Nature: A clock that uses quantum mechanics to measure time also provides an alternative way to define the standard measurement of mass. Holger Müller of the University of California, Berkeley, created two matter waves from a cloud of ultracold cesium atoms. One half was given a set of precisely calibrated momentum kicks with a laser, after which it was recombined with the other, unaffected half. At 3 × 1025 Hz, the matter waves’ characteristic frequency is far too high to be measured directly. However, recombining the two halves creates an interference pattern whose frequency can be determined accurately with a laser. What’s more, because the frequency depends on the mass of an atom, the laser measurement allows for a direct calculation of a single atom’s mass. In principle, the exact number of atoms in 1 kg of different elements can therefore be determined. The current standard for mass is a 1-kg block of metal, whose mass is slowly changing because of microscopic contamination. The new single-atom clock joins two other options that are vying to replace the current definition of the mass standard.
Daily Archives: January 11, 2013
Nanomachine capable of simple protein assembly
Nature: Ribosomes are the molecular machines that translate RNA into proteins. A nanomachine created by Dave Leigh of the University of Manchester, UK, and his colleagues possesses a very simplified version of that ability. The nanomachine is preloaded with a sequence of amino acids and, when heated, sequentially combines the amino acids to form short proteins called peptides. Although the system is much less efficient than real ribosomes, it is evidence that nanomachines can be used to create biochemicals. This is a significant step forward from the two-century-old process of chemical synthesis through repeated refinement and combination. The research team hopes that the next step with their molecular machine will be to design it so that it can “reload” itself with more amino acids to repeat the process. Making the process repeatable and finding ways to accelerate the peptide construction will be the first steps in developing a useful replacement for traditional laboratory chemical synthesis.
DOE funds research center for rare earth elements
Talking Points Memo: The US Department of Energy has established a $120 million, 5-year grant to fund a new research center at Ames National Laboratory in Ames, Iowa. The Critical Materials Institute will focus on securing a steady supply of the five rare earth elements that are most likely to run out. Rare earth elements are a group of 17 metals used in a wide range of modern electronics from cars and earbuds to smartphones and computers. The limited supply of rare earth elements is due to Chinese restrictions on their export and the difficulty of obtaining the individual elements. Because of their chemical similarities, rare earths tend to all occur in the same raw ore. Current processes for isolating them from that ore return only 5% purified material. The Hub, as the new institute is already known, will be working to develop improved methods for the extraction and isolation of rare earths and distributing that information to mining companies.
Milky Way may be less massive than previously thought
Science: Estimating the total mass of a galaxy is not an exact science—partly because most of the mass is due to dark matter, which can’t be seen. An earlier estimate of the Milky Way’s mass, made in 2009 and based on measurements of its rotation speed, put the total at a few trillion times the mass of the Sun. New data from the European Southern Observatory in Chile and the William Herschel Observatory in Spain, however, show that the stars farthest from the galactic center are moving much more slowly than previously thought. Using that information, Alis Deason of the University of California, Santa Cruz, and colleagues have determined that the galaxy’s mass could be less than half the 2009 estimate. The researchers presented their results at this week’s annual meeting of the American Astronomical Society.