Wikipedia:Reference desk/Archives/Science/2021 January 8

= January 8 =

Steam traction in France
When was the last De Glehn compound retired from revenue service? 2601:646:8A01:B180:1D12:2DA5:3989:77E3 (talk) 12:13, 8 January 2021 (UTC)
 * Our Compound locomotive article says: "Many gave long service: a 4-6-0 230.D locomotive introduced 1909, stationed at Creil could often still be seen at the Gare du Nord, Paris in the late 1960s" (but no reference). This article says "the last was retired in 1965". The French Wikipedia article for these locomotives is 230 Nord 3.513 à 3.662. Alansplodge (talk) 15:11, 8 January 2021 (UTC)

Steam locomotive comparison
Of the various steam trains on different railroads, which ones were the cleanest and which ones were the dirtiest? Were there any steam trains which were cleaner than contemporary (1930's to 1950's) diesel trains? Also, was it true that the Delaware, Lackawanna & Western Railroad's steam trains were particularly clean (as they claimed with their Phoebe Snow ads), or was it hype? 2601:646:8A01:B180:1D12:2DA5:3989:77E3 (talk) 12:19, 8 January 2021 (UTC)


 * How do you want to quantify cleanliness? Locomotives produce many different pollutants. For some pollutants I expect most steam locomotives to be more polluting than diesels (course soot particles, sulphur dioxide), for others I expect the opposite (fine particulate matter, nitrogen oxides). A lot depends on the quality of the fuel too. The same locomotive can burn both clean and dirty fuel, resulting in a difference in particular for sulphur dioxide. And the most visible pollution is not the most dangerous pollution. PiusImpavidus (talk) 10:45, 9 January 2021 (UTC)


 * Well, I was thinking the sum total of the various pollutants (PM10, NOx, VOC's, ozone, SO2) -- and as for the fuel question, the answer would be to consider the fuel the engine in question uses normally. 2601:646:8A01:B180:90B8:2AE2:E52D:F73D (talk) 05:18, 14 January 2021 (UTC)
 * In the United States, at least, many steam locomotives could be converted fairly easily to operate with firewood, coal or fuel oil. And they were frequently sold back and forth among various railroads or industrial users in a marketplace like a used car lot. So, how do you evaluate "normally" in this context? Cullen328  Let's discuss it  05:27, 14 January 2021 (UTC)
 * In Europe they weren't so often sold from one railway company to the other, as by the 1930s most countries were in the process of merging all their railway companies into a single, state-owned operator. But railway and tramway companies often sold their old locomotives to industrial users and industrial users sold to each other. Nearly all of them burned coal, but the exact quality of the coal depended on what was available though trade or from nearby mines. And that, of course, changed as mines were opened and closed and some world wars disrupted trade. Swiss railways even temporarily switched to burning wood during WW1 (and then electrified). PiusImpavidus (talk) 10:41, 14 January 2021 (UTC)
 * It's a bit hard to add pollutants together. By mass, by health impact or by environmental impact? And the impact of a particular pollutant depends on the environment. Now it appears that the claim of the DL&WR about its clean locomotives was based on low soot emission caused by burning anthracite coal, so that the lady's white dresses stayed white. So, yes, in terms of soot emission I guess they were really clean, but that says nothing about sulphur dioxide emission, causing smog and acid rain. PiusImpavidus (talk) 10:41, 14 January 2021 (UTC)
 * How much sulfur in Pennsylvania #9 coal (which is what they used)? As for how to sum it up, it would make the most sense to add it by health impact -- and as for the fuel being used "normally", that would be the fuel used by the railroad which was the original buyer of the engines in question. 2601:646:8A01:B180:F84D:6B4F:9537:7CB5 (talk) 04:07, 15 January 2021 (UTC)

Firefighting trains
When using a steam train for firefighting, is it feasible to work a master stream or at least 1 or more fire hoses off of the live steam injector, or would it not work for some reason (not enough mass-flow, insufficient pressure, etc.)? 2601:646:8A01:B180:1D12:2DA5:3989:77E3 (talk) 12:22, 8 January 2021 (UTC)


 * Google has failed to find me an instance of a steam locomotive being used for firefighting - I imagine that the constraint would be that any fire would need to be conveniently close to some rail tracks. Perhaps you are thinking of steam pump fire engines that were pulled along the road by horses? Alansplodge (talk) 15:00, 8 January 2021 (UTC)


 * That's weird -- last time I asked, there were plenty of references to firefighting trains (mostly modern diesel trains, but at least one steam train as well)! 2601:646:8A01:B180:1D30:C04:B153:1804 (talk) 10:13, 9 January 2021 (UTC)
 * D'oh! I even found an example myself! I must be losing my touch... Alansplodge (talk) 16:45, 9 January 2021 (UTC)
 * The steam injector can handle enough pressure to force water into the boiler, which would be a few megapascals. That should be enough for some firefighting. Given the water consumption of an express steam locomotive, it should be able to handle on the order of one litre per second, which is well below the massflow of a master stream. Raising steam in a big steam locomotive takes hours, a luxury you don't have if you want to fight a fire. So, given the limited usefulness and the requirement to keep one on hot stand-by, I don't think firefighting steam locomotives are a good idea. But somebody may have tried it. It makes more sense to take an ordinary (steam) pump, put that on a flat wagon and push it to the area of the fire with any powered rail vehicle you have at hand. PiusImpavidus (talk) 11:28, 9 January 2021 (UTC)
 * Thanks! So, enough pressure but not enough mass-flow for serious firefighting?  (And raising steam would not be a problem, since it was in fact normal practice to keep steam trains on hot standby at all times when not in maintenance). 2601:646:8A01:B180:F84D:6B4F:9537:7CB5 (talk) 04:10, 15 January 2021 (UTC)

Nerve response in a dead body
If I understand correctly, the nerve impulses in a dead body wouldn't be fired, no matter what stimulus is applied (temperature, puncturing, etc). So assuming the dead body is largely intact (with all associated neural pathways, etc) and not damaged by decomposition, what prevents the impulses to be fired in response to a stimulus? My takeaway after reading our article is that after the death the voltage in cell membranes drops to zero, thus making the firing impossible. If I got that right, then there's question of why the voltage drops after the death (assuming it's autonomous, akin to charged battery, and independent of brain death). Thanks. 212.180.235.46 (talk) 17:14, 8 January 2021 (UTC)
 * The precise moment of death is hard to define; while there are medical and legal definitions (which may differ between jurisdictions) they are not based on some scientifically fundamental principle, so drawing the boundary between alive and dead has some unavoidable arbitrariness. The actual transition is not instantaneous; it may be brief, but it is nevertheless a gradual process. Under most definitions, some processes that are characteristic of life will continue for some time after the moment of death. This also holds for nerve impulses firing in response to stimuli, unless one defines death as the ceasing of nerves firing. --Lambiam 22:03, 8 January 2021 (UTC)


 * You're talking about membrane potential. This is actively maintained and requires energy in the form of ATP. Therefore, if the cell dies, it will not be maintained. However, death is hardly instantaneous, and with he right care, tissues can remain electrically active even after death of the organism. This is a common technique in research. Maintaining slices of brain (oganotypic slice cultures, oddly no article) in the right conditions can keep them active for days or weeks outside of the body. Fgf10 (talk) 10:39, 9 January 2021 (UTC)

Yo-yo and Maxwell pendulum
From what I see, devices working just like Maxwell pendulum (no article yet, but googleable) have been designed before, as per Yo-yo (particularly in ancient Greece). Or aren't they slightly different things? 212.180.235.46 (talk) 20:45, 8 January 2021 (UTC)
 * "In the twentieth century the yo-yo definitively entered into the physics labs as a didactic instrument in the version known as Maxwell's pendulum". --Lambiam 21:48, 8 January 2021 (UTC)
 * Thanks. 212.180.235.46 (talk) 10:49, 9 January 2021 (UTC)