Tag: biomechanics

Mosquitoes' Clever Little Trick to Survive Collisions With Raindrops: Being Little

By Sophie Bushwick | June 6, 2012 11:23 am

What’s the News:

For a mosquito, venturing out during a heavy rainstorm means risking collisions with droplets 50 times its weight—but this doesn’t deter it from living in humid, rainy climes. In fact, researchers have discovered that the mosquito’s low mass, along with a sturdy exoskeleton, helps it weather (so to speak) the impacts of raindrops without much trouble.

How the Heck:

  • The researchers confined three-millimeter-long Anopheles mosquitoes in a “drop impact chamber,” an acrylic cage five centimeters wide and twenty centimeters tall. To keep the mosquitoes confined and airborne, a mesh top blocked the insects’ exit while still admitting water droplets, and the cage vibrated once every few seconds to prevent the bugs from landing on the walls.
  • A high-speed camera filmed the collisions as the researchers either pumped jets of water into the chamber with the speed of a falling raindrop, or released slower droplets to let the camera get a better view. Although a direct body hit could drag the bug down in a five- to twenty-body-length fall before the mosquito escaped the water, droplets tended to hit the mosquitoes’ long wings and legs instead, rolling off their water-repellant bodies and only slightly skewing their flights.

 

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CATEGORIZED UNDER: Environment, Top Posts

The Secret of the Flea’s Famous Jump

By Patrick Morgan | February 10, 2011 2:40 pm

Fleas are remarkable jumpers: They can travel 200 times their own body length in a single leap, and can withstand acceleration forces of 100 Gs. But exactly how do they make such incredible jumps? Although we’ve known for decades that fleas store energy in a springy protein called resilin before they launch into the air, it’s remained a mystery whether they use the flea-equivalent of feet (called tarsi) or knees (called trochantera) to transmit that energy to the ground. But with 21st-century high-speed cameras, researchers have now put the debate to rest: the answer is in the feet.

Now, the first task in experimenting with fleas is to find fleas. Luckily, the warmhearted individuals at England’s St. Tiggywinkles Wildlife Hospital Trust have flea-ridden hedgehogs just waiting to lose a few bugs–and so that wonderfully named hospital donated a few fleas to a good cause.

The study, published in the Journal of Experimental Biology,  included both video and flea-leap simulations. But the researchers–led by Gregory Sutton at the University of Cambridge–made their first insights using the same methods that were used decades ago:

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CATEGORIZED UNDER: Living World

Study: Humans Could Outrun Neanderthals

By Andrew Moseman | February 4, 2011 2:59 pm

Neanderthals: They weren’t really into distance running. According to research by David Raichlen in the Journal of Human Evolution, they were more the power walking type: The shape of a Homo sapiens heel compared to that of a Neanderthal would have allowed our ancestors to be much more efficient runners over long distances.

Raichlen stated with living humans, studying them as they ran on treadmills.

By looking at MRI scans of their ankles, he found that the distance between a point on the heel bone just below the ankle bone, and the back of the heel bone where the Achilles tendon attaches, was proportional to the runner’s efficiency. The shorter this distance, the greater is the force applied to stretch the tendon – and the more energy is stored in it. This means that people with shorter distances are more efficient runners, using less energy to run for longer. [New Scientist]

With this knowledge, Raichlen and colleagues looked at the remains of Neanderthals as well as humans of the same era. The difference, he says, was distinct.

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CATEGORIZED UNDER: Human Origins

How the Seahorse Got Its Curvaceous Shape

By Patrick Morgan | January 26, 2011 5:31 pm

If you’ve ever wondered why the seahorse has its elegantly curved body (aside from luring snorkelers into the water), wonder no more: it helps them hunt.

Researchers at the University of Antwerp in Belgium, led by biomechanicist Sam Van Wassenbergh, analyzed video footage of seahorses on the hunt and used mathematical models to come to the conclusion that a seahorse’s curvy neck lets it strike at more distant prey.

“They rotate their heads upward to bring their mouth close to the prey [passing above],” explained Dr Wassenbergh…. The creatures’ curved bodies mean that when they do this, their mouths also moved forward, helping to bring passing small crustaceans within sucking distance of their snouts. [BBC News]

He even has an evolutionary theory to back up his observations.

“My theory is that you have this ancestral pipefish-like fish and they evolved a more cryptic lifestyle,” said Dr Wassenbergh. [BBC News]

Unlike the seahorse, the related pipefish has a straight body and swims while attacking its prey. Seahorses, on the other hand, tend to hide out and wait for the prey to come to them. And according to this study, published in the journal Nature Communications, a longer striking distance is a big advantage for a couch-potato creature.

“Once this shift in foraging behavior is made, natural selection will favor animals that can increase the strike distance, which according to our study puts a selective pressure to increase the angle between head and trunk and to become what we now know as sea horses,” [said] researcher Sam Van Wassenbergh. [LiveScience]

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DISCOVER: Your Inner Fish

Image: flickr / oscar alexander

CATEGORIZED UNDER: Living World

Video Reveals How a Flying Snake Slithers Through the Air

By Jennifer Welsh | November 23, 2010 1:20 pm

gliding-snakeThey may not be as adorable as sugar gliders, but they’re just as accomplished: Five species of Asian snake have also developed the ability to “fly” or glide from tree to tree, flattening out their bodies to travel up to 80 feet.

Researcher Jake Socha and his team studied the glide of Chrysopelea paradisi snake and took videos of the snakes in flight, which Socha presented at an ongoing meeting of the American Physical Society. He found that before a snake takes the leap it curls its body into a J-shape, and then launches itself from the tree branch. In the air, it flattens its body and undulates, as if slithering through the air.

The snake differs from other gliding species, like gliding lizards and flying squirrels, in that it doesn’t have specialized body parts that act as wings.

“The whole snake itself is just one long wing,” Socha said. “That wing is constantly reconfiguring, it’s constantly reforming and contorting.” [LiveScience]

Hit the jump for a video of the snake in action.
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CATEGORIZED UNDER: Living World

Pterosaurs May Have "Pole Vaulted" to Take Flight

By Andrew Moseman | November 15, 2010 12:21 pm

PterosaurWittonThe enormous wings of pterosaurs testify to the idea that these giant reptiles, which lived at the same time as dinosaurs, would have been masters of flight. But there’s one thing that nags paleontologists: pterosaur takeoff. Just how does a giraffe-sized creature get off the ground?

Not the way birds do, say Mark Witton and Mike Habib, biomechanists who for years have been modeling pterosaur flight, and have a new study forthcoming in PLoS One.

Birds rely on the strength of their legs to leap into the air or run to gain speed for take-off. Pterosaurs walked on all four limbs, and Habib has developed an anatomical model to explore how they might have launched themselves using their small hind limbs and larger “arms” which formed part of their wings. The animal could have launched itself like a pole vaulter, pushing forward with its hind limbs and using its powerful arms to thrust it high enough into the air to stretch its wings and fly away. [New Scientist]

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CATEGORIZED UNDER: Living World

Each Time Your Cat Takes a Sip, It's a Marvel of Physics

By Eliza Strickland | November 11, 2010 3:54 pm

From Ed Yong:

Cats have been our companions for almost 10,000 years. They have been worshipped by Egyptians, killed (or not) by physicists, and captioned by geeks. And in all that time, no one has quite appreciated how impressively they drink. Using high-speed videos, Pedro Reis and Roman Stocker from the Massachusetts Institute of Technology has shown that lapping cats are masters of physics. Every flick of their tongues finely balances a pair of forces, at high speed, to draw a column of water into their thirsty jaws.

Read the rest of the post at Not Exactly Rocket Science, where Yong explains that each sip is a tug-of-war between inertia and gravity. Here’s a little of that high-speed video:

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CATEGORIZED UNDER: Living World, Physics & Math

Ostriches Are Endurance Runners, Thanks to the Spring in Their Steps

By Andrew Moseman | October 28, 2010 12:35 pm

OstrichNo, 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]

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CATEGORIZED UNDER: Living World

Running by the Books: Math for the Marathoner

By Jennifer Welsh | October 22, 2010 2:39 pm

marathonerAbout two-fifths of marathon runners “hit the wall” on the big day. That means they completely deplete their body’s stash of readily available energy, which makes them feel wiped out and severely limits their running pace; it sometimes forces people out of the run completely.

Marathoner and biomedical engineer Benjamin Rapoport has been physically and mentally struggling with this phenomenon for years, and had the bright idea to turn it into a research project. He published a mathematical theory in the journal PLoS Computational Biology describing how and why runners hit the wall–and how they can avoid it.

By taking into account the energy it takes to run a marathon, the body’s energy storage capacity and the runner’s power, the researchers were able to accurately calculate how many energy-rich carbohydrates a runner needed to eat before race day and how fast to run to complete all 26.2 miles (42 kilometers). [LiveScience]

Rapoport’s studies of marathoners were prompted by his desire to run in the Boston Marathon in 2005, and his teacher’s desire for him to be in class. In return for missing class, Rapoport was tasked with giving a class lecture on the physiology of the marathoner. That same year, Rapoport himself hit the wall while running the New York Marathon.

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CATEGORIZED UNDER: Health & Medicine, Physics & Math

Proved By Science: Wearing High Heels Can Damage Leg Tendons

By Joseph Calamia | July 16, 2010 10:24 am

heelHigh heel wearers likely guessed it: Walking around on your tiptoes isn’t great for your calf muscles. Researchers looking at leg sonograms of women who frequently wear 2-inch or higher heels found that these women had calf muscle fibers that were an average of 13 percent shorter than their flat-wearing counterparts.

The small study, published yesterday in the Journal of Experimental Biology, has given some credence to complaints of lasting pain even after the pumps come off.

Anecdotally it has long been said that regularly wearing high heels shortens the calf muscle. Study leader Professor Marco Narici, from Manchester Metropolitan University, said in the 1950s secretaries who wore high heels complained that they struggled to walk flat-footed when they took their shoes off. [BBC]

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CATEGORIZED UNDER: Health & Medicine
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