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Please Fasten Your Seatbelts
Severe turbulence（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 turbulence up to 10 seconds before an aircraft hits it.
Clear-air turbulence often catches pilots by surprise.Invisible to radar,it is difficult to forecast and can hurl（用力抛出去）passengers about the cabin.In December 1997 , one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 meters in a few seconds.
However,passengers can avoid serious injury by fastening their seatbelts."It is the only antidote（对 策）for this sort of thing,"says Rod Bogue, project manager at NASA's Dryden Flight Research Center in Edwards,California.
The Center's new turbulence detector is based on lidar,or laser-radar.Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air.The technique depends on the Doppler Effect（多普勒效应）.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 turbulence.
In a series of tests that began last month,a research jet flew repeatedly into、 disturbed air over the mountain ridges（山脉）near Pueblo , Colorado.The lidar detector spotted turbulence between 3 and 8 kilometers ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.
Bogue says that he had"a comfortable amount of time"to fasten his seatbelt.The researchers are planning to improve the lidar's range with a more powerful beam.The system could be installed on commercial aircraft in the next few years.
We can infer from the fifth paragraph that____＿.
A.the lidar detector can successfully forecast turbulence
B.researchers are not sure about the effectiveness of the lidar detector
C.passenger planes will be used in further experiments
D.no more test flights are needed
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Exercising Your Memory
1. Aging does not mean a dramatic decline in memory power,unless you help it happen by let-ting your mind go.
2. That's not to say that memory doesn't change throughout life.Researchers divide memory into categories based on the length of time when memories are stored.One system divides it up as short-term(less than one minute;remembering a telephone number while you dial,for in-stance),long-term(over a period of years)and very long-term memory(over a lifetime).
3. Short-term memory isn't mastered until about age 7,but after that you never lose it.Long-term memory,however,involves more effort and skill and changes more through life .It's not until the early teens（十几岁）that most people develop a mature long-term memory.
4. First,we must get information into our heads through learning. Learning strategies can get rusty（生锈）without constant use. High school and college students , who are forced to repeatedly exercise their long-term memory abilities(at least long-term enough to get them through a final exam),usually do well on memory tests.The longer you stay in school,the more chance you get to polish your learning skills.It's no wonder that more highly educated people have more effective memory skills throughout life.
5. Although older people in general learn somewhat more slowly than they did when younger,a dramatic difference exists between those who stay intellectually active-reading,discussing,taking classes,thinking-and those who do not. Giving the brain daily workout（锻炼）is just as important as exercising your muscles.Brainwork keeps your learning strategies in shape,and this helps your memory to function at full capacity.
6. The next part of a healthy long-term memory is retention（记忆力）,the ability to store what you have learned. Memory researchers still do not know whether memories are lost-whether they still exist in the brain but our mental searching cannot turn them up,or have disappeared entirely as our brain ages.
7. The third necessity for memory is recall,the ability to bring to mind the memories we have stored.Again,while aging has widely different effects on the recall abilities of different people, research indicates that the older we get,the longer it takes to recall facts But slower recall is still recall. In fact,aging does not seem to have any effect on forgetting at all,which takes place at the same rate in younger and older people.
Exercising your brain every day is beneficial______.
A.for younger and older people
B.to the proper function of your memory
C.is called long-term memory
D.the capacity to store what you have learned
E.belongs to very long-term memory
F.the ability to remain mentally healthy
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Energize Yourself and Your Family
Being healthy and active can help give you the energy to keep up with the demands of your busy life,take better care of yourseff,and be there for the people who depend on you.
If you are overweight and inactive,you are more likely to get Type 2 diabetes,heart disease, high blood pressure,stroke and certain forms of cancer. You may improve your health if you move more and eat better!Here are some tips on how to get moving and eat well even when your life is busy.
Try to do at least 30 minutes of moderate-intensity physical activity (like brisk walking) on most days of the week.It is not as hard as you may think,and you do not have to do the whole 30 minutes at one time.Give up the typical excuse such as"I don't have time for physical activity". You can"sneak"it into your day,a few minutes at a time.Get started by making small changes in your daily routine,for example,get off the bus or subway one stop early and walk the rest of the way. You do not have to do your entire workout in one block of time.Break it up一taking three 10- minute walks during your day may be easier than taking one 30-minute walk.
Physical activities do not have to be chores.You can make them fun.Do things you enjoy,like walking,dancing,swimming,or playing sports.Walk or take an exercise class with a friend or a group.Be active with your kids-ride bikes or toss a softball.
It may be hard to eat healthy if you do not have time to cook or your kids want fast food.Here are some ways that you and your family can eat better. Eat breakfast every day.Try a whole-grain cereal like raisin bran with fat-free or low-fat milk,or whole-wheat toast spread with jam. Enjoy some fruit with your breakfast too.Teach kids that healthy foods taste good.Choose fat-free or low-fat milk,yogurt,and cheese instead of full-fat dairy products.Choose whole-grain foods like whole-wheat bread,oatmeal,and brown rice more often than refined-grain foods,like white bread and white rice.Snack on fruits and vegetables. Keep a bowl of fruit on the table,bags of mini carrots in the refrigerator,and boxes of raisins in the cupboard.Do not keep a lot of sweets like cookies,candy,or soda in the house.
Set goals.Move at your own pace.Celebrate your successes.Allow for setbacks.Let your family and friends help you.And keep trying一you can do it!
Healthy foods do not taste good.
A.Right
B.Wrong
C.Not mentioned
