Wikipedia:Reference desk/Archives/Science/2014 December 11

= December 11 =

Voice impersonation
VOICE12.227.148.77 (talk)Can the voice of one person be recorded, analyzed and then be used(dubbed)to show that this person was present in a conversation between others? — Preceding undated comment added 01:57, 11 December 2014 (UTC)


 * Yes, but you'd need a large number of samples, to get all the phonemes you need. And even then the voice samples would tend to vary in tone, volume, and speed, so you'd need to adjust them to match and do some very careful blending or it would sound very choppy. StuRat (talk) 02:04, 11 December 2014 (UTC)

No, it would be obvious due to room noise (which probably wasn't recorded). If the recorded people were in a studio setting (totally low noise floor, high quality recording) of course it's easy. In an actual recording, you can forget it. I mean this even if the person literally were willing to read their lines - you still can't splice it in.

Secondly, I think you should not think about putting people into conversations they weren't in. I wouldn't be friends with someone who framed people this way, and most people I know are the same. I'm sure you'd like to live as a better person, rather than successfully frame someone into a conversation they weren't in while passing it off as reality :) don't take this too harshly though, I did answer your question. 212.96.61.236 (talk) 03:54, 11 December 2014 (UTC)


 * One could charitably assume that the OP is concerned about detecting fraud rather than committing fraud. —Tamfang (talk) 09:15, 11 December 2014 (UTC)


 * More to the point (and [User:212.96.61.236]] deserves a small slap on the wrist here) Wikipedia requires us to Assume Good Faith. So we assume that our OP is a good person, asking for perfectly reasonable purposes...until/unless shown otherwise. SteveBaker (talk) 16:41, 11 December 2014 (UTC)


 * Unit selection synthesis is essentially 100% convincing - and if you have enough recorded speech from the person, it can be indetectable. The issue of room noise in the recording isn't much of an issue because it's not done by naively chopping the speech up like splicing together bits of audio tape - there is more sophistication involved than that. SteveBaker (talk) 04:31, 11 December 2014 (UTC)


 * Roger Ebert had a synthetic voice made from his recordings. I didn't think it sounded much like him.  The company that made it customarily has the subject read a script that takes several hours, iirc; but that was not possible in his case. —Tamfang (talk) 09:55, 11 December 2014 (UTC)


 * Yeah - I heard that too. It wasn't their best work - but lack of good source material is always an issue.  Some of their other recreations are amazingly (eerily) good actually. SteveBaker (talk) 16:41, 11 December 2014 (UTC)


 * In a few years we'll have new movies coming out with Katherzatz Hepburn and Humphry Fauxgart. That'll be cool if it's well done. μηδείς (talk) 01:49, 13 December 2014 (UTC)


 * Not impersonation, but have a look at: Vocaloid, Hatsune Miku, and .Phoenixia1177 (talk) 11:06, 13 December 2014 (UTC)

How can fresh cavities form at the margins of sliver amalgam fillings on teeth?
Question by Ram nareshji deleted as probable copyvio Nil Einne (talk) 14:58, 16 December 2014 (UTC)
 * Amalgam fillings are made from an alloy. The properties of the chemical elements bound into an alloy are different than the properties of those elements in different forms. The fillings do not release any biologically significant form or biologically significant amount of either silver or mercury.  They are essentially inert.  — Preceding unsigned comment added by 173.49.91.231 (talk) 13:21, 11 December 2014 (UTC)


 * Plus silver isn't an automatic magic bullet that kills 100% of all bacteria. It's antibacterial effects are quite modest.  The existence of fine cracks and gaps between amalgam and tooth provide wonderful hiding places for bacteria - and that shelter is probably more important to the bacteria than any negative effects of the silver. SteveBaker (talk) 16:37, 11 December 2014 (UTC)

effect of pupil responses on the electroretinogram
Question by Ram nareshji deleted as probably copyvio Nil Einne (talk) 14:58, 16 December 2014 (UTC)
 * Perhaps the temporal pattern of responses would distinguish the photoreceptor response from the pupillary response. Wouldn't the retina process light input into a nerve response much faster than the pupil would constrict as a result of the light stimulus? The pupil takes over 180 milliseconds to respond to light, since the response is mediated centrally, with both pupils responding to light shined in one eye. What is the latency of the electroretinogram components of interest to you? The Wikipedia article Electroretinography does not provide much discussion of response latencies, but from various Google search results it looks like the a and b waves happen long before the pupillary response. Also, does the placement of the electroretinogram electrodes limit the response to pupillary activity? The article also does not discuss whether the subject is treated with drugs to prevent pupillary response or blinking, which could affect muscular response. Edison (talk) 17:17, 12 December 2014 (UTC)

What is the reason for low blood pressure during pregnancy?
In general, pregnancy women have low blood pressure compared to their normal values. What is the physiology reason for that? (I ask about the general phenomenon not about someone specific)213.57.13.167 (talk) 06:47, 11 December 2014 (UTC)


 * Medicinenet's "Low Blood Pressure During Pregnancy" article says "circulation expands during pregnancy and hormonal changes cause the blood vessels to dilate, leading to a lowering of blood pressure." This is also discussed in Wikipedia's Maternal physiological changes in pregnancy which notes that blood pressure typically returns to pre-pregnancy levels by 36 weeks. - EronTalk 07:06, 11 December 2014 (UTC)
 * Thank you, but I saw both of them before I asked my question, but still no one of them say accurate what specific hormonal change make this thing. 213.57.13.167 (talk) 13:35, 11 December 2014 (UTC)


 * From Maternal physiological changes in pregnancy: "The systemic vascular resistance also slightly decreases due to smooth muscle relaxation and overall vasodilation caused by elevated progesterone." The elevated progesterone is the specific hormonal change causing a reduction in blood pressure. Are you looking for something more specific than that? - EronTalk 17:27, 11 December 2014 (UTC)
 * Thank you, now it's more understood. How this hormone causes to low levels of BP?? 213.57.13.167 (talk) 18:21, 11 December 2014 (UTC)


 * One effect of progesterone on the body is that it relaxes smooth muscle tissue. This includes vascular smooth muscle which makes up the walls of the blood vessels. In effect, the blood vessels become "looser" (the technical term is vasodilation); this reduces blood pressure. - EronTalk 18:39, 11 December 2014 (UTC)
 * Thank you! 149.78.29.78 (talk) 07:46, 12 December 2014 (UTC)
 * See also, eclampsia, for a reason one does not want high blood pressure during pregnancy. μηδείς (talk) 19:06, 11 December 2014 (UTC)

A/D using digipot?
I am looking for references that describe using digipots like the MAX5160 etc to make a crude A/D. Any pointers?--86.184.57.96 (talk) 13:18, 11 December 2014 (UTC)
 * This technote from Maxim might be a useful start. If anything, the tendency in the industry is the other way (to use DACs rather than digipots), unless you're interested in setting the current rather than the voltage, or you need the setting to be non-volatile.  But the devices are generally interchangable for many applications. Tevildo (talk) 15:52, 11 December 2014 (UTC)
 * To actually answer your question (sorry), what you can do is use the digital-to-analog element (DAC or digitpot) in a servo or Wheatstone bridge arrangement with the signal you want to measure as the other input - the value of the digital input needed to balance the bridge or null the loop will track the value of the input signal. Tevildo (talk) 23:17, 12 December 2014 (UTC)

Why does Vitamin E called "antisterility"?
213.57.13.167 (talk) 14:40, 11 December 2014 (UTC)


 * The name seems to have arisen from the way Vitamin E was discovered. Rats fed a purified diet with vitamin supplementation (i.e. foods processed to provide just the necessary protein and carbohydrate plus known mineral and vitamin supplements) did not reproduce normally. Researchers noted that adding yeast or fresh lettuce to the diet restored fertility. They referred to the (then unknown) nutrient that had this effect as the "anti-sterility factor". Further research eventually isolated what came to be called Vitamin E.


 * For more information see, for example, Vitamin E and this book excerpt. - EronTalk 17:37, 11 December 2014 (UTC)


 * This was a question on Jeopardy the following day, interestingly enough: "thise substance, chemically alpha tocopherol, was discovered by studying rat metabolism." 23:47, 14 December 2014 (UTC)

Candies' strange behavior
I noticed that some Mac Iver candies I had moved from their original glass jar to a candy box (photo) started to melt down, although they don't do that in the glass jar and I don't keep the jar in the fridge. Both containers stand about 15-25 cm apart in the room temperature and the outdoor temperature have been around 1 to 5 centigrade in recent days. Still, the candies in the candy box seem to continue melting down, while those in the glass jar don't. Why is that? Some natural air layer (insulation) in the covered glass box? Brandmeistertalk  17:29, 11 December 2014 (UTC)
 * OK, this is a WAG because I know nothing about 'Mac Iver candies' (being, for one thing, on the right-hand-side of the Pond), but it might steer someone else in the right direction.
 * Mac Iver seems to be a trademark of Lidl, a German company. —Tamfang (talk) 09:27, 14 December 2014 (UTC)
 * Some substances readily absorb moisture from the air and liquefy (deliquesce) as a result: common household substances that do this include washing powder and instant coffee granules, and to a lesser extent sugar in some forms. It might be that the coating or an ingredient in these mysterious-to-me confectioneries exhibits this behavior. In the (sealed) glass jar they would be unable to do this, but in the box they are, presumably, freely exposed to the air. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) — Preceding undated comment added 19:49, 11 December 2014 (UTC)
 * Ok, I think the cooking steam and the resulting humidity are to blame (some cookies in the kitchen went damp previously). Brandmeistertalk  08:45, 12 December 2014 (UTC)

what was the incidence rate of general opc by 2007?
in the wikipedia article on hpv positive oropharyngeal cancer, it says the incidence rate by 2007 was 3.2 per 100,000 males a year, and 1.9 per 100 000 all sexes/year. But when i looked at the cited source, it didn't mention this anywhere, so i don't trust what the article says.Whereismylunch (talk) 19:55, 11 December 2014 (UTC)


 * A few things: If you want us to help you, we can do better if you help us a little first. For instance, it looks like you were reading HPV-positive oropharyngeal cancer, is that right? The citation for incidence of 1.9/100k leads to this table here . It says that males in USA have mortality of 3.9/100k, and females 1.4. It gives incidence rates that are higher.
 * Having that information will help the volunteers here figure out what's going on. At a glance, it seems that someone didn't properly understand the table, or perhaps made some typos. This brings me to my next point:
 * Wikipedia is not a reliable source -- it is an encyclopedia that anyone can edit, and you shouldn't really trust anything you read here if the correctness of the information is very important to you.
 * Finally, here are some other references for OPC incidence  that you may find informative. SemanticMantis (talk) 20:58, 11 December 2014 (UTC)

Yes, thats right. i was reading HPV-positive oropharyngeal cancer. I thought i stated that clearly.24.207.79.50 (talk) 21:29, 11 December 2014 (UTC)
 * Ok, well in the future it will help if you link to articles you are asking about, and in this case the reference as well. Also it will be easier to participate here if you follow WP:indent style so that we can tell who's talking to whom. SemanticMantis (talk) 21:31, 11 December 2014 (UTC)

why doesn't the atmosphere burn if it contains oxygen?
Not that this is a good idea, but can't (at the risk of the 'tragedy of the commons', eventually suffocating everyone) someone just get 'free' (stolen from the rest of the planet) energy by burning the atmosphere directly, since it contains oxygen?

Wouldn't this have been simpler historically than mining up coal and oil etc, since anywhere in the world you can just start burning the atmosphere. What am I missing? 82.131.223.148 (talk) 21:59, 11 December 2014 (UTC)
 * Oxygen itself will not burn - it needs a source of fuel before combustion can take place. Fire triangle might also be an informative article.  Tevildo (talk) 22:04, 11 December 2014 (UTC)
 * Oxygen doesn't burn, but rather serves as an oxidizer in combustion reactions. That means you need a fuel that is in a reduced state to react with the oxygen. If we looks at atmosphere gas components, we don't really see something for with which it can burn. 78% N2, which is almost inert, 21% oxygen, 1% argon, which is inert, and only trace amounts of other compounds. So in terms of gas amounts, there isn't anything for oxygen to oxidize. If we look even at the trace gases, CO2 is already the most oxidized form for carbon, and most of the other gases are inert. --OuroborosCobra (talk) 22:07, 11 December 2014 (UTC)


 * (ec) I think what the OP is asking is - why does atmospheric nitrogen not burn in presence of atmospheric oxygen? The answer to that one is - because the bond between the two nitrogen atoms in the N2 molecule is too strong. That is, it would take too much energy to burn the nitrogen; so it won't burn under normal conditions. In fact, lightnings do produce some nitrogen oxides, as does solar UV radiation; but the energy balance of these chemical reactions is such that most of the atmosphere "prefers", thermodynamically, to stay as a mixture of N2 and O2 molecules and not as a mixture of various nitrogen oxides.  --Dr Dima (talk) 22:14, 11 December 2014 (UTC)


 * is there a chemical (e.g. laws of thermodynamics type thing) reason that it would be impossible through some catalyst-like or other process to turn the nitrogetn bonds into some different form (without putting in too much energy?) I mean could it be the case that the nitrogen comprising most of the atmosphere 'happens to be' inert but could be made reactive without putting in much more energy? (through some novel method that doesn't happen by itself and would be artficial.)  If this is going to blow up the planet you should probably reply on my talk page with an email instead of here.  I wouldn't want to give anyone any ideas.  (For my part, I certainly woulnd't ravage the planet if this is possible.) thanks.  82.131.223.148 (talk) 22:33, 11 December 2014 (UTC)
 * If you are suggesting changing the form of the dinitrogen triple bond to a less stable form, and I don't know of such a form, that would be inherently endothermic. As to burning the nitrogen itself, that is likewise endothermic.  Oxides of nitrogen are a form of atmospheric pollution, produced in automobile engines (although less so than in the past), and are undesirable precisely because of their instability.  They are themselves oxidants.  Combining the nitrogen with the oxygen would be an endothermic process.  The atmosphere is diatomic oxygen and diatomic nitrogen because that is a stable mixture of gases.  As mentioned, argon really is inert.  After nitrogen, oxygen, and argon, air contains carbon dioxide and water vapor, and they cannot burn because they are already oxidation products.  Robert McClenon (talk) 23:06, 11 December 2014 (UTC)
 * The air itself, as mentioned, is stable. The juxtaposition of air containing oxygen and a biosphere is only metastable.  Once forest fires start, they will continue until they burn out or are put out.  Robert McClenon (talk) 23:08, 11 December 2014 (UTC)
 * "Burn" is not a good scientific term. Oxygen reacts with allot of materials all the time but it does not react with itself ofcourse and processes need "enough" Oxygen to start. So its very doubtfull you could even theoretically "burn it all". Additionally there is allot Oxygen bound in Rust and other "oxydations" and plants as well as micro organisms keep producing it. --Kharon (talk) 23:15, 11 December 2014 (UTC)


 * To answer the OP's second question, whether there is a catalytic or other way to make nitrogen react more readily with something else: you may want to look at the Nitrogen fixation article and the links therein. If you have further quaestions, please ask. --Dr Dima (talk) 23:53, 11 December 2014 (UTC)
 * On the "ravaging the planet" issue, the OP may also be interested in Polywater. Tevildo (talk) 00:34, 12 December 2014 (UTC)


 * This idea is the subject of Larry Niven's sci-fi novel The Nitrogen Fix. An interesting property of the system is that at high temperatures nitrogen oxides are more stable than separate nitrogen and oxygen, leading to the production of NOx in car engines; but at lower temperatures less so; hence the need for the three-way catalytic converter.  I'm not entirely clear on whether the chemical equilibrium at low temperature sufficiently explains the observed scarcity of these compounds in the atmosphere (see  - it says the Gibbs free energy is just 9.2 for N2O4)  I wonder (don't know) if it is actually interactions with other compounds i.e. hydrocarbons that helps shape the low levels, much as in a NOx adsorber regeneration process. Wnt (talk) 13:58, 12 December 2014 (UTC)
 * That's Hal Clement's novel, not Larry Niven. Scared me for a second. μηδείς (talk)
 * D'oh!. Shoulda known that... Wnt (talk) 00:38, 13 December 2014 (UTC)
 * Only knew that because I've read everything Niven has actually written, but I'm requesting the Clement on ILL. μηδείς (talk) 01:45, 13 December 2014 (UTC)