Physics Today Daily Edition
BBC: Twisting light, which involves manipulating its orbital angular momentum, has been done since the 1990s. When researchers add a twist to polarized light, they provide photons with an infinite amount of possible orientations. The technique has been used to encode more information on each photon over fiber optics, and now Mario Krenn of the University of Vienna and his colleagues have transmitted twisted light through the air. They sent a green laser through a controlled LCD that applied a twist to the photons, which were then detected 3 km away. At the detector, the beam became a ring of dots, the arrangement of which changed depending on the amount of twist. The researchers then defined 16 of those patterns to correspond with 16 shades of gray and transmitted a series of grayscale images via the laser. The detector and computer program to reassemble the images were able to reproduce the transmitted images with just a 1.7% error rate.
Washington Post: Capping his visit to the Asia Pacific Economic Cooperation summit in Beijing, President Obama appeared with Chinese president Xi Jinping to announce a deal to limit greenhouse gas emissions. China will cap its carbon emissions and will increase the proportion of non-fossil-fuel-based energy production to 20% by 2030. In exchange, the US has agreed to increase its planned reduction of emissions from 17% below 2005 levels by 2020 to 26–28% by 2025. The agreement is the first time that China has agreed to put a cap on its greenhouse gas emissions. The two countries account for 45% of the world's emissions. Both countries' goals will require significant effort to increase restrictions on polluters and to build new zero-emission power plants over industry and political opposition.
MIT Technology Review: Transcranial direct current stimulation (TDCS) uses electrodes on your head to send electrical pulses to the brain. A device developed by Jamie Tyler of Arizona State University and his colleagues and now marketed by the startup Thync instead sends those pulses to the nerves and muscles and the scalp. The company has found that depending on the location of the stimulation, TDCS can produce a short-lived energizing effect similar to drinking a caffeinated beverage, or it can produce a calming effect. The duration and strength of the effect also vary depending on the person. Thync recently announced that it had received $13 million in funding and hopes to have a commercially available version of its device in early 2015. Researchers at the company are also examining an alternative that uses ultrasound as a potential treatment for psychiatric and other brain disorders.
Science: Hawaii and Yellowstone National Park are far from the tectonic plate boundaries that provide openings to Earth’s mantle, which makes the presence of magma near the surface in those areas something of a mystery. Alexander Goncharov of the Carnegie Institution of Washington and his colleagues believe they have found an explanation. They subjected a glass, which had a similar chemical composition to magma, to pressures equivalent to those found between the planet’s mantle and outer core, some 3000 km below Earth’s surface. As the pressure increased, the atomic structure of the glass changed, allowing heat to pass through the material more quickly. They propose that pockets of magma surrounding the outer core may get squeezed and heated up by the extreme pressure there and then transfer that localized heating to the mantle, creating plumes of hot mantle rock that rise to the crust, even in areas far from active tectonic regions. Although they admit that the theory is plausible, some scientists point out that it isn’t certain that magma behaves the same way as the glass. Until a similar experiment is done with molten rock, the researchers’ findings remain speculative.
New York Times: Of all the countries in the world, Denmark is pursuing the most ambitious plan regarding climate change. It is working to end the burning of fossil fuels by 2050, not only for electricity production but for motor vehicles as well. So far the country is producing 40% of its power from renewable sources and is pushing for 50% by 2020. However, there are two main obstacles to achieving its goals. Increased use of solar, wind, and other renewables can drive conventional plants out of business, but they are needed to provide backup power when the Sun doesn’t shine and the wind doesn’t blow. Also, electric car technology is not yet advanced enough or inexpensive enough to supplant gas-powered cars. To try to smooth the transition to renewable electricity generation, Denmark has been installing smart meters and smart appliances that can decide when to turn on and off to try to match consumption with generation.
Nature: The six Italian seismologists accused of misleading the public about earthquake risk have been acquitted after a 30-day appeals trial. A government official convicted with them had his prison sentence reduced from six years to two. The charges stem from the days leading up to the magnitude 6.3 earthquake that struck the town of L’Aquila on 6 April 2009. Months before the big quake, the area had been experiencing a series of low-magnitude tremors. The prosecution alleged that the experts had met to discuss the potential for a larger quake and downplayed the danger, and as a result, many of the town’s residents were killed because they did not evacuate their homes when the quake began. The scientists said the incident was the result of miscommunication. The ruling may not be final, however—the families of the deceased have said they intend to challenge it in Italy’s supreme court.
New York Times: In an effort to promote fracking to its citizens, the UK government led by Prime Minister David Cameron announced it would use the proceeds earned from shale-gas extraction to establish a sovereign wealth fund. Although fracking has been successfully used in the US and has resulted in lower domestic gas and global oil prices, it has met with strong resistance in Europe because of fears that it will pollute local water supplies and cause increased traffic and noise. The UK has numerous coal-fired and nuclear power plants, but they are getting old, and the country is growing increasingly dependent on imported fuel. More wells will need to be drilled to determine whether the UK has enough shale gas to make such an enterprise worthwhile.
New Scientist: A team of researchers has developed a tiny equipment-laden backpack that when attached to the back of a cockroach turns the insect into a mini cyborg. Alper Bozkurt of North Carolina State University in Raleigh and colleagues have called their creation the RoboRoach and are marketing it on Kickstarter. They have equipped Madagascar hissing cockroaches with a backpack containing either a single microphone or a trio of microphones. The microphones pick up sound waves and send them to neurons located in the cockroaches’ antennae. The neurons then convey the information to the brain. Through the use of such microstimulation, the researchers have been able to direct the cockroaches in specific directions by making them think there is an obstacle in their path. Although for the moment the insect robots are more an exercise in neuroscience engineering, the researchers hope that one day they could have many useful applications, such as in search-and-rescue operations by picking up sounds from people trapped after a disaster.
Nature: On 29 October, the University of California (UC) system reversed its 2013 decision that UC Observatories should find outside funding for Lick Observatory. Located on Mount Hamilton in California, the observatory accounts for $1.3 million of UC Observatories' $5 million budget for research and staff expenses. That budget also covers the Keck Observatory and the construction of the Thirty Meter Telescope, both in Hawaii. Lick currently hosts a 3-m telescope with modern instrumentation and a new 2.4-m automated planet-finding telescope. Opened in 1888, Lick was the first permanent mountaintop observatory, and it has contributed to the development of techniques for finding extrasolar planets and to the Nobel Prize–winning discovery that the universe's expansion is accelerating.
Ars Technica: One process developed to capture the carbon dioxide emitted by power plants generally uses amines to separate the CO2 molecules from the other gases being released. Certain amine solutions require high temperatures to work effectively. Because they use some of the plant’s generated heat, the amount of heat available to generate electricity is reduced, and so is the plant’s efficiency. Others amines can work at lower temperatures, but are so slow that the amount of CO2 that they trap is reduced. Industry researchers wanted to combine the lower temperature amines with carbonic anhydrase, an enzyme many organisms use for the fast transport of CO2. However, the enzyme does not function well in hot and acidic conditions, such as those found in coal power plants. Now a group of researchers has shown that it is possible to customize the enzyme via controlled mutations to make it resistant to those conditions. By artificially selecting versions of the enzyme that showed increased resistance, they were able to significantly increase the effectiveness of the enzyme even under extreme conditions. When the modified enzyme was introduced to the slow amine solution, it captured carbon 25 times faster.
Nature: From 2010 to 2012, sounding rockets carried the Cosmic Infrared Background Experiment (CIBER) into space multiple times to look at the IR background, which is made up, in part, of myriad distant and unresolved galaxies. After eliminating light from the Milky Way, Michael Zemcov of Caltech and his colleagues found that a significant portion of the light CIBER detected was not redshifted enough to have come from old galaxies. When they extrapolated the data to cover the entire universe, they realized that the light detected couldn’t have come from known galaxies. That finding suggested that the source of the light was stars scattered in the space between galaxies. Those stars could have escaped low-mass galaxies or been ejected by collisions of galaxies. However, the stars are too faint to be detected individually. By Zemcov and colleagues’ calculations, the number of extragalactic stars could equal the number of stars in all the known galaxies.
Telegraph: When someone reports having seen a ghost, it may really be just a figment of the imagination, according to a recent study published in Current Biology. Researchers in Switzerland set up a robot system, in which the human subjects used their index finger to control the movements of a master robot. Those movements were relayed to a slave robot located behind the human subjects that touched their back. That sensation alone felt weird enough to the test subjects, but it became stranger still when a delayed reaction was introduced between the subjects touching the robot button and their backs being touched. Then the subjects reported feeling as if they were being watched and touched by invisible people. The researchers say that the phenomenon occurs when the functioning of the human brain gets disrupted, which can happen when subjected to such conditions as illness, extreme cold, oxygen deprivation, or exhaustion. Two of the 12 participants were so upset by the experiment that they asked that it be stopped.
BBC: At least one species of bat has been observed to emit sound signals that interfere with its competitors so it can snatch food. Aaron Corcoran of Wake Forest University in North Carolina decided to study Mexican free-tailed bats after noticing one member of the species appearing to jam the echolocating signal of another in the hunt for insects. Corcoran and colleagues illuminated the night sky and set up a camera to record the bats’ movements and microphones to record their sounds. They found that when hunting for food, the bats were able to produce just the right frequency to interfere with others’ signals. Corcoran says the finding was unexpected and he plans to look into whether the behavior is unique to that particular species.