Wikipedia:Reference desk/Archives/Science/2008 May 11

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May 11

absolute zero

Does all motion stop at absolute zero —Preceding unsigned comment added by 74.47.169.87 (talk) 01:05, 11 May 2008 (UTC)

Take a look at Absolute zero, the first couple of lines should answer your question. --Tango (talk) 01:10, 11 May 2008 (UTC)

Expanding on this a little. All particles with mass would be stationary, but all massless particles would be traveling at the speed of light as they always do. It would be very interesting to see what a neutrino did under such conditions. GameKeeper (talk) 22:47, 12 May 2008 (UTC)

Why does this microwave have electric-plug-shaped ventilation holes?

The microwave ventilation holes at the bottom are shaped like a variety of electric plugs.

Microwaves have ventilation holes in the rear; but after closely investigating many microwaves, we noticed that there is consistently inclusion of "ventilation holes" which are exactly shaped and sized like various international electric plugs. Any ideas why this exists? We have exhausted a lot of possible explanations to no avail. There is no electric connectivity to these plug holes, they just go through the sheet metal casing. Ideas? Saket (talk) 04:47, 11 May 2008 (UTC)

Just a wild guess, but it could be because they used those holes to test whether plugs were shaped correctly during some sort of Q&A analysis. Seems a bit weird, though... Titoxd^{(?!? - cool stuff)} 04:54, 11 May 2008 (UTC)

Here's a random idea - maybe that rear panel of the microwave is used in several different models of microwaves, some of which have power inputs in that location? That could explain the various power-plug shaped holes. Although it seems odd that the female power junction is on the microwave - usually it's just on the wall outlet... it's just a wild guess. --Bmk (talk) 05:02, 11 May 2008 (UTC)

Or perhaps it's part of some metal-shaping quality control procedure in the factory? Kind of like the colored patches you can find under cardboard flaps on cereal boxes? I can't think what the purpose would be though... --Bmk (talk) 05:03, 11 May 2008 (UTC)

Is it a place to "park" the plug while in its box? Julia Rossi (talk) 05:24, 11 May 2008 (UTC)

We thought of all of these possibilities. We should mention that one of our microwaves (not the one in the photo) only has european-style holes in the ventilation panel EVEN THOUGH it is an American model with a US-style plug. This seems to invalidate many of the above possibilities... Saket (talk) 05:31, 11 May 2008 (UTC)

The one not-yet-mentioned possibility is that this particular model was designed to konfuze WP Reference Desk editors. :) -- Fullstop (talk) 05:35, 11 May 2008 (UTC)

Aww, my microwave is boring, no plug holes. How about this: a built-in template for the workers to figure out what country the microwave is going to, so they don't get them mixed up in the factory. The workers don't have to be able to read or anything, it's all done with diagrams. For the exception above, that factory is just wiring North America and Europe-style plugs, so they only need one template to check against. Franamax (talk) 06:43, 11 May 2008 (UTC)

By my count, there are 9 hole patterns in that pic. Thats covers pretty much every type, not just the North Am + European ones. -- Fullstop (talk) 07:01, 11 May 2008 (UTC)

Yes, that one came from a factory supplying the whole world. The other one mentioned above at 05:31 is from a factory with less scope. Franamax (talk) 07:04, 11 May 2008 (UTC)

I think it's for packaging purposes; when the microwave was packaged, the plug was perhaps inserted into the relevant holes and excess cable bunched up with a wire tie thing. ----Seans Potato Business 07:51, 11 May 2008 (UTC)

Packaging maybe not, but assembly more likely. You could feed the terminal end of a pre-assembled cord through a hole in the panel and then store the plug. That way it doesn't dangle around while you move that sub-assembly to the next step. Process wise feeding the cord through is a process (grip, position, feed, pull) that is quite different from fixing the cord and putting the back panel on (grip, position, fix screws). Either a human or a machine would have to change tools, so it would make sense to do it at 2 separate stations. But who knows. Lisa4edit (talk) 09:15, 11 May 2008 (UTC)

I vote for packaging, I have unpacked items myself that had the plug stored in this way. SpinningSpark 09:47, 11 May 2008 (UTC)

See reference at 5:31 to a model of a microwave oven with an American plug and only European holes on the back panel. That only makes sense for assembly if the plug was replaced after assembly (say, as part of the importing process), and makes even less sense for packaging. Or did they just screw up with that model? 128.12.187.10 (talk) 11:34, 11 May 2008 (UTC)

Well it could still make sense for packaging. UK plugs are horrible blocky things with pins sticking out sideways causing problems getting it into the box. You need somewhere for the pins to go. US plugs on the other hand are slimmer and with the pins pointing along the cable axis. Coiling the cable and tieing may be sufficient. Also (not sure if this point applies), are not some US power cords detachable like IEC power cords are? If it is not captive then it is not such a problem packing, it is put in the box after the main item. SpinningSpark 12:14, 11 May 2008 (UTC)

No reason you can't have an IEC style UK plug. Computers, rice cookers, kettles in the UK and/or Malaysia use them Nil Einne (talk) 16:58, 11 May 2008 (UTC)

Yes, but that was not the point. The question is, does the US microwave mentioned above have one? I suspect the answer is probably no as it is uncommon to find detachable cords on power devices as it is cheaper for the manufacturer to make the cord captive (kettles are a special case because of the need to pour). SpinningSpark 17:40, 11 May 2008 (UTC)

No it doesn't.128.12.190.172 (talk) 22:12, 11 May 2008 (UTC)

But my point was, if the US plug was detachable, then surely the UK plug would be as well? Why make an IEC style detachable plug and then make the UK one fixed and the US one detachable? And if the US/UK one was detachable, then the issue of it not being a problem packing because it's put into the box after the main item equally applies. So it just seems to me it's irrelevant whether or not it was detachable as to an explaination for why it owuld have holes for a UK plug but not a US plug Nil Einne (talk) 15:50, 12 May 2008 (UTC)

If the plug is there you can pretty much rest assured it is not plugged into the wall. 71.100.14.205 (talk) 15:38, 17 May 2008 (UTC)

It's not only microwave ovens that have these holes. I have a stereo amplifier with the same holes. I've always considered them as a place to stow the mains plug when carrying the unboxed appliance around. Not something that happens very often I admit, but putting the plug safely in these holes stops it unravelling and tripping you up whilst carrying it. Quite a simple explanation - I'm surprised noone else has suggested this. I could be wrong of course. smiler (talk) 14:30, 30 May 2008 (UTC)

Concentrate Juice vs Non-Concentrate

<moved from miscellaneous desk>
How much of a difference is there between fruit juices that are "made from concentrate" and those that are "not made from concentrate"? Suppose if Juice A is made from concentrate with just filtered water and juice concentrate as its ingredient and Juice B is not made from concentrate (like Tropicana), how much of a nutrient difference is there? Is the juice not made from concentrate "healthier" for you? Acceptable (talk) 21:31, 10 May 2008 (UTC)

Well the effective food miles of from concentrate is way lower so you really shouldn't touch the "not from concentrate" stuff. I have tried blind taste off from concentrate with bits versus not from concentrate and they are indistinguishable but real freshly squeezed of course is quite different. --BozMo talk 08:30, 11 May 2008 (UTC)

I guess you've seen our articles food miles, concentrate and juice? In the last, sugar's a health issue. Julia Rossi (talk) 10:10, 11 May 2008 (UTC)

I don't understand why "from concentrate" juice should have fewer food miles - could you explain Boz? -Bmk (talk) 15:34, 11 May 2008 (UTC)

While the concentrate may have travelled just as far, the water has hardly gone anywhere. --Tango (talk) 16:20, 11 May 2008 (UTC)

Right so the "litre-kilometres travelled" per litre drunk is less. --BozMo talk 20:33, 11 May 2008 (UTC)

BozMo's point that fresh-squeezed juice tastes different is due, I believe, to the pasteurization process, which heats the juice to the point where some chemicals are altered, resulting in a flavor change. In my experience, juices that have been flash pasteurized more closely approximate the flavor of fresh-squeezed juices.

Assuming that both the concentrate and not-from-concentrate juices have been equally pasteurized, I would say there are minor differences, but they would be indistinguishable. When boiling away the water in a vaccuum at low temperature, other volatiles in addition to water can get boiled away too. This may result in a slightly different chemistry between the concentrate and original, which may result in a detectable difference in aroma if not flavor. =Axlq 06:07, 12 May 2008 (UTC)

Platinum

<moved from miscellaneous desk>
I have a piece of what apears to be platinum that was melted down in a crucible and was wondering how do I go about finding out what it is?--66.191.106.19 (talk) 08:31, 11 May 2008 (UTC) Probably just as simple as taking it to a jeweler, if that doesn't work, ask said jeweler for any contacts of his. —Preceding unsigned comment added by 121.222.146.142 (talk) 10:32, 11 May 2008 (UTC)

Well...there is a test, which is that if it isn't attacked by either concentrated nitric acid or hydrochloric acid, but it does react with the combination of the two (aqua regia), then it's probably platinum. But I would take it to a jeweler - if you do it yourself you run the risk of damaging your sample or yourself. --Bmk (talk) 18:18, 11 May 2008 (UTC)

One way is determine the density. If it looks pure with no bubbles or inclusions, weigh it, and find the volume by water displacement. Platinum is one of the densest metals, so it should be heavy, but there are a few other dense silvery metals too, such as osmium or iridium. A metalurgist may have equipment such as xrays that could determine what it is too. Graeme Bartlett (talk) 21:29, 11 May 2008 (UTC)

Density may not work particularly well if the sample isn't pure. If it's alloyed with something else, the density could be significantly different from the density you would find in a textbook for pure platinum.. --Tango (talk) 00:17, 12 May 2008 (UTC)

Oh, and platium is worth a lot (US$2000/once) so get it to a jeweler.118.90.102.125 (talk) 12:33, 13 May 2008 (UTC)

crystals

where and when were crystals discovered —Preceding unsigned comment added by 76.29.128.29 (talk) 13:34, 11 May 2008 (UTC)

I imagine they've been known about since pre-historic times. --Tango (talk) 16:17, 11 May 2008 (UTC)

According to our article on crystals, they were indeed known to (if not understood by) the ancient Greeks, and probably most other ancient civilizations as well. Nicolas Steno, a Danish geologist, is sometimes credited with beginning the modern science of crystallography and minerology when he observed in 1669 that any sample of a single crystalline substance has the same angles between faces. --Bmk (talk) 18:39, 11 May 2008 (UTC)

Nutrient needs of brain

Are there any nutrients which have been shown to be essential or particularly beneficial to the brain, more than to the rest of the body? Also, how many calories(assuming average calorie intake, which I think is 2000 daily) does the brain alone require every day? Hence, what would be the daily nutritional needs of the proverbial "brain in a vat" which maintains mental functions without a body? —Preceding unsigned comment added by 69.224.182.55 (talk) 14:58, 11 May 2008 (UTC)

You average calorie intake is unlikely to have much effect on the energy requirements of your brain. (Your average calorie intake doesn't have much effect on the energy requirements of your body either although the heavier you get, the more energy your body needs to move you around) Nil Einne (talk) 16:53, 11 May 2008 (UTC)

I think the question was what percentage of the daily calorific intake is used by the brain, not how does calorific intake affect what the brain uses. --Tango (talk) 19:01, 11 May 2008 (UTC)

The brain has an almost absolute requirement for glucose. It does not metabolize fatty acids. However, it will use ketone bodies for energy if glucose is not in abundance. Wisdom89 _{(T / ^C)} 17:36, 11 May 2008 (UTC)

The absolute fuel requirement for an adult brain is about 4-6 mg/kg/minute of glucose, where kg is the person's body wt, not brain wt. Glucose provides about 4 cal per gram of glucose. —Preceding unsigned comment added by 159.14.240.230 (talk) 21:08, 14 May 2008 (UTC)

ionizing radiation

What is the simplest definition of ionizing radiation? Mr Beans Backside (talk) 17:30, 11 May 2008 (UTC)

Electromagnetic radiation (high energy EM waves/particles) or radioactive particles (beta particles, neutrinos, alpha particles etc..etc..) that strip electrons and produces ions of neutral elements. Wisdom89 _{(T / ^C)} 17:33, 11 May 2008 (UTC)

"Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions" - from http://dels.nas.edu/potassium_iodide/glossary.html Regards, CycloneNimrod^Talk? 17:45, 11 May 2008 (UTC)

Dark matter

Why doesn't dark matter reflect light? I was wondering because of the recent story reporting the discovery of a dark planet. I seemed to have forgotten what it was exactly that was discovered, and can't find the story now. Maybe I dreamed it! But I thought it said something about gravitational lensing. Any help, or am I losing it? Mr Beans Backside (talk) 17:31, 11 May 2008 (UTC)

You're not losing it. Dark matter (see that article, it should answer your questions) either does not emit electromagnetic radiation or doesn't emit enough of it to be detected directly. Instead, we detect it by it's gravitational effects on matter. Not entirely sure why it doesn't reflect light, though.. Regards, CycloneNimrod^Talk? 17:43, 11 May 2008 (UTC)

Light is an electromagnetic wave - only charged bodies interact with it. So (presumably uncharged, certainly the upper limits on its charge are very small) dark matter particles don't interact with it. The electrons in your body are what reflect light - a big brick o' neutrons would reflect very little light indeed (only through virtual particles. WilyD 17:46, 11 May 2008 (UTC)

How do we know the upper limits on the charge are small? Wouldn't our observations just tell us the upper limits on the net charge? Objects with a zero net charge can still reflect light by being made up of equal numbers of positive and negative charges (eg. atoms). --Tango (talk) 18:59, 11 May 2008 (UTC)

That's correct. But we can put small upper limits on the charge of each particle. Your body is neutral because it contains equal numbers of electrons and protons, but the negative electrons still reflect light. So DM can't be made of negative and positive particles lumped together like 'normal' (Baryonic) matter is, or we'd see it. Olaf Davis | Talk 20:41, 11 May 2008 (UTC)

If the charge is not small, then dark matter particles would be created quite often in particle accelerator experiments, where it would show up as missing mass and momentum. Null results from such experiments limit the charge of any unknown particle (this depends on the mass of the unknown particle). This method does not depend on whether or not the particles actually exist.

There are other ways to contrain the charge of dark matter particles. E.g. one can exploit the fact that the millicharged DM background would become polarized in an electric field. You can try to measure the electric field inside a cavity of a conductor when there is a strong elecric field outside, see here. Other possible experiments are discussed here and here. Count Iblis (talk) 21:02, 11 May 2008 (UTC)

(ec)First of all, no one has proved dark matter exists. Astrophysicists would like it to exist because if it does not there are severe theoretical difficulties with our theories of the universe. There are many ideas of what dark matter might be and why we cannot see it, as Cyclonenim said, look at the article for the various possibilities. I think the claimed discovery you are referring to is a galaxy rather than a planet, also mentioned in the article. SpinningSpark 17:50, 11 May 2008 (UTC)

I concur with Spinningspark - I'm not sure about the "dark planet" thing, but I guarantee it wasn't a planet made of dark matter. At this point dark matter is just a hypothesized (but as of yet not directly observed) substance introduced to explain gravitational anomalies in the universe. Some physicists have proposed a model of what dark matter might be like if we ever detect it - it's known as a WIMP. Basically, WIMPs are particles that interact only via the gravitational force and weak nuclear force, like neutrinos. So if dark matter exists and is made up of something like WIMPs, that would mean that they would not emit or absorbe any electromagnetic radiation (light), and would be literally "dark". But again, it's all highly hypothetical at this point. --Bmk (talk) 18:45, 11 May 2008 (UTC)

These are both realistically misrepresentations. Science never proves anything exists - The level of confidence among astronomers that is such that working with ~100 astronomers, I don't know any who take seriously an alternative explanation. But there's no evidence of "dark matter planets" - "dark planet" would presumably mean a planet that's just too dim - a planet discovered through radial velocities or gravitational lensing probably won't be visible, nor would a free-floating planet (you might call it a planemo if you want to avoid the ire of certain astronomers, who'll remain nameless). Dark matter might form compact objects, but it seems unlikely - all the observations we have of it suggest its not very collisional - see bullet cluster, for instance, and maybe read MACHOs. WilyD 18:56, 11 May 2008 (UTC)

According to the article 'bullet cluster', stars arent very collisional either-"The major components of the cluster pair, stars, gas and the putative dark matter, behave differently during collision, allowing them to be studied separately. The stars of the galaxies, observable in visible light, were not greatly affected by the collision, and most passed right through, gravitationally slowed but not otherwise altered". Em3ryguy (talk) 21:07, 11 May 2008 (UTC)

That's right. There are actually models (admittedly bit far out) that predict DM analogous to ordinary matter. So-called [mirror matter] is an example and this article actually suggests that some close in extrasolar planets might actually be made of this invisible mirror matter :). See also here. Count Iblis (talk) 21:16, 11 May 2008 (UTC)

math and physical difference in mental ability

is there any conclusive data that asain people are better at math because of a physical difference in there brain or learning ability that gives them an advantage over other races? —Preceding unsigned comment added by 206.75.0.220 (talk) 17:54, 11 May 2008 (UTC)

Not all Asian individuals are as intelligent as you imply. However, when they are, it tends to be as a result of how they were schooled rather than a physical difference. Regards, CycloneNimrod^Talk? 18:26, 11 May 2008 (UTC)

If you are pondering why a lot of good engineering is presented by Asian tigerstates, Japan and Asia in general, the answer should not lie quite in the brain. The dominant religion, for instance, is one which stresses subordination to mentors and the importance of learning skills; to strive for a common goal. Now, that's merely the gist of things. Greater political factors have a lot to do with how industry in Asia has gone well after the second world war. Confucianism, Japan and Four Asian Tigers should give you a quick introduction, while better, Asian-wide topics can be reached from these. Merely google something like "industry in asia", or "asian economy". Does this help you? I hope my interpretation was correct, or at least not completely wrong. Scaller (talk) 18:34, 11 May 2008 (UTC)

I may be heading down a slippery slope here, but see Race and intelligence. SamuelRiv (talk) 19:57, 12 May 2008 (UTC)

Concentrated Blackcurrant Juice

What would be the effects of "hypothetical person A" drinking too much concentrated Blackcurrant Juice? Would it be enough to kill them? ps this is not medical its science in hypothetical terms. Mr Beans Backside (talk) 18:07, 11 May 2008 (UTC)

It is hypothethically possible to drink enough of virtually any liquid to kill yourself, but the amounts are really quite excessive. See: water intoxication. Dragons flight (talk) 18:41, 11 May 2008 (UTC)

Do you mean without diluting it? I'm not sure it's strong enough to harm you, but if it is, it could dehydrate you and cause damage to the liver and kidneys, I expect. I'm just guessing, really, though. I expect someone here knows better than I do. --Tango (talk) 18:54, 11 May 2008 (UTC)

Why was I born to my parents in my town at a specific time?

moved to HumanitiesDesk

Taste of apple seeds

I've read that apple seeds contain cyanohydrins (see hydrogen cyanide) and that cyanide has a "faint bitter almond-like odor". I've also noticed that apple seeds (at least for Cripps Pink and Golden Delicious and some other varieties I've tried) taste quite strongly of almond. Is this a coincidence, or am I indeed tasting the hydrogen cyanide present in the apple seeds? Eric. 81.157.250.169 (talk) 20:15, 11 May 2008 (UTC)

Well cyanohydrins are produced by reaction with HCN. Also, the almond taste of such seeds is mostly subjective. For instance, I personally don't taste it. Cyanohydrins are derived from ketones, for instance, which can have a fruity/distinctive smell. This could possibly explain the taste. Wisdom89 _{(T / ^C)} 20:48, 11 May 2008 (UTC)

I thought that it was really bad for you to eat apple seeds? Never really thought to question it but I was told as a child that they were toxic and were always to be discarded... --Kurt Shaped Box (talk) 21:37, 11 May 2008 (UTC)

See Archive May 1 "Cyanide and almonds" same goes for apple seeds Lisa4edit (talk) 00:13, 12 May 2008 (UTC)

Ah, interesting. So the taste is due to benzaldehyde? I see. Eric 81.157.250.169 (talk) 12:52, 12 May 2008 (UTC)

I've had around 20 or so apple seeds in one sitting before (chewed, not swallowed whole), so either they're almost harmless or I'm working on being the next Rasputin. Eric 81.157.250.169 (talk) 12:52, 12 May 2008 (UTC)

Many plants and seeds contain glycosides in varying low does concentrations. Among them such healthy foods as spinach. One of those glycosides is amygdalin which is contained in the pits of stone-fruit and apple seeds. If you add enzymes to amygdalin HCN is split off. HCN is toxic in very low concentrations to plants and animals. Plants contain both the amygdalin and the enzyme, but they are stored separately from each other. When you chew the seed, the enzyme gets mixed with the amygdalin and reacts. Some amygdalin passes through to your digestive tract and reacts with enzymes there. HCN is also further broken down by enzymes into HCNO which is not toxic. But the body only has a limited capacity for that to happen. Some bacteria also process the HCN into HCNO. Individual apple seed have less bulk than bitter almond. I've dug around for concentrations and found one source [1] that states 690-790 ppm (mg/kg). Based on this study another source [2] created this scenario The ADI (acceptable daily intake) described for cyanide has been reported at 0.05 mg/kg. If all amygdalin would be converted into cyanide this would corresponds to an ADI for amygdalin of 0.85 mg/kg. For a person of 75 kg this equals an acceptable intake of amygdalin of 63 mg daily. Assuming that all amygdalin from apple seeds is extracted from the seeds (which will be an overestimation), this equals the consumption of 80 g of apple seeds. Before you start upping your daily consumption to that amount you should consider that the ADI includes intake from all sources. (lima beans, bamboo shoots, juice, cider, and even corn to name just a few). It also presumes that you are in perfect health otherwise and weigh 75 kgs. Lisa4edit (talk) 19:52, 12 May 2008 (UTC)

Thanks for the thorough research & information -- I considered asking for specific concentration information but thought that was a bit much to hope for. Fortunately 80 g of apple seeds is well beyond my appetite for them. I found your first reference helpful for putting such information in context. Eric 81.157.250.169 (talk) 04:15, 13 May 2008 (UTC)

Aluminum chloride

Is aluminum chloride the same as aluminum zirconium tetrachlorohydrez glycine? Mr Beans Backside (talk) 20:41, 11 May 2008 (UTC)

Take a look at aluminium chloride and zirconium + glycine and tell us Nil Einne (talk) 20:50, 11 May 2008 (UTC)

Hardness of water

Is the hardness of water a consequence of pipe scaling? What technology and major steps are involved in the purification of drinking water and the treatment of waste water? Mr Beans Backside (talk) 20:43, 11 May 2008 (UTC)

To the first one, er no... As Hard water and Fouling may tell you, it's more likely to be the reverse. For the second one, is there anything in particular that Water treatment doesn't tell you? Nil Einne (talk) 20:56, 11 May 2008 (UTC)

Pressure and altitude

Could someone explain why pressure decreases but temperature varies as altitude increases? Mr Beans Backside (talk) 20:44, 11 May 2008 (UTC)

Erm, well as a general rule, temperature decreases with altitude so I'm not entirely sure where you got this impression from. Regards, CycloneNimrod^Talk? 21:02, 11 May 2008 (UTC)

Once you get high enough, that's not the case any more. The Thermosphere can get extremely hot, for example. However, since it's so thin, the actual amount of thermal energy is very low, so it wouldn't feel warm. --Tango (talk) 21:53, 11 May 2008 (UTC)

You should look at atmospheric pressure for pressure (obviously) and lapse rate for temperature. SpinningSpark 21:21, 11 May 2008 (UTC)

Different sources of heat become significant at different altitudes, which is what causes the variation in temperature, rather than just a gradual cooling as you might expect. Earth's atmosphere will tell you more. --Tango (talk) 21:53, 11 May 2008 (UTC)

Energy sources

I know there's electric, solar, wind, hydroelectric, geothermal, coal, oil, natural gas, and nuclear. What other energy source are there, or are those them all? Mr Beans Backside (talk) 20:48, 11 May 2008 (UTC)

Biomass? Fribbler (talk) 20:57, 11 May 2008 (UTC)

No, that is not all. There is tide and wave power for a start. There are many more, take a look at List of energy topicsSpinningSpark 21:00, 11 May 2008 (UTC)

(EC) There are lots and lots of potential energy sources. Energy development has most/all of the ones currently of most interest. List of energy resources has a lot of other things including means of energy storage and energy conservation Nil Einne (talk) 21:01, 11 May 2008 (UTC)

What about potential energy? User:Yetmotega/1 Yetmotega (talk) 22:00, 11 May 2008 (UTC)

Potential energy is energy stored in a field. So you need to specify which force of nature we are discussing know the energy type, eg electric, magnetic, gravitational etc. SpinningSpark 22:30, 11 May 2008 (UTC)

E=mc² so basically everything is an energy source. GameKeeper (talk) 22:52, 12 May 2008 (UTC)

The most basic energy sources are nuclear fission/fusion and cosmic motion. Motion of the heavenly bodies causes tidal forces. Natural nuclear fission (decay) of Uranium in the earth's crust cases it to heat up, giving us geothermal energy. Nuclear fusion makes the sun 'burn', which (directly) gives us light, thermal solar energy and photovoltaic energy, but also causes the air and water to heat up, causing wind (thus wind energy) and evaporation, rain and thus hydro-energy. The difference in salinity of this water and the sea water can also be used (blue energy). The oceans heat up unevenly, so the difference in temperature between top and bottom water can be used to produce energy. And of course we can let plants grow on the sunlight, giving us biofuel. Let that rot for a while and you get fossilised fuels (coal, oil, gas). So apart from tidal and geothermal it's all solar energy. And then there is man-made nuclear energy, but why bother when we already have the sun doing that for us, while we have barely sratched the surface of the possibilities that gives? (Sorry, a bit of politics in there. :) )

Note that 'electric', which you mention is an energy form, not an energy source. And while I'm at it, hydrogen is not an energy source, but a way of storing energy.

I'm sure I missed a lot of the resultant energy sources too. And then there are combined technologies like the solar chimney. The possibilities are endless. Too bad we've only recently started lookiong into all these options and are still barely investing in such research compared to the shitloads of money poured into fossil fuels and nuclear fission. DirkvdM (talk) 09:04, 14 May 2008 (UTC)

Which genes flank TJP1

How do I find out which genes flank TJP1 in humans? I figure one of the many genomic databases would be able to help but they're terribly complicated and intimidating. ----Seans Potato Business 21:04, 11 May 2008 (UTC)

On the link you provided, scroll down to the section Genomic context. This will tell you the chromosome the gene is present on and it's location. By searching the position before it or after it should give you your answer. Regards, CycloneNimrod^Talk? 21:11, 11 May 2008 (UTC)

Its actually a bit complicated this one. However, 5' of TJP1 appears to be necdin-like 2, while 3' is CHRNA7-FAM7A fusion isoform 1 (which is a very odd locus). There may be other genes in between, but they have not been characterized. Rockpocket 21:53, 11 May 2008 (UTC)

How did you get those? ----Seans Potato Business 21:59, 11 May 2008 (UTC)

Okay, this isn't working. I'd like to know in which order the genes TJP1, NDNL2, GREM1, SLC12A6 and SPRED1 occur. I know they're in the same region, but I want to determine if there are any genes between them and in what order the occur. If I search for each gene I get:

ndnl2 15q13.1

slc12a6 15q13-15

tjp1 15q13

grem1 15q13-15

spred1 15q14

Yet none of these shows up on the 'genomic context' diagram of any of the others. How can I interpret this mess? Does SPRED1 exist on an exon inside both GREM1 and SLC12A6 which both exist in exons of each other? I suppose one may be on the antisense strand, but there's going to be overlap somewhere here. ----Seans Potato Business 21:55, 11 May 2008 (UTC)

According to Ensembl (by searching for each gene on the human genome):

• Ndnl2.. can be found on Chromosome 15 at location 27,347,645 - 27,349,325 and is anti-sense.
• Tjp1.... can be found on Chromosome 15 at location 27,778,863 - 27,901,998 and is anti-sense.
• Grem1.. can be found on Chromosome 15 at location 30,797,497 - 30,814,158 and is sense.
• Slc12a6 can be found on Chromosome 15 at location 32,309,489 - 32,417,557 and is anti-sense.
• Spred1. can be found on Chromosome 15 at location 36,331,808 - 36,433,526 and is sense.

Are there intervening genes? Yes in all cases, except between Ndn12 and Tjp1. Rockpocket 22:35, 11 May 2008 (UTC)

Okay, this is really helpful of you. Thanks. However, now I have a conflict; SPRED1, according to this is at 15q14 while GREM1 according to this is at 15q13-15. If 15q13-15 means 15q13 to 15q15, then why do those numbers you (kindly) provided not overlap? And how did you find out whether they were sense or anti-sense? --Seans Potato Business 22:48, 11 May 2008 (UTC)

The "q" refers to chromosome regions while the numbers (13-15) refer to cytogenetic bands identified by staining. That nomenclature is an old skool way of positioning genes on chromosomes and is not particularly accurate. Now we have a fully sequenced genome we can precisely identify exact positions of genes. In this case 15q13-15 means that Grem1 resides somewhere within bands 13-15, rather than meaning it spans that huge length. I used Ensembl to find the info, and identified the strand from that. For example, have a look at the diagram on the TJP1 page, under the "transcripts" sub-section. Find the thick blue line that says "DNA (contigs)". Now any gene identified above that line is on the forward strand (sense orientation) and any genes under that line is on the reverse strand (anti-sense). TJP1 is directly underneath the line, therefore it is anti-sense.

If you don't wish to use Ensembl, the NCBI site you were using gives the same info. On the Spred1 page, on the right hand side of the "genomic context" section there is a link to "See SPRED1 in MapViewer" If you follow that link [3], you can see that the Spred1 gene is located on the right hand side vertical line spanning roughly the same distance I provided (36331k to 36433k). If you want exact values, you can always zoom in by clicking on the gene. Note also the little black arrow beside the Spred1 gene name. The arrow points downwards, indicating the gene is on the sense strand. If it was to point upwards, you would know your gene of interest was anti-sense. Rockpocket 01:22, 12 May 2008 (UTC)

How does something vibrate in 10 dimensions?

An article I read awhile back about an atom's parts said that superstrings are the smallest part of the atom. It went on to say it vibrates in 10 dimensions.

Huh? How do they determine this? If you cant actually see it with a microscope, how can you determine with fancy math that something can exist in 6 dimensions we cant even imagine?--Sam Science (talk) 21:40, 11 May 2008 (UTC)

There is very little experimental evidence for superstring theory at this point, as far as I know. It's mostly maths and mathematicians can imagine all sorts of things that don't fit in our everyday understanding of the world. If you can work out the maths of something vibrating in 3D, you can work it out for something vibrating in 10D, the maths is pretty much the same, just with different numbers. It turns out that if you do things in just the right way (that's the hard part) those vibrating strings happen to interact with each other in the same way we observe elementary particles interacting. --Tango (talk) 21:47, 11 May 2008 (UTC)

I think you're a tad confused with what you read in that article. String theory is theoretical, as the name suggests and it is hoped it'll fill in a lot of gaps in physics, but it certainly isn't proven. Also the theories state that the strings vibrate in one dimension, not ten. You're quite right in thinking we can't see them with microscopes, we can't even see atoms themselves properly. As I said, it is not a proven theory, simply something that is being made up to fix gaps in the theories of physics. Regards, CycloneNimrod^Talk? 21:50, 11 May 2008 (UTC)

"Proven theory" is a contradiction in terms. Theories can't be proven, you can just gather evidence for them until it becomes very unlikely that they're wrong. Proof is a mathematical concept, you prove theorems, not theories. And what do you mean by them vibrating in one dimension? They are one dimensional objects vibrating in 10 dimensional space. --Tango (talk) 21:55, 11 May 2008 (UTC)

Physicists use mathematics to describe the universe, using vectors and matrixes to describe space. In simple models these are 4-element matrixes - 3 space-like and 1 time-like (see Minkowski space). It may be surprising, but this often makes the mathematics a lot simpler - for example, electricity and magnetism join messily (using several equations) using 3 space dimensions and keeping time separate (using maxwells equations), but join simply (using one equation) when using the 4 element vectors (using the electromagnetic tensor). Maxwell's equations and the electromagnetic tensor are equivalent - the only difference is how they're expressed.

Theoretical physicists find that their theories work when these vectors and matrixes have more than 4-elements - generally the theories use either 10 or 11 elements in their vectors and matrixes, and this corresponds to 10 or 11 dimensions. The reason why a new theory is needed is to express the four fundamental forces and lots of fundamental constants more simply. This is cutting-edge physics - a lot of the work on these theories is currently working out how to detect how this is different from the standard model. --h2g2bob (talk) 22:43, 11 May 2008 (UTC)

The various string theories only work at all in a particular number of dimensions (10, 11, 12 or 26 depending on which variant you're talking about). I don't know what goes wrong otherwise, but it might be a violation of unitarity (meaning, basically, that the theory predicts events happening with a probability greater than one). So if you want to use string theory as a physical theory, you're committed to having those extra dimensions. There's no other reason to think they exist. -- BenRG (talk) 01:17, 12 May 2008 (UTC)

One of the things that fails is that photons are not massless. More generally, there is a mapping problem. If you assume that all particles are associated with vibrational string modes and that there are X independent classical properties of particles (e.g. charge, spin, color, etc.) then you require at least X extra dimensions to map those properties onto geometric structures. (You can get away with less than X if you assume that they aren't ultimately independent.) Dragons flight (talk) 05:43, 12 May 2008 (UTC)

Dogs in heat

How many times should a female dog mate while shes in heat to ensure she becomes pregnant? And at what point during her being cycle should she mate for the most success? Mr Beans Backside (talk) 22:07, 11 May 2008 (UTC)

• For the most success she should mate each day during her 3 most fertile days.Mieciu K (talk) 21:27, 12 May 2008 (UTC)

Chemists: solvents for spot cleaning carpet?

I have some dried emulsion paint (might be called latex paint in the US?) I want to remove from a carpet.

I do not know what the carpet is made of, but I do not think it is wool. Many capets in the UK seem to be made of polypropylene or perhaps nylon.

My questions are - 1) as an alternative to the below, would white spirit, turpentine substitute, or even WD-40 be just as good please? And 2) would Nail Polish Remover dissolve the carpet? I.E. It dissolves the paint, it does not dissolve the carpet!

Rug Doctor "Traffic Lane Cleaner" (carpet pre-washing spray): active ingrediant Ethylene Glycol Monobutyl Ether - has worked well removing dried chewing gum and unknown stains from a carpet. Have not tried it on paint yet.

Nail Polish Remover: Acetone, Glycerine, Cetylacetate, Oleyl Acetate, Acetylated Lanolin Alcohol, Polysorbate 80. Highly recommended for carpet paint removal here http://www.thriftyfun.com/tf991362.tip.html

Stardrops cleaner: Sodium dodecylbenzene sulphonate, Alkyl ether sulphate, Alcohols C9-11, ethoxylated Bitrex (Denatonium benzoate) solution, Bronopol (2-bromo-2-nitropropane-1,3-diol).

Cheaper and to-hand alternatives: white spirit, WD-40.

Thanks. 80.2.195.209 (talk) 22:54, 11 May 2008 (UTC)

Whatever you do, do a "spot-test" first on an inconspicuous area of the carpet (e.g. part that's always covered). --Seans Potato Business 22:58, 11 May 2008 (UTC)

I would guess that white spirit will work (it will almost certainly remove the paint, I'm just guessing it won't ruin your carpet). As Seans says, you should definitely test it somewhere out of the way first. If it were me, I would just have a go with white spirit somewhere hidden and see what happens, but you may want to wait for more informed answers (I've never been one to follow instructions!). --Tango (talk) 23:01, 11 May 2008 (UTC)

Not based on any chemical analysis, but merely OR. Undiluted "Pine Sol" and elbow grease along with a pile of paper towels worked well. A generic "compare to" product didn't. Since you aren't in the US I don't know if you can get it and whether you get the same stuff under that label. We're out and I threw out the old bottle, so I can't tell you the composition. Trying in a hidden area is always a good idea. Lisa4edit (talk) 23:46, 11 May 2008 (UTC)

Emission line

Where can learn more about the spectral lines of substances? In particular, there is apparently an argon emission line at 750.38 nm and I'd like to know if it belongs to the argon atom or an ion and what the cross section for its activation is as a function of incident electron energy. I imagine there are reference works for this kind of data and would be glad for directions. Thanks. —Bromskloss (talk) 23:09, 11 May 2008 (UTC)

Atomic spectral line has an explanation and a link at the bottom that should help answer your question. --Lisa4edit (talk) 23:33, 11 May 2008 (UTC)

Thanks, but I'm not looking for an explanation of how it works. What I need is a data collection where I could look up argon, see a list of all its lines and preferably the corresponding cross section for electron-argon collisions that would result in emission in this line. —Bromskloss (talk) 23:46, 11 May 2008 (UTC)

I recommend the CRC Handbook of Physics and Chemistry at http://www.hbcpnetbase.com/. It's quite comprehensive. The data you're looking for will probably be found in Section 10: Atomic, Molecular, and Optical Physics. --Bmk (talk) 02:08, 12 May 2008 (UTC)

Thanks for the tip. That one could be useful for the future. However, I look at the table Line Spectra of the Elements, but there is no mention of an argon line at 750.38 nm. :-( (And no cross secions, as far as I can see.) —Bromskloss (talk) 08:54, 12 May 2008 (UTC)

No, the Argon I line at 750.3 nm is listed there!! I must defend the honor of the CRC handbook!! :) The lines are listed in Angstroms, rather than nm, so you can find it at 7503.8 A. But no, I'm not sure where you can find the crossection. --Bmk (talk) 14:05, 12 May 2008 (UTC)

Ah, I didn't see that! It's a good thing for me you came to defend it. :-) —Bromskloss (talk) 09:11, 13 May 2008 (UTC)

Lol - after your comment I spent a few horrified minutes looking for 750.38 before I realized I was also using the wrong units :) --Bmk (talk) 01:51, 15 May 2008 (UTC)

A quick google search reveals that it is from ArI - ie non ionized. It is one of the main emmission lines. But this is not a systematic method! Graeme Bartlett (talk) 03:56, 12 May 2008 (UTC)