每做完一份新托福听力题目，就把听力原文拿出来，跟着听力里面的人反复朗读，跟上他们的语速，模仿他们的发音。然后是作标记：1 把其中经常听不清的地方标出来，反复跟读，2 把get, go, take等万能词的词组标起来，多多记忆，一方面可以排除听力障碍，一方面可以为作文所用 3 标出指示词，如表示原因的词，表示转折的词等等，让自己形成习惯，对这些词敏感起来，因为题目往往设置在这种地方。
Last week, tens of thousands of gallons of sewage gushed into urban streams in Baltimore, because of leaky pipes and flooding rains. And when that happens, it's not just organic matter and microbes that get flushed into aquatic habitats. It's drug residues, too: caffeine, antihistamines, headache drugs... even amphetamines and heroin.
Researchers actually detected all those drugs a few years ago, in a survey of urban and suburban streams in Baltimore. And they wanted to see what effect illegal drugs, like amphetamines, might have on aquatic ecosystems. So they built artificial streams in the lab, stocked with insects and real creek rocks—slippery ones with biofilms of algae and bacteria growing on them. Then they doped half the streams with amphetamine residues—similar to the concentrations found in real urban streams.
After three weeks, the mix of microbial life in the amphetamine-laced streams changed significantly, compared to the untainted waters. And insects like midges emerged earlier than usual—suggesting that drug residues might be able to alter food webs underwater, and on land, too. The results appear in the journal Environmental Science and Technology.
Previous studies have shown that even treated sewage has lots of drug residues in it—because most wastewater treatment plants weren't built to filter out pharmaceuticals. One solution, the researchers say, is more up-to-date wastewater infrastructure. Think of it as preventive medicine…for the nation's aquatic life.
1. because of 因为;由于;
例句：He had given up his job because of failing health.
2. be similar to 相像的;相仿的;类似的;
例句：My opinions are similar to hers.
3. compared to 与…相比;和…比起来;
例句：This problem was insignificant compared to others she faced.
4. filter out 滤除;滤掉;
例句：Children should have glasses which filter out UV rays.
This is Scientific American — 60-Second Science. I'm Cynthia Graber.
As humans developed civilizations in Eurasia and Northern Africa, they also domesticated animals for food and labor: horses, cows, goats, pigs, sheep and a few others. But no evidence existed for the deliberate cultivation and breeding of animals in North or Central America—until now.
"So at this ancient city of Teotihuacan in particular, which is really one of the earliest urban cities in North America..."
Andrew Somerville of the University of California San Diego, talking about the metropolis that once existed some 30 miles northeast of present-day Mexico City.
"...previous excavations have found a lot of rabbits. But at one compound in particular they found more evidence that they were interacting with rabbits more intensively. There was a statue of a rabbit. There was evidence that maybe they were butchering them. And this compound, which is called Oztoyahualco, actually had almost twice as many rabbit bones relative to the other complexes at the city. So it did seem like something was different with this particular compound."
Somerville and colleagues tested 134 rabbit bones at the 2,000-year-old site, as well as 13 contemporary samples. If the ancient rabbits fed on wild vegetation, the carbon isotopes in the bones would show evidence of what's known as the C3 photosynthetic pathway. But the domesticated crops of that time, such as corn and cactus fruit, employ what's called the C4 pathway—which leaves a different carbon isotope ratio in the bones.
"Fortunately we were able to actually show that rabbits from this compound did actually have higher carbon values, significantly higher carbon values. Which means that they did have significantly different diets from other rabbits within the city, and also significantly different diets than wild rabbits from around the region. Which is pretty strong evidence we say to show that they were actually being provisioned by humans, fed by humans, managed by humans."
The research is in the journal PLoS ONE.
It's true that the carbon evidence could also be the result of the rabbits being trapped in corn fields, where they were scavenging. But the presence of the dedicated pen and the statue of a rabbit led the scientists to conclude that the animals were in fact being raised—which changes our understanding of New World cities.
"That is one of these assumptions about the new world—that they just didn't have as intensive relationships with animals. That husbandry, especially with mammals, wasn't as important of a factor in their organization and supporting these big cities. So what we're showing is that maybe they were just as intensive in some respects as these old world cities but they're just less archaeologically visible. A rabbit leaves a much smaller footprint than a cow or a horse does."
索默维尔和同事对这个已有2000年历史的地方出土的134块兔子骨头和13块现代兔子骨头样本进行了检测。如果古代兔子食用的是野生植被，那它们骨头中的碳元素将会显示出C3 光合途径。而玉米和仙人果等当时家养的作物，采用的是C4 光合途径，这就会在兔子骨头中留下不同的碳同位素比率。
1. in particular 尤其;特别;
例句：He studies in particular the fishes of the Indian Ocean.
2. as well as 除…之外;也;还;
例句：He can shoot as well as riding horse.
3. be known as 认为…是;把…看作是;
例句：The policeman was known as a drug buster.
4. in fact (用于修正、引出相反意见或对比等)事实上，其实;
例句：In fact we were innocent of the crime.