Wikipedia:Reference desk/Archives/Science/2018 May 8

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May 8

Is this true?

This page says; "Burn wounds use glucose for energy. In fact, they can't use any other source." Is this actually true? Does that mean people following a ketogenic diet cannot recover from burn wounds? Thankies. — Preceding unsigned comment added by 85.9.70.51 (talk) 16:02, 8 May 2018 (UTC)

Looks like a good source, but I can't say for sure. As for the latter question, no, if needed the liver produces glucose via gluconeogenesis. If blood glucose gets too low, you die. Organs including the brain and liver need some glucose to function, as do mammalian red blood cells, which don't have organelles and therefore can't "burn" other chemicals for energy. The brain does adjust its glucose requirements downward in the event of prolonged ketosis, but it still has a minimum requirement. --47.146.63.87 (talk) 17:58, 8 May 2018 (UTC)

This paper didn't answer your question, but what's interesting is that it describes a huge range of opinions, and some surprising biology. Apparently burn victims often and very suddenly come down with something akin to type II diabetes (stress-induced hyperglycemia) with insulin resistance. Not long ago this was considered a normal response, but now people are saying it increases the risk of death and that lowering blood glucose improves survival. But some have a goal of 110 mg/dL, for some it's 140 or 180. (This one seems to settle on 130-150) So whether eating lots of carbohydrates is a good idea for patients with something like type II diabetes? I have to express skepticism. Grimmest part is reading that 20,000 people a year are getting admitted to burn centers. Jesus... Ah, this book might have an answer: "the major constituents of granulation tissue are anaerobic cells (i.e. fibroblasts, leukocytes, and epithelial cells". And the wounds, which consume a lot of glucose, are returning lactate to the circulation as that would suggest (or v/v). Wnt (talk) 00:34, 9 May 2018 (UTC)

What are the widest subway cars ever in service?

Sagittarian Milky Way (talk) 22:53, 8 May 2018 (UTC)

Not an easy question to find a good answer for, partly because there have been many models of rolling stock and partly because of the variation between different places as to what you call the thing. For example, who say "subway" normally mean that at least part of it must be underground— people who call it a "metro" may use the word to include systems that are entirely above ground. So even if you found a single source for all the world's "metros", it might not answer the question.

I googled on the phrase "widest subway cars" and, besides this thread itself, the other hits were all on phrases like "among the widest subway cars" or "the widest subway cars I know about". I checked up on some of those. But the widest ones that I was able to identify, at 3.2 meters or 10'6", were these Singapore MRT trains. --69.159.62.113 (talk) 06:45, 9 May 2018 (UTC)

10'6" inches also happens to be the size of the BART, on a track-gauge of 5'6".

Nimur (talk) 14:11, 10 May 2018 (UTC)

I don't know of the data quality but this table has a bunch of systems. For some reason sorting by width doesn't seem to work at all but looking manually 3.2m seems to be the widest [1]. (Some have multiple width or lack width but I'm not talking about that. At least for me it always seems to sort by track length even the simple ones stay the same order.) Nil Einne (talk) 15:54, 11 May 2018 (UTC)

I wonder why it shows at least 10 cities with 3.2m/10.5' but none higher. Is that a convenient stopping point for standard gauge stability or something? Sagittarian Milky Way (talk) 19:53, 11 May 2018 (UTC)

It's because they have to squeeze through tunnels and/or fit onto viaducts over narrow city streets, and the wider you make a tunnel or viaduct, the more it will cost per mile. 2601:646:8A00:A0B3:8476:9D85:4610:EA41 (talk) 05:05, 15 May 2018 (UTC)

• Look at Rapid transit technology, and Loading gauge. there are a lot of constraints on car dimensions. -Arch dude (talk) 00:04, 11 May 2018 (UTC)