第二篇 Where Have All the Frogs Gone?
In the 1980s, scientists around the world began to notice something strange: Frogs were disappearing. More recent research has shown that many kinds of amphibians (两栖动物) are declining or have become extinct. They have been around for a long time - over 350 million years. Why are they dying out now?
Scientists are seriously concerned about this question. First of all, amphibians are an important source of scientific and medical knowledge. By studying amphibians, scientists have learned about new substances that could be very useful for treating human diseases. Further research could lead to many more discoveries, but that will be impossible if the amphibians disappear.
The most serious aspect of amphibian loss, however, goes beyond the amphibians themselves. Scientists are beginning to think about what amphibian decline means for the planet as a whole. If the earth is becoming unlivable for amphibians, is it also becoming unlivable for other kinds of animals and human beings as well?
Scientists now believe that amphibian decline is due to several environmental factors. One of these factors is the destruction of habitat, the natural area where an animal lives. Amphibians are very sensitive to changes in their habitat. If they cannot find the right conditions, they will not lay their eggs. These days, as wild areas are covered with houses, roads, farms, or factories, many kinds of amphibians are no longer laying eggs. For example, the arroyo toad (蟾蜍) of southern California will only lay its eggs on the sandy bottom of a slow-moving stream. There are very few streams left in southern California, and those streams are often muddy because of building projects. Not surprisingly, the arroyo toad is now in danger of extinction.
There are a number of other factors in amphibian decline. Pollution is one of them. In many industrial areas, air pollution has poisoned the rain, which then falls on ponds and kills the frogs and toads that live there. In farming areas, the heavy use of chemicals on crops has also killed off amphibians. Another factor is that air pollution has led to increased levels of ultraviolet (UV) light. This endangers amphibians, which seem to be especially sensitive to UV light. And finally, scientists have discovered a new disease that seems to be killing many species of amphibians in different parts of the world.
All these reasons for the disappearance of amphibians are also good reasons for more general concern. The destruction of land, the pollution of the air and the water, the changes in our atmosphere, the spread of diseases - these factors affect human beings, too. Amphibians are especially sensitive to environmental change. Perhaps they are like the canary (金丝雀) bird that coal miners once used to take down into the mines to detect poisonous gases. When the canary became ill or died, the miners knew that dangerous gases were near and their own lives were in danger.
36 Losing amphibians means losing
A knowledge about fatal human diseases.
B knowledge about air and water pollution.
C a chance to discover new medicines.
D an opportunity to detect poisonous gases.
37 Amphibians lay their eggs
A in any stream they can find,
B in places without UV light,
C only on sand.
D only in the right conditions
38 The arroyo toad is disappearing because
A it has been threatened by frogs.
B it is losing its habitat.
C a disease has been killing its eggs.
D it can't bear the cold of winter.
39 Coal miners once used the canary bird to detect
A poisonous gases.
B air pollution.
C water leakage.
D radiation.
40 Scientists think that the decline of amphibians could
A cause environmental change.
B cause a decline in other kinds of animals.
C be a warning signal for human beings.
D be a good sign for human beings.
第三篇 Controlling Robots with the Mind
Belle, our tiny monkey, was seated in her special chair inside a chamber at our Duke University lab. Her right hand grasped a joystick (操纵杆) as she watched a horizontal series of lights on a display panel. She knew that if a light suddenly shone and she moved the joystick left or right to correspond to its position, she would be sent a drop of fruit juice into her mouth.
Belle wore a cap glued to her head. Under it were four plastic connectors, which fed arrays of microwires-each wire finer than the finest sewing thread- into different regions of Belle's motor cortex (脑皮层), tile brain tissue that plans movements and sends instructions. Each of the 100 microwires lay beside a single motor neuron (神经元). When a neuron produced an electrical discharge, the adjacent microwire would capture the current and send it up through a small wiring bundle that ran from Belle's cap to a box of electronics on a table next to the booth. The box, in turn, was linked to two computers, one next door and the other half a country away.
After months of hard work, we were about to test the idea that we could reliably
translate the raw electrical activity in a living being's brain-Belle's mere thoughts-into signals that could direct the actions of a robot. We had assembled a multijointed robot arm in this room, away from Belle's view, which she would control for the first time. As soon as Belle's brain sensed a lit spot on the panel, electronics in the box running two real-time mathematical models would rapidly analyze the tiny action potentials produced by her brain cells. Our lab computer would convert the electrical patterns into instructions that would direct the robot arm. Six hundred miles north, in Cambridge, Mass, a different computer would produce the same actions in another robot arm built by Mandayam A. Srinivasan. If we had done everything correctly, the two robot arms would behave as Belle's arm did, at exactly the same time.
Finally the moment came. We randomly switched on lights in front of Belle, and she immediately moved her joystick back and forth to correspond to them. Our robot arm moved similarly to Belle's real arm. So did Sriniwlsan's. Belle and the robots moved in synchrony (同步), like dancers choreographed (设计舞蹈动作) by the electrical impulses sparking in Belle's mind.
In the two years since that day, our labs and several others have advanced neuroscience, computer science and microelectronics to create ways for rats, monkeys and eventually humans to control mechanical and electronic machines purely by "thinking through," or imagining, the motions. Our immediate goal is to help a person who has been unable to move by a neurological (神经的) disorder or spinal cord (脊髓) injury, but whose motor codex is spared, to operate a wheelchair or a robotic limb.
41 Belle would be fed some fruit juice if she
A grasped the joystick.
B moved the joystick to the side of the light.
C sat quietly in a special chair.
D watched lights on a display panel.
42 The wires fixed under Belle's cap were connected to
A a plastic box next door.
B a computer at Cambridge University,
C a box of electronics in the booth.
D a box which, in turn, was linked to two computers
43 Which of the following is NOT true of the robot built by Srinivasan?
A It was directed by signals converted from the electrical activity in Belle's brain
B It converted the electrical patterns into instructions for the other robot.
C It was six hundred miles away from where Belle was.
D It could perform the same function as Belle did.
44 Which of the following statements indicates the success of the experiment?
A Belle responded to the robots successfully.
B Belle and the robots danced beautifully.
C Belle and the robots responded to the lights at the same time.
D The two robots moved the joysticks successively.
45 The short-term goal of the research is to help a person
A whose motor cortex is seriously damaged.
B who can operate a wheelchair but not a robotic limb.
C who has spinal cord injury but is able to move a wheelchair.
D who is unable to move but whose motor cortex is not damaged
