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UPC is the most important invent in last centruy.
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By using UPC, the computer can record and give stock level information of the store.
Origins of a Plague
Some gaybashers believe it is God's way of punishing homosexuals(同性恋). Some Africans suspect it is just another of the white man's weapons of genocide(种族灭绝). Others have suggested that it was hatched in a biologicalweapons laboratory. There has been no shortage of theories about the origins of the virus that caused the current worldwide AIDS epidemic, but most have ranged from truly bizarre to scientifically implausible at best.
Scientists were drawn into the battle earlier this month, when an article in Rolling Stone magazine contended that the AIDS epidemic was sparked 30 years ago by a polio (小儿麻痹症) vaccine(疫苗), which was accidentally contaminated with a monkey virus. The controversial idea had been completely dismissed by most scientists as simplistic and unprovable, but it does reveal one major point of consensus: African monkeys are almost certainly the source of the deadly virus. Just how the virus made the leap from its simian(猴类的) host to people is still being hotly debated, however, and the more likely explanations are far more complex, involving shifts in African society that turned an isolated disease into a plague.
The polio vaccine theory was actually first proposed in a 1988 editorial in Child and Family, by Herbert Ratner, a former public health officer in Illinois. But the story begins in the mid1950s with Hilary Koprowski, former director of the Wistar Institute in Philadelphis, who, like his colleagues Jonas Salk and Albert Sabin, was racing to produce the vaccine that would protect the world against the scourge(折磨) of polio.
According to the scenario painted in Rolling Stone, batches of Koprowski's vaccine were inadvertently(不小心地) contaminated with a simian AIDS virus. Unlike Salk's vaccine, which contained polio virus that had been killed with formaldehyde, Koprowski and Sabin created their vaccines from a weakened strain of polio virus that would invoke immunity but was too weak to cause disease. Sabin and Koprowski manufactured their vaccines by culturing this weakened strain of polio virus on monkey, kidneys, a fertile medium for the microbe(微生物) and supposedly the source of the simian AIDS virus, now called SIV.
Such accidental contamination is not as farfetched as it might seem. Between 1954 and 1963, an estimated 10 million to 30 million Americans were inadvertently infected with SV40, an apparently harmless monkey virus borne as a silent passenger by both Salk's and Sabin's polio vaccines. SV40 was not discovered until 1961, and the U.S. Food and Drug Administration has since acted to ensure against similar contamination. Vaccine cultures are now carefully screened for all manner of viral contaminations.
Nor is it implausible that human AIDS came from monkey. Researchers got their first hint of this possibility in the mid1980s, when it was discovered that a group of Asian monkeys used for biomedical research had fallen ill with a virus picked up from other monkeys caught from Africa. The germ turned out to be SIV, and subsequent research showed that in the wild at least six species of African monkeys carry their own strain of the virus. It does not make the African monkeys sick, but it proved deadly to Asian monkeys.
Though researchers initially resisted the idea that human AIDS also came from African monkeys, that fact now seems wellestablished. Later last year, molecular(分子) virologists Beatrice Hahn and George Shaw of the University of Alabama presented convincing evidence that the simian virus. that infects sooty(似煤烟般黑的) mangabey, a type of monkey found in West Africa, carries virtually the same genetic material as HIV2, one of the two strains of human AIDS virus. This finding, says Shaw, provides direct evidence that AIDS originated in monkeys.
If the AIDS virus did infect humans through a polio vaccine, Koprowski's is the most likely candidate. The Sabin v
● Read the article below about a book.
● For each question 23-28, choose the correct answer.
● Mark one letter (A, B or C) on your Answer Sheet.
The Bosses Speak
John Stuart is an executive recruitment specialist who has turned to writing. The result is this book, based on interviews with twenty Chief Executives.
Each top manager--none of them famous names, surprisingly--is given a short chapter, and there is some introductory material and a conclusion. This means you can jump from one person to another, in any order, which is good for people who are too busy to read a book form. cover to cover. For a management book it isn't expensive, although whether it's good value for money is doubtful.
Some of the twenty interviewees started their own businesses, while others joined a company and fairly new in their position, and others have had years of experience, though, strangely, Stuart doesn't seem interested in these differences. The interviewees work in everything, from retailing to airlines to software, and it is this variety that forms the main theme of Stuart's book.
I have to say that Stuart's approach annoys me. He rarely stays at a distance from his interviewees, who are mostly presented in their own, positive words. If this were always the case, at least you would know where you were. But he seems to dislike certain interviewees. As a result, I don't know whether to accept any of his opinions.
It also means that the book gives no clear lessons. At the very least, I expected to learn what makes a successful Chief Executive. But these people seem to share two types of qualities. Some of them are very common, suggesting that anyone can be equally successful, which is definitely not the case. And the other qualities are ones which most successful bosses I've seen definitely do not have. So in the end I'm no wiser about what really goes on.
Perhaps I'm being unfair. As long as you don't think about whether you'd like them as friends, and pay no attention to most of the advice they give, the most readable parts are where the bosses describle their route to their present position.
Stuart seems to think that his book would be useful for people aiming for the top, and that it might even make a few want to start their own company; but, in fact, what they could learn here is very limited Seen as light business reading for a doctor or teacher, though, this book would provide some good entertainment.
The reviewer suggests that one advantage of the book is that ______ .
The reviewer cannot accept Stuart's opinions because Stuart ______.
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