Every time I see a CrustalTrudger answer in a geology thread, I know it's going to be a great explanation. I got my undergraduate degree in geography (and minor in geology), so I'm not a novice on the subject by any means, but your explanations continue to introduce new concepts and theories on tectonics to me.

I would like a neurologist/immunologist to correct me if I'm wrong but. Isn't the biggest reason is that while differenciating leukocytes reacting with brain's molecules aren't destroyed the same way ones reacting with other irgans are? So basically they see a foreign material and attack it?

It's a fairly niche area, I'm not surprised that you didn't cover it in Undergrad.

I had a class on Interfacial Thermodynamics that covered the theory relevant to this (that I remember almost nothing about other than it having 80 or so 'essential' equations to comprehend in a 10 lecture course), surfactants weren't discussed explicitly in the class but thermo is thermo and applies to all systems equally.

I came across this particular area of knowledge doing some post-doctoral work for an excellent physical chemist who specialised in surfactants.

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The answer that was removed kind of boiled down to 'if it forms micelles it forms foam' with some very vague statements in support. It was poorly written, didn't use scientific language, mixed up cause and effect. Most of the facts weren't wrong, but they weren't factors in foaming behaviour. It actually made it pretty difficult to dispute, which is why I didn't bother to explicitly address it. Didn't want to get drawn into a potential pedantry showdown!

The bit I remember was a dubious claim that seemed to suggest that the air partitions into the core of the micelle, which is completely untrue (but was hard to understand exactly what he meant because of the lack of technical language). FYI when you bubble air into a surfactant solution you are in fact creating a new area of air/water interface along which the surfactant forms a typical monolayer.

Anyhoo! Not a problem anymore.

The main cause of post-vaccination pain is the needle has physically damaged your body. You do have a new unplanned hole in your skin, muscle, fat layer, etc. It's very operator dependent.

Erythema is redness in the skin due to increased blood flow to the capillaries in your skin. Same as any skin injury.

Induration is your skin thickening/hardening after an injury. It is a result of inflammation response from a skin injury. Your body has only a handful of responses to an injury, and inflammation is an easy one.

Sub-cutaneous nodules, or little bumpy lumps under your skin. Usually from local inflammatory reactions or immune-mediated responses.

That is all dependent on how much volume was the dose, where it had to go, how quickly it diffuses away from the injection site.

Next is the adjuvant chemicals that are triggering the immune response.

There are different stimulants in different vaccines that force your body to recognize something has happened. It can induction of cytokines and chemokines (inflammation, hey, look over here), recruitment of immune cells (swelling, lets bring lots of workers to the site), enhancement of antigen uptake and presentation (swelling as it opens up your internal paths), and promoting antigen transport to drain stuff away into your lymph nodes (itching, got to physical push stuff into the lymph system).

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There's several reasons for this. There are many things in the blood stream that would be toxic to neurons if they passed the blood-brain barrier. Also, blood spilling out of a hemorrhagic stroke doesn't oxygenate the brain in the normal way though capillaries, where the blood ells progress to veins and then eventually are re-oxygenated. Blood spilling out onto the brain causes most neurons downstream to be deprived of oxygen and nutrients.

The very best foaming products contain at least two surfactants.

The classic foaming surfactants are anionic such as sodium dodecyl sulfate (SDS) and sodium laureth sulfate (SLES). They form great foam heights but the bubbles collapse really quickly.

Foam stabilizer chemicals are added to consumer products, such as laureth-3 or 4, cocamide DEA. These usually don't make foam by themselves, but what they do is like iron rebar in concrete, they reinforce the bubble that has formed.

Baby shampoo is a nice example. It's usually the mixture of SLES and cocamido propyl betaine (an amphoteric surfactant). The previous stabilizer mentioned is fantastic, but it is a skin irritant and burns your eyes. The amphoteric cocamido is very mild but less effective, hence, you need a lot more of it (higher cost) or you get a lower foam height / short stability time.

The difference between two-product formulas and solid bar soap, is the bar soap is usually a single surfactant maybe with some glycerol added. The bar soap needs a shitload of mixing energy to make a stable foam. You need to use a foaming brush and lots of stirring to input enough energy so that the molecules align correctly and get the best ratio of air/water/surfactant. Even after all that energy is put in, it still doesn't last as long as a two-surfactant mixture.

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Thanks for your information!

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I've always wondered about this too, and it was never addressed during my undergrad chemistry degree. Thanks for the great explanation! I didn't get the see the answer you are referring to before it was removed, but the molecular organization you are describing (the air/surfactant/water/surfactant/air organization) certainly sounds a lot like a micelle structure to me? What am I missing (again I didn't read the other comment).

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Kamaʻehuakanaloa is far to close to the big island to be the next island in the chain, it will join with the island soon after breaching the surface, if Kilauea doesn't fill in the gap before then. In fact, if the increased magma output doesn't slow down, I would expect individual islands to stop being a thing except at the tail end of the landmass, roughly where Kauai currently is.

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Go on https://timetree.org/ type Felidae in "build a timetree, Specify a Group of Taxa " then choose species and see the (time-scaled, ie. age of common ancestors) tree you get

You'll find 5 other Felis species with MRCA from 1.5 to 6 million years. Adding the few Prionailurus species with MRCA 9 million years you'll get something roughly equivalent to the Homo-Pan lineage in term of evolutionary history.

The Felis species really look like cats and the Prionailurus species are a bit wilder but still cattish, need to go farther to find something more like a Lynx or a Panthera (MRCA 12 million years so similar to the Apes lineage);

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Think of it like a neuron is your house and the blood is a Highway. We need the things traveling on the highway (like people, Amazon orders, etc) to make the house function. But there are a lot of other things on the road that if they directly contacted the house (like a 16-wheeler moving at 60 mph) would cause damage. Our neurons need the oxygen and nutrients, but sometimes the things that bring the oxygen (like hemoglobin which contains iron) can be toxic if they are released onto bare neurons. That’s why neurons are separated from direct contact with blood by other cell types like astrocytes and pericytes which more carefully regulate how neurons get what they need from blood.

just want to make sure I'm understanding this correctly... would this be a decent Eli5 version of your 3 factors?...

1. The hotspot is higher than the ocean floor around it, so the island right on the hot spot is starting from a higher sea floor than the others
2. The volcano has been particularly volcano-y for the last couple of million years, so it's making bigger islands now than it has in the past
3. Volcanic islands get smaller over time if they're not actively volcano-ing, so the island that has the volcano right now is bigger than the ones that haven't had it for a while.

Is that about right?

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