Wikipedia:Reference desk/Archives/Science/2015 April 13

= April 13 =

Definitions
I am doing an Assignment on Statistics, and one part of it involves flooding in parts of a River, and some of the definitions have eluded me. I just want to clarify the meaning of the term Coarse Grain Channel Fill - am I correct in thinking that this is coarse ( not fine ) shingle or stones that make up the main Channel of a River Bed ? If not, and any one knows, please enlighten me. Also, I am slightly confused about the idea of Sinuosity - is this the same as Meander, and if part of the Meander of the River is referred to as straight, even though the same part has high Sinuosity ( over 1.5 ), what does this mean. Also, am I correct in thinking that a Chute on a River is a kind of Water Fall ? Finally, we are looking at Logistic Regression and Poisson Regression - how would I do these in R for such data on the River, where some is Categorical, such as whether there is Channel Fill or not, or if the area is grassy or agricultural, but some is Quantitative, like Channel Width, which I assume is with Width of the River at the Point in Question. Also, how would I do both a Poisson and Logistic Regression in R for a study on numbers and proportions of Students by Gender either accepted or not accepted into a number of Departments in a University, and what would it all mean - what is the point of it ? I have some Statistical knowledge, but have missed out on some over the Years. Thank you. Chris the Russian Christopher Lilly  08:16, 13 April 2015 (UTC)


 * I'm no geologist but a google search finds that the definition of a chute is "A narrow "short cut" across a meander bend, formed in flood as the main stream flow is diverted into a trough between point bars" . Channel sinuosity is explained here. Richerman    (talk) 09:31, 13 April 2015 (UTC)

That is interesting, because I was aware of such process from before, and have even mentioned in the the aforementioned Assignment. This brings new light to the meaning, and will allow me to adjust what I have written in the Assignment so as not to appear too ignorant. Thank You. I shall have a look at the rest also. In addition, if anyone else has any answers to the other questions, please feel free. Thanks All. Chris the Russian Christopher Lilly  11:07, 13 April 2015 (UTC)

Chimp evolution driven by interaction with gorillas?
A friend just told me to have seen a TV documentary claiming that the evolutionary split between common chimpanzee and bonobo was driven by the fact that the former share their habitat with gorillas, which made them stronger and more aggressive. While this claim is compatible with their respective distributions, chimps and gorillas rarely interact in any way. So what was the reason? Did chimps turn into hunters to reduce food competition with gorillas? --KnightMove (talk) 10:19, 13 April 2015 (UTC)


 * Careful with just so stories - this is a reasonable explanation, but it's hard to really back up that kind of assertion. Also keep in mind TV series are as a rule happy to play fast and loose with reasonable hypotheses discussed as though they were facts, especially if the researcher responsible for the claim is presenting the case. Most all the research I see on Chimp/Bonobo speciation is purely genetic in nature, and does not appeal to the paleoecology of chimp/gorilla competition (which would be difficult to reconstruct, to say the least, and note that the ranges you display are current, not for ~1 million years ago, about when the chimp/bonobo split happened). Here is a paper that uses a multi-population model with isolation and migration . I haven't dug in to the methods, but it seems that it is at least consistent with the claim above. SemanticMantis (talk) 13:18, 13 April 2015 (UTC)


 * I was going to say pretty much the same thing. (How would you do an experiment to see if this was the reason?  The best you could do would be to turn up some extra intraspecific correlations, but... correlation isn't causation.) Wnt (talk) 01:34, 14 April 2015 (UTC)
 * Ok, thanks to you 2. Unfortunately I don't know whether this was a just-so story or based on any evidence, not having seen the documentary. --KnightMove (talk) 07:48, 14 April 2015 (UTC)
 * perhaps I should clarify - There probably is at least some evidence for the claim, event poor quality TV documentaries don't usually completely make things up :) What I'm saying is that I cannot find specific mention of it in the literature with a few minutes of searching. But I am confident that this is not strongly supported with good evidence, and is not a widely accepted explanation in the speciation of apes. There's a wide gulf between "reasonable, with some supporting evidence" and "correct explanation." SemanticMantis (talk) 14:28, 14 April 2015 (UTC)

Highest area of the sky covered by moons of a terrestrial planet?
Sometimes on Fantasy/Sci-Fi worlds, you see a large number of moons in the sky. While it is certainly possible to have multiple moons on a terrestial planets, the idea that each of them would have the visual diameter of the Earth's moon just seems wrong. Assuming the Planet is more than a billion years old, is it possible to have two moons that large (assume made of standard "moon stuff") to the eye?Naraht (talk) 16:00, 13 April 2015 (UTC)
 * Can you find an example or two? ←Baseball Bugs What's up, Doc? carrots→ 16:23, 13 April 2015 (UTC)
 * I'm pretty certain anything like that would be unstable - but then again articles like Physicists Discover a Whopping 13 New Solutions to Three-Body Problem should tell me to shut up ;-) There are a couple of stable solutions known besides things like the sun moon earth where the biggest mass is far away from the other two, see Lagrangian point, but nothing like what you want as the body at a Lagrangian point has to be much smaller for stability. Dmcq (talk) 17:09, 13 April 2015 (UTC)not known yet


 * Jupiter's_moons.jpg can be used to look for other similar views in the universe.]]See Extraterrestrial_skies. Io_(moon) in particular is about the size of our moon, and would appear larger in Jupiter's sky. So what you are asking isn't that outlandish, Jupiter's got one moon that looks bigger than ours, 3 more about that size, and many other smaller moons. They are a bit dimmer, because Jupiter only gets about 3% of the sunlight that Earth does. But all you have to imagine to fulfill your scenario is either something like Jupiter with a much brighter sun, or closer to the sun. (Also, last time I something like what you describe, I was playing Mass effect - but this was a view from a moon, so the planet loomed quite large, and other smaller moons were also visible. My point is that large "moons" in sci-fi skies may also be planets, if the view is from a moon :) SemanticMantis (talk) 18:08, 13 April 2015 (UTC)


 * Well yes it is certainly possible if the planet is huge, I was thinking in terms of earthlike planets in sci-fi with a red sky tall buildings in the background and some insect creature in the foreground. But then as you say it might be circling a Jupiter like planet which could occupy a very large part of its sky. So yep I hadn't considered the possibilities. Dmcq (talk) 09:24, 14 April 2015 (UTC)
 * Right, and I probably wasn't paying enough attention to "terrestrial planets" in the question - Terrestrial_planet has some info, I'm not really sure what the largest planets are with hard rocky surfaces. I agree that planets with Earth-like mass would be unlikely to have several satellites with apparent diameters comparable to our moon, but aside from waving at the three body problem as you correctly did, I don't know enough astrophysics to support the claim further. SemanticMantis (talk) 14:23, 14 April 2015 (UTC)

Tomato-based products on clothes vs. containers
I find tomato-based products, such as salsa, bloody mary mix, or even curries, to rinse off of glass or plastic containers very easily—even in the face of water that isn't warm or very pressurized. Yet tomato-based stains on clothing can be very difficult to remove. What's going on there? I figure it has to do with the chemical makeup of tomatoes. --BDD (talk) 16:53, 13 April 2015 (UTC)


 * My experience seems to be a little different. Tomato-based products stain my plastic Tupperware more than anything else.  Since lycopene, which is distinctively present in tomatoes, is a hydrocarbon, a bit unusual for biomolecules, maybe that is the chemical culprit.  Deli nk (talk) 18:34, 13 April 2015 (UTC)


 * I think it's just the acidic nature of tomatoes - that would make them rinse off glass easily (cf vinegar as a glass cleaner), but also make them etch plastic . That probably is a factor in clothing staining too, but I'm not as clear on that. SemanticMantis (talk) 18:42, 13 April 2015 (UTC)


 * The main pigment is lycopene; our article says that it is insoluble in water (which definitely looks right by the structure; it could use sourcing though); it also says it dissolves into plastic because it's hydrophobic, which too makes sense. I would guess that if lycopene doesn't dissolve in water, then the lycopene is not initially going to be dissolved and can be washed away as a suspension, more or less.  In fabric soap would work.  But why does a "set" tomato stain in fabric become more resistant?  My guess is that those double bonds you see in the structure get into mischief, find something to undergo some sort of addition reaction to, and become covalently attached.  But that's just a guess. Wnt (talk) 01:32, 14 April 2015 (UTC)


 * If a plastic container becomes stained from tomatoes, for sanitation reasons is it best to discard it? Or does it matter? ←Baseball Bugs What's up, Doc? carrots→ 08:50, 14 April 2015 (UTC)


 * That's actually a medical advice question, so I can't tell you what you should do. In general, if lycopene dissolves into plastic, that is a chemical moving into the container, not a large chunk of material - bacteria shouldn't dissolve into plastic the way the chemical does.  Now if spoiled food contained toxic chemicals of some sort... but I don't know of such a case.  I imagine if you left the container full of something really nasty long enough you could wash it thoroughly and still complain there's a bad smell in it, from a few miscellaneous putrescine molecules or something.  The more interesting thing is that chemicals in plasticizer, like bisphenol A, are able to move out of the container just as the tomato pigment can move in.  So your decision of whether to get a new container properly ought to depend on what is in it, but of course, who knows? Wnt (talk) 11:03, 14 April 2015 (UTC)


 * Well, my question really was, is it possible that food particles (and hence microbes) could find a permanent home in the container. Your answer indicates a possible "yes". I'm reminded of folk wisdom saying you shouldn't use china with cracks in it, for the same reason. I reckon it comes down to the old saying "if in doubt, throw it out." ←Baseball Bugs What's up, Doc? carrots→ 13:36, 14 April 2015 (UTC)


 * Throwing out cracked china seems over-reactive and wasteful to me, but that's just my opinion. Again, we can't give safety advice. You might be interested in this write up on the topic of plastic food containers and microbes, with links to scientific research within . SemanticMantis (talk) 14:18, 14 April 2015 (UTC)


 * Actually, my point was that food particles are different from dissolving chemicals. Your plastic could have cracks, pores, crevices etc. for microbes to hide in; but that is a different mechanism than hydrophobic chemicals actually dissolving into the plastic.
 * To give a related example: Suppose you're doing an old fashioned Northern blot.  You have a bag of oh, I think it might be polyethylene but I forget, which is heat sealed to contain a piece of nitrocellulose with various nucleic acids on it which is bathed in several milliliters of highly radioactive fluid (it contains radiolabeled nucleic acid probes and doubtless some loose inorganic phosphate-32).  Well, you can take a very hydrophobic lab marker and write on the outside of the bag which probe you just added, and the ink will pass straight through the bag and onto the surface of the nitrocellulose blot.  But the marker will not become radioactive, because the hydrophilic P32 doesn't want to make the reverse trip (otherwise you would have a problem!)  So this sort of "filter" by dissolving through plastic blocks P32, nucleic acids, and yes, whole bacteria, but not lab markers or (presumably) tomato pigment. Wnt (talk) 15:53, 14 April 2015 (UTC)


 * I find any reaction between my food and the containers to be completely unacceptable. Therefore, I use glass containers exclusively, whenever possible.  I don't understand why others continue to use plastic.  It's not like glass is prohibitively expensive.  It's made from sand, after all, and there's no shortage of that (although there apparently is a shortage of river sand, which is used to make concrete). StuRat (talk) 01:48, 15 April 2015 (UTC)


 * I asked a related Q some time ago, noting that tomato juice seems to act as a weak detergent, keeping cooking pots from becoming greasy. Not as powerful as real detergents, of course, but it is "organic". StuRat (talk) 01:55, 15 April 2015 (UTC)