Wikipedia:Reference desk/Archives/Science/2010 April 21

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April 21

tongue map

hey everyone. In biology class I've got to find a tongue taste map for the lab investigation in taste we are doing. the professor says not to use wiki, so I need an accurate tongue map from a reliable source. Any idea where I can find one? <3 ~Liviya —Preceding unsigned comment added by 76.235.111.187 (talk) 00:45, 21 April 2010 (UTC)

Did you try typing "tongue map" into google images? --Jayron32 00:48, 21 April 2010 (UTC)

Have you tried a printed encyclopedia? APL (talk) 00:56, 21 April 2010 (UTC)

It may be of interest that recent articles in the popular scientific media (sorry, can't immediately find a linkable reference, but New Scientist is a likely source) have asserted that the hallowed 'map' of highly differentiated taste areas on the tongue was based on a very old and flawed study that has now been discredited. Apparently the 'buds' for the various tastes are only weakly concentrated in different areas, and these concentration areas vary between individuals. You might want to follow up this line (don't just take my unsupported word for it) and surprise (or possibly gratify) your professor. 87.81.230.195 (talk) 01:05, 21 April 2010 (UTC)

Oh! Good point. If you look at the Tongue map article, you'll see that the "research" section of the article has two cites (footnotes) that link to articles explaining that tongue maps have been discredited. (The Nature article is a pay article, I'd try the Scenta article.)

With a little google searching I was also able to fine this article. APL (talk) 01:24, 21 April 2010 (UTC)

Ouch! That's going to make for a tough class! Our article also mentions how this falsified concept is still taught in schools. I suggest you read the references that say that it's discredited very carefully - so you are sure of your facts, find a "Tongue Map" someplace (so you can reasonably claim that you did your assignment no matter that the entire premise of it is incorrect) - and carefully write about how it's wrong. If you are doing a 'lab' and are planning on testing whether the maps are right or not - be aware that anyone who has looked at one of these maps is an invalid test subject as they are pre-conditioned to expect what they found when they did their assignment. Good luck with that! SteveBaker (talk) 04:54, 21 April 2010 (UTC)

The tongue taste map is a good example of a scientific misconception or a lie-to-children. ~AH1^(TCU) 00:19, 22 April 2010 (UTC)

It's a good scientific misconception, but I'm not sure it's a "lie to children". It's not an oversimplification of some scientific truth, nor is it an intentionally incorrect to help students learn some other material. It's simply an error.

You'll notice that the Lie-to-children article actually lists the tongue-map as an example of something that is not a lie-to-children. APL (talk) 00:57, 22 April 2010 (UTC)

I never took the tongue map seriously. I did an experiment of my own several times by placing salt, and sugar on various spots on my tongue. I was able to taste it regardless. --Kvasir (talk) 16:24, 24 April 2010 (UTC)

toba bottleneck

I was wondering if any thought has been given to the loss of technology during the toba eruption and bottleneck. IE. construction of the pyramids, astrology, etc.  ???? —Preceding unsigned comment added by 68.34.218.91 (talk) 01:45, 21 April 2010 (UTC)

Yes. It's in the article, Toba eruption#Genetic bottleneck theory. ~ Amory (u • t • c) 04:21, 21 April 2010 (UTC)

The article Toba catastrophe theory does not mention pyramids or astrology. The only direct evidence of how the Toba eruption must have devastated the life of people living at the time of the eruption has been found in Malaysia. A large and long-established "palaeolithic workshop" named Kota Tampan, had been found [1]. 'Pompeii-Like' excavations in southern and northern India shed light on the kind of human settlements existing before and after the Toba super-eruption 74,000 years ago.[2]. The earliest known Egyptian pyramid was constructed much later 2630 BCE–2611 BCE. Cuddlyable3 (talk) 09:06, 21 April 2010 (UTC)

No, of course not - as you say way too far off, for one, and beyond impossible to determine. But the question as I read it was asking "Hey, if the population of humans didn't plummet into such a bottleneck, would maybe we be more advanced now?" The answer, of course, is nobody can ever know, although it could make a good sci-fi/fantasy novel. ~ Amory (u • t • c) 14:30, 21 April 2010 (UTC)

There's a theory that pyramids were constructed as early as 10,000 years ago, during the Age of Leo. See that article for more information on astrological ages but it does not mention events prior to the end of the ice age. ~AH1^(TCU) 00:16, 22 April 2010 (UTC)

information disinformation. Cuddlyable3 (talk) 13:20, 23 April 2010 (UTC)

cleaning up chemical spills

i notice in this vid

http://www.youtube.com/watch?v=f5M3rUqaEYs

he spills concentrated acid and powdered sodium hydroxide. how exactly is this cleaned up? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 02:01, 21 April 2010 (UTC)

Sodium bicarbonate solution for acid, vinegar for alkali, then hose down the area with lots of water. (Careful, don't burn yourself!) 24.23.197.43 (talk) 22:24, 21 April 2010 (UTC)

I expect that this could be very dangerous advice. If there are significant quantities of sodium hydroxide then poring vinegar on will produce a fast exothermic reaction that will probably splatter sodium hydroxide everywhere. I could be wrong but I would be very cautious with this advice. -- Q Chris (talk) 14:52, 22 April 2010 (UTC)

You might want to dilute them first, with water, then add the chemicals to nuetralize the acidity and alkalinity. StuRat (talk) 15:01, 22 April 2010 (UTC)

Using sodium bicarbonate you may neutralize both base and acid. The CO3 part can react with acids to form CO2 gas, and the H can react with bases to form water. --Cheminterest (talk) 21:29, 26 April 2010 (UTC)

Wrongly cleaned copper nickel coin resulting in light copper colored stains.

How do I remove light copper colored stains on a copparnickel coin due to contact with washing detergent?02:05, 21 April 2010 (UTC)

I first tried to clean the coin with backing soda, salt and a aluminum foil like with silver without any improvments. Then I tried with vinegar with no result there either. With toothpaste all the dark brown stains disapeared and only the light copper colored stains remained. Also tried with lemon juice, nothing. The same with handsoap.

I've also heared using about 25% diluted amonia. Could that be something to me or have I permanently destroyed the coin?83.233.65.220 (talk) 02:05, 21 April 2010 (UTC)

I appreciate all the answers I'll get.

Thanks

Presuming this is some kind of old, valuable coin (or you presumably wouldn't be asking!) - you probably destroyed most of its' value the instant you started cleaning it. Collectors of antiquities like for them to have all of their original 'patina' and cleaning things like this doesn't improve their value at all. The more you do, the worse you are making it. Salt and toothpaste are both abrasives and that's a definite no-no! I think you should quit while you can. SteveBaker (talk) 03:07, 21 April 2010 (UTC)

He might just be the obsessive type thinking "I'll be darned if this stain is gonna beat me !". StuRat (talk) 05:15, 21 April 2010 (UTC)

The only other thing I can think of to try is tomato juice. StuRat (talk) 05:16, 21 April 2010 (UTC)

How would washing detergent cause a copper colored stain? The dark stains are from corrosion presumably, but the copper one? Perhaps you cleaned the coin so well you removed the surface plating, and you are revealing the copper underneath? What kind of coin is it? If it's not plated but rather a Cupronickel alloy, is it possible the black stain was nickel corrosion (the nickel leached out of the alloy)? Although nickel oxide is usually green, it could be black. And once you cleaned it off you have a section with just copper and no nickel? Just guessing, but try to figure out what the stain is made off. Ariel. (talk) 09:14, 21 April 2010 (UTC)

@SteveBaker Your right it's a rare and valueable defects characterized cupronickel coin worth about $30-$70 US I've seen it being put out for. I whished I'd known not to try to wash it, but now I know and will never make that mistake again. @StuRat You're also right "I'll be darned if this stain is gonna beat me !" :) I now have nothing to lose so I'll try to use tomato juice depending on if Ariel can help me with salvaging the coin. @Ariel I used a ultrasonic cleaner with washing detergent containing 15-30% zeolites, 5-15% non-ionic, anionic and <5% soap, phosphonates, perfume and enzymes. Only the one side of the coin is affected and that's the one in direct contact with the detergent. I think that you are closest or right on of what have happened to my coin. The coin is made of a cupronickel alloy 75% copper 25% nickel. I'm 99% sure that the stains on my coin is copper because of its color now when you have told me about leaching and the "black". Is it possibe to remove this copper except damaging the nickel futher?83.233.65.220 (talk) 20:55, 21 April 2010 (UTC)

Thanks all of you who helped me with this subject. It has been very enlightning and hope that you will be kind enough to help me further.

When you clean the tarnish off an old coin, this instantly destroys most of its antique value. Also take a look at numismatics if you are interested. However, if you wish to make the coin appear new (and unvaluable), a slow method of un-tarnishing the coin involves using ketchup (tomato acid) or mustard (vinegar). I've also discovered a new method of instantly removing the tarnish from a coin today: place the coin in a bowl with a small quantity of tap water at the bottom, then pour salt over the coin. Drop some cola (phosphoric acid) over the coin into the water, until it starts to mix. Next, take half of a lemon and squeeze a few drops of lemon juice over the coin—the tarnish should come off instantly, then repeat with the other side. However, since salt is abrasive, this process should also work without the salt, but I haven't tried that myself. To re-add the tarnish to the coin, which would make it look old again but not in its original state, either place the coin on a paper, cardboard or wooden surface for several days, or leave it in a shallow dish of water overnight, but don't add additives to the water. However this method may cause any fingerprint stains on the coin to become more visible, so the coin should always be held by the edge. Hope this helps. ~AH1^(TCU) 00:08, 22 April 2010 (UTC)

The best stuff I know for cleaning that dark stuff off of copper, brass and other similar kinds of metal is "Duraglit" - it's a weird kind of cottonwool-like stuff that's impregnated with who-knows-what. It comes in a can about the size of a soda can - with an airtight lid. Rubbing a thumb-sized chunk of this stuff on a grungy-looking 1 cent coin makes it look like it's just been minted. It's claimed to be non-abrasive. I use it in car restoration...where keeping things crudded up with "patina" isn't so popular. SteveBaker (talk) 01:02, 22 April 2010 (UTC)

I have to disagree with the idea that the more tarnish on a coin the more valuable it is. On the contrary, a coin in "mint condition", meaning no tarnish or wear at all, is the most valuable. However, if the level of tarnish is incongruous with the wear, then that might bring the value down, as it's obviously been "messed with". So, I think removing the weird stain on the coin won't destroy it's value. Think of it like restoring an antique. As long as it's done properly, it can increase the value. Do a shoddy job, and the value drops. StuRat (talk) 03:46, 22 April 2010 (UTC)

I absolutely agree that there is no idea that dirty coins are worth more. What is expected is that the degree of tarnish is appropriate to the age and degree of circulation that the coin has undergone. So a coin that's been preserved in "mint" condition since it was first struck (and which therefore has no tarnish) might well be worth more than a worn and tarnished coin of the same type and age - which in turn would be worth more than a worn and cleaned coin - which in turn might be worth more than a coin that was so heavily corroded that it was almost unrecognisable. But in none of those four situations would cleaning the coin increase its value. SteveBaker (talk) 14:12, 22 April 2010 (UTC)

The American Numismatic Association says the following:

8. Should I clean my coins?
The short answer is “NO!” Cleaning a coin often presents an enigma. A coin that has circulated and shows signs of wear has an altered appearance if it has been cleaned. In essence, what you would have is a coin that is bright but worn. Generally, a coin will lose some of its value after being cleaned. Most experienced numismatists are able to spot a cleaned coin fairly easily. If a coin is so corroded that it is unrecognizable, you may try a solution of mild dish soap and distilled water. Rinse the coin thoroughly with distilled water and allow the coin to air dry otherwise you should leave coin cleaning to professional services such as NCS.

— American Numismatic Association, General FAQ

AlmostReadytoFly (talk) 08:54, 22 April 2010 (UTC)

They don't seem to cover the current case, where a coin has more tarnish than it's wear would indicate. In such a case, cleaning it until it matches might increase the value. StuRat (talk) 15:16, 22 April 2010 (UTC)

Self-replicating molecules

I hear a lot of talk about self-replicating molecules being a precursor to life on Earth, but despite working in chemistry, I have yet to see a self-replicating molecule. I'm not talking about DNA, that needs a rather complex system of enzymes to replicate during cell division. What is an example of a simple molecule that can make a copy of itself? Or do people mean something else when they talk about a 'self-replicating' molecule? 24.150.18.30 (talk) 02:22, 21 April 2010 (UTC)

Chemistry is not my strong subject - but you might want to read about the work of Julius Rebek who is a pioneer in this field. Our article on Self-organization (especially the sections on chemistry and biological self-organizers), the Abiogenesis article has a lot of information about RNA as an alternative to DNA as a way for the process of evolution to be 'kick-started' (see also RNA world hypothesis) - and in that context, Error threshold (evolution) is a really interesting article. The general concept of Autocatalysis and Autocatalytic sets is very relevant to this topic. There are also entire families of Peptide nucleic acid, Threose nucleic acid and Glycerol nucleic acid that are candidates for this kind of behavior. PAH world hypothesis is also interesting. Yet weirder possibilities are explored in Iron-sulfur world theory. SteveBaker (talk) 03:24, 21 April 2010 (UTC)

Polymer. Cuddlyable3 (talk) 08:37, 21 April 2010 (UTC)

And since when did your plastic shopping bags acquire the ability to self-replicate, Cuddlyable3? ;-) 24.23.197.43 (talk) 04:35, 22 April 2010 (UTC)

Ribozyme. --Mark PEA (talk) 15:50, 21 April 2010 (UTC)

If you're asking for a truly self-replicating molecule (i.e. replicating w/o external assistance), one example would be a prion.24.23.197.43 (talk) 04:33, 22 April 2010 (UTC)

Correction: prions don't really self-replicate the way DNA does, they only transform protein molecules into more copies of the prion. My mistake. 24.23.197.43 (talk) 04:40, 22 April 2010 (UTC)

Sunset color on a different planet

Considering we can't see one from the planets (excluding titan in that, but we can't see anything from the surface of titan, or rather we can't see the sun, well, I suppose we could, but we'd have a hell of a time getting a sunset there.) that have an atmosphere like Earth's and also aren't deadly to anything short of tungsten (see Venus, crushed a lot of spaceships down there), I'd like to come up with a theoretical planet for this one. The planet's size is three earth masses, and it orbits a star with a spectral class of K2V. The atmospheric composition is 29% Oxygen, 61% Nitrogen, 9% Carbon Dioxide, and 1% other gases such as methane, argon and helium. For referencing the star size in the sky, it orbits just on the inner edge of the habitable zone, and the star is about 0.89 solar masses. Now, based on these hypothetical values, can anyone think of what a sunset would look like on the planet, if either a human or something with very close to human vision were to see it? If you have to ask, no, it's not for an astrophysics paper or anything, just a book I'm writing. If you need more information, I'll probably have to come up with something. 173.50.148.216 (talk) 04:07, 21 April 2010 (UTC)

You may be interested in this image I've put up here - it's a sunset from Mars. As to your question, I haven't the foggiest idea, but you'd also need 1. the radius of the planet (to calculate gravity) and 2. a better definition of habitable zone, as it's not entirely clear what that would be for such a situation. ~ Amory (u • t • c) 04:16, 21 April 2010 (UTC)

Oooh, purty

Ah, I'm afraid I can't figure out the radius of the planet. Saying three earth radii would be incorrect, as I'm certain that's too big. As for the habitable zone, it's about close enough that most of the non-polar area is tropical, and not boiling off its oceans (the rest of the non-polar area is a sand desert. The planet is large enough that further north and south of the general 'antarctic and arctic zones' you start finding frozen carbon dioxide and liquid methane (though I don't know if that would freeze sooner or later than CO2, so take that with a grain of salt). Now, I would say that the gravity in multiples of Earth is about 3.02, but then Jupiter ended up with something like 2.0 or some odd completely unexpected number that I would've expected out of a planet much smaller. Gravity seems to be a tricky thing. Perhaps 13.6m/s2 is a good value for the acceleration due to gravity.173.50.148.216 (talk) 04:29, 21 April 2010 (UTC)

I think you need to calculate the color of the sky using Rayleigh scattering and Mie scattering equations - then figure out which colors will be refracted the most and thereby bent around the curvature of the planet by the setting star. Of course the spectral characteristics of the star and dust/liquid droplets suspended in the atmosphere would play into this too. That's going to be pretty tough to figure out. I don't think anyone predicted the weird orange-sky with blue sunsets on Mars before the first photos of it were taken. SteveBaker (talk) 04:46, 21 April 2010 (UTC)

Assuming it is being observed by a human eye, the sky and sunset should be pretty similar to how it is on Earth. The Rayleigh scattering should be pretty much the same as on Earth since the visible spectrum is very narrow, so it will all the affected the same way with just the simple dependence on wavelength that we see on Earth, which results in a blue sky and red sunsets. Mie scattering caused by larger particles happens fairly evenly across the spectrum, if memory serves, so that will result in the sky looking overcast to varying degrees. It is dust in the atmosphere that causes the red Martian sky and the sun isn't blue at sunset, it has a blue halo. The halo exists for the same reason we have a blue sky, but Mars only has enough air for Rayleigh scattering to outweigh the dust when the light is going through the much greater amount of air between the observer and sun at sunset. So, in summary, I think the most important factor is what dust/ice/etc. is in the atmosphere. Atmospheric pressure will be a factor too, but only in determining how bright the different colours are. --Tango (talk) 18:44, 21 April 2010 (UTC)

Not really directly relevant to the question, but if the mass of the planet is 3 times Earth's and the gravity is 3g on the surface, then radius would be about the same as Earth's (so triple the density). Keep in mind that gravity is proportional to m/r², and mass is proportional to r³ρ where ρ is the average density. Rckrone (talk) 05:29, 21 April 2010 (UTC)

Volcanic ash vs other jet engines

The volcanic ash destroys turbojets but are Ramjets theoretically immune to this due to the simple design? —Preceding unsigned comment added by 74.105.225.192 (talk) 04:41, 21 April 2010 (UTC)

Yes - I believe that is true. SteveBaker (talk) 04:47, 21 April 2010 (UTC)

Agree --BozMo talk 06:20, 21 April 2010 (UTC)

I don't think anyone has tried pouring ash into an operating ramjet. They do not offer a solution to the present air transport crisis because not even Concorde at Mach 2 flew fast enough for a ramjet to be useful. However it is comforting to think that an ICBM should make it through the ash plume. Cuddlyable3 (talk) 08:31, 21 April 2010 (UTC)

ICBMs are solid fuel rockets. No one flies ramjets, they are test engines only. Ariel. (talk) 09:19, 21 April 2010 (UTC)

At top speed, the SR-71 was effectively ramjet-powered: the turbine core of the engine wasn't producing any thrust. --Carnildo (talk) 00:28, 22 April 2010 (UTC)

That's not entirely accurate: the turbine core was still drawing air into the afterburner, helping the latter to function as a ramjet. This configuration could be classified as a "turbo-ram ejector" or a "topping-cycle ramjet". BTW, many surface-to-air missiles and some cruise missiles use true ramjet propulsion. FWiW 24.23.197.43 (talk) 04:47, 22 April 2010 (UTC)

What about piston engine powered propellor planes? Count Iblis (talk) 16:01, 21 April 2010 (UTC)

These still have to intake a huge amount of air, which is contaminated by volcanic ashes. If the filter was not developed with this purpose in mind, it will clog and the motor will stop working.--ProteanEd (talk) 16:11, 21 April 2010 (UTC)

Car engines are piston engines...not much different (in principle) from aero engines. I've said it a half dozen times in the past week - but the US Geological Survey folks say that if you are driving your car through volcanic ash, you should change your engine oil, oil filter and air filter every 50 to 100 miles(!)...so, no - piston engined aircraft are definitely no better off (and quite possibly much worse off) than jet engines in these kinds of conditions. SteveBaker (talk) 18:40, 21 April 2010 (UTC)

Additionally, car engines are mostly operated at a fairly small fraction of their peak power (low RPMs/low throttle). I would definitely expect this to be true of a research vehicle in an ash cloud. Piston aircraft engines are continuously operated closer to their peak power. Since the amount of air going through the engine is roughly proportional to power output, the aircraft is going to be even worse off than a car. -- Coneslayer (talk) 18:52, 21 April 2010 (UTC)

A rocket plane may be a more practical alternative for flying through an ash plume. StuRat (talk) 13:16, 21 April 2010 (UTC)

I guess the other alternative would be pulse jets - those (typically) only have one moving part - but like ramjets, they are ungodly noisy, and therefore probably unusable as a replacement for turbofan jet engines. SteveBaker (talk) 18:43, 21 April 2010 (UTC)

In theory I guess some form of geometric filter of the inlet air is possible. Obviously not a mesh, but perhaps a tight corner which flung all the larger particles out (centrifuging glass out of air) and only left smaller ones which would be carried by the flow. No doubt in some corner of the universe some civilisation coping with massive aviation on a volcanic planet has sorted it out. Meanwhile for us the development and research cost just isn't worth it. --BozMo talk 20:13, 21 April 2010 (UTC)

I dunno - the $2 billion that the airlines alone have lost during the last 6 days would pay for an awful lot of engine research! SteveBaker (talk) 00:47, 22 April 2010 (UTC)

Too much pressure drop, BozMo. 24.23.197.43 (talk) 04:42, 22 April 2010 (UTC)

blood-vessel building

I am curious about how blood vessels have such regular arrangements within the body, especially since angiogenesis factors can create new blood vessels. What guides their order? Especially the development of the heart -- it seems sort of curious how you get one vessel to coil around the other without having them merge. John Riemann Soong (talk) 04:54, 21 April 2010 (UTC)

Just checking some stuff now, there seem to be a myriad of factors that play a role in vasculogenesis, most notably various Vascular Endothelial Growth Factors (VEGF). That article's point, however, is that you also need the right receptors. There's also a protein discovered a year ago that ends up being responsible for differentiation into different vessel types. Essentially, it seems that initially there's just endothelial tissue, but by week 4 the embryo is starting to develop more specific cells for veins and arteries. This is mostly done through a process called sprouting angiogenesis, wherein endothelial cells "sprout" off the main vessel, then connect back, expanding the original. ~ Amory (u • t • c) 14:12, 21 April 2010 (UTC)

I think it's called angiogenesis and the regular arrangement is really just for the large bore vessels we fondly refer to as arteries and veins. When you take a step down to arterioles and venules (not to mention metarterioles, capillaries and the same levels of lymph vessels), there are no names (except for vague reference to specific plexi) because there is such variation. I'd say the large vessels are so consistent because they body relates to them as much as it would to an organ -- they are necessary for survival. Then again, there's always transposition of the great vessels if you'd like to peruse some variation. DRosenbach ^{(Talk | Contribs)} 02:47, 22 April 2010 (UTC)

Genotype and drug resistance

If a creature is resistant to a drug, its genes are certainly modified in a way that the creature exerts resistance. Here, i wonder whether that particular gene which is mutated codes for a different protein which is obviously new for the bodily functions. Cockroach has always been a wonder to me as it quickly adapts or is resistant to many types of poisonous drugs when administered against it. please explain the phenomenon behind the 'genotype and drug resistance' and also let me know if cockroaches are 'special'in evolving better - Anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 09:21, 21 April 2010 (UTC)

When a species evolves some kind of resistance to drugs or disease or whatever, that change will likely be a genetic one (there are a few other possibilities - for example: a new kind of gut flora might be picked up from the environment somehow that is subsequently passed from one generation to the next). If genetic then it would have to be in genes that are expressed in some way (versus "junk DNA") - which means that either some new protein will be formed or some "normal" protein will cease to be formed, or (most likely) there will be a very small change to an existing protein. SteveBaker (talk) 13:04, 21 April 2010 (UTC)

Also note that more complex animals can exhibit behavioral changes to adapt to a toxin. These can then be passed down from generation to generation. For example, some monkeys eat charcoal as an anti-toxin. Of course, avoiding or limiting exposure to the toxin is far more common. StuRat (talk) 13:12, 21 April 2010 (UTC)

Also, there is no reason to believe that roaches evolve better than any other animal. Dauto (talk) 14:14, 21 April 2010 (UTC)

Remember that individuals don't evolve, populations do. A certain cockroach will not see a change in its DNA, but many many generations later, the population living under your or my sink may have a higher proportion of those with resistance. ~ Amory (u • t • c) 14:16, 21 April 2010 (UTC)

(after edit conflict) See Xenobiotic metabolism. There are many enzymes in the body that detoxify various substances, and each of the genes for these enzymes can have different alleles in the population that result in slightly different enzyme activities. Thus, individuals in a population will have different combinations of genes for drug metabolizing enzymes that give them a unique enzymatic profile. The most likely explanation for development of drug resistance in a given organism is NOT a new mutation that somehow generates a novel enzyme that can break down a particular compound, but rather selection for those genotypes that most effectively neutralize the compound. It's a great example of population genetics and natural selection. Cockroaches are not (to my knowledge) any different than the rest of us in terms of drug metabolism; they just have faster generation times and are the subject of external selective forces that magnify a process that would otherwise happen very slowly. --- Medical geneticist (talk) 14:22, 21 April 2010 (UTC)

is clozapine antiaromatic?

The seven membered ring seems to be ... does the molecule try to "prevent" this by making the protic nitrogen between the two rings sp3, e.g. basic? John Riemann Soong (talk) 11:02, 21 April 2010 (UTC)

I'm not sure yet, but in my searching on Wikipedia I've discovered that the seven member ring appears to be an Azepine derivative. There are many derivatives of this, and they all would appear to have the same problem. Buddy431 (talk) 14:22, 21 April 2010 (UTC)

Here's (I think it's free) a paper discussing Azepine and Dibenzazepine. Yes, it appears that they are antiaromatic (presumably Clozapine would be too). They can partially relieve this by protonating the nitrogen and forming a Homoaromatic cation. Funky stuff. Buddy431 (talk) 14:30, 21 April 2010 (UTC)

Very interesting. I wonder what significance the enamine motif comes into play. I'm kind of puzzled by the 7-membered cyclisation step in the article's given synthesis of clozapine, I would expect the amide center to be very non-electrophilic (being an amide, having a phenyl ring donating into it + enamine donating electrons by proxy). John Riemann Soong (talk) 18:17, 21 April 2010 (UTC)

John, thanks for bringing this up. It has reminded me to fix the image at Clozapine, which incorrectly shows a planar diazepine ring.

The structure of clozapine has been determined by X-ray diffraction: Acta Cryst. (1982). B38, 1750-1753 and J. Chem. Soc., Perkin Trans. 2 (1976) 1415-1420. The ring is actually puckered, as is the case for all the diazepines I've come across. When I made File:Clozapine-3D-vdW.png in 2006, I didn't know about antiaromaticity and Accelrys Discovery Studio Visualizer incorrectly minimized the ring to a planar geometry.

Hückel's rule says that molecules with (4n+2) π electrons (in a planar, conjugated ring) are aromatic, whereas those with (4n) π e⁻ are antiaromatic, where n is an integer. Clozapine has 8 π e⁻, which is 4n with n = 2, and is thus Hückel antiaromatic. Addition of two more π e⁻ would result in an aromatic dianion (10 π e⁻, 4n+2 with n = 2), and removal of two of the eight π e⁻ would give an aromatic dication (6 π e⁻, 4n+2 with n = 1).

Ben (talk) 19:56, 21 April 2010 (UTC)

Hmm I do wonder because depending on how you draw the benzene ring (or interpreted a resonance structure), you can make it seem like it has 6pi or 10 pi electrons. Of course this is at cost to benzene's own ability to have multiple resonance structures, so there's a tradeoff. Also, you can draw resonance structures such that you have one big ring of 16 pi electrons. Do you know what I mean? (Or should I draw them in chemdraw?) It's these alternate aromatic-looking ring structures, in competition with the antiaromatic ones, that intrigue me. John Riemann Soong (talk) 21:29, 21 April 2010 (UTC)

How can you make a benzene ring have 10 pi electrons?

Ben (talk) 18:36, 26 April 2010 (UTC)

Fish trachea

Do fish possess a trachea? Should the vertebrate trachea article be renamed to tetrapod trachea? -Craig Pemberton 15:18, 21 April 2010 (UTC)

No, and no. The trachea connects the mouth with the brachii in the lungs. Fish don't have lungs. Even lungfishes don't have tracheas. The article name is fine. -- Flyguy649 ^talk 16:55, 21 April 2010 (UTC)

Thank you. That means article title is misleading because it suggests that a trachea is a vertebrate synapomorphy. -Craig Pemberton 17:52, 21 April 2010 (UTC)

No really. The naming is to distinguish between vertebrate tracheas and invertebrate tracheas. -- Flyguy649 ^talk 18:31, 21 April 2010 (UTC)

Scientific Principle

What's the name of the scientific principle where the conclusion of a study seems obvious after it's proven but it seemed unlikely prior to study? TheFutureAwaits (talk) 16:50, 21 April 2010 (UTC)

That's not a scientific principle, but perhaps it's covered by the expression "hindsight is 20-20". StuRat (talk) 16:54, 21 April 2010 (UTC)

Peripherally related, look at disruptive technology / disruptive innovation. For example, after the computer mouse, its concept seems obvious and its implementation seems trivial - but before Douglas Engelbart, nobody really thought about controlling a numerical calculating machine with your bare hands! Nimur (talk) 17:11, 21 April 2010 (UTC)

That's not even remotely true! The mouse was neither invented first - nor marketed first - nor in common use first! I used touch-screens (invented in the 1940's), trackballs (invented in 1952) joysticks (invented in 1944) and digitizing tablets (invented in 1888!) in college and in my first job around 1977 - long before the mouse (invented in 1963) appeared on the market in 1981. The significant difference Engelbart made was in reducing a $500 device to a $10 device that achieves 20% of the functionality of the most common alternative - (which at the time was probably the digitizing tablet). Nowadays, the little digitizing tablets you find on laptop computers (now we call them "touch-pads") are comparable in price to the mouse - but have lost most of their functional benefits because they are only used to (poorly) emulate a mouse. You couldn't describe the mouse as a significant breakthrough - either scientific or technological. The only real claim to fame is cheapness. SteveBaker (talk) 18:20, 21 April 2010 (UTC)

Well, the use of a mouse in an operating system GUI was a significant breakthrough. Comet Tuttle (talk) 21:07, 21 April 2010 (UTC)

Interestingly there are commercial examples as well of ideas which people thought they hated but which were successful in practice. Selling sandwiches in Service Stations is one (all the market research implied the association of a service station with the unpleasant taste and smell of fuel would make it impossible). However it turned out to be commercially very successful (albeit with airconditioning in the shop). --BozMo talk 17:18, 21 April 2010 (UTC)

There is no such "principle." --Mr.98 (talk) 17:53, 21 April 2010 (UTC)

Psychology refers to this as Hindsight bias. ☯  Zenwhat (talk) 18:03, 21 April 2010 (UTC)

Thanks Zenwhat, that's exactly what I was looking for. And Mr. 98 maybe don't be so quick to dismiss questions in the future! TheFutureAwaits (talk) 21:09, 21 April 2010 (UTC)

He didn't dismiss the question. He simply pointed out (correctly) that this is not a scientific principle. Dauto (talk) 22:15, 21 April 2010 (UTC)

Though in all fairness I probably could have been more creative and less literal in interpreting what was intended by "scientific principle"—I thought the OP was implying that it was some basic principle of science that it would work in this way (that is, a statement about science rather than one provided by science, in this case, psychology). I see now that a different meaning was intended. --Mr.98 (talk) 01:28, 22 April 2010 (UTC)

Muscle tingling after exercise?

Why might a person feel a pleasurable tingling sensation in the muscles worked, after strength training?

This Yahoo answers page attributes it either to reduced blood-flow, dehydration, or decreased oxygen supply, but all these things affect the extremities -- not the muscles worked during exercise (like shoulders, chest, or abdominal muscles).

To clarify, the sensation feels similar to a massage and seems to occur near the end or after recovering from delayed onset muscle soreness. 96.255.178.76 (talk) 17:59, 21 April 2010 (UTC)

I'm feeling this right now a bit in my lower legs and feet. I have run for half an hour about 20 minutes ago and I'm now sitting in front of the computer. I think this is just the blood flow. During the exercise this was at a huge level compared to rest. If you stop running then the blood won't flow at the usual resting rate immediately. This is also very clear from my heart rate. During the exercise it was about 160 bpm and now it is 58 bpm but in rest it should be about 40 bpm. Count Iblis (talk) 19:20, 21 April 2010 (UTC)

40 bpm, are you sure? That seems really low to me, I thought that 60 was more common, unless you are an Olympic class athlete. Googlemeister (talk) 19:43, 21 April 2010 (UTC)

I've had a resting heart rate below 50 at least since primary school. My primary school teacher told us one day how to measure the heart rate. and I was the one with the lowest in class, which my teacher verified. I also noticed that I actually don't need to put my finger on my wrist to feel and count my heart rate; I can usually feel my heart beating in my body. When running this is very convenient, no expensive heart rate monitors ae needed, I can just look at my watch for ten seconds and count the number of beats.

I don't think I'm an Olympic class athlete. My recuperation time is way more than that of top sporters. My heart rate takes quite a long time to return to the resting value. I will typically exercise two or three days in a row. On my resting day, my resting heart rate will be slightly higher e.g. 43 bpm instead of 40 bpm. A top sporter will be able to pack my three day training effort into a single day and still be fully recovered only a few hours later. So, unfortunately, I've a long way to go before I become as fit as Miguel Indurain "His cardiac output is 50 litres a minute; a fit amateur cyclist's is about 25 litres a minute. Also, Indurain's lung capacity was 8 litres, compared to an average of 6 litres. In addition, Indurain's resting pulse was as low as 28 BPM". Count Iblis (talk) 20:57, 21 April 2010 (UTC)

Well mine comes out at 72bpm, so I must be in lousy shape :(

Count Iblis, the Yahoo seems relevant to your case, because it's cardio exercise and you feel the tingling in your extremities. I'm talking about strength training where the tingling isn't in the extremities, but the particular muscles that were worked on. 96.255.178.76 (talk) 21:33, 21 April 2010 (UTC)

The resting heart rate's normal range varies by age. It could be up to even 95 bpm and still be normal. However in the tachycardia range at rest is when it becomes dangerous to the body for prolonged periods. ~AH1^(TCU) 23:51, 21 April 2010 (UTC)

PDF

how do i make a pdf form writable so i can fill it out on the computer instead of printing it out? —Preceding unsigned comment added by Tom12350 (talk • contribs) 18:21, 21 April 2010 (UTC)

Specifically, there are means of adding editable form fields to PDFs such that someone with the free Reader software can fill out the page electronically. I'm not familiar enough with the software to comment on how exactly that's done. Then there are intermediate solutions, with varying effectiveness, like importing the PDF into a word processor and typing over it. Generally, though, if you have a PDF you've downloaded from somewhere, there is no provision for changing it. — Lomn 20:32, 21 April 2010 (UTC)

Well, the ordinary use model is that it should not be changed. That's not the same thing as saying it can't be changed. See PDFedit for software specifically designed for that purpose. I haven't tried it and can't tell you how well it works. --Trovatore (talk) 20:47, 21 April 2010 (UTC)

Adobe Acrobat has a "typewriter" feature which works pretty well for filling out forms (it lets you just add text wherever you want). Unfortunately you have to have (or have access to) the expensive, full-featured version of the program for that to work. Googling a bit, there are suggestions as to how to use Microsoft Word to do something like this, though how good it will look, I don't know. This site claims to allow you to easily fill out PDF forms that do not have form fields, as does this software... I haven't used either, personally. There's no real difficult technical reason that this shouldn't be doable for free. --Mr.98 (talk) 20:47, 21 April 2010 (UTC)

In addition, Acrobat allows you to add form fields to make it into a proper form (there's also an automatic conversion thing, but from my experience it doesn't work very well) so it can then be filled in by people with just the reader if you get the settings right. I'm not BTW particularly sure why this is on the science desk since it's better suited to the computing desk Nil Einne (talk) 23:49, 21 April 2010 (UTC)

That's true, though that's generally only good for if you have a form you want others to fill out. It's a whole lot of hassle for a form you're filling out yourself (Typewriter works a lot better for that). Agreed that this should be moved to computing. --Mr.98 (talk) 01:23, 22 April 2010 (UTC)

Personally I prefer the form way so it's easier to change and edit in the future including from Reader if necessary, but then again I'm a stickler for these sort of things. Depending on the complexity of the form and how accurate you want it to be it doesn't take that long, say 10-20 minutes Nil Einne (talk) 14:29, 25 April 2010 (UTC)

Foxit Reader also has a typewriter mode, and is free. -- Coneslayer (talk) 13:56, 22 April 2010 (UTC)

That is good to know for future reference! --Mr.98 (talk) 21:51, 22 April 2010 (UTC)

Force of a magnet on metal

Is there a way to calculate the force induced on a piece of metal by a magnet (assumed it is a simple dipole), if you know the magnet's field strength, the distance? There is one more variable necessary, one that makes the reaction of aluminium and iron different. I think it is called 'magnetic permeability', but I might be wrong. But given that variable as well, how would you find it? KyuubiSeal (talk) 19:17, 21 April 2010 (UTC)

It is not easy to write an equation which accurately states the strength of attraction to a piece of metal from a permanent magnet or electromagnet. It is not as simple as using Ohm's Law to calculate the current through a specified resistance, since geometry is critical. There are complicated edge effects due to fringing. In practice, a magnet which fits smoothly against the metal will lift far more than one which is not an exact fit. The strength of the the magnet, the thickness and nature of the metal, and the shape of the poles are important. As you note, the distance from the magnet poles to the surface is important. See Magnet# Calculating the magnetic force which gives some simple cases but not quite the situation you described of a dipole separated from a piece of metal. Edison (talk) 19:41, 21 April 2010 (UTC)

Cast iron object unknown

Hello. Can someone help identify the type of thing this cast iron object is.

object

other side

Very faint markings on the second side appear to say "DINNY" ? Sf5xeplus (talk) 19:52, 21 April 2010 (UTC)

Could you give us an estimate for the size and weight? I am having trouble telling the size.

It looks like a cover plate for a hole in a flat metal sheet. Graeme Bartlett (talk) 22:04, 21 April 2010 (UTC)

The squared sheets maybe A4. Could it be a gearbox? The short arc may be an idler gear control. Swing it (the idler gear) out of the way, then bring the other long arc lever (controlling the driven gear) to the opposite extreme, then swing the idler gear back -to re-engage. Magically, the contrivance now revolves on the opposite direction.--Aspro (talk) 22:21, 21 April 2010 (UTC)

The short arc is better suited for a safety stop that blocks the main (longer) arc movement. NVO (talk) 08:24, 22 April 2010 (UTC)

Is it flat or rounded? If it's rounded, I've seen similar plates on axles of lorries. --TammyMoet (talk) 08:36, 22 April 2010 (UTC)

~10" diameter , ~1/2" rim thickness (less inside rim), it's flat.

Where on a truck? Did you mean the plate that covers the differential - eg File:T138 podvozok.jpg - that's usually curved like you say? or something else. Sf5xeplus (talk) 11:00, 22 April 2010 (UTC)

Yes that's the one. --TammyMoet (talk) 13:53, 22 April 2010 (UTC)

I think it is a cover plate through which two levers protruded with which an operator could control a mechanism. That is what others seem to be saying above. I don't think it has to be automotive in origin, though gear shift and clutch do seem to be a possibility, as suggested by others above. Bus stop (talk) 11:12, 22 April 2010 (UTC)

How would one calculate the total entropy of the sun?

How would one calculate the total entropy of a star, for example the sun?

I was adding an entry to Orders_of_magnitude_(data) (which also covers information and entropy -- or should do). The entropy of the sun is quite interesting in its own right as the entropy of a great big physical thing; but, also, as something to compare with the entropy of a one-solar-mass sized Schwartzschild black hole.

Using the Black Hole entropy formula, and 2.0 × 10³⁰ kg for the mass of the sun, the Black Hole entropy works out as about

1.4 × 10⁵⁴ J K^-1 = 1.0 × 10⁷⁷ nats = 1.5 × 10⁷⁷ bits.

For the sun, Bekenstein (1973), Black Holes and Entropy, Physical Review D 7 2338 gives a figure for the entropy as about

10⁴² erg K^-1 = 10³⁵ J K^-1 = 7.2 × 10⁵⁷ nats = 10⁵⁸ bits.

Other sources say "about 20 orders of magnitude less than a solar mass black hole" or "about 22 orders of magnitude less".

So: how does one calculate the entropy of a star? I believe it's a standard question on some astrophysics courses, to calculate the entropy of the sun, and compare it to the entropy of a neutron star of the same mass. But I haven't seen any answers.

It's straightforward to calculate what the entropy of the same mass of helium and dissociated hydrogen would be at S.A.T.P.

There would be about (3/4) * 2.0 * 10^30 / (1.0 * 10^-3) = 1.5 * 10^33 moles of dissociated Hydrogen, and (1/4) * 2.0 * 10^30 / 4.0 * 10^-3 = 1.25 × 10^32 moles of Helium. If they were at S.A.T.P., the standard molar entropy would be about 100 J K^-1 (126.0 J K^-1 for Helium), which would give a total of about 1.6 * 10^35 J K^-1 = 1.6 * 10^58 bits

Of course, the temperature of the sun is not 25°C, nor is its pressure 1 atm.

According to the Sackur-Tetrode equation for a monatomic gas, S = N (ln (V / N Λ³) + 5/2) nats, where Λ is the thermal wavelength, Λ = h / sqrt(2π m kT)

Plugging in m=1.67 × 10^-27, T=15 × 10⁶ I get Λ=4.49 × 10^-13 m Then with N = 1.5×10³³ * Avogadro's constant, = 9.0×10⁵⁶, and V = 1.4×10²⁷, I get S=9.0×10⁵⁶ * 19.2 nats = 2.5×10⁵⁸ bits.

Is that along the right lines? Are there other contributions I've missed?

I guess there should also be a contribution from the electrons, since it will be a plasma. The mass being (1/1836) smaller would give a thermal wavelength 43 times larger, so 3 ln 43 = 11.2 nats fewer per particle, so about 8 nats per electron, taking the total entropy up to about 3.5×10⁵⁸ bits.

So the numbers seem to be in about the right ball-park (if I haven't made any numerical errors), but does anybody have a reliable source or lecture notes for the method that would be more dependable? Jheald (talk) 21:37, 21 April 2010 (UTC)

You also need to add the contribution of the photons. If I remember correctly, the entropy density of a photon gas is 4/3 u/T where u is the energy density, which in turn can be related to the Stefan-Boltzmann law via sigma T^4 = c/4 u. Count Iblis (talk) 22:04, 21 April 2010 (UTC)

Thanks. Right, so again taking V=1.4×10²⁷ m³ and T=15×10⁶ K, I get U = 4σVT⁴/c = 5.4×10⁴⁰ J calculation, so S = 4U/3T = 4.8×10³³ J K^-1 calculation = 5.0×10⁵⁶ bits.

So important, but not as important as the contribution from the protons and electrons. Jheald (talk) 12:03, 22 April 2010 (UTC)

This model homework solution (problem 3.15), extending an earlier problem 1.17c (cf our Equipartition of energy#Stellar physics), finds that a star has a heat capacity C = -(3/2) Nk, giving an entropy S = constant - (3/2) N K ln(T).

This suggests that the entropy is smaller the larger the temperature is. (Based I think on the faster the particles are going, the further down the gravity well they must be, so the more negative the gravitational part of their energy must be). I'm not at all sure whether or not this and the previous calculation - which basically ignored gravity - can be compatible. Would need to think more about this. Jheald (talk) 20:52, 22 April 2010 (UTC)

Note that you are using some effective volume in the calculation. It is that volume which is relevant here. In principle you can model the whole Sun and then you will see that gravity determines the size of the star which then turns out to depend on the core temperature. Count Iblis (talk) 03:18, 23 April 2010 (UTC)

I found a nice discussion in qualitative terms of the entropy changes in star formation here which gives a good big picture, and touches on the negative heat capacity (how removal of heat from the system actually increases its temperature; the star contracts, its entropy falls, but that is more than made up for by the increase in entropy in the rest of the universe on transferring the heat there.

You're right. The two calculations should be marryable together. The first simply uses an approximate static picture, of a constant temperature and pressure inside an effective volume to give a ballpark estimate. The second captures more of the dynamic responsiveness of what's going on, and (I think) probably lends itself reasonably easily to a simple model of the temperature and the pressure falling off with distance in a spherically symmetric way. The Wallace paper linked [3] I think has the equations, but I haven't yet had time to go through it, to check whether it comes to a numerical answer, and how this compares to the rough-and-ready estimate in the first calculation above. Jheald (talk) 12:46, 23 April 2010 (UTC)