Wikipedia:Reference desk/Archives/Science/2013 December 20

= December 20 =

High pressure animals
What's the highest pressure that an animal can create? I've looked through articles for the likely candidates (bombardier beetle came to mind) but we don't seem to list any actual figures for the pressure generated. 12.217.87.18 (talk) 14:35, 20 December 2013 (UTC)
 * Alpheidae might be a pretty good contender (if not the winner). Article gives 80kPa as an estimate for the pressure generated, that'll be hard to beat. 80.254.147.164(talk) 15:40, 20 December 2013 (UTC)
 * The pistol shrimp or mantis shrimp are probably the winners, but they generate pressures outside their body. 8.17.117.40 (talk) 15:47, 20 December 2013 (UTC)
 * An elephant can put the squeeze on almost anything. ←Baseball Bugs What's up, Doc? carrots→ 16:29, 20 December 2013 (UTC)
 * What about internally generated pressure, though? 12.217.87.18 (talk) 19:37, 20 December 2013 (UTC)
 * That wasn't in the original question. ←Baseball Bugs What's up, Doc? carrots→ 19:54, 20 December 2013 (UTC)
 * That question may be hard to answer, depending on what you mean by "creating pressure": transient or sustained, pressure between two surfaces or inside a fluid, functional or "accidental"...
 * Pressure between teeth surfaces snapping together can be enormous, and pressures inside for example the synovial fluid between the articular cartilage would be high, but that's probably not what you're looking for. High pressure pulses may also be of minor interest, they can be achieved by rapid decelaration, in other words by hitting something. Surface tension can create considerable pressure when the radius is small enough, osmotic pressure can reach high values (ocean water has an osmotic pressure of 27 atm).
 * "Useful" pressure, doing more than just greasing joints, can be found in spiders: most species use hydraulic pressure to extend their legs (and muscles to flex them). A paper published in 1959 measured the pressure inside the legs of house spiders (not sure if they used the domestic or the giant house spider) and found peaks of 45 cm Hg (or 60 kPa) during movement. A 1975 study found pressures up to 40 kPa in the Southern house spider I would expect spiders with thinner legs to use (need) higher pressures, but measurement would be more difficult probably.
 * Couldn't find how much pressure archerfish develop when spitting, must be more than 30 kPa if they can shoot insects three meter high. Ssscienccce  (talk) 04:17, 21 December 2013 (UTC)


 * Found a few other examples:


 * In Crotalus (rattlesnakes), pressure spikes up to 261 kPa were measured during venom release. Source: Venom Delivery of Snakes as High-Pressure and Low-Pressure Systems.
 * The Hershey and Chase experiments showed that phages infected cells by inserting their DNA, and it was assumed that this happened by injection powered by the (osmotic) pressure inside the viral capsid which can reach 30 to 50 bar. But while two phage genomes could be injected from virions into liposomes in vitro, the first two in vivo infections observed were using other mechanisms. Not sure what the latest theories are, more on it can be found here.
 * Stinging Jellyfish catch their prey with little poisoned harpoons fired from cnidocyte cells. The pressure of 15 MPa (150 bar) inside these cells is released in only 700 nsec but the 1 nanogram projectiles reach accelerations of more than five million g's, giving them enough energy to penetrate even thick crustacean shells. (source). Ssscienccce  (talk) 15:13, 21 December 2013 (UTC)
 * There was an article in the last few months that said that due to the shape of our windpipe, a human sneeze generates an acceleration of up to 500mph in milliseconds, but I can't find the article or translate that to a pressure. μηδείς (talk) 16:40, 21 December 2013 (UTC)
 * I did find a source giving similar figures, but that's a parody of National geographic. A study on PubMed gives a speed of 4.5 m/sec or 10 mph: Airflow dynamics of human jets: sneezing and breathing - potential sources of infectious aerosols, although I'm always suspicious about articles published on April 1... Ssscienccce  (talk) 22:42, 21 December 2013 (UTC)


 * It's not really a very meaningful question. Pressure is force divided by area.  If you can push your hands together with a force of (say) one newton - then the pressure you generate will be drastically different between (say) pushing two books together and (say) pushing the heads of two pins together. If the books have a surface area of (say) 50,000mm2 and the pin-heads have areas of 2mm2, The amount of force a particular muscle can produce is easily known - but the amount of pressure varies by at least a  factor of 25,000 to one, depending on what they are pressing onto. SteveBaker (talk) 00:01, 22 December 2013 (UTC)
 * Yes, it's hard to limit the question to meaningful cases. The OP probably meant only pressures in fluids and gasses, but because it's easier to contain high pressures in small volumes (the stress in the wall scales with the radius) you'll find higher pressures at microscopic scales, and often as a result of osmotic pressure rather than "actively" generated by the animal. Including transient or localised pressure peaks is also problematic, the 80 kPa quoted for pistol shrimps for example may seem high, but it's only accoustic pressure generated by much higher pressures occuring during the collapse of the cavity bubble (studies of sperical cavity bubbles found pressures in the order of 1 GPa). To exclude all these you'd need a convoluted definition, something like: pressure in a macroscopic volume of fluid (to exclude thin layers like synovial fluid in joints) inside the body, generated (to exclude osmotic pressure) or initiated (to include the bombardier beetle) by muscle contraction. Interesting question nevertheless. Ssscienccce  (talk) 15:36, 22 December 2013 (UTC)
 * I agree, I could have been much more technical in my question, but I was trying not to artificially limit any answers. I suppose that these animals have specialized cells that can withstand these pressures? Or do they just sacrifice x number of cells due to cell wall damage each time? 12.217.87.18 (talk) 14:50, 23 December 2013 (UTC)
 * Simulation of the bombardier beetle spraying mechanism gave results most consistent with observed data when a pressure of 1.1 bar was assumed; this is absolute pressure, so an overpressure of 0.1 bar or 10 kPa. Ssscienccce  (talk) 15:36, 22 December 2013 (UTC)

Pedunculated fibroma
What is a pedunculated fibroma? I heard the term recently (some sort of mole?) but don't particularly understand what it is, and the stuff I'm finding online, e.g. through PubMed, typically mentions the condition (example) without explaining what it is, at least in a way I can understand. Nyttend (talk) 18:15, 20 December 2013 (UTC)
 * A Fibroma is a benign growth on the skin, superficially resembling a wart, but with different cause. A peduncule is a stalk.  So a "pedunculated fibroma" is a small flesh growth which extends from the skin on a stalk-like structure.  Do a search in google images to get an idea.  -- Jayron  32  18:35, 20 December 2013 (UTC)

IUPAC names
I posted some questions regarding the details of IUPAC chemical names at, but have not received any guidance there yet. Can someone familiar with chemical names have a look? (Note that this is not seeking medical advice – it's only about the technical naming issues of some substances that happen to have medicinal uses.) Thanks. —&#91;  Alan M 1  (talk) &#93;— 18:50, 20 December 2013 (UTC)
 * I've responded there. -- Jayron  32  19:00, 20 December 2013 (UTC)

Are Clostridium difficile spores completely killed by bleach?
I am trying to find a article I read about a year ago that was a hospital study that tested different products against Clostridium difficile spores on hospital surfaces and then they would swab and test these surfaces afterwards. And I believe it said that Clostridium difficile spores were not completely killed by bleach, only like 30% of them were. I need help finding that article again.--Johnsmith777555 (talk) 19:59, 20 December 2013 (UTC)
 * This is such a study, although it may not be the one you read. It shows good results for bleach (sodium hypochlorite), moderate results for hydrogen peroxide, and poor results for isopropyl alcohol. Tevildo (talk) 21:17, 20 December 2013 (UTC)

I don't think that's the study I was looking for. The one I'm looking for showed significant Clostridium difficile spores on surfaces even after cleaning with bleach. --Johnsmith777555 (talk) 21:51, 20 December 2013 (UTC)
 * Off-topic peeve &mdash; why does everyone seem to pronounce this dee-fee-SEEL like it's French? It's Latin; should be dee-FEE-kee-leh or dee-FEE-chee-leh. --Trovatore (talk) 21:52, 20 December 2013 (UTC)
 * I use and have only heard the French-like pronunciation. But the Latin would be /dif-'fi-ki-le/. μηδείς (talk) 01:29, 21 December 2013 (UTC)
 * Do you have a source for how the Romans pronounced Clostridium difficile? HiLo48 (talk) 23:54, 20 December 2013 (UTC)


 * You can easily find sources for Latin pronunciation. Probably our Latin article has them.  Now, I take your point to be that we don't have any actual proof, just the post-hoc analysis of linguists, with no way of checking how accurate these are, and that's true, but not all that relevant.  It's scientific Latin rather than the language of Cicero, but even if it were the latter, it's still clear that dee-fee-SEEL is not doing the best we can. --Trovatore (talk) 00:45, 21 December 2013 (UTC)
 * See http://capewest.ca/pron.html, which says "see dif-ISS-il-ee".
 * —Wavelength (talk) 01:26, 21 December 2013 (UTC)
 * See also Clostridium difficile.
 * —Wavelength (talk) 01:29, 21 December 2013 (UTC)


 * It's going to be a matter of degree. Bleach in sufficient concentration will kill any becterium.  The question should be how resistant C. difficile is to the moderate concentrations that result from ordinary cleaning. Looie496 (talk) 00:44, 21 December 2013 (UTC)


 * I looked at a few studies comparing H2O2 and chlorine containing products last month after reading the hydrogen peroxide article. Reference 40 given there mentions some studies, others that I found seemed to agree that chlorine will kill all spores IF the minimum contact time is respected. That contact time is 10 minutes or more, depending on the dilution used, a condition that may not be met during normal cleaning. Not sure if it's what you are looking for, but the study by Barbut et al seems to match your description reasonably well. Ssscienccce  (talk) 05:17, 21 December 2013 (UTC)


 * I agree that it's a matter of the bleach concentration and exposure time. However, sufficient exposure to bleach to kill all the nasties might well require closing off the area and sending in a hazmat team, as it poses a serious respiratory, skin damage, and eye damage risk. StuRat (talk) 07:40, 21 December 2013 (UTC)

Geology of Seven Stones reef
What is the geology of the Seven Stones reef? -- 20:53, 20 December 2013‎ (UTC)


 * This sounds like a homework question. The sources the article is based upon may be a good place to look for answers. Do you have a specific question? μηδείς (talk) 21:24, 20 December 2013 (UTC)
 * The OP has been online for a couple of years and first edited that article in 2012. If the information is not within the article, he would be well advised to research the subject, and then maybe would be willing to improve the article. ←Baseball Bugs What's up, Doc? carrots→ 21:44, 20 December 2013 (UTC)
 * I have been looking for the answer for some time now. The geology maps that I have access to do not show the reef. Books and websites refer to the wreck of the Torrey Canyon and little else. Hence the reason for the question! Jowaninpensans (talk) 21:54, 20 December 2013 (UTC)
 * I haven't looked for online sources about that reef in particular since I assume you've already come up empty, but you should find Caledonian orogeny interesting in general. Note that the Isles of Scilly have been reduced to scraps of what was present in Roman times.  A search along those lines dumps me at  which seems to claim that the Seven Stones Reef itself was the capital of Lyonesse, or Ictis, before it starts going on about it being Atlantis... there's such a fine line between history and fantasy.  But no myth is that whatever was there was above water sometime after the last Ice Age, so a determined explorer ought to be able to come up with some fabled lost city out of it, even if it's only a few huts and a couple of shell beads. Wnt (talk) 23:28, 20 December 2013 (UTC)


 * I found a reference to the "Seven Stones Granite between Land's End and the Scilly Isles" by Sabine and Snelling from 1969, although I've not managed to find the original paper online. It makes sense to me that it's part of the cornubian batholith, possibly forming a small granitic intrusion between the Isles of Scilly and Land's End granites. Mikenorton (talk) 23:59, 20 December 2013 (UTC)
 * That's confirmed by a map in another paper here (I can get a you a copy of the paper if you would like one), which shows it as a small granite. Mikenorton (talk) 00:06, 21 December 2013 (UTC)


 * Apparently divers visit the area and describe it as granite ; the story is that the Land of Lyonesse was drowned in the 6th century.  The excellent cornubian batholith article explains that the granite intrusion is associated with tin, as was suggested for Ictis, so the idea above isn't seeming so implausible.  I wonder what the odds are that artifacts in good condition can still be found entombed in the ancient tin mines, protected from all the vicissitudes of nature. Wnt (talk) 00:13, 21 December 2013 (UTC)


 * With respect to the rock type, I suspected it was granite but did not want to make an assumption; the nearby Wolf Rock is not granite. I am happy just to use the reference that has been provided if that is ok. Jowaninpensans (talk) 19:50, 21 December 2013 (UTC)
 * The original paper that describes the offshore geology is Smith, Stride and Whittard 1965, but I don't have access to a copy. The stones are also shown on the BGS map viewer, where the bedrock is described as "Unnamed Igneous Intrusion, Carboniferous To Permian - Felsic-rock. Igneous Bedrock formed approximately 251 to 359 million years ago in the Permian and Carboniferous Periods. Local environment previously dominated by intrusions of silica-rich magma." Mikenorton (talk) 14:03, 22 December 2013 (UTC)


 * With regards to Lyonesse it will get a mention in the article, although there are local variations to the wikiarticle. There are various claims (some to the actual day!) for the inundation but the remains of trees, exposed at low tides, off Penzance, are thousands of years old. There are no tin mines at the Stones I'm afraid, it is just fanciful idea. Some ships hit the Stones and slipped down to sixty fathoms. Many thanks for the replies (apart from the patronizing first two. lol) Jowaninpensans (talk) 19:50, 21 December 2013 (UTC)

Sex and Pregnancy Question in Regards to Castrated Males
If a formely fertile human male gets himself castrated and then pees right afterwards, it is possible for him to [b]ever[/b] get a female pregnant after having sex with her after he already did both of these things (getting himself castrated and then peeing afterwards)? I would think that the answer to this question would certainly be No, but I just want to make sure about this. And Yes, this is a completely serious question. Futurist110 (talk) 21:34, 20 December 2013 (UTC)
 * I assume you mean himself? The answer is yes. Sperm cells are stored in the prostate, among other places. They will eventually disappear, but not right away. If in doubt, consult your friendly neighborhood urologist. ←Baseball Bugs What's up, Doc? carrots→ 21:40, 20 December 2013 (UTC)
 * Yes, himself. Sorry for that--that was an obvious typo on my part. Also, how long exactly will it take for these sperm cells to disappear (as in one is 100% sure that every single one of them disappeared)? For the record, with this current question, I am not talking about myself, but rather asking about a hypothetical scenario here. Futurist110 (talk) 21:44, 20 December 2013 (UTC)
 * I also assume (or hope) that you're talking vasectomy rather than castration. But either way, from what I knew of the subject, the patient would take a sperm count test on a monthly basis until there were two consecutive sperm-cell-free months. However, that was some years back, and the testing instructions may have changed. So if you or anyone you know has notions of doing this, they need to consult a urologist or other professional physician for the current standard procedure. In fact, if you're curious enough, just call one and ask the question. ←Baseball Bugs What's up, Doc? carrots→ 21:49, 20 December 2013 (UTC)
 * No, I was talking about a man getting castrated here, rather than getting a vasectomy. Also, I perfectly know what (a) castration is (the permanent removal of both of a man's testicles) and what it results in (the need for hormone replacement therapy, et cetera). And for the record, I am obviously not going to apply the info here in making decisions in regards to this issue. Rather, I am asking this question here to get some background information about this, with the intention of asking a (qualified) doctor later on about this if I decide to follow through on this. Futurist110 (talk) 21:53, 20 December 2013 (UTC)
 * So be it, then. You need to read everything Wikipedia has about the production and retention of sperm cells. There are typically always sperm cells in the prostate, as old ones die off and are absorbed by the body, and newer ones are created. Vasectomy or castration (literally) cuts off the source. So eventually the prostate becomes sperm-free. But it can take a while. ←Baseball Bugs What's up, Doc? carrots→ 22:00, 20 December 2013 (UTC)
 * Do you know how long exactly this should take? Futurist110 (talk) 22:01, 20 December 2013 (UTC)
 * It could be a number of weeks, but it might vary per individual. That's why you need to consult a urologist. ←Baseball Bugs What's up, Doc? carrots→ 22:04, 20 December 2013 (UTC)
 * Thank you very much. Will do, if I ever indeed decide to actually go down this path/route.


 * Based on your knowledge (and don't worry, I will certainly double-check this with a urologist later on), though, it should never take more than one year, correct?


 * (Oh, and for the record, thank you very much for not being judgmental of me in regards to this. I was asking this question here in a hypothetical sense, but I myself am interested in the idea of me eventually getting castrated for various reasons.) Futurist110 (talk) 22:15, 20 December 2013 (UTC)
 * 1. Well, to each his own. 2. It seems like the extreme approach. 3. Though I could imagine, at some point, if someone for some reason some jerk accused you having no cojones, you could say, "Yes, and your point is...?" 4. As regards "never", I couldn't say. Everyone is different. And keep in mind the old saying: "Always remember to never say 'always' or 'never'." ←Baseball Bugs What's up, Doc? carrots→ 01:54, 21 December 2013 (UTC)
 * 1. Yep! ; 2. Maybe for you and for some other people, but perhaps not for me. ; 3. LOL! Yes, that would be nice and funny to say. ; 4. Fair enough. I might as well continuously use at least one back-up even in the case of me getting castrated. Of course, if my urologist screws up and my back-up(s) don't work, then hopefully I will at least be able to sue this urologist for a huge amount of money. Futurist110 (talk) 00:38, 22 December 2013 (UTC)
 * It is really predictable how a medical question that involves sex or genitals always attracts replies which disregard the "no medical advice" rule, even when they are frivolous - as in this case.(see "Biochemistry" below, for example) "You need to read everything Wikipedia has about the production and retention of sperm" - NO, you need to talk to a urologist and a counsellor!! Richard Avery (talk) 08:18, 22 December 2013 (UTC)
 * Actually, I want to point out that I explicitly previously said that I was asking this here to get some background information on this issue. As I previously said here, I obviously have the intention of discussing this issue with a qualified medical professional if I decide to do this later on. Futurist110 (talk) 19:29, 22 December 2013 (UTC)
 * I lost track of how many times I told the guy to see a professional IF he's serious about doing this. But if you think this question crosses the line, feel free to box up or delete this section. ←Baseball Bugs What's up, Doc? carrots→ 10:09, 22 December 2013 (UTC)
 * If it is necessary to lock this question, please do so, but please don't delete it. Thank you very much. Futurist110 (talk) 19:29, 22 December 2013 (UTC)
 * Seems like we're getting a long, long way into the sort of medical advice we shouldn't be giving. Remember - no warranty here!  For example, does any of us know if there are ever embryonically separated bits of testicle that don't get excised? Wnt (talk) 15:42, 22 December 2013 (UTC)
 * Can you please elaborate on your last sentence here? Thank you very much. Futurist110 (talk) 22:32, 22 December 2013 (UTC)
 * I think what he's getting at is, what if they botch the operation and leave some viable portion of a testicle in place which is capable of producing sperm cells. ←Baseball Bugs What's up, Doc? carrots→ 23:44, 22 December 2013 (UTC)
 * I was only speculating, but I finally thought of a good search term ("three testicles") and indeed there is a condition polyorchidism in which more than two testicles exist, some of which may not descend to the scrotal sac. According to the article it is extremely rare, but it just goes to show that you never can really say "impossible" in biology. Wnt (talk) 02:14, 23 December 2013 (UTC)
 * Hence the need for two consecutive sperm-cell-free tests. Even at that, though, there are no guarantees, only probabilities. ←Baseball Bugs What's up, Doc? carrots→ 11:09, 23 December 2013 (UTC)