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The hardness of plastics closely correlates to wear or abrasive resistance.
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It is a curious paradox that we think of the physical sciences as "hard", the social sciences as "soft", and the biological sciences as somewhere in between. This is interpreted to mean that our knowledge of physical systems is more certain than our knowledge of biological systems, and these in turn are more certain than our knowledge of social systems. In terms of bur capacity to sample the relevant universes, however, and the probability that our images of these universes are at least approximately correct, one suspects that a reverse order is more reasonable. We are able to sample earth's social systems with some degree of confidence that we have a reasonable sample of the total universe being investigated. Our knowledge of social systems, therefore, while it is in many ways extremely inaccurate, is not likely to be seriously overturned by new discoveries. Even the folk knowledge in social systems on which ordinary life is based in earning, spending, organizing, marrying, taking part in political activities, fighting and so on, is not very 'dissimilar from the more sophisticated images of the social system derived from the social sciences, even though it is built upon the very imperfect samples of personal experience.
In contrast, our image of the astronomical universe, of even of earth's geological history, can easily be subject to revolutionary changes as new data comes in and new theories are worked out. If we define the "security" of our image of various parts of the total system as the probability of their suffering significant changes, then we would reverse the order of hardness and see the social sciences as the most secure, the physical sciences as the least secure, and again the biological sciences as somewhere in between. Our image of the astronomical universe is the least secure of all simply because we observe such a fantastically small sample of it and its record-keeping is trivial as compared with the rich records of the social systems, or even the limited records of biological systems. Records of the astronomical universe, despite the fact that we see distant things as they were long ago, are limited in the extreme.
Even in regard to such a close neighbor as the moon, which we have actually visited, theories about its origin and history are extremely different, contradictory, and hard to choose among. Our knowledge of physical evolution is incomplete and highly insecure.
The word "paradox"(Para. 1) means "（）".
A.implication
B.contradiction
C.interpretation
D.confusion
Most AIDS researchers agree that vaccines will be the only effective way to control a virus that has killed 28 million people and infected 42 million more worldwide.
Two dozen other vaccines are being tested on 12,000 human volunteers, but none has advanced as far as VaxGen's, and any successful candidate is years away. Officials at Brisbane, Calif-based VaxGen said the Thai results underscored again how wily AIDS is in thwarting the immune system. The findings also show "how important it is for the international public health community to redouble the effort to develop an effective vaccine," President Dr. Donald Francis said.
VaxGen's vaccine, like most others being tested, did not contain the virus itself and cannot cause AIDS. Instead, the vaccine contained small, manmade genetic bits of the virus that scientists had hoped would provoke an immune response strong enough to stop the virus from invading healthy cells. Three years ago, the company enrolled 2,546 people in and around Bangkok who were at high risk for HIV because they habitually swapped needles to inject drugs. Half were given the experimental vaccine and half were given a placebo. All volunteers were given extensive risk-reduction counseling, the company said. In the end, the vaccine offered no greater protection: 105 people given the placebo became infected with HIV, while 106 people given the vaccine tested positive. In February, VaxGen announced its vaccine was ineffective against a different AIDS strain found in North America.
The failure of this experimental vaccine reinforces the hardness of anti-AIDS battle, and the ultimate success seems to emerge years later. However, mankind is not so vulnerable to be completely defeated by AIDS.
Where is the experimental AIDS vaccine tested？
A．In Thailand
B．In North America
C．At Brisbane
D．In Africa
