Christian Science Monitor: Since the nuclear meltdown at Japan’s Fukushima Daiichi plant last year, hundreds of bags of radioactive dirt and other contaminated debris have been buried in parks and other public areas, writes Winifred Bird for the Christian Science Monitor. Although sanctioned by the Japanese government as a way to reduce local radiation levels, the burials have for the most part been kept secret from local residents. As news of the cover-up has started leaking out, it has added fuel to the growing protest movement against Japan’s aura of secrecy regarding its nuclear industry.
Nature: Astronomers have identified two new supernovae that occurred more than 10 billion years ago, one of which is the oldest known supernova. Both supernovae were originally identified in deep-sky images from the 3.6-m Canada-France-Hawaii telescope. Jeff Cooke of the Swinburne University of Technology in Australia and his colleagues then used the 10-m Keck I telescope to take spectral measurements of the supernovae. The spectra obtained had redshifts of 2.05 and 3.9, setting the ages of the supernovae at 10.4 billion and 12 billion years, respectively. The universe itself is only 13.7 billion years old. The observational data from the younger of the two suggests that the star that exploded had a mass of about 250 suns. The explosion appears to have been a pair-instability supernova, where gamma rays produced internally become matter and antimatter particles that annihilate each other. The data from the older supernova aren’t clear enough to determine the type of supernova or the exact mass of the star, though it had to have been more than 100 solar masses.
Science News: For the past several decades, scientists have been in agreement that a 1200-year-long cold spell called the Younger Dryas was probably triggered by the massive melting of North American ice sheets some 13 000 years ago. But what path the floodwaters took has been the source of some debate. New computer simulations of ocean currents show that the most likely pathway was the Mackenzie Valley in Canada’s Northwest Territories; meltwater rushing through the valley would have been directed into the Arctic Ocean, where coastal boundary currents would have carried it toward the North Atlantic near Greenland. Because the lighter freshwater would have tended to stay on top of the ocean’s denser salt water, the massive inflow could have disrupted normal ocean circulation, resulting in cooler air temperatures. Understanding the conditions that led to Earth’s last Big Freeze could be important for understanding modern climate change. The researchers’ results were published online yesterday in the Proceedings of the National Academy of Sciences.
Ars Technica: The US Navy currently spends approximately $2 billion per year on fuel for gas turbine engines in its ships and aircraft. Gas turbines are already highly optimized, so to meet its goals of increasing engine power levels by 10% and reducing fuel consumption by 25%, the navy is looking at alternative designs. The Naval Research Laboratory is working on rotating detonation engines (RDEs), a variation on pulse detonation engines (PDEs) that have been developed over the past 20 years. In an RDE, a series of micro-injectors pump a fuel–air mixture into a long ring-shaped combustion chamber in a sequential, circular manner. When the detonation is initiated, the resulting shock wave ignites each injection of fuel in turn, rotating its way around the chamber. The hot exhaust gases are forced by the shock wave to expand out of the cylinder and are expelled through a nozzle, which generates thrust. RDEs are still very experimental, but navy scientists have run simulations that show potential efficiencies of 85–89% of an ideal detonation cycle.