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Need to block a coffee ring? Send in the torpedoes
Xavier DESMIER/RAPHO/camera press
IN BRIEF Electronic tattoo monitors your vitals
Penguins don’t freeze, but they do get very, very cold JUVENILE king penguins may huddle together not for warmth, but to get a good night’s sleep. The penguins appear to be able to conserve energy when they need to by allowing their body temperature to drop. Yves Handrich of the University of Strasbourg, France, and his colleagues inserted temperature sensors into several organs in 10 chicks in the Crozet Islands of the Southern Indian Ocean, then let them go about their daily lives for about seven months. They found that parts of their bodies dropped by up to 15.7 °C when they were inactive, local temperatures fell or when fed cold meals
(Nature Communications, DOI: 10.1038/ncomms1436). The ability to survive despite large drops in body temperature – known as heterothermy – probably helps the penguins live through long winters. “Reducing body temperature even by one degree provides a considerable saving in energy expenditure,” says penguin physiologist Lewis Halsey of Roehampton University in the UK. Small mammals and birds can allow their body temperature to drop in this way, but it has never been seen in an animal this large. Until now, the largest known heterotherm was the buzzard, weighing up to 800 grams. Coming in at up to 10 kilograms, the king penguin chicks are enormous by comparison. The huddles may help juveniles rest undisturbed and escape predators, says Handrich.
Torpedoes block ‘coffee ring’ effect DRIP coffee on a table, let it dry and the stain will be shaped like a ring. Now there’s a way to stop this pesky “coffee ring effect”, which causes paints and inks to coat surfaces unevenly. As a splotch of coffee loses water to evaporation, its outer rim refuses to shrink inwards, held in place by the microscopic roughness of the tabletop. Instead, water flows from the 16 | NewScientist | 20 August 2011
drip’s centre to the rim and evaporates there, leaving behind the dark particles that give coffee its colour. The same thing occurs in particle-laden inks and paints. In a bid to beat the problem, Peter Yunker of the University of Pennsylvania in Philadelphia and colleagues watched drops of alcohol dry. When laden with polystyrene spheres, the particles concentrated into a ring. But
when the particles were torpedoshaped, they coated the surface uniformly after drying. This was also true when a small fraction of elongated particles made up a solution of mainly spherical ones (Nature, DOI: 10.1038/ nature10344). The torpedoes don’t slide along as easily as the spheres, it seems. Adding a few jamming torpedoes to ink or paint could be enough to block the flow of particles, leading to an even coat.
A NEW generation of skin-worn electronics may offer doctors a discreet alternative to the bulky systems normally used to monitor patients’ vital signs. John Rogers at the University of Illinois at Urbana-Champaign and colleagues fashioned brittle silicon and gallium arsenide semiconductors into wires thin enough to be flexible – each was just a few nanometres thick. They then used them to create a circuit between microscopic sensors, and embedded it in a stretchable patch that could be rubbed onto the skin like a temporary tattoo (Science, DOI: 10.1126/ science.1206157). Rogers’s team has used the patch to detect the electrical changes beneath the skin that occur when muscles move. “We can also use the device to stimulate muscle contractions,” he says. This work, only in rats so far, has yet to be published.
Brain cells that resist a stroke SOME brain cells are naturally protected against a stroke – and now we know why. Jack Mellor at the University of Bristol, UK, exposed slices of rats’ hippocampi to the low-oxygen conditions typical of a stroke. Neurons in the hippocampi known to resist stroke damage acted differently from a population of vulnerable cells: they removed receptors for the neurotransmitter glutamate from their cell surface, reducing their sensitivity to the chemical. Glutamate floods the brain during a stroke. Making other brain cells less sensitive to glutamate during a stroke could improve their survival prospects too, Mellor suggests (Journal of Neuroscience, DOI: 10.1523/jneurosci.1183-11.2011).
IN BRIEF Electronic tattoo monitors your vitals
Penguins don’t freeze, but they do get very, very cold JUVENILE king penguins may huddle together not for warmth, but to get a good night’s sleep. The penguins appear to be able to conserve energy when they need to by allowing their body temperature to drop. Yves Handrich of the University of Strasbourg, France, and his colleagues inserted temperature sensors into several organs in 10 chicks in the Crozet Islands of the Southern Indian Ocean, then let them go about their daily lives for about seven months. They found that parts of their bodies dropped by up to 15.7 °C when they were inactive, local temperatures fell or when fed cold meals
(Nature Communications, DOI: 10.1038/ncomms1436). The ability to survive despite large drops in body temperature – known as heterothermy – probably helps the penguins live through long winters. “Reducing body temperature even by one degree provides a considerable saving in energy expenditure,” says penguin physiologist Lewis Halsey of Roehampton University in the UK. Small mammals and birds can allow their body temperature to drop in this way, but it has never been seen in an animal this large. Until now, the largest known heterotherm was the buzzard, weighing up to 800 grams. Coming in at up to 10 kilograms, the king penguin chicks are enormous by comparison. The huddles may help juveniles rest undisturbed and escape predators, says Handrich.
Torpedoes block ‘coffee ring’ effect DRIP coffee on a table, let it dry and the stain will be shaped like a ring. Now there’s a way to stop this pesky “coffee ring effect”, which causes paints and inks to coat surfaces unevenly. As a splotch of coffee loses water to evaporation, its outer rim refuses to shrink inwards, held in place by the microscopic roughness of the tabletop. Instead, water flows from the 16 | NewScientist | 20 August 2011
drip’s centre to the rim and evaporates there, leaving behind the dark particles that give coffee its colour. The same thing occurs in particle-laden inks and paints. In a bid to beat the problem, Peter Yunker of the University of Pennsylvania in Philadelphia and colleagues watched drops of alcohol dry. When laden with polystyrene spheres, the particles concentrated into a ring. But
when the particles were torpedoshaped, they coated the surface uniformly after drying. This was also true when a small fraction of elongated particles made up a solution of mainly spherical ones (Nature, DOI: 10.1038/ nature10344). The torpedoes don’t slide along as easily as the spheres, it seems. Adding a few jamming torpedoes to ink or paint could be enough to block the flow of particles, leading to an even coat.
A NEW generation of skin-worn electronics may offer doctors a discreet alternative to the bulky systems normally used to monitor patients’ vital signs. John Rogers at the University of Illinois at Urbana-Champaign and colleagues fashioned brittle silicon and gallium arsenide semiconductors into wires thin enough to be flexible – each was just a few nanometres thick. They then used them to create a circuit between microscopic sensors, and embedded it in a stretchable patch that could be rubbed onto the skin like a temporary tattoo (Science, DOI: 10.1126/ science.1206157). Rogers’s team has used the patch to detect the electrical changes beneath the skin that occur when muscles move. “We can also use the device to stimulate muscle contractions,” he says. This work, only in rats so far, has yet to be published.
Brain cells that resist a stroke SOME brain cells are naturally protected against a stroke – and now we know why. Jack Mellor at the University of Bristol, UK, exposed slices of rats’ hippocampi to the low-oxygen conditions typical of a stroke. Neurons in the hippocampi known to resist stroke damage acted differently from a population of vulnerable cells: they removed receptors for the neurotransmitter glutamate from their cell surface, reducing their sensitivity to the chemical. Glutamate floods the brain during a stroke. Making other brain cells less sensitive to glutamate during a stroke could improve their survival prospects too, Mellor suggests (Journal of Neuroscience, DOI: 10.1523/jneurosci.1183-11.2011).