FYFD

Tag: biology

  • Featured Video Play Icon

    Schooling Relies on Vision

    For fish, collective motions like schooling rely on a few mechanisms, including flow sensing and — as beautifully demonstrated in this experiment — vision. Researchers used an infrared camera to track fish motions both in light and dark conditions and compared how orderly the school of fish was in each. As expected, the school’s motion was much more orderly when the fish could see one another clearly. Interestingly, the researchers then ran an experiment in which the illumination rose continuously from dark to fully bright. The fish school’s organization grew continuously with the light! The better they could see one another, the more organized their schooling. (Video and research credit: L. Baptiste et al.)

  • Turbulence in Flight

    Turbulence in Flight

    Eagles and other birds spend much of their lives in the turbulence of our atmospheric boundary layer. Some of their interactions with turbulence — like using topographical effects to aid their flight — are well-known, but much remains uncertain. One team of researchers looked at a tagged golden eagle’s flight data, compared with known wind conditions, and looked for evidence of turbulence’s influence. To do this, they drew on years of research into how turbulence interacts with inertial particles — particles that are heavier than the surrounding fluid and thus unable to follow the flow exactly.

    What they found is that turbulence seems to be baked into many aspects of the eagle’s flight. Even the basic accelerations of the eagle’s body during flight showed characteristics that match those of turbulent flows. The findings suggest that turbulence — rather than something to be avoided — is an integral part of flight for birds, an energy source they’ve learned to exploit. (Image credit: J. Wang; research credit: K. Laurent et al.; submission by G. Bewley)

  • Luminous Fruits

    Luminous Fruits

    Light shines through citrus and melon in this photographic photorealistic series of paintings from artist Dennis Wojtkiewicz. The strong illumination reveals the underlying structure of pith, pulp, and juice. The deformable pockets of fluid in the peel of citrus fruits are the source of some incredible microjets. When the peel bends, it compresses these tiny fluid-filled pockets, creating incredibly high pressures that eventually drive a burst of oil at g-forces comparable to those felt by a bullet fired from a gun. Learn more about citrus jets here and see more of Wojtkiewicz’s work and purchase prints here on his site. (Image credit: D. Wojtkiewicz; via Colossal)

    ETA: Thanks to A.J. for pointing out that Wojtkiewicz is, in fact, a painter (and not a photographer), making his work all the more astounding! We regret the error.

  • Inside a Coronavirus Aerosol

    Inside a Coronavirus Aerosol

    This is a glimpse inside a tiny aerosol droplet with a single SARS-CoV-2 coronavirus inside it. The numerical simulation required a team of 50 scientists, 1.3 billion atoms, and the second most powerful supercomputer in the world. By simulating every atom, the researchers hope to observe what happens to a coronavirus in these micron-sized, long-lasting droplets. Does the virus survive? How do variants fare?

    Their simulation shows that the positive charge of the coronavirus’s spike proteins helps attract mucins that shield the virus and protect it from the droplet interface where evaporation could destroy it. Variants like Delta and Omicron have even more positive charge to their spike proteins, giving themselves a better cloak of mucins and potentially making them all the more infectious. Definitely check out the full New York Times write-up for more spectacular visualizations from the work. (Image and research credit: R. Amaro et al.; via NYTimes; submitted by Kam-Yung Soh)

  • Featured Video Play Icon

    Insects Taking Flight

    As awkward as they look sometimes, insects are amazing fliers. In this video from Ant Lab, we see all kinds of insects taking flight. Some, like the mantis, execute flying leaps to get in the air, whereas weevils begin flapping from a tripod stance. Watching these videos I’m always struck by how flexible insect wings are. They flex far more than I would imagine. And these insects have a lot of excess lift. Just check out that carrion beetle taking off despite being covered in mites! (Image and video credit: Ant Lab)

  • Hagfish Slime

    Hagfish Slime

    The eel-like hagfish is a superpowered escape artist, thanks to its slime. When threatened, the hagfish releases long protein-rich threads that, when combined with turbulent sea water, unravel to form large volumes of viscoelastic slime that clog the gills of its predators. A new study shows that larger hagfish produce longer and thicker threads in their slime, enabling them to escape larger predators than their smaller brethren can.

    The properties of hagfish slime are tuned for defense. When stretched, the long protein threads resist, making the slime more viscous. Since most fish use suction methods to catch prey, that means a predator attacking a hagfish will quickly exacerbate its slimy problems. But the hagfish itself can easily escape its slime by tying itself in a knot. The threads inside the slime collapse when sheared, so the knot-tying of the hagfish slips the slime right off. (Image credit: T. Winegard; research credit: Y. Zeng et al.; via Ars Technica; submitted by Kam-Yung Soh)

  • Better Inhalers Through CFD

    Better Inhalers Through CFD

    As levels of air pollution rise, so does the incidence of pulmonary diseases like asthma. Treatments for these diseases largely rely on inhalers containing drug particles that need to be carried into the small bronchi of the lungs. To better understand how the process works, researchers used computational fluid dynamics to simulate how air and particles travel through the human respiratory tract.

    The team found that larger particles tended to get stuck in the mouth instead of making it down into the lungs. This problem was made worse at high inhalation rates because the particles’ inertia was too large for them to make the sharp turn down into the trachea. In contrast, smaller particles could travel down into the lungs and into the smaller branches there before settling. The authors concluded that inhalers should use fine drug particles to maximize delivery into the lungs. They also note that adjusting inhalers to deliver more medication to the lungs may also lower the overall price because less of the dosage gets wasted in the patient’s mouth.

    Of course, the study’s results also serve as a warning about the dangers of air pollution from fine particulates. Here in Colorado, our summers are punctuated with wildfire smoke, much of it in the form of tiny particles about the same size as the drug particles in this study. If fine drug particles are effective at making it into the smaller branches of our lungs, so are those pollutants. That’s a good reason to stay inside in smoky conditions or use a high-quality N-95 mask while out and about. (Image credit: coltsfan; research credit: A. Tiwari et al.; via Physics World; submitted by Kam-Yung Soh)

  • Stingray Eyes

    Stingray Eyes

    With their flexible, flattened shape, rays are some of the most efficient swimmers in the ocean. But, at first glance, it seems as if their protruding eyes and mouth would interfere with that streamlining. A new study uses computational fluid dynamics to tackle the effects of these protrusions on stingray hydrodynamics.

    With their digital stingrays, the team found that the animal’s eyes and mouth created vortices that accelerated flow over the front of the ray and increased the pressure difference across its top and bottom surfaces. The result was better thrust and the ability to cruise at higher speeds. Overall, the ray’s eyes and mouth increased its hydrodynamic efficiency by more than 20.5% and 10.6%, respectively. The lesson here: looks can be deceiving when it comes to hydrodynamics! (Image credit: D. Clode; research credit: Q. Mao et al.)

  • Animals Lapping

    Animals Lapping

    Without full cheeks, cats, dogs, and many other animals cannot use suction to drink. Instead, these animals press their tongue against a fluid and lift it rapidly to draw up a column of liquid. They then close their mouth on the liquid before it breaks up and falls down. (Cats are a bit neater about it, but as the high-speed images above show, dogs use the same method.)

    A new study takes a look at the mathematics behind this feat, specifically how long it takes for the liquid column to break up. Normally, we describe that problem using the Plateau-Rayleigh instability, but in its usual form, the PR instability doesn’t account for the kind of acceleration drinking animals apply to the fluid. This new study modifies the equations to account for acceleration and finds that the predicted time it takes for breakup is consistent with the timing of animals closing their mouths on the water. In other words, cats and dogs are likely timing their lapping to maximize the amount of water they catch with each bite. (Image credits: top – C. van Oijen, others – S. Jung et al. 1, 2; research credit: S. Jung)

  • Spiral Shark Intestines

    Spiral Shark Intestines

    We’ve seen previously just how fluid dynamically impressive sharks are on the outside, but today’s study demonstrates that they’re just as incredible on the inside. Researchers used CT scans of more than 20 shark species to examine the structure of their intestines. Sharks have spiral intestines that come in four different varieties; two of those types look like a stacked series of funnels (either pointing upstream or downstream). These funnel-filled spirals, the researchers found, are incredibly good at creating uni-directional flow without any moving parts, much like a Tesla valve does. The spiral structure also seems to slow down digestion, which may factor into the shark’s ability to go long periods between meals. Incredibly, the fossil record indicates that spiral intestines — in some form — evolved in sharks about 450 million years ago — before mammals even existed! Clearly we engineers are way behind sharks when it comes to controlling flows!

    Animation of a 3D scan of a shark's intestine, showing the spiral internal structure.

    (Image credit: top – D. Torobekov, scan – S. Leigh; research credit: S. Leigh et al.; via NYTimes; submitted by Kam-Yung Soh)