Wikipedia:Reference desk/Archives/Science/2008 June 23

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June 23

Lobster

Why do does the shell of a lobster turn red when boiled? --Kurt Shaped Box (talk) 01:14, 23 June 2008 (UTC)

The carotenoid pigment complex crustacyanin gives the living lobster its bluish-greyish hue. Boiling denatures crustacyanin, releasing astaxanthin which gives the carapace a bright red color. ---Sluzzelin talk 01:29, 23 June 2008 (UTC)

Alternatively, in English, the heat breaks down blue-grey pigments into red ones. :) Mac Davis (talk) 22:48, 23 June 2008 (UTC)

Thanks muchly, guys. Now I know the name of the pigment that makes flamingos pink too... :) --Kurt Shaped Box (talk) 00:39, 24 June 2008 (UTC)

Coffee

What chemical in coffee could cause an upset stomach (assuming the person is not allergic to any constituents of coffee)? Ζρς ι'β' ^¡hábleme! 01:51, 23 June 2008 (UTC)

Caffeine? "Furthermore, because caffeine increases the production of stomach acid, high usage over time can lead to peptic ulcers, erosive esophagitis, and gastroesophageal reflux disease." Or, less specifically, coffee itself is generally pretty acidic, which can upset a stomach quite easily. --98.217.8.46 (talk) 02:29, 23 June 2008 (UTC)

Yes, it probably is caffeine now that I think about it. Thanks, Ζρς ι'β' ^¡hábleme! 20:43, 23 June 2008 (UTC)

Hi. How does acid upset the stomach? Your stomach acid is one of the most acidic substances that exist, so it should be able to handle most acidic substances in food. This may be like saying that orange juice, which is about 50x more acidic than water, or food dipped in vinegar, which is about 5000x more acidic than water, would be bad for the stomach. Thanks. ~AH1^(TCU) 21:09, 23 June 2008 (UTC)

As reply to 98.217.8.46 and AstroHurricane, the acid idea is an outdated answer. Barry J. Marshall and J. Robin Warren won the Nobel Prize in Physiology or Medicine in 2005 for discovering the "bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease." Mac Davis (talk) 22:47, 23 June 2008 (UTC)

(edit conflict) Mac Davis: the acid idea is not an outdated answer. The idea that most peptic ulcers are linked to stress is outdated. Read the peptic ulcer article yourself, you'll see in the introduction that 20% of ulcers are not linked to Helicobacter pylori. Gastroesophageal reflux disease is a common example, and can be provoked by coffee consumption. --Shaggorama (talk) 06:44, 24 June 2008 (UTC)

USB-based data acquisition system -- recommendations?

I've transferred this question to the Computing desk, here, as that's clearly probably the best place for it. --Anonymous, 04:44 UTC edited 19:12, June 23, 2008.

Experimental Design vs Procedure

Hello. What is the difference between experimental design and procedure? Thanks in advance. --Mayfare (talk) 03:30, 23 June 2008 (UTC)

What's the context for this question? Both terms are approximately synonymous, with the specific technical meanings (and therefore differences) depending on who is talking about what. For example, some lab-report specs I've seen use "experimental design" to refer to the specific procedures being followed (therefore synonymous) whereas others distinguish between the conceptual/overview of the processes and types of tests vs the actual step-by-step recipe with amounts to measure, etc. DMacks (talk) 04:21, 23 June 2008 (UTC)

I am talking about lab reports in particular. --Mayfare (talk) 19:55, 23 June 2008 (UTC)

Although this interpretation is by no means universal, I think of experimental design as analogous to strategy and procedures and as analogous to tactics. The experimental design is the overall plan for testing a hypothesis, and the procedures are specific details about how measurements are made, etc. ike9898 (talk) 00:42, 24 June 2008 (UTC)

This sounds to me like you are talking about section headings of a formal lab report for a high school or college science course. Chances are, your teacher wants it structured very specifically so I'd take their word over any advice you get here. But since you asked, my guess is that experimental design is how you set up the experiment and procedure is what you actually did to accomplish it. Ike's interpretation looks feasible as well. Actually, scratch all that. I'm with Ike: I think "experimental design" is a discussion of the hypothesis and your general strategy to test it and "procedure" is your materials and methods. --Shaggorama (talk) 06:36, 24 June 2008 (UTC)

Ground-effect birds

Are there any birds that take advantage of the ground effect? --12.169.167.154 (talk) 05:30, 23 June 2008 (UTC)

Probably. In black skimmers (Rliyncops nigra) ground effect was estimated to reduce induced drag by 50-90% (Withers & Timko, 1977). In Brown pelicans (Pelecanus occidentalis), gliding at 24—45 cm altitude gives induced drag savings ranging from 41 to 58% (Hainsworth, 1987). Both are often to be found gliding close to the ground, presumably to take advantage of the aerodynamics. Rockpocket 06:32, 23 June 2008 (UTC)

Cormorants on Lake Champlain routinely travel miles just a three or four feet over the surface of the lake; I've always believed they were using the ground effect. Or maybe they were just fishing? But I never saw them dive from their "cruise position" and I can't imagine they could see or react to fish well while traveling at cruising speed.

Atlant (talk) 12:10, 23 June 2008 (UTC)

Gold thesis

Hello. I am a grade 11 student from South Africa. We have been given a project about "gold" in January, and it's due next week. My project is almost finished, though, to say in it what the other students fail to mention, I need interesting information, such as weird applications, the influence gold has had on human politics, the environment, etc, and other interesting facts about gold. Yes, the project's title is just "gold", so it's basically that we have to write as much as we can (minimum 20 pages of content) about, just "gold". So I would like to add further information. Any help is greatly appreciated!  — Adriaan (T★C) 08:55, 23 June 2008 (UTC)

I trust this is just to get you thinking, so... There's a nice section about symbolism[1] in our article Gold. For applications, there are gold isotopes and nano-gold and food decoration. Will you include "goldness" as a gold-implied value that makes objects desirable when decorated with say gilding or plating; and the way gold or applications of gold, or gold in visual signifiers such as in advertising gives precious metal status to property and status to owners by association? An example is the golden egg in a certain insurance company's ads. Then there's gold in fairy tales and metaphors: the goose that laid the golden egg, the yellow brick road of the Wizard of Oz, the lessons of King Midas in Greek mythology and maybe there are African fables and tales that are similar. And I'm guessing, what gold meant to the Spaniards who conquered the Aztecs then were disappointed to find that much of what looked like solid gold was actually only gold leafed covering and that it was the significance of the object, not the gold as such that gave it value to the Aztecs (afaik). One more is the artist Yves Klein who exploited people's desire for gold in "Anthropométries" in that article. Have fun, Julia Rossi (talk) 09:21, 23 June 2008 (UTC)

I've read in the past that all the gold ever mined by humans through history would fit in a ball 90 feet or so in diameter, and that more than 90% of that gold is still in human hands - it's that rare and precious. And something like 75% of that gold sits in vaults doing nothing at all. If you could dig up references for any of that, it might help your project. And if you do find those references, post them back here too please! Franamax (talk) 09:46, 23 June 2008 (UTC)

Thanks!  — Adriaan (T★C) 12:25, 23 June 2008 (UTC)

Goldwasser and Goldschläger may be of interest --hydnjo talk 18:47, 23 June 2008 (UTC)

Gold was coveted for some time in hip-hop fashion before being replaced in the mid- to late 1990s by platinum. Mangostar (talk) 08:44, 25 June 2008 (UTC)

Unconscious mind

Is there any scientific research that proves the existence of unconscious mind? Or is it just a hypothesis of some thinkers?--218.102.124.108 (talk) 11:05, 23 June 2008 (UTC)

How did the unconscious mind article fail to answer your question? Did you read it all? ~Amatulić (talk) 20:49, 23 June 2008 (UTC)

See the Research section of the unconscious mind article.--Fang 23 (talk) 21:04, 23 June 2008 (UTC)

Bohr Diagrams

Could all of the 118 elements of the Periodic Table have those beautiful bohr diagrams please? I would make good use of them. Also the Lewis diagrams will come in handy.

Any others from other sources are messy and unsuitable. Could they all be the same resolution, even though some will take up less space?

Thankyou so much for your time.

Nicholas Johnson

7:15, Perth, WA. 23-06-2008. —Preceding unsigned comment added by 58.7.47.156 (talk) 11:17, 23 June 2008 (UTC)

Commons:Category:Electron shell diagrams looks like it has Electron shell diagrams for all elements up to 118. This search finds a few Lewis structure images.-84user (talk) 14:16, 23 June 2008 (UTC)

Weird lights when rubbing eyes

What is the actual mechanism of the weird lights and patterns you see when you rub your eyes? Does the pressure cause the release of the photosensitive chemicals, or are you stimulating the optic nerves directly, or what? When I rub my tongue/nose, I don't experience random tastes/smells, so why are the eyes different? Thanks. --Sean 11:33, 23 June 2008 (UTC)

When I rub my nose, I get a sense of bitter smell, actually. Don't know if I am just smelling my own inside flesh, or if it has anything to do with nerves.  — Adriaan (T★C) 12:48, 23 June 2008 (UTC)

Apparently, it's direct stimulation of the nerves. See Phosphene. Smells and tastes involve the matching of molecules to specific receptor proteins (see Olfaction, for example). Deor (talk) 12:52, 23 June 2008 (UTC)

You're experiencing a mechanical stimulation of the retina causing phosphenes. It's not bad for you, if you might have come to wonder that. Mac Davis (talk) 22:31, 23 June 2008 (UTC)

chemistry: acid's strength

why is Hydrochloric acid [HCl] said to be more strong than acetic acid [CH3COOH] even though both have liberate only 1 H+ ion in an aqueous solution? —Preceding unsigned comment added by 59.93.76.236 (talk) 11:35, 23 June 2008 (UTC)

At equilibrium, no acid completely dissociates in an aqueous solution. HCl disassociates almost completely in the typical aqueous solution (making it a 'stronger' acid), while CH3COOH has higher concentrations of reactants when equilibrium is reached. —Akrabbim^talk 12:38, 23 June 2008 (UTC)

CH₃COOH ⇌ CH₃COO^- + H⁺

HCl → H⁺ + Cl^-

The sign where the arrow faces just forward (→) means the H⁺ is fully dissociated. The sign where the arrow faces forward and backwards (⇌) means the H⁺ is partially dissociated. This leads to difference in pH. --88.17.181.5 (talk) 18:58, 23 June 2008 (UTC)

I'm not sure how far along you are in your study of chemistry, but the short answer is that acidity is not really a function of how many hydrogen ions are available for release. Acidity is really all about how stable the molecule becomes after liberating hydrogen, how well the resulting negative charge is dealt with within the molecule itself and with assistance from the surrounding solution. Hydrochloric acid's Conjugate base is Cl-, a single ion which becomes surrounded in a shell of solute molecules whose dipoles serve to counter balance the effect of the ion's charge in solution. Acetic acid is a weaker acid because its conjugate base isn't as good at handling the charge that results from the release of a proton (although it is a special case: carboxyl groups stabilize charge pretty well via resonance). Because the charge isn't dealt with as well in the case of acetic acid, its conjugate acid is more likely to snatch back protons from the solution than Cl-. In you particular example, another way to think of it is in terms of bond strength: it takes less energy to snatch a proton out of an ionic bond (HCl) than from a covalent bond (acetic acid). --Shaggorama (talk) 06:19, 24 June 2008 (UTC)

Cowry shell probabilities

When using cowry shells as dice, what is the probability of a cowry shell landing with the "mouth" up? —Preceding unsigned comment added by 75.6.10.1 (talk) 11:42, 23 June 2008 (UTC)

One, minus the probability of the shell landing mouth down. That's almost impossible to answer without detailed knowledge of the shell and the landing surface. The wider mouth might stabilize the shell in the downward position more often than not. You might be better off making a hundred throws yourself and getting a friend to count them up. Franamax (talk) 13:26, 23 June 2008 (UTC)

It's not difficult to do the experiment. "Roll" the shell a set number of times and tally the results. With 100 rolls you should get a good approximate answer. Let us know how you go. —Pengo 20:57, 23 June 2008 (UTC)

Since we're talking about dice, I'll wager that the probability of landing mouth-up is significantly greater than 50%, more like 75%.

It will land either on the flat side, or the round side. Imagine a cube where you round two opposing faces so that the cube can land on only 4 faces. The probability of landing on any one face is then 25%. If you round out all the remaining faces except one, the probablity of landing on that one remainining flat face would be about 25%. What you now have is a ball-shaped object with one flat side, which somewhat represents a cowry shell, with the flat face representing the "mouth". The probability of not landing on the mouth would be about 75%. ~Amatulić (talk) 23:46, 23 June 2008 (UTC)

Another good way to do the tally is to take $100 and bet someone a buck a throw. You'll certainly remember the results, especially if you pick the wrong way :) Franamax (talk) 00:19, 24 June 2008 (UTC)

STD transmission from female to male

Not medical advice, but I've been thinking about this and I can't find any satisfactory answers on google or the STD page. What STDs can be most easily transmitted from female to male when the female is performing oral sex on the male? —Preceding unsigned comment added by 69.127.231.186 (talk) 12:08, 23 June 2008 (UTC)

An example that springs to mind is Herpes. Have a look at the Transmission and Prevention section. Fribbler (talk) 12:57, 23 June 2008 (UTC)

And maybe more common is Chlamydia infection, which often goes undiagnosed. Franamax (talk) 13:20, 23 June 2008 (UTC)

Also, the oral sex article has a section on disesase transmission. Fribbler (talk) 13:25, 23 June 2008 (UTC)

I would have thought the risk of most STI's through oral sex is pretty much the same as the only way from female-to-male is if the woman has a cut in her mouth which comes int contact with the urethral opening of the penis. Presumably, if there is more chance of catching one particular STI, it'd be the fasting replicating virus or reproducing bacteria. — CycloneNimrod ^talk?_contribs? 19:11, 23 June 2008 (UTC)

No, beacuse many diseases can be carried in saliva. StuRat (talk) 20:05, 23 June 2008 (UTC)

Silly me, forgot about that. Although the principle is the same, logically the most contagious bacterium or virus would be that which was either a) the most prominent in the saliva or blood, or b) the fasting replicator/reproducer. — CycloneNimrod ^talk?_contribs? 20:50, 23 June 2008 (UTC)

In highschool, they taught us that micro-abrasions in the mucous membranes (I think) of the genetalia and the mouth could result in transmission of viruses even if there aren't any "open wounds". They also mentioned that these micro-abrasions can occur during intercourse. Firstly, is this true or were they just saying that to make us scared? If this is true then is there any merit to the argument that oral sex is not vigorous whilst ordinary sex can be vigorous therefore ordinary sex is more likely to result in micro-abrasions and therefore transmission? Of course, this would depend on the nature of the mucous membrane in the mouth compared to the penis/vagina. Zain Ebrahim (talk) 21:08, 23 June 2008 (UTC)

I expect it's true, although the risk is probably rather low (compared to unprotected vaginal intercourse, at least). --Tango (talk) 23:36, 23 June 2008 (UTC)

I found this page at Sexually transmitted disease#Pathology. The information you're looking for is found under "Unprotected Fellatio (Getting)" (I'm not vouching for the accuracy of that page). Zain Ebrahim (talk) 19:45, 23 June 2008 (UTC)

Plenty of sexually-transmitted infections are present in the mouth. Primary chancres of syphilis are pretty common in the mouth, and gonorrhea is pretty frequently cultured from the throats of sexually active teens. HIV transmission from oral sex is pretty well-established. One thing to keep in mind is that the numbers may be distorted with regard to direction of spread, because if someone has a lesion in the mouth and reports some oral sex and some intercourse then oral sex is clearly implicated, whereas if someone has a lesion on the penis and engages in some oral sex and some intercourse, then it's hard to tell which is implicated. Scray (talk) 03:07, 24 June 2008 (UTC)

According to http://www.dph.sf.ca.us/SFCITYCLINIC/stdbasics/stdchart.asp (awesome reference btw), known risks are Chlamydia, Gonorrhea, NGU, Herpes, and Syphilis, and HPV is unknown. I assume things not listed are negligible risk. Mangostar (talk) 08:34, 25 June 2008 (UTC)

water discharged by AC

i need distilled water for my car battry. its manufacturer advises to top up it with distilled water. can the water discharged by my AC be used as distilled water —Preceding unsigned comment added by 220.226.25.22 (talk) 14:09, 23 June 2008 (UTC)

I'm not sure where you are, but around me, most grocery stores sell distilled water (actually reverse osmosis water) for as little as $0.60 per gallon. Just make sure you don't get mineral water or purified water that has had minerals added back in for flavor. (I might not trust the stuff coming off the AC - it may have dust/bacteria in it.) -- 128.104.112.147 (talk) 14:19, 23 June 2008 (UTC)

The query's IP address is in Asia. ~Amatulić (talk) 23:38, 23 June 2008 (UTC)

As the above poster says, why take chances when the proper product is readily available and very cheap ? In the UK, Halfords sells de-ionised battery top-up water at £3.49 for 5 litres. Your local garage or car parts retailer almost certainly stocks a similar product. Gandalf61 (talk) 14:33, 23 June 2008 (UTC)

I thought car batteries these days were all sealed systems, which don't lose water. Is this a very old battery ? StuRat (talk) 18:42, 23 June 2008 (UTC)

They are. The original poster is probably actually referring to one of those voodoo Brown's gas generators that have all those infomercials and claim to violate conservation of energy. Funnily enough, most of those ask you to get distilled water and add sodium hydroxide... EagleFalconn (talk) 19:54, 23 June 2008 (UTC)

I expect it depends on where you are. Around here, non-sealed batteries are still sold. Some people prefer them because, with proper maintainence, they'll last longer than sealed batteries. --Carnildo (talk) 21:48, 23 June 2008 (UTC)

Why is that ? StuRat (talk) 23:05, 23 June 2008 (UTC)

...and nobody has answered the OP's question, which was "can the water discharged by my AC be used as distilled water?" The answer is: theoretically yes, but practically no. Yes, the water discharged by your AC comes from condensed water vapor, and qualifies as "distilled" water. However, the surfaces on which the vapor condenses may have unacceptable contaminants, such as oil deposits, mold, mildew, dust, algae, etc. Therefore, once you have collected the water, it is unlikely to be as pure as actual distilled water because of stuff the water has touched. If distilled water isn't available, other highly pure water (such as what you get from a reverse osmosis water filter) can work in batteries too. ~Amatulić (talk) 23:38, 23 June 2008 (UTC)

I thought we had answered that such water is not acceptable. The water will also contain dust particles and bacteria from the air, so doesn't qualify as distilled water even if the container is clean. StuRat (talk) 10:01, 24 June 2008 (UTC)

The water from the ac is usually dirtier than other water. The people I know have just used the cleanest rainwater they can find. The battery failure is pretty much always due to being flattened too often. Polypipe Wrangler (talk) 21:49, 28 June 2008 (UTC)

Human Cell division and Gravity

Do Human Cells divide vertically in the direction of the centre of gravity of the Earth? Duncan.77.194.97.112 (talk) 14:26, 23 June 2008 (UTC)

Seems to be that the direction of division is random. Here's a paper on the subject: [2]. Fribbler (talk) 14:29, 23 June 2008 (UTC)

Is paper really a good barrier against germs?

In doctors' offices examination rooms have a table covered with paper (at least in the US). And in restrooms, there are paper toilet seat covers. What diseases does wafer-thin paper really protect people from? --70.167.58.6 (talk) 18:59, 23 June 2008 (UTC)

Yes. Filter paper is routinely used for extracting microbes from liquids. It is certainly possible for paper to block germs (microbes more easily than viruses). Things will work their way through and around a paper barrier if you try to use the same sheet for a long time, but in the examples you give, the paper would generally be changed relatively frequently and does provide some protection. Dragons flight (talk) 19:37, 23 June 2008 (UTC)

Also, the point is probably more to protect the examination table from germs and other stuff on your skin than vice versa. Without the paper, whenever you touched the table, a part of any dirt, sweat and bacteria on your skin would stick to the table, from which it could then pass on to the next person touching the same table. With the paper in between, most of that stuff will get absorbed by the paper, which is then discarded and replaced with new, clean paper before the next person comes in. —Ilmari Karonen (talk) 19:44, 23 June 2008 (UTC)

But obviously there are limits. If one patient has a bout of severe diarrhea on the exam table, changing the paper is totally inadequate to protect the next patient. StuRat (talk) 19:52, 23 June 2008 (UTC)

Another way of looking at that paper is as protection for the nurses: it's clearly much easier to throw away a strip of paper and then wipe down a table than to clean up the diarrhea with no paper involved. --Sean 22:43, 23 June 2008 (UTC)

Another way of looking at this stuff is as beneficial security theatre: there's really not much risk in catching your death from a toilet seat, so that strip of paper brings people's level of discomfort up to the level of actual risk. Bruce Schneier recently wrote an article on similarly good security theatre, which he normally derides. --Sean 22:43, 23 June 2008 (UTC)

The paper on the exam table may not be much of a barrier, but is an indicator of moisture. If it's simply rumpled, it gets replaced. If it's wet, the exam table gets disinfected with bleach (or other sterilizing) solution. Scray (talk) 02:51, 24 June 2008 (UTC)

Can I crush a Tramadol Pill and drink it in water instead of swallowing the pill whole?

My doctor prescribed Tramadol for a fractured foot instead of the lortab that I was taking since lortab gives me a headache. I would only be taking 1-2 pills at the most in a 24 hour period. The dosage strength is 50mg. Thank you —Preceding unsigned comment added by 98.211.38.189 (talk) 19:33, 23 June 2008 (UTC)

Please contact a doctor, nurse, or pharmacist. The Wikipedia Reference Desk is not allowed to provide information about the administration of medication. Dragons flight (talk) 19:41, 23 June 2008 (UTC)

Note that, in general, crushing or chewing of pills is generally not advised, as it defeats most time release mechanisms. (E.g. a pill is constructed to slowly release 100 mg over the course of 12 hours, but crushing or chewing the pill will release all 100 mg in less than 5 minutes, so you'll get a hundred fold overdose). You also have some medicines which are safety-coated to avoid side effects (e.g. aspirin is sometimes safety coated to avoid stomach upset). Crushing/chewing bypasses this, and may expose you to complications. You really do need to talk to a licensed medical professional familiar with your prescription - there is no way we'd be able to know how your particular pills are constructed. -- 128.104.112.147 (talk) 19:50, 23 June 2008 (UTC)

You should always follow the instructions given to the letter unless specifically told otherwise by a medical professional. There is generally a good reason for the instructions, as the anon above explained in this case. --Tango (talk) 20:30, 23 June 2008 (UTC)

As there have already been replies given I won't remove the question. That said, please see your physician for his advice, although take heed of 128.104.112.147's wise advice, it is not advisable to crush medications. — CycloneNimrod ^talk?_contribs? 21:37, 23 June 2008 (UTC)

I'm going to be very naughty, and paraphrase everyone, with my own veneer. Never, ever ever and for good measure ever, crush a pill. Some of them are enteric coated, some are time released, and some just need to avoid contamination. Why would you want to crush it anyhow? Take it as you were advised. Fribbler (talk) 23:38, 23 June 2008 (UTC)

Some people struggle to swallow pills, crushing them makes them easier to take. Unfortunately, they just have to learn how to do it, crushing them is not a viable alternative! --Tango (talk) 23:47, 23 June 2008 (UTC)

And next time, you can ask for tramadol capsules instead. (Same dosage is available.) --jpgordon^∇∆∇∆ 23:58, 23 June 2008 (UTC)

One can buy pill crushers or cutters at a pharmacy. Crushing may be necessary for administering medication to severely ill or disabled people, or those with impaired swallowing, putting it in their food or other routes. But as others said, don't do anything like this without medical advice.John Z (talk) 07:39, 24 June 2008 (UTC)

If you're having trouble swallowing the pill, try putting it into a spoonful of apple sauce. Grandma always did that for her grandkids, and it worked pretty well. — The Hand That Feeds You:^Bite 22:44, 24 June 2008 (UTC)

One thing that helps me swallowing pills a lot is leaning my head backwards. – b_jonas 13:06, 27 June 2008 (UTC)