Physics Today Daily Edition
IEEE Spectrum: Diodes are electrical components that allow electricity to flow in only a single direction. Now a diode has been made from an 11-base-pair length of DNA combined with two molecules of coralyne. The combined molecule, which is roughly 4 nm long, allows electrical current to flow through it 15 times as strongly in one direction as in the other. The researchers believe that the coralyne molecules fuel the one-way movement of electricity by creating an imbalance in the distribution of electrons in the DNA.
New Scientist: Due to Mars's thin atmosphere, dust devils require strong winds to keep the sand grains swirling off the ground. Gerhard Wurm of the University of Duisburg-Essen in Germany suggests that the temperature difference between shadowed and sunlit ground may be enough to kick extra dust into the air. To test his theory, he dropped a capsule full of Mars-like sand down a 110 m drop tower, shined a laser light on the dust as it fell, and measured the dust grains as they bounced around inside. When Wurm switched off the laser, he noted that the grains' movement increased by a factor of 10, which he attributed to the cooling of the dust. He says that on Mars the dust devil's shadow could have a similar cooling effect. The resulting temperature changes could cause gases in the Martian soil to move around and, after a buildup of pressure, explode and lift sand into the air. That feedback effect could fuel the large dust storms occasionally seen on Mars.
New Scientist: Assuming a distant star is aligned with Earth's orbital plane, inhabitants of that star system would see Earth transiting the Sun for about 10 hours per year. According to David Kipping and Alex Teachey of Columbia University, a 30 MW laser pointed at that star from Earth would be able to mask evidence of the transit, hiding Earth from any aliens looking for exoplanets. Alternatively, the researchers say that the same laser could be used to warp the sunlight in a way that would act as a signal to indicate the presence of intelligent life on Earth. Kipping and Teachey now want to look through data collected by the Kepler space telescope to see if any aliens have arrived at the same idea of trying to cloak or amplify transit signals.
Scientific American: Discovered in 2004, the super-Earth 55 Cancri e was thought to be a large rocky world with a thick, hot atmosphere. By mapping thermal changes of the planet's surface using the Spitzer Space Telescope, Brice-Olivier Demory of the University of Cambridge and his colleagues have now found that the planet is likely airless. The scientists discovered that the planet is tidally locked with its parent star, meaning that one side is perpetually covered in sunlight. The data from the telescope showed that the dark side of the planet reached temperatures of 1000 °C and that the lit side was more than twice as hot. If the planet had an atmosphere, winds would distribute the heat more evenly and minimize the temperature difference. However, the hottest spot on the planet is not directly in line with the star, suggesting that something is redistributing the heat. Demory's team believes that the hot spot, which is shifted eastward, is most likely caused by the movement of molten lava circulating heat from the dayside surface toward the nighttime one, where it cools and solidifies.
BBC: Gravimeters, which are used to measure local variations in gravity, are generally large and cost about $100 000. Now Richard Middlemiss of the University of Glasgow, UK, and his colleagues have developed a cheap, postage stamp–sized gravimeter based on the tiny accelerometers commonly found in smartphones. The new gravimeter employs a block of silicon suspended between two thin bands. As gravity pulls the block downward, the block's shadow—cast by light shining through the device—also moves and that movement is detected by a photodiode. Researchers can calculate the strength of the gravitational pull by measuring the amount of current the light-sensitive diode produces. The team tested the device by measuring Earth's tides over the span of several days. The device was more than sensitive enough to detect the changes in gravity due to tidal forces; it could also detect variations as small as those caused by a 1 m diameter tunnel located 2 m below ground. Distributing a network of the small gravimeters around a volcano could provide continuous localized monitoring for a fraction of the cost of a conventional gravimeter.