Although the term ‘dry ice’ is generally used for solid CO2, it’s much more accurate to call this ‘dry snow’, as, rather than being actual solid blocks, they are effectively snow that’s been compressed really tightly. While not really necessary for most applications of dry ice, it is possible to make blocks of actual CO2 ice, and thus [Hyperspace Pirate], as someone with a healthy obsession with cold things had to make some of his own.
The way that the sense of smell works is that olfactory sensory neurons (OSNs) are wired up to olfactory receptors (ORs) in the nasal epithelium, from which they send signals to the brain. Once arrived there, a hierarchy of processing results in us experiencing the sensation of ‘smelling’. Exactly how the olfactory receptor-to-brain mapping works during development, and whether its physical pattern in the nasal epithelium is replicated in the brain, remained major questions until now. In a study published in Cell by [David H. Brann] and others, many of these questions have now been answered, at least for mice.
As it turns out, the mapping between OSNs and ORs isn’t performed by a random selection process, but instead creates a receptor map that’s closely matched between the nasal epithelium and the brain. What has complicated answering this question up till now is that the nasal epithelium isn’t a flat surface, but a convoluted labyrinth that maximizes surface area to smell better.
The second issue was linking the physical location of OSNs and gene expression in the nasal epithelium. Using a new approach, the researchers showed an intricate patterning in this epithelium, with the basal stem cells from which it regenerates maintaining this patterning. This makes for a system very similar to, for example, the auditory system, where the detection of frequencies in the inner ear, as a linear system, is found to be replicated in the brain.
Although it does not provide us with all the answers yet about how this genetic patterning works, it offers a glimpse at a fascinating system that would seem to be used repeatedly across sensory systems. It may also provide potential treatments for medical conditions affecting the olfactory system, whereby the sense of smell is missing, reduced, or oddly miswired, for example, after a SARS-CoV-2 infection of the olfactory nerve that leads to symptoms such as a constant sensation of a burning smell.
Microplastics absolutely saturate the Earth’s environment, and that’s probably not a good thing unless you’re looking for a sediment marker for the Anthropocene period. On the other hand, environmental contamination only becomes a really big problem if it bioaccumulates– that is, builds up in the tissues of plants and animals. At least when it comes to worms, that’s not the case with microplastics, according to new research from the Canadian Light Source at the University of Saskatchewan.
Pictured: Not an Igloo. Credit: David Stobbe / Stobbe Photography, via University of Saskatchewan
The Canadian Light Source isn’t just some hoseheads in an igloo with a flashlight– it’s a 2.9 GeV Synchrotron tuned to produce high-energy photons. Back when Synchrotrons were used for particle physics, Synchrotron radiation was a very annoying energy sink, but nobody cares about 2.9 GeV electrons anymore. So rather than slam them into each other or a static target, the electrons just whip about endlessly, giving off both soft- and hard X-rays for material science studies– or, in this case, to observe the passage of polyethelyne microplastic particles through the guts of some very confused earth worms. To make them detectable by x-ray, the polyethylene was bonded to barium sulfate, an x-ray absorber. Equally opaque barium titanite glass microspheres were used with different worms, as a control.
Despite being fed soil enriched with far more plastic than you’ll find outside of a 3D print farm, it seems the worm’s digestive system was able to reject the particles, even those as fine as 5 microns. That’s a good thing, because if the worms were absorbing plastic from the soil, it’s likely their predators would absorb it from the flesh of the worms, so and so forth up the food chain in the sort of cascade that made DDT a problem and makes mercury compounds so serious. If the worms are rejecting these compounds, there’s a chance other creatures can too– and at the very least, it means they aren’t building up on this bottom rung of the foot chain. If you’re looking for a more technical read, the full paper is available here.
It’s too early to say what this means for how microplastics get into humans and other animals, but it’s hopeful. Equally hopeful was the recent finding that studies that don’t rely on football-field sized X-ray machines might be picking up on microplastics from lab gloves, skewing results.
Header image: the digestive systems of earth worms as imaged by the Canadian Light Source. Credit Letwin, et al,
Environmental Toxicology and Chemistry, vgag072, https://doi.org/10.1093/etojnl/vgag072
Making stuff cool and keeping it that way has been a pretty essential part of human civilization for thousands of years, with only in the past few hundred years man-made methods having become available that remove the reliance on the whims of nature and lugging around massive blocks of ice. The most important cooling method is undoubtedly that of vapor-compression refrigeration, but this is hardly the only method to transfer thermal energy from one location to another.
For example, we recently covered an elastocaloric cooling project by a group of scientists that uses strips of NiTi metal. By flexing these they induce a cooling effect which when put in a number of stages serves to transfer a significant amount of thermal energy between both sides, much like a vapor-compression system but without the gases and compressor. Meanwhile the Seebeck effect is relatively well-known from Peltier thermocouple devices, and features heavily in portable refrigerators and kin where these solid-state devices can also transfer thermal energy.
Of course, along with how they function the major question with all of these cooling technologies is how efficient they are, as this determines when you’d want to even consider them for a specific application.
Normally, when you design an electronic gadget, you worry about how hot it will get. Automotive-grade components, for example, often have higher allowable temperatures than commercial parts. However, extremely cold environments, such as deep space or the interiors of quantum computers, are also challenging. Researchers at King Abdullah University of Science and Technology believe gallium oxide may be key to operating near absolute zero.
According to [Vishal Khandelwal], one of the researchers, most conventional electronics fail below -173C or 100K. Quantum computers routinely operate at 4K. However, β-Ga2O3 is a wide-bandgap semiconductor that has low current leakage and works at high temperatures up to 500C. However, it also avoids the freeze-out effect that traps electrons in other semiconductor materials.
Solid state batteries, we are told, are the new hot battery technology that will replace lithium-ion batteries. Soon. Not that we haven’t heard that before. One reason it isn’t dominating the market today is that it’s prone to short circuits during charging. [Dr. Yuwei Zhang and others have published a paper detailing why the shorts happen, which could lead to strategies to improve the technology.
Solid state batteries employ a solid electrolyte and a lithium anode. It is known that, sometimes, lithium metal from the anode forms dendrites that penetrate the ceramic electrolyte and cause it to crack. This is somewhat of a mystery as the lithium is a soft metal: to quote [Zhang], “like a gummy bear”.
There were two leading hypotheses for the observations. [Zhang’s] team showed that hydrostatic stress made the lithium dendrites act like a water jet, enabling them to penetrate the hard ceramic.
There is still work to figure out what to do about it, but understanding the root cause is certainly a step in the right direction. We’ve looked at these batteries before. We’ve also seen how changing the anode construction might help with the problem.
A lot has been made about a post-quantum computer future in which traditional encryption methods have suddenly been rendered obsolete. With this terrifying idea in mind, it’s reassuring to see some recent pushback to the idea with some factual evidence. In a recent blog post by [Filippo Valsorda] – a cryptography engineer – the point is raised that 128-bit symmetric keys like AES-128 and hashing algorithms like SHA-256 are not at risk of being obliterated in a post-quantum future.
Rather than just taking [Filippo]’s word for it, he takes us through a detailed explanation of the flawed understanding of Grover’s algorithm that underlies much of the panic. While it’s very true that this quantum search algorithm can decrease the amount of time required to find a solution, the speed-up with a single thread is quadratic, not exponential. While asymmetric cryptography systems like ECDH, RSA, and kin are very much at risk courtesy of Shor’s algorithm, the same is not true for symmetric systems.
An interesting detail with Grover’s is also that you cannot simply run a search in parallel to get a corresponding speed-up, as it’s not a parallel problem. Barring a breakthrough that replaces Grover’s with something that lends itself better to such a parallel search, it would seem that we won’t have to abandon classical encryption any time soon.
Incidentally, even for Shor’s algorithm, there are still some hold-ups. Current quantum computers are not even able to factor 21 yet. Meanwhile, supposed quantum computing breakthroughs are being trolled with a Commodore 64.
Although the term ‘dry ice’ is generally used for solid CO2, it’s much more accurate to call this ‘dry snow’, as, rather than being actual solid blocks, they are effectively snow that’s been compressed really tightly. While not really necessary for most applications of dry ice, it is possible to make blocks of actual CO2 ice, and thus [Hyperspace Pirate], as someone with a healthy obsession with cold things had to make some of his own.
