- Ecosmackdown: Pets Versus Solar Panels
- Scent of Fear Keeps Male Bed Bugs From Mating With Each Other
- Short Heels and Long Toes: A Surprising Recipe for Speed
Posted: 30 Oct 2009 04:32 PM PDT
It takes 17 times more land to feed American pets than would be required by solar farms producing enough electricity to meet all the demand in the United States.
Why do we know this?
A new book by Robert and Brenda Vale, two architects at Victoria University of Wellington in New Zealand, looked into the ecological foodprints of the world's pets, New Scientist reported.
By examining the land and resources necessary to produce the meat and grains that compose pet food they discovered something startling: It takes over 90,000 square feet of land (that's two whole acres) to feed a medium-sized dog and 16,000 square feet of land to feed a cat.
The Humane Society estimates Americans own about 75 million dogs and 88 million cats. We did the math and found that feeding those animals takes about 294 thousand square miles of land. That's a little bigger than Texas!
That got us thinking because a default criticism of solar power has been to attack the amount of land it requires relative to nuclear or fossil fuel plants. Disingenuous or not, the idea that solar takes up too much land is widespread. For example, Senator Lamar Alexander, R-Tenn., a long-time nuclear supporter, decried "energy sprawl" in a Wall Street Journal editorial last month.
The amount of land required to generate electricity for the nation does sound like an awful lot, sometimes. One recent calculation led by Vasilis M. Fthenakis, an environmental engineer at Columbia University's Center for Life Cycle Analysis, found that it would take covering 16,602 square miles[pdf] of land in the southwestern desert with solar energy converters like cadmium telluride photovoltaic panels to generate the 3,816,000,000 megawatt-hours of electricity that is used in the U.S. ever year. (Other estimates have found smaller solar land needs.)
That's why it's important to compare solar's land requirements with other American practices. Multiply anything by the scale of the United States and the numbers start to sound absurdly big. When feeding our pets takes 17 times more land than feeding our supposedly rapacious electricity demand, it's difficult to argue that energy sprawl, for solar, is a major problem.
Posted: 30 Oct 2009 10:47 AM PDT
Male bed bugs get confused in bed. Now a scientist has found a bug chemical signal that translates, "Whoa, buddy. I'm a guy too."
Male bed bugs grasp and try to mate with any other member of their Cimex lectularius species that has had a full meal of blood recently, says chemical ecologist Camilla Ryne of Lund University in Sweden. Single-minded males don't seem inclined, or even able, to distinguish other males from females at first.
At first contact, sex recognition for these insects works largely by trial and error, Ryne says. What corrects those errors, she has found, is a blend of chemicals that earlier work has also described as the bed bug alarm pheromone.
"This is the first time to my knowledge that anyone has shown that alarm pheromones are used for sexual recognition," Ryne says.
Females can release the substance when disturbed but typically don't when grasped by a male, Ryne says. But males do exude the scent when grabbed by another male. After a whiff of the stuff, misguided suitors back off, Ryne reports online October 24 in Animal Behaviour.
Considering that bed bugs are making a comeback as a pest in the industrialized world, "knowing how they mate is important," says entomologist Joshua Benoit of Ohio State University in Columbus. He too has been studying the alarm pheromone, and he agrees that the bugs use it in several ways.
Pheromones may have achieved their fame in popular culture as dizzying lures for the opposite sex, but biologists have discovered plenty of other kinds of pheromones. Compounds can fuel aggression among male mice or urge baby rabbits to search for a nipple.
Bed bugs release the pheromone blend of the small, volatile molecules (E)-2-octenal and (E)-2-hexenal when disturbed, Ryne says. A mating attempt might indeed be disturbing, since males deliver their sperm by what's called traumatic insemination. They ignore the opening to the female reproductive tract and inject sperm with a needlelike appendage directly through the outer covering of a mate's body. In the abdominal area most commonly pierced, female bed bugs grow a mass of the kinds of cells associated with immune defense. Males, though, have no extra protection there.
To test the idea that the alarm pheromone helps mistakenly targeted males free themselves, Ryne painted nail polish over the glands that produce the substance, thus blocking its release. Males that couldn't signal chemically ended up in longer embraces than males dabbed elsewhere with nail polish.
For a different test, Ryne collected the substance by washing disturbed males with a solvent. When she applied wafted the extract over mating pairs of males and females, the males backed off. The finding showed that even in the presence of a suitable mate, the signal disturbed the males, she says.
Ryne herself can smell the pheromone, she says. It's a bit like almond, but not particularly pleasant. "Older people say that you used to be able to tell whose house had bed bugs because it had a peculiar smell," she says.
Images: 1) A male and femal bed bud mate. 2) A bed bug feeding on blood from a person. Rickard Ignell/Swedish University of Agricultural Sciences
Posted: 30 Oct 2009 10:11 AM PDT
Track coaches have long claimed that the best sprinters are born, not made. Now, new research on the biomechanics of sprinting suggests that at least part of elite athletes' impressive speed comes from the natural shape of their foot and ankle bones.
Using ultrasound imaging, researchers compared the feet of 12 top college sprinters with those of 12 mere mortals. Surprisingly, the athletes had particularly short heels and longer-than-average toes — features that actually put them at a mechanical disadvantage when running.
"What we found is that sprinters actually had less mechanical advantage than the non-sprinter subjects that we tested," said biomechanics researcher Stephen Piazza of Penn State University, co-author of the study published Friday in the Journal of Experimental Biology. "This was surprising to us because we expected that sprinters needed all the help they could get."
Piazza and his co-author, kinesiology graduate student Sabrina Lee, launched their study after they happened to measure the Achilles' tendon of a former NFL wide receiver, and were shocked by how little leverage his tendon provided.
"If you think of your foot as being kind of like a wheelbarrow," Piazza said, "when you grab the handles of the wheelbarrow and pull up, you're doing what the Achilles tendon does. The longer those handles are, the easier it is going to be to lift up the load. If you had really short handles, you would have poor mechanical advantage."
Similarly, having a short "lever arm" on your Achilles tendon makes it harder to pull your foot off the ground — which is why the researchers were surprised to find short heels on a professional sprinter. But further research proved the football player wasn't an aberration: On average, top sprinters had heels that were 25 percent shorter than their non-athlete counterparts, as well as significantly longer toes.
To understand the paradox, the researchers set up a computer model of a sprinter's push-off. The simulation revealed that despite providing a mechanical disadvantage, the short lever arm of a sprinter's heel actually produced more force than the longer lever arm of a non-sprinter.
"It turns out that there's a trade-off that we think is going on," Piazza said. "The larger the lever arm of the Achilles tendon, the more the tendon has to travel up when you point your toes. What that means is that the calf muscles have to shorten more rapidly, and muscle that is shortening more rapidly can't generate much force."
In other words, sprinters sacrifice the mechanical advantage of a long lever for the benefit of a stronger push-off. Since quick acceleration over a short distance is the key to winning a short race, Piazza says the trade-off makes sense for sprinters. "He has to be able to generate a lot of force, but he also needs that leverage," he said. "It turns out that by giving up some leverage, you actually gain more in terms of force generation and get a net benefit."
According to the computer simulation, having long toes also makes sprinters speedier, by extending the time that a runner's foot makes contact with the ground. "Early in the race, the only way you have to speed up is through interaction with the ground," Piazza said. "If you want to speed up quickly, you need to have some meaningful interaction with the ground."
But like short heels, long toes come with a cost. Earlier this year, a group of anthropologists reported that long toes are less energetically economical for long-distance running. Led by evolution researcher Campbell Rolian of the University of Calgary, the group found that modern humans have much shorter toes than their early hominid ancestors, suggesting that the need for endurance probably superseded the need for speed and acceleration in our ancient relatives.
"The two studies are actually nicely complementary, and show that long toes provide more power for propulsion, but that this comes at a cost of greater muscle effort," Rolian wrote in an e-mail to Wired.com. "So there may be an optimal length at which you can get both a capacity to push off and some muscle economy."
Of course, without studying athletes over time, it's impossible to know whether elite sprinters are born with short heels and long toes, or whether these beneficial features result from constant sprinting.
"We usually think of the shapes of your bones as things that shouldn't be changeable with time," Piazza said. On the other hand, he points out that there are plenty of examples of diseases or activities that can gradually change how bones and tendons fit together, so it's possible that intensive training could affect the shape of an athlete's foot.
"I'd love to do a longitudinal study to follow kids or athletes doing sprint training," he said, "and see if there are changes in how their tendons attach on their bones."
Image 1: Michael Lokner/Flickr. Image 2: The Achilles tendon, from Gray's Anatomy/Wikipedia Commons.
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