Wikipedia:Reference desk/Archives/Science/2013 October 13

= October 13 =

Floor tile material
I'm trying to determine the material some floor tiles are made of. At first, I thought they were vinyl, but after examining a few broken pieces, I now think it's something else. The tile pieces seem too heavy (dense) to be vinyl. They also feel cool to the touch, suggesting a higher thermal conductivity than familiar plastics. The tiles are about 1/8 inch thick (~ 3.2 mm). When I looked at the side of a broken piece, I noticed a rough texture that you're expect from broken earthenware. I also noticed a few sparkling (reflective) particles. What material could that be? Any educated guesses? --173.49.18.190 (talk) 03:06, 13 October 2013 (UTC)
 * Ceramic, just like you thought. Was that a bathroom tile? 24.23.196.85 (talk) 06:10, 13 October 2013 (UTC)


 * Ceramic is a possibility that I considered, but one thing I didn't mention was that the tiles seem at least somewhat flexible, as they seem to conform to and reveal the unevenness of the concrete floor below it. The location is not a bathroom. The tiles don't have any features that suggest they are designed for bathrooms. --173.49.18.190 (talk) 13:07, 13 October 2013 (UTC)


 * If it's from an older house, especially pre-1950's, it could be linoleum. Linoleum was made by mixing all manner of mineral powders, wood flour, etc, in a mixture of pine resin and linseed oil as a binder.  The pine resin and linseed oil cured to a hard plastic, and the back side was often given a rough surface.  Linoleum is extremely durable and you still sometimes find it.  The fillers used, which probably account for >95% of the mass, do provide a higher thermal conductivity and considerably more thermal inertia that modern plastics. 121.221.33.239 (talk) 07:49, 13 October 2013 (UTC)


 * They could well be linoleum but a word of warning. Many vinyl floor tiles made between 1920 and 1990 contain asbestos and you should get professional advice before disturbing them see: here. Richerman ''   (talk) 09:19, 13 October 2013 (UTC)
 * I don't know the vintage of the tiles, but they don't seem to have been laid during the period you mentioned (I think they're newer.) Do tiles that contain asbestos have markings or other telltale signs identifying them as such? --173.49.18.190 (talk) 13:07, 13 October 2013 (UTC)
 * No. In my country there are laboratories that will examine a sample and for a small fee tell you if there is asbestos. I guess there will be similar labs in other Western counries.  121.221.33.239 (talk) 15:08, 13 October 2013 (UTC)
 * No - if you look at the website I mentioned above it says "Vinyl flooring and wallpaper that contain asbestos cannot be recognized on sight" but it does tell you how to deal with them. However, it's not for me to say whether you should follow that advice or not - you must decide that for yourself. Richerman ''   (talk) 19:21, 13 October 2013 (UTC)
 * It sounds like vinyl composition tile (VCT), which is a mixture of clays and other minerals in a vinyl resin binder. It's the ubiquitous 12" x 12" tile material seen in schools, large grocery and discount stores (Walmart uses square miles of the stuff), and institutional buildings all over North America. It replaced the more-durable vinyl asbestos tile (VAT), which used asbestos fibers as part of the composition, in the 1970s. It's not always obvious which is which, though VAT isn't especially dangerous unless it's been abraded or pulverized. Usually (but not always) VAT is more brittle than VCT, which will bend a little before breaking, and tends to come in 8" x 8" or 9" x 9" configurations as well as 12" x 12". There is no specific marking for asbestos tiles, since at the time they were being made and installed, asbestos was considered a good thing and was incorporated into a wide range of building products. Here's one manufacturer .   Acroterion   (talk)   19:05, 14 October 2013 (UTC)

Vegetable identification
Hi guys. What is the vegetable behind the Apple? Thanks. Ben-Natan (talk) 05:39, 13 October 2013 (UTC)


 * It looks like a gourd. Plasmic Physics (talk) 06:26, 13 October 2013 (UTC)
 * Some variety of Cucurbita pepo, perhaps a yellow crookneck squash. μηδείς (talk) 20:32, 13 October 2013 (UTC)

Solution book of University Physics with modern Physics 13th edition
While solving problems of Sears and Zemansky's University Physics (by Hugh D. Young and Roger A. Freedman) 13th edition, I face two problems. First, answers of only odd-numbered problems (not the even-numbered problems) are given in the end of book. Whenever I solve even-numbered problems, I am not able to check whether my answers are right or wrong. Second, some problems are really very tough. Also, neither my teachers nor my friends use that book, and they often make excuses whenever I ask my unsolved problems to them. Therefore, I need a link to a website or any solution book. Thanks for helping me. Scientist456 (talk) 07:49, 13 October 2013 (UTC)


 * You need this booklet with answers to even numbered questions which should have come with the book. You can buy second hand copies from Amazon Marketplace (sorry, I can't post a link, the site seems to be on the blacklist) but most of them do not specify which edition they are for and I don't know how different the questions are between editions.  Spinning  Spark  10:41, 13 October 2013 (UTC)

What is a prepalate?
I am contributing to the article on Kitab al-'Ayn, the first dictionary for the Arabic language. The author arranged the letters according to the source of pronounciation instead of alphabetically. "Oh, that's a question for the language section of the reference desk." No, ominous voice. I don't need to know about linguistics, I just need to know what a prepalate is. Is that another word for the hard or soft palate, for example? MezzoMezzo (talk) 10:33, 13 October 2013 (UTC)


 * This diagram comes from our article Places of articulation. The prepalate is at 6, between the very back of the alveolar ridge and the hard palate.  The hard palate is at 7 and the soft palate further back still, at 8.  It's a small area and often seems to be subsumed into the areas surrounding it for linguistics purposes.  A Google search reveals that oral surgeons do often refer to it as a discrete area in the context of describing the extent of cleft palate.  -  Ka renjc (talk) 12:10, 13 October 2013 (UTC)

What is the scientific explanation for this !
on link http://www.youtube.com/watch?v=jxOyST6gM_A — Preceding unsigned comment added by 37.237.196.193 (talk) 11:03, 13 October 2013 (UTC)


 * Very amatuerish camera trickery, eg stop motion shooting/editing. For arms shown projecting thru solid objects, chromakeying is the proffessional way to fake it, but this video is sufficiently rough and blurry that they could simply have made a hole in a sheet of fibreboard or similar. 121.221.33.239 (talk) 12:53, 13 October 2013 (UTC)


 * This is not amateurish camera trickery. The video quality isn't as good as one might expect under the circumstances, but the person involved is Criss Angel, a famous magician, and the video is apparently a (somewhat low quality) copy of an episode of his TV show Criss Angel Mindfreak, which presumably was broadcast with a much higher video quality.  Criss Angel is easily rich enough to afford a high-quality custom built trick gate.  Red Act (talk) 03:28, 14 October 2013 (UTC)


 * Your search keywords are "revealed" and "exposed". There are hundreds of videos trying to explain these magics tricks. Cacycle (talk) 17:47, 14 October 2013 (UTC)


 * A very rich dude acting as a boofhead and using professional staff and equipment to do work with a very amatuerish look then. 121.215.39.252 (talk) 23:51, 14 October 2013 (UTC)
 * Well, yeah, that's kind of his shtick. His genre is guerrilla magic, so it fits the style he's aiming for to look like an unpolished amateur "average joe" that you might happen to see walking down the street on an average day, except that he's doing something astonishing.  I think the idea is that the "magic" is supposed to seem more amazing if it takes place under ordinary circumstances involving an ordinary guy, instead of taking place on a stage under the auspices of a guy in a fancy outfit, under circumstances that are clearly highly controlled.  Red Act (talk) 01:28, 15 October 2013 (UTC)

Is there any picture of the mixed flow compressor in the pratt and whitney pw 600f?
hey guys do you know if any picture of the mixed flow compressor in the Pratt and whitney pw 600f exists? cause pratt and whitney mentioned this themselves and the wikipedia artickle says it but there is only one patent picture buzt it downt shows rhe mixed flow compressor..Saludacymbals (talk) 17:12, 13 October 2013 (UTC)


 * You've seen our Pratt & Whitney Canada PW600 article I take it?  Spinning Spark  21:33, 13 October 2013 (UTC)

yes i saw the article but there is only the picture of the fan and not the compressor. so is there any picture of it?

amazing spider web bridge line (which type of spider?
http://www.youtube.com/watch?v=zubftSpCg2E in this video you can see an amazingly thick bridgeline of a spider web but there is a photo in the description of this type of spider. dguys do you know wich type it is? maybe darvins bark? Saludacymbals (talk) 18:36, 13 October 2013 (UTC)

Male and female variation, height and puberty
It is often said that men are taller than women; however, some women are taller than some men.

It is often said that girls begin puberty somewhat earlier than boys; is it also true then that some boys begin puberty earlier than some girls?--Whatdeanerwastalkingabout (talk) 23:57, 13 October 2013 (UTC)


 * While the logical link you are suggesting is fallacious, the answer is yes, some boys begin puberty at an earlier age than some girls. Puberty onset depends on a variety of factors, including sex, genes, nutrition and social circumstances. So boys with favorable factors for early puberty will experience it earlier than girls with unfavorable such factors. Effovex (talk) 01:56, 14 October 2013 (UTC)


 * It is often said that women are more fallacious than men. But some men are more fallacious than women. μηδείς (talk) 02:18, 14 October 2013 (UTC)


 * The trouble with women is that they all make sweeping generalisations :) Richerman ''   (talk) 09:09, 14 October 2013 (UTC)


 * People say men are cunning linguists. However, some women are more cunning linguists then men. — Crisco 1492 (talk) 09:15, 14 October 2013 (UTC)


 * Hmmm... I was going to say something about women being more fellatious but thought better of it. Richerman ''   (talk) 09:24, 14 October 2013 (UTC)


 * What in the world did you think I was punning about? μηδείς (talk) 18:56, 14 October 2013 (UTC)


 * You could always try phallacious. --   Jack of Oz   [pleasantries]  11:06, 14 October 2013 (UTC)


 * Note being one to engage in such puns and frivolity, let me try to give a straight answer. Things such as you describe generally follow a bell-shaped curve.  I'm limited to what I can draw here, using ASCII text, but here's a rough idea of what it looks like:

^      _   |      / \ N |     /   \ |   / MEN \ +>       Height
 * That graph shows the number of men at each height. Note that there are more men of average height than very short or very tall men.  If we did the same graph for women, we would find a similar pattern. although the average would be less than for the men:

^   _   |   / \ N |  /   \ | /WOMEN\ +-->    Height


 * If we then graph both together, we get lots of overlap:

^   _  _   |   / \/ \ N |  /  /\  \ | /W / \ M\   +> Height


 * So, this shows that the average woman is shorter than the average man, but there are some women taller than some men. It's also likely that the tallest man will be taller than the tallest woman, and the shortest woman will be shorter than the shortest man, although not always, as the bell-shaped curve tends to become more variable at the ends.  Now, you will sometimes find a pair of bell-shaped curves which don't overlap, like the weight of adult mice versus the weight of adult cats:

^   _        _   |   / \      / \ N |  /   \    /   \ | /Mice \ /Cats \ +--->         Weight


 * In that case, we could say that all adults cats are heavier than all adult mice. StuRat (talk) 13:05, 14 October 2013 (UTC)


 * Any two bell-shaped curves overlap by definition, a normal distribution does not have upper or lower limits. It's just that the overlap in some cases is negligible, so the chances of finding a cat smaller than a mouse are very small (assuming that their sizes really follow the bell-curve). - Lindert (talk) 14:06, 14 October 2013 (UTC)


 * Which of course brings us to the point of contention that most readily occurred to me, because they aren't necessarily likely to follow a bell curve at all. Stu's initial framing premise that "things such as the [the OP describes] generally follow a bell-shaped curve" is not necessarily at all true.  It would depend greatly on the feature being considered (with considerable variation even amongst the obvious and superficial phenotypical features). Snow (talk) 22:06, 14 October 2013 (UTC)


 * Hippety Hopper. DMacks (talk) 14:10, 14 October 2013 (UTC)


 * Well no, it may not always be the best model, but I think he did a good job of showing how overlapping distributions lead to plenty of cases that happen differently than the average case. And because of the Central limit theorem, bell curves pop up all over the place in nature. In the case of height or start of puberty, it makes sense to expect a roughly bell-shaped curve, even though it obviously won't go off to infinity like an ideal one, and may have other deviations explainable by the properties of the things being measured. K ati e R  (talk) 14:46, 15 October 2013 (UTC)


 * Yes, it's not possible to have an infinite height or a zero/negative height. For puberty, I suppose it's possible for somebody to have some medical condition which causes them to live their entire life without hitting puberty.  Puberty could also begin at, or even before, birth, due to some medical condition, but obviously can't start before conception.  I have no idea whether such medical conditions actually exist, but they are theoretically possible. StuRat (talk) 17:48, 15 October 2013 (UTC)
 * Delayed puberty has many possible causes, some of which may "delay" it indefinitely. DMacks (talk) 03:40, 17 October 2013 (UTC)