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
Tag: science
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.
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.
Multi Density Water
Water, the most commonplace of liquids, is also the strangest. It has at least 66 properties that differ from most liquids – high surface tension, high heat capacity, high melting and boiling points and low compressibility. 1 school of thought is that water is not a complicated liquid but ‘2 simple liquids with a complicated relationship’. For some, this statement contradicts the basic principles of physical chemistry; for others it explains just why water behaves in such an anomalous way. Researchers have been searching for this putative liquid–liquid phase transition ever since, and evidence has slowly accumulated that it really exists. New experiments now supply what seems to be a direct observation of such a transformation between liquid states of different density – not in pure water but in solutions of the sugar trehalose. Understanding how such supercold solutions behave could have implications for biology and cryopreservation – where damage to biological tissues by ice crystals must be avoided – as well as for the water-rich states that might exist in the atmospheres of gas giants. Liquids are structurally disordered, so it’s not immediately obvious how they can support 2 distinct structures with different densities. But that does seem to be possible for liquids in which some degree of directional bonding, such as hydrogen bonds between adjacent water molecules, makes distinct local structures possible.
Vai Script
The Vai script of Liberia was created from scratch in about 1834 by 8 completely illiterate men who wrote in ink made from crushed berries. Because of its isolation, and the way it has continued to develop up until the present day, we thought it might tell us something important about how writing evolves over short spaces of time. The 8 Vai creators set out to design symbols for each of their language’s syllables, inspired by a dream. Their chosen symbols represented physical things like a pregnant woman, water, and bullets, as well as more abstract traditional emblems. Over the first 171 years of its history, the Vai script did become increasingly compressed. The simplification occurred over generations of users; symbols with the highest complexity were simplified the most. These changes are far from random. Languages pass a kind of natural selection process via memory and learning, where the hardest to recall features do not survive. As the letters became less complex, they also became more uniform. This is despite the language never having been adopted for mass production or for bureaucratic needs. These uses are what seemed to help standardize other languages – for example, Mesopotamia’s writing standardization coincided with the implementation of state-wide systems.
Competitive AI
OpenAI:
We built a neural theorem prover for Lean that learned to solve a variety of challenging high-school olympiad problems. These problems are not standard math exercises, they are used to let the best high-school students compete against each other. The prover uses a language model to find proofs of formal statements. Each time we find a new proof, we use it as new training data, which improves the neural network and enables it to iteratively find solutions to harder and harder statements. We achieved a new state-of-the-art (41.2%) on the miniF2F benchmark, a challenging collection of high-school olympiad problems.
DeepMind:
we created a system called AlphaCode that writes computer programs at a competitive level. AlphaCode achieved an estimated rank within the top 54% of participants in programming competitions by solving new problems that require a combination of critical thinking, logic, algorithms, coding, and natural language understanding.
Gregor J. Rothfuss 