SNIPPETS.

SNIPPETS.

That hole in the sky

Whatever happened to the ozone hole and should we still be worried about it? What is called the ozone hole is an area of severe depletion of the gas ozone in the upper atmosphere above the Antarctic. It still appears every year, though it gets less publicity than it did when it was first discovered. And the ozone hole still concerns scientists.
Its size and persistence are evidence that Earth is being exposed to high levels of harmful ultraviolet-B radiation from the sun because the ozone ‘umbrella’ is too thin. UV-B radiation hurts both creatures and crops, causing, for example, skin cancer and plant damage.
NASA tracks the ozone hole with satellite readings. In 2015, NASA reported that the hole was large than in recent years, but formed later. The seasonal depletion of Antarctic ozone, a highly reactive molecule of oxygen called O3, was first reported in the journal Nature in 1985.
The researchers theorised that the very low temperatures from midwinter into early spring permitted chemical reactions that removed ozone from the atmosphere. It was discovered that the biggest threat came from the release of molecules containing chlorine and bromine in some refrigerants and fire suppressants.
A worldwide effort to limit such releases followed under a 1987 international pact called the Montreal Protocol. As a result, atmospheric levels of ozone-depleting chemicals are slowly declining and are predicted to be back to where they were in 1980 by 2070.
C Claiborne Ray

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Cassini’s final mission: obliteration
Since 2004, the Cassini spacecraft has twirled around Saturn, studying the gas giant’s rings, storms and moons. Now it has begun preparations to plunge into the planet’s atmosphere and vapourise next year. NASA doesn’t want to risk contaminating a moon with hardy microbes that may have survived aboard the craft. Saturn, with a gaseous surface consumed by hydrogen and helium, is inhospitable.
Titan, the planet’s biggest satellite, has an atmosphere that is much less hostile. It’s a wet world similar to Earth, except that it is awash in methane. Researchers have called the spacecraft’s swan song the Cassini Grand Finale because it includes an ambitious manoeuvre: 22 loops through the gap between Saturn’s surface and its innermost rings.
Nicholas St Fleur


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Lab-grown bonesimplanted in pigs
The pigs, all 14 of them, are fine. Given that they were retrofitted with bone grown in a laboratory, that was a pleasant surprise.
“The pigs woke up, and a half-hour later, they were eating,” said Gordana Vunjak-Novakovic, a professor at Columbia University, USA.
We thought they would be in pain. But no, they’re doing great.” Gordana and her colleagues have managed to create living bone from stem cells. First, they made a CT scan to create a three-dimensional image of each pig’s jaw.
From cow bone, they sculpted a ‘scaffold’ — a 3-D copy of the pig bone. They put the scaffold in a nutrient solution with stem cells extracted from the pigs. The cells attached to the scaffold, forming a new bone identical to the original.
Then the researchers implanted the new bone in each pig. They reported their results in Science Translational Medicine. Clinical trials in humans are at least three years away.
Nicholas Bakalar


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Plants can make good judgments about risks
Plants may not be getting enough credit. Not only do they remember when you touch them, it turns out that they can make risky decisions that are as sophisticated as those made by humans, all without brains or complex nervous systems. Ecologists at Oxford University, UK grew pea plants and split their roots between two pots. Both pots had the same amount of nutrients on average, but in one, the levels were constant; in the other, they varied over time. Then the researchers switched the conditions so the average nutrients in both pots would be equally high or low, and asked, which would the plant prefer?
When nutrient levels were low, the plants laid more roots in the unpredictable pot. But when nutrients were abundant, they chose the one that always had the same amount. This supports an idea called risk sensitivity theory: when choosing between stable and uncertain outcomes, an organism will play it safe when things are well and take risks when times are hard.
Joanna Klein
The New York Time


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