| Antibiotic resistance doesn’t just
make pathogens(病原体) difficult to treat, It also makes them harder to track
Traditionally, epidemiologists(流行病专家)following the paths of disease-causing
microbes have identified their suspects by features of bacterial
polysaccharide(多糖) coats, susceptibility to different antibiotics, or other
schemes But these tracking techniques "are losing their relevance (相关性,实用性),
"says Alexander Tomasz, a microbiologist at Rockefeller University in New York
City. With the increase in drug resistance, a variety of resistant microbes can
now wear the same coat or be resistant to the same drugs, making it harder and
harder to keep tabs on individual strains (菌株). Epidemiologists, therefore, are increasingly turning to more precise molecular typing techniques, such as DNA fingerprinting, to distinguish resistant strains. [单项选择]Over the centuries, scientists have been trying hard to find satisfactory substitutes for precious stones but failed many times.
Many years ago, a chemist surprised the world by saying: It should be possible to make a precious stone that not only looks like the real thing, but that is the real thing. The only difference should be that one crystal would be made by man, the other by nature. At first this did not seem like a particularly hard task. Scientists began to try making synthetic diamonds towards the end of the eighteenth century and discovered a key scientific fact: diamonds are a form of carbon, which is a very common element. Then, why not change a cheap and plentiful substance, carbon, into a rare and expensive one, diamond This change takes place in nature, so it should be possible to make it happen in the laboratory. It should be possible, but for 150 years every effort failed though several people believed that they had solved the diamond riddle A. it is a real thing that man was able to make a precious stone as nature can do. B. man should be able to make a precious stone that is exactly the same as a natural one. C. there is only a little difference between a man-made crystal and a nature-made one. D. scientists expect a small difference between a man-made crystal and a nature-made one. [单项选择]
Hair Detectives Scientists have found a way to use hair to figure out where a person is from and where that person has been. The finding could help solve crimes, among other useful applications. Water is central to the new technique. Our bodies break water down into its parts: hydrogen and oxygen. Atoms of these two elements end up in our tissues and hair. But not all water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. Different forms of a single element are called isotopes. And depending on where you live, tap water contains unique proportions of the heavier and lighter isotopes of hydrogen and oxygen. Might hair record these watery quirks That’s what James R. Ehleringer, an environmental scientist at the University of Utah in Salt Lake City, wondered to find out he and his colleagues collected hair from barbers and hair stylists in 65 cities in 18 states across the United States. The researchers A. Ehleringer was successful in his research. B. Ehleringer failed in his research. C. Ehleringer can be a successful detective. D. Ehleringer’s research proved successful in China 我来回答: 提交
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