Wikipedia:Reference desk/Archives/Science/2020 December 3

= December 3 =

What material would remove the most oxygen from a space in a short period of time?
This is a fun, theoretical question. Barium is was historically used as a getter in vacuum tubes, and that got me wondering "what element/chemical/etc could I use to remove the oxygen from a room?", and I thought that'd be a fun question with a hopefully fun answer. I know that on the long term, rusting iron can turn a room uninhabitable, but that's quite slow. —moonythedwarf (Braden N.) 15:19, 3 December 2020 (UTC)
 * Most educational examples burn magnesium ribbon, which is a fun experiment. In terms of efficiency defined as weight-for-weight removal of the oxygen, then I guess the answer has to be Hydrogen. Stand well back and stay safe! Mike Turnbull (talk) 15:25, 3 December 2020 (UTC)
 * In terms of mass; something like Lithium will react with oxygen without the need for combustion. Hydrogen, as a diatomic molecule and as a gas has two issues:  It is relatively stable, and the reaction of H2 with O2 has a rather large activation energy.  It's certainly vigorous when it reacts, but given that you need twice as many molecules of hydrogen as oxygen to complete the combustion, and given that the room is 20% oxygen, you're looking to have to fill the room up to 40% with hydrogen gas before having to spark that mixture?  A light, reactive metal like lithium ought to do the trick since 1) there's no need for a spark and 2) as a solid, you would need a much smaller volume of it.  -- Jayron 32 15:30, 3 December 2020 (UTC)
 * (ec) Isn't a vacuum pump enough? :) --CiaPan (talk) 15:29, 3 December 2020 (UTC)
 * That will remove everything, not just the oxygen. -- Jayron 32 15:30, 3 December 2020 (UTC)
 * , Goal is not to just use a pump :P —moonythedwarf (Braden N.) 15:38, 3 December 2020 (UTC)
 * Since the goal is speed rather than efficiency and we want to avoid pumps and combustion, I suppose filling the room with politicians would serve the purpose well (perhaps two purposes, if you left them in after the oxygen was all gone). Someone clever could probably work out the actual speed from what's provided in our article. Matt Deres (talk) 21:35, 3 December 2020 (UTC)
 * Politicians and diapers should be changed often and for the same reason. -- Jayron 32 15:10, 4 December 2020 (UTC)
 * If you remove the oxide layer from the surface, e.g. with mercury, aluminium will react with oxygen and 'rust' like iron, but at a much, much faster rate. 31.185.251.44 (talk) 13:38, 8 December 2020 (UTC)

why there is no rabies vaccine?
Why we don't have a life long vaccine for rabies? --Exx8 (talk) 21:54, 3 December 2020 (UTC)
 * We at least have a rabies vaccine. ←Baseball Bugs What's up, Doc? carrots→ 22:22, 3 December 2020 (UTC)
 * This confirms there is no life-long vaccine. I think you'll find that a number of vaccines do not last for life. ←Baseball Bugs What's up, Doc? carrots→ 22:43, 3 December 2020 (UTC)
 * the question is why.--Exx8 (talk) 23:22, 3 December 2020 (UTC)
 * Why don't we have a permanent flu vaccine? Why are they saying the COVID-19 vaccine may only last a couple of years? ←Baseball Bugs What's up, Doc? carrots→ 02:34, 4 December 2020 (UTC)
 * In fact the rabies vaccine provides a partial protection for the rest of life. The post-exposure vaccination schedule is significantly shorter for previously vaccinated people and the immunoglobulin is not necessary either. Ruslik_ Zero 08:34, 5 December 2020 (UTC)
 * The memory T cells and memory B cells are the keepers of the immunological memory that provides adaptive immunity against a pathogen, based on a specific, earlier encountered antigen (as administered in a vaccine). For most antigens, these memory cells eventually die out, as in "use it or loose it". The question can be rephrased as, why do they not die out for some other antigens, such as those introduced by the yellow fever vaccine, also when a vaccinee never encounters that specific antigen again? I do not know how well this is understood, but heterologous effects as seen for some vaccines may also play a role in vaccine-provided immunity being boosted by different, naturally encountered pathogens. This is a link to a research article discussing heterologous immunity (cross-reactivity of adaptive immune cells). --Lambiam 06:47, 4 December 2020 (UTC)
 * The immune system is complex, and there are a WIDE variety of ways in which the immune system can be activated to respond to invaders, both naturally and by injection, and if you can think of a way for it to work, it probably does. Some vaccinations work for life, some work for a year or two, some cover a wider swath of pathogens, some only cover a specific variety of a specific pathogen.  There are some weird ways in which immunity works; historically it was known that cowpox infections offered some protection against smallpox, though they are distinct (but related) pathogens.  More recently, research suggests that some kinds of herpesvirus infections may ward off Yersinia pestis, a bacteria that causes black plague, which runs completely counter to how the classic models of immunization works.  We should not be surprised when some particular vaccination works differently than another one does.  The system is very complex, and there are LOTS of variables and ways it works.  -- Jayron 32 12:52, 4 December 2020 (UTC)