You may have heard adults say they are uncomfortable in the morning without a cup of coffee. One reason they may feel that way is that coffee contains caffeine(咖啡因). Caffeine appears naturally in coffee, tea, and cocoa beans, which are used to make chocolate. But now food makers are adding it to many products, from potato chips to water.

    The US government is especially worried about the problem. That's why the Food and Drug Administration (FDA) is studying the health effects of caffeine on young people. Studies show that too much caffeine can make people nervous and unable to sleep. What's more, caffeine is habit-forming. Those who consume it regularly and stop suddenly may experience headaches and feel tired.

    One of the biggest concerns is the large amount of caffeine added to so-called energy drinks, like Red Bull. A 12-ounce can of cola has about 35 milligrams of caffeine. A similar serving of Red Bull contains more than three times that amount.

    The Institute of Medicine is also working on caffeine-safety measures. “Teenagers should not drink beverages that contain caffeine. They should be aware of caffeine's effects on health and on how the brain works. Take, for example, teenagers who consume caffeine to stay awake and study for a test. They will remember less of what they just studied,” said Stallings, a member of the institute.

    Companies that make products with added caffeine claim they do not advertise them to kids. However, there is no law to stop children from buying them. So the FDA needs to set limits on caffeine, especially in energy drinks. As for added caffeine in foods, the government should just say no. If not, the amount of caffeine should be printed on food labels to remind consumers. The government must do that.

    Doctors say kids should avoid caffeine. If you need extra energy, try these natural boosters: eat right, exercise, and get plenty of sleep.

    Edgar Allan Poe was an American writer who helped shape the course of American literature. His life was full of tragedy and despair, but he managed some of the most influential American literature of the 19th century and continues to influence writers to this day.

    The early life of Edgar Allan Poe was quite miserable.Born in 1809, Poe was not yet three years old when his parents died.Adopted by a wealthy family,he got into trouble at school.He  entered the United States Military Academy at West Point,but he dropped out without graduating. His misery continued to his adult life.Later,because of a failed marriage, he suffered from mental illness. He was so upset about real life that he turned to writing.Expressing himself in an unreal and imaginary world was his only comfort.

    The tragedies in Poe's life influenced the tone,style and contents of his writing.His stories usually include death,which help build his reputation as a master of"dark"literature.In his The

    Tell-Tale Heart, the main character goes crazy and kills his roommate while in The Black Cat, the narrator kills his cat in a fit of madness.

    Poe died at the age of 40 in 1849.His life was tragic and short,but his legacy(遗产) is enormous.Poe is credited with creating crime fiction,and many say he contributed greatly to the appearance of science fiction.Fascinated by the scientific theories and new inventions of his time, he wrote about imaginary societies in the future.Writers such as Arthur Conan Doyle,the author of Sherlock Holmes,regarded Poe as the father of detective fiction. Jules Verne, a French writer who helped popularize science fiction,said Poe's work had a direct influence on the stories he wrote.

    Getting less sleep has become a bad habit for most American kids. According to a new survey(调查) by the National Sleep Foundation, 51% of kids aged 10 to 18 go to bed at 10 pm or later on school nights, even though they have to get up early. Last year the Foundation reported that nearly 60% of 7- to 12-year-olds said they felt tired during the day, and 15% said they had fallen asleep at school.

    How much sleep you need depends a lot on your age. Babies need a lot of rest: most of them sleep about 18 hours a day! Adults need about eight hours. For most school-age children, ten hours is ideal(理想的). But the new National Sleep Foundation survey found that 35% of 10- to 12-year-olds get only seven or eight hours. And guess what almost half of the surveyed kids said they do before bedtime? Watch TV.

    “More children are going to bed with TVs on, and there are more opportunities(机会) to stay awake, with more homework, the Internet and the phone,” says Dr. Mary Carskadon, a sleep researcher at Brown University Medical School. She says these activities at bedtime can get kids all excited and make it hard for them to calm down and sleep. Other experts say part of the problem is chemical. Changing levels of body chemicals called hormones not only make teenagers' bodies develop adult characteristics, but also make it hard for teenagers to fall asleep before 11 pm.

    Because sleepiness is such a problem for teenagers, some school districts have decided to start high school classes later than they used to. Three years ago, schools in Edina, Minnesota, changed the start time from 7:25 am to 8:30 am. Students, parents and teachers are pleased with the results.

    March 21 has been declared World Sleep Day, a time to recognize and celebrate the value of sleep. Many sleep experts hope it will be a wake-up call.

    According to a poll (民意调查) by the National Sleep Foundation, nearly 4 in 5 Americans don't get as much sleep as they should during the workweek. On average, adults are thought to need at least eight hours of sleep a night, although some can manage with less and some won't do well without more. But the survey found that, on weekdays, only 21% of Americans actually get a full eight hours of sleep, and another 21% get less than six hours.

    To many of us, the thought of spending more time sleeping is, well, a big yawn. On the other hand, the thought of being smarter, thinner, healthier and more cheerful has a certain appeal. And those are just a few of the advantages that can be ours if we consistently get enough sleep, researchers say. Also on the plus side: We're likely to have better skin, better memories, better judgment, and, oh, yes, longer lives.

    “When you lose even one hour of sleep for any reason, it influences your performance the next day,” says Dr. Alon Avidan, director of the UCLA Sleep Disorders Center.

    A study published last year found the same to be true even of children. When kids aged 8 to 12 slept for just one hour less for four nights, they didn't function as well during the day.

    But sleeping has an image problem.“We see napping or sleeping as lazy,” says Jennifer Vriend, a clinical psychologist in Ottawa, Canada, and the leading author of the study with children.“We put so much emphasis on diet, nutrition and exercise. Sleep is in the back seat. In fact,”she adds,“no matter how much we work out, no matter how well we eat, we can't be in top physical shape unless we also get plenty of sleep.”

    Mary Anning was an English fossil(化石)collector，dealer and paleontologist(古生物学家).Her fossil-hunting helped change the way people thought about the world.

    Mary was born into a poor family in England on May 21, 1799. She lived in the seaside town of Lyme Regis, in Dorset. The family had nine children. Only Mary and her brother Joseph grew up. Mary's father took his children along the beach. They picked up shells and stones to sell to visitors. Mary did not go to school much. Her family was too poor. And schools did not teach children about fossils. Mary could read and write. She taught herself. She learned about rocks and how bodies are made.

    In 1811 when Mary and Joseph were fossil hunting, Joseph saw a bone sticking out of the rock. Mary had a hammer to chip away at the rock. Very carefully she uncovered it. She found the first complete fossil of the ichthyosaur(鱼龙).

    Since then, Mary became crazy about fossil hunting. She liked to hunt on the beach after a storm. The wind, rain and waves made the rocks crumble. It was easy to spot fossils. Most days Mary went fossil hunting with her dog, Tray.

    Rich friends helped Mary by selling fossils for her. They sent her money. Scientists wrote letters and came to see her. One good friend was William Buckland, a professor at Oxford University. Mary also opened a shop to sell fossils, stones and shells. She chatted with visitors.

    Mary Anning died in1847. How evolution(进化)works was explained by Charles Darwin not long after Mary died. Her fossils had helped scientists understand how things began.

VAZOnepwr Blade 5 Dual

Cordless Blade 5 is a great one for sheer suction(吸力) power. It's easy to use it under furniture and it works well on all surfaces. The dust tank holds 0.7 litres and it comes with two batteries for 90 minutes of charge. If you're on a budget, the Blade 4 is a good option (now£250,from£450;vax. co.uk)

MIele Complete C3

At 890W, this corded vacuum is "exceptionally powerful" and its "Air Clean" filtration traps even tiny particles. It has a 12m radius(半径) and comes with three tools, stored in the body(£219;miele.co.uk)

Shark CZ500UKT Duo Clean

This 880W corded vacuum has remarkable suction power. It can switch between cleaning carpets or hard floors, and has an anti-hair-wrap brush roll and an LED light to show up dust (£330; sharkclean.co.uk)

Dyson Ball Animal Multi-floor

Unusually easy to move or turn skillfully thanks to its responsive rollerball, this bagless vacuum delivers strong suction and is great for getting up pet hair. A bit heavy at 7.4kg, it has a ten-metre cord and 3.5-litr e caddy, which ejects at the touch of a button (£380; dyson.co.uk)

Henry HVR 160-11

A long-standing favourite, the Henry is famously strong and great value. It has a large six-litre dust bag, and packs 620W of power. Its cord is a generous ten metres, and it has a long 2.2m hose, which is useful for cleaning up high and under sofas (£130; myhenry.com).