Wikipedia:Reference desk/Archives/Science/2009 August 17

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August 17

Bell peppers

Are bell peppers true berries under the botanical definition? --✶♏‭ݣ 01:52, 17 August 2009 (UTC)

Yes, they are.CalamusFortis 01:58, 17 August 2009 (UTC)

Phases of matter -- all relative

Are all elements in gaseous form on the surface of the Sun? DRosenbach ^{(Talk | Contribs)} 03:38, 17 August 2009 (UTC)

I'm struggling to understand exactly what you mean by your question. Something that I think is relevant is that the Sun does not really have a "surface". There is giant ball of gas and it gets denser and hotter until it is opaque to electromagnetic radiation. That's what we see when we look at the sun. It's a gradient, not a absolute line. If you were to move towards the centre of the sun, there would be no specific point where you would say I was just above the surface and now I'm just below. Vespine (talk) 04:25, 17 August 2009 (UTC)

I think the answer to your question is yes. On what looks to be the surface of the sun, every substance we know of on the earth is a gas, it is too high for solids or liquids to exist. Graeme Bartlett (talk) 08:39, 17 August 2009 (UTC)

..or no, depending on how one reads the question. First, I'd suspects most elements are actually a plasma anywhere near the "surface" of the sun. A plasma is or is not a gas, depending on the ontology (if the 4 states of matter are disjoint, its not, from a thermodynamic POV it is). But secondly, are all elements on the surface of the sun? Probably not. I'd suspect that all naturally occurring ones are, though. --Stephan Schulz (talk) 09:10, 17 August 2009 (UTC)

I would suspect that the dense elements (Uranium, lead etc) would not be at the surface but in the center of the sun, but perhaps there are trace amounts at the surface. Googlemeister (talk) 14:16, 17 August 2009 (UTC)

My question may not have been my stated in the proverbial, but intention was to ask it in that way -- would all elements be in gaseous form at or near what appears to be the surface of the sun? DRosenbach ^{(Talk | Contribs)} 23:16, 17 August 2009 (UTC)

It is a little difficult to work out because boiling points depend on pressure. If we assume that at the surface the pressure is near to zero (which makes sense for the edge of the sun - there isn't much outside it) then you basically can't have liquids, they would boil instantly, so we're actually looking at the temperatures at which elements under low pressure sublime. Unfortunately we don't seem to have a List of elements by low pressure sublimation point (we have lots of other lists of elements, but not that one) article, so I'm drawing a blank! I'm also not sure about the pressure at the surface of the sun being near zero, the corona is usually considered to be outside the surface and it will cause some pressure, I'm just not sure if it is negligible or not. --Tango (talk) 00:28, 18 August 2009 (UTC)

Also our Sun does not contain "all" the naturally occuring elements, including lead and uranium. Those do not exist on the Sun as far as we know even in trace amounts. Only more massive stars have enough oomph to spit out heavier elements. Our sun is made up Hydrogen and Helium and of only about 10 other elements, none of which are heavier then iron or nickel.Vespine (talk) 00:50, 18 August 2009 (UTC)

If they are on Earth, then they will be in the Sun. The Earth formed out of the same nebula as the Sun. They are greater abundance on the Earth (proportionally speaking) because the Earth has lost most of its hydrogen and helium, but that doesn't change the absolute amounts. --Tango (talk) 00:54, 18 August 2009 (UTC)

According to Sun, the "effective surface temperature" of the sun is at 5778 degK. List of elements by boiling point says that Rhenium has the highest boiling point of all elements - and both it and Tungsten would just barely be liquid at 5778K (Tungsten boils at 5828K and Rhenium at 5869K). However, the sun's corona is at 5 million degrees and the core is at 16 million degrees...so this is a fairly 'careful' answering of our OP's question. SteveBaker (talk) 01:13, 18 August 2009 (UTC)

What is the meaning of effective surface temperature in relation to actual temperature? DRosenbach ^{(Talk | Contribs)} 02:10, 18 August 2009 (UTC)

"The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation." - Effective temperature. Stars are pretty good approximations to black bodies, so the actual temperature isn't far off the effective temperature, maybe a few hundred degrees difference. --Tango (talk) 02:39, 18 August 2009 (UTC)

Those temperatures are for standard atmospheric pressure. There is no reason to believe the surface of the Sun is at standard atmospheric pressure. --Tango (talk) 01:57, 18 August 2009 (UTC)

And getting a measurement for that pressure would be problematic since you are probably going to melt your equipment. Googlemeister (talk) 13:26, 18 August 2009 (UTC)

You can estimate pressure indirectly. Really, the problem is deciding where the surface is. --Tango (talk) 17:39, 18 August 2009 (UTC)

Squinting

Is it just me, or does looking at this make you want to squint, even though it's no brighter than a pure white screen? Is it like an optical illusion, because your brain thinks it's looking at the sun, so you squint by reflex? DRosenbach ^{(Talk | Contribs)} 04:14, 17 August 2009 (UTC)

I looked at it and the corners of my eyes tightened, and then I forced them back by telling myself that it was just a picture. But while looking at it, I felt nervous about something. So yes, I'm programmed to not look directly at the sun. Whew. Awickert (talk) 04:18, 17 August 2009 (UTC)

Me too. Very cool effect - I would not have expected this at all. --Stephan Schulz (talk) 13:13, 17 August 2009 (UTC)

Yes, same response here, I guess the eye tightening is a sort of acquired reflex. 86.4.181.14 (talk) 13:23, 17 August 2009 (UTC)

Could it be that it is simply a higher contrast image than a blank white screen? —Akrabbim^talk 13:56, 17 August 2009 (UTC)

I'm inclined to agree with Akkrabbim here, though I can't cite any studies to back it up. You're looking at this picture, and it appears that the figure in the middle is blown out by the 'bright' subject — so you squint to try to see missing detail that's been washed out. TenOfAllTrades(talk) 14:09, 17 August 2009 (UTC)

This (and many other) tricks are well-known to us evil computer game graphics geeks who seek to elicit real-world emotions from people staring at tiny, dim, flat screens! If you animate it to simulate the rate of change of light perception due to your irises rapidly shrinking to tiny little dots, it's even more effective. SteveBaker (talk) 20:21, 17 August 2009 (UTC)

Ah, so making the image darker, makes the viewer think they are looking at a very bright object. You are truly an evil genius :) 83.100.250.79 (talk) 20:28, 17 August 2009 (UTC)

A plain white filled circle would not cause the squinting reflex. The streaks and secondary images are characteristic of an "overloaded" eye lens + retina, to which sight the iris muscle is programmed to contract. Cuddlyable3 (talk) 21:27, 17 August 2009 (UTC)

It would be interesting to discover if people's irises actually do contract when viewing such images at the same brightness as a simple, white circle. I kinda suspect not...but anything is possible! SteveBaker (talk) 12:29, 18 August 2009 (UTC)

(undent) See here for a modified photograph -- i cut away a portion of the central circle of the sun and, in boxes of various shades, placed adjacent squares of eye-dropper copied central core (left) and cut away white background (right) to see if I could tell the difference. Granted the eye-dropper only works off one pixel and the central circle is likely not uniformly bright -- but perhaps it was so bright that all that could be captured digitally was a maximum, uniform whiteness. DRosenbach ^{(Talk | Contribs)} 13:57, 18 August 2009 (UTC)

Actually, the center is uniformly bright: using Paint's fill-with-color function, I selected a random pixel in the middle of the glare and told it to fill with black, and this resulted. The center in the image really is white: if you take the sun-with-boxes version and fill-with-color the borders around the boxes to be white, then order them to become some other color, both the eyedropped bit from the center of the disk and the background will turn, so it's obviously the same color. Nyttend (talk) 04:12, 23 August 2009 (UTC)

Sleep deprivation and hallucinations

How long must sleep deprivation generally be maintained to achieve hallucinations? Is it always the safest method of doing so? NeonMerlin 04:35, 17 August 2009 (UTC)

Hallucinations are not a guaranteed side effect of sleep dep, they are a possible side effect. My record is staying awake for 4 days (over 80 hours) and I don't think I experienced any hallucinations, well nothing vivid or memorable anyway. I also do not believe intentional sleep deprivation is considered "safe". I am not aware of any safer and legal ways to more reliably achieve hallucinations, though there are several safer but illegal ways to do it, which I could not recommend in a public forum but for purely informative purposes you can start with the article on hallucinogen. Vespine (talk) 04:56, 17 August 2009 (UTC)

The definition of hallucination should also be taken into account. I believe sleep deprivation produces deliriant-like hallucinations, which is where one is unable to determine what is real or not (it is often compared to dreaming whilst being awake). The hallucinations produced by psychedelics can usually be distinguished from reality by those intoxicated, and they are generally stereotyped as things such as: colourful lines, streaks, shimmers, halos, etc.

We can't give medical advice on what is the safest way of achieving hallucinations. I suggest you read the articles that are wikilinked in this discussion. I should also mention that being delirious can lead to behaviour putting one's life into danger. The man in this article took nowhere near the lethal dose of diphenhydramine, but it sounds as though the delirium led him to fatally wound himself with an electric fan. --Mark PEA (talk) 16:08, 17 August 2009 (UTC)

I think sleep deprivation is reasonably safe if you avoid any sort of risky situation, but the level necessary to get hallucinations is so unpleasant that I can't imagine anybody doing it for that reason, especially considering that the hallucinations themselves are likely to be unpleasant. Looie496 (talk) 17:25, 17 August 2009 (UTC)

This is fun reading. (Unrelated, but fun reading.) Bus stop (talk) 20:41, 17 August 2009 (UTC)

I think it will depend on how you stay awake. If you just do it by willpower alone then you'll probably be fine - your body will force you to sleep before it becomes harmful, the human body is generally very good at stopping us from doing stupid things. If something happens to wake you up every time you start to drift off then you could reach dangerous levels of sleep deprivation. --Tango (talk) 01:01, 18 August 2009 (UTC)

Like Lindbergh during his transatlantic flight? 98.234.126.251 (talk) 01:41, 18 August 2009 (UTC)

That flight only took 33.5 hours, that doesn't really count as sleep deprivation. That's just an all-nighter, students do them the night before a deadline all the time! --Tango (talk) 02:44, 18 August 2009 (UTC)

He also didn't sleep much the night before, and toward the end of the flight he was getting kinda delirious, imagining he was seeing land where there was none. FWiW 98.234.126.251 (talk) 22:40, 18 August 2009 (UTC)

Press releases on research papers

Do any scientists regularly produce press releases on their own research papers to improve the accuracy of media coverage? NeonMerlin 07:06, 17 August 2009 (UTC)

See here for the scary truth. --Stephan Schulz (talk) 09:12, 17 August 2009 (UTC)

LOL! That is marvellous :) — QuantumEleven 15:11, 17 August 2009 (UTC)

We publish our results in as many places as we can. It's not the fault of the science community that the majority of the world prefers to consume media from secondary and tertiary sources - academic journals are widely available. Nimur (talk) 16:53, 17 August 2009 (UTC)

Indeed. In fact, most of the short pieces in science news magazines such as "New Scientist" are based on press releases. Sad to say, some scientists show much less discipline in writing press releases than in the journal articles they are based on, although the pressure for glitz from university press offices certainly comes into play. Looie496 (talk) 17:19, 17 August 2009 (UTC)

(ec) That comic is pretty accurate, and the next one too. Probably most of the science articles in a typical newspaper are adapted (or quoted verbatim) from a press release, but the press releases are not written to improve the accuracy of the reporting, they're written to make the sponsoring university look good so that they can attract more donors. Sometimes the researchers themselves write documents apparently intended to help reporters, like this one, but it's pretty uncommon. -- BenRG (talk) 17:21, 17 August 2009 (UTC)

At many universities there are people paid full time to figure out what researchers are up to and to try and publicize it. It's not a bad job, I hear, given the current state of journalism in general. --98.217.14.211 (talk) 19:11, 17 August 2009 (UTC)

No fish native to a river is poisonous?

I saw it on TV. True or false? I know that certain fishes, like the Candiru or Piranhas can seriously harm or kill you, but couldn't find any poisonous river fish.--Quest09 (talk) 11:28, 17 August 2009 (UTC)

Not sure - some catfish have spines (not teeth) that include a poisonous secretion http://www.google.co.uk/search?hl=en&q=catfish+spine+poison&meta=&aq=f&oq=

Perhaps it meant a posionous bite?83.100.250.79 (talk) 11:59, 17 August 2009 (UTC)

Then they meant "venomous" not "poisonous" (common mistake). --Tango (talk) 13:28, 17 August 2009 (UTC)

Or not? Catfish have venom- but not in the bite.83.100.250.79 (talk) 14:44, 17 August 2009 (UTC)

The flesh of all animals is edible (so says a survival handbook I once read). It is only the internal organs that could be poisonous, if you are careful to avoid them you should be fine. --Tango (talk) 13:28, 17 August 2009 (UTC)

The closest thing I can think of is the platypus which has poisonous/venomous/ouchy spurs. Aaadddaaammm (talk) 13:37, 17 August 2009 (UTC)

That depends on how broadly one interprets 'native' (and 'river'). (I'm also assuming, per Tango, that you're going for 'venomous' here.) There are a number of families of marine fish which have developed species adapted to river life. The stonefish, for instance, primarily occupy coastal waters of the Pacific, but a few species (like Notesthes robusta) have adapted to life in streams and tidal estuaries. Trichinus draco, the Greater weever, is now found in the Thames. There are a number of other 'edge cases' which rather blur the general rule you heard. TenOfAllTrades(talk) 14:02, 17 August 2009 (UTC)

The Greater weever doesn't seem to match Tango's description of venomous, there are plenty of venomous purely freshwater species that use venom as a defence.83.100.250.79 (talk) 14:44, 17 August 2009 (UTC)

I never gave a description of venomous, I just said that delivering a toxin by biting is venomous. Venom can be delivered by bites or stings. Poison has to be ingested. --Tango (talk) 17:49, 17 August 2009 (UTC)

You are right. Isn't venomous a subset of poisonous though?83.100.250.79 (talk) 18:52, 17 August 2009 (UTC)

Venomous = poisons things by attacking without dying, like a venomous snake. Poisonous = poisons things when those things eat it, like a poisonous fruit. Dcoetzee 21:02, 17 August 2009 (UTC)

Is catfish defensive spine venomous or poisonous or both?83.100.250.79 (talk) 21:12, 17 August 2009 (UTC)

Venomous, you don't get harmed by eating the spine, you get harmed by being stabbed by it. Of course, the venom glands (or whatever) of a venomous animal will presumably be poisonous. --Tango (talk) 01:02, 18 August 2009 (UTC)

This needn't be the case. Many venoms are protein-based and therefore would be destroyed in the stomach. Looie496 (talk) 17:47, 18 August 2009 (UTC)

Not a good idea to try drinking venom if you have an ulcer. Googlemeister (talk) 20:22, 18 August 2009 (UTC)

Good point. As Googlemeister says, there is a risk if the venom can reach your bloodstream when you eat it. --Tango (talk) 21:17, 18 August 2009 (UTC)

THERMODYNAMICS AND FLUID MACHINERY

1) In a stirling cycle,the volume varies between 0.03 and 0.06m3,the maximum pressure is 0.2MPa and the temperature varies between 540oC and 270oC.The working fluid is air. a)Find the efficiency and the workdone per cycle for the simple cycle. b)Find the efficiency and the workdone per cycle for the cycle with an ideal regenerator,and compare with the carnot cycle having the same isothermal heat supply process and the same temperature range.

referance:stirling  cycle.

2)A boat moved by a jet propulsion,discharge water through a jet of area 0.02m2,the water being drawn from inlet opening facing the direction of motion.The total drag is estimated to be 17.66u2Nm,where u is the speed of the boat in m/s.If the boat moves at 54km/h,determine:

          a)relative  velocity of jet;
          b)energy supplied by the jet and power of the motor required to work the  pumps;
          c)efficiency  of  propulsion.
Take the density of water 1020kg/m3 and efficiency of the  pump set 75%.
 referance :FLUID MACHINERY.  —Preceding unsigned comment added by 41.197.25.6 (talk) 11:41, 17 August 2009 (UTC) 

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not 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 how to solve such problems. Please attempt to solve the problem 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. Thank you.

What lizard is this?

I was in Istanbul and saw this lizard. I was wondering if it could be used if there isn't a decent picture of this particular species of lizard. It was waiting for me to take its picture.

• 

  Spiderone (talk) 12:19, 17 August 2009 (UTC)

Personally, I'd place my bet on it being in the Lacertidae family, but I could never identify the genus, let alone the species. Perhaps someone at WP:WikiProject Amphibians and Reptiles would be more useful here.--91.148.159.4 (talk) 14:35, 17 August 2009 (UTC)

I was thinking of a variety of anole, Polychrotidae family. But I am not too confident on that one. --Jayron32 15:41, 17 August 2009 (UTC)

I would opine -- in fact, I do -- that it is not an anole. The body ornamentation + overall appearance of the skin folds of the neck/stockiness tell me that it is not an anole. I used to have anoles as pets. DRosenbach ^{(Talk | Contribs)} 02:12, 18 August 2009 (UTC)

Definitely not an anole, wrong continent for them anyway. Reminds me of a skink, but I really don't know anything about Old World lizards. I would second the recommendation to ask at the WikiProject. Guettarda (talk) 03:21, 18 August 2009 (UTC)

This certainly looks like a Lacertidae member. There are quite a few species found in Turkey: Lacerta anatolica, Lacerta cappadocica, Lacerta cyanisparsa, Darevskia parvula, Darevskia raddei, Podarcis sicula, etc... I can't identify the species of the one in the picture though. Sorry. --Dr Dima (talk) 05:29, 18 August 2009 (UTC)

Prion Terrorism

Could concentrated and extracted "Mad Cow" prions be a potential terrorist or state bio-weapon? Could they be distributed as a fine mist? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 12:19, 17 August 2009 (UTC)

It wouldn't be very effective for terrorism. Even if it could be manufactured in sufficient quantities and distributed like you describe, most people wouldn't even be aware that they were 'infected' for many decades, or perhaps not until they were autopsied fifty years from now. Wouldn't give much terror bang for the buck. Much easier and more effective to blow something up. APL (talk) 12:58, 17 August 2009 (UTC)

With that being said, odds are if someone created a scare of prions, that cuuld cause high levels of panic and life alteration in a society. ~ Amory (user • talk • contribs) 15:07, 17 August 2009 (UTC)

It's not particularly useful as a state or military weapon; as APL notes the development of symptoms would take years, and infected individuals would be unlikely to transmit infection. (There's no point to using a weapon that doesn't have any effect until years after the war is over, unless you want to invite retribution by similar means.) As a terrorist weapon, it wouldn't have any immediate visible effect, so it's not going to kill people. It could be very effective as a scare tactic, however. A 'fine mist' would be difficult to use, and probably not an effective route of administration. Far more effective to spike food or beverages. Transmission in animals requires several milligrams of brain homogenate from an infected animal: [1]. The effective dose in humans is very uncertain. TenOfAllTrades(talk) 14:24, 17 August 2009 (UTC)

Quibble: Sure there could be a point to using a weapon with a really long "fuze". Suppose Country #1 wanted to wipe out the population of Small Country #2, and Country #1 had access to an effective, nonreversible sterility agent with a secret formula. Country #1 disperses it all throughout Small Country #2. Ten years later, nobody in Small Country #2 is having any kids, and in 50 years the population has crashed, or Small Country #2 is 90% immigrants and is pliable to new political suggestion from Country #1. Mission accomplished! That said, this speculation has nothing to do with prions. Tempshill (talk) 17:06, 17 August 2009 (UTC)

You've been watching Stargate. Vimescarrot (talk) 20:52, 17 August 2009 (UTC)

I dispute this! Cool, it works galactically, too. Tempshill (talk) 06:39, 18 August 2009 (UTC)

In general, bioterrorism in reality is a lot more difficult and a lot less effective than "security experts" would have you believe. Aum Shinrikyo learned this the hard way: they're one of the richest and most well-connected terrorist organizations in the world, and after several expensive, botched attempts at bioterrorism, they finally managed to kill a total of 12 people with sarin, which (unlike prions) is a highly lethal nerve agent. As APL succinctly put it, it's much easier and more effective to blow something up. --Ashenai (talk) 15:14, 17 August 2009 (UTC)

For a wonderful, short little history of how easy it is to blow something up, see Mike Davis, Buda's Wagon: A Brief History of the Car Bomb. --98.217.14.211 (talk) 21:40, 17 August 2009 (UTC)

Turbopumps on rockets

Turbopumps are used on liquid-fuelled rockets to pressurise the fuel and oxidiser before they reach the combustion chamber. What powers the turbopumps (turbochargers on cars use the car exhaust for power, what does a rocket turbopump use)? — QuantumEleven 14:56, 17 August 2009 (UTC)

The turbopumps are powered by a preburner, which burns a small amount of fuel and oxidizer to run the turbopumps. In the picutre, the preburner is number 6. The preburner provides hot gas to run the turbine (number 5), which drives the turbopumps (numbers 3 and 4). anonymous6494 15:25, 17 August 2009 (UTC)

(ec) There's a fairly extensive discussion in this page linked from our article. For cryogenic fuels and oxidizers (liquid oxygen, liquid hydrogen), some pumps can be driven simply by heating the liquid to ambient temperature or above and allowing the expanding gas produced to drive the turbine. With other fuels, a preburner can be used which combines fuel and oxidizer to generate a small amount of hot, pressurized gas. There are several variations on these themes, which offer different methods of preheating the fuels, and which vent the turbine exhaust in different ways. TenOfAllTrades(talk) 15:27, 17 August 2009 (UTC)

It depends on the design. Sometimes, the turbos are powered by a totally separate source (e.g. a battery or a small separate combustion engine). Other times, they tap off the main propulsion energy source, or use the decompression of a refrigerated fluid to power the pump. All of these scenarios have various advantages and disadvantages to the stability, robustness, and mass budget of the rocket. If mass and flight-time is not an issue, the probable best solution is an electric motor; but this requires a large battery (and suffers from scalability - large mass-flux rockets can't really work off an electric turbo pump) - so more often, the turbo either kicks in later or gets an electric start and eventually draws energy from the primary propulsion source. Nimur (talk) 16:56, 17 August 2009 (UTC)

color

What color is pure gold if there is no light shining on it? Is it possible to have color without having reflected light? Googlemeister (talk) 16:36, 17 August 2009 (UTC)

The same. What colour is blue paint in the dark? <rhetorical>83.100.250.79 (talk) 16:39, 17 August 2009 (UTC)

(EC with above)This sounds like "If a tree falls in the forest, and no one hears it, did it make a sound" sort of metaphysical discussion. How do you define color:

• As wavelength(s) of electromagnetic radiation
• As human perception of those wavelengths
• Is the potential to do something the same as actively doing it?

There's just way too many ways to interpret the question to answer it with a definative answer. --Jayron32 16:42, 17 August 2009 (UTC)

It is possible to have color without reflected light. I have a keychain that has a combination of tritium and phosphorus it appears pale green even in pitch blackness. This is because it emits a pale green light. Light has to be involved one way or the other. APL (talk) 16:45, 17 August 2009 (UTC)

Maybe the atomic absorption/emission spectrum of gold is relevant here. That's about as close to the "natural" inherent color of atomic gold as any definition can come. But because gold is a noble metal, and a transition metal, its valence electron behavior is a bit pathological - I'm not sure there's a very well-defined emission spectrum (at least, not as simple as, say the Hydrogen spectrum). Nimur (talk) 17:00, 17 August 2009 (UTC)

True, but then we get involved in the metaphysical discussion of whether or not something which normally has a color can be said to have a color even if it is not currently emitting/reflecting light. Is it enough to say that something has a color if we define a set of conditions where light could not possibly be involved? Its the "tree falling" discussion all over again... --Jayron32 16:59, 17 August 2009 (UTC)

Color, as most philosophers currently see it, is fundamentally a property of a material -- the color of an object defines the relationship between the light that strikes it and the light it emits. So it is completely proper to say that the color of gold is orange. What complicates things is that we perceive light itself as having a color, but these perceptions are tricky and paradoxical in some respects.

If the gold is hot enough, it will emit light, but the spectral distribution will vary with temperature. Edison (talk) 18:52, 17 August 2009 (UTC)

This is purely a linguistic thing. We use the word "color" for at least two phenomena: Firstly, the spectral characteristics of light coming from an object towards our eyes. Secondly, the inherent reflectivity-as-a-function-of-frequency (or transmissivity-as-a-function-of-frequency) of a material. So if you are talking about the color of gold in the first sense - then the answer depends on what color of light you're shining on it...or indeed if you are shining light on it at all. In this first sense of the word, the gold is black when there is no light shining on it. The second sense implies a property of gold (that it is golden) that is the same irrespective of whether there is light shining onto it or what color that light is. For some senses of the term, we actually use different descriptive words. We say that gold is "golden" - and not "orange" because we know that gold is highly reflective and "orange" somehow doesn't seem right. This problem is most clearly demonstrated when you ask what color a mirror is. Most people (if forced into giving an answer) would say "silvery" - implying something that reflects all frequencies equally - but "white" would be an acceptable answer. What gets difficult is when you have highly reflective surfaces that don't have these "special" names...a "green" car doesn't look at all green under an old-fashioned orange street-lamp. When this happens, we have to resort to circumloqutions like "That green car looks yellow!"...as is so often the case, language is a mess - but the science is quite clear. SteveBaker (talk) 20:13, 17 August 2009 (UTC)

Gold leaf can be beaten thin enough to become translucent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red.<http://www.webexhibits.org/causesofcolor/9.html> Cuddlyable3 (talk) 21:04, 17 August 2009 (UTC)

(replying to Steve) It's even trickier than that, because our color perceptions are to a substantial degree illumination-invariant. This can lead to some weird effects. For example, suppose you are in a room with fluorescent lights, and looking at a piece of white paper next to an active computer monitor. Suppose you change from fluorescent to incandescent lighting (which is bluer) -- what you will perceive is that the image on the computer monitor shifts color while the piece of paper keeps the same color, exactly the opposite of what happens to the light they emit. Looie496 (talk) 21:19, 17 August 2009 (UTC)

Back when I was in Yeshiva University, I took 2 philosophy courses in order to fulfill my history requirements. In Philosophy 1, I wrote a proof paper on "Color does not exist," and in Philosophy 2, I wrote a proof paper that "Color does exist." The second was a much more difficult endeavor. In any event, it's not nearly as simple as the discussers above have made it seem -- there are apparently claims that only 1 family of bird (or no species) are actually green or blue in that they possess green or blue pigmentation. All other birds that appear green or blue merely do so because the air bubbles/pockets within the feather fibers are of a size that specifically absorbs non-blue/green light, thereby making it appear as though the feathers are blue or green, when in fact, they are not. But does that mean the feathers are not blue? If color is defined by pigment color? How do we know what the pigment color is...is it not only because we perceive it as being colorful? How then can we assert that something else absorbs and reflects light in a similar manner but is not that color? I think I remember the answer being that, microscopically, it was seen that these air pockets were hollow rather than filled with non-gaseous matter known as pigment by virtue of the fact that it causes us to perceive color. So it's sort of like a cyclical definition. I now notice that I've written a lot, perhaps without saying much...but now I'm done. DRosenbach ^{(Talk | Contribs)} 02:28, 18 August 2009 (UTC)

This is exactly the kind of thing that gets philosophers excited - and also the reason why philosophers are a waste of quarks! There really isn't any problem at all here. The science is clear and unambiguous - we understand exactly what's going on. Such difficulty as arises in the discussion is entirely due to imprecise use of language. If we use more precisely defined words like 'emissivity', 'reflectivity', 'transmissivity', 'pigmentation' and 'light-spectrum' and assiduously avoid this vague word 'color' then all of the complication falls away and such philosophical BS as "Color does/does-not exist" evaporates and can be replaced by the simple, true, and verifiable statement: "The word color is ambiguous". SteveBaker (talk) 12:25, 18 August 2009 (UTC)

See Elitzur–Vaidman bomb-tester. It should be possible to detect the wavelengths gold reflects without interacting with it by shining any photons at it. Dmcq (talk) 10:21, 18 August 2009 (UTC)

Indeed - but the OP wasn't asking about something so easy as what wavelengths it reflects - the question is about "color" - which is an ill-defined word in this context. SteveBaker (talk) 12:25, 18 August 2009 (UTC)

Ants sting instead of bite?

Am I the only person who assumed that ants bite with their mandibles instead of stinging with . . . something else? The ant in this photograph has scary-looking jaws, but apparently they are not responsible for the ant's painful "sting". Where exactly do they keep the sting? Do they spray or inject (the ant article mentions both as a possibility)? I've pulled up all of the information I can find on this species on the 'net, and they are consistently referred to as having a sting and not a bite, but no further details are given. Maedin\^talk 16:50, 17 August 2009 (UTC)

Our article on fire ants is informative. It states that most ants use a "bite and spit" combination to "sting"; while a fire ant uses an abdomen-mounted stinger, much like a bee, to do so. So the answer to your question is "it depends on the species of ant". --Jayron32 16:56, 17 August 2009 (UTC)

To elaborate, an ant clamps down with its mandibles, but the actual injury is sustained when it stings the target. Ants are related to bees and wasps.CalamusFortis 17:12, 17 August 2009 (UTC)

Didn't you see Them!? B00P (talk) 18:59, 17 August 2009 (UTC)

Obviously I didn't, ;-) Thanks a lot for your responses; it would still be nice to know whether Myrmecia esuriens stings with a stinger in its abdomen, or bites (or clamps) and spits. I don't see any specific mention of a physical stinger in any of the sources I could find, so I will have to assume that it's the latter method. Maedin\^talk 19:41, 17 August 2009 (UTC)

I have one of Their records, but what's the relevance? —Tamfang (talk) 06:49, 6 December 2009 (UTC)

Recycled ants?

I crushed an ant on a window sill and left it there. A few minutes later I returned and found what appeared to be another ant carrying my first victim away. What is the purpose of this behavior? Do ants bury their dead? —Preceding unsigned comment added by 75.52.255.4 (talk) 17:18, 17 August 2009 (UTC)

More likely the first ant will be lunch. Googlemeister (talk) 17:46, 17 August 2009 (UTC)

Perhaps a ceremonial lunch in which the recently deceased will be remembered fondly for its contributions to ant culture. Bus stop (talk) 17:49, 17 August 2009 (UTC)

^†The decedant? DMacks (talk) 17:59, 17 August 2009 (UTC)

The ant's religious affinities are not known at this time. Bus stop (talk) 18:07, 17 August 2009 (UTC)

Protestant. DMacks (talk) 18:16, 17 August 2009 (UTC)

You've heard of "the Elephants' Graveyard," but, it seems, not "the Ants' Cemetary," Also the corpse is being studied by the ant equivalent of Gil Grissom to determine who the killer is. I'd leave town if I were you. B00P (talk) 19:15, 17 August 2009 (UTC)

I suppose the ant version of Grissom understands and is obsessed with humans? ~ Amory (user • talk • contribs) 19:18, 17 August 2009 (UTC)

I would think that, prior to deciding if the body should be carried off, they would determine the antecedant cause of death. StuRat (talk) 00:17, 18 August 2009 (UTC)

There was an interesting thing about this behavior on TV sometime ago. Evidently the dead ant gives off some kind of smell/pheremone that the other ants detect which kicks them into "Remove the body from the nest" behavior. The researcher (sorry - I forget his name) figured out what the chemical was and had a lot of fun smearing microscopic drops of it onto live ants - who would be grabbed and carried screaming and kicking from the nest by their former colleagues. As soon as they dumped the "corpse" outside the nest, it would immediately come scurrying back in - only to be grabbed and ejected again. Pretty funny actually. So evidently, the nest-mates don't eat the corpse (that would probably be a bad idea anyway because this could cause the spread of diseases through the nest). I have no idea what the smell causes them to do when they're outside the nest...but evidently there is still some behavior involved. SteveBaker (talk) 20:00, 17 August 2009 (UTC)

Maybe it was E. O. Wilson, who studies myrmecology. Bus stop (talk) 20:14, 17 August 2009 (UTC)

Wilson doesn't do stuff with chemicals... And I'm sure Steve would remember if it was E.O. Wilson! --98.217.14.211 (talk) 20:36, 17 August 2009 (UTC)

OK. I couldn't even think of E. O. Wilson's name. I had to search for ant man or some such search terms. Bus stop (talk) 20:44, 17 August 2009 (UTC)

Chemically-induced bullying... very funny, I'm sure, Steve. --Tango (talk) 20:04, 17 August 2009 (UTC)

Actually, this only applies to ants who are infected by a particular killer spore. Ants can tell normal dead ones from ones killed by a dangerous contagious disease. Dcoetzee 20:59, 17 August 2009 (UTC)

As to what Steve said there was some furthur thing with the ant pheromone and it didn't work precisly that way. I just can't remember how it was different. I'll post link if I can remember. EDIT: Here's the link from where I first heard the story Steve heard. Now if only I can find the later story that added some stuff to this one...66.133.202.209 (talk) 23:29, 17 August 2009 (UTC)

Yeah - that's the story I remembered (I can't believe I forgot that it was E.O.Wilson though...) - it's pretty funny. SteveBaker (talk) 01:45, 18 August 2009 (UTC)

Sounds like a standard EO error, I get them all the time. StuRat (talk) 01:10, 19 August 2009 (UTC)

Digital Electronics

What exactly is the differece between priority encoder and a priority decoder??

This FAQ may contain your answer. As I assume you know, a priority encoder gives a binary code telling you which is the highest-priority input (e.g. an interrupt) that is active. It seems that a priority decoder is just an ordinary decoder that converts the binary code from the priority encoder back to one of many outputs (e.g. interrupts again). In other words, a priority decoder is logically the same as an ordinary encoder, but it just has the word 'priority' added to indicate that it is being used in conjunction with a priority encoder. --Heron (talk) 20:10, 17 August 2009 (UTC)

This question was cross-posted on the Computing desk. I'm merging it to here. Nimur (talk) 20:47, 17 August 2009 (UTC)

What exactly is the differece between priority encoder and a priority decoder?? —Preceding unsigned comment added by Piyushbehera25 (talk • contribs) 18:41, 17 August 2009 (UTC)

Have you read Encoder and Decoder? An encoder reduces the number of bits, while a decoder increases the number of bits. Cascading the two devices, you can reconstruct the original signal (one device performs the adjoint operation to the other). Nimur (talk) 20:16, 17 August 2009 (UTC)

@Heron: thanks for your answer...but still i'm not quite clear...so you are saying that both the priority encoder and priority decoder are the same thing??I was also thinking the same but then why use 2 different names??

@nimur: yes i'v read those and know their functions...my question was what's the differece between priority encoder and priority decoder(if any)...please clarify if anyone knows —Preceding unsigned comment added by Piyushbehera25 (talk • contribs) 08:35, 18 August 2009 (UTC)

You clearly DON'T understand their functions or you'd know the difference! A priority encoder takes some number of input bits that are numbered from 0 to N. It finds the highest numbered input that contains a '1' bit and outputs the number of that bit in binary.

Hence, (if we number our bits with the highest bit on the left and bit zero on the right), a 4 bit priority encoder would work like this:

• 0001 ==> 00 (the highest numbered '1' bit is bit zero).
• 1101 ==> 11 (the highest numbered '1' bit is bit three).
• 1000 ==> 11 (the highest numbered '1' bit is bit three).
• 0110 ==> 10 (the highest numbered '1' bit is bit two).

...and so on.

A priority decoder is the opposite of this...but because information is lost in the priority encoder (we go from a 4 bit number down to a 2 bit number)...connecting a priority encoder to a priority decoder doesn't result in the same thing coming out as went in. eg:

• 00 ==> 0001 (generate a '1' bit on bit zero)
• 01 ==> 0010 (generate a '1' bit on bit one)
• 10 ==> 0100 (generate a '1' bit on bit two)
• 11 ==> 1000 (generate a '1' bit on bit three)

So if you connected the priority encoder in my first example to the priority decoder in my second, then you'd get:

• 0001 ==> 00 ==> 0001
• 1101 ==> 11 ==> 1000
• 1000 ==> 11 ==> 1000
• 0110 ==> 10 ==> 0100

...and so on.

You could imagine something like an elevator controller using this kind of circuit. In this building, the high up executives live in the upper floors of the building and the workers in the lower floors. The elevator is designed to pick up the managers first - even if multiple "call" buttons have been pressed. You might then connect all of the call buttons to the priority encoder. It would find the highest floor that is calling for the elevator and output the number of that floor. A priority decoder could then turn that into a single output bit representing the floor to which the elevator has been called. In a sense, the circuit has made a decision as to which call button has the highest priority and is ignoring all of the lower priority buttons. Once the call button on that floor is released, the priority encoder would then find the second highest floor with the call button pressed and send the elevator there. This is obviously a silly example - but it should give you the basic idea of what the priority encoder and decoder can do for you.

I hope this clarifies things a little. SteveBaker (talk) 12:10, 18 August 2009 (UTC)

Thanks that helped...that's exactly what I wanted to know...I was confused as to how the priority decoder will know the exact input when fed with the output of the priority encoder clearly it's impossible...so there's no such thing as a priority decoder,it's just a simple decoder(i.e the function and working of priority decoder and a normal decoder is the same)...Please correct me if i'm wrong...

thanks again —Preceding unsigned comment added by Piyushbehera25 (talk • contribs) 15:09, 18 August 2009 (UTC)

Correct - an encoder (especially a priority encoder) can be considered a hardware implementation of lossy compression. The exact signal cannot be reconstructed - only an approximation to it. The term "priority encoder" describes one method for deciding the scheme of that lossy compression. Any time that you take 4 bits and generate 2 bits, you have lost some information; the decoder will assume the simplest reconstructable signal and output that. Nimur (talk) 17:26, 18 August 2009 (UTC)

The name "Priority decoder" redirects[2][3] to Decoder where the name is not found. Perhaps another editor can break that redirection because it gives an incorrect impression that there exists some special kind of decoder called a "priority decoder". Cuddlyable3 (talk) 20:11, 18 August 2009 (UTC)

Certainly you don't often hear them called 'priority decoder's - the (approximate) inverse of a priority encoder is more often called a "single bit decoder". Many of the first few Google hits for the term are actually talking about a priority encoder instead! (This book on switching theory, for example has a page that starts with the heading "Priority Decoder" that has the logic table for what Wikipedia calls an encoder). It's a tough call. I think there should probably be a disambiguation page that says something like "The term 'priority decoder' can either refer to a priority encoder or to it's inverse - a 'single bit decoder'". SteveBaker (talk) 00:08, 19 August 2009 (UTC)

Thank you all for helping me out here...i'm totally clear on the matter now...and yes the google and wikipedia search results also did contribute to my initial confusion...and something must be done to clarify this aspect... —Preceding unsigned comment added by Piyushbehera25 (talk • contribs) 19:14, 20 August 2009 (UTC)

DNA ligation in vitro

I have a mix of standard d(N)₆ random DNA hexamers, and I want to ligate them to the 3' end of an arbitrary single-stranded DNA oligomer. Neither is currently modified in any way. Does anybody have any suggestions for a relatively cheap and easy way of going about this? – ClockworkSoul 18:42, 17 August 2009 (UTC)

Aha! This should do nicely. – ClockworkSoul 19:09, 17 August 2009 (UTC)

I misread the title as "DNA litigation in vitro". Gave rise to some interesting mental images! --Anonymous, 20:26 UTC, August 17, 2009.

suppository

what is the lube covering suppository for constipation. it looks like vasaline but i dont think its that —Preceding unsigned comment added by 74.65.3.30 (talk) 21:05, 17 August 2009 (UTC)

You'd have to tell us which brand of suppository you have to know for sure. Suppositories are often encased in a capsule of glycerin, which is itself a lubricant. Just the warmth of your finger (or other parts) can cause some melting so that the suppository is self-lubricating. It is very unlikely to be Vaseline or any other non-water-soluble lubricant, for a variety of reasons. --Sean 21:26, 17 August 2009 (UTC)

i dont know the brand it was it was in the 90s. there was lube all over it it was goopy like vasaline. they were not induvidulaly packaged. i think they were in a round tin. —Preceding unsigned comment added by 74.65.3.30 (talk) 22:39, 17 August 2009 (UTC)

Can't you check the packet? It should have a list of active and non active ingredients, or similar.

Could probably find ingredients-info in a PDR of that era. DMacks (talk) 15:08, 19 August 2009 (UTC)

Cant (road/rail)

I have taken issue with this article as it appears to be about two separate things. Camber and bank, the former being the raise in the middle of a road in both straight and curved sections that is there for drainage reasons, and secondly bank, the slope of a road on a curved sections to allow vehicles to pass at higher speed.

But before taking action I thought it best to agree with some people to which of these both cant and camber actually refer. Particularly as I have not heard of the term "cant" before. Thank you. Elocute (talk) 21:34, 17 August 2009 (UTC)

Cant (rail) is the same as superelevation (ie similar to a banked track)- ie the tilt of the track at right angles to the direction of travel. I don't know about roads.83.100.250.79 (talk) 11:48, 18 August 2009 (UTC)

Wiktionary provides this definition for "cant": slope, the angle at which something is set. Both camber and bank are examples of cant because both are reasons to apply slope to a road or railway track. I don't see anything wrong with our article. SteveBaker (talk) 11:51, 18 August 2009 (UTC)

Camber is not an overall slope but a curvature, and so has on average has no angle of deviation from the vertical. I see no real reason for you to fight me on this issue as they are clearly different things which serve different purposes. For example no railway has camber. Elocute (talk) 12:39, 18 August 2009 (UTC)

The definition of cant doesn't say anything about "average slope" - there is a slope on one side of the road and a roughly opposite slope on the other...there are undoubtedly slopes - so using the word 'cant' for each side of the road is perfectly acceptable. 'Cant' is really a synonym for 'slope'...not 'average slope'. If you're going to go around randomly averaging things - then I'll point out that if you take a long enough stretch of railroad track, the bank angles will very likely average out to roughly zero too. SteveBaker (talk) 23:51, 18 August 2009 (UTC)

I think 'camber' may require disambiguation. http://www.thefreedictionary.com/camber defines it as arch like, but it's clear that many regard it as being synonymous with cant/bank (possibly incorrectly).

Also if you are going to fix it please note that the section in Camber angle#Road camber should be moved too.83.100.250.79 (talk) 12:56, 18 August 2009 (UTC)

I don't think anyone is looking for a fight, Elocute; we're merely discussing how these words are used. As .79 says above, cant is a term commonly applied to railway tracks (in the UK at any rate) which means the same as superelevation or banking on a road (and in railway parlance, "elevation" and "banking" are used for two different and quite unrelated concepts, so might cause confusion if used in connection with the tilting sense). Your definition of road camber is strictly correct, but (again in the UK at any rate) "camber" is often used by laypersons (i.e. not civil engineers) more loosely to refer to banking, most often in the construction "reverse camber" when referring to a bend where the camber and banking combine sub-optimally to make negotiating the bend unexpectedly difficult. I suggest that recourse to a Civil Engineering textbook might help to compose a comprehensive and authoritative explanation of the terms that would take into account the common misuse of "camber." 87.81.230.195 (talk) 13:18, 18 August 2009 (UTC)

A romantic notion, but unfortunately I have neither the spare time or the academic resources to produce a conclusive treatise on this issue, I was merely trying to include the small amount information that I do have to offer into the article and make it more understandable. I shall see what I can put together in my userspace and invite you to comment before editing the articles. But on another note I fear you saw more aggression in my usage of the term "fight" than was intended, maybe "oppose" would have been a better choice of word. Elocute (talk) 18:54, 18 August 2009 (UTC)

The Ref Desk isn't the place to do that. You ask questions - we answer them. The place to discuss the appropriateness of a change to an article is in the article's own Talk: page. Also, if you're pretty sure that you're right - and the change isn't of earth-shattering importance to humanity - you should probably just "be bold" and alter the article. SteveBaker (talk) 18:55, 19 August 2009 (UTC)

Well in my experience no matter how benign an alteration one makes to an article, if it 'undoes' something someone else has done they usually get upset and the discourse degrades into pedantry followed by edit war. So all I was trying to do is find out if what I believed to be the case was actually correct or not before editing. Elocute (talk) 19:34, 19 August 2009 (UTC)

Suppositories - q for the medical people here

How common is it for patients to swallow prescribed suppositories by mistake? You hear stories about it but is it a particularly widespread error? --84.65.32.44 (talk) 21:55, 17 August 2009 (UTC)

I have been a nurse and involved with caring for people all my long life and I have never heard of a real case where this happened. I think it is rare. —Preceding unsigned comment added by 86.4.181.14 (talk) 07:01, 18 August 2009 (UTC)

Yes, they'd have to be a total butt-head with sh** for brains to do that. :-) StuRat (talk) 12:41, 18 August 2009 (UTC)

So, similar to the other apocryphal 'stupid patient' tales that medical staff like to swap with each other? Like the woman who goes to see her doctor complaining that she's still having heavy periods, despite swallowing a tampon every month - or the guy who says that he feels pain every time he touches his legs or his left arm, to which the doctor replies "your right hand is broken". Or the couple who claim to be having problems conceiving a child, despite 'sleeping together every night for two years' - and the doctor eventually discovers that *sleeping in the same bed every night* is *all* that they've been doing, both having failed to grasp the basic concepts of sexual reproduction... ;) --Kurt Shaped Box (talk) 17:10, 18 August 2009 (UTC)

What kind of effects would you expect if they did? Vimescarrot (talk) 11:08, 18 August 2009 (UTC)

Well, one reason for using a supository is that the drug is absorbed by the bowel/colon. Blood from here does not flow through the liver prior to entering the inferior vena cava. Some drugs are rapidly deactivated by the liver, so by bypassing the liver, the drug has a longer halflife in the body. Also, absorption through the colon has different kinetics than does absorption through the stomach/small intestine. There may also be a question of the drug being sensitive to the acidity of the stomach. I'm sure there are other reasons as well. In sum, I suspect less of the drug would enter the person's system and or that which does would do so more slowly if someone swallowed a suppository. A pharmacist may have more insight. -- Flyguy649 ^talk 16:23, 18 August 2009 (UTC)

Looking for a nutrition web site

No big deal, you say ? Well, I'm looking for a site which will list foods which are good for diabetics, those with high blood pressure, those with kidney failure, etc. Still no big deal ? Well, I want it to recommend foods for those with multiple medical conditions. (Note that I'm not asking anyone here to recommend any foods, just a site where I can look it up myself.) Ideally you should be able to weight the medical conditions, say if you only have slightly high blood pressure but have severe diabetes. In that case avoiding foods with a high glycemic index would be more important than avoiding salt. It should also list foods from best to worst, for the given medical conditions and weighting factors. So, does such a site exist, or must I create it myself ? StuRat (talk) 22:24, 17 August 2009 (UTC)

For advice that personalised I would suggest people get their doctor to refer them to a professional nutritionist. I think there are too many factors involved for a website to give reliable results. --Tango (talk) 01:05, 18 August 2009 (UTC)

I disagree. The Best Buy web site can do something similar with appliances right now. You give it some parameters, like the size of monitor, it's resolution, and cost range, and they give you a list of monitors that match. The same thing could easily be done with foods, where the parameters become low glycemic index, low salt, etc. The site nutritiondata.com already has this info, I just need it to be made "searchable" and "sortable". As for refering to a doctor, you tend to get doctors with various specialties each of whom only know the foods which are good or bad for those conditions, not for the overall health of the patient. I also tried the nutritionist approach, but she gave me several lists (one for each condition) and wanted me to to the work of cross-referencing it all. And the lists only had maybe 100 foods each (and they weren't even the same foods on each list), which meant there were only like 3 foods on the "good" list for all the conditions. If you started with more like 1000 foods you'd end up with a more respectable list of maybe 30 foods good for all conditions. And cross-referencing such a large number of foods manually is truly a daunting task which really should be automated. I can think of no better use for a computer than automating such drudgery for the benefit of mankind (well, ok, maybe distributing porn is a better use, :-) ). StuRat (talk) 12:12, 18 August 2009 (UTC)

A question from an answerer! Here are some contributions toward an answer and an explanation of why this is not so simple. Foods that are considered good for diabetes can be (a) foods that are healthy for everyone, since nearly all adults with diabetes need to eat less of some things (calories) and more of others even more than the rest of us; (b) those rare plants that might contribute to lowering blood glucose by various mechanisms, but plant names can be vague and overlapping and are rarely available as food (e.g., gymnema or cinnamon) and the hypoglycemic effect is small, and the efficacy claims often come from folk medicine sources and may be not well proven; (c) those things that might help if the person is deficient in a single nutrient (e.g., foods high in chromium); (d) foods that slow absorption of carbohydrates (e.g., high fiber and fat foods) can make it easier to match injected insulin with a meal; (e) carbohydrate foods that are more slowly digested and hence easier to dispose of by someone with limited insulin responses or on injected insulin (e.g., low glycemic index foods are better than high); and (f) dietary changes that would be helpful for the conditions often associated with adult diabetes (e.g., less calories for the overweight, less salt for the hypertensive, less fat for the hyperlipidemic, less potassium and protein for those with impaired kidney function). The really depressing answer for anyone developing type 2 diabetes with mildly high blood pressure and heart risk is that "eat a lot less of everything you like and have been eating for most of your life" is actually far more accurate and efficacious than attempting to add anything else from the list above. Good luck. alteripse (talk) 01:59, 20 August 2009 (UTC)

I both ask and answer questions all the time (hopefully not the same Q's.) The nutrition site could even bypass the possibly contentious issue of what is good and bad for various medical conditions by merely allowing you to sort foods by parameters you define, like low sodium, low glycemic index, etc. They would never need to ask your medical problems, in this way. As I mentioned, nutritiondata.com already lists these things about all foods, but looking through thousands of foods to find those which match my criteria is extremely time-consuming. StuRat (talk) 14:35, 20 August 2009 (UTC)

If you restrict the search criteria to simply ranking by a single food constituent per serving, you make the problem much simpler but a bit less applicable to real life. You might try looking for discussion forums about nutrition or for dieticians and ask if anyone knows a database in which you can do a rank sort by a specific column. This restricts you to the foods measured and added to the database. It also restricts you to someone else's idea of portion size. If you then wanted to sort by specific nutrients such as trans fat or chromium, you would find that many foods might not have values listed. And perhaps the most important aspects of ranking might be personal palatability. Forgive my cynicism from long experience, but for an individual patient with diabetes, I would still match the last decision heuristic I provided above against the usefulness even of a database that perfectly met your criteria.

However, if we set aside real life medical or nutritional efficacy and think of it as a pure internet database search problem, your question is interesting. I wonder if any of the newer quantitative search engines could provide rank sort manipulation of any recognizable row-column database on any website? Why don't you try asking this at the computer ref desk and see if anyone knows of such a program? alteripse (talk) 22:30, 20 August 2009 (UTC)

Thanks, I'll try cross-posting there. StuRat (talk) 00:27, 21 August 2009 (UTC)