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Frequent Sighing Helps Keep You Alive

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Good news for hopeless romantics and the perpetually dismayed: All that sighing is good for you. In fact, you’d die without it. Scientists have now pinpointed the region in the brain that transforms normal breathing into a life-giving sigh. They published their findings this week in the journal Nature.  Let’s start with the mechanics. Physiologically speaking, sighing is a way of keeping your lungs inflated. “A sigh is a deep breath, but not a voluntary deep breath,” study co-author Jack Feldman said in a press release. “It starts out as a normal breath, but before you exhale, you take a second breath on top of it.” Whether you realize it or not, you do this about 12 times an hour, and even more than that when you’re stressed or anxious. And it’s a good thing you do. “If you don’t sigh every five minutes of so, the alveoli will slowly collapse, causing lung failure,” Feldman said. “That’s why patients in early iron lungs had such problems, because they never sighed.” The machines had not been programmed to give patients regular deep, lung-filling breaths. One group of researchers sifted through nearly 19,000 gene expression patterns in the active brains of mice, looking for the root of the sigh reflex. It was much smaller than they expected: just one little bundle of 200 cells in the brain stem, releasing one of two molecules called peptides. They shared their data with Feldman’s lab, and together the team found another set of 200 cells on the peptide receiving end.

A mouse's sigh clusters. Image credit: Stanford/Krasnow Lab

When the scientists prevented one peptide from reaching its goal, the rate of the mice’s sighing was cut in half. Blocking both peptides caused the mice to stop sighing altogether.  “Unlike a pacemaker that regulates only how fast we breathe, the brain’s breathing center also controls the type of breath we take,” co-author Mark Krasnow noted in the press release. “It’s made up of small numbers of different kinds of neurons. Each functions like a button that turns on a different type of breath. One button programs regular breaths, another sighs, and the others could be for yawns, sniffs, coughs, and maybe even laughs and cries.” It’s highly unusual for such small clusters of neurons to have so much power, Feldman said. “Sighing appears to be regulated by the fewest number of neurons we have seen linked to a fundamental human behavior.”  The team’s findings may someday lead to treatment for people with diseases that limit their breathing. “These molecular pathways are critical regulators of sighing, and define the core of a sigh-control circuit,” Krasnow said. “It may now be possible to find drugs that target these pathways to control sighing.” 

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Belly Flop Physics 101: The Science Behind the Sting
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Belly flops are the least-dignified—yet most painful—way of making a serious splash at the pool. Rarely do they result in serious physical injury, but if you’re wondering why an elegant swan dive feels better for your body than falling stomach-first into the water, you can learn the laws of physics that turn your soft torso a tender pink by watching the SciShow’s video below.

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What's the Saltiest Water in the World?
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Saltwater is common around the world—indeed, salty oceans cover more than two-thirds of the globe. Typical saltwater found in our oceans is about 3.5% salt by weight. But in some areas, we find naturally occurring saltwater that's far saltier. The saltiest water yet discovered is more than 12 times saltier than typical seawater.

Gaet’ale is a pond in Ethiopia which currently holds the record as the most saline water body on Earth. The water in that pond is 43.3% dissolved solids by weight—most of that being salt. This kind of water is called hypersaline for its extreme salt concentration.

In the video below, Professor Martyn Poliakoff explains this natural phenomenon—why it's so salty, how the temperature of the pond affects its salinity, and even why this particular saltwater has a yellow tint. Enjoy:

For the paper Poliakoff describes, check out this abstract.

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