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Shark teeth have natural toothpaste

The dense, flat and crushing teeth of sharks contain fluoride keeping that is an active component of most toothpastes and dental care mouthwashes, an in-dept look at their teeth has found.

This helps to explain why sharks are so effective at either tearing or cutting their prey.

While shark teeth contain the mineral fluoroapatite (fluorinated calcium phosphate), the teeth of humans and other mammals contain hydroxyapatite, which is an inorganic constituent also found in bone, explained co-author Matthias Epple. “In order to make teeth more acid resistant, toothpaste often contains fluoride,” Discovery News quoted Epple, a professor of inorganic chemistry at the University of Duisburg-Essen, as saying. “In the surface of human teeth after brushing, a small amount -- much less than 1 percent -- of hydroxide is exchanged by fluoride.
“In contrast, (the surface of) shark teeth contains 100 percent fluoride. In principle, sharks should not suffer from caries. As they live in water and as they change their teeth regularly, dental protection should not be a problem for sharks,” he said.

Mysteries of icy comets solved

Scientists have solved two solar system puzzles – explaining how did icy comets obtain particles that formed at high temperatures, and how did these refractory particles acquire rims with different compositions.

Carnegie’s theoretical astrophysicist Alan Boss and cosmochemist Conel Alexander are the first to model the trajectories of such particles in the unstable disk of gas and dust that formed the solar system.

They found that these refractory particles could have been processed in the hot inner disk, and then travelled out to the frigid outer regions to end up in icy comets.

The young Sun is thought to have experienced a series of outbursts caused by the rapid infall of disk gas onto the Sun. The leading mechanism for explaining such outbursts is a phase of disk instability. The researchers modelled the trajectories of several hundred centimeter-sized melilite mineral particles during a phase of disk instability. These particles are similar to calcium-aluminum-rich inclusions (or CAIs), the refractory particles often found in well-preserved meteorites, as well as the comet Wild 2.

Their disk model assumed a marginally gravitationally unstable, fully three-dimensional disk, with a mass of about 5 percent of today’s Sun and temperatures ranging from a frigid –350 degree F (60K) in the outer regions, to a scorching 2240 degree F (1500K) near the center.

Butterflies with darker wings have greater ability to fly

Monarch butterflies who have dark orange wings fly further than those with light orange wings, a new study has revealed.

Previous work has shown that monarch colouring is intended to warn their predators about their bitter taste and toxicity, and that migratory butterflies are darker coloured than non-migratory ones, suggesting an association between darker colour and increased fitness.

The current work, led by Andrew Davis of the University of Georgia, provides further evidence for this association.

The researchers tested 121 captive monarchs in an apparatus called a tethered flight mill, where they can quantify butterfly flight speed, duration, and distance, and found that those with darker orange wings overall flew longer distances than those with lighter wings.

“Butterfly researchers don’t often look closely at colour variation between individuals of the same species. The results of this project will pave the way for a new line of inquiry into the significance of butterfly wing colour,” Davis said.

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