Imagine being face-to-face with a woolly mammoth（猛犸象）. It would be quite a sight. Scientists believe it would tower above 11 feet tall. It would have a sloping back, a long, powerful trunk, and sharp, curved tusks that stretch up to 10 feet. Its thick hair would be up to three feet long. It would weigh six tons—about as heavy as a bus.

You’ve probably never seen a giant furry elephant before. Actually, you definitely haven’t. The species has been extinct for thousands of years.

But a few years from now, you might be able to see a woolly mammoth for yourself. Scientists believe they have the technology to recreate it.

A team of Korean and Russian scientists plan to clone a woolly mammoth. How will they do it?

Several woolly mammoth bodies have already been discovered in Siberia, an icy region in Russia. The scientists plan to take cells from these frozen mammoths. In a laboratory, they’ll use them to create a new cluster（群）of cells called an embryo. The embryo will be placed into the womb of a living female elephant. That elephant will then give birth to a baby woolly mammoth.

The scientists believe the whole process will take five years. Many scientists and animal lovers can’t wait. It will be so exciting to be able to bring a creature that has been extinct for thousands of years back to life. People would travel from around the world for the chance to see a living woolly mammoth. By observing the way the creature looks and acts, scientists might make brand-new discoveries about the history of animal life.

Other experts aren’t so sure about the woolly mammoth project. One big question is what to do with a mammoth. The Earth has changed in the thousands of years since these animals roamed the planet. Where would the creature live and would it be able to survive in today’s climate? Some believe that the money being spent on the experiment could be better spent on other important scientific projects, such as fighting disease.

But the South Korean and Russian scientists are sticking to their plan. They admit they have a big challenge ahead. There is no guarantee that they will succeed, but they’re hopeful.

Have you ever heard that some animals can understand zero as well? Experiments with monkeys and birds have proven that they can master it. But now, the understanding of zero has been found in a most unlikely candidate (候选人): bees.

According to a recently published study in the journal Science, Australian and French researchers worked together to do experiments to prove that bees are the first insects (昆虫) to“understand that zero belongs at the lower end of a sequence (序列) of numbers ”, according to a report by Science Daily.

Scarlett Howard, a researcher at RMIT University in Melbourne, trained bees to choose from several cards with different numbers of shapes printed on them. Correctly choosing the card with the fewest shapes earned them a reward (回报) of sugar water. For example, the bees learned to choose three elements when given three versus four; or two elements when given two versus three. And then these bees were given a challenge - a card that was entirely plain and that they had never seen before. But 64 percent of the time, they chose to fly toward the plain card instead of the card that had shapes on it. This suggests that the insects understand that zero stands for something less than two or three, according to Science magazine.

The researchers said that the findings have opened a door to new understandings of how different brains understand zero. “If bees can understand zero with a brain of less than a million neurons (神经元) (compared with the 86, 000 million neurons of a human brain), it suggests there are simple and useful ways to teach AI new tricks.”

What Are the Warning Signs of a Stroke?

The Centers for Disease Control and Prevention estimate that stroke (中风) kills about 140,000 Americans each year. Someone in the US has a stroke every 40 seconds. 【小题1】. Although stroke risk increases with age, about one-third of people hospitalized for stroke are under 65 years old.

Yet, in spite of these dire (可怕的) statistics, the American Stroke Association says that stroke “is preventable and treatable”. 【小题2】. The faster you recognize the signs and symptoms of a stroke and begin treatment, the more like you are to prevent long-term disability and death.

【小题3】. The most common type is called ischemic stroke. This is when a blood vessel supplying blood to the brain is obstructed by fatty deposits in the vessel lining, which is known as atherosclerosis. The ASA says about 87% of all stroke are ischemic in nature.

Hemorrhagic strokes, which comprise about 13% of stroke cases, result when a weakened blood vessel ruptures, 【小题4】. The blood builds up and compresses the surrounding brain tissue, causing tissue damage and cell death.

In each case, the longer the condition lasts, the more damage occurs. 【小题5】-every second the stroke lasts, more brain cells are damaged and die.