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TEXT E In the 1960s scientists begin to recognize that environmental contaminants could not only affect the health and survival of individual animals but also alter the prospects for their off-spring and thereby potentially change the genetic makeup of entire populations. Researchers were first altered to problems in wildlife in the 40s after the populations of eagles, falcons, and the other fish-eating birds in Britain plummeted. In nest after nest the birds’ eggshells were so thin that they cracked under the weight of the adults during incubation. In the 1960s David Peakall and other wildlife toxicologists demonstrated that the accumulation of very high levels of such pesticides as DDT in the birds’ tissues had seriously impaired their productive capabilities. Some of these declines resulted in the complete disappearance of populations from large portions of their former range. In North America, for example, the eastern population of the peregrine falcon was virtually wiped out. More recently, the Golf Coast population of the brown pelican disappeared as a result of eggshell thinning thought to be caused by the organochlorine pesticides dieldrin and endrin. Since then, researchers have provided additional evidence that environmental pollution can affect future generations. For example, exposure to high levels of PCBs has been shown to affect the learning and behavior of children. In the 1980s Snadra W. Jacobson and Joseph L. Jacobson of Wayne State University, Detroit, Michigan, studied a group of children whose mothers had eaten PCB—contained fish from Lake Michigan. The researchers found that the children’s prenatal exposure to these compounds resulted in neurological anomalies at birth and developmental delays in motor function during infancy. The Jacobson retested the children at age 11. In a 1996 report they noted that the children exhibited significantly poorer intellectual function, amounting to a 6.2 point deficit in the IQs of the most highly exposed subjects. Contaminants also have been linked to a critical loss of genetic variability in populations of living organisms. One of the best studies of this phenomenon was published in 1994 by M. H Murdoch and P.D.N. Hebert of the University of Guelph, Ontario. The study measured the variations in the mitochondrial DNA (mtDNA) of populations of brown bullhead catfish in the Great Lakes, comparing bullheads from pristine reference areas with bullheads living in heavily contaminated with such pollutants as organochlorines and petrochemicals. The two researchers used one of the most powerful tools of modern molecular population genetics-molecular analysis of DNA. By revealing differences in the specific code, i.e., in the sequence of nucleotides, contained in the DNA of a particular gene, the technique can help identify and quantify genetic variety within and among populations. For their study, Murdoch and Hebert examinated variations in genes of the cellular mitochondria, which possess their own DNA (mtDNA) that is distinct from the DNA found in the cell nucleus. Because mitochondrial genes are not "shuffled" in the production of sperm and egg cells, as are nuclear genes, and because they are transmitted to offspring only by the mother, they are ideal for charting the relatedness and evolutionary history of spaces. The researchers found that although the numbers of fish were abundant in both types of sites, the levels of genetic variability were always significantly higher in the pristine areas. The most likely explanation is that bullheads populations in polluted waters crashed after their initial contact with contaminants, but the remaining fish were able to repopulate because a few individuals possessed rare genes that allowed them to adapt and survive. Thus, even though the bullhead populations appeared to be thriving in contaminated areas, the genetic makeup of their populations had undergone a damaging simplification, a depletion of the storehouse of adaptations that animals can draw upon to surmount environmental challenges such as the introduction of a new disease of fluctuations in climate. Their genetic diversity potentially could be quickly increased by the influx of new genes from migrant fish, but most fish from other populations might survive in the polluted sites long enough to contribute to the gene pool. What is David Peakall
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钢铁在酸性介质中发生的另一类电化学腐蚀叫析氢腐蚀，在析氢腐蚀中阴极发生的反应是( )。
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TEXT A Several years ago I visited Egypt. After leaving Cairo and traveling through the hot desert sands I eventually found myself standing in the shadow of the Great Pyramid of Cheops—one of the mighty wonders of the ancient world. Entering a small doorway in the pyramid’s base I climbed upwards towards the center. And there I was at the heart of this great stone mountain in the burial chamber of a Pharaoh. As I stood there, I reflected on where I was. Was I in the middle of the tomb of a king, the most powerful ruler the world has ever known Or was I at the center of something much more mysterious A monument of such mathematical accuracy and advanced architecture that the modern world can only marvel at A magical shape built by a civilization whose knowledge and wisdom have been lost today I was silent in wonderment. The Great Pyramid at Giza, built for the Pharaoh Cheops, is large, to say the least. It is built from 2300000 blocks of stone, each weighing 15 tons, and as Napoleon’s scientists calculated, it contains enough stone to build a huge wall all around France. At the time when it was completed (over 5,000 years ago), it must have been magnificent-covered in white limestone and topped by a cap of solid gold. Yet ever today it is a marvel—and even more than that, a mystery. How did the Egyptians (who still hadn’t discovered the wheel) build such a huge monument; each stone put together with such precision that architects today would have difficulty copying How were these huge stones cut, carried and lifted into place, when the people only had simple wooden rollers, levers and primitive tools But perhaps these are the least of the Great Pyramid’s mysteries. For it is quite possible that this pyramid was not used as a tomb at all. In A.D. 800, when the Sultan of Baghdad, Al Mamud, finally managed to reach the central burial chamber of Cheops (after tunelling passed large stones that blocked the entrance), he found nothing! The chamber was empty. Unlike other tombs that possessed the kings’ priceless treasures, this one was completely empty. Nothing was there. Was the Great Pyramid something other than a tomb In 1638 an Oxford professor measured the king’s chamber and was shocked by its "exact" size. Even Sir Isaac Newton became interested in the pyramid’s perfect shape. However, it was John Taylor, the editor of The Observer, whose studies brought about the most amazing discovery. He showed, quite clearly, by the measurements of the pyramid, that the early Egyptians must have known the value of pi. Amazingly, they were 4000 years ahead of their time. The Pyramid of Cheops now became a great mystical symbol with strange magical powers. It has even been suggested recently that it was built with the help of aliens from outer space. A UFO landed and its occupants taught the Egyptians all their skills. On a more realistic level, British astronomer Richard Proctor believed that the pyramid was a hut observation room for viewing the stars and calculating the movement of the heavens, Not only are the sides of the pyramid perfectly lined to the tour points the compass, but the passage to the king chamber is precisely in line with it Pole Star. It became, obvious that builders of the pyramid also knew that the World was round. They knew the exact itude of the Earth, the length of the Earth’s orbit around the sun, the acceleration of gravity and the speed of light. Another idea is that this shape is a giant clock-its great shadow use for calculations on the sand. The Egyptians could keep a constant record of time and know easily the length each year. In fact the Czech engineer Karel Drbal was so interested in all he heard about the Great Pyramid that he built a small replica of it out of wood. He found a definite relationship between the shape of the space inside the pyramid and the physical, chemical and biological processes going on inside the space. Into his pyramid he placed a razor blade (at the same level as the king Chamber) and, to his astonishment, he found it always saved sharp. However much he shaved with it, if he put it back in the pyramid it remained sharp. Today you can even buy the Cheops Razorblade Sharpener in the shops and there arc also pyramid-shaped milk and yogurt cartons that are said to keep their contents fresher for a longer period of time. Sleeping within a pyramid structure is supposed to give beautiful dreams and a much rested body and mind in the morning: Buts of all the mysteries of the Great Pyramid, it is the one offered by the Institute of pyramidology (yes, there is one!) in London that stirs my imagination most. They say that by using the measurements and mathematical properties of the shape, the future can he predicted. They claim that Cheops predicted the crucifixion is of Christ and the beginning of World War One. And what of tomorrow Well, if the Great Pyramid is right, then at least those of us in the 20th century are saved, The Day of Judgment, the "end of the world", will be in 2979. Perhaps then, when the dust clears (and that is left standing is the Pyramid of Cheops), a UFO land at once again and little green men (the same ones hijacked the planes in the Bermuda Triangle) will jump out and dance on the hot sands. (938 words) Isaac Newton was interested in the pyramid’s ______.
TEXT C No company likes to be told it is contributing to the moral decline of nation. "Is this what you intended to accomplish with your careers" Senator Robert Dole asked Time Warner executives last week. "You have sold your souls, but must you corrupt our nation and threaten our children as well" At Time Warner, however, such questions are simply the latest manifestation of the soul searching that has involved the company ever since the company was born in 1990. It a self-examination that has, at various times, involved issues of responsibility, creative freedom and the corporate bottom line. At the core of this debate is chairman Gerald Levin, 56, who took over for the late Steve Ross in 1992. On the financial front, Levin is under pressure to raise the stock price and reduce the company’s mountainous debt, which will increase to ＄17.3 billion after two new cable deals close. He has promised to sell off some of the property and restructure the company, but investors are waiting impatiently. The flap over rap is not making life any easier for him. Levin has consistently defended the company’s rap music on the grounds of expression. In 1992, when Time Warner was under fire for releasing Ice T’s violent rap song Cop Killer, Levin described rap as a lawful expression of street culture, which deserves an outlet. "The test of any democratic society," he wrote in a Wall Street Journal column, "lies not in how well it can control expression but in whether it gives freedom of thought and expression the widest possible latitude, however disputable or irritating the results may sometimes be. We won’t retreat in the face of any threats." Levin would not comment on the debate last week, but there were signs that the chairman was backing off his hard-line stand, at least to some extent. During the discussion of rock singing verses at last month’s stockholders’ meeting, Levin asserted that "music is not the cause of society ills" and even cited his son, a teacher in the Bronx, New York, who uses rap to communicate with students. But he talked as well about the "balanced struggle" between creative freedom and social responsibility, and he announced that the company would launch a drive to develop standards for distribution and labeling of potentially objectionable music. The 15-member Time Warner beard is generally supportive of Levin and his corporate strategy. But insiders say several of them have shown their concerns in this matter. "Some of us have known for many, many years that the freedoms under the First Amendment are not totally unlimited," says Lute. "I think it is perhaps the case that some people associated with the company have only recently come to realize this." (458 words) In face of the recent attacks on the company, the chairman ______.
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