Wikipedia:Reference desk/Archives/Science/2015 October 1

= October 1 =

Why is there foaming at the mouth while epilepsy attack?
One of the symptoms of epilepsy is foaming at the mouth. When looking at around of the mouth it's possible to see foaming. My question is what is the physiological process or process that cause it and how is this foaming created? (I heard that the salivary gland secrete saliva, but it doesn't explain the form of the foaming) 02:31, 1 October 2015 (UTC) — Preceding unsigned comment added by 37.73.244.207 (talk)


 * It really is just saliva. In epileptic seizes, the salivary glands produce more saliva than normal (Hypersalivation). And since you're not swallowing normally, the majority of it stays in the mouth. Coupled with rapid erratic breathing that churns the saliva, the result is frothy saliva.-- O BSIDIAN  †  S OUL  03:33, 1 October 2015 (UTC)


 * Just to be pedantic, 'epilepsy' is a blanket term for a wide range of pathological conditions characterised by abnormal electrical activity in the brain which results in different sorts of seizures which may vary from blank staring to a tonic-clonic seizure (formerly called 'grand mal' siezure). The questioner seems to be asking about the latter. Foaming at the mouth only occurs in some people undergoing a tonic-clonic seizure and is never considered a sign of epilepsy but as a result of the clenching of the teeth, tightening of the facial muscles, including the lips, and rapid breathing. There are several other important signs to be considered when verifying a diagnosis of 'epilepsy'. Further pedantry warning - a medical sign is something seen or measured objectively by a physician or carer, a symptom is something felt or experienced by the patient. Thus a bump on the head is a sign but a headache is a symptom. Sadly these terms are tending to become synonymous and lose their grammatical value. (Steps down from soap box.) Richard Avery (talk) 07:00, 1 October 2015 (UTC)


 * Foamy saliva is also a hallmark of rabies, due to the same mechanisms. You might find the foam article interesting. --71.119.131.184 (talk) 18:22, 1 October 2015 (UTC)

Richard, can you give a source for this thing? "but as a result of the clenching of the teeth, tightening of the facial muscles, including the lips, and rapid breathing.". Thank you — Preceding unsigned comment added by 78.111.186.129 (talk) 00:05, 3 October 2015 (UTC)


 * Sorry for the slow response I have been away for a few days. Here are two references which indicate the tightening up jaw muscles and thus implying the general tensing of the facial muscles. 1, 2. In answering the question I drew on personal experience as a registered nurse having observed tonic-clonic seizures on many occasions including a case of status epilepticus. I guess the websites giving information about seizures don't go into minute details because it is not a pleasant scenario. I have never seen 'foaming at the mouth' but I have seen slightly bubbly saliva being expelled with force at the person regains conciousness and starts a snorty sort of breathing. But the presentation is variable and less dramatic in some cases. Richard Avery (talk) 06:49, 5 October 2015 (UTC)

Is Bufferin identical to aspirin?
A search for an article about the pain reliever Bufferin, seen in a 1950's TV show commercial at 29:03 redirects to Aspirin. But old TV commercials for Bufferin distinguished the two, and said that aspirin added its acidity to the natural stomach acid to produce excess acid, while Bufferin prevented this because it included the ingredient "di-alminate", which buffered the acidity of the aspirin, When I search on the internet for "di-alminate" I only find "diy laminate" about flooring I could install myself. So the topic question naturally arises. Did the buffering benefit of "di-alminate" only arise in the advertising agencies of Madison Avenue? Does Wikipedia only allow articles about the principal ingredient of medical combination drugs, as opposed to an article about Bufferin with 322,000 Google results, whether it is a panacea or a big hoax? The Physicians Desk Reference online version says Bufferin is aspirin buffered with calcium carbonate, magnesium carbonate,and magnesium oxide. Is there any policy or guideline which says there cannot be an article conveying this information. even if there is no medical benefit compared to plain aspirin? It may well satisfy [WP:N] via book/magazine coverage such as  In 1959 Anacin and Bufferin accounted for 50% of the OTC pain reliever market per. See also which has significant negative coverage. Edison (talk) 03:49, 1 October 2015 (UTC)


 * Bufferin is mentioned in the section Aspirin. Maybe the redirect should be directly to that section.  Rojomoke (talk) 04:17, 1 October 2015 (UTC)
 * I guessed "alminate" was "aluminate" and dredged up . Apparently there were respectable claims that it worked at the time - though I didn't actually look into them.  (Remember that pharmaceutical companies fund research studies, and they oddly seem to get positive results much of the time, and they only have to keep the preponderance of positive results going until the patent expires, at which point having their product debunked, ideally banned, becomes a good thing, to stop it from competing with the next one.  This is the way it always has been) Wnt (talk) 07:52, 1 October 2015 (UTC)
 * To be fair, a positive result due to funding bias is virtually indistinguishable from one caused by publication bias. Makes plausible deniability that much easier. InedibleHulk (talk) 08:55, 1 October 2015 (UTC)
 * I don't think it warrants its own article as there is not that much to say about it, so I've changed the redirect to go to Aspirin as suggested above. Richerman    (talk) 09:38, 1 October 2015 (UTC)
 * So if Bufferin also had a version with ibuprofin or acetominaphin in addition to the "aspirin plus other ingredients" version like Anacin and Anadin ten it could have an article discussing its marketing and other history like those painkillers? I'm puzzled why a major advertisor/consumer product only is supposed to get a passing reference in Wikipedia.  Are there other OTC painkillers with their own articles, which are aspirin/ibuprofin/acetominaphin plus dubious ingredients? Edison (talk) 12:46, 1 October 2015 (UTC)
 * WP:BOLD! ;-) Ssscienccce  (talk) 14:47, 1 October 2015 (UTC)

Metal detectors and film
If I take photography film through an airport metal detector, will it hurt the film? What about one of those body scan machines--108.46.106.100 (talk) 13:25, 1 October 2015 (UTC)


 * The canonical answer has always been "yes" - broadly speaking, these types of machines produce X-ray radiation, which damages photographic film. Here's a technical bulletin from Kodak, formerly the world's largest manufacturer for camera film: Baggage X-ray Scanning Effects on Film (2003), with pictures!
 * But... let's take this apart a little farther. That publication was more than a decade ago.  And, the question has asked about "metal detectors" and "full body scanners."  In the last fifteen years, airport scanning technologies have changed pretty dramatically.
 * Metal detectors work by a totally different physical process - they emit low frequency radio signals, and/or they detect a change in antenna impedance due to electromagnetic induction. It's probably safe to say those will never damage photographic film.
 * Full body scanners come in a variety of types: there are backscatter X-ray machines and there are full body scanners that operate in the microwave/millimeter-wave regime. If you travel in America, you are more probably going to be exposed to microwave than to X-ray (because millimeter-wave is safer and it produces a better image).  See, for example, TSA's Advanced Imaging screening video.  In a handful of other countries, you as a human might actually be subjected to X-ray radiation at an airport screening checkpoint.  Microwave scanners will not affect film; but TSA checkpoints will not allow you to carry your film in the scanner anyway.
 * Finally, even baggage-scanning X-ray devices have improved a lot in the last decades. Today, most airport machines advise "no damage" to films graded at ISO-800 or slower.  This is because new machines use lower intensity x-ray to obtain the same image quality.
 * Nimur (talk) 14:39, 1 October 2015 (UTC)
 * While not disagreeing with Nimur, remember that on a long trip (and return) the film might be taken through detectors a number of times and the, individually minor, effects will be cumulative. Photographers used to be advised to ask for hand searches to avoid irradiating their film, but in today's World of Security Theatre and more numerous, less customer-friendly security staff I understand this is usually futile. {The poster formerly known as 87.81.230.195) — Preceding unsigned comment added by 185.74.232.130 (talk) 18:44, 1 October 2015 (UTC)
 * I fly England to Australia and back every year and I always put my film in a lead bag. Only once have they asked me to open it. The rest of the time they see the blob on the scanner, twiddle a knob and it changes colour on their screen. They know what it is and push it through. I've always found the scanner people to be very helpful, so when in doubt ask the item to be hand examined. TrogWoolley (talk) 15:47, 2 October 2015 (UTC)


 * Silly answer I know because it is not answering the OP's question, but with a digital camera one can  FTP all one's  boring travel snaps back home before one even gets near to the airport.  Cheaper too! Unless one is in say Antarctica (forget that continent – no decent restaurants and bars – no night life at all in the summer (err... maybe  because there is no night) and no internet connection to keep in-touch with one's employees to make sure they still  have noses to the grind stone whilst you're away). Yet, for most people, FTP is a breezes – and a lot less  breezy as it can get in  Antarctica. Also, if one uses the good old tradition film in say the Australian desert at high temperatures, the lower gamma or toe of the emulsion (the darker parts of the image) becomes grainy. That is  why, when Lawrence of Arabia was filmed in Spain (don't ask) they stored the film in fridges. --Aspro (talk) 18:15, 2 October 2015 (UTC)
 * There are lots of other places in the world, and even in England, where an internet connection is impossible or difficult.   D b f i r s   08:32, 3 October 2015 (UTC)


 * Oh, come on! Name me a place at an international airport (which  has scanners) but  where there are no telecommunications. A telephone is  all one needs to use a dial-up modem. FTP works down any  telephone line  (but just slower sometimes). Just include the necessary equipment along with one's sun-tan lotion,  diarrhea and malaria medication.  Of course, if  Michael  O'Leary of Ryanair decides to start landing some of his aircraft in the middle of Dartmoor, then I grant you, that his passengers may have a little problem. Gosh, I hope that  O'Leary isn't reading this as he might decide to do it and end up frightning all the ponies. --Aspro (talk) 11:13, 3 October 2015 (UTC)
 * Have you ever tried to upload pictures using a dial-up modem? I have, and had to give up in despair!    D b f i r s   11:23, 3 October 2015 (UTC)
 * Also note that uploading the 100-odd Gigs of photos I took on a recent holiday might take quite a while using FTP in an airport. Rather longer than the wait for the plane, so you'd miss it.--Phil Holmes (talk) 11:44, 3 October 2015 (UTC)


 * I take it that you are talking about the Baud rates of some years ago. Telecoms have upgraded their systems (we are now more than half way through 2015). Name a place where an inter-national air-ports don't have satellite or fiber-optics connection. (with  exception places like  the Antarctic)?  To-day, one can be on top of mount Everest or in the middle of the Pacific Ocean and still phone home. . Penguins (quite wisely IMO) don't want to use  the W.W.W. So there is no commercial reason to provide such a service to them (and telecoms satellites don't orbit that far south away).  Yet, for  humans, they come across a scanner or x-ray machine only,  in areas where there is a point in having a scanner or x-ray machine. Those areas have 21st Century connectivity. Unless, of course, you can point out an exception. When one goes on vocation, does one not take  any necessary prophylactic medication in case it is not available locally? Same with information technology. Otherwise, one may not stray further afield than a Holiday Inn. Period. I sympathize (really for reasons, too long to go into) with Phil Holmes who was uploading Gigs. Plan a head. Then go to sleep whilst it uploads. Yet it sounds like he was using digital.  Post copies  off in a jiffy bag (remember - create back-ups), (sorry to disillusion you but isn't that what your laptop is for -creating back-ups. If you what to writ a travel log, then use a pencil and paper and and NO rubber eraser. Not the laptop. One's first impression are often the best and one does not want to erase them). After all, one doesn't want to  lose those precious photos, so that one get home, one can't  bore the pants off friends and neighbors buy showing them your amassing vacation snaps. Here's one of me standing next to a penguin. Oh, and you can't miss this of me and Ethel standing next to a  penguin and this one of  Ethel  shacking hands with a  penguin  - shot that myself without using the camera's Auto function; yes really, I choose 250 at f 4  an an ISO which I've forgotten.  All the other  photos came out under exposed on Auto.  Oh, and look here`! -Another photo of a millions and millions  of penguins. Next year we are going to Australia and I can't wait to show you   my photos of all the lamas and hippopotamuses out there.  - Etc.''--Aspro (talk) 15:13, 3 October 2015 (UTC)


 * I studied photography and back in the 90s I traveled overseas twice, on each occasion shooting close to 1000 photos on film. I never worried about lead bags or hand checks or anything, just kept the canisters in my kit bag in my check in luggage. As far as I can tell I never had a single shot ruined by airport x-rays. Vespine (talk) 21:54, 5 October 2015 (UTC)

Ask an Australian
So how do the yabbies get into the dam in the first place? It's not connected to any waterways. SpinningSpark 21:57, 1 October 2015 (UTC)
 * Stocked by the farmer eg http://nswaqua.com.au/fish-species/the-yabby-cherax-destructor/ Graeme Bartlett (talk) 22:44, 1 October 2015 (UTC)
 * Well the ones in the dam at the place I visited in the Adelaide Hills were certainly not put there by the residents, they hated them. They were liable to painfully nip toes when we went swimming in the dam as you walked through the mud.  But it was a Victorian era cottage, so maybe they were put there a long time ago. SpinningSpark 22:49, 1 October 2015 (UTC)


 * How do you swim "in" a dam? ←Baseball Bugs What's up, Doc? carrots→ 23:42, 1 October 2015 (UTC)
 * Dam_(disambiguation) covers the AU usage - "dam" for what we'd call a "reservoir" in the USA. I'm still unclear how it could be totally isolated though. Maybe "dam" can also mean "pond" down under? SemanticMantis (talk) 01:36, 2 October 2015 (UTC)
 * If they call a reservoir a dam, what do they call a dam? ←Baseball Bugs What's up, Doc? carrots→ 03:25, 2 October 2015 (UTC)
 * Damned if I know. Shock Brigade Harvester Boris (talk) 03:37, 2 October 2015 (UTC)
 * Isn't 'reservoir' a term that's too specific in this context? In NZ and possibly Aus, a reservoir is water trapped by a dam for human drinking and washing, as in a town or city supply. I don't think it's used for naturally trapped water that forms a pool that keeps a more or less constant level and serves no purpose. That would be simply called a pool. Water trapped by a dam on a farm for irrigation of pasture and drinking source for livestock would be called an irrigation pond. The OP never clarified exactly what type of dam the yabby was found in, so it seems a little premature to push for the use of reservoir. Akld guy (talk) 05:58, 2 October 2015 (UTC)
 * I was just going by the DAB link. Our article Reservoir does not restrict to drinking water or city water supplies. In AmEng, you might call it a lake, reservoir, pool etc. Many reservoirs are not used for municipal water, but instead used for pleasure craft, agriculture, etc. Suffice it to say that "swimming in the dam" is perfectly cromulent in AusEng. SemanticMantis (talk) 14:11, 2 October 2015 (UTC)


 * For the non-antipodians, a yabby is also known as a crayfish or crawdad. This paper details an American species invasive in Portugal, but the general principles of their aggressive colonization probably apply to species moved around AU as well. This  talks about how anglers can easily spread crayfish through use as bait, another possibility in AU. This paper  discusses the dispersal of crayfish by water birds, i.e. ectozoochory (our article is focused on plants, but many animals, particularly freshwater critters that inhabit ephemeral pools can disperse via zoochory).  SemanticMantis (talk) 01:33, 2 October 2015 (UTC)
 * Apologies for not linking the terms right away, but it helped to limit initial responses to those who actually knew the answer rather than those who wanted to speculate. Here is a picture of the actual dam in question.  It is on top of a hill and there is no running water anywhere for miles.  I would surmise that it is definitely man-made. SpinningSpark 15:48, 2 October 2015 (UTC)
 * Well I knew what a yabby was but I'll admit I would not have called that a dam, it would be a pond in AmEng. Anyway, I don't think we can say for certain without additional historical info, but my scholarly refs above suggest that arrival by bird is a possibility, even if there had been no intentional stocking or dispersal via human anglers. I'm not an Australian but I am a biologist, and know a few things about Biological_dispersal. Hope the refs help even if they are not AU specific; looks like a lovely place :) SemanticMantis (talk) 16:08, 2 October 2015 (UTC)
 * In the south of Western Australia a similar native animal is endemic; called the Jilgie. It was a traditional food source for certain of the original inhabitants. Dolphin  ( t ) 00:11, 3 October 2015 (UTC)
 * Here's an enlargeable picture of John Crichton spearfishing a jilgie. μηδείς (talk) 18:42, 4 October 2015 (UTC)
 * I live in Australia, no where near any dams, streams or ponds, I live on the edges of suburbia on the side of a hill and I have found yabbies in my back yard. These are a bit different to common yabbies, but even the common ones can survive for years during dry periods (this is mentioned in our article) and they will spread far and wide during wet periods and times of flooding. So even if there's NO running water anywhere near your "dam" if there has been any flooding or a wet period in the last several years, the yabbies have plenty of opportunity to spread. There probably isn't many placse in Australia that don't experience a wet period every few years.Vespine (talk)


 * Assuming a yabbie is the same as a crayfish or crawdad, they migrate over land when they need to. When our marsh begins to go dry, you can see them moving in large groups across the land to get to a better water hole. If things go bad, they just dig a hole and bury themselves. 209.149.113.94 (talk) 15:58, 5 October 2015 (UTC)

Formation of diverse particles
I don't completely get particle production. Does mass–energy equivalence explain why the converted energy of one particle produces the mass of another particle? How did quarks alone in hadron epoch formed diverse baryons simply by binding together? Why two massless and chargless photons can produce a charged electron and positron but not themselves? An apple can't produce bananas and if you collide two apples you either get chunks of the same apples or one bigger apple, but not bananas. Yet for some reason quarks produced a set of baryons, including protons and neutrons. --93.174.25.12 (talk) 22:25, 1 October 2015 (UTC)
 * Baryons are made of quarks. When you combine three quarks to get a proton or neutron, you don't have to put in extra energy to make the proton or neutron; you get out extra energy because the bound state is more stable.  The quarks are still there afterward, just bound together.  This is similar to how you get out extra energy by combining together several atoms to make a molecule.  It's a different case when you're talking about photons colliding to make an electron-positron pair.  Then you're really getting something different.  There's no law of conservation of photons or law of conservation of electrons; there are various conserved quantum numbers, but it's only the total that's conserved.  There are lots of collections of particles with different properties that could add up to the same totals (such as zero total charge in this case), so there are lots of possible end states for a collision. --Amble (talk) 22:50, 1 October 2015 (UTC)
 * Reading your response regarding the lack of conservation of electrons, I was reminded of the idea of the One-electron_universe. Not especially relevant to the question, but OP may find it interesting just the same. SemanticMantis (talk) 01:23, 2 October 2015 (UTC)


 * Our pages on this are at quark, Color confinement, Pair production, and Hadronization (binding together of quarks). Graeme Bartlett (talk) 23:06, 1 October 2015 (UTC)


 * The particles are probably best thought of as different types of motion of a single quantum field. They "turn into each other" because there's not much difference between them in the first place. Quarks and hadrons are a bad example, though, because hadrons are not distinct particles from quarks, as Amble already said.
 * (I disagree with what Amble said about combining three quarks to get a proton or neutron. You can't do that because isolated quarks don't exist: they are always bound to other quarks from the moment they come into existence. The actual origin of protons and neutrons in the early universe was more like a single "giant hadron" (a quark-gluon plasma) splitting into small pieces.)
 * Two photons can produce two photons: it's called photon-photon scattering.
 * I suppose that you could collide two apples and end up with two bananas, but the probability of it is very low (akin to a tornado in a junkyard assembling a 747). -- BenRG (talk) 04:45, 2 October 2015 (UTC)
 * From what I read, it's not that "there's not much difference between them in the first place". Particles are distinguished by mass, charge, spin, etc and are treated separately. How on earth two photons with zero mass and zero charge produce two new particles with mass and charge? 0+0=0, but not 1 or 2. Per pair production, the photon must be near an atomic nucleus in order to satisfy conservation of momentum, so an electron-positron pair producing in free space cannot occur. It smells like mass–energy equivalence is either imprecise or flawed in that it seems to allow an electron-positron pair producing in free space, but this can't happen. At the same time the mass–energy equivalence seems to cheat by saying yes, photon's energy can be converted to mass, but only in the presence of atomic nucleus. Brandmeistertalk  13:20, 2 October 2015 (UTC)
 * Charge is conserved, so a photon produces a positron (+1) and an electron (-1). 0+0=(+1)+(-1).
 * Mass and energy are equivalent, so a photon with energy x(c^2) produces particles of mass x-y, with energy y(c^2). x(c^2)=(x-y)(c^2)+y(c^2). At no point are you getting something from nothing. Photons have zero mass, but mass and energy are interchangable.  Something else is required to ensure that momentum is conserved, but it doesn't have to be an atomic nucleus - provided there is another particle to dump some momentum onto, pair production can occur.  Mass-energy equivalence doesn't pretend to be the whole picture - it says that if you can convert mass to energy, then this is the equivalent relationship, but does not provide constraints on when and how this can occur.  Other rules, such as conservation of charge, momentum, spin, etc. provide those constraints. MChesterMC (talk) 14:52, 2 October 2015 (UTC)


 * photon ↔ electron + positron can't happen in free space because of energy-momentum conservation. A photon's energy-momentum vector is inclined at 45° to vertical up, and can have any length. An electron or positron's energy-momentum vector is inclined at less than 45° to vertical up (it also has to lie on the mass shell but that doesn't matter here). The sum of two vectors inclined at less than 45° is also inclined at less than 45°, so it can't equal the energy-momentum of a photon. But photon + photon ↔ electron + positron can happen because the sum of two vectors inclined at 45° (in different directions) can be any vector inclined at less than 45°.
 * Pair production near a nucleus is really photon + nucleus → electron + positron + nucleus. -- BenRG (talk) 18:56, 3 October 2015 (UTC)
 * Sure, the quarks aren't isolated before you make a hadron out of them, but I take asymptotically free to be a good enough approximation for purposes of the OP's question.
 * Someone should probably also point the OP to the totalitarian principle, which says that every outcome you can imagine happens some of the time, unless it violates one of the conservation laws. --Amble (talk) 22:04, 2 October 2015 (UTC)
 * Is there any evidence that there has ever been a free quark, in the sense of a quark separated from all other quarks? (I understand they can be free of any specific other quark in a quark-gluon plasma, but they are still always near other quarks, which is what "shields" them, isn't it?  There's no one-quark quark-gluon plasma, ever, right?) Wnt (talk) 16:36, 3 October 2015 (UTC)
 * I think a quark has never been free in that sense. Amble is talking about a different kind of freedom, namely the fact that quarks move more or less freely within a strong-force "bag". Quarks are free in that sense in a quark-gluon plasma, but also free in that sense in a proton, but they'd also be said to be bound in the proton, so the terminology isn't great. At any rate, I may be wrong but I don't think quarks in the plasma grouped together in threes to make baryons; I think the big QGP bag broke into smaller (color-neutral) bags like water breaking into droplets. Maybe they are different descriptions of the same thing. -- BenRG (talk) 18:56, 3 October 2015 (UTC)