- Marathon Math: How Not to Hit the Wall
- The Moon Hides Ice Where the Sun Don’t Shine
- DIY Bat-Saving: Build Your Own Bat House
- Physics of Wet Dogs Shake Out in High-Speed Videos
- Video: Sloth’s Strange Walk Is Really Just Upside Down (and Sloooow)
- 8 Most Overlooked Endangered Species Candidates
Posted: 21 Oct 2010 02:46 PM PDT
A marathoner's worst nightmare — hitting "the wall" — may be completely avoidable if athletes adhere to personalized pace limits proposed by a biomedical engineer and runner. Benjamin Rapoport's mathematical formula, published online Oct. 21 in PLoS Computational Biology, shows the speediest pace any marathoner can sustain for the entire race.
"A 10-second difference in pace per mile could make the difference between success and a dramatic failure," says Rapoport, of Harvard Medical School and MIT, who experienced his own traumatic wall splat in the 2005 New York City Marathon. He started out pushing too hard, he says, and was out of steam by the last few miles. Rapoport finished, but with a slower time than he wanted.
To avoid this scenario, a runner has to maintain a pace that conserves carbohydrates, the body's main source of quick-burn energy, all the way to mile 26.2. Rapoport calculates the ideal pace from a measure of aerobic capacity called VO2max, along with a few other variables. VO2max indicates how efficiently a body consumes oxygen.
"This is a unique area that hadn't been addressed in the medical literature in any substantial way," says Mark Cucuzzella, a physician and running coach based in Harpers Ferry, W.Va. "He's lending some hard numbers to what experienced runners and coaches have been doing."
A man with a VO2max of 60 — which, after training, is attainable by only the top 10 percent of male runners — can achieve a 3:10 marathon finish time, according to the model. This time happens to be the cutoff for 18- to 34-year-old men to qualify for the Boston Marathon.
Elite male marathoners clock in with a VO2max in the high 70s. The average untrained young man's number is in the 40s. (Incidentally, Rapoport, who has run 18 marathons, has a VO2max above 70 and breezes through marathons in less than three hours.)
VO2max is usually measured with specialized equipment while someone exercises at maximum exertion, but the value can also be estimated by measuring heart rate while running at a constant pace.
Rapoport's model also shows that a slightly faster pace can be maintained by consuming a midrace snack.
This carb-eating strategy can help, but it can't win races, since the body can store only so much fuel, says Cucuzzella, chief medical consultant for the Air Force Marathon and a marathoner himself. "It's not about how much sugar or spaghetti you eat the night before a race," he says. "There's a critical pace."
Rapoport plans to put an easy-to-use version of his formula on the Internet to help runners calculate their ideal pace. "My primary goal is to give any marathon runner a qualitative plan for their training," he says.
Image: Flickr/Stijn Bokhove
Posted: 21 Oct 2010 12:30 PM PDT
The moon is pockmarked with cold, wet oases that could contain enough water ice to be useful to manned missions.
A year after NASA's Lunar Crater Observation and Sensing Satellite (LCROSS) smashed into the surface of the moon, astronomers have confirmed that lunar craters can be rich reservoirs of water ice, plus a pharmacopoeia of other surprising substances.
On Oct. 9, 2009, the LCROSS mission sent a spent Centaur rocket crashing into Cabeus crater near the moon's south pole, a spot previous observations had shown to be loaded with hydrogen. A second spacecraft flew through the cloud of debris kicked up by the explosion to search for signs of water and other ingredients of lunar soil.
And water appeared in buckets. The first LCROSS results reported that about 200 pounds of water appeared in the plume. A new paper in the Oct. 22 Science ups the total amount of water vapor and water ice to 341 pounds, plus or minus 26 pounds.
Given the total amount of soil blown out of the crater, astronomers estimate that 5.6 percent of the soil in the LCROSS impact site is water ice. Earlier studies suggested that soils containing just 1 percent water would be useful for any future space explorers trying to build a permanent lunar base.
"The number of 1 percent was generally agreed to as what was needed to be a net profit, a net return on the effort to extract it out of the dark shadows," said NASA planetary scientist Anthony Colaprete in a press conference Oct. 21. "We saw 5 percent, which means that indeed where we impacted would be a net benefit to somebody looking for that resource."
Water could lurk not just in the moon's deep dark craters, but also as permafrost beneath the sunlit surface. Based on the impact data, water is probably mixed in to the soil as loose ice grains, rather than spread out in a concentrated skating rink. This distribution could make the water easier to harvest.
"The water ice is in this rather malleable, dig-able kind of substrate, which is good," Colaprete said. "At least some of the water ice, you could go in and literally just scoop it up if you needed to."
But the plume wasn't just wet. A series of papers in Science report observations from both LCROSS and LRO that show a laundry list of other compounds were also blown off the face of the moon, including hydroxyl, carbon monoxide, carbon dioxide, ammonia, free sodium, hydrogen, methane, sulfur dioxide and, surprisingly, silver.
The impact carved out a crater 80 to 100 feet wide, and kicked between 8,818 pounds and 13,228 pounds of debris more than 6 miles out of the dark crater and into the sunlight where LCROSS could see it. Astronomers, as well as space enthusiasts watching online, expected to see a bright flash the instant the rocket hit, but none appeared.
The wimpy explosion indicates that the soil the rocket plowed into was "fluffy, snow-covered dirt," said NASA chief lunar scientist Michael Wargo.
The soil is also full of volatile compounds that evaporate easily at room temperature, suggests planetary scientist Peter Schultz of Brown University, lead author of one of the new papers. The loose soil shielded the view of the impact from above.
Data from an instrument called LAMP (Lyman Alpha Mapping Project) on LRO shows that the vapor cloud contained about 1256 pounds of carbon monoxide, 300 pounds of molecular hydrogen, 350 pounds of calcium, 265 pounds of mercury and 88 pounds of magnesium. Some of these compounds, called "super-volatile" for their low boiling points, are known to be important building blocks of planetary atmospheres and the precursors of life on Earth, says astronomer David Paige of the University of California, Los Angeles.
Compared to the amount of water in the crater, the amounts of these materials found were much greater than what is usually found in comets, the interstellar medium, or what is predicted from reactions in the protoplanetary disk.
"It's like a little treasure trove of stuff," said planetary scientist Greg Delory of the University of California, Berkeley, who was not involved in the new studies.
Astronomers picked Cabeus crater partly because its floor has been in constant shadow for billions of years. Without direct sunlight, temperatures in polar craters on the moon can drop as low as -400 degrees Fahrenheit, cold enough for compounds to stick to grains of soil the way your tongue sticks to an ice cube.
Other factors, like micrometeorite impacts and ultraviolet photons that carry little heat but significant amounts of energy, can release these molecules from the moon's cold traps. The composition of the lunar surface represents a balancing act between what sticks and what is released.
The fact that so many different materials, most of which are usually gaseous at room temperature and react easily with other chemicals, remain stuck to the moon gives astronomers clues as to how they got there.
"Perhaps the moon is presently active and there's all kinds of chemistry going on and stuff being produced, continually collecting in these polar regions," Delory said. "Maybe it'll tell us the moon is in fact a much more active and dynamic system than we thought, and there's water being concentrated at the poles by present-day ongoing processes."
Another possibility is that these materials hitched a ride on comets or asteroids, Schultz suggests. Compounds deposited all over the moon could have migrated to the poles over the course of billions of years, where they were trapped by the cold or buried under the soil.
There's only one sure way to find out.
"We need to go there," Delory said. Whether the water will be a useful resource for future astronauts or not, the ice itself is a rich stockpile of potential scientific information, he said. "That's as much a reason to go there, for the story that this water tells."
Image: 1) The debris plume about 20 seconds after LCROSS impact. Science/AAAS. 2) Temperature map of the lunar south pole from the LRO Diviner Lunar Radiometer Experiment, showing several intensely cold impact craters. UCLA/NASA/Jet Propulsion Laboratory, Pasadena, Calif./Goddard
Posted: 21 Oct 2010 11:12 AM PDT
Looking for a simple, outdoorsy fall project that could help save threatened bats from dying out? Then it's time to put up a bat box. If you put it up now, bats will have a chance to scout it out — and, come next summer, you might have your very own colony.
Full instructions are available from Bat Conservation International. If — like me — even an Ikea bookshelf blueprint makes your brain seize, GardenFork's Eric Rochow shows how it's done in the video above.
If you don't have all of Eric's power tools, not to worry: Hand tools and a bit more elbow grease will work just fine. And if you'd rather skip all that, you can always buy a bat house ready-made.
Spot.us is a micropayment-based service that enables people to directly support journalism they care about. And for a limited time, you can raise money for my story — and dozens of others — just by taking a poll. (Go to the pitch, and click on "Free Credits.") It's as simple as that.
– Brandon Keim
There are many benefits to having a bat house, not least the sheer neatness of having them around. (Trivia time: Bats are more closely related to elephants than rodents. Some can live for up to 30 years. They represent one-fifth of all mammal species on Earth.) And they've achieved such spectacular evolutionary success by exploiting a basic, extraordinarily useful ecological niche: They eat insects at night, in the air.
If you're a gardener, they might eat your pests. And though mosquitoes are not a major part of bat diets, they'll often eat whatever flies near their home, said Pennsylvania Game Commission biologist Cal Butchkoski. Before putting a pair of bat boxes in his backyard, Butchkoski says he couldn't sit on the porch in the summer. Now he's there every evening.
Unfortunately, Butchkoski's backyard population has dropped from 1,000 to about 400 as a result of White Nose Syndrome, a virulent bat-killing disease. (To learn more, see my citizen-funded Spot.us White Nose Syndrome story.) There's no cure for this disease — which doesn't affect humans, so don't worry about getting infected — but by having bat boxes around, you could make the bats' lives that much easier. That extra boost could help get them through winter, when the disease hits hardest.
At this point in the year, most cave-dwelling bats are already underground and getting to hibernate, but it's still a good time to put them up. Butchkoski said they make scouting runs in the fall, looking for places to roost next spring.
"They evolved dealing with trees, and trees fall down. We think that once the young bats start flying, they start checking out other roosts," said Butchkoski. "Often, there will be just one or two in late November or early December. Then the next spring, a large number moves in."
Video: Eric Rochow
Posted: 21 Oct 2010 10:25 AM PDT
By Duncan Geere, Wired UK
The last time a wet dog looked Andrew Dickerson in the eye, readying a shake, he didn't flee in terror like most people would. Instead, like any true physicist, he whipped out a slow-motion video camera to see if he could capture the exact frequency at which its body was oscillating.
Dickerson, along with some colleagues from the Georgia Institute of Technology, has written "The Wet-Dog Shake," published in Fluid Dynamics. They attempt to calculate the optimum speed at which dogs should shake to most efficiently dry their fur.
The team built a mathematical model of the processes involved, reasoning that surface tension between the water and the dog's hair is what keeps the dog wet. Overcoming that tension requires a centripetal force that exceeds it.
As centripetal force varies with distance from the centre of the creature, its radius is therefore crucial to work out the speed of the oscillations. The team arrived at an equation that calculates the frequency of that oscillation as R0.5.
To test that hypothesis, the team filmed a wide range of dogs shaking, and used the images to calculate the period of oscillation. For a labrador retriever, that turned out to be 4.3 Hz. He then expanded the search, filming animals as small as mice (27 Hz) and as large as bears (4 Hz).
So the bigger the animal, the slower it can shake to achieve comparable drying, but the relationship isn't linear. Instead, it approaches a limit of 4 Hz as an animal grows in size.
The team also found that their initial equation was off too. Fitting the data to a graph revealed that the correct calculation was in fact R0.75. Dickerson offers a possible explanation for this. In the team's model, the radius is the distance from the center of the animal to its skin. The fur might make a difference, he said.
If all those equations whooshed over your head a little, then just hit Play on the video above and enjoy the adorable slow-motion videos of doggies shaking themselves dry.
Posted: 21 Oct 2010 09:20 AM PDT
Two-toed sloths spend a lot of time hanging upside down from tropical tree branches in Central and South America, and looking very odd. But new research suggests they move just like a mirror image of many upright four-legged creatures.
"Mammals seem to move their legs in very standardized fashion during locomotion, whether walking on land, on branches or suspended under branches," said graduate student John Nyakatura of Friedrich-Schiller University in Jena, Germany, lead author of the study appears this month in Zoology. "What differs is the way muscles are arranged, and "the attachment sites of muscles are much more variable in evolution and can completely alter the functionality of limbs."
Sloths don't grasp branches but instead suspend themselves from tree limbs with long, hook-like claws on their sideways-oriented hands and feet. Given how weird sloths are, it seemed possible they may have evolved a different way of moving from other mammals. To investigate whether strange anatomy translated to strange locomotion Nyakatura and colleagues used video and x-rays to see inside sloths as they moved along a wooden pole and a motorized "treadpole" they were trained to move along for a snack.
They found that the sloths didn't simply lumber along the branches at a slow-and-steady pace. Not only did their velocity vary from 0.02 meters per second to 0.47 meters per second, but they also used several different gaits while moving. In the "exploratory gait," the sloths assumed an inverted crouch position in which they held their nose close to the pole, while in the "traveling gait" they extended their arms further to increase their stride.
The range of movements in sloths overlaps with those of other tree-dwelling mammals that either run over the tops of branches or grasp them for support. In particular, the sloths used what is called a diagonal couplet gait in which the front limb on one side and the hind limb on the opposite side move together. Researchers have suggested this kind of gait allows animals to securely touch down on branches as they move.
While sloths don't have to worry about falling off the top of a branch, the scientists suspect they use this gait while moving quickly to allow them to draw back if a branch cracks. Even though sloths moved upside down, they used some of the same locomotor strategies of animals that move along the tops of tree limbs. Though sloths evolved the strange habit of traveling along the underside of branches, "the way the legs themselves are moved remained very similar to other mammals," Nyakatura.
Strangely, this repertoire of upside-down locomotion may have evolved twice in sloths. Although not specifically studied in the new research, Nyakatura's team proposes three-toed sloths might move using the same strategies. And if this is correct, it would be a case of evolutionary convergence.
Superficial appearances to the contrary, two-toed and three-toed sloths are not very closely related to each other and last shared a common ancestor over 21 million years ago. Because both lineages became adapted in similar ways to living in trees, however, it is likely both types of sloths co-opted some of the anatomy of their ancestors to allow them to make that move into the trees.
Based upon the close relationships of sloths to anteaters and armadillos, as well as some peculiar anatomical traits in their postcranial skeletons, Nyakatura suspects that the last common ancestor of each of these lineages was a digger. This means that some of the specializations that allowed sloths to move into trees evolved first as adaptations to digging.
It may be that life on the ground caused sloths to evolve the anatomical specializations that allow them to suspend themselves from the forest canopy today.
Posted: 21 Oct 2010 04:00 AM PDT
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Think of endangered species, and you probably think of Florida panthers or blue whales or California golden condors -- big, charismatic animals that easily move the heart.
But endangered species can be small, odd and unappealing, too. These animals are no less special; they're still one-of-a kind works of evolutionary art, sculpted over millions of years.
On the following pages are some of the animals that the U.S. Fish and Wildlife Service decided this year to consider for endangered status. Many steps remain in their bureaucratic journey to protection, which can take years, even decades, and may end with a decision that they're not endangered.
They could also suffer the fate of the Gunnison Sage Grouse, which the USFWS said last month that it ought to protect, but couldn't, because it didn't have the resources. The federal government spends just $140 million for all Endangered Species Act-related activities.
Image: Matthew Niemiller, University of Tennessee
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