Wikipedia:Reference desk/Archives/Science/2010 November 22

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November 22

Human Dissection

Hello. Pretend that I was born yesterday. Why is the identity of a human subject about to go under dissection concealed? Thanks in advance. --Mayfare (talk) 04:21, 22 November 2010 (UTC)

Well the obvious one is in case someone observing knows the donor. Do you need more reason then that? Vespine (talk) 05:37, 22 November 2010 (UTC)

There are laws[1] [2] [3] against desecrating corpses. Perhaps the dissector(s) wish to avoid a writ of Habeas corpus.
I congratulate the OP on their first day of speaking English. Cuddlyable3 (talk) 08:57, 22 November 2010 (UTC)

That's high praise indeed from you, C3! Actually, the rights of the prosector are generally protected by the various Human Tissue Acts against prosecution for desecration of a corpse where the decedent has donated their body. I know C3's comments about habeas corpus represents comedy for the linguist, but I thought I'd just clarify that. The main reason is as per Vespine's response, and to preserve confidentiality for the donor and his or her family. Mattopaedia ^{Say G'Day!} 10:14, 22 November 2010 (UTC)

engineering survey

What are the importance of surveying to the engineers?

We have articles on Surveying, Civil engineering and Military engineering that may be of interest. Itsmejudith (talk) 13:35, 22 November 2010 (UTC)

Something interisting: about a year ago a company I used to work for, employed a brand new technology (at least in New Zealand). This technology basically uses sonar scanning to methodically confirm the homogenity of newly cast concrete support columns. Homogenity is important in establishing the strength of concrete. Concrete that is not mixed well, has large zones of differing densities. Even if the bulk of a structure is dense and strong, a single weak spot of low density may cause a catastrophic failure. This may not answer your question, but I think that applying sonar technology in such a way is really neat.

Surveying is very important to engineers, no actually, it is key. Without surveying, engineers would basically be out of a job. Surveying gives crucial information about the terrain, so that engineers know what they're dealing with. It allows them to know how to stop a building from sinking into the ground or toppling over. Plasmic Physics (talk) 13:56, 22 November 2010 (UTC)

Please note that not all engineers work with buildings. Surveying is not very important to electrical, chemical or aerospace engineers. Googlemeister (talk) 15:06, 22 November 2010 (UTC)

Tin(IV) sulfate?

From the tin(IV) oxide article:

Similarly, SnO2 dissolves in sulfuric acid to give the sulfate:[3]

SnO2 + 2 H2SO4 → Sn(SO4)2 + 2 H2O

Does tin(IV) sulfate really form like that? If it is so easy to make, it deserves an article. --Chemicalinterest (talk) 15:25, 22 November 2010 (UTC)

Be WP:BOLD! shoy (reactions) 16:01, 22 November 2010 (UTC)

But does it exist? Unfortunately, my chemistry experiments have been terminated and I am unable to do some WP:OR to prove that it does or doesn't exist. --Chemicalinterest (talk) 17:49, 22 November 2010 (UTC)

Stannic sulfate appears to be CAS 19307-28-9. Can also be made by dissolving certain forms of tin metal in concentrated sulfuric acid.(ref: doi:10.1021/ie50259a027) Commercially available from Fluka (maybe as a sulfuric-acid adduct, if you feel like believing their catalog), with a note that it's a reagent used for some standard analytical-chemistry procedure. DMacks (talk) 18:13, 22 November 2010 (UTC)

Electric heater efficiency

I just got a "Nordik Ceramic Heater" (the kind of electric heater that won't set things on fire if they touch it) and on the box it claims "HIGH EFFICIENCY ceramic elements power consumption / instant settings at High and Low". Am I wrong that (other than radiative losses through windows, sound energy escaping the room, etc.) all electric heaters are ~100% efficient, that pretty much being the definition of a resistive electric load? And that there is essentially no difference in conversion efficiency between a ceramic-element heater and a wire-element heater? And if I'm right, what could be the basis for the claim of "high efficiency"? Thanks! Franamax (talk) 17:44, 22 November 2010 (UTC)

You're not wrong; the basis might be different meanings of "efficiency". For instance, one could make such a safe heater by wrapping an unsafe heater in a large amount of (non-flammable) insulation, but then it wouldn't heat as quickly (and you would probably have to run the heating element only part of the time to prevent overheating). If they've made a heater with no exposed extreme temperatures but also have some (convective?) system for emitting heat quickly, that could be called "more efficient" in that you wouldn't wait so long for the effects. It might also radiate more rather than conduct; then if you sit by it more of it heats you directly rather than heating a rising plume of air that you're not sitting in. Then you would feel warmer for the same energy spent (or feel as warm for less energy). --Tardis (talk) 18:42, 22 November 2010 (UTC)

(ec)Yes, that's true from a heat/temperature point of view. But humans don't measure temperature, they measure how fast heat is gained or lost by the skin. So a process that makes the skin feel warm, without actually heating the room can be more than 100% efficient by some measures. That's the idea here - it sends infrared heat to your skin, without (fully) heating the room in between. How effective this is is debatable, because it will only work for the side of you that is facing the machine. Ariel. (talk) 19:33, 22 November 2010 (UTC)

Sounds a lot like the EdenPURE heaters with highly dubious and misleading claims, hawked by Bob Vila infomercials and direct mail ads, and sold for over 10X what a normal space heater would cost. I agree that all electric space heaters are probably over 99% efficient, with light and sound going through the windows, and chemical changes such as burning dust on the electric wires, being the sources of the <1% inefficiency. So, it's simply not relevant to compare this type of efficiency in an electric heater.

Other types of inefficiency mentioned in the EdenPURE ads were:

1) Heating the ceiling more with other space heaters. This is definitely an issue with convection heaters, not sure I believe their claim that other forced air heaters are worse than them that way.

2) Heating the basement, walls, and duct work. An issue with central heating, but then again, you need to heat those areas somewhat or your pipes will freeze.

3) Heat going up the chimney. Also an issue with central heating, but you need some heat to go up the chimney or you get condensation and poor draft. StuRat (talk) 19:05, 23 November 2010 (UTC)

Can we really digest enzymes "whole," or are they broken down?

So much natural food these days touts the amount of enzymes they contain, and there is so much advice about eating raw or less-cooked foods so that we don't "destroy" the enzymes in the foods.

My question is: don't we digest all proteins into amino acids? And if so, does it matter if we're not consuming enzymes in our newest energy bars or raw foods, so long as we're consuming all the amino acids we need to consume?

I'm tried to research this, but the enzyme page doesn't talk about it, and searching "digest enzymes" on Google comes up with all the enzymes that are used in order to digest things. Is there any published information that deals with the question of whether proteins and enzymes are broken down by the digestive system before they are absorbed, and whether it actually makes any difference to your body whether the proteins have been denatured by cooking?

Thanks! — Sam 63.138.152.135 (talk) 17:51, 22 November 2010 (UTC)

From here, "The enzymes naturally present in food play an important role in digestion by helping to predigest the ingested food in the upper stomach". I used the Google search term "health benefits enzymes in food". The claim sounds plausible, although I'm not sure whether the enzymes in the food would still function in the acid environment of the stomach. Franamax (talk) 17:59, 22 November 2010 (UTC)

Hmmm, that's interesting, and is likely what people are talking about when they refer to the benefits of eating enzymes. That said, I can't find anything about "Enzyme University," and they don't have any sources, and they seem to be (passively) pushing supplements, so I'm not certain that they're an authoritative source. — Sam 63.138.152.135 (talk) 18:16, 22 November 2010 (UTC)

Yes, note I said "sounds" plausible, not "is" plausible. The top Google hits are all sites that think they have something that would be good for you if only you would buy it on a regular basis. They seem to support their claims with anecdotal evidence like "people have more energy" rather than double-blind studies or analysis of undigested nutritive content in the stool. And how would you do a double-blind study anyway? people can usually tell the difference between cooked and raw food. It's also possible that people feel more energy because they get tired of chewing the raw food and don't overstuff themselves as on tasty cooked food. The key measure is how active these enzymes are in the time between mastication of the food and saturation in stomach contents at pH 3.5-4.5, and how active the enzymes are at that pH level. You would likely have to find a much more detailed source to get that information. Franamax (talk) 20:51, 22 November 2010 (UTC)

I located an "Enzyme University" at [4]. Those responsible for the site clearly have a better knowledge of biology than the average quack, they cite patents that they've developed, and they appear to have some common basis with known products such as the lactase in Lactaid (see [5]). That said, I think that some caution is still required, because I don't think that they are marketing these things as drugs — they aren't mentioning safety and efficacy studies in these pages. The enzymes come from various odd sources, such as fungi, which might not ordinarily be eaten.

I would question the advisability, for example, of trying to replace pepsin activity lost by antacid with an outside enzyme that is active throughout the digestive tract [6], because I would worry that if it works, it might digest signalling proteins on the outside of cells in the gut and end up causing cancers. (Note that chronic use of antacid is definitely a problematic treatment in itself, addicting the user by increasing the stomach's acid production...) Human digestive proteins might have special safety features still unknown to science, and the acid requirement that the product circumvents is a basic safety shut-off that prevents them from damaging the duodenum and other portions of the gut. I should note that the Japanese have been the undisputed masters of coming up with various enzymes and artificially digested foods, but they also have such a high rate of stomach cancer that they have to get tested for it routinely like people get colonoscopies in the U.S.

I think that when you take something as a nutritional supplement rather than a drug, you should know for sure that it is something that has been consumed, either as food or as herbal medicine, for hundreds if not thousands of years. Otherwise you should demand clear, modern evidence of safety. Wnt (talk) 22:18, 22 November 2010 (UTC)

I agree that that site isn't entire quackery but: "The enzymes naturally present in food play an important role in digestion by helping to predigest the ingested food in the upper stomach. Cooking and processing destroys the natural enzymes found in foods. This places the full digestive burden on the body, which can cause extra stress on the digestive system, leading to incomplete digestion. As a result, vital nutrients may not be released from the food for assimilation by the body." is pretty flawed reasoning in my opinion. The reason we cook food is to break down plant cell walls and denature proteins so that our digestive enzymes can get at the molecules in food and digest them. Cooking will stop enzymes in naturally present in food from functioning, because they aren't enzymes that breakdown food as our enzymes do, since self-digesting isn't a good idea! Also plant have been fighting an evolutionary war against herbivores for millions of years, some of these defences, e.g. tannins and protease inhibitors, decrease the nutritional quality of plants to try and make herbivores eat other plants. It's unlikely that plants contain enzymes that would do the opposite and make themselves more digestible. We've evolved so that we are now fairly dependent on cooking to pre-digest food and I find it difficult to believe that our bodies need any help in digesting food, since the human gastrointestinal tract seems to do a pretty good job. There are of course far more enzymes in our guts than just the ones we produce due to the gut flora which digest many compounds which we can't digest ourselves. I'm always extremely sceptical of a company saying their product is useful, especially when what they are selling is basically just purified mould as they obviously have a conflict of interest. I can't find any independent studies about these supplements and their own research is based on a mechanical model (!) of the digestive system which also "set out to prove" they were effective - not a good way of doing science. SmartSE (talk) 14:57, 23 November 2010 (UTC)

I fully agree with you that the "we need enzymes in our food to aid digestion" notion is dubious, but I would hesitate to endorse the claim that the (major) purpose of cooking is to break down foods so that our own digestive enzymes can get at them. It's worth remembering that most cells do contain and can manufacture enzymes designed for partial or total self-digestion (see autophagy, apoptosis), but that their function is generally tightly regulated while the organism is still alive. As well, many foodstuffs fresh from the field are going to come with (often-undesirable) hangers-on: microbial contaminants that very much do want to digest their hosts, and secrete all the necessary enzymes to do so. Cooking, smoking, salting, drying, and pickling are all techniques that we use to denature proteins in order to discourage spoilage and inactivate pathogens that would otherwise very quickly pre-digest our foods — whether we wanted them to or not. (It goes without saying that these preservation techniques all also inhibit or inactivate the pathogens responsible for many diseases, which is another perq of a fully-cooked diet.)

Cooking also has the benefit (in many cases) of improving the taste of food. We have evolved to prefer sweeter, fattier foodstuffs (in order to get the calories we need and avoid starvation); cooking foods allows us to simulate these flavors and satisfy that evolutionary imperative (through caramelization and the Maillard reaction for sweetness, and the liquefaction of animal fats for that fatty mouthfeel). Cooking is (evolutionarily speaking) a very recent development; I would be extremely surprised to find that we were in any way dependent on it. TenOfAllTrades(talk) 15:43, 23 November 2010 (UTC)

Cooking food with fire is far from a recent development: it seems to older than homo sapiens: Control of fire by early humans. The human gut is shorter because we eat cooked food, and so don't need such long digestion to extract nutrition. I have never heard (in a reliable source) of someone maintaining a raw food diet at a stable weight: every account I've seen, the person loses weight until they reintroduce non-raw food, or they keep some processed/cooked food in their diet. We are half-cyborg, reliant on our technology :) 86.166.40.102 (talk) 19:20, 23 November 2010 (UTC)

Niña

Is there a name for a ship like the Niña that has two square-rigged sails in the front and then a lateen sail at the back? --The High Fin Sperm Whale 19:31, 22 November 2010 (UTC)

a Carrack. --Dr Dima (talk) 20:14, 22 November 2010 (UTC)

More recently, a barque. Mikenorton (talk) 23:00, 22 November 2010 (UTC)

Actually, barques have a gaff rigged sail at the back. Thanks anyway. --The High Fin Sperm Whale 23:31, 22 November 2010 (UTC)

The Nina and the Pinta were Caravels, originally caravela latinas (lateen sails on all three masts), but re-rigged as caravela redondas to follow the trade winds on the outward leg. And our article on the caravel could really use some work! --Stephan Schulz (talk) 07:52, 23 November 2010 (UTC)

Soda can exploding

I'm sorry for posting what is probably a trivial question, but why does a can of soda "explode" when opened after shaking? I've checked online, but all of the answers seem either very vague or plain wrong.

Correct me if I'm wrong, but as I understand it, carbonated liquid contains dissolved CO₂, like a solution. But some of the gas can form microbubbles (on their own accord or with the help of nucleating sites? I don't know...). When an unshaken can is opened, the liquid's pressure drops, and the microbubbles are then able to grow in size and leave the liquid. But why would shaking cause so many more bubbles to form? 70.52.44.192 (talk) 21:16, 22 November 2010 (UTC)

Part of it could be the same reason why bubbles appear in a shaken container of water, a simple mechanical action. But I do wonder if that's not all.

Because when I've shaken a sealed can of soda, it felt like the can became cooler... Wnt (talk) 21:43, 22 November 2010 (UTC)

There's an article at livescience. The fizz has to do with pressure equilibrium in that when you open the bottle, the pressure inside the bottle equalizes with whatever the pressure is outside the bottle. It may get slightly colder since the diluted carbon dioxide may take some energy to escape. See Solubility, Vapor pressure, partial pressure, Le Chatelier's principle, Pressure, and Boyle's law.Smallman12q (talk) 00:10, 23 November 2010 (UTC)

That explains the fizz, which I understand, but not why there's a massive increase in bubbles when the soda is shaken (I don't qualify the webpage's explanation, which says that shaking "adds the zing needed to unleash more tiny bubbles and add real splash to a celebration", as a good explanation).

It's very simple: your soda can is not full to the brim with soda. Rather, to keep the soda carbonated during storage, it contains a quantity of compressed gas. When you open a can of unshaken soda, the gas is at the top of the can and can escape freely. When you open a shaken can, the gas is mixed with the soda, and carries a good deal of the soda with it as it escapes. --Carnildo (talk) 00:25, 23 November 2010 (UTC)

That's certainly part of it, but it can't be all of it. Try it with a clear coke bottle. Shake the bottle vigorously and then open it as soon as the bubbles on the surface break. (Tap the bottle to speed this process.)

In any case, the volume of soda lost from a shaken can often far exceeds the volume of undissolved air in the can, which would not be possible in your theory. APL (talk) 03:38, 23 November 2010 (UTC)

Do you happen to know the answer to the question then? 70.52.44.192 (talk) 05:01, 23 November 2010 (UTC)

There is a link at the bottom of the carbonation article which has the answer you are looking for: Whirlpools in a soda pop Explains why shaken soda bottle will spray soda when opened. Vespine (talk) 05:56, 23 November 2010 (UTC)

Thanks Nil Einne (talk) 11:56, 23 November 2010 (UTC)

I forgot to mention, but the proper term for "fizzing" would be effervescence.Smallman12q (talk) 13:03, 23 November 2010 (UTC)

Your clear-bottle experiment doesn't take into account microbubbles. When you vigorously shake the bottle/can, you break up the large gas bubble into a range of bubble sizes, some of which are very small. They'll re-dissolve/merge with the big bubble eventually, but are stable on a short (minutes) timescale. When you release the cap, the sudden decrease in pressure means that the dissolved carbon dioxide comes out of solution on those small nucleation sites, resulting in rapid bubble expansion. As to your second point, there is a fair quantity of liquid in soda foam. If you pour a glass of soda with a large head of foam, and then watch the soda level, you'll see that it comes up a fair bit as the foam breaks. Having the foam be 50% liquid is not unheard of. In addition, as the microbubbles are distributed throughout the bottle and expansion is rapid, the ones at the bottom can push the soda out of the bottle. -- 140.142.20.229 (talk) 18:36, 23 November 2010 (UTC)

Does the above explain the fountain or geyser you get when you drop a polo mint into a large bottle of cola? Edit: this Diet Coke and Mentos eruption. 92.15.6.86 (talk) 13:10, 23 November 2010 (UTC)

The article that you linked contains the explanation and links to further research. TenOfAllTrades(talk) 14:52, 23 November 2010 (UTC)

Thanks. 70.52.44.192 (talk) 15:11, 23 November 2010 (UTC)

Flaxseed oil and autism

Is there is any real evidence for a connection between taking flaxseed soil, or omega 3 fatty acids and preventing autism? Or if autism has anything to do with dopamine. Thanks in advance. AdbMonkey (talk) 22:23, 22 November 2010 (UTC)

This is too controversial a subject, to attempt to answer. The best and most informative book I have ever come across is this one. [7] Borrow a copy from your local friendly medical library. You will not ever, get a sensible discussion about this subject here. It is too specialised.--Aspro (talk) 23:21, 22 November 2010 (UTC)

Ohhh. Thank you. AdbMonkey (talk) 05:34, 23 November 2010 (UTC)

See Autism#Causes for a general discussion. From the article, it looks like environmental factors are suspected by some to play a role, but genetics is definitely a factor. Paul (Stansifer) 13:27, 23 November 2010 (UTC)

As for the general medical consensus on nutritional supplements, it could be summarized as this:

"If a deficiency of a particular nutrient is present, then a supplement may be useful. However, mega-doses of most nutrients are not helpful, and may be harmful in certain cases".

StuRat (talk) 17:59, 23 November 2010 (UTC)

Chemicals with humorous formulas

Is it possible for Argon Selenide to exist, and if so, would its chemical formula be ArSe? Also, is it possible to manipulate Arsenic sulfide under laboratory conditions so that its ions have equal charges, thereby changing its symbol to AsS?--99.251.211.17 (talk) 23:24, 22 November 2010 (UTC)

Would Arsole do? We have a subjective list of names at List of chemical compounds with unusual names...though not formulas.Smallman12q (talk) 23:59, 22 November 2010 (UTC)

That page has been nominated for deletion five times (some Wikipedians do not like articles of a humorous tone). If one of the AFDs ever succeeds, then the article is likely gone forever. If you feel it is an appropriate article, you might wish to watchlist it. I do not feel that this is canvassing, since there is presently no AFD in process. Edison (talk) 14:49, 23 November 2010 (UTC)

See this for a pretty comprehensive list, with pictures, structure and discussion. Ariel. (talk) 00:10, 23 November 2010 (UTC)