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大家好，胖胖翔来了! 这两天雨下得好爽，空气清新，心情也舒畅~这次的科技文内容丰富：生物、气候、心理、天文。有一篇讲鲸类动物的，专有名词很多，不必纠结，完全可用A,B,C来代替。enjoy~
Part I：Speaker 【Rephrase1】 Article 1 Sky Map Satellite Becomes Asteroid Hunter
[Dialog,1:16]
[Transcript hided]
Last week we told you about the end of an era: NASA ended the Kepler spacecraft's exoplanet-hunting mission, following an irreparable mechanical failure. This week, news of rebirth. NASA's WISE satellite is a space telescope that carefully surveyed the universe in infrared light. In 2010 it ran out of the cryogenic coolant that enabled its primary mission of mapping the skies. But WISE still found work, scanning for asteroids near Earth. Finally in 2011 NASA put the orbiting observatory into hibernation. Now NASA is planning to reboot WISE to find more asteroids. The space agency will fire it up in September for a three-year run. WISE should be able to find some 150 new near-Earth asteroids and get a better handle on another 2,000. Altogether more than 10,000 near-Earth asteroids, and almost 100 near-Earth comets, have been discovered by astronomers. That census includes most of the really big ones, but the vast majority of smaller asteroids remain to be discovered. And as we saw in February—when a small asteroid exploded over Russia, breaking windows in thousands of buildings—even the little ones can still do big damage.
Source: http://www.scientificamerican.com/podcast/episode.cfm?id=sky-map-satellite-becomes-asteroid-13-08-26
Part II：Speed 【Time 2】 Article 2 The Saddest Spot in New York
If you could look down from space and see the emotional state of every person in a city, what would it look like? We don’t have that technology yet, but Twitter is providing the next best thing. In a new study, researchers harvested every tweet that was geographically tagged to Manhattan and its surrounding boroughs during a 2-week period in April 2012. That was the easy part. The trick was deciphering the emotional content of those 604,000 utterances. Luckily, a large portion of tweets come with emoticons—for example,  and  for a smile or frown. By using these tweets as a training set, the team taught a computer to distinguish negative, positive, and neutral emotions. After projecting those emotions as colors on a map of New York City (pictured)—blue for positive, red for negative—the city’s mood landscape was suddenly revealed. Some of the patterns are no surprise. For example, people tended to be happiest near green areas such as Central Park and unhappiest around transportation hubs such as Penn Station and the entrance to the Midtown Tunnel. But the fine-grained details are striking. The closer people were to Times Square, the happier they got. And the city’s mood had a daily rhythm, mirroring that of the individuals who live and work there. People’s feelings—both positive and negative—were muted in the morning and peaked around midnight. The happiest place in Manhattan was Fort Tryon Park; the location is way uptown and thus takes effort to get to—the kind of effort people make when they're enjoying a day off. The saddest? Hunter College High School. No surprise there. The data were collected the week students returned from vacation.
字数[283] Source: http://news.sciencemag.org/brain-behavior/2013/08/scienceshot-saddest-spot-new-york
【Time 3】
Article 3 Hawaiian Paradise for Dolphins and Whales
Eighteen species of odontocetes—the toothed whales and dolphins, which include sperm whales and bottlenose dolphins—call the Hawaiian Islands home. But until now, little was known about where most of these 18 species dwell in these waters, what depths they prefer, and their population numbers. A team of scientists has helped fill in the blanks via a unique, 13-year survey made in small boats, ranging in size from 5.5 to 18 meters. Over the years, they covered 84,758 kilometers of survey lines, spotted 2018 odotocetes, and photographed as many of them as possible to ensure that each species was correctly identified. The slideshow above shows some of the rarer species. The team reports its findings online today in Aquatic Mammals. Knowing which cetaceans live where in the ocean and at what depths is important, the scientists say, in order to mitigate any problems that may occur from human activities, such as aquaculture, energy development, and Naval training exercises. Most troubling, the survey revealed that many of the cetaceans have strong preferences for living at specific depths. For instance, bottlenose dolphins and spinner dolphins were most often found in very shallow water (less than 500 meters), while striped and Risso’s dolphins and sperm whales preferred deeper waters (over 4000 meters). It’s unlikely, the scientists note, that aquaculture ventures will find a place free of fish-stealing dolphins, because they occupy such a range of depths. Similarly, the U.S. Navy will have trouble finding areas in Hawaii that don’t overlap with cetaceans, such as beaked and melon-headed whales, and pygmy killer whales, that are adversely affected by the type of active sonar used in training exercises. They live at the full range of depths that the Navy’s sonar uses, too.
字数[288] Source: http://news.sciencemag.org/plants-animals/2013/08/scienceshot-hawaiian-paradise-dolphins-and-whales
【Time 4】 Article 4 Stem cells mimic human brain 'Mini-brains' help researchers to study neurological diseases in living human tissue.
With the right mix of nutrients and a little bit of coaxing, human stem cells derived from skin can assemble spontaneously into brain-like chunks of tissue. Researchers provide the first description and application of these ‘mini-brains’ today in Nature.
“It’s a seminal study to making a brain in a dish,” says Clive Svendsen, a neurobiologist at the University of California, Los Angeles, who was not involved in the study. “That’s phenomenal.” A fully formed artificial brain might still be years away, he notes, but the pea-sized neural clumps developed in this work could prove useful for researching human neurological diseases.
Researchers have previously used human stem cells to grow structures resembling the eye and even tissue layers similar to the brain's cortex. But in the latest advance, scientists developed bigger and more complex neural-tissue clumps by first growing the stem cells on a synthetic gel that resembled natural connective tissues found in the brain and elsewhere in the body. Then, they plopped the nascent clumps into a spinning bath to infuse the tissue with nutrients and oxygen.
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【Time 5】
An imperfect copy Under a microscope, researchers saw discrete brain regions that seemed to interact with one another. But the overall arrangement of the different proto-brain areas varied randomly across tissue samples — amounting to no recognizable physiological structure.
“The entire structure is not like one brain,” says Knoblich, adding that normal brain maturation in an intact embryo is probably guided by growth signals from other parts of the body. The tissue balls also lacked blood vessels, which could be one reason that their size was limited to 3–4 millimetres in diameter, even after growing for 10 months or more.
Despite these limitations, the authors used the system to model key aspects of microcephaly, a condition that causes extremely stunted brain growth and cognitive impairment. Microcephaly and other neurodevelopmental disorders can be difficult to replicate in rodents because of species-specific differences in brain development.
The researchers found that tissue chunks cultured from stem cells derived from the skin of a single human with microcephaly did not grow as big as clumps grown from stem cells derived from a healthy person. They traced this effect to the premature differentiation of neural stem cells inside the microcephalic tissue chunks, depleting the population of progenitor cells that fuels normal brain growth.
The findings largely confirm prevailing theories about microcephaly, says Arnold Kriegstein, a developmental neurobiologist at the University of California, San Francisco. But, he adds, the study also demonstrates the potential for using human-stem-cell-derived tissues to model other disorders, if cell growth can be controlled more reliably.
“This whole approach is really in its early stages,” says Kriegstein. “The jury may still be out in terms of how robust this is.”
字数[280] Source: http://www.nature.com/news/stem-cells-mimic-human-brain-1.13617
【Time 6】 Article 5 Traveling with elders helps whooping cranes fly straight Birds get more efficient the more they migrate
Here’s a lesson on road trips from whooping cranes: For efficient migration, what matters is the age of the oldest crane in the group. These more experienced fliers nudge youngsters away from going off course on long flights.
“The older birds get, the closer they stick to the straight line,” says ecologist Thomas Mueller of the University of Maryland in College Park, who crunched data from 73 Grus americana migrating between Wisconsin and Florida.
One-year-olds traveling with other birds of the same age, the analysis says, tend to deviate about 76 kilometers from a direct route. But if they fly in a group with an 8-year-old crane, they stray 38 percent less, or about 47 kilometers, Mueller and his colleagues report in the August 30 Science.
Eight years of data on these endangered cranes summering in Wisconsin’s Necedah National Wildlife Refuge offered a rare chance to parse how birds find their way. Conservationists have been rebuilding this eastern migratory population of the once widespread birds. Researchers release captive-bred cranes in Wisconsin and lead each class of newbies, just once, with an ultralight aircraft to Florida’s Chassahowitzka National Wildlife Refuge for the winter. Cranes navigate back to Wisconsin on their own.
Age and presumably experience mattered more than genetics for efficient migration, Mueller says. Each bird’s pedigree is known, and closely related birds didn’t navigate in noticeably similar ways.
Whether this is a true case of social learning, with young birds picking up migration savvy from flying with older ones, is a question that intrigues behavioral biologist Dora Biro of the University of Oxford in England. Youngsters might not be learning from their flight mates so much as benefiting short-term from the older birds’ expertise. The difference is not just semantics, she says, but is important for understanding how generations might be transmitting information about migration.
For his part, Mueller suspects that the younger birds do learn from the older ones, he says, which poses a concern for those trying to re-create crane populations with captive-bred birds. “They may have a culture that has been lost,” he says. “To rebuild it — that won’t happen overnight.”
字数[355] Source: http://www.sciencenews.org/view/generic/id/352889/description/Traveling_with_elders_helps_whooping_cranes_fly_straight
Part III： Obstacle
【Paraphase7】
Article 6 How soot killed the Little Ice Age Industrial revolution kicked off Alpine glacier retreat fifty years before warming began.
Rising air pollution in the wake of the Industrial Revolution seems to be the explanation for a long-standing enigma in glaciology. The emission of soot from Europe’s proliferating factory smokestacks and steam locomotives explains why glaciers in the Alps began their retreat long before the climate warming caused by human activities kicked in, a study suggests.
The 4,000 or so large and small Alpine glaciers — which today are acutely threatened by rising air temperatures — did well throughout the relatively cool 500-year period known as the Little Ice Age, which began around the end of the thirteenth century. At its maximum in the middle of the nineteenth century, the extent and volume of Alpine glaciers was at least twice what it is now.
But then these glaciers suddenly began to retreat. Other regions of the world may also have been affected — the decline was only well documented in the Alps — and, conventionally, climate scientists consider the Little Ice Age to have ended soon after 1850.
However, despite the glaciers' shrinking, average global temperatures did not rise significantly until the end of the century. In fact, Alpine climate records — among the most abundant and reliable in the world — suggest that glaciers should have continued to grow for more than a half century, until around 1910.
“Something gnawed on the glaciers that climate records don’t capture,” says Georg Kaser, a glaciologist at the University of Innsbruck in Austria and a member of the team that built the case against black carbon, or soot, this week in Proceedings of the National Academy of Sciences1. “A strong decline in winter snowfall was often assumed to be the culprit,” he says. “But from all that we know, no such decline occurred.”
Retreat riddle At a glacier-science workshop two years ago at the Pontifical Academy of Sciences at the Vatican, Kaser discussed the riddle with Thomas Painter, a snow hydrologist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who had been researching the climate impact of atmospheric particles, known as aerosols. Might soot particles from the burning of organic fuels be the overlooked cause of the untimely melting of Alpine glaciers? The pair decided to investigate.
Because darker surfaces absorb more heat, if enough soot deposits onto snow and ice it can accelerate melting. Historical records suggest that by the mid-nineteenth century, the air in some Alpine valleys was thick with pollution. “Housewives in Innsbruck refrained from drying laundry outdoors,” says Kaser.
Scientists had thought it unlikely that sufficient soot had been carried high enough to affect glacier melting, but it seems they were mistaken. When Kaser's team looked at ice cores previously drilled at two high-elevation sites in the western Alps — the Colle Gnifetti glacier saddle (elevation 4,455 metres) on Monte Rosa near the Swiss–Italian border and the Fiescherhorn Glacier (3,900 metres) in the Bernese Alps — they found that at around 1860, layers of glacial ice started to contain surprisingly large amounts of soot.
The team converted the energetic effect that this soot that would have had on glaciers at the time into equivalent changes in air temperature. When included in a simplified mass-balance model, the melting effect of black carbon nicely explained the observed Alpine glacier retreat without the need for unrealistic increases in precipitation to be made to the model.
“The modelling could be further refined,” says Andreas Vieli, a glaciologist at the University of Zurich in Switzerland who was not involved in the study. “But even so, this study offers a very elegant and plausible explanation for the glacier conundrum. It appears that in central Europe soot prematurely stopped the Little Ice Age.”
Only after around 1970, when air quality began to improve, did accelerated climate warming become the dominant driver of glacier retreat in the Alps, Kaser says. If glaciers in the region continue to melt at the rate observed during the past 30 years, there is a risk that nearly all of them will vanish before the end of the century, he adds.
字数[677] Source: http://www.nature.com/news/how-soot-killed-the-little-ice-age-1.13650
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发表于 2013-9-3 23:17:32
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