The Hunt For The Higgs Boson Explained
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Harnessing The African Sun
The most recent instalment of our iq2 Shorts series, ‘Solar Farming in Africa: Green Electricity Powered by the Sun‘. It is adapted from our Professor Michael Düren’s talk at our Switched On event ‘Energy Game Changers‘, which took place on March 28, 2012.
Add To Reddit Climate Change Boosts Then Quickly Stunts Plants, Decade-long Study Shows
Global warming may initially make the grass greener, but not for long, according to new research results.
The findings, published this week in the journal Nature Climate Change, show that plants may thrive in the early stages of a warming environment but then begin to deteriorate quickly.
“We were really surprised by the pattern, where the initial boost in growth just went away,” said scientist Zhuoting Wu of Northern Arizona University (NAU), a lead author of the study. “As ecosystems adjusted, the responses changed.”
Ecologists subjected four grassland ecosystems to simulated climate change during a decade-long study.
Plants grew more the first year in the global warming treatment, but this effect progressively diminished over the next nine years and finally disappeared.
The research shows the long-term effects of global warming on plant growth, on the plant species that make up a community, and on changes in how plants use or retain essential resources like nitrogen.
“The plants and animals around us repeatedly serve up surprises,” said Saran Twombly, program director in the National Science Foundation (NSF)’s Division of Environmental Biology, which funded the research.
“These results show that we miss these surprises because we don’t study natural communities over the right time scales. For plant communities in Arizona, it took researchers 10 years to find that responses of native plant communities to warmer temperatures were the opposite of those predicted.”
The team transplanted four grassland ecosystems from a higher to lower elevation to simulate a future warmer environment, and coupled the warming with the range of predicted changes in precipitation–more, the same, or less.
The grasslands studied were typical of those found in northern Arizona along elevation gradients from the San Francisco Peaks down to the Great Basin Desert.
The researchers found that long-term warming resulted in loss of native species and encroachment of species typical of warmer environments, ultimately pushing the plant community toward less productive species.
The warmed grasslands also cycled nitrogen more rapidly. This should make more nitrogen available to plants, scientists believed, helping plants grow more. But instead much of the nitrogen was lost, converted to nitrogen gases in the atmosphere or leached out by rainfall washing through the soil.
Bruce Hungate, senior author of the paper and an ecologist at NAU, said the study challenges the expectation that warming will increase nitrogen availability and cause a sustained increase in plant productivity.
“Faster nitrogen turnover stimulated nitrogen losses, likely reducing the effect of warming on plant growth,” Hungate said. “More generally, changes in species, changes in element cycles–these really make a difference. It’s classic systems ecology: the initial responses elicit knock-on effects, which here came back to bite the plants. These ecosystem feedbacks are critical–you can’t figure this out with plants grown in a greenhouse.”
The findings caution against extrapolating from short-term results, or from experiments with plants grown under artificial conditions, where researchers can’t measure the feedbacks from changes in the plant community and from nutrient cycles.
“The long-term perspective is key,” said Hungate. “We were surprised, and I’m guessing there are more such surprises in store.”
Co-authors of the paper include George Koch and Paul Dijkstra, both at NAU.
Add To Reddit Ocean Acidification Killing Farmed Oysters
Marine researchers have definitively linked the collapse of oyster seed production at a commercial oyster hatchery in Oregon to an increase in ocean acidification.
Larval growth at the hatchery declined to a level considered by the owners to be “non-economically viable.”
A study by the scientists found that increased seawater carbon dioxide (CO2) levels, resulting in more corrosive ocean water, inhibited the larval oysters from developing their shells and growing at a pace that would make commercial production cost-effective.
As atmospheric CO2 levels continue to rise, this may serve as the proverbial canary in the coal mine for other ocean acidification impacts on shellfish.
Results of the research are published this week in the journal Limnology and Oceanography, published by the Association for the Sciences of Limnology and Oceanography (ASLO).
The research was funded by a grant from the National Science Foundation (NSF)’s Science, Engineering and Education for Sustainability (SEES) Ocean Acidification solicitation.
“Studies funded by NSF’s SEES Ocean Acidification solicitation are well-positioned to determine the specific mechanisms responsible for larval mortality in Pacific Northwest oyster hatcheries,” said David Garrison, program director in NSF’s Division of Ocean Sciences.
“This is one of the first times that we have been able to show how ocean acidification affects oyster larval development at a critical life stage,” said Burke Hales, an Oregon State University (OSU) chemical oceanographer and co-author of the paper.
“The predicted rise of atmospheric CO2 in the next two to three decades may push oyster larval growth past the break-even point in terms of production.”
The owners of Whiskey Creek Shellfish Hatchery at Oregon’s Netarts Bay experienced a decline in oyster seed production several years ago and looked at potential causes, including low oxygen and pathogenic bacteria.
Alan Barton, who works at the hatchery and is a co-author of the journal article, was able to eliminate those potential causes and shifted his focus to ocean acidification.
Barton sent samples to OSU and to the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory for analysis.
The results clearly linked the production failures to the CO2 levels in the water in which the larval oysters were spawned and spent the first 24 hours of their lives. That first day is a critical time when the oysters develop from fertilized eggs to swimming larvae and build their initial shells.
“The early growth stage for oysters is particularly sensitive to the carbonate chemistry of the water,” said George Waldbusser, a benthic ecologist at OSU.
“As the water becomes more acidified, it affects the formation of calcium carbonate, the mineral in shells. As the CO2 goes up, the mineral stability goes down, ultimately leading to reduced growth or to mortality.”
Commercial oyster production on the West Coast of North America is a 273-million-dollar industry each year. It has depended since the 1970s on oyster hatcheries for a steady supply of the seed used by growers.
In recent years, the hatcheries that provide most of the seed for West Coast growers have suffered persistent production problems.
At the same time, non-hatchery wild stocks of these oysters also have shown low recruitment, putting additional strain on a limited seed supply.
Hales said that Netarts Bay, where the Whiskey Creek hatchery is located, experiences a wide range of chemistry fluctuations.
The researchers believe that hatchery operators may be able to adapt to take advantage of periods when water quality is at its highest.
“In addition to the impact of seasonal upwelling, the water chemistry changes with the tidal cycle and with the time of day,” Hales said. “Afternoon sunlight, for example, promotes photosynthesis in the bay. That production can absorb some of the carbon dioxide and lower the corrosiveness of the water.”
The researchers also found that larval oysters showed a delayed response to the water chemistry, which may cast new light on other experiments looking at the impacts of ocean acidification on shellfish.
In the study, they found that larval oysters raised in water that was acidic, but non-lethal, had significantly less growth in later stages of their life.
“The takeaway message here is that the response to poor water quality isn’t always immediate,” said Waldbusser.
“In some cases, it took until three weeks after fertilization for effects from the acidic water to become apparent. Short-term experiments of just a few days may not detect the damage.”
The research was also supported by NOAA and the Pacific Coast Shellfish Growers Association.
Other authors of the journal article include Chris Langdon of OSU’s Hatfield Marine Science Center and Richard Feely of NOAA’s Pacific Marine Environmental Laboratory.
Add To Reddit South Pole Telescope Provides New Insights Into Dark Energy And Neutrinos
Analysis of data from the National Science Foundation- (NSF) funded 10-meter South Pole Telescope (SPT) in Antarctica provides new support for the most widely accepted explanation of dark energy, the source of the mysterious force that is responsible for the accelerating expansion of the universe.
The results begin to hone in on the tiny mass of the neutrinos, the most abundant particles in the universe, which until recently were thought to be without mass.
The SPT data strongly support Albert Einstein’s cosmological constant–the leading model for dark energy–even though researchers base the analysis on only a fraction of the SPT data collected and only 100 of the over 500 galaxy clusters detected so far.
“With the full SPT data set we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos,” said Bradford Benson, an NSF-funded postdoctoral scientist at the University of Chicago’s Kavli Institute for Cosmological Physics.
Benson presented the SPT collaboration’s latest findings, Sunday, April 1, at the American Physical Society meeting in Atlanta.
These most recent SPT findings are only the latest scientifically significant results produced by NSF-funded researchers using the telescope in the five years since it became active, noted Vladimir Papitashvili, Antarctic Astrophysics and Geospace Sciences program director in NSF’s Office of Polar Programs.
“The South Pole Telescope has proven to be a crown jewel of astrophysical research carried out by NSF in the Antarctic,” he said. “It has produced about two dozen peer-reviewed science publications since the telescope received its ‘first light’ on Feb. 17, 2007. SPT is a very focused, well-managed and amazing project.”
The 280-ton SPT stands 75 feet tall and is the largest astronomical telescope ever built in the clear and dry air of Antarctica. Sited at NSF’s Amundsen-Scott South Pole station at the geographic South Pole, it stands at an elevation of 9,300 feet on the polar plateau. Because of its location at the Earth’s axis, it can conduct long-term observations.
NSF manages the U.S. Antarctic Program through which it coordinates all U.S. scientific research on the southernmost continent and aboard ships in the Southern Ocean as well as providing the necessary related logistics support.
An international research collaboration led by the University of Chicago manages the South Pole Telescope. The collaboration includes research groups at Argonne National Laboratory; Cardiff University in Wales; Case Western Reserve University; Harvard University; Ludwig-Maximilians-Universität in Germany; the Smithsonian Astrophysical Observatory; McGill University in Canada; the University of California, Berkeley; the University of California, Davis; the University of Colorado Boulder; and the University of Michigan, as well as individual scientists at several other institutions.
SPT specifically was designed to tackle the dark-energy mystery. The 10-meter telescope operates at millimeter wavelengths to make high-resolution images of Cosmic Microwave Background (CMB) radiation, the light left over from the big bang.
Scientists use the CMB to search for distant, massive galaxy clusters that can be used to pinpoint the properties of dark energy and also help define the mass of the neutrino.
“The CMB is literally an image of the universe when it was only 400,000 years old, from a time before the first planets, stars and galaxies formed in the universe,” Benson said. “The CMB has travelled across the entire observable universe, for almost 14 billion years, and during its journey is imprinted with information regarding both the content and evolution of the universe.”
The new SPT results are based on a new method that combines measurements taken by the telescope and by NASA and European Space Agency X-ray satellites, and extends these measurements to larger distances than previously achieved.
The most widely accepted property of dark energy is that it leads to a pervasive force acting everywhere and at all times in the universe. This force could be the manifestation of Einstein’s cosmological constant that assigns energy to space, even when it is free of matter and radiation.
Einstein considered the cosmological constant to be one of his greatest blunders after learning that the universe is not static, but expanding.
In the late 1990s, astronomers discovered the universe’s expansion appears to be accelerating according to cosmic distance measurements based on the relatively uniform luminosity of exploding stars. The finding was a surprise because gravity should have been slowing the expansion, which followed the big bang.
Einstein introduced the cosmological constant into his theory of general relativity to accommodate a stationary universe, the dominant idea of his day. But his constant fits nicely into the context of an accelerating universe, now supported by countless astronomical observations.
Others hypothesize that gravity could operate differently on the largest scales of the universe. In either case, the astronomical measurements point to new physics that have yet to be understood.
As the CMB passes through galaxy clusters, the clusters effectively leave “shadows” that allow astronomers to identify the most massive clusters in the universe, nearly independent of their distance.
“Clusters of galaxies are the most massive, rare objects in the universe, and therefore they can be effective probes to study physics on the largest scales of the universe,” said John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, who heads the SPT collaboration.
“The unsurpassed sensitivity and resolution of the CMB maps produced with the South Pole Telescope provides the most detailed view of the young universe and allows us to find all the massive clusters in the distant universe,” said Christian Reichardt, a postdoctoral researcher at the University of California, Berkeley and lead author of the new SPT cluster catalog paper.
The number of clusters that formed over the history of the universe is sensitive to the mass of the neutrinos and the influence of dark energy on the growth of cosmic structures.
“Neutrinos are amongst the most abundant particles in the universe,” Benson said. “About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with ‘normal’ matter.”
The existence of neutrinos was proposed in 1930. They were first detected 25 years later, but their exact mass remains unknown. If they are too massive they would significantly affect the formation of galaxies and galaxy clusters, Benson said.
The SPT team has been able to improve estimates of neutrino masses, yielding a value that approaches predictions stemming from particle physics measurements.
“It is astounding how SPT measurements of the largest structures in the universe lead to new insights on the evasive neutrinos,” said Lloyd Knox, professor of physics at the University of California at Davis and member of the SPT collaboration. Knox will also highlight the neutrino results in his presentation on Neutrinos in Cosmology at a special session of the APS on Tuesday, April 3.
NSF’s Office of Polar Programs primarily funds the SPT. The NSF-funded Physics Frontier Center of the Kavli Institute for Cosmological Physics, the Kavli Foundation and the Gordon and Betty Moore Foundation provide partial support.
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