题目内容
Music
Music is one of the most beautiful forms of artistic expressions ever invented. In movies and plays, music has an added function: it not only moves people but also can shock people.
Our eardrums can withstand sound within 20 to 80 decibels (分贝 ) . Once sound exceeds this limit, even beautiful music will become car-splitting noise and harm health. A strong blast (响声 ) of high sound can twist and break a solid iron sheet. High sound of 150 decibels can kill a healthy rat.
In movies, sometimes the hero can produce a sound that ordinary people can&39;t hear and only those who have the same ability can feel. In nature, there is actually sound that is beyond our hearing. In physics, the sound that exceeds 20,000 hz is called ultrasonic (超音波的). Dolphins, whales and bats can make such high-frequency sound. It does no harm to health.
Sound less than 20 hz is called infrasonic (次声 ) waves. When we move, the air will vibrate.
The vibration of air can produce infrasonic waves. As the frequency of infrasonic waves is close to that of people&39;s internal organs, infrasonic wave may cause resonance (共振) in human bodies. As a result, people&39;s vision may weaken and internal organs may rupture (断裂). However, whether an infrasonic wave can be used as a weapon depends on its intensity. If its intensity is very low, it won&39;t damage internal organs or a person&39;s health. If the intensity of infrasonic wave exceeds 160 decibels, it is extremely harmful. When wind blows at a force of 3 or 4 over the sea, it will produce infrasonic waves of several decibels. Only typhoons can produce infrasonic waves of over 100 decibels. At present, scientists can only produce infrasonic weapons in the lab with the help of advanced scientific tools and powerful electric power.
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When We Are Asleep
Everyone dreams, but some people never recall their dreams, or do so very rarely. Other people always wake up with vivid recollections (记忆 ) of their dreams, though they forget them very quickly. In an average night of eight hours&39;sleep, an average adult will dream for around one hundred minutes, probably having three to five dreams, each lasting from ten to thirty minutes.
Scientists can detect when someone is having a dream by using an instrument which measures the electrical waves in the brain. During dreaming, these waves move more quickly. Breathing and pulse rate also increase, and there are rapid eye movements under the lids, just as though the dreamer were really looking at moving objects. These signs of dreaming have been detected in all mammals (哺乳动物) studied, including dogs, monkeys, cats, and elephants, and also some birds and reptiles (爬行动物) .This period of sleep is called the "D" state for around 50% of their sleep; the period reduces to around 25% by the age of 10.
Dreams take the form. of stories, but they may be strange and with incidents not connected, which make little sense. Dreams are seldom without people in them and they are usually about people we know. One estimate says that two-thirds of the "cast" of our dream dramas are friends and relations. Vision seems an essential part of dreams, except for people blind from birth. Sound and touch senses are also often aroused, but smell and taste are not frequently involved. In "normal" dreams, the dreamer may be taking part, or be only an observer. But he or she cannot control what happens in the dream.
However, the dreamer does have control over one type of dream. This type of dream is called a "lucid"(清醒的) dream. Not everyone is a lucid dreamer. Some people are occasional lucid dreamers. Others can dream lucidly more or less all the time. In a lucid dream, the dreamer knows that he is dreaming.
Some people dream but cannot remember their dreams. 查看材料
Easy Death
In ancient Greek, the term euthanatos meant "easy death". Today euthanasia (安乐死)generally refers to mercy killing, the voluntary (自愿) ending of the life of someone who is terminally ill. Like abortion, euthanasia has become a legal, medical, and moral issue over which opinion is divided.
Euthanasia can be either active or passive. Active euthanasia means that a physician or other medical personnel takes an action that will result in death, such as giving an overdose of deadly medicine. Passive euthanasia means letting a patient die for lack of treatment, or stopping the treatment that has begun. Examples of passive euthanasia include taking patients off a breathing machine or removing other life-support systems. Stopping the food supply is also considered passive.
A good deal of the debate about mercy killing originates from the decision-making process.
Who decides whether a patient is to die？ This issue has not been solved legally in the United States.
The matter is left to state law, which usually allows the physician in charge to suggest the option of death to a patient&39;s relatives, especially if the patient is brain dead. In an attempt to make decisions about when their own lives should end, several terminally ill patients in the early 1990s used a controversial suicide device, developed by Dr. Jack Kevorkian, to end their lives.
In parts of Europe, the decision-making process has become very flexible. Even in cases where the patients are not brain dead, patients have been put to death without their approval at the request of relatives or at the suggestion of physicians. Many cases of passive euthanasia involve old people or newbom infants. The principle justifying this practice is that such individuals have a "life not worthy of life".
In countries where passive euthanasia is not legal, the court systems have proved very tolerant in dealing with medical personnel who practice it. In Japan, for example, if physicians follow certain guidelines they may actively carry out mercy killings on hopelessly ill people. Courts have also been somewhat tolerant of friends or relatives who have assisted terminally ill patients to die.
A terminally ill patient is one who __________. 查看材料
Nuclear Radiation
Nuclear power&39;s danger to health, safety and even life itself can be summed up in one word : radiation.
Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can&39;t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can&39;t detect then, sense them, without a radio receiver. Similarly, we can&39;t sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.
At very high levels, radiation can kill an animal or human being outright by killing masses of cells in vital organs. But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be significant. This is the case when only a few cells are hit. And if they are killed outright, your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in a deformed way. They can grow into cancer. Sometimes this does not show up for many years.
This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can be irradiated and feel fine, then die of cancer five, ten or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents.
Radiation can hurt us. We must know the truth.
According to the passage， the danger of nuclear power lies in__________ 查看材料
《铁路工务安全规则》规定，当允许速度160km/h＜υmax≤200km/h时，作业人员下道避车，距轨头外侧距离应不小于2.5m。（)
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