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The new detection technology has an identification rate of
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Part A
Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D. (40 points)
Could HIV, the virus that causes AIDS, be weakening？ The results of a study conducted in Belgium, at the Institute of Tropical Medicine in Antwerp, seem to suggest that in one corner of the world it might be. The report, published in the latest issue of AIDS, a specialist journal, concludes that HIV's ability to replicate (known technically as its virulence) may have decreased since the start of the pandemic. Kevin Aden, the lead author of the paper, stresses that the study is based on a small set of samples and does not prove that HIV's virulence is attenuating around the world. However, it does offer new insights into the evolution of the disease.
Dr. Arien looked at 24 blood samples collected from untreated patients attending an HIV/ AIDS clinic in Antwerp. A dozen of these samples were taken between 1986 and 1989; the other 12 were collected between 2002 and 2003. First, he analyzed the samples to find their viral load (the number of virus particles per cubic centimeter) and the subtype of virus involved. In Europe and North America, the predominant subtype is B; in sub-Saharan Africa, where the epidemic is at its worst, the predominant subtype is C. Most of Dr. Arien's samples were of subtype B. Having done this analysis, he paired the samples off for a series of replicative "duels". Each sample from the earlier series was matched with the most similar one from the later series, and they were placed in identical cell cultures to see which would multiply the most. The result was that 75% of the viruses from 2002-03 were less virulent than apparently similar counterparts from 1986-89—a statistically significant observation.
Dr. Arien's caution is sensible, at least until someone replicates the work elsewhere. But his conclusion is not necessarily surprising. Such viral attenuation, as it is known, is one way that vaccines are produced.
What causes attenuation in wild viruses, though, is a matter of speculation. Dr Arien believes that in this case the attenuation could be the result of what he calls "serial genetic bottlenecks" during transmission from host to host. These act to reduce the genetic diversity (and thus the replicative fitness) of the virus. Genetic diversity is known to be an important component of HIV's virulence. But what might cause the bottlenecks is still unclear.
A second reason for caution besides the small size of the study is, as Geoffrey Garnett, a professor of microparasite epidemiology at Imperial College, London, points out, that the ability of a virus to infect cells in a test-tube is not the same as its ability to cause disease and death in a human host. Nevertheless, Dr Aden's result is intriguing, and surely worth following up in a larger piece of research.
The word "attenuating"(Paragraph 1) most probably means
Why does Prada ignore the sales on Web.？
This should be a season of celebration. After all, by many measures, there's never been a better time to be a woman. In places like Scandinavia and Britain, a third or more of all corporate managers are now women. The number of female executive directors of FISE 100 companies nearly doubled from 2000 to 2004. Latin America has seen a 50 percent jump in the number of women politicians in the last decade. Japan voted 26 new female parliamentarians into office this year. Of course, the jewel in the equal-opportunity crown was this fall's election of Angela Merkel—once nicknamed "the Girl" by Helmut Kohl—to Germany's highest office.
But as always, statistics tell a multifaceted story. Sure, it's no longer an anomaly to have a female CEO—but there are still only 17 female executive directors in the largest FTSE 100 companies. In the EU Parliament, only 23 out of 162 members are female. In Britain, studies show that women have never been more dissatisfied with the workplace. No wonder: the EU pay gap between men and women shrank only one point in the last couple of years, to 17.5 percent.
So where does all this leave us？ With some big challenges that require more female leadership to solve. At some major companies—including Shell and British Telecom—women are combating the old-boys' club atmosphere by starting their own networks, linking top female leaders with up-and-comers they can mentor. Labor flexibility is also on the agenda; in parts of Europe, top female legislators have fought to give employees with children or elderly parents the right to ask for adjustable hours. Perhaps most important, there is an increasingly vibrant debate around work-life balance. Study after study shows that it is a working woman's second full-time job—as caregiver—that makes it most difficult for her to stay on the career ladder. While extra benefits and longer maternity, leave can help, they aren't a complete solution.
Clearly, some out-of-the-box thinking is required. And that's where women come in. In countries like Cameroon, Bolivia and Malaysia, greater numbers of women in public office have resulted in less spending on the military and more on health, education and infrastructure. Norway's woman-heavy Parliament recently passed a law mandating that 40 percent of directors on corporate boards be women. And in Germany, the archetypal outsider—a woman who grew up on the wrong side of the Iron Curtain—will likely take the helm in a country with virtually no other women in top positions of power. No longer "the Girl" but poised to become the chancellor, Merkel is a symbol of how far women have come—and the work that remains to be done.
According to paragraph two, what is the most important issue of women's achievement in politics？
We can learn from the third paragraph that
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