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阅读理解

　　Going to sleep may seem pretty boring compared with all the fun things there are to do while you're awake．But there's a lot going on in your mind and body while you're tucked under those covers．

　　Sleep, in fact, is as important to your survival as eating and drinking．Sleep improves your mood, makes you a better athlete, and helps you remember and understand what you learned during the day．During sleep your temperature drops．Your heart rate slows．Down goes the pressure of the blood moving through your veins．A chemical that controls growth(called a hormone)surges into your bloodstream．Scientists think sleep restores energy and improves your immune(免疫)system．We know what happens while we're asleep because scientists study volunteers who sleep in laboratories．The sleepers are hooked up to machines that measure brain waves, eye movements and muscle activities．

　　Sleep is like a school day：it's divided into different periods, or stages．When you're awake, your brain waves fire rapidly．As you begin to relax and drift into the first stage of sleep, your brain produces slower-moving waves and you lose awareness of your surroundings．As you slide to deeper sleep, your body repairs itself from the normal wear and tear of daily life．Then, as you begin to drift back up to a lighter sleep, your mind becomes more alert(机警), and your dreams begin．You're in REM sleep．

　　REM was names far the“rapid eye movement' that happens while you're dreaming．During REM sleep, your eyes move back and forth behind your timed lids, as though you were washing a movie．During other stages, you might move at that in bed, but during REM sleep you're still．That's probably because if you could move, your body would act out your dreams．As you get closer to morning, you spend more time in REM than in deep sleep, so you dream more．Researchers know that during REM sleep the part of the brain that handles learning and thinking is very active．

　　Getting too little sleep can affect your personality．Experts recommend that children get at least nine hours d sleep a night．So sleep fight．

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阅读理解

　　Space is a dangerous place, not only because of meteors(流星), but also because of rays from the sun and other stars．The atmosphere again acts as our protective blanket on the earth．Light gets through, and this is necessary for plants to make the food which we eat．Heat, too, makes our environment suitable to live．Various kinds of rays come through the air from outer space, but enormous quantities of radiation from the sun are screened off．As soon as men leave the atmosphere they are exposed to this radiation but their spacesuits or the walls of their spacecraft, if they are inside, do prevent a lot of radiation damage．

　　Radiation is the greatest known danger to explorers in space．The unit of radiation is called “rem”．Scientists have reason to think that a man can put up with far more radiation than 0.1 rem

　　without being damaged; the figure of 60 rems has been agreed on．The trouble is that it is extremely difficult to be sure about radiation damage a person may feel perfectly well, but the cells of his or her sex organs may be damaged, and this will not be discovered until the birth of deformed(畸形的)children or even grandchildren．Missions of the Apollo flights have had to cross belts of high radiation and, during the outward and return journeys, the Apollo crew accumulated a large amount of rems．So far, no dangerous amounts of radiation have been reported, but the Apollo missions have been quite short．We simply do not know yet how men are going to get on when they spend weeks and months outside the protection of the atmosphere, working in a space laboratory．Drugs might help to decrease the damage done by radiation, but no really effective ones have been found so far．

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阅读理解

　　Few of us make money by losing sleep．But three graduate students at Brown University in Providence built a company around sleep deprivation(睡眠不足)．

　　Jason Donahue, Ben Rubin and Eric Shashoua were working late nights in Brown’s business and engineering schools．They began thinking about ways to sleep better．They discovered they weren’t alone in burning the midnight oil．Around 20％ of Americans get less than six hours of rest a night．

　　The friends imagined a smart alarm clock that could track how much time people spend in the most restorative(有回复作用的)stages of the sleep cycle：REM(rapid eye movement)and deep sleep．What would it cost to design such a thing? Five years of research, 20 employees, ＄14 million and a whole lot of doubting from investors and scientists．

　　Their company, Zeo, based in Newton, Mass, launched its product in June, 2009．The Zeo device uses a headband with tiny sensors(传感器)that scan your brain for signs of four sleep states －REM, light, deep and waking sleep．The smart alarm clock displays a graph of your sleep pattern and wakes you as you’re not in REM sleep(which is when you’re least groggy)．In the morning you can upload the data to the company’s Web site, and so track your sleep over time．Most of the feedback comes in the form of Zeo’s ZQ score showing how well you’ve slept．

　　“Zeo allows people to unlock this black box of sleep,” says Dave Dickinson, a health-care CEO．

　　Whether any of this actually improves sleep is up to the consumer, who will also need to make lifestyle changes like cutting out alcohol before bedtime or caffeine after 3 pm．

　　For now the company is selling Zeo online only．Dickinson also plans to spread it to countries such as Australia, where sleep deprivation approaches US levels．

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