FYFD

Tag: biology

  • Surface Fat Gives Chocolate’s Mouthfeel

    Surface Fat Gives Chocolate’s Mouthfeel

    Understanding the interactions of food and our mouths is incredibly difficult. There are lots of changes going on: shape changes from chewing, viscosity changes as saliva lubricates the food, and, sometimes, phase changes from the heat of our bodies. Add to that the sensitivity of our papillae-covered tongues, and it’s a lot to manage all at once. Recently, researchers have turned to 3D-printing to create a more realistic lab version of our mouths.

    The team 3D-printed a papillae pattern matching the size and distribution of an actual human tongue, then molded that pattern onto a silicone elastomer. The result? A replica tongue that matches a human one in terms of softness, wettability, and surface roughness. They then attached their tongue to a rheometer to measure the friction between the tongue and dark chocolate.

    Their experiments simulated licking, eating, and swallowing the confection. During licking and eating, they found that the chocolate was lubricated by a layer of fat directly between the tongue and the food. Their results suggest that one way to make healthier chocolate options is to concentrate fat into the surface layer of the chocolate while lowering the fat content inside the bar. (Image credit: D. Ramoskaite; research credit: S. Soltanahmadi et al.; via APS Physics)

  • Flamingo Fluid Dynamics

    Flamingo Fluid Dynamics

    Flamingos strut and dance and bob, but there’s more to these comical birds than meets the eye. Flamingos can thrive in nutrient-poor environments that other birds eschew, like salt flats and alkaline lakes. Their secret, it turns out, is a mastery of fluid dynamics.

    Researchers studying the behaviors of the Nashville Zoo’s flamingo flock discovered that their seemingly silly behaviors all had fluid dynamical consequences. When the birds stomped and danced in small circles, it stirred up the muck in the water they eat from. With their beaks below the surface, the birds then opened and closed their mouths, darting their tongues in and out; this generated suction to carry food particles toward them. Periodically, they’d bob their heads up, creating a vortex for extra suction. Even their walking, which they did while skimming the water surface with their bills facing backward, generated flows that helped carry food to their mouths. (Image credit: cshong; research credit: V. Ortega-Jiménez et al.; via Science; submitted by Kam-Yung Soh)

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    “aBiogenesis”

    Many theories posit the physical and chemical origins of life. In the short film “aBiogenesis”, CGI artist Markos Kay imagines one such theory — the lipid world theory — in which cellular life began as a soup contained within immiscible fatty membranes. Chemicals trapped within these vesicles interacted and ultimately formed the building blocks of life as we know it, including RNA. Kay’s interpretation is a beautiful exploration of this intersection of physics, chemistry, and biology. (Image and video credit: M. Kay; via Colossal)

  • Drag Reduction for Swimming Shrimp

    Drag Reduction for Swimming Shrimp

    Marsh grass shrimp, despite their small size, are zippy swimmers. They move using a series of closely-spaced legs that stroke asynchronously. Researchers found that the flexibility and stiffness of the legs are critical for the shrimp’s efficiency. During the power stroke, the shrimp’s leg is held stiff, maximizing the force it’s able to transfer to the water. But during the forward-moving recovery stroke, the shrimp bends its legs almost horizontal and presses both legs in the pair together tightly. This action minimizes the area of the leg pair and reduces the drag they cause as they move into position for the next stroke. (Image, video, and research credit: N. Tack et al.; via Ars Technica; submitted by Kam-Yung Soh)

    https://www.youtube.com/watch?v=hWOtF0RXTwk
    A close-up view of the shrimp’s leg as it swims.
  • Where Fresh and Salty Meet

    Where Fresh and Salty Meet

    Waterways twist through the wetlands of Adair Bay in this astronaut-captured image of northwestern Mexico. The estuary marks the transition between the Great Altar Desert and the Gulf of California. Fresh and salt water mix in the sediment-rich waterways. Mangroves and other salt-tolerant vegetation flourish in the coastal marsh. During low tides, evaporating water leaves behind salt flats, seen here in gray and white. High tides flood the area with nutrients that support both the vegetation and abundant aquatic life. (Image credit: NASA; via NASA Earth Observatory)

  • Seashore Hunting

    Seashore Hunting

    Watch sea gulls, plovers, and other birds hunt in the tidal zone, and you may notice them stepping over and over in the same spot. This is part of bird’s hunting strategy. Each footfall compresses the wet sand and drives water out. Mechanically, this is the same thing that happens when a human walks on wet sand; you’ll see the sand go from a glossy appearance to a matte one as the local water level falls. Once the weight is removed, the water will seep back and the sand appears glossy again.

    Illustration of a gull's hunting process. Compressing the sand by stepping on it drives water out of the area. Once the bird's foot is removed, water floods back, diluting the sand, and making it easier for the bird to reach its prey without digging.
    Illustration of a gull’s hunting process. Compressing the sand by stepping on it drives water out of the area. Once the bird’s foot is removed, water floods back, diluting the sand, and making it easier for the bird to reach its prey without digging.

    For the birds, the flood of returning water loosens and dilutes the sand. That makes prey easier to expose and reach without the additional effort of digging. (Image credits: bird – C. Davis, illustration – P. Fischer; via Physics Today)

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    Simulating Schools

    In nature, fish school for many reasons: protection from predators, increased sensing, and hydrodynamic advantages. To capture this complex behavior, researchers are building their own digital fish, governed by known rules. Here, scientists give each fish social rules — based on vision range and preferred distance from a neighbor — and hydrodynamic rules — based on a fish’s wake. With the rules in place, they can then observe the schooling behaviors of their digital fish. Like their real counterparts, these schools show different flocking based on apparent “moods”. (Image and video credit: J. Zhou et al.)

  • Why Moths Are Slow Fliers

    Why Moths Are Slow Fliers

    Hawkmoths and other insects are slow fliers compared to birds, even ones that can hover. To understand why these insects top out at 5 m/s, researchers simulated their flight from hovering to forward flight at 4 m/s. They analyzed real hawkmoths flying in wind tunnels to build their simulated insects, then studied their digital moths with computational fluid dynamics.

    During hovering flight, they found that hawkmoths generate equal amounts of lift with their upstroke and downstroke. As the moth transitions into forward flight, though, its wing orientation shifts to reduce drag, and the upstroke stops being so helpful. Instead, the upstroke generates a downward lift that the downstroke has to counter in addition to the insect’s weight. At higher forward speeds, this trend gets even worse.

    The final verdict? Hawkmoths don’t have the flexibility to twist their wings on the upstroke the way birds do to avoid that large downward lift. Since they can’t mitigate that negative lift, the insects have a slower top speed overall. (Image and research credit: S. Lionetti et al.; via APS Physics; submitted by Kam-Yung Soh)

  • Fluid Flow For Digestive Health

    Fluid Flow For Digestive Health

    During digestion, our intestines use two different patterns of muscle contraction to move food through our bodies. Scientists have long wondered why we have this added complexity. Using numerical simulations of the fluid flow created by these contractions, researchers have uncovered the answer.

    Our intestines use peristalsis, a forward-with-occasional-backward flow pattern, as the main driver. The strength of the muscle contractions determines how fast the average flow speed is. When the speed is slow, our bodies have more time to absorb nutrients, but that also allows more time for bacteria to flourish on those same nutrients. The other flow pattern, segmentation, creates a weaker flow overall but with much more mixing, which again enhances nutrient uptake.

    Switching between the two patterns, the researchers found, gives the body the best of both. Segmentation can enhance mixing and provide good nutrient uptake, then peristalsis can move the contents along quickly enough that bacteria don’t have time to grow before getting flushed out. (Image credit: Kindel Media; research credit: A. Codutti et al.; via APS Physics)

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    “Reconfiguring It Out”

    Leaves flutter and bend in the breeze, changing their shape in response to the flow. Here, researchers investigate this behavior using flexible disks pulled through water. The more flexible the disk and the faster the flow, the more cup-like the disk’s final shape. Adding tracer particles to the water allows them to visualize the flow behind the disk. Every disk leaves a donut-shaped vortex ring spinning in its wake, but the more reconfigured the disk, the narrower the vortex. This, ultimately, reduces drag on the disk. That’s why trees in heavy winds streamline their branches and leaves; that flexibility lowers the drag the tree’s roots have to anchor against. (Image and video credit: M. Baskaran et al.)