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July 27

Synthesis of ZnS

I'm trying to make some zinc sulfide for an experiment that I'm doing. I'm using the following reaction:
$ZnSO_{4}(aq)+Na_{2}S(aq)\rightarrow ZnS(s)+Na_{2}SO_{4}(aq)$
At first I didn't bother weighing out stoichiometric amounts since I'm not interested in the yield or anything, so I just mixed the two solutions together, filtered out the precipitate and washed it a few times to remove any remaining reactants and the sodium sulfate and then dried it in a dessicator at room temperature. The result looked like brown sugar, and not at all like the white solid described in the wikipedia article. So, I tried weighing out stoiciometric amounts and washing very thoroughly with hot deionised water, but again, I'm getting dark coloured crystals that don't seem to be very pure. Also, when mixing the two solutions in the first place, I can smell hydrogen sulfide. That indicates to me that I'm not going to have the stoichiometric amount of sodium sulfide present anymore, but the excess zinc sulphate is so water soluble I figure it should easily wash out. Any ideas what's going on here? 203.27.72.5 (talk) 02:32, 27 July 2012 (UTC)

Your sodium sulfide could easily lose some H2S and become more alkaline, so you may have precipitated some zinc hydroxide. If you had sodium hydroxide you can get sodium zincate. in Qualitative inorganic analysis ammonium chloride, ammonium hydroxide, and hydrogen sulfide gas gives a white precipitate with a zinc solution. If you have lead it will be brown or black, and if it is cadmium you will get yellow precipitate. Graeme Bartlett (talk) 12:03, 27 July 2012 (UTC)

I've actually bubbled H₂S through a solution of ZnSO₄ before to make a white precipitate of ZnS (at least I figure that' what it must have been), but the particles were so fine I couldn't filter them with the filter papers I have here; so what does the ammonium chloride and ammonium hydroxide do in that analysis? I've done a similar thing with lead to make PbS which was black as you said and the particles were easy to filter out. For that I used a ferric chloride solution to get the lead to dissolve.

If the impurities are zinc hydroxide and sodium zincate then they're probably not going to interfere with the rest of my experiment anyway. I'm developing a method to distinguish between sulfate and sulfide in ore. The idea is that if I add conc HCl to my sample of ore and heat it to dryness, then any sulfates will remain in the residue but any sulfides will be lost as H₂S. I'm just trying to confirm with pure ZnS that essentially all of the sulfur will be lost as H₂S, and then I want to do the same thing with ZnSO₄ and PbSO₄ to show that sulfate remains. 203.27.72.5 (talk) 23:47, 27 July 2012 (UTC)

You should buy it pure instead. Is there any reason you can't or don't want to? The reaction you've chosen is fraught with practical difficulties and side reactions. 207.224.43.139 (talk) 21:23, 28 July 2012 (UTC)

I'm at remote mine site, so shipping bought products takes weeks and I want to do my test work a fast as possible. 203.27.72.5 (talk) 22:17, 28 July 2012 (UTC)

Don't ask Wikipedia how to do your job. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:27, 28 July 2012 (UTC)

I'm not sure of the wisdom, but it's allowed if you're not a physician or an attorney.

Everyone has the right to be stupid, but where one's stupidity might kill or seriously injure others, as in mining, stupidity is less acceptable. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:48, 28 July 2012 (UTC)

Consulting a encyclopaedia or library reference desk when doing my job in entirely appropriate. And I'm doing a lab scale experiment in a 500mL beaker, not designing a 400 cube reaction vessel. I'm also qualified to interpret the answers according to a couple of universities. 203.27.72.5 (talk) 23:52, 28 July 2012 (UTC)

Zinc sulfide#Laboratory preparation suggests combustion. Will that work? If not, see if you can get [1] at WP:RX, as long as you use it to expand that section of that article. 207.224.43.139 (talk) 22:36, 28 July 2012 (UTC)

Finely powdered zinc and sulfur do "burn" releasing plenty of heat when they react. I have seen it used as a rocket fuel. Graeme Bartlett (talk) 23:40, 28 July 2012 (UTC)

I don't have any pure elemental sulfur, ethylenediamine or triethanolamine, so I can't do any of that. I looks like I've managed to get reasonably pure stuff using my above method by controling the pH. The assay is 31.9% S and 67.5% Zn which is close enough for me. 203.27.72.5 (talk) 23:52, 28 July 2012 (UTC)

Resolved

Sun

When did people find out that the Sun was a star? 71.146.10.213 (talk) 05:34, 27 July 2012 (UTC)

There's some good content at Star#Observation_history. Basically, the idea that stars were just far away suns is as old as ancient Greece, but was not a popular until the 18th century. It would not be until the 19th century that spectroscopic data was available to really study stars in any detail beyond their motions. Someguy1221 (talk) 05:42, 27 July 2012 (UTC)

Thank you. 71.146.10.213 (talk) 20:12, 27 July 2012 (UTC)

Follow up. Can our scientific knowledge be understood any other way than it is? 2

What if the equations of physics were formulated from the perspective of a single quark? Would they be recognizable?GeeBIGS (talk) 05:50, 27 July 2012 (UTC)

Physicist George Gamow wrote a series of books that elucidate the recognizable and unrecognizable effects of physics, using unlikely hypothetical scenarios where relativistic and quantum-mechanical effects would have observable and macroscopic effects. If I can nitpick the books - the consequences of changing the speed of light or the Planck constant were not followed through to their logical conclusions; in the story-books, these effects were isolated only to certain observed phenomena, as opposed to affecting everything - but altogether, the stories help you stretch your mind a little bit, as far as thinking about fundamental interactions. Nimur (talk) 06:03, 27 July 2012 (UTC)

You can look right now at the various formulations of existing theories, and they can be made to look completely different. Take for example Hamiltonian mechanics, Lagrangian mechanics, and classical mechanics. Or for that matter, the differential and integral forms of Maxwell's equations (there are also Hamiltonian Maxwell's equations, but I can't find an article on them). In the case of the first three and the second two, you have the exact same laws written from different perspectives. Without the necessary mathematical training, they look like completely different physics. But what you will find, however, is that while each form makes different problems easier to solve, they make identical predictions. And so while you could reformulate the Standard model of physics from "the perspective of a single quark" (not entirely sure what that means), if you do it correctly it will make the exact same predictions as the normal formulation, even if the equations are unrecognizable. Someguy1221 (talk) 06:21, 27 July 2012 (UTC)

Also to continue the previous thread.... Just substitute a very useful and recent discovery with a very useful yet old discovery and see what would and would not have been possible.GeeBIGS (talk) 06:30, 27 July 2012 (UTC)

You can change the perspective of practically every equation and end up with the same results. By itself that isn't very philosophically interesting — there are lots of cases where two different approaches to physics give exactly the same outcome, because ultimately they are both different ways of describing the same thing. (The Nobel Prize in Physics for 1965 was to three people who came up with three different ways of describing the same thing, which all turned out to be physically equivalent. Maxwell's Equations, as written up by Heaviside, look quite different than when they were written originally by Maxwell, though they give the same physical results. There are many such examples in the history of physics.) An obvious, straightforward approach would be the differences in describing orbits using traditional Cartesian coordinates or by using orbital elements; two such descriptions of the Moon's orbit would look superficially quite different but, when you know what everything means, clearly describe the same thing. The only interesting bit to this, in my view, is that it highlights that the math itself is hardly canonical — at best, it is just a form of formal description for physical reality, but there are many ways in which even the math can be differently expressed. --Mr.98 (talk) 13:48, 27 July 2012 (UTC)

Spider identification needed

I'm in the UK, just found a spider which I've never seen before. It's about 13mm leg span, body about 6mm long. Colour is white-very pale green with a red patch on its back. Unfortunately my camera isn't up to macro work otherwise I'd have taken a picture. Any ideas as to which spider this is please? Mjroots (talk) 07:13, 27 July 2012 (UTC)

Was it in a web? 203.27.72.5 (talk) 07:43, 27 July 2012 (UTC)

Based on your description, I would suggest that it could be either a Tibellus or a a recently moulted Diaea dorsata. 203.27.72.5 (talk) 07:51, 27 July 2012 (UTC)

Definitely not a tibellus, they aren't native to UK. Diaea dorsata is a distinct possibility though. Mjroots (talk) 09:51, 27 July 2012 (UTC)

According to [2] and [3] they are in the UK. I don't know if they're native or introduced though. 1.124.170.168 (talk) 10:14, 27 July 2012 (UTC)

Other possibilities:

• Flower spider (Misumena vatia) - females can change colors from bright yellow to pale green, and they have red stripes at the sides (sometimes absent). Note that it's a crab spider like Diaea dorsata.
• Candystripe spider (Enoplognatha ovata) - females about the same size, translucent green or white, usually with two red stripes on the abdomen
• Green huntsman spider (Micrommata virescens) - males are green with red/white abdomens
• Cucumber spiders (Araniella cucurbitina, Araniella opisthographa, etc.) - both very similar, body usually pale green, dorsal surface of abdomen has pale stripes making it look like a cucumber (sometimes absent), identifiable by red spot on the spinnerets

If it's not the above. Did it resemble any spider you do know, e.g. orbweavers, wolf spiders, jumping spiders, crab spiders, lynx spiders? -- OBSIDIAN†SOUL 17:39, 27 July 2012 (UTC)

Latent heat

I read the statement "Latent heat of vapourisation of water has higher value than latent heat of fusion of ice". Why is it so? Sunny Singh (DAV) (talk) 15:01, 27 July 2012 (UTC)

This link should explain it for you. Tombo7791 (talk) 15:23, 27 July 2012 (UTC)

It seems intuitive that boiling water, which requires breaking surface tension, would take more heat input than just melting it. μηδείς (talk) 22:24, 27 July 2012 (UTC)

Is the volume of solid ice at 0°C greater than liquid water at 0°C? If so that's negative work being done which will further decrease the energy requirement. Obviously, water at 100°C has a much smaller volume than steam at 100°C, that accounts for a large proportion of the latent heat of vapourisation. 203.27.72.5 (talk) 23:22, 27 July 2012 (UTC)

We should be able to do better than the linked article provided by Tombo. It has 2 answers: the first does not actually answer the question - it essentially just says the vaporisation heat is greater because it's greater. The 2nd part seems to answer it, but not very clearly. I think the author is implying that to go from solid to liquid, inter-molecular bonds are reduced, but to get to a gas, all bonds are subtantially eliminated.

It should be noted that while latent heat of fusion is in practical terms independent of pressure, latent heat of vaporisation varies with pressure, being maximum (= 42.8 MJ/kmol, about 6.5 times the latent heat of fusion) at the triple point pressure (0.617 kPa), and zero at the critical point (22064 MPa). This reduction to zero latent heat at the critical point would be reasonable to expect, if, as pressure rises, the vaporisation/boiling temperature increases - and at the critcal point temperature (647 K), heat absorbed by thermal capacity was equal to the latent heat of vaporisation at the critical point. Actually, its a good bit less, 36.2 MJ/kmol. However, fundamental to the OP's question is why the latent heat of vaporisation at the triple point is the comparitively large positive value that it is. So why is it? Surface tension seems to be a key, as surface tension decreases as temperature increases (does it smoothly become zero at the critical point temperature?). Volume occupied seems not involved, as specific volume at the critical point is most certainly NOT infinite. Ratbone58.169.250.134 (talk) 05:04, 28 July 2012 (UTC)

I'm not sure what you mean about the specific volume not being infinite at the critical point. I'm not great at thermodynamics, but maybe you could explain it in terms I understand. It seems to me that when you take 0.018L of water and turn it into 22.4L of steam you've done some work to push back the atmosphere. When you take 0.018L of ice and turn it into ~0.018L of water, the work done is either very low, zero, or slightly negative. So doesn't that account for some of the difference between the heat of fusion and the heat of vapourisation? 203.27.72.5 (talk) 06:05, 28 July 2012 (UTC)

As every expert, teacher, and self-proclaimed whizz has said as least once when caught out with telling a complete nonsense, I was just testing you.... Of course, specific volume is not the key, but the change in specific volumes upon vaporisation is a key. At the tripple point, the change in specific volume is maximum, smoothly decreasing to zero change in specific volume at the critical point. It's the change in specific volume that means work done on the surroundings, as W203.27.72.5 has said. But, as he indicated, that only accounts for part of the change in heat of vaporisation from the triple point to the critical point, as a glance at a temperature vs internal energy loop chart will show. Ratbone120.145.22.128 (talk) 10:45, 28 July 2012 (UTC)

Even after this discussion I don't get a simple answer of my question. Will you please make it more clear? Sunny Singh (DAV) (talk) 13:18, 30 July 2012 (UTC)

Partly because for vapourisation you have to overcome the surface tension of water for the molecules to escape as a gas whereas for melting you don't, and; partly because for vapourisation you have to do significant work pushing back the atmosphere in order to increase the volume of water to that of steam whereas for melting the volume is about the same. 203.27.72.5 (talk) 20:27, 30 July 2012 (UTC)

Calculate properties of chemical compounds given the properties of chemical elements

Given some chemical elements, why do you have to perform a real life experiment to discover the properties of a derived chemical compound? Couldn't you just calculate (almost) everything in a kind of chemical CAD on steroids? Where does the unpredictability comes from? OsmanRF34 (talk) 16:02, 27 July 2012 (UTC)

It depends on the elements, number of atoms, and their arrangement in the molecule (i.e., "what specific derived chemical compound?") and the properties (and accuracy and precision of them, i.e., "what do you want to know about it?") of interest. Some are easily doable, some are easy to approximate, some are possibly doable but have many known exceptions/mismatches vs reality especially depending on computational power, some are fairly hopeless to get anything much better than a wild guess or mental approximation based on other knowns. DMacks (talk) 16:09, 27 July 2012 (UTC)

But, is our knowledge about properties of elements accurate and definitive? Or is it something like decimal places of Pi, which can be always expanded? OsmanRF34 (talk) 17:38, 27 July 2012 (UTC)

Again, it depends on the elements and properties of interest. DMacks (talk) 18:38, 27 July 2012 (UTC)

I suspect that even if we did have a formula or a simulation to predict the melting point of a novel compound, the requisite computing power to carry out the simulation would be greater than all such power available on the Earth. Someguy1221 (talk) 19:08, 27 July 2012 (UTC)

See protein folding and protein structure prediction. μηδείς (talk) 21:48, 27 July 2012 (UTC)

In principle it all follows from quantum mechanics. The bound state of atoms forming a particular molecule is a particular eigenvector of the the Hamiltonian, the eigenvalue is the energy of the bound state. The properties referring to the dynamics of the molecule follow from the enitre spectrum of eigenvectors and eigenvalues. In practice when doing such first principle calculations, elaborate approximation techniques have to be used, such as the Density functional theory. Count Iblis (talk) 22:09, 27 July 2012 (UTC)

And to follow on from Count Iblis, since you can't exactly solve the quantum mechanical Schroedinger equation for a two electron system, you usually can't make accurate predictions of the properties of compunds. Just doing the experiment isn't usually that hard anyway. You may be interested in computational chemistry. 203.27.72.5 (talk) 23:28, 27 July 2012 (UTC)

Indeed. This video illustrates how small perturbations in outer electron bands can have profound structural implications, e.g. on volume and density. It's absurdly difficult to try to derive melting and boiling points or even density from simulations for this reason. However, with Monte Carlo simulations of the Schroedinger equations it is certainly possible with sufficient computing power, which often isn't too much to be practical for reasonable amounts of accuracy. 207.224.43.139 (talk) 21:36, 28 July 2012 (UTC)

Rectifier

• If I install two rectifiers in parallel configuration, would that double the possible draw of amps? Since rectifiers with lower amps rating are much cheaper I'd rather install two small ones if possible. Thanks,TMCk (talk) 17:23, 27 July 2012 (UTC)

• Add a question: this is the rectifier I intent to use. If I solder the connections, do I have to be overly careful so that the heat doesn't destroy it? It has male terminals (will look up the kind and post shortly Done and according to WP they're called blade connectors) but I need to save as much space as possible. That's why I'd like to solder the connections. Again, thanks for any helpful response.TMCk (talk) 00:14, 28 July 2012 (UTC)

• Add yet another question: Rectifier is rated for 50 V but I'll only draw about 20 V from it. Is there a problem I should know about?TMCk (talk) 00:18, 28 July 2012 (UTC)

Two bridge rectifiers in parallel can carry twice the current of one, as long as they're not so close that they interfere with each other's cooling. Running at a lower voltage won't be a problem. --Carnildo (talk) 00:44, 28 July 2012 (UTC)

It is quite foreseeable that when two rectifiers are connected in parallel, one might have a smaller voltage drop/lower resistance and "hog the load," such that it overheated and burned out, leaving the surviving rectifier to carry all the load, whereupon it also burned out. If you're very lucky, they would divide the load equally and all would be sunshine and roses. Edison (talk) 02:52, 28 July 2012 (UTC)

Ah, thanks, to both of you. @Edison: since one could carry the constant current and the other would be mostly to make sure they both together can handle the starting current I guess I have a good chance this configuration with the proper cooling of course would handle what I have in mind with little to no danger for breakdown. Is this a fair conclusion?TMCk (talk) 03:45, 28 July 2012 (UTC)

You have a better chance of survival. You can purchase matched rectifier diodes, which should have similar characteristics and be less prone to the problem. Graeme Bartlett (talk) 08:16, 28 July 2012 (UTC)

I bought an identical pair so they should be very close in their actual characteristics. When I'll get on with the project I'll give it a try :) TMCk (talk) 16:24, 28 July 2012 (UTC)

This can depend on the characteristics of the other elements of the circuit. Answering correctly is a job for electronic circuit simulation, e.g. with SPICE. 207.224.43.139 (talk) 21:40, 28 July 2012 (UTC)

That would be above my paygrade ;) The other elements of the circuit are simply an altered transformer and some cordless tools. The transformer will get a cooling fan and maybe the former battery pack where I'll place the rectifiers will get one two. I like it save and fancy :) TMCk (talk) 01:46, 29 July 2012 (UTC)
I know something about electric but when it comes to electronics I'm pretty much lost with my very limited knowledge about it. I know how a transistor works but don't ask me how to use it in a circuit.TMCk (talk) 01:52, 29 July 2012 (UTC)

There are some fantastic beginner simulators these days, with white-box block libraries for tens of thousands of commercial components including common power tool motors. Try https://www.circuitlab.com/ and http://ngspice.sourceforge.net/ before spending money on something like http://www.simetrix.co.uk/ (which has a free demo that can probably handle your circuit anyway, so maybe start with that.) 207.224.43.139 (talk) 05:53, 29 July 2012 (UTC)

As I said, that goes beyond my needs and expertise and needs but thanks, I'll keep it in mind in the future for more delicate projects.TMCk (talk) 23:34, 29 July 2012 (UTC)

Camel urination and defecation

Camels have far less water in both, so how does this work ? Specifically:

1) How do they avoid kidney stones ?

2) How can they defecate with dry stool ? In humans this causes constipation and impaction. StuRat (talk) 18:00, 27 July 2012 (UTC)

Without knowing anything specific about camels per se, it should be noted that the digestive and excretory systems of mammals shows a wide enough variation in other animals that the answer is that camels don't work like humans. Cows and other ruminants have an organ called the Rumen, which doesn't exist in humans, that produces the cud they chew. There is no reasonable analogue for that process or that organ in humans. Rabbits don't chew cud, but they do have two types of droppings, one of which the re-eat, again something humans don't often do (at least, unless there are two girls with one cup). Camels can defecate with dry stool because they have evolved a digestive canal that allows them to defecate with dry stool. Likewise, their kidneys likely work differently from humans. Humans do their own weird things. For one thing, we sweat; something many mammals don't do. The simple answer is that camels are not humans, so don't look for them to work exactly as you do. It must work for them, because they exist and thrive. If it didn't work well enough, they wouldn't and that'd be the end of that. --Jayron32 03:57, 28 July 2012 (UTC)

Feces is (are?) excreted covered in mucus. Mucus is low in water content--think of slug trails and the fact that they don't dessicate because of them. They probably have large turds, because the larger the less relative surface area to lubricate. μηδείς (talk) 05:24, 28 July 2012 (UTC)

Jayron, do you have a citation that many mammals don't sweat? 203.27.72.5 (talk) 05:49, 28 July 2012 (UTC)

See perspiration. Many mammals sweat to some extent but very few use sweating for thermoregulation. Gandalf61 (talk) 08:14, 28 July 2012 (UTC)

Thanks, I had already read that though. I'm interested in the many mammals that don't sweat at all, regardless of whether it's for thermoregulation or some other purpose. 203.27.72.5 (talk) 09:10, 28 July 2012 (UTC)

It's likely that water is absorbed through the camel bladder, concentrating the urine and recycling water. Similarly, many ruminants produce hard pellet feces, from which water can be absorbed by the intestines before defecation more readily than from smooth primate feces. 207.224.43.139 (talk) 21:43, 28 July 2012 (UTC)

Thanks. Can you verify that a camel's bladder can absorb water, unlike a human bladder ? Also, wouldn't this just lead to bladder stones rather than kidney stones ? And how are hard pellets moved through the digestive tract ? StuRat (talk) 21:46, 28 July 2012 (UTC)

[4] says that urine production is reduced in a dehydrated camel, but with no indication of whether that's a function of the kidneys or the bladder. "Camel kidneys have long loops of Henle and can manage salts. Camel can take sea water without any side effects and can excrete sea water with a salt concentration almost double that of sea water," suggests that it might be more of an adapted kidney function. Pellets don't constipate like dehydrated smooth feces with ordinary intestinal contractions. Think peanuts versus peanut butter. 207.224.43.139 (talk) 22:05, 28 July 2012 (UTC)

Camels have the reputation of being fractious beasts, prone to kicking, biting, and spitting, for reasons only understood by the individual camel. Imagine the veternary assistant assigned to don a rubber glove and manually "deimpact" the colon of a constipated camel. The scenario makes many marginal jobs seem idyllic. Edison (talk) 04:51, 31 July 2012 (UTC)

Densest substance at standard conditions?

It's known that osmium is the densest known (naturally occurring) element, but what is the densest known substance at standard conditions? A discussion at Talk:Osmium#Densest_element_or_densest_substance.3F did not bring definite results. This (reliable?) source claims that an Ir-Os alloy is slightly denser than pure osmium, but is it actually the densest substance known? Is there an upper limit for how dense a substance could be at standard conditions? --Roentgenium111 (talk) 22:59, 27 July 2012 (UTC)

It is possible that strangelets can exist under standard conditions (although there is no evidence either way, as far as I know). If they can, then they would be extremely dense - orders of magnitude denser that anything made of atoms. --Tango (talk) 23:25, 27 July 2012 (UTC)

Hassium is probably far denser than osmium. 203.27.72.5 (talk) 00:18, 28 July 2012 (UTC)

Hs could have a density of 41 g/cm³, almost twice that of Os. Double sharp (talk) 13:42, 29 July 2012 (UTC)

Thanks for the answers, but I was thinking of a "normal" substance, i.e. made up of atoms of the naturally occurring chemical elements (Z<99). Any ideas there? User: Stonemason89 suggested doting osmium with hydrogen atoms, this might also be denser than pure osmium (see below). --Roentgenium111 (talk) 15:09, 29 July 2012 (UTC)

To have a higher density than osmium, a material could have either a higher average atomic mass or denser packing or a smaller average atomic radius, or some combination of the three. The atomic mass is dependent on the nuclear characteristics, and the packing and atomic radius is dependent on the electronic characteristics. Obviously, plently of materials have higher atomic masses than osmium, but their packing is so much less efficient and/or their atomic radii are so much larger that they're less dense over all. Osmium, and the other elements in the platinum family, happen to occur in a region of the periodic table where the atomic radius is at a minimum, the crystal structure is very efficiently packed, and they're in a period far enough down that they have high atomic masses, but not so far that they're unstable (as in hassium). Any compounds made with elements from outside the platinum group would have to significantly increase the average atomic mass without offsetting that increase by changing the packing struture or average atomic radius too much. I don't think any of the heavier elements are suitable, because they all have much longer radii, and may not want to sit in the same packing structure as osmium. Just having atoms of a different size in the same lattice causes interstitial defects which increases the void between the packed atoms thereby decreasing your packing efficiency. Maybe you can slightly increase the density by making an alloy of different platinum group metals (as indicated by your source), but I don't really see what mechanism is at work there. 203.27.72.5 (talk) 01:08, 28 July 2012 (UTC)

Thanks for that great overview on the problem. According to Atomic_radius#Empirically_measured_atomic_radii, at least fluorine and deuterium seem to have substantially larger "atomic density" (:= atomic mass/volume of the atom) than osmium, but of course they're gases at STP. (But OsF_x could be denser than Os, if it can be packed as closely; but osmium hexafluoride is in fact much less dense.) All the elements with higher atomic mass given there have lower atomic densities.

Do you know which exact crystal structure osmium has? Our article says only "hexagonal", but is it the hexagonal close-packed or something less closely packed? In the first case I would also doubt that IrOs can be denser, but in the second case the alloy might form a denser crystal structure than that of pure osmium. And I would expect that interstitials could in principle also increase the density of a material, if you fill the "empty spaces" left between the closely packed osmium atoms with atoms small enough to completely fit into such a hole (hydrogen or helium should be small enough for this). --Roentgenium111 (talk) 15:57, 29 July 2012 (UTC)

Osmium hexafluoride has a much lower average atomic mass than pure osmium (~43Da vs 190.2Da), and it's crystal structure is orthorhombic so the packing is much less efficient. That accounts for the very low density relative to osmium metal. The structure of osmium is very close to a perfect close packed hexagonal configuration. I calculated the density of osmium from the atomic mass (190.2Da) and radius (135pm) assuming a hcp structure and actually got 21.39g/cm³ which is less than the empirically measured value of 22.59g/cm³. I found that very small changes to the atomic radius changed the result wildly, with 132.6pm giving the accepted value for the density. The data page for atomic radii gives 130pm for the empirical value and 180pm for the calculated, but 135pm for the metallic element. In any case, with such great variation I think it's fair to say that 132.6pm is a fair fudge and the structure is hcp. Both iridium and osmium already have the most efficient packing possible (or very very close to it), so I can't see how Os-Ir alloy could have a denser crystal structure. I think the answer most likely has to do with electronic interactions in certain Os-Ir alloys reducing the effective atomic radius and thereby leading to a higher density. The behaviour of electrons in high atomic mass elements is extemely complicated due to the relativistic speeds of the electrons. You're quite right about the very small interstitial particles like Hydrogen. You could perhaps boost the density a bit by saturating the metal with hydrogen. 203.27.72.5 (talk) 02:03, 30 July 2012 (UTC)

July 28

Cloning

How far has science made progress with cloning in the last 10 years? Bulkbot84 (talk) 05:04, 28 July 2012 (UTC)

Have you read the cloning article? Looie496 (talk) 05:14, 28 July 2012 (UTC)

You may be interested in List of animals that have been cloned. 203.27.72.5 (talk) 05:17, 28 July 2012 (UTC)

Psychology and historical context

I am interested in finding out what areas were considered mainstream psychology, and what areas were considered fringe psychology, in the late 1970s. Can anyone give me any pointers please? --TammyMoet (talk) 09:27, 28 July 2012 (UTC)

This is about when homosexuality went from being classified as a mental disease to an alternative lifestyle. So, before the 1970's, studying the "mental disease of homosexuality" would have been mainstream, while, after the 1970's, those who still believed in that would have been thought of as just a fringe group. StuRat (talk) 09:59, 28 July 2012 (UTC)

Assuming you meant psychiatry (treatment & management of disease) What is considered a mental disease requiring prescribed treatment or management, and what is just considered a bit odd by lay persons, has always varied from region to region. Diagnostic rigor has always varied considerably from region to region. An extreme example of the variation significant up to the 1970's is classification of political/economic views - In the USA, seriously objecting to the system of government would only have been viewed as being a bit stupid at worst, and maybe just exercising your rights. In Iron Curtain countries, it could get you admitted to a mental assylum. For an American view of diagnostic criteria, you might like to dig out old versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) published by the American Psychiatric Association. It's updated about every 10 years or so. Any good university library should have every version.

Assuming you meant psychology (understanding of normal behaviour & capability)- developmental psychology, industrial psychology, etc), then you need to look at things like aptitude testing for emploment, aptitude testing for allocation for suitable school clases etc. For example, Raven's Progressive Matrices was considered a good tool for determining whether you would make a good clerk, tradesman, etc, up to perhaps the 1960's, then went out of fashion, and now in the 2010's, back in fashion again. Up to the 1960's IQ testing was considered objective good stuff, then progressively less well thought of. In the 1960's, if you applied for a job in Australian Government Service, you would have sat a three-part exam: an IQ test, a raven-style test combined with a basic arithmetic test, and a general knowlege test. If they needed 15 people, and you scored in the top 15, you got the job. No employer would be that silly now - they would at least interview you and check references.

Wickwack121.221.223.145 (talk) 12:14, 28 July 2012 (UTC)

Oh that makes sense: I did my psychology degree in 1980, and in the last semester we studied things like graphology, personality tests, hypnotherapy. I've been racking my brains trying to think (a) why we would have studied them and (b) what else we would have studied. Hence the question. Any other suggestions are welcomed. --TammyMoet (talk) 14:07, 28 July 2012 (UTC)

Graphology is quite old I think. You might want to look at Ink Blot Testing. I think it faded out in the 1960's, but many American industrial psychologists were fans of the ink-blot test - a very subjective and dubious method of ascertaining personality traits and fitness for work. If I remember correctly, the US Navy in the 1950's and 1960's required yearly fitness reports for senior officers, and it incuded a psychological report, usually based on ink blot testing. By the 1970's, at least in my country (Australia), the term "ink-blot merchant" came into use for when one wanted to refer to an industrial psychologist in a derogatory way (now an obsolete term). Wickwack124.178.33.116 (talk) 15:30, 28 July 2012 (UTC)

Yes I remember looking at Rorschach tests, but I think it was right at the start of my degree as part of the History of Psychology. Thanks also for "industrial psychologist" - I remember looking at that field because of the Milk Round (where companies tried to woo final year students) getting me an interview at a car parts factory. I didn't get it. --TammyMoet (talk) 17:04, 28 July 2012 (UTC)

I was given a Rorschach inkblot in the early 90s, so it was still somewhat in use at that point. And, um, I'm feeling much better now... :) Matt Deres (talk) 23:06, 29 July 2012 (UTC)

You might be interested in the fact that it was considered normal for adults to be sexually attracted to teenagers in that era, but that has recently become such an extreme controversy in the latest revision of the DSM in progress that some of its editors want to declare such attraction to be an abnormal mental illness. I am not making this up! PMID 21110392, PMID 21389170, PMID 20336359, PMID 18923891, PMID 18686026, PMID 21389175.... 207.224.43.139 (talk) 21:53, 28 July 2012 (UTC)

Most important genes of life

Are there any genes, which are identical (or highly similar) among all cellular live forms? With no known exceptions. --Ewigekrieg (talk) 13:47, 28 July 2012 (UTC)

You might refine your search by reading about metabolic pathways, such as glycolysis, that are common amongst nearly all known biological organisms. The genetic and other biochemical structures that regulate such pathways provide strong evidence for common ancestry between almost all Earth life-forms. You may also want to read Last universal ancestor, which discusses the scientific study to determine whether Earth life descends from a single source. This entire field presents many questions whose answers are difficult to determine with certainty. We have very limited capability to decipher "fossil" biochemistry evidence; so we must often test our hypotheses by tracing back biochemical evidence from present-day data. There is a lot of scientific data, and there are many good theories, but there will be several questions that can't be answered conclusively. "No known exceptions" is almost always impossible in observational science. A better way to frame the question is: when we find an exception, what does that imply? Does it provide evidence that life on Earth originated multiple times, or that it diverged evolutionarily? Does it provide concrete evidence, as many scientists theorize, for extraterrestrial origin of some biochemical material present in today's Earth life? On the same line of reasoning: if we cannot find any exceptions, how should we formulate our theory? Nimur (talk) 15:11, 28 July 2012 (UTC)

You may also find this week's post on NASA's main astrobiology page interesting: “How Life Turned Left”, regarding biochemical chirality. This is a topic I've heard a lot about, the claim is (loosely) that "all" biologically-created organic molecules have the same chirality. I've seen ths claim a lot, and it seems to be a really significant empirical discovery; but as I am not a chemist, I don't fully understand the evidence or the implications. Nimur (talk) 15:21, 28 July 2012 (UTC)

Ribosomal genes are the most conserved, since they deal with gene transcription. "The 16S and 23S ribosomal RNA genes scored as the most highly conserved sequences." μηδείς (talk) 18:19, 28 July 2012 (UTC)

See conserved genes, 16S ribosomal RNA, and 23S ribosomal RNA. μηδείς (talk) 21:15, 28 July 2012 (UTC)

Yes. In fact, most housekeeping genes are like that, to varying degrees. This is especially true if we restrict what we mean by conserved to the general 3-d structure of the protein and its interaction sites. Yaniv256 (talk) 01:53, 29 July 2012 (UTC)

Wireless energy

From what I assume about wireless energy transfers is, electrons are sent wirelessly to loads that need it. But similar to radiation, won't electrons flying around a room pose a threat to human life (causing diseases like cancer?) Thanks, 64.229.5.242 (talk) 16:32, 28 July 2012 (UTC)

Electrons as radiation are called beta particles and can cause molecular damage leading to cancer, but there are no electrons involved in wireless energy transfer. -- BenRG (talk) 16:55, 28 July 2012 (UTC)

Most wireless energy transfer occurs without the bulk movement of charge. That means the energy is carried by an electromagnetic wave, not by moving electrons. For the same reason that light can travel in a vacuum - electric and magnetic fields can exist independent of any transmission medium or "substrate" - energy can propagate (wirelessly) via an electromagnetic wave even when there is no movement of electric charge or matter. In most practical systems that have been built to-date - inductive energy transfer - the energy takes the form of an evanescent wave. Nimur (talk) 17:52, 28 July 2012 (UTC)

What would it be like to walk on Gliese 581g?

What would it feel like for a human being from Earth if they could walk on the surface of a planet with 1.5 or more time the gravity of Earth? If the atmosphere was also denser, what would it feel like to walk through it? And would that mean it was harder to see long distances?184.147.121.51 (talk) 18:12, 28 July 2012 (UTC)

It helps if you provide a link to the subject you are talking about. Gliese 581g. μηδείς (talk) 18:15, 28 July 2012 (UTC)

The gravity would be fairly easy to simulate, aboard the "vomit comet", for example. A more convenient, but not quite as good, simulation can be obtained by carrying weights all over your body equal to half your body mass.

Thicker atmosphere would make movement more like swimming, but would also reduce your apparent mass weight, due to buoyancy. It would make it harder to see through, if it was identical the Earth atmosphere other than density. However, it might have fewer particulates, and thus be clearer, as high gravity would tend to cause particulates to settle out quicker. StuRat (talk) 18:33, 28 July 2012 (UTC)

StuRat, buoyancy has no effect on mass - apparent or otherwise. You can model buoyant force as a change in net weight (though it's more physical and more common to model buoyancy as a separate force); but it's incredibly uncommon to model buoyant force as a change in mass. Please don't confuse weight and mass. Nimur (talk) 18:41, 28 July 2012 (UTC)

OK, fine, "apparent weight", although the only two ways individual humans have to infer mass is from weight and inertia, both of which would appear reduced in a thick atmosphere (the gravitational attraction caused by each person is a third method, but beyond our ability to perceive without powerful instruments). StuRat (talk) 19:02, 28 July 2012 (UTC)

Buoyancy reduces apparent weight but not inertia. The friction of a thicker atmosphere might well reduce momentum in some situations, but might also increase "apparent inertia" in others. Dbfirs 08:11, 29 July 2012 (UTC)

How would a thicker atmosphere increase the apparent inertia of a person ? It seems to me you will be slowed more by the thick atmosphere than you would in a thinner atmosphere. StuRat (talk) 08:25, 29 July 2012 (UTC)

It would be pretty easy to distinguish higher air resistance from a change in inertia. More air resistance would make it more difficult to pick up speed (think about trying to walk underwater), which is vaguely similar to having higher inertia. However, once you are moving and started to coast, the increased air resistance would slow you down faster, which is vaguely similar to having lower inertia (consider throwing a piece of paper vs throwing a metal sheet the same size - the paper slows down faster). In reality, air density simply doesn't have any effect on inertia and cannot be meaningfully modelled as a change in inertia. --Tango (talk) 17:12, 29 July 2012 (UTC)

An atmosphere 10 times as dense as earth's would buoy about 1.5% of a person's weight, see the calculation below. That effect would be unnoticeable. μηδείς (talk) 19:39, 28 July 2012 (UTC)

(Edit conflict)

This question should really be broken down into its constituent sub-questions:

• What would it be like on Gliese 581g? In truth, we don't know, because we know very little about Gliese 581g. What we do know was learned through indirect observations - the way its parent star wobbles - from which we fit model parameters based on what we know about sun-and-planet systems.
• What does 1.5g gravity feel like? This one is fairly easy: you would weigh 1.5 times as much; you would be heavier. We can "easily" simulate 1.5 g forces using airplanes, or elevators, and so forth.
• Would the atmosphere be denser? Probably, yes, if all else is equal; because that fits our model of atmospheric formation. We have an article on atmospheric modeling. And, if you study aerodynamics, you will some-day encounter the Standard Atmosphere; if you study astronautics or planetary science, you will extend the standard atmosphere to a general atmospheric model for any gas mixture on any planet under any other circumstance. I recommend Lissauer and de Pater's Planetary Science text if you're interested in following such details with scientific rigor.
• Would it be hard to see through a denser atmosphere? All else equal, yes; we have an article on optical density. We also have the somewhat more practical article, visibility, about the concept used in meteorology. It would be difficult to estimate how much the optical density changes, without knowing a lot about the other atmospheric parameters. For example, consider the atmosphere on Mars: all other things are not equal: the temperature, pressure, and gas composition are totally different from Earth. The Martian air is much much thinner - nearly a vacuum, compared to Earth's surface - and yet, the major optical attenuators are aerosols, fogs, and hazes. Even thin air can be optically dense.

Nimur (talk) 18:39, 28 July 2012 (UTC)

• A human weighing 200lbs occupies about 89 liters of space, about four moles of gas at standard temperature and pressure. Four moles of O2 weighs about 0.128kg. In a breathable atmosphere 10 times as dense as the earth's the 200lb man's body would displace a little under three pounds of gas, the weight of a full bladder and a good bowel movement. He would not notice that difference. μηδείς (talk) 19:25, 28 July 2012 (UTC)

Perhaps the greatest effect of denser atmosphere would be increase difficulty in exhaling? While it may not be especially difficult to breathe while awake, I wonder if sleep apnea would be more common in a dense atmosphere scenario. BigNate37_(T) 19:43, 28 July 2012 (UTC)

No, the higher pressure would be equal inside and outside your lungs. A higher vapor density of Oxygen would actually make it easier to breath, to the point of getting too much O2. μηδείς (talk) 19:47, 28 July 2012 (UTC)

It would take more effort to exchange a full lung's worth of air, since it now has more mass. However, since you would need less air to get the same oxygen, you might breath less often, and take shallower breaths, when resting. But, of course, the higher gravity and the extra effort to move through the thicker atmosphere (especially on a windy day) would also increase the amount of energy needed to move around, and thus increase your respiration rate. StuRat (talk) 19:59, 28 July 2012 (UTC)

Physics of mace (club)-like weapons

If you have several different versions of a blunt weapon, which consist of a heavy ball attached to a handle (flexible or not) or a chain, like a mace (club) or flail (weapon). What's the difference, regarding the impact force, between the versions? OsmanRF34 (talk) 19:03, 28 July 2012 (UTC)

You're probably asking about the potential to get it going faster, like a whip, but a whip works by having the tip be lighter than the the rest, not heavier, so I don't think that would happen here, or at least not to the same extent. StuRat (talk) 19:14, 28 July 2012 (UTC)

But, doesn't it make any difference if the handle is a chain or a rod? (given the same mass). — Preceding unsigned comment added by OsmanRF34 (talk • contribs) 19:24, 28 July 2012 (UTC)

Not sure if it would make any difference in the force it would deliver unopposed, but it certainly would make other differences. The chain mace would be more portable, could be easier to use at less than the total length, and would be harder for the enemy to stop by grabbing at the shaft. It would also eliminate force or vibration on the hands when it strikes an object. StuRat (talk) 19:35, 28 July 2012 (UTC)

A mace can be modelled in a similar way to a baseball bat or golf club, both of which have ample physical analyses out there. Using a club-like weapon (or any rigid weapon, including a fist) allows for follow-through, where the user attempts to put the weapon "through" the target; follow-through allows the user to continue imparting force through the weapon after the point of initial contact. Contrast with a flail: the user must first accelerate the striking mass, at which point the force of impact is effected by the mass' momentum alone, with no means for the user to supply additional force on impact. I'm afraid I'm ill-prepared to discuss it quantitatively, though. Another obvious difference is that a rigid weapon allows for more precise control (given sufficient strength) whereas a flail must be accelerated towards the target with some foresight. Changing angle of attack or aborting an attack with flail is very difficult, and potentially very unsafe. In a combat scenario, it would be difficult to avoid telegraphing your movements. Those are trade-offs against the disadvantages Stu mentions above in using a club in a combat scenario. BigNate37_(T) 19:37, 28 July 2012 (UTC)

The amount of force you can exert after contact is quite low. Considering the baseball example, if you started with the baseball stationary and in contact with the ball (let's say a T-ball setup), how far do you think you could move the ball ? StuRat (talk) 20:07, 28 July 2012 (UTC)

Your example is not quite a correct analogy. It precludes the possibility of flex in the weapon due to initial force, which prevents prolonging the time of impulse. Were the follow through as ineffective at imparting force as you imply, golf clubs and hockey sticks would not be designed for extra flex. However, I suppose with an effective grip and stance I could move said ball something like 5–15m, which is perhaps an order of magnitude less than a full swing, a non-negligible amount of force. BigNate37_(T) 20:21, 28 July 2012 (UTC)

That flex is mostly due to force exerted prior to contact, not after. That 5-15m seems rather high, to me. Time for an experiment ! StuRat (talk) 21:40, 28 July 2012 (UTC)

Right, the flex and impulse extension is not itself providing supplemental acceleration, but by extending contact time, I'm asserting that it widens the window during which the follow through adds force. Perhaps snap shot vs. slap shot is a more appropriate analog? It's easy enough to find sources that admit flex is important, but it's harder to find anything that specifically addresses the matter of follow through force or lack thereof. BigNate37_(T) 15:32, 29 July 2012 (UTC)

I don't think it's a good analogy to using a mace in combat, because you can maintain contact for a long time and distance with the hockey stick, since the puck is so light (even the baseball analogy was generous in this regard). Presumably you can't accelerate a (much heavier) enemy with a mace in a similar fashion. StuRat (talk) 19:11, 29 July 2012 (UTC)

Well, a rigid club striking an opponent should have ample contact time too, but for a different reason. Rather than displacing the target, you are deforming it via an inelastic collision. But perhaps I've stated my thoughts as clearly as I can, and now I'm just repeating myself. BigNate37_(T) 19:27, 29 July 2012 (UTC)

Do you have a baseball and bat ? If so, I'd like you do that experiment to see if you can get 5-15m. (If you lack a t-ball setup, you can just place the ball on a porch or ledge, but no fair kicking the baseball bat.) StuRat (talk) 19:11, 29 July 2012 (UTC)

I do not have access to a baseball bat or a tee. I'm also not convinced a ledge or railing is a practical replacement tee, either, unless we substitute a softball or something with a sufficiently large diameter to allow the bat to clear the "tee." I could try that with my goalie stick and a floor hockey ball when I get back home next week, but that's essentially just going to be a wrist shot, and the outcome of that thought experiment isn't in question. BigNate37_(T) 19:27, 29 July 2012 (UTC)

• From the latter article, "The chief tactical virtue of the two-handed flail was its capacity to defeat a defender's shield or avoid it entirely." You know how today we see stories about weird curved guns from World War II that could shoot around corners? Well, this is a club that can shoot around corners. Or at least that's my guess. Wnt (talk) 14:31, 1 August 2012 (UTC)

Levelling

A recent TV programme mentioned that an instrument that had been placed on the moon had to be levelled which made me wonder what was the datum used, what was it levelled against? This raised the same question in my mind, what is the datum on earth, it can't be sea level since that differs everywhere. Any advice please?--85.211.195.59 (talk) 21:14, 28 July 2012 (UTC)

Presumably they mean they used some form of level (such as a laser line level) to make sure the device wasn't at an angle. These use gravity to determine what "level" is. For a large body, this can very closely be approximated as the pull towards the center of the object. StuRat (talk) 21:24, 28 July 2012 (UTC)

As for measuring altitude, sea level does not vary by much, only a few meters, counting tides. I believe they average all those out, however. Rivers and lakes can vary by quite a bit more (usually higher, but sometimes lower, as in the Dead Sea). Rivers also have the problem of varying altitude from source to mouth. These days, I imagine a GPS system is the best way to measure altitude (air pressure is also used, but can vary a bit due to high and low pressure cells, and even more in a hurricane). StuRat (talk) 21:31, 28 July 2012 (UTC)

Whereas on earth the datum used for measuring altitudes is sea level, this obviously can not be used on the moon. Therefor, various organizations such as NASA, the U.S. Geological Survey and others have established an artificial lunar datum plane at approximately 1,738 km from the center of the moon. It varies depending on location because the moon, like the earth, is not quite spherical. The full explanation is here.    → Michael J Ⓣ Ⓒ Ⓜ 06:31, 29 July 2012 (UTC)

NASA has a great amount of information available on specific experiments. If you can recall the mission, or the experiment package, we can probably help you find more specific information. Here's a general overview of Apollo Lunar Surface Experiment Packagess. In many cases, experimental devices were leveled using the UHT (the Universal Handling Tool - a NASA acronym for poking them around in the sand-like regolith with an aluminum pole until they seemed "level"). Other experiments were much more precise. Apollo 17 used a gimballed antenna with 2-axis bubble level lines (similar to what you'd use on Earth). The infamous laser corner-reflectors self-align, because they are corner reflectors, so did not require any precision alignment at all. Nimur (talk) 15:46, 29 July 2012 (UTC)

July 29

Need a flat metal surface for heat sinking - suggest melting aluminium or solder?

I have a couple of brass candelabras which I'm using in a lighting project. The light will come from high power LEDs inside the candle cups. I need a good thermal connection between the rear of each LED bead (I intend not to use the star-mounted LEDs) and the metal candle cups. In order to obtain a good connection, I need a flat surface in the bottom of each cup. To obtain a flat surface, I was thinking I should melt some metal in the bottom of each cup. Aluminium has a lower melting temperature than brass and may be a possibility. However solder has an even lower melting temperature and may be much easier to work with, although its thermal conductivity is lower. Would solders containing a flux core pose a problem for this application? — Preceding unsigned comment added by 2.97.18.184 (talk) 01:33, 29 July 2012 (UTC)

The thermal conductivity of solders varies quite a bit, with ordinary tin-lead eutectic not very good. See http://www.electronics-cooling.com/2006/08/thermal-conductivity-of-solders/. In contrast, the thermal conductivity of alauminium is about 250 W/m.K (http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html), about 5 times better than ordinary solder. Never-the-less, depending on the cup size and shape, it is probably the case that even tin-lead solder will be good enough. By mathemically modelling the volume of the metal as concentric thin cups of simple half-sphere & cylinder shape you can calculate the therml conductivity from LED to cup outside surface, and you can roughly estimate the heat conduction from cup to air with Pressman's formula: R = 7400 A^-0.7 (R in ^oC/W, A in mm²) You probably won't get a sufficiently flat surface due to surface tension, and depending on what metal the cups are made of, you may have issues with the melt disolving some of the cup material - this can significantly increase surface tension. Surface tension may force you to spot-face machine the surface to get it flat. Flux residue can be dissolved off with citrus-tpe solvents, but if you are going to machine the surface, that will get rid of teh flux as well. Keit121.215.49.33 (talk) 03:40, 29 July 2012 (UTC)

Standard practice is to use thermal paste, which makes the matter of surface machining moot. It isn't adhesive, though, so you'd likely need to use a fastener to attach the LEDs, and you would still need to have two surfaces that are roughly complimentary shapes (i.e. matching concavity/convexity). BigNate37_(T) 03:52, 29 July 2012 (UTC)

+1. I've also seen metal rods of an appropriate diameter soldered as close to the hot component (LEDs) as possible on the lead which you can ground to the fixture, and then soldered to the fixture, and then smothered in thermal ceramic/silicone paste over the solder. 207.224.43.139 (talk) 05:29, 29 July 2012 (UTC)

Note that the usual sorts of thermal paste sold for electronics heatsinking purposes is not at all thermally conductive compared to metals. It's only designed to go as a thin smear between two "mill finish" flat surfaces bolted together. My Radiospares catalog gives thermal conductivities ranging from 1 to 3 W/m.K. Compare that to aluminium (250 W/m.k). Such thermal pastes provide a small benefit because transistor/diode/etc surfaces and heatsink surfaces are normal machined surfaces and not mirror polished - this means that without the paste there is microscopic air gaps btween high spots, and even 1 W/m.k conductivity is orders of magnitude better than air. Using such pastes in other than a thin smear will not do anything useful. Keit120.145.177.174 (talk) 06:41, 29 July 2012 (UTC)

Silicone thermal compound based on aluminum nitride is better than solder at over 100 W/m*K, so you can slather it to protect the solder joint. I don't know if that's typical for heatsink compound. 207.224.43.139 (talk) 07:20, 29 July 2012 (UTC)

Do you know any trade names, product codes, manufacturers, etc, that we can use to to trach down & purchase such wondrous stuff? The link provided for silicon nitride in the Wikipedia article on thermal grease is a dud. Keit120.145.141.39 (talk) 12:09, 29 July 2012 (UTC)

Use a table spoon to melt solder over a gas stove and pour it into the light fitting if the light fitting has a watertight metal form. You may be able to epoxy shut small escape routes for the molten solder in the base of the cups, but do that outdoors for certain because the epoxy will give off even more volatile fumes than the melting solder. (Do it on a BBQ) Use a pedestal fan. Place the fan very close to the work as you are melting and pouring, with the fan facing away from the work and away from you. It will suck away the fumes without disrupting your work. I agree to take full legal responsibility for your head falling off and the city catching fire, so be sure to email this note to your lawyer first. You might also try running a led embedded in putty in the fitting, or silicone sealant, or mixing metal shavings in, Then measure the temperature of the LED after 5 minutes and see which gives the lowest reading. You can ask a local engineering shop or handyman to turn some pieces of aluminium for you and use heatsink grease for the gap. (And always remember, don't solder while naked) Penyulap ☏ 14:42, 29 Jul 2012 (UTC)

Does it matter? LEDs don't produce a lot of heat. That's what makes them so energy efficient compared to incandescent bulbs. Why isn't air cooling sufficient? --Tango (talk) 17:23, 29 July 2012 (UTC)

A few watts a piece if it is the large ones, the ones the requester says they won't use, if it is a simple 5mm or 3mm two lead package, then the power consumption is tiny and no heat sink is required. But as they are mounted flat, it seems to be a package somewhere in between, which makes sense as the small ones can't light up a room really. I think the best thing to do is to hook one up and then enclose it in the same manner it is meant to be in permanently, and measure the final temperature as I said. It's most likely there is enough conductance to keep it cool. But any high brightness led say, over 100mA can get quite hot so long as it is thermally insulated, most of the time it is not, and certainly open air cooling is enough to cool it. Keeping the heat contained is what the enclosure will or won't do. I'd say just give epoxy a go. Penyulap ☏ 17:57, 29 Jul 2012 (UTC)

For a high power LED it does matter. Since the OP isn't even putting it on a star or round heatspreader there's a good chance they will kill probably within seconds to minutes it without a good thermal connection to some heatsinking. This doesn't mean aircooling isn't sufficient, simply that it needs a good thermal connection to a resonably sized heatsink. The LED datasheet should give good info on what is required (every power LED datasheet I've looked at had a section on thermal management). Personally I'm far from convinced the solder idea is sufficient but the OP will need to look in to the requirements themselves. Also the OP hasn't exactly specified what sort of power LED they're referring to and what their target current range is. E.g. the requirements for an XM-L run at 3A (maximum rated) would be quite different from one run at 350mA (or for that matter a XB-D run at 350mA). I suspect the OP isn't considering something like a large LED array, e.g. a Bridgelux BXRA-56C9000-J-00 [5] with a typical forward voltage of 30.4V run at 3.75A (maximum rated) but who knows?

Remember that while LEDs may be fairly efficient they have a much smaller surface area and volume and also do not like to get hot losing efficiency i.e. generating more heat for less light as they get hot (which from the end user POV generally means if the designer knew what they were doing and used a good constant current driver, the LED can get visibly dimmer as it warms up) and also lowering their lifespan possibly quite significantly depending on the running temperature. And their efficiency is also helped by the low amount of non visible light (which doesn't hang around the LED). I've discussed all this in more detail with references in the past if there is still any confusion.

Nil Einne (talk) 10:44, 30 July 2012 (UTC)

Does atrioventricular block benefit the heart of athletes?

Here it is mentioned that athletes can have certain heart conditions that in non-athetes would be considered to be heart diseases:

"First degree atrioventricular block and second degree Möbitz type 1 block occurred more frequently in athletes. Atrioventricular dissociation and Möbitz type II block were not observed in controls but did occur in athletes."

So, does having an atrioventricular block benefit someone who does a lot of endurance training? Count Iblis (talk) 01:52, 29 July 2012 (UTC)

You might wish to look at our atrioventricular block article. I can't imagine that it would be beneficial for the atria and ventricles to lose their usual synchrony, but our article says that in athletes it may be "benign". Looie496 (talk) 04:13, 29 July 2012 (UTC)

Origin of HIV/AIDS

In a recent question on the humanities desk the OP repeated something I've frequently heard before that I have never been able to find a reliable source for, or even a reliable source debunking it, namely; that HIV was first transmitted from simians to humans though sexual contact. I can think of numerous reasons why this is highly unlikely (a human is unlikely to have been the receptive participant, the penetrative participant has a low chance of contracting the virus and this probably isn't something that happens regularly, the apes in question are very strong and not likely to enjoy such treatment, etc.). The scientific consensus as far as I'm aware is that it was people eating bushmeat contaminated with the virus that caused the initial transfer to humans (contracting the virus in this way is also unlikely, though I suppose this happens frequently enough to explain it). Can anyone provide references or links to discussions on this dubious hypothesis? 203.27.72.5 (talk) 01:58, 29 July 2012 (UTC)

Reading History of HIV/AIDS as well the reviews cited in the transfer section don't even mention sexual contact as a possibility. If the article accurately portrays the neutral point of view, then I would say that human-chimp sexual contact as the point of entry of HIV into our species is an extreme minority viewpoint. Someguy1221 (talk) 02:24, 29 July 2012 (UTC)

I'm sure it is an exteme minority viewpoint amongst medical professionals and anyone who has stopped to think about what they're saying, but I keep hearing it or reading it which leads me to believe it is some sort of a relatively common misconception. I'm not going to attempt a google search right now because I'm on a work computer, but I'd think there would be quite a few hits for people restating the hypothesis in forums, etc. I'd like to know where it came from and I'd really like to see where some expert in the field has debunked it. 203.27.72.5 (talk) 03:47, 29 July 2012 (UTC)

Bushmeat#Role in spread of diseases explains the much more likely vector, and [6] is the most recent review you want, citing this specific detailed primary source. Sexual contact between chimps, apes, or monkeys and humans is very rare, with bushmeat being much more common as per that source. 207.224.43.139 (talk) 05:40, 29 July 2012 (UTC)

Thanks, but neither of those mention the hypothesis I'm asking about. There is an (unsourced) mention of the the misconception at Misconceptions_about_HIV/AIDS#Origin_of_AIDS_through_Human-monkey_sexual_intercourse, so if someone finds a source I can add it to that. Apparently one Republican state senator from TN repeated it in an interview. 203.27.72.5 (talk) 09:34, 29 July 2012 (UTC)

The fact is that our data is too limited for the specific means of transmission to be anything other than a guess. However, sexual relations is a quite poor one. Either being bitten by a wild or pet monkey (which would also have a lesion of some kind or to suffer an injury, since saliva is not a viral reservoir), or having contact with a recently slaughtered monkey while having a cut (This could easily be imagined if one is preparing the monkey to be a meal) is much more likely. But if a Tennessee politician thinks he can gain votes in his district by guessing sex, it isn't impossible. There is no reason any authoritative scientific source would discuss it. Bestiality with monkeys in Africa is almost certainly rare or non-existent and other avenues are not anywhere near as implausible.173.15.152.77 (talk) 12:52, 29 July 2012 (UTC)

I'm not sure what you're looking for. It's pretty obvious where the misconception comes from - HIV is sexually transmitted in humans, it is thought to have originated in monkeys, so people put two and two together and get five. I'm sure loads of people have independently come to the same misunderstanding, so you aren't going to be able to find the origins of the misconception. --Tango (talk) 17:49, 29 July 2012 (UTC)

On a related question, if you eat the meat of a human who is infected with HIV, can you contract HIV? ScienceApe (talk) 16:22, 29 July 2012 (UTC)

Contracting HIV by giving oral sex to someone that is infected has an extremely low chance of infection (although it is increased if you have any sores or cut in and round your mouth). Eating infected flesh would presumably be similar. (Note, it being very rare to catch it this way doesn't invalidate the bushmeat hypothesis - as long as there were enough people eating enough infected bushmeat, someone would get infected sooner or later.) I can't find a reliable source for the likelihood of catching HIV from oral sex, but I'm sure I've seen one before. The best I can find is this CDC page saying it is probably less likely than from anal or vaginal sex, but it doesn't give any numbers. --Tango (talk) 17:49, 29 July 2012 (UTC)

I can't help but recall something Frank Zappa said in the early years when the monkey story came out: "So who's been screwing those monkeys?" ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:06, 29 July 2012 (UTC)

Eating is only part of it. The hunting and butchering part is the more dangerous end of the bushmeat trade. Wounds and blood galore.

Anyway I found this source: HIV/AIDS, Health and the Media in China. It closely parallels that Stacey Campfield's reasons for segregating the people who can get infected, and those who can't. In the senator's reasoning, it's a gay disease brought on by bestiality and "unnatural" sex acts. In early Chinese propaganda, it was a yuanshi (primeval) disease and the result of the Africans being "naturally" wild and uncontrolled. Both are bizarre and quite dangerously ignorant. *shakes head at the fact that this guy is a senator*

But anywho, yes. It's a common enough joke. Ricky Gervais in GTA 4 jokes about... SPOILER ALERT!... how the patient zero accedes to having received it from eating bushmeat to avoid having to admit that he had sex with an ape; and then confronts the chimpanzee who at first denies eating monkeys, but then agrees he did when the only other alternative is that he had sex with a monkey. Doesn't sound that funny when I say it like that. :P -- OBSIDIAN†SOUL 21:03, 29 July 2012 (UTC)

In his original post above, User:W203.27.72.5 claims that "the penetrative participant has a low chance of contracting the virus". Is this actually true? If so, wouldn't it imply that heterosexual men should have much lower rates of HIV than women? —SeekingAnswers (reply) 22:00, 30 July 2012 (UTC)

Check out out articles that give risks like our ones (e.g. HIV/AIDS). If it's a decent article, they nearly always give different risk estimates for penetrative/insertive and receptive intercourse, normally in the range of 1/5 and 1/10 difference although as our article shows, there tends to be fairly wide variance in estimates risk (although I think something went wrong with our insertive anal intercourse figure). However your assumption doesn't necessarily hold, it will depend on things like the frequency of high risk activity. Nil Einne (talk) 13:26, 31 July 2012 (UTC)

Argon fluorohydride

Does HArF contain Ar(II) or Ar(0)? Double sharp (talk) 06:14, 29 July 2012 (UTC)

According to Argon fluorohydride it's a hydride, so that would make the Ar²⁺. 203.27.72.5 (talk) 06:18, 29 July 2012 (UTC)

Actually, no, it's Ar(0). Argon is more electronegative than hydrogen, but less electronegative than fluorine. Therefore, the oxidation number of hydrogen is +1, the oxidation number of argon is 0, and the oxidation number of fluorine is -1. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:28, 29 July 2012 (UTC)

Nope, from this article in Chemical and Engineering News,

"Many recent findings, including the first evidence for an argon compound, have come from matrix-isolation studies at the University of Helsinki in Finland (Markku Räsänen and coworkers). These studies have established the existence of a large variety of novel compounds, all stable up to 40 K. Included are HXeOH, HXeCCH, HKrCN, HKrCCH, and HArF. The last requires comment, because of the nonexistence of ArF2.

In all of these compounds, the vibrational spectroscopic findings indicate that the canonical form ([HNg]+Y–) contributes importantly to the binding of the molecules. The tiny proton is highly electronegative, and it bonds covalently to Ng in these molecules. The proton affinities of the noble gases are the following: He, 1.8; Ne, 2.2; Ar, 3.0; Kr, 4; and Xe, 6 eV."

So the form is [HAr]⁺F^-. Therefore the argon can only be Ar²⁺. 203.27.72.5 (talk) 06:56, 29 July 2012 (UTC)

Actually, having drawn the Lewis structures the argon must be Ar⁰ because of the relative electronegativities as Whoop said. The electronegativity of argon isn't extactly known, but the trends indicate it should be about 3.5 on the Pauling scale. 203.27.72.5 (talk) 07:56, 29 July 2012 (UTC)

Or if you want to get really technical, the oxidation number (as opposed to oxidation state) is what is denoted by Roman numerals (as in the OP question) and there the convention is for the electrons to be considered to reside with the ligands, which in this case is the H and F, so that would make the argon (II). 203.27.72.5 (talk) 08:01, 29 July 2012 (UTC)

Radon

Are any Rn(IV) and Rn(VI) compounds known to exist? If they do, could specific examples be given? Double sharp (talk) 06:19, 29 July 2012 (UTC)

From the same external article I linked to above,

"Although the easier ionization of radon leads one to expect the most extensive chemistry for that element, the high instability of even the most stable isotope has severely limited studies of it. L. Stein, of Argonne, established (in 1962) the existence of a fluoride--probably RnF2--but he and others were unable to confirm the existence of oxides or relatives of the perxenates."

So, it sounds like no, they cannot be confirmed to exist due to the instability of radon, but they do probably form. 203.27.72.5 (talk) 07:02, 29 July 2012 (UTC)

Most likely nobody tried to establish a research project on radon chemistry lately. Today there are good methods to do chemistry on instable elements, but not back in the 1960s.--Stone (talk) 12:40, 29 July 2012 (UTC)

Locking car doors to prevent being thrown out

I've met a few people who always lock the car doors to prevent them from opening in case of an accident (and they try to convince me to do the same). I always thought the claim was weak for several reasons, but that's just based on my uniformed guesses. So the question is: will locking your car doors decrease the risk of you being thrown out of the car in case of an accident? Vehicle door is of no help.Sjö (talk) 08:45, 29 July 2012 (UTC)

Well, during an accident you could conceivably have something get caught on the door handle and pull it open, but this doesn't seem very likely. The better safety justification for locking doors is that it keeps a criminal with a knife from jumping in and carjacking you while stopped at a light. And, of course, kids or pets might manage to open the door while the car is in motion, and locking them makes this harder.StuRat (talk) 09:10, 29 July 2012 (UTC)

I would think that wearing a seatbelt would be a much better way of ensuring that you're not thrown from the car (or onto the steering wheel, or through the windscreen) in a crash. Mitch Ames (talk) 10:03, 29 July 2012 (UTC)

Car Talk says locking provides a small improvement in keeping the door closed in a crash, and that keeping the door closed is very important for overall protection of the occupant in ways unrelated to "staying inside".[7] DMacks (talk) 10:09, 29 July 2012 (UTC)

Bad idea. Very bad idea. Car door locks are designed in such a way that accidental opening is quite unlikely, unless the crash is so severe it becomes meaningless. And if you have at least half a brain you'll be wearing a seatbelt anyway. But locking the doors will make life more difficult for emergency crews to get you out, should you be dazed and/or confused. If they can't open the door, they'll use "jaws of life" gasoline-powered cutting tools to get you out, thereby writing off your car, which in many cases would be otherwise repairable. If your insurance company finds out you locked the door, they might pay out only the cost of the repair instead of the full replacement value. Quite apart from the risk of you being killed by fire (fires is not very likely in cars made by American manufacturers & their regional offshoots, but is something that does happen significantly often with Aisan cars). Should you be dazed/unconscious or whatever, and there is a fire in your car due to crushed wiring or whatever, you want bystanders &/or emergency guys to get you out immediately, before they get scared for themselves wrt explosions, and not be frustrated by a locked door. The exception is certain European cars eg Mercedes, that automatically unlock all doors if at least one airbag is triggered. Wickwack120.145.165.103 (talk) 12:21, 29 July 2012 (UTC)

A mild awareness of all factors is a good alternative to a rule. If you are driving a route that takes you across or beside a body of water, or into a tunnel, it is better to leave them unlocked. Escape in these situations could be a little easier (in the case of the water, it won't make a difference once the car actually enters the water, only before). Procedures for water entry are complex. The primary case for locking your door is when you don't always wear a seatbelt, in those cases, even if you don't notice it, you do lean against the door. If it is not closed properly, it can and often does, open and eject the occupant (much to their surprise) so locking the door is an added step which helps you actually check that the door is closed properly, and may indeed help stop it opening if it is faulty. Extra levels of protection are worthwhile, but fake strategies like driving with headlamps lit during the daylight hours should be avoided.

Short answer, LOCK your doors normally, UNLOCK them when approaching a waterway or tunnel and then lock them again afterwards. Probably a good idea to google some safety guidelines for tunnels as well, as Europe has a great many, and they are a whole world of hurt apart from regular roads. It is worthwhile knowing what to do, what not to do, and to generally avoid tunnels under certain circumstances. Penyulap ☏ 12:47, 29 Jul 2012 (UTC)

As you pointed out the OP is from Sweden and Daytime running lamps are required. I notice too that studies seem to say that DRL do improve safety in certain conditions. CambridgeBayWeather (talk) 15:23, 29 July 2012 (UTC)

Yes yes, and the oil companies tell countries to go to war as well, look at Tony Blair, Britain was his own personal militia to take the oil companies of Africa, so a little legislation is trivia. Headlights use electrical current from the alternator, which loads up the car's engine and uses more fuel for a given distance. The studies do not address the cause of the statistics, they only count the raw data. If you started a rumour that wearing a Poodle Hat whilst driving improved safety, then on the grounds that there are idiots who will believe anything you tell them, some idiots will take up the challenge and wear poodles whilst driving. If you then study the poodle group compared to the rest of us, you will also find they take ALL advice seriously, they always wear seat belts, always drive slow, never drink alcohol and so on. Those factors are showing through in the raw statistics and are published to perpetuate the myth. It's just another grapefruit diet sure you'll lose weight by starving yourself, it works, and the citrus co makes money. If you drive and see a RV with glaring lights you must look away from it, so how does that make it anything but invisible on this planet ? Hype. locking and unlocking must depend upon the environmental conditions and expected anomalies along the way, so computing the chance of requiring a speedy abandonment of the vehicle or the chance of car-jacking is probably sufficient to override the norm, which overall, would probably fall on the lock side so you don't fall out. (for worldwide) Penyulap ☏ 17:21, 29 Jul 2012 (UTC)

If the oncoming traffic is causing glare that is making you look away then there is something wrong with the oncoming vehicle. I've never had a problem with the lights of oncoming vehicles. How do you cope with the glare at night when all vehicles have their lights on? CambridgeBayWeather (talk) 23:11, 29 July 2012 (UTC)

As I have seen it done, drivers at night often hold their hand up to block the view of the headlights without blocking the view of the road, but I've only seen them do this in dark stretches where their eyes adjust to the darkness fully, I think you wouldn't see it as much in built up areas. Penyulap ☏ 03:30, 30 Jul 2012 (UTC)

Some very questionable advice above, about the importance of NOT locking the doors. Cars I've owned in recent years AUTOMATICALLY lock the doors when the car starts moving. Carjacking is a danger that is lessened by locking the doors. Rescue squads, firemen, and police just break the glass, rather than sending for the "jaws of life" when the car door is locked. I question the claim that the insurance company will pay less if the doors are locked. A locked door might be less likely to allow ejecting an unbelted idiot when the car flips.Edison (talk) 13:34, 29 July 2012 (UTC)

It's quite appropriate advice because I have taken into account the enquirers local conditions. They live in Sweden I believe. These factors come into account as carjacking is not universal. Insurance company rules vary widely between companies let alone countries. Penyulap ☏ 14:09, 29 Jul 2012 (UTC)

Btw, my comments on my userpage aren't about you, they are about the other Edison :) Penyulap ☏ 14:16, 29 Jul 2012 (UTC)

European cars such as Mercedes do automatically lock the doors as you start moving, but they also automatically unlock if an airbag is triggered - that is a safety requirement for the reasons I gave above. In the old days (not so old days with some brands) when cars were locked by a simple mechanical up/down button on the door sill, yes, that's what rescue chaps did - they bashed the glass, and then pulled up the lock button to open the door. But with modern cars, there's generally no such button - the deadlocks are electrically operated by either key or keypad. That may not be accesible, and an accident may cause an electrical fault disabling the unlocking (automatic unlock will happen momentarily before that happens). So, yes indeed, they will use "jaws of life" (which incidentally of course involves first smashing the glass out). Wickwack124.178.48.62 (talk) 13:52, 29 July 2012 (UTC)

"...when you don't always wear a seatbelt." With all due respect to Penyulap, but as I stated above, if you don't always wear a seatbelt, you're a half-wit. With and without accident statistics are very clear. See http://www.carrsq.qut.edu.au/publications/corporate/seat_belts_fs.pdf - not weraing a seatbelt increases the probablity of injury or death by up to a factor of 10. I owned a Ford Falcon - a very common car here in Australia. I was hit while doing 60 km/hr almost head on by another vehicle that went thru a red light at 80 km/hr - it wrote both cars off - wrecked them. I was wearing a seatbelt and walked away without a scratch. The other driver, who was in a small Japanese car, had only a slight scratch. Without a seatbelt, an 80+60 km/hr impact will seriously injure if not kill. Most folk who have been in a serious accident will tell a similar story. Wickwack124.178.48.62 (talk) 13:41, 29 July 2012 (UTC)

Again wearing seatbelts is a local variation, although cars in Australia are designed with the expectation that all occupants will wear a seatbelt, it is not the case in the United States. In the US, cars are sold with airbags that deploy with a far greater force than those in Australia, as it is every Americans right to be a moron and not wear a seatbelt. The manufacturers take that into account and make the airbag support the whole torso and head of the occupant, while in australia, it's just the ole noggin that needs attention, blimey mate get with the program. struth. Penyulap ☏ 14:16, 29 Jul 2012 (UTC)

Every state in the US has seat belt laws, only one state is lax enough to enforce the law just for minors, so I'm not sure what you are talking about when you say we have the right not to wear them...we have just as much a right to speed like a moron, meaning not at all. 71.195.84.120 (talk) 16:39, 29 July 2012 (UTC)

Cool, I wasn't aware of that, my memory must be faulty, but then, the airbag thing must point clearly to some large market where seatbelt use is lower than Japan or Australia for example. Penyulap ☏ 17:21, 29 Jul 2012 (UTC)

Airbags provide additional protection, especially in the event of a head-on collision. They used to be available only on luxury cars, but now they're pretty much standard issue in America. And just to reiterate, many states have what they call "click it or ticket" laws, meaning it is not a right to drive without a seatbelt. (In fact, driving itself is not a right - it's a privilege regulated by the government(s).) ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:03, 29 July 2012 (UTC)

Airbags are not meant to be used without a seatbelt. They form part of what's known as the Supplemental Restraint System. To quote the wikpedia article; "severe or fatal injuries can occur to vehicle occupants very near an airbag or in direct contact when it deploys. Such injuries may be sustained by unconscious drivers slumped over the steering wheel, unrestrained or improperly restrained occupants who slide forward in the seat during pre-crash braking". Increasing the force of airbag deployment for unrestrained passengers just sounds like a way to smack them even harder with the thing after they've already made contact with the dash or steering wheel. 203.27.72.5 (talk) 00:07, 30 July 2012 (UTC)

I assume the thing about locking cardoors is mostly aimed at reducing the odds that kids manage to open them at the wrong time; I'm really sceptical of the carjacking issue, which seems like a very low risk indeed, and it's not like you can't be carjacked straight through a closed window, unless you have bullet proof glass. Wnt (talk) 03:33, 30 July 2012 (UTC)

A locked door can still be opened from the inside (at least in every car I've tried it) so it won't prevent accidental opening, but there are often child safety latches (don't know what they are called in English) that disengage the inside door handle.Sjö (talk) 12:56, 30 July 2012 (UTC)

It is written in the article itself, outside the US, airbags are wearer as they are based upon the idea that people wear seatbelts more often, that is how they do the testing. I'm not saying people don't usually wear seatbelts in the US, they do, I'm saying the statistics vary according to country. I'll be happy to eat my keyboard and post the pics if every country wears seatbelts as often as the other. Penyulap ☏ 03:41, 30 Jul 2012 (UTC)

Having rules against not wearing seatbelts has nothing to do with the percentage of people who do, or the manufacturers efforts to compensate appropriately for it. Copyright. they have rules against it too, doesn't mean nobody does it. Penyulap ☏ 03:43, 30 Jul 2012 (UTC)

Having rules, publicising those rules and (perhaps most importantly) enforcing those rules with penalties for non-compliance probably does affect the percentage of people who wear seatbelts. At least the Western Australian Office of Road Safety seems to think so. Mitch Ames (talk) 10:04, 30 July 2012 (UTC)

Kinky tails on asian cats

Does Wikipedia have an article on the genetic defect which cause many cats from Thailand and Malaysia to have kinky tails? -- 203.82.81.154 (talk) 12:09, 29 July 2012 (UTC)

I've not found one, but I found this article which says "Kinked tails are seen commonly in many breeds of cat, particularly Siamese, Burmese and Oriental breeds. The kinks typically result from deformities of the bone and are listed as defects by most breeding authorities. However, they are usually only of aesthetic relevance as they cause no pain or discomfort to the cat." I would suggest that because the deformity is of no real significance, there's not a lot written about it, and my searches so far have confirmed it. --TammyMoet (talk) 12:45, 29 July 2012 (UTC)

my daughter has apha thalassemia

moved from Talk:Thalassemia#my daughter has apha thalassemia

my daughter has alpha thalassemia and I'm trying to get a better understanding of this. The doctor have advise that she cannot marrie anyone who has the same trait. what will effect will it cause when thry have a child together?

[Author unknown] 86.136.221.113 (talk) 11:36, 27 July 2012 (UTC)

I think this is worthwhile answering, please assume good faith. Penyulap ☏ 12:32, 29 Jul 2012 (UTC)

Genetic counseling definitely crosses into our policy of no medical advice. The original poster should find a genetic counselor to explain this in more detail. The doctor in this case was simply indicating that by classical Mendelian inheritance, someone who expresses alpha thalassemia is usually someone with a double-recessive of the gene in question. If they procreate with someone else who is also a double-recessive, 100% of their children will be double-recessive. If they procreate with someone who is merely a carrier (one copy of the thalassemia gene, which is not enough to express the disease), the children will have a 50% chance of being a double-recessive and a 50% chance of being only a carrier. If they procreate with someone who lacks the thalassemia gene altogether, their children will be 100% carriers. The probabilities of classical genetics are straightforward, but the real-life implications and the real-life complications are often not — and this is why a genetic counselor should be talked to. --Mr.98 (talk) 13:18, 29 July 2012 (UTC)

For more information on what Mr.98 is talking about, see autosomal recessive (also linked in the first sentence of thalassemia). --Tango (talk) 21:56, 29 July 2012 (UTC)

The above explanation may be applicable to beta thalassemia but is incorrect for alpha thalassemia, which results from the expression of two pairs of genes. --202.28.181.200 (talk) 09:46, 30 July 2012 (UTC)

You're right — the genetics are much more complicated than I'd realized. It actually depends quite specifically on exactly the way genome is expressing in the daughter and the potential mate -- you get very different results if you make different (legitimate) assumptions (the most common form of alpha thalassemia is either -/a -/a OR a/a -/-, and these produce very different Punnett square crosses with others of the same or the alternative form). The results can be anything from a carrier with almost no expression, to a fetus that cannot survive outside the uterus. The good news is that there is probably more flex to this than the original doctor said; the bad news is that the bad results could be even worse than I originally assumed. Again, a genetic counselor is definitely needed in this situation. --Mr.98 (talk) 15:09, 30 July 2012 (UTC)

Resources we can offer: We cannot comment specifically on your daughter's condition. However, we can suggest you read the articles Thalassemia, for a broad overview, and Alpha-thalassemia for the condition you are asking about. The external links sections at the bottom of these articles will suggest other websites, resources, and support groups you may find informative, likely more informative than we can be. Specifically the section Types in the Alpha-thalassemia article describes the concern for potential different effects on a child depending on how many copies of the affected genes it inherits from each of its parents. μηδείς (talk) 17:33, 29 July 2012 (UTC)

I certainly agree that we should not suggest whether they should marry or not. However, we are here to assist in research, even if it is not as notable as that of Augusto and Michaela Odone. I am glad you have given some guidance towards research, I would not like to see someone genuine turned away from the project if they are earnestly seeking to learn more. Penyulap ☏ 14:23, 29 Jul 2012 (UTC)

Don't forget, Kainaw's criterion is there if you're unsure about answering medical questions. BigNate37_(T) 15:12, 29 July 2012 (UTC)

My hesitation to go into any more detail comes from the fact that there can be many individual caveats to such an explanation. I attempted to answer the question in general terms as to what the doctor was probably trying to say, but even then I hesitate to put words into a doctor's mouth. Basic Mendelian genetics is relatively straightforward, but real genomes are usually much more complex, even for very simple traits. --Mr.98 (talk) 16:06, 29 July 2012 (UTC)

Oh, it wasn't my intent to call your judgment into question! Apologies if that's how it sounded. BigNate37_(T) 16:15, 29 July 2012 (UTC)

Please see http://ghr.nlm.nih.gov/condition/alpha-thalassemia, http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001613/, http://www.aafp.org/afp/2009/0815/p339.html, and http://asheducationbook.hematologylibrary.org/content/2009/1/35.long 207.224.43.139 (talk) 21:33, 29 July 2012 (UTC)

Collimated electromagnetic field

Is it possible to collimate electromagnetic field into a beam similar to a laser? ScienceApe (talk) 16:20, 29 July 2012 (UTC)

A laser beam is a collimated electromagnetic field. Do you mean a static, non-oscillating field? If so, I'm pretty sure the answer is no, except in the interior of structure such as a coil. Looie496 (talk) 16:27, 29 July 2012 (UTC)

Do the lines of force of a magnetic field count: [8] ? StuRat (talk) 19:00, 29 July 2012 (UTC)

Those are not collimated -- see collimation. Looie496 (talk) 19:17, 29 July 2012 (UTC)

A directional antenna looks different at each wavelength. A parabolic dish antenna, or a Yagi, serve to collimate an RF electromagnetic field to some extent. At optical wavelengths, we tend to use refractive optics - that is, lenses - rather than reflective optics (mirrors) - because we can conveniently build such effective, compact structures. But, if you ever look at a radio telescope, you'll see that it's just a Newtonian telescope mirror designed to focus a very large wave.

Finally, keep in mind that a laser is not just a collimated beam. It is a special type of light amplifier - and as a side effect, produces monochromatic light, which is very easy to collimate. You can collimate a beam of light even if it did not come from a laser source. So, by the same token, we can create amplifiers at other wavelengths to create strong radio or other electromagnetic waves; and we can also collimate those beams using appropriately designed "optics" suitable for the frequency. Nimur (talk) 19:28, 29 July 2012 (UTC)

No. (K.I.S.S.) Penyulap ☏ 03:50, 30 Jul 2012 (UTC)

Penyulap, while your answer was certainly succinct, it is also entirely incorrect. A laser beam is an electromagnetic wave. And, as earlier answers have explained, the concept can be extended to other electromagnetic radiation. Brevity is no substitute for accuracy. Nimur (talk) 14:28, 30 July 2012 (UTC)

de-colorized iodine

I saw something in the first aid aisle called de-colorized iodine. How do they de-colorize iodine? Does it affect its properties? --Wrk678 (talk) 18:03, 29 July 2012 (UTC)

From what I can see online, it is probably potassium iodide, but might be another iodine compound -- you will probably see exactly what it is if you look at the ingredients label. If it is indeed an iodine compound, the properties will be quite different from those of ordinary tincture of iodine. Looie496 (talk) 18:24, 29 July 2012 (UTC)

I'm not sure what that would be doing in first aid. My understanding is that the usual first-aid use of iodine is to kill bacteria (and viruses, I suppose) by oxidation; potassium iodide is not going to oxidize anything. Sometimes KI is taken orally when there are worries about iodine-131 in the environment after a nuclear mishap, but that's not a standard first-aid concern.

Tincture of iodine isn't used that much anymore because there are safer alternatives (and maybe because big brother is worried about people using it to make meth). --Trovatore (talk) 21:34, 29 July 2012 (UTC)

Sorry, I thought "tincture" was the term for the usual brown stuff. Anyway, my take from what I saw scanning the web is that "de-colorized iodine" is a product whose utility for first aid is, um, not well established. Looie496 (talk) 23:14, 29 July 2012 (UTC)

isint potassium iodide yellow? And how are the properties different?--Wrk678 (talk) 21:18, 29 July 2012 (UTC)

The article on potassium iodide explains why KI yellows due to impurity or age. BigNate37_(T) 23:21, 29 July 2012 (UTC)

There is also potassium triiodide which is likely what our OP is asking about. You make it by dissolving iodine in KI solution. Graeme Bartlett (talk) 06:58, 30 July 2012 (UTC)

But that solution is not colourless (which I assume is what is meant by "de-colorized"). See the left most testtube in the picture under "Testing for Starch" 203.27.72.5 (talk) 07:24, 30 July 2012 (UTC)

Curiously, according to this De-colorized Iodine label it's just tincture of iodine, and the active ingredient is the alcohol, with the iodine and iodide being listed as inactive. 203.27.72.5 (talk) 07:39, 30 July 2012 (UTC)

In this particular instance, this is a clear case of angel dusting, where the amount of iodine is insufficient to have any effect or change the color, but is dishonestly marketed as if the iodine was in sufficient quantities to provide an antiseptic effect, when, in fact, the alcohol does that. Their ruse is rather transparent; they must feel they can sell it for more if people think it's an iodine antiseptic than an alcohol antiseptic. StuRat (talk) 08:19, 30 July 2012 (UTC)

What is exceptional about the human body ?

...relative to other animals. Here's what I came up with so far:

1) There's our brain, obviously, although the much larger size of whale brains suggests they much have abilities we lack, like remembering every detail of their lives, perhaps. We do have the greatest division of labor among any species, I believe, as a result of our brains.

Now for ones I'm less sure of:

2) The opposable thumb does give us the ability to use tools. However, this ability is shared by other primates.

3) Our permanent bipedal motion allows us to walk long distances using little energy, see farther, and also to carry and use tools more effectively. (We do, however, pay for it with a slow sprint speed and lots of back problems.) Ostriches and other birds seem to share this ability, however, and without all the negatives.

4) Our starvation response seems to allow us to survive a month or two without food. Short of hibernation, this seems pretty decent. How does this compare with other animals ?

5) Our adaptive immune system seems able to provide us with immunity to a wide range of diseases after we've been exposed to them. How does this compare with other species ?

6) Our eyesight seems to be good overall, except for the huge percentage of us who are near-sighted or far-sighted. While other species have eyesight that can magnify more, see additional wavelengths, or see in the dark better, etc., we seem to have decent combo, especially the parts involving our brain, like motion detection and pattern recognition. How does this compare with other animals ?

7) Our omnivore abilities appear to allow us to eat a large variety of foods, with the exceptions of decomposing food, feces, grasses and wood, and foods containing various toxins. How does the wide range of foods we can eat compare with other animals, such as bears ?

8) Our lifespan seems to be near the top end of most animals.

Are there any other ways in which the human body is exceptional ? StuRat (talk) 18:56, 29 July 2012 (UTC)

I wouldn't say humans are exceptional in precise ways like that. Historically, pretty much every claim of the form "Humans are the only animal that..." has been disproven. The combination of the things you mention may be exceptional, but I expect an animal can be found for each of them that is "better" than humans. I think the most exceptional things about humans are the extent to which we use language and technology (neither of those is unique to humans, but I don't think any other animals use them as extensively and in as advanced a form). --Tango (talk) 22:14, 29 July 2012 (UTC)

The most important thing about humans ecologically is that we are the most K selected animals for body mass on the planet. This is a direct result of the success of human culture as a survival strategy, and the long period of acculturation (for things such as language acquisition which it requires. See K and r selection. Basically animals can invest a lot in a few children or invest a little in a lot of children. The latter, r selected animals, tend to live very short lives, most only a year or a season, and some only a day or a month as adults. Whales and elephants are the most K selected non-human animals, and live about as long as us, but they hugely outweigh us. Each human life is a huge biological investment so far as reproduction goes. We can't reproduce successfully on average til our late teens. We can only successfully raise one baby every two years on average. Historically, women may have had 10 or 12 babies in a lifetime, but on average they only had two or three that survived to adulthood, a fact which has not changed with modern demographics. And the presence of grandparents is a proven success strategy with humans. This means we are selected for strong immune systems, big brains, and long life in general, with the traits that support it. Other animals of our body size tend to have small litters, like big cats, or one precocious offspring like deer. They become independent in the fist year and reproductive within a few years at most. Humans are the epitome of altricial animals. No other animal takes a year to be able to walk or swim. It is the huge reproductive investment in each human that makes us unique and so successful. μηδείς (talk) 22:17, 29 July 2012 (UTC)

• Our social and communication systems are light-years more complex than that of any other animal.
• We're tool users. Creating what other animals have to evolve to.
• We have the longest childhood/adolescent dependency period of any animal by far. The second closest are orangutans and elephants, whose children stay with their parents for up to 10 years.
• We're one of the few animals where the females have concealed ovulation.
• We're one of the few animals who sweat for thermoregulation. The only other I can think of atm are horses.
• Binocular vision gives depth perception. But it's also common among other predators.
• Trichromacy makes us remarkable among mammals. But pretty average to weak in terms of other animals like birds.
• For a large mammal, we're relatively hairless. I just thought of elephants and whales! LOL
• We're one of the few animals that have recreational sex. Though admittedly other mating animals probably don't know they're reproducing either.
• Lactase persistence, we're one of the few mammals that can still derive nutrition from milk at adulthood. At least the humans who've been lucky enough to inherit the several mutations for it. Also random : don't feed your cat milk, they like it but they can't digest it and get stomachache, kthx.-- OBSIDIAN†SOUL 22:49, 29 July 2012 (UTC)

On brain size, a more useful index than raw mass of brain tissue is the ratio of brain mass to body mass — see the Encephalization quotient. Basically a lot of any brain is taken up with the motor skills and regulatory work of a large body. So animals that have big brains relative to their mass tend to be using more of their brains for being smart. Dolphins come out well in that comparison, as do chimps. Whales, not so much, but they may be an exception in any case because of their ridiculous amount of mass. Elephants are quite intelligent despite the inflated brain size because of their mass — it's still larger than average. In any case, it's pretty clear that raw brain size isn't really the trick — the trick is having certain specialized organs in the brain wired up in useful ways.

Humans are not exceptional in that we possess any one thing that other animals don't. But we are fairly tailored towards complex linguistic, social, and cerebral applications. These paired with excellent hands for tool-making has, over the long term, made us feel fairly dominant. (Whether we are dominant is an open question. Insects still have a one-up on us in terms of raw numbers and future prospects. From the point of view of krill, humans have just shown up and haven't been doing too much of interest.) --Mr.98 (talk) 23:21, 29 July 2012 (UTC)

You do realize biologists consider dolphins whales? μηδείς (talk) 00:39, 30 July 2012 (UTC)

Our dolphin article says "Dolphins are marine mammals closely related to whales and porpoises". This isn't the same as being a whale. StuRat (talk) 02:24, 30 July 2012 (UTC)

(ec)I think Looie is by far and away the most qualified to comment on this but my understanding is that whales need large brains just to control and receive feedback from their massive bodies. I don't think there's any suggestion that they have super abilities to remember everything or anything like that. 203.27.72.5 (talk) 23:22, 29 July 2012 (UTC)

I am glad you assigned winning prize in the spelling bee to the student who, because he was absent on the day of the test, didn't get any questions wrong. As for whale, I already posted the link to encephalization quotient. You might find reading it surprising, especially if you compare the size of the brains of sauropods and dolphins. μηδείς (talk) 00:37, 30 July 2012 (UTC) * 203.27.72.5 (talk) 03:25, 30 July 2012 (UTC)

When I said "Looie is by far and away the most qualified to comment on this" I was only refering to point 1) about the brain size since Looie apparently has a PhD in Neuroscience. But since you obviously feel left out, I left you a gold star :) 203.27.72.5 (talk) 03:25, 30 July 2012 (UTC)

I appreciate that star, I'll move it to my user page if you don't mind. I agree with Looie's statement below on the vagueness of the thread. But I think the answer is quite clear that our big brains, long childhoods, and longevity, making us the most K selected animal on the planet, all have to do with the success of culture and the traits it encourages the selection of. μηδείς (talk) 18:46, 30 July 2012 (UTC)

This topic is too diffuse for me. If it were only about brain size I might have something to say, but I don't like topics that are bound to meander all over the place. Looie496 (talk) 03:45, 30 July 2012 (UTC)

I think a major thing is that humans spend a huge amount of effort trying to learn and explore for the sake of interest and curiosity as opposed to simply finding out what we need to know to survive. I could be wrong about this being exclusive to us though. Juliancolton (talk) 03:01, 30 July 2012 (UTC)

We should not overlook fine motor skill. Bus stop (talk) 04:05, 30 July 2012 (UTC)

The answers seem to be going off track here. I want to know in what ways, if any, humans are PHYSICALLY superior to other animals, not all of the ways we are mentally superior. StuRat (talk) 04:07, 30 July 2012 (UTC)

How about our ability to sweat? An interesting and related article is Endurance running hypothesis. Bus stop (talk) 06:10, 30 July 2012 (UTC)

Regarding question #5 (how does our adaptive immune system compare with other species), see the article you linked to (Adaptive_immune_system#Alternative_adaptive_immune_system). All vertebrates except the most primitive ones (jawless vertebrates) have an adaptive immune system that is similar to ours. Vaccination is routine practice in fish farming, see for example this link. --NorwegianBlue ^talk 17:56, 30 July 2012 (UTC)

The ability to get scurvy (inability to synthesize vitamin C)? is fairly exceptional, though not unique. --catslash (talk) 18:48, 30 July 2012 (UTC)

Aren't humans the only animals capable of abstract thought? --146.7.96.200 (talk) 19:38, 30 July 2012 (UTC)

StuRat, this documentary video may interest you. (Warning: Some content may be objectionable to some viewers.) (Disclaimer: I do not necessarily agree or disagree with general or specific points made in the video.)

• The Superior Human? | Watch Free Documentary Online (1:13:33)

—Wavelength (talk) 20:21, 30 July 2012 (UTC)

Care to give me a summary, before I invest over an hour in watching it ? StuRat (talk) 23:05, 30 July 2012 (UTC)

The narrator discusses about 18 "alleged reasons" for the claim of human superiority, with "counterarguments" for all of them. The "alleged reasons" include: intelligence, language, culture, tool-making, opposable thumbs, bipedal locomotion, longevity, population, and position atop the food chain.

—Wavelength (talk) 23:56, 30 July 2012 (UTC)

But we're not even at the top of the food chain. 203.27.72.5 (talk) 01:34, 31 July 2012 (UTC)

Actually, we are on top of the food chain (we are an apex predator). Other animals only rarely eat humans, and we eat them more often than they eat us. So, if we aren't an apex predator, then no animals is. StuRat (talk) 05:13, 31 July 2012 (UTC)

Gustave regularly eats people. No one eats him. He's an apex predator. 203.27.72.5 (talk) 07:51, 31 July 2012 (UTC)

He may end up being eaten by people eventually, or maybe just made into belts. StuRat (talk) 09:39, 31 July 2012 (UTC)

I don't see this mentioned above, which seems surprising: an awareness of self and mortality which gives us the possibility of surving the destruction of the planet or a solar event by deliberately colonizing others, although we're not there yet; and, the imagination that we may arrive as visitors. Dru of Id (talk) 23:25, 30 July 2012 (UTC)

Melted cheese, part 2

I previously asked about why melted cheese tastes batter and got my answer, thank you.

I'm surprised more businesses don't sell previously melted cheese, considering how it makes a mess to melt it yourself, and you can't always melt it when on the road. Those portable string cheese containers, for example, could contain previously melted cheeses, which you could squeeze out like with Go-Gurt. It does seem to be potentially more messy than unmelted cheese, but we do eat plenty of other potentially messy foods, like grape jelly, and, in Wisconsin, at least, cheese curds. So, is there another problem with it ? Does it decay more quickly ? StuRat (talk) 19:40, 29 July 2012 (UTC)

Have you ever actually tried melting cheese and leaving it to sit for a day? The oil separates from the rest, and you get something approximating rubber coated with oil. It's not anything I would want to eat. It seems like what you are searching for here is Cheez Whiz. Looie496 (talk) 19:47, 29 July 2012 (UTC)

If you melt real cheese while somehow keeping the fat from separating from the protein matrix (with emulsifiers or melting salts usually or... dunno, very very slowly?), it will solidify into something else - processed cheese! :P -- OBSIDIAN†SOUL 20:09, 29 July 2012 (UTC)

Yes, processed cheese#Advantages sums it up. "...extended shelf-life, resistance to separation when cooked, and uniformity of product." The big clincher is that real cheese changes flavour and texture rather unpredictably when partially melted, which is not optimal from a convenience food standpoint. BigNate37_(T) 20:15, 29 July 2012 (UTC)

July 30

Explain how ducks & chickens stay alive without their heads.

Warning: The videos show slaughter of ducks and chickens for their food. The channel is "TheTimeToHunt," and they are filmed by farm hands who also specialize in hunting. The video about the ducks is also age-restricted. If you don't wish to view the slaughter of farm animals, please don't watch.

• Duck slaughter
• Chicken slaughter

As you can see, after the slaughter, their bodies move around without their heads, for a relatively long while. The chicken, particularly, seems to flail around as if in sheer anger, toward the end of its video. (What is it trying to do?)

Also, I believe it seems to bawk furiously, but how would it without its head?

Anyways, without a brain to control bodily movements, how exactly would their bodies move anyhow?

And have there ever been incidences of decapitated human bodies moving around in a similar fashion? How long did the longest post-decapitation movement last? Thanks. --70.179.170.114 (talk) 00:11, 30 July 2012 (UTC)

Well, http://www.damninteresting.com/lucid-decapitation/ cites some literature on the topic of human decapitation if you're interested in tracking down non-anecdotal information. BigNate37_(T) 00:19, 30 July 2012 (UTC)

(edit conflict) A simple way to think about it is that not all your brains are in your brain. Many basic bodily movements and reflexes — like your instinctual reaction to being burned — are governed by your spinal cord (in the case of being burned, this has an obvious evolutionary advantage — the spinal cord burn reflex is much faster because it skips the brain until after the fact). Presumably many bird motor functions are handled by non-brain nervous connections. As for people, I don't know about bodies moving after decapitation in anything but very uninteresting ways (and the amount of blood lost in decapitating a human would be immense due to the importance of the jugular veins which would kill the body off very quickly), but two things come to mind: 1. brain death, whereby your body can stay quite alive provided that certain basic needs are met for it, despite the upper functions of your brain being decidedly dead; 2. the opposite question, whether a decapitated head can survive long outside the body, has been studied. The answer is not long — again, the key factor here being the sudden change in blood pressure and lack of fresh oxygen, which is quickly fatal to humans and probably all animals above a certain mass. --Mr.98 (talk) 00:24, 30 July 2012 (UTC)

Also, the brain stem is the most vital part of the brain, and is below the rest, so can be left after a "decapitation". In one case, a chicken survived for years with only it's brain stem. StuRat (talk) 00:37, 30 July 2012 (UTC)

See also Mike the Headless Chicken. 207.224.43.139 (talk) 01:14, 30 July 2012 (UTC)

Surgeons with serious ego problems have a fetish for killing siamese twins because they figure it looks good on a resume. One such case comes to mind, where the co-joined twin was not fully formed, I can't recall the name of that condition, but it is quite common. One twin had only fully developed down to their neck, and no further. They lived for their whole life dependent upon their sibling for life support, and lived a good life by their own standards, being sentient, emotional, basically everything any generic quadriplegic mute would be. However surgeons always overlook the fact that twins can live quite happily together forever in their mad rush for fame and the spotlight. The child was murdered by the surgeons in the eyes of the local religious leaders and any reasonable human being, and a funeral took place. So as for the brain living without a body, that can go on for quite some time. As for a body living with no brain, I believe the surgeons are still alive today doing this kind of thing.

I haven't watched any videos, but have read about chickens kept alive for a long time spoon fed after their brains were sliced in a particular way. But you can also study brain death. Penyulap ☏ 04:02, 30 Jul 2012 (UTC)

How is this relevant to the question? Either way, I think you should be careful making those kind of accusations. There are significant medical, ethical and legal questions surrounding the separation of conjoined twins and it is not remotely as simple as you make out. These days, separation is normally done only if both twins stand a good chance of surviving, or if there is a good chance that both will die if they don't separate them (and that at least one will live if they do). Quality of life is not generally a significant concern - what they think about is whether they will live at all. (This was not always true - separations were performed in the past with lives lost where they wouldn't have been today. There will also be some differences from country to country, but I think the basic goal is the same everywhere, there are just differences in judgement.) --Tango (talk) 13:14, 30 July 2012 (UTC)

Names of a couple of extremely hazardous chemicals

Looking at List of extremely hazardous substances, I noticed that one of the entries was Phosphonothioic acid, methyl-,. Wanting to know what it was, I put it into Google and was pointed to Phosphonothioic acid, methyl-, s-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester, but I didn't learn anything about the first compound. This prompted a series of questions in my mind:

• What's the significance of ", methyl-," at the end of the first one? Does it have an extra methyl group somewhere? And regardless of why it's included, why is it tacked onto the end with commas and a concluding hyphen?
• All of those nested parentheses on the second one (VX nerve gas) confused me, because I can't remember seeing parentheses in a compound name before. What do they signify? IUPAC discusses compound naming only very quickly and doesn't mention nested parentheses. Nyttend (talk) 01:51, 30 July 2012 (UTC)

If you look at the first intermediate product in the image to the right, it looks like it's analagous to your "phosphonothioic acid, methyl-", and it's called methyl phosphonous dichloride. I think your compound should be written "methyl-phosphonothioic acid" but they wanted to make it appear in alphabetical order next to Phosphonothioic acid, methyl-, s-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester. 203.27.72.5 (talk) 02:13, 30 July 2012 (UTC)

See the Blue Book Online for examples of parenthese in organic compound names with explanations. 203.27.72.5 (talk) 02:29, 30 July 2012 (UTC)

The list gives the source for its information, http://ehs.uark.edu/DocumentPages/ExtremelyHazardousChemicals.pdf, and a look at that source shows that two of the entries for Phosphonothoic acid variants have been truncated in the table. That particular one should be Phosphonothioic Acid, Methyl-, O-(4-Nitrophenyl) O-Phenyl Ester. Looie496 (talk) 02:15, 30 July 2012 (UTC)

I find myself wondering if some of these listings are motivated by political rather than toxicological factors, i.e. use as precursors to something, e.g. piperidine and aniline, which don't AFAIK rate as particularly deadly. (Not really sure why aniline rates even by this explanation, actually...) Of course, the list has a particularly heavy emphasis on nerve gasses and precursors thereof. Wnt (talk) 03:22, 30 July 2012 (UTC)

I don't understand the point of the list at all. It has things as common place as ammonia but neglects things as hazardous as nitroglycerin and TNT. About half of the listed chemicals don't even rank as a High Hazard according to my ChemAlert database. It doesn't list any of the toxic lead compounds, some of which are very hazardous (lead sulfate, nitrate, acetate, bromide, chloride, fluoride, iodide, oxide, thiocyanate, chromate, etc.). And as the amount of red ink on the page testifies, a lot of it is ridiculously obscure. 203.27.72.5 (talk) 04:09, 30 July 2012 (UTC)

That's a valid point. It should probably be moved to another title, one that reflects its legislated nature. I've been following this section and it wasn't until you made that remark that I opened the article and realized that list is based on some American law. I would have assumed it was based on something more quantitative, or at least something more academically authoritative. BigNate37_(T) 04:27, 30 July 2012 (UTC)

As for piperidine and aniline; piperidine is considered highly hazardous with an LD₅₀ of 30 mg/kg (mouse, ingested) plus high flammability and causes burns; aniline is considered moderately hazardous with an LD₅₀ of 195 mg/kg (dog, ingested), though humans have a much greater tolerance for it (TD_Lo (ingestion): 3125 mg/kg (child)). It's also a possible carcinogen. 203.27.72.5 (talk) 04:35, 30 July 2012 (UTC)

If you're still interested in finding out about methylphosphonothioic acid, the PubChem article might be what you're looking for. 203.27.72.5 (talk) 05:15, 30 July 2012 (UTC)

The answer to this puzzle is actually pretty banal. Those chemicals are there because they appear explicitly in the text of the Emergency Planning and Community Right-to-Know Act, which requires them to be handled in a specific way. Looie496 (talk) 05:19, 30 July 2012 (UTC)

It's not even a puzzle, it's explicitly stated in the first two sentences of the page! One could certainly propose renaming it to a more clear title, but you can't say the page itself is at all unclear about the listing/inclusion criteria. DMacks (talk) 05:28, 30 July 2012 (UTC)

My problem wasn't so much with the article, but rather with the list as written by the legislators. Why would you title the list "extemely hazardous substances" when some of the things aren't really that hazardous? Why does the list name some very obscure substances while totally missing out more common and much more dangerous ones? Presumably, other legislation will refer to this list for various purposes. It seems like this list ought to a least be named in a way that makes it a bit clearer what exactly it lists, and better would be word or two as to the criteria for inclusion. 203.27.72.5 (talk) 06:01, 30 July 2012 (UTC)

Actually the current list is managed by the EPA through the CFR. I'm not looking at the text of the original bill... but even when congress itself writes technical lists like this there's usually input from committees and relevant science. I'm sure they have their own internal criteria for what goes on the list at the EPA. Shadowjams (talk) 09:00, 30 July 2012 (UTC)

Other agencies and other countries may have different priorities and different lists (yes yes, risk knows no language, but priorities do vary in reality). We shouldn't have an article which presents the EPA's list as though it's a global or agency-independent list of the most hazardous substances. A list which drew together items from different sources might be better; either that or rename the article. No? bobrayner (talk) 12:49, 31 July 2012 (UTC)

Sustainable athletics

Watching the Olympics, it seems like it's more often than not that the athletes are trying to recover from some injury - ACL tear, Achilles tear, etc. Often they're going in with visible signs of injury - it's amazing how many of the volleyball players have two fingers taped together for some reason, for example. Question: is it possible, if people wanted, to arrange the competition not to be a bloodsport, to come up with a way to design things so that the athletes have a lower lifetime risk of injury? Is anyone trying to do that practically? Wnt (talk) 03:50, 30 July 2012 (UTC)

As an athletic trainer of some years, I can tell you that many tapings are preventative. Many healthy football and basketball players get wrists and ankles taped before each game. Much like compression stockings and compression sportswear, this tape tension applied to joints can give the muscles a tighter "skin" in which to operate; this has the effect of preventing injuries. In the case of volleyball players, multiple fingers are taped together because the paired taping protects the fingers without impairing control of the ball surface. The tape itself can have a positive effect on ball contact. Boxers use a specific taping/wrapping technique which prevents injury of the hands despite constant pounding. Often athletes of Olympic caliber are pressing the body to feats few can achieve. Occasional injuries are often unavoidable. The use of compression taping is one legal and practical method of preventing injuries which otherwise might occur. BusterD (talk) 05:01, 30 July 2012 (UTC)

Well, they could wear protective gear, like helmets and pads, but who would want to watch a gymnast wearing all that ? They could add more springiness to the ground or equipment, but any substantial change like this makes comparison of new records with old records difficult. StuRat (talk) 08:29, 30 July 2012 (UTC)

That doesn't help. Statistics show that injuries don't change when protective gear is introduced. People just take more risks. --Tango (talk) 13:18, 30 July 2012 (UTC)

I'd like to see those statistics. If true, why do American football players wear so much of it ? StuRat (talk) 19:48, 30 July 2012 (UTC)

Because it's a spectator sport and the crowd loves to see the players take risks....and to see them not pay off. 203.27.72.5 (talk) 19:59, 30 July 2012 (UTC)

No. Atheletes will always push themselves to the limits in order to maximise their performance. When you do that, there is always a risk that you will go slightly beyond your limits and injure yourself. --Tango (talk) 13:18, 30 July 2012 (UTC)

Malcolm Gladwell wrote an interesting portrait of a long-distance runner in the New Yorker recently. Basically this guy is one of the best in the world because he can disconnect the part of him that says, "hey, you are at your limit" and will more or less run until he is very nearly dead. He's almost died on numerous occasions. That seems to be what it takes to be one of the great athletes. I'll pass, personally... --Mr.98 (talk) 14:16, 30 July 2012 (UTC)

In most sports, people are working constantly to better protect players, through rule changes, education and training, better equipment, more severe punishments for offenders, etc, particularly in more dangerous sports like American football[9][10]. I'm unclear if the question is asking specifically about rules to protect volleyball players, but even in volleyball there have been efforts to improve the safety of volleyball players[11][12]. --Colapeninsula (talk) 16:18, 30 July 2012 (UTC)

That first link is remarkable - not being a sports fan, I didn't have any idea the rules had been changed much for this purpose, let alone so often! It's interesting. Though the page doesn't really say how much all this accomplished. Wnt (talk) 02:37, 31 July 2012 (UTC)

• There can also be superstition around various kinds of tape or special garment; athletes may believe that it helps their performance even if there's no solid evidence to support this belief. Of course, a placebo can still cause a real performance improvement - and something which looks more drastic and medical may have a bigger placebo effect. I don't know whether power bracelet type stuff is allowed in olympic competition (it might be banned for advertising rather than performance-enhancing reasons) but that kind of thing is very popular in various sports. So, some of the visible stuff you see might not be a way of repairing an existing injury, or preventing a future injury, but simply a lucky rabbit's foot.
• Also, there will be some observation bias because these athletes are in the spotlight and generally wearing uniform garments which don't cover all their bodies, so anything on their skin will really catch the eye. Sometimes it's just a bit of tape; no biggie. I used to tape my toes to reduce chafing when I trained intensively; chafing from a single event wouldn't be a crisis, but the cumulative effect would be uncomfortable, and tape is cheap. bobrayner (talk) 12:45, 31 July 2012 (UTC)

I have concluded that the more/better the pading and protective gear in american football the more numerous and severe the injuries based on observing the helmet to helmet and body charging especially when you can support the helmet with the shoulder pads so that there is almost no risk of damage to tackler from a spear-type tackle. Rugby has just as much if not more contact and they seem to have the same injury rate. When you don't have all the protection you reconsider how bezerk you will go on the opponent.165.212.189.187 (talk) 13:42, 31 July 2012 (UTC)

Rough food

While reading the article Halitosis, I found a term rough food in Management section under point 2. Can you provide me some examples of rough food? Sunny Singh (DAV) (talk) 13:55, 30 July 2012 (UTC)

It would seem that this refers to the texture of the food, so maybe toast or cereals. I conclude this because the section refers to the scraping action on the back of the throat. --TammyMoet (talk) 14:24, 30 July 2012 (UTC)

See "Roughage" (—> "Dietary fiber") and wikt:roughage.

—Wavelength (talk) 20:58, 30 July 2012 (UTC)

Energy density of springs and the like

What is the energy density of springs, elastics and other mechanical devices for the storage of energy? OsmanRF34 (talk) 17:13, 30 July 2012 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

We have an entire section in our article on Hooke's law - the thermodynamics of elastic materials. However, in most basic physics texts, you'll see this question come up as a standard example problem for calculating conservative work. Depending on what you're doing, you may be able to get by with simple algebra. Nimur (talk) 18:03, 30 July 2012 (UTC)

Human interaction

Often a male assumes that if a female smiles at them a lot, then the female is attracted to the male. However in human interaction, the majority of people will smile after making eye contact regardless of gender. So why do so many males have this false predisposition. 176.250.151.7 (talk) 18:49, 30 July 2012 (UTC)

Wishful thinking. thx1138 (talk) 19:09, 30 July 2012 (UTC)

It depends on the context. If the receptionist smiles at you, you understand it's just her job. If a woman sitting at the bar keeps looking at you and smiling, it means she is attracted to you, or you are funny looking. :-) StuRat (talk) 19:52, 30 July 2012 (UTC)

True but other than a bar, generally most people will smile, unless they are in a bad mood. I think smiling is more of a friendly gesture than one that suggests attraction. 176.250.151.7 (talk) 20:22, 30 July 2012 (UTC)

It's more the eye contact than the smile. A woman who doesn't want attention from a man will carefully avoid making eye contact with him. Looie496 (talk) 20:33, 30 July 2012 (UTC)

(edit conflict) Most people can tell the difference between an initial eye-contact followed by a friendly smile, and repeated non-accidental eye-contact (with or without the smile) that indicates special interest of some kind -- not necessarily sexual, but usually taken to be, especially in a bar. Most females make similar assumptions. Dbfirs 20:35, 30 July 2012 (UTC)

This is very much a cultural phenomenon. I remember when I was living in (the former East) Germany, the people there thought Americans were strange because they always smile during general interaction. They didn't find it unpleasant, just odd. Javanese that live in Bali often point out how Balinese people never smile, but foreign tourists there often talk about the glowing receptions they receive from Balinese everywhere they go. How men interpret the smiles they receive from women is entirely dependent on their own background, experiences and predispositions. 203.27.72.5 (talk) 22:50, 30 July 2012 (UTC)

If the male assumes the smiling female is smiling at him because she is attracted to him, and he is wrong, then he might end up suffering some social embarassment, but no other negative consequences. If, on the other hand, he is right, he might end up mating with her and producing offspring. If the male does not assume the female is attracted to him, then whether she actually is or not, he will not be mating and producing offspring with her. Therefore, natural selection favors males who assume that smiling females are attracted to them, since there is very little cost to him being wrong and much to gain if he is right, so the answer to your question "why do so many males have this false predisposition" is evolution. —SeekingAnswers (reply) 01:34, 31 July 2012 (UTC)

Except that "some social embarrassment" can mean "comes off as that creepy guy who doesn't read body language or respect boundaries, and treats the slightest friendliness as a sign of sexual attraction: alarming" which can strongly negatively affect future prospects. Even if you're assuming the usual strange world proposed by the typical evolutionary psychologist, it is likely to get the guy beaten up by the men that the women are actually attracted to, and possibly shunned. See also: Schroedinger's rapist, which should really be required reading for all pleasant but slightly awkward men who are attracted to women [13]. 86.161.208.94 (talk) 14:33, 31 July 2012 (UTC)

There must indeed be cultural differences between regions if Looie496 is correct in his region. I (an Australian male) find that virtually all females smile and look me in the eye - its just natural friendliness and means nothing. I can normally distinguish without any difficulty or even needing to think about it, three situations: (1) Smiling, eye contact, & general friendliness as part of their job, cf StuRat's receptionists, (2) Smiling etc in just being friendly, eg neighbors, someone met while waiting for a train, and the like, and (3) Smiling etc as part of sexual attraction. I don't go on smiles or eye contact - I go on body language and what she does. For example, if she leans forward to you while talking, it may mean she wants you. If you notice that she's slighly (or more than slightly) more vivacious with you than with other males, that is a strong hint she wants you. If she laughs at your weak jokes, that's a good sign. If she fiddles with her clothing, or asks you about her clothing, that's a strong sign. If you pay her a compliment (eg "that dress looks good on you") and she just says "thank you", she's just friendly - but if she responds extra brightly and straightens her back or rotates, that's a good sign. But just a smile, no matter how warm - means nothing. Eye contact - means nothing.

I think SeekingAnswers is on very shaky ground in asserting males taking friendly smiles as come-ons is due to evolution. In the "cave-man" days, folk lived in small groups and tribes. In such cases, specialisation was most desirable (some made good spear points, others good at spearing animals, still others good at first aid & herbal remedies etc), teamwork essential, and no-one could survive on their own. So friendship and bonding with all tribe members was essential, and distinct from sexual pairings to raise children. A male who imposes himself on a female that doesn't want him has always been a disruptive thing that threatens the team/tribe. This means that evolution may have meant some pressure against propagating males who misread the friendship of females.

So, what's the answer to the OP's question? It assumes that many males do misread - is this true? If it is, maybe its social inexperience. Perhaps some males haven't found the right girl yet, and have lowered their filtering criteria. Perhaps an artifact of modern western living, which does not involve small tribes. Or chaps who went to all-boy schools and not co-ed schools. Some males spend their early working life in jobs where they don't have any female work-mates. Those that do can practice their social skills.

Wickwack124.178.41.15 (talk) 02:59, 31 July 2012 (UTC)

7 billion pieces of paper

(This topic could possibly be posted to the Mathematics of Entertainment desk, but since it involves applied math and possibly the behavior of falling objects I've chosen Science.)

After Team GB entered the stadium during the Olympic opening ceremony, the commentators (both BBC and NBC) claimed that 7 billion pieces of paper were released. I presume this figure was part of the press package. Starting with an conservative estimate of one square inch per slip (say 1/2 inch by 2 inches), 144 slips per square foot, and a rough interior stadium area of 500,000 square feet, I calculate that the resulting accumulation would be on the order of 100 slips deep. The actual results appeared to be only fractional coverage of the track and other areas of the stadium. Am I missing something or has the LOCOG stretched reality a bit? -- Tom N (tcncv) talk/contrib 18:50, 30 July 2012 (UTC)

In case anyone wonders whether you misheard billion for million, that 7 billion number is reiterated by The Telegraph, Dallas Morning news, and ESPN - the wording of each so similar it does sound like it's from the same source. Each says the pieces were "tiny" but not how big. One thing we do know - they were all dropped from a single helicopter. This says the paper-drop copter was an AgustaWestland AW101, which says it can take an internal cargo of about 3000 kg or an external (hooked) cargo of about 5500 kg; I can't find a photo of the drop (showing the helicopter) so lets run with 5500 kg. I'm too busy to do the arithmetic, but if you take that and paper density you can figure out the area of paper (given different candidate paper densities) that it would cover, and so how big a 7 billionth of that would be. Given that it's just one helicoper and not an armada of them, I'd guess the fragment size is of the order of 1 square mm. -- Finlay McWalterჷTalk 19:47, 30 July 2012 (UTC)

That 7 billion sounded too high to me, too, at the time. I don't think a square millimeter would work, it would just look like you were dropping powder on the field from a camera far away. You want it large enough so you can see individual flashes as each piece turns into and out of the light, from any camera in the stadium. StuRat (talk) 19:56, 30 July 2012 (UTC)

Standard office paper is 80g/m² - I would expect thin confetti to be half that (or even less). A m² has a million mm². Since the 7 billion slips of paper represent the 7 billion people on earth, we talk about a short scale billion - i.e. a thousand million. 40 g times 7000 is only 280 kg, so the paper slips can be up to about 20 mm² without too much trouble. --Stephan Schulz (talk) 20:03, 30 July 2012 (UTC)

I think the 7 billion figure was supposed to represent the global human population. As for the paper size, my impression from the video feed (where several slips could be seen momentarily landing on the athletes and stirring around near their feet) was that the slips were roughly finger-sized, much bigger than 20 mm² - more like in the 1000s of mm². That would seem to eliminate the possibility of a helicopter drop if these figures are correct. -- Tom N (tcncv) talk/contrib 21:19, 30 July 2012 (UTC)

I just checked - apparently, one can get paper with as little as 7 g/m². That gives us another factor of 5 or so compared to my computation, i.e. 100 mm² per slip, or e.g. 4 mm times 25 mm - still small, but not extremely tiny. --Stephan Schulz (talk) 21:54, 30 July 2012 (UTC)

After another look at the video and noting several slips riding the girls behind the British flag bearer, I would put my best guess at 15 mm x 60 mm. Using the 7 g/m², I get about 44 tonnes of paper. Also a few shots of video appear to show multiple sources, possibly ground-based blowers, rather than a single overhead drop. Back to the end-result - I only see somewhere between 1% and 10% ground coverage, which is about 1/1000 to 1/10000 of what I would expect from 7 billion pieces. Should we call this an extreme case of embellishment or is there some other explanation? -- Tom N (tcncv) talk/contrib 23:36, 30 July 2012 (UTC)

So far we've just assumed that all the pieces are the same as one another. They could quite reasonably be dropping 100,000 larger ones and the rest be 3mm chads. -- Finlay McWalterჷTalk 23:48, 30 July 2012 (UTC)

I'd just like point out that so far all answers have assumed that the pieces are of equal size. That is almost certainly wrong and if you assume a broad size distribution all that is essential is that the average is very small for the weight to be signifiantly reduced. With a small average size it's still possible that the particular pieces for which their size can be estimated are from the larger end of the distribution. 203.27.72.5 (talk) 00:23, 31 July 2012 (UTC)

And interesting point based on the two answers above. Assuming the 7 g/m², 63 million pieces of paper sized 15 mm x 60 mm would be 396.9 kilograms kilograms. That leaves 5103.1 left of the 5500kg. So the other 6,937,000,000 pieces of paper could be about 736 micrograms each or still ~105 square milimetres each. Nil Einne (talk) 08:29, 31 July 2012 (UTC)

That would make a plausible theory but for the fact that I see no evidence of a "dusting" of the arena, for which I calculate an expected average depth of about 10 1-cm² particles over an area 60,000 m². Confetti of that size would also be evident in people's hair. -- Tom N (tcncv) talk/contrib 13:32, 31 July 2012 (UTC)

Isn't there a difference between US billion and UK billion? Which one is the press release using? There might be another factor of 1000 to account for. RudolfRed (talk) 03:33, 31 July 2012 (UTC)

As noted by Stephan above, it's short scale (i.e. US) billions. 203.27.72.5 (talk) 04:12, 31 July 2012 (UTC)

If it was long scale, that would be 7 trillion (short scale), and the people on the field would be buried alive. StuRat (talk) 05:03, 31 July 2012 (UTC)

Note that as the article mentions, there's little difference any more as the short scale is very rarely used in English (as the article also notes, usage in other languages is more variable). (Also as hinted at by StS the human population of the earth is the same (estimated figure), whatever you call the number.) Nil Einne (talk) 07:42, 31 July 2012 (UTC)

Don't you mean the long scale is rarely used in English ? StuRat (talk) 08:40, 31 July 2012 (UTC)

Ooops yes sorry for any confusion. Nil Einne (talk) 09:57, 31 July 2012 (UTC)

Foraging worker ant behavior

Some questions about foraging worker ant behavior:

1. Do foraging worker ants eat any of the food they find while they're out foraging, or do they bring all of it back to the colony first?
2. After bringing food back to the colony, do the worker ants eat any of the food, or do they just starve and give the food to other castes like queens, drones, larvae, and pupae?
3. If a foraging worker ant is separated from its colony and unable to find its way back, does it attempt to survive on its own, or does it just run around aimlessly looking for the colony until it dies?

—SeekingAnswers (reply) 21:48, 30 July 2012 (UTC)

In most cases, the foragers do not eat the food directly. As with soldier castes, many of them lack the mouthparts to feed themselves. Helper ants within the colony feed the soldiers and foragers. A good example are the leaf-cutter ants; the foragers are collecting leaves, while the ants eat only the mold grown on those leaves, so it must be processed within the mound before being fed to anyone. Foragers would usually have no way of surviving on its own and would soon starve. Matt Deres (talk) 00:43, 31 July 2012 (UTC)

July 31

Very specific spider question

I guess you can phrase this question in one of two ways: What is the smallest spider, in proportion to the web it weaves? OR What spider produces the largest web, in proportion to its own size? Evanh2008 ^{(talk|contribs)} 03:23, 31 July 2012 (UTC)

Apparently, it's the Darwin's bark spider [14] [15]. 203.27.72.5 (talk) 03:29, 31 July 2012 (UTC)

Cool! Thanks! Evanh2008 ^{(talk|contribs)} 04:03, 31 July 2012 (UTC)

Cells Experiment

Cheek Cell — Preceding unsigned comment added by 175.140.182.174 (talk) 03:39, 31 July 2012 (UTC)

There are many such in the cheeks. Did you have a question about them? —SeekingAnswers (reply) 03:45, 31 July 2012 (UTC)

Doctors may also be called upon to remove cells from the cheeks. (Sorry for being cheeky.) StuRat (talk) 05:07, 31 July 2012 (UTC)

One of my fairly early biology lessons involved removing cheek cells from the inside of one's own (face!) cheeks (with a sterile spatula or suchlike, I think), and then viewing them under a microscope to confirm that one's cheeks were indeed made up of cells. I suspect this question is somehow related to such an experiment. --Demiurge1000 (talk) 08:25, 31 July 2012 (UTC)

Ha! That's one great leap of logic there Demiurge. You got all that out of "Cell Experiment Cheek Cell"? — Preceding unsigned comment added by 101.172.42.165 (talk) 09:10, 31 July 2012 (UTC)

What Do Women and Gay Men Find Attractive in Men?

This is a serious question. I am a straight male but I was wondering what others who are attracted to men see in men. Most men are hairy, stinky, and overweight/obese. Also, a lot of men are very aggressive. All of these seem to be serious turn-offs, so I'm wondering if there have been any scientific studies done showing what people find sexually attractive about men? Futurist110 (talk) 06:04, 31 July 2012 (UTC)

Muscles are attractive to many, as is height, and a deep voice. And even the attributes you list as unattractive are desired by some. StuRat (talk) 06:11, 31 July 2012 (UTC)

I don't think that anyone finds stinkiness attractive. Futurist110 (talk) 06:17, 31 July 2012 (UTC)

They do. There is a Greek dance where the men put handkerchiefs in their armpits to get them good and sweaty, then present them to their woman, who sniff it approvingly. It's only our culture where body odor is considered unpleasant (excluding the French, of course). :-) StuRat (talk) 06:33, 31 July 2012 (UTC)

Yep stinkiness is attractive. LOL. Futurist110, you underestimate the range of human fetishes. Smell is actually very important in human sexuality - pheromones. See

• "Sexy" Smells Different for Gay, Straight Men, Study Says (National Geographic)
• Pheromone attracts straight women and gay men (New Scientist)
• Do Pheromones Play a Role In Our Sex Lives? (Scientific American)
• How the Nose Can Control Human Sexuality (Mental Floss Magazine)

As for the visual and behavioral stimuli, the same things men find attractive in women: lots of different stuff. Some men like blondes, some brunettes, some like them scrawny, some like them big, some like them assertive, some like them shy, adventurous/conservative, smart/innocent, etc. I bet if I asked you what you find attractive in women your list will be very different from the next guy. Except the criteria will be different for men of course.

If it consoles you, "gold star" (exclusively homosexual) gay men can't understand why men find women attractive as well. I can appreciate feminine beauty quite easily, but there's zero sexual attraction. Same thing with smell. Women smell pleasant enough, male sweat however is sexy. See Sexual attraction and Neuroscience and sexual orientation.-- OBSIDIAN†SOUL 06:41, 31 July 2012 (UTC)

What school did you go to where they gave out gold stars for that ? :-) StuRat (talk) 06:44, 31 July 2012 (UTC)

Not a school. The Gay Mafia! lulz. They send it by mail, and you get discounts at gyms and salons with it.-- OBSIDIAN†SOUL 06:54, 31 July 2012 (UTC)

Just curious--are you into bears? Futurist110 (talk) 07:22, 31 July 2012 (UTC)

LOL, that's a bit personal. If you're asking if body hair or size also factors into attraction. Yes. As I said, different criteria. In the same way that men have idealized archetypes of women they find attractive; so do women and gay men. i.e. the criteria is not just "must have penis". And body hair and size are some of those criteria in the same way that breasts and long legs are for straight men.

I do notice something though. Gay men tend to be more into the idealized rugged alpha male. While women tend to be more into bishōnen-types (the success of boy bands for example) or supermodel-sh guys (what one blogger describes as the Johnny Depp factor). Not always, but often enough to be notable. Some researches link this with the economic environment and the perceived parenting skills. i.e. Women in richer countries tend to prefer the "feminized" men; while women in poorer or more dangerous places tend to be attracted to the macho men. I guess the "dangerous" part of the latter applies to gay men as well, even in rich countries. Others just link it with an innate finickiness in each gender.

• Why women now prefer Johnny Depp to Sean Connery (The Telegraph)
• Why Women Don't Want Macho Men (The Wall Street Journal)
• Gay Men Prefer Masculine-Faced Men, Study Suggests (Science Daily)

To quote from the last article:

"Our work showed that gay men found highly masculine male faces to be significantly more attractive than feminine male faces. Also, the types of male faces that gay men found attractive generally did not mirror the types of faces that straight women found attractive on average," says Glassenberg. "Men, gay or straight, prefer high sexual dimorphism in the faces of the sex that they are attracted to. Gay men and straight men did not agree on the types of male faces they considered attractive."

Weird, huh. :P-- OBSIDIAN†SOUL 09:06, 31 July 2012 (UTC)

Let's be very clear that the 'attractive' sort of smell is typically a fresh sweat smell, rather than a stale sweat smell. So, if you want to attract women, you do typically need to wash regularly. If you're a particularly sweaty person, or going to a particularly sweaty situation, antiperspirant will reduce the unpleasant dampness while not completely impeding fresh sweat. Spraying yourself with throat-catchingly stinky bodyspray/aftershave is a typical teenage mistake that few find actually attractive, and will mask the useful smells. Going without a shower and then spraying with boy-perfume is just unpleasant. 86.161.208.94 (talk) 14:25, 31 July 2012 (UTC)

Word.-- OBSIDIAN†SOUL 15:18, 31 July 2012 (UTC)

And don't forget, to put it scientifically, that many are attracted to the twig and berries. StuRat (talk) 06:35, 31 July 2012 (UTC)

Twig and berries? Futurist110 (talk) 07:49, 31 July 2012 (UTC)

This pic should make my meaning explicit: [16]. :-) StuRat (talk) 08:25, 31 July 2012 (UTC)

Also, consider the things men don't do, which many find unattractive in women, like menstruation/PMS/menopause/bloating/cramps and crying (well, most men don't). StuRat (talk) 06:38, 31 July 2012 (UTC)

Women aren't too keen on most of those things either. As to the things men do that women generally don't find attractive, I don't even know where to start. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:16, 31 July 2012 (UTC)

Does Occam's Razor Make the Existence of Gods Unlikely?

• Occam's Razor = The hypothesis/theory that makes the fewest assumptions is the best.
• Hypothesis 1 = Since everything is (or can/will be) explained by natural/scientific forces, God doesn't exist.
• Hypothesis 2 = There is an invisible, undetectable, walk-through, see-through, very powerful immortal being out there.

Futurist110 (talk) 07:35, 31 July 2012 (UTC)

• Well, Occam's Razor is that the simplest scientific hypothesis which explains everything should be used, and, while "God did it" is a very simple explanation for everything, it's by no means scientific. Since God isn't science, Occam's Razor doesn't apply. StuRat (talk) 08:43, 31 July 2012 (UTC)

(EC) the application of Occam's Razor is mentioned in the article you linked and also briefly mentioned in Existence of God and also given how often it's something that's brought up in plenty of other sources e.g. [17] [18] (there must be more total discussion then the entire RD archives combined). It may be helpful if you explain what parts are still confusing you. Nil Einne (talk) 08:50, 31 July 2012 (UTC)

Just looking at the original wording "that entities be not multiplied save of necessity" tends to suggest the answer to the question is yes. --TammyMoet (talk) 09:47, 31 July 2012 (UTC)

Before reaching any conclusions, define "God". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:13, 31 July 2012 (UTC)

Occam's razor is a principle for deciding between competing theories. It doesn't actually say anything about the liklihood of those theories. --Tango (talk) 12:25, 31 July 2012 (UTC)

The problem with Occam's razor is that 1. a lot of real-world things are pretty complicated, and 2. it can be quite arbitrary to decide which of two theories is the most simple. So let's say our two theories are, "there is a God" and "there is not a God." Which of those is simplest? Superficially you can count up the number of Gods in each and proclaim "not a God" the winner, but that's naive. Adding a God radically simplifies certain aspects of cosmology, biology, and morality. Getting rid of the God requires also developing elaborate and complex theories of where we came from, why the universe exists rather than doesn't, and so forth. It's not at all clear to me which is simpler — they're both pretty complex, when you start hashing out the implications. Even then, Occam's razor is, at best, a heuristic — a philosophical short-cut — and not a proof or even theory whatsoever. So I really don't see it getting one out of this sort of bind with any kind of straightforward action, if one is intellectually honest. (I say this as a subscriber to the no-omniscient-God theory, but for different reasons.) --Mr.98 (talk) 13:06, 31 July 2012 (UTC)

Very poorly worded - I would say that everyday more and more scientists are saying things like Hypothesis #2: "There is an invisible, undetectable, walk-through, see-through, very powerful immortal (being[something]) out there." Aand less and less are saying things like Hypothesis #1 because they realize that it might be immpossible for them to actually "explain everything". 165.212.189.187 (talk) 13:29, 31 July 2012 (UTC)

Why would the heat shield fly forward and not go back into the parachute?

I'm talking about time 3:03 of the video in the Landing section of Curiosity rover. This big thing is hurtling toward the surface, and even if for a moment pyrotechnics on board blow it forward, I'm not seeing how that big disc, once it's free of the payload and therefore much lower mass by itself, but essentially a big frisbee, isn't getting thrown back by the wind resistance (even if Mars' atmosphere is really thin, the thing's going incredibly fast) and into that very huge parachute that is right behind it. Of all the parts of that video, that disc nicely speeding out and away in front of the craft is the strangest part to me. Can someone explain why it's acceptable to believe that that disc would behave as it does in the video from 3:03 to about 3:10 and not flit back into the parachute? 20.137.18.53 (talk) 15:37, 31 July 2012 (UTC)

How much space and time is required to compute a simple weather model?

I recently ran into the problem where computing 23 recurrence plots (for a time process of about 8000 intervals) took a prohibitive amount of time and space (because I had to deal with 23 8000x8000 matrices). This made me wonder, how much time and space is required for simpler weather models? I imagine a simple resolution of 5000 intervals for experiment would require at least (5000)^4 * 32 bytes = 18 million GB of disk space. Then there are other multidimensional computational problems involving tensors, such as stress calculations.

Also, how are 9-dimensional, 11-dimensional string theory models processed for a simple particle-particle interaction ? 76.104.28.221 (talk) 15:39, 31 July 2012 (UTC)