The snowy, wind-blown Scottish archipelago of St. Kilda may be inhospitable, but because it is inhospitable, it is an ideal natural laboratory. The last people left this place behind nearly a century ago, but the sheep stayed. And the in absence of human interference in their breeding, the sheep of St. Kilda have shown scientists something peculiar.
It has to do with the relationship between the immune system and reproduction. Andrea Graham and colleagues have studied the islands’ Soay sheep for years and years, and found the average lifespan of the ewes to be about 6 years. However, there’s great variation in there: Some lived just a few years, and some as many as 15.
The short-lived ewes had lower concentrations of antibodies than the longer-lived ones, which suggested why their lives were so short. But why was natural selection not weeding them out? Dr. Graham said the researchers found this to be a puzzle: “What are all these sheep doing with low antibody concentrations?” [The New York Times]
A new study of 218 Chinese men found that even low levels of the controversial plastics chemical bisphenol A (BPA) can lower sperm quality and count.
For the study, which was published in the journal Fertility and Sterility, researchers noted the participants’ sperm quality and urine BPA levels over five years. When compared to participants without detectable levels of the chemical, men with BPA in their urine were three times more likely to have low quality sperm.
“This adds additional human evidence that BPA is bad,” said [the study's first author] De-Kun Li…. “The general public should probably try to avoid exposure to BPA as much as they can.” [Washington Post]
That’s a tough order, because BPA is all over the place. It’s found in everything from sports equipment to medical devices to the plastic lining in canned foods.
Li’s previous studies have shown sexual effects of high levels of BPA, including inducing impotence in male factory workers exposed to it. Those studies were done with men exposed to about 50 times as much BPA as the average U.S. man, so the results might not apply to your average Joe.
When the space shuttle Discovery launches on Thursday (weather and technology permitting), it will be ferrying an unusual passenger to the International Space Station: Robonaut 2. This humanoid robot was designed by NASA and General Motors to work alongside astronauts on the space station, and could eventually take over some tedious or dangerous tasks.
Human beings who dream of becoming astronauts acquire things like advanced science degrees or the ability to fly jet planes in hopes of catching NASA’s eye and being chosen as astronaut candidates. If they do become candidates, there’s still scads of training before they can take a flight up to the ISS. But how does a robot qualify for and prepare for that trip to orbit? DISCOVER spoke with Marty Linn, General Motor’s principal engineer of robotics, to find out.
Physical Fitness: Human astronauts have to pass the NASA long-duration space flight physical to prove that they’re healthy, fit, and strong enough for astronaut duties. Robonaut 2 has to be pretty strong, too: Here on Earth, he proved that he can do arm curls with 20-pound free weights. “The limitation is grasp strength,” says Linn. “The weak link is how strong the fingers are.” The robot didn’t have to spend any time on the treadmill, though, because this model doesn’t have lower limbs—it’s simply a torso with arms and a head.
Intelligence: To be honest, R2 (as its buddies call it) isn’t that bright—it can’t make independent decisions. NASA’s top priority for the experimental bot is guaranteeing that it won’t pose a threat to the astronauts or the space station, so for now R2 will be under the strict control of astronauts and ground crew. R2 “isn’t going to go berserk,” Linn stresses, but it’s still nice to have an off switch. He also explains that the robot’s actions can be programmed joint by joint, or it can be controlled by a tele-ops system, in which an astronaut dons the tele-ops gear and puts the robot through its paces by moving her own arms or head.
Vision: NASA has always paid careful attention to the eyesight of its astronaut candidates, and only recently decided that people who have gotten laser surgery to correct their vision can still be considered for the job. R2′s vision is top-notch. It’s equipped with high-resolution digital cameras, can detect motion and distinct objects, and has a 3D mapping tool to allow it to determine where objects are in space. It also has lower resolution cameras for tele-operation, Linn explains, which “allow the operator to see through the eyes of the robot.”
This week China unveiled a new supercomputer that’s pretty darn quick.
The Tianhe-1A machine housed at the National Supercomputing Center in Tianjin reportedly works at the rate of 2.5 petaflops (a petaflop being about a thousand trillion operations per second), and reportedly will take the top spot in the rankings of world supercomputers when the people who attend to this list release the new version next month. That will bump the top U.S. machine down to number 2.
Personally, I’m not going to panic until China leapfrogs the United States on the Princeton Review list of top party countries or People Magazine’s sexiest countries in the world. But the announcement brought talk of American unease about being bested by China, and American alarm over China’s growing technological expertise. So is the vague, festering worry about the Chinese supercomputer justified? Let’s look at both sides of the argument.
Putting aside the issue of our wounded national pride, some experts say the real concern is whether the United States has the organization to match what China has done. CNET interviewed Jack Dongarra of Oak Ridge National Laboratory, keeper of the former fastest supercomputer, who called China’s achievement a “wake-up call.”
A bountiful archaeological site in South Africa has given up another discovery showing humans becoming sophisticated tool users. According to a study out in the journal Science, 75,000-year-old artifacts in the Blombos Cave appear to show signs of pressure flaking, a process of finely shaping hard material. Before this, study author Paola Villa says, the oldest evidence of humans using the technique was dated to just 20,000 years ago.
Pressure flaking consists of trimming the edges of a finished tool by pressing with a bone point hard enough to remove thin slices of rock. This process creates the narrow, evenly spaced grooves found on flint tools from Europe’s 20,000-year-old Solutrean culture and prehistoric Native American groups. Wider, more irregular grooves characterize 36 pressure-flaked Blombos tools, which were made from silcrete, Villa says. This rock, a silica-rich material, is of lower quality than flint and requires heating to ready it for pressure flaking. [Science News]
It’s not easy to tell from these artifacts whether their makers simply hammered them into shape or used the more sophisticated flaking method to polish them off. So the team, led by Vincent Mourre, found silcrete around the cave site and tried to make their own.
Spotting mistakes is a crucial part of typing (and indeed, life) and according to Gordon Logan and Matthew Crump, it’s a more complicated business than it might first appear. Using some clever digital trickery, the duo from Vanderbilt University found that the brain has two different ways of detecting typos. One is based on the characters that appear on the screen, and the other depends on the strokes of our fingers, as they tap away at the keys.
Logan and Crump asked 22 good typists to type 600 words presented on a screen, one at a time. Their efforts appeared below the target word, but all was not as it seemed. Throughout the experiment, Logan and Crump occasionally took control to the display. Sometimes, they put up the correct word, regardless of what the recruits actually typed so that their mistakes never appeared. On other trials, they deliberately introduced mistakes, which the typists hadn’t actually made.
To see whether the typists realized they were being toyed with, check out the full post at DISCOVER blog Not Exactly Rocket Science.
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The universe abounds with Earth-sized planets. That hopeful notion has been reinforced by individual planets finds like possible Goldilocks planet Gliese 581g, by the hordes of planet candidates discovered by the Kepler mission, and now, by a census of a small space in the sky that tells us one in four sun-like stars should possess worlds that are close to the size of Earth.
Take a moment to think about that: One in four.
In Science, exoplanet hunters Geoffrey Marcy and Andrew Howard published their team’s census of 166 nearby stars like ours, of which they picked 22 at random to investigate for planets. They watched the stars’ doppler shifts to hunt for planets over the last five years, and used the results to extrapolate how common terrestrial planets must be far beyond just this set of stars.
The retreat of the ice covering “Snowball Earth” 700 million years ago might have been the key to the Cambrian explosion that seeded our planet with diverse forms of life. But the trigger may not have been the changes to the climate, but rather the release of phosphorus into the ocean.
During this time period, called the Cryogenian or Snowball Earth stage, the entire planet was covered in snow and ice, and the oceans may even have been frozen. Many researchers believe that the ice receded twice during this freezing period, first around 700 million years ago and then again around 635 million years ago. In a paper published in Nature this week, a team of researchers propose that these receding sheets released phosphorus into the oceans.
In the scheme offered by [Noah] Planavsky and his colleagues, the snowball ice sheets would, as their modern counterparts do, grind up continental rock that would release phosphorus when the glaciers retreated. That phosphorus would wash into the ocean, where it would fertilize algal blooms that could drive a surge in the production of organic matter and oxygen. And the added organic matter that settled into the mud on the ocean bottom would leave additional oxygen behind, eventually boosting atmospheric and oceanic oxygen. [ScienceNOW]
No, this ostrich is not decked out early for Halloween. The bird’s glowing get-up is part of an experiment that settled just why these elongated creatures can run so much faster and farther than us: They have twice as much bounce in their step.
Jonas Rubenson and colleagues adorned the tame ostriches with the reflectors at points that would show how their joints moved as they sprinted down a test track. The team watched the birds run and then sampled human volunteers the same way. Rubenson’s study appears in the Journal of the Royal Society Interface.
“Cheetahs and lions are great sprinters, but they use a lot of energy when moving,” he says. “However ostriches, horses and antelopes are adapted to running fast and economically over long distances.” Rubenson says previous work had shown the ostrich uses 50% less energy running when compared with humans, yet can run at twice the speed. [Australian Broadcasting Corporation]
Where once there was a star 20 times the size of our sun, now there is a record breaker. Astronomers report this week in Nature that when the huge star went supernova, it collapsed into a neutron star that is heaviest they’ve ever seen, with twice the mass of our sun compacted into a tiny space. Aside from taking its place in the record books, this massive monster could reveal what truly goes on deep in the heart of a deceased star.
The neutron star is part of a binary star system called J1614-2230, in which it and a white dwarf are locked in a spin cycle. Thanks to the neutron star’s steady emission of radio waves and a handy trick of relativity, scientists can measure the size of the two objects despite the fact that they’re 3,000 light years from here.
The astronomers took detailed measurements of the radio pulses that reached Earth. As these pulses, which originate from the rotation of the neutron star, passed by the companion white dwarf, their timing was delayed due to the highly warped nature of spacetime—an effect known as Shapiro delay. In a highly inclined, nearly edge-on system such as J1614-2230 the effect allows astronomers to make very accurate measurements both of the neutron star and its companion. [Ars Technica]