Archive for the ‘Physics’ Category

It’s the drag that helps the humble hagfish slime predators so quickly

January 17th, 2019

Courtesy of University of Wisconsin, Madison.

The homely hagfish might look like just your average bottom feeder, but they have a secret weapon: they can unleash a full liter of sticky slime in less than one second. That slime can clog the gills of a predatory shark, for instance, suffocating it. Scientists are unsure just how the hagfish (affectionately known as a "snot snake") accomplishes this feat, but a new paper in the Journal of the Royal Society Interface suggests that turbulent water flow (specifically, the drag such turbulence produces) is an essential factor.

Scientists have been studying hagfish slime for years because it's such an unusual material. It's not like mucus, which dries out and hardens over time; hagfish slime stays slimy, giving it the consistency of half-solidified gelatin. That's due to long, thread-like fibers in the slime, in addition to the proteins and sugars that make up mucin, the other major component. Those fibers coil up into "skeins" that resemble balls of yarn. When the hagfish lets loose with a shot of slime, the skeins uncoil and combine with the salt water, blowing up more than 10,000 times its original size.

Yet the precise mechanism for slime deployment is still poorly understood, according to co-author Gaurav Chaudhary of the University of Illinois, Urbana-Champaign. Recent research showed that sea water is essential to the formation of the slime, and that hagfish skeins can unravel spontaneously if ions in the sea water mixes the adhesives that hold the fibrous threads together in skeins. Chaudhary says that what's missing in this earlier work is taking the fast time scales into account. A 2014 study, for instance, showed that any spontaneous unraveling of the skeins would take several minutes—yet the hagfish deploys its slime in about 0.4 seconds.

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Posted in Biology, fluid dynamics, hagfish, Physics, science, slime and mucus | Comments (0)

Magnets: How do they stop working?

January 9th, 2019
Magnets: How do they stop working?

Enlarge (credit: Getty / Aurich)

Magnetism is slightly weird. Iron becomes magnetic because lots of electrons agree to align their individual magnetic moments. If you hit a thin layer of iron with a strong, very short pulse of light, however, the strength of its magnetic field will drop almost immediately.

How does this happen? Well, until now, we weren’t really sure. Thanks to the magic of X-ray lasers we now know why: sound waves carry angular momentum of electrons away.

Disappearing magnetism induces a headache

The problem with disappearing magnetism is related to something called the conservation of angular momentum. Think of the Earth, a gigantic spheroid spinning in space: its spin is angular momentum, which is always conserved. If the Earth loses angular momentum, something else must gain angular momentum to compensate.

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Posted in how do they work, magnetism, magnets, optics, Physics, pump probe spectroscopy, science, X-ray crystallography | Comments (0)

Quantum physicists in the 1920s helped found field of quantum biology

January 6th, 2019
There is some evidence that quantum effects might play a role in the process of photosynthesis.

Enlarge / There is some evidence that quantum effects might play a role in the process of photosynthesis. (credit: Mikel Bilbao/VW Pic/Getty Images)

In 1944, quantum physicist Erwin Schroedinger wrote a short book called What is Life: The Physical Aspect of the Living Cell, exploring how the relatively new field of quantum mechanics might play a role in biological processes. It is considered by many to be one of the earliest forays into "quantum biology," a rarefied field that attempts to apply quantum principles to living systems. But the field actually dates back to the earliest days of quantum mechanics in the 1920s, according to a recent paper published in the Proceedings of the Royal Society A.

"Quantum biology is wrongly regarded as a very new scientific discipline, when it actually began before the Second World War," said co-author Johnjoe McFadden, a microbiologist at the University of Surrey and co-director of the Centre for Quantum Biology there, with his Surrey colleague and co-author Jim Al-Khalili. "Back then, a few quantum physicists tried to understand what was special about life itself and whether quantum mechanics might shed any light on the matter."

Frankly, quantum biology has suffered from a lack of credibility until the last decade or so, when a number of intriguing studies suggested that there might be something to the idea after all. For instance, there is growing evidence that photosynthesis relies on quantum effects to help plants turn sunlight into fuel.  Migratory birds might have an internal "quantum compass" that helps them sense Earth's magnetic fields as a means of navigation. Quantum effects might play a role in the human sense of smell, helping us distinguish between different scents.

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Posted in 12 days of Christmas, History, history of science, Physics, quantum biology, quantum mechanics, science | Comments (0)

Let’s kick off 2019 by pondering the dismal future prospects for humanity

January 1st, 2019
Astronomer Royal Lord Martin Rees speaks at Stephen Hawking's memorial service at Westminster Abbey on June 15, 2018 in London, England.

Enlarge / Astronomer Royal Lord Martin Rees speaks at Stephen Hawking's memorial service at Westminster Abbey on June 15, 2018 in London, England. (credit: Ben Stansall/WPA Pool /Getty Images)

Human kind has long harnessed the fruits of scientific research into revolutionary technologies, with a few tradeoffs along the way. The benefits have generally outweighed the risks. But we are now in an era when the choices we make over the next two decades really could determine the fate of our life here on Earth—a critical tipping point for the human race, if you will. That's the message from Britain's Astronomer Royal, Lord Martin Rees, in his recent book, On the Future: Prospects for Humanity, published by Princeton University Press.

While the primary focus of his life has been science, Rees has long been engaged in politics, starting with anti-nuclear weapons campaigns when he was still a student. But over the last 20 years that engagement has widened, and his influence has grown. He served as president of the Royal Society, and wields real political influence these days in the British Parliament's House of Lords. (Technically, he is Lord Martin Rees, Baron of Ludlow. But he'll probably ask you to call him Martin, because he's chill like that.) "That made me not just a scientist, but an anxious member of the human race," he said.

It's a thoughtful anxiety that informs every page of On the Future, as self-proclaimed "techno-optimist" Rees explores the many ways in which humanity's fate is tightly linked to continued progress in science and technology—and how we choose to wield that knowledge (or not). Ars sat down with Rees in September in London to learn more about his thoughts on our future.

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Posted in books, Gaming & Culture, Physics, science, Tech | Comments (0)

The secret to champagne’s universal appeal is the physics of bubbles

December 31st, 2018
Making champagne is fairly simple, but the physics behind its bubbly delights is surprisingly complex.

Enlarge / Making champagne is fairly simple, but the physics behind its bubbly delights is surprisingly complex. (credit: Jon Bucklel/EMPICS/PA/Getty Images)

It's New Year's Eve, and revelers around the globe will be breaking out the bubbly in massive quantities to usher in 2019. Why do humans love champagne and other fizzy beverages so much, when most animals turn up their noses when it's offered? Roberto Zenit, a physicist at Mexico's National Autonomous University of Mexico, and Javier Rodriguez-Rodriguez of the Carlos III University of Madrid in Spain, posit in the November issue of Physics Today that carbonation triggers the same pain receptors in our deep brains that are activated when we eat spicy food.

"This bubbly sensation you have when you drink a carbonated beverage basically triggers similar taste buds," said Zenit. "Champagne is just wine; what makes it special is the carbonation. It's a sad day when you drink flat champagne."

He and Rodriguez-Rodriguez study the behavior of various fluids (including paints), and carbonation is a particularly fascinating topic within that discipline. When the bubbles in champagne burst, they produce droplets that release aromatic compounds believed to enhance the flavor further. (When bubbles in a carbonated beverage like beer don't burst, the result is a nice thick head of foam.) And here's another interesting fact: the bubbles in champagne "ring" at specific resonant frequencies, depending on their size. So it's possible to "hear" the size distribution of bubbles as they rise to the surface in a glass of champagne.

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Posted in 12 days of Christmas, bubbles, champagne, fluid dynamics, foam, Physics, science, Wine | Comments (0)

Caltech scientists use DNA tiles to play tic-tac-toe at the nanoscale

December 29th, 2018

Courtesy Qian Lab/Caltech.

Scientists at Caltech have created the world's smallest game board for playing tic-tac-toe out of DNA strands. What's more, it's possible to swap hundreds of DNA strands in and out at once to reconfigure the nanostructure at will, making it possible in principle to build complicated nanomachines in different custom patterns. The scientists described their work in a December paper in Nature Communications.

Back in 2006, Caltech bioengineer Paul Rothemund figured out how to fold a long strand of DNA into simple shapes, demonstrating this "DNA origami" technique by producing a smiley face. All you need is a long strand of DNA, plus several shorter strands ("staples"). Combine them in a test tube, and the shorter strands pull various parts of the long strand together so that it folds over into any number of simple shapes. DNA origami was a huge advance for nanotechnology, but to really achieve its full potential, scientists needed to be able to create larger and more complex structures.

Last year, Rothemund's Caltech colleague Lulu Qian introduced a cheap means of getting DNA origami to assemble itself into large arrays. The best part: you could create custom patterns. The array was a bit like a blank canvas, and Qian demonstrated the power of her technique (dubbed "fractal assembly") by creating the world's smallest version of Leonardo da Vinci's "Mona Lisa," visible only with atomic force microscopy.

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Posted in 12 days of Christmas, DNA origami, nanotechnology, Physics, science, tic-tac-toe | Comments (0)

Science says your cat’s tongue is ideally suited for grooming fur

December 28th, 2018

That sandpaper-like texture of your cat's tiny pink tongue is what makes it ideal for grooming fur. The secret: hundreds of hollow, rigid spines lining the surface of the tongue, according to a recent paper published in the Proceedings of the National Academy of Sciences.

This is just the latest bit of colorful research from David Hu, who runs a biolocomotion laboratory at the Georgia Institute of Technology studying how various creatures move. He is perhaps best known for his work with fire ants, but his lab also studies water striders, snakes, various climbing insects, mosquitos, and, um, animal bodily functions like urine. (One of his students, Patricia Yang, recently made headlines with her insights into why wombats produce cubed poo.)

It was another of Hu's graduate students, Alexis Noel, who came up with the idea for the cat tongue experiments. She was watching her cat try to "groom" a fluffy microfiber blanket one night and noticed its tongue kept getting snagged in the fibers. She found very little prior research on the biomechanics of cat grooming, and concluded the topic was ripe for experimentation.

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Posted in biolocomotion, biomimicry, biophysics, cat science, Physics, science | Comments (0)

Study: modern masters like Jackson Pollock were “intuitive physicists”

December 26th, 2018
<em>Collective Suicide</em> (1936), by Mexican muralist David A. Siqueiros, is an example of the "accidental painting" technique developed by the artist.

Enlarge / Collective Suicide (1936), by Mexican muralist David A. Siqueiros, is an example of the "accidental painting" technique developed by the artist. (credit: A. Aviram/MOMA, New York, via R. Zenit)

There's rarely time to write about every cool science story that comes our way. So this year, we're running a special Twelve Days of Christmas series of posts, highlighting one story that fell through the cracks each day, from December 25 through January 5. Today: the fluid dynamics of modern painting techniques.

In the 1930s, a small group of New York City artists began experimenting with novel painting techniques and materials, including Mexican muralist David A. Siqueiros and Jackson Pollock. For the last few years, a team of Mexican physicists has been studying the physics of fluids at work in those techniques, concluding that the artists were "intuitive physicists," using science to create timeless art.

"One of the things I have come to realize is that painters have a deep understanding of fluid mechanics as they manipulate their materials," said Roberto Zenit, a physicist at the National Autonomous University of Mexico who is leading the research. "This is what fluid mechanicians do. The objective is different, but the manipulation of these materials that flow is the same. So it is not a surprise that fluid mechanics has a lot to say about how artists paint."

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Posted in 12 days of Christmas, art, fluid dynamics, Gaming & Culture, Jackson Pollock, painting, painting techniques, Physics, science | Comments (0)

Study brings us one step closer to solving 1994 thallium poisoning case

December 25th, 2018
The 1861 notebook of Sir William Crookes, containing all his data on thallium samples.

Enlarge / The 1861 notebook of Sir William Crookes, containing all his data on thallium samples. (credit: SSPL/Getty Images)

There's rarely time to write about every cool science story that comes our way. So this year, we're running a special Twelve Days of Christmas series of posts, highlighting one story that fell through the cracks each day, from December 25 through January 5. First up: a tale of attempted murder and the geologist who hopes he can help solve the case.

A new trace analysis of the victim's hair sheds fresh light on a famous unsolved cold case by establishing a timeline for the thallium poisoning of Chinese college student Zhu Ling in 1994. Published in October in the journal Forensic Science International, the work could one day lead to catching the culprit, and could help solve future heavy-metal poisonings.

Zhu Ling was a sophomore majoring in physical chemistry at Tsinghua University in Beijing, China, when she mysteriously began losing hair, with accompanying stomach pain and muscle paralysis, sinking into a coma four months later. Doctors were initially baffled, but friends posted her symptoms to a Usenet group, drawing attention to Zhu Ling's plight—likely the first telemedicine trial. Physicians around the world agreed the likely cause was thallium poisoning (a toxic heavy metal sometimes used in rat poison), and her doctors treated her with the commercial dye Prussian blue, the most common antidote.

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Posted in 12 days of Christmas, chemistry, cold cases, forensics, Physics, poison, science, thallium poisoning, Zhu Ling | Comments (0)

Pulsars could convert dark matter into something we could see

December 20th, 2018
Image of a blue-white sphere, representing the star.

Enlarge / Neutron stars may produce radio signals when interacting with dark matter. (credit: NASA's Goddard Space Flight Center)

Dark matter is proving elusive. Apart from the gravitational evidence, which is strong, all the other potential indications of it haven't held up to scrutiny. One issue may be that we simply don’t know how to look for it, so detectors are based on informed guesses about how we might expect to find dark matter. One approach to these searches is to look for places in the Universe that might generate a dark matter signal.

This is exactly the approach taken by some physicists in a recent Physical Review Letter. In their case, they suggest that dark matter might produce a weak, but quite narrow, bandwidth radio signal from neutron stars.

This team is not the first to propose looking for dark matter signatures in the Universe. Excess gamma rays from the center of our own galaxy were, for a while, thought to be a possible signature of dark matter. But, as with all these proposals, the work focuses on a particular version of dark matter.

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Posted in astrophysics, axions, Dark Matter, neutron stars, particle physics, Physics, pulsars, science | Comments (0)