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February 19, 2011

One small leap for a flea represents one giant biomechanical feat

Excerpts from Carl Zimmer's February 10, 2011 New York Times Science section story about what's behind the flea's amazing jumping ability follow.

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When fleas jump, it is no ordinary leap. The insects can shoot as high as 38 times their body length, about three inches. And the acceleration is so intense that fleas have to withstand 100 Gs, or 100 times the force of gravity. “You and I pass out if we experience five Gs,” said Malcolm Burrows, an expert on insect jumping at the University of Cambridge.

Dr. Burrows and his Cambridge colleague Gregory Sutton obtained the fleas... to try to answer a question that had vexed naturalists for centuries: how fleas manage their spectacular jumps. In a paper published Thursday in The Journal of Experimental Biology, they report that the insects turn themselves into catapults, storing up energy that they release as they push off the ground with what passes, in fleas, for feet.

In the 1960s, Eric Lucey, a biologist at the University of Edinburgh, filmed the insect with what was then the most advanced high-speed camera, at a thousand frames a second. Dr. Lucey showed the film to Henry Bennet-Clark, an expert on insects who was also at the University of Edinburgh at the time. Dr. Bennet-Clark realized that the fleas were generating a hundred times more power than their muscles could actually provide.

He noticed that just before leaping, the flea bends the closest segment of its hindmost legs toward the body for about a tenth of a second. When Dr. Bennet-Clark dissected fleas, he discovered that their leg muscles were connected to pads of stretchy protein called resilin. In 1967, Dr. Bennet-Clark and Dr. Lucey proposed that the fleas stored energy in springlike tissues, which they then released.

In 1972, another British naturalist, Miriam Rothschild, published a similar study and came to much the same conclusion. But Ms. Rothschild and Dr. Bennet-Clark disagreed about how the force from the spring actually lifted the flea off the ground. Ms. Rothschild argued that fleas planted a kneelike joint called the trochanter to jump. Dr. Bennet-Clark, on the other hand, thought the fleas pushed off from the footlike segments at the end of the legs, called the tarsi.

Unfortunately, their films were too blurry to determine who was right. In 2009, Dr. Burrows reread the original papers and decided it was time to attack the question anew, using 21st-century technology. Over the course of a week, Dr. Sutton filmed 51 jumps, which were then analyzed on a computer.

The scientists noticed that the fleas sometimes jumped with trochanters and tarsi both planted on the Styrofoam. But sometimes only the tarsi made contact. “These two jumps appear to be the same,” said Dr. Sutton.

It seemed that, as Dr. Bennet-Clark had argued, only the tarsi mattered. And Dr. Sutton and Dr. Burrows got the same result when they developed mathematical models of the forces produced in flea jumps. The actual jumps matched Dr. Bennet-Clark’s hypothesis. So it seems that fleas leap by channeling their stored energy down to the tips of their legs.

But Dr. Sutton acknowledged that some of the most important secrets of fleas remain to be worked out. No one knows how fleas lock their springs in place and then release them, for instance. And no one knows how fleas snap their two rear hindmost legs at the same time. If they weren’t so precise, the insects would spin wildly off course.

“If you’re half a millisecond off, you’re done, and we have no idea how they do it,” Dr. Sutton said. “It’s one step at a time — we’re just going have to take on the next problem and solve that.”

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Here's a video that accompanied the Times article.

Below, the abstract of the paper cited above.

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Biomechanics of jumping in the flea

It has long been established that fleas jump by storing and releasing energy in a cuticular spring, but it is not known how forces from that spring are transmitted to the ground. One hypothesis is that the recoil of the spring pushes the trochanter onto the ground, thereby generating the jump. A second hypothesis is that the recoil of the spring acts through a lever system to push the tibia and tarsus onto the ground. To decide which of these two hypotheses is correct, we built a kinetic model to simulate the different possible velocities and accelerations produced by each proposed process and compared those simulations with the kinematics measured from high-speed images of natural jumping. The in vivo velocity and acceleration kinematics are consistent with the model that directs ground forces through the tibia and tarsus. Moreover, in some natural jumps there was no contact between the trochanter and the ground. There were also no observable differences between the kinematics of jumps that began with the trochanter on the ground and jumps that did not. Scanning electron microscopy showed that the tibia and tarsus have spines appropriate for applying forces to the ground, whereas no such structures were seen on the trochanter. Based on these observations, we discount the hypothesis that fleas use their trochantera to apply forces to the ground and conclude that fleas jump by applying forces to the ground through the end of the tibiae.

February 19, 2011 at 05:01 PM | Permalink | Comments (0) | TrackBack

Nikon Limited-Edition Set of Three f/1.4 Lenses

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From Michael Zhang's post on PetaPixel: "A special limited edition set of three Nikon f/1.4 lenses [above] is being sold in certain European countries (currently Belgium and Sweden). Limited to only 100 sets, each set includes a Nikkor AF-S 24mm, 35mm and 85mm."

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"What's strange is that unlike what you typically see with limited-edition gear, these sets are actually selling for considerably less than if you purchased each lens separately."

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"In Belgium the set is priced at €4,899, or about €1,000 (~$1,370) less than the sum of the individual lens prices on Amazon. No word on whether we’ll ever see this kind of thing in the US."

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[via Nikon Rumors]

February 19, 2011 at 03:31 PM | Permalink | Comments (3) | TrackBack

"The Burning Plain" — not time travel, exactly...

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This excellent 2009 film gathers power with its revelations as it moves forward and backward in time.

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Directed by Guillermo Arriaga (screenwriter for "21 Grams," "Amores Perros," and "Babel"), it features powerful performances from Jennifer Lawrence (before her Academy Award nomination-winning performance in "Winter's Bone"), Kim Basinger, and Charlize Theron, who is superb as a woman tormented by a horrible secret in her past, attempting without success to free herself from its hold on her.

France

I'd never even heard of this movie until after watching "Winter's Bone" on Apple TV or Netflix — I can't remember which — and seeing it among the "People who liked this movie also liked" titles.

I'm thinking it went straight to video, like so many wonderful films which for one reason or another never make it into the movie listings or theaters.

Whenever I happen on a film in this fashion — or a book, for that matter — I wonder what the denominator is, i.e., how many hundreds or thousands of other superb works lie buried in obscurity.

To tell you more about this film than I have would potentially give away a mystery that's better seen than read about.

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The film's on Netflix and Apple TV (in English) for those with such access.

February 19, 2011 at 02:01 PM | Permalink | Comments (2) | TrackBack

$100 tablet is here

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Wrote Warren Buckleitner in a February 15, 2011 New York Times Gadgetwise blog post about the new Leapfrog LeapPad Explorer (above), "It comes with a 5" color LCD mono-touch screen, microphone, headphone jack, SD card slot, USB port, game controls, stylus and camera."

"[It's] powered by four AA batteries, with built-in accelerometers [that enable] such grown up capabilities as automatic screen rotation and a new breed of motion-sensing games."

Don't get your baggies in a twist trying to get one: according to Buckleitner the device was previewed at this past week's Toy Fair in New York City and is scheduled to be in stores later this year.

I'll take one whenever.

February 19, 2011 at 01:01 PM | Permalink | Comments (2) | TrackBack

BehindTheMedspeak: "We'd show an Alzheimer's survivor here, if there were one"

Alzheimer's

Powerful ad from the Alzheimer's Association which ran in the New York Times a few months ago.

 

February 19, 2011 at 12:01 PM | Permalink | Comments (1) | TrackBack

World's best miniature screwdriver set is fast, cheap & puts you in control

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When I featured these screwdrivers back in November of 2004 they cost $4.99 at Amazon.

Now they're $6.06.

Cheap at three times the price.

Here's the November 23, 2004 post from the past.

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World's best miniature screwdriver set

Last week I went to Wal-Mart for a few odds and ends, among them a small — real small — Phillips screwdriver.

Every now and then you need one, most often to remove the battery cover on poorly designed devices that require an extraneous tool.

I came across this smartly packaged set and couldn't believe the price: $5.88.

For six screwdrivers: 0-point and 1-point Phillips and 1.4, 2.0, 2.4, and 3.0 mm slotted.

They have nicely-shaped ergonomic shafts and rubber-cushioned grips for traction and maximum power.

Bonus: the clear-plastic-covered container is cleverly designed to let you slide the tool tray out.

But wait, there's more.

The top of the container pivots and tucks back under the tray.

A bookofjoe Design Award 2004 winner.

Even better: Amazon sells it for $4.99.

Just put "Stanley 66-052" in the Google search box and you're there.

I bought three sets: one for my car, one for my workshop, and one for my office.

Superb stocking stuffer for your techie friends.

February 19, 2011 at 11:01 AM | Permalink | Comments (5) | TrackBack

3D Photo App turns snapshots into Picasso-esque cubist portraits

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99 cents

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at the App store.

[via Bob Tedeschi and the New York Times]

February 19, 2011 at 10:01 AM | Permalink | Comments (0) | TrackBack

Chloe ring

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Hammered 7/8" diameter disc atop a 1/8"-wide band; 18-k gold-plated or sterling silver.

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$95.

 

February 19, 2011 at 09:01 AM | Permalink | Comments (0) | TrackBack

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