英語聽力綜合訓(xùn)練mp3材料

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★英語聽力頻道為大家整理的英語聽力綜合訓(xùn)練mp3材料,供大家參考。更多閱讀請查看本站英語聽力頻道。
    Does An Onion A Day Keep The Doctor Away?
    Have you ever wondered why your eyes water when you chop onions?
    Like Tear Gas
    Despite what you might think, the smell of onions is not what makes most people cry. You see, an onion gets it distinctive taste from compounds that contain sulfur atoms. When you slice an onion, you damage its cells, triggering a chemical reaction that converts these compounds into an acid that acts like tear gas.
    At the same time, the byproducts of this reaction condense to form the molecules responsible for the onion’s pungent odor. In other words, the same chemical reaction that makes you weepy also releases the onion’s smell.
    Garlic And Health Benefits
    A similar thing happens when you chop garlic. When it’s still in bulb form, garlic doesn’t smell like much. It’s only when you mince or dice the garlic’s cells that a chemical reaction releases the smell we associate with garlic.
    However, no one cries from slicing garlic. This is because the byproducts of the chemical reaction that takes place in garlic are different from the byproducts you get when you chop an onion.
    Scientists suggest that the same chemical that gives garlic and onions their distinctive smell helps them fight off bacteria and fungus and parasites. There might be something after all behind all those reports that garlic and onions are good for you.
    每日一個洋蔥就能和醫(yī)生說再見嗎?
    你考慮過為什么當(dāng)你切洋蔥時,眼睛會留下淚水嗎?
    如同催淚瓦斯
    不管你怎么想,洋蔥的氣味并不會導(dǎo)致多數(shù)人流淚,你瞧,洋蔥的特殊味道來源于含有硫離子的復(fù)合物,當(dāng)你切洋蔥時,你破壞了它的細胞,以至于激發(fā)化學(xué)反應(yīng),這種反應(yīng)會使本身的化合物轉(zhuǎn)化成某種像催淚瓦斯一樣的酸。
    與此同時,這種反應(yīng)的副產(chǎn)品澤濃縮成為洋蔥刺激氣味的某種份子,換句話說,讓你淚眼汪汪以及釋放洋蔥味道的正是這種化學(xué)反應(yīng)。
    大蒜與健康
    當(dāng)你切蒜的時候也會發(fā)生類似的事情。當(dāng)大蒜呈鱗球莖狀態(tài)時,氣味并不濃郁。只有當(dāng)你切碎或者是破壞大蒜細胞時,化學(xué)反應(yīng)釋才會放出大蒜的氣味。
    但是,切片大蒜不會讓人流淚,這是因為在大蒜中發(fā)生化學(xué)反應(yīng)的副產(chǎn)品同你切洋蔥時的得到的副產(chǎn)品不同。
    科學(xué)家認為相同的化學(xué)反應(yīng)賦予大蒜洋蔥獨特的氣味,這種氣味幫主它們擊退細菌,真菌以及寄生蟲。在關(guān)于大蒜洋蔥對你有好處報道的背后,或許有更多科學(xué)有待我們探究。