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Late-Night Drinking

Coffee lovers beware. Having aquick" pick-me-up" cup of coffee late in the day will playhavocwith your sleep. As well as being astimulant, caffeine interrupts the flow of melatonin, theB．rain hormone that sends people into asleep.

    Melatonin levels normally start to rise about two hours before bedtime. Levels then peak be-tween 2 am and 4 am, before failing again. "It's the neurohormone that controls our sleep tells ourB．ody when to sleep and when to wake, "says Maurice Ohayon of the Stanford Sleep EpidemiologyResearch Center at Stanford University in California. but researchers in Israel have found that caf-feinated coffee halves the body's levels of this sleep hormone.

    Lotan Shilo and ateam at the Sapir Medical Center in Tel Aviv University found that six vol-unteers slept less well after acup of caffeinated coffee than after drinking the same amount of de-caf. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, comparedwith 415 minutes after decaf. They also took half an hour to drop off--twice as long as usual--andjigged around in bed twice as much.

    In the second phase of the experiment, the researchers woke the volunteers every three hoursand asked them to give aurine sample. Shilo measured concentrations of abreakdown product ofmelatonin. The results suggest that melatonin concentrations in caffeine drinkers were half those indecaf drinkers. In apaper accepted for publication in Sleep Medicine, the researchers suggest thatcaffeine blocks production of the enzyme that drives tnelatonin production.

because it can take many hours to eliminate caffeine from the body, Ohayon recommends thatcoffee lovers switch to decaf after lunch.

        The author mentions" pick-me-up" to indicate that__________.                  查看材料

Transport has made it possiB．le for people to eat whatever food they want__________ 查看材料

In the trade of modern society the transmission of information plays as important __________arole as 查看材料

Only when goods can be carried to all parts of the world quickly __________ 查看材料

The development of modern means of transport__________ 查看材料

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Transport and Trade

1Transport is one of the aids to trade.by moving goods from places where they are plentiful toplaces where they are scarce, transport adds to their value. The more easily goods can be broughtover the distance that separates producer and consumer, the better for trade. When there were norailways, no good roads, no canals, and only small sailing ships, trade was on asmall scale.

    2The great advances made in transport during the last two hundred years were accompanied byabig increase in trade. bigger and faster ships enabled atrade in meat to develop between britainand New Zealand, for instance. Quicker transport makes possible mass-production and big busi-ness, drawing supplies from, and selling goods to, all parts of the globe. big factories could not ex-ist without transport to carry the large number of workers they need to and from their homes. bigcity stores could not have developed unless customers could travel easily from the suburbs andgoods were delivered to their homes. big cities could not survive unless food could be brought fromadistance.

    3Transport also prevents waste. Much of the fish landed at the ports would be wasted if it couldnot B．e taken quickly to inland towns. Transport has given us amuch greater variety of foods and goods since we no longer have to live on what is produced locally. Foods which at one time could be obtained only during apart of the year can now be obtained all through the year. Transport hasraised the standard of living.

    4by moving fuel, raw materials, and even power, for example, through electriccables, transporthas led to the estaB．lishment of industries and trade in areas where they would have been impossi-ble before. Districts and countries can concentrate on making things which they can do better andmore cheaply than others and can then exchange them with one another. The cheaper and quickertransport becomes,the longer the distance over which goods can profitably be carried． Countrieswith poor transport have alower standard of living.

    5Commerce requires not only the moving of goods and people but also the carrying of messagesand information. Means of communication, like telephones, cables and radio, send informationabout prices, supplies, and changing conditions in different parts of the worlD． In this way, ad-vanced communication systems also help to develop trade.

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