FYFD

Tag: biology

  • Jamming Inside

    Jamming Inside

    Worm-like Spirostomum ambiguum are millimeter-sized single-cell organisms that live in brackish waters. In milliseconds, these cells can retract to half their original length, generating g-forces greater than a Formula One driver experiences when cornering. How, researchers wondered, do these cells avoid shredding their internal structure with forces that strong?

    Spirostomum ambiguum, they found, contain fluid-filled sacs called vacuoles that are entangled with the folds of a membrane-like structure called the endoplasmic reticulum. The researchers constructed a simulated cell, based on the properties of the living ones, and tested it under retraction. Without the endoplasmic reticulum, the insides of their model acted like a liquid, with vacuoles moving past one another readily. That’s not good for staying alive since swapping positions can disrupt bodily functions.

    An artificially-colored micrograph highlights the different structures inside Spirostomum ambiguum. The red strings are a membrane-like endoplasmic reticulum entangled between yellow, fluid-filled vacuoles.
    An artificially-colored micrograph highlights the different structures inside Spirostomum ambiguum. The red strings are a membrane-like endoplasmic reticulum entangled between yellow, fluid-filled vacuoles.

    With the vacuoles connected by a model endoplasmic reticulum, the cell’s insides acted more like a solid during retraction. The vacuoles deformed but fewer of them traded places, instead jamming together to prevent rearrangement. Mimicking this structure at a larger scale, the team suggests, could enable new types of shock absorbers. (Image and research credit: R. Chang and M. Prakash; via APS Physics)

  • A Better Ear Plug

    A Better Ear Plug

    Ear plugs can be wonderful at blocking outside noise, but they come with a downside: they typically amplify internal bodily sounds, like our heartbeat, breathing, and chewing. This effect, called occlusion, is distracting enough for some users to forego ear protection or hearing aids. But a new prototype offers a hope for an occlusion-free future without requiring active noise-cancelling.

    Most devices fit a short way inside our ear canals, which blocks outside sound well, but creates a little resonance chamber between the plug and our ear drums. It’s this gap that amplifies the low-frequency sounds within our bodies, making them seem much louder. To counter that, the team’s new plug contains foam sections arranged with hollow spaces between. By tuning the properties of the 3D-printed foam, they created a resonant structure inside the earbud that damps out those low-frequency body noises while still blocking outside sound.

    Illustration of the earbud's interior. The blue and green areas are foam-filled cavities.
    Illustration of the earbud’s interior. The blue and green areas are foam-filled cavities.

    So far the prototype has only been tested with an artificial ear designed for auditory tests; that’s enough to show that the concept works, but next they’ll redesign the bud to fit a human ear canal more comfortably. (Image and research credit: K. Carillo et al.; via APS Physics)

  • Understanding Cyanobacteria

    Understanding Cyanobacteria

    Over 2 billion years ago, cyanobacteria emerged as Earth’s first photosynthesizing organisms. Today they are widespread and critical contributors to both carbon and nitrogen cycles. Colonies can form large mats, like those pictured above, but, even at the microscale, cyanobacteria are actively forming patterns among individual bacteria. A recent study considers cyanobacteria as active matter.

    At the microscopic scale, cyanobacteria form different patterns.
    At the microscopic scale, cyanobacteria form different patterns, depending on their density.

    By simulating the cyanobacteria as filaments that interact through a series of simple rules, the researchers were able to reproduce the complex patterns bacterial colonies form. Their physical model also offered an explanation — based on the relative importance of advective and diffusive transport — for the characteristic length scales found in the bacterial patterns. (Image credit: Yellowstone – B. Cappellacci, patterns – M. Faluweki et al.; research credit: M. Faluweki et al.; via APS Physics)

  • Swimming Through Mud

    Swimming Through Mud

    At the bottom of ponds, nematodes and other creatures swim in a world of mud. They squirm their way through a sediment of dirt particles suspended in water. Mud, of course, is notoriously impossible to see through, so to understand these creatures’ movements, scientists turn instead to biorobotics. Here, a team uses a magnetic head attached to an elastic tail to mimic these tiny creatures.

    To drive the robot’s motion, they use an oscillating magnetic field, which forces the magnetic head to rotate. Combined with the elastic tail and the drag caused by surrounding materials, this causes the robot to swim in a fashion similar to its biological inspirations.

    A biomimetic robot swims through immersed grains. The robot's magnetic head is forced with an oscillating magnetic field. It swims through an underwater bed of hydrogel beads, whose diameter is smaller than that of the robot's head.
    A biomimetic robot swims through immersed grains. The robot’s magnetic head is forced with an oscillating magnetic field. It swims through an underwater bed of hydrogel beads, with diameters smaller than that of the robot’s head.

    To mimic the muddy environment of a pond’s bottom, scientists used a bed of hydrogel beads immersed in water. Looking at the experimental video above, you’ll see no sign of the beads. That’s because the hydrogel beads have nearly the same index of refraction as water. Once you pour water in, they seem to disappear. That allows the researchers to focus instead on the robot’s motion. In other experiments, they added dye to the beads so that they could see how they moved around the robot.

    They found that the robot’s motion fluidizes the grains around it. Effectively, the robot’s motion creates an area with fewer grains and more water for it to move through. Once it’s passed, however, more grains settle in, and the bed returns to a denser packing. (Image credit: nematode – P. Garcelon, experiment – A. Biswas et al.; research credit: A. Biswas et al.)

  • Imitating a Cough

    Imitating a Cough

    Coughing and sneezing create violent air flows in and around our bodies. As that fast air rushes over mucus layers in our lungs, throat, and sinuses, the resulting flow breaks up the mucus into droplets. To explore the details of that process, researchers built a “cough machine” that sends a rush of air over a thin film of water mixed with glycerol. The setup allows them to observe the physics in a way that’s nearly impossible in a human cough or sneeze.

    Imitating a cough: high-speed video shows how a thin film made of water and glycerol breaks down in a strong airflow. Parts of the film inflate into hollow bags that form thinner weak spots. When the film breaks in those places, it forms rims and ligaments that break up into droplets.
    Imitating a cough: high-speed video shows how a thin film made of water and glycerol breaks down in a strong airflow. Parts of the film inflate into hollow bags that form thinner weak spots. When the film breaks in those places, it forms rims and ligaments that create a spray of droplets.

    As seen above, air flowing past shears the viscous fluid, stretching it out. The leading edge of the film destabilizes and breaks into large drops, but it’s what comes next that really gets things going. Areas of the film inflate to form hollow bags. When sections of the bag thin to about 1 micron, the film ruptures and the bags burst. This triggers a cascade of instabilities in the film’s rim that ultimately rip the film into a spray of tiny aerosol droplets. The researchers found that, despite their tiny size, these droplets collectively carry a large volume of liquid, making them all the more important for understanding transmission of respiratory illnesses. (Image credit: top – A. Piacquadio, experiment – P. Kant et al.; research credit: P. Kant et al.)

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    Blood Flow in a Fin

    This award-winning video shows blood flowing through the tail fin of a small fish. Cells flow outward in a central vessel, then split to either side for the return journey. In this microscopic video, the speed of individual cells seems quite fast, even though the vessels themselves are only wide enough for the blood cells to move in single file. Flow at the microscale can be counterintuitive like that. (Video and image credit: F. Weston for the 2023 Nikon Small World in Motion Competition; via Colossal)

  • Snake Tracks

    Snake Tracks

    Moving across sand is quite challenging for bipedal creatures like us, but other animals have their ways. Photographer Paul Lennart Schmid caught this snake on the move, with impressions of its passage still in the sand. X-ray observations of snakes moving in sand show that they swim through the granular medium. Snakes are quite efficient in their swimming, moving most of their body through the tunnel created by their head, thereby reducing their overall effort. (Image credit: P. Schmid; via Nature TTL POTY)

  • Spreading Spores

    Spreading Spores

    Mushrooms are the fruiting bodies of much bigger, largely underground fungi. Being fruit, mushrooms have the job of spreading spores so that the fungus can reproduce. Some mushrooms rely on the wind; others create their own wind. Still others use vortex rings to carry their spores higher. Who knew such fascinating and beautiful physics lies along the forest floor? (Image credit: top – A. Papatsanis, bottom – I. Potyó; via Wildlife POTY)

    Photo by Imre Potyó.
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    Scuba-Diving Fly

    Mono Lake, three times saltier than the ocean, is an extreme environment by any measure. But for the alkali fly, it’s home. This extremophile insect dives into the lake, protected by a bubble sheath, to eat and lay eggs. The fly’s wings and body are covered in tiny, waxed hairs that repel water. That traps a bubble of air around the insect, allowing it to breathe. Fresh oxygen can diffuse into the bubble from the water, replenishing the supply. (Image and video credit: Deep Look)

  • Diving From Above

    Diving From Above

    Blue-footed boobies, like many other seabirds, climb to a particular altitude before folding their wings and diving head-first into the water. This acrobatic feat balances the bird’s force of impact and the depth it can reach to ensnare fish swimming there. It’s an incredible process to watch, a fascinating one to study, and, here, a beautiful glimpse of the natural world from a perspective we don’t typically see. (Image credit: H. Spiers, Bird POTY; via Colossal)