53-54考研英语阅读报刊资料

精品值得阅读相信相信的力量阅读使人快乐，成长需要时间How does the brain know when carbohydrates have been or should be consumed? The answer to this question is not known, but one element in the explanation seems to be the neurotransmitter sero-tonin (血清素), one of a class of chemical mediators that may be released from a pre-synaptic neuron and that cause the transmission of a nerve impulse across a synapse (突触) to an adjacent postsynaptic neuron. In general, it’s been found that drugs that selectively facilitate serotonin-mediated neuro-transmission tend to cause weight loss, whereas drugs that block serotonin-mediated transmission often have the opposite effect: they often induce carbohydrate craving and consequent weight gain. Serotonin is a derivative of tryptophan (色氨酸), an amino acid that is normally present at low levels in the bloodstream. The rate of conversion is af-fected by the proportion of carbohydrates in an in-dividual’s die: carbohydrates stimulate the secretion of insulin, which facilitates the uptake of most amino acids into peripheral tissues, such as muscles. Blood tryptophan levels, however, are unaffected by insulin, so the proportion of tryptophan in the blood relative to the other amino acids increases when carbohydrates are consumed. Since tryptophan competes with other amino acids for transport across the blood-brain barrier into the brain, insulin secretion indirectly speeds tryptophan’s entry into the central nervous system where, in a special clus-ter of neurons, it is converted into serotonin.The level of serotonin in the brain in turn af-fects the amount of carbohydrate an individual chooses to eat. Rats that are allowed to choose among synthetic foods containing different propor-tions of carbohydrate and protein will normally al-ternate between foods containing mostly protein and those containing mostly carbohydrate. However, if rats are given drugs that enhance the effect of serotonin, the rats’ carbohydrate intake is reduced. On the other hand, when rats are given drugs that interrupt serotonin-mediated neurotransmission, their brains fail to respond when carbohydrates are eaten, so the desire for them persists.In human beings a serotonin-like drug, fenfluramine 氟苯丙胺(which releases serotonin into brain synapses and then prolongs its action by blocking its re-absorption into the pre-synaptic neuron), selectively suppresses carbohydrate snacking (and its associated weight gain) in people who crave carbohydrates. In contrast, drugs that block serotonin mediated transmission or that in-teract with neurotransmitters other than serotonin have the opposite effect: they often induce carbo-hydrate craving and subsequent weight gain. People who crave carbohydrates report feeling refreshed and invigorated after eating a carbohydrate-rich meal (which would be expected to increase brain serotonin levels). In contrast, those who do not crave carbohydrates become sleepy following ahigh-carbohydrate meal. These findings suggest that serotonin has other effects that may be useful indi-cators of serotonin levels in human beings.1 Which one of the following best states the main idea of the passage?(A) The body’s need for carbohydrates varies with the level of serotonin in the blood(B) The body’s use of carbohydrates can be reg u-lated by the administration of serotonin-like drugs (C) The role of serotonin in regulating the con-sumption of carbohydrates is similar in rats and in humans(D) The body’s desire for carbohydrates can be i n-fluenced by serotonin or serotonin-like drugs(E) Tryptophan initiates a chain of events that regu-lates the body’s use of carbohydrates2 The term “rate” (para.2) refers to the rate at which (A) serotonin is produced from tryptophan (B) carbohydrates are taken into the body(C) carbohydrates stimulate the secretion of insulin (D) insulin facilitates the uptake of amino acids into peripheral tissues(E) tryptophan enters the bloodstream3 It can be inferred that a person is likely to crave carbohydrates when(A) the amount of insulin produced is too high (B) the amount of serotonin in the brain is too low (C) more tryptophan than usual crosses the blood- brain barrier(D) neurotransmission by neurotransmitters other than serotonin is interrupted(E) amino acids other than tryptophan are taken up by peripheral tissues4 The information in the passage indicates that if human beings were given a drug that inhibits the action of serotonin, which one of the following might be expected to occur?(A) Subjects would probably show a preference for carbohydrate-rich snacks rather than protein-rich snacks(B) Subjects would probably become sleepy after eating a carbohydrate-rich meal(C) Subjects would be more likely to lose weight than before they took the drug(D) Subjects’ blood tryptophan levels would prob a-bly increase (E) Subjects’ desire for both carb o-hydrates and proteins would increase5 The primary purpose of the second paragraph in the passage is to (A) provide an overview of current research concerning the effect of seroto-nin on carbohydrate consumption(B) contrast the role of tryptophan in the body with that of serotonin (C) discuss the role of serotonin in the transmission of neural impulses(D) explain how the brain knows that carbohydrates精品值得阅读相信相信的力量should be consumed(E) establish a connection between carbohydrate in-take and the production of serotonin6 It can be inferred that after a person has taken fenfluramine, he or she will probably be (A) inclined to gain weight (B) sleepy much of the time(C) unlikely to crave carbohydrates (D) unable to sleep as much as usual(E) likely to secrete more insulin than usual7 The author’s primary purpose is to(A) defend a point of view (B) correct a miscon-ception (C) assess conflicting evidence (D) suggest new directions for investigation(E) provide information that helps explain a phe-nomenonWill the 21st be another American century? Don’t bet on it, for American empire is doomed, and the cause is coffee. First, the facts. Denny’s the chain of 1,700 downscale eateries, is switching to freshly ground whole-bean coffee. Dunkin’ Donuts is testing espresso in 200 outlets. 7-Eleven began to sell “gourmet blends” last year. So do various McDonald’s around the U.S.Alas, they do not know the iron law of history that says bad coffee fuels expansionism, machismo and the warlike passions while good coffee wafts with civility, pacificity and abandon.Just take the great martial powers of modern times: the U.S., the Soviet Union, Germany, Britain, Japan, China and Israel. The age of America’s e x-pansion in the 19th century was marked by the low- tech coffeepot that was left on the fire until the brew inside had thickened into a blackish acid just right for tanning buffalo hides.Or the old Soviet Union: toxic mud and tepid water. But the Red Army went all the way to Berlin in 1945. It blithely crushed revolts in various satel-lite countries, moved into Cuba, Africa and Af-ghanistan. Prussia-Germany? In the old days, only the rich could afford real coffee; the masses had to make do with a blend of burnt barley and chicory. But that stuff took the Wehrmacht to the gates of Moscow and Cairo.Japan & China? Between Tsushima, where the Japanese sank the Russian fleet, and Pearl Harbor, where they wiped out America’s, the sons of Ni p-pon did not even know from coffee; all they had was green tea. Ditto to the Chinese when they chased American soldiers down the Korean Penin-sula. Ditto the British, who for 400 years ruled the seas while swilling Java that was as tasty as their food. Tiny Israel has bested the Arabs in five wars. W hy? Because Israeli “coffee” could e at through the armor of a Soviet-built T-72 in three minutes.Now look at the other side. As every Middle East hand knows, Arab (or Turkish) coffee, espe-cially when spiced with cardamom, is among the best in the world. But when did Arabs last win a war? Or the Italians, who have given the world the Gaggia and the macchiato ? Indeed, the Muslim states are the best case in point. Arab power was done in for good when Ferdinand and Isabella de-molished the last Moorish stronghold on Iberian soil in 1492. This was no accident, comrades, as the Soviets used to say. It so happens that qahwa came into widespread use throughout the Islamic world in the mid- 15th century. Fifty years later, Arab power was finished. And soon after, so was the Ottoman Empire. In 1699, the Turkish advance was stopped once and for all at the gates of Vienna. But now it was the Habsburgs’ turn. Retreating, the Turks left their coffee sacks behind, and the Austrians took to mocha with the same passion they later devoted to waltzing along the D anube. In Austria’s legendary coffeehouses, a great culture grew — from Mozart (who, alas, did not write the Coffee Cantata ; that was Bach) to Kafka and Freud. The Habsburg Em-pire was, however, doomed, battered by the French in the 18th century and trounced by the chico-ry-gulping Prussians in the 19th century.But to make this grand theory truly watertight, we must show that it also works in a dynamic way. Ergo: when bad-coffee countries discover the bliss of Kenyan Blue , they should lay down their assault rifles at the first hiss of a milk steamer.Precisely. In Germany, once the most militaris-tic society on earth, you can now get a perfect cap-puccino on every block. And Germans have become as aggressive as Caspar Milquetoast . The Russians? Moscow has turned into latte land and so the rem-nants of the Red Army cannot even overwhelm a bunch of bedraggled Chechens. Why does Israel, a modern-day democratic Sparta, talk withdrawal from Lebanon? Just count the espresso machines on Tel Aviv’s Shenkin Street.Which brings us to the decline and fall of the American empire. Yes, the mightiest nation on earth still slugs it out with the Saddams and the Milosevics. But willpower is melting away like foamed milk on top of a double-shot decaf. The numbers speak for themselves. At the beginning of this decade, there were but 500 “gourmet coffe e-houses” in the US , says the National Coffee Associ-ation; now there are 7,000, including 2,000 Star-bucks.Why great empires thus falter was explained by a 16th century Arab physician. Imbibe the brew, he warned, and “the body becomes a mere shadow of its former self. The heart and the guts are so weakened…” Or, in modern parlance, you polish either you gold-plated Melior or your M-16. You can’t launch a Hellfire missile with a frappuccino in hand. Pleasure trumps prowess.So, move over, America — and we can forget about Europe. The 21st century will belong to China and精品值得阅读India. They have a billion tea-slurping people each,and there isn’t a Starbucks in sight on TiananmenSquare.相信相信的力量。