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Sleep makes bad memories stick
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in Brief Single spider dads care for young
Physics behind Boston’s deadly 1919 Molasses Flood ON 15 January 1919, a storage tank in Boston’s North End ruptured and a wave of molasses more than 7 metres high swept through the streets, flattening buildings and killing 21 people. For nearly a century, historians have wondered why a famously slow-moving fluid caused such devastation. Now, the first physics analysis of Boston’s Great Molasses Flood shows that cold temperatures and unusual currents conspired to turn the sticky goop into a speeding wave. Nicole Sharp, an aerospace engineer who runs a Tumblr blog on fluid dynamics, and Jordan Kennedy at
Harvard University gathered data from historical records and ran experiments on how molasses flows under various conditions, then fed it all into computer models. The culprit seems to have been gravity currents, which come into play when a dense fluid spreads horizontally into a less dense fluid (in this case, molasses into air). The density of the molasses alone would account for the speed of its initial spread. It was like being bowled over by a sticky-sweet tsunami, says Sharp. The initial onslaught left people covered in suffocating molasses as rescuers struggled to save them, waist-deep in the goo. Here the cold temperatures played a deadly role: as the molasses cooled it became even more viscous. Much like quicksand, the more people thrashed about, the more deeply they found themselves trapped.
Sleep makes bad memories stick DON’T go to bed angry. Now there’s evidence for this proverb: it’s harder to suppress bad memories if you sleep on them. In a study, 73 male students memorised 26 mugshots, each paired with a disturbing image, such as a mutilated body. The next day they were asked to think about the images associated with half the mugshots, and to actively suppress memories of the images
associated with the others. They were then directed to memorise another 26 pairs of mugshots and nasty images. Half an hour later they again thought about half the associated images and actively suppressed memories of the rest. Finally, they were asked to describe the image associated with each of the 52 mugshots. The idea was to see if trying to suppress a memory works
better before or after sleep. The participants struggled most to remember suppressed images for the mugshots they saw on the second day, suggesting that sleep makes it harder to erase bad memories (Nature Communications, DOI: 10.1038/ ncomms13375). This seems to support a previously explored idea of using sleep deprivation to suppress bad memories and prevent conditions like post-traumatic stress disorder.
MOST male spiders bail out after mating – but not one South American species. Male Manogea porracea not only help with childcare, they also often end up as single dads. The male builds a web above the female’s and helps to maintain a “nursery” web between the two that holds the egg sacs. He also defends the eggs from predators and removes rain from the surface of egg sacs. By the end of the mating season, 68 per cent of egg sacs are being cared for by males alone, says Rafael Rios Moura at the Federal University of Uberlândia in Brazil (Animal Behaviour, doi.org/btrg). Moura found that significantly more hatchlings emerge from egg sacs tended by males than those left alone. Males often outlive females, which may have led to them evolving to take on paternal duties – the first such known case in a solitary spider species.
Being popular is good for the health LIFE at the bottom of the social ladder can be tough. Rhesus monkeys reveal how the stress of low social status can damage the immune system. Luis Barreiro at the University of Montreal, Canada, and colleagues sorted female rhesus monkeys who had never met into groups and observed as they formed a social pecking order. Monkeys introduced to their groups earlier tended to be ranked higher than those introduced later. To find out how rank affected health, the activity of 9000 genes in the animals’ immune cells was measured (Science, doi.org/btr5). White blood cells that fight infection were more active in higher-ranking monkeys, giving them better protection. 3 December 2016 | NewScientist | 15
in Brief Single spider dads care for young
Physics behind Boston’s deadly 1919 Molasses Flood ON 15 January 1919, a storage tank in Boston’s North End ruptured and a wave of molasses more than 7 metres high swept through the streets, flattening buildings and killing 21 people. For nearly a century, historians have wondered why a famously slow-moving fluid caused such devastation. Now, the first physics analysis of Boston’s Great Molasses Flood shows that cold temperatures and unusual currents conspired to turn the sticky goop into a speeding wave. Nicole Sharp, an aerospace engineer who runs a Tumblr blog on fluid dynamics, and Jordan Kennedy at
Harvard University gathered data from historical records and ran experiments on how molasses flows under various conditions, then fed it all into computer models. The culprit seems to have been gravity currents, which come into play when a dense fluid spreads horizontally into a less dense fluid (in this case, molasses into air). The density of the molasses alone would account for the speed of its initial spread. It was like being bowled over by a sticky-sweet tsunami, says Sharp. The initial onslaught left people covered in suffocating molasses as rescuers struggled to save them, waist-deep in the goo. Here the cold temperatures played a deadly role: as the molasses cooled it became even more viscous. Much like quicksand, the more people thrashed about, the more deeply they found themselves trapped.
Sleep makes bad memories stick DON’T go to bed angry. Now there’s evidence for this proverb: it’s harder to suppress bad memories if you sleep on them. In a study, 73 male students memorised 26 mugshots, each paired with a disturbing image, such as a mutilated body. The next day they were asked to think about the images associated with half the mugshots, and to actively suppress memories of the images
associated with the others. They were then directed to memorise another 26 pairs of mugshots and nasty images. Half an hour later they again thought about half the associated images and actively suppressed memories of the rest. Finally, they were asked to describe the image associated with each of the 52 mugshots. The idea was to see if trying to suppress a memory works
better before or after sleep. The participants struggled most to remember suppressed images for the mugshots they saw on the second day, suggesting that sleep makes it harder to erase bad memories (Nature Communications, DOI: 10.1038/ ncomms13375). This seems to support a previously explored idea of using sleep deprivation to suppress bad memories and prevent conditions like post-traumatic stress disorder.
MOST male spiders bail out after mating – but not one South American species. Male Manogea porracea not only help with childcare, they also often end up as single dads. The male builds a web above the female’s and helps to maintain a “nursery” web between the two that holds the egg sacs. He also defends the eggs from predators and removes rain from the surface of egg sacs. By the end of the mating season, 68 per cent of egg sacs are being cared for by males alone, says Rafael Rios Moura at the Federal University of Uberlândia in Brazil (Animal Behaviour, doi.org/btrg). Moura found that significantly more hatchlings emerge from egg sacs tended by males than those left alone. Males often outlive females, which may have led to them evolving to take on paternal duties – the first such known case in a solitary spider species.
Being popular is good for the health LIFE at the bottom of the social ladder can be tough. Rhesus monkeys reveal how the stress of low social status can damage the immune system. Luis Barreiro at the University of Montreal, Canada, and colleagues sorted female rhesus monkeys who had never met into groups and observed as they formed a social pecking order. Monkeys introduced to their groups earlier tended to be ranked higher than those introduced later. To find out how rank affected health, the activity of 9000 genes in the animals’ immune cells was measured (Science, doi.org/btr5). White blood cells that fight infection were more active in higher-ranking monkeys, giving them better protection. 3 December 2016 | NewScientist | 15