- Secret of Big Caves Revealed by Math
- Senate Passes Historic Food-Safety Reform
- Computer Game Makes You a Genetic Scientist
- Yellow-Bellied Marmots May Inherit Social Victimization
Posted: 30 Nov 2010 02:45 PM PST
Spelunkers look at a cave and wonder how to explore its deepest reaches. But physicists look at it and wonder how it got there in the first place.
A new mathematical analysis solves a longstanding cave-formation puzzle: how a trickle of water laced with carbonic acid manages to quickly dissolve rock to create massive conduits. The trick, it seems, is that fluid flow focuses rapidly in certain channels, which grow at the expense of others and allow the acid to penetrate deeply.
"Most of the models in cave formation today don't have this mechanism at all," says Piotr Szymczak, a physicist at the University of Warsaw. He and his colleague Anthony Ladd, a chemical engineer at the University of Florida in Gainesville, lay out their new equations in a paper to appear in Earth and Planetary Science Letters.
The work could improve understanding of the safety of dams, waste storage sites, or anywhere else fluid might be seeping through the ground.
For more than a century, researchers have known the basics of how limestone caves form: A tiny fracture opens in the rock, perhaps due to some internal stress, and water begins percolating through it. Most water contains some carbon dioxide, making it a weak acid that can eat away at the calcium carbonate in limestone. The question is how that dissolution can happen fast enough to produce deep penetration and allow long cave systems to form. The longest known system in the world is Mammoth Cave in Kentucky, with at least 580 kilometers of passageways.
Earlier work had suggested that the rate at which rock dissolved could speed up dramatically when the fluid is nearly saturated with carbon dioxide. But the new study can explain cave formation without invoking such a mechanism, says Szymczak.
The researchers showed how the equations describing fluid flow in the rock always contain a mathematical instability. The fact that this instability exists means that very soon after a fracture opens, fluid flow begins to focus along tiny ripples and build some bigger channels at the expense of others. "This mechanism of channeling speeds your dissolution time quite a lot," says Szymczak. "That's what allows it to penetrate so deep."
The mathematical analysis is likely to bring new insight into ideas that have been circulating since the 1990s, when the notion of focused flow in limestone was first proposed, says Harihar Rajaram, a hydrologic engineer at the University of Colorado at Boulder. The new work, says Szymczak, builds on that foundation by showing that the instability always exists in the math, no matter what materials are involved.
The work, he adds, could help explain why caves sometimes form faster than expected beneath dams. The equations might also help improve modeling of how fluid seeps through rocks, a ke question raised about the once-planned nuclear waste repository at Yucca Mountain, Nevada.
The researchers next want to look into what happens when engineers inject liquid carbon dioxide from power plants deep underground, in an attempt to keep the carbon from entering the atmosphere.
Image: This simulation shows how fluid flow (in this case, from left to right) can lead to deep penetration in a rock. At first (panel at left) channels begin developing almost equally, but over time (right) certain channels gain in size at the expense of others. Credit: Piotr Szymczak
Posted: 30 Nov 2010 01:32 PM PST
The U.S. Senate has approved the first major food-safety legislation in more than 70 years, by a 73-to-25 vote.
The Food Safety Modernization Act will give the Food and Drug Administration more power, providing better food tracking systems and more inspections of large-scale food production operations, especially those with poor track records. The cost of increased FDA funding and food prices is expected to run around $1.7 billion, small change compared to the estimated $152 billion annual cost of food-borne illnesses.
That any major legislation could be passed at such a partisan moment speaks to a deep level of American concern with food production. A spate of high-profile disease-risk recalls over the last several years, from lettuce to peanut butter to 380 million salmonella-tainted eggs, has driven home a bipartisan truth: When something goes wrong in the industrial food chain, it spreads fast.
The Senate bill survived a last-minute amendment that would have eliminated its strongest provisions. The amendment was sponsored by Tom Coburn (R-Oklahoma), who said, "The problem with food safety is, the agencies don't do what they're supposed to be doing now. They don't need more regulations. They need less." The bill did include an amendment that exempts small farmers, whom organic and local food advocates feared would be unable to afford the bill's requirements.
President Obama supports the Senate bill, which must now be reconciled with an even stricter version already passed by the House. Final approval is expected in December.
Posted: 30 Nov 2010 10:02 AM PST
A new online game harnesses the computational power of idle brains to help decipher the origins of genetic diseases.
The game, called Phylo, stands on the shoulders of crowdsourced science giants like the protein-folding game Foldit and the celestial object identification powerhouse Galaxy Zoo. Each project takes advantage of humans' prowess at pattern recognition, something computers are notoriously terrible at.
"There are some tasks that humans can do better than computers, like solving puzzles," said bioinformatics expert Jerome Waldispuhl of McGill University, one of Phylo's project leaders. The game was officially launched Nov. 29.
Phylo players move colored squares representing the four nucleotides of DNA to find the best alignment between snippets of DNA from two different species. These particular sections of DNA, called promoter regions, determine which parts of the genome end up as traits in the organism, whether it be blue eyes or heart disease.
Seeing where the genes line up across species can help biologists pinpoint the sources of genetic disorders.
"If some region is conserved across all species after alignment, it probably was conserved for some very specific reason," Waldispuhl said. "We should be able to provide better understanding of the reason for which mutation potentially will create a disease, or why this disease appears."
Unlike in Foldit or Galaxy Zoo, the science in Phylo is pretty well hidden. It feels like an abstract puzzle game, with colorful shapes and jazzy music. That was deliberate, Waldispuhl says.
"We don't want to be restricted only to the people interested in science," he said. Science geeks won't need as much convincing to play a game that helps research move forward, he says. The Phylo developers want the game to appeal to people who would otherwise play Farmville.
"If it's not fun, people won't play it," Waldispuhl said. "We wanted a good trade-off between what's fun, and what's the interesting information in science… so that when we provide the game on the web, people won't think about the biological problem, but just have fun and be entertained."
The team hopes to make versions of the game for smart phones and tablets, and eventually to incorporate it into social networking sites like Facebook. The game already has its own Facebook page, where you can leave feedback.
"The only way to make it better for the community is to release it to the community, and open it to comments from around the world," Waldispuhl said.
Posted: 30 Nov 2010 08:33 AM PST
An unusual study of an animal social network suggests that ending up as the butt of unfriendly interactions could be in part inherited.
It's receiving incoming social attention, particularly in grouchy interactions, that showed a small but intriguing genetic influence, Blumstein says. Aspects of initiating interactions in a network, whether to dish out snubs or snuggles, showed no evidence of heritability, according to the paper posted online November 29 in the Proceedings of the National Academy of Sciences.
"I am completely blown away by this paper," says James Fowler, professor of medical genetics and political science at the University of California, San Diego. In human networks, he and his colleagues have found the marmotlike pattern of heritability in aspects of received social ties but not in initiated ones. Fowler had suspected that the asymmetry in people came from a quirk of limiting the number of friends in the study. Marmots didn't have that limitation though, he says, "so the idea that there may be something systematic here between species is extremely interesting."
Marmots don't have Facebook yet, but animals living among clusters of burrows in Colorado do interact enough for observers to plot networks with each marmot as a node. An exchange might be friendly, such as a marmot grooming a neighbor or settling down tranquilly nearby. Or a social interaction might go sour, with one marmot nipping or chasing another. "Marmots are grumpy with each other," Blumstein says, but rarely cause serious injuries.
As in other network studies, marmot researchers examined such features as the number of ties individuals have as well as broader aspects of social life such as the likelihood that two "friends" of an individual are connected to each other.
Finding a genetic influence on being the recipient in negative interactions may reflect an overlooked aspect of a valuable social trait, Blumstein says. Marmots that are in the middle of things socially appear to thrive, but plentiful social interactions mean more bumps and grumps. "If you want to be in a group, you have to take the nasty stuff," Blumstein says. Being able to tolerate that abuse instead of shying away from interactions that might end unfortunately could indeed be a trait favored by evolutionary forces.
Yet most studies of social interactions focus on the beneficial relationships. Now coauthor Amanda Lea, also of UCLA, suggests, "We need to rethink our traditional view of affliative interactions as good and agonistic ones as bad."
Image: In a study of the social networks of yellow-bellied marmots, it's receiving rather than dishing out snubs or encouragement that has a genetic component, according to a novel new study. Shown here: Yellow-bellied marmot pups. Credit: Flickr/Alan Vernon
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