Wikipedia:Reference desk/Archives/Science/2016 June 23

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June 23

Naegleriasis cause of death

Is the ultimate cause of death in cases of naegleriasis damage from the pathogen itself, such as from necrosis or bleeding? Or is the cause of death related to inflammation of the brain? Does the human body mount a significant immune response to the parasite? Someguy1221 (talk) 04:42, 23 June 2016 (UTC)

From this paper [1]:

Basically, "yes". N. fowleri...deeply penetrates the cortex to the periventricular system, and incites meningoencephalitis with rapid cerebral edema, resulting in cerebellar herniation. The olfactory bulbs and orbitofrontal cortices are necrotic and haemorrhagic. Histology has shown acute inflammatory reaction, mainly composed by neutrophils with extensive areas of lytic necrosis with the presence of several trophozoites.... Increased intracranial pressure and herniation are usually the cause of death. Opabinia regalis (talk) 05:47, 23 June 2016 (UTC)

So yes, there is a significant immune response, and yes the cause of death is inflammation, not really the necrosis or direct impact of the pathogen. SemanticMantis (talk) 13:40, 23 June 2016 (UTC)

Well.... technically, according to that source, the increased ICP caused by the inflammation is the cause of death, not the inflammation itself. Nitpicking, I know, but it's a causal sequence, infection causes neuroinflammation, which causes oedema, which causes raised ICP, which causes death. The inflammation is only halfway through the process. Fgf10 (talk) 22:49, 23 June 2016 (UTC)

Fair enough. I think the important thing is that the causal chain is long. At some point, the amoeba is responsible as an ultimate cause, but it's not really "trying" to kill you, the way many/most other diseases are (please excuse the teleological shorthand and consequent scare quotes). SemanticMantis (talk) 16:21, 24 June 2016 (UTC)

I'll forgive the shorthand, but I'm unsure about the "many/most" comment. Surely almost every microbe simply "wants" to survive and multiply. Our deaths do almost nothing to help that, so my guess is that it would actually be quite rare for a microbe to intentionally bump us off. I'm no epidemiologist, but I can't think of a single one where our death would provide a benefit to them. Matt Deres (talk) 18:21, 25 June 2016 (UTC)

Necrosis itself also can cause edema, causing raised ICP...etc., though I don't know how much that contributes in this particular sequence of events. Opabinia regalis (talk) 23:08, 23 June 2016 (UTC)

Slow-moving water

What's the difference between a bayou and a slough, at least in its North American use? I understand that the former term is more common in the southern USA than elsewhere, but one can find bayous and sloughs together in the same areas farther north, and the definition in the latter article does a good job of defining places that are typically named "bayou", whether today or in 1820 (both links address the same location), as well as defining places such as Levy Slough at 37°51′5″N 88°0′19″W. I'm not clear if the terms are generally used as synonyms (e.g. "creek" and "brook") or if there's some distinction between them. Nyttend (talk) 14:36, 23 June 2016 (UTC)

Mostly synonymous, as per our articles and the dictionaries I just checked. My NOAD says bayou: (in the southern US) a marshy outlet of a lake or river. from Louisiana French, from Choctaw 'bayuk'. Slough:a swamp, a muddy side channel or inlet. That bayou definition is a bit narrower, and I prefer the broader sense given in our article (what does Oxford really know about Louisiana French anyway - though it does clarify that nobody really talks about bayous much outside of the southern USA)

There are perhaps some differences in denotation, but then we get into regionalisms and personal preferences. E.g. some people do think there's a difference between a brook and a creek (and a rivulet and a stream, etc.), but it's not really correct to say those are well-supported distinctions. Anyway, if you want subjective denotations: Bayous often have cypress knees, sloughs don't. Slough gets used sometimes for human-engineered backwaters/drainage things, bayou doesn't. Bayou is usually reserved for something rather larger, sloughs can be pretty small. SemanticMantis (talk) 17:45, 23 June 2016 (UTC)

Thanks for the checking. I've always lived in hillier areas nearer headwaters (the only river city in which I've lived sits half on a bluff and half on a narrow plain along a somewhat entrenched river), so I've only known either bayous or sloughs as a visiting outsider. I should have made it more clear that I was indeed looking for solid, well-agreed-upon distinctions, because indeed I wasn't interested in personal preferences or individual distinctions. Nyttend (talk) 18:54, 23 June 2016 (UTC)

I still can't find any authority attempting to carefully formalize a definition for either. This is the stuff of folk taxonomy, methinks. Anyway, neither word appears in this fairly comprehensive glossary of hydrology [2]. Neither word appears in our Glossary_of_geography_terms. They have brief and ever-so-slightly different definitions in this National Geographic glossary [3]. SemanticMantis (talk) 19:46, 23 June 2016 (UTC)

In England, a "slough" is only to be found in the pages of The Pilgrim's Progress (the "Slough of Despond"), unless you count Slough of course. Alansplodge (talk) 20:52, 23 June 2016 (UTC)

There is a nature reserve in Coventry called Wyken Slough though. --TammyMoet (talk) 11:23, 24 June 2016 (UTC)

English also has [4] slough n. an outer covering that can be shed such as the cast-off skin of a snake, and slough v. to cast off (hair, skin, horn or feathers), from 1720. AllBestFaith (talk) 21:19, 23 June 2016 (UTC)

According to our articles and to [5] a Bayou has slow moving or stagnant water and a slough is only sporadically filled with water[6]. What I find interesting is that in British English we don't use it as a noun in that sense any more, although, as Alansplodge says, we have the town of Slough - pronounced "slau". However in BE we have "plough" - which is now spelled "plow" in American English, but for some reason slough has kept its old spelling in AE. Incidentally, when the word is used as a verb in BE i.e. to "slough off", it is pronounced "sluff" like the word "clough" - which is a wooded valley in Northern England - or "enough". Complicated or what? According to the Oxford dictionary definition given above the difference in pronunciation is because the noun derives from middle english and the verb from low German. Richerman (talk) 23:30, 23 June 2016 (UTC)

"Slough" doens't rhyme with "plow" in American English so why should it be spelled the same. "Slough" rhymes with "slew". Rmhermen (talk) 18:15, 24 June 2016 (UTC)

As does "through". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:53, 24 June 2016 (UTC)

According to Merriam Webster it can be pronounced either slau or slew in AE - it probably depends where you come from. Richerman (talk) 19:13, 25 June 2016 (UTC)

I remember seeing a claim that American English is actually less altered from ancient usage than British English; presumably the dispersal of colonists and the relative paucity of culture slowed down linguistic innovation for a bit? But that's a topic for a different question... in any case, "slough" is specifically mentioned in the American English article, alas with 'citation needed' beside it. Wnt (talk) 23:43, 23 June 2016 (UTC)

This discussion has been closed. Please do not modify it.
The following discussion has been closed. Please do not modify it.
So does "slough" in AE not rhyme with "plow"? In Britain, if anyone talked of a caterpillar "sluffing" off its old skin they would be laughed out of the office. 92.23.53.54 (talk) 18:38, 25 June 2016 (UTC) Then I suggest you look at the pronunciation in wiktionary and the OED [7]. Richerman (talk) 19:17, 25 June 2016 (UTC) That one word "slough" comes from different roots with different meanings, which could help explain the different pronunciations.[8] ←Baseball Bugs What's up, Doc? carrots→ 18:42, 25 June 2016 (UTC) Er, yes, I think I explained that above. Richerman (talk) 19:13, 25 June 2016 (UTC)

Big Rip, black holes

If and when a big rip occurs, will black holes be ripped apart also?144.35.45.67 (talk) 19:33, 23 June 2016 (UTC)

They gradually lose mass due to accretion of phantom energy, see here for details. Count Iblis (talk) 20:38, 23 June 2016 (UTC)

The Big Rip hypothesis assumes that the Speed of gravity is finite such that in a continually accelerating expanding universe all matter eventually becomes unbound by gravity. There could then be no Event horizon boundary between the inside and outside of a Black hole. AllBestFaith (talk) 21:07, 23 June 2016 (UTC)

Fear of heights totally absent on a ship, why?

Being on the fifth story of an appartment building I feel less than perfect. However, being up much heigher on a cruiseship I feel totally comfortable. Looking down from a balcony: zero problem even when the ship is docked and I'm looking down at the dock. Why is that? Joepnl (talk) 20:56, 23 June 2016 (UTC)

Handrail. AllBestFaith (talk) 21:22, 23 June 2016 (UTC)

Nope Joepnl (talk) 21:26, 23 June 2016 (UTC)

Think this is simply different mental reference points of fearful situations. Unease in building is possibly an implicit memory formed years ago (with the original experience that formed it forgotten). Some people can't bring themselves to climb to the top of a three extension ladder but thoroughly enjoy their vocation jet leaving the runway. It is all to do with context. You may have become older-and-wiser by the time you first experienced a cruse ship and thus your implicit memory didn’t trigger due to the different context, which was not down to hight itself but the situation, but cruse ships were not part of the experience, when your naïve implicit memory formed. So, being on a cruse ship doesn’t trigger anything from the past. There is a technique called 'search back', where by think back to the time when the unease was first noticed – a re-examination of the event can nullify the unease. --Aspro (talk) 22:13, 23 June 2016 (UTC)

There's maritime law and the law of gravity, but no maritime law of gravity. So nothing to fear. InedibleHulk (talk) 22:59, 23 June 2016 (UTC)

A very interesting post. Anna Frodesiak (talk) 23:02, 23 June 2016 (UTC)

Seriously though, it might have to do with solid straight lines. If they converge, as in the side of a building against a street, that can give you a different perspective from the wavy, curvy lines. A bit easier to discern how far you'd fall, I find. InedibleHulk (talk) 23:05, 23 June 2016 (UTC)

Can you even see the side of a ship from a railing at all? If not, and you're ever close beside something your own height, try scanning to the bottom of that thing instead. I'll bet you'd feel at least a bit sweatier. InedibleHulk (talk) 23:37, 23 June 2016 (UTC)

I'm not so sure the OP wants tips on how to increase his anxiety level. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:06, 24 June 2016 (UTC)

I don't mind an experiment for science :)

@InedibleHulk Yes you can and still no problem. But you are right, I have no fear of heights at all in an airplane. It's also not that the ship is made of "safe" metal compared to "unsafe" bricks or concrete. The Eiffel Tower is terrible as well :) But thinking of a floating Eiffel Tower, I think I'd have no problem climbing it! It really is strange. Joepnl (talk) 00:34, 24 June 2016 (UTC)

Also strange is how pictures can have the same effect, despite the viewer knowing damn well they're perfectly safe. Spiderman 2 messes me up worse than any "more realistic" game I've seen since. And Turok: Dinosaur Hunter still makes me carsick, while cars don't. InedibleHulk (talk) 13:56, 24 June 2016 (UTC)

Pictures like that make my hands sweaty, knowing that not only the building is perfectly safe, but that I'm just looking at a picture of it as well :) Joepnl (talk) 13:52, 25 June 2016 (UTC)

I'm pleased that xxx is enquiring enough to asked this question, because the contradictions (in feelings) can appear baffling to one's own logical side of the brain. So, sure the the OP is looking for an answer -so would I in his situation if I didn't I know the answer already (don't all you jump on me together for RS proof - just pointing it out). One's own instincts are a wonderful thing. When one is young and can't intellectualize a potential danger, instincts are your friend -they protect you from harm. As young ones, we get bombarded from every-side, with advice from adults saying such things as don't stand too close to the edge, you may fall etc. Up a three-extension-ladder they might say be very careful. Again these comments reinforce unease. Yet, get onto a holiday jet that has to wait 20 minutes from push back to finally getting to take off and everyone on board is jubilant. They have paid good money to the airline who has (one hopes) employed and air crew that takes on the responsibility for ones safety. So, no trigger. One does not have to 'take care' of oneself as it is being done by others -the air crew. Note too. The OP mentions that if the Eiffel Tower was floating they would have no trouble. Is this not a bit like sky-divers who when early on exiting a planes feel great trepidation -like walking off a edge of a cliff... When they progress to doing free-fall at much higher altitudes, their minds become so focused on free-fall techniques that they can step out of the plane without using will-power to over come their initial instinctive fears. Think about it. Face it: One has to be completely nuts to exit an aircraft with just a main and secondary cute to prevent you from becoming strawberry jam when you hit the ground. But with experience, one over comes those instinctive fears. Lets take this to the extreme - for added emphasis. Bet the last thing on the astronauts mind that do EVA's on the ISS is getting splattered on a side-walk 200 hundred miles below. The context is so much different. I mention Reachback earlier and now you have the link. Do it and you will not only be able to look over the edge of the Eiffel Tower but come to the UK and experience the "Walk of Faith" and enjoy the experience. This is no more than just a glass floor on Blackpool Tower to stop one plummeting down to the side walk below. What is the difference between a concrete floor or a glass floor? (Imagination, that's all). Blackpool Tower Eye (Glass Floor Walk, Lift and Ballroom)--Aspro (talk) 15:01, 24 June 2016 (UTC)

A glass floor is also much more pleasant to fall through, since concrete doesn't fall around you. Still no picnic, though, warning signs or no. And imagining you'll be fine is pretty useless. That said, everyone should see the CN Tower before they die. InedibleHulk (talk) 15:47, 24 June 2016 (UTC)

But never ever reach back like this. InedibleHulk (talk) 15:56, 24 June 2016 (UTC)

@Aspro, while as I child I didn't experience fear of heights, I'm quite sure it's not related to an incident (that I might have forgotten). It feels totally normal to be afraid of potential dangers, and looking down from a cliff is certainly a danger. Other people are terrified by spiders and while my brain doesn't mind them I don't think it's absurd. There is a certain evolutionary advantage to having phobias. A text written in red will have drawn your attention, and you cannot "unlearn" that red texts are more important than black ones. So, I'm totally OK with my fear of heights and it's not something I have to "deal with". Last time I enjoyed a beer when my friends climb the Eiffel Tower. However, the lack of the same fear of heights in planes or on ships is IMHO interesting. I wonder if other people have that experience as well and what could be an explanation that makes sense. I think it's very well possible that small adjustments to the design of high buildings (fountains? moving art? wood? Suggesting that the building actually is a ship?) could completely undo fear of heights. One of the most common phobias must have more research than Acrophobia has. Joepnl (talk) 22:41, 24 June 2016 (UTC)

You seem to have painted yourself into a corner, which stops you standing back and looking at that -which will solve your puzzling. I stated that instincts are good and so I agree that it is not something you have to "deal with". Just pointing it that the unease can be dissolved -if you so wish. Just a 'quick think' will not do it, because if the causative events come to mind that quickly you would have already realign your mind-view of the early perceived danger; that you once or twice sensed long, long ago. Should you take the time to dissolve the unease you will thereby answer your own query by seeing how it originally took hold. P.S. Next time you’re considering climbing the Eiffel Tower, consider taking the lift instead. That option may offer more drinking time but not for beer, rather try Absinthe. A few goblets of that and you'll end up abseiling back down without ropes.--Aspro (talk) 00:21, 25 June 2016 (UTC)

I had a very unpleasant meeting with a cat as a child, but I'm not afraid of cats. I don't think the millions of people who fear heights all had some bad experience they cannot remember. Surely, I would remember "my experience" right away because it should include at least a concussion or a fracture to make heights a special thing. Anyway, I didn't come here for medical advice. I really couldn't care less about "suffering" from acrophobia. My question is just: what's so special about a floating structure that, for me at least, it removes fear of heights. I think that's really strange and worthy of more research, which I was hoping had already been done. Joepnl (talk) 13:52, 25 June 2016 (UTC)