How Bats Prevent Doppler Acoustic Interference

September 7, 2026 by Maya Posch 13 Comments

https://commons.wikimedia.org/wiki/File:Bat(20070605).jpg — Lesser horseshoe bat. (Credit: Lylambda, Wikimedia)

As great as echolocation is, things can get rather messy once it’s not just you chirping away, but also hundreds of your buddies in roughly the same area. This is the scenario that the typical colonies of bats have to deal with. In a recent study by [Haruhito Matsumoto] et al. in Journal of Comparative Physiology they investigated how colonies of greater Japanese horseshoe bats deal with this issue.

Echolocation in animals can use a variety of methods, including frequency modulation (FM, varying the pitch) or constant frequency (CF), with both having their uses during hunting as well as obstacle avoidance. One big advantage of CF is that it can be used for Doppler shift, giving very precise information about location and velocity of objects in the environment, but if used in a busy colony the acoustic interference would effectively render them blind.

What researchers have found is that the CF component frequencies differ per bat colonies, with the mixing of wild-caught and resident horseshoe bats in this experiment showing them adjusting the dominant second harmonic (CF2) to match, with bats using a lower frequency CF2 adjusting it upwards. In this way frequency convergence is used as a strategy to avoid acoustic interference using a so-called ‘silent spectral window’.

As this spectral window for effective Doppler tracking is found above the CF2 frequency, it therefore makes sense that the bats at a lower CF2 harmonic would adjust their CF upwards to match that of their neighbors. Although more research is required to fully confirm these findings, it sheds some more light on the use of echolocation by these amazing flying mammals.

Kelvin–Helmholtz Instabilities Found To Drive Plasma Mixing On The Sun

September 7, 2026 by Maya Posch 3 Comments

As easy as the Sun is to observe, it’s simultaneously very hard to study due to how extreme the conditions are, even on the surface of a rather unassuming star. One of these study topics is the interaction between the Sun’s plasma and magnetic field, as this drives much of the dynamism of the Sun’s surface layer (i.e., the photosphere). Recent observations by the 4-meter solar telescope in Hawaii have now led to interesting new findings, as detailed in a paper in Nature by [David Kuridze] et al.

Despite popular portrayal, this photosphere is not a boiling liquid, but rather pockets of plasma at various temperatures. The plasma moves within the magnetic field and convective movements that create the ‘boiling’ pattern, which gives the illusion of a boiling liquid surface.

Within this photosphere, [Kuridze] et al. were able to observe Kelvin-Helmholtz instabilities, which are fluid instabilities caused by velocity shearing in either a continuous fluid or due to a velocity difference between two fluids. This is also observed in clouds in Earth’s atmosphere, where they cause the billowing effect, somewhat similar to watching a boiling liquid.

In a MURaM simulation (see heading image), these findings were confirmed, showing how these instabilities drive the transport of plasma in the Sun’s photosphere.

How Charged Water Drops Induce Corrosion

September 6, 2026 by Maya Posch 12 Comments

Generally, we do not look at the gentle patter of raindrops on a surface with much concern, but according to a study by [Zhongyuan Ni] et al. in Nature, we should probably regard these droplets with a little scrutiny for their corrosion potential. What they found is that these drops can gather a significant electric potential as they gently slide down a surface, with over 1 kV measured. By first having droplets charge up on an insulating surface before hitting a target metal surface, they were able to induce significant corrosion.

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3D Printed Cubes Provide Passive Cooling

September 4, 2026 by Donald Papp 36 Comments

Passive evaporative cooling has been used for centuries to reduce temperatures. Heat is drawn off as water evaporates, which in turn reduces temperature. The more efficiently this process happens the greater the temperature differential, and that’s exactly what the 3D-printed structure pictured above aims for. Created at the Graz University of Technology in Austria, the cubes noticeably reduce surrounding air temperature thanks to their careful construction. As long as they’re kept wet, anyway.

The key is exposing the maximum amount of water to the maximum amount of airflow, and there are two ways the prototype cooling wall — which is 3D printed from a special clay mixture — does this.

First, the macro design of the 3D-printed blocks maximizes surface area. If the cube in the image above looks familiar, that’s because it’s the gyroid infill pattern. Gyroid is a porous pattern with no “dead ends” or closed sections, and the fact that it 3D prints cleanly with no supports also makes it an ideal structural candidate.

The second advantage is the clay used for the blocks themselves. Firing clay at a low temperature keeps it porous, but this particular mixture goes even further. It’s a bio-inspired formulation of clay, fungal mycelium, and wood chips. After printing, the cubes are fired and the fungus and wood chips burn away, leaving a network of thread-like capillaries with occasional larger pockets throughout.

The result is a porous ceramic cube with a massive evaporative surface area relative to its size. A practical test in a hot attic showed the air near a water-laden cube was nearly 7º C lower, a noticeable difference.

A home experimenter might not have access to fancy mycelium-laced clay mixtures, but it still strikes us as something that could be tried out at home. After all, clever hackers have successfully made DIY versions of passive cooling paint.

Harvesting Namib Desert Fog With High Voltage

September 2, 2026 by Maya Posch 24 Comments

As fun as mucking about with simulated environments in a laboratory is, at some point you have to do those field tests to demonstrate that your prototype actually works in the real world, under real conditions. This is what the [Plasma Channel] recently did for their fog harvesting system by setting it up in the Namib desert.

We previously covered the atmospheric water harvesting attempts, using electrostatic precipitation to draw the moisture in the air onto the collectors where it can then be harvested. This is rather different from existing approaches with e.g. fine meshes and hoping that enough water molecules bump into your mesh, so theoretically it should be much more efficient. In the lab it worked well, but reality always has the last word.

The Namib desert is at the top of the world’s most arid regions, competing with the Atacama desert. What it does have going for it is regular fog rolling in that lasts until sunrise, providing a good target for water harvesting. Interestingly, this field test was performed together with the University of Namibia.

Of course, moving the prototype in check-in luggage for the flight to Namibia took some redesigning and testing. Fortunately everything, including the solar panel, arrived intact, allowing trials to commence. This initially took place at the campus of the University of Namibia, joining a number of other atmospheric water harvesting projects that had been previously installed there.

Unfortunately the fog proved to be rather elusive, leading to a few fruitless attempts. It also proved that the salt in the air from the ocean spray, even a few kilometers inland, was highly corrosive, especially to high-voltage electronics. Although the system basically worked, happily harvesting water under the right conditions, it does need some redesign before it’ll be tested next in the Atacama desert.

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Creating The Greenest Possible Clothing With Living Fungi

September 2, 2026 by Maya Posch 22 Comments

Despite the wide variety of fabrics used for our clothing, they all share the property of not being living tissues. This could be due to them never having been part of an organism, or having been removed from said organism. Another approach here entails so-called engineered living materials (ELMs), with a recent research article by [Ke Li] et al. in Science Advances providing a good example of a fungal platform for such living textiles.

Although it may seem frivolous to create something like this, the direct benefits would be to have a fabric that can self-heal and respond to its environment, including blocking UV radiation and changing its coloring through pigmentation.

The research demonstrated in this paper covers essentially a platform for creating a living textile that can be adapted to a wide variety of applications and colorizations. Of note is that the researchers have not yet tested aspects like washability, abrasion resistance, breathability and wearer comfort, so this should definitely be regarded as setting the stage for more research.

For the basic material the fungi Cordyceps militaris was chosen, which were subsequently placed between films. To this additional microbial cultures were added, including the pigment-producing S. cerevisiae and melanized A. niger for UV blocking.

As for what it can look like with clothing, this article at De Zeen gives somewhat of an idea, as well as how the living textile is prepared.

Sloan Digital Sky Survey Releases New Map Of Supermassive Black Holes

August 26, 2026 by Maya Posch 2 Comments

The Universe is a large place, yet despite it being mostly empty space, there are still a lot of things to find and catalogue. This includes mildly terrifying things like supermassive black holes (SMBHs), one of the study subjects of the Sloan Digital Sky Survey (SDSS) project. In their 20th data release of the fifth all-sky survey (SDSS-V), the results of the Black Hole Mapper (BHM) program provides a lot of new insights into these SMBHs.

For a good primer on the SDSS’s ongoing survey, you can read this paper by [Kollmeier] et al. from 2017 in which this fifth survey and its three programs, including the BHM, are explained. This comes after four previous phases of the SDSS, all of them focusing on multispectral imaging and spectroscopic redshift survey with the 2.5 m Apache Point Observatory (APO) in New Mexico.

With SDSS-V a second 2.5 m observatory at Las Campanas (LCO) was added, with both observatories combined able to observe the entire sky, not just as static images, but also any changes over time. While these observations are in the near-infrared, combined with the data from other observatories this gives us probably one of the most comprehensive maps of the Milky Way and everything therein, including black holes.

This 20th data release gives us one of the clearest glimpses yet at the formation, growth and behavior of SMBHs and similar objects over time. A big part of this achievement are the automatic positioning robots at the observatories that handle the fiber optics that feed spectrographs, enabling faster and more accurate observations.