Wikipedia:Reference desk/Archives/Science/2012 September 30

= September 30 =

pink nebula
In Apple's splash screen, is that pink thing a real nebula or aurora or what? —Tamfang (talk) 08:08, 30 September 2012 (UTC)
 * Well, it's called "Aurora Leopard" in the sceensaver preferences on OS X Mountain Lion. So it probably is an aurora. I suspect its "real" in that it is based on a real photo, but I suspect that either the photographer or the designers at Apple, or both, have worked with real and digital filters to enhance the colours. --Stephan Schulz (talk) 08:56, 30 September 2012 (UTC)


 * Make that OS X 10.5 Leopard. hydnjo (talk) 21:29, 30 September 2012 (UTC)


 * There is some discussion of it here which I found interesting. The star pattern is duplicated in the background which suggests that the very minimum that it's a manipulated photograph or that it's been entirely generated anyway. It seems not unrelated to whatever they used to generate the intro sequence. I suspect it's entirely generated. --Mr.98 (talk) 14:58, 30 September 2012 (UTC)

abbreviation question
In this cite, what does "CC" stand for?

"Figs. B I, B II, B III. Three sections of a Pristiurus-embryo. B I is through the heart, B II through the anterior part of the dorsal region, and B III through a point slightly behind this. Drawn with a camera. (Zeiss CC ocul. 2.)"

69.138.178.234 (talk) 11:20, 30 September 2012 (UTC)
 * That parenthetical phrase refers to components used in microscopy: a specific Zeiss objective (see example here), and a specific ocular (eyepiece). For those familiar with the terminology, this phrase would describe the microscopic method (of course, it's jargon to the rest of us).  -- Scray (talk) 12:33, 30 September 2012 (UTC)

Pancreatin use
Re:http://en.wikipedia.org/wiki/Pancreatin

Are these supplements meant merely to supply deficient enzymes? Is there a supplement which will decrease the body'w own production of amylase and lipase, as by a negative feedback mechanism? Is there a difference in this in regards to pancreatin vs. pancrealipase, pre-enzymes vs. active enzymes? I'm unsure how passage through the stomach affects these enzymes before they reach the small intestine. — Preceding unsigned comment added by 173.28.222.74 (talk) 15:42, 30 September 2012 (UTC)


 * Definitely these digestive enzymes can destroy some food allergens if used outside the body, before eating.

The downside is that (I would say - the paper doesn't) in order for this to be effective, you pretty much have to reduce the food to some sort of amino acid supplement pap, unless, that is, you devise some extraordinarily clever enzyme that can seek out and destroy the specific epitopes responsible and not much else, which I think can be done, but drawing you a blueprint is another matter again. I would view other uses with considerable skepticism. Note that pancreatin itself can cause hypersensitivity to repeated exposure.[ ] I would have some suspicion that extensive exposure to non-human digestive enzymes, especially in persons prone to allergy, would be a Bad Thing, and that there would even be some risk of subsequent allergic rejection of the person's own digestive enzymes, but I have no proof for this, and admittedly, people have been exposed to pancreatin and some other enzymes in freshly butchered kills for millions of years, and regulatory agencies approve that these products are handled incidentally as contact lens cleaners by large numbers of people without obvious drawbacks. Wnt (talk) 17:24, 30 September 2012 (UTC)

cool melting
is there any explaining about cool melting in wikipedia? --Akbarmohammadzade (talk) 17:06, 30 September 2012 (UTC)akbarmohammadzade--78.38.28.3 (talk) 17:04, 30 September 2012 (UTC)
 * Can you explain your question more fully? In the meantime, see NaK which is molten and cool in both senses. μηδείς (talk) 17:10, 30 September 2012 (UTC)
 * Perhaps, he means to say sublimation - whereby a solid changes phase to a gas without passing through the liquid phase. Alternatively, he could be talking about the pressure dependence of a melting point. I agree, he needs to either rephrase the question, or provide a meaningful description of what he means to say. Plasmic Physics (talk) 22:50, 30 September 2012 (UTC)
 * I'm melting! Melting! Oh, what a world! Clarityfiend (talk) 00:33, 1 October 2012 (UTC)
 * Does our article on melting not answer your question?--Shantavira|feed me 07:10, 1 October 2012 (UTC)

thanks!ok, i couldn't find any thing about cool melting there.Akbarmohammadzade — Preceding unsigned comment added by 78.38.28.3 (talk) 05:00, 2 October 2012 (UTC)

cool melting may occur by effect of radio waves .three phases of matter have common point named triple point in thermodynamic ,the solid matter can pass from liquid phase direct to vapor case .This process is  in thermodynamic for amounts of pressure and temperature and volume ,but radio waves can melt solid matter in very  cool temperature.akbarmohammadzade--78.38.28.3 (talk) 04:09, 2 October 2012 (UTC)
 * I am not familiar with this concept, but you may be interested to read Laser ablation, Induction heating, and Dielectric heating. Plasmic Physics (talk) 05:26, 2 October 2012 (UTC)
 * Based on your field of study, I assume that you may be most interested in dielectric heating. The methods above are examples of non-contact heating, which is to say, they are examples of electromagnetic heating. Plasmic Physics (talk) 05:44, 2 October 2012 (UTC)

All right ,so — Preceding unsigned comment added by 78.38.28.3 (talk) 06:14, 2 October 2012 (UTC)

theoretical extent of hydroplaning -- how to calculate?
Given water thickness h, water viscosity η, water density d, wetted tire surface area A, and vehicle velocity v, how do I find the force slowing down the vehicle, if the tires do not make contact with the road?

To solve this homework problem I've used my professor's cited (empirical? N-S derived?) relation of skin drag coefficient = 1.33 / sqrt(Re), where Re is Reynold's number. Then I used the drag equation to compute the force. For example, if the mass of the vehicle is 1000 kg, A = 0.1 m^2, h=0.1mm, and v = 10 m/s and dynamic viscosity of water is 1.002 * 10^-3 N*s/m^2 and water density 0.9982 g/cm^3, I get a stopping distance of 206m, assuming the water plane thickness h and wetting area A do not change.

However, something doesn't sit right with me (for example, I don't think *all* of the drag is skin drag) and I'm looking for an alternate way to solve this problem. 71.207.151.227 (talk) 17:32, 30 September 2012 (UTC)


 * I see a couple problems there. One is that air resistance is ignored.  That might make sense in normal braking, where it's not very significant compared to the much larger friction force against the road, but, in this case, it may be significant.  The second issue is that, when you slow to a certain speed, the vehicle will cease to hydroplane, at which point you must switch calculation methods.  However, if you want to get an A, I suggest you ignore reality and do as your Prof suggests. StuRat (talk) 07:20, 1 October 2012 (UTC)

Are these images useful?
I stumbled across two images, File:AWaveEquation.gif and File:AWaveEquation2.gif, that apparently describe some kind of wave equation. I don't know what they mean, and I can't tell if they are meaningful or useful. I've listed them for deletion because they aren't used anywhere; see. If someone here can see that these images are potentially useful for some encyclopedic purpose, please contribute to the deletion discussion there. —Bkell (talk) 18:40, 30 September 2012 (UTC)

Does the Vagainal Mucos and Vagainal Lubrication are same?
except urine, female-semen, and lubrication, what else is released by the fluid-releasing vaginal parts? Thx. 58.11.229.10 (talk) 21:26, 30 September 2012 (UTC)


 * I'd be surprised if they synthesised semen. AndyTheGrump (talk) 00:37, 1 October 2012 (UTC)

Please answers. — Preceding unsigned comment added by 58.11.113.153 (talk • contribs) 04:13, 1 October 2012


 * I don't understand the question, but the following corrected links may help (many will consider these links NSFW): Vaginal mucus, Vaginal lubrication -- Scray (talk) 04:17, 1 October 2012 (UTC)


 * (ec) First let me spell them correctly so you can find our articles: vaginal mucus & vaginal lubrication. StuRat (talk) 04:18, 1 October 2012 (UTC)


 * Vaginal mucosa is the vaginal tissue which produces mucus. By vaginal semen the OP may mean female ejaculation. μηδείς (talk) 04:22, 1 October 2012 (UTC)