanation that fits with other cosmological theories. Using the Pan-STARRS1 telescope and NASA's Wide-Field Infrared Survey Explorer, Szapudi's team found a vast region of space with a much lower density of galaxies than average, about 1.8 billion light-years wide and located just 3 billion light-years from Earth. They propose that as the CMB radiation passed through that "supervoid," it may have lost considerable energy, which explains why there is a cold spot.

Most accurate simulations of colliding black holes yet

21 April 2015
Nature: Modeling collisions of black holes is extremely complex. Most simulations simplify various parts of the systems, including the application of general relativity. Now Stuart Shapiro of the University of Illinois at Urbana-Champaign and his colleagues have developed a model that fully incorporates general relativity, allowing for the most in-depth three-dimensional rendering of black hole collisions yet. Shapiro's team was able to couple Einstein's equations with the equations that represent the motion of matter moving at a large fraction of the speed of light in a magnetic field. The new simulations are well-timed because recent observations suggest that the two black holes assumed to be present in the system PSO J334.2028+01.4075 are likely to merge in the next seven years.

Pages