This article reminded me of a story I heard second hand. In the Karoo of South Africa, sheep farmers provided lambs with feed containing the ground up stomaches of older sheep who lived in the area. If this was not done, then the lambs would fail to thrive when grazing. Presumably the ingested intestines transmit bacteria conferring the ability to digest otherwise indigestible material.
"Intervals", "Scales", and "Chords" are good terms to search for. They are elementary concepts present in a lot of music. Ten Steps use six notes of the C Major Scale, all of which belong to either the I or IV chord. The I and IV chords use, by definition, an interval of 1-4-7.
For an entertaining overview, check out Leonard Bernstein's 1973 Norton lectures, "The Unanswered Question"[0]
Nice, I've used an image like this one as guide: https://qph.fs.quoracdn.net/main-qimg-378ba2572d2033b70ef10d... each note om my game is a sine wave with the hertz described in this picture (i randomly choose the rage between 500 - 700, but I don't know what that means).
On my other project, I'm planning on doing like a small "synthesizer" that can play a note "c, d, e f..." and the use it to try and create music, using procedural generation and machine learning.
Anyways, I'll look into what you told me and I'll watch the video. Thanks a lot.
Diamond anvil cells are amazing tools. If you find this stuff interesting, check out Emma McBride's public SLAC lecture[1], "New Materials at the Pressures of Earth's Core"
^ That's pretty darn cool, thanks. Among the things you'll learn:
- Around 4000 miles into Neptune's crust, there is a sea of hydrogen where carbon crystallizes into diamond which falls like rain to the center of the planet forming a diamond layer. And that layer is actually solid crystals of diamond inside a sea of metallic liquid carbon. Lol wat? Damn, nature.
Can anyone here explain to me how a diamond anvil cell works? The metal gasket is under the same pressure as the diamond, so presumably it would deform and let the pressure out?
And if it were strong enough to contain the pressure, why not make the whole thing out of the same metal?
My Physics classes are rusty, but if you've 400GPa across a 1mm^2 surface, and the back of the two opposing diamonds is e.g. 1cm^2, then you've a straight pressure reduction then and there -- not unlike what might happen with a lever or a pulley. So you can then apply a smaller force on the outside, allowing you to use a less sturdy/expensive cristal or metal (or liquid, apparently [0]).
This doesn't answer the question of why diamond if the gasket material can also stand up to the pressure, though. You can certainly make a truncated cone-ish shape out of metal.
Not an expert, but I believe one big benefit of using diamond is that it's easier to observe the sample through it (visually as well as X-ray imaging techniques, etc.).
Heh, thanks. Whatever, though. I don't care about downvotes and I'd have jumped in even if it were somebody else's comment—I just really don't like to see collective moderation tools (is that the right term?) used by people who have no clue what they're talking about to shut down discussion.
I'm a little sorry to have used such "uncivil" language ... but also, I'm not.
The gasket does deform. But that doesn't let the pressure out.
I'm not in this field, but I know several experts in it. I've helped out on experiments and have loaded DACs myself up to 20GPa or so.
I'll describe how it works in practice at that kind of pressure, and then what I understand of the different techniques needed for the extreme pressures used in this paper.
Loading the DAC is fiddly and done by hand. You start off looking through a microscope at the bottom side of the DAC. The lower diamond is pointing up at you. The tip of it is truncated at the point to give a flat end face around 100um across. With tweezers and a steady hand, you place your gasket - basically a rhenium washer with a maybe ~50um inner diameter - on top of that, with the outer edge of the gasket overhanging the edges of the diamond tip.
Then you need to drop two things into the hole in the middle. A little fragment of your sample material, and a tiny piece of ruby. The ruby is your pressure gauge! Ruby fluoresces, at a wavelength that varies with pressure in a known way. So when the cell is loaded, you can shine a laser through the ruby and look for the spectrographic line of the fluorescence to get the pressure.
Now you have your sample and your ruby sitting inside the gasket, but they're surrounded by air. That's not going to work. You need the space around them to be filled with a liquid, to act as a medium to distribute the pressure. So you take a little syringe and plop a drop of whatever your chosen liquid is into the hole. There are different things you might use depending on the experiment.
Now that you have everything in there ready, you can attach the top side of the DAC and bring the second diamond down onto the top of the gasket. The cell will need to have been carefully aligned beforehand to ensure that the diamond tips meet up flat in the middle.
With everything together, you can now start applying pressure. In simple DACs this is literally just a case of tightening screws around the outside by hand. For more precise/automated control, you can get cells with a built in gas membrane.
But your question was about the gasket - what role does it play? Well, firstly you need something there to hold your sample and your ruby and your liquid in place while you prepare and load the cell. If you just pushed the two diamonds together the liquid would just flow out, the diamonds would hit the sample or the ruby and crush them at a point, rather than compressing them under hydrostatic conditions.
But you need the gasket to give way when you start applying pressure, which is what it does. It gets thinner, and material is pushed out of the sides. When you eventually unload the cell, you can look at what's left of the gasket and see the imprints of the ends of the diamonds in it.
You still need the gasket to be made out of something very strong so that it doesn't pull apart completely. But it's playing a very different role to the diamonds. They need to be hard. The gasket needs to be tough.
The diamonds, by the way, usually sit in tungsten carbide seats, because that's hard enough to take the pressure transmitted through the wide end of the diamond, which is still pretty high. The carbide seats then widen out further to the point where the rest of the cell can be made from stainless steel.
But that's all at the measly 20GPa or so that I'm vaguely familiar with.
What I got from chatting to an expert about this paper was something like the following.
425GPa is crazy pressure. That's four million atmospheres. At this point you're actually beyond the compressive yield strength of diamond. If you tried to use flat-ended diamonds like I described, they'd shatter before you got half way to that pressure.
Instead, they use a focused ion beam to machine a recess in the face of each diamond, giving what's called a toroidal cell. You can actually see that in the compressed shape of the gasket in Figure 1a. The force is distributed in a ring around the outside, so that it stays within the range of what the diamonds can handle.
The sample in the middle is being compressed from above and below by the diamonds, and also from the sides by the gasket material being pushed inwards by the raised rings on the diamond faces coming together. So you're actually using it to help pressurise the sample even though you're way past the yield strengths of both materials.
It will have required some incredible capabilities to design, build, align and load that cell. Even aside from the question of metallic hydrogen, there's some serious showing off here just in terms of techniques.
I think a more refined version of your parent poster's question might be, why doesn't the gasket continue to extrude itself out of the gap, even though its ultimate strength has been exceeded by possibly several orders of magnitude?
You could say the small center area of pressure is acting on a very thick cross-section of gasket (like a big pipe with a tiny inside diameter), but isn't there a limit to this where the pressure doesn't care how much extra material you pile on?
Or for a more layman example, Jello has some amount of tensile strength, but you can't exactly build a cannon out of it regardless of how thick the barrel is.
Metal at these pressures probably behaves more like jello than metal, so what's keeping it together in this case?
I'm not a materials scientist, so I probably don't really know the right answers to these questions or what the correct terms are. All I can do is try give you an idea of what happens in practice from my limited experience, and my working understanding of it.
> I think a more refined version of your parent poster's question might be, why doesn't the gasket continue to extrude itself out of the gap, even though its ultimate strength has been exceeded by possibly several orders of magnitude?
It does continue to extrude itself out of the gap. The more you increase the pressure, the more gasket material comes out. And this isn't an elastic, reversible process - it's plastic deformation which leaves the gasket permanently thinner after you unload the cell. So the gasket material has failed, in terms of what we'd usually use "failure" to mean in an everyday mechanical structure.
But your expectation seems to be that beyond the point of failure, the gasket material should basically just flow freely, like a liquid. That's not what happens. Failure is just the point at which permanent damage starts to occur. There's a whole separate region of behaviour beyond that point, which depends on the material and the conditions.
I mentioned that in this work, they go beyond the yield strength of diamond. If you look at Fig 6 in the actual paper [0], they have an electron microsope image of the diamond tip after unloading the cell. It's permanently and severely damaged, with concentric ring cracks around the tip. So the diamond did "fail", in the formal sense of that word. But that doesn't mean it didn't do the job they needed it to do anyway.
> You could say the small center area of pressure is acting on a very thick cross-section of gasket (like a big pipe with a tiny inside diameter), but isn't there a limit to this where the pressure doesn't care how much extra material you pile on?
There probably is! But that's not what failure means, and so it's not what numbers like yield strength refer to. Failure for your big pipe is the point at which the internal pressure starts to permanently bulge the pipe. It's not necessarily the point at which it ruptures. That can happen at any point beyond failure, depending on the material and the conditions.
> Or for a more layman example, Jello has some amount of tensile strength, but you can't exactly build a cannon out of it regardless of how thick the barrel is. Metal at these pressures probably behaves more like jello than metal, so what's keeping it together in this case?
Let's take a layman's example that better fits the question at hand, and requires a bit less hypothesising about jello.
Rubber has some amount of tensile strength, but you can't build a car's engine block out of it.
It works just fine for the head gasket, though, where it has to successfully contain the extreme pressures that occur in the cylinders during the combustion cycle. It works in practice in the conditions where it's compressed between the head and the block.
And that's exactly the role that the rhenium gasket plays in a DAC.
In both cases, there is some pressure beyond which it will no longer do the job. But there probably isn't a simple number you can look up which will tell you when that will happen, based only on the material.
Diamond tetramers have good compressibility; aluminum exactly that of Reynold's Wrap happens to have not only adequate alumina and vanadium alloyed with it so that when it is thinned by pressure flow it to under 5nm it will be solid.
Pressurizing is done carefully so that nothing important is sacrificed to flowing or a flowable channel of metal! The ruby can help, with staged failsafes of pressure removal e.g. of hydraulic oil to mics pressurizing the anvil.
Doesn't cover doing it at microkelvin with a helium still co-located, which seems special! Can't one just be happy with experimental cosmology (to find a purified hydrogen body in telescope range...)
Video is highly engaging, and moving images are very useful. I wanted to include videos in an electronic book, but it turned out that auto-playing videos are too interesting and they ruin the flow. Instead, I ended up playing the videos frame by frame according to scroll position. The effect is pretty neat: https://goeiebook.ca/story/bussing/
In other words, you need to write more than just words. This has certainly been my experience over the last decade or more of chasing the thing. At this point I've written some fairly solid web code and a decent narrative, but as for the marketing... well, let me just post a link[0].
In Len Beadell's book "Blast the Bush", he describes a solution (pun?) developed while building the Woomera Rocket Range. Apparently the groundwater had a terrible taste; so they built a distillation facility. But the distilled water was unpalatable because it was too pure. So, they experimented by mixing distilled water with small amounts of groundwater, eventually arriving at a drinkable ratio.
The Issus genus of jumping insects (planthoppers)[0] have a gear mechanism connecting their rear legs. The gear synchronizes the motion of the two back legs; thereby reducing 'yaw rotation' when jumping[1]. The gear communicates motion faster than a purely neurological system.
There was also a converse experiment: a population of dogs was un-domesticated by breeding for a strong wild response. I don't have the exact reference, but recollect that the process also took a remarkably low number of generations.
I wonder what sort of physical attributes/neurochemistry would develop in increasingly wild populations of dogs.
Australian Dingos maybe used to be (semi-)domesticated before they were introduced to Australia, originally having been bred in China, then gone 'wild' between 5000 and 18,000 years ago (https://en.wikipedia.org/wiki/Dingo#Origin_and_genetic_statu...). There is some research into the genome on that page, but AFAIK there is no whole genome assembly yet. You can tame those but wild dingoes are very dangerous animals, as many Australian tourists can tell you.
Zebras, on the other hand, are generally thought to be very hard to domesticate, with only a few successes of taming in the last hundred years, and zero success for domestication: https://en.wikipedia.org/wiki/Zebra#Domestication
This could have relevance to dog breeds originally selected for fighting or baiting, then subsequently selected for companionship. Maybe if a fighting or baiting dog is n generations into social breeding it can be considered safe?
Dogs are kind of a weird case, from an animal population standpoint. On one hand, there are a ton of 'purebred' populations that undergo very specific selection and which are fairly genetically isolated from the rest of the species. These are your fighting dogs, your hunting dogs, your ratters, your herders, your companions, etc etc. On the other, there's this huge pool of castoffs and mutts, which aren't really undergoing any concerted deliberate selection at all. However, the castoffs from the specific breed dogs are constantly being shunted into the general population.
So to answer your question in that context: Yes, it would be more than possible to take a population of dangerous fighting dogs and use them as the base stock for a pet breed, provided that the breeding program was well designed. However, the general mutt population will always have fighting dog traits mixed into it so long as there are fighting breeds around.
