英语听力听写练习原文

英语听力听写练习原文

〈2014.7〉第一集

1.

Ocean Plastic Particles Could Get in Gills

Sea creatures eat plastic dumped in the ocean, but they also might be accumulating plastic by sucking up tiny particles with their siphons and gills. Christopher Intagliata reports.

There are now at least five major garbage patches in the world's oceans, and much of that trash is plastic. But last month researchers said they can only account for one percent of the plastic they'd expect to find in the oceans. So, where'd the rest of it go?

Well, animals eat some of it. Plastic has been found in turtles, seabirds, fish, plankton, shellfish, even bottom-feeding invertebrates. But there's another way sea creatures might be accumulating plastic: by sucking up tiny plastic particles with their siphons and gills.

Researchers added common shore crabs—Carcinus maenas—to tanks of seawater containing millions of tiny plastic particles, just 10 microns in diameter. After 16 hours, all the crabs had plastic lodged in their gills. And the particles stuck around for up to three weeks, too. The results are in the journal Environmental Science and Technology. [Andrew J. R. Watts et al, Uptake and Retention of Microplastics by the Shore Crab Carcinus maenas]

The longer plastic sits in an animal, researchers say, the better the chances it will travel up the food chain. Meaning all our plastic waste could come back to bite us—or rather be bitten by us.

"Of course we eat mussels whole, without the shells. But we're potentially eating plastic, if they're from a site where there's plastic present." Lead researcher Andrew Watts, of the University of Exeter. "We don't know how much plastic we have in our stomachs… chances are we do have some."

—Christopher Intagliata

2.

Salmonella's Favorite Food Could Be Its Achilles' Heel

Salmonella's primary fuel source is the molecule fructose-asparagine. Starving it of that fuel in an infected person could kill it without harming beneficial gut bacteria. Karen Hopkin reports

Summer’s here and with it come picnics, barbecues and of course salmonella. The germ is notorious for contaminating a variety of favorite warm-weather foods. But the bacteria’s palate is more limited than ours. Once salmonella makes its way into your system, it relies on a single unusu al nutrient to survive. That’s according to a study in the journal PLoS Pathogens. [Mohamed M. Ali et al, Fructose-Asparagine Is a Primary Nutrient during Growth of Salmonella in the Inflamed Intestine]

Most people tough it out when they get food poisonin g from salmonella. That’s because treatment with antibiotics would eliminate the infection, but also get rid of the gut bacteria that promote good health.

To figure out how to target salmonella specifically, researchers screened for genes vital for the m icrobe’s survival during the active phase of infection. And they identified a cluster of five genes that work together to allow the bacteria to digest a molecule called fructose-asparagine. No other organisms are known to use this chemical for fuel, so starving salmonella of it could be a new strategy for fighting this foodborne bug while leaving desirable intestinal inhabitants unharmed.

Next, the researchers plan to see which foods contain large amounts of salmonella’s go-to snack. But please, don’t send unsolicited samples of Aunt Agnes’s egg salad.

—Karen Hopkin

3.

Education Level Linked to Nearsightedness

In a German study, half of those with a university degree were myopic compared with less than a quarter of folks who quit after high school or secondary school. Karen Hopkin reports

Nothing says “overeducated egghead” like a pair of coke-bottle glasses. But even clichés sometimes hit the nerd on the head. Because a new study finds that nearsightedness is linked to the number of years spent in school. The findings can be viewed in the journal Ophthalmology. [Alireza Mirshahi et al, Myopia and Level of Education]

In the past century, the prevalence of myopia—science-speak for being able to see only what’s right in front of you—has be en on the rise. So much so that it can’t all be blamed on geeky genes.

To nail down the potential environmental influences, researchers focused on the classroom. They gave eye exams to nearly 5000 German subjects in a project called the Gutenberg Health Study.

The researchers found that individuals with 13 years of education were more myopic than those who didn’t get past primary school. And more than half of those with a university degree could use a set of specs, compared to less than a quarter of the folks who quit after high school or secondary school.

All that learning takes a lot of reading. Which itself is associated with nearsightedness. Or the nearsighted may gravitate toward pursuits easier to see—like hitting the books. Either way, seems that being a good student may not require great pupils.

—Karen Hopkin

4.

Give Us This Day the Bread Wheat Genome

A preliminary map of the bread wheat genome includes the locations of more than 75,000 genes. Cynthia Graber reports

Wheat hel ped create civilization in the Middle East. It’s a staple crop for 30 percent of the world’s population. And now, with the publication of four articles in the journal Science, we’re close to a detailed understanding of the bread wheat genome. [Kellye Eversole et al, Slicing the wheat genome]

Wheat is tough to sequence. It’s gone through multiple hybridizations, making its genome five times larger than a human one. Plus there are many redundancies: more than 80 percent of the genome is made of repeated DNA sequences. So the typical whole-genome shotgun approach—breaking genomes into segments and then reassembling them—doesn’t work for wheat.

Instead, an international consortium devised another strategy, involving physically mapping individual chromosomes and chromosome arms.

One paper details a draft of the entire genome of bread wheat. Another identifies all the genes on the largest of the plant’s 21 chromosomes. Some 75,000 genes have been mapped. The methods in the second paper will help scientists map the remaining chromosomes. They say it should take another three years.

Knowing exactly which genes are responsible for talents such as tolerating drought or improving yields should allow researchers to mine the genome and to quickly produce new and better wheat varieties to bring us our daily bread.

—Cynthia Graber

5.

Supercooled Organs Could Stretch Time to Transplant

Liver transplant time from human donor to patient is limited to 12 hours, but rats that got livers specially stored for three days were going strong three months later. Cynthia Graber reports

If you need a new liver, doctors have about twelve hours to transport it from a donor. That ticking clock severely limits the ability of doctors to get organs to patients.

Now researchers have demonstrated a method that kept rat livers viable up to four days.

The scientists lowered the livers to below freezing temperatures, while flooding the tissue with antifreeze chemicals to prevent the formation of damaging ice crystals.

But such c ooling alone is not sufficient, due in part to the liver’s wide variety of cell types and functions. So the researchers also used machine perfusion: as the livers were cooled they were flushed with solutions that kept them operational. They were perfused again as they were brought back to above-freezing temps.

All the rats that were implanted with 3-day-old livers survived for three months. Nearly 60 percent of the rats with four-day-old livers survived. In contrast, no rats that received 3- and 4-day-old livers preserved by currently used methods survived. [Tim A. Berendsen et al, Supercooling enables long-term transplantation survival following 4 days of liver preservation, in Nature Medicine]

This work is an early step toward creating a system that could work in humans, which would dramatically improve the chances of getting organs to people who desperately need them.

—Cynthia Graber

6.

Space-Based Data Collection Better Predicts Floods

Satellite data can help geologists predict major floods up to 11 months in advance in areas where snow melt or groundwater is a significant contributor. Cynthia Graber reports

Want to know where—and when—the next major river flood will hit? Just look up, to the satellites.

Conventional estimates of river volume come from rainfall, of course, and from measurement of the water that seeps from soil and groundwater reserves.

But NASA’s GRACE satellites, for Gravity Recovery and Climate Experiment, can pick up changes in the gravity field in a given river basin. The more water in the basin, the higher the gravity signal.

Scientists used GRACE results from 2003 to 2012 to see if they could have predicted the 500-year flooding event in the Missouri River basin in 2011. Preceding the flood were two significant storms, record snow melt, saturated soils and particularly high groundwater.

With GRACE data, the researchers found that they could have predicted the Missouri River floods months before current prediction models. They say that the technique could be used to forecast floods up to 11 months before such events take place in areas where snow melt or groundwater is a significant contribution.

The research was published in the journal Nature Geoscience. [J. T. Reager, B. F. Thomas and J. S. Famiglietti, River basin flood potential inferred using GRACE gravity observations at several months lead time]

Snow melt and major rain storms are predicted to increase with climate change. Which puts a premium on better flood prediction.

—Cynthia Graber

7.

Mobile Phones Carry Owners' Microbiomes

The bacteria found on someone's mobile phone is a good match for the most common kinds of bacteria that live on their hands. Christopher Intagliata reports

This year, the number of mobile phones on cell networks is expected to surpass the Earth's population. "More people now own cell phones than actually have access to working toilets." James Meadow, a microbial ecologist at the University of Oregon. Hidden in the data is the reality that some people work on their phones…o n toilets.

If that grosses you out, consider this: "So it turns out we're just really leaky animals. We just, we leave our bacteria everywhere we go." Including, of course, our phones.

Meadow and his colleagues took a census of the bacteria on thumbs and index fingers of 17 volunteers—and on their smartphone touch screens. Overall, they ID’ed over 7,000 types.

Looking at just the most common bacteria, those that appear more than 0.1 percent of the time, they found an 82 percent similarity between the microbiomes of fingers and phones. Meaning our phones are a pretty good mirror of ourselves, microbially, at least. The results appear in the journal PeerJ. [James F. Meadow, Adam E. Altrichter and Jessica L. Green, Mobile phones carry the personal microbiome of their owners]

"We have always been covered in bacteria… and we will always be covered in bacteria." So the fact that our phones are also covered in bacteria is no reason for concern. In fact, the researchers say that mobile phones may hold untapped potential as personal microbiome sensors. App developers, take note.

—Christopher Intagliata

8.

Malarial Mice Smell Better to Mosquitoes

Mice infected with the parasites that cause their type of malaria produce odorous compounds that attract mosquitoes, increasing the odds that the parasites will be spread to the next victims

Getting malaria stinks. Literally. According to a new study, malaria victims give off odors that attracts mosquitoes. And the insects that feed on the infected sufferer are then more likely to spread the disease. The work appears in the Proceedings of the National Academy of Sciences. [Consuelo M. De Moraes et al, Malaria-induced changes in host odors enhance mosquito attraction]

Malaria is caused by plasmodium parasites, which are transmitted by mosquitoes. A decade ago, scientists found that Kenyan kids infected with plasmodium were more attractive to mosquitos than were kids who were parasite-free. But they did not know what drew the bloodsuckers to the unfortunate infected children.

To find out, researchers took mice that harbored the rodent version of malaria and put the animals in a wind chamber. And they found that mosquitos flocked toward the infected animals, attracted by their smell alone.

By chemically analyzing the animals’ scents, the researchers found that the parasites boost the levels of a variety of odorous compounds that attract mosquitoes. So plasmodium is manipulating both its victim and its carrier to get itself spread far and wide.

The find ing may help with malaria prevention: if we can mask or harness the eau d’ infection, maybe we could nose the mosquitoes away from people.

—Karen Hopkin

9.

Professors Still View MOOCs Skeptically

A survey of professors finds that most see online courses as inferior to in-class lessons--but those who have taught online are more open to their potential. Larry Greenemeier reports.

The New York Times calls 2013 “the year of the MOOC.” But massive open online courses still fail to get high marks from most educators.

In a recent survey of more than 2,200 professors, only one in five thought that online courses could be as effective as classroom curricula. Their biggest concern: limited interaction between teachers and students. The survey was done by Gallup and the website Inside Higher Ed.

Respondents linked MOOC credibility to whether an online course was offered by an accredited school and to a student’s ability to receive credits.

Faculty skepticism isn’t surprising. New technologies often t urn crafted products and services into bland commodities, something no teacher wants. On the other hand, resistance to change, especially when it involves computers, tends to be a losing strategy in most fields.

An important wrinkle in the data: much MOOC criticism comes from faculty who’ve never taught an online course. Of the 30 percent of professors polled who had taught a MOOC, most thought that online coursework can deliver roughly the same results as the classroom.

—Larry Greenemeier

10.

Electronic Skin Could Bring Touchy Robots

Paper-thin sensor networks might someday give machines the ability to feel their surroundings. Larry Greenemeier reports

Our skin tells us about our surroundings by detecting temperature, pressure and other external conditions. If a pot handle is too hot to touch, we can feel this heat before burning our hand.

Robots may someday have this protection too. A team of researchers at the University of California, Berkeley, has developed a large-area sensor network integrated into a thin plastic film that acts like an electronic skin. They demonstrated the concept with an

e-skin sample about the size of a postage stamp that lights up in the specific places it’s

touched. The work is in the journal Nature Materials. [Chuan Wang et al., User-interactive electronic skin for instantaneous pressure visualization]

The harder the e-skin gets pressed, the brighter the light.

The researchers envision that flesh and blood users could have an e-skin smart bandage that monitors wounds. A large sheet of the material covering the wall of a room could even operate like a display screen. And a robot with such a surface could more effectively interact with its environment.

Of course, we don’t want our robots to be too sensitive. Then they might balk at cleaning up nuclear waste or spending years at a time all alone on Mars.

—Larry Greenemeier