High-entropy alloys (HEAs) are alloys that are formed by mixing equal or relatively large proportions of (usually) 5 or more elements. Prior to the synthesis of these substances, typical metal alloys comprised 1 or 3 major components with smaller amounts of other elements. For example, additional elements can be added to iron to improve its properties, thereby creating an iron-based alloy, but typically in fairly low proportions, such as the proportions of carbon, manganese, and others in various steels. Hence, high-entropy alloys are a novel class of materials.
These alloys are currently the focus of significant attention in materials science and engineering because they have potentially desirable properties. Some HEAs have considerably better strength-to-weight ratios, with a higher degree of fracture resistance, tensile strength, and corrosion and oxidation resistance than conventional alloys
Author: Gregor J. Rothfuss
Shadows
Shadows are so visually telling that it takes little to move into emotionally tinged narratives. But it is the visual aspects that we primarily deal with here, with a special focus on several types of misrepresentations of shadows — shadows doing impossible things — that nevertheless reap a payoff for scene layout and do not look particularly shocking.
Painters have long struggled with the difficulties of depicting shadows, so much so that shadows — after a brief, spectacular showcase in ancient Roman paintings and mosaics — are almost absent from pictorial art up to the Renaissance and then are hardly present outside traditional Western art.
We have singled out some broad categories of solutions to pictorial problems: depicted shadows having trouble negotiating obstacles in their path; shadow shapes and colors that stretch credibility; inconsistent illumination in the scene; and shadow character getting lost.
Mechanochemistry
This sounds very promising, both for refinery purposes as well as gas storage. Still not convinced that hydrogen is a good fuel though.
The team found a super-efficient way to mechanochemically trap and hold gases in powders, with potentially enormous and wide-ranging industrial implications. Mechanochemistry is a relatively recently coined term, referring to chemical reactions that are triggered by mechanical forces as opposed to heat, light, or electric potential differences. In this case, the mechanical force is supplied by ball milling – a low-energy grinding process in which a cylinder containing steel balls is rotated such that the balls roll up the side, then drop back down again, crushing and rolling over the material inside. This process could separate hydrocarbon gases out from crude oil using less than 10% of the energy that’s needed today. Distillation is responsible for 15% of global energy use.
The gas separation use case would be a pretty huge advance all by itself, but by storing gas securely in powders, the team believes it’s also unlocked a compelling way to store and transport hydrogen, which could play a key role in the coming clean energy transition. The powder can store a hydrogen weight percentage of 6.5%, which is 2x the current record.
Trigger Waves
Biomechanical interactions, rather than neurons, control the movements of one of the simplest animals. The discovery offers a glimpse into how animal behavior worked before neurons evolved.
We show a minimal mechanism — trigger waves — by which these walking cells may work together to achieve organism-scale collaboration, such as coordination of hunting strikes across 100k cells without central control.
The behavior of Trichoplax can be described entirely in the language of physics and dynamical systems. Mechanical interactions that began at the level of a single cilium, and then multiplied over millions of cells and extended to higher levels of structure, fully explained the coordinated locomotion of the entire animal. The organism doesn’t “choose” what to do. Instead, the horde of individual cilia simply moves — and the animal as a whole performs as though it is being directed by a nervous system. The cilia’s dynamics exhibit properties that are commonly seen as distinctive hallmarks of neurons.
2022-03-30: Physical gradients
Much of the research to date on self-generated gradients has looked at chemical signals, but cells can create gradients in other physical attributes, too, including mechanical properties. The recent paper analyzing migrating neural crest cells revealed a self-generated gradient of stiffness.
2022-07-13: Embryogenesis involves the extracellular matrix contracting
Mechanical forces induce embryonic chicken skin to create follicles for growing feathers. Just as surface tension can pull water into spherical beads on a glass surface, so too can the physical tensions within an embryo set up patterns that guide growth and gene activity in developing tissues. As an organism grows and develops, the cells in its tissues pull and push on each other and on the supportive protein scaffolding (extracellular matrix) to which they are intricately linked. Some researchers have suspected that these forces, coupled with changes in the pressure and rigidity of the cells, might direct the formation of complicated patterns. Until now, however, no studies were able to tease apart the effect of these physical forces from the chemical stew in which they simmer.
Reuse Design
Aluminum panels are marked by grade and the car is designed for disassembly; at the end of its life, technicians can easily sort the materials for recycling by specific type, rather than melting different aluminum grades together and compromising the material. The company is doing away with the standard practice of bonding unlike materials in the interior. When you glue a veneer to a plastic, then glue metal trim around the edges of it, you’ve rendered all 3 materials unrecoverable. In contrast, Missoni and his team have designed all of the soft-touch interior elements to be monomaterial, made of “a highly recyclable thermoplastic.” These interior elements “can be recycled as one material, and not only that, they can be recycled over and over again.”
Ukraine
Collecting a few pointers to how this might play out in the longer term. It seems clear that this will accelerate the move away from petro-kleptocracies towards renewable energy as a national security matter.
Europe can stop buying Russian gas. Russia might have trouble selling it because you can’t build new pipelines overnight. Russian oil will find a home somewhere else by boat, rail, or truck. It turns out a ban isn’t necessary anyway. Oil and natural gas supply and demand curves are inelastic. Small changes in supply or demand move prices dramatically. It costs money to produce oil and gas. Reducing the price by 40% might reduce profits by 80%-90%. And a 2%-3% demand decrease might be enough to do the trick. Focus on lowering the profits. Oil is a global market in a way natural gas is not. Europe has to do the heavy lifting for natural gas. There are many economical options available, especially for substitution. Increasing oil and gas supply requires massive changes in the law for European countries. Europe has to keep investing in new gas supply and reducing demand to prevent future price spikes. Eventually, new technologies that create synthetic gas or shift industrial processes to electricity will pick up the slack. Maybe even a few nuclear power plants will get built.
The optimal end to this war is for Russian leadership — generals, spymasters, oligarchs, and politicians — to simply remove Vladimir Putin from power, form a new government, and withdraw Russian troops from Ukraine. The whole war can be blamed on Putin, and Russia and the West can quickly go back to having good relations.
The current sanctions give them a number of incentives to do this. The fall in the ruble, the crashing of the Russian economy, the cutoff of economic relations with the West, and sanctions against Putin-allied individuals all mean that the globetrotting comfy lifestyle Russian leaders have gotten used to over the past two decades is no longer available. If the war ends, these sanctions will presumably be reversed, and something like the old normal can be restored.
And this needs to be made explicit. EU leaders and Biden need to announce clearly and repeatedly that if Russian troops pull back from Ukraine, the sanctions will all be quickly dropped. The part about removing Putin from power doesn’t need to be stated; it will be implicit.
But in fact, the EU and US need to promise Russia much more than this. The reason is that all the stuff I described in the last section — the long-term replacement of Russia’s economic lifeblood with renewable energy — is going to happen anyway, war or no war. The threat of climate change, and the rapid progress in solar, wind, and storage technology, mean that the world’s days of dependence on oil and gas are numbered. Russia is in big long-term trouble no matter what it does.
This gives the EU and US an additional lever — the promise of a Marshall Plan to help the Russian economy retool. Dropping sanctions will restore Russian oil and gas revenue in the short term, but in the long term Russia needs things like infrastructure investment, FDI in manufacturing industries, trade agreements to facilitate European and American purchases of Russian-made goods, and so on. The EU and the US can provide all this. We can make numerical guarantees and specify sectors — railroads, roads, aerospace, IT, whatever.
Hadean Oceans
Oceans formed far more quickly than expected:
The Hadean eon, following the global-scale melting of the mantle, is expected to be a dynamic period, during which Earth experienced vastly different conditions. Geologic records, however, suggest that the surface environment of Earth was already similar to the present by the middle of the Hadean. Under what conditions a harsh surface environment could turn into a habitable one remains uncertain. Here we show that a hydrated mantle with small-scale chemical heterogeneity, created as a result of magma ocean solidification, is the key to ocean formation, the onset of plate tectonics and the rapid removal of greenhouse gases, which are all essential to create a habitable environment on terrestrial planets. When the mantle is wet and dominated by high-magnesium pyroxenites, the removal of carbon dioxide from the atmosphere is expected to be more than ten times faster than the case of a pyrolytic homogeneous mantle and could be completed within 160 ma. Such a chemically heterogeneous mantle would also produce oceanic crust rich in olivine, which is reactive with ocean water and promotes serpentinization. Therefore, conditions similar to the Lost City hydrothermal field may have existed globally in the Hadean seafloor.
Lost Literature
To estimate how much medieval literature once existed, book historians compare ancient book catalogs, which are incomplete, with the number and scope of surviving texts. Another estimate borrowed a technique from ecology called the “unseen species” model. The researchers turned to lists of surviving medieval texts—and those suspected to have been lost—written between 600 and 1450 C.E. in Dutch, French, Icelandic, Irish, English, and German. There were 3648 texts in total. When they ran those numbers through the unseen species model, the algorithm suggested just 9% of medieval texts from that period survived to the present day. That’s rather close to traditional estimates of 7%. The new study also broke things down by region: The model suggests only about 5% of English vernacular works have survived, compared with 17% and 19% for Icelandic and Irish vernacular works, respectively.
Plant synthetic biology
Historically, synthetic biology has heavily focused on using well understood microbes such as E. coli as the “chassis” for engineering new biological processes—which at times has been criticized as a shortcoming of the field. Plants grow to an astounding number of different sizes and shapes, feed us, clothe us, provide the majority of our materials, and are estimated to constitute ~80% of the total biomass on Earth. Despite their central role in our existence, plants have been largely ignored in synthetic biology because of the difficulty associated with engineering them.
A central goal of synthetic biology has been to improve our ability to design new genetic circuits capable of carrying out complex processes. This type of computation is not a metaphor. An active area of research has been to establish a hardware description language for cells, where engineers can describe their intended process, and compile it into a DNA sequence with the appropriate circuits. They were specifically interested in lateral root density, which quantifies the number of outgrowths branching to the side from the main descending root. A higher lateral root density enables plants to better sample their environment for water and nutrients. Being able to precisely engineer this type of trait has global implications—this type of technology may be essential for sustaining agriculture in the future, and could be used as a tool to mitigate challenges plants will face in a warming climate.
2D Polymers
Using a novel polymerization process, MIT chemical engineers have created a new material that is stronger than steel and as light as plastic, and can be easily manufactured in large quantities. The new material is a 2D polymer that self-assembles into sheets, unlike all other polymers, which form 1D, spaghetti-like chains. Until now, scientists had believed it was impossible to induce polymers to form 2D sheets. Such a material could be used as a lightweight, durable coating for car parts or cell phones, or as a building material for bridges or other structures. “We don’t usually think of plastics as being something that you could use to support a building, but with this material, you can enable new things. It has very unusual properties and we’re very excited about that.” The new material’s elastic modulus — a measure of how much force it takes to deform a material — is 4-6x greater than that of bulletproof glass. Its yield strength, or how much force it takes to break the material, is 2x that of steel, even though the material has 15% the density of steel. An important aspect of these new polymers is that they are readily processable in solution, which will facilitate numerous new applications where high strength to weight ratio is important, such as new composite or diffusion barrier materials. Another key feature of 2DPA-1 is that it is impermeable to gases. While other polymers are made from coiled chains with gaps that allow gases to seep through, the new material is made from monomers that lock together like LEGOs, and molecules cannot get between them. “This could allow us to create ultrathin coatings that can completely prevent water or gases from getting through. This kind of barrier coating could be used to protect metal in cars and other vehicles, or steel structures.”
Unclear if more plastic use is helpful, but if the alternative is more concrete, that’s not great either. And if we’re extra lucky, it helps to prevent corrosion at scale, which would give all structures a much longer lifetime.
Gregor J. Rothfuss 