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Pay attention to that rumbling belly
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TITAN, Saturn’s largest moon, may have its own Dead Sea. A fake lake simulating conditions there hints that the moon may host ethane pools saturated with benzene, just as the Dead Sea is packed with salt. Titan is arguably the most Earth-like body in the solar system, boasting lakes, rivers, clouds and rainfall. But the moon’s frigid temperatures mean its liquids are hydrocarbons like ethane or methane, not water. The atmosphere also churns out fresh hydrocarbons like benzene, a chemical found in gasoline, and these fall like snow. Michael Malaska at the Jet Propulsion Laboratory in Pasadena, California, and his colleagues wondered how much of this snow could dissolve in the lakes. They filled a small tube with liquid ethane, chilled it to a Titan-like -179 °C and added benzene.
NASA/JPL/U. ARIZONA/SCIENCE PHOTO LIBRARY
To their surprise, the benzene dissolved quickly. This suggests that over geological timescales, so much hydrocarbon snow would have dissolved in Titan’s lakes that they would have become saturated with the stuff (Icarus, doi.org/tzb). Excess benzene could build up in a mud-like sludge on the shores and on the lake floors. Some of these deposits could be eroded by ethane rain, forming a complex, cave-riddled landscape.
Japanese paper cuts make graphene extra stretchy THE world’s strongest material becomes a softie when cut in just the right places. Computer simulations show that making patterned cuts in superstrong graphene yields flexible sheets that stretch to more than 160 per cent of their original size. The approach, which mimics the Japanese paper-cutting technique kirigami, should have a host of uses, such as flexible sensors for the body or foldable TV screens. Graphene is just a single carbon atom thick, yet more
than 100 times stronger than steel. “It’s very counter-intuitive,” says Harold Park of Boston University. “Graphene is the thinnest possible material, but it’s the strongest material.” Experiments have shown that cutting graphene into patterned sheets, akin to cutting paper into intricate snowflakes or flowers, makes the material stretchable. Park’s colleague Zenan Qi made various simulated cuts, and found a pattern involving numerous overlapping rectangles had the most effect on the stretchiness
of the sheets. While ordinary graphene tears when stretched less than 30 per cent, the kirigami graphene elongated roughly 65 per cent before tearing (arxiv. org/abs/1407.8113). Figuring out where, how and when graphene rips is important for using the material, says Paul McEuen of Cornell University in New York, who is using graphene kirigami to make electrodes that could wrap around cells and eavesdrop on them. “These are questions you can’t answer by playing with a sheet of paper.” Davide Bonnadonna
Titan’s lakes brim with benzene
Pay attention to that rumbling belly GRUMBLE… grumble-rumble… The gurgles made by a hungry belly are familiar to us all, but they are not just the side effect of an empty stomach. Brain cells not normally associated with communication send out a signal when they detect blood glucose levels are running low, and this triggers the stomach contractions. Richard Rogers of the Pennington Biomedical Research Center at Louisiana State University and colleagues used a drug called fluorocitrate to knock out the function of certain astrocytes and neurons in the brains of rats, blocking the sensation of hunger. Only when astrocyte function was restored did the gastric grumbles return, showing that it is these cells that respond to low glucose levels (Journal of Neuroscience, DOI: 10.1523/JNEUROSCI.1406-14.2014). The feeling of discomfort you get when hungry is called “hypoglycaemia awareness”. “For most people this is only slightly unpleasant, but for diabetics whose glucose levels can drop significantly, [being hungry] can be dangerous,” says Rogers. “It’s important to understand how this mechanism works.”
Shrink a bit more and add feathers IT TOOK 50 million years of continual shrinking to turn massive dinosaurs into the first flying birds. “No other dinosaur group has undergone such a long and extended period of miniaturisation,” says Mike Lee of the South Australian Museum in Adelaide. His team studied theropods, the two-footed dinosaurs like Velociraptor from which birds evolved. They tracked how 1549 skeletal features changed in 120 theropods over 50 million years. They found 12 major evolutionary steps where theropod groups split to form new kinds of dinosaur. At each
break, the ones that ended up evolving into birds shrank. They went from 238 to 0.5 kilograms, and changed four times as fast as other theropods (Science, doi.org/tx7). Shrinking must have been beneficial, says Lee. “It would have permitted them to chase insects, climb trees, leap and glide, and eventually develop powered flight.” Being small may also have helped birds survive the dinosaur extinction, says Bhart-Anjan Bhullar of Yale University. It looks like the extinction “took out all landlocked animals above a certain size”.
9 August 2014 | NewScientist | 15
TITAN, Saturn’s largest moon, may have its own Dead Sea. A fake lake simulating conditions there hints that the moon may host ethane pools saturated with benzene, just as the Dead Sea is packed with salt. Titan is arguably the most Earth-like body in the solar system, boasting lakes, rivers, clouds and rainfall. But the moon’s frigid temperatures mean its liquids are hydrocarbons like ethane or methane, not water. The atmosphere also churns out fresh hydrocarbons like benzene, a chemical found in gasoline, and these fall like snow. Michael Malaska at the Jet Propulsion Laboratory in Pasadena, California, and his colleagues wondered how much of this snow could dissolve in the lakes. They filled a small tube with liquid ethane, chilled it to a Titan-like -179 °C and added benzene.
NASA/JPL/U. ARIZONA/SCIENCE PHOTO LIBRARY
To their surprise, the benzene dissolved quickly. This suggests that over geological timescales, so much hydrocarbon snow would have dissolved in Titan’s lakes that they would have become saturated with the stuff (Icarus, doi.org/tzb). Excess benzene could build up in a mud-like sludge on the shores and on the lake floors. Some of these deposits could be eroded by ethane rain, forming a complex, cave-riddled landscape.
Japanese paper cuts make graphene extra stretchy THE world’s strongest material becomes a softie when cut in just the right places. Computer simulations show that making patterned cuts in superstrong graphene yields flexible sheets that stretch to more than 160 per cent of their original size. The approach, which mimics the Japanese paper-cutting technique kirigami, should have a host of uses, such as flexible sensors for the body or foldable TV screens. Graphene is just a single carbon atom thick, yet more
than 100 times stronger than steel. “It’s very counter-intuitive,” says Harold Park of Boston University. “Graphene is the thinnest possible material, but it’s the strongest material.” Experiments have shown that cutting graphene into patterned sheets, akin to cutting paper into intricate snowflakes or flowers, makes the material stretchable. Park’s colleague Zenan Qi made various simulated cuts, and found a pattern involving numerous overlapping rectangles had the most effect on the stretchiness
of the sheets. While ordinary graphene tears when stretched less than 30 per cent, the kirigami graphene elongated roughly 65 per cent before tearing (arxiv. org/abs/1407.8113). Figuring out where, how and when graphene rips is important for using the material, says Paul McEuen of Cornell University in New York, who is using graphene kirigami to make electrodes that could wrap around cells and eavesdrop on them. “These are questions you can’t answer by playing with a sheet of paper.” Davide Bonnadonna
Titan’s lakes brim with benzene
Pay attention to that rumbling belly GRUMBLE… grumble-rumble… The gurgles made by a hungry belly are familiar to us all, but they are not just the side effect of an empty stomach. Brain cells not normally associated with communication send out a signal when they detect blood glucose levels are running low, and this triggers the stomach contractions. Richard Rogers of the Pennington Biomedical Research Center at Louisiana State University and colleagues used a drug called fluorocitrate to knock out the function of certain astrocytes and neurons in the brains of rats, blocking the sensation of hunger. Only when astrocyte function was restored did the gastric grumbles return, showing that it is these cells that respond to low glucose levels (Journal of Neuroscience, DOI: 10.1523/JNEUROSCI.1406-14.2014). The feeling of discomfort you get when hungry is called “hypoglycaemia awareness”. “For most people this is only slightly unpleasant, but for diabetics whose glucose levels can drop significantly, [being hungry] can be dangerous,” says Rogers. “It’s important to understand how this mechanism works.”
Shrink a bit more and add feathers IT TOOK 50 million years of continual shrinking to turn massive dinosaurs into the first flying birds. “No other dinosaur group has undergone such a long and extended period of miniaturisation,” says Mike Lee of the South Australian Museum in Adelaide. His team studied theropods, the two-footed dinosaurs like Velociraptor from which birds evolved. They tracked how 1549 skeletal features changed in 120 theropods over 50 million years. They found 12 major evolutionary steps where theropod groups split to form new kinds of dinosaur. At each
break, the ones that ended up evolving into birds shrank. They went from 238 to 0.5 kilograms, and changed four times as fast as other theropods (Science, doi.org/tx7). Shrinking must have been beneficial, says Lee. “It would have permitted them to chase insects, climb trees, leap and glide, and eventually develop powered flight.” Being small may also have helped birds survive the dinosaur extinction, says Bhart-Anjan Bhullar of Yale University. It looks like the extinction “took out all landlocked animals above a certain size”.
9 August 2014 | NewScientist | 15