Wikipedia:Reference desk/Archives/Science/2017 December 15

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December 15

Rod vision color

Wavelength responsiveness of short (S), medium (M) and long (L) wavelength cones compared to that of rods (R)

I'm trying to create a "color" that approximates the R curve in this graph. Suggestions? —2606:A000:4C0C:E200:E1C0:A059:2D66:D4C4 (talk) 00:50, 15 December 2017 (UTC)

Cyan?--Jayron32 05:43, 15 December 2017 (UTC)

Gray. But when bright enough to overpower the rods it looks like grue. Or bleen. [1]Sagittarian Milky Way (talk) 05:48, 15 December 2017 (UTC) (Jayron was the original answerer (erased cause I was only up to checking for edit conflicts 95-99% of the time) and this isn't much different but I'll keep it since it was replied to. The edit conflict window has way too many false negatives, even 97% show changes isn't enough..) Sagittarian Milky Way (talk) 20:00, 15 December 2017 (UTC)

The 498 nm (blue/green) does correspond with the peak, but what about the rest of the curve -- that would include contribution from other frequencies (hue vs. luminosity and/or chromaticity perhaps?). —2606:A000:4C0C:E200:791C:B79C:EA4D:5BB3 (talk) 06:19, 15 December 2017 (UTC)

Related

The above question is related to creating a light that maximizes stimulation of rod cells while minimizing stimulation of cone cells; perhaps as an approximation of moonlight. Is there any correlation between rod vision and moonlight? Relatively recently, depictions of night in films, art, etc. tend to be green-lit rather than previous blue-tones used to suggest moonlight. Is there any scientific basis for this or is it simply a modern artistic trend? —[OP]:2606:A000:4C0C:E200:ACD6:943D:BA3A:3FD4 (talk) 03:05, 17 December 2017 (UTC)

An positron and proton have opposite charges.

Would they "annihilate" each other, even partially? In general how would they interact?155.97.8.169 (talk) 02:03, 15 December 2017 (UTC)

A positron and a proton have the same charge, namely +1. They would repel one another. --Trovatore (talk) 02:19, 15 December 2017 (UTC)

For some light reading on complex, unconventional antiparticle interactions, here's the website of Antimatter at CERN, where several active experiments are exploring exotic matter, including mixtures of particles and antiparticles.

Positron interactions are well-understood; the main positron experiment shut down two decades ago to make room for the LHC. If you want to do cutting-edge antimatter experimental physics, these days the trick is making antiprotons and keeping them around for non-trivial amounts of time - in 2015, the longest lived antiprotons lasted for about a thousand seconds; and more recently, atoms of anti-hydrogen (a stable antiproton/positron system) have been kept in a cryo-trap for a full year.

Mixed atoms that have no net charge are really hard to confine - without a usable charge, there's no way to apply a Lorentz force, and the samples eventually bang into the walls of the container, and annihilate on whatever ordinary matter the walls are made of. The antiprotons will hit an hydrogen nucleus - or worse[2] - and the positrons will rip an atomic electron off whatever atom they hit first; and you're left with some nasty gamma rays and ions - and usually, antimatter experiments only have a tiny number of particles to begin with - so the sample dissipates within a very short amount of time.

All the latest and greatest anti-proton stuff comes out of CERN; here in the USA, it's really hard to find a good home for a poor fragile antiparticle; they need to be kept cool and clean and safely isolated from almost everything on Earth that would otherwise cause premature annihilation. So: if you like antimatter interactions, it's a great idea to start by learning scientific French! Les antihydrogènes, elles sont tres difficiles, mais les ions sont si facile!

Nimur (talk) 06:33, 15 December 2017 (UTC)

Mechanical hemolytic anemia

I've just spotted the article mechanical hemolytic anemia which shows that red blood cells are prone to mechanical induced damage - running, drumming, etc. This looks somewhat paradoxical, because I instantly compared it to microscopic insensitivity to macroscopic processes, e.g. trying to kill bacteria with a hammer. How the red blood cells are different? Thanks. 212.180.235.46 (talk) 10:06, 15 December 2017 (UTC)

How do you know that hitting bacteria with a hammer won't harm at least some of them? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:19, 15 December 2017 (UTC)

Pound some bacterial surface and let me know how many of them you managed to kill. The point is why RBCs are so prone to mechanical influence. The article says in particular that "Repetitive impacts to the body may cause... bursting (hemolysis) of red blood cells". 212.180.235.46 (talk) 17:19, 15 December 2017 (UTC)

Apparently some can be harmed. hydnjo (talk) 16:57, 15 December 2017 (UTC)

That stands to reason. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:23, 15 December 2017 (UTC)

One difference is their short lifespan of just 100–120 days. Young humans even have a much faster metabolism. So in case you are 20 years old the red blood cells in you are already in their 60th-100th generation. Cells of the outer skin have an even shorter lifespan but internal cells have a much longer lifespan in general i believe. I only know basics about medicine and biology but i read red blood cells are like the outer skin cells kinda cannonfodder soldiers of our body. --Kharon (talk) 03:16, 16 December 2017 (UTC)

Bacteria are surrounded by a cell wall (the specifics differ from gram positive to gram negative though). Red blood cells have a cytoskeleton but they are also designed to be relatively flexible to fit through small spaces (like capillaries and the spleen). More to the point, evolutionarily, bacteria are meant to survive, period, while red blood cells that suffer damage are supposed to break up and get removed from circulation for the greater good. If you took a vortexer and went at a tube of blood and a tube of bacteria, my money is on the bacteria. I should also add that red blood cells, being confined to capillaries, might suffer odd effects based on abrupt changes in pressure and flow rate as the total body part is squeezed, but I don't know how to begin thinking about that. Wnt (talk) 16:08, 17 December 2017 (UTC)