During weightlessness, the forces within the body undergo dramatic change. Because the spine is no longer compressed, people grow taller. The lungs, heart and other organs within the chest have no weight, and as a result, the rib cage and chest relax and expand. Similarly, the weights of the liver, kidneys, stomach and bowels disappear. One astronaut said after his flight: “You feel your guts floating up. I found myself tightening my belly, sort of pushing things back。”
41.
Meanwhile muscles and bones come to be used in different ways. Our muscles are designed to support us when stand or sit upright and to move body parts. But in space, muscles used for support on the ground are no longer needed for that purpose; moreover, the muscles used for movement around a capsule differ from those used for walking down a hall. Consequently, some muscles rapidly weaken. This doesn’t present a problem to space travelers as long as they perform only light work. But preventing the loss of muscle tissue required for heavy work during space walks and preserving muscle for safe return to Earth are the subject of many current experiments。
Studies have shown that astronauts lose bone mass from the lower spine, hips and upper leg at a rate of about 1 percent per month for the entire duration of their time in space. Some sites, such as the heel, lose calcium faster than others. Studies of animals taken into space suggest that bone formation also declines。
42.
Needless to say, these data are indeed cause for concern. During space flight, the loss of bone elevates calcium levels in the body, potentially causing kidney stones and calcium crystals to form in other tissues. Back on the ground, the loss of bone calcium stops within one month, but scientists do not yet know whether the bone recovers completely: too few people have flown in space for long periods. Some bone loss may be permanent, in which case ex-astronauts will always be more prone to broken bones。
43.
These questions mirror those in our understanding of how the body works here on Earth. For example, elderly women are prone to a loss of bone mass. Scientists understand that many different factors can be involved in this loss, but they do not yet know how the factors act and interact; this makes it difficult to develop an appropriate treatment. So it is with bone loss in space, where the right prescription still awaits discovery。
44.
Many other body systems are affected directly and indirectly. One example is the lung. Scientists have studied the lung in space and learned much they could not have learned in laboratories on earth. On the ground the top and bottom parts of the lung have different patterns of air flow and blood flow. But are these patterns the result only of gravity, or also of the nature of the lung itself? Only recently have studies in space provided clear evidence for the latter. Even in the absence of gravity, different parts of the lung have different levels of air flow and blood flow。
45.
Not everything that affects the body during space flight is related solely to weightlessness. Also affected, for example, are the immune system and the multiple systems responsible for the amount and quality of sleep(light levels and work schedules disrupt the body’s normal rhythms). Looking out the spacecraft window just before going to sleep(an action difficult to resist, considering the view) can let enough bright light into the eye to trigger just the wrong brain response, leading to poor sleep. As time goes on, the sleep debt accumulates。
For long space voyages, travelers must also face being confined in a tight volume, unable to escape, isolated from the normal life of Earth, living with a small, fixed group of companions who often come from different cultures. These challenges can lead to anxiety, depression, crew tension and other social issues, which affect astronauts just as much as weightlessness—perhaps even more. Because these factors operate at the same time the body is adapting to other environmental changes, it may not be clear which physiological changes result from which factors. Much work remains to be done.
Passage 3
Directions: you are going to read a list of headings and a about what personal qualities a teacher should have. Choose the most suitable heading from the list A-F for each numbered paragraph (41-45). There is one extra heading which you do not need to use. Mark your answer on ANSWER SHEET 1. (10 points)
A) It’s the teacher’s obligation to be upright.
B) Good characteristics are important.
C) Teachers should show endurance.
D) Teachers can make quick adjustment.
E) Teachers should never stop learning.
F) Teachers should identify with students.
G) Teachers’ duties are given by government.
Here I want to try to give you an answer to the question: What personal qualities are desirable in a teacher? Probably mp two people would draw up exactly similar lists, but I think the following would be generally accepted.
41____________________
First, the teacher’s personality should be pleasantly live and attractive. This does not rule out people who are physically plain, or even ugly, because many such have great personal charm. But it does rule out such type as the over-excitable, melancholy, frigid, sarcastic, cynical, frustrated, and over-bearing: I would say too, that it excludes all of dull or purely negative personality. I still stick to what I said in my earlier book: “that school children probably suffer more from ‘bores than from brutes’”.
42.___________________________
Secondly, it is not merely desirable but essential for a teacher to have genuine capacity for sympathy---in the literal meaning of that word: a capacity to tune into the minds and feelings of other people, especially, since most teachers are school teachers, to the minds and feelings of children. Closely related with this is the capacity to be tolerant--- not, indeed, of what is wrong, but of the frailty and immaturity of human nature which induce people and again especially children, to make mistakes.
43.________________
Thirdly, I hold it essential for a teacher to be both intellectually and morally honest. This does not mean being a plaster saint. It means that he will be aware of his intellectual strengths and limitations, and will have thought about and decided upon the moral principles by which his life shall be guided. There is no contradiction in my going on to say that a teacher should be a bit of an actor. That is part of the technique of teaching, which demands that every now and then a teacher should be able to put on an act--- to enliven a lesson, correct a fault, or award praise. Children, especially young children, live in a world that is rather larger than life.
44.______________
A teacher must remain mentally alert. He will not get into the profession if of low intelligence, but it is all too easy, even for people of above- average intelligence, to stagnate intellectually ---and that means to deteriorate intellectually. A teacher must be quick to adapt himself to any situation, however improbable and able to improvise, if necessary at less than a moment’s notice.
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