FYFD

Category: Research

  • Holding Steady

    Holding Steady

    Before a mammalian cell divides, the spindle — a protein structure — divides the cell’s genetic material in two. As it does, the cytoplasm inside the cell forms a toroidal flow (below, left). Researchers wondered how the spindle manages to stay in place with this flow; the spindle sits just where the flow diverges, a spot that seems ripe for unstable shifts in position. But, contrary to expectations, their analysis showed that — although a smaller spindle would be unstable in that spot — the protein spindle is large enough that its size distorts the cell’s flow and creates a pressure that moves it back into place if it shifts. (Image credit: top – ColiN00B, illustration – W. Liao and E. Lauga; research credit: W. Liao and E. Lauga; via APS Physics)

    Left: illustration of the toroidal flow near the spindle (purple) in a cell. Right: schematic of flow near the spindle's fixed point.
    Left: illustration of the toroidal flow near the spindle (purple) in a cell. Right: schematic of flow near the spindle’s fixed point.
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  • Tracking Ice Floes

    Tracking Ice Floes

    To understand why some sea ice melts and other sea ice survives, researchers tracked millions of floes over decades. This herculean undertaking combined satellite data, weather reports, and buoy data into a database covering nearly 20 years of data. With all of that information, the team could track the changes to specific pieces of ice rather than lumping data into overall averages.

    They found that an ice floe’s fate depended strongly on the route it took: ice that slipped from its starting region into warmer, more southern regions was likely to melt. They also saw region-specific effects, like that thick sea ice was more likely to melt in the East Siberian Sea’s summer, possibly due to warmer currents. The comprehensive, fine-grained analyses possible with this ice-tracking technique offer a chance to understand why some Arctic regions are more vulnerable to warming than others. (Image credit: D. Cantelli; research credit: P. Taylor et al.; via Eos)

  • Dry Plants Warn Away Moths

    Dry Plants Warn Away Moths

    Drought-stressed plants let out ultrasonic distress cries that moths use to avoid plants that can’t support their offspring. In ideal circumstances, a plant is constantly pulling water up from the soil, through its roots, and out its leaves through transpiration. This creates a strong negative pressure — varying from 2 to 17 atmospheres’ worth — inside the plant’s xylem. If there’s not enough water to keep the plant’s inner flow going, cavitation occurs — essentially a tiny vacuum bubble opens in the xylem. That cavitation isn’t silent; it creates a click at ultrasonic frequencies above human hearing. But just because we don’t hear it doesn’t mean that sound goes unheard.

    In fact, recent research suggests that, not only do moths hear the plant’s cavitation cries, female moths will avoid laying eggs on a healthy plant that sounds like it’s cavitating. Evolutionarily, this makes sense. Hatchlings rely on their birth plant for food and habitat; if an adult moth picks a dying, drought-stressed plant, its offspring won’t survive. It pays to be sensitive to the plant’s signs of distress. (Image credit: Khalil; research credit: R. Seltzer et al.; via NYTimes)

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  • Active Cheerios Self-Propel

    Active Cheerios Self-Propel

    The interface where air and water meet is a special world of surface-tension-mediated interactions. Cereal lovers are well-aware of the Cheerios effect, where lightweight O’s tend to attract one another, courtesy of their matching menisci. And those who have played with soap boats know that a gradient in surface tension causes flow. Today’s pre-print study combines these two effects to create self-propelling particle assemblies.

    The team 3D-printed particles that are a couple centimeters across and resemble a cone stuck atop a hockey puck. The lower disk area is hollow, trapping air to make the particle buoyant. The cone serves as a fuel tank, which the researchers filled with ethanol (and, in some cases, some fluorescent dye to visualize the flow). Like soap, ethanol’s lower surface tension disrupts the water’s interface and triggers a flow that pulls the particle toward areas with higher surface tension. But, unlike soap, ethanol evaporates, effectively restoring the interface’s higher surface tension over time.

    With multiple self-propelling particles on the interface, the researchers observed a rich series of interactions. Without their fuel, the Cheerios effect attracted particles to each other. But with ethanol slowly leaking out their sides, the particles repelled each other. As the ethanol ran out and evaporated, the particles would again attract. By tweaking the number and position of fuel outlets on a particle, the researchers found they could tune the particles’ attractions and motility. In addition to helping robots move and organize, their findings also make for a fun educational project. There’s a lot of room for students to play with different 3D-printed designs and fuel concentrations to make their own self-propelled particles. (Research and image credit: J. Wilt et al.; via Ars Technica)

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  • Inside the Squirting Cucumber

    Inside the Squirting Cucumber

    Though only 5 cm long, the squirting cucumber can spray its seeds up to 10 meters away. The little fruit does so through a clever combination of preparation and ballistic maneuvers. Ahead of launch, the plant actually moves water from the fruit into the stem; this reorients the cucumber so that its long axis sits close to 45 degrees. It also makes the stem thicker and stiffer.

    This high-speed video shows the explosive release of the squirting cucumber's seeds.
    This high-speed video shows the explosive release of the squirting cucumber’s seeds.

    When the burst happens, fruit spews out a jet of mucus that propels the seeds at up to 20 m/s. The initial seeds move the fastest — thanks to the fruit’s high-pressure reservoir — and fly the furthest. As the pressure drops, the jet slows and the fruit’s rotation sends the seeds higher, causing them to land closer to the original plant. With multiple fruits in different orientations, a single plant can spread its seeds in a fairly even ring around itself. (Research and image credit: F. Box et al.; via Gizmodo)

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  • A Seismic Warning for the Tongan Eruption

    A Seismic Warning for the Tongan Eruption

    In mid-January 2022, the Hunga Tonga-Hunga Ha’apai (HTHH) volcano had one of the most massive eruptions ever recorded, destroying an island, generating a tsunami, and blanketing Tonga in ash. Volcanologists are accustomed to monitoring nearby seismic equipment for signs of an imminent eruption, but researchers found that the HTHH eruption generated a surface-level seismic wave picked up by detectors 750 kilometers away about 15 minutes before the eruption began. They propose that the seismic wave occurred when the oceanic crust beneath the caldera fractured. That fracture could have allowed seawater and magma to mix above the volcano’s subsurface magma chamber, creating the explosive trigger for the eruption. Their finding suggests that real-time monitoring for these distant signals could provide valuable early warning of future eruptions. (Image credit: NASA Earth Observatory; research credit: T. Horiuchi et al.; via Gizmodo and AGU News)

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  • Inside a Big Cat’s Roar

    Inside a Big Cat’s Roar

    The roars of big cats — tigers, lions, jaguars, and leopards — carry long distances. In part, this reflects the animals’ size: large lungs exhale lots of air through a large voice-box, whose vibrations resonate in a large throat. But size alone does not make the roar. Below are examples of two big cat voice-boxes. On the left is the nonroaring snow leopard; on the right is the voice-box of a roaring jaguar. The red boxes labeled “VF” mark each cat’s vocal folds. Nonroaring cats have triangular folds, while roaring ones have thick square or rectangular vocal folds. These rectangular folds are more aerodynamically efficient, allowing them to produce a wider range of output levels. They’re also more resilient to the intense forces of a roar, thanks to the cushioning effect of fat deposits inside them. If interested, you can learn more over at Physics Today. (Image credit: tiger – T. Myburgh, voice box – E. Walsh and J. McGee; research credit: E. Walsh and J. McGee)

    The vocal folds (VF) of nonroaring cats are triangular (left), whereas roaring cats have rectangular vocal folds (right).
    The vocal folds (VF) of nonroaring cats are triangular (left), whereas roaring cats have rectangular vocal folds (right).
  • A Magnetic Tsunami Warning

    A Magnetic Tsunami Warning

    Tsunamis are devastating natural disasters that can strike with little to no warning for coastlines. Often the first sign of major tsunami is a drop in the sea level as water flows out to join the incoming wave. But researchers have now shown that magnetic fields can signal a coming wave, too. Because seawater is electrically conductive, its movement affects local magnetic fields, and a tsunami’s signal is large enough to be discernible. One study found that the magnetic field level changes are detectable a full minute before visible changes in the sea level. One minute may not sound like much, but in an evacuation where seconds count, it could make a big difference in saving lives. (Image credit: Jiji Press/AFP/Getty Images; research credit: Z. Lin et al.; via Gizmodo)

  • Growing Flexible Stalactites

    Growing Flexible Stalactites

    Icicles and stalactites grow little by little, each layer a testament to the object’s history. Here, researchers explore a similar phenomenon, grown from a dripping liquid. They’re called “flexicles” in homage to their natural counterparts, and they start from a thin layer of elastomer liquid. Though it begins as a liquid, elastomer solidifies over time.

    Timelapse video showing the formation of an initial layer of flexicles from a dripping elastomer.
    Timelapse video showing the formation of an initial layer of flexicles from a dripping elastomer.

    To form flexicles, the researchers spread a layer of elastomer on an upside-down surface and allow gravity to do its thing (above). Thanks to the Rayleigh-Taylor instability, the dense elastomer forms a pattern of drips that, after hardening, creates a pebbled surface. Subsequent layers of elastomer will drip from the same spots as before, slowly growing longer flexicles (below). The team envisions using them for soft robotics, but, personally, I just really want poke at them and wiggle them. (Image and research credit: B. Venkateswaran et al.; via APS Physics)

    A stitched composite photo showing flexicles on a cylinder growing layer by layer.
    A stitched composite photo showing flexicles on a cylinder growing layer by layer.
  • Reinterpreting Uranus’s Magnetosphere

    Reinterpreting Uranus’s Magnetosphere

    NASA launched the Voyager 2 probe nearly 50 years ago, and, to date, it’s the only spacecraft to visit icy Uranus. This ice giant is one of our oddest planets — its axis is tilted so that it rotates on its side! — but a new interpretation of Voyager 2’s data suggests it’s not quite as strange as we’ve thought. Initially, Voyager 2’s data on Uranus’s magnetosphere suggested it was a very extreme place. Unlike other planets, it had energetic energy belts but no plasma. Now researchers have explained Voyager 2’s observations differently: they think the spacecraft arrived just after an intense solar wind event compressed Uranus’s magnetosphere, warping it to an extreme state. Their estimates suggest that Uranus would experience this magnetosphere state less than 5% of the time. But since Voyager 2’s data point is, so far, our only look at the planet, we just assumed this extreme was normal. (Image credit: NASA; research credit: J. Jasinski et al.; via Gizmodo)