Answer:
Every winter, Arctic sea ice grows around the pole, its frozen tendrils threading along northern coasts. Right now sea ice has just passed its peak coverage for the year, and will begin to shrink with the coming of spring. It’s a crucial time for polar bears, whose food supply is inextricably linked to sea ice.
And in recent decades, sea ice has been shrinking faster than ever. According to the National Snow and Ice Data Center, 2019 has the seventh-lowest sea ice cover in the Arctic since they began collecting satellite data 40 years ago.
This year “doesn't break any records, but it's the trend that matters,” says University of Alberta polar bear scientist Andrew Derocher. “The downward trend in Arctic sea ice across all months is the concern,” he says, and “now we wait to see what spring conditions bring.” (Read more about global warming’s link to polar bears.)
A cold spring allows ice to linger, giving polar bears easier access to one of their favorite foods: seals. A warm spring cuts short the availability of their food super-highway....
Answer:
Because your final periods can be irregular, menopause is confirmed 12 months after your last period. It is not normal to bleed or spot 12 months or more after your last period. Bleeding after menopause is usually a sign of a minor health problem but can sometimes be an early sign of more serious disease.
The big yellow thing in the sky
<span>Myelination enhances the speed of action potential propagation.
The difference between myelinated and unmyelinated axons are in the propagation of action potential. In unmyelinated axons, the action potential travels continuously through the axons. On the other hand, among the myelinated nerve fibres, transmembrane currents can only occur at the nodes of Ranvier where the axonal membrane is exposed, so the excitation of the axonal membrane jumps from node to node. This propagation is called saltatory conduction and this movement of depolarization wave is much faster than in unmyelinated fibres.</span>
