style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentrations (浓度. of these pollutants were altered by various chemical reactions; they became components in biogeochemical( 生物地球化学. cycles. These serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature's output of these compounds dwarfs that resulting from human activities. However, human production usually occurs in a localized area, such as a city. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    In this localized region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an increased concentration of noxious( 有害的. chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0.08 parts per million(ppm., which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.

    It is hard to track the blue whale, the ocean’s largest creature, which has almost been killed off by commercial whaling and is now listed as endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/　　So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy’s formerly top-secret system of underwater listening devices spanning the oceans. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/　　Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/　　Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption (爆发) for the first time and that they plan similar studies. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/　　Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures. The speed of sound in water is roughly one mile a second—slower than through land but faster than through air. What is most important, different layers Of ocean water can act as channels for sounds, focusing them in the same way a stethoscope (听诊器) does when it carries faint noises from a patient’s chest to a doctor’s ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles

《期货交易管理条例》的施行时间是（ ）。

      Engineering students are supposed to be examples of practicality and rationality, but when it comes to my college education I am an idealist and a fool. In high school I wanted to be an electrical engineer and, of course, any sensible student with my aims would have choose a college with a large engineering department, famous reputation and lots of good labs and research equipment. But that’s not what I did.
     I choose to study engineering at a small liberal-arts(文科) university that doesn’t even offer a major in electrical engineering. Obviously, this was not a practical choice; I came here for more noble reasons. I wanted a broad education that would provide me with flexibility and a value system to judge me in my career. I wanted to open my eyes and expand my vision by interacting with people who weren’t studying science or engineering. My parents; teachers and other adults praised me for such a sensible choice. They told me I was wise and mature beyond my 18 years, and I believed them.
      I headed off to college, sure, I was going to have an advantage over those students who went to big engineering "factories" where they didn’t care if you have values or were flexible. I was going to be a complete engineer, technical genius and sensitive humanist all in one.
     Now I’m not so sure. Somewhere along the way my noble ideals crashed into reality, as all noble ideals eventually do. After three years of struggling to balance maths, physics and engineering courses with liberal-arts courses, I have learned there are reasons why few engineering students try to reconcile engineering with liberal-arts courses in college.
    The reality that has blocked my path to become the typical successful student is that engineering and the liberal arts simply don’t mix as easily as I assumed in high school, individually they shape a person in very different ways; together they threaten to confuse. The struggle to reconcile the two fields of study is difficult.

      Engineering students are supposed to be examples of practicality and rationality, but when it comes to my college education I am an idealist and a fool. In high school I wanted to be an electrical engineer and, of course, any sensible student with my aims would have choose a college with a large engineering department, famous reputation and lots of good labs and research equipment. But that’s not what I did.
     I choose to study engineering at a small liberal-arts(文科) university that doesn’t even offer a major in electrical engineering. Obviously, this was not a practical choice; I came here for more noble reasons. I wanted a broad education that would provide me with flexibility and a value system to judge me in my career. I wanted to open my eyes and expand my vision by interacting with people who weren’t studying science or engineering. My parents; teachers and other adults praised me for such a sensible choice. They told me I was wise and mature beyond my 18 years, and I believed them.
      I headed off to college, sure, I was going to have an advantage over those students who went to big engineering "factories" where they didn’t care if you have values or were flexible. I was going to be a complete engineer, technical genius and sensitive humanist all in one.
     Now I’m not so sure. Somewhere along the way my noble ideals crashed into reality, as all noble ideals eventually do. After three years of struggling to balance maths, physics and engineering courses with liberal-arts courses, I have learned there are reasons why few engineering students try to reconcile engineering with liberal-arts courses in college.
    The reality that has blocked my path to become the typical successful student is that engineering and the liberal arts simply don’t mix as easily as I assumed in high school, individually they shape a person in very different ways; together they threaten to confuse. The struggle to reconcile the two fields of study is difficult.

    Coincident with concerns about the accelerating loss of species and habitats has been a growing appreciation of the importance of biological diversity, the number of species in a particular ecosystem( 生态系统., to the health of the Earth and human well-being. Much has been written about the diversity of terrestrial organisms ( 陆生生物., particularly the exceptionally rich life associated with tropical rain-forest habitats. Relatively little has been said, however, about diversity of life in the sea even though coral reef.systems are comparable to rain forests in terms of richness of life. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    An alien exploring Earth would probably give priority to the planet's dominant, most distinctive feature-the ocean. Humans have a bias toward land that sometimes gets in the way of truly examining global issues. Seen from far away, it is easy to realize that land masses occupy only one-third of the Earth's surface. Given that two-thirds of the Earth's surface is water and that marine life lives at all levels of the ocean, the total three-dimensional living space of the ocean is perhaps 100 times greater than that of land and contains more than 90 percent of all life on Earth even though the ocean has fewer distinct species. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    The fact that half of the known species are thought to inhabit the world's rain forests does not seem surprising,considering the huge numbers of insects that comprise the bulk of the species. One scientist found many different species of ants in just one tree from a rain forest. While every species is different from every other species, the genetic makeup constrains them to be insects and to share similar characteristics with 750,000 species of insects. If basic, broad categories such as phyla( 门. and classes( 纲. are given more emphasis than differentiating between species, then the greatest diversity of life is unquestionably in the sea. Nearly every major type of plant and animal has some representation there. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    To appreciate fully the diversity and abundance of life in the sea, it helps to think small. Every spoonful of ocean water contains life, on the order of 100 to 100,000 bacterial cells plus assorted microscopic (极小的. plant sand animals, including larvae( 幼虫. of organisms ranging from sponges and corals to starfish and clams( 蛤蜊.and much more. 

    Once you're prepared for a situation, you're 50 percent of the way toward overcoming nervousness. The other 50 percent is the physical and mental control of nervousness; adjusting your attitude so you have confidence, and control of yourself and your audience. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    I was in the theater for many years and always went to work with terrible stage f--until I was in The King and I. While waiting offstage one night, I saw Yul  Brynner, the show's star, pushing in a lunging( 冲. position,against a wall. It looked as though he wanted to knock it down.   "This helps me control my nervousness,”he explained. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    I tried it and, sure enough, freed myself from stage f. Not only that, but pushing the wall seemed to give me a whole new kind of physical energy. Later I discovered that when you push against a wall you contract the muscles that lie just below where your ribs(肋骨. begin to splay(开展.. I call this area the vital mangle. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    To understand how these muscles work, try this: sit in a straight-backed chair and lean slightly forward. Put your palms together in front of you, your elbows pointing out the sides, your fingertips pointing upward, and push so that you feel pressure in the heels of your palms and under your arms. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Say ssssssss, like a hiss(嘶嘶声) As you're exhaling(轻轻发出) the s, contract those muscles in the vital triangle as though you were rowing a boat, pulling the oars(船桨. back and up. The vital triangle should tighten.Relax the muscles at the end of your exhalation, then inhale gently. 
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/You can also adjust your attitude to prevent nervousness. What you say to yourself sends a message to your audience. If you tell yourself you're afraid, that's the message your listener receives. So select the attitude you want to communicate. Attitude adjusting is your mental suit of armor(铠甲. against nervousness. If you entertain only positive thoughts, you will be giving out these words: joy and ease, enthusiasm, sincerity and concern, and authority.