Physics Today Daily Edition
Ars Technica: The continued miniaturization of electronic devices has recently been hindered by the difficulty in miniaturizing energy storage. The size of such batteries severely limits their storage capacity. Now Paul Braun of the University of Illinois at Urbana–Champaign and his collaborators have combined 3D holographic lithography with traditional photolithography to create a 2-mm-square, 10-µm-thick lithium-ion battery. The holographic lithography was used to create a regularly patterned 3D lattice. Photolithography was then used to apply 2D electrodes to the internal structure. The resulting battery has lithium manganese dioxide cathodes, nickel–tin anodes, and an energy density of 6.5 μWh cm−2 μm−1.
New Scientist: Small calcium carbonate deposits called otoliths form in the inner ears of salmon as they age and collect trace amounts of other elements in the water. As otoliths grow, they create layers similar to tree rings. Sean Brennan of the University of Alaska Fairbanks and his colleagues have now used the strontium isotopes in those mineral records to map where individual Chinook salmon have been and for how long. Strontium, which lies below calcium in the periodic table, dissolves out of river rocks, and different regions have different isotope concentrations. Using water and other samples they took from the Nushagak River in Alaska, the researchers were able to determine the exact birthplaces of more than 400 salmon caught in 2011. They also found that 70% of the fish stayed in the same stream they were born in, with the rest migrating to other habitats.
BBC: A massive comparison of dead and dying galaxies and active galaxies has provided clues to the late stages of galactic life. Yingjie Peng of the University of Cambridge and his colleagues combed through images collected by the Sloan Digital Sky Survey to examine 23 000 galaxies that are no longer producing stars and 4000 galaxies that are producing stars. In the unproductive galaxies, Peng's team detected significantly more heavier metals than in the productive galaxies. If the galaxies had stopped producing new stars due to the sudden loss of gas clouds, the metal concentration would not have continued to grow. That suggests that the death process is drawn out over time. And the images showed that the active, star-forming galaxies were, on average, 4 billion years younger than the inactive galaxies.
Nature: A 33-page paper published on 14 May in Physical Review Letters has only 9 pages of text about the experiment and data; the remaining pages list the 5154 contributors to the project. It is the first joint paper by the ATLAS and CMS teams at CERN's Large Hadron Collider. The two teams decided to publish together because their combined data narrowed the mass of the Higgs boson to within ±0.25%. Both teams have been listing all the scientists involved because they believe there is no fair way to split credit for the project. A CMS paper from 2008 was the first to surpass 3000 authors.
Smithsonian: Quasars are massively bright, short-lived objects thought to be the result of material falling into supermassive black holes. Finding two of them near each other is unusual, but Joseph Hennawi of the Max Planck Institute for Astronomy in Germany and his colleagues were even more surprised to find four within 600 000 light-years of each other. The grouping was found as part of a survey of quasars using the Keck observatory in Hawaii. The images also revealed that all four are inside a large cold cloud of gas. Only about 10% of quasars are in similar clouds; hot clouds are much more common. That suggests current models of quasar formation may need to be adjusted. Hennawi's group thinks that the quasar quartet may represent the early stages of a galaxy cluster forming, because the region surrounding the collection has many more galaxies in it than does the average region of space.
Ars Technica: Superlubricity is a phenomenon that occurs when the coefficient of friction between two surfaces is dramatically reduced to near 0. Until now, it had only been detected in small samples of pairs of incompatible crystalline surfaces. Now a team from Argonne National Laboratory has produced superlubricity on a larger scale. Initially working with graphene and diamond, they tested two surfaces, one covered in graphene and one covered in diamond. The coefficient of friction was low, but not to the point of superlubricity. They noticed, however, that the graphene splintered and created curls of material that then collapsed under the pressure. Adjusting the setup, they placed nanoscopic diamonds between the two surfaces, and the coefficient of friction dropped dramatically. Electron micrographs revealed that the curls of graphene wrapped themselves around the nanodiamonds, which acted like ball bearings.
BBC: A new robotic arm has been developed by Tommaso Ranzani of the Sant'Anna School of Advanced Studies in Pisa, Italy, and his colleagues. The device lacks a rigid skeleton, similar to the tentacles of octopi. Inflatable compartments surround a central tube filled with coffee grounds. As compartments are inflated and deflated to change the length and bend of the arm, suction is applied to the central tube, which causes the granular material to "jam" and the arm to become rigid. Ranzani's team hopes to develop the arm for use in surgical systems.
Science: Radiation exposure, even at life-threatening levels, can be hard to detect until a patient becomes symptomatic. Several studies have shown that an analysis of the microRNA that circulates in blood can reveal whether a person has been exposed to radiation. Now Dipanjan Chowdhury of Harvard Medical School and his colleagues have used microRNA to determine the level of exposure and predict survival. They exposed mice to a range of radiation levels, from mild to lethal, and compared microRNA analysis from the next day with blood and bone marrow samples taken at four later times. Out of 170 microRNAs identified, the concentrations of 5 of them varied markedly depending on the amount of radiation the mice received. From those concentrations, Chowdhury's group could determine how much radiation was received well before the bone marrow samples showed damage.
New Scientist: Inspired by a rare molecule, Eugene Oks of Auburn University in Alabama has suggested the possibility of an unusual orbit for a planet in a binary star system. In Oks's proposed system, the planet follows a corkscrew path back and forth around a line between the two stars rather than circling both stars. Oks draws a comparison with the one-electron Rydberg quasimolecule in which the electron follows a similar corkscrew path due to electromagnetic forces. Although the presence of a planet in such systems could be found using current exoplanet detection techniques, distinguishing them from traditional orbits would be challenging.