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多为溶血性链球菌
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Oceanography Oceanography has been defined as "the application of all sciences to the study of the sea. " Before the nineteenth century, scientists with an interest in the sea were few. Certainly Newton considered some theoretical aspects of it in his writings, but he was reluctant to go to sea to farther his work. For most people the sea was remote, and with the exception of early intercontinental (大陆间的 ) travelers or others who earned a living from the sea, there was little reason to ask many questions about it, let alone to ask what lay beneath the surface. The first time that the question-" what is at the bottom of the oceans" had to be answered with any commercial consequence was when the laying of a telegraph cable from Europe to America was proposed. The engineers had to know the depth profile(起伏形状)of the route to estimate the length of cable that had to be manufactured. It was to Maury of the LIS Navy that the Atlantic Telegraph Company turned, in 1853, for information on this matter. In the 1840s, Maury had been responsible for encouraging voyages during which soundings(测水深) were taken to investigate the depths of the North Atlantic and Pacific Oceans. Later, some of his findings aroused much. popular interest in his book "The Physical Geography of the Sea". The cable was laid, but not until 1866 was the connection made permanent and reliable. At the early attempts, the cable failed and when it was taken out for repairing it was found to be covered with living creatures, a fact which defied contemporary scientific opinion that there was no life in the deeper parts of the sea. Within a few years oceanography was under way. In 1872, Thomson led a scientific expedition (考察), which lasted for four years and brought home thousands of samples from the sea. Their classification and analysis occupied scientists for years and led to a five-volume report, the last volume being published in 1895. "defied" in the paragraph 5 probably means______.
常用于前列腺癌诊断的肿瘤标志物是
Geologists believe that oil and coal are composed of organic molecules______(因为它们本身来自于生物).
Birdsong A male zebra finch chirps away to himself. Suddenly he notices a female bird nearby. He realizes he has an audience and immediately changes his song. Can the female tell the difference in his performance According to a new study, the female zebra finch knows. And she prefers the special trills he creates when he sings to her. A male zebra finch changes his song when singing to a female in ways that people can barely detect. But the female finch can tell the difference. Scientists had noticed slight variations in the songs of male zebra finches based on whether they were singing alone or whether there was a female (and potential mate) nearby. With an audience, the males sped up the pace of their songs and controlled the notes they used. For this study, researchers Sarah C. Woolley and Allison Doupe at the University of California, San Francisco decided to focus attention on the listening females, which have not been well studied in the past. In the study, Woolley and Doupe set up, a long cage with a sound speaker at each end. One broadcast the sound of a male zebra finch singing to himself, like someone singing in the shower. The other speaker broadcast a male performing for a female audience, as if he was giving a concert. Female birds were placed between the two speakers. Some of the birds had mates, others didn’t. The females shifted around a bit, and then most of them hopped over to sit beside just one speaker. All the birds that made a clear choice liked songs meant for a female audience, even if they’d never met the male. Mated females also had a chance to listen to two different performance songs, one from an unknown male, and one from their mate. They spent more time listening to the concert version of their mates’ songs. This suggests that after a while, females learn to recognize and prefer the songs of their mates. Scientists then studied the brains of the females. They found certain areas of the brain perked up when the birds listened to the concert songs. These brain areas may be involved in recognizing and evaluating the songs, and storing the memories of them. This research deals with what’s called directed communication, when the communicator, or sender, focuses the message for a specific audience. One example is the way moms speak to their babies. Mothers around the world use the same sort of high-pitched sing-song chatter, and the babies respond best to those sounds. Songbirds are one of the only other species known to learn their communication, in this case their songs. What did the researchers find in their study of female zebra finches
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