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December 17

Blood cells discarded per day

Page does not say how many blood cells die and are discarded per day in the human body. Anyone know?--Light current 00:13, 17 December 2006 (UTC)

Because of the different lifespan of red and white cells, it probably depends of their kind. According to Arizona Science Center, ca. 2 million die per second, so 172,800,000,000 die in 24 h. --Brand спойт 01:11, 17 December 2006 (UTC)

That seems like a rather large number, unless my math is off. Speaking only of red blood cells (and most of the blood cells are RBCs), their normal life-span is 120 days (this can be lower in intensively training athletes). Each day about 1% of RBCs are replaced. The blood volume in one human is approximately 4.7 liters or 4700 milliliters. There are about 5 million RBCs per milliliter. So that's 23,500,000,000 RBCs/human, and 1% of that is 235,000,000 replaced per day. Calculating another way, if there are 23,500,000,000 and they are replaced in 120 days, each day about 430,833,333 are replaced. So maybe a good estimate would be 300,000,000 RBCs/day. - Nunh-huh 02:19, 17 December 2006 (UTC)

Valence orbitals

Why do atoms "want" to have full valence shells? BenC7 02:05, 17 December 2006 (UTC)

It's the most stable configuration. --Wooty Woot? contribs 03:54, 17 December 2006 (UTC)

"Full" valence shell is a misnomer, of course. All atoms "want" is an s²p⁶ arrangement. A "full" valence shell would be 2n² electrons, where n is the number of the shell. This s2p6 arrangement seems to have the highest ionisation energy, and lowest electron affinity, of any, and that is why it is a "stable" arrangement. --G N Frykman 08:51, 17 December 2006 (UTC)

"Wanting to have full valence shells" is the standard oversimplified explanation of molecular bonding. It more or less works as an explanation for highly polarised ionic bonds. However, in real life, the explanation of molecular bonding is much more complex and not completely understood - see valence bond theory, covalent bond, metallic bond and molecular orbital. Gandalf61 10:54, 17 December 2006 (UTC)

It's also possible that full valence shells have a spherically symmetrical distribution of 'charge' whereas unfilled shells don't - it's possible to make the link with the stability of full shells through 'hand waving' explanations.87.102.13.235 16:10, 17 December 2006 (UTC)

Note that Tin forms +2 and '+4' oxidation states - in the +2 case the valence shell is not full - but the complounds are stable - however the s shell is full. (correction Tin (2) usually attains a full valency shell by coordination with other lone pairs)83.100.250.252 09:18, 18 December 2006 (UTC)

In general this phenomona happens because there is a big gap in energy between the full valence shell and the state with "full valence shell plus one electron" - the difference is so large that it's very rare to find the valence shell 'overfilled' (I can't think of a single example), however having partially filled valence shells does sometimes happen (though the resultant products are reactive).

Explaing why there is stabilty for full shells is very difficult to do.83.100.132.121 18:03, 17 December 2006 (UTC)

As others have said, and perhaps I can just re-phrase, the metaphor of atoms as "wanting" agents is a bad approach to this. If you take for granted that full valence shells is the most stable condition, then by definition it is what atoms are going to fall into when they get the opportunity. Why stable states are, by definition, more stable, is a much more difficult and problematic question, because you are really trying to take apart what the definition of "stability" really is in physical terms. If I understand this correctly, which I don't pretend to necessarily do. --24.147.86.187 20:34, 17 December 2006 (UTC)

That seems like a good explanation - the first part. As I see it the problematic part is explaning why 'octets' and the like are stable - which is reasking the question again - even the latest theories of the atom don't actually explain why certain states are stable, or why the stabilty occurs at certain values 2,8,18 etc. There are formulas giving the number of electrons in each successive valence shell - but unfortunately no explanation of why those formulas (and not others) apply..83.100.132.121 22:16, 17 December 2006 (UTC)

The explanation for a configuration being stable is simply that the atoms want to be in that configuration :-P  --Lambiam^Talk 00:00, 18 December 2006 (UTC)

You just restated the question, didn't answer it..83.100.250.252 09:18, 18 December 2006 (UTC)

Ha, I remember in grade 9 and 10 science where to explain bonding, when you had ionic forms of atoms, they'd be the happiest with full valence shells, so in order that they don't become unhappy, they bond. 74.102.89.241 00:26, 18 December 2006 (UTC)

OK, so basically it is that they are more stable with a full valence shell. I knew that already. But why (usually) eight? Why not seven, or six? I am studying to be a science teacher and I want to be able to explain to students the reason why it is more stable to have a total of eight electrons per atom, given that it is more intuitive that an atom would simply want the number of electrons equal to its atomic number. I don't want to say to students "well, it's just more stable that way" when it would, on the surface, appear to be less stable. BenC7 00:59, 18 December 2006 (UTC)

In chemical science it's not 8 it's as the row increases 2,8,18,32 - if you want to be a chemistry teacher you'll should do a degree in chemistry - after 3 years the reasons for this (and the many flaws and discrepencies) will become apparent. As the second poster said this turns out to be a 'lie to children' in most part. The 'rules' are found experimentally and attempts made to fit the behaviour to a mathematical pattern. There is no real satisfactory answer to this question. I can only suggest you learn more (and formulate your own ideas) - (personally I've come to the conclusion that the current simplified teaching of chemistry leaves a lot to be desired - as it introduces concepts without giving an adequate explanation - as you have found out). There's a lot of infomation - but to get you started I suggest you look at platonic solids, atomic orbital, Symmetry group, Chemical bond and follow the links as necessary. Check everything you read for yourself - just because it's been printed doesn't mean it's right. Try to develop your own theories of bonding etc and Good Luck!(And remember the interpretation of experimental facts through a flawed theory may produce confusing results..)83.100.250.252 09:31, 18 December 2006 (UTC)

8 is a "magic number" for the following reasons. Electrons in an atom can be divided into shells. Within each shell, the electrons fall into orbitals. The lowest level orbital, called the s orbital, can contain up to 2 electrons; the next orbital, called the p orbital, can contain up to 6 electrons. These limits are due to various reasons to do with the Pauli exclusion principle, electron states and quantum numbers - see atomic orbital#Limitations on the quantum numbers for a quantitative explanation. So an atom with full s and p orbitals in its outer shell has 2+6=8 electrons in this shell. Combine this with the fact that full shells are stable configurations and you get the "wants to have 8 electrons in its outer shell" rule, which is a reasonably good rule of thumb for the simple chemistry of elements until you get to the transition metals where a d orbital enters the picture for the first time, and life gets more complicated. To see how complicated it can get, take a look at this table of oxidation states for transition metals. Gandalf61 15:47, 18 December 2006 (UTC)

Kill Mosquito Larvae in a Water Tank

How do I kill mosquito larvae in a drinking water tank without poisoning myself?203.202.140.72 02:12, 17 December 2006 (UTC)

A tank with decaying larvae? You probably should drain the tank. I've heard that a thin layer of oil on the water surface will suffocate the larvae by plugging their breathing tubes. But then you'd have both the dead larvae and some rancid oil. --Wjbeaty 04:29, 17 December 2006 (UTC)

I seem to remember that somewhere the WHO used styrofoam beads to cover the surface of ponds and prevent mosquitos from breeding without interfering with the fish living there. Dr Zak 05:01, 17 December 2006 (UTC)

Why not just skim them? And may I say that (for whatever reason, I'm not squeamish about bugs or much else), this is the grossest topic I've ever seen on the RD? ;-\ Anchoress 05:07, 17 December 2006 (UTC)

I don't think the OQ was asking about decaying larvae, but living ones. Apparently mosquito dunks are safe. User:Zoe|(talk) 06:48, 17 December 2006 (UTC)

Yeah but after he kills them, they will have to decay. --Username132 (talk) 10:02, 17 December 2006 (UTC)

Aaaaaand there's even an article about them here on Wikipedia. Mosquito dunk. Anchoress 10:05, 17 December 2006 (UTC)

So the question is how do you eliminate the dead and rotting mosquito carcasses? Adaptron 14:24, 17 December 2006 (UTC)

Why not filter it? --V. Szabolcs 16:50, 17 December 2006 (UTC)

Because only the undesolved products of the rotting larvae carcasses can be filtered effectively. Adaptron 19:09, 17 December 2006 (UTC)

Get a local river fish (like, say, a trout) into the tank it will efficiently get rid of all the larvae. Depending on a lot of factors it can either stay there for a rather long time or you will have to release it back into the river. Keria 17:14, 17 December 2006 (UTC)

yes that's a real solution - but suggest a smaller fish - remember the fish will polute the water. Hillstream loach and Chaetostoma (bulldog) plecs have actually been (reported) to have been used for this purpose. I wouldn't suggest trying this though - if the larvae are all eaten the fish will probably starve, die, rot and then pollute the water even worse!83.100.132.121 17:45, 17 December 2006 (UTC)

So the question now is how do you get rid of the bacteria and disolved fish feces and urine? Adaptron 19:09, 17 December 2006 (UTC)

For the original question: We use

1. Barrier netting, mounted on a suitable frame, to stop mosquitoes getting to the water, if the reservoir tank does not have a lid.
2. One of the Juvenile hormones (methoprene, pyriproxyfen) for killing an established infestation. The mosquito dunk idea seems pretty good, but I have never used the stuff (on reading the name I first thought it was a joke about a food or drink of some kind:)), and I wonder what it does to a lab bacteriological test.

From what I read in the Mosquito dunk article and references all of the test on mice - oral, inhalation and introvenus - were "acceptable." Like the viral bacteriocides this stuff is so specific that virtually everything else is safe. Adaptron 19:54, 18 December 2006 (UTC)

1. Filter through basin of clean river sand if water is not clear, though a simple fine sieve regularly is mostly good enough. Clean filter regularly.
2. Depending on your circumstances, you could chlorinate and filter the water with high tech apparatus, but unless you have serious contamination (lab test for bacteria - people tend to under utilise these facilities) it should not be necessary. --Seejyb 20:51, 17 December 2006 (UTC)

six pack

is there a name for not getting aligned six packs? —The preceding unsigned comment was added by 219.88.164.105 (talk) 06:35, 17 December 2006 (UTC).

No. Maybe you could invent one.--Shantavira 09:41, 17 December 2006 (UTC)

Just don't add it to an articel here untill it gets some external coverage. 68.39.174.238 23:13, 17 December 2006 (UTC)

Maybe you'll get more help at a bodybuilding or similar forum. From the quick search I did though, everyone was saying that's just the way it is for some people. They also says it better to have non-symmetrical [but defined] abs than a loads of fat.. --Username132 (talk) 10:07, 17 December 2006 (UTC)

Actually there is loads of fat, but if i compress my stomach i can see the non symmetrical six pack

Also one side of my six pack is bigger than the other

Which kinds of cells undergo cellular respiration?

I can't seem to find exactly what kind of organisms undergo cellular respiration. Which ones do besides plants and animals? Is it just eukaryotes? Thanks. --Proficient 06:40, 17 December 2006 (UTC)

Don't they all? I mean, the cellular respiration article defines it as "the metabolic reactions and processes that take place in a cell to obtain chemical energy from fuel molecules". That seems pretty universal to me; I dunno. --Spoon! 07:55, 17 December 2006 (UTC)

I can't think of any exceptions, and as far as I know there aren't any - it is the way organisms liberate energy, and if it can't get energy it can't live. It can be either aerobic respiration which uses oxygen, or Anaerobic respiration which doesn't. You may also like to check out Respiration. --jjron 12:43, 17 December 2006 (UTC)

It is this "breathing" connotation of respiration which seems to cause confusion, and one has to blame earlier generations of biologists for this. Retrospectively it was not a good choice. Remember that: viruses are not "cells", so they have no cellular respiration mechanisms. Here is a question to consider: Erythrocytes do not contain mitochondria; do the have cellular respiration? --Seejyb 21:07, 17 December 2006 (UTC)

Of course red blood cells have cellular respiration - from the article "Mammalian erythrocytes also lose their other organelles including their mitochondria and produce energy by fermentation, via glycolysis of glucose followed by lactic acid production". Prokaryotes like bacteria don't have mitochondria either, and of course they also respire. Re viruses, this is part of the reason for the debate on whether they are actually 'living' organisms. --jjron 07:12, 18 December 2006 (UTC)

All cells engage in cellular respiration. those without mitochondria (prokaryotes) simply respire through all of their cytoplasm as opposed to concentrating within organelles. However, don't confuse resperation with glycolysis or the kreb cycle those only occur in some cases Beckboyanch 06:15, 21 December 2006 (UTC)

SL & XR

Whats the difference between Sustained Release version of Wellbutrin compared to the Extended Release version? --Delma1 10:43, 17 December 2006 (UTC)

Sustained release tablets are standard pills which dissolve slowly and are generally taken twice a day to maintain therapeutic drug levels. The Extended Release versions consist of an insoluble shell filled with an aqueous solution of the drug. A small hole in the insoluble shell (covered over by a permeable membrane) allows the slow diffusion of the medication out of the pill over an extended period, allowing once a day dosing. (This is a drug delivery mechanism originally designed for Procardia XL). - Nunh-huh 11:01, 17 December 2006 (UTC)

Quick release tabs dissolve all at once, being compounded with something like starch. The SR is formulated so that the active ingredient is embedded in a matrix of insoluble substance (various: some acrylics, even chitin, these are often patented) so that the dissolving drug has to find its way out through the holes in the matrix. In some SR formulations the matrix physically swells up to form a gel, so that drug has first to dissolve in matrix, then exit through the outer surface. I believe that the holes in XL tabs are laser drilled. You may find that some SR and XL preparations use different salts of the active drug (I do not know whether this is true of bupropion). This is apparently something to do with the binding and solubility is in the matrix. Since novel delivery systems are patented, and quite profitable, specific manufacturing information is rather difficult to find. Maybe we should try the patent office:) --Seejyb 23:00, 17 December 2006 (UTC)

Thank you very much. It feels good to know. If there were some sources I would create the article based on above information regarding Quick release, Sustained Release & Extended Release--Delma1 04:28, 18 December 2006 (UTC)

water heater corrosion

Does the build up of sediment in the bottom of the water tank as well as the corrosion of the tank come from the reaction of the copper electrode and the iron lining of the tank and pipes or does it come from the temperature change of the water? Adaptron 14:05, 17 December 2006 (UTC)

I think most of it comes from the water itself. You will get sediment in a plastic tank too. Filtration can only remove so much gunk.--Shantavira 14:51, 17 December 2006 (UTC)

A bit of both. Sedimentation just happens when you hold water still in any tank, and there's not much you can do about it other than clean it out from time to time. Galvanic action, on the other hand, requires very specific conditions. A magnesium sacrificial rod is often used to stop this effect. Some corrosion will still occur with the rod, but at a greatly reduced rate. StuRat 14:52, 17 December 2006 (UTC)

Thanks. Galvanic action answers most of my question and that the corrosion comes from the reaction of oxygen in the water with the iron in the tank which the magnesium electrode prevents by reacting with the oxygen first. What I am wondering now is whether an electric current through an inert electrode would substitute for the magnesium or whether possibly some form of hydrogen interface or injection could be used? Adaptron 15:17, 17 December 2006 (UTC)

But what is the overall goal ? I would think a continuous electrical current would cost more than the magnesium rod, and could also pose a safety hazard. Another option is to line the water heater with something inexpensive and corrosion resistant, like glass. That does make them very heavy, unfortunately. StuRat 21:59, 17 December 2006 (UTC)

Living where I live is not inexpensive but if you work at it you can reduce living costs. Not only do magnesium rods cost $40 to $60 USD but most of the time you can not get them out of the water heater even using a torch. Since aluminum will also work it is possible to use it instead of magnesium but hey I have aluminum in my diet. The objective then is to find a better way to A.) reduce material costs and B.) to reduce labor costs. If an inert anode would evolve minute but sufficient amounts of hydrogen to keep those little oxygen molecules entertained then hey, let me use a carbon welding rod and a very low current and voltage circuit and goodbye corrosion forever or at least as long as I can afford to pay the electric bill. Adaptron 20:47, 18 December 2006 (UTC)

The US$40-$60 mag rod last for several years. Do you really think you can run an electrical device, even a low current and voltage circuit, for less than that ? StuRat 17:30, 20 December 2006 (UTC)

Why has no one mentioned water hardness as a cause?87.102.4.227 19:18, 20 December 2006 (UTC)

Well, you certainly can put a water softener in before the water heater, but I consider the salty water produced to be quite unacceptable, myself. I'd much prefer straight tap water to that. StuRat 22:20, 21 December 2006 (UTC)

Tin Reactions

As part of a lab, pieces of tin metal were emmersed in copper(II) nitrate and hydrochloric acid. Contrary to the activity series of metals, however, reactions did not take place. Are there any explanations for this? I have looked all over the internet. Thanks. -- Sturgeonman 15:31, 17 December 2006 (UTC)

What are your thoughts about the hydrochloric acid? --HappyCamper 15:41, 17 December 2006 (UTC)

Can you be a bit clearer - was the tin put in copper nitrate and then HCl or both at once.87.102.13.235 16:13, 17 December 2006 (UTC)

It's possible than the tin is coated with layer of tin oxide on the surface preventing reaction with the copper sulphate. I can't explain why it would not react with hydrochloric acid.83.100.132.121 17:55, 17 December 2006 (UTC)

tin should react with both. --75.73.155.34 00:07, 18 December 2006 (UTC)

Digital Extension

I have a very difficult question, one which many career anatomist, two physiatrists, and a hand surgeon have not been able to answer, but I thought maybe I'd get lucky here. Put your hand palm side down on a flat surface. Now flex your fourth digit so that it is bent under your palm, and the proximal phalange is flat on the surface. All other fingers should be straight. Now try to extend your third digit. Notice that there is a small range of movement. Now reposition your hand so that the third digit is flexed underneath and attempt to extend the fourth digit. In this case, there is no range of movement whatsoever. Why is it that extension is possible in one situation but not in the other? Consider that it is possible to move the "immobile" digit through extension with another mechanism (like the other hand) without pain, and that this phenomenon occurs with the second and third digit in the positions above too. Tuckerekcut 16:27, 17 December 2006 (UTC)

Actually, experiment proves that a small range of movement is possible, but only through quite a considerable amount of pain in the bent finger, as the controlling tendon is placed under extreme strain. (Thanks for putting me through that!) The answer is that while there are indeed four tendons in the back of the hand, one for extending each finger, there are only three muscles (located in the wrist) controlling those tendons, one for the little finger and two shared between the three middle fingers. Find someone with low body fat and watch them flexing the fingers to see the tendons move through the skin on the back of the hand; or get a hand from your anatomy friends, remove the skin, and play with the muscles of the wrist yourself. (On the base of the hand it's much simpler; each segment has its own muscle, although not everyone has the neurological ability to address those muscles separately.) Thus when one finger is at full flexion, the body is unable to restore the adjacent finger to full extension, because when the muscle pulls on the adjacent finger's tendon it is also pulling on the flexed finger's tendon - which cannot be extended. EdC 18:47, 17 December 2006 (UTC)

None of my colleagues were able to extend the fourth digit in the situation described, if you were able to, kudos to you. However I am most interested in knowing why there is such a difference in the difficulty between the third and fourth digits as described. I realize that the extensor digitorum provides extension for digits two through five, with ex. dig. minimi and indicus adding in for 2 and 5, but this does not explain the difference in difficulty, which really is the part that stumps me. Tuckerekcut 20:35, 17 December 2006 (UTC)

Incidentally, I meant no sarcasm with my last remark, if it seemed that way. I also wanted to point out that the pain seems (to me) to be in the muscular region of the extensor muscle, rather than the tendinous region, thus weakening your argument slightly. Tuckerekcut 20:38, 17 December 2006 (UTC)

Nah, to me it's definitely in the tendon, where it passes through the knuckle. I have a feeling the reason I'm able to do that might be that I broke my middle finger a while back, so it probably doesn't count.

Still, this a purely mechanical problem; the neurological wiring doesn't enter into it. Think of the hand as a series of hinges with springs to force them shut (the flexor muscles).

When the ring finger is fully flexed, the extensor tendon is close to full stretch. When the middle finger is fully flexed, even more so; when the index finger is fully flexed the extensor tendon is almost completely at full stretch. Thus when the ring finger is flexed the tendon can still be retracted a short distance, extending the other fingers. When the middle finger is extended the tendon can be retracted a little, giving less movement in the index finger than when the ring finger is extended, but even when the tendon is fully retracted this is insufficient to overcome the residual tension in the ring finger, so it does not extend.

Oh, and I'm not sure why it is possible to extend the ring finger when it's the index finger that's flexed. I suspect some amount of rotation or lateral movement is going on with the tendon, or it might be due to lateral banding. I'd have to get a hand to play with to be sure. --EdC 02:41, 18 December 2006 (UTC)

Fish mate

Someone told me of a deep sea fish specie of which the male is a 10th the size of the female. When finding a partner the male grabs the female and taps into her blood system (?) and insures she has a constant suply of sperm. The female then feeds for him and the male lives off their joint bloodstreams. What is the name of the fish? Are there other examples of such extreme couplings? Thank you. Keria 17:06, 17 December 2006 (UTC)

I'm sure it's not exactly what you're looking for, but here's one. And please don't let my humorous answer deter anyone from offering serious ones. Anchoress 17:53, 17 December 2006 (UTC)

It an anglerfish: [1]. Rmhermen 18:13, 17 December 2006 (UTC)

You might be looking for Anglerfish see Anglerfish#Reproduction, no doubt there are other deep sea fishes that do a similar thing.

"When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were females"..."When a male of one of these species hatches .... extremely well developed olfactory organs .... They have no digestive system, and thus are unable to feed independently. They must find a female anglerfish, and quickly, or else they will die."..."When he finds a female, he bites into her flank, and releases an enzyme which digests the skin of his mouth and her body, fusing the pair down to the blood vessel level"..."then atrophies into nothing more than a pair of gonads"..."when the female is ready to spawn, she has a mate immediately available"...83.100.132.121 19:02, 17 December 2006 (UTC)

Thank you very much. Keria 00:06, 18 December 2006 (UTC)

Some gastropod molluscs from the genus Enteroxenos have just as 'extreme couplings'. --jjron 07:35, 19 December 2006 (UTC)

Parasitic Worm

I saw this video [2] on ebaumsworld and it says that a parasitic worm controls a crickets mind and forces it to commit suicide. While I know thats probably not true, can anyone tell me what exactly happened in this video? Imaninjapirate^{talk to me} 17:54, 17 December 2006 (UTC)

This sort of parasite mind control has been a popular recent topic - even as it relates to humans. Can't find any links right now though. Rmhermen 18:08, 17 December 2006 (UTC)

It's a Nematomorpha, otherwise known as a Gordian Worm. It apparently does make the grasshoppers seek out water and drown themselves, returning the worm to the water. Super creepy. I added a super-legit reference to the article (Nature, 2006) which is where that video is from. --24.147.86.187 20:01, 17 December 2006 (UTC)

Another similar example of brain control might be the rabies virus, which attacks the brain, increasing the aggressive tendencies of an animal, making it bite other animals and thus spread rabies to new hosts. StuRat 21:52, 17 December 2006 (UTC)

Wow that is scary. I didn't think of the connection between that and rabies either. I just didn't think a parasite would actually be able to control an animal like that. Imaninjapirate^{talk to me} 22:30, 17 December 2006 (UTC)

It's one of those extreme specialization things, like Emerald cockroach wasp. The downside to such controll is that they really don't know how to do anything else... 68.39.174.238 23:15, 17 December 2006 (UTC)

A similar phenomenon is the "brainwashing" of carpenter ants by the Cordyceps unilateralis fungi. The fungal spores get into the ant via its spiracles and starts to grow mycelia filaments inside the ant, being careful to avoid any vital organs. When its ready to sporulate, it projects mycelia to the ants brain. It then forces the ant to climb to the top of a plant and attach itself firmly to a leaf by biting with its mandibles. Now that its in a suitable position, the fungus will eat the ant's brain, sprout outwards through its head and explode, showering the area with spores that will try to invade other ants. As told in the BBC's Planet Earth, When other ants detect that one of their own has been infected, the carry the unfortunate ant as far away from their nest to die, in the hope that when the fungus sporulates, it will limit the chances of infecting the entire colony. There are lots of different types of fungus that do this, with different species being specific for diffferent types of arthropod. You can see more info, including footage here. Rockpocket 23:20, 17 December 2006 (UTC)

I don't think the parasitic barnacle sacculina driectly attacks the crab's brain, but it does attack its gonads to sterilise it, and then uses the crab's mating behaviour for its own procreation. --ColinFine 23:41, 17 December 2006 (UTC)

For more examples of parasitic "mind control", see Dicrocoelium dendriticum and Toxoplasma gondii.  --Lambiam^Talk 23:48, 17 December 2006 (UTC)

Of course, it's the "mind control" idea that intrigues the press, but it's a little bit silly and anthropomorphic. These are parasites that cause a change in behavior in their hosts, but there's no "mind control" in play. - Nunh-huh 01:25, 18 December 2006 (UTC)

Are you drawing a distinction between "mind control" and "brain control" ? StuRat 01:30, 18 December 2006 (UTC)

No, I wasn't. I suppose there is one, but that wasn't what I was trying to point out, which is that "control" implies the existence of a will on the part of the controlling agent, which is certainly lacking in these instances. - Nunh-huh 02:00, 18 December 2006 (UTC)

Can't one be controlled by inanimate things, such as money ? StuRat 03:38, 18 December 2006 (UTC)

Some people like to think so, but I would characterize people pursuing money as doing so under their own control. I don't think the alcohol made you do it, or really anything but yourself. - Nunh-huh 08:18, 18 December 2006 (UTC)

I'd call effecting a very calculated and deliberate change in behavior "mind control" under most people's common definitions. I'm not sure what other definition of "mind control" one would want to use. --24.147.86.187 01:48, 18 December 2006 (UTC)

If it were "calculated" or "deliberate", you'd have a point. But it's not, as there is no intelligent agency doing any calculating or deliberating. That's precisely the point. - Nunh-huh 01:58, 18 December 2006 (UTC)

There doesn't have to be an intelligent agency, that's the beauty of natural selection—you can render "nature" itself as a theoretical selecting agency. In any case, I don't think you've yet given a good reason for not considering it "mind control". Anything which can directly alter an organisms mental behavior in such a dramatic way sounds like "mind control" to me. --24.147.86.187 03:25, 18 December 2006 (UTC)

I understand the mechanism of evolution quite well. And to me, control implies a controlling agency (and in the instances cited, the parasite ain't it.) Your mileage may differ. - Nunh-huh 08:18, 18 December 2006 (UTC)

Sensitiveish Microphone Advice

I want a microphone that will pick up my voice from a few meters away so I can have Skype conversations when I leave my headphones somewhere or just don't feel like wearing them. My old headphone needs to be right near my face in order to pick up my voice clearly and is therefore not sensitive enough. Can someone advise me on how to choose a suitable (cheapest microphone effective at three meters for Skype) microphone on ebay? Micrphone type? Sensitivity level likely needed? --Username132 (talk) 19:29, 17 December 2006 (UTC)

Can you clarify Skype OK found it.?--Light current 19:30, 17 December 2006 (UTC)

Have you looked up microphone? You need to decide if you want unidirectional or omnidirectional response. I suspect you want omni to pickup your voice wherever you are in the room. It looks like you need an omni with a large diaphragm [3]. Have you considered using a LS in reverse? 8-)--Light current 19:39, 17 December 2006 (UTC)

I don't think that will work, even with a great microphone. To hear the other party you'll have to run Skype's output through the PC's speakers - and the microphone will hear that too. It's very hard to position things so you don't just get runaway feedback, and even then it'll sound garbage. If you must do this, you need to get a proper speakerphone attachment. Speakerphones implement advanced DSP algorithms to suppress feedback and echo. Googling for "skype speakerphone" shows a number of manufacturers make compatible units. I've not used their Skype unit, but Polycom's other conference phones are very good (not not at all cheap). -- Finlay McWalter | Talk 19:51, 17 December 2006 (UTC)

Yes Finlay is correct in that on a 2 wire line (full duplex) system you do need some sort of hybrid transformer system to prevent positive feedback. These are naturally buit in to (speaker) phones. I'm not sure if the Skype has such a hybrid system built in. One way to test would be to bring the headset mic close to the ear phones and listen for howling. If no howling then youre ok and the separate mic idea should work/.8-)--Light current 20:13, 17 December 2006 (UTC)

I really meant sonic echo, not electrical feedback (although if both parties had such homebrewed speaker & mic systems, you'd get insane sonic feedback too). That's sound (the remote party talking) coming out of the speakers, it bounces off walls and stuff, and flies back into that nice sensitive omnidirectional microphone. And because your room probably has four or more hard walls (plus the ceiling, plus large pieces of furniture) then the mic receives not one echo but one for each such surface, each at a different delay from the original sound. That's why fancy speakerphones play a little tune when you turn them on - they're measuring the echoes of those different surfaces, and their frequency-absorption characteristics. -- Finlay McWalter | Talk 20:26, 17 December 2006 (UTC)

Ohhh, you clever people. Skype doesn't stop this feedback but I've made a 'feature request' on their forum. --Username132 (talk) 20:35, 17 December 2006 (UTC)

You mean you actually tried the mic next to the earphoes and it howled? What frequency? 8-)--Light current 20:41, 17 December 2006 (UTC)

When my friend called me on her laptop (speaker and microphone), I could hear my own voice with a delay (I hated it). --Username132 (talk) 21:06, 17 December 2006 (UTC)

OK you got sonic echo!--Light current 21:44, 17 December 2006 (UTC)

Bluetooth works, but I find the extra weight uncomfortable. --Seejyb 22:37, 17 December 2006 (UTC)

Evil Beth

[According to Beth], I should bake my cake mixture for one hour at 180 C. After baking for just 20 minutes, the thing began to burn and make smoke. Is Beth really evil, or is there another, less sinister explanation? --Username132 (talk) 21:12, 17 December 2006 (UTC)

No, that is a pretty standard recipe and temperature for banana bread. Rmhermen 21:21, 17 December 2006 (UTC)

I wonder if the oven (I set to 350) is in Faranheit or Celcius... it's an oven in the Netherlands, but wouldn't an oven that goes to 350 Celcius be quite special and expensive? Maybe I should set the temperature lower and or have heat come from only the bottom of the oven (instead of also the top). --Username132 (talk) 21:37, 17 December 2006 (UTC)

Heat come from the top? Sounds like you've turned on the grill! My friend has an oven where it is possible to do this too. If you are baking you only want the heat from the bottom. Also, 180 degrees C is medium low, so depends what the scale of your oven is, what's the minimum and max you can set it to? My oven is in C and it goes from about 100 to 300 I think, so 350 might not be outrageous if it's near the top of the scale. Vespine 22:10, 17 December 2006 (UTC)

I suspect there's a problem with the temp sensor in your oven and it's not kicking off when it reaches the proper temp. Do you have a meat thermometer ? If so, stick it in the oven and see what it says the temp is. StuRat 22:16, 17 December 2006 (UTC)

There could also be a problem with the temp selection dial. Does it seem to turn properly or does it turn with difficulty or show some other problem ? StuRat 22:33, 17 December 2006 (UTC)

I agree with StuRat, get an oven thermometer so that you know in future exactly what that oven is doing - if you are baking cakes it sounds as if you are settling in for a longish stay. A baking neighbor may have one to lend. To what maximum is the oven marked? If it is in the region of 500 or more, then it is almost certainly in °F, but then I would expect an oven in the Netherlands to use the Celsius scale. Generally: If the pan is placed directly over the heating element one can burn the bottom of the cake, it may need to be shielded by a separate baking tray. The upper element/grill would not normally be used during baking (sometimes for preheating) --Seejyb 22:39, 17 December 2006 (UTC)

Max setting is 360. --Username132 (talk) 23:03, 17 December 2006 (UTC)

That iffy, it's either a Fahrenheit-scale oven that doesn't go very high or a Celsius scale oven that gets very hot, indeed, perhaps a self-cleaning oven ? StuRat 23:57, 17 December 2006 (UTC)

I'd bet on Celsius then. Even the mildest of cooking ovens should reach 430°F/220°C --Seejyb 05:20, 18 December 2006 (UTC)

I vote Celsius, my oven goes to 300, I don't think 380 is ridiculous. 180 celsius on my oven is if I turn the dial a little over half way. But also, read my post above! Heat should NOT be coming from the top! I BET you have a grill coil at the top of your oven that can be turned on, my friend has exactly the same thing and we burned our garlic bread by accidentally turning the grill coil on as well as the oven. Vespine 01:03, 18 December 2006 (UTC)

• Since you said: "I wonder if the oven (I set to 350) is in Faranheit or Celcius..." I assuming you set it to 350. Since you're in the Netherlands it's almost certain you have a oven with Celcius scale, if you set it to 350 instead of 180, it's simply too hot. - Mgm|^(talk) 11:14, 18 December 2006 (UTC)

If you don't want to buy a thermometer, try putting a glass of water into the stove and setting the temperature to 150. If the water boils, your stove is on Celsius. If it doesn't boil, your stove is on Farenheit. --Bowlhover 21:57, 19 December 2006 (UTC)

And if the glass breaks, you know your glassware isn't oven safe. ;-) Anchoress 22:04, 19 December 2006 (UTC)

Is the (north) polar ice cap floating ?

Or is it attached to the ocean floor ? Does this vary from summer to winter ? If it is attached, is there a risk of it breaking free soon due to global warming ? StuRat 22:30, 17 December 2006 (UTC)

The ice over the pole is floating, the ice cap over greenland is on the land. -- Finlay McWalter | Talk 22:33, 17 December 2006 (UTC)

In that case, what keeps the floating ice from drifting in the currents until it crashes into land ? StuRat 22:36, 17 December 2006 (UTC)

Yes, it floats (there is no land under most of it - the nearest bits of solid land to the North Pole are Ellesmere Island and Greenland). There is nothing "stopping" the ice from floating away (bit of ice, also known as icebergs, break off the polar ice cap all the time! The Titanic hit one, for instance...), but this doesn't affect the cap as a whole, because it only "exists" where the temperature is cold enough. As a thought experiment to understand this: Take the ice cap as it is at present, and move it a bit in one direction. Some of it will now be in a warmer region of the world (nearer the Equator), that bit will melt, while a bit of ocean in a colder part of the world will now become exposed, that bit will freeze. End result: The ice cap stays where it is.

Of course, the ice cap shrinks and expands considerably between summer and winter!

Something to remember about the northern polar cap: melting bits of it (because of global warming) will not change sea levels, because when you melt ice that's floating in water, the overall level of water doesn't change. Melting ice sheets which sit on top of land (eg Antarctica), that's where the problem is, for any melting there equates to a sea level rise.

Well, actually, Melting of Floating Ice Will Raise Sea Level (Discussion at PhysOrgForum). (When ice melts – to freshwater – it takes up a greater volume than the volume of salt water it displaced as ice, so the overall sea level rises.) Not by that much, but by enough to make a difference. --EdC 03:08, 18 December 2006 (UTC)

Finally, the northern ice cap has been shrinking in recent years due to rising temperatures - if it continues, the Northwest passage may actually open up part of the year! — QuantumEleven 22:41, 17 December 2006 (UTC)

have a look at the arctic in September and February. -- ExpImp^talkcon 22:45, 17 December 2006 (UTC)

That pic seems to show that the ice touches land (Greenland and Ellesmere Island), even in summer, but just barely. Perhaps in just a few years that land bridge will be gone and it will be free to drift ? StuRat 00:06, 18 December 2006 (UTC)

This image

suggests that pretty soon, around Greenland and Ellesmere island will be about the only place the ice remains. Makes sense; in the open ocean the water gets heated up by sun and currents, but around the land the ice gets protected and replenished by calving glaciers. --EdC 03:08, 18 December 2006 (UTC)

On a tangent that is related to the North Pole, ice, and water:

I have a 1970's National Geographic Atlas here that suggests that Greenland is really more of an atoll than a solid island: on the western coast, there is a huge inlet, and a space in the middle filled with water. Because the whole lot is covered in ice, though, most of us mistakenly think of it as being one big block of solid land. Vranak 16:47, 18 December 2006 (UTC)

See Geography of Greenland#Climate change but note that the depressed land will slowly rise again after the ice melts as is still occuring in North America from the last ice age. Rmhermen 22:55, 18 December 2006 (UTC)

Thanks for the info, I wasn't aware of that atoll. :-) StuRat 17:09, 20 December 2006 (UTC)

Neurologist/Neurosurgeon

I read both articles, but what are the actual practioners doing? Are neurologist and neurosurgeon synonymous ? does a neurologist only give medication ? Thanks in advance.-- ExpImp^talkcon 22:37, 17 December 2006 (UTC)

No, they are not synonymous. A neurosurgeon is a surgeon. A neurologist was considered a sub-specialist of internal medicine and does not perform surgeries. A neurosurgeon typically operates on the brain (eg. removing brain tumors) and some do spine operations and operates on nerves (eg. for carpal tunnel syndrome). Neurologists treat diseases like strokes, epilepsy, and Parkinson's disease, etc. - Cybergoth 22:53, 17 December 2006 (UTC)

Thanks very much. But how do Neurologist treat them, if they don't operate? drugs?-- ExpImp^talkcon 22:55, 17 December 2006 (UTC)

Well, drugs is one option. Diet modification is another. In the case of stroke victims, they may need to relearn certain things and in the case of epilepsy victims, they may need to learn to avoid certain things which trigger seizures (blinking red lights, for example). StuRat 00:09, 18 December 2006 (UTC)

Yes, medication usually. Neurologists might also prescribe physiotherapy, speech therapy, and occupational therapy for stroke patients for example. - Cybergoth 03:54, 18 December 2006 (UTC)

They might prescribe it, but they dont actually do therapy themselves.

Ive seen 3 neurologists. The first 2 asked a lot of questions and hit my joints with rubber hammers, and scratched me with sticks. The third one spent a lot of time sticking big needles into my arms and legs and giving me electric shocks and looking for responses on a monitor. I do not recommend this procedure 8-)--Light current 13:45, 18 December 2006 (UTC)

</noinclude>

December 18

trismus &faciculations of upperlimb during menstrual cycle

married women aged 29yrs with h/o subserosal fibroid (4.5*2.3cms ) (primary infertility )h/o trismus& fasiculation during menstrual cycleon &off episodes -2yrs .Are these symptoms related to menstrual cycle 0r there might be systemic cuase —The preceding unsigned comment was added by 202.54.91.201 (talk) 03:56, 18 December 2006 (UTC).

Not enough info, and probably too individual a case to give a general answer. Obviously, see a doctor for a better answer. alteripse 04:02, 18 December 2006 (UTC)

Sexual abstinence

What are the biological effects of prolonged male sexual abstinence?141.161.34.125 05:43, 18 December 2006 (UTC)

You'll probably find the information you're looking for at Go Ask Alice!, which can be found here. --HappyCamper 13:14, 18 December 2006 (UTC)

I believe that a British study last year concluded that there are no negative effects in your average male -- for about five days. After that... you do the math. :) Vranak 16:42, 18 December 2006 (UTC)

See also Blue balls.  --Lambiam^Talk 16:57, 18 December 2006 (UTC)

If I not mistaken, 'blue balls' traditionally refers to the condition where a male has been excited by his partner, but not to the point of *******. Not simple abstinence. Vranak 17:41, 18 December 2006 (UTC)

Maybe the user is looking for specific information, along the lines of this: Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables. Perhaps there are effects on blood serum of various hormones as well? Effects of that? Any specific, scientific information? This is a science reference desk, correct?141.161.98.108 21:43, 18 December 2006 (UTC)

See also this: Prostate Specific Antigen Levels: Effect of Sexual Activity. "Determine whether six lifestyle factors (dietary fat, smoking, sleep, alcohol consumption, physical, and sexual activities) associated with non-prostate cancer-related, elevated prostate specific antigen (PSA) levels" "Men who were more sexually active at time T1 were at higher risk of a falsely elevated PSA level >4.0 ng/ml at time T2."141.161.98.108 21:50, 18 December 2006 (UTC)

Does abstinence in this case include masturbation, or sexual intercourse only? I can't imagine how they would be different in health benefits. (Excluding those old ideas like blindness) Crisco 1492 07:53, 21 December 2006 (UTC)

Human Adaptations

I had a weird train of thought, and then thought of this -- I tired looking for answers but I couldn't find anything:

When the species Homo Sapien evolves, what new key characteristics will it possess (micro or macro evolutionary changes)? —The preceding unsigned comment was added by 68.15.52.92 (talk) 06:51, 18 December 2006 (UTC).

I saw an article on this in the newspaper a few weeks ago, I think it was adapted from a reputable source like Nature. But the reality is any prediction for how something may evolve in the future is simply guesswork, whether it be humans or anything else. Organisms will adapt to their environment but we can't predict what the environment will be like, or what adaptations may be favoured, especially as other organisms are also evolving. The best guesses tend to continue on the main trends in human evolution over the last few million years - e.g., further increased brain size, continued hair loss, etc. But as I said above, no one can really say. That's one of the interesting things about historical processes like evolution - they're perfectly explicable after they happen assuming you have enough details, but can't be predicted beforehand. Of course, there's also the possibility that we will be able to use our technology to control our own evolution, such as through genetic engineering, nanotechnology implants, etc. Try a Google search on something like predictions human evolution, you'll find stuff like this--jjron 07:21, 18 December 2006 (UTC)

Arent we,like all other animals, evolving slowly all the time?--Light current 13:36, 18 December 2006 (UTC)

Resistance to disease would be one major adaptation. For example, those who live in Africa and are resistant to AIDS, either based on their behavioral drives or immune system, have a substantial evolutionary advantage over those who aren't. In the developed world the evolutionary pressure is less, because fewer people die, and are thus unable to pass on their genes, due to AIDS. StuRat 13:59, 18 December 2006 (UTC)

The evolutionary pressure is certainly not "less" in the developed world, just different. There would be no pressure only if every person had exactly the same chance of reproduction. Please can we stamp this notion out? alteripse 20:17, 18 December 2006 (UTC)

My post was on resistance to disease. Since disease has less of an effect on reproductive success in the developed world, there is less evolutionary pressure to increase resistance to disease there. However, there is likely more evolutionary pressure in other areas of human biology, yes. StuRat 02:29, 19 December 2006 (UTC)

Which means simply that the factors favoring or impeding reproduction in the developed world are different than those in the underdeveloped world, not that they are less-- that is the misconception suggested by your assertion and re-asserted explicitly by the uneducated author of the next comment. alteripse 15:27, 19 December 2006 (UTC)

Saying the factors are different is essentially the same thing as saying that some factors (like disease resistance) are more important in certain regions (like Africa) than they are in other regions (and, symmetrically, other factors are more important in the reverse regions). We aren't disagreeing here, just using different terminology for the same thing. StuRat 15:46, 19 December 2006 (UTC)

(Edit conflict) Nonsense. In the first world, modern medicine and civilisation has dramatically increased the chance of a human being surviving from conception to reproductive age. It hasn't removed selection pressure entirely (that's basically impossible) but it has decreased the evolutionary drive by a huge amount. Maelin (Talk | Contribs) 02:34, 19 December 2006 (UTC)

You are simply and utterly wrong on this. Modern humans have not transcended reproductive selection, just altered the major factors. Your message suggests you lack a basic understanding of natural selection. Educate yourself. alteripse 15:27, 19 December 2006 (UTC)

I would suggest precisely such a lack of understanding on your part, except that I try not to be so rude in debates. Selection pressure is strongest when it is hard for an organism to survive from conception to reproduction. In such a situation, every biological advantage is precious and every disadvantage is severe. For humans in the first world, it's now quite easy to survive to adulthood - which is obvious from the recent (last few hundred years) increase in human populations. Where once a child born blind would almost certainly not survive to adulthood, now they are marrying happily and having children of their own. Where once susceptability to disease would have likely killed a person during childhood, now modern medicine saves their life - and on they go. We aren't altering the major factors, we're eliminating them. Some new ones may arise as a result of our new lifestyles, but there is no reason to believe they will be as strong as the ones we are steadily working to remove. Maelin (Talk | Contribs) 02:12, 20 December 2006 (UTC)

You really don't understand reproductive selection, do you? Any heritable characteristic that is not universally present in all human beings and is associated (just asssociated, not even causally) with more less reproductive success than average for the population is subject to natural selection. This can be skin color, by a dozen putative direct and indirect mechanisms, it can be susceptibility to environmental chemicals that affect the estrogen receptors, it can be metabolic efficiency and tendency to gain fat or defend fat in food-abundant or food-sparse environments, it can be a differential social habit like breastfeeding or age of first childbearing that is associated with a host of heritable ethnic factors, it can be ability to detoxify environmental chemicals, or the fashion of underwear (affecting sperm count) if the underwear choice has a statistical association with any genetic/ethnic factors, or it can be personality tendencies like libido, shyness, or risk-taking, or cultural practices that delay childbearing like valuing education and women's rights, or genetic susceptibility to addictive substances in the environment that might impair bearing and protecting an infant. You have absolutely no evidence whether or which of these factors might be as important as the genes associated with susceptibility to cholera, or rotavirus, or measles, or malaria, or tuberculosis, or AIDS. You have far too narrow an understanding of possible selection pressures. And yes, ignorance that stubbornly defends itself against evidence and education does strain my civility. alteripse 02:37, 20 December 2006 (UTC)

Please do not post in this thread again until you can do so in an adult fashion. I have not attempted to belittle your intelligence and I'd appreciate the same courtesy. Debate can not continue in the face of outright aggression. Now, I find your assertion that things like choice of underwear and support for the women's rights movement pose as much of a selection pressure as things like susceptability to tuberculosis to be difficult to swallow at best. Sure, there are still selection pressures operating on humanity. I never disputed that. My claim is that existing pressures are insignificant in comparison with those of the past. Obviously there are still external factors that affect whether a child will grow up and procreate. However, I dispute that those selection pressures that exist today have as strong an effect as those that existed before we began to alter our environment to suit ourselves. Maelin (Talk | Contribs) 02:53, 20 December 2006 (UTC)

There are several factors that determine if a person or other animal passes on it's genes. Surviving to reproductive age is one, yes, but there is also the number of offspring produced and the portion of them which survive to reproductive age. While the first and third factors are now less significant in the developed world, due to the high percentage of survivors, this makes the second factor, number of children produced, an even more important measure of reproductive success. StuRat 15:53, 19 December 2006 (UTC)

Remember that survival means nothing to evolution if one does not reproduce. So while medicine has reduced mortality and increased potential fecundity remember natural selection is only relevent if an indvidual reproduces. Beckboyanch 06:52, 21 December 2006 (UTC)

Humans in the future will smell better. —Pengo ^{talk · contribs} 08:02, 28 December 2006 (UTC)

A drop of water in space

I wonder what would happen to a drop of room temperature water when suddenly released into space (or into a vacuum chamber with a temperature of nearly absolute zero). Would it just freeze to a small block of ice, or it wouldn't have time to freeze and it would boil (or possibly explode) first because of the extremely low pressure? Is it the same thing that happens to water when released from the captivity of pressure and the plasma in a particle accelerator when it is no longer contained by the electromagnetic field? --V. Szabolcs 09:03, 18 December 2006 (UTC)

It would slowly evaporate. A vacuum has no temperature; only matter can have a temperature. In space there is nothing to conduct heat away from the water.--Shantavira 09:26, 18 December 2006 (UTC)

It might freeze (cold) and then sublime (low pressure) - I doubt it would explode - a large piece wood be so cooled by any evaporation that the process would stop until it is warmed by some external source, this is the case with comets which are mostly ice..83.100.250.252 09:38, 18 December 2006 (UTC)

As for the plasma/ice comparison - it's similar - but I don't know enough to say more.83.100.250.252 09:38, 18 December 2006 (UTC)

Let me first talk about something I know. If you put water in a vacuum system, at room temperature, and pump the air away, parts of it will boil while other parts freeze. (If the water contains much dissolved air, the boiling will be violent.) Presumably it is evaporative cooling that causes some parts of the water to get cold enough to freeze. After a short time while, you have only ice left, and then, if you wait for many hours, the ice will sublimate away. Now for your actual question. If the water drop was in zero gravity and not in a container, the boiling would probably break it into pieces. (If the water had a lot of dissolved air, this would be many tiny pieces.) After a short time you would have a few ice shards. Eventually these would sublimate away. Cardamon 09:51, 18 December 2006 (UTC)

Shanti is correct in that there is nothing to conduct heat one way or another. However the mechanism at work must be that of radiation. Every body above absolute zero will radiate electromagnetic energy (heat) into space. The maount radiated will depend onthe emissivity and temperatureof the body according to [4] I think. Also every body that is not completely refelective or transmissive at all wavelengths must, by definition, absorb energy. Now we have the dileema: does it freeze or does it boil?

The temperaure of such an object can be calculated by using an energy balance equation such that the radiated enegry is equal to the absorbed energy. In this case the temperature must be stable. In the case of a blob of water, it is highly unlikely to recieve more radiation than it emits (unless near a star) and therfore would probably end uo as ice (like some comets).However, to be sure one would have to do the energy balance calculations 8-)--Light current 12:58, 18 December 2006 (UTC)

OTOH See [[5]] and an interesting question is: what would happen if you threw a small lump of ice into space? Would it sublimate?--Light current 13:23, 18 December 2006 (UTC)

During the Mercury program, and the Gemini program when the astronaut dumped urine from a container out into space, or when water vapor was vented, it froze into little crystals of ice, which reflected sunlight in a sparkling pattern. They referred to it as the "Constellation Urion." [6] Granted, ammonia isn't water, but an ammonia leak on the International space station left an astronaut covered with an inch thick layer or ammonia crystals. He was instructed to brush off what he could, then just stay outside an extra orbit, sightseeing, while more of the crystals sublimated. So I would go with the answer that is would quickly freeze into crystals, then sublimate in a matter of hours. Edison 15:56, 18 December 2006 (UTC)

OK well we cant deny the facts, but what would you say actually cuases the sublimation. Is it just the low (zero) pressure?--Light current 16:01, 18 December 2006 (UTC)

Yes the low pressure (and the vast emptiness of space) - if a water molecule evaporates it's very unlikely to find it's way back - space after all is pretty much the opposite of a closed system.83.100.250.252 17:40, 18 December 2006 (UTC)

Hmm the phase diagram [[7]] for water shows that at low pressure and temp, water could be either solid or gaesous. —The preceding unsigned comment was added by Light current (talk • contribs) 16:17, 18 December 2006 (UTC).

Thanks for the explanations. As I understand now, maybe it boils for a very very short period of time, after which its fill freeze quickly and after that, sublimate. --V. Szabolcs 20:38, 19 December 2006 (UTC)

Or maybe not 8-)--Light current 04:50, 27 December 2006 (UTC)

Formation of a comet

The above question reminded me of another question: How do comets form (or reform) ? That is, they have been described as "dirty snowballs", so the ice should sublimate at a low rate all the time, and at a high rate as they near the Sun (shown by the trail). So, how do they replace this lost mass ? Is it just by ramming water molecules found in space ? They don't appear to be large enough to have a very substantial gravitational field which would be sufficient to pull in water molecules at the speeds they move through space. And, if they don't replace this mass, I would expect comets to have lost all their mass by now, if they are as old as the solar system. StuRat 13:54, 18 December 2006 (UTC)

Why should the ice sumblimate without heat? I dont believe its does. I believe that comets do get some of their ice sublimated as they approach the sun. THis results in the famous comet tails which always point away from the sun due to the solar radiation/particles etc. Since most of the time the comets are a long way from the sun, their icy shells do not sublimate most of the time. Also the amount of ice necessary to give those tails is probably minimal. So Halleys comet should have its tail for a few more million years hopefully. 8-)--Light current 14:00, 18 December 2006 (UTC)

Comets are short-lived (cosmologically speaking). They lose 0.1-1 percent (some sources say even more) of their mass each time they enter the central solar system. They may gain some insignificant amounts of mass back when they are far away from the Sun (at perihelion any collisions with external particles are more likely to reduce mass than increase it.) Eventually what's left is an asteroid, or simply nothing if the comet had no rocky nucleus to begin with. Better hurry if you want to see Halley's Comet; some estimate it is going to lose its volatiles in just another 5600 years. The good news is that the Oort cloud has a good supply of fresh comets; as old comets evaporate, new ones are hurtled towards the inner solar system when they randomly destabilize each others' orbits. Weregerbil 14:19, 18 December 2006 (UTC)

They do not replace their mass if they are in a orbit close to the sun. They slowly desintegrate and after some cycles (depending on course mass and composition) they break apart and are absorbed by the planets of the solar system as meteors, you see in the night, or like the ones which hit Jupiter. I never heard of a comet with a rock as nucleus so thea desintegrate to near nothing. The question how comets form is unsolved. The ice and carbondioxide and the organic materials need low temperatures to form solide bodies, this indicates low temperatures. The minerals detected by stardust and deep impact indicate temperatures above 1000°C at their formation. This gives a slight difference and a monstrous headache for some comet scientists. Rosetta (spacecraft) will give all answers you want in 2014!--Stone 14:49, 18 December 2006 (UTC)

There is speculation that at least some comets have enough mass to end up as asteroids: [8]]. But much of this is indeed conjecture. Btw, the 5600 year remaining lifetime for Halley's comet I quoted above is something I found on one web site; can't say how they came up with that figure. Another site says it loses 0.1% each pass, giving it of the order of ten times that long. Who knows. Weregerbil 15:12, 18 December 2006 (UTC)

Yeah thanks Weregerbil. Thats why i 'vaugified' my previous answer.--Light current 15:15, 18 December 2006 (UTC)

Decaffinated coffee beans

Can someone explain how coffee beans are made 'decaffinated'?

At what point, and how is the caffine removed from the beans?

thanks

81.129.212.135 12:07, 18 December 2006 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see Decaffeination. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. --Shantavira 12:58, 18 December 2006 (UTC)

Then what do we do with the unwanted caffeine? To make billion tons of Red Bull? -- Toytoy 13:50, 18 December 2006 (UTC)

Put still this is not enough. They make artefical one, because the demand is high for coke and pepsi!--Stone 14:52, 18 December 2006 (UTC)

---

Very good question!

The word 'decaffinated' is a massive fraud.

Beans are not decaffinated: they are caffeine-free by default. Only by roasting beans do you develop caffeine. Vranak 16:39, 18 December 2006 (UTC)

That's contradicted by Caffeine, Decaffeination, Coffee processing, and Coffee. DMacks 17:21, 18 December 2006 (UTC)

Yes, I can't find anything that supports it either. Vranak, what chemical do you think is present in raw coffee beans that is turned into caffeine by roasting? —Keenan Pepper 17:24, 18 December 2006 (UTC)

It is easy to extract caffeine from green coffee beans! Water is good enough! So there is caffeine already in green beans!--Stone 17:34, 18 December 2006 (UTC)

I believe I read this off a placard in Starbucks. However, if this is contradicted across numerous articles in Wikipedia, what I said earlier should be regarded as suspect and wrong until I can check back. Cheers Vranak 17:37, 18 December 2006 (UTC)

Caffeine, like many other plant alkaloids, is the weapon created by plants against insects and other plant eaters. Humans have big livers, therefore, we can break down many plant alkaloids. We even enjoying taking some of them. Anyway, caffeine exists in live plants. Roasting only makes coffee beans taste better. End of story. -- Toytoy 22:30, 18 December 2006 (UTC)

Drying out silica gel

Can I revive a sachet of silica gel beads (dehydrate them again) in the microwave? --Username132 (talk) 16:03, 18 December 2006 (UTC)

• According to this, yes (but be careful.) --jpgordon^∇∆∇∆ 16:09, 18 December 2006 (UTC)

Of course once the gel is dry, the water will be gone and it wont heat so efficiently, will it? What happens if it overheats? --Username132 (talk) 16:24, 18 December 2006 (UTC)

If it gets very hot - it could sinter (possibly) or fuse (ie melt together - unlikely) - this would reduce the ability of the gel to absorb the water next time.83.100.250.252 17:42, 18 December 2006 (UTC)

Walking

what is the right amount of walking i should do weekly? —The preceding unsigned comment was added by 82.167.47.141 (talk) 16:14, 18 December 2006 (UTC).

It will depend upon:

• Your current physical condition

• Your end goal (for example, weight control, desire to become a long-distance race walker, etc.)

Perhaps you want to tell us more? And, of course, only your doctor can tell you whether a given amount of walking will be good for you, personally.

Atlant 16:30, 18 December 2006 (UTC)

Couldn't agree more -- it's totally dependant on how you feel. Weather plays a huge factor here. I find that even if I'm full of energy and the temperature outside is nice, if there's a lot of glare through the clouds, I don't like being outside much.

That said, I walk many kilometers each day (usually), and I consider it to be the second most vital factor in my continuing well being. The first of course is a healthy diet.Vranak 16:37, 18 December 2006 (UTC)

Well assuming you are in good health (the recommendation is to always check with your doctor before embarking upon a fitness routine), IIRC the documentary Supersize Me said 4-5 kilometres a day of walking (including just getting from A to B) was the threshold between healthy and not so much. I don't know if that info is any use to you. Anchoress 16:41, 18 December 2006 (UTC)

Walking alone isn't enough to keep you fit and healthy. You need to do some sort of exercise that will get your heart rate up 3 times a week to lower your risk of heart disease and otherwise stay healthy. Walking is probably better than nothing though, especially if you live in a hilly area. You need to check with your doctor if you plan NOT to do exercise ever in your life. —Pengo ^{talk · contribs} 20:54, 18 December 2006 (UTC)

Pengo, that information isn't consistent with my recent reading; do you have refs for your assertion? I know that used to be the belief, but I've seen a lot of recent data that suggests close to VO2 max exercise isn't necessary for heart health. Anchoress 21:01, 18 December 2006 (UTC)

Walking 'not enough to get fit' (bbc news). My claims likely misrepresenting this study, but it doesn't look like it's out of date as yet. It compares a 10,000-step exercise programme (as mentioned by Chairboy+Rmhermen below) with a more traditional fitness regime of moderate intensity. —Pengo ^{talk · contribs} 01:40, 19 December 2006 (UTC)

Yeah, but the walking participants in that study were working 'at their own pace', and (contrary to the description), the article doesn't say that walking cannot provide the health benefits of a moderate exercise program, but specifically the 10,000 steps program of light exercise apparently does not. It's possible for a lot of people to walk quickly enough to, as the article describes, be winded but able to speak a couple of sentences at the end of the workout. Anchoress 07:20, 19 December 2006 (UTC)

Mmm, I would say that broadly speaking, walking 10-30 kilometers per week will be quite enough to keep you in shape. That said, I do favor more vigorous exercise, say, once a week. I find jogging to be terrible for your joints over the long term. Sports like hockey and soccer that demand lots of moving, turning, flexibility, and overall robustness will really get you in good shape, as long as you don't over-do it. Vranak 21:59, 18 December 2006 (UTC)

A common figure used to describe a healthy amount of walking is 10,000 steps a day. The distance this would cover would be dependent on your stride, of course. - CHAIRBOY (☎) 21:33, 18 December 2006 (UTC)

Link to 10,000 Steps Program Rmhermen 22:39, 18 December 2006 (UTC)

books

How do I go about obtaining printed books from Wikipedia

I don't think that Wikipedia sells books.--Azer Red Si? 16:36, 18 December 2006 (UTC)

If you read German, there's de:Wikipedia:Publikationen, but I don't know of similar projects for any other languages yet. —Keenan Pepper 17:14, 18 December 2006 (UTC)

Video games a cure for ADD?

I heard somewhere a while ago that video games actually help to relieve the symptoms of ADD/ADHD by stimulating the areas of the brain that are underdeveloped because of ADD, and that people with ADD have a higher tendency to become addicted to them because their brains unknowingly crave that stimulation that they provide. Is this credible or no?--Azer Red Si? 16:36, 18 December 2006 (UTC)

Without having any field-specific knowlege, I'd say it is quite doubtfull. General sonsensus is that videogames may increase the occurance of ADD/ADHD becuase they reward a short attention span. If you can find the source that you heard this from, it may be easier to evaluate credibility. 216.254.24.10 19:10, 18 December 2006 (UTC)

But maybe the argument will work on your parents... alteripse 01:40, 19 December 2006 (UTC)

Quantum Mechanics

Hello,

I recently started studying Quantum Mechanics and find the mathematical beauty of this theory quite exceptional. But I haven't really had the opportunity of working with real example, and am still baffled by many animations I find on the net (e.g. http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/104_18a.html or http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/107_12c.html). I would have liked a little link or explanation on how it would be possible to obtain these results (for example, being able to find the curve in the second example as a function of time and position to be able to reproduce a similar graph). And generally, what is the method to obtain such visualizations (e.g. http://winter.group.shef.ac.uk/orbitron/, which obviously depends on isosurfaces, but how would one obtain the equations corresponding to the wave functions ?) ?

In general, I would like to know how one obtains such visualisations (are numerical methods important ? etc...).

Thanks --Xedi 17:22, 18 December 2006 (UTC)

Yes, the topic is very beautiful...it's sort of tricky to answer your question, so let's see if this is good enough to keep you interested. There are a small number of quantum mechanical systems which can be solved exactly, so for those, generally, the plots are based on analytic solutions. The hydrogen-like atom is an example. For more complicated systems, you'll need to resort to more advanced methods such as density functional theory. Numerical methods are at the heart of advanced approaches (and also where all the neat research is taking place today), so in a sense, it's good to know. However, to understand the general concepts, typically, small systems which can be solved with pencil and paper give plenty insight into quantum mechanics. --HappyCamper 20:05, 18 December 2006 (UTC)

Thanks for the hydrogen-like atom link, it's very helpful ! But then, what about the rest ? I mean, for the tunnel effect, for example, where does that visualisation comes from (I mean, mathematically) ? --Xedi 20:18, 18 December 2006 (UTC)

There's some stuff at Quantum tunnelling...but isn't so clearly written. Finite potential barrier (QM) has better information. Essentially, what you do is solve the Schrodinger equation for a system with a step potential, and the one of the solutions that comes out of the calculations is this "tunneling". It depends on the energy of the step and the incident particle. There's a nice drawing at the bottom of the article too. --HappyCamper 21:45, 18 December 2006 (UTC)

Personally I think the best bet is to go through it historically - start with the failings of classical mechanics at the turn of the 20th century (the UV catastrophe and such) and work forward from there. If you can get a cheap second-hand copy, there's a chapter of Atkins' Physical Chemistry which has an excellent introduction. As it's an undergrad chemistry text there's a decent balance between the maths and the actual qualitative effects. Sockatume 05:12, 20 December 2006 (UTC)

Weight Fluctuations

I watch my weight on a daily basis, and note that it fluctuates by as much 2Kg on successive days, eg. 94Kg, 92Kg, 93Kg, 94Kg. Measurements taken at the same time each day on a fully functional scale, with a pretty much regular exercise, eating , drinking, toilet habit. The question then is how can one account for these wide weight fluctuations over such a short period ? Does atmospheric pressure perhaps vary sufficiently from one day to the next to create the effect of "more atmosphere pressing down on my shoulders ?" --Dr snoobab 17:52, 18 December 2006 (UTC)

Water retention. Anchoress 18:00, 18 December 2006 (UTC)

I have had similarly-anomalous weight fluctuations, that I cannot account for merely by thinking about water retention or defecatory diminishment. I am inclined to say that atmospheric conditions can indeed affect weight measurements, in the order of a kilogram or two.

However, I will not say this. I will instead ask: on what surface are your placing your weigh scale? Carpet will not do! Vranak 19:18, 18 December 2006 (UTC)

How on earth can atmospheric conditions affect body mass? Actually, fluid retention is a much more likely explanation. If Mick Jagger, who's 145lbs of solid bone and muscle, can lose 5 pounds during a concert, you or I can gain or lose a pound or two of water weight in a day, due to excess carbohydrate consumption, excess salt consumption, or the reverse. Anchoress 20:49, 18 December 2006 (UTC)

How about temperature effects? I'm sure the reading on the scale depends on ambient temperature, although it might take very large temperature swings to make that much of a difference. -anonymous6494 20:57, 18 December 2006 (UTC)

Well, atmospheric conditions will affect your skin, flesh, and pores, of course. Mick may lose a few pounds of fluid during a concert via evaporation and perspiration. So I guess we're saying the same thing: fluid retention or fluid loss will account for the difference. I'm merely adding that atmospheric conditions will affect how much fluid you retain, or lose. Vranak 21:55, 18 December 2006 (UTC)

Type and quantity of food you eat, water retention (or excretion), bowel movements, swaeting, loss of moisture overnight all have a part to play.--Light current 23:59, 18 December 2006 (UTC)

What type of scale is it ? A balance scale ? StuRat 02:15, 19 December 2006 (UTC)

Normal Bathroom Scale in good condition on a solid flat tiled floor. Thanks for the answers so far !--Dr snoobab 03:54, 19 December 2006 (UTC)

When you say 'normal' scale, I assume you mean the ones with a dial and needle setup rather than say the digital ones. These are a bit notorious for minor fluctuations in measurements, especially the cheaper ones. When using these you must also be wary of parallax errors. These are very easy to make and are independent of the device (i.e., they're an error of the user). Can I suggest you do a little experiment. Weigh yourself say ten times over a ten minute period where the other factors suggested above will have no effect, and see if you get identical results. Try a similar experiment over a longer period, say five times over an hour (without eating, drinking, going to the toilet, or moving the scales) but go away and do something else between measurements and again compare results. See if you get any variations, and if so, whether the variations show a trend. --jjron 14:38, 19 December 2006 (UTC)

I had a "normal" bathroom scale which would tend to stick when the air was moist, like right after a shower. Thus, it would either read high or low, depending on where it decided to stick. StuRat 16:44, 20 December 2006 (UTC)

How does panting reduce heat?

I've been wondering this from some time. According to your article, "Animals with a body covered by fur have limited ability to sweat, and rely heavily on panting to increase evaporation of water across the moist surface of the tongue and mouth". Apparently it has something to do with evaporation of water, which I'm guessing is a release of heat. But this makes no sense; how does increased evaporation in the mouth help cool off the entire body? Much help appreciated ! Xhin 20:41, 18 December 2006 (UTC)

Just like any other cooling mechanism (sweating, elephant ears, etc). The cooled blood flows through the body, distributing the cooling properties. Anchoress 20:51, 18 December 2006 (UTC)

Also, evaporation and radiation have an effect. Evaporation has a cooling effect from any membrane that's wet, and radiation comes into play: By breathing, you're effectively increasing the available surface area for heat to be transfered to. Before breathing/panting, you only have your skin. When you breathe, you pull cool air into your lungs, it is heated by the radiated heat of your internal surfaces, and when you breathe out, the air carries heat with it. Panting would increase the airflow that this cooling method uses, much like blowing a fan over something carries heat away faster, assuming it is suspended in a medium that is cooler than the object. It's all about entropy in the end. - CHAIRBOY (☎) 21:31, 18 December 2006 (UTC)

Panting gets outside air into the body, and inside air out of the body, so to speak. As internal body temperatures are hotter than outside temperatures (unless you live on Venus), panting is an expediant way of swapping hotness for coolness. Vranak 21:52, 18 December 2006 (UTC)

Thanks for your help! As a follow-up question, how does it help when the external temperature is hotter than the internal temperature? (say, a hundred and five or so degrees.) Again, much help appreciated ! Xhin 22:13, 18 December 2006 (UTC)

It is not just a matter of heat being "carried away". Evaporation does actually absorb heat from the environment, thereby cooling it. That is also how the refrigeration of most fridges works, by the evaporation of the refrigerant, thereby achieving temperatures way below the external temperature.  --Lambiam^Talk 22:26, 18 December 2006 (UTC)

Evaporative cooling has the potential to lower the temp of a damp object relative to the surrounding temps. StuRat 23:55, 18 December 2006 (UTC)

I reckon than an overheated dog will cool down faster if he's panting in a freezer than panting in a sauna. In fact, I'm quite certain of that.

That said, your body has to put some effort into 'warming up' frigid air, so keeping comfortable when overheated is not a trivial linear equation by any stretch of the imagination. Vranak 00:01, 19 December 2006 (UTC)

Think of evaporative cooling this way: the temperature of water is the average amount of energy its molecules have. If you evaporate some of the water, the hottest molecules escape, because only the hottest molecules can escape. What are left are cooler molecules, so the temperature goes down.

If you pant in 40-degree weather, evaporative cooling will cool down the blood in your tongue, which will cool down the rest of your body. However, the hot air itself will warm up the blood in your lungs, which will warm up the rest of your body. So I think panting in 40-degree weather will actually make you hotter. --Bowlhover 01:42, 19 December 2006 (UTC)

I disagree. It would be a zero-sum gain, meaning the air is warmed up no more than the tongue is cooled down. However, the heat in the air will mostly not go back into the dog's body. Instead, mostly 40 degree air would be drawn into the dog's lungs, cooling it further. (Note that I was assuming 40 F, which is just over freezing temp, you probably meant 40 C, which is just over body temp. Still, evaporative cooling might work up until something like 50 C.) StuRat 02:01, 19 December 2006 (UTC)

Yes, I was talking about 40 degrees Celsius (that's the world standard, isn't it?). Of course evaporative cooling still works at that temperature, but even if it cools the tongue as much as the air itself heats the lungs, the lungs have more blood and will therefore have a greater effect on body temperature. --Bowlhover 03:12, 19 December 2006 (UTC)

Did anyone find a reference in Wikipedia for panting? I do not find a description of the physiology of panting. --Seejyb 12:06, 19 December 2006 (UTC)

The energy lost from panting when external tempature is hotter than internal tempature do to the energy lost due to phase changes. Q=ml where q is in joules m is mass and l is the latent heat of vaporization. for water that number is 2.26x10^6 j/kg so for every kilogram of water vaporized one loses 2.26x10^6 joules even if the external temp is hotter than the internal. compare this to the energy lost by the change in temp. the equation is heat supplied or removed in changing the heat of a substance is Q=mcΔT where q is the the heat supplied or lost (in joules) m is mass c is the specific heat of the substance and ΔT is the change in temp (in C) waters specfic heat is 4186 j/kgC. so for a ten degree C change in temp for 1 kg of water is 41860 J about 2% of the erngy lost due to phase change. (feel free to check my math i did it all in my head) Beckboyanch 07:17, 21 December 2006 (UTC)

Gargle salty liquid

Why does gargling with really salty water help sooth a sore throat? I've been doing this whenever I have a sore throat for years and it works like a charm! Dismas|^(talk) 21:31, 18 December 2006 (UTC)

According to Gargling, " Gargling with a solution of table salt is known to provide relief for a sore throat because as a natural dehydrator, salt draws water from the inflammations in the throat by osmosis, killing the bacteria which cause the sore throat." Friday (talk) 21:33, 18 December 2006 (UTC)

Generally speaking, swimming, washing, frollicking in, bathing wounds in, and even gargling with unpolluted sea water is wonderful for just about any ailment -- except thirst. Vranak 21:44, 18 December 2006 (UTC)

I don't think the question has been answered. Killing bacteria should not cause INSTANT pain relief, but this salt water method does, at least for 30 minutes or so. --Username132 (talk) 09:33, 23 December 2006 (UTC)

Through the process of osmosis, the swelling is nearly instantaneously eradicated. The swelling causes pain; thus, instant pain relief. —The preceding unsigned comment was added by 70.114.249.248 (talk) 22:48, 23 December 2006 (UTC).

How dangerous, if ingested, is shampoo?

I have swallowed a small amount of shampoo about an hour ago (around 0430 at +8 GMT, malaysia) containing the following: Water, Sodium Laureth Sulfate, Lauramidopropyl Betaine, Sodium Cocoamphoacetate, cocamide MEA, laureth-4, Fragnance (That's all it says), Glycerin, Sodium Benzoate, Polyquanternium-10, alchohol, sodium citrate, PEG/PPG-20/22, Butyl ether Dimethicone, Bis(C13-15 Alkoxy), PG Amodimethicone, Quaternium-33, Citrus Aurantium Bergamia (Bergamo) Fruit extract, Butylene Glycol, propylene glycol, Cl 42053, Methylcloroisothiazolinone, Mentha piperita (peppermint) leaf extract, methylisthiazoline, and eucalyptus globulus leaf extract. The product was Feather® Nature Plus Fresh & Lively Shampoo.

Since I'm feeling fine now my question is: "Is the shampoo really dangerous and, if it is, how much of it would it take to cause permanent and/or fatal consequences?"

—The preceding unsigned comment was added by 219.95.43.30 (talk) 21:41, 18 December 2006 (UTC).

Seek immediate medical attention. Hipocrite - «Talk» 21:43, 18 December 2006 (UTC)

Simply call your GP, or the GP on duty. They know the proper way to get toxicity information. Wikipedia is hardly the place for this. Arakrys 02:40, 28 December 2006 (UTC)

Where I live, in North America, it's common for phone books to list emergency numbers at the front, and they often have free, 24 hour poison control phone numbers that people can call for advice. Does something like that exist in your region? If so, call them. If not, I agree with the previous posters about medical attention. Anchoress 21:51, 18 December 2006 (UTC)

I have removed two comments which attempted to diagnose the severity of the poster's medical condition, prescribed a course of action, or offered a prognosis. I ask that people remember that we can't diagnose or prescribe here on the Reference Desk, that we definitely don't do so in emergent cases, and that we absolutely don't do so for minors. TenOfAllTrades(talk) 23:05, 18 December 2006 (UTC)

I feel almost completely fine now though except for the headache-nausea thing which could be easily explained by 10 hours at the computer. What I've been reading so far about Sodium Laureth Sulfate so far has me still a little worried, stuff like this that I know are biased but still put me into minor panic mode when I read stuff like "can't be metabolized by the liver" and "male fertility loss". Since there's no more need to diagnose and offer prognosises my latest query would then be on the severity of the shampoo in question or any shampoo. I've edited the top with links and the relevant query.--219.95.43.30 23:43, 18 December 2006 (UTC)

Check out some of these links. Anchoress 23:19, 18 December 2006 (UTC)

Did you swallow the actual liquid shampoo or the lather? I can understand accidentally getting lather in your mouth. --24.249.108.133 23:19, 18 December 2006 (UTC)

Actual lather but a while ago I used some liquid soap as mouth wash with no ill effects. I'll check the contents in a moment. It had Sodium Laureth Sulfate, too. And formaldehyde! Hmm. I never swallowed, though. Anyway could you guys tell my how much of the Feather® Nature Plus Fresh & Lively Shampoo would it take to kill a person please? It'd make an awesome opening for conversation (Did you know if you somehow ended up drink x amount of shampoo you'd suffer x horrible symptoms and die?!)--219.95.43.30 23:43, 18 December 2006 (UTC)

Now that you're all well and nothing I say could be construed as medical advice, here goes. I would venture to say that a healthy adult would not be able to kill her or himself by ingesting regular shampoo. Is it a good idea? -absolutely not, it will make you terribly sick, detergents tend to cause violent diarrhea, but this actually helps the stuff pass through you more rapidly. There were a lot of chemicals in that bottle you had, but probably in pretty small amounts; ingredients are listed by weight, and you need very little perfume to smell up a bottle, so probably anything listed after "fragrance" is not too copious. Anyway, even if it smells good, shampoo probably tastes awful, and the near instant vomiting reflex will prevent too much from getting into you anyhow. Also, I would recommend very strongly against getting medical information from the internet unless you are very confident in the source. The web site you linked has no credibility in my book. And neither does much of anything here. If you want medical advice, ask a physician. If you want information on chemicals, look up the MSDS. If you want to settle a bet or are just mildly curious, that's when to consult wikipedia. Tuckerekcut 00:40, 19 December 2006 (UTC)

The MSDSs often go way over the top though, just look up sodium chloride for a good example of this. Plugwash 00:59, 19 December 2006 (UTC)

Haha, the first hit for "MSDS sodium chloride" gives the M. musculus intracervical LD50. (It's 131μ, in case you care). Remember girls, cervical dilators and the dead sea don't mix.Tuckerekcut 01:54, 19 December 2006 (UTC)

Keep in mind that SLS is also an ingredient in most toothpastes and shaving gels. Formaldehyde is usually found in ultra-cheap generic brand shampoos, at least in the USA. It's a cheaper preservative than parabens (but even $2 Suave shampoos are formaldehyde free). --24.249.108.133 23:34, 21 December 2006 (UTC)

For future reference the National Poison Centre [9] would probably be your best bet if your unsure. If you don't know the number, call up Telekom directory services. In some cases, the product may have a number on the back which you can dial. With fairly toxic substances, there will usually be emergency medical instructions as well. Of course, you could either head to hospital or dial 999 if you're genuinely concerned or unsure. If you do head to hospital, make sure you bring the product with you. I would say in many countries, arguably Malaysia as well, if the product doesn't have specific warnings you're probably okay if it's a small amount. You might get sick, but it's unlikely to be anything serious enough to require hospitalisation or emergency medical treatment IMHO. But I can't guarantee this and would urge anyone who ingests something to seek help just in case Nil Einne 14:35, 21 December 2006 (UTC)

Creation of the VCR internal clock

I read the article regarding video machines and it gave very good information regarding the history of vcr's.

I am trying to determine who the inventor of this aspect of the vcr machine is.

Can you help? —The preceding unsigned comment was added by Dedele34 (talk • contribs) 22:56, 18 December 2006 (UTC).

Good question. The VCR article discusses the evolution of the timer mechanism throughout the article, but the word "clock" is never even used. —Pengo ^{talk · contribs} 01:50, 19 December 2006 (UTC)

I remember the older style VCR machines that had an inbuilt clock (I think usually LEDs) which you could also program your shows by, but a separate mechanical counter for the tape. The mechanical counter didn't give you an indication of the actual time taken, just like the tape counters in the old audio tape decks. So which aspect of the clock do you mean, the clock, the program timer, or the counter? Really, all of these were adapted from earlier devices as mentioned, they weren't actually invented for the VCR. Setting the timer to record a show is really just a modification of what alarm clocks do. --jjron 07:46, 19 December 2006 (UTC)

IIRC, some very early Sony U-matic video cassette recorders actually used an analogue clock mechanism; I think I owned one once. I'm not sure the idea of putting a clock in a VCR was ever really "invented"; I think it would have to count as being "obvious". Even a pretty old audio cassette recorder of mine has a switch you can flip that will cause it to automatically enter either record or play mode when power is first applied. Combined with an external timer switch, even it can record programs in your absence.

Atlant 12:30, 19 December 2006 (UTC)

Sense of touch

I often have a very unpleasant feeling while touching some kinds of textiles (something like a combination of formication and kicking by current), and the feeling remains some time after. What's going on (and eventually how to avoid this, except wearing gloves). :) Bisley

The obvious first question: what type of textiles? Man-made fibers (polyester, acrylic, nylon, spandex etc), I am guessing? Vranak 23:55, 18 December 2006 (UTC)

Wool and acrylic, may be some other types used for pullovers in particular. --Bisley —The preceding unsigned comment was added by 83.142.184.86 (talk) 00:32, 19 December 2006 (UTC).

Hyper sensitivity to electrostatic discharge? That's my guess. I don't even know if that's a condition. —Pengo ^{talk · contribs} 01:41, 19 December 2006 (UTC)

I have no idea how to explain this or what to recommend. I think reading about reiki might help though. Vranak 02:36, 19 December 2006 (UTC)

Maybe you have hyperesthesia. - Cybergoth 05:14, 19 December 2006 (UTC)

Quite a few people cannot touch a peach, and even the idea of touching one makes them shiver. If you have the same, it has something to do with the fuzziness. Spandex should be fine, but velvet is sheer torture. It is a tactile equivalent of what other people have with the sound (and the idea) of a nail scratching the blackboard. There is almost certainly a word for this condition, but I don't know it. For eating a peach, it may help to wet it, but wetting is usually not practical and also possibly not helpful for textiles. Other than avoiding it, there seems to be little choice but enduring it.  --Lambiam^Talk 09:12, 19 December 2006 (UTC)

Interesting that our article formication redirects to anogther page ... --HappyCamper 16:35, 19 December 2006 (UTC)

Another name may be paresthesia. That does not explain your sensation, simply labels it:-) --Seejyb 23:23, 19 December 2006 (UTC)

Perhaps a bit OT, but I know someone who can't stand wool. Personally, I don't really have a problem with any fabric but I absolutely can't stand the sound of polystyrene. Nil Einne 14:38, 21 December 2006 (UTC)

December 19

Forensic bloods tests...

I just had this, I think, ridiculous argument with my neighbour about certain substances in the blood, that are tested for forensically. I haven`t checked any of your resources here, sorry. I thought I needed a specific response. 'She' said that cocaine is AUTOMATICALLY tested for, in blood tests, but that anti-freeze, ethyline glycol isn`t. " I " said that ANYTHING 'has to be' tested for...nothing is AUTOMATIC. Who is correct. Thank you for ANY replies. Andrrea216.218.116.1 01:05, 19 December 2006 (UTC)

There are many types of "forensic blood test"s-- the term refers to any test done for legal purposes (as opposed to medical treatment or research, say). An alcohol level drawn after suspected drunk driving is a forensic blood test, as is a sample run on a corpse to determine whether certain kinds of drugs were involved in a death, or drawn from a criminal suspect to see if he can be connected to crime evidence. What context were you arguing about? alteripse 01:37, 19 December 2006 (UTC)

Ty Alterprise...the 'keyword' here is AUTOMATIC. Is cocaine automatically tested for in a port-mordem blood test, regardless of asuumptions of cause of death. I hope that clears my querry somewhat. Andrea216.218.116.1 01:55, 19 December 2006 (UTC)

It also depends on the location, some places will test for more things than others. StuRat 01:56, 19 December 2006 (UTC)

"everything" could be tested for, but that would consume two things the police don't have spare: time and money. so i'd say they test for things they suspect in the real world (as opposed to shows like CSI, where a battery of random testing can be done in a single montage). Xcomradex 02:38, 19 December 2006 (UTC)

The police, like hospital emergency rooms, use standard "tox screens" offered by commercial laboratories. These generally include drugs of abuse (cocaine, amphetamines, opiates, alcohol, benzodiazepines, barbiturates), but generally don't include substances which are ingested only accidentally (or administered for nefarious purposes), such as ethylene glycol. Obviously if foul play or poisoning or a specific poison were suspected, a different toxicology test would be ordered. Ethylene glycol poisoning is most often suspected on the basis of a suggestive history, the presence of an increased anion gap, acidosis, and confirmed by testing only after treatment has begun. A routine post-mortem toxicology screen would almost always include cocaine, and almost always not include ethylene glycol. - Nunh-huh 03:28, 19 December 2006 (UTC)

Nothing is tested for "automatically", whatever you mean by that. Someone makes a policy at a local level, or makes an individual decision for an individual case. The specific tests obtained according to policy or for the individual case would depend on what was available readily and what specific problems were suspected. As mentioned by Nunh-hunh, in many areas there are standard "batteries" of tests referred to as a "toxicology screen" that are obtained if a drug or poison effect is suspected. The contents of these screens have varied in different years, different locations, and different laboratories. alteripse 04:55, 19 December 2006 (UTC)

The difference with your neighbour may simply be in the point of view associated with the use of the term "automatic". When she says it is "automatically tested for", she may mean that the people ordering the test don't have to do "something specific" to get the cocaine screening, since it is routinely tested for, so from their point of view it will happen as it were "by itself", "automatically". The lab people probably have to do something specific to obtain the lab results; from their point of view it is not quite automatic.  --Lambiam^Talk 09:27, 19 December 2006 (UTC)

Thank you all for your fine responses. Andrea216.218.116.1 16:05, 20 December 2006 (UTC)

Pseudoephedrine shelf life

What is the shelf life of pseudoephedrine pills? Can they last for decades? Do they have to be stored in an especially cool or dry place?

The reason I ask is that I just found out about the stupid sales restrictions in the US and I'm worried it might become even harder to obtain. In that case a supply will have been a good investment, and if not, it doesn't matter because I use it often and would have bought that much eventually anyway. And if some people from the FDA come to see me, I don't care because I'm not running a meth lab. Is there anything wrong with this plan? —Keenan Pepper 03:06, 19 December 2006 (UTC)

Based on Sudafed, the tablets should have shelf-life of a couple years if kept in a light/water proof pill bottle at room temperature. As with any question of this kind, you should refer primarily to the documentation accompanying the pills. Dragons flight 16:02, 19 December 2006 (UTC)

Pseudoephedrine of itself if kept in a closed dark bottle (no light, limited oxygen) would last for many many years. Exposure to light - especially outdoors with uv is a sure way to cause it to 'go off'. This shouldn't be a problem for you.

Cool dark dry places are always the best - but the difference between store at 20C and 10C would be negligable.

Keep them in the packaging - or if they are in a bottle - you could put cling film or similar between bottle and lid to ensure an airtight seal - probably not necessary though.

Other substances in the pills eg the filler might alter the shelf life.83.100.158.248 18:18, 19 December 2006 (UTC)

I remember reading in an article in some magazine that the efficacy of medicines in pill form lasted far longer (years) than the "use by" date, although it might drop a little (say 95% effective instead of 100%). In fact, a quick Google search revealed [10]. howcheng {chat} 18:40, 19 December 2006 (UTC)

I was wondering what you want the pseudoephedrine for - and what are these sales restrictions. 83.100.158.248 18:56, 19 December 2006 (UTC)

Pseudoephedrine is a very effect nasal decongestant. Unfortunately it can also be used to create methamphetamine. Thus, in the US there are federal regulations as to how it can be sold. Not having bought any recently (the phenylephrine that replaced it works decently for me), I can't testify as to the restrictions, but I remember reading in the papers that it's basically a cap on the amount you can purchase, and I believe you may have to sign a log book when you buy it (like when you pick up a prescription). However, it's still widely available at all major pharmacies -- just at the pharmacy desk instead of on the shelf. howcheng {chat} 19:00, 19 December 2006 (UTC)

I can't help noticing that phenylephrine would be a good precursor for methoxyamphetamine - maybe that will be controlled as to the amount that can be bought too.

(above wasn't added by me) Here in NZ, it's quite restriced as well. Not sure of the specifics. But many pharmicies, especially the smaller ones don't stock it (to avoid being robbed) and I think some of the ones that do will only sell it to customers they have an existing relationship with (I don't think this is a legal requirement) Nil Einne 14:42, 21 December 2006 (UTC)

I should take the opportunity to point out that if you knowingly take medicines that are past their sell by date you may be at a disadvantage legally if something goes wrong. I just have to mention that obviously - the sell by date is there for your safety (and safety of the company that produces them from expensive legal cases etc etc). I wouldn't recommend stockpiling.83.100.158.248 19:09, 19 December 2006 (UTC)

The chemistry with link to MSDS page says that it is "stable", mentioning also: "Combustible. Incompatible with strong oxidizing agents. May discolour upon exposure to light." The requirement for the MSDS "stability" entry is that it must state: "1. Conditions to avoid. 2. Incompatibility with other materials. 3. Hazardous decomposition products. 4. Hazardous polymerization." So if there are no warnings about such events, and the stuff is kept dry, dark, and cool, (in N2?) it seems pretty safe. The original articles (Pubmed) describing the "stability of pseudoephedrine" are dated 1955 and thereabouts, so one would have to search a live library for those. --Seejyb 23:48, 19 December 2006 (UTC)

Not a lawyer by any means but are you sure of your claims from a legal standpoint? Here in NZ, I would say if something did happen to you because of the drug, you would probably still be entitled to compensation or whatever if something happened to you because of the drug provided you could prove it wasn't because of the drug being past it's sell by date. This could be difficult in some case, but I would say if the effect was a documented problem with the drug that later became known. If there was believe the drug being past it's sell by date could have made the problem worse, then there would probably be a consideration of relative liability I guess. Of course it can be rather difficult to prove a drug was the cause of your problem, and liability issues are different in NZ anyway so you don't tend to get the big lawsuits that seem to be the norm in the US. Nil Einne 14:53, 21 December 2006 (UTC)

Contradicting Articles

Unless I'm mistaken, the marijuana article implies in the lethal dose section that more marijuana is required orally for a lethal dose than smoked, while the THC article implies that more is required smoked than eaten for a lethal dose. If I am mistaken, could somone please say so and possibly explain why, or if I'm not could somone tell me which article is correct. BeefJeaunt 06:18, 19 December 2006 (UTC)

Both of the articles that you linked specify 1270 mg/kg as the LD50 for THC administered orally. I see no contradiction.141.161.222.56 09:07, 19 December 2006 (UTC)

For the LD50 (in rats) I see this:

Cannabis (drug): orally: 1270 mg/kg; inhalation: 42 mg/kg.

Tetrahydrocannabinol: orally: 1270 mg/kg; smoking: "much more".

To reconcile these claims, we need to assume that "much more" than 96.7% of the THC is lost through burning or exhalation, which seems really high to me (no pun intended). Rather, I suspect the editor of the "much more" statement in the THC article mistakenly assumed that the inhalation LD50 is essentially the same as for oral administration, so that the wording "much more" reflects the editor's (reasonable) assumption that in smoking much more than 0% of the THC does not make it to the body.  --Lambiam^Talk 09:55, 19 December 2006 (UTC)

You're probably right. That was apparently added here [11] in an attempt to improve the previous anon's addition. More importantly perhaps, there's IMHO no such thing as a LD50 that's much more. LD50 is a specific measure and it's determined in a specific way. If you haven't determined it, then you don't know what the LD50 is. There's also AFAIK no such thing as a smoking as a method of ingestion. Only inhalation. LD50 also only works on pure compounds. There'no such thing as an LD50 of marijuana or of table salt. Only THC and sodium chloride Nil Einne 15:12, 21 December 2006 (UTC)

Parasitic wasps and humans

What would happen if a parasitic wasp were to try to lay its eggs into a human? JIP | Talk 10:34, 19 December 2006 (UTC)

What species? 68.39.174.238 13:47, 19 December 2006 (UTC)

It'd get swatted :-). No, seriously, parasitic wasps tend to lay their eggs in invertebrates, predominately other arthropods such as caterpillars, moths, flies, spiders, etc, and generally in the immature stages of these arthropods. The wasp larvae are internal parasites of the host, and ultimately kill it. Thus the hosts are fairly specific, and are probably genetically programmed into the wasp. If, despite this, it did try to lay in a large mammal like a human, even if it did get the eggs laid it would only be in or just below the epidermis and the eggs would either be destroyed by the body's defences or would not be able to get to a suitable location in the body in order to survive. And if it did overcome all these obstacles, when the larva matured, it would not kill the host, so would probably die itself anyway. --jjron 14:15, 19 December 2006 (UTC)

parasitic wasps (braconidae, ichneumonidae, sphecidae, etc.) paralyse their prey temporarily or permanently; the prey is then consumed slowly by the vasp larva(e). Some wasps also remove antennae of the prey insect. The larvae are "genetically programmed" not to gnaw at the vital organs of the prey until the very last moment, to keep the prey alive as long as possible (sad but true). I do not think that would work with large mammals as prey, so human kind is probably safe. Why there are no wasps preying, say, on mice is beyond me. Oestridae flies, on the other hand, are known to parasitize large mammals. Larvae develop under the skin (see botfly), in nasal passages, or in the intestines. The results are rather nasty, though very seldom fatal. Dr_Dima.

Not really adding anything to the discussion in terms of wasps, but did you guys read about those couple of botflies that were burrowed into a guy's balls for three weeks and then surgically removed while still alive? (Warning: Crude language in the poem.) DAY-um! That's got to be way worse than that one time I swallowed some shampoo. Waaay worse.--Itrade

aromatic carbon

Heya,

I usually read the articles in spacedaily every day and today there is an article entitled:

The Basic Rules of the Universe.

In it, Pascale Ehrenfreund states a great deal concerning carbon found in the universe and puts special importance on aromatic carbon.

Unfortunately I loose her around here - what is aromatic carbon? Why is it so important? Is it what makes carbon able to create the complex structures which allow life?

So I've had a little look at google but all the answers are hard core chemistry - which isn't much use when I'm not getting the fundimental idea of what it is or what it relates to.

Any/all help would be greatly appreciated.

Kind regards. —The preceding unsigned comment was added by 194.63.116.72 (talk) 13:33, 19 December 2006 (UTC).

This may be of use to you: Aromatic_hydrocarbon. —The preceding unsigned comment was added by Moffo (talk • contribs) 13:37, 19 December 2006 (UTC).

Hi, (it always helps if you can link to stuff you're asking about - I found it anyway here http://www.spacedaily.com/reports/The_Basic_Rules_Of_The_Universe_999.html I put it in so other people can read it.)87.102.5.69 13:47, 19 December 2006 (UTC)

"Aromatic" in organic chemistry means there's a benzene ring in it somewhere: Basically six carbon atoms in a hexagonal circle. 68.39.174.238 13:48, 19 December 2006 (UTC)

Polycyclic aromatic hydrocarbon is definately the article you should look at.87.102.5.69 13:56, 19 December 2006 (UTC)

A little more here http://www.astrochem.org/PAHs.html87.102.5.69 13:57, 19 December 2006 (UTC)

To add one more to the list of recommended reading; see aromaticity. --Ed (Edgar181) 13:58, 19 December 2006 (UTC)

Personal allergy

Is it possible for one person to be allergic to another? Marco polo 20:16, 19 December 2006 (UTC)

Ye-es...though it's pretty rare. The most-reported manifestation (though still quite unusual) is for a woman to be allergic to her sexual partner's sperm: [12].

If you have allergic reactions when a person is present, it's much more likely a reaction to that person's cosmetics, perfume, deodorant, skin cream, laundry detergent, fabric softener, pet dander or fur, etc. than to the person himself. TenOfAllTrades(talk) 20:36, 19 December 2006 (UTC)

I don't see how someone could be allergic to an actual person, instead of the things the person wears/eats/uses. We're all made up of almost the same substances. --Bowlhover 20:42, 19 December 2006 (UTC)

As noted in the article I linked, women can be allergic to male sperm. Sperm contains (among other things) proteins secreted by the prostate gland. These proteins are not going to be present in a normal human female body—and may, therefore, be recognized as foreign by her immune system. That's why sperm is just about the only bit of a human being likely to provoke an allergic reaction. TenOfAllTrades(talk) 20:48, 19 December 2006 (UTC)

Right. I meant other than sperm. --Bowlhover 21:53, 19 December 2006 (UTC)

The need for matching blood types is essentially another example. Getting donor blood with the wrong antigens will provoke an immune response. Dragons flight 21:56, 19 December 2006 (UTC)

If we're talking internally, people generally don't match in their Human leukocyte antigens. Donor organs ideally need to match. BTW, while people can be allergic to sperm I believe, if they're allergic to one of the proteins in semen but not sperm, I would suggest it's more accurate to say they're allergic to semen. Nil Einne 05:39, 22 December 2006 (UTC)

Super Natural Events

Hi. I read somewhere there was a phenomenon where a Different You from a Different Dimension crosses over to visit the You Now in This Dimension. Does anyone know what this is called or where I can read information on this?

It's a popular science fiction device. Murray Leinster is often credited with writing the first story to use it ("Sidewise in Time", 1934). (My mistake; the characters do switch universes, but don't meet their counterparts.) See Parallel universe (fiction). Clarityfiend 21:52, 19 December 2006 (UTC)

So there isn't actual documentation of people experiencing this?

There isn't really any scientifically verified documentation of ANYTHING supernatural happening, full stop. Otherwise organisations like Skeptics Society would probably have to give up... As far as documentation of people claiming things like this happening, there are plenty. JZ Knight is one contemporary example of such a person. Not quite exactly the situation you are talking about though. Vespine 00:18, 20 December 2006 (UTC)

It would be something like seeing your Doppelgänger, thought to be a bad omen. Edison 04:04, 20 December 2006 (UTC)

I imagine you would teach your Doppelganger some of the differences between your dimensions, and you'd both learn a valuable moral lesson before he/she left. He'd go on to jump the shark in the fourth season and dwindle into obscurity. Sockatume 06:29, 20 December 2006 (UTC)

Ouch! I'm *sure* you aren't talking about a certain vampire slayer! ;) --24.249.108.133 21:36, 22 December 2006 (UTC)

Blind People

I've been wondering can a person who is born blind, form mental images and visualize things? --soccerman —The preceding unsigned comment was added by 204.16.236.254 (talk) 23:08, 19 December 2006 (UTC).

Your 'mind's eye' is informed by far more than just visual information. Even memory plays a big role. Vranak 15:42, 20 December 2006 (UTC)

(after edit confict) The term "mental image" usually denotes a more abstract concept than image in the sense of a picture offering a two-dimensional visual representation. While people born blind do not visualize things in the latter, stricter sense, they have mental imagery like everyone else in the more general sense. They can certainly form an internal "image" of shapes and spatial relationships, and for instance mentally rotate objects to see how they would fit together, often better than most seeing people. And yes, they use the verb "to see" metaphorically themselves just like I did in the last sentence.  --Lambiam^Talk 15:50, 20 December 2006 (UTC)

I work with the blind, and they do fine with things that are both visual, and non-visual, like object shapes. Those who have been blind since birth do have trouble with things that are only visual, though, like colors and shades. Light, on the other hand, can be "visualized" by feeling sunlight on their faces. StuRat 16:24, 20 December 2006 (UTC)

You might be interested to read "The Country of the Blind" a short story by H.G.Wells about a man with normal sight visiting a country whose inhabitants have been blind for 15 generations. Not particularly scientific but very enlighting. Keria 17:04, 20 December 2006 (UTC)

Thanks to everyone who has helped answer my question. You've all been very helpful. --soccerman

Musical Appeal

I was wondering, why does some music appeal to some people while not to others? (Is there a Wikipedia article about this?)--Codell ^{[ Talk]} 23:20, 19 December 2006 (UTC)

Same reason art or food or anything appeals to some people while not to others. —Keenan Pepper 17:07, 20 December 2006 (UTC)

December 20

New cochleas

Due to the ossification of a person's cochleas, a cochlear implant is only partially provided. Typically, a string of electrodes are fed into a cochlea that has dead or damaged "hairs". However, with cochlear ossification, such threading is not possible. A drill, being straight, cannot make room along the spiral shape of the cochlea, but instead penetrate the cochlea at two angles for insertion of only a partial array of electrodes. This damages the cochlea permanently, which is why cochlear implant users generally leave one ear available for future advancements. My question is this: What would be the science behind providing someone with new cochleas, if the damaged cochlea was the reason for a person's deafness? I imagine two methods -- growing cochleas in a petri-dish in the lab (someone grew an organ successfully this past month, so this seems possible), or the implantation of cochleas from an organ donor. What would be the difficulties with these methods as well? —Erik (talk • contrib) - 00:32, 20 December 2006 (UTC)

In mammals, it can be tricky to get axons to grow to their "normal" targets in an adult brain. Regeneration and replacement in the vertebrate inner ear. --JWSchmidt 01:02, 20 December 2006 (UTC)

What about cochlear implantation, not the artificial method? —Erik (talk • contrib) - 01:55, 20 December 2006 (UTC)

Same problem as JWSchmidt pointed out: it's not just the ear it's the brain that has lost the ability to hear. --Cody.Pope 03:24, 20 December 2006 (UTC)

Not sure if I understand. Where would the axon growth take place? When people go deaf, their hearing can be restored with cochlear implants because the technology serves as a substitute function to the cochleas. I don't think it means that the brain loses the ability to hear, as I know someone who has been deaf for 7 years and will get a cochlear implant in the coming year based on doctor's recommendation. What is the difficulty in placing organ donors' cochleas in deaf people to replace the damaged cochleas -- is it the connection between the new cochlea and the old brain that must be made? —Erik (talk • contrib) - 03:47, 20 December 2006 (UTC)

When signals from a sensory organ cease traveling to the brain, the areas of the brain receiving those signals go into atrophy. Meaning that over time, those brain areas decay. Depending on the age of the individual, reconnecting or replacing the organ can have some effect. However, as we age the brain become less plastic, meaning that it becomes harder and harder to re-grow/re-connect those areas lost to atrophy. So, concerning a cochlear implant, whether it be artificially or an actual donor implant, the amount of information that brain can interpret as sounds will always be far less than before. --Cody.Pope 04:01, 20 December 2006 (UTC) Also, sorry about the minor confusion as I didn't read JWSchmidt comment quite close enough. --Cody.Pope 04:07, 20 December 2006 (UTC)

What if the implantation of organ donors' cochleas happened shortly after a person went deaf? For example, the person is stricken with bacterial meningitis and loses his hearing. Can the person recover his hearing by receiving new cochleas shortly after his hearing loss? I'm just curious about the issue of implanting foreign cochleas (like how it compares to receiving a new hand) or what medical constraints prevent us from doing that now. —Erik (talk • contrib) - 05:36, 20 December 2006 (UTC)

I'm not sure, but if you check out the image, I'd say the area is just to delicate to remove. The cochlea is directly connected to the vestibular canals, and if you did anything to them you'd loss your sense of balance. The implant, while somewhat invasive, is just placed in the cochlea. --Cody.Pope 22:12, 20 December 2006 (UTC)

There is some research investigating the ability of new axons to grow into the Organ of Corti; Engraftment and differentiation of embryonic stem cell-derived neural progenitor cells in the cochlear nerve trunk: growth of processes into the organ of Corti, Auditory hair cell explant co-cultures promote the differentiation of stem cells into bipolar neurons. --JWSchmidt 14:30, 20 December 2006 (UTC)

Sauna questions

1) Should I have any doubt bringing a Ipod or a water bottle in the sauna? I keep thinking that it's possible that the humidity or sweat will mess up the inside of the Ipod.

Hrm. I'd advise against it. The humidity might well be an issue. --Brad Beattie (talk) 01:28, 20 December 2006 (UTC)

2) How many calories burn while in the sauna?

3) Also, do calories always burn at a steady pace no matter how long you go (doing the same thing for a long time) or do they burn more and more as you keep burning?

4) AND, how do you change the color of your signature? PitchBlack 01:04, 20 December 2006 (UTC)

Check out the my preferences link at the top right of the page when you're logged in. The signature field is where you want to change things. Try to make sure you respect the signature guidelines when you change things though. --Brad Beattie (talk) 01:28, 20 December 2006 (UTC)

(Edit Conflict)

1) The inside of a sauna is extremely dry, so humidity is very low. The high temperature might not be great for your iPod if you put it down on a hot surface, and your sweat will be bad for it if it gets inside, but if those two things don't happen, the iPod will be able to outlive you in a sauna.

2) Fewer than you would burn at the bus stop. Since a sauna is hotter than your body temp, your body will try to scrub off heat by sweating, opening peripheral blood vessels, and slowing metabolism. You will dehydrate faster, but you will burn calories slower.

3) A given movement/exercise/lifestyle will always burn the same amount of calories (more or less, I know I'm gonna get heckled for that one), however, the energy source your body uses for that exercise will change over time from sugars to fats and protein (I won't get into it...). You can add two 30 min aerobic sessions together and get the equivalent of a one-hour session, if that is what your asking.

4) see Customisation#User_name_and_signatures Tuckerekcut 01:41, 20 December 2006 (UTC)

So, will you have any benefit of burning calories for a long time (about an hour), or will it be the same as if you do 6 10-minute aerobic sessions? PitchBlack 02:39, 20 December 2006 (UTC)

Should be about the same. Tuckerekcut 02:47, 20 December 2006 (UTC)

Don't bring water or iped into sauna. The water can ruin the heating mechanism, and the heat can ruin the music mechanism. Second, don't worry about how many calories you burn. The idea of a sauna is something like 'sweating out toxins', though even this is probably not quite accurate. Vranak 03:27, 20 December 2006 (UTC)

Googling for sauna calories (try it!) suggests a sauna does burn calories at a pretty high rate. Are those search results based on medical studies or are they marketing? You tell me! As to an iPod in a sauna: don't. If you look at the manual of most any electronic device it will specify an operational temperature range, and a sauna is almost certainly way out of that range. Some types of saunas have high moisture ("steam room"), some are dry, so that may or may not kill your iPod too. Weregerbil 13:31, 20 December 2006 (UTC)

empirical formula

how do i get the empirical formula, when given percent composition of a substance :49.3% C, 6.9% H, 43.8% O. i got 4.10 for the ratio of C and cant figure out from there will someone please walk me through,thanks --69.140.210.163 03:35, 20 December 2006 (UTC)

Assuming the percentages refer to weight/mass, you need to convert all three to moles (you've already calculated it for C). You'll end up with decimal places, so multiply them till you get the smallest integers. Clarityfiend 04:54, 20 December 2006 (UTC)

A good way to get to integers here is to divide through by the smallest value. For example if you wind up with 0.12 H, 2.38 C, 5.43 O (just pulling numbers out of thin air) you'd divide each by 0.12. Sockatume 05:18, 20 December 2006 (UTC)

Following on from what the others have said you should get the ratio:

49.3/12 carbon : 6.9/1 hydrogen : 43.8/16 oxygen (the atomic masses of carbon, hydrogen and oxygen are 12,1 and 16 respectively)

4.108c:6.9h:2.7375o = 1.5c :2.52h : 1o (divide by 2.7375)= 3c : 5.04h : 2o

So it's probably C3H5O2 - did that make sense?87.102.4.227 11:43, 20 December 2006 (UTC)

Text Color

In Wikipedia, how do I change the color of the text that I encode? For example, some usernames have different text colors and even different color combinations. How do I do that? I'm creating a userbox and I want to make color combinations on the text. Moonwalkerwiz 04:05, 20 December 2006 (UTC)

Like this? Clarityfiend 04:39, 20 December 2006 (UTC)

Better, like this (or better yet, never mix color information in with the content, and let the CSS stylesheet handle it). —Keenan Pepper 17:03, 20 December 2006 (UTC)

Please don't do that in your signature, though, I hate having to edit a page where most of the text is for the fancy signatures, so I can barely even find the actual content. I don't think anyone over the age of 5 really needs to have a Punky Brewster [13] signature, anyway. StuRat 15:58, 20 December 2006 (UTC)

honey

Can eating a lot of honey be bad for you (other than making you fat)? --Shanedidona 04:46, 20 December 2006 (UTC)

Have you looked under honey --Light current 04:53, 20 December 2006 (UTC)?

I think eating too much of anything can be bad for you, especially something as sugary as honey. --jjron 09:06, 20 December 2006 (UTC)

Typical honey analysis

   * Fructose: 38%
   * Glucose: 31%
   * Sucrose: 1%
   * Water: 17%
   * Other sugars: 9% (maltose, melezitose)
   * Ash: 0.17%

Which sugars? --Light current 09:17, 20 December 2006 (UTC)

I don't see too many complex carbohydrates in there! Or anything else particularly nutritious. --jjron 09:43, 20 December 2006 (UTC)

I have to disagree with some of the misconceptions above. I happen to think that natural-esque sugars (honey, maple syrup, unadulterated fruit juice etc) are fine. You'll stop eating them when your body has had enough. It's stuff like high-fructose corn syrup and refined white sugar that you have to be leary of, as they seem to be added to just about everything made north of Mexico.

Also, the quality of honey makes a big difference. Try to get honey made on a small scale by a small company, not in a generic 10-pound tub at the nearest MegaMart. Vranak 15:36, 20 December 2006 (UTC)

Honey is one of the best forms of sugar, but it's still sugar, so you should limit consumption as much as possible. StuRat 15:53, 20 December 2006 (UTC)

Hmmmm! I thought bees made honey (not companies)--Light current 17:25, 20 December 2006 (UTC)

Think of bees as little cows -- you gotta treat them right for them to produce good honey. Or at least have nice flowers nearby for them to drink nectar from.

Also, limit[ing] consumption as much as possible is not quite what I recommend. If you have a sweet tooth, it's because your body craves sugar. Why would you fight a natural urge? Vranak 23:12, 20 December 2006 (UTC)

Well, just limiting your "natural urges" to food and drink, you would likely eat an extremely unhealthy diet rich in bad fats, bad cholesterol, sugar, salt, excess calories, and other nasties, and totally devoid of vitamins, minerals, fiber, etc., leading to an unhealthy life and an early death. StuRat 21:19, 21 December 2006 (UTC)

Large amounts of sugar consumption can be bad for your teeth. BenC7 01:17, 21 December 2006 (UTC)

This is true. But the healthier you are (and thus the healthier your mouth is), the less sugar troubles your teeth. Vranak

I am skeptical about a different appetite for "natural" sugars versus any other sugars. Do not ASSume that fructose is somehow superior to glucose. Edison 05:52, 21 December 2006 (UTC)

Another potential downside of honey is that it has a relatively high glycemic index:

Sugar      GI
========   ==
honey    - 73
sucrose  - 65
lactose  - 46
fructose - 23 [14]

This means that, relative to other forms of sugar, it rapidly increases your blood sugar level, causing your body to rapidly produce insulin to compensate, resulting in a "sugar crash" later on. So, don't avoid honey completely, but do try to limit your consumption. StuRat 16:26, 23 December 2006 (UTC)

Chemical Reaction

I have a problem with a certain AP Chemistry word problem. I am supposed to turn this into a chemical equation. "A clean iron rod is inserted into a solution of iron (III) sulfate" Would adding more iron simply push the equilibrium further to the products side. Would I wind up with Fe + Fe³⁺ + 3SO₄^2- → Fe₂(SO₄)₃? This problem seems so simple, but it's making me feel so stupid, like I'm missing something extremely obvious. Thanks. Ivan 05:22, 20 December 2006 (UTC)

I suddenly had a thought that it might be redox. Is it? If it is, I'm still stuck. Ivan 05:29, 20 December 2006 (UTC)

The reaction between the iron rod and the iron sulfate solution is indeed redox (note that the net charge is not balanced on the two sides of your equation), but the answer does not require actually using the balanced redox equation for it. Rather, note that the question tells you it's an equilibrium reaction, and consider what kinds of chemical things one includes when talking about an equilibrium. Insoluble solids? Soluble molecules and ions? Gases? Solvents? Catalysts? Etc. DMacks 06:39, 20 December 2006 (UTC)

A study of the relevant redox potentials will tell you that the following redox equilibrium will be established. It is technically reverse disproportionation. The sulphate ions play absolutely no part at all. Fe + 2Fe³⁺ <----> 3Fe²⁺. --G N Frykman 07:24, 20 December 2006 (UTC)

Adding more iron does not change the equilibrium constant, since it is calculated based on the concentration of the chemicals involved in the reaction. Solids have a concentration of 1, so adding more would not change it. BenC7 01:20, 21 December 2006 (UTC)

Evolution question

If evolution is correct, are European people more physically related to monkeys than, say, African people? European people resemble monkeys' pink skin and straight hair... is it fair to assume then that black people are in more advanced stages of human evolution, because they don't physically resemble monkeys? They don't have the skin and hair of monkeys. So what now? I'm not an expert on this field... so tell me. PS: I don't think I've ever seen a monkey with black skin. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 06:32, 20 December 2006 (UTC)

If evolution is correct? No, human beings are all the same species, certain races are not more or less related to other primates. Variations in skin tone and hair colour and texture are adaptations only tens of thousands of years old which occurred in response to environmental differences. Anchoress 06:37, 20 December 2006 (UTC)

Human skin color might be of interest. —Erik (talk • contrib) - 06:38, 20 December 2006 (UTC)

Look in the face of a Gorilla! Its black! He is related to me to the same degree than to African people, because we all come from a small group of people who lived in east Africa millions of years ago. To use the skin colour as marker for evolution has a long tradition, and caused some of the awful theories of Herrenrasse and other ideas which made alot of people suffer.--Stone 08:31, 20 December 2006 (UTC)

According to the most widely held views of scientists, all modern humans are descended from a small group of people living in Eastern Africa some time in the last 200,000 years. The article on Mitochondrial Eve may be of interest to you. As the others have said, no human group is more or less related to apes or monkeys than any other group - we are all equally related to the same common ancestors as apes such as chimps and gorillas some time in the last 5 - 8 million years. (Incidentally, this group split from monkeys much earlier. Contrary to repeated use in popular culture, chimpanzees are apes, not monkeys.) Skin colour is a lousy determinant of anything; in some human groups it is thought skin colour is controlled by as little as a single gene. Hair also tells you little - my mum has curly hair, my sister and brother have wavy hair, I have straight hair, we all have dark hair but my other sister has straight blonde hair; ultimately, so what? Which of us is more like a monkey? --jjron 09:01, 20 December 2006 (UTC)

I believe that primates, and mammals in general, typically have either black skin or pink skin. Pink is more typical under fur, with black being more common in areas exposed to light, such as lips, noses, finger/toe pads, etc. Straight hair/fur is also far more common in mammals than curly hair. StuRat 15:49, 20 December 2006 (UTC)

Based on skin colour, I'd think that maybe European people are more related to domestic pigs, and African people to Wild Boars.  --Lambiam^Talk 16:07, 20 December 2006 (UTC)

People don't evolve from monkeys. Rather people and monkeys evolve from a common ancestor. From an evolutionary viewpoint I think it is fair to say that Europeans, Africans and monkeys are equivalently advanced as a species with their own adaptations and traits.

Cool, thanks. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 06:03, 21 December 2006 (UTC)

A bit late but bear in mind Race is a contentious issue in science anyway. Not all scientists feel it's a meaningful concept Nil Einne 10:57, 21 December 2006 (UTC)

lysergic acid diethylamide

given determination and a basic understanding of organic chemistry (college course), would it be in the realm of possibility to synthesize this with obtainable chemicals using obtainable glassware and lab equipment? i ask this as a fan of the substance, and as someone with an interest in chemistry. i figure i would be enjoying myself with the process, but also gaining something useful.

Why not take a trip to LSD?--Light current 09:28, 20 December 2006 (UTC)

The sythesis of LSD from readily obtainable chemicals and glassware would be a difficult undertaking. I doubt that it could be accomplished by anyone without graduate-level experience in organic synthesis and lots of money. In the lab LSD is instead made easily from lysergic acid which is isolated from ergot fungus and not something that just anyone can go out and buy. --Ed (Edgar181) 15:14, 20 December 2006 (UTC)

No-op microprocessors

As all microprocessor instructions finally boils down to 0/1 through output pins. This means that we can build a microprocessor that does nothing but just generates 0/1 through output pins, in a desired way. Functionalities can be built on the top of such microprocessors. Such processors would be very much simple (?) to build. Do we already have any thing like this? V4vijayakumar 09:59, 20 December 2006 (UTC)

See Programmable logic array. Also ROMS serve in such a capacity as well as its many, many variations. Essentially you put an address in and get the desired data out.Adaptron 10:39, 20 December 2006 (UTC)

DSP digital signal processor might be of interest as well. Very specialised digital circuits may fit the bill - eg a chip that decodes Mpeg audio to pcm - need no instructions (though note in this case 'instructions of a sort' are built into the compressed data)- sorry I don't know enough to give you a specific example.

I very very simple example of what you describe would be a logic gate on a chip an example of this is 7400 series. (Good question in my opinion by the way)87.102.4.227 12:31, 20 December 2006 (UTC)

Look up Microsequencer and Microcode and Bit slicing. Back in the mainframe days, microprocessors were built up from very simple parts; far simpler than a microprocessor chip. Inside of each complicated machine language instruction, the microsequencer would be executing several simple instructions in microcode. Even today, some hobbyists use these concepts when building their own computers from logic chips, or from AND gates, or even from individual transistors. --Wjbeaty 03:37, 21 December 2006 (UTC)

ASICs I think is what you are looking for. Microprocessors derived from ASICs. Microprocessors derived from ASIC requirements for multiple digital watches. Rather than create different chips for each watch product, they designed a single chip that did the basics (fetch, decode, shift/add, store) and could be put in mulitple products with a ROM of instructions to implement the specific function. --Tbeatty 03:20, 21 December 2006 (UTC)

owner/investor model

In terms of economics or business science I know there is an ownership/investor model in which only management and labor, i.e., the employees are the owner/investors and that this model of ownership/investment is highly successful but is there also a model to replace conventional non-profit foundations in which contributors for instance to the Wikipedia can benefit financially as well? Adaptron 10:37, 20 December 2006 (UTC)

A project with a model similar to what you're proposing is used in microloans. StuRat 15:41, 20 December 2006 (UTC)

Not really. microloans suggest financial assistance. The model I am looking for is directed not at assistance but at just compensations for services contributed voluntarily but with a sence of obligation for intellectual, social or other esoteric reasons more so than personal financial gains. Kind of like when mom bakes you some cookies not for any financial reward or compemsation but becasue she loves you and so you take out the trash not because you get an allowance but becasue you love her. Adaptron 18:02, 20 December 2006 (UTC)

I think you might misunderstand the purpose of microloans, which is twofold:

1) Lending money to help people, and the community, by giving them "seed money" to start or expand a small business.

2) To make a profit from interest paid on the loans.

Thus, it's not entirely a charity or entirely a business, but a bit of both. StuRat 03:08, 21 December 2006 (UTC)

You might also be interested in communes, where each person is expected to contribute in a different, non-financial, way. StuRat 03:11, 21 December 2006 (UTC)

Ions affecting Rheumatoid Arthritis

Good day,

I am looking for any documented research regarding the subject of ions affecting Rheumatoid Arthritis. My dad is 56 and has suffered from this disabling disease for over 30 years. Rheumatoid Arthritis is the inflammation of tissue. He experiences severe joint and muscle pain, fatigue, and other common related symptoms. He suffers excruciating pain with little-no relief. His condition has worsened substantially and his joints have gradually become grotesquely deformed. Although there is currently no conclusive 'cause or cure', he is adamant that ions affect his disease. He experiences severe attacks before thunderstorms or whether changes. We live in South Africa and are exposed to climate changes such as thunderstorms and cold fronts. Is there any documented literature relating to how and why ions affect Rheumatoid Arthritis, and how this can be prevented?

I sincerely appreciate your help.

Regards, Claudie FreemanClaudie33 11:54, 20 December 2006 (UTC)

I believe that storms do affect rheumatoid arthritis, but not because of "ions", the air pressure changes common in storms (typically a rapid air pressure drop) cause the inflamed membranes to swell to equalize the pressure, which can be quite painful. This suggest that one treatment would be a hyperbaric chamber, where the pressure could be slowly increased and kept at a high level. Unfortunately, once removed from the chamber, his symptoms would return, and quite possibly be worse than before. Thus, this isn't a good treatment, after all. StuRat 15:07, 20 December 2006 (UTC)

There is a fairly small body of rigorous scientific study of potential links between arthritis pain and changes in the weather. Nevertheless, if you search PubMed using a search term like arthritis AND barometric pressure then you will hit some studies. Some papers suggest no statistically significant correlation [15], while others find a weak correlation [16], [17].

For studies that found a statistically significant correlation, increased pain tended to associated with lower temperatures, high humidity, and/or falling barometric pressure. Note that these conditions tend to be common right before thunderstorms. The mechanism which ties these factors to an increase in arthritis pain are not well understood; the explanation provided by StuRat above has been proposed as one possibility. TenOfAllTrades(talk) 15:13, 20 December 2006 (UTC)

Additionally, cold can worsen the condition and should be avoided. The living human body is full of ions, and the influence of the weather on that is completely negligeable. Some discussion of the effect of the weather: [18], [19], [20].  --Lambiam^Talk 15:20, 20 December 2006 (UTC)

In humans there seems to be not one, but various meteorological factors that alter pain perception (as opposed to arthritis as such), but these have not been defined. Whatever the cause, one would expect your dad's doctor to institute effective pain management. --Seejyb 23:59, 20 December 2006 (UTC)

Is my daughter being poisoned?

My children have never been sickly. But in the last nine months both have had severe illnesses!!! My daughter who is 12 years old is scheduled for a colonoscopy and an endoscope this friday. Is this normal for someone so young? In march of this year my 15 year old son had headaches so severe he was getting paralized on his right side with each worsoning headache. He had all the major tests done, ie, MRI, CAT Scans, Spinal Tap, Blood work...etc. but in the end NOTHING!!!! His symtoms stopped withing two weeks of me arriving where they live. About six weeks later, my daughters symtioms started. Her symtoms don't include headaches though. She is having trouble eating and drinking anything!!! She has been very ill!!! Then someone pointed out that maybe it's not my children, but their stepmom. I don't want to jump to any conclusions, but this is my children I'm talking about and I'm at a loss here!!!!! I always thought she was great with my children, but she has done everything she could to keep me from even knowing about my children's illnesses, and I'm still in the dark about almost everything!! The childrens father seems to be no help whatsoever, so that isn't an option. Any suggestions or symtoms of poisonings that match would be greatly appreciated!!!

Thank You from the bottom of my heart!!!!

Kristie L. Hawkes concerned Mom

We are not able to help with medical diagnosis. Please seek medical attention. If you are unsatisifed with your current doctors, seek second opinions. Hipocrite - «Talk» 13:03, 20 December 2006 (UTC)

You should in any case discuss your fears with the doctors treating your children.  --Lambiam^Talk 14:49, 20 December 2006 (UTC)

Might be psycological. From what you have said this is far to serious to expect reliable help here in Wiki. Find a competant mental health counsellor. I would suggest getting HFS involved, but sometimes getting them into your life can be a Trojan Horse.

When the above poster said psychological, h/she meant for your children, not you. --68.149.31.252 09:34, 21 December 2006 (UTC)

Agreed, have them specifically test for common poisons. I don't know how you can bring this up with your children in a subtle way, but perhaps you could say "Don't ever eat or drink anything that tastes even the least bit 'funny', as it may have gone bad or be contaminated". The idea here is to get them to be cautious without making unproven accusations of poisoning that could destroy your family. StuRat 15:03, 20 December 2006 (UTC)

Regrettably, this is not the forum for making diagnoses, even if we could help. Vranak 15:33, 20 December 2006 (UTC)

As long as you understand that medical advice here may be worth what you pay for it, I will give you some. Intentional poisoning seems far less likely than many other explanations. There have been very few cases of parents or stepparents giving a chronic poison (chronic means over a long period of time) to two children except in the context of Munchausen by proxy syndrome, and this sort of thing has a very distinct flavor: the parent is driving the medical evaluations and simply moves on to another doctor when the doctor is unwilling to "play" any more. It would take two different poisons to produce such disparate responses; how likely is an adult to choose two different ones? To produce what result and for what motive? It would also mean that your previous assessment of her as a caring parent was in error, and I would tend to trust that assessment. I would drop that line. I would not recommend questioning your children about funny tasting things: it would not confirm or refute your suspicion and it will be disturbing to them (either about you or her) if they understsnd what you are getting at.

Finally, there are far more common explanations for the symptoms you mentioned. Headaches with transient one-sided weakness and a negative workup is a recognized migraine variant, and there are no tests that will be positive. You havent told us why your daughter "is having trouble eating and drinking anything" --- whether that is because of pain, or vomiting, or fear of something like choking or fatness, or because someone is trying to make her do so. For unexplained gastrointestinal symptoms that persist, sooner or later a doctor will offer endoscopy. It is what gastroenterologists do. Good luck. alteripse 22:16, 20 December 2006 (UTC)

If not intentional, are you sure it's not something environmental? Sometimes mold allergy for example can get very severe if the mold is toxic. It is an invisible deadly killer and difficult to diagnose. Mold can be very difficult to find, such as a leaking bathtub affecting a bedroom wall behind cupboards. Your house may have to be tested for toxins especially mold. Sandman30s 14:06, 21 December 2006 (UTC)

To Refreeze.. Or not to Refreeze

Why is it considered so bad to refreeze meat products?

Micro-organisms survive the freezing process, and multiply upon thawing. Their colonisation and digestion activities are made easier by the microscopic tears that occur in frozen meat due to the formation of ice crystals. Re-freezing just puts these new micro-organism colonies in cold storage, waiting to again multiply upon defrosting, and the degradation of the meat fibres due to ice crystals repeats upon the second freeze. And finally, the meat decomposes faster after freezing due to the previously-mentioned factors, decreasing the quality of the meat. Anchoress 16:30, 20 December 2006 (UTC)

But to "save" the meat, one can cook it thoroughly and freeze the prepared dish. --Seejyb 11:23, 21 December 2006 (UTC)

Although if you're not going to cook it within a day or so and you're not going to throw it away, I would suggest refreezing is better then leaving it in the fridge. Nil Einne 11:39, 22 December 2006 (UTC)

Random Question

Ok sorry for the mad random question but I thinik its necessary to get an answer. Anywayz, my gf and I are planning on having a serious romp tommorrow and I want to be more than prepared. Is there a way to increase the amount of semen I produce, or is there not a way to do anything. Thanks, yo, I'll be coming back later. Peace.— Preceding unsigned comment added by LukeHughes (talk • contribs) 16:33, 20 December 2006

Semen production is relatively constant, I think. One obvious way is to conserve it ahead of time by not ejaculating for a while. Friday (talk) 16:42, 20 December 2006 (UTC)

According to the manual, masturbating until you are close to ejaculation a few hours before intercourse does the trick. I'm not sure how increased output will make you "more than prepared", though. yandman 16:51, 20 December 2006 (UTC)

It would if pregnancy is the goal. Anchoress 16:57, 20 December 2006 (UTC)

Producing more semen does not automatically mean producing more sperm. Friday (talk) 17:01, 20 December 2006 (UTC)

Eat lots of protein and don't ejaculate until then. StuRat 17:24, 20 December 2006 (UTC)

As most people think 'beef or chicken' when the word protein is used, I would remind you that dishes containing lentils, rice, beans, nuts, seafood and so on are excellent sources of protein that no one suspects as having any negative long-term effects.

Also, auto-stimulation sans release may help, as Yandman suggested. Regardless, the main thing is to enjoy yourself, and not get all caught up in volumetric analysis. If your girlfriend is doing her part, such considerations are needless. Vranak 17:39, 20 December 2006 (UTC)

And drink plenty of fluids too. And if you want to go that way, stimulate your prostate, not producing more sperm but more seminal fluid.

Well what you want to do is up to you, but unless you've both recently been checked for STDs and are in a commited relationship and pregnancy is the goal I would suggest the amount of semen you produce is unimportant since it should all end up in the condom/s you use. At the very least, I hope you've considered birth control... Nil Einne 10:52, 21 December 2006 (UTC)

Where is the origin/homeland of the Mongol (Chinese) race?

H.G. Wells in his outline of history suggests that Chinese civilization has a different origin from the rest of the world. What was the route of the Chinese race from their origins most likely in Africa to their current position today? For example the homeland of the Caucasian race has been suggested in Tibet, India, Iran and of course the Caucaus, I'm not aware of any theories for the Mongoloids. I would really appreciate a geographical trace from their origins to the present. How and where did the Mongoloids begin diferentiating from the human common ancestor? I've heard theories of them evolving from both caucausiod and negroid sources as well as theories of independent evolution. --Maddoz 17:37, 20 December 2006 (UTC)

The recent single-origin hypothesis suggests we all evolved in Africa and then spread across the globe. --Cody.Pope 20:56, 20 December 2006 (UTC)

Alternatively Multiregional hypothesis gives a slightly different view suggesting that homo erectus and homo sapiens are the same species and local populations or 'races' have come about by "selection, mutation, genetic drift, and gene flow." (from the article)

and Hybrid-origin hypothesis emphasises two (or more) distinct 'species' of human that had evolved separately: "..all of the genetic variation between the contemporary human races is attributable to genetic inheritance from at least two widely divergent hominid species, or subspecies, that were geographically dispersed throughout ... prior to the evolution of modern Homo sapiens sapiens"87.102.4.227 21:15, 20 December 2006 (UTC)

So that's the background - I too would be interested in an answer..87.102.4.227

LD50

Does anyone know of a good database for various LD50s? My usual database is ok, but it's a bit dated--74.66.242.190 18:06, 20 December 2006 (UTC)

B12

Around what peak wavelength is the Soret band for vitamin B12? Does it have one?? Just curious since it looks so much like a heme--74.66.242.190 18:39, 20 December 2006 (UTC)

Even if it doesn't have a Soret band, doesn't it at least have a strong absorption band in the visible/near visible range? Any response would be appreciated--74.66.242.190 13:47, 21 December 2006 (UTC)

weight

if a bag of cotton and iron bar reads 100gmsin a weighing machine . in reality which is heavier?why? (i think its got something to do with uptrust) answer before 21st december2006,10pm

This almost sounds like a homework question. Our articles on weight and mass be helpful. Friday (talk) 19:57, 20 December 2006 (UTC)

This is a variation on a classic brain teaser. The U.S. version goes something like this: "Which is heavier, a pound of feathers or a pound of lead?" Googling will most assuredly give you more info than you'll ever need. The key question is - what do you mean by "heavier"? -- 21:28, 20 December 2006 (UTC)

See also Buoyancy and Weighing scale.  --Lambiam^Talk 09:04, 21 December 2006 (UTC)

I prefer "which is heavier, a 16 ounces of feathers or 16 ounces of gold ?", as that brings into play the fact that most things are measured in avoirdupois weight, but precious metals are measured in troy weight. StuRat 01:15, 21 December 2006 (UTC)

That doesn't work, because only an idiot uses ounces for feathers :-P Nil Einne 10:47, 21 December 2006 (UTC)

Are you using the snow leopard def of "ounce" ? StuRat 22:08, 21 December 2006 (UTC)

Matter

Given the exchange and dispersion of matter, how likely is it/how often do we inhale/consume and/or incorporate into our own protein structure molecules that were once in some historical figure, say Abraham Lincoln? 216.130.233.77 22:46, 20 December 2006 (UTC)

The probability that molecules have been incorporated is pretty low; after we die, our complex macromolecules tend to get digested. The food that we eat comes from plants (which survive pretty much on water and carbon dioxide) or from animals that ate plants. So there's little likelihood that whole biomolecules made it through. (It is possible that you're breathing some of Lincoln's oxygen or drinking some of his water, though.)

If we just look at atoms, we can take a rough guess. Figure you weigh about sixty kilograms and that about a third of that is carbon. That works out to about 1500 moles of carbon atoms. (Obviously, you're made of other atoms, but this is just back-of-the-envelope.) Roughly speaking, that's about 10²⁷ atoms.

Let's see here—there's about 1900 gigatons of carbon in the biosphere (see carbon cycle for more info). Figure that about 1% of the total available carbon (we include water-dissolved carbon dioxide, surface carbonate deposits, and atmospheric carbon dioxide and carbon compounds) is in the biosphere at any given time; that gives us a total of about 10⁴³ carbon atoms from which living things might be made.

So, about one carbon atom out of every available 10¹⁶ is incorporated into your body. To make a Lincoln takes about 10²⁷ carbon atoms; yeah—the odds are pretty good that some of those are common. (Your odds get even better if we choose to look at all the atoms of the body, and if we count all the atoms that you've consumed, excreted, inhaled, or exhaled over your lifetime.) TenOfAllTrades(talk) 23:16, 20 December 2006 (UTC)

John Allen Paulos briefly mentions this sort of thing in his book Innumeracy. According to him, the probability that you just breathed a molecule exhaled by Julius Caeser's last breath is over 90%! The argument is similar to the one given by TenOfAllTrades. — Kieff 00:29, 21 December 2006 (UTC)

Here's a passage from A short history of nearly everything:

We are each so atomically numerous and so vigorously recycled at death that a significant number of our atoms—up to a billion for each of us, it has been suggested—probably once belonged to Shakespeare. A billion more each came from Buddha and Genghis Khan and Beethoven, and any other historical figure you care to name. (The personages have to be historical, apparently, as it takes the atoms some decades to become thoroughly redistributed; however much you may wish it, you are not yet one with Elvis Presley.)

Lincoln was born much later than these people, so I would guess we all have ten million of his atoms. Of course, people who live close to where Lincoln lived have many more of his atoms than someone from China. --Bowlhover 00:34, 21 December 2006 (UTC)

"We are all made of star dust...or dinosaur crap...it all depends on how you choose to look at things." StuRat 01:07, 21 December 2006 (UTC)

Good point, Stu. I'd say dinosaur crap is mostly made of star dust :) Dr_Dima.

I'd like to take this opportunity to point out the difference between atoms and molecules. Although you're most assuredly going to have some of the atoms of any given historic person, it's doubtful you'll have any of the molecules. Even simple molecules like water and oxygen get rearranged. In biological systems water is broken apart routinely in the synthesis and destruction of biological molecules. Even in a "inert" glass of water, water molecules are feverishly exchanging hydrogens. Oxygen molecules are split up upon respiration and combustion, and then reformed with different partners in photosynthesis. Even nitrogen molecules get broken and reformed during nitrogen fixation and denitrification. So atoms are reused, but molecules, even simple ones, are not. -- 17:35, 21 December 2006 (UTC)

December 21

Name this bug

Okay, like a silverfish, but 90% grey and not opaque in any way. No longer than a quarter of an inch, likely about 4 mm. It lives in the Greater Toronto Area, and invades bathrooms of commercial buildings. Any ideas? -- Zanimum 00:09, 21 December 2006 (UTC)

Would it be possible to get us a picture of it? Also, you might be interested in this website called What's That Bug? — Kieff 00:15, 21 December 2006 (UTC)

Sorry, I kill them as soon as I see them. Seeing that website, they actually look not at all like a silver fish. They're essentially a tear drop shape, and there's no visible antenna or legs. The colour I'd say is more of a Prussian blue meets Old Lavender. -- Zanimum 00:21, 21 December 2006 (UTC)

That bug site is great! The profiled sow bug was also from Toronto and had also invaded. [21] --Zeizmic 01:52, 21 December 2006 (UTC)

Pantheon building maintenance ?

Template:Strict ({{strict}} template added for demonstration purposes only.)

Question reposted from Humanities:

How can a building with a large hole in the top be practical ? I'm assuming it's completely open to the outside air, although, with modern technology, it could be closed off with a window. There are several issues I would think having a large hole in the dome would cause, how are each of these addressed ?

• Water damage from rain. StuRat 00:59, 21 December 2006 (UTC)

• Sun damage from UV light. StuRat 00:59, 21 December 2006 (UTC)

• Birds and flying insects living in the building. StuRat 00:59, 21 December 2006 (UTC)

• Temperature control. StuRat 00:59, 21 December 2006 (UTC)

The interior is concrete (the upper part) and marble, and will suffer very little from rain and sunlight. Rome is not a very rainy city anyway, but rain will only reach the floor, and there are little holes all around the middle to drain any rain water. Rome has a mild climate and is also rarely very cold (the average low in the coldest month is 5 Celsius), and when it is hot the oculus actually helps.

I see. How do they handle birds and flying insects ? StuRat 19:50, 21 December 2006 (UTC)

5 C average isn't cold? Are you insane? When it reaches 10 degrees C here I think it's cold... :-P Nil Einne 11:37, 22 December 2006 (UTC)

Insects would get in anyway through the "front door". I see birds (pigeons, starlings) all the time in large public buildings, like train stations and shopping malls; here, if they get in, at least they'd know how to get out again.  --Lambiam^Talk 21:19, 21 December 2006 (UTC)

While some can get in anyway, it seems like the problem would be much worse with a giant hole in the roof. StuRat 16:08, 23 December 2006 (UTC)

Melons

How are seedless watermelons grown? Crisco 1492 01:38, 21 December 2006 (UTC)

Have you read the article seedless fruit? Anchoress 01:45, 21 December 2006 (UTC)

That would do it. I just searched specifically for melons. Crisco 1492 07:48, 21 December 2006 (UTC)

tension in a rope

If the two ends of a rope in equilibrium are pulled with forces of equal magnitude and opposite direction, why is the total tension in the rope not zero? -Sruthi

A homework question? Remember that Tension involves internal forces. --Wjbeaty 03:28, 21 December 2006 (UTC)

My high school physics teacher said that in a movie where barbarians rip a man in half by tieing him between 4 horses, they could do just as well with 2 horses and a fixed object. Maybe that will be helpful. Edison 05:59, 21 December 2006 (UTC)

Sruthi, imagine yourself in the position of Edison's man where you are being pulled in two directions with forces of equal magnitude. Though you are in equilibrium, would you not feel the tension and pain? :-). The tension in the rope would be zero if it is being pulled in just one direction by just one force, but then it wouldn't be in equilibrium. It would move in the direction of the force. -- WikiCheng | Talk 06:35, 21 December 2006 (UTC)

I think, though, that the objective of quartering someone is to rip them into four parts, not three. So two horses and two fixed objects is insufficient, although three horses and one fixed object would be (sufficient). But Edison, did you have had the same sadistic physics teacher that I had? Mine used the example of dangling one of the long-haired young women in the class from our second-story classroom window to illustrate tension -- sheesh! Atlant 12:35, 21 December 2006 (UTC)

The net force on the rope (or on any part of the rope) is zero, because the rope is in equilibrium. But the tension is not the same as the net force. The tension is the internal force in the rope (in either direction) that must exist in order to conform to Newton's third law - in other words, if you pull on a rope with force T, it pulls back on you with force T. Gandalf61 08:52, 21 December 2006 (UTC)

How can you tell if a gemstone is real?

Much help appreciated. 68.67.112.91 03:16, 21 December 2006 (UTC)

Well, Id think about the only way to be sure is to have it appraised by a jewller, or similar. Vespine 03:24, 21 December 2006 (UTC)

Well, what are things that the jeweler does that a layman can do? 68.67.112.91 03:47, 21 December 2006 (UTC)

According to Gullible.info: "Pearls will dissolve in vinegar, opals in chlorine bleach, and cubic zirconia in hydrogen peroxide." I guess you could try that, for starters. bibliomaniac15 03:58, 21 December 2006 (UTC)

Apart from pearls I don't think the above is right? Could the web sites name 'gullible' have anything to do with it?87.102.7.27 11:00, 21 December 2006 (UTC)

It all depends on what type of gem it is (or might be). Each gem is different (obviously) so different tests are usually needed to distinguish each type from likely imitations of that it. DMacks 04:01, 21 December 2006 (UTC)

If you have a good eye, you can generally just tell if something is valuable. It's no coincidence that precious gemstones refract light in pleasing ways. ←Vranak→

One test, for diamonds, is that they will scratch glass. There are some other things hard enough to scratch glass, too, but if your "diamond" won't, then it's not real. StuRat 07:59, 21 December 2006 (UTC)

Of course it also depends on what you mean by real. A number of gemstones can now be produced artificially with such a quality that they are difficult if not impossible to distinguish from 'natural' gemstones. Indeed, I recall a programm quite a while back where the people claimed they could produce rubies just like 'natural' rubies. The only reason you could tell them apart was because these people chose to put some sort of UV reactive dye I believe. Similarly there was an article in New Scientist I think sometime the last year or two where it was mentioned that the only reason someone was able to tell the gemstone was artificial was because it was too perfect. I think it was diamond which agrees with this link I found [22]. Point being, if by real you mean natural, it's getting increasingly difficult to tell the difference Nil Einne 13:51, 21 December 2006 (UTC)

Yes, diamonds, for example, can be made out of coal. (In fact, they are nothing else than a form of carbon) With high enough pressure and temperature, they can be created artificially. Maybe that's the way how the natural ones were formed a few million years ago. --V. Szabolcs 16:34, 21 December 2006 (UTC)

Did somebody say Occam? ←Vranak→

Different diffraction implies different material. Mr.K. 21:44, 21 December 2006 (UTC)

Somepeople can tell what a gemstone is just by looking at it, maybe with the aid of a loupe (magnifying glass), clearly a jeweller will not use a destructive test to check a gemstone. The tests I am aware of rely on refraction - measure the refractive index, and spectrum - measure the color spectrum of the gem. Other forms of spectroscopy can also be used - such as infra-red spectroscopy. The results no doubt are compared with known values for specific types of gem.. A gem dealer or jeweler will probably have the equipment to do this in the 'back room'.87.102.11.80 13:41, 22 December 2006 (UTC)

As User:Vranak says "If you have a good eye, you can generally just tell if something is valuable." - there's no real need for the above tests I mentioned.. though they can be useful in grading a gem for quality or certificating them.87.102.11.80 13:44, 22 December 2006 (UTC)

Craft

If I built a craft that had a balloon that gave the craft lift(but not all of it to reduce ballon size) and I had engines capable of producing 300 pounds of thrust and the craft wieghed around 300 pounds what is the smallest the balloon can be?72.147.86.89 05:04, 21 December 2006 (UTC)

If the weight, including engine and payload, is W, you need a total upwards thrust of more than W for lift-off. If the upwards thrust of the engines equals T, and T is less than W, you need an additional amount exceeding W−T to be supplied by the balloon. The data you give (W is around 300 lbf, T = 300 lbf) is not sufficient to determine if you need any additional lift at all, and if so how much. Using the metric unit of kgf (where 300 lbf = 136 kgf), it is the case that for a helium balloon you get about 1 kgf of lift for every cubic metre. So if, for example, W = 150 kgf, you need a balloon of 14 m³ (or actually a bit larger because that is just on the border, and there is also the (small) weight of the balloon itself). That is about the volume of a sphere whose diameter is 3 metre.  --Lambiam^Talk 09:40, 21 December 2006 (UTC)

I Like that answer thank you.

Query if the lift needed is 150kg and I get 1kg lift per cubic meter - don't I need 150m³ balloon?87.102.11.80 13:36, 22 December 2006 (UTC)

No, because that 14 meter cubed is only giving me part of the lift while my 300 pound thrust engines are giving me the rest. I have mislabled lift it is actually buyancy that the ballon is giving be.208.61.154.198 21:21, 22 December 2006 (UTC)

The darkest hour is just before dawn.

Is there any truth in this statement. It would seem more likely that the darkest hour would be at the midpoint between sunset and sunrise. Is there a scientific explanation that would make this clear.

davidwinkelaar

I believe that night, between maybe an hour after sunset and maybe an hour before dawn, is of equal darkness, except that the position of the Moon may also have an effect. The saying means "things seem the worst right before they get better". StuRat 07:51, 21 December 2006 (UTC)

Yeah. It's a statement of psychology, I'd say. It isn't really any darker just before dawn, but it's been dark for a long time, and you're getting tired of it. --Anonymous, December 21, 08:26 (UTC)

I largely agree with StuRat except to point out it's more complicated then just the moon. Obviously stars can have an effect. Most stars are obviously in a fairly constant position in one day but planet's especially, like Venus do vary. Obviously this pales in comparison to the moon but if the moon isn't visible it could arguable have enough effect. More importantly though, cloud cover can obviously very significantly affect how dark it is. Obviously this depending on the weather, not the time of day but it's an important factor to consider. And the level of ambient light will probably vary depending on the time of night if you're in a urbanised area. Even if you can't necessarily see many lights, anyone interested in star gazing will probably know how much light 'pollution' there is in cities (obviously atmospheric pollution is another factor) . Of course, a lot of this is fairly constant but in residential areas especially, there will be a difference depending on the time of night. So in conclusion, when it's the darkest depends on a lot of factors so it's difficult to actual say. The statement is simple a metaphor Nil Einne 10:08, 21 December 2006 (UTC)

You are right, the statement is wrong - the darkest hour is indeed halfway between sunset and sunrise (excluding the moon). The coldest hours are just before dawn however. I agree with the above posters that the statement only makes sense as a metaphor. If it was used as a scientific statement it is just wrong.87.102.22.58 11:18, 21 December 2006 (UTC)

I've spent many days outside at dawn this year, and while it is most certainly coldest right before dawn, I haven't noticed any trend in the photon department. Vranak 16:44, 21 December 2006 (UTC)

I think the darkest hour is the hour before dawn (or rather, the hour before astronomical twilight). By that time, most people would have gone to sleep and turned off their lights, reducing light pollution. You might think light pollution doesn't have a large effect on sky brightness, but in large cities it has a much larger effect than even the Moon.

By the way, the Sun doesn't affect the sky anymore after astronomical twilight. It doesn't matter if it's 19 degrees below the horizon or 53 degrees below; it's set too far to matter. --Bowlhover 17:06, 21 December 2006 (UTC)

Are you sure about this? Here in the northern hemisphere, I notice that the sky still retains a slight azure tint throughout cloudless summer nights -- but during the winter, not so much. →Vranak←

In my area (Toronto), the sky is always bright blue, even in the dead of night. I think this is due to light pollution, since the sky was completely dark when I visited the Dominican Republic (which doesn't have as many city lights).

Although the Moon does affect sky brightness, the stars and planets have a negligible effect. Even the Milky Way, the zodiacal light, and the [[gegenschein] contribute more to sky glow. --Bowlhover 04:44, 22 December 2006 (UTC)

I guess the key question is in the absence of the moon (as I mentioned), light polution (i.e. in a very rural area), the zodiacal light (which AFAIK doesn't occur in equtorial regions so this isn't that uncommon) whether the stars and planets will still have a neglible effect Nil Einne 05:16, 22 December 2006 (UTC)

I am aware of the metaphorical meaning of the statement. Also, the moon, stars, city lights, cloud cover, etc. are all variable and would all have an impact on a given day. Living in the northern hemisphere, latitude 54, I am also aware that the sky in the summer can glow long after sunset, and begin to glow long before sunrise, even on a cloudless day, but if we could eleminate the effects of all these and other variables, I was wondering if there could be some scientific reason I am not aware of for the literal meaning of the statement. [davidwinkelaar]

The saying is perfectly true for humans, and refers to what we see, not to the optical instrument measurement of light levels. It describes our experience, not the reality of that which is outside of ourselves. Given constant low light levels through the night, humans see less just before dawn. Reason: Due to a diurnal cyclic changes, the threshold for discrimination is at its highest just before dawn, meaning it takes more light to trigger the optic system. Therefore it seems darkest. See this article:Visual resolution in humans fluctuates over the 24 h period. Remember high threshold = low sensitivity. Possible problem: Given the very high levels of light contamination in Northern hemisphere countries (see The World Atlas of the Artificial Night Sky Brightness, especially the detailed maps), it may be that a present day citizen of those coutries would never in his life discover this basic fact which has been known to humans for millenia. --Seejyb 09:45, 22 December 2006 (UTC)

Yes - that would be great - if it were true - but it starts to get brighter hours before dawn. Which people can see, with their eyes..87.102.11.80 12:33, 22 December 2006 (UTC)

Plus 'visual resolution' means the accuracy with with you can see - it doesn't mean 'light sensistivity'.87.102.11.80 12:36, 22 December 2006 (UTC)

Water and Sodium Electric Power

I'll appreciate to receive information about water and sodium can make electric power. It's related to fuel cells. Thank you

Don't know much about this but fuel cell has a list of which Direct borohydride fuel cell and Molten-carbonate fuel cell may be of interest. I don't think anyone has ever suggested elemental sodium be used for a fuel cell. I don't think this would be a good idea somehow. If you're interested in what happens when you mix sodium and water, take a look at this link [23] which has a bunch of videos such as [24] (although as far as I know the skipping behaviour has been observed and was known about long before this experiment) Nil Einne 10:45, 21 December 2006 (UTC)

It's simple - simply connect a sodium rod to a wire, connect another wire to another elctrode (copper or iron would do), connect the two wires to a load eg lightbulb/ dc motor etc and then put both the wires in water - it's an electrochemical cell - however from the above posts you can see that this is not a safe thing to do.

The electrode reactions would be...

Na >> Na+ + e-     2e- + 2H20 >> H2 (gas) +2OH-

Sodium is a very reactive metal - the "sodium rod" would not make a particularly good electrode. The half cell reactions would proceed quite fast. In a fuel cell, you typically want slow, sustained reactions. --HappyCamper 12:20, 21 December 2006 (UTC)

Yeah like the videos I linked to above so. Not something you would want for a fuel cell IMHO :-P Nil Einne 11:47, 22 December 2006 (UTC)

I found Molten salt battery and a molten pure sodium battery. [25] No such fuel cells though. --Zeizmic 14:13, 21 December 2006 (UTC)

My guess is that Nil Einne's answer is what the questioner was asking about, and possibly for a public relations reason. In the DaimlerChrysler article about their minibus, they use the phrase "...the minivan, which runs on salt and water,..." This may well become the popular concept of what a sodium borohydride fuel cell is. Calling the thing "Natrium" makes this even more likely. Is this then a PR job: homely, simple, "obviously safe", making it more man in the street friendly? --Seejyb 20:59, 21 December 2006 (UTC)

Actually I don't really know whether calling the thing natrium or sodium would be better. What happens when videos of sodium explosions start propping up and people don't understand the difference? I do think saying the thing runs on salt is a bit misleading, since sodium borohydride isn't what people think of when you talk about salt and I wouldn't want someone using it instead of normal table salt... But I guess that doesn't stop companies using it :-P Nil Einne 11:43, 22 December 2006 (UTC)

Papular Mucinosis

Papular Mucinosis

Any extra information on this condition would be greatly appreciated.

Wikipedia does not yet have usable information. You can look for "Lichen Myxedematosus" on the web. The sites rarediseases.about.com and www.emedicine.com are places to start. The former is much easier to understand than the latter (for which you may have to look up every third word:-)). --Seejyb 22:34, 21 December 2006 (UTC)

Vacuum balloon

Is there a material which is strong enough that a hollow sphere (or other form) of it can be evacuated without collapsing, yet light enough that with a vacuum inside it, the average density of the structure becomes less than that of air, and therefore it floats? Laïka 14:58, 21 December 2006 (UTC)

Great question. I saw a poster in FSU's physics building that discussed assembling a lot of long, thin balloons into a cylinder, covering the ends, then evacuating the center of the cylinder. They had all these fancy equilibrium equations that proved it could work, and I think someone had already built one. Unfortunately I can't find any mention of it with Google, because I can't think of any good keywords. —Keenan Pepper 15:36, 21 December 2006 (UTC)

http://www.freepatentsonline.com/4534525.html seems to involve something like it. —Keenan Pepper 15:39, 21 December 2006 (UTC)

Well if the thickness is t (the density of the substance d) and radius is r the mass of the sphere is 4πr²td, and the volume 4/3 πr³. The density is of air 1.2 kg/m3, so the thickness must be given by

4πr²dt = 4/3 πr³ x 1.2

dt = 1.2r/3

t = 1.2r/(3d) (or less) (in SI units d is in units of kg/m3)

Now all you need is the thickness of a given solid capable of not breaking under a pressure of ~10⁵ Pa (Nm^-2)... Maybe someone else can help here.87.102.22.58 16:16, 21 December 2006 (UTC)

Also if S is the force a planar sheet of a material can support without breaking there is the relationsip (note S is the maximum tensile or compressive load)

S = Pr where P is the pressure, and r is the radius of curvature of the sphere.

So if S is proportional to t the thickness we get: (S=kt)

S/k =t and t <= 1.2r/(3d)

Pr/k <= 1.2r/(3d)

3Pd/k <= 1.2

3Pd/1.2 <= k

So we need a material that has k (the ratio of breaking force to a given thickness "Newtons per meter") that is greater than 3Pd/1.2 = 250,000d where d is the density (in kgcm^-3).

Can anyone supply this figure for different substances?87.102.22.58 16:54, 21 December 2006 (UTC)

I think we can safely assume that a sphere is the optimal shape since it would enclose the most vacuum (can you enclose nothingness?) for the least surface area (so weight of surface material). Plus, its uniform shape would best withstand the compressive forces of the outside atmosphere.

Still, my engineering gut feel suggests there's no material yet that's strong enough, although I'd bet that a carbon composite material comes close, and I'd love to be proven wrong just for the fun of seeing a practical device.

Atlant 16:57, 21 December 2006 (UTC)

I think I made a mistake in the above relating force required to support a spherical arch - I've corrected that now.

Given that k is the ration of the maximum tensile strength to thickness k will be the yield strength eg for glass ~4000MPa, steel ~400MPa,

So 3.10⁵6000(density steel)1.2=1,500,000,000Pa (1,500MPa>400MPa not strong enough)

and 3.10⁵4000(density steel)1.2=1000,000,000Pa (1000MPa<4000MPa strong enough)

So it looks like (in my simplification) that a glass sphere would be strong enough - but not a steel one. (I can't guarantee I haven't made a mistake here - the equations I have used don't take into account the change from tensile load to compressive load as one goes from outside the sphere to inside..double correction - the load is all compressive unless the sphere deforms..)

But it looks to me a the strength to weight ratio of a glass (and by extension a ceramic such as alumina) is great enough to hold back the pressures inside a sphere containing a vacuum of sufficient size to make the overall thing big enough to float.87.102.22.58 17:33, 21 December 2006 (UTC)

However actually making such a thing is another thing...87.102.22.58 17:34, 21 December 2006 (UTC)

There seems to be a lot of discussion on this, found with Google. From my engineering perspective, the structural forces are huge, and you have very little lift force. You can see from the typical construction of a bell jar (sad article), that glass has to be very thick, and a steel vacuum chamber is also very heavy. --Zeizmic 17:53, 21 December 2006 (UTC)

yes bell jars are thick (1cm to 1inch) but much thinner glass vessels will support vacuums - provided there are no hairline cracks! - a big factor in the thickness of bell jars is pure safety.87.102.22.58 18:03, 21 December 2006 (UTC)

I agree that bell jars are 'overbuilt'. I pull hard vacuum on regular lab vials all the time and I've never had one break. ike9898 18:22, 21 December 2006 (UTC)

Agree about the forces - using the method above the thickness seems to be 0.1/(yield strength in MPa) times radius - so for a 1m glass balloon the thickness will be 0.1/4000 m = 0.025mm - quite thin! (but not impossible!!)87.102.22.58 18:00, 21 December 2006 (UTC)

The implosion of an evacuated glass balloon would be a wonderful thing to see, but I would not want to be riding in its basket! Still, this is a wonderful example of Ref Desk at work: to run the calcs and compare the required material properties with the existing. Thre would have to be a safety factor, so that the strength would need to be some multiple of the calculated minimum. Edison 19:19, 21 December 2006 (UTC)

As an aside I can't help thinking of blowing a bubble of 'bubble gum' - made of a polymer that cross links when exposed to uv light - when the bubble is big enough - turn on the uv - to cross link and harden - then evacuate...83.100.255.234 19:23, 21 December 2006 (UTC)

But that ex-post-facto evacuation will be problematic; one of the many reason's you'll need Edison's safety margin is that the omphalos from which you evacuate the sphere will be a point where implosion stress accumulates.

Atlant 14:02, 22 December 2006 (UTC)

The join between the sphere and the inlet could easily be specifically strengthened - it would only contribute a miniscule amount to the total mass if the balloon is 1cubic meter, and the 'evacuation pipe' is say 0.5cm.. (Thanks for saying omphalos by the way)87.102.11.80 15:10, 22 December 2006 (UTC)

(You're welcome. How often does one get a chance to use that word, ehh ;-) ? Atlant 19:28, 22 December 2006 (UTC))

Rather than discuss if it's possible, let me assume that it is, and instead discuss if it's desirable. That is, would such a device have a superior lift per volume than a similar-volume balloon, filled with hydrogen or helium, floating in air.

Air = 1.293  g/L
He  = 0.1785 g/L
H   = 0.089  g/L

Helium has a density of 14% of air and hydrogen has a density of 7% of air. So, the best improvement you could hope to make on lift is 14% (16%, technically) relative to a helium balloon and 7% (8%, technically) relative to a hydrogen balloon. I don't see any possibility of creating a pressure structure adequate to withstand normal air pressure for less than a 16% weight gain. So, it's a completely impractical way to proceed. StuRat 19:34, 21 December 2006 (UTC)

Is everybody just ignoring what I said? You stick a bunch of inflated balloons together, then evacuate the hollow space between the balloons. It's the only good way to do it. StuRat, you're ignoring that helium costs money. —Keenan Pepper 02:32, 22 December 2006 (UTC)

But how would you evacuate the air without making the balloons' skins stick to each other? About the cost of helium: it's pretty cheap, but is it cheaper than making a container that can withstand vacuum? Considering what the other users said about using a thin layer of glass, I really don't know. --Bowlhover 05:04, 22 December 2006 (UTC)

The poster just asked if it were possible - not for a cost analysis.. (By the way no way will "You stick a bunch of inflated balloons together, then evacuate the hollow space between the balloons" ever work - unless I have greatly misunderstood.87.102.11.80 12:42, 22 December 2006 (UTC)

Bowlhover, the balloons are wedged tightly together, and the vacuum is helping to keep them together. 87.102.11.80, what do you think will happen? —Keenan Pepper 22:41, 22 December 2006 (UTC)

I don't understand. If the balloons are together, that means there's no vacuum. --Bowlhover 02:06, 23 December 2006 (UTC)

Come on, think a little harder. Say there are ten long, thin balloons arranged in a cylinder. Balloon number one is touching balloon number two, but balloon number one is not touching balloon number three. There's a big hollow space in the middle, which can be sealed off with two end caps, and it's not going to implode if you suck the air out of it. The system is in mechanical equilibrium, and the overall density is less than that of air. —Keenan Pepper 04:44, 23 December 2006 (UTC)

If you try to evacuate such a space the balloons would just expand inwards to fill it. Think about a balloon in a bell jar - when the pressure is decreased the balloon expands.87.102.4.34 10:35, 23 December 2006 (UTC)

Evolutionary Biology perspectives on Fear of Speaking in Public

In the past years I've been amazed at how so many of the strange social behaviors and feelings of humans and other animals have been explained so well by evolutionary biology.

My question is -- has anyone heard of an evolutionary explanation for the very prevalent phobia of public speaking (glossophobia)? Wikipedia says that 75% of people have some sort of fear of public speaking -- yet, my intuition tells me that being able to comfortably speak in front of a group would greatly improve one's chance of gaining a mate. Why the disconnect? Why are so many brains afraid of something so socially beneficial?

Thanks in advance for any answers, theories, ideas! -Quasipalm 19:38, 21 December 2006 (UTC)

I have studied evolutionary strategies extensively, as well as the human condition. Although it may be human vanity that leads us to draw a line between ourselves and 'the animals', this distinction is not altogether a bad one to hold.

Human society is much more complex and convoluted than animal colonies, so it's not always a good idea to apply methodologies used to study the latter to the former.

In layman's terms: us humans are a relatively messed-up bunch. Fear of speaking in front of others is more a reflection of that, than features inherited through evolution, I think.

Caveat: When I say 'us humans', I can and only should speak for the society I'm most familiar with: Anglo-North American. ←Vranak→

Speaking in front of a group puts one in the focal point of atention. This is not a spot a lot of people want to be in. You are screaming hey, look at me I'm important listen! In a sense you are placing yourself above the others since they are supposed to listen to you. now this isn't a big problem with small groups of people or people you know. It gets iffy when you need to speak to a group of strangers. Imagine being a prehistoric human meeting a strange tribe. Would you wnat to draw atention to yourself? Heck no, you want to get the heck outa there.

Not to mention the fear that you might fail. You might get ridiculed or worse. Otherwise I can't really think of anything else right now. 62.194.89.68 20:38, 21 December 2006 (UTC)

"Blending in" is an excellent survival strategy. Until recently, an invading army would often execute all opposing "public figures", but leave the bulk of the population alive. So, speaking in public and thus becoming a public figure, was not the best survival strategy. Also, speaking in public when you said something that people disagreed with would often get you killed, as well. Keeping your opinions to yourself can help to keep your head on your shoulders: "Swear allegiance to the flag, whatever flag they offer, never hint at what you really feel." - Silent Running - Mike and the Mechanics. StuRat 20:56, 21 December 2006 (UTC)

Whatever the theory, it would have to be based on genetics, with a reasonable correlation between a fear of public speaking and an increased rate of reproduction. That seems rather unlikely to me. Less tenuous may be that an appropriate fear of failure may lead to an increase in survival and reproductive efficiency. Could it be that 75% of persons get appropriate and inappropriate fear "mixed up", as Vranak suggested, and that this inappropriate fear is determined to a large extent by upbringing, education and environment, not by your evolutionary biology? Then again it may be that inappropriate fear is indeed a characteristic that improves survival and reproductive rate, so that fear of public speaking is but a manifestation of this irrationality that may have evolutionary advantages. --Seejyb 22:23, 21 December 2006 (UTC)

Just a thought, fear of public speaking = fear of rejection, by peers and possible mates, this whould certianly have serious consequences on one's reporductive fitness. --Cody.Pope 22:35, 21 December 2006 (UTC)

This seems like a rather complex phenomena, some mixture of generic fear and things of that nature. I too am skeptical that there could be a good evolutionary explanation that wasn't just a just-so story. --24.147.86.187 23:35, 21 December 2006 (UTC)

I guess I would rephrase my question as performance anxiety rather than just fear of public speaking. I've read up on it and the fear many (most) people experience when speaking in public is often cited as a fight-or-flight response. Including the release of adrenalin, increased heart and lung action, etc. That's what got me thinking of the causes of a response and evolution. It seemed strange to me that standing in front of a crowd and speaking would illicit such a response. Overall these are very thought provoking responses everyone! -Quasipalm 00:26, 22 December 2006 (UTC)

Well the "fight or flight" response is a general response to stressful situations and for the reasons described above, it is a stressful situation. Perhaps the name is confusing you, althought it's called that, don't assume your response must be to literally fight or flee, especially given the complexities of human social interactions. Of course you are fighting in a way. Speaking in public can be taught of as a form of "fighting". The alternative is "flight" i.e. don't take part. At a guess, I would say quite a number of people, especially teens exhibit the same response in response to infatuations but again, it's not fighting literally but pursuing the infactuation is a form of fighting (e.g. calling the person, asking the person out on a date etc) Nil Einne 05:11, 22 December 2006 (UTC)

You talk of fear and anxiety but let’s not forget quite a few people actually get a big kick out of it (is it adrenalin?) some I’m sure to the point of a form of addiction. Keria 11:17, 22 December 2006 (UTC)

"Stable" Hydrogen?

This is purely a construct; I need a bit of "pseudo science" for a book plot:

Is there a plausible chemical method to render hydrogen less reactive? I'm looking for a cheaper alternative to helium to use as a lifting gas for giant blimps, "cities in the sky" etc., but without the dangerous flammability of hydrogen. Yes, I know it isn't actually possible, what I want is a plausible lie. The plot may connect the substance to a search for a safer way to store and transport hydrogen for the coming "hydrogen economy," so spending a few megabucks in research would be plausible.

It seems to me that, as carbon can form stable forms via co-bonding with other carbon atoms, so, perhaps, "stable hydrogen" might be formed by similar hydrogen-hydrogen bonds? The result would be a diatomic molecule, functionally similar to monatomic helium, but without the messy nuclear fusion reaction needed to create real helium.

Any ideas?

Well, it's completely nonflammable in the absence of oxygen, so why not use that ? You could also have it mixed with some gas, like Halon, which bonds with any free oxygen it finds. StuRat 19:53, 21 December 2006 (UTC)

A couple of minor nitpicks. The Halons don't bond with free oxygen; rather, they quench radicals that are generated as part of the burning process (species like H· and ·OH) which normally perpetuate the combustion reaction. Bear in mind that adding Halon in sufficient quantities to prevent combustion (typically about 5% by volume) will totally blow the buoyancy benefit you got from using hydrogen.

That said, might you be able to get away with a double-envelope design? Make the bulk of the envelope hydrogen, surround it with a layer of helium (or even fire suppressant of some sort) and add sensors to the outer envelope to detect hydrogen. Again, it's a question of whether or not the extra envelope weight blows the buoyancy benefit of hydrogen. (Of course, if I'm holding up a city then I'd want the balloon to have double walls and lots of compartments anyway....)

Or, for floating cities, get rid of the lifting gas entirely. Suspend the whole thing on carbon nanotube cables (see skyhook (structure) for various related principles).

It all depends on how far in the future you want to set this, and which sorts of techniques might make useful plot devices. :D TenOfAllTrades(talk) 20:14, 21 December 2006 (UTC)

Thanks for ideas so far, but we're moving too far afield. I'm not looking for plot devices, just a stable form of hydrogen. Any chemists out there?

I do not see stable hydrogen being easy to make in plausible way, but you do have the claims of cold fusion to work with, i.e. it produces helium (and energy) from hydrogen at low temperatures in the appropriate circumstances. You have a reasonable literature on the possibility of such processes already, and you are not bound by the need for real life observations to develop it further. Such a process may be modified specifically for helium production, with energy as merely a beneficial byproduct. --Seejyb 21:56, 21 December 2006 (UTC)

"The University of Queensland, Australia, has just spun off a company to manufacture a new storage medium for hydrogen, using magnesium allows (sic) with a sponge-like nanostructure"[26] So perhaps some nano-engineered metal-hydride sponge structure that allows an unprecedented packing efficiency. Use for example palladium[27], which might be doped with rare earth metals.  --Lambiam^Talk 23:09, 21 December 2006 (UTC)

Lets call it Aerogel but from metal. Acting like the copper net used for miners lamps to make it impossible that the fire goes through the net, because the heat is absorbed so fast that the flame deminishes. This small metal bubles are filled with hydrogen and its like building a wooden raft you simply take a few m3 of this airfloating material and you stand on it. Take several km3 and build your city in the sky!--Stone 23:17, 21 December 2006 (UTC)

Regarding the diatomic hydrogen being stable, hydrogen already exists as H₂, which is presumably what hydrogen balloons used, so that wouldn't be the answer. 80.169.64.22 11:45, 22 December 2006 (UTC)

H₂ is stable - but burns/explodes with air - eg Hindenberg disaster.87.102.11.80 13:29, 22 December 2006 (UTC)

I would suggest if you going to use psuedo science why not go the whole hog and totally make up a new element.87.102.11.80 13:29, 22 December 2006 (UTC)

Two suggestions 1) A Device that disables the ability of the hydrogen to form chemical bonds. 2) A Device that fills the blimp with free electrons. The electrons natural repulsion would fill the blimp, and the electrons have even less mass than Hydrogen. The blimp material would have to be a non conductor, and/or the device would have to be able to repentish the electrons as fast as they bleed away. Of course, the fire hazard would be replaced by danger of electrocution. Jokem 14:53, 22 December 2006 (UTC)

I don't know about anyone else, but I personally hate science fiction writers who give "scientific" explanations which are demonstably wrong (with current scientific knowledge). It's sort of an uncanny valley type of effect. I have no issue with science fiction devices and explanations which are theoretically possible but not yet feasible (e.g. space elevator) and even those which the theoretical possiblity is still debatable (wormholes, time travel). On the other side, I can completely except and enjoy science fantasy and even fantasy writing where the author deliberately ignores physical reality and just waves his hands about explanations. What really annoys me is those authors who want to have it both ways -- make up devices that we know *can't* exist, and then make up some pseudoscientific explanation, flaunting the fact that they've read A brief history of time (but probably not understood much of it). Unfortunately, as I understand it, simultaneously non-flammable and buoyant hydrogen is something current science "knows" can't exist. Sure there are some theories like Blacklight Power's hydrinos, but those are pretty universally held to be quackery. My suggestion to you is to go the Science Fantasy route -- wave your hands. E.g.:

Naive Farm-Planet Raised Protagonist: "They're filled with hydrogen? Isn't that dangerous?"

Knowledgeable City Dweller, Who Takes the Protagonist Under His Wing: "Not at all. They call it 'The Soltero Process.' You have to be a Fifth-Level Quantum Physicist to understand the math, but it renders hydrogen completely safe."

You can thus "explain" why hydrogen doesn't react, but not have the explanation be grating to someone who is more knowledgeable on the topic than you are. -- 16:23, 22 December 2006 (UTC)

Of course, in a science fiction setting, Helium should be cheap. It is the second most common element in the universe ... WilyD 17:44, 22 December 2006 (UTC)

You could say that because it's the future, there are materials strong enough to make a vacuum balloon (see two posts above). This would be both incredibly safe (you can't set fire to a vacuum!) and fairly cheap (assuming it's the future, some sort of carbon fibre, which could be made from just about anything, would be a lot cheaper than hard to get helium). Laïka 18:47, 22 December 2006 (UTC)

EE - Why do fast battery chargers have larger power bricks?

I was looking into rechargable NiMH AA and AAA batteries. I noticed that the faster the charger, the larger the "power brick" needed for the unit. "Slow" chargers (4-8 hours) don't even use power bricks. But 60 min charger use a medium sized brick and 15 min chargers use huge bricks that are larger than the actual charger. Why is this? --24.249.108.133 22:56, 21 December 2006 (UTC)

An interesting observation. Most likely because it takes more watts and more amps to charge the batteries to the same volt-amp rating in a shorter time. This requires bigger wire in the transformer windings to limit voltage drop and heating of the conductor, as well as a larger cross section in the iron laminations of the transformer core to prevent saturation of the metal. Edison 00:29, 22 December 2006 (UTC)

I also noticed this when I worked in a power tool shop. Cordless tools follow a similar pattern, the crappy chargers are small no frills type things while the super duper fast chargers are quite large and fancy. I don't know the details but the fancy super fast chargers actually have quite a lot of circuitry in them, I always guessed to monitor temperature and voltage and vary the input for the optimum effect. Vespine 03:08, 22 December 2006 (UTC)

The problem is likely to be that as charging time decreases, current increases in inverse proportion, e.g. from a 60min to a 20min charger, the current has to triple. But, according to Joule's law, heat production increases exponentially with current, i.e. by the square of the current. So in our example we would have nine times the heat production, and have to build the transformer correspondingly more robust. For the slowest and quickest of the chargers you described, the difference in heat production is (24x24) 576 fold .--Seejyb 11:17, 22 December 2006 (UTC)

Listing of AC power cord plugs?

While I found Electrical_plug very useful, I'm also looking for a list of the female ends of AC power cords. There seem to be two popular styles in the USA. There is the triangular three hole used to power computers, monitors, Xbox360 and other high-draw equipment. And there is the two hole type used to power VCRs, DVD players, and other consumer electronics (some are rounded on the left and the right while others are squared off on one side). What are their official names? --24.249.108.133 23:11, 21 December 2006 (UTC)

Aren't these just the "Type A" and "Type B" North American ones described on that Electrical plug page? Those descriptions refer to the NEMA connector page, where you can learn about the different specific designations of them. DMacks 23:44, 21 December 2006 (UTC)

I know what you mean - see IEC connector - was I right?87.102.22.65 02:26, 22 December 2006 (UTC)

You are surely correct; there are several styles of "IEC Inlet Connectors" depending on the amount of current and the need (or not) for a safety ground/earth connection. These are worldwide standards and make it easier for the manufacturer to sell their equipment anywhere in the world, simply by exchanging the power cords (and assuming, of course, the ability to work with both "120" and "240" volt power).

Atlant 14:10, 22 December 2006 (UTC)

Spot on! Thank yo very much! --24.249.108.133 22:15, 22 December 2006 (UTC)

black holes

black holes are theorized to form from neeutron stars right. so when a neutron star collapses onitself it slows light down more and more until bam it can escape, so would a black hole apear to be a neutron star, based on the same theory that makes it apear as tho an object goin into a black hole issuspended in space. iwould appreciate someone giving their thoughts on this because i dont know enough fysics yet but am doin a paper on them. --69.140.210.163 02:30, 22 December 2006 (UTC)

Once I figured out what you were saying it seems exactly right. Quote from the article Black hole:

Such objects for a while were called frozen stars since the collapse would be observed to rapidly slow down and become heavily redshifted near the Schwarzschild radius. The mathematics showed that an outside observer would see the surface of the star frozen in time at the instant where it crosses that radius. —Keenan Pepper 02:36, 22 December 2006 (UTC)

One correction. It doesn't slow light down, it just bends its path so it can't get out. Clarityfiend 04:28, 22 December 2006 (UTC)

In order for you to continue seeing something, photons have to keep hitting your eye. Those photons would normally be continuously emitted by the star, but that's not the case for black holes. It may be that the last light to escape the star would show you how it looked just before collapse, but that light would not remain visible for long. — BRIAN0918 • 2006-12-22 17:04Z

I recall my undergrad astronomy teacher saying that the "final image" you would see would eventually fade into blackness. That never made sense to me — I would expect it to be a sudden disapperance, as the light either could or could not cross the radius. But I am neither a physicist or an astronomer. --Fastfission 17:39, 22 December 2006 (UTC)

No, fade into blackness is correct. Basically, the "time dialation" you see for the object increases to infinity as it approaches the event horizon, and so you never see it cross the event horizon. But because time passes for the object very slowly (from your perspective) it releases less and less photons per second, and so gets dimmer and dimmer (plus increased gravitational redshifting makes it redder and redder. WilyD 17:42, 22 December 2006 (UTC)

Poseidon

Is the wave phenomenon used in the movie Poseidon real, and if so, what is its cause? I was watching the movie yesterday and the wave broke my suspension of disbelief because it seemed utterly impossible. I considered a tsunami, but the ship was too far out to see for that to have had an effect. Crisco 1492 03:00, 22 December 2006 (UTC)

It's real (although, not having seen the movie, I don't know how close the depicted wave was to real ones). See rogue waves, and its section on causes. --Anonymous, December 22, 2006, 03:22 (UTC).

If i remember well in the first movie the wave occured by a clear calm night and as such doesn't seem possible. Keria 11:08, 22 December 2006 (UTC)

Rogue waves can travel great distances, far from the storms that provoke them. Essentially, they are just the extremes of the stochastic processes that produce any ocean waves. IIRC, there was once a famous one that swept hikers off an oceanside cliff in Maine.

Atlant 14:21, 22 December 2006 (UTC)

The main believability problem I had with the wave scenario is that at sea, waves tend to have a very minor amplitude since they have a LOT of water to work with, and then when they come ashore the full strength of the surge is realized as water gets shallow and the energy becomes concentrated. I am no environmental scientist, but I really doubt a several hundred foot high wave can exist for more than a mile or two out at sea before it flattens dramatically. --66.195.232.121 16:07, 22 December 2006 (UTC)

66.195.232.121 is correct. Tsunamis and other waves in the deep ocean do not have large amplitudes at the surface; this occurs near land when the water bottom shallows. Geologyguy 16:22, 22 December 2006 (UTC)

Read the article. --Anon, Dec. 22, 18:30 (UTC).

RTFA? (Read the fucking article?) X [Mac Davis] (DESK|How's my driving?) 01:42, 23 December 2006 (UTC)

The wave occurs on a clear night, like the original. And, having read the article, I'm still confused. It seems beyond the realm of possibility for said wave to occur, although if they've been tracked scientifically, it may be true. I personally don't think too many people are aware of the Rogue wave phenomenon, and as such, most critical viewers would lost said suspension of disbelief. Crisco 1492 23:30, 22 December 2006 (UTC)

Until they see the evidence! We have a few satellites that have tracked them, I bet you can find sites in the ex links. X [Mac Davis] (DESK|How's my driving?) 01:42, 23 December 2006 (UTC)

This site has a nice pic of an approximately 25 meter (81 foot) high rogue waves breaking over the deck of an oil freighter: [28]. StuRat 15:57, 23 December 2006 (UTC)

Solar system and stardust

Where did it come from. If we are all made of stardust, which star?--Light current 04:57, 22 December 2006 (UTC)

I think Timeline of the Big Bang and Big Bang should provide your answers Nil Einne 05:03, 22 December 2006 (UTC)

If any star contributed to the nebula that formed the solar system, it probably contributed by adding supernova debris. Any star that went through a supernova is dead, and therefore not a star anymore. --Bowlhover 05:15, 22 December 2006 (UTC)

The sun is at least a third generation star (based on the relative abundance of heavy elements), meaning that it is star that coalesced from material that had been mixed with supernova ejecta from previous stars that had in turn already been mixed from supernova ejecta of previous stars. Dragons flight 09:57, 22 December 2006 (UTC)

Yes so if were all made fronm the original nebula, both the sun and the planets were made from the same stuff?--Light current 15:38, 22 December 2006 (UTC)

The sun and planets originally formed from the same stuff, but over time, objects have bombarded the planets, adding new stuff. — BRIAN0918 • 2006-12-22 16:50Z

I would say both were, and are, made of the same stuff. However, the original mix was very heavily weighted towards hydrogen and helium, but most of this was lost from the planets, especially the terrestrial planets, as they have insufficient gravity to hold light elements in the atmosphere. Such elements tend to be blown away by the solar wind. Thus, free hydrogen and helium are now somewhat rare on the terrestrial planets. StuRat 15:51, 23 December 2006 (UTC)

The stellar population article tells that "As of 2006, no Population III stars have been found", meaning that original nucleosynthesis of elements heavier than helium, such as carbon and oxygen that form organic molecules is still a theory : We are stardust, but of virtual stars.

The fact that we cannot observe those stars or reproduce the exact condition prevailing when they were born does not mean that science requires acts of faith. It just means that some science facts are not in the reproductible paradigm, thanks G.D. -- DLL ^{.. T} 19:18, 22 December 2006 (UTC)

December 22

Electric Kettles

Just to clarify, by an electric kettle, I mean a device into which you pour water, turn it on, and then it boils the water and turns off automatically, not a device which maintains water near boiling point.

One day I wondered how a home-variety electric kettle knows when the water is boiling, so as to stop operating.

A few tests showed that (at least the four or five different kettles I tested, all of different brand and make) there is a small hole inside the kettle, near the top (above the maximum amount of water line), which is evidently intended for the steam produced by boiling the water.

I verified that assumption with the following three experiments.

Firstly, I removed the lid of the kettle, and started the boiling process, and waited. The kettle didn't stop heating the water even as it was boiling, and then almost immediately after closing the lid, the kettle shut down. I repeated this process several times to make sure it wasn't just chance that immediately after I replace the lid the kettle shut down.

The next experiment was to remove the lid of the kettle, and cover it, so that the small hole is outside the closed area. Again, several times, the kettle never stopped, until I removed the covering, and then closed the lid.

The final experiment was to cover the kettle in the same way as the previous experiment, except to include the hole in the closed space. This time, the kettle stopped by itself.

My conclusion is that the kettle's stopping mechanism relies on the small hole near the top of the device.

I raised three hypotheses as to what mechanism is actually used:

1. Testing conductivity - Air is very resistive, perhaps air with steam is a better conductor
2. Pressure - As the water is heated, steam is generated, increasing air-pressure inside the kettle
3. Temperature

The question is, what IS the mechanism? I haven't gone as far as taking apart a kettle, but I did try to find the answer on the web, and neither wikipedia nor HowStuffWorks had an answer, and web-searches gave only one answer, but the site in which it was seemed dubious.

--89.0.134.155 12:26, 22 December 2006 (UTC)

Just too say I too can confirm this experiment and believe the small hole to contain the 'mechanism'.87.102.11.80 12:46, 22 December 2006 (UTC)

I'm pretty sure mine works with a simple bleed-off pressure switch, the pressure build-up is similar to a whistling kettle. But I've looked everywhere and can't find anything definitive. If you go to Google Patents, you find every sort of mechanism that is possible. --Zeizmic 14:24, 22 December 2006 (UTC)

A suggestion for another experiment: put the nozzle of your hoover near the spout, and turn it on at the same time as the kettle. It should lower the pressure enough for a pressure switch not to work. What happened? yandman 15:29, 22 December 2006 (UTC)

THe most common method IMO, is a pressure trip mechanism attached to the on/off switch. You could test that simply by actrivating the on switch and blowing down the hole( keetle empty and disconnected). Souldnt take miuch presssure to trip it off.--Light current 15:44, 22 December 2006 (UTC)

OTOH, thinking about it more, after the steam has dipersed anand the kettle emptied, I cant get my kettle to switch on again. So in mine, it cant be pressure. It could be a bimetallic strip attached to the on/off switch--Light current 15:49, 22 December 2006 (UTC)

Coffee makers commonly and teakettles sometimes use a "Klixon" thermostat [29]. This is a small metal button with two Faston tabs that connect to the electrical circuits. In "drip style" coffee pots, the thermoswitch is set just above boiling point so when the main heating element runs dry, the switch heats above boiling and opens the electrical circuit to the main heater. A small heater in parallel with the thermostat now can operate, keeping the coffee in the caraffe warm. Hysteresis keeps the theromstat from re-closing until it has become quite cool (but it does cycle occasionally while the coffee is being kept warm). Percolators (and presumably, Light current's teakettle) use a slightly different scheme so the termostat can open before the water has boiled away but only after boiling has occurred for a given period of time, short for the tea kettle and longer for the percolator.

Atlant 16:05, 22 December 2006 (UTC)

Actually, I forgot to mention that I already did test blowing into the hole to see if it would trigger the switch, and it wasn't triggered, which points against the whole pressure idea.

But, thermostats seem unreliable for too - water's boiling point varies with air-pressure, and I haven't heard of special makes for people living in high altitudes (in which water boils at a measurably lower temperature, which may cause such thermostats never to trigger).

89.0.134.155 23:01, 22 December 2006 (UTC)

my friend took his broken kettle apart one day and said (hes an enigneer) theres a bimetallic strip in the switch that clicks it off —The preceding unsigned comment was added by 86.29.50.118 (talk) 01:00, 23 December 2006 (UTC).

All the recent (past 15 years) automatic kettles I've seen had this steam hole. The switch in a kettle which I converted from automatic to non-automatic was a bimetallic strip - which I assume they still are. The strip was specifically shaped to be bistable, i.e. tended to stay shut until it has absorbed enough heat to very rapidly flip over to the open state. This is where your hysteresis comes in, it is built in to stop a buzzing switch, and sparks flying, and the smell of burning plastic... The metal strip flips when it has absorbed a certain amount of heat, and this rate of heat absorption has to be greater than that which it is losing by conduction and radiation. Hot air (low thermal capacity) in relatively small volumes would not heat the strip up quickly enough to overcome heat loss , but steam would, since it gives off heat of condensation to the metal strip (but see "Even later, more breaking news" below). The pressure in the kettle at boil is not much above atmospheric, so that a kettle set for a certain pressure alone would not work at higher altitudes (Which is patently not the case, these switches do work at higher altitude. For living altitudes of 0-2000m, we cannot buy high altitude and low altitude kettles, the way we can low and high pressure tennis balls). Nevertheless, while the switch itself is not pressure activated, there does need to be enough pressure inside the kettle to cause an adequate flow of steam through the orifice to the switch, else it would simply not cycle - as when the lid is not closed properly. Late breaking news: My 20 year younger kettle flips the switch when mains power is cut, which implies that the strip is held by an electromagnet - its shape is probably not that important. This is likely to be a more recent safety feature, in that a stable closed contact (ON) can be maintained only while current flows. The over heat cut out switch (dry run protection) is mounted in the base, next to where the mains power enters. Even later, more breaking news: A point which my wife now made to me (While pointing out that my imminent application of a screw driver to the new kettle would be seen as a death wish, and that "as she loves" me she would fulfill my wish:-) is that one cannot get a steady flow of hot air from a dry kettle, so that my theory about thermal capacity is probably over complicating the issue. I will test that with a hair dryer rigged up to ventilate the switch, but Occam is often right. --Seejyb 05:50, 23 December 2006 (UTC)

Is it possible that a bimetallic strip could be used to control a much greater current by means of an electrical relay - thus avoiding 'sparks flying' when the bimetallic strip switches..87.102.4.34 10:38, 23 December 2006 (UTC)

Yes, quite likely, what with steam being involved. The bistable nature would explain the hysteresis, the sparking being less relevant. --Seejyb 14:52, 23 December 2006 (UTC)

Why are skis no longer made from wood?

I was wondering what are all the adventages that modern carbon fibre skis hold over their wooden counterparts? (Also it would be greatly appreciated if you could explain the physics behind an answer) Thanks —The preceding unsigned comment was added by 81.145.240.41 (talk) 13:00, 22 December 2006 (UTC).

A higher modulus, more strength, better formability, ease of integrating steel "edges", better durability with little care, and no rot.

Atlant 14:28, 22 December 2006 (UTC)

Consistency. Using synthesised materials means that every ski will perform exactly the same, and cannot fail due to some chance element in the grain of the wood.--Fangz 15:18, 22 December 2006 (UTC)

Hmm I believe making skis from wood can be a knotty problem but the Heroes of Telemark did it!--Light current 01:08, 23 December 2006 (UTC)

Be quiet, LC, ... or should I say schuss ? :-) StuRat 15:34, 23 December 2006 (UTC)

Textual vs Pictorial Memory

How do textual and pictorial memory compare? In the short term, and in the long term?--Fangz 15:16, 22 December 2006 (UTC)

In the brain or in computers?

Atlant 15:55, 22 December 2006 (UTC)

I suspect he means the brain; it would likely have been phrased quite differently if it was in respects to computers. --24.147.86.187 16:54, 22 December 2006 (UTC)

It varies from person to person. What would one expect of an analphabet or a blind person - I don't know. You could get some ideas at How do Presentation Modality and Strategy Use Influence Memory for Paired Concepts?, and take it from there. --Seejyb 18:22, 22 December 2006 (UTC)

I am told that people remember things better in pictures and sounds, rather than in words (spoken or written). I think intuitively most people would agree - but I have only anecdotal evidence. 220.253.91.28 01:07, 23 December 2006 (UTC)

Water displacement

Does an object in water displace the same weight of water as the object?129.112.109.250 16:35, 22 December 2006 (UTC)

• If you put a bowling ball in a tub full of water, and then put a balloon (the same size as the bowling ball) in the water, they both displace the same amount of water, but they weigh a lot different. So, the two objects don't weigh the same, but what do they have in common? — BRIAN0918 • 2006-12-22 16:46Z

• Archimedes Principle may be what you're looking for. WilyD 17:39, 22 December 2006 (UTC)

Short answer: yes. In Brian0918's example, the situation is different because you would have to force the balloon down. If no force is applied, it would displace its itsy bitsy teeny weeny weight. Clarityfiend 17:56, 22 December 2006 (UTC)

But only if the object does not sink. If it is made of iridium, it weighs more than 20 times the water it displaces.  --Lambiam^Talk 18:11, 22 December 2006 (UTC)

Ok, if I am understanding this, it sounds like if 2 objects have the same volume the amount of water they displace is equal regardless of their weight.129.112.109.252 18:29, 22 December 2006 (UTC)

If they float, they displace a volume of water equal to their weight. Clarityfiend 18:38, 22 December 2006 (UTC)

If they sink they displace a weight of water equal to their volume. Jokem 19:03, 22 December 2006 (UTC)

As phrased these two together have a curious chiastic structure. I'd formulate it as follows:

• If they float, they displace an amount of water of the same weight.
• If they sink, they displace an amount of water of the same volume.

 --Lambiam^Talk 21:16, 22 December 2006 (UTC)

If you want to know the weight and the volume of an object fill a container that will hold it to the very top with some arrangement to direct the overflow into a container with volume marked off in increments. Place the object in the water and catch the overflow. If the object floats the weight of the overflow is the weight of the object. This can be found approximately from volume: 1 kg of water is approximately one liter of water (approximately). Next then submerge the object without allowing your hand to go below the surface of the water. The total volume of overflow will then equal the volume of the object. If the object sinks then its weight can be measured by hooking the end of a rope thru a ceiling mounted pulley and the other to a big bucket. Fill the container with water until the object lifts off the ground. The weight of the water will equal the weight of the object. (Correct me if i'm wrong.) 71.100.6.152 19:45, 22 December 2006 (UTC)

I see Harvard has a cannon ball boat puzzle illustrating the above on one of their sites. Which reminded me of a story about the person who had to check whether the king's (or emperor's) gold cannons were really gold, and use immersed displacement of water for volume, and Archimedes' principle - using barges - for weight, thus calculated density. Was it in a novel? Eastern, possibly Siam?? I forget... It would make a nice reference for this question, which surely comes up every now and then. --02:14, 23 December 2006 (UTC)

Are you thinking of Hiero's crown (Vitruvius, On Architecture 9.9[30])? EricR 02:32, 23 December 2006 (UTC)

No, this was definitely cannon, but I shall research Hiero's crown and keep it as a reference for the purpose of questions. It is seems to be a similar story, and the smaller object may make a demonstration possible. The name "Shogun" popped up in my head, but I have no copy of the book. That would make the reference recent fiction, rather than old legend, and I would go for the legend angle. --Seejyb

Slight nitpick: the weight of an object which is floating actually is equal to the sum of the weight of the water displaced and the air displaced. While the weight of the air displaced is normally trivial, this isn't true for light objects, where there may be little, or no, water displaced. It's wrong to conclude from this that a balloon or other lighter-than-air object is weightless, however. StuRat 15:23, 23 December 2006 (UTC)

Something else interesting, is that the water is sometimes displaced without having anything but air in that location. Insects, lily pads, etc., which use surface tension to float "above the water", actually deform the surface of the water somewhat:

      bug
--+   ***   +---- waterline
   \  /|\  /
    +-----+

StuRat 15:29, 23 December 2006 (UTC)

Gauss (unit)

The article relates Tesla (unit) to Gauss (unit) but no where can I find pounds of force per square inch pull or repulsion related to Guass or Tesla. Can you provide a definition? 71.100.6.152 18:57, 22 December 2006 (UTC)

More info on the force exerted will be found at Electromagnet. Please ask for more info if needed beyond what is in the article. Edison 19:03, 22 December 2006 (UTC)

Perhaps it will help if I explain what I am doing... I'm drawing a diagram of a horseshoe permenant magnet on top and a horseshoe electromagnet on the bottom so that you have the shape of a racetrack. In the Java or Excel code I am letting the viewer/user enter by mean of control knobs the surface area of the permanent and electro core faces, the Gauss for the permanent magnet, the weight of the permanent magnet, the weight of anything sitting on top of it, the number of turns of wire around the electromagnet core, and the amperes and voltage being supplied to the electromagnet. The code then displays the lifting force and other parameters of the unit for the purpose of measuring the weight of the load per the amount of ampers required to keep the cores from touching. It seems like all of the necessary information is there but I keep getting hung up on what seem to be extraneous variables like air gap which might possibly be ignored. 71.100.6.152 21:17, 22 December 2006 (UTC)

Experience such as that of Michael Faraday showed that the smoothness of the contact between the surfaces had a huge effect on the lifting power due to small air gaps. The electromagnet article shows the relation of the different variables: the ampere turns, the ares, the length, etc. Not sure why you want to use a permanenet magnet and an electromagnet; it might be simpler to posit an electromagnet and a soft iron pole piece/ keeper. Faraday in the 1830s went from electromagnets lifting ounces to electromagnets lifting thousands of pounds, and did some nice parametric experiments, with parallel versus series windings, number of turns, etc. Edison 08:18, 23 December 2006 (UTC)

The reason is as a classroom, science fair or museum interactive educational software. The reason for the permanent magnet is that I'm in this demonstration levitating (repulsing) rather than attracting. 71.100.6.152 10:37, 23 December 2006 (UTC)

Bromelain, the protease enzyme in pineapple

Why does pineapple, which is not made of protein, contain a protein digesting enzyme?

For my A-level biology coursework I am finding the optimum pH of Bromelain. This is an enzyme (possibly a group of enzymes?) present in pineapple fruits, (Papaya has a similar enzyme, papain). I assume that enzymes are energetically expensive for the plant to make, but I can't work out how this one benefits the plant. Some possible theories I have come up with:

-The earlier bromeliads which later evolved into the pineapple plant were insectiverous and used the protease to digest their food (if so, why is the enzyme present in the actual fruit of the plant?)

-Pineapples disperse by explosion. The protease digests part of the fruit which is made of protein to make the dispersion more successful.

I would also be grateful if anyone knows the optimum pH of bromelain. 81.154.254.217 19:07, 22 December 2006 (UTC)Siobhan

This scholarly review may give you some clues towards another theory of why plants evolved protein digesting enzymes. Rockpocket 20:05, 22 December 2006 (UTC)

Oh, and bromelain extracts typically have an effective pH from 4.0 - 8.0 and an optimal pH from 4.5 - 5.5. (see this pdf file). Rockpocket 20:16, 22 December 2006 (UTC)

This article: Multifunctional role of plant cysteine proteinases(pdf) gives an overview of the functions of all of these proteases. I gave it a quick look through, and it does suggest answers in a general way - they have many functions, but there seems to be much work still to be done. Following up on the references section of the article may help to provide specific detail. This article I cannot access the full text: Kotaro Konnoi, Chikara Hirayamai, Masatoshi Nakamurai et al. Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex. The Plant Journal. Volume 37 Issue 3 Page 370 - February 2004. doi:10.1046/j.1365-313X.2003.01968.x. The url is to an abstract. This is more pay to get science: Andreas Schaller, A cut above the rest: the regulatory function of plant proteases. Planta, Volume 220, Number 2 / December, 2004. DOI 10.1007/s00425-004-1407-2. I hope it helps, one grows weary of sifting through enzyme ads targeting the public gullibility about life saving foods:-) --Seejyb 04:07, 23 December 2006 (UTC)

I would guess that it's a protection from insects. StuRat 15:12, 23 December 2006 (UTC)

Motorway building

How long does it take to build a motorway from scratch? Forget about greenbelt land and planning rejections and pretend that it's 100 miles long. Living in the 21st Century, I seem to take motorways for granted, there seems to be a lot of roads built in very little time and I can't comprehend how it's happened so quickly. How many people would you need to employ? How much tarmac would you need. It just doesn't make sense! ImbalancedZero 23:17, 22 December 2006 (UTC)

Without trying to come up with exact numbers, I'll just observe that the time required depends critically on how many people (and machines) are used. At one extreme you could have one crew starting at one end of the road, building one carriageway, working toward the other end, stopping work on the main road whenever they had to build a bridge or a slip road, and finally working back building the other carriageway. At the other extreme, if there are 25 intersecting roads, you could send out 25 bridge-building teams and 100 road-building teams, building both carriageways in both directions from each cross road until they met. In practice something in between would apply, of course. But there would be a real difference between a road needed as a top-priority military project and one being built because there was a bit of money left in this year's budget.

As to "how much tarmac", I think modern freeways are normally paved mainly with concrete, and an optional layer of asphalt (tarmac) on top. The total thickness of the two materials, supposing that to be what you really wanted, is probably something like 18 inches or say 50 cm. Four lanes (say 18 feet wide) and four paved shoulders (say 10 feet) makes a total width of 112 feet (say 35 m). 100 miles is 160 km. So that's 0.5 x 35 x 160,000 = 2,800,000 cubic meters of asphalt and concrete. If it's say 2.5 times as dense as water, that'd be 7 million tons. Plus a bit more for slip roads (ramps) and a fair bit more bridges. Understand that this is just a rough estimate -- I don't know the actual width or thicknes. It shouldn't be too far off, though. --Anonymous, December 23, 00:04 (UTC)

Battery Producing Two Voltages Simultaneously?

Say I was constructing an electrical device to be battery powered and I needed both 12v and 9v supplies. Would it be acceptable to create a 12v battery from eight 1.5v cells and by inserting an additional connection in between the sixth and seventh cells, get a 9v and 12v connection from the same battery? --Username132 (talk) 23:45, 22 December 2006 (UTC)

This will work, but the cells supplying 9 V will be discharged sooner. Consider: if the 12 volt load is 0.3 amps, and the 9 V load is .1 amps, then the 6 cells making up the 9 V section will have a load of.4 amps, which would discharge them long before the additional 2 cells supplying only the .3 amp load go flat. Because of this, the 9 volt load would see its supply voltage drop a little faster than the 12 Volt load. If you had a charger charging the entire battery at 12 volts, the cells would be unevenly charged and the whole arrangement would give unsatisfactory service. If the cells were promary cells or if they were removed from the device and all charged individually, you would have better operation. If the tapped 9 V circuit drew only a much smaller current tham the 12 volt load, or if it were intermittent, you would also get better service. You could always change the cells around periodically to even out the load. Edison 00:29, 23 December 2006 (UTC)

But using a suitable resistor would allow me to get about 9v from 12c supply, supposing that the reistance of the 9v device was constant? --Username132 (talk) 01:33, 23 December 2006 (UTC)

If the 9 volt load is reasonably constant, a voltage divider circuit can produce the 9 volts, at the expense of a constant flow of wasted current through the two resistors comprising the voltage divider. If the 9 volt load is a constant resistance a single dropping resistor might work, at the cost of the energy dissipated in the dropping resistor. A three terminal regulator circuit could be used to produce a constant 9 volts over wide variations of load, once again at some small constant flow of wasted current, but could certainly be a sound choice. Integrated circuits are also available which could step up a lower battery voltage to a higher voltage for some part of the circuit. Edison 08:10, 23 December 2006 (UTC)

Kettle Boil Off

My math's teacher had a "boil-off" with some friends in which they used their kettles to boil a certain amount of water, hoping that their kettle would be the fastest. He was asking us (his A level students) for advice. It's all over now, but I have wondered many times since, how could one optimise one's chances of winning a boil off? How difficult would it be to modify a kettle to include two heating elements, powered by seperate plug sockets? --Username132 (talk) 23:55, 22 December 2006 (UTC)

Electricity, water, and red hot heating elements are a recipe for accident or injury, so modification of the electric kettle is not recommended. Edison 00:31, 23 December 2006 (UTC)

Given the constraint that you have no post consumer modification of the electric kettle, the question is which kettle should you bring to the competition. (i.e. which kettle on the store shelves should you buy. Since you are looking into converting electrical energy into thermal energy, you aren't really concerned with "efficiency", as due to the law of conservation of energy and the laws of thermodynamics, any energy which you "lose" in inefficiency will be converted to heat (which is what you want anyway). Thus, what you want is the kettle capable of drawing the most electrical energy, or the one with the highest wattage. -- 01:27, 23 December 2006 (UTC)

And one with good insulation, to make sure that the heat generated by the element is retained in the water. Maelin (Talk | Contribs) 09:25, 23 December 2006 (UTC)

Lowering the pressure can cause water to boil sooner, even at room temperature. Now, how you can lower the pressure of the water without making it obvious, that's the trick. StuRat 15:06, 23 December 2006 (UTC)

Brightest Bulb On 12v At Low Cost

I want to make a device the flashes as brightly as possible, so it might be seen from 50+ meters away in daylight. Device must operate from 12v and be (as always) as cheap as possible. What kind of bulb might do such a thing? --Username132 (talk) 23:59, 22 December 2006 (UTC)

Does the flash unit on cameras count? --Bowlhover 01:30, 23 December 2006 (UTC)

It does! There are xenon flash blubs available on ebay - suppose I want to power such a thing from a 12v car battery - what circuitry am I going to need? It needs a "trigger" apparently, but these have three prongs - how does it wire up? --Username132 (talk) 04:47, 23 December 2006 (UTC)

Could you adapt a disposable camera? It has all the circuitry in place. - CHAIRBOY (☎) 05:55, 23 December 2006 (UTC)

I'm hoping for something higher powered. I failed to mention that I want the flash to be seen at 50+ meters in _all_ directions. --Username132 (talk) 05:59, 23 December 2006 (UTC)

Another possibility: visit the local car spares and accessories shop, and examine one of the rotating roof lights that plug into the accessory power plug (c******** lighter) of your car, being attached to the roof by a permanent magnet. Those that emergency workers use are 12V, easily visible in daylight, and should not be too difficult to emulate using scraps. They are, however not as bright as camera flash lights. --Seejyb 06:04, 23 December 2006 (UTC)

Please do not tinker with electronic flash circuitry, since it steps up the battery to hundreds of volts and stores the energy in capacitors. This can cause electricution, similar to the units hospitals use to defibrillate. People have died tinkering with electronic flashes. Perhaps find a pre-assembled strobe unit which just plugs into the 12 volts. Edison 08:05, 23 December 2006 (UTC)

But those beacons aren't bright enough for my application. One watt simply wont do. I probably wont electrocute myself because the circuit will be enclosed when I switch it on. --Username132 (talk) 09:01, 23 December 2006 (UTC)

I'm no expert but it seems to me that you can in theory make a one-off flash as bright as you like, no matter how limited your power source is, as long as you have a large enough capacitor and a quick and efficient means of discharging it. However, storing a large amount of energy in a capacitor and discharging it rapidly sounds like a risky thing to do, especially if you are inexperienced - read this hazards and safety section. So I would second the views of other responders - find a ready-made solution or find an expert to help, but do not attempt a DIY solution. This sounds like it could turn into a Darwin Awards situation ! Gandalf61 09:34, 23 December 2006 (UTC)

Perhaps some old-fashioned magnesium flash bulbs would be in order. They generate their light from combustion, so need very little energy to trigger the rapid oxidation of magnesium. Of course, they are one-time use, as well, so you could only use them for a limited number of flashes, depending on how many you buy. Eventually your car battery would go dead, but that would be after hundreds or thousands of flashes. StuRat 14:55, 23 December 2006 (UTC)

Correlation

1) Is there ANY correlation between dirty/sweaty hair and acne?

2) Is technology something that can be progressed gradually, or can we make a huge leap with what we have now?

3) I've read somewhere around here, I think in "Senescence" that one day we'll have the technology to stop aging. According to that, can there be any guesstimate as of how long it will take for us to achieve that? PitchBlack 00:23, 23 December 2006 (UTC)

1. In my experience, yes. They are both symptoms of an underlying conditon, though, so washing your hair will generally do little to improve complexion.
2. In my observance, technology does indeed improve in fits and starts. Right now, there seems to be a lot of rapid improvement across all areas of science.
3. I question the assumption that technology is the key to immortality. Why not just a good diet and outdoor exercise? ←Vranak→

1. No. See Acne#Causes of acne.

2. It's not necessarily a case of either-or. Both can occur. See innovation and invention.

3. See wishful thinking. BenC7 01:17, 23 December 2006 (UTC)

1) I would say both are symptoms of excessive fat consumption, and, in the case of acne, trans-fats in particular.

2) Both. World wars seem to particularly spur on technology leaps.

3) I think we can lengthen the lives of biological bodies, but not extend them forever. The weak link is the brain. We might eventually get to the point where we can replace every other organ when the old one fails, but replacing your brain means replacing "you". However, if the brain can be copied into a computer, then, with backups and redundancy, it would be possible for that "brain" to live forever. Of course, many would argue that the brain in the computer isn't really "you", but rather a soulless copy of you. I would expect these type of advancements over the course of centuries, not decades. StuRat 14:49, 23 December 2006 (UTC)

HOW TO find a PDF copy of the book?

the title of the book is: Futures, Options, and Swaps, by R. Kolb, Blackwell publishing, 4th ed. 2003 —The preceding unsigned comment was added by 150.210.171.79 (talk) 00:10, 23 December 2006 (UTC).

Wouldn't that be an illegal copy? Then, we cannot help you. — Kieff 02:14, 23 December 2006 (UTC)

Not necessarily; some websites that sell books also sell them in electronic format. After a Google search, however, I couldn't find any PDF copy of "Futures, Options, and Swaps". --Bowlhover 04:02, 23 December 2006 (UTC)

In that case if you must have one the only option seems to be to contact the publishers adn ask if they can do that for you.87.102.4.34 11:47, 23 December 2006 (UTC)

Casino Royale Poison

Template:Spoiler In the latest James Bond movie, he suffers a cardiac arrest after drinking a spiked martini. Is there really such a poison that can create that effect in that little time? --The Dark Side 02:10, 23 December 2006 (UTC)

A google search for "fastest-acting poison" turns up this forum page which suggests that nicotine taken orally in sufficient quantities could cause unconciousness within a few seconds and death within a minute. --Robert Merkel 03:41, 23 December 2006 (UTC)

If I remember correctly, the poison in the move was identified as either digitonin or digitoxin. They're related compounds, both of which are used in small amounts as heart medications; overdoses can cause arrhythmia, tachycardia, fibrillation, and cardiac arrest. As far as that goes, the movie gets it mostly 'right'. On the other hand, as far as I know neither one acts as quickly as the movie suggests. In real life, oral doses take tens of minutes to hours to get into the bloodstream and take effect. They are occasionally administered intravenously if more rapid action is required, but obviously the movie martini was taken orally and not IV. (This is the same school of movie science that lets investigators on CSI run a sample through a gas chromatograph in thirty seconds.)

Something that might fit the bill is batrachotoxin: one of the very potent toxins secreted by certain species of poison dart frog. It is efficiently absorbed through the mucous membranes and generates cardiac symptoms similar to those seen with digitonin overdose. On the other hand, it may also cause paralysis (batrachotoxin is a neurotoxin); perhaps we could write that off as the explanation for James' loss of coordination.

Our article doesn't identify an antidote, though it does offer suggestions on what treatments might work if you're desperate enough. Perhaps MI6 has some very good medical researchers on staff. TenOfAllTrades(talk) 06:40, 23 December 2006 (UTC)

I believe high doses of caffeine can also cause a heart attack (much higher levels than you can get from drinking coffee). StuRat 14:41, 23 December 2006 (UTC)

Estimating backup time of a electric backup power device

Is it possible to estimate the length of time an electric device can be powered by a battery-based uninterruptible power supply (UPS)? I was thinking one could use a device such as the Kill-A-Watt[31] to measure how much electric power was needed for a device. But how would one use that information along with the specifications of a UPS to know how long the UPS could power the device? Thanks for any ideas! --71.171.1.236 02:27, 23 December 2006 (UTC)

Typical UPS specifications include: Watts, VA and time. The VA is volts times amps, which is greater than the watts because anything other than a resistive load draws more volt-amps than it does watts. With a resistive load they would be the same. I tested early personal computer UPS units over 20 years ago with a resistive load box. When new, it would supply the rated volt amps for the specified time. Examining the current from the batteries, it was clear that it was stressing the batteries toward the end of the time. As their voltage dropped, the invertor circuit drew more and more current from the batteries to maintain the rated output to the bitter end. This was a somewhat destructive test, since the batteries were being drained at about a 1 hour rate (the rated time) instead of a more normal 10 hour rate. If the load were, say, half of the rated load, the carry time would more than double. Thus there is no simple mathematical answer to the question posed, except to say that a well designed UPS, when new, should supply the stated watts (or volt*amps) for the stated time, and should supply a lower load for a correspondingly longer time, but to a longer time than simple reciprocity would suggest. On the other hand, if the battery is beyond its service life, or has been repeatedly discharged to shutoff, the carry time at full load will be less than when it was new. I do not recommend loading it beyond its rated load. Edison 07:55, 23 December 2006 (UTC)

Faraday Cage Use In Security

The pharmaceutical production plant where I work is enclosed in a Faraday cage but I want to know why? There are no radio communications in there that I'm aware off - does it protect again interference that may damage equipment? --Username132 (talk) 05:57, 23 December 2006 (UTC)

Do you mean there is a metal or wire mesh structure surrounding the building, or than each room is separately in such a cage. or that all internal walls are covered in sheet metal or wire mesh? It would be more common to enclose certain labs in a Faraday Cage. If the entire building were externally shielded, cell phones radios and pagers would not work, but when someone tried to make a cel call or used a Walkie Talkie it could affect the delicate equipment being shielded. There are various industry standards for the level of electromagnetic interference a piece of equipment should withstand. Edison 08:01, 23 December 2006 (UTC)

Is is possible that the whole metal cage is grounded to earth - a way of preventing sparks?87.102.4.34 10:44, 23 December 2006 (UTC)

Why quarantine astronauts?

Respected Reader, I would like to ask you this question, "Why are astronauts quarantined after they come from space. --""""

There are various reason. Radiation, disease, etc. Read the article quarantine. Sign your posts with four tildes, rather than quotations by the way. :) --Proficient 08:46, 23 December 2006 (UTC)

Until we are not sure that no extraterrestrial viruses or bacteria exists against which we have no immunity, it seems logical to impose a quarantine.--V. Szabolcs 10:19, 23 December 2006 (UTC)

I'm not sure that "quarantine" is quite the right word, as that implies the public is being protected from infectious diseases they may have. I think it's more that they need time to recuperate, especially from the negative effects changes in gravity have on the body. StuRat 14:22, 23 December 2006 (UTC)

Historically, the early Apollo astronauts who went to the Moon were quarantined on their return because, at the time, scientists weren't absolutely certain that the Moon was free of disease-causing organisms. This precaution was dropped after it was determined that the lunar surface is sterile.

As far as I know, astronauts since are not quarantined after their return from space. However, NASA does keep a watchful eye on their returning astronauts. Though not quarantined, a returning astronaut might as well be—there will be a post-flight debriefing and any number of medical tests. As StuRat says, an astronaut who has spent an extended length of time in freefall will take some time to re-adapt to live in one gee.

Before launch, astronauts are quarantined to prevent them from being exposed to any nasty communicable diseases, and to allow any infections they do have to surface. In addition to being kept isolated, their diet is also carefully monitored. (You don't want to send someone to space with salmonella poisoning or the flu, right?) Access to medical care is very limited in space, and a sick crewmember can't work very hard (if at all). TenOfAllTrades(talk) 14:48, 23 December 2006 (UTC)

Critical criteria for human life...?

Where can I find the exhaustive and extensive list of ranges of values of the criteria necessary for human life to evolve from the Big Bang to the present, i.e., size of the sun, the distance from the sun of the life supporting planet, formation of an atmosphere, evolution of amino acids and certain proteins and cycles such as the Krebs cycle, etc.? I am looking for things that are absolutely critical to the evolution (existence and then maintenance) of human life anywhere in the cosmos. Adaptron 10:01, 23 December 2006 (UTC)

For a general overview see rare Earth hypothesis, anthropic principle and fine-tuned universe - although I doubt that you will find the precise quantitative data you ask for, as many parts of the argument involve the extrapolation of probabilties from very few examples. For the other side of the argument see mediocrity principle, Texas sharpshooter fallacy and survivor bias. Gandalf61 11:30, 23 December 2006 (UTC)

I also think it's a mistake to assume that all other life must be identical to humans and thus require identical environments. Just on Earth, we see an amazing variety of life, including life that isn't dependent on the Sun for energy, but feeds off deep ocean sulfur vents. There's no reason to think that such organisms couldn't eventually, or on some other planet, evolve intelligence comparable or beyond our own. StuRat 14:13, 23 December 2006 (UTC)

Its quite possible that even more "exotic" life forms exist but my inspiration for asking is not so much to consider the other life forms that could have evolved but rather but rather because of the realization that of how many, many thing had to fall and stay within certain range values, time frames and sequences of events in order for human life to exist at all. I mean think about it. The universe is basically the inside of a vacuum chamber and yet here I am able to make these comments today. Adaptron 16:31, 23 December 2006 (UTC)

anyone got a manometer?

What is the pressure inside an inflated party balloon? 1.1atm,2atm,1000atm????87.102.4.34 11:45, 23 December 2006 (UTC)

If the graph on page 4 of this Word document is accurate and for a typical balloon, it is about 110 to 112 kPa, or 1.09 to 1.11 atm. I hope you don't think human lungs could supply a pressure of 1000 atm: that is about the pressure when you dive to a depth of 10 km, well beyond the crush depth of even an Alfa class submarine. That is about the depth of the Challenger Deep, the deepest known point in the oceans.  --Lambiam^Talk 14:41, 23 December 2006 (UTC)

Excellent thanks.

My back of envolope tells me that the energy stored (and released when it pops), for a smallish party balloon is (1 litre volume) of the order of 10 Joules..87.102.4.34 15:51, 23 December 2006 (UTC)

That's the equivalent of 0.000000000002 kilotons of TNT (or 0.002grams of TNT [bang!]).87.102.4.34 15:56, 23 December 2006 (UTC)

resultant forces

Is it true that the resultant of a gravitational force is also gravitational,that of an electromagnetic force is electromagnetic and so on?

-Sruthi

There may be a problem with terminology here. The term "resultant" in mathematics and physics is usually applied to the net result of adding two or more forces (or other vector quantities). You could have the resultant of a single force, but it would just be a very indirect way of referring to the force itself, so it would be unusual to use the word "resultant" in this sense. But in this rather odd sense, then yes, the "resultant" of a gravitational force is a gravitational force. On the other hand, if you mean "result" rather than "resultant", then the "result" of applying one or more forces to a body is an acceleration - see Newton's second law. Accelerations don't come in different types - they are just accelerations. So it would be incorrect to say that the "result" of a gravitational force is a "gravitional acceleration" - it is just an acceleration (or, alternatively, a change in momentum). Gandalf61 13:27, 23 December 2006 (UTC)

You might have meant "for an object in equilibrium, (zero resultant forces), is it necessary that all forces be of the same type ?". In that case, the answer is no, with a boat being a simple example. Gravity pulls it down and water pressure/buoyant force pushes it up. StuRat 14:08, 23 December 2006 (UTC)

Ear remedy for loud bang

Having been subjected to a firecracker explosion within close proximity of my private hearing space, I was wondering what I could do to somehow attentuate any bad effects that may arise form this occurance. There is a bluntness in my right ear, closest to describing it would be a clogged ear sensation.

-:(

Medical advice and diagnosis comment deleted. -- TenOfAllTrades(talk) 16:42, 23 December 2006 (UTC)

Suggested diagnosis comment deleted. -- TenOfAllTrades(talk) 17:13, 23 December 2006 (UTC)

Unfortunately, we can't diagnose your condition over the internet. You should seek the advice of a qualified medical professional, who can discuss the incident with you in detail, analyze your symptoms, and – if necessary – call you in for a physical exam or to prescribe tests. More briefly—call your doctor with any questions. TenOfAllTrades(talk) 16:42, 23 December 2006 (UTC)

Capacitor Calculations

What specification of capacitor is required to deliver 300 J at 150 V over 5 seconds and what to deliver 1 J at 12 V over 0.01 seconds? This is not for homework (I'm not a students and when I was (and hopefully will again be in a few months), it's biologically orentated!). I would like to know how you arrive at these specifications, so I can work things out again when I get more precise info. --Username132 (talk) 15:29, 23 December 2006 (UTC)

See our article on capacitance for the relationship between energy, capacitance and voltage. Note that the discharge time does not affect the capacitance, although it may affect the type of capacitor that is best for the job. Note also that the voltage across the capacitor does not stay constant as it is discharged, but decreases linearly with the charge left on the capacitor. Gandalf61 16:47, 23 December 2006 (UTC)

You're going to have to be a bit more specific about your needs. Bear in mind that the voltage and current from a capacitor (discharged across a constant resistance load) fall off with a first-order exponential decay. To get something close to a constant voltage, you either need to have a capacitor that has much higher capacitance and won't discharge fully, or employ some electronics.

The time that a capacitor takes to discharge (for moderate rates of discharge) is largely dependent on the load to which you attach it. (Lower resistance = higher current = faster discharge, and vice versa.) If you're planning on rapidly and repeatedly charging and discharging, be aware that you may need to provide cooling for the capacitor.

The total amount of energy stored in a capacitor is given by

$E_{\mathrm {stored} }={1 \over 2}CV^{2}.$

For example, if you want to have a starting voltage of 150 V and total stored energy 300 J, then you need at least a 0.027 Farad (27 mF) capacitor. Note that such a capacitor will only start out delivering 150 V. The voltage will decay to zero as the capacitor discharges. (For reference, the leftmost capacitor in the back row of Image:Capacitors Various.jpg is rated at 5 mF and 100 V.)

If instead you had a 100 mF capacitor at 150 V (this would be a very substantial capacitor), you would only be down to about 130 V by the time you had drawn off 300 J. TenOfAllTrades(talk) 17:09, 23 December 2006 (UTC)

Blood color ?

Template:Strict ({{strict}} template added for demonstration purposes only.)

If grasshoppers have white blood and lobsters have blue blood, does this mean they lack red blood cells (made red by the presence of iron in hemoglobin) ? If so, how do they transport oxygen ? StuRat 16:47, 23 December 2006 (UTC)

There is a pretty good list of alternatives to iron-based hemoglobin for the transport of oxygen at Hemoglobin#Other_biological_oxygen-binding_proteins. I believe lobsters have Hemocyanin which is copper based; not sure about grasshoppers. --TeaDrinker 16:56, 23 December 2006 (UTC)

Medicine books

Can somebody, please, tell me a list of books typically needed for a medicine degree? Thank you very much.

Searching for a way of contacting Neurosurgeon Yasargil and his Swiss Surgeon Team

I am searching for the address to contact Yasargil and his team ( supposedly the best in the world) because my friend, a 41 years old mother of three, desperatley needs a second opinion concerning breastancer with metastasis to the brain. Norwegian Healthcare does not have any more treatment to offer her. Is there anyone who knows the address of this fabulous team? If so I will be for ever grateful! Merry Chistmas.

Best regards

Vigdis Bjørnøy Totengata 10 0658 Oslo Norway