单选

The outbreak of swine flu that was first detected in Mexico was declared a global epidemic on June 11 , 2009. It is the first worldwide epidemic【B1】______by the World Health Organization in 41 years.

  The heightened alert【B2】______an emergency meeting with flu experts in Geneva that assembled after a sharp rise in cases in Australia, and rising【B3】______in Britain, Japan, Chile and elsewhere.

  But the epidemic is"【B4】______"in severity, according to Margaret Chan, the organization's director general ,【B5】______the overwhelming majority of patients experiencing only mild symptoms and a full recovery, often in the【B6】______of any medical treatment.

  The outbreak came to global【B7】______in late April 2009, when Mexican authorities noted an unusually large number of hospitalizations and deaths【B8】______healthy adults. As much of Mexico City shut down at the height of a panic, cases began to【B9】______in New York City, the southwestern United States and around the world.

  In the United States, new cases seemed to fade【B10】______warmer weather arrived. But in late September 2009, officials reported there was【B11】______flu activity in almost every state and that virtually all the【B12】______tested are the new swine flu, also known as (A) H1N1 , not seasonal flu. In the U. S. , it has【B13】______more than one million people, and caused more than 600 deaths and more than 6, 000 hospitalizations.

  Federal health officials【B14】______Tamiflu for children from the national stockpile and began【B15】______orders from the slates for the new swine flu vaccine. The new vaccine, which is different from the annual flu vaccine, is【B16】______ahead of expectations. More than three million doses were to be made available in early October 2009, though most of those【B17】______doses were of the FluMist nasal spray type, which is not【B18】______for pregnant women, people over 50 or those with breathing difficulties, heart disease or several other【B19】______. But it was still possible to vaccinate people in other high-risk groups; health care workers, people【B20】______infants and healthy young people.

【B1】

  • A.criticized
  • B.appointed
  • C.commented
  • D.designated
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Part B

Copying Birds May Save Aircraft Fuel

  Both Boeing and Airbus have trumpeted the efficiency of their newest aircraft, the 787 and A350 respectively. Their clever designs and lightweight composites certainly make a difference. But a group of researchers at Stanford University, led by Ilan Kroo, has suggested that airlines could take a more naturalistic approach to cutting jet-fuel use, and it would not require them to buy new aircraft.

  The answer, says Dr Kroo, lies with birds. Since 1914, scientists have known that birds flying in formation—a V-shape—expend less energy. The air flowing over a bird's wings curls upwards behind the wingtips, a phenomenon known as upwash. Other birds flying in the upwash experience reduced drag, and spend less energy propelling themselves. Peter Lissaman, an aeronautics expert who was formerly at Caltech and the University of Southern California, has suggested that a formation of 25 birds might enjoy a range increase of 71 % .

  When applied to aircraft, the principles are not substantially different. Dr Kroo and his team modelled what would happen if three passenger jets departing from Los Angeles, San Francisco and Las Vegas were to assemble over Utah, assume an inverted V-formation, occasionally change places so all could have a turn in the most favourable positions, and proceed to London. They found that the aircraft consumed as much as 15% less fuel (coupled with a reduction in carbon-dioxide output). Nitrogen-oxide emissions during the cruising portions of the flight fell by around a quarter.

  There are, of course, knots to be worked out. One consideration is safety, or at least the perception of it. Would passengers feel comfortable travelling in companion? Dr Kroo points out that the aircraft could be separated by several nautical miles, and would not be in the intimate groupings favoured by display teams like the Red Arrows. A passenger peering out of the window might not even see the other planes. Whether the separation distances involved would satisfy air-traffic-control regulations is another matter, although a working group at the International Civil Aviation Organisation has included the possibility of formation flying in a blueprint for new operational guidelines.

  It remains to be seen how weather conditions affect the air flows that make formation flight more efficient. In zones of increased turbulence, the planes' wakes will decay more quickly and the effect will diminish. Dr Kroo says this is one of the areas his team will investigate further. It might also be hard for airlines to co-ordinate the departure times and destinations of passenger aircraft in a way that would allow them to gain from formation flight. Cargo aircraft, in contrast, might be easier to reschedule, as might routine military flights.

  • As it happens, America's armed forces are on the case already. Earlier this year the country's Defence Advanced Research Projects Agency announced plans to pay Boeing to investigate formation flight, thought the programme has yet to begin. There are repor
  • Findings of the Stanford University researchers will promote the sales of new Boeing and Airbus aircraft.
  • A.True
  • B.False
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