It's theoretically related to color blindness, so you'd expect it to be as common. But the problem is even if your eye has the extra primary, your brain may not have developed the ability to "see" it. They had to test quite a few people with the proper genetic background before they finally found one.
That's fair but even colour blindness is mostly undiagnosed in practice - even with the comparatively high prevalence & awareness, actual figures for colour blindness are still grounded in speculative extrapolation.
I think it fundamentally comes down to whether your sense anomaly represents a significant disability. Colour blindness is a disability, but not one that's significant for the vast majority of people who suffer from it - I've worked with multiple colour blind graphic designers & they were good at their job. There's very little impetus to even seek diagnosis - if they weren't working in a colour-focused industry I suspect they may not have ever realised they had a disability at all.
Tetrachromacy then is an even harder case because it's not a disability at all. The impetus to seek "diagnosis" is zero. Also, even though as you mention there's technically multiple ways of detecting the various factors that need to coexist in tetrachromacy (i.e. (1) sensory testing, (2) physical presence of extra primaries, (3) neurological processing pathways), the latter two are either not directly detectable or never directly tested for - even in speculative cases of people having a 4th primary, the number of primaries present is generally hypothesised via some other avenue like testing for anomalous trichromacy. Ultimately we're heavily relying on direct sensory testing which is almost nonexistent in the general population. There's no way to accurately speculate on how prevalent it might be.
It took me about a second to realize the link took you to a list of articles. It took another second to realize the article referenced was second in the list.
I've never understood one vital thing - if PFAS is by nature totally inert and unreactive, how is it harmful? If you drank a glass of the stuff, what would happen?
As I understand it they discovered a long chain molecule which was highly inert and wouldn’t stick to anything. Which was a useful feature but you know makes it hard to attach to anything. So they created a similar smaller chain molecule which had a reactive tip but was still super stable. Unfortunately it’s also a bit amino acid like. So we ended up with a molecule which is very durable and accumulates in living things.
Then of course we produced it at industrial scale for decades flooding the entire planet with this stuff.
For example PTFE is a large molecule with strong bonds, and as a consequence isn't very reactive and likely safe.
On the other hand, perfluoroalkyls such as PFOA have the same shape as fatty acids, so they bind to the same places such as in the liver, which makes them grave health hazards.
Many precursors used for making PFAS are also toxic, so for example, even if PTFE is safe, manufacturing it isn't.
The bioaccumulate part I understand, for the body to eliminate something it has to bind to it somehow. Tough to do if the chemical won't react with anything.
I'm not sure what "biologically inert" means specifically. Are you saying there are biological chemicals that actually do interact with this stuff? A single example would help me understand.
I don't know the details here for PFAS (and they likely would vary enormously for the different molecules that fall into this broad category). But in general a molecule doesn't have to react to be accumulated. Inert usually means it doesn't react with other substances in a normal environment. It doesn't mean you can't make it react if you add enough energy. For example nitrogen gas is considered inert. Bacteria (or chemical plants) can make it react and produce different nitrogen-containing molecules from it.
Inert doesn't really say anything about toxicity, it's not directly related to that. The opposite is though, pretty much any strongly reactive chemical is dangerous or toxic in some way since it will react with stuff humans are made from.
With PFAS the inert example is also usually Teflon. That is also a solid polymer, so not many individual molecules. There isn't much you body could do to process a macroscopic chunk of Teflon, so you'd almost certainly just excrete it.
Edit: Nevermind, Wikipedia makes it pretty clear that even the non-broken-down PFAS are totally unsafe, evil things which we knew were dangerous since the 70s and did nothing about until recently
As far as I understand the nomenclature, PFAS covers both the inert final products like Teflon and reactive intermediates, degradation products and reactants. It's a very broad category of chemicals.
My understanding is that the bigger danger is e.g. a Teflon-producing plant than the final Teflon products (assuming the Teflon isn't damaged and heated too much). Because the plant has to handle the reactive ingredients, and those can leak into the environment.
Fluoroalkyl chemicals are only "inert and unreactive" in a relatively narrow sense of "wouldn't catch fire", "don't react with strong acids and bases", and similar.
They are plenty reactive in a sense of interacting with enzymes and other cellular machinery.
Not really accurate. These chemicals are quite unreactive. Precursors from manufacturing waste can be very reactive, but most of the problematic contamination regards the forever chemicals themselves, not precursors. This paper is probably the best scientific review of what is going on in the human body. https://www.sciencedirect.com/science/article/abs/pii/S03043...
Maybe sci-hub has a copy of the full paper. Not sure.
As briefly as possible, and therefore glossing over many many details, the toxic effects are mainly due to cell membrane perturbation, cell membrane transport disruption, and binding to hydrophobic protein cavities (thus disrupting the usual function of these cavities).
Making PFAS and having to dispose of byproducts is the nasty part as far as I understand. There is also some kind of reaction that can happen where it will off gas nasty enough stuff to kill your pet bird if you overheat your pan.
PFAS used to be considered totally inert but later research showed correlations between bad health effects and higher concentrations of PFOA and PFOS.
3M and DuPont knew since the 1970s and suppressed the information, not dissimilar to how tobacco and oil industries created disinformation about externalities.
One Google feature that I think is killing the internet is actually useful in this case - the AI summary. If your vital information is on a platform that I will never join, I can't see it directly. But Google can, and many times I can find what I need in the summary. Of course it's not perfect, like when I'm trying to find holiday hours.
You can combine the Sieve and Wheel techniques to reduce the memory requirements dramatically. There's no need to use a bit for numbers that you already know can't be prime. You can find a Python implementation at https://stackoverflow.com/a/62919243/5987
I'd be interested in seeing an explanation of the code, since it looks pretty incomprehensible to me. Per the arbitrary rules I set for myself, I'm not allowed to precompute/hardcode the wheel (looks like this implementation uses a hardcoded wheel of size 2x3x5=30). I wonder if/by how much the performance would suffer by computing and storing the coprime remainders in memory instead of handing them directly to the compiler.
I wrote this in a semi obfuscated style to make it fit on one screen.
It's indeed a hardcoded 2x3x5 wheel; but I suspect computing all those
constants would have made the program significantly longer.
They've always said you spend a lot more time reading code than writing it. If suddenly you're writing a lot more code, you're going to spend a ton more time reading it.
There's nothing new about this pattern. When the tractor was invented, the farmer didn't get to knock off early. He just started producing 10x more. Then the tractors got bigger and more powerful, and the things you used them with got more sophisticated too and suddenly you're producing 100x more.
And the only people who could afford to tractor at scale are Cargill/Monsanto who bought out most of the small/medium-sized farms while leaving farms that didn't take the offer to slowly die...
And yet there isn't widespread unemployment. Fewer farmers were needed so fewer people became farmers. Food became cheap and plentiful. Everyone else went on to do other things that they couldn't afford to do before. Software will do the same; we will make more software with fewer people and it will become ubiquitous to the point that people will just quickly generate whatever software they need rather than do many monotonous tasks manually.
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