Please Fasten Your Seatelts

    Severe turulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turulence up to 10 seconds efore an aircraft hits it.

    Clear-air turulence often catches pilots y surprise. Invisile to radar, it is difficult to forecast and can hurl (用力抛出去) passengers aout the cain. In Decemer 1997, one passenger died and hundred others were injured when unexpected rough air caused United Airlines flight over the Pacific to drop 300 metres in few seconds.

    However, passengers can avoid serious injury y fastening their seatelts. “It is the only antidote (对策) for this sort of things,” says Rod Bogue, project manager at NASA’s Dryden Flight Research Center in Edwards, California.

    The centre’s new turulence detector is ased on lidar, or laser radar, Laser pulses are sent ahead of the plane and these are then reflected ack y particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane’s airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turulence.

    In series of tests that egan last month, research jet flew repeatedly into distured air over the mountain ridges (山脉) near Puelo, Colorado. The lidar detector spotted turulence etween 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turulence that the plane encountered.

    Bogue says that he had “ comfortale amount of time” to fasten his seatelt. The researchers are planning to improve the lidar’s range with more powerful eam. The system could e installed on commercial aircraft in the next few years.

 What does “clear-air turulence” proaly mean? (Paragraph 1)

The last paragraph tells us, among other things, that

“Salty” Rice Plant Boosts Harvests     British scientists are reeding new generation of rice plants that will e ale to grow in soil containing salt water. Their work may enale aandoned farms to ecome productive once more.     Tim Flowers and Tony Yeo, from Sussex University’s School of Biological Sciences, have spent several years researching how crops, such as rice, could e made to grow in water that has ecome salty.     The pair have recently egun three-year programme, funded y the Biotechnology and Biological Sciences Research Council, to estalish which genes enale some plants to survive salty conditions. The aim is to reed this capaility into crops, starting with rice.     It is estimated that each year more than 100 hectares (公顷) of agricultural land are lost ecause salt gets into the soil and stunts (妨碍生长)plants. The prolem is caused y several factors. In the tropics, mangroves (红树林) that create swamps (沼泽) and traditionally formed arriers to sewater have een cut down. In the Mediterranean, series of droughts have caused the water tale to drop, allowing sewater to seep (渗透) in. in Latin America, irrigation often causes prolems when water is evaporated (蒸发) y the heat, leaving salt deposits ehind.     Excess salt then enters the plants and prevents them functioning normally. Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.     To overcome these prolems, Flowers and Yeo decided to reed rice plants that take in very little salt and store what they do asor in cells that do not affect the plants’ growth. They have started to reed these characteristics into new rice crop, ut it will take aout eight harvests efore the resulting seeds are ready to e considered for commercial use.

  Once the characteristics for surviving salty soil are known, Flowers and Yeo will try to reed the appropriate genes into all manners of crops and plants. Land that has een aandoned to nature will then e ale to loom again, providing much needed food in the poorer countries of the world. Which of the following statements aout Flowers and Yeo is true?

  Once the characteristics for surviving salty soil are known, Flowers and Yeo will try to reed the appropriate genes into all manners of crops and plants. Land that has een aandoned to nature will then e ale to loom again, providing much needed food in the poorer countries of the world. Which of the following statements aout Flowers and Yeo is true?

Flowers and Yeo have started programme

Which of the following is NOT mentioned as cause of the prolem discussed in the pass

 The word “affect” in Paragraph 6 could e est replaced y