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Among those, Fe plays an outsized role for tons of redox reactions. But some of the rarer ones (including Mo and Va) have been utilized in rather critical enzymes and have not been replaced by more common metals, which in itself is interesting. If you are interested, there are whole fields on metalloenzymes, with recent approaches how various moieties in these large enzyme complexes might move during the various electron transfer processes. Not entirely my world, but it pops up frequently (and sometimes you get to work with folks on things like these). And also the work with them is annoying, just getting your media and glass ware free of metals is a nightmare.

Not quite. The net reaction of photosynthesis are two separate reactions which are not really mechanistically coupled. Specifically, it initiates an electron transfer chain (functionally similar to respiration) in order to pump protons which then chemoosmotically generate ATP. Water functions as electron donor during the water splitting event. I do think that the chemical notation masks a little bit the underlying biology, especially as carbon fixation in some bacteria happens without light, but that is neither here nor there). I probably should add that glycolysis happens in the cytosol, and the pyruvate is then delivered to hydrogenosomes. The reaction in hydrogenosomes is simpler and ATP formation is by substrate level phosphorylation, as mentioned before. Hydrogen is basically formed to re-oxidize ferredoxin, which is needed for the decarboxylation reaction from pyruvate to acetyl-CoA. Not entirely sure if I get it right but it should be something like: Pyruvate + 2 [H+] + Ferredoxin(ox) -> Acetate + H2 + Ferredoxin(red) + CO2 One way to think about this is that respiration (aerobic or anaerobic) is basically using a redox potential to energy generation, rather thinking that a particular compound being fuel or waste. Basically, if you have a nice electron donor and acceptor pair that generate a nice potential, you can use that potential by using to drive an electron transport chain, that also pumps protons out of the cell to generate a proton gradient that is then used to generate ATP. This means that depending on which pair the cell uses, the same compound can be used as donor or acceptor. Hydrogen is used by many bacteria as electron donor but is also released often in fermentation processes (or the reaction above) to essentially balance the redox budget of the cell (and as you can imagine, released hydrogen can be used by other bacteria, creating interesting cycles within bacterial communities).

Following on from @Moontanman's thread on a new nitrogen-fixing organelle, I started wondering how biological nitrogen fixation first arose at the dawn of life. I found the linked paper, which I thought very interesting on the subject: https://www.sciencedirect.com/science/article/pii/S0966842X23000914 The writers focus on the metal atoms (or metal/sulphide complexes) which are at the heart of nitrogenases, which can bind nitrogen, lower the strength of the triple bond and progressively add H+ and electrons to form eventually 2 molecules of ammonia. There are 3 variants of nitrogenase, one using just Fe, one using Fe and Mo (molybdenum) and one using Fe and V (vanadium). I was surprised to see these 2 transition metals have such a biologically important role, but there you go. It seems there is evidence the first nitrogenase appeared in the Archaean, before the Great Oxygenation Event (i.e. global-scale photosynthesis), which I suppose is not a surprise, seeing as a lot of life would be needed to geo-engineer the planet, and that would require a lot of fixed nitrogen. They suggest that, before the GOE, there would have been a lot of Fe²⁺ in the oceans, whereas under oxidising conditions this would go to Fe³⁺, the salts of which tend to precipitate from aqueous solution, so would be less bio-available. So a system incorporating Fe is not hard to explain. Curiously, though, phylogenetic analysis suggests that the version incorporating Mo as well as Fe was the first to appear, even though the concentration of Mo in the early ocean was apparently very low. That version has better kinetics, which may have favoured it, but it still leaves open the issue of where the Mo came from. They speculate that there may have been higher local concentrations in the zones where the first nitrogenase arose, perhaps in hydrothermal vents. But this is very much open-ended and needs further research. By the way I found the chemistry of these nitrogenases really interesting. There seems to be some very unusual chemistry, involving bridged hydrides to supply the extra electrons needed for the reduction. But that's another subject. It seems the evidence is that nitrogenases are an "evolutionary singularity", meaning this little family of 3 closely related variants, using the 3 metal combinations mentioned, seems to have evolved once only in the whole history of life on Earth. But absolutely vital to the whole enterprise of course.

There is another hint: nitrogenase are sensitive to oxygen so they do not work well if too much oxygen is present. From what I remember, nitrogen is thought to be limiting during evolution of early life and the ability to fix nitrogen would have been a massive benefit. Nitrogenases and their cofactors (especially FeMoCo) have a massive body of lit (and I dabbled a bit with it as a grad student) so there is a lot to read on this topic :).

OK, but telephone numbers like this don't tell us a great deal until put into context. What concentration of NOx is this thought to have generated? Especially in the marine environment where life is thought to have started.

..billions of years of lightning strikes make a difference.. https://en.wikipedia.org/wiki/NOx "Scientists Ott et al.[13] estimated that each flash of lightning on average in the several mid-latitude and subtropical thunderstorms studied turned 7 kg (15 lb) of nitrogen into chemically reactive NOx. With 1.4 billion lightning flashes per year, multiplied by 7 kilograms per lightning strike, they estimated the total amount of NOx produced by lightning per year is 8.6 million tonnes. However, NOx emissions resulting from fossil fuel combustion are estimated at 28.5 million tonnes.[14] "

Don't forget about ammonia, it is thought to have been present as well.

Hardly enough for much, I'd have thought. But maybe just enough to get some biochemistry started. I suspect N availability would have been one of the key constraints at the beginning. But I may have found a good paper on this. Let me read it and start a new thread if it's what I'm after.

I get that- but being a biologist rather than chemist I understand things better if I view it from a mechanistic perspective. It just helps to explain functions better and avoids confusion for reactions that might chemically look similar, but functionally are very different (as in this case). Yes, I know. His research output was low which got him in trouble regarding his teaching position. But his books were so popular, that it hardly mattered. What I meant is that in his most active years, substrate-level phosphorylation was still the basic assumption. So would be curious how much was out in lit, when he wrote the story.

So nothing conclusive means no value? Maybe in 20 years we'll have controlled fusion, we've only been pursuing this for 80 years or so and it's always just 20 years away but we continue to gather info hoping that eventually we will figure it out. Gathering accurate data about something potentially so important is never a useless endeavor. Ridiculing something because you just can't imagine how it could be possible is such a great way to figure something out.

I just read some comments on the video. Seldom had more fun. Here a selection: This woman is a legend, first clear UFO footage in history Finally a clear picture of a ufo instead of the usual dark and blurry images (Eise: yup, therefore it was so easy to recognise) This is the best clearest footage of UFO I have ever seen. US Government: "Relax it's just a weather balloon." (Eise: no, it was't...) Literally the best footage of a “ufo” to date …bravo!! U guys deserve something as a news station SERIOUSLY! probably the best video/picture caught of a UFO ever lol 1. It wasn't fast, the aircraft was, that's why you see it zipping through the video. 2. It's a blade propelled object judging from its inclination, probably a drone. 3. The drone was operated by the government or related agency because even considering how dangerous this was for the airliner, no news about investigation had been announced. Why is everyone so scared to say what it really is?? (Eise: because it would shock your world view) That’s our own government. Stop Do you really think you caught it on your home camera and the government doesn’t know? They have been here for thousands of years. Cylinder Aka cigar shaped crafts are one of the most common UFOs. Legit sighting in my opinion. Great catch.. (Eise: obviously a real expert!) This is one of the best UFO footage in recent decades (Eise: his emoticons, sorry that they became so big...) Etc etc. Naivety, conspiracy theories... There are however a few who notice that it looks to fly fast, but that it could be the speed of the plane. Some examples: The plane flying at 2 to 300 miles per hour, if you look closely, that object could have very well been stationary given the travel direction of the plane if you look at the land while it's flying and how the object seems to fly by at a high speed but could very well be almost sitting still. Black balloon with helium? It’s not moving, you are. (Eise: close, very close...) And the price goes to:

It does have lower heat conduction; Kr is even lower. Probably a function of the higher mass - diffusion rates should be dependent on that.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2907586/ states that 'possibly endosymbiotic' rod-like methanogenic prokaryotes were seen in close proximity to the hydrogenosomes during scanning electron microscopy. If so then perhaps the circle is closed at least in part by the reasonably exothermic (and biological carbon fixing) of CO2 reduction by H2.

Sorry to disappoint, but I recognised it immediately: The speed is the speed of the plane. It was 'a close encounter of the daily kind'. Blow it up in a cool place on a hot day (inside your home or in the shadow), bring it into the sunlight, until it lifts and let it go, and you will never see it again. From this Swiss site. Costs 12 Swiss bucks. What a fuzz about a funny, but physically interesting toy. I once 'launched' one. Ah, there is even a wikipedia article bout it: That was a fast +1, Moontanman. Small correction: blow it up on a cool but sunny day. Obviously there also much bigger ones...

I think this is where a misunderstanding arose, as the discussion shifted away somewhat from the OP. I take your and @toucana point as to where the thread started, so I didn't make clear that I thought the thread had moved a bit and was trying to follow that. My point goes to the substantial difference (especially re the fate of Earth's supporting ecosystems) between any nuclear exchange and all the other historical forms of massive death you described. I won't rehash that, but anyone who wants to review previous posts is welcome to. I agree there is a legitimate moment of self-defense in a war, but I tried (and failed) to make some points as to how a nuclear "defense" can ultimately kill so many people who are not attacking. Therein lies the problem of proportionality, as well as Geneva issues, plus the migration of radionuclides and weather effects to friendly nations, also addressed by me and others. Again, I didn't communicate well that I see this as more than just a form of the Trolley Problem, because of the unique implications of annihilating an entire (or several entire) cities (and what that opens up, in terms of a larger war). We don't have to explore them here. I gave it a shot, but will step aside so others can resume with the original question.

If we had a snail's pace (with no extra acceleration or deceleration) the difference in the clocks would be similar or identical but ,as an example it could be a billion years as against a billion and one years , depending on a great distance and a slow speed.Make sense? It only stands out as remarkable when the speeds are relativistic.

Show me where. It is, but show me where cosmological redshift is interpreted as a decrease in frequency then. This is how the FLRW fits observations of cosmological redshift and interpretation of it as space expansion. You can't use a parametisation to prove it's assumptions.

It is the equation. a(t) = V(t)/s(t)^2 or miles/hours^2 aka mph^2 Position=S(t)->(distance over time) Velocity=v(t)->s(t)/time Acceleration=a(t)->v(t)/S(t)->distance/time^2 Time squared, yes it is covering the same distance over more time. Hence the outside world is experiencing a greater passage of time. Whether or not the observer is experiencing more time as well is a matter of debate. We really can't go fast enough to tell.

Here's why the math is irrelevant. I do not know how to quantize the toroid's precessional movement but the variables it will require are in the definition of the shape. To accomplish the quantization, the mathematician will have a near infinity of options when assigning delta in XYZ to the different hidden variables represented by the measurements of the Toroid. The proof that it is the theory of everything is logical, not mathematical, because there will be many different ways to setup those variables so as to purposely represent a specific experiment's superposition space. This is the logical proof: 1. 3d is logical and the entirety of evidence points to 3d. 2. The Holonomic Toroid can represent the quantum in 3d. It's the only shape that can. That's it. I don't need to provide a mathematical solution because the problem was logical and tautological, not quantizeable. It has been fully quantized. What was missing was a unifying logic. Moreover, even when someone does the math, it will not prove that the shape is what is there. It will only prove that the specific configuration can be molded to the superposition space. To PROVE it, as a scientist, one would have to design a 3d falsification experiment, in 3D.