大家好，胖胖翔来晚了咯，抱歉！标题用白色标记的，在正文上面~
Part I: Speed
[Time 1] Article 1 ( Check the title later )
U.K. Parliament Adds to Pressure on Pesticides
The environment committee of the United Kingdom's House of Commons is calling for a ban of three common pesticides in order to protect honey bees and other pollinators. "We believe that the weight of scientific evidence now warrants precautionary action," the chair of the Environmental Audit Committee, Joan Walley, said in a statement.
The number of honey bees and many wild pollinators have declined in the United Kingdom from a variety of causes, including habitat loss and disease. There is debate about the role of pesticides in the loss of honey bee colonies, but evidence is growing that they do harm bumblebees. In September, the Parliament's Environmental Audit Committee began an inquiry into how the United Kingdom should be regulating pesticides.
Meanwhile, the European Food Safety Authority issued a report in January that three pesticides are an "acute risk" to honey bees and should not be used on corn and other crops from which bees collect pollen. Later in the month, the European Commission, which had requested the study, proposed a 2-year ban of three common neonicotinoids for four crops. Member nations then voted down the ban, and the United Kingdom abstained.
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Source: Science http://news.sciencemag.org/scienceinsider/2013/04/uk-parliament-adds-to-pressure-o.html
When Does Your Baby Become Conscious?
For everyone who's looked into an infant's sparkling eyes and wondered what goes on in its little fuzzy head, there's now an answer. New research shows that babies display glimmers of consciousness and memory as early as 5 months old.
For decades, neuroscientists have been searching for an unmistakable signal of consciousness in electrical brain activity. Such a sign could determine whether minimally conscious or anesthetized adults are aware—and when consciousness begins in babies.
Studies on adults show a particular pattern of brain activity: When your senses detect something, such as a moving object, the vision center of your brain activates, even if the object goes by too fast for you to notice. But if the object remains in your visual field for long enough, the signal travels from the back of the brain to the prefrontal cortex, which holds the image in your mind long enough for you to notice. Scientists see a spike in brain activity when the senses pick something up, and another signal, the "late slow wave," when the prefrontal cortex gets the message. The whole process takes less than one-third of a second.
Researchers in France wondered if such a two-step pattern might be present in infants. The team monitored infants' brain activity through caps fitted with electrodes. More than 240 babies participated, but two-thirds were too squirmy for the movement-sensitive caps. The remaining 80 (ages 5 months, 12 months, or 15 months) were shown a picture of a face on a screen for a fraction of a second.
Cognitive neuroscientist Sid Kouider of CNRS, the French national research agency, in Paris watched for swings in electrical activity, called event-related potentials (ERPs), in the babies' brains. In babies who were at least 1 year old, Kouider saw an ERP pattern similar to an adult's, but it was about three times slower. The team was surprised to see that the 5-month-olds also showed a late slow wave, although it was weaker and more drawn out than in the older babies. Kouider speculates that the late slow wave may be present in babies as young as 2 months.
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[The rest]
This late slow wave may indicate conscious thought, Kouider and colleagues report online today in Science. The wave, feedback from the prefrontal cortex, suggests that the image is stored briefly in the baby's temporary "working memory." And consciousness, Kouider says, is composed of working memory.
The team displayed remarkable patience to gather data from infants, says cognitive neuroscientist Lawrence Ward of the University of British Columbia, Vancouver, in Canada, who was not involved in the study. However, the work, although well executed, is not the last word, he says. "I expect we'll find several different neural activity patterns to be correlated with consciousness."
Comparing infant brain waves to adult patterns is tricky, says Charles Nelson, a neuropsychologist at Harvard Medical School in Boston. "ERP components change dramatically over the first few years of life," he writes in an e-mail. "I would be reluctant to attribute the same mental operation (i.e., consciousness) in infants as in adults simply because of similar patterns of brain activity."
"He's right, the ERP components are not exactly the same as in adults," Kouider responds, but the ERP signature he saw had the same characteristics.
Kouider next hopes to explore how these signals of consciousness connect to learning, especially language development. "We make the assumption that babies are learning very quickly and that they're fully unconscious of what they learn," Kouider says. "Maybe that's not true."
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Source: Science http://news.sciencemag.org/sciencenow/2013/04/when-does-your-baby-become-consc.html?ref=hp
[Time 3]
Article 3
First Australians may have been migrants rather than drifters
Indirect estimates based on carbon dating point to intentional settlement by a large population.
At least 1,000 Aboriginal founders first arrived in Australia some 50,000 years ago, a reconstruction indicates — numbers that could be evidence of an intentional migration rather than the accidental stranding of a few individuals at a time. The study also finds that the population was devastated during the latest Ice Age, but later rebounded.
The prehistoric settlement of Australia has long been considered a simple story: a founding group of 150 people or fewer made it to the Australian mainland 50 millennia ago and grew to no more than 1.2 million by the time European settlers arrived in 1788. Debate focused on whether the founding population grew immediately after colonization or boomed later, in the past 5,000 years.But a paper published today in Proceedings of the Royal Society B1uses radiocarbon dating to estimate prehistoric populations, and reveals a more complex plot.
Southern living
To tease out a demographic signal from the past, Alan Williams, an archaeologist at the Australian National University in Canberra, amassed the most comprehensive radiocarbon data set ever put together for the continent, from both published and unpublished sources. He analysed the dates of 4,575 artefacts from 1,750 archaeological sites.
Applying methods that others had developed to analyse a similar dataset from North American artifacts2, Williams graphed the number of data points for each 200-year period, and made the assumption that for each given area, changes in the number of data points from one period to the next were a good indication of changes in population size — while correcting for the fact that some types of archaeological site can be lost over time owing to processes such as erosion. Assuming that the population would be between 750,000 and 1.2 million by the eighteenth century, he fit a smooth population curve to the data.
According to Williams' curve, 1,000–2,000 founders would be necessary to reach the population that was in place when the Europeans arrived. After the founders arrived, the population would have stabilized at low levels, but crashed during the most recent Ice Age, around 20,000 years ago. “To quantify the impacts of the last glacial maximum — and see a 60% reduction in population — is quite horrendous,” says Williams. After the Ice Age, population growth rates began to increase in pulses, starting 12,000 years ago.
A large founding population suggests the potentially controversial notion that the first settlers arrived through deliberate migration, rather than being accidentally stranded on the Australian mainland, as has been assumed, says Williams.
Demographic dating
The technique of using radiocarbon dates as a proxy for demographic numbers is gaining traction among researchers. “This is the first time an actual evidentiary data set has been used to construct continent-wide pre-European demographics, which is a significant step forward,” says Sean Ulm, an archaeologist and director of the Tropical Archaeology Research Laboratory at James Cook University in Cairns, Australia.
But not everyone has embraced it. “Using radiocarbon dates to reflect levels of human activity is not a method well-substantiated among archaeologists,” says Peter White, an archaeologist at the University of Sydney in Australia and editor of Archaeology in Oceania. The quantity and locations of radiocarbon dates measured by researchers at archaeological sites has little to do with past human activity, he says. For example, Williams' work shows more data points in the eastern half of Australia than in the west, not because more prehistoric peoples necessarily lived there, but because most of the country’s archaeologists live and work in the east.
Simon Holdaway, an anthropologist at the University of Auckland in New Zealand, agrees — but thinks that Williams adequately acknowledges these concerns. And Holdaway expects the trend towards analysing continent-wide data sets to continue, encouraging researchers to refine the data sets. “Any proxy measure brings with it a series of concerns that we need to understand,” he says.
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Source: Nature http://www.nature.com/news/first-australians-may-have-been-migrants-rather-than-drifters-1.12865
[Time 5]
Article 4
IceCube neutrinos came from outer spaceTwo ultra-high-energy neutrinos captured by the IceCube experiment probably came from outside the Galaxy, according to an analysis posted by the collaboration today.
“We’re pretty excited about it. They’re the highest energy neutrinos that have ever been seen,” says Thomas Gaisser, an IceCube member at the University of Delaware in Newark. IceCube consists of 86 strings of detectors sunk in a cubic kilometre of ice near the South Pole.
The two neutrinos, which were announced in 2012 but had not at that time been analysed, had energies of more than a petaelectronvolt (PeV), which makes them 100 million times more energetic than the neutrinos emitted by supernovae that have reached Earth. One possibility is that they are produced in the atmosphere through the interactions of high-energy cosmic rays there, but given their high energy, that is unlikely, the collaboration finds. If they are instead astrophysical in origin, then they are probably produced by the same sources that make ultra-high-energy cosmic rays, the origin of which is one of the longest-running mysteries in astrophysics. Two possibilities are the gamma-ray bursts emitted from collapsing stars, or active galactic nuclei, the jets emanating from massive black holes at galactic centres, but it’s unknown which. The collaboration puts the possibility of the particles having an astrophysical origin at a statistical confidence level of 2.8 sigma, falling just short of the 3 sigma needed to constitute hard evidence in physicists’ terminology.
IceCube’s detectors (see image) pick up the light emitted when neutrinos and other particles pass through. The two recently analysed neutrinos were plucked from events collected between 2010 and 2012 after the collaboration filtered out lower-energy data. The team is now re-running the analysis with a lower threshold to see whether they can uncover more events from the same sources and reveal their origin.
For years, astronomers and physicists have collected the flighty neutrino particles emitted in the Sun and from supernovae. But being able to observe distant sources from outside the Galaxy would take the field to a new level, and would be a sign that IceCube is now working like a telescope, says Gaisser. “It opens up a new way of looking at the cosmos,” he says.
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Source: Nature http://blogs.nature.com/news/2013/04/icecube-neutrinos-came-from-outer-space.html
Part II: Obstacle
Article 5
First Australians may have been migrants rather than drifters
Sensor-studded plots in the Amazon forest will measure the fertilizing effect of the gas.
One of the wild cards in climate change is the fate of the Amazon rainforest. Will it shrivelas the region dries in a warming climate? Or will it grow even faster as the added carbon dioxide in the atmosphere spurs photosynthesis and allows plants to use water more efficiently? A dying rainforest could release gigatonnes of carbon into the atmosphere, accelerating warming; a CO2-fertilized forest could have the opposite effect, sucking up carbon and putting the brakes on climate change.
Climate modellers trying to build carbon fertilization into their forecasts have had precious few data to go on. “The number one question is, how will tropical forests react if we put more CO2 into the atmosphere?” says Carlos Nobre, a climate scientist who heads research programmes at the Brazilian Ministry of Science, Technology and Innovation in Brasilia. “We don’t know.”
Now an international team of scientists is developing an ambitious experiment in the central Amazon that could study the effect in the real world. Hosted in Washington DC by the Inter-American Development Bank (IADB), a group of some 30 scientists met this month to flesh out the details of a project that would bathe a patch of rainforest in extra CO2 and, over the course of a decade or more, measure how the plants respond. The experiment, the first of its kind in the tropics, would be modelled on free-air CO2 enrichment (FACE) experiments conducted over the past couple of decades in the young and biologically simpler temperate forests of the Northern Hemisphere.
The experiment’s results could foretell the future of the Amazon. In 2000, a team at the UK Met Office’s Hadley Centre in Bracknell proposed that drought caused by global warming could devastate the rainforest1, although other climate modellers disagreed. Since then, the Hadley team has lowered its estimates of the likelihood of drying and the resulting forest dieback2. But the Hadley Centre’s simulations, like all climate models, assume a substantial CO2-fertilization effect in the tropics.
In an atmosphere of elevated CO2, not only do plants grow faster, but also their stomata (tiny openings on their leaves) do not need to open as widely or for as long. This means that less water escapes through transpiration, which makes plants better able to withstand heat and drought. The net result is that, at least in climate models, the extent of CO2 fertilization largely determines the Amazon’s resilience to global warming.
Because of the sheer volume of carbon cycling through the tropics, the fertilization effect has a massive impact on the amount of carbon that forests take up globally — and on how much remains in the atmosphere. Using the Hadley Centre climate model, UK modellers showed last year3 that atmospheric CO2 levels in 2100 depended largely on the magnitude of the fertilization effect, and could vary from 669 to 1,130 parts per million (CO2 levels today stand at 395 parts per million). That range corresponds to a 2.4 °C rise in global temperatures. Richard Betts, a member of the Hadley team, says the paper showed that the effect of the CO2-fertilization feedback was potentially much larger than had been thought. “This is why we have been really keen for people to go out and study the Amazon forest,” says Betts. “Our model indicates CO2 enrichment, and we need to know how realistic it is.”
The experiments in temperate forests — rings of towers that inject CO2 into circular plots — showed an initial fertilization effect, although the long-term response varied depending on the availability of nutrients in the soil, such as nitrogen4. In theory, the fertilization effect should be stronger in the tropics, where warmer temperatures work in concert with higher CO2 levels to increase the rate of photosynthesis (but plants shut down altogether if the temperature gets too high). Nitrogen is also more plentiful in the tropics, although other nutrients, such as phosphorus, could be limiting factors.
The idea of conducting a FACE experiment in the tropics has been around for years, but proposals have tended to fizzle out amid concerns about the feasibility of working in a mature tropical forest. First among them is the forest’s diversity: how could an experiment be large enough to be representative of a forest that has thousands of species of canopy trees and a cascade of plants beneath? On this point, the scientists meeting in Washington simply threw up their hands. “At the end of the day, no experiment is representative of the totality of the biome,” says Evan DeLucia, an ecologist at the University of Illinois in Urbana-Champaign and one of the principal investigators in a FACE experiment on young pines in South Carolina.
Another challenge is developing tools to track nutrient cycles in the soil and to monitor the peculiar growth dynamics of tropical forests. For instance, most of the trees in a mature tropical forest are hardly growing, with a minority quickly filling in gaps created by the death of old trees, says Jeff Chambers, an ecologist at Lawrence Berkeley National Laboratory in Berkeley, California.
After two days of discussion, the group was able to converge on a basic design (see ‘Gas ring’). A pilot project, north of Manaus in the central Amazon, would consist of a ring of about 16 towers circling an area 30 metres in diameter. Sensors would monitor background CO2 levels and winds, and CO2 would be injected from the towers as needed, to boost levels within the circle by 200 parts per million. Extra rings would be added in subsequent phases to allow replication and provide improved statistics.
The team is exploring different options for acquiring the CO2, which could cost several million dollars annually for the full experiment. Options include buying the gas from a local beer and soft-drinks factory, and producing it independently, along with methane, from a local landfill. The team must also decide whether to build a pipeline for the CO2 or to maintain a road for the large trucks that would deliver the gas. So daunting are the challenges that the team plans to ask the engineering arm of the Brazilian military for help.
The pilot project would cost about US$10 million for the first few years, and scientists are looking to the IADB and the Brazilian Ministry of Science, Technology and Innovation for seed money. Nobre has encouraged the team to apply for a large grant from the Amazon Fund, a pot of money that Brazil uses to combat deforestation and promote sustainable development. The tentative goal is to begin fieldwork next year and to bring the pilot facility online in 2015.
Some scientists wonder whether the project will provide the answers they need at a price that politicians are willing to pay. But so far, its planners are finding themselves in the enviable position of being pushed to think big by potential funders. “Let’s do it right,” said Jerry Melillo, a senior scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, who proposed a FACE experiment in Brazil more than a decade ago. “We only get one chance.”
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Source: Nature http://www.nature.com/news/experiment-aims-to-steep-rainforest-in-carbon-dioxide-1.12855
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发表于 2013-4-24 11:05:38
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ne,the diversity;two,developing tools.
