Tag: chemistry

Cheapium

In the search for cheaper materials that mimic their purer, more expensive counterparts, researchers are abandoning hunches and intuition for theoretical models and pure computing power.In a new study, researchers used computational methods to identify 10s of platinum-group alloys that were previously unknown to science but could prove beneficial in a wide range of applications.

i hadn’t thought beyond proteins, but computational chemistry can be used to find radically cheaper catalysts than platinum, and in general, revolutionize materials science. this is potentially a very big deal, as advances in materials science are one of the few areas that tend to benefit all of mankind equally.

Synthesis optimization

The software combines long syntheses of compounds into shorter and more economical routes, and identifies suspicious chemical recipes that could lead to chemical weapons.

Their main trick seems to be to combine multiple steps into steps that can happen at once, what they call “one pot”.
2022-02-23: Nice analogy on the energy landscape for reactions, twisty pathways along the edges of steep ridges.

What would it take to have software that showed you the best synthesis for a given compound, though? Now that’s a dream that even I think is out of reach for us, at least for as far out into the future as I can imagine. And this paper illustrates why! Look at all the tiny variations that end up making a difference, and sometimes a big difference. If we could model or compute our way to the answers in such situations, believe me, we would do that rather than set up endless arrays of reactions just to see what happens. Everyone who’s done research-level synthetic organic chemistry has experienced this: you flip one chiral center in your molecule, or made a chain 1 carbon longer, you change the solvent from one ether to another, raise or lower the temperature a bit, switch a sodium salt for a potassium one, change a ligand on your palladium catalyst, whatever, and all sorts of craziness breaks loose. And it’s often not easy to see why things changed so much. Ex post facto you can sometimes come up with hypotheses, and use those to fix things up if you’re right. But there are plenty of throw-your-hands-up moments that just never get explained at all.

Organic chemistry wobbles and teeters across an energy landscape that (from the viewpoint of any given reaction) is full of huge hills, deep valleys, and twisty little pathways that are followed by walking along the edges of steep, crumbling ridges. But from a distance, all that topography is compressed into a pretty narrow thermodynamic range. The differences between a reaction working and not working, between it giving you mostly Product A, mostly Product B, mostly returned starting material, or mostly scorched pan drippings are energetically very small. All sorts of little changes can send things off in different directions, and these can be largely inside the error bars of our attempts to model them. Organic chemistry is indeed a mature science, but don’t confuse that with thinking that it’s a solved problem. If you just want the molecules, damn the cost, to answer other questions we can generally provide them. But if you want them made elegantly, you’ll need to take a seat – and you better have packed some lunch with you.

Concrete

bye bye potholes!

BacillaFilla is a gengineered bacterium based on Bacillus subtilis that has been modified to fill and bond cracks in cement caused by earthquakes and other violence. The bacteria burrow into the concrete until they have filled all its cracks, then they politely turn into calcium carbonate and die.

2012-06-24: Romans were better at concrete than we are. No modern concrete building will last 2000 years like the Roman Pantheon.

Modern concrete—used in everything from roads to buildings to bridges—can break down in as few as 50 years. But 1000s of years after the Roman Empire crumbled to dust, its concrete structures are still standing. Now, scientists have finally figured out why: a special ingredient that makes the cement grow stronger—not weaker—over time. Scientists began their search with an ancient recipe for mortar, laid down by Roman engineer Marcus Vitruvius in 30 BCE It called for a concoction of volcanic ash, lime, and seawater, mixed together with volcanic rocks and spread into wooden molds that were then immersed in more sea water. History contains many references to the durability of Roman concrete, including this cryptic note written in 79 BCE, describing concrete exposed to seawater as: “a single stone mass, impregnable to the waves and everyday stronger.” What did it mean? To find out, the researchers studied drilled cores of a Roman harbor from Pozzuoli Bay near Naples, Italy. When they analyzed it, they found that the seawater had dissolved components of the volcanic ash, allowing new binding minerals to grow. Within 10 years, a very rare hydrothermal mineral called aluminum tobermorite (Al-tobermorite) had formed in the concrete.

2013-10-28: 3D printed concrete will topple the slow, corrupt construction “industry”. a house can be printed in 20h, to much finer tolerances.

The process could accelerate the $1T (US only) construction industry 200x. Projections indicate costs will be around 20% of conventional construction.

3D-printing startup Apis Cor recently completed its latest claim to greatness: the “world’s largest” 3D-printed building to date. The 700m2, 10m-tall structure was built in Dubai

2015-09-30: Concrete is extremely CO2 heavy

The concrete industry is one of 2 largest producers of CO2, creating up to 5% of worldwide man-made emissions

2016-08-02: Mesh concrete. Another small step to turn construction from a super slow, error-prone process into a fast and accurate one.

Mesh Mould Metal “focuses on the translation of the structurally weak polymer-based extrusion process into a fully load-bearing construction system” by replicating the process in metal. Specifically, the current research delves into the development of “a fully automated bending and welding process for meshes fabricated from 3-millimeter steel wire.”

2021-07-26: Self-supporting concrete

By 3D printing concrete at specific angles, the collaborative team was able to produce blocks with layers “orthogonal to the flow of compressive forces,” allowing them to design differently-shaped blocks for different portions of the bridge. The blocks stick together through gravity, meaning no mortar is required. No steel reinforcements are necessary, either. And if needed, the entire bridge can simply be disassembled and reassembled elsewhere.

2021-08-09: Construction Physics describes how 3D printed concrete is at the bottom of an S curve:

For the most part, despite the hype, the current state of building 3D printing is fairly unimpressive. The resolution is poor, the process is sluggish (Icon’s printer can print a 3m x 3m in little over 8 hours – not terrible but not setting the world on fire), the material options are extremely limited, the equipment is expensive and finicky, and the results are generally worse on multiple axes than what you could get from conventional construction.

2022-02-03: The scale of concrete production

Human civilization is basically a machine for producing concrete and gravel.

Concrete will naturally absorb CO2, a process known as carbonation (even normal concrete will absorb roughly 30% of the CO2 emitted during the production process over the course of its life.) Companies like Carbicrete, Carboncure, Carbonbuilt and Solida all offer methods of concrete production that allow the concrete to absorb CO2 during the production process, substantially reducing embodied emissions. Interestingly, these producers mostly claim that their concrete is actually cheaper than conventional concretes, which would obviously be a massive tailwind for the technology’s adoption.

It’s not obvious what the best path forward is for addressing concrete CO2 emissions (like with most things, I suspect it’ll end up being a mix of different solutions), but understanding the parameters of the problem is necessary for solving it.

2022-03-25: Economics of concrete decarbonization

Full decarbonization with CCS is expected to double the cost of Portland cement, now about US$100 per tonne. Cement subsidies would need to match that. 0-emissions steel is expected to cost 20–40% more than standard steel, which is typically about $600 per tonne — so steel subsidies would need to reach $240 per tonne. For the EU, we estimate that could cost up to $200 billion over 10 years.

2023-01-12: The chemistry of roman concrete has been decoded

For many years, researchers have assumed that the key to the ancient concrete’s durability was based on one ingredient: pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples. This specific kind of ash was even shipped all across the vast Roman empire to be used in construction, and was described as a key ingredient for concrete in accounts by architects and historians at the time.

Under closer examination, these ancient samples also contain small, distinctive, millimeter-scale bright white mineral features, which have been long recognized as a ubiquitous component of Roman concretes. These white chunks, often referred to as “lime clasts,” originate from lime, another key component of the ancient concrete mix. “Ever since I first began working with ancient Roman concrete, I’ve always been fascinated by these features. These are not found in modern concrete formulations, so why are they present in these ancient materials?”

Previously disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials, the new study suggests that these tiny lime clasts gave the concrete a previously unrecognized self-healing capability.


But this doesn’t mean that we can simply replace all concrete with this new formula

If we have the possibility of building more durable concrete buildings, why don’t we? Using unreinforced concrete dramatically limits the sort of construction you can do – even if the code allows it, you’re basically limited to only using concrete in compression. Without reinforcing, modern concrete buildings and bridges would be largely impossible.

Other methods of reducing reinforcement corrosion also have drawbacks, especially cost. Stainless steel rebar is 4-6x as expensive as normal rebar. Epoxy coated rebar (commonly used on bridge construction in the US) is also more expensive, and though it can slow down corrosion, it won’t stop it. Basalt rebar won’t corrode but can apparently decay in other ways.

2023-03-23: The 3D printing concrete dream won’t die. These savings are quite modest but a 24 / 7 operation should speed things up another factor of 4

This 100-house addition to the 2500 homes planned for Wolf Ranch is called “the Genesis Collection,” and as the world’s largest 3D-printed community, it is indeed sui generis. 3D-printed homes cost 10-30% less to build than conventional construction, while Coleman expects construction time to be cut 30% at Wolf Ranch. Concrete is carbon-intensive, but the material’s use at Wolf Ranch creates nearly airtight buildings that will reduce homeowners’ heating and cooling costs, while the solar panels installed on each residence will supply carbon-free electricity. Icon’s 3D-printed walls have exceeded building code strength requirements by 350% which allows them to better withstand hurricanes and wildfires. “We are trying to make the case that not only do our robots not need smoke breaks or anything like that, they also are very quiet and should be allowed to work around the clock.”

Prebiotic Chemistry

The RNA hypothesis is very popular but doesn’t explain how fragile RNA can survive in hostile environments.

Dr. Joyce has been studying the possible beginning of history by developing RNA molecules with the capacity for replication. RNA, a close cousin of DNA, almost certainly preceded it as the genetic molecule of living cells. Besides carrying information, RNA can also act as an enzyme to promote chemical reactions. Dr. Joyce has developed 2 RNA molecules that can promote each other’s synthesis from the 4 kinds of RNA nucleotides. “We finally have a molecule that’s immortal”

2016-02-21: Talk of RNA-like

Perhaps before biology arose, there was a preliminary stage of proto-life, in which chemical processes alone created a smorgasbord of RNAs or RNA-like molecules. “I think there were a lot of steps before you get to a self-replicating self-sustaining system”. In this scenario, a variety of RNA-like molecules could form spontaneously, helping the chemical pool to simultaneously invent many of the parts needed for life to emerge. Proto-life forms experimented with primitive molecular machinery, sharing their parts. The entire system worked like a giant community swap meet. Only once this system was established could a self-replicating RNA emerge.

2019-06-30: Viroids, survivors from the RNA World?

Because RNA can be a carrier of genetic information and a biocatalyst, there is a consensus that it emerged before DNA and proteins, which eventually assumed these roles and relegated RNA to intermediate functions. If such a scenario–the so-called RNA world–existed, we might hope to find its relics in our present world. The properties of viroids that make them candidates for being survivors of the RNA world include those expected for primitive RNA replicons: (a) small size imposed by error-prone replication, (b) high G + C content to increase replication fidelity, (c) circular structure for assuring complete replication without genomic tags, (d) structural periodicity for modular assembly into enlarged genomes, (e) lack of protein-coding ability consistent with a ribosome-free habitat, and (f) replication mediated in some by ribozymes, the fingerprint of the RNA world. With the advent of DNA and proteins, those protoviroids lost some abilities and became the plant parasites we now know.

2022-05-06: RNA “species”

Over 100s of hours of replication, 1 type of RNA evolved into 5 different molecular “species” or lineages of hosts and parasites that coexisted in harmony and cooperated to survive, like the beginning of a “molecular version of an ecosystem”. Their experiment, which confirmed previous theoretical findings, showed that molecules with the means to replicate could spontaneously develop complexity through Darwinian evolution. Some of these results confirmed the predictions of earlier experimental studies of how complexity can arise in viruses, bacteria and eukaryotes, as well as some theoretical work.
“Without parasites, this level of diversification is probably not possible”. Evolutionary pressures that parasites and their hosts place on each other lead both sides to split into new lineages.


2024-02-01: Obelisks

A new kind of viruslike entity that inhabits bacteria dwelling in the human mouth and gut. These “obelisks” have genomes seemingly composed of loops of RNA and sequences belonging to them have been found around the world. The Stanford search yielded 30k predicted RNA circles, each consisting of ~1000 bases and likely representing a distinct obelisk. They were unlikely to be bona fide viruses because RNA viruses typically have many more bases. But some of the obelisk sequences encoded proteins involved in RNA replication, making them more complex than standard viroids. Like viroids, however, obelisks don’t seem to encode proteins that make up a shell. Because obelisks contain genes that are unlike any discovered so far in other organisms, they “comprise a class of diverse RNAs that have colonized, and gone unnoticed in, human, and global microbiomes”