- Bigger, Better Telescopes Needed to Find Near-Earth Asteroids
- Removing Part of Skull Makes for Better Brain Scans
- New Hi-Res Flyover of Haiti Will Aid Recovery and Research
- Slime Mold Grows Network Just Like Tokyo Rail System
Posted: 22 Jan 2010 03:51 PM PST
If we're going to protect the Earth from an asteroid, we need to find the dangerous ones whizzing about in the emptiness of space.
Unfortunately, the United States will not complete the survey of large near-Earth objects by 2020 as mandated, but not funded, by Congress in 2005. That's the conclusion of a new National Resource Council Report, Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies, released Friday.
The current budget and astronomical tools are just not sufficient to find all near-Earth objects larger than 140 meters (460 feet) across. Better telescopes than we currently have will be needed. While this has been known within the NEO science community, the final report could bring the realization to the policymakers and politicians who control the purse strings.
"There's no longer time to meet the goal by 2020," said Michael A'Hearn, a University of Maryland astronomer and co-author of the report. "There's no way to do the survey in that length of time because the equipment isn't even built yet. We say it is not unreasonable to set a new deadline of 2030 and start funding now. We probably can do the job by then."
Despite the large number of NEO discoveries over the past several years, our current detection instruments like the Catalina Sky Survey, are not up to the task of completing the Congressional mandate, known as the Gordon Brown Survey.
"The current instruments, no matter how you operate them are not capable of doing the George Brown survey," A'Hearn noted.
And that's to say nothing of the smaller asteroids, those in the 30- and 50-meter (90 to 165 foot) range, which hit Earth far more often than larger objects. Finding and tracking those little guys will require new telescopes like the Large Synoptic Sky Survey and Panstarrs, neither of which currently has the funding to complete construction.
Scientists have increasingly come to understand that the risk of asteroids and comets hitting Earth is real, but quantifying the risk that humans face from such events is much trickier.
"Our estimates of the risk could easily be wrong by a factor of two or three," A'Hearn said. "I don't think they are wrong by a factor of 10, but the boundaries, again, haven't been explored."
Even the Tunguska asteroid, which exploded over Siberia in 1908, remains something of a mystery. It's unclear even how large the object was, A'Hearn said, which makes it difficult to know how common such an impact is. The rareness of the event makes it very tough to compare the risk from an asteroid strike with that from automobile collisions or other prosaic problems.
Right now, National Research Council scientists estimate the risk of being killed by an NEO impact is comparable to the risk of being one of the 50 or so people who die on an amusement park ride each year. The difference is that a major asteroid would kill many people all at once.
Another area of high uncertainty is the physics of asteroid impacts. Near-Earth objects of different types may require different mitigation strategies.
"The first thing we need to do is understand what the hazard is," A'Hearn said. "That's partly finding them and partly understanding what their effect is. We have to understand in more detail how we'd mitigate against them."
Former astronaut Rusty Schweickart, a tireless campaigner for asteroid risk awareness, said the latest report was the best of its kind, surpassing an earlier NASA report to Congress on near-Earth object risk.
"I can certainly say that Irwin Shapiro, who I know very well personally, did a terrific job in putting this review together," Schweickart said.
Lindley Johnson, program executive at NASA's Near Earth Object Program, which wrote the NASA report agreed.
"It looks to be a very good report," Johnson said. "It had a very strong team of top scientists in the area on the committee. They had the right people and it looks like they looked at all the right things."
Differences begin to emerge between people who study near-Earth objects when mitigation options come up. The new report looks at two main ways of deflecting asteroids, following previous reports. First, the asteroid could be hit with some kind of impactor, either conventional or nuclear. Second, a longer-term, more precise technique like a gravity tractor could be employed.
Schweickart argued, however, that a gravity tractor, which would slowly push an asteroid off a collision path with Earth, should be considered a necessary but not independent part of any Earth defense.
"It's the icing on the cake of stronger deflection needs," Schweickart said. "It's not comparable to and should never be considered the primary means of deflection."
Image: U.S. Geological Survey/Composite: Tim Warchocki
Posted: 22 Jan 2010 02:57 PM PST
Removing a chunk of the skull can make way for stronger, clearer signals from a common method of monitoring brainwaves. The skull-free electroencephalography could make neural prostheses like bionic arms or eyes less invasive.
"It's notoriously hard to have a long-term electrode implanted in the brain," said University of California at Berkeley neuroscientist Bradley Voytek, lead author of the study to be published in a forthcoming issue of the Journal of Cognitive Neuroscience. So if you can get around that by just having a small hole drilled into the skull, that would be very helpful."
Doctors sometimes treat patients who have suffered severe head trauma, such as gunshot or knife wounds, with what is known as a hemicraniectomy. A surgeon cuts out a chunk of skull that's the diameter of an orange or grapefruit, to give the brain room to swell.
Surgeons usually reattach the piece of bone four to six months later, once the swelling has subsided and the skin has healed. In the meantime, the patient's scalp and a helmet protect the exposed area. And doctors stitch the skull fragment into the abdomen, "bathed in the body's own fluids," to prevent it from deteriorating, Voytek said.
Voytek's team took advantage of this brief window of time to compare EEG signals from people with and without the skull as a barrier. Patients performed simple tasks like squeezing a person's hand or listening to an "oddball stimulus" of three low-pitched sounds followed by a higher one, he said.
During these tasks the team measured a patient's brain waves on both sides of his head. On one side, just a thin flap of skin separated the brain from the EEG electrode, while on the other side the skull was intact. Signals from the skull-free side were, unsurprisingly, much stronger, less noisy and easier to pinpoint to a specific task and region of the brain.
UC Berkeley psychologist Robert Knight, a co-author of the study, first noticed 28 years ago that EEG signals from patients with holes drilled in their heads "looked really weird because they were freakishly strong," Voytek said. But he only thought to quantify the difference after he saw the unusually strong EEG signals from a recent hemicraniectomy patient, one who was brought in clinically dead but revived with the surgery.
"It provides insight into the signal properties [and] how hybrid implants might capture very local activity in the brain which is inaccessible from the surface of the head," neuroscientist Kai Miller of the University of Washington wrote in an e-mail to Wired.com. "These might be captured by placing devices beneath the skull, but without invading the subdural space."
Implanting electrodes requires cutting through the dura, the outermost protective layer of the brain, which can cause scar tissue and damage nearby neurons, Voytek said. "If someone's had a stroke or they're paralyzed, in the future, the goal of the surgeon is to be able to implant the electrodes into the person's brain."
Placing an implant between the skull and the dura may make neural implants less dangerous.
Via Mind Hacks
Image: CT reconstruction of the skull, with fMRI of the brain. EEG signals in color.
Citation: "Hemicraniectomy: A New Model for Human Electrophysiology with High Spatio-temporal Resolution," by Bradley Voytek, Lavi Secundo, Aurelie Bidet-Caulet, Donatella Scabini, Shirley I. Stiver, Alisa D. Gean, Geoffrey T. Manley and Robert T. Knight, Journal of Cognitive Neuroscience.
Posted: 22 Jan 2010 12:44 PM PST
New three-dimensional radar and hi-resolution aerial images of Port-au-Prince and the surrounding areas to be released starting Friday could boost both recovery and research efforts in Haiti in the wake of the magnitude 7.0 earthquake that struck on Jan. 12.
Satellite images and aerial photos have been important resources, but the flatness of those images makes it hard for viewers to identify what they're looking at.
"We have dozens of points located along [a satellite image of] the fault with annotations after these points saying things like, 'I don't know. This may be a footpath or maybe it is a fracture,'" said U.S. Geological Survey geophysicist Ken Hudnut, who's been trying to map the Enriquillo-Plantain Garden fault that caused the earthquake. "With the resolution of the [old] imagery … it's hard to be conclusive."
On Thursday, remote-sensing scientists from the Rochester Institute of Technology in New York began collecting new aerial images of the Port-au-Prince area. They're using a twin-engine Piper PA-31 Navajo that houses numerous sensors, including a light-detection and ranging, or LiDAR, instrument that generates the 3-D data. It has a camera that shoots with enough resolution to make out cars and occasionally people and multiple infrared instruments that sketch out details invisible to the naked eye, such as hidden sources of heat and water.
The preliminary 6-inch resolution data shows enormous refugee areas dotted with brightly colored red and blue tents. "You can't miss them," said Stefi Baum, director of RIT's imaging-science center. It also shows rubble piled precariously along hillsides, which could amplify the threat of mudslides. "Everything is OK until the rainy season," Baum said. "But then all of that rubble will just flow down those structures."
The data they gather will also help identify access roads that have been cut off by debris, broken bridges and unstable buildings that remain standing, as well as provide much clearer images of the fault, said RIT remote-sensing specialist Jan van Aardt, one of the project's coordinators.
Scientists studying Haiti are most excited about the LiDAR instrument, which emits a pulse of light and then measures how fast that light takes to return to the aircraft. Because data from taller points will arrive faster than data from lower points, the points stitch together to form a 3-dimensional snapshot of the scene.
"You can almost hold up your fist in the middle of the air and assign it an 'X' a 'Y' and a 'Z' [coordinate]," van Aardt said. "You can think of LiDAR data as millions of such positions … each with an X a Y and a Z coordinate." Those points will also be tied to geographic coordinates to help people pinpoint specific locations on the ground.
Sorting out the logistics of the $200,000 World Bank-funded project has been challenging, van Aardt said. Because of limited air space in Haiti, the team will be based in Puerto Rico and refuel every four hours in the Dominican Republic. Every night, researchers at the University of Puerto Rico will help the RIT team transfer the aerial images to Rochester and the huge LiDAR data files to Kucera International aerial imaging company in Ohio, where they will be processed. Then the images will be made public.
Companies, such as GoogleEarth, Microsoft and Yahoo, have all expressed interest in uploading this data, said Ron Eguchi, CEO of ImageCat, a California-based company that specializes in disaster management, and an RIT partner.
Because RIT's team plans to assess damage in Port-au-Prince first, Hudnut will likely have to wait a day or two to receive images of the Enriquillo fault, which lies just outside the city. The new data could reveal major ruptures along the fault. With no such ruptures currently visible, Hudnut and his colleagues are worried that the ground beneath Port-au-Prince remains under a great deal of stress that could potentially trigger another, even larger earthquake.
"Our dour view of the situation is that it looks like where the fault broke is pretty far to the west and we're now concerned that it didn't rupture in the eastern part," Hudnut said.
Because the possibility of another major earthquake of equal or greater magnitude remains low — around 3 percent over the next 30 days — even if no major ruptures are found, researchers hope to use these images primarily to create computer models that show how the fault has behaved in the past and how it might behave in the future.
For instance, about five years ago, researchers used LiDAR data to map the San Andreas fault in California. Scientists had previously concluded that an earthquake in 1857 caused the ground to shift 30 feet. But the LiDAR data made clear that the shift was caused not by one, but two, earthquakes.
"Past earthquakes … leave their imprint on the Earth," said Eric Calais, a geophysicist at Purdue University. LiDAR data records those imprints, such as distinctive fracture patterns in rock and furrows in the topography of the land. Scientists should be able to use the Enriquillo images to predict the strength of future earthquakes and calculate how often the fault has ruptured in the past. "Then this information can be used to prepare a city, prepare a country," Calais says.
We will update with 3-D LiDAR images as they become available.
Images: Rochester Institute of Technology Chester F. Carlson Center for Imaging Science.
Posted: 22 Jan 2010 11:56 AM PST
Talented and dedicated engineers spent countless hours designing Japan's rail system to be one of the world's most efficient. Could have just asked a slime mold.
When presented with oat flakes arranged in the pattern of Japanese cities around Tokyo, brainless, single-celled slime molds construct networks of nutrient-channeling tubes that are strikingly similar to the layout of the Japanese rail system, researchers from Japan and England report Jan. 22 in Science. A new model based on the simple rules of the slime mold's behavior may lead to the design of more efficient, adaptable networks, the team contends.
Every day, the rail network around Tokyo has to meet the demands of mass transport, ferrying millions of people between distant points quickly and reliably, notes study coauthor Mark Fricker of the University of Oxford. "In contrast, the slime mold has no central brain or indeed any awareness of the overall problem it is trying to solve, but manages to produce a structure with similar properties to the real rail network."
The yellow slime mold Physarum polycephalum grows as a single cell that is big enough to be seen with the naked eye. When it encounters numerous food sources separated in space, the slime mold cell surrounds the food and creates tunnels to distribute the nutrients. In the experiment, researchers led by Toshiyuki Nakagaki, of Hokkaido University in Sapporo, Japan, placed oat flakes (a slime mold delicacy) in a pattern that mimicked the way cities are scattered around Tokyo, then set the slime mold loose.
Initially, the slime mold dispersed evenly around the oat flakes, exploring its new territory. But within hours, the slime mold began to refine its pattern, strengthening the tunnels between oat flakes while the other links gradually disappeared. After about a day, the slime mold had constructed a network of interconnected nutrient-ferrying tubes. Its design looked almost identical to that of the rail system surrounding Tokyo, with a larger number of strong, resilient tunnels connecting centrally located oats. "There is a remarkable degree of overlap between the two systems," Fricker says.
The researchers then borrowed simple properties from the slime mold's behavior to create a biology-inspired mathematical description of the network formation. Like the slime mold, the model first creates a fine mesh network that goes everywhere, and then continuously refines the network so that the tubes carrying the most cargo grow more robust and redundant tubes are pruned.
The behavior of the plasmodium "is really difficult to capture by words," comments biochemist Wolfgang Marwan of Otto von Guericke University in Magdeburg, Germany. "You see they optimize themselves somehow, but how do you describe that?" The new research "provides a simple mathematical model for a complex biological phenomenon," Marwan wrote in an article in the same issue of Science.
Fricker points out that such a malleable system may be useful for creating networks that need to change over time, such as short-range wireless systems of sensors that would provide early warnings of fire or flood. Because these sensors are destroyed when disaster strikes, the network needs to efficiently re-route information quickly. Decentralized, adaptable networks would also be important for soldiers in battlefields or swarms of robots exploring hazardous environments, Fricker says.
The new model may also help researchers answer biological questions, such as how blood vessels grow to support tumors, Fricker says. A tumor's network of vessels start out as a dense, unstructured tangle, and then refine their connections to be more efficient.
|You are subscribed to email updates from Johnus Morphopalus's Facebook notes |
To stop receiving these emails, you may unsubscribe now.
|Email delivery powered by Google|
|Google Inc., 20 West Kinzie, Chicago IL USA 60610|