September 12, 2013
To the best of our knowledge, the mechanical gear—evenly-sized teeth cut into two different rotating surfaces to lock them together as they turn—was invented sometime around 300 B.C.E. by Greek mechanics who lived in Alexandria. In the centuries since, the simple concept has become a keystone of modern technology, enabling all sorts of machinery and vehicles, including cars and bicycles.
As it turns out, though, a three-millimeter long hopping insect known as Issus coleoptratus beat us to this invention. Malcolm Burrows and Gregory Sutton, a pair of biologists from the University of Cambridge in the U.K., discovered that juveniles of the species have an intricate gearing system that locks their back legs together, allowing both appendages to rotate at the exact same instant, causing the tiny creatures jump forward.
The finding, which was published today in Science, is believed to be the first functional gearing system ever discovered in nature. Insects from the Issus genus, which are commonly called “planthoppers,” are found throughout Europe and North Africa. Burrows and Sutton used electron microscopes and high-speed video capture to discover the existence of the gearing and figure out its exact function.
The reason for the gearing, they say, is coordination: To jump, both of the insect’s hind legs must push forward at the exact same time. Because they both swing laterally, if one were extended a fraction of a second earlier than the other, it’d push the insect off course to the right or left, instead of jumping straight forward.
The gearing is an elegant solution. The researchers’ high-speed videos showed that the creatures, who jump at speeds as high as 8.7 miles per hour, cocked their back legs in a jumping position, then pushed forward, with each moving within 30 microseconds (that’s 30 millionths of a second) of the other.
The finely toothed gears in their legs allow this to happen. “In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can’t,” Burrows said in a press statement.
The gears are located at the top of the insects’ hind legs (on segments known as trochantera) and include 10 to 12 tapered teeth, each about 80 micrometers wide (or 80 millionths of a meter). In all the Issus hoppers studied, the same number of teeth were present on each hind leg, and the gears locked together neatly. The teeth even have filleted curves at the base, a design incorporated into human-made mechanical gears because it reduces wear over time.
To confirm that the gears performed this function, the researchers performed a neat (albeit morbid) trick with some dead Issus. They manually cocked their legs back in a jumping position, then electrically stimulated the main jumping muscle in one leg so that the leg extended. Because it was rotationally locked by the gears, the other non-stimulated leg moved as well, and the dead insect jumped forward.
The main mystery is the fact that adults of the same insect species don’t have any gearing—as the juveniles grow up and their skin molts away, they fail to regrow these gear teeth, and the adult legs are synchronized by an alternate mechanism (a series of protrusions extend from both hind legs, and push the other leg into action).
Burrows and Sutton hypothesize that this could be explained by the fragility of the gearing: if one tooth breaks, it limits the effectiveness of the design. This isn’t such a big problem for the juveniles, who repeatedly molt and grow new gears before adulthood, but for the mature Issus, replacing the teeth would be impossible—hence the alternate arrangement.
There have been gear-like structures previously found on other animals (like the spiny turtle or the wheel bug), but they’re purely ornamental. This seems to be the first natural design that mechanically functions like our geared systems.
“We usually think of gears as something that we see in human designed machinery, but we’ve found that that is only because we didn’t look hard enough,” Sutton said. “These gears are not designed; they are evolved—representing high speed and precision machinery evolved for synchronisation in the animal world.”
September 10, 2013
If, in the midst of a Szechuan pepper-heavy meal, you have the presence of mind to ignore the searing hot pain that fills your mouth, you might notice a more subtle effect of eating the hot peppers: a tingling, numbing sensation that envelops your lips and tongue.
What’s behind this strange phenomenon, scientifically known as paresthesia? Scientists believe that it has something to do with a molecule called hydroxy-alpha-sanshool, naturally present in the peppers.
Research has shown that the molecule interacts with our cell’s receptors differently than capsaicin, the active ingredient in the world’s hottest chili peppers. Capsaicin produces a pure burning sensation by binding to the same sorts of receptors present in our cells that are activated when we’re burned by excessive heat, but the Szechuan peppers’ active chemical appears to act on separate receptors as well, perhaps accounting for the distinctive tingling that can persist for minutes after the burn has gone away.
Now, in a study that required some uncommonly compliant volunteers—they let their lips get brushed with ground Szechuan pepper—researchers found that the peppers produce the tingle by exciting tactile sensors in our lips and mouth. In other words, it seems that apart from tasting the peppers’ spiciness, we feel it too, as though our lips are being physically touched by the chemicals present in the Szechuans.
As part of the study, published today in the Proceedings of the Royal Society B, a group of neuroscientists from University College London gathered 28 people and subjected them to ground Szechuans and small metal vibrating tools. Initially, they ground up the peppers, mixed them with ethanol and water, and brushed them onto the lips of the participants, who reported the level of tingling they felt.
Then, to try figuring the exact frequency of the tingling—a concept that becomes a bit more intuitive if you think of the tingling, or numbness, as the lips being vibrated quickly—they held a small vibrating tool up to the volunteers’ fingers. They could control how fast or slow the tool vibrated, and were asked to set it so that it matched the same feeling as the tingling on their lips. After the Szechuan tingling had time to die down, the vibrating tools were placed on their lips in the same spot, and again the participants could control the vibrating to make it resemble the pepper numbness as closely as possible.
When they looked at the records of the tool’s frequency, they found that the participants consistently set it to vibrate at 50 hertz (another way of saying 50 cycles per second). This consistency across people was telling—specific classes of tactile receptors in our cells are each activated by different frequencies (when touched, they pass along an electric current through nerve fibers, ultimately signaling to the brain that physical contact has occurred), so it supported the idea that touch receptors were involved. Which class of receptor, though, is activated by Szechuan peppers?
The scientists say that frequency of the Szechuan’s numbing sensation fell within the range of vibration typically conveyed by a highly-sensitive type of tactile receptor called Meissner receptors, which cover around 10-80 hertz. Previous work has shown that in human nerve cells cultured in petri dishes, the sanshool molecule caused fibers associated with Meissner receptors to fire, passing along a burst of electricity.
This experiment showed that in the real world, the Szechuans’ active ingredient seems to do the same thing, triggering activity in this set of receptors and causing them to pass along tactile stimuli towards the brain, thereby making our lips feel numb, as though they’ve been vibrated quickly. It’s a strange idea, but not unlike the feeling of spiciness: When you eat the pepper, you’re not actually being burned, but your heat-sensitive receptors are being activated, making it seem that way. In the same way, if you’re daring enough to bite into a Szechuan, the touch receptors in your lips and mouth will be stimulated, and as a result, they’ll go numb in a few minutes.
September 9, 2013
Mosquitoes are utterly, stupendously annoying. They can also carry diseases, such as malaria and West Nile virus. Some people—those with type O blood and robust colonies of bacteria on their skin, among other traits—are especially prone to getting bitten by them, and there’s growing evidence that many of the insects are evolving resistance to DEET, the main repellant we’ve relied upon for years.
All of which makes an ongoing project led by Ulrich Bernier, a chemist at the U.S. Department of Agriculture (USDA) Mosquito and Fly Research Unit, especially exciting. He’s taking a new approach to battling mosquitoes: Instead of developing chemicals that repel mosquitoes with unpleasant scents, he’s searching for substances that disrupt their ability to smell in the first place.
And as he announced today at the annual meeting of the American Chemical Society, his group has isolated a few chemicals that are naturally present on human skin in trace quantities and appear to inhibit mosquitoes’ capability to smell and locate humans. If one of these chemicals—mostly likely one called 1-methylpiperzine, which has been the most successful so far—holds up in future tests and can be produced synthetically on a bigger scale, wearing it could be a way of rendering yourself effectively invisible to mosquitoes.
Conventional insect repellants take advantage of the fact that the creatures rely mainly on their sense of smell to locate humans (they can smell us from as far as 100 feet away). DEET, which was developed during World War II, works mainly because it smells unpleasant to mosquitoes and other insects, so when you wear it, they prefer to fly elsewhere.
But DEET may be gradually growing less effective and has other drawbacks. Some people avoid using it because of evidence that it can, in rare cases, cause central nervous system problems—the EPA found (PDF) that it causes seizures in roughly one out 100 million users.
“We are exploring a different approach, with substances that impair the mosquito’s sense of smell,” Bernier explained in a press statement on his presentation. “If a mosquito can’t sense that dinner is ready, there will be no buzzing, no landing and no bite.”
To find these kinds of substances, he looked back at USDA research that started in the 1990s and was aimed at finding the natural compounds that attracted mosquitoes to human skin. As researchers isolated and analyzed 277 different substances that we naturally secrete in trace quantities, though, they found a handful that seemed to have the opposite effect, making mosquitoes less likely to come near.
Bernier and colleagues have since tested larger quantities of these chemicals to precisely measure their effect on the insects. In a lab, they built a cage divided in half by a screen. One half was filled with a swarm of mosquitoes; in the other half, they sprayed each of the chemicals to see how many of the mosquitoes would try to cross over.
Many of the compounds (most notably 1-methylpiperzine) seemed to inhibit the mosquitoes’ sense of smell, leaving them unable to detect other chemicals they normally find quite appealing. In trials, lactic acid—a substance that occurs in large amounts in sweat—pulled about 90 percent of the mosquitoes toward the screen, but when they mixed in a bit of 1-methylpiperzine, the mosquitoes stayed in place, seemingly unaware of the lactic acid nearby.
The group proceeded to tests with actual human skin and found the same results. “If you put your hand in a cage of mosquitoes where we have released some of these inhibitors, almost all just sit on the back wall and don’t even recognize that the hand is in there,” Bernier said.
He says that these inhibitors induce anosmia (the inability to detect odors) in the insects, making the secretor invisible. As it turns out, some people produce more of these inhibitors than others—which may account for part of why, for example, some people can emerge from an hour outside with bites on every inch of exposed skin, while a friend nearby can come back from the same place entirely unscathed.
The next step is figuring out how to incorporate these chemicals into commercial products. Bernier’s group isn’t the only one analyzing these natural inhibitors, and so far, others have run into a key problem: It’s hard to get the substances to stay on human skin instead of evaporating off, as they naturally do over time. But if they can figure that out and produce insect sprays that inhibit mosquitoes, rather than simply repelling them, all of us may someday be able to enjoy the same benefits as the lucky few who secrete these chemicals naturally.
September 5, 2013
Last month, James Hammond, a volcanologist at Imperial College London, traveled with Clive Oppenheimer and Kayla Iacovino of the University of Cambridge to install six seismometers on Mount Paektu—an active volcano on the border of China and North Korea that is famous for, among other things, being the alleged birthplace of Kim Jong-Il. Hammond has previously placed seismometers in locales as far-flung as Eritrea, Ethiopia and the Seychelles, but installing them in North Korea was a new challenge.
“When I first told people about the project, there was a bit of disbelief. People thinking, ‘you must be mad,’” Hammond says. “At times, I even thought myself that it wouldn’t work out.”
His team isn’t the only group of Western scientists to work in North Korea in recent years, but they are one of just a handful, and the first to install scientific equipment in the country’s natural environment. Their project began, Hammond explains, as a result of interest from North Korean researchers.
“The volcano has a pretty dramatic history,” he says. “About 1000 years ago, there was a huge eruption—it was among the top ten eruptions in recorded history, and it dropped ash more than 1000 miles away—so it’s got the potential to be very explosive.” Between 2002 and 2006, researchers on the volcano’s Chinese side observed increased seismic activity, along with slight swelling—both factors that could be harbingers of an upcoming explosion.
This increased unrest in the volcano led researchers in the Korean Earthquake Bureau to seek outside expertise in studying Paektu (sometimes spelled Baekdu, and called Changbai in China). They approached the Beijing-based Environmental Education Media Project (EEMP), which contacted Richard Stone, who was then the Asia editor of Science and had previously traveled in North Korea to document the country’s fight against tuberculosis. He, in turn, recruited Hammond and Oppenheimer to install equipment to help characterize the volcano’s activity and perhaps enable scientists to someday predict when it’ll erupt next.
After a weeklong information-gathering trip in 2011, they set about planning a research project, which Stone documents in a news article published today in Science. “No one had done much research into what drives the volcano, from a scientific point of view,” Hammond says.
That’s not a huge surprise, given both the international sanctions that prevent most people from visiting North Korea—let alone bring in scientific equipment—and the country’s ultra-secretive regime. Over the next few years, the group worked to cut through the bureaucratic red tape that prohibits bringing and using virtually all outside technology (including flash memory drives) into the country in preparation for their trip.
Then, last month, the trio returned and spent 16 days in the country. One of their primary goals was installing six seismometers in specially-built concrete huts on the mountain. The instruments—which precisely measure seismic movement in the ground—will eventually help Hammond and other scientists better understand the internal dynamics of Paektu.
“Essentially, whenever earthquakes occur anywhere in the world, we’ll record them in North Korea, and use the way that energy interacts with the ground underneath to build an image of what the inside of the volcano looks like,” Hammond says. “If we can understand that, that can guide us in thinking about the potential for future eruptions.”
Additionally, Oppenheimer and Iacovino gathered geologic samples, mostly pumice, from a variety of sites around the mountain. “From collecting the rocks, you can get an idea of what state the volcano was in just before it erupted,” says Hammond.
They stored some of their equipment in the houses of local villagers, most of whom had never seen a Westerner before. “They were incredibly nice, really friendly,” Hammond says. “We even got to eat lunch with them on occasion. Everyone seemed happy to be involved, and recognized this was something important that needed to be done.”
Similar to how the few Westerners who visit North Korea as tourists are required to take part in a state-organized sightseeing tour, Hammond’s team was taken to see a series of officially-sanctioned sites. “We went to Kim Jong-Il’s birthplace, which is actually on the flanks of the volcano,” Hammond says. “And we saw Arirang, which is really special—it’s like 100,000 people doing gymnastics, and at the back they have 10,000 people holding cards that they flip around to make pictures.” Some of the cards, in fact, showed Paektu, which is traditionally considered an ancestral origin of Korean culture, in addition to Kim Jong-Il’s birthplace.
Hammond counts the trip as a big success. Logistical hurdles obviously remain—for the foreseeable future, for example, the seismometers’ data will be downloaded and sent out every few months by the Korean Earthquake Bureau, instead of transmitted in real time. Still, he found that working with North Korean researchers was not much different from working with scientists anywhere.
“Communication can be hard, but I found that once we got into the science, there was something of a common language for all of us,” he says. “They want to understand that volcano—that’s what drives them, and that’s what drives us as well.”
September 4, 2013
Sometime in the next two or three months, something special will happen: the magnetic field that emanates from the Sun and extends throughout the entire solar system will reverse in polarity.
“It’s really hard to say exactly when it’s going to happen, but we know it’ll be in the next few months, for sure,” says Andrés Muñoz-Jaramillo, a researcher at the Harvard-Smithsonian Center for Astrophysics who studies the Sun’s magnetic cycle. “This happens every solar cycle, and it’s a very special day when it does.”
First, the basics: the Sun, like Earth, naturally generates a magnetic field. The massive solar magnetic field is a result of the flow of plasma currents within the Sun, which drive charged particles to move from one of the Sun’s poles to another.
Every 11 years, the strength of this magnetic field gradually decreases to zero, then emerges in the opposite direction, as part of the solar cycle. It’s as if, here on Earth, compasses pointed towards the Arctic as “North” for 11 years, then briefly wavered, then pointed towards Antarctica as “North” for the next 11 years (in fact, the Earth’s magnetic field does reverse as well, but it occurs with much less regularity, and takes a few hundred thousand years to do so).
Recent observations indicate that the next solar magnetic reversal is imminent—in August, NASA announced that it was three or four months away. The reversal, explains Muñoz-Jaramillo, won’t be a sudden, jarring event but a gradual, incremental one. “The strength of the polar field gradually gets very close to zero,” he says. “Some days, it’s slightly positive, and other days, it’s slightly negative. Then, eventually, you see that it’s consistently in one direction day after day, and you know the reversal has occurred.” His research group’s measurements of the magnetic field suggest this reversal is a few months away, but it’s impossible to say for sure which day it’ll occur.
Because the region that the solar magnetic field influences includes the entire solar system, the effects of the reversal will be felt widely. “The magnetic field flows out into interplanetary space, and it forms a bubble that encloses the solar system as it travels through the galaxy,” Muñoz-Jaramillo says.
One aspect of this bubble—formally known as the heliosphere—is an invisible electrically-charged surface called the current sheet pervades the solar system and resembles a twisted ballerina’s skirt, because the rotation of the Sun twists its far-flung magnetic field into a spiral. The reversal of the field will cause the sheet to become more rippled, which in turn will lead the Earth to pass through the sheet more frequently as it orbits the Sun.
Passing through more often could cause more turbulent space weather, potentially leading to disruptions in satellite transmissions and telecommunications equipment. On the other hand, the current sheet also blocks high-energy cosmic rays that arrive from other areas of the galaxy, so a more wavy sheet could provide satellites and astronauts in space more robust protection from harmful radiation.
Additionally, the magnetic field reversal coincides with the maximum of other solar activity, which means a greater number of sunspots, more powerful solar flares, brighter aurorae and more frequent coronal mass ejections. Most of these events have little or no effect on Earth, but an especially powerful flare or plasma ejection aimed in the right direction could knock out Earth-based telecommunications systems. At the same time, this solar cycle has been especially weak—NASA solar physicist David Hathaway called it “wimpy” in an interview with Scientific American—so there’s not a ton to worry about with this particular reversal.
For Muñoz-Jaramillo, who spends his days monitoring and analyzing the Sun’s magnetic activity, the reversal will also have personal significance. “Because the cycle is such a long process, in terms of a human’s lifetime, a solar scientist is going to see maybe four reversals in a career,” he says. “That makes every turning point special—and this is the first time I’m seeing one of these since I started studying solar physics.”
For more on the solar reversal, take a look at NASA’s video: