FYFD

Tag: biology

  • Placental Fluid Dynamics

    Placental Fluid Dynamics

    The placenta, critical as it is to human life and development, is likely the least-studied organ in the body. Reasons for that abound, from the ethics of studying pregnant people to the historical marginalization of female bodies in medical studies. But what little we do know shows that the placenta is quite incredible.

    Shaped somewhat like a flattened cake, the placenta contains a tangle of fetal blood vessels — an estimated 550 kilometers’ worth — bathed in maternal blood. The enormous surface area — nearly 13 meters squared — enables the exchange of oxygen, glucose, and urea through diffusion. These exchanges don’t take place in still conditions, though; blood is always flowing through the vessel network. This means that each exchange depends on both the speed of diffusion and the speed of the flow, a relationship that’s captured with the dimensionless Damköhler number.

    Illustration of the intertwined blood vessels of the placenta.
    Illustration of the intertwined blood vessels of the placenta.

    Some exchanges, like carbon monoxide and glucose, are diffusion-limited, meaning that increased blood flow cannot speed up the process (though additional blood vessel surface area could). In contrast, carbon dioxide and urea are flow-limited exchanges. Fascinatingly, oxygen is close to being both diffusion- and flow-limited, suggesting that the organ has optimized for this exchange. Since pregnancy also involves a large increase in maternal blood volume and changes in lung capacity to help provide oxygen, it seems like the pregnant body heavily emphasizes delivering oxygen to the developing fetus. (Image credit: newborn – J. Borba, placenta – iStock/Sakurra; via Physics World; submitted by Kam-Yung Soh)

  • Breaking Clots With Sound

    Breaking Clots With Sound

    Clots that block blood flow away from the brain are one of the most common causes of strokes for younger people. If caught early, anticoagulants can sometimes resolve the issue, but the treatment fails in 20-40% of cases. Now researchers are investigating a new ultrasound technique capable of quickly and effectively removing these clots.

    An illustration of the vortex ultrasound technique breaking up a blood clot.
    An illustration of the vortex ultrasound technique breaking up a blood clot.

    The group attached a 2 x 2 array of ultrasound transducers to the tip of a catheter like those doctors feed through blood vessels in other interventions. The offset between each ultrasound transducer creates a vortex-like flow when the array is activated. The helical wavefront creates shear stress along the clot’s face, helping to break it up faster. In one test, the new technique broke up a clot and completely restored flow in just 8 minutes. Pharmaceutical treatments take at least 15 hours and average closer to 29 hours.

    The team is moving forward to animal trials next and hope, with success there, to bring the technique to clinical studies. (Image credit: abstract – C. Josh, illustration – X. Jiang and C. Shi; research credit: B. Zhang et al.; via Physics World)

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    A Look at Hagfish

    Hagfish are the lords of slime. Their viscoelastic protection mechanism is so effective that they’ve hardly changed up their game in the past 300 million years. Instead, at the first sign of trouble, they release a mucus that rapidly expands in salt water. When attacking fish try to pull water into their gills, they get clogged with slime instead, sometimes suffocating and becoming the hagfish’s meal instead. To get out of their slime, hagfish knot themselves and wipe it away, thanks to its shear-thinning properties. (Image and video credit: Deep Look)

  • Dandelion Seeds

    Dandelion Seeds

    Each seed on the head of a dandelion has a preferred wind direction, according to new research. Seeds facing the breeze are most likely to release from the head, with those facing other directions holding on tens to hundreds of times harder — until their breeze comes along. To measure the force needed to pluck a dandelion seed, researchers superglued a fine wire to individual seeds and pulled from different directions. This seed-by-seed removal mimics winds from varying angles and allowed the researchers to test the directional dependence of seed release. With seeds poised to release in every direction, the dandelion ensures its successful spread. (Image credit: S. Chaudhry; research credit: J. Shields and C. Roh; via Science News; submitted by Kam-Yung Soh)

  • Swimming Intermittently

    Swimming Intermittently

    Many fish do not swim continuously; instead, they use an intermittent motion, swimming in a sudden burst and then coasting. This intermittent swimming is tough to simulate, due to its unsteady nature, but a new study does so using some clever computational techniques.

    Animation showing a fish swimming in a burst-and-coast pattern.
    Animation showing a fish swimming in a burst-and-coast pattern.

    Researchers suspected that the energy intensity of a fish’s burst could be balanced by the low-drag, low-effort phase of coasting. And, indeed, that’s consistent with the team’s results. But they found that the swimming method does require careful optimization; with the wrong cadence, the burst-and-coast technique can be incredibly energy intensive. In nature, of course, fish have had millions of years to optimize their technique, but the results serve as a warning to those building fish-based robots. Those biorobots will need careful optimization to benefit from this swimming style. (Image credit: tetra – Adobe Stock Images, simulation – G. Li et al.; research credit: G. Li et al.; via APS Physics; submitted by Kam-Yung Soh)

  • 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)