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November 26

Must an element's pth ionization energy be greater than its qth ionization energy if p>q?

I think the issue of 12th ionization energy of Aluminium in Molar ionization energies of the elements has been left there for some years. There is a note saying 12th ionization energy, which is 223366KJmol "Should be less than the 13th; perhaps 201266." 201266 is the value in Ionization energies of the elements (data page), while 223366 seems unreferenced. By the way, is it possible that 12th ionizaton energy is greater than 13th one?--chao xian de lun zi (talk) 01:45, 26 November 2013 (UTC)

Feel free to change it, I saw a graph of the ionization energies in a book, no exact values given but the 12th was in the region of 200000, and definitely lower than the 13th, so 201266 seems reasonable, certainly better than 223366. Ssscienccce (talk) 15:33, 26 November 2013 (UTC)

Real life transformer

In real life, do they match the primary coil turns with designed input voltage (so 220v means 220 primary coil turns)? Because in science questions I frequently encounter 120v for 240 turn coil 140.0.229.39 (talk) 13:28, 26 November 2013 (UTC)

It's strictly the ratio of the turns of the two coils that matters. The resulting voltage can vary very quickly if the input voltage changes. Hcobb (talk) 13:47, 26 November 2013 (UTC)

The number of turns per volt depends on the core area, the frequency and the maximum flux density of the core (limited by saturation losses) ; the rated power VA determines the core area needed, say for example 10 cm for 100VA (at 50Hz). The Transformer universal emf equation gives you the E_rms that the maximum flux density will produce: E_rms=4.44.f.a.N.B_peak With a maximum flux density of 1.5 Tesla and a frequency of 50 Hz, you get E_rms/N=333a, a= 0.001m so E_rms/N=0.333. So a core of 10 cm will require 3 turns per volt. Ssscienccce (talk) 15:27, 26 November 2013 (UTC)

Numbers in exam/revision questions rarely have anything to do with real life examples. They are chosen more to make it easy for the writer to set, the student to calculate, and the teacher to check. It is frequntly the case that if your answer isn't a whole number or a simple fraction then you have done something wrong in a test question. Conversely, in real life answers are rarely simple or whole numbers. A mains transformer will usually have many more turns on the primary than the number of input volts. SpinningSpark 15:36, 26 November 2013 (UTC)

I have spent a fair amount of time working with transformers and offer an observation (which could be readily backed up by references). I really liked Ssscienccce's response with very specific design information. When the other windings of a transformer are open(unloaded), and you excite the primary winding with its rated voltage at rated frequency, the transformer and the winding should act as an inductor with sufficient inductive reactance to limit the exciting current to a reasonable low value. Thus there will be a minimum number of primary turns for satisfactory operation. If you had too few turns in the winding, excessive exciting current would flow, causing overheating of the winding or blowing a fuse, even if there were no load on other windings. This exciting current has both real (overcoming resistance of the wire) and reactive components. To the extent other windings are then "loaded" by drawing current to a load, the primary current will increase above the exciting current. A caveat: in a large utility transformer the initial inrush of exciting current will vary somewhat depending on the point in the cycle it is energized and the previous recent magnetization history of the transformer. Edison (talk) 17:39, 26 November 2013 (UTC)

Possibility of chromatophore bacteria using complex pigmentation for crypsis

Is there a chemical reason why there could not be chromatophore bacteria that use the right pigments to achieve the same level of crypsis as chameleons, if not better? I'm aware no such species of microorganism is known to exist, however would a living incredibly stealthy pigment goo be as scientifically impossible as something like faster than light speed time travel? I cannot think of a reason such a bacteria would have access to all those pigments in nature without being mobile like higher organisms such as chameleons; so I'm assuming this would have to be made by scientists or be from space. Even an example from science fiction of such a bacteria would be welcomed. CensoredScribe (talk) 22:11, 26 November 2013 (UTC)

Would visual camouflage help a bacterium hide? The only bacteriovores i can think of do not hunt by sight. Someguy1221 (talk) 01:03, 27 November 2013 (UTC)

I agree with you that visual camouflage is largely ineffective against most animals as they rely more on smell; however if the pigments it used were highly poisonous as well, like a lot of commercial paints, that could give the bacteria an additional level of protection against predators. Smell would also not be a factor in anaerobic conditions, like an asteroid; I don't know why it develop camouflage in a cave where there is little if any visible light. Nor would being able to survive on it's own be important where it artificially created in a laboratory environment; where that the case it's only means of survival could well be in forming a symbiotic relationship with humans.

Coincidentally, some of the photorhabdus toxins are bright red, but I don't think that has anything to do with warding off predators, and certainly nothing to do with camouflage. Someguy1221 (talk) 03:04, 27 November 2013 (UTC)

Bacterivores basically hunt by touch, not by sight or smell. As our bacterivore article obscurely points out, the only way for bacteria to camouflage themselves is by altering their cell wall chemistry. Looie496 (talk) 02:21, 27 November 2013 (UTC)

Acid rusted tools

I accidentally exposed some of my sockets in my cheap socket set to very concentrated hydrochloric acid and now they've rusted up. Can they be saved? It's not a fancy set but I'd like to keep them if I can. I'm not sure how they were manufactured/what their composition is. --78.148.107.181 (talk) 22:12, 26 November 2013 (UTC)

A l-o-n-g time since I had a chemistry class, so chemistry experts please be kind. This is not advice, but Hydrochloric acid says the acid is used to remove rust from steel, in a "pickling" process which has as inputs the acid, surface rust, and the iron itself and , with results ferrous chloride and water. There would be some loss of the metal, and perhaps pitting. Perhaps the acid removed a protective chrome layer. An article about mild steel in hydrochloric acid notes pitting and evolution of hydrogen . Have you tried washing it to remove acid residue, drying, wirebrushing to remove rust (while wearing suitable personal protection against eye injury or inhalation of particles and spraying with WD40 to discourage additional rust? If there is significant pitting and loss of metal I'd pitch the damaged sockets, since "cheap" socket sets can be had for a few dollars, and they will be even less useful than they started out, especially the works inside a ratcheting socket wrench. says that while concentrated hydrochloric acid removes rust from steel, a dilution of the acid causes rapid rusting. Edison (talk) 23:57, 26 November 2013 (UTC)

The acid just removed the very thin coat of oil that is applied in the factory, allowing oxidization to precede rapidly. Get some more hydrochloric acid (an excellent rust remover) and diluted down to 5%. Adding acid-to-water. The original strength will be written on the container (use some eye protective goggles). Dunk all sockets in this, until the rust has been removed ( just a few minutes will do). Wash in boiled water and 'immediately' coat in oil. Anything will do, like engine oil but something really tenacious like Wynn’s engine oil additive or STP engine oil additive is even better. Wipe off surplus oil. --Aspro (talk) 00:17, 27 November 2013 (UTC)

If you want to avoid messing around with hydrochloric acid, there are plenty of rust treatments out there that chemically remove the rust - most car parts stores stock many kinds. But (as Aspro points out) - the important thing is that you should wipe your tools with an oily rag afterwards to prevent the rust from coming back. (You should do this periodically with most metal tools anyway.) SteveBaker (talk) 14:56, 27 November 2013 (UTC)

If you choose a propriety rust Rust Treatment, steer clear of a Rust converter. That will just stabilizes the crud and so the sockets may no longer fit over the nut. Hydrochloric Acid based treatments are better. Phosphoric acid is not bad but it tends to leave a coat on the metal and so not so good for high tolerance parts. The advantage of these branded products are that they sold at the most effective dilution strength (but you pay dearly for the added water and product marketing). So they are very expensive. As you appear to already have access to hydrochloric, a little dilution should be a cheaper and a more edifying option. As soon as the sockets are clean, drain and wash in a little acetone to remove the water and drain again. Then heat until they are 100 plus Celsius over an electric cooker ring (acetone is flammable so drain well). That will drive off the last of the moister and make it easier for the oil to thoroughly coat them. Wynns is so tenacious you wont probably need to re-oil in you life time. I think I can say this with a little confidence as I used to de-rust things in an R&D lab. Yet as Steve indicates it is a good habit to get into. Every year, we religiously re-oil our gardening tools before winter and often during use, so that some, have now lasted several generations. This is especially important for tools like scythes (they are far quicker than a modern string trimmer as they give you a wider sweep (they keep you fit too). The razor thin edge is constantly being wiped clean of the protective oils by friction. So they need daily wiping with an oilrag to stop the morning dew coating it with rust. But once rust permeates the blade, that really sharp edge can never be recovered. Linseed oil is recommended for the wooden handles. --Aspro (talk) 18:55, 27 November 2013 (UTC)

November 27

Correct approach to deriving the shell theorem?

I know the easy approach to proving the shell theorem is to take a point particle, integrate all the force elements over an infinitesimally thin shell, integrate over all shells, and then integrate all the point particles. I now asked myself, why not do it all at once? The problem is that it arises in a nested volume integral.

Here, let V₁ and V₂ represent the regions occupied by my two spherical objects (assuming they do not overlap). Let the center of the first object be at the origin, and let d be a displacement vector between a mass element in the first object and another mass element in the other object, taken to point towards the second object. Let dM be a mass element of the first object and dm a mass element of the second. Let u, v, and w represent the position of dm and x, y, and z the position of dM (u=v=w=x=y=z=0 at the center of V₁, the u-axis coincides with the x-axis, the v-axis with the y-axis, and the w-axis with the z-axis). Let f(R) and g(r) be the densities of the two objects respectively (they are functions of the radius only, as required by the shell theorem), and finally, let the center of the second sphere be located at a displacement vector of X=<A,B,C>. G is the universal gravitation constant.

Then: ${\displaystyle \mathbf {F} =-G\iiint \limits _{V_{1}}(\iiint \limits _{V_{2}}{\frac {dm*\mathbf {d} }{d^{3}}})dM=-G\iiint \limits _{V_{1}}f({\sqrt {x^{2}+y^{2}+z^{2}}})(\iiint \limits _{V_{2}}{\frac {\mathbf {d} *g(\Vert \mathbf {d} -\mathbf {X} \Vert )}{d^{3}}}dV_{2})dV_{1}}$ ${\displaystyle =-G\iiint \limits _{V_{1}}(\iiint \limits _{V_{2}}{\frac {f({\sqrt {x^{2}+y^{2}+z^{2}}})((u-x)\mathbf {\hat {i}} +(v-y)\mathbf {\hat {j}} +(w-z)\mathbf {\hat {k}} )g({\sqrt {(u-x-A)^{2}+(v-y-B)^{2}+(w-z-C)^{2}}})dV_{2}}{((u-x)^{2}+(v-y)^{2}+(w-z)^{2})^{\frac {3}{2}}}})dV_{1}}$

In the integration, X is fixed but arbitrary, so the six variables of integration are u, v, w, x, y, and z. As you can see, I don't have many ideas on how this reduces to (using my notation) ${\displaystyle \mathbf {F} ={\frac {-GMm\mathbf {X} }{X^{3}}}}$, because f and g are arbitrary continuous functions of one variable that determine the densities of the two objects as functions of their radii, and entire integrand is very convoluted. If I were to evaluate the whole thing using one set of substitutions, then the Jacobian determinant would have to be of order 6 (!). Therefore, I have to do something to simplify the mathematics. I know this is a convoluted approach, but really, this is what is really done when we apply the shell theorem - summing up the forces contributed by all the possible pairs of mass elements. If the above notation is not correct, how would this "all-at-once" approach be executed?--Jasper Deng (talk) 01:39, 27 November 2013 (UTC)

(edit conflict)At another glance, ${\displaystyle -G\iiint \limits _{V_{1}}f({\sqrt {x^{2}+y^{2}+z^{2}}})dV_{1}}$ reduces to -GM, but the remaining integrand is still overly convoluted.--Jasper Deng (talk) 01:46, 27 November 2013 (UTC)

Oh, wait, you can't do that because the second integral is a function of x,y, and z.--Jasper Deng (talk) 01:49, 27 November 2013 (UTC)

I will note that this is equivalent to showing that the shell theorem is valid regardless of what f and g are (as long as they are continuous).--Jasper Deng (talk) 01:00, 29 November 2013 (UTC)

This is not a good approach to proving shell theorem. There are two statements to shell theorem and it is not necessary to do integrals to show either of them. 1) There is net force on a particle inside an infinitesimally thin mass shell. To show this we see that there is a 1-to-1 relationship between microscopic elements either side of the test particle whose forces cancel in the infinitesimal limit, thus there is no net force. 2) There force on a mass outside the shell acts as if concentrated at the centre. For this we take a similar approach and show that if we vary the radius of the shell by a small amount there there is a 1-to-1 relationship between mass elements such that the net change in force caused by the pair of them due to the variation in radius is zero, hence we are at liberty to collapse the shell to its centre without changing the force on the test particle. — Preceding unsigned comment added by 109.158.148.43 (talk) 22:43, 29 November 2013 (UTC)

This answer is unfortunately not acceptable for my purposes because it does not rigorously show why that is so. The shell theorem article uses Riemann sums, and I insist on a method using Riemann sums.--Jasper Deng (talk) 23:04, 29 November 2013 (UTC)

Show why what is so? I didn't show anything, I just outlined the arguments. They're perfectly good arguments which just show that the force integral (or Riemann sum as you insist) over a spherical mass is zero/(the same as a point mass at its centre) for a test particle inside/(outside) the sphere by construction, when constructed in the right way. See here: . Its much more elegant than actually bothering to evaluate these nested integrals. Besides, if you insist, at least give up trying to use Cartesian coordinates, there's nothing to be gained by denying the symmetry of the problem. — Preceding unsigned comment added by 109.158.148.43 (talk) 00:02, 30 November 2013 (UTC)

What I was thinking of was to use two parallel spherical coordinate systems, one for x, y, and z, and another for u, v, and w, and then taking the Jacobian of that six-way transformation. But the problem that remains, which the document you linked does not take into account, is that there's no dependence on f and g.--Jasper Deng (talk) 00:28, 30 November 2013 (UTC)

You haven't used any spherical coordinates, you have used only Cartesian coordinates, besides spherical coordinates arent appropriate either, your problem has cylindrical symmetry. You appear to not understand the purpose of shell theorem tohugh, it is not just a mathematical curiosity which can be shown by doing some integrals, the point of it is to show that (in your terms) the form of f and g is irrelevant, and thus one can avoid having to ever do the integrals which you are trying to do in your 'proof'.

No, I've gone through the usual proof outlined in the article and know that it's the reason why Newton could publish his law of universal gravitation (he had previously had doubts about it not applying to anything but point particles). You're not really answering my question - I do tend to insist that the "true" method here, which is done by Riemann sums, works. It suffices, I shall say, to show that if I can transform coordinates here in a suitable manner, I can convert it to the integrals used in the article.--Jasper Deng (talk) 21:49, 30 November 2013 (UTC)

So far as I know, the shell theorem is relying on two things: first, that the integral of the forces from a homogeneous spherical shell happens to work out to be (from outside) equal to a point mass at the center, second, that most things like planets are fairly close to equal density within each spherical shell, and third, that you're looking at the planet from outside, so you don't need to work out what proportion of the mass is below you to get the gravity. These assumptions break down under certain circumstances, like in lower lunar orbits on account of the mascons of the Moon, where it might make sense to do the entire 3D integral based on some model you've worked up of the mass distribution throughout the object. But if you want to do it other than numerically you may end up leaking purple tapioca at the eardrums. :) Wnt (talk) 23:31, 1 December 2013 (UTC)

Let me repeat: the point of shell theorem is you are never required to do volume integrals. If you look again at the article, you will see there are no volume integrals.

You clearly are not getting the whole reason I asked this question and are being of no help. The shell theorem can only be extended to solid spheres because of further integration that is dimensionally equivalent to volume integration.--Jasper Deng (talk) 05:30, 3 December 2013 (UTC)

True, I misspoke. I was thinking of a common use of the shell theorem (as I've added in brackets above) but the shell theorem itself is, well, about the shell. Wnt (talk) 14:39, 4 December 2013 (UTC)

(To be clear, that comment wasn't directed to you, but at the IP's comment immediately below your comment).--Jasper Deng (talk) 20:38, 4 December 2013 (UTC)

Historical humans and race

Our Neanderthal article says "An estimated 1 to 4 percent of the DNA in Europeans and Asians (French, Chinese and Papua probands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (Yoruba and San probands)". On the other hand, Neanderthal genome project says "99.7% of the base pairs of the modern human and Neanderthal genomes are identical". So colour me confused. Can someone explain how to reconcile these two statements ? Gandalf61 (talk) 12:11, 27 November 2013 (UTC)

Not an expert, but I find the "99.7% base pairs" to be somewhat misleading. As I understand it, we share somewhere around 70% with fruit flies and over 99% with chimpanzee's. I suspect the difference is when comparing uniquely human DNA between various groups do we find 1-4% of it being shared with ancient neanderthal DNA. As I understand it, the human genome went through a "narrowing" experience where most variations died off and then recovered with all modern DNA traceable to the narrowed surviving strain. How and when ancient neanderthal DNA would have re-entered or whether the narrowing was not universal is what I believe is the focus of research. --DHeyward (talk) 14:24, 27 November 2013 (UTC)

(ec)The problem is that 99.7% of base pairs being identical between two species doesn't tell you much. We share 98.8% of our DNA with Chimpanzees, and 50% of our DNA is shared with bananas - men and women have only 97% of our DNA in common...so a male human shares much more DNA with male chimpanzees than with female humans (which, my wife tells me, explains a lot!). But base-pair comparisons are not the same thing as numbers of genes shared. Take (for example) the gene that allows adults to digest lactose: "LCT". It only differs by a single base-pair from the defective version of that gene that causes lactose intolerance. But look at the numbers here:

• The LCT gene contains about 50,000 base-pairs - only one of which has to be wrong for it to be counted as "the gene for lactose intolerance" rather than "the gene that allows us to digest lactose".
• We have about 20,000 genes.
• Human DNA contains about 3,000,000,000 base-pairs.

So if we imagine two people who are identical twins - except that one of them is lactose intolerant - their DNA is identical to within one part in three billion, but their genes are only identical to within one part in twenty thousand. As percentages, those two numbers are radically different - yet both descriptions are talking about a single base-pair difference. Now, the question is whether the Neanderthal article is talking about percentages of base-pairs or percentages of genes. The article also qualifies that percentage as being of "non-modern" DNA - so it's (presumably) excluding genetic changes since the time of extinction of Neanderthals - where the Neanderthal genome project is talking about the amount of difference between modern humans and Neanderthal...but doesn't really make sense because it's saying that we're more like neanderthals now than we were back in "non-modern" times?!?

There are plenty of other sources of confusion possible here. You'll also find articles saying that (for example) first cousins share 12.5% of their DNA...which as a strict count of base-pairs is clearly nonsense because that would our cousins more different from us (by far) than we are from bananas! What is probably meant is that 12.5% of the natural genetic variation that makes us unique from other humans is the same between first cousins...which would mean that (of course) we're much more similar to each other than we are to chimpanzees, neanderthals or bananas.

I agree that both articles should qualify those percentages much more carefully...it's a mess.

SteveBaker (talk) 14:51, 27 November 2013 (UTC)

http://www.nature.com/news/mystery-humans-spiced-up-ancients-sex-lives-1.14196 - truth is, we still know fairly little and our ideas continue to change rapidly. Wnt (talk) 23:34, 1 December 2013 (UTC)

How to produce magnesium carbonate?

I want to produce 100g of magnesium carbonate by using magnesium sulfate and sodium bicarbonate. How much magnesium sulfate and sodium bicarbonate do I need? And how much water do I need to mix it up? Thank u :-) — Preceding unsigned comment added by 110.159.119.154 (talk) 06:54, 27 November 2013 (UTC)

This appears to be a stoichiometry question. Are you doing this for homework?--Jasper Deng (talk) 07:10, 27 November 2013 (UTC)

How you do it is to work out how many moles of magnesium carbonate you want to make. Work out your chemical formula. Work out how many moles of each ingredient you want, then multiply by the formula weight of each raw material to work out the mass required. You will have to know the amount of water in the magnesium sulfate hydrate that you have. Graeme Bartlett (talk) 00:53, 28 November 2013 (UTC)

Adding nitrogen gas to chemical bottle to protect from moisture in the air

I have DEPC in a bottle which is still unopened. The manufacturer's instructions state that moisture from the air will cause it to decompose and so a layer of nitrogen (or argon) gas should be layered over the DEPC before closing the bottle. I have access to liquid nitrogen. Can this be used to protect the chemical from the atmosphere? The mist surrounding nitrogen is presumably water vapour from the air, right? I don't want that getting to the DEPC! --78.148.107.181 (talk) 09:23, 27 November 2013 (UTC)

What is DEPC? See Guiness in the composition section. N₂ is used in bottling. Also, nitrogen , especially in the large commercial liquid nitrogen tanks, are very dangerous as an asphyxiation hazard. Don't do it indoors if you don't have oxygen sensors. Unlike CO₂, your body does not react to higher levels of nitrogen (or Argon or Helium) and people pass out and then die before they even know the oxygen level is low. There is no feeling of shortness of breath or anxiety like with CO₂. Many have died working with nitrogen in confined spaces.. --DHeyward (talk) 10:07, 27 November 2013 (UTC)

Diethyl pyrocarbonate? Depending on what you are using it for, the minimal amount of decomposition resulting from moisture in the air trapped in the bottle as you close it might be acceptable. Liquid nitrogen would not be an ideal source of dry nitrogen because of the impracticality of handling a small amount of it without exposing it to air causing condensation of moisture, as you suggest. Laboratories commonly have inert gas lines, such as dry nitrogen. If you access to something like that, that would be ideal - blow a light stream of nitrogen into the top of the bottle as you are closing it. Otherwise, just minimize the amount of time you have the bottle opened to air. -- Ed (Edgar181) 10:21, 27 November 2013 (UTC)

I agree, a lab will either have an inert gas line for such purpose, or high-purity, dry nitrogen from a cylinder with a pressure regulator. If it's not the first time DEPC is being used, so if you're asking us because you don't want to bother the people who will know the correct procedure at your lab, reconsider. If it is the first time DEPC will be used, then consider buying a flushing system before proceeding, or take Edgar181's advice and minimize the amount of time the bottle is open. Don't improvise, in my experience, when improvised procedures go wrong, the results are often much worse than the problem one was trying to fix. Ssscienccce (talk) 11:52, 27 November 2013 (UTC)

I know we have carbon dioxide lines but I think they might be solely for connecting to cell culture incubators. I already consulted people in our lab and they were unaware that the manufacturer advises this protection from atmospheric moisture. 129.215.47.59 (talk) 12:53, 27 November 2013 (UTC)

There will be very few biology labs with a nitrogen line, as the OP says, CO₂ lines are common, but N₂ certainly not (I've never seen them anyway). Anyway, might be better to make up a stock solution in a suitable solvent (EtOH?), rather than opening the stock bottle repeatedly. Must admit having never made up stocks myself, don't use it much. People are far too paranoid in RNA work! Fgf10 (talk) 16:57, 27 November 2013 (UTC)

If you're looking for dry nitrogen in a biological department/institute try a serious biochemistry lab, a structural biology lab or a protein production core facility - these are the people that seem to have cylinders of it in our institute. You can take some back to your lab in a balloon attached to some sort of valve with a rubber band - attach it to a needle to fill the bottle with nitrogen before closing. As far as being too paranoid around RNA, that does rather depend on what you are doing - if you are just doing some basic qPCR on large samples (and make sure you reverse transcribe with random hexamers like you're supposed to) then yes, excess paranoia is not justified, but if you are trying to, for example, do long-read cDNA sequencing from tiny amounts of non-optimal starting material a healthy paranoia is just what you need. I have to say that most biology labs have probably been using DEPC for years without the precaution of storage under inert gas, but then most biology labs probably wouldn't notice if their DEPC was totally ineffective. Equisetum (talk | contributions) 21:26, 27 November 2013 (UTC)

DEPC is hydrolysed to EtOH and CO2, so if an EtOH solution is acceptable then the OP has nothing to worry about. A quick calculation shows that if a 1 liter bottle is used for small doses of 2 ml, and each time 20 ml air at 20°C and 50% humidity enters the bottle, then by the time there's 100 ml DEPC left it will have absorbed 20mg water, and therefore contain about 100 mg ethanol. Assuming DEPC + H2O -> 2EtOH + 2CO2 is the only reaction that occurs, but that's something I'm not sure about. If it's stable at room temperature then why does it have to be stored at 2 to 8 degrees C, and why do I find references to a publication titled "Spontaneous hazardous chemical explosion of unopened bottles of diethyl pyrocarbonate"... Ssscienccce (talk) 22:34, 27 November 2013 (UTC)

It is not hard to rig a nitrogen bottle to a line with a needle on the end. You put a rubber septum on the stock bottle insert your positive pressure nitrogen line and insert your needle or canula to draw off your sample. No difficult contruction required. Standard practice when your chemicals burst into flame in open air. 75.41.109.190 (talk) 20:16, 27 November 2013 (UTC)

Penguins near the South Pole

How close, at best, can penguins (no matter the species) come to the South pole? --80.122.110.238 (talk) 12:33, 27 November 2013 (UTC)

According to Penguin, they spend about half their time in the water, so it's unlikely they would venture very far from the ocean. Given that, whatever the closest penguin habitat is to the geographic south pole, would be about as close as they would get to it. ←Baseball Bugs carrots→ 12:55, 27 November 2013 (UTC)

I suggest you watch the documentary March of the Penguins. The Emperor penguins walk far inland on Antarctica to breed, apparently to get away from any predators. A secondary benefit might be the elimination of the unfit from the breeding pool, as they can't make the journey. And they also seem to fast the whole time, living off their fat stores. It's an amazing feat. StuRat (talk) 21:20, 27 November 2013 (UTC)

If you look at the breeding areas of the Emperor penguin they probably come to as near as something like 1000km of the pole. They'd probably be quite happy wandering around the pole in the middle of Winter, it's just there isn't any food around there and they're safe enough where they do breed. Dmcq (talk) 13:03, 27 November 2013 (UTC)

Looking at that range again i looks like they go within 500km of the pole. Dmcq (talk) 13:09, 27 November 2013 (UTC)

Are you looking at the map? The text says 77°. If the Emperor penguin gets closest (and I suspect it does) then this says they reach 78° south which is about 720 nautical miles (1,330 km; 830 mi) from the South Pole. Thincat (talk) 13:24, 27 November 2013 (UTC)

This set me thinking about the famous Worst Journey in the World to get an Emperor penguin egg at Cape Crozier for which our article now says "Cape Crozier is within a restricted area and permission is required to visit it". The Heroic Age of Antarctic Exploration has drawn to a close! Thincat (talk) 13:33, 27 November 2013 (UTC)

Presumably the penguins are exempt from that restriction? ←Baseball Bugs carrots→ 13:40, 27 November 2013 (UTC)

The map at Emperor penguin shows it living further than 85° south (I think). But is this really true? Antarctic Plateau specifically says penguins don't live there "... because there is nothing there for them to eat". Thincat (talk) 13:52, 27 November 2013 (UTC)

The southernmost point of the Amundsen Coast is just over 300 mi (500km) from the pole; that's not the plateau (which rises dramatically just south of there). But it is the depths of the Ross Ice Shelf, so I too don't see what penguins (who live off fish) would eat there either. -- Finlay McWalterჷTalk 14:02, 27 November 2013 (UTC)

Yes, I was wrong to mention the plateau. This suggests they (and Adelie penguins) live on the northern edge of the Ross Ice Shelf but no further south. 78° near enough. Thincat (talk) 14:35, 27 November 2013 (UTC)

If I get the map straight, there is a little bit of breeding (green) area within 80°, close to 81°, which would mean a distance of roughly 1000-1100 km. --KnightMove (talk) 19:11, 27 November 2013 (UTC)

Old style mechanical railway signal boxes

Why did the signalmen always use a cloth when operating the levers? SpinningSpark 14:14, 27 November 2013 (UTC)

"The steel lever handles were cleaned every week with emery cloth and it was more than my life’s worth to pull a lever by grasping it with my hands as this would corrode the metal. It was necessary to hold the lever with a duster provided so as not to tarnish the brightwork." AndyTheGrump (talk) 14:19, 27 November 2013 (UTC)

As an engineer that has pulled lots of leavers I can't believe that for a moment. It take a lot of force to change a point and the lever is 'round'. Meaning all the force is exerted on only a very small part of your hand and doing that all day long will soon make your hands painful. The signal man's duster or cloth spreads that force out. See here at 3mins and 36 seconds ] That is why manual cars have big knobs at the end of a gear shift stick and commercial vehicles have even bigger ones.--Aspro (talk) 00:13, 28 November 2013 (UTC)

Did the signalmen always use a cloth when operating the levers? HiLo48 (talk) 23:57, 27 November 2013 (UTC)

It was at least extremely common. I have seen it done that way in numerous old films and documentaries. Just search You Tube for "signal box" and you will find lots of videos of signalmen doing it. Oddly, the first You Tube result doesn't use a cloth, but he is only a relief signalman and the location, Brewery Sidings, might be significant! SpinningSpark 01:39, 28 November 2013 (UTC)

Suicide

Do any other animals (or living things) commit suicide? Or is this phenomenon only seen in humans? Thanks. Joseph A. Spadaro (talk) 20:11, 27 November 2013 (UTC)

Bees invariably die after stinging - which they do in protection of their hives. So yes, there is at least one kind of animal that does that kind of thing. SteveBaker (talk) 20:28, 27 November 2013 (UTC)

Thanks, Steve. Well, your answer made me re-think my original question. The bee situation is not really a suicide, correct? That is, they don't choose to end their life; they choose to sting (which then has the "side-effect" of ending their life). For example, say that I saw that a child was about to get hit by a car; I jump in front of the car to save the child's life; the child is saved, but I die. I would not really call that a "suicide", even though I made a choice that had the effect of losing my life. That is (sort of) how I see the bee stinging situation; it is a death, but not really a suicide. So ... I guess what I meant in my original question was more along the lines of this: do any other animals/living beings commit suicide in the same way that humans do (i.e., they are typically sad and/or depressed; they feel that life is not worth living, for whatever reason; and, as such, they make an affirmative decision to end their life)? Thanks. Joseph A. Spadaro (talk) 20:49, 27 November 2013 (UTC)

If you insist on that interpretation of your question, then we cannot possibly answer it. We don't really know for 100% sure what other people are really thinking - let alone animals. Can we be sure that people who commit suicide really understand what death truly means? If we can't be sure with people - then we stand no chance. Every conceivable instance we might come up with can always be countered with "Did they really know they'd die - did they truly understand what death actually is?"...so we have no answer for you. SteveBaker (talk) 21:02, 27 November 2013 (UTC)

Thanks, again. Two points. (Point 1) Certainly, we do indeed know how/what human beings are really thinking. No? I think there is a lot of data about human suicide. Perhaps, we can't know "100%" of what the dead person was thinking (of course). But, there are suicide survivors, etc., that provide quite a bit of data about the human phenomenon of suicide. It's not as if we are "stabbing in the dark", as far as human suicide is concerned. (Point 2) I thought I remember reading/seeing somewhere about how elephants (or was it apes?) expressed grief, sadness, etc., at the death of one of their own; and they even had some sort of funeral ritual. Which led me to the thought that animals, on some level, can experience sadness and grief (and perhaps depression?). Who knows (of course)? But, I wondered if science ever studied this phenomenon among animals. Thanks. Joseph A. Spadaro (talk) 21:08, 27 November 2013 (UTC)

I think we can at least infer what animals understand. For example, elephants will go out of their way to visit the bones of their dead relatives. This implies that they associate those bones with their memories of those relatives, and have some concept of death. StuRat (talk) 21:07, 27 November 2013 (UTC)

I think an essential component of suicide is understanding what death is and that your actions will result in your death. I doubt if a bee qualifies here. There are also animals that, when stressed, will stop eating until they die, but I doubt if that's intentional suicide. Whales sometimes beach themselves repeatedly, and this might be suicide, or maybe their navigation system is just messed up somehow. It's not clear. See whale beaching. StuRat (talk) 20:56, 27 November 2013 (UTC)

I have an abandoned cat whose kittens recently died pulling one of those hunger strikes right now. So far, no note or list of demands. But, from a human perspective, she seems depressed as hell. She certainly knows death exists, if not how to make it. I'd wager a bee knows what's going to happen, as it's likely seen it before. But hive animals basically have infinite clone lives, and the queen is who matters, so suicide isn't the major decision it is for others, if individual bees even can decide. InedibleHulk (talk) 04:51, 28 November 2013 (UTC)

I definitely think some animals can be depressed. The most intelligent birds seem to be particularly susceptible, and I believe there is even a drug marketed to owners with depressed dogs. However, many animals probably can't envision their own death, even if they are aware of the deaths of others. StuRat (talk) 11:31, 1 December 2013 (UTC)

In general, humans can talk and animals can't. That makes it all the more difficult to know what's in an animal's head. That doesn't mean human suicides are readily explainable all the time. But at least there's a chance. Some years ago I recall seeing some show about suicides on the Golden Gate Bridge. They had a couple of survivors, who both said that the moment they let go, they wished they hadn't. I expect a lot of suicides don't necessarily want to die, they just want the pain to go away. ←Baseball Bugs carrots→ 22:40, 27 November 2013 (UTC)

How come this is a very long thread but no one has given the answer that Misplaced Pages has an article on animal suicide? SpinningSpark 09:08, 28 November 2013 (UTC)

Wow, thanks. I did not know that article existed. I will take a look at it. Joseph A. Spadaro (talk) 16:21, 28 November 2013 (UTC)

I have no doubt that we can come up with plenty of examples of animals who killed themselves - my example at the start of this thread (bees, stinging in defense of their hive) is one such situation. However, our OP has now stipulated that we must consider the motives and whether the animal fully comprehends the idea of death. I can't imagine any way to reliably do that. In the case of the dog who seemingly committed suicide by drowning itself - we don't know whether it thought that by staying underwater for long enough, it might become less depressed - or perhaps it would be able to sleep better or something. Maybe it was just curious about what might happen if it resisted the temptation to breathe. We truly cannot ever really know that. Hence we cannot answer this (modified) version of the question...it's totally impossible. SteveBaker (talk) 15:01, 28 November 2013 (UTC)

Actually, the animal suicide article (referred to above) suggests otherwise. Joseph A. Spadaro (talk) 16:24, 28 November 2013 (UTC)

It's true that we cannot know for certain what an animal is feeling emotionally. We also do not know for certain what other humans are feeling, but the scientific principle of accepting the explanation that requires the fewest assumptions until forced otherwise by observation would lead us to assume that other humans feel emotions as we do ourselves whenever they exhibit behaviours or physiological responses that we would associate with a given emotion. I believe others feel grief because I recognise the emotion I have felt myself. Extending that principle to animals is merely sticking to scientific reasoning. For instance, it is known that elephants appear to mourn dead relatives. At one time, a typical scientist response to such suggestions would be "no, no, animals don't have emotions, they just act on instinct". In more recent years it has become accepted that elephants do indeed feel grief.. SpinningSpark 15:29, 28 November 2013 (UTC)

And seem to wrap their heads around vengeance and angst. InedibleHulk (talk) 01:01, 29 November 2013 (UTC)

Thanks, all, for the above input. It was very helpful. Much appreciated. Joseph A. Spadaro (talk) 14:42, 29 November 2013 (UTC)

• The animal suicide article is basically synthesis heapt upon nonsense, and should be deleted if not better sourced. μηδείς (talk) 03:18, 2 December 2013 (UTC)

Is it a fact that ghosts are/aren't real?

In a discussion, a user argued that it is fact that there is no such thing as ghosts. Regarding the validity of this statement, is it a proven fact that ghosts do not exist? I understand that here are skeptics, but is there any hard evidence that they do not exist? Admiral Caius (talk) 20:27, 27 November 2013 (UTC)

It's hard to prove a negative.

We can say that there is absolutely zero scientific evidence for their existence - and that if they did exist, it would violate all manner of scientific principles that we believe to be well-established.

People keep attributing all sorts of qualities to ghosts that would make them undetectable (they are invisible, maybe they only show up to people who believe in them, maybe they are insubstantial, maybe...maybe, maybe)- this is probably an unfalsifiable hypothesis. The question you have to ask is that if there is no solid evidence of the existence of something - why would you believe in it instead of all of the other infinite number of things for which there is also no evidence. Why would you believe in ghosts, but not (for example) believe my claim that there are families of purple piano-playing Aardvarks living in caves on the dark side of the moon? If you (more reasonably) say that all unprovable things are equally likely - then there are a literal infinity of things that you'd have to believe in. At that point, you realize that this is impossible - and the only logical way to proceed is to believe in none of them...until/unless some evidence appears to confirm them. This is the essence of ideas such as Russel's teapot and Occams razor which, while not hard-and-fast rules, are never the less rational ways to proceed with you life. SteveBaker (talk) 20:39, 27 November 2013 (UTC)

Another interesting thought is that, if ghosts hang out where they died, you would expect a far greater density of ghosts in places like Rome, which have been heavily populated for centuries. So, I'd expect constant ghost sightings there. StuRat (talk) 20:51, 27 November 2013 (UTC)

Who says there aren't frequent sightings in Rome? ←Baseball Bugs carrots→ 22:24, 27 November 2013 (UTC)

If they were, say, 1000 times more common there than in newly populated areas, I'd think this trend would have been noticed. StuRat (talk) 08:07, 3 December 2013 (UTC)

A logical, scientific (mathematical, formal) proof needs a given system of Well-defined elements and rules for drawing conclusions. In law and juridiction an evidence is subject to being qualified by Court or judge in its worthiness and relevance. "In the area of oral and written communication such as conversation, dialog, rhetoric, etc., a proof is a persuasive perlocutionary speech act, which demonstrates the truth of a proposition." .

I'm afraid, none of these apply for `appearances´ or other mental phenomena ;o])   You can also not give any `hard evidence´, that you like apples and dislike peers, just like proving an equation. .. Yet phenomena related to human brain are being studied, examined and explored and obvious or well funded statements be made about dreams, déja vu´s, hallucinations and many more. The words "proof, hard evidence, fact" do'nt make sense in terms of individual, subjective perception of non-physical things. --217.84.99.238 (talk) 13:51, 28 November 2013 (UTC) Senseful, reasonable proving in this way is - heaven thanks! - `ghostproof´. ;o]) --217.84.99.238 (talk) 14:06, 28 November 2013 (UTC)

A bridge for consent: the notion of "belief" applies very well. "In the areas of epistemology and theology, the notion of justification plays approximately the role of proof " (justification of a personal or common belief). So, what is one´s `personal reality´ needn´t be another´s. Ghost can thus be part of culture, even though they don't exist. O.-o --217.84.99.238 (talk) 14:27, 28 November 2013 (UTC)

I don't think anyone disputes that the belief in ghosts exists. In the words of Philip K. Dick, "Reality is that which, when you stop believing in it, doesn't go away." TenOfAllTrades(talk) 14:34, 28 November 2013 (UTC)

Ghosts that can observe our World without affecting it cannot exist. They would cause decoherence which can be detected. Experiments are being done to see if besides environmental decoherence there exists a fundamental decoherence. The results of these experiments also set a limit on the rate of information transfer between our World and the Ghost World. Count Iblis (talk) 21:46, 29 November 2013 (UTC)

If you take the time back and forth, parallel universes are created, if you returns the time on the dead person, and revival it by changing its course, you will apply a transparent effect in parallel for his body in this world. And some reference in science term are the many worlds theory. Thanks water nosfim

TV Tropes has some half serious questions and answers about ghosts here--Pacostein (talk) 18:21, 30 November 2013 (UTC)

I'm late to the party and the posters above have done an excellent job sounding erudite. As XKCD covered, though, yeah, for all practical purposes, we can be pretty damned sure that there are no ghosts that receive/emit light/sound or move objects within the developed world. Even Africa already has a phone in every third person's hand, but presumably it'll take a decade or so until most of them are camera-equipt. — LlywelynII 16:05, 4 December 2013 (UTC)

Eating indigestible foods: what's the point?

As the title suggests, I want to find out what benefit the human body receives from eating foods generally seen as indigestible.

My reason for asking is that I'm quite curious as to why we consume foods such as Sweetcorn and Broad (Lima) beans, where we essentially see most of what goes in, "come out" pretty much intact.

Do we actually derive any nutritional benefit from foods we basically don't break down during the digestive process?

Thanks in advance for any help.

CharlieTheCabbie (talk) 22:02, 27 November 2013 (UTC)

See Dietary fiber. When I were a lad, this was the universal panacea for all known medical conditions, although medical opinion seems to have changed. Tevildo (talk) 22:21, 27 November 2013 (UTC)

Also note that what appears to come out undigested isn't necessarily so. Corn, for example, has an indigestible shell, and a digestible interior. Since each corn kernel is open at the end, where it was ripped from the cob, the digestive juices get inside and remove the nutrients. The reverse could also be true, where a food is broken down into a paste, but not digested, even though no sign of it is visible "at the other end". StuRat (talk) 00:32, 28 November 2013 (UTC)

Sort of seems like a waste to just throw away the bottle. InedibleHulk (talk) 04:59, 28 November 2013 (UTC)

Sweetcorn kernels only '"come out" pretty much intact' if you have swallowed them whole without chewing. Alansplodge (talk) 08:43, 28 November 2013 (UTC)

"The point" of eating food is not always nutritional, many foods taste good and provide a pleasant experience in their consumption. Corn certainly is good to eat, not so sure about broad beans. What is the point of meringues or sticky-toffee pudding or fried/toasted bread - I mean, all that hassle with dubious nutritional value? Richard Avery (talk) 14:19, 28 November 2013 (UTC)

Seems like someone needs to learn about properly chewing. Dauto (talk) 14:36, 28 November 2013 (UTC)

I do chew properly, but in a previous job I had a lot of contact with the "out" end of food, and it made me curious. Not everyone chews well, and it's quite possible to see faecal matter with seemingly undigested food in it. It just lead me to question how it benefitted us. Thanks anyhow. CharlieTheCabbie (talk) 14:43, 28 November 2013 (UTC)

What lovely job was this ? StuRat (talk) 17:47, 28 November 2013 (UTC)

I used to work as a porter/assistant in a nursing home for the Elderly, and one of my jobs was to assist with cleaning out commodes, spraying off and washing bedsheets where residents had...well, I'll leave you to guess the rest. :) CharlieTheCabbie (talk) 21:19, 28 November 2013 (UTC)

Hopefully in your current job, presumably as a cab driver, most of the passengers don't leave any feces behind as a tip. StuRat (talk) 03:54, 29 November 2013 (UTC)

Killing animals with carbon dioxide

If I'm not mistaken, the UK Home Office approves the use of carbon dioxide for killing (some?) animals in certain circumstances. Is this considered humane? My understanding is that carbon dioxide build up is what causes the unpleasant aspects of suffocation, whereas nitrogen gas would be much more peaceful. Is it to ensure safety of the operators? --78.148.107.250 (talk) 23:46, 27 November 2013 (UTC)

Misplaced Pages has an article titled hypercapnia on the subject. If that doesn't answer your question, links and references in that article, or at least searching other media with that term, may help. -Jayron32 00:06, 28 November 2013 (UTC)

I agree that it's not very humane. However, it does have the advantage that, if a little leaks out, it won't harm humans, whereas other poisonous gases certainly could, so require much stricter handling. StuRat (talk) 00:27, 28 November 2013 (UTC)

(EC, glad to see certain refdeskers responding who obviously have no idea what they're talking about.....) Yes, exposure to CO₂ is a Schedule 1 approved method under the Animals (Scientific Procedures) Act. Although I personally normally prefer cervical dislocation unless working with large groups of animals, exposure to CO₂ is a very effective method for sacrifice. In my experience with mice and rats, they are not particularly stressed, the key is the legally mandated slowly rising concentration. Animals will be somewhat agitated at first when put in the CO₂ chamber, but will quickly become lethargic and drift off pretty peacefully. All this of course only happens when the concentration is correct. There are still unfortunately impatient people who use an excessive concentration, in which case animals will be far more agitated and stressed almost immediately. EDIT: above mentioned 'other poisonous gasses' are most certainly not allowed, as I mentioned, the main alternatives are cervical dislocation and injection of an overdose of drugs such as pentobarbital. EDIT2: also, the other consideration for using CO₂ over cervical dislocation is whether neck/brainstem tissues need to be harvested intact for histology etc, as these get severely damaged in cervical dislocation. Fgf10 (talk) 00:38, 28 November 2013 (UTC)

See Animal euthanasia#Inhalants. It talks about concentrations and using anesthetics and a bit on nitrogen. It would seem minimal agitation would mean both a minimum and maximum flow rate. Also Inert gas asphyxiation#Animal_slaughter has details. --DHeyward (talk) 00:50, 28 November 2013 (UTC)

Here in the USA, we mainly use captive bolt stunners (what, no article?) to slaughter animals. The advantage is, it kills the animal instantly -- like a bullet through the head. 24.23.196.85 (talk) 01:51, 28 November 2013 (UTC)

Redirect added. --Tardis (talk) 02:05, 28 November 2013 (UTC)

I'm pretty sure that's for cows and horses. Broilers, small rodents and pigs all use the anesthetic properties of CO2 at the correct flow and concentrations to limit hypercapnia responses. For pigs, they are bled out while unconscious. Broilers are sometimes stunned in an electrified bath. Only male broilers are kept. Females are destroyed. --DHeyward (talk) 03:21, 28 November 2013 (UTC)

One other point, I don't know of any animals commercially used for slaughter for human consumption are killed through any other mechanism than being bled out (except for wild game killed by hunters or farmers that use their meat for their own consumption). Stunning either by captive bolt, electric shock or CO₂ merely render them unconscious. The damage may be fatal but the animal does not die between stunning and slaughter. Animals that are euthanized prior to bleeding out are generally not fit for human consumption. For example, a cow that stumbles out of a chute and breaks a leg 10 feet from the stunning floor will be euthanized by a vet and at that point (dead) is unfit for human consumptions. The methods may eventually prove fatal but the goal is that the animal is alive and unable to feel pain when it is slaughtered. Stunning is different than using method for euthanizing pests or injured animals but the goal of minimizing suffering is the same. --DHeyward (talk) 07:45, 28 November 2013 (UTC)

This is a common question on Reference Desk, and often provokes misinformed answers. It is humane when done correctly. The fact is, CO2 in low concentrations stimulates breathing with no ill effects (that's why it is used in in the mix with gas fire suppression in computer rooms and aircraft flight decks), at somewhat higher but low percentage concentrations causes distress that builds up over time, but at high concentrations causes pain-free and distress-free unconsciousness, followed by death. The trouble with the hypercapnia article wrt this question is that it is written from the viewpoint of surviving abnormal CO2 concentrations, and stops at the 7% limit described in the article. When CO2 is used to kill animals in abbatoirs, a higher concentration is used. If the animals are removed to fresh air before death, they may recover consciousness with severe brain damage and be very distressed, but since the idea is to kill them while they are unconscious, this is not a problem. Except that the main disadvantage of CO2, apart from the time required (a bolt fired into the brain is a lot quicker, as is electrocution) is that poorly run or poorly supervised abatoirs may not wait long enough for death to occur. 1.122.117.242 (talk) 01:02, 28 November 2013 (UTC)

So what is the actual mechanism behind the discomfort when you are unable to breathe? CO2, blood pH, something else? Thanks. Someguy1221 (talk) 01:15, 28 November 2013 (UTC)

See Hypercapnia --DHeyward (talk) 03:23, 28 November 2013 (UTC)

I've seen the article. It neither mentions the pain in the lungs nor describes the mechanism connecting CO2 concentration to any symptoms. Someguy1221 (talk) 07:45, 28 November 2013 (UTC)

Signs and symptoms list "panic" for certain levels. But you are correct the exact mechanism is not listed but the reference cited for it does. Catecholamines increase with increasing hypercapnic acidosis. This can trigger the panic fight-or-flight response in humans. Inhaled CO₂ has the same effect as metabolically produced CO₂ which is like physical exertion or holding breath underwater. Respiration normally is driven by the need of the body to remove metabolic CO₂ The body can adapt to gradual changes in CO₂ up to 3-4% and still maintain the same blood pH. Sudden changes though, can upset the buffer balance and pH too quickly. The hormonal response is not just pH related as other types of acidosis such as lactic acidosis does not trigger the same hormonal response. Respiration also naturally decreases during sleep which causes dissolved blood CO₂ to rise but the buffer process normally maintains the pH. The concentration of C0₂ in the blood while asleep is similar to raising the atmospheric level to 2% while awake (from the natural level of 0.03%). I don't know if this is the narcotic effect. --DHeyward (talk) 09:38, 28 November 2013 (UTC)

I think the OP is right, it has more to do with the safety of the people performing it: With nitrogen you get no warning signals, with CO2 you do. If "humane" was the main criterium, one wouldn't choose the one gas that alerts the body of asphyxia. Ssscienccce (talk) 11:19, 28 November 2013 (UTC)

See here for some NIH guidelines .

As hinted there, there are some studies on the usage of various agents, trying to ascertain what methods are effective while least likely to cause distress, in the case of gases as some others have mentioned, this includes stuff such as flow rates, whether to prefill the chamber etc (or from 1994). Remember also that if the animals are intended to be studied after death, you also need to avoid anything which will affect what will be studied . You also have to consider the risks of non perfect application, particularly with methods like cervical dislocation which require a fair degree of skill.

As with many things, without decent research you need to be careful about assuming what applies to humans will apply to other animals, particularly ones more distantly related or physically and physiologically different. For example, nitrogen doesn't actually appear to be effective for rodents, or at least rats . Argon is better, but still appears worse than carbon dioxide . There is a trend towards anaesthetics gases to replace carbon dioxide but as this source hints at but there's still some uncertainty over the effect of anaesthics.

Note, as mentioned in one of the earlier sources, sometimes methods may be combined or this may even be the recommendation, for example anaesthetic agents or carbon dioxide exposure followed by cervical dislocation .

BTW my response in 2012 Misplaced Pages:Reference desk/Archives/Science/2012 February 13#What is done with the mice babies? may be of interest here, note that although the original question concerned baby mice where carbon dioxide is not recommended by most guidelines, my response largely concerned adult rodents, where it still often is considered acceptable.

P.S. Rereading my 2012 response, I was reminded about one thing which the sources I provided here also demonstrated. There does seem to be an assumption in some sources that if the method takes to long, it's not humane. Whereas arguably it's more important to try and ascertain discomfort and pain.

Of course if there is some discomfort, then the length of time will come in to play and you will ultimately get in to complicated questions over whether it's better to use a method which causes a relatively slow death with some minor discomfort or pain versus a method which causes a relatively quick death but greater level of discomfort or pain.

Tying this back in to what I said earlier, you may also have to consider whether to use a method with no discomfort 999 times when it goes right and major discomfort/pain the 1 time it goes wrong. (Of course trying to determine such statistics and determine the level of pain when things go wrong is going to be even more difficult than the generalised case, particularly for something like cervical dislocation.)

Nil Einne (talk) 12:49, 28 November 2013 (UTC)

They seem to use effective as a synonym for fast-acting, or efficient. Since in all three cases no oxygen is present, one could argue that with CO2 and argon the animal may be experiencing more stress causing it to expend its oxygen reserve more quickly. Ssscienccce (talk) 13:55, 28 November 2013 (UTC)

Indeed, it's ridiculous that the (I don't have access to the full text) states that the nitrogen caused unconsciousness and death and then states that nitrogen was ineffective. They also say that the couldn't assess the distress of the rodents but I think it's telling that nitrogen didn't increase MAP or HR. 129.215.47.59 (talk) 14:26, 28 November 2013 (UTC)

I'm very surprised those studies used pre-filled chambers. That's always been a big no-no in any place I've ever worked. It causes far more distress to the animals. Fgf10 (talk) 15:51, 28 November 2013 (UTC)

The main advantage of CO2 over nitrogen is that it's heavy. So you can pipe some into a chamber with some mice at the bottom, let air escape from a tube at the top, and be pretty sure there are no unstirred voids of room air remaining inside it.

Some time ago from curiosity I tried breathing the CO2, which at first on its own as a gas (as in the chamber or in a soda bottle) just produces a "tired from exercise" feeling with the usual visual fireworks. Of course, I don't know how it goes all the way down the tunnel! Breathing CO2 fog from a dry ice bucket through the nose produces an altogether different, unpleasant "soda up the nose" sensation, but it is, well, no better or worse than any time I've had soda go up my nose.

The main issue with mouse euthanasia, in my opinion, is that it is impossible to underestimate the resilience of fetal mice or newborn pups to asphyxiation, under conditions where adults die right away. You can assume they're dead after half an hour "not breathing" and find out you're wrong. Personally, I favor the idea that after you're "sure" they're dead you crush them utterly (which isn't hard) to be positive about it, but I'm in no position to advise you. Wnt (talk) 22:07, 1 December 2013 (UTC)

Human genetics and prehistoric movement in East Asia

Could some of you guys with a background in genetics stop by Yangtze River and look over a study someone posted? It seems like the Chinese scientists involved are trying to prove an awful lot from a few corpses and (especially given the page gets 1k–2k views a day) I'm curious how justified they are in some of the abstract's assertions. — LlywelynII 16:11, 4 December 2013 (UTC)

November 29

Polar opposites on the globe

If two geographic locations are exactly opposite each other on the globe, are they referred to as "polar opposites"? Or is that term strictly limited to the actual poles (North Pole and South Pole)? If "polar opposite" is not the correct word to describe the locations, what is the correct term? Also, is there a web site at which one can enter a specific geographic location, and its precise "polar opposite" would be identified? For example, what is the polar opposite of New York City ... or of Rome ... etc.? Thanks. Joseph A. Spadaro (talk) 00:35, 29 November 2013 (UTC)

See Antipodes. Red Act (talk) 00:48, 29 November 2013 (UTC)

A-ha, perfect. Thanks! Joseph A. Spadaro (talk) 04:53, 29 November 2013 (UTC)

There's various consequences of the Borsuk–Ulam theorem like for instance there is always a pair of antipodal points with exactly the same temperature and pressure. Dmcq (talk) 12:43, 29 November 2013 (UTC)

For example, the American Midwest is chilly, and the Indian Ocean is likewise experiencing a cold snap. Or are they? ←Baseball Bugs carrots→ 14:14, 29 November 2013 (UTC)

The theorem, of course, knows nor cares nothing about the physics of the Earth's weather. But it's an interesting thought — where would you expect to find two such points? I'd probably start looking near the Equator, because there the antipodal points are at the same latitude, and near the terminator, because there you have one point at sunset and one at sunrise. Except, sunrise is probably colder than sunset, other things being equal, because it takes things a while to warm up and it takes them a while to cool down. So actually you want to be a little (maybe half an hour?) after sunrise/sunset at each of the points, which unless I've made a minus-sign mistake, means you want to be maybe 5-10 degrees east of the terminator. No guarantees, but if I had to start looking, 5-10 degrees east of the terminator on the Equator is where I'd probably start. --Trovatore (talk) 06:00, 1 December 2013 (UTC)

And the earth's weather, of course, knows nor cares nothing about some guy's theorem. I'm sure there are plenty of places on earth whose weather happens to match some other place or places, and it's always possible one such pair of points could be antipodes - likely near the equator, as you say, although the north and south poles might also be similar, on or near an equinox. ←Baseball Bugs carrots→ 07:05, 1 December 2013 (UTC)

Well, mathematics trumps physics — the theorem constrains the weather, not vice versa. --Trovatore (talk) 07:07, 1 December 2013 (UTC)

Yeah, right. Like the mathematicians who proved the bumblebee can't fly. ←Baseball Bugs carrots→ 07:10, 1 December 2013 (UTC)

Who would those be, exactly? --Trovatore (talk) 07:17, 1 December 2013 (UTC)

Some character named Antoine Magnan. ←Baseball Bugs carrots→ 07:21, 1 December 2013 (UTC)

A search-engine-optimization consultant in Bangkok? --Trovatore (talk) 07:46, 1 December 2013 (UTC)

Except he later recognized he made a mistake in his analysis and retracted that claim. DMacks (talk) 13:00, 3 December 2013 (UTC)

So, if I read that article (antipodes) correctly, there are absolutely no parts of the USA that have a land-based antipodes opposite them ... correct? The antipodes for all locations in the USA is in the water/ocean somewhere. Joseph A. Spadaro (talk) 14:49, 29 November 2013 (UTC)

Just about. There's an island that's antipodal to a small portion of the US-Canada border; there's a slice of Alaska that's antipodal to a slice of Antarctica; and the Hawaiian islands are antipodes of various points in southern Africa. Aside from those, it's ocean. ←Baseball Bugs carrots→ 15:40, 29 November 2013 (UTC)

I think there may be a few more islands: the Crozet Islands seem to be antipodal to a spot in southeastern Washington, for example. Ile St.-Paul and Ile Amsterdam match up with two spots in Eastern Colorado. If you count US territories there could be more. --Amble (talk) 16:02, 29 November 2013 (UTC)

Thanks, all. Very helpful. Joseph A. Spadaro (talk) 13:49, 30 November 2013 (UTC)

Here's a truly wonderful map tool for exactly this purpose: Tunnel to the Other Side of the Earth]. --Amble (talk) 17:36, 30 November 2013 (UTC)

See Geography of the United States#Antipodes, Geography of Colorado#Antipodes, Montana#Antipodes, Geography of Alaska#Antipodes, and Hawaii#Antipodes. — kwami (talk) 07:50, 1 December 2013 (UTC)

Checking the helpful articles Kwami linked, I find that I miscalculated on the Crozet Islands. Their antipodal point is a bit off the coast of Washington. --Amble (talk) 03:00, 2 December 2013 (UTC)

Dreams

When I sleep with my electric blanket on, I think that I remember my dreams better than if I slept with it off. Am I just imaging things, or is there a reason for this? Seattle (talk) 02:15, 29 November 2013 (UTC)

Are you, by any chance, dreaming about being fried on a griddle? ←Baseball Bugs carrots→ 05:35, 29 November 2013 (UTC)

Do you, by any chance, wake up suddenly when you get too hot ? If so, this could explain it. When you wake up slowly the brain has time to purge your dreams, but waking suddenly prevents that. They do tend to then quickly fade, unless you concentrate on them or write them down, though. StuRat (talk) 09:25, 29 November 2013 (UTC)

Our article on sleep says that the brains oxygen consumption during REM sleep is higher than when we are awake. Studies in children have shown total oxygen consumption increasing when they switched from NREM to REM sleep. Dreams occur mostly during REM sleep and dream recall is more likely when waking up during a dream. So it could become too warm during REM sleep and wake him up, but that explanation won't work if he simply wakes up whenever his alarm clock goes off... Ssscienccce (talk) 15:48, 1 December 2013 (UTC)

I have experienced the same thing, not only remembering dreams but having particularly strange dreams too. Vespine (talk) 23:02, 1 December 2013 (UTC)

All sorts of changes in sleeping conditions, length of time, time of day, comfort and depth of sleep, mouth breathing or sleeping on sore limbs, displaced clothing, changes in light, temperature or sound during sleep, and so forth, can account for dreams of greater or lesser vividness and changes in their character. As I have aged, I have noticed my body has improved at interpreting signals. If I have a cold and mouth breath I will dream my teeth are covered in rubber or ash, or have fallen out. Just the other night I dreamt I went to work naked, and woke to find my undergarments riding low, in the same position I felt in the dream. My dreams will be unpleasant if I eat spicy food, and very vivid when I get good sleep after a period of bad sleep. I have no sources for this, since it is usually treated as anecdote (OR) by most sources. But I think most old-wives' tales are true. μηδείς (talk) 05:53, 2 December 2013 (UTC)

I must understand in simple words

How this amazing Google In-Street navigation technique works ! It amazed me ! Please explain this to me in the simplest way you could. How could it be that i navigate there so easily? Ben-Natan (talk) 02:41, 29 November 2013 (UTC)

Hulk no explain. Hulk wonder. Wonder why link to Flash Player storage settings, but dressed as amazing navigation technique? Hulk suspect plan, but miss point. InedibleHulk (talk) 02:52, November 29, 2013 (UTC)

Hulk make nobody laugh. μηδείς (talk) 04:44, 29 November 2013 (UTC)

Can't give away my good stuff for free. The important thing is the question (if it is a question) needs clarity or the right link. InedibleHulk (talk) 05:42, November 29, 2013 (UTC)

In the meantime, nosh on a Hulkaburger. ←Baseball Bugs carrots→ 05:52, 29 November 2013 (UTC)

can't you guys explain how Google has the ability to shot in such an informative way? Ben-Natan (talk) 14:02, 29 November 2013 (UTC)

I assume you mean "shoot"? And it would take someone who's in-the-know about Google. Someone like that may turn up here, but there's no guarantee. ←Baseball Bugs carrots→ 14:12, 29 November 2013 (UTC)

Are you asking about Google Street View? Does that article give you the information you want?--Shantavira| 16:46, 29 November 2013 (UTC)

Steiner Route? --DHeyward (talk) 03:51, 4 December 2013 (UTC)

Ben, I can't actually tell what you're asking. You linked to a webpage about flashplayer settings. Could you describe what you want an explanation for? I thought it may be Google Street view as well, which Shantavira linked above, but I wasn't sure. Someguy1221 (talk) 04:01, 4 December 2013 (UTC)

Heaven's Gate cult

I just read this section about how Heaven's Gate began, and began getting very curious. I googled Chuck Shramek, the amateur astronomer whose CCD photo led to the cult, and saw many links denouncing Shramek's claims. However, I couldn't find out exactly what Shramek's claims were. Our article implies that he simply took a photo, didn't recognize the bright object as a star because of a software error, and asked people what the object was. If that's all he did, what was he denounced for? If he made additional claims, can someone with better Google skills help me find them? Thanks. --Bowlhover (talk) 06:20, 29 November 2013 (UTC)

As I recall, Shramek's only contributions to the whole episode were his photograph and his comments that he observed a "Saturn-like object" that appeared next to the comet in his photograph. After checking some star charts, he couldn't identify what that object was and appeared on the Art Bell radio show to ask listeners if they had any idea what that object could be. As far as I know, he never made any claims about what it was, just raised questions. Art Bell and his listeners took up the issue and ran with it and it grew from there. As the "hysteria" spread, the claims that the object was a UFO were wrongly attributed to Shramek. A quick google search found articles such as this one that seem to agree with what I remember from the time.--William Thweatt 06:32, 29 November 2013 (UTC)

That being said, Shramek turning to Art Bell and his fringe/conspiracy theory-themed Coast to Coast AM radio show for "answers" instead of professional academics or astronomers speaks volumes about his beliefs and/or motives.--William Thweatt 06:39, 29 November 2013 (UTC)

Ahh, thanks, I didn't know that Coast to Coast was a fringe-themed station. Now I'm even more puzzled. I'm an amateur astronomer too, and apparently, Shramek was a very competent amateur--competent enough to take a CCD photo through a telescope (which is much harder than it sounds). Yet he didn't know how to set the limiting magnitude on his star chart program, didn't know what stars looked like through his own telescope, and never thought to take another CCD image a few hours later to see if the mystery object moved and/or changed brightness. (I'm assuming that our article is accurate and that he claimed the Saturn-like object was following the comet, not just close to the comet.) I never thought an astrophotographer could be this ignorant. --Bowlhover (talk) 07:28, 29 November 2013 (UTC)

Because so many of the original pages have been removed it's hard to be sure, but it seems like Shramek might be getting an unfair rap in our article. In any case, he should no more be blamed for the suicide than the truck driver who transported Oswald's rifle to the post office should be blamed for the Kennedy assassination. Wnt (talk) 21:56, 1 December 2013 (UTC)

Mechanisms of gene regulation

What are mechanism of gene control in prokaryote?74.14.28.186 (talk) 07:50, 29 November 2013 (UTC)

Maybe this link helps. Ssscienccce (talk) 15:57, 1 December 2013 (UTC)

Read operon and follow the links from it. That isn't everything but it's a lot of the fundamentals. Wnt (talk) 23:41, 1 December 2013 (UTC)

Chargers and mobile phone

I am trying to understand what Common External Power Supply practically means. Can I charge any mobile phone with compatible socket with any charger that fits into the socket? I understand the voltage is fixed to around 5 V, but how about the current? Is there a danger of damaging the phone using the wrong charger or could it happen that the phone is just not charging? bamse (talk) 10:19, 29 November 2013 (UTC)

Provided the phone and the charger both properly implement the standard (and for anything coming from a big company, this can be assumed), they will be interchangeable. It's worth noting that this only applies to phone charging with micro-USB connectors, plugging some other charger into some other socket has no such guarentee. Also worth noting that there have been proof-of-concept attacks using chargers with some computing power, which allowed the charger access to the phone memory (without notification on the phone) via the USB connection. Currently the only source I can find is for iPhone , but in principle it could be possible for other mobile devices. MChesterMC (talk) 10:36, 29 November 2013 (UTC)

Many tablets use a micro-USB connector, but charge poorly from a standard phone charger, because the tablet requires more current than the charger can deliver. They will charge slowly while asleep, but may not charge while in use. Otherwise, things should be compatible.--Srleffler (talk) 08:08, 1 December 2013 (UTC)

The science of bike puncture repair kits

I was wondering how a bicycle puncture repair kit works.

1. What's in the vulcanising solution?
2. Why does it need to dry before you apply the patch?
3. Can it get too dry (what would be the optimal window for applying the patch)?
4. How long does it take to reach maximum strength of repair?
5. Why do patches seem to have a black layer and an orange/red layer?
6. Can these layers degrade over time?

— Preceding unsigned comment added by 78.148.107.250 (talk) 11:46, 29 November 2013 (UTC)

For those not familiar with these kits, and their mysterious properties, there's a picture one of one at Outline_of_bicycles. AndrewWTaylor (talk) 12:28, 29 November 2013 (UTC)

• I don't know the specifics, but the basic story is that the vulcanizing solution dissolves the rubber of the tube and patch into a viscous liquid. After you apply the patch, the liquid solidifies, giving a single layer of rubber uniting the patch with the tube. The time it takes to solidify is quite variable -- it depends on the amount of solution you use, how wet it is when the patch is applied, temperature, and perhaps other factors. If you do it ideally, it only takes a minute or so.

People who ride road bikes with high-pressure tires rarely use those patch kits, because they are a huge pain in the ass and the result often fails anyway, either immediately or very quickly. It's much better to carry a spare tube, and perhaps a patch kit in case the spare tube fails. It's possible that people who use lower-pressure tires have better luck with them; I don't know. Looie496 (talk) 16:53, 29 November 2013 (UTC)

The OP specifically states that the patch is applied after the vulcanizing solution has dried, which suggests it is used as a contact adhesive. We do have an article on vulcanization but it only talks about vulcanizing rubber to make it usable, such as to manufacture the inner tube in the first place. I imagine that the cross-linking of the polymer chains is still applicable though, except that it now happens between the patch and the inner tube. Richerman (talk) 17:37, 29 November 2013 (UTC)

I don't think that's correct. The adhesive should be nearly dry, but still tacky. If you wait until it is completely dry it won't work. The trick is to get it into a state where it will solidify very rapidly after you make the join -- it's a tricky operation. (I've used those things a number of times, but I gave up on them years ago, so my memory might have faded a bit.) Looie496 (talk) 17:56, 29 November 2013 (UTC)

If you're right that answers point 3. I imagine that you need the solution partly cured to ensure the adhesive has bonded to both surfaces but you want enough uncured solution left to form new bonds when you bring them together. It's years since I used one of these kits too :) Richerman (talk) 18:18, 29 November 2013 (UTC)

Are tire repair kits intented to be long-lasting, or are they only intended to keep you going until you can get to the bike shop? ←Baseball Bugs carrots→ 20:46, 29 November 2013 (UTC)

I'm sure I remember them lasting a long time on standard road bike tyres when I used to cycle to work and back. Richerman (talk) 22:32, 29 November 2013 (UTC)

I've never seen the point of visiting a bike shop for a flat tire. Takes more time than patching it yourself, and I've definitely had patched tires last for years of regular use. - Lindert (talk) 22:51, 29 November 2013 (UTC)

The OP asked if the patch would wear out over time. Of course it will. How often do tires go flat due to wear, vs. punctures? ←Baseball Bugs carrots→ 00:09, 30 November 2013 (UTC)

From the way you say that, you're probably not aware that in a bicycle you have a soft inflatable tube inside a more or less rigid tire. If you inflate a tube that isn't encased by a tire, it will blow up like a balloon. Tires wear, but tubes do not -- unless the tire is worn all the way through, in which case the tube will fail almost instantly. A patch goes on a tube, not on a tire. To apply a patch, you have to take the tire off the rim, pull out the tube, apply the patch to the tube, inflate the tube a little bit and put it into the tire, put the tire back on the rim, then inflate to full pressure. It is a laborious process. When a patch fails, it isn't because of wear, it's because the patch isn't well sealed onto the tube. It typically takes thousands of miles for a tire to wear through -- it depends greatly on the quality of the tire -- but a tube can be punctured by any sharp thing that penetrates the tire, a thorn for example. A tube typically costs $5-10, but a high quality tire can cost $50 or more. Looie496 (talk) 02:51, 30 November 2013 (UTC)

I meant, do the patches degrade over time while unused. 78.148.107.9 (talk) 00:58, 1 December 2013 (UTC)

I knew they used to be that way, and it appears they still are. So it would make sense that the patch would last until or if it gets punctured along with the inner tube. ←Baseball Bugs carrots→ 03:33, 30 November 2013 (UTC)

In my experience, a well-set patch lasts as long as the tube. You are in trouble if there are new punctures close to the old ones (you cannot stack patches), but other than that, they work very well. However, I've moved to puncture-proof tires, and ever since had only one puncture in 10 years (with about 30000-50000 km on the bike). The single exception was due to a glass dagger that would have killed your average vampire... --Stephan Schulz (talk) 18:36, 30 November 2013 (UTC)

One puncture in 10 years? What tires are these? I managed two punctures in two years with Schwalbe Marathon Plus tires. 78.148.107.9 (talk) 01:02, 1 December 2013 (UTC)

Yeah, what are these "puncture-proof tires"? I haven't found anything that works in acacia scrub. Puncture-proof tires combined with double Toughies and puncture-resistant inner tubes, and if I ride over a caltrop I'm flat in under three seconds. And I'll get three or four flats a day if I don't go far. (But then, I don't think even automobiles can use pneumatic tires in that terrain.) — kwami (talk) 07:17, 1 December 2013 (UTC)

I'm using Schwalbe Marathon Plus with good results. But then I'm in Europe and cycling (mostly) on streets. --Stephan Schulz (talk) 16:20, 1 December 2013 (UTC)

I examined one of these patches: after stretching them they curl up with the orange layer on the outside. So I think the black patch is vulcanized rubber and the orange layer is unvulcanized rubber: vulcanized rubber will deform elastically so return to its original form after stretching, the unvulcanized will deform plastically and be longer after stretching. When you apply the patch with the vulcanizing solution, crosslinks will be formed between the polymer chains and maybe between the patch and the tire. I assume unvulcanized rubber is used precisely because it's plastic instead of elastic: it will take on the shape of the tire surface, and keep that shape after vulcanization. Ssscienccce (talk) 16:42, 1 December 2013 (UTC)

CCHR

November 30

Density Matrix

How does one calculate the density matrix of a system? 150.203.188.53 (talk) 03:16, 30 November 2013 (UTC)

I think that question is too broad to have an answer other than what you'll find in the article. The density matrix is ${\displaystyle \sum _{i}p_{i}|\psi _{i}\rangle \langle \psi _{i}|}$. If it's the notation that's confusing you, ${\displaystyle |\psi _{i}\rangle \langle \psi _{i}|}$ is the outer product of the vector ${\displaystyle \psi _{i}}$ with itself. In more conventional column-vector notation it would be ${\displaystyle \sum _{i}p_{i}\psi _{i}\psi _{i}^{\dagger }}$, where † indicates the adjoint. -- BenRG (talk) 07:49, 30 November 2013 (UTC)

But how do you calculate the density matrix of a system from the data you have about the system? 150.203.188.53 (talk) 10:00, 30 November 2013 (UTC)

So, for example, how would you calculate the density matrix if you just knew some of the macroscopic thermodynamic quantities, like temperature? 150.203.188.53 (talk) 15:00, 30 November 2013 (UTC)

In that case it is the sum over n of exp(-E_n/(k T)) |n><n|

where the summation is over all the energy eigenstates of the system.

But how do you find the probabilities, in general, for the data you have? I.e. how would you calculate ${\displaystyle p(|n\rangle |data)}$? For example, ${\displaystyle p(|n\rangle |T)\propto e^{-{\frac {E_{n}}{kT}}}}$. And how would you find the energy eigenstates? Wouldn't you need to know the Hamiltonian? But the Hamiltonian is dependent on the number of particles, isn't it? And that's not always known, or constant (e.g. see Grand canonical ensemble) 150.203.188.53 (talk) 01:37, 1 December 2013 (UTC)

Bird ID

What is the bird depicted here? It's tagged "bird of paradise" but doesn't look like any of those species. 69.111.73.99 (talk) 04:17, 30 November 2013 (UTC)

It is hard to believe that is a real image. This site says japanese paradise flycatcher and we have Japanese Paradise Flycatcher. μηδείς (talk) 14:33, 30 November 2013 (UTC)

The picture does look fakey (more like a taxidermy display than a snapshot of live birds), but that seems like the right bird. Thank you! 69.111.73.99 (talk) 17:46, 30 November 2013 (UTC)

I think you are right. The tail is too long, the log too clean, an altricial chick like that would not be outside the nest or running about flapping its wings. The background is uniformly out of focus. It's either stuffed, or photoshopped, or both. μηδείς (talk) 03:01, 2 December 2013 (UTC)

Waste products

(a) Is there any living entity that has no waste products? If, as I suspect, the answer is No:

(b) Could the universe, taken as a single entity, be considered a counter-example? -- Jack of Oz 09:18, 30 November 2013 (UTC)

This is more a question of the definition of "living entity". See Life#Definitions, where metabolism is listed as a (possible) essential characteristic of life, although there isn't a universally-agreed list of such characteristics. However, I don't think the universe as a whole could be considered "alive" - it doesn't reproduce (and therefore isn't visible to natural selection), and it doesn't maintain a local negative entropy gradient. Tevildo (talk) 10:53, 30 November 2013 (UTC)

I see. Thank you. -- Jack of Oz 00:55, 1 December 2013 (UTC)

While living thing create waste products, from their own POV, those waste products can still be quite useful to other organisms. The honeydew produced by aphids and consumed by ants is a prime example. StuRat (talk) 01:36, 1 December 2013 (UTC)

Viruses might qualify as not creating any waste, in that they are just genetic code that inserts itself into the host cells' DNA. However, the host cell produces waste, and you could allocate some of that waste to the virus. Also, some may not consider viruses to be a life form. Similar considerations apply to prions. StuRat (talk) 01:43, 1 December 2013 (UTC)

• Plants don't really have waste products per se, since they can reuse the oxygen (and carbon dioxide) they produce. They give off waste heat and leave husks when they die, but this is not the same as producing feces. μηδείς (talk) 19:20, 1 December 2013 (UTC)

Leaf litter is much like a waste product - the plants can't reuse it directly and rely on other organisms to recycle it; it acts as a sort of fertilizer to improve the environment, which I suppose is marginally analogous to animal dung. To find something without a waste product you really have to have a sealed container of it growing/metabolizing/converting energy in the absence of any other species (including fungi), I think. Wnt (talk) 23:45, 1 December 2013 (UTC)

A semi-closed system with an influx of light and an outflow of heat can be fairly balanced. My grandfather had a large sealed bottle with insects and salamanders and a lot of ferns, moss and algae that was never opened as long as I remember. See Ecosphere. But entropy increases, and even Biosphere 2, with humans, needs influxes of nutrients rather quickly in its basically failed two-year mission. μηδείς (talk) 02:58, 2 December 2013 (UTC)

FOOD DIGESTION

We eat three times a day but we pass stools once. Where the digested food accumulates? In the large intestine? Thank you.175.157.126.249 (talk) 09:37, 30 November 2013 (UTC)

Indeed it does. See Alimentary canal and Large intestine. Tevildo (talk) 10:48, 30 November 2013 (UTC)

The digested food doesn't accumulate - it slowly makes it way through the alimentary canal and the useful components are extracted along the way to be used by the body for many different processes. The waste products - the parts that can't be digested - accumulate in the large intestine until they are eliminated. See Digestion. Richerman (talk) 11:13, 30 November 2013 (UTC)

Regarding your "pass stools once", it is a quite interesting fact that human defecation rates vary enormously; anything from three times a day to three times a week is considered normal.--Shantavira| 14:14, 30 November 2013 (UTC)

Phase-Change Material

Hello,

I would like to ask the author for this article about the Thermophysical properties of selected PCMs (the table in the article). How do I communicate with him?

Kind Regards Dudi 79.176.222.17 (talk) 14:26, 30 November 2013 (UTC)

Misplaced Pages articles are built collaboratively. Phase-change material was started in 2005 and has had numerous contributors. All past versions of a Misplaced Pages page, along with the contributors, can be seen by clicking on the "view history" tab at the top of the page: here is the edit history of the page in question. You can communicate with any other user by editing their user talk page and leaving a message there, but if that user has not edited recently, you may not necessarily get a speedy reply. - Karenjc (talk) 23:13, 30 November 2013 (UTC)

Cold effect on stomach

It is often said that people should eat less fatty foods when they have a cold as the stomach can be affected by a cold. But is the stomach directly affected by the cold virus or is it more an indirect effect, such as having less energy to digest food as well or irritation from medication or the stress of being ill? 82.40.46.182 (talk) 15:37, 30 November 2013 (UTC)

I think they are being a bit sloppy when they use the word "cold", and also including things with similar symptoms, like the flu, which do affect the digestive system. StuRat (talk) 01:31, 1 December 2013 (UTC)

Swimming in water in space

How would swimming in a "pool" of water (or rather a room filled with water) in space differ from swimming in a regular pool of water on Earth? --CesarFelipe (talk) 17:03, 30 November 2013 (UTC)

If it was in freefall, you would stand a good chance of drowning since the water and air would become thoroughly mixed and the air "bubbles" would be too small to breathe.--Gilderien Converse|List of good deeds 18:08, 30 November 2013 (UTC)

If you were suitably equipped with breathing equipment and the room were complete filled, it would still be more like floating in space, but with more resistance. You wouldn't float or anything as there still is no up or down to cause the water to have increasing pressure at greater "depth". It would be of uniform pressure, whatever it might be. Mingmingla (talk) 19:14, 30 November 2013 (UTC)

And, if you rotate the space station, or just the pool, then it would be more like swimming on Earth, allowing for normal breathing, with the unique feature that you could have a cylinder of water, and swim continuously in one direction (a completely new type of endless pool). The rotation speed and diameter set the g-force, and whatever it was at the surface, it would be more at depth. The result is that pressure would increase more quickly as you dive, as compared to a static g-force environment. StuRat (talk) 01:27, 1 December 2013 (UTC)

Of slight relevance might be the Neutral Buoyancy Laboratory in Houston where astronauts train underwater for Extra-vehicular activities. HiLo48 (talk) 02:40, 1 December 2013 (UTC)

In weightless conditions, swimming underwater in scuba gear wouldn't be much different than in a swimming pool here on earth. But for swimming unaided on the surface, life would be chaotic and dangerous! For one thing, you'd no longer float preferentially on the surface of the water - you'd be equally likely to drift up into the air "above" the pool or to sink down into it...and of course the water wouldn't remain neatly separated from the air for very long - pretty soon the air and water would be all mixed up and breathing would become difficult at any depth. Getting your head sufficiently clear of the water to take a breath would be a scary, dangerous business. SteveBaker (talk) 05:48, 1 December 2013 (UTC)

(I'm just making this up, I wonder if it's true:) Hmmm, if you had sufficiently hydrophobic clothing - or an oily beard :) - maybe you could get away with it like a diving bell spider. Assuming the water was kept reasonably well churned up with the air by some means, you could have a layer near your body that attracts air, and exchanges it with the bubbles you encounter. Wnt (talk) 21:19, 1 December 2013 (UTC)

Why do newborn chickens have yellow plumage?

It seems yellow is noticeable in the wild: among the green grass, the brown ground etc., so for predator it is easier to catch yellow chickens. It's like against evolution.--Lüboslóv Yęzýkin (talk) 21:08, 30 November 2013 (UTC)

Certain breeds might have mostly yellow plumage but most of the 8-10 breeds that I have raised have varied in color with quite a few combinations of black, brown, and grey. Dismas| 21:22, 30 November 2013 (UTC)

See, for instance, this image to the right. Dismas| 21:28, 30 November 2013 (UTC)

I don't know from chickens, except the packaged ones in the stores. Is the yellow color of (some) chicks a fictional stereotype, or is it only in certain breeds of domestic chickens? (Which would suggest it was maybe unintentionally a consequence of the artificial selection process used to develop a given breed.) ←Baseball Bugs carrots→ 22:32, 30 November 2013 (UTC)

Not sure about these ones.  Card Zero  (talk) 22:41, 30 November 2013 (UTC)

(ec)The traits of domesticated animals are influenced by selective breeding rather than the selective pressures of evolution. Many of the characteristics we select for, or those that come about as a by product of the traits we select for, would be a disadvantage in the wild. And yes, the chicks from some of the common breeds are bright yellow. However, as Dismas said, they also come in many other colours see: Richerman (talk) 22:42, 30 November 2013 (UTC)

I am not an expert in chicken breeds but while living in the countryside during my childhood I saw predominately clear lemon yellow or pale yellow chickens. Only a few had dark plumage. When they raised to several weeks or so they became more camouflaged and reminded of adult birds.--Lüboslóv Yęzýkin (talk) 02:21, 1 December 2013 (UTC)

• The ancestors of chickens are thought to be the red junglefowl and grey junglefowl, which mainly inhabit environments where there are plenty of large plants to provide concealment for chicks. Looie496 (talk) 01:04, 1 December 2013 (UTC)

• As far as possible reasons, one might be so the mother hen can find them, as lost chicks are almost certain to die. And, if this trait was indeed selected for during breeding, that would both be so the mother and farmer can find them. It's also possible that this trait evolved all on it's own, in domestic chickens, since there the advantage of being visible to the mother hen outweighs the disadvantage of being visible to predators, since presumably domestic chicks are kept relatively safe from predators. Therefore, this keeps them from getting lost outside the chicken coop and freezing to death at night, etc. StuRat (talk) 01:20, 1 December 2013 (UTC)
  • Seems legit. But as I remember local crows, magpies and similar birds were real disaster they could wipe out an entire chicken brood.--Lüboslóv Yęzýkin (talk) 02:21, 1 December 2013 (UTC)
  • You also lead me to another thought. Many animals while domesticated lost their camouflage and became clear white, black, or of other simple colour. Though I don't know the exact mechanism of this.--Lüboslóv Yęzýkin (talk) 02:26, 1 December 2013 (UTC)
    • Simple googling helps.--Lüboslóv Yęzýkin (talk) 02:34, 1 December 2013 (UTC)
• The yellow of those chicks is a rather drab shade, probably even moreso to colorblind mammalian predators. Note also they are countershaded, dark on top, and lighter on the bottom. μηδείς (talk) 02:00, 1 December 2013 (UTC)

Many decades ago at the Royal Melbourne Show one of the gimmicky exhibits was green and pink and blue plumaged chickens, apparently created by injecting dye into the eggs before hatching. HiLo48 (talk) 02:36, 1 December 2013 (UTC)

This and the sale of died bunnies is common in the US where legal at Easter. Fortunately, that is an American holiday not celebrated overseas. μηδείς (talk) 01:08, 2 December 2013 (UTC)

Typically those critters were dyed before the holiday, and too often died after it. ←Baseball Bugs carrots→ 02:28, 2 December 2013 (UTC)

Sheeit. μηδείς (talk) 02:49, 2 December 2013 (UTC)

Easter is certainly a holiday in the UK. Good Friday and Easter Monday are public holidays and Easter Sunday is one of only two days of the year - the other is Christmas Day - that big shops have to stay closed. However, I have never, ever heard of dyed animals being sold before and I hope I never will again. Richerman (talk) 23:08, 2 December 2013 (UTC)

I assume that must be due to all the US GI's "over there" during WWII, popularizing the holiday in Britain. In the US Easter was started by FDR as a way to stimulate the chicken and rabbit-meat industries. Oddly enough, Dingus day is not a public holiday in the States, possibly due to its sexist nature. μηδείς (talk) 23:24, 2 December 2013 (UTC)

Er, no it's because it was always considered the most important time in the Christian calendar and some of the Easter traditions such as egg rolling and egg decorating date back to pagan times. I don't think there was much time for holidays in Britain during WWII. Richerman (talk) 23:47, 2 December 2013 (UTC)

Do be aware we Americans don't call a week off from work a holiday--that's vacation. Like Christmas Vacation. (During the War, American vacations were postponed by law, with interest. That's why the entire Baby Boomer generation of the 50's and 60's was conceived between Dec 1, 1945 and March 1, 1946, during the three month vacation after demobilization was complete.) Rather, holidays are Christian holy days, like Thanksgiving, established by New Testament tradition. μηδείς (talk) 01:38, 3 December 2013 (UTC)

December 1

Are deer "nearly blind by human standards" ?

This was the assertion by the Nature episode The Private Life of Deer. They said they only see blurry shapes, except when those shapes move. Deer have large enough eyes, so this assertion seems questionable to me. This program was focused on white-tailed deer, but I'm unclear if the comment applied to all deer of just that type. If true:

1) How do we know this ?

2) Why exactly can't they see stationary objects well ?

One thought I had is that they appear to lack the dilation/contraction response of humans and many other mammals, and therefore to be able to see at night they must get way too much light during the day, and perhaps this blinds them. I'd expect it to cause permanent eye damage, too. Is there some chemical change to alter the sensitivity of the receptors in daylight ? StuRat (talk) 01:51, 1 December 2013 (UTC)

This page seems to have some good information. --Onorem (talk) 02:04, 1 December 2013 (UTC)

A key thing to note is that deer don't have a fovea but a visual streak (mentioned briefly in retina, someone should start an article...) 20/200 is the threshold of legal blindness, which is what deer were rated at; macular degeneration can put people below that. However, I would be concerned that we may miss some of the tricks involved in having a visual streak, due to a lack of intuition about it. Hunters generally have a practical sense of what deer miss and see. Wnt (talk) 21:15, 1 December 2013 (UTC)

That seems to explain the quote in question. Somehow I bet we are missing something, though. I understand that the image our eyes produce is also much worse than we think, and the reason is that our brain does a wonderful job of filling in the gaps. Perhaps a deer's brain is also able to make more out of the input from their eyes than we think. StuRat (talk) 12:53, 2 December 2013 (UTC)

Thanks all, for the answers so far. StuRat (talk) 12:53, 2 December 2013 (UTC)

Chloroauric acid

Where can I find information on the chemistry of anhydrous chloroauric acid, that is the substance with the formula H
₃O? How is this substance obtained (not H
₃O or )? Plasmic Physics (talk) 07:07, 1 December 2013 (UTC)

Google suggests anhydrous chloroauric acid is crystallizeable from ethanol, but not clear how hydrated it begins. I see you made major changes to the article, including the very definition of the topic itself...need cites that the chemical named "chloroauric acid" and widely identified as just HAuCl₄ by formula is assumed to contain at least one water intrinsically as a hydronium (with then 2–3 more as the hydrated salt form). For example, VWR's catalog calls the chemical with 3 waters total in the formula the "trihydrate". DMacks (talk) 07:50, 1 December 2013 (UTC)

It is a well known fact within the chemistry domain, that no known compound contains free protons. By convention, salts purported to contain free protons, in actuality contain solvent coordinated protons. This case the common solvent is water. HAuCl
₄ is the canonical, but technically incorrect formula. Plasmic Physics (talk) 08:12, 1 December 2013 (UTC)

How do you know it's exactly *one* "water solvating the proton in the chemical? Some articles identify "HCl" as one of the ligands, which seems unlikely, but you seem to take for granted the opposite extreme, that is completely non-coordinating/basic itself. You're the one making specific claims about a specific chemical that on their face contradict other information in the literature. WP:BURDEN's on you to make the specific case from the literature. DMacks (talk) 08:32, 1 December 2013 (UTC)

It is standard practice to attribute one water to a proton. I don't suppose that
is non-coordinating/basic itself, what I am supposing, is that it is the structurally irreducible anion that is participant to chloroauric acid. Furthermore, I suppose that it does coordinates very well, but not as strongly as a proton, hence why H
₃O decomposes rather than dehydrate when subjected to elevated temperatures. Plasmic Physics (talk) 08:51, 1 December 2013 (UTC)

It may be standard practice to attribute one water molecule, but is it standard practice to write one water molecule. WP:BURDEN applies, the standard form as written should be written but it has been removed instead. Citation not explanation please. Dmcq (talk) 11:33, 1 December 2013 (UTC)

could also rather be H
₃O•H
₂O, which contains genuine lattice water. Plasmic Physics (talk) 09:13, 1 December 2013 (UTC)

Oops, correction: the later two formulae should be

• (or H
  ₃O•H
  ₂O) and
• (or •H
  ₂O, or H
  ₃O•2H
  ₂O).

Plasmic Physics (talk) 12:15, 1 December 2013 (UTC)

Sorry, I'm really suspicious of this. "oxonium tetrachloridoaurate" isn't getting me any hits at PubChem and only this article on Google. I think it is very standard practice to write HCl, HI, HF, etc. (and these do exist as molecules in gas phase, therefore exist in equilibrium in liquid phase, and I'd assume they can exist as pure solids if you catch some of those gas molecules where they have nothing to join up with. Whether those solids are ionized, covalent, polymerized, coordinated, whatever is another question). Show me a synthesis or purification procedure where somebody has actually shown that H3OAuCl4 has a discontinuity in its tendency for losing/gaining water at a 1:1 stoichiometry and I'll believe you. Wnt (talk) 21:04, 1 December 2013 (UTC)

Your mistake is that you assume that in the hypothetical H, the proton could be directly attached to the anion. It cannot, it is wholly unlike the hydrogen halides. Plasmic Physics (talk) 21:17, 1 December 2013 (UTC)

Are you sure? Chlorine can make more than four bonds if it wants. Wnt (talk) 21:43, 1 December 2013 (UTC)

Yes, the acid is known as matter of fact to contain discrete
ions. Plasmic Physics (talk) 22:37, 1 December 2013 (UTC)

That's a far cry from saying that HAuCl4 never occurs, or that having less than HAuCl4*1H2O would be impossible. I mean, my gut feeling is that "anhydrous" means "no H2O". It's like a sultan coming back to his hareem and finding his ninth wife with another man, but don't worry, he's her lover and he's the only one she can't do without. :) Wnt (talk) 23:20, 1 December 2013 (UTC)

Even if H does occur as you suggest, it would do so for a vanishingly small time, before decomposing into AuCl
₃ and HCl. Plasmic Physics (talk) 23:42, 1 December 2013 (UTC)

Hmmm, then why doesn't H3O-AuCl4 decompose to H2O + AuCl3 + HCl...? Maybe that's not a valid comparison - in any case I shouldn't have taken your word for the H not having another way in. According to the structure of AuCl4H is actually the gold in the center and all five ligands arrayed around it. (It's too easy for me to forget that transition metal chemistry is just different from the organic...) Wnt (talk) 08:39, 2 December 2013 (UTC)

One thing you'll learn with some experience, is that commercial catalogues are unreliable when it comes to structural information on compounds. Plasmic Physics (talk) 22:11, 2 December 2013 (UTC)

Actually, H
₃O decomposes to AuCl, Cl
₂, HCl, and H
₂O. Plasmic Physics (talk) 22:14, 2 December 2013 (UTC)

May I suggest yet again that what should lead in the lead is the formula as normally written in reliable sources. All the argument above is irrelevant to that. Dmcq (talk) 09:35, 2 December 2013 (UTC)

I'll second that. --Jayron32 15:24, 2 December 2013 (UTC)

December 2

RMWI?

Hello, as a part of my grade 11 chemistry assignment, we have to write a report on the arsenic levels in chicken, and how much of it is consumed in a sample of ten people. One of the questions it deals with is to find the "Recommended Maximum Weekly Intake (RMWI) for each person." Now, the only thing we were given was the toxicological reference value (TRV) of chicken being 0.024µg As/kg BW per day, and so we had to research the RMWI ourselves. This link gives the formula:

${\displaystyle {\frac {TRV\times BW\times 7}{CF}}}$ , where
TRV = toxicological reference value (µg/kg body weight/day)
BW = body weight (kg)
CF = concentration in food.

I tried the equation, using the TRV value given (0.024 µg/kg) and the weight of a sample person (68kg), but I do not have the concentration in food, nor could I find it online. Does anyone have any idea of what this concentration could be, or if there is a better formula available? Thanks. 50.101.203.177 (talk) 00:19, 2 December 2013 (UTC)

I'm not absolutely sure, but I think your 0.024 ug/kg is the 'concentration in food' where the people are concerned, and what you still need to get is the reference value for how much arsenic a person can consume in ug/kg body weight/day.... nay, wait a minute, the figure you gave is an intake per day for the chicken, hmmm. Are you sure about that? Which are you calculating this for - what maximum intake of ?grain? is needed to keep the chicken meat below a specific arsenic concentration, or what the maximum intake of chicken is to keep the level of arsenic in the humans below a certain level (and if so what level?) Wnt (talk) 01:49, 2 December 2013 (UTC)

Quick reality check: has people talking about 0.6 to 3 micrograms of arsenic per kg of chicken, with the organic people crowing and cackling about the lower level in their product because they don't use roxarsone. Jeesh, the commercial folks should take a page from the laetrile salesmen and call it "vitamin As" :) Anyway, I have to recognize you are giving me a ug/kg/day figure then, not a ug/kg figure. I think there's something missing in the definition of this problem. Wnt (talk) 01:54, 2 December 2013 (UTC)

Oh, and according to the dosage of roxarsone is "22.7 to 45.4 g roxarsone/ton feed"; assuming a metric ton (1000 kg) for now, that is 22.7 to 45.4 mg/kg of roxarsone, which is 75/263 arsenic... hmmm, that seems waaay higher than the figure given. Even the organic chickens ought to be getting much more. Hmmm, I should return here and see if I slipped up. Wnt (talk) 02:00, 2 December 2013 (UTC)

I'm guessing the CF in this case would refer to arsenic concentration in chicken meat, and the TRV to maximum arsenic intake from chicken alone (considering that other foods and drinks may also contain As). In that case you still need the arsenic concentration in chicken meat; the FDA limit is 500 ppb or 500 ug/kg (and 2000 ppb for chicken liver). But that's huge in comparison with 0.024 microgram/kg BW /day, it gives you an RMWI of only 22.8 gram for someone weighing 68 kg. This study from 2006 lists arsenic content in chicken meat from several suppliers. In uncooked chicken the maximum found was 21.2 ppb, In fast food chicken the Church's chicken thighs contained 46.5 ppb. The 21.2 would result in an RMWI of 530 grams for the same person. So it all depends on which value you take for CF... Ssscienccce (talk) 16:27, 2 December 2013 (UTC)

California coastal oak balls

I am going nuts. Every year I see the acorns on the ground & I see them in the trees. However, I also see these perfectly round balls on the ground & for the life of me I can't find any in the tree. Where do they come from? Are they formed from the acorn top left in the tree? Many thanks! — Preceding unsigned comment added by 24.23.237.218 (talk) 01:37, 2 December 2013 (UTC)

They are probably some type of oak gall. μηδείς (talk) 02:47, 2 December 2013 (UTC)

Maybe, but it would be helpful to have a picture. Looie496 (talk) 16:39, 2 December 2013 (UTC)

A Sex Change (Dramatically) Changing One's Sexuality?

Is it possible for a sex change (especially the hormone replacement therapy, et cetera) to (dramatically) change one's sexuality (such as previously being completely or predominantly attracted to females and then becoming completely or predominantly attracted to males)? Also, if so, then how frequently does such a (dramatic) change in one's sexuality occur in such cases? Thank you very much. Futurist110 (talk) 05:18, 2 December 2013 (UTC)

Yes, I have seen a documentary (I'll look for it) where female to male post-transexuals have changed orientation. This article suggests heterosexual males who have transitioned to females become attracted to males at a significant rate (6 out of 20). μηδείς (talk) 05:37, 2 December 2013 (UTC)

This article suggests that 40% of presumably female-attracted female to male transexuals become attracted to gay men to some extent within 10 years of transitioning. μηδείς (talk) 05:41, 2 December 2013 (UTC)

It must depend on the person's will to change. There is probably a placebo effect. The effect of hormone therapy vis-a-vis sexual attraction may reduce with age. The reason why I don't believe that hormone therapy inherently changes sexual preference is that a standard and commonly used treatment for men with prostate cancer for 40 years has been hormonal therapy (there are other treatments - eg surgery) as prostate cancer is hormone dependent. The hormone dosage is sufficient to stimulate breast growth, and in some cases the breasts can be quite prominent. A workmate of mine aquired breasts about size 42C - looked at little odd on a 6 foot 3 inch muscular man. But such men do not change partner preference. There is usually some loss of libido. If the man has difficulty getting an erection (say due to circulatory issues or diabetes), the hormone treatment may kill it off completely, but they are still men and they still want real females. There is of course no way that other sex change procedures (eg cosmetic surgery) can change one's preference. 58.169.252.71 (talk) 10:16, 2 December 2013 (UTC)

Hormone replacement therapy is more than just estrogen pills. A trans woman who has not had reassignment surgery or an orchiectomy will still produce testosterone, which is why she would also be on spirolactone or some other androgen antagonist. If she elects for one of those surgeries, then her body will no longer produce testosterone at all. Her estrogen dose would also be designed to raise her bodie's estrogen level to one similar to other women. Progesterone is also commonly used to encourage some of the physical feminization. This means you can't just compare the medical effects of estrogen for prostate cancer to those for HRT. The majority of trans people I know have had confusion about their orientation in the past, likely due to gender issues, and then settle on something as they figure themselves out during transition. In my case I went from thinking i was straight man to a bi man, then realizing I was a woman and for a while identifying primarily as a lesbian right in the middle of the hard parts of the realization and early transition, then back to being a bi woman as things settled down, and that was all pre-HRT. I would describe those shifts (except for maybe straight to bi) as real, and they had nothing to do with transition related medical procedures - it was all personal development as I learned more about who I am. Hormones and other procedures end up having a profound mental effect on trans people, so even if there isn't a direct medical link, I can understand the personal development that comes along with finally having a body that matches one's gender identity leading to changes in orientation. Katie R (talk) 12:47, 2 December 2013 (UTC)

This doesn't sound treatment-wise much different to hormone therapy for prostate cancer. Such treatment includes drugs to stop testosterone production (it won't stop it completely, but then neither will sex change therapy, in any case some testosterone is present in natural females) plus optionally an estrogen or estrogen analogue course. Other androgen receptor blocking drugs are also used in some cases. It sounds from your post that rather than the hormone treatment driving a change in partner preference and persona, it just made it mentally easier to achieve an orientation you wanted or subconsciously had built in anyway. In contrast, men with prostate cancer don't want to change partner preference or their own sex persona, and are not a feminine person trying to get out, so they don't change, regardless of the treatment. All the best for your future though Katie. 58.169.252.71 (talk) 15:28, 2 December 2013 (UTC)

That's interesting to know - I've heard the estrogen side mentioned several times, but not the anti-androgens, but I've never really looked into prostate cancer treatment. It just happens to come up in discussions of HRT sometimes. But yes, aside from pointing out what I thought was different in the treatments, the main point I was trying to make was that there is a lot going on on the mental side of things, and even if a specific procedure doesn't have a direct medical link to orientation changes it can still trigger the change as a part of the personal development going on at the same time. I think we agree there - I just wanted to explain to the OP how those sorts of changes can happen during transition regardless of the specific medical procedures involved, because it sounded like he might be interested in orientation changes in general, even though he mentioned medical procedures in the question. Katie R (talk) 16:12, 2 December 2013 (UTC)

• Here's part one of at least on of the documentaries of which I was thinking above: http://www.youtube.com/watch?v=-c9ZnpMppHQ. μηδείς (talk) 02:05, 3 December 2013 (UTC)

If you watch part 3/4 of this documentary, the men and women discuss for a bit the statistics and their personal experience with orientation changes after to the physical changes. It is very interesting that heterosexual men tend, if they change, to become heterosexual women, while lesbian females often become gay males. μηδείς (talk) 01:45, 4 December 2013 (UTC)

Autonomous vehicle

Has any autonomous vehicle, other than spacecraft, circumnavigated the world? --140.180.255.56 (talk) 08:07, 2 December 2013 (UTC)

There is nothing listed at List of circumnavigations but it looks as though such a feat is now theoretically possible .--Shantavira| 12:28, 2 December 2013 (UTC)

Yes, and I can think of 3 different ways: airplane (although here fuel might run short), helium or hydrogen balloon, and boat. A land vehicle would also be possible, if not for the fact that the trip would be interrupted by oceans. StuRat (talk) 12:41, 2 December 2013 (UTC)

You can think of 3 ways, but have any of them ever been done? --Bowlhover (talk) 22:07, 2 December 2013 (UTC)

There is a team working on a robotic, solar powered boat that will, or has done this. I remember reading about it some time ago. 217.158.236.14 (talk) 13:36, 2 December 2013 (UTC)

Doubt it has happened yet, some google results about the idea itself (forums etc), but nothing on it having been achieved. Shouldn't be too hard for a balloon or airship, specially if you make it buoyancy neutral at some fixed height. Judging by the global wind patterns all you need then is launch it with the trade winds. Ssscienccce (talk) 16:49, 2 December 2013 (UTC)

This has actually been done by a superpressure balloon (a type of stratospheric weather balloon), but I forgot the name of the reference. 24.23.196.85 (talk) 00:32, 3 December 2013 (UTC)

From Aerobot#The Mars aerobot effort:

The French had already conducted extensive experiments with solar Montgolfieres, performing over 30 flights from the late 1970s into the early 1990s. The Montgolfieres flew at an altitude of 35 kilometers, where the atmosphere was as thin and cold as it would be on Mars, and one spent 69 days aloft, circling the Earth twice.

but I agree with Dismas below that this wouldn't meet the requirement of being being autonomous. -- ToE 13:32, 4 December 2013 (UTC)

• I am not sure what you mean by autonomous, but Steve Fossett flew around the world in a balloon. μηδείς (talk) 21:26, 2 December 2013 (UTC)

He means an unmanned vehicle that isn't remotely controlled. See for example autonomous underwater vehicle or autonomous car Ssscienccce (talk) 22:39, 2 December 2013 (UTC)

There has been discussions of using a novel wave-powered craft to do this - without the need to carry fuel, and with simple satellite navigation, it seems plausible that a very small craft could make the trip. That would make it a fairly cheap device (by the standards of other circumnavigation efforts) - but there are no reported successes as yet. Liquid Robotics have a device called "Wave Glider" that is a semi-submersible powered by waves and solar cells. The craft is around 7 feet long and looks like a surf-board with solar panels on the top. The Wave glider has successfully travelled 9,000 miles on a year-long autonomous mission as a part of the "PacX" challenge to cross the pacific and holds the current Guinness world record for autonomous travel. The accepted minimum distance for a "circumnavigation" is 24,800 miles (40,000km) - so this craft has managed more than a third of that and there is no reason to assume that it couldn't complete the entire journey if so desired. The Suntory Mermaid II (manned trimaran) demonstrates that even a 3 tonne vessel can be propelled by wave-power alone at between 1 and 2 knots - so even if a much larger vessel is required, this is clearly "do-able". But at a speed of 1 to 2 knots - covering the required 40,000 km will take at least 11,000 hours and probably more like 22,000 hours (30 months!). That means that the reliability of the craft - especially in extreme conditions - becomes a critical matter. Having something that can survive the worst weather conditions continuously for two or more years at sea is not such a simple problem to solve I suspect!

Since we have had successful non-stop circumnavigations in an aircraft (Virgin Atlantic GlobalFlyer), it ought to be possible to program a drone-pilot to make the same trip in a similar craft (the necessary additional computers, cameras and batteries being lighter than the pilot and engineer from the manned trip) - but since there isn't really a compelling record to be broken, I doubt people are working towards doing that. SteveBaker (talk) 00:12, 3 December 2013 (UTC)

As far as surviving bad weather at sea, I suggest a boat that can detect bad weather and submerge to a safe depth until it passes. StuRat (talk) 08:04, 3 December 2013 (UTC)

You are probably not going to have an autonomous vehicle transiting the canals (what, with robotic line handlers in Panama?), so it would circumnavigate via the great capes, and what passes for good weather in the southern ocean is bad weather elsewhere. Boats there expect to sail during typical gale force winds, and only heave to or tow warps or drogues during stronger storms. Insolation is limited, what with the high latitude and cloud cover, so I suspect that a Wave Glider could cross the Pacific back and forth a dozen times easier than it could circumnavigate via the great capes. Generating electrical power from wind turbines or towed water generators is very practical at those latitudes, and would mesh well with solar generation used is the low winds of the equatorial Atlantic, so it shouldn't be too difficult to build an autonomous sailboat which powers its own sail controls from these sources, but, as others have mentioned, reliability would be the big issue. You need a design which can go for many months in all types of conditions without human assistance unjamming caught lines, replacing chaffed and broken ones, and stitching up torn sails. -- ToE 13:32, 4 December 2013 (UTC)

Speaking to the idea of releasing a balloon into the trade winds, that doesn't seem like it would fit the OP's requirement of the vehicle being autonomous. "Autonomous", in every case I've seen, at least implies that the thing has some sort of control over its own workings. A balloon simply set adrift on the winds has no way of making any changes to altitude, speed, or heading. Dismas| 05:13, 3 December 2013 (UTC)

That's a good point, but how much would it have to do to qualify ? If it just monitors it's progress and then releases gas to descend when it reaches the target, would that qualify ? (I bet it would need to do more than that, though, like change altitude to avoid weather, get into the proper wind currents, etc.) StuRat (talk) 08:01, 3 December 2013 (UTC)

Certainly you could imagine a vehicle that can inflate or deflate a balloon to control altitude being described as "autonomous" - but only if it does so in order to achieve some degree of control over the flight path. It could perhaps be informed of the wind speeds at different altitudes at its location and autonomously control altitude in order to control direction. However, the amount of information available to it about wind speed versus direction over the entire earth might be problematic...so then you'd have to imagine it either measuring that information with some kind of doppler-effect thing - or perhaps moving up and down to experimentally discover the best height to be at. This seems like a fairly challenging problem - so I doubt that this kind of gadget would be the first autonomous circumnavigation. My bet is definitely on the Liquid Robotics boat - it's already travelled 9,000 miles and since it doesn't require fuel, there is no particular reason to assume that it couldn't go the whole distance...although reliability issues over a 2 to 3 year voyage, and some lack of desire on behalf of the owner to actually make the attempt might prevent it from being the first to do this. SteveBaker (talk) 15:13, 3 December 2013 (UTC)

I would think "navigate" would be a factor whether a human program or artificial intelligence (animals wouldn't count). Dropping a bottle with a message into the ocean might traverse the globe but it has no navigational ability. Ferdinand Magellan and Juan Sebastián Elcano made navigation decisions to circumnavigate the globe. Similarly, simply tracking a whale wouldn't count either. --DHeyward (talk) 09:21, 4 December 2013 (UTC)

December 3

Skin color and auto accidents

According to a report by the Centers for Disease Control and Prevention, the death rate for American pedestrians in auto accidents, 2001-2010, was much higher for blacks than for whites. This report was the only solid source I could find that's at all relevant to skin color, so I'll have to ask for help finding something that interprets the data. Is anyone aware of studies that directly address the effect of skin color on rates of auto-pedestrian collisions? I was left wondering about skin color itself while walking along a street after nightfall this evening: I'm left wondering if my light-skinned face and hands are more visible to a driver than they would be if my skin were dark. Since statistically average white and black Americans differ in much more than just skin color, we obviously can't say that the different death rates are purely the result of drivers seeing white pedestrians more easily than black pedestrians. Has anyone done a study that seeks to control for all other factors (e.g. controlling for percentages of people of each race walking in places without sidewalks, walking at night, walking while drunk, etc.), leaving only the visibility of the skin as a variable? Lest this be misinterpreted: I'm not fishing for anything, nor suggesting anything about common black culture versus common white culture; I would ask the same question if common concepts of race relied primarily on eye color and ignored skin color entirely. It's purely a question of the relationship between melanin and optics. Nyttend (talk) 02:14, 3 December 2013 (UTC)

• Seriously? (Are you from the Alps? Methinks thou dost protest too much.) Blacks in the US are overrepresented as part of the urban population, where car-pedestrian impacts are most common. μηδείς (talk) 03:43, 3 December 2013 (UTC)

I think you'd definitely need a controlled study under strictly defined conditions to rule out all of the confounding variables such as differences in fashion. I don't think you can take actual incidents and control every factor like that, because for example how would you categorize every garment every person was wearing? (I know there are definitely some colors that are more popular with people of a particular race in a given area) Wnt (talk) 03:39, 3 December 2013 (UTC)

<sigh> Recite ten times: "Correlation does not imply causation" (then read our fine article: Correlation does not imply causation).

It is true in the US that (for example) on the average, (per Racial wage gap in the United States) black people only have 65% of the income of an average American. So perhaps the truth is really: "Poor people have a higher death rate than the middle classes in pedestrian auto accidents". Perhaps they live in neighborhoods with worse street lighting and the real news is "People who live in well-lit neighborhoods have a lower death rate in pedestrian auto accidents"...which takes us from a socially divisive message to a socially useful one that says "We should improve street lighting in the poorer parts of America"....or not. We don't know because the science wasn't done right.

For all scientific studies, you absolutely must employ at least one control group - and for this study, you'd need MANY control groups before jumping to any kind of conclusion whatever. So in this case, one would want to control for income by (say) comparing the death rates for people of different skin colors in identical income groups - and who live in identical parts of the city, etc, etc.

Jumping straight to the conclusion that skin color is the "cause" is a very, very bad idea when all you have is a single "correlation".

So this study (as it stands) is entirely useless and may safely be filed away under the heading of "unqualified data" until we see some halfway reasonable study about why pedestrian accidents happen.

SteveBaker (talk) 03:40, 3 December 2013 (UTC)

Have you read any of the study, or even the question, before denouncing the study as "entirely useless"? The study makes absolutely no claim about why black people have more accidents. It simply lists accident rates by race, gender, urbanization level, age, and other factors, and doesn't even put any emphasis on race.

If you read the question, you'd know the OP asked "Since statistically average white and black Americans differ in much more than just skin color, we obviously can't say that the different death rates are purely the result of drivers seeing white pedestrians more easily than black pedestrians. Has anyone done a study that seeks to control for all other factors..." He's asking precisely for a controlled study. --Bowlhover (talk) 04:36, 3 December 2013 (UTC)

The first thing missing that I see is a comparison to other accidental death rates and non-accidental death rates. Considering that it's only 13% of vehicle related deaths, the next study I would look at is wheher vehicle/vehicle accidental deaths are correlated in the same way as pedestrian/vehicle deaths (that seems surprisingly missing). Those studies should be available broken down by the same categories. The next question is whether pedestrian/auto deaths are a significant cause of accidental death in each group or is it in the noise (this is particularly egregious omission as it appears to be raising alarm bells for an aging population - death rates increase by age but do other accidental death rates, such as falling, increase faster? We don't know.) . Accidental death rates by cause are available as well. As a whole, the study starts with auto accidents being overall #1 cause (but not pedestrian/auto) of accidental deaths. Then makes a scary number for elderly pedestrian death rates but fails to rank it for the elderly group. That's pretty poor. Also, as it states, the study doesn't control for alcohol but uses cause of death on death certificates. "Vehicular assault" is not accidental and may vary by geography as to whether it's accidental or not. The study clearly indicates that there is a correlation to urbanization and that within those areas, the other factors correlate to each other. "Approximately three fourths of all pedestrian deaths in 2010 occurred in urban areas (3). Higher pedestrian death rates in urban areas are, at least in part, a result of more concentrated vehicle and pedestrian activity in these areas. The current study found that for many age groups and racial/ethnic populations, patterns in pedestrian death rates by level of urbanization were similar to those for overall pedestrian death rates" which seems to mean that for 3/4ths of all pedestrian deaths, race/ethnicity was not a factor and the differences appear when non-metro areas are factored in. --DHeyward (talk) 14:06, 3 December 2013 (UTC)

My first thought was the same as Medeis, i.e. it could have to do with being relatively more clustered into urban as opposed to rural populations. In the latter, you almost have to try to get hit. ←Baseball Bugs carrots→ 04:51, 3 December 2013 (UTC)

One might also check whether the death rate mentioned covers deaths in pedestrian–car collisions only or also caused by such collisions, and then consider the time and quality of medical service available to those injured. --CiaPan (talk) 06:36, 3 December 2013 (UTC)

Some thoughts:

1) As stated before, blacks tends to live in high density communities where car-pedestrian accidents are more common.

2) Also, blacks who live in such places are less likely to own a car, so more likely to be a pedestrian.

3) I have noticed, however, that there seems to be a black cultural habit of walking down the middle of the street, versus on the sidewalks. This seems to be particularly true of male teens. I even posted a question about that once on the Ref Desk.

4) I've also noticed a total lack of reflective clothing, although I suppose being able to hide from those who wish to do you harm, like the police, in some cases, might explain this. StuRat (talk) 07:53, 3 December 2013 (UTC)

The intro states that the highest death rates are native americans and those > 75 y/o. There needs to be lots of controls before assigning causative vs. correlative. In addition, there is no analysis of whether the differences are statistically significant. The study starts off with about 33,000 vehicle deaths and then states about 13% are pedestrian related. The biggest glaring hole that I see is that it fails to compare accidental deaths of pedestrians against other accidental deaths (i.e. trips/falls, drowning, etc). It's pretty bold to say that the aging population may suffer more pedestrian/auto deaths if it's dwarfed by trip/fall deaths or auto/auto deaths. Even though as a whole, auto/auto deaths are the leading cause of accidental death (and it doesn't even state whether they consider alcohol related deaths to be accidental or vehicular assault), the study doesn't seem to break down whether pedestrian/auto deaths are, as a whole, significant. Nor does it break down each group and identify whether pedestrian/auto deaths as a cause of accidental death is higher or lower than other causes. It's number 1 overall but even though it's a higher death rate for > 75 y/o's, it could be the 5th highest cause of accidental death for > 75 and trending lower as the cause of accidental death even while the rate goes up. There's a lot of inferences made that don't seem to have a rigorous mathematical underpinning of sampling statistics and correlations. --DHeyward (talk) 13:29, 3 December 2013 (UTC)

For people wearing dark clothing at night, against a dark background, it would make a difference for the distance at which one is first noticed. Weber's law and Ricco's law would be relevant. Weber's ratio seems to have the best correlation with detection distance according to this. Skin reflectance for different populations: African (Black) 5 - 10%, African (Pigmy) 10 - 15%, Indian (India) 15 - 30%, Iranian 20 - 40%, European 35 - 60%, source: Jablonski, N.G. and Chaplin, G., The evolution of human skin coloration. J Hum Evol 2000; 39: 57-106, quoted on a photography forum. Pictures like this or this suggest that when dressed in dark non-reflective clothing at night, the skin would be the most (or only) visible feature. In those circumstances white people would be detected at a greater distance than black people. And (available) time to react depends on detection distance. Same would apply to blond versus black hair when seen from the back. That doesn't mean of course that the difference in death rates are caused by skin color, we don't even know when these accidents happen, but the idea that skin color can affect visibility and therefore the risk at night seems quite reasonable. I doubt however that anyone has studied this, might be controversial... Ssscienccce (talk) 14:08, 3 December 2013 (UTC)

Just because something is controversial doesn't mean it hasn't been statistically studied. For example, the U.S. Army and the Marine Corps have determined beyond a reasonable doubt that these skin colors are the most difficult to see. Sort of a pixelated grayish green with brown and olive patches to break up the outlines... these patterns are not arbitrary; they are the result of a century of statistical testing on human perception. I'm sure we can find hundreds of papers listing variations on those experiments. In some cases, bright high-contrast colors and geometric shapes are more difficult to see. In any case, I think we can thoroughly discredit the idea that visibility due to skin coloration is the determining factor in automobile-pedestrian collisions. The studies that Nyttend actually linked to implore further research into other sociological factors to provide new explanatory variables. Nimur (talk) 14:21, 3 December 2013 (UTC)

More than once while driving at night, I've nearly hit white guys wearing dark clothes and not paying sufficient attention to traffic. Skin color isn't much of an issue, as you only see a small portion of their bodies. It's the clothing that's the problem. That's what a study should look at. ←Baseball Bugs carrots→ 15:13, 3 December 2013 (UTC)

I meant studies specifically looking at pedestrians being killed due to low visibility of their skin color: inadequate street lighting will be more prevalent in poor neighborhoods, so a study telling them their skin color is "to blame" might seem a bit cynical... Ssscienccce (talk) 16:58, 3 December 2013 (UTC)

That's another "obvious" claim with no basis in reality. The most well lit neighbourhoods I have ever lived in were black and Latino neighbourhoods in NYC and urban areas of New Jersey with low income residents. The most poorly lit were upper middle-class ones in rural-suburban South Jersey and at the Jersey shore. μηδείς (talk) 03:16, 4 December 2013 (UTC)

And I'm saying that for a given person, there's a lot more clothing visible than skin. So clothing is more likely to be a determining factor. Obviously, if a black person is wearing dark clothing, their odds of being seen are liable to decrease. But I'm also telling you, from experience, that a white person wearing dark clothes is also difficult to see. ←Baseball Bugs carrots→ 18:49, 3 December 2013 (UTC)

I was responding to Nimur, not you. And of course clothing is much more important, that's why every autumn we see safety campaigns with people dressed like glowstick adverts on tv. I didn't say white persons in black clothes are easy to see at night, I'm saying that skin color will make a difference in visibility level in some situations. I didn't say anything about it's relative importance. Ssscienccce (talk) 22:12, 3 December 2013 (UTC)

And that's why I always get off the street when a car comes along, even though my skin is light, since most of my cold-weather clothes are dark. Since rural and suburban residents are more white than urban residents, I figured that the sidewalk factor might be a big issue: most streets in urban settings are accompanied by sidewalks, unlike many streets/roads in suburban and rural settings, and many of those suburban or rural thoroughfares are lit only by the moon and the stars, so place of walking and quality/quantity of street lighting aren't purely a problem for the urban resident. For example, I know a woman whose father was killed while running along a Kansas farm road in the 1970s, because of factors other than visibility; of course that incident might only be anecdotal, but non-visibility factors such as simple inattentiveness would definitely need to be controlled for the kind of study I was envisioning. Nyttend (talk) 01:15, 4 December 2013 (UTC)

How can we characterize the quality of OECD data on working hours vs productivity?

Recently on the Humanities Reference Desk, this relation between hours worked per year and productivity from an article in The Economist was called "low quality." While there do appear to be bifurcated strands along the same trend, I am not sure I would call such a correlogram particularly low quality. What do Science reference deskers say? EllenCT (talk) 08:28, 3 December 2013 (UTC)

The Economist article linked to this paper that found the same result from a totally different data set. The paper formally reviews their data collection and processing, including the statistical significance of their conclusion. It seems that we can't realistically attack this correlation by attributing it to poor data, nor to poor methodology, nor to statistical insignificance. A complete run-down of the statistics in that paper rule out several confounding factors, and make a strong case for the significance of the correlation (which they term the "elasticity" of hours worked versus compensation rate). From a purely statistical point of view we can confidently say that this correlation is strong, it is significant, and it emerges from multiple different data sets. So, if we want to maintain a scientifically valid standpoint, we should seek a causal explanation for the data.

The authors provide four plausible causal hypotheses, and because they are behavioral economists, they have a preference for a behavioral explanation: the workers are choosing to end their days early when they earn well; they have a fixed income target. I am more inclined to believe their liquidity-constraint hypothesis, based on my personal experiences; but the authors provide compelling counter-evidence by showing that high-capital laborers exhibit the same behavior as low-capital laborers.

I think the most critical point might be that productivity, as defined by the OECD and most other economists strictly refers to economic productivity: activity that has monetary value. That may differ from your intuitive notions about productivity. The next time you pull long hours at school or at your job, you might be working very hard, and you might even be making progress toward some end goal. But consider, for a while, whether your activity is productivity as an economist sees it: are you measurably increasing the GDP ?

Nimur (talk) 13:44, 3 December 2013 (UTC)

In that topic someone said "the data quality is likely to be poor", claiming that in his industry the nominal number of hours was 1620 while the actual number was about 3000. According to OECD Measures of Total Hours Worked, "in many countries actual hours are derived from establishment surveys for production and non supervisory workers in employee jobs and from labour force surveys (LFS) for self-employed, managers and supervisory workers, farm workers and public sector employment. Hours lost due to sickness are estimated from the number of days not worked from social security registers and/or health surveys..."

Germany recently revised its system to better account for workers with few hours, France is now excluding short rests and work breaks from the total (which is contrary to the guidelines)...

Labour force surveys seem to overestimate the number of hours worked and underestimate the hours not worked due to holiday, vacation, sickness, maternity leave etc.. the difference with establishment-based surveys was 1 to 3% (in France, Germany, Netherlands and Switzerland). 3% won't make much of a difference to the graph.

The data may not be totally accurate, but it's likely the best data available. Ssscienccce (talk) 20:23, 3 December 2013 (UTC)

2011 Tōhoku earthquake and tsunami.

Was it the largest in Japan? The 869 Sanriku earthquake was believed to could have been around 9.0. Applies to Japan. --78.156.109.166 (talk) 10:20, 3 December 2013 (UTC)

The earthquake was the largest in the vicinity of Japan since recording began. It's impossible to say whether there were larger quakes earlier. Note though that the Tohoku quake had its epicenter well offshore. The shaking on the mainland lasted for a long time but was not all that intense. There have been many quakes that caused more intense shaking at points on the mainland, and more severe shaking-related damage. The damage from the Tohoku quake was mainly due to the tsunami rather than the shaking. Looie496 (talk) 17:07, 3 December 2013 (UTC)

How much damage/casualties from the quake? --78.156.109.166 (talk) 19:52, 4 December 2013 (UTC)

Sex determination by the father?

Do "normal healthy" human males produce 2 kinds of sperm, one kind that results in male children and another kind that results in female children? (option A)

Or do "normal healthy" human males produce 1 kind of sperm that can result in either male or female children, depending on something else? (option B)

If the answer is A, are there conditions in which some men only produce one kind or the other? In other words, are there some men who can only have sons or only have daughters?

If the answer is B, what are the main things that determine whether child is male or female?

Thank you, CBHA (talk) 18:09, 3 December 2013 (UTC)\

The father is the sex-determinant of the child. It has to do with whether a given sperm cell has the X-chromosome or the Y-chromosome. And of course there are gazillions of sperm cells in a given "batch". I'm sure there is a great deal of info here. Try gamete for a start, and see where it leads. ←Baseball Bugs carrots→ 18:47, 3 December 2013 (UTC)

For the most part, "the sex-determinant of the child" is not so much the father, as it is random chance. Yes, the winning sperm is the one that determines the child's sex, but the father as such has very little influence over which sperm "wins". --Trovatore (talk) 21:16, 3 December 2013 (UTC)

Sure it's random, for the most part. I didn't say the father had a choice. But he's still the biological determinant of the child, as opposed to the mother, who isn't. ←Baseball Bugs carrots→ 00:19, 4 December 2013 (UTC)

Well, no, sorry, that's wrong. The father is not the biological determiner of the child's sex. Which kind of sperm happens to win, that's the determiner, but not the father. --Trovatore (talk) 07:49, 4 December 2013 (UTC)

The problem is a linguistic one. That is, 'determines' means different things to different people. To many it sounds like a synonym for "chooses", as in "I will determine which movie we see". In that interpretation of the word, the father does not "determine" the sex of the offspring. StuRat (talk) 09:47, 4 December 2013 (UTC)

(EC) As described in the Spermatozoon article, human males produce two kinds of sperm cells: some contain a Y chromosome, which will produce a boy, and some contain an X chromosome, which will produce a girl. I can't find any condition that results in a man only producing one of the two types of sperm cells. But see Human sex ratio#Factors affecting sex ratio in humans. Red Act (talk) 18:52, 3 December 2013 (UTC)

Males have two sex chromosomes, an X and a Y. Sperm cells are the result of meiosis, a process involving cell division, where one cell will get the Y chromosome and the other the X chromosome. These cells split again to create four sperm cells, two with X and two with Y. So a man should produce the same number of X and Y sperms. Ssscienccce (talk) 19:28, 3 December 2013 (UTC)

One thing I looked into is whether an aneuploidy involving a lack of an X chromosome could produce a man who could only father boys. However, according to Aneuploidy#Types, having no X chromosome is lethal. Red Act (talk) 20:47, 3 December 2013 (UTC)

Thank you all. Followup question - are there "factors" in the female (chemistry for example) which differentially affect sperm? Ie, that make it more likely that a particular woman would have male children or female children even though the sperm she received had a 1-1 sex ratio? CBHA (talk) 22:08, 3 December 2013 (UTC)

There was a brief splash made back in the Seventies or so (update: actually Sixties) when some researcher claimed he had a method of making a boy or girl more likely, depending on parent preference, based on the pH of the woman's system. He claimed that an acidic environment was hostile to all sperm, but that the X sperm were tougher and more likely to survive it, so an acidic environment favored girls and an alkaline environment boys (because the ratio is not in fact 1–1; it's actually about 2–1 in favor of Y sperm, if I remember correctly). Here it is: Shettles method. It appears that it is not now considered to work. --Trovatore (talk) 22:14, 3 December 2013 (UTC)

And see also Sex selection. The only preimplantation methods which are known to work I'm aware of, and mentioned in our article, are those which involve artificial insemination or in vitro fertilisation. in other words, any method which is supposed to use sexual intercourse for conception has no evidence of working. Note that while controversial, there is a fair amount of interest in sex selection particularly male selection in certain cultures, so there is some degree of research. So for many popular methods, there's a fair chance the is something which has shown the method may not work (or alternatively it may be there's good reason to think it won't work even without research). (You can of course use post conception selection with sex but that's even more controversial and doesn't seem to be what the OP is getting at.)

And there any plenty of supposed natural methods , many even more junky than Wheelan or Shettles .

Incidentally the sperm sorting methods could provide a clue as to what could potentially work. However the methods known to work and even some that don't appear to are not the sort of thing you can expect to emulate. Of course as with most things, this sort of research gets confusing. As per the prior link, there's some evidence sorting via the Ericsson method doesn't actual achieve any sort of specific sex sperm enrichment, but there's also some evidence (as per our article) it produces a non expected sex ratio at birth. (Sperm sorting is also of strong generally uncontroversial interest for use in non human mammals. While there's no guarantee these methods will cross over and methods which may work in humans may not work for other mammals particularly somewhat more distantly related ones like cows but it's another area of research or relevance.)

P.S. For completeness I should mention I believe there is some evidence the sex ratio varies depending on the health of the mother . This could be pre implantation or post implantation or both. I think most think it's more likely to be predominantly post implantation (with at least some degree perhaps even most being non concious factors). But even if there is some degree of pre implantation causation, I don't think many would seriously suggest starving the mother for a minor change in the sex ratio.

Nil Einne (talk) 23:02, 3 December 2013 (UTC)

Maybe. See Maternal influence on sex determination. Red Act (talk) 23:20, 3 December 2013 (UTC)

There is related information at http://www.boygirldiet.com/index.htm.

—Wavelength (talk) 23:26, 3 December 2013 (UTC)

Very interesting, though I'm not sure that's a WP:RS, let alone authoritative. I make no judgment, just flagging for propriety :) SemanticMantis (talk) 00:41, 4 December 2013 (UTC)

To answer the original question, there are chromosomal karyotypes that result varying chromosomal counts. See Klinefelter syndrome for description of the most common anomaly. I don't know how often that karyotype produces viable sperm or what the M/F ratio might be. --DHeyward (talk) 09:36, 4 December 2013 (UTC)

Best breeding age for human females

After what age does the offspring become likely to be genetically bad? At what age should the femaile be impregnated and by what age male to insure the child is genetically fit? — Preceding unsigned comment added by 74.14.28.186 (talk) 21:15, 3 December 2013 (UTC)

It's a sliding scale for the probability of Down's syndrome, for example. But even young, healthy mothers frequently have miscarriages. There may be an optimal age range for carrying children, but there are no guarantees. ←Baseball Bugs carrots→ 00:22, 4 December 2013 (UTC)

Your heading only says "Best breeding age" while your question only refers to genetics. As Teenage pregnancy says, there are other problems with young mothers. I suspect (don't know) that if we only look at genetics then younger is generally better. Other health factors are more important when you for example go from 20 to 13, so I don't recommend the latter. PrimeHunter (talk) 01:08, 4 December 2013 (UTC)

Constrictor snakes' skin

We've all seen the discussions of the ways by which constrictor snakes are sometimes able to swallow large prey, e.g. the goat or deer pictured here. But what about their skin? How does the skin stretch to facilitate a temporarily far larger snake? How doesn't it just tear in pieces and kill the snake by blood loss? Force an adult human into children's clothing and you'll up with little bits of torn cloth; since the snakes eat much too fast for the skin simply to grow big enough to accommodate the large prey, I don't see the difference. After all, a hungry constrictor snake doesn't have massive amounts of extra skin, which one might initially imagine as the expansion mechanism. Nyttend (talk) 23:17, 3 December 2013 (UTC)

Here's a start, it's all about the collagen structures. Here's a paper "Mechanical behaviour of snake skin", that says

(emphasis mine). As usual, just ask me (or at WP:REX) if anyone needs access to the full paper. My understanding is that comparing snake skin to human, with respect to ductility and elasticity (two different kinds of "stretchiness") is (somewhat) analogous to comparing different weaves or knits of the same fiber -- they can have vastly different mechanical properties, even though they are (mostly) made of the same stuff. E.g. most cotton sweaters can stretch much more than cotton T-shirts, even though they are both made of cotton. Things like gauge of the yarn, and pattern of weave, have a huge effect! SemanticMantis (talk) 00:34, 4 December 2013 (UTC)

• Keep in mind that the scales we see are not the skin itself, but overlapping (for the most part) and embedded in it. The skin itself resembles chicken skin. If a snake swallows a large meal, the scales go from overlapping to widely separated.

• Using the clothing analogy, we could design clothes that could expand that much, using elastic, pleats, etc. StuRat (talk) 10:23, 4 December 2013 (UTC)

December 4

Lagrange's equilateral triangle solution

I've tried googling but with no luck- what are the conditions on the initial velocities / masses for Lagrange's equilateral triangle solution to the three body problem? 68.0.144.214 (talk) 00:05, 4 December 2013 (UTC)

Lagrange points L4 and L5 - those which are described by an equilateral triangle whose base is the line between n₁ and n₂ - have no constraint on mass of n₃. In the rotating frame of reference, there is no net velocity; equivalently; the velocity of the L4 and L5 points is the orbital velocity of n₂ about n₁. If you're looking for Lagrange's actual mathematics, you can find the link in our article on Lagrangian point: Essai sur le Problème des Trois Corps. Lagrange's notation is actually almost identical to the sort of modern differential equations I used in university - so his work is a lot easier to read than, say, that of Isaac Newton - except, of course, that you need to be fluent in French. He sets up the equations for constant angular offset in Article XLII ("Page 308" in the PDF file); and also in Article XXV: Ainsi les Corps B et C ne feront que tourner autour du Corps A avec vitesse angulaire constante et égale à ${\displaystyle {\sqrt {\frac {A+B+C}{r^{3}}}}}$. Granted, this is a little bit more obtuse than stating "L4" and "L5" outright, as you will find in a modern physics book; but if you really get the points, you probably don't need to enumerate the points. Nimur (talk) 01:33, 4 December 2013 (UTC)

Awesome answer, thanks Nimur! SemanticMantis (talk) 02:25, 4 December 2013 (UTC)

Hm, ok. Are there configurations with non-zero velocity that maintain the equilateral triangle while the distance between the three bodies changes? 68.0.144.214 (talk) 03:41, 4 December 2013 (UTC)

Not quite, but the horseshoe orbit is an almost stable orbit around L4 or L5 that has a non-zero relative angular velocity between the second and third bodies: as the angular distance varies, the leg lengths of the triangle also vary and are not equilateral. It is not possible to thus maintain an equilateral triangle: varying the velocity changes the distance between n₂ and n₃ - that implies that you are varying all the leg lengths; that would change the orbital radius of the second body, but not in a stable way. The radial period can not be resonantly locked with the orbital period of n₂ and n₃: as you set up your scenario, they have different velocities! The resulting behavior would be a non-stable orbit and proceed in a chaotic way. The system would rapidly decay into unstable motion. You can develop an intuition about the metastability of these orbits; there are actually very few stable 3-body configurations, even in an ideal system. Nimur (talk) 04:03, 4 December 2013 (UTC)

Twins

Do identical twins (or triplets, etc.) have DNA that is exactly identical? Or is it somehow different? Also, do identical twins (or triplets, etc.) have distinct fingerprints or identical fingerprints? Thanks. Joseph A. Spadaro (talk) 05:38, 4 December 2013 (UTC)

Identical DNA. Identical fingerprints. HiLo48 (talk) 06:25, 4 December 2013 (UTC)

No, they do not. The process that creates fingerprints is not determined by genetics. Even identical twins have distinguishable fingerprints. See http://www.straightdope.com/columns/read/1277/do-identical-twins-have-different-fingerprints for reference. Someguy1221 (talk) 06:30, 4 December 2013 (UTC)

No they don't. See Fingerprint. It's rather disturbing that a reference desk answer with no citation would contradict a WP article. Identical twins do not have identical fingerprints. If HiLo48 has a source that contradicts the article s/he should update it. If s/he doesn't, s/he shouldn't guess. --DHeyward (talk) 06:36, 4 December 2013 (UTC)

Sorry. No source. Just mistaken confidence in my knowledge. HiLo48 (talk) 07:12, 4 December 2013 (UTC)

It's also not true that twins have identical DNA. In fact, due to mutation, a random pair of twins probably don't. See , which found that the average pair of twins have 359 genetic differences that occurred early in development. (Mutations that occur late in development would only be shared by a small fraction of the twin's cells.) --Bowlhover (talk) 07:43, 4 December 2013 (UTC)

However, that's a very small portion of the total, so, if your evil identical twin kills somebody, and they compare his DNA from the murder scene with your own, they might very well declare it a match, unless you can prove you have an identical twin and they then do more detailed DNA testing. StuRat (talk) 10:18, 4 December 2013 (UTC)

stingless bees finding their hive

Note this curious detail in an article today on our local stingless bees in the Sydney Morning Herald"

"They can find their way back to the hive if it is moved less than a metre or more than a kilometre, but anything in between means some bees will never find their way home."

http://www.smh.com.au/environment/animals/no-sting-in-this-tale-of-homely-bees-20131203-2yoq7.html

I am trying to figure out how that could possibly be. (Note, downside of our indigenous stingless bees - a hive produces half a kilo of honey each year.)

From same article:

"For most Australians the only connection they have with insects is from the wrong end of a spray can."

Is this arse-about? If there is a "right end" of a spray can, surely it is at the end where you push the button, not the end which where the target of the spray is.

Whether it is arse-about depends on your point of view. But the article seems to be rubbish anyway. Given the methods bees use to get back to the hive (they sense the polarisation of light from the sky to get general direction, and then use landmarks to localise on the hive), it is reasonable to expect bees to be tricked by moving the hive perhaps a few metres, but unreasonable to expect them to somehow recover their ability to find the hive if it is moved a larger distance. I have kept bees myself, and have found that moving the hives a few metres is not a problem - however I had 4 hives in a group in an open area at least 20 metres form any tree or structure. So they had to 1) find their way back to the clear area, and 2) pick which of the 4 hives is theirs. Quite a few Australians have more contact with insects than as something to spray at. Red Back spiders, very poisonous, infest toilets, garden sheds, and other structures that have a fair bit of ventilation to outside air. Squirting them with flyspray can make them struggle about as though drunk, and then they recover. I squirt them with CRC - that imobilises and suffocates them. And CRC is nowhere near as harmful to humans as poisons designed for spiders. Many Australians live in old suburbs in old houses built with wooden floors (houses built in the last 40 years or so mostly are brick with concrete floors and are easy to keep cockroach-free). These tend to be infested with cockroaches, which require treatment by a pest exterminating company (while you stay in a hotel for a few nights, or get it done before you move in) to really get rid of. Then there are wasps that crawl into your can of beer or soft drink while you are not looking. In areas close to fresh water, mosquitoes are a nuisance - anit-mosquito burners & candles are best for them. 1.122.59.94 (talk) 06:59, 4 December 2013 (UTC)

Without commenting on whether the statement is correct, I could propose a reason why that might not be able to find the hive after a moderate move. It could be that they have two distinct detection methods, one short-range and one long-range. The short-range method would be used normally, while the long-range method might be used to find the hive if it needed to be moved in an emergency (perhaps a fire), where presumably they would move it a good distance. What could this long-range location system be ? Perhaps smell ? In this case, if they were too close to the old hive, it's smell might overpower the scent of the new hive, since it seems more familiar, so they would need to move outside the range where they could smell the old hive to detect the new one. StuRat (talk) 10:14, 4 December 2013 (UTC)

The only interpretation I can think of that seems to make sense is that if you move a hive, with the bees inside(!), to another location nearby, once a bee comes across a place she "knows" she will take the route home she remembers best, which is the one to the old location. That can't happen if you move the hive far enough so the old and new foraging areas don't overlap; the old memories can't override the new route she learned. I guess for small displacements the hive could be found by accident and the bees would take the new route eventually, but the number of bees lost would increase with distance; and likewise when the areas overlap only slightly, you'd only lose the ones who happen to wander into the old territory. Ssscienccce (talk) 12:36, 4 December 2013 (UTC)

I think you're more or less right. See which while not an RS, says something similar. If you move more than a metre but less than 500 metres or so, their homing instinct will bring them back to the old location so they will never find the hive (during previous foraging, they would have learnt the old routes to return). If you move more than 500 metres or whatever, this is further than they ever normally forage so they will I guess learn the new foraging routes (having no old routes as reference) and generally return to the new location. This must be referring to bees inside the hive, bees outside will still I presume return to the old location. Nil Einne (talk) 19:44, 4 December 2013 (UTC)

At the risk of being accused of being pedantic, Red Back spiders are not one of the insects come into contact with. Bazza (talk) 13:09, 4 December 2013 (UTC)

I don't understand that comment, but in any case let me give a pointer to our Redback spider article. Looie496 (talk) 15:46, 4 December 2013 (UTC)

I think despite the extremely confusing indenting and location, Bazza is replying to our resident banned Perth engineer with many names, and pointing out that Red back spiders are arthropods but not generally considered insects. Therefore not one of the insects Australians or anyone else ever come in to contact with, whether on the wrong/right end of fly spray or in some other fashion. Nil Einne (talk) 19:48, 4 December 2013 (UTC)

Skin wearing thin during writing

I'm left handed and when I write for an extended period of time, the skin of my middle finger which interfaces with the pen seems to wear thin and it becomes uncomfortable to write. Does this happen to everyone or do most people get calluses? Is it related to left-handedness (I guess I'm pushing the pen rather than pulling it)? It's not really a medical problem so I couldn't justify wasting my (NHS) GP's time but I might ask next time I'm there, not that I'd expect he could prescribe anything or even have anything insightful to say. I remember it bothered me at school but I just assumed everyone was the same. ----Seans Potato Business 12:20, 4 December 2013 (UTC)

My suggestion would be a pen with a soft grip. This can be more comfortable. Also, I think larger diameter pens might be better. Perhaps the larger diameter pen distributes pressure over a larger area of interface between pen and fingers resulting in lower pressure per square unit of contact. Bus stop (talk) 12:32, 4 December 2013 (UTC)

Those would be my suggestions as well. I know the phenomenon, although it was a long time ago. Also, adding some kind of anti-slip material would likely lower the amount of force you're using to hold the pen: This study suggests that a lower-level neural mechanism adapts the force used by each finger to the surface condition under that finger, a sort of anti-slip strategy. When lifting an object by a handle that had a different surface for every digit, each finger applied the amount of pressure and force that assured a stable grip on that specific surface. So it's likely that people unconsciously apply more pressure when holding a pen that is smooth and relatively "slippery". Ssscienccce (talk) 13:55, 4 December 2013 (UTC)

Don't know if there's a medical term for it, people get calluses from writing and blisters from more intensive friction/irritation. I think it's somewhere in between the two, too much friction/rubbing/pressure/irritation for a callus, to little for a blister... Ssscienccce (talk) 14:14, 4 December 2013 (UTC)

Will light inhibit dark dependent flowering once it's beun?

I have some poinsettias I deadheaded, grew outside over the summer, and rebloomed from last year by bringing them in as the season darkened, around Oct 1. One of them is in "full bloom" (it doesn't have actual flowers yet, but the bracts have changed color richly.

If I bring the poinsettia into an environment where it's on show, but gets low and irregular artificial light when it's dark outside, will this inhibit further blooming? Thanks. μηδείς (talk) 20:58, 4 December 2013 (UTC)

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