单选题 Fat: what is it good for? Absolutely nothing, or so you might think. But obesity seems to protect mice against a fatal form of malaria-cerebral malaria. Working out how it has this effect might lead to new treatments for people. Although obesity is now on the rise in the developing world, it has traditionally been seen as a malaise of the rich. In contrast, malaria tends to be regarded as a disease of the poor, so few people have studied how the two conditions affect each other. In mice meanwhile, there are signs that diabetes, which often affects obese people, might offer some protection against malaria. To find out more about how obesity affects malaria in mice, Vincent Robert at the Institute for Development Research (IRD) in Paris, France, and colleagues injected 14 obese and 14 non-obese mice with the malaria parasite Plasmodium berghei. After six days, eight of the non-obese mice died from cerebral malaria, which causes coma and death in humans, and the rest died about two weeks later from severe anemia because the parasite had destroyed their red blood cells. In contrast, none of the obese mice showed signs of cerebral malaria. Although they all eventually succumbed to severe anemia and died 18 to 25 days after infection, anemia can be treated-so obesity did seem to offer mice some useful protection. Exactly how the obese mice resist malaria is not clear, says Delphine Depoix from the Museum of Natural History in Paris, but there are several possibilities. One clue lies in a mutation in the gene coding for the leptin, a hormone produced by fat cells, which makes the mice obese, but also controls the immune response. Previous research has shown that obese mice with the leptin mutation often react to infections with a "Th2" rather than "Th1" response. As Th1 in mice is thought to trigger the inflammation that helps cerebral malaria to kill its victims, Depoix speculates that the Th2 response might be protecting the obese mice. Another possible explanation is that the abnormally high blood sugar associated with obesity in both mice and people "might compensate" for the low blood sugar caused by severe malaria, says Depoix, allowing the mice to better cope with parasite infection. Andrew Prentice of the London School of Hygiene and Tropical Medicine says that figuring out how the mice resist malaria will be crucial to developing new treatments for people with malaria. His colleague Christopher Whitty warns that any insights drawn from these results are preliminary: "Mouse models are always useful in raising hypotheses but cannot settle them as far as cerebral malaria is concerned."

单选题According to the passage, the decline of Shell

单选题Compared to the yearly price changes that actually occurred on foreign agricultural markets during the 1880’s American farmers would have most preferred yearly price changes that were

单选题In the United States today, coffee is a more popular drink (1) tea, but tea played (2) interesting part in the history of the United States. Before they won their (3) from Britain, the colonists were forced to (4) taxes on many goods imported into America. The tax money was (5) to support colonial governors and officials sent to the colonies by the British. In 1770 the British Prime Minister had repealed most of the taxes, but King George (6) on retaining the tax (7) tea. The King saw the tax as a (8) of the British right to tax the colonies. American merchants (9) smuggled nine-tenths of America's tea into the country and (10) paying the taxes. (11) the tax savings, the price of tea remained expensive due. to (12) shipping costs. When the British Parliament (13) a new law which would allow British companies to import tea more (14) than American shipping companies, the (15) were alarmed and they (16) a protest. In Boston citizens and merchants, who (17) disguised as Indians, boarded a British ship and (18) ＄15000 worth of tea into the harbor. This protest (19) Great Britain is known as the Boston Tea Party. It was one of the earliest acts of (20) against British rule.

单选题The statement"... but made a vast number of 35-year-olds redundant" in the last paragraph refers to the fact that?

单选题The word "deter" in the last paragraph probably means ______

单选题As pointed out in the text, the video art technology is characterized by its

单选题 The technology revolution may be coming to poor countries via the mobile phone, not the personal computer, as it did in rich ones. And just as the Internet encouraged an entrepreneurial philosophy, and with it the creation of a few too many dotcom firms, Africa's surge in mobile-phone use may {{U}}unleash{{/U}} the same sort of business energy, but tailored to local needs. One such initiative is about to begin. TradeNet, a software company based in Accra, Ghana, will unveil a simple sort of eBay for agricultural products across a dozen countries in West Africa. It lets buyers and sellers indicate what they are after and their contact information, which is sent to all relevant subscribers as an SMS text message in one of four languages. Interested parties can then reach others directly to do a deal. Listing offers is free, as is receiving the texts. TradeNet plans to earn revenue by putting advertisements in the messages, though it hopes the service will become so useful that recipients will eventually want to pay. For the moment, though, the company is busy signing up users and swallowing the cost of sending the messages. Mobile-phone use in sub-Saharan Africa is soaring. Whereas only 10% of the population had network coverage in 1999, today more than 60% have it, a figure expected to exceed 85% in the coming year, according to the GSM Association, an industry trade group. This provides the infrastructure for businesses like TradeNet to function. TradeNet is the brainchild of Mark Davies, a British dotcom tycoon who gave up the rat race and went to Africa in 2000. In 2005, he started the prototype for TradeNet using around ＄600,000 of his own money and about ＄200,000 from aid agencies. An early set of trials last year generated a surplus of trades, such as a sale of organic fertilizer between a person in Yemen and another in Nigeria. A number of other mobile-phone market-places taking shape also started as aid projects. For example, Trade at Hand, a project funded by the UN's International Trade Centre in Geneva, provides daily price information for fruit and vegetable exports in Burkina Faso and Mali, with plans to add more countries. And Manobi, a telecoms firm based in Senegal, providing real-time agricultural and fish prices to fee-paying subscribers, is also backed by aid money. But TradeNet's approach is unique so far because it collects valuable economic data-names, locations, business interests and telephone numbers-and then sells them to advertisers. The price of economic development may be junk mail by mobile phone.

单选题Americans no longer expect public figures, whether in speech or in writing, to command the English language with skill and gift. Nor do they aspire to such command themselves. In his latest book, Doing Our Own Thing: The Degradation of Language and Music and Why We Should, Like, Care , John McWhorter, a linguist and controversialist of mixed liberal and conservative views, sees the triumph of 1960s counter-culture as responsible for the decline of formal English. Blaming the permissive 1960s is nothing new, but this is not yet another criticism against the decline in education. Mr. McWhorter"s academic speciality is language history and change, and he sees the gradual disappearance of "whom", for example, to be natural and no more regrettable than the loss of the case-endings of Old English. But the cult of the authentic and the personal, "doing our own thing", has spelt the death of formal speech, writing, poetry and music. While even the modestly educated sought an elevated tone when they put pen to paper before the 1960s, even the most well regarded writing since then has sought to capture spoken English on the page. Equally, in poetry, the highly personal, performative genre is the only form that could claim real liveliness. In both oral and written English, talking is triumphing over speaking, spontaneity over craft. Illustrated with an entertaining array of examples from both high and low culture, the trend that Mr. McWhorter documents is unmistakable. But it is less clear, to take the question of his subtitle, why we should, like, care. As a linguist, he acknowledges that all varieties of human language, including non-standard ones like Black English, can be powerfully expressive—there exists no language or dialect in the world that cannot convey complex ideas. He is not arguing, as many do, that we can no longer think straight because we do not talk proper. Russians have a deep love for their own language and carry large chunks of memorized poetry in their heads, while Italian politicians tend to elaborate speech that would seem old-fashioned to most English-speakers. Mr. McWhorter acknowledges that formal language is not strictly necessary, and proposes no radical education reforms—he is really grieving over the loss of something beautiful more than useful. We now take our English "on paper plates instead of china". A shame, perhaps, but probably an inevitable one.

单选题It never rains but it pours. Just as bosses and boards have finally sorted out their worst accounting and compliance troubles, and improved their feeble corporation governance, a new problem threatens to earn them -- especially in American--the sort of nasty headlines that inevitably lead to heads rolling in the executive suite: data insecurity. Left, until now, to odd, low-level IT staff to put right, and seen as a concern only of data-rich industries such as banking, telecoms and air travel, information protection is now high on the boss's agenda in businesses of every variety. Several massive leakages of customer and employee data this year-- from organizations as diverse as Time Warner, the American defense contractor Science Applications International Corp and even the University of California, Berkeley——have left managers hurriedly peering into their intricate IT systems and business processes in search of potential vulnerabilities. "Data is becoming an asset which needs to be guarded as much as ally other asset," says Haim Mendelson of Stanford University's business school. "The ability to guard customer data is the key to market value, which the board is responsible for on behalf of shareholders". Indeed, just as there is the concept of Generally Accepted Accounting Principles (GAAP), perhaps it is time for GASP. Generally Accepted Security Practices, suggested Eli Norm of New York's Columbia Business School. "Setting the proper investment level for security, redundancy, and recovery is a management issue, not a technical one." he says. The mystery is that this should come as a surprise to any boss. Surely it should be obvious to the dimmest executive that trust, that most valuable of economic assets, is easily destroyed and hugely expensive to restore -- and that few things are more likely to destroy trust than a company letting sensitive personal data get into the wrong hands. The current state of affairs may have been encouraged -- though not justified-- by the lack of legal penalty (in America, but not Europe) for data leakage. Until California recently passed a law, American firms did not have to tell anyone, even the victim, when data went astray. That may change fast: lots of proposed data-security legislation is now doing the rounds in Washington, D.C. Meanwhile, the theft of information about some 40 million credit-card accounts in America, disclosed on June 17th, overshadowed a hugely important decision a day earlier by America's Federal Trade Commission (FTC) that puts corporate America on notice that regulators will act if firms fall to provide adequate data security.

单选题We learn from the passage that dot-com companies

单选题 It seems to happen with depressing frequency-surely skies turn to rain just as the weekend arrives. Now Spanish researchers say they have evidence that in some parts of Europe the weather really does follow a weekly cycle, although not in the straightforward way that the anecdote might suggest. Evidence has been mounting over the years that the weather in certain parts of the world, including the US, Japan and China, can be driven by the weekly cycle of human activity. This is because we tend to produce more air pollution during the week and less at the weekend. Evidence that such an effect occurs in Europe is controversial and has been harder to come by. Arturo Sanchez-Lorenzo of the University of Barcelona, Spain, and his colleagues examined data gathered between 1961 and 2004 from weather stations across Spain to see whether such a pattern existed. They claim to have found it in Spain, as well as hints of weekly changes in air circulation more broadly over Western Europe. The result is puzzling, but it is known that airborne pollutants produced by human activity can affect the weather in a variety of ways. For example, particles can be heated by absorbing sunlight, which in turn heats the air and changes air circulation patterns. Pollutant particles can also provide seeds for cloud formation. Exactly which effect has the greatest influence seems to depend on conditions that vary season by season. They also found signs that air pressure in Western Europe tends to be lower midweek than at the weekend in data from a global database. This suggests that the human influence on weather goes beyond known local effects, says team member Josep Calbó of the University of Girona in Spain. However, it is not clear whether the team's findings are statistically significant, says Thomas Bell of NASA's Goddard Space Flight Center in Greenbelt, Maryland, who was part of a team that found a stronger weekly cycle in the US. "This whole enterprise of looking for weekly cycles is rife with possibilities for misleading oneself." Why a weekly cycle would be less noticeable in Europe than in the US and Asia is still unknown. No weekly cycle has ever been found in the UK, probably because the weather is dominated by large systems blowing in from the Atlantic Ocean. These larger systems may be harder for weekly pollution cycles to influence, points out Douglas Maraun of the University of East Anglia in Norwich, who studies UK precipitation. "I doubt that there is a weekly influence of human activity on such a large weather system," he says.

单选题Why does the author mention the visible-light microscope in the first paragraph?

单选题In the Gilded Age, people who possessed a calling card______