Wikipedia:Reference desk/Archives/Science/2008 June 14

= June 14 =

Flood stage and topographic maps:Cedar Falls,Iowa: A question touching on the sciences of mapping and hydrology.
In the recent flood news in Iowa, I am left confused by the lack of relation between the river being "so many feet above flood stage" and how that relates to topographic maps showing only how many feet above sea level various parts of a town are."Flood stage" is an arbitrarily river level at which it "starts to do damage" and cannot readily be determined from a toporaphic map. For instance, in Cedar Falls, Iowa, how many feet above sea level is "flood stage?" A USGS topo map, 7.5 minute, downloadable at shows the river normally at about 841 feet above sea level, and the first contour lines shown near the riverbank are 850 feet, but how is one to know if the water getting there "starts to do damage" or just makes some mud a bit wetter? On the other hand some structures seem to be below the 850 contour, basically at the normal river level. Where is a tabulation of "flood stages" for various cities in relation to elevation above sea level? Where are maps showing the 100 year and 500 year flood plains for that city?(or other cities in general)? Also, some news stories give the river level in "gauge" relative to some arbitrary historic measurement point. Where is a listing of "gauge" levels relative to actual elevation? Edison (talk) 00:13, 14 June 2008 (UTC)
 * I finally tracked dow a site relating "gage" and "flood stage" to topographic map elevation for this town, but I still would like a general source for 100 year/500 year flood maps for various U.S. locations. Thanks. Edison (talk) 00:39, 14 June 2008 (UTC)

Ants native to the South Pole
Are there any ants native to the South Pole? 122.107.192.10 (talk) 06:41, 14 June 2008 (UTC)


 * There is no life native to the South Pole. Antarctica, couldn't say. N (t/c) 07:42, 14 June 2008 (UTC)


 * I'm relatively sure that there are no ants at either of the poles, it's simply too cold. If you mean the southern hemisphere, i'm sure someone can help you. Regards, CycloneNimrod talk? contribs? 07:50, 14 June 2008 (UTC)


 * According to our article on ants, ants are native to all continents in the world except Antarctica. (see subsection here). So, the short answer would be no, there are no ants native to the South Pole or Antarctica. Eric  (EWS23) 08:28, 14 June 2008 (UTC)


 * Ants, being insects, are cold-blooded. All cold blooded insects need a warm enough environment to keep them from freezing solid.  Some insects do have the ability to freeze and then thaw when the temp warms up, but the temp never warms up enough to thaw an ant at the South Pole.  Also, there would be nothing for the ants to eat at the South Pole, as nothing else (plants or animals) can live at those temps for long. StuRat (talk) 14:21, 14 June 2008 (UTC)


 * No ants in antarctica? Edison (talk) 20:00, 14 June 2008 (UTC)


 * It was too cold for them so they all "said uncle", and left. StuRat (talk) 02:05, 15 June 2008 (UTC)


 * Hi. Um... there is no life native to Antarctica? What about Emporer penguins, Arctic Terns, ice mites, plankton, fish, moss, and tundra plants? I've read about mites being able to survive the -80C temperatures, could that be it? Thanks. ~ A H  1 (TCU) 17:37, 15 June 2008 (UTC)
 * There's no life at the South Pole. That's different from there being no life on the entire continent. As for mites surviving at such low temperatures - if it's true, they would do so by becoming dormant, so they couldn't spend their entire life at those temperatures. --Tango (talk) 18:04, 15 June 2008 (UTC)
 * So the mites would just become dormant? Edison (talk) 03:22, 17 June 2008 (UTC)
 * Followup: According to Antarctica, there are mites in Antarctica that can survive very low temperatures because of "antifreeze" (glycerol) in their bodily fluids, but it says they can survive down to -34C, not -80C. I don't think any life can spend a significant amount of time at -80C without being dormant. --Tango (talk) 22:58, 15 June 2008 (UTC)
 * So the truth outs: the secret is antifreeze. Edison (talk) 03:24, 17 June 2008 (UTC)
 * Not ants, but there are the extremophiles Obligate psychrophiles... Julia Rossi (talk) 01:15, 16 June 2008 (UTC)

Biology
i want some nice topics on biology so that i can prepare a project.Pls suggest some good topics.I am in 12th standard.

Evidence for biological evolution can be a good topic --Fang 23 (talk) 19:30, 20 June 2008 (UTC)

You can do a project on Microbiology and how microscopic organisms interact with people.--Apollonius 1236 (talk) 19:48, 20 June 2008 (UTC)

Sociobiology and Evolutionary psychology.--Apollonius 1236 (talk) 19:50, 20 June 2008 (UTC)

Question on atomic structure
Hi! I'm a grade 10 high school student and this has been a doubt that has been persisting for long...... In Bohr's model of the atom, he says that the electron doesn't lose energy as long as it's revolving in the same orbit. But why?? why doesn't it lose energy? I've had people explaining it as, because of centrifugal force, but in one of my textbooks, I read that Rutherford proposed the same thing in his model of the atom; but he was later proved wrong, as "according to electrodynamics", to quote from the book, "a charged particle revolving around an oppositely charged particle should lose energy and its radius should decrease, ultimately causing the electron to collapse into the nucleus. As this does not happen in the case of an atom, Rutherford's model failed to explain the stability of the atom". I know Bohr made a major advance, where models of atoms are concerned, with the quantization of energy concept,but I still don't understand how the electron could keep accelerating(by change of direction) along a circular path without losing energy...........can anyone tell me how he explained it? none of the books I have gave a satisfactory explanation on that part. Surely he must have had a good explanation for that statement?? 116.68.76.47 (talk) 11:17, 14 June 2008 (UTC)A 15-year old


 * The Bohr model is actually a very primitive model and not representative of the real situation. You are probably taught this model in school because it is easy to explain and understand, however it is a very simple view and is fundamentally incorrect. In reality, the electron does not actually orbit the nucleus at all, in the way described by the Bohr model.  We move onto the more complex valence shell model of the atom.  In this model, the electron is not considered a particle and instead exhibits wavelike behaviour, see Wave–particle duality.  The electron may exist in a particular region, or spatial distribution, around the nucleus.  The shape of this region is dependant upon the particular quantum state of the electron.  This region is called an orbital but this may be mis-leading, since due to the wierdness of quantum mechanics, the electron may exist in all regions of the orbital simultaneously. I hope this helps in your understanding and I commend you for asking such a question, it only goes to show that you shouldn't believe everything you are taught in school.  Jdrewitt (talk) 11:35, 14 June 2008 (UTC)


 * If the electron is moving in a path of constant electric field potential (ie in a spherical shell at constant distance (radius) from the proton(s) ) ... and E(total) = E(kinetic) + E(potential).. E(total) cannot change.. so...87.102.86.73 (talk) 11:36, 14 June 2008 (UTC)


 * No, any charged particle undergoing a circular trajectory will emit electromagnetic radiation, see cyclotron radiation. So the Bohr model, although nicely introducing quantised energy states etc, doesn't get around the fact that the electron will eventually lose its kinetic energy and the electron will fall into the nucleus.  The only way to overcome this problem is to introduce the electronic probabilty distribution valence shell model as described by quantum mechanics. Jdrewitt (talk) 12:05, 14 June 2008 (UTC)
 * From the point of view of the nucleus ie proton - the electron isn't moving.. Only from the point of view of an external observer is a changing dipole observed - consider that.87.102.86.73 (talk) 07:25, 15 June 2008 (UTC)
 * Bohr feigned no hypothesis regarding the reason for the fixed orbitals. His only justification was that it led to correct predictions, which was also Newton's only justification for his inverse-square law of gravity. But Bohr's model, unlike Newton's, turned out to be wrong in almost every respect. In a real (unexcited) hydrogen atom, the electron essentially does fall into the nucleus. See my comment in this thread. Of course, my explanation appeals to the uncertainty principle, about which we also feign no hypothesis. -- BenRG (talk) 22:18, 14 June 2008 (UTC)
 * It's nonsense to say that we "feign no hypothesis" on the origin of the uncertainty principle. The uncertainty principle is rigorously derived from the time-dependent Schrödinger equation. -- Tim Starling (talk) 07:43, 16 June 2008 (UTC)

We are being taught the quantum mechanical model of the atom and the wave- particle duality of electrons at school, and I've learnt that Bohr's model is incorrect, but I thought he would have an explanation for his ideas anyway, that's why I asked. So is it just a hypothesis then? —Preceding unsigned comment added by 116.68.76.47 (talk) 10:05, 15 June 2008 (UTC)


 * The Schr&ouml;dinger ("valence shell") model of the atom doesn't really explain why the electrons don't radiate. It still has accelerating electrons, so if you applied classical electrodynamics to it, you would find that there is still radiation. I believe quantum electrodynamics has a more satisfactory answer to this problem, but I haven't studied it myself. Note that in the Schr&ouml;dinger model, electrons can't spiral into the centre of the atom as in the purely classical models that preceded it. So perhaps it's more a question of "how" the radiation is suppressed, rather than "why". -- Tim Starling (talk) 06:25, 16 June 2008 (UTC)

Thanks for explaining everyone! —Preceding unsigned comment added by 116.68.76.173 (talk) 14:21, 17 June 2008 (UTC)

Eutanasia
Regards, CycloneNimrod talk? contribs? 12:03, 14 June 2008 (UTC)
 * I don't see anything in the deleted question that's a request for medical advice. The question asks for names of hospitals that provide certain services in a certain locale. This is the type of information that a dentist referral service would provide. --71.162.233.228 (talk) 14:49, 14 June 2008 (UTC)
 * Agreed. Doesn't look like medical advice to me. I'll talk to Cyclonemim on his/her talk page. --Tango (talk) 15:31, 14 June 2008 (UTC)
 * Perhaps you're right, i'm not really sure, I kind of saw euthanasia and a request and, wrongly, assumed. Feel free to restore it. Apologies! Regards, CycloneNimrod talk? contribs? 16:32, 14 June 2008 (UTC)

The question was:


 * In what hospitals of Belgium the procedure of eutanasia is made for woman`s been ill for some years. She in the terminal state. No :treatment is of help.
 * Help,please !


 * ///,,,... —Preceding unsigned comment added by 92.47.113.132 (talk) 11:49, 14 June 2008 (UTC)

Anyone know the answer? --Tango (talk) 17:38, 14 June 2008 (UTC)


 * From this it sounds as though euthanasia is pretty tightly regulated in Belgium. Given tight regulation and a progressive health-care system like Belgium's, it would seem reasonable for the patient to make the request of her physician, in accord with the regulation referred to in the article I cited.  Sounds as though they'd have to assess appropriateness (the law apparently requires "constant  and unbearable physical or psychological pain" among other things) and then if appropriate either assist or refer to the proper specialist.  Sorry I don't have a more direct answer. Scray (talk) 19:31, 14 June 2008 (UTC)
 * It also depends on the personal willingness of the physician, and in practice many catholic hospitals are unwilling to allow euthanasia requests. So if you would like to get euthanised in Belgium, and do fulfil all the criteria, your best best would be a large, publicly run or university hospital. The full law (in Dutch) can be found here Random Nonsense (talk) 16:09, 15 June 2008 (UTC)

Ununoctium
Can anyone tell me why, according to it's article, Ununoctium is expected to have a tetrahedral shape in a molecule with fluorine, whereas the other noble gases have planar shaped molecules? Regards, CycloneNimrod talk? contribs? 14:32, 14 June 2008 (UTC)
 * The article tells you (read the "Properties" and "Compounds and uses" sections of the Ununoctium article) and provides cites to explain further the principles and the actual full details of the calculations leading to this conclusion. DMacks (talk) 18:20, 14 June 2008 (UTC)

bread mold causing dancing
i heard a rumor that sounds fake (i would be shocked if it were true)

its that there was a town during the medieval period that danced for hours and it was due to a mold in their bread that was caused by them not cleaning their grain and apparently (this is where the story goes from bad to worse) the type of mold refered to is used in the production of the drug "acid"

so am i wrong?

is this true?
 * See the article Ergotism. Ergotamine, the principal alkaloid produced by the ergot fungus, is, in fact, closely related to LSD. Deor (talk) 16:00, 14 June 2008 (UTC)

Growth rings versus Wood grain
The question here: : what is the distinction (if there is one) between Growth rings and Wood grain. Answers on Talk:Wood grain please. Thank you. --VanBurenen (talk) 20:36, 14 June 2008 (UTC)


 * Growth rings are the circles seen in a cross-section of a log. Grain is the pattern seen running longitudinaly down the length of a sawn log.  Sp in ni  ng  Spark  23:59, 14 June 2008 (UTC)


 * That's right, they are really growth cylinders. If you cut them across, you get circles, if you cut them lengthwise, you get lines.  If you cut them at an angle, you can even get growth ellipses. StuRat (talk) 00:11, 15 June 2008 (UTC)


 * I agree with the descriptions of growth rings, but isn't grain whatever pattern one sees in a cut surface of wood (cross-sectional or longitudinal)? Scray (talk) 00:44, 15 June 2008 (UTC)


 * Well, the grain does come from the growth rings. There are variations in the rings where branches join the trunk, where there is a knot, or damage from insects, disease, storms, or human activity.  All this will also affect the grain produced when the wood is cut in the opposite direction. StuRat (talk) 02:03, 15 June 2008 (UTC)


 * This is my understanding... The rings are visibly separate from the grain. A tree can be seen as a bunch of very tiny tubes that carry water from the roots to the limbs.  When a tree is turned into a long plank of wood, it is rarely done by cutting across the tree rings (cutting a disk out of the trunk).  You cut the trunk lengthwise.  So, the rings end up as lines in the wood running from one end of the plank to the other.  Because many trees are not perfect cylinders, you get some nice looking curves from the tree rings.  As for the grain, it runs from one end of the plank to the other.  Depending on the type of tree and how close to the center the cut was made, you can get a plank with very nice grain or a plank with grain at an angle that easily splinters off. --  k a i n a w &trade; 02:09, 15 June 2008 (UTC)


 * (answering Scray) Well grain is a woodworking term and woodwork isn't exactly full of scientific rigour. However, there is a definite implication in the terminology that "grain" runs along the length of the wood.  For example, there are the terms "end-grain" and "against the grain".  StuRat, growth ellipses, for goodness sake.  If you really want to be geometrically precise then they are neither perfect circles nor ellipses, but the homotopic group of the circle.  Sp in ni  ng  Spark  11:38, 15 June 2008 (UTC)
 * As Scray, it seems parallel fibres are "grain" or texture wherever the wood is cut. It's a cross section determiner for what you get by cutting lengthwise or crosswise. There's a nice sketch to show the different grain achieved from cutting a log's different areas in the wood grain article. Julia Rossi (talk) 00:54, 16 June 2008 (UTC)
 * Forgot the other bit, but it's been answered, that growth rings are older areas of the tree in a central position and the living area is between that and the bark which as the tree ages, adds to the centre. It functions differently but isn't really different in structure. It's all grain, Julia Rossi (talk) 01:05, 16 June 2008 (UTC)

Polyphenylethene residues
I recently dissolved a large quantity of expanded polystyrene in propanone. As I understand it, this involves the structure of the polyphenylethene changing so that the polymer molecules are more densely packed.

However, after the reaction, there was left a beige residue. I removed this from the vessel and it was extremely sticky, like melting plastic. From the articles on polystyrene and propanone, I can't work out what this was: phenylethene is a liquid at room temperature and polyphenylethene a brittle solid. Perhaps this is an oxide?

Hopefully I am missing something obvious. Thanks very much in advance for your help!

86.149.177.103 (talk) 22:59, 14 June 2008 (UTC)
 * There's no reaction as such - the propanone simply dissolves the polymer. What was left behind was almost certainly undissolved polystyrene possibly in a gel like state with propanone - A lot like polystyrene cement see Glue87.102.86.73 (talk) 07:18, 15 June 2008 (UTC)

That seems to make sense - it is slowly solidifying. Thanks! 86.149.177.103 (talk) 10:06, 15 June 2008 (UTC)