Wikipedia:Reference desk/Archives/Science/2011 April 28

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April 28[edit]


Does DNA have physical potential energy in addition to chemical as it is coiled like a spring, similar to a rubber band that is twisted to form coils on coils? Is there tension within the structure of the DNA? —Preceding unsigned comment added by (talk) 00:15, 28 April 2011 (UTC)

I don't think there is a clear distinction between "physical" and "chemical" on the molecular scale, at that scale isn't it all Electromagnetism?. Vespine (talk) 00:22, 28 April 2011 (UTC)
I'm pretty sure DNA does have potential energy associated with its springiness, twistiness, Writhe etc. See e.g. the first few papers here [1]. They discuss how stress, strain, torsion, and topology can influence gene expression. As Vespine alludes above, these forces are the result of chemical/electromagnetic interactions, but they can produce effects similar to what you see at the macroscopic scale. SemanticMantis (talk) 00:39, 28 April 2011 (UTC)
Generally this is termed as DNA supercoiling. But the energy involved is managed very actively - histones wrap the DNA around themselves, topoisomerases release tension, helicases unwrap the DNA so DNA polymerases can copy it, etc. Also see PCNA, a neat little object. There are bits of data (such as the physical binding of DNA polymerases on the leading strand and lagging strand) that make it pretty clear that the DNA in the cell really is handled more like the tape going through a tape recorder than as some immobile passive object as is sometimes implied by drawings you might see. Wnt (talk) 00:57, 28 April 2011 (UTC)

So is part of the DNAs mass this tensile energy? —Preceding unsigned comment added by (talk) 01:55, 28 April 2011 (UTC)

Wow. Must be, but I don't even know how you formalize this. A strained supercoiled DNA must have higher-energy lowest-energy states for torsional vibrations of some sort, I suppose. You'd never be able to measure the difference in mass, I don't think - it would be something on the order of terahertz, I think. I hope there's a hard core biophysicist hero to chime in here. =) Wnt (talk) 02:11, 28 April 2011 (UTC)

Or just a softcore biophysicist that knows more than you. —Preceding unsigned comment added by (talk) 14:56, 28 April 2011 (UTC) You might not be able to measure one strand but extrapolate that to a whole human body. —Preceding unsigned comment added by (talk) 02:30, 28 April 2011 (UTC)

steel I-beam (H beam / double T beam) color?[edit]

In classic American cartoons I-beams are always reddish orange. It occurred to me recently that this is not the default color for steel. I decided I-beams were either previously this color for some reason unknown to me, or the cartoon illustrators used that color instead of black/dull gray because it looked better on the screen. Does anyone know the real reasons? The Masked Booby (talk) 01:26, 28 April 2011 (UTC)

Oxidation98.221.254.154 (talk) 01:52, 28 April 2011 (UTC)

Red lead paint for protection against oxidation. (talk) 02:08, 28 April 2011 (UTC)

Iron(III)oxide based primer paint. It's definitely not lead based paint unless the beams are older than your grandfather! Roger (talk) 14:36, 28 April 2011 (UTC)

Red lead was used into the 1960s - it's an issue in renovation, where the lead has to be removed if you want to cut or weld to existing beams. Red oxide was substituted from the 1970s and is similar in color. Nowadays most steel is primed with a dull grayish primer. Steel that will receive fireproofing is entirely unprimed to promote adhesion, so it ends up pretty rusty before the fireproofing is applied. Acroterion (talk) 03:34, 29 April 2011 (UTC)
By the way, they're generally called wide-flange beams nowadays in North America, or W-sections. I-beams (the old S-sections) are rarely used anymore as they're structurally inefficient and have comparatively narrow flanges. When employed as columns or pilings they're called H-columns or H-pilings. Acroterion (talk) 12:55, 29 April 2011 (UTC)

Is dishwashing liquid safe on plastic water bottles?[edit]

Specifically, mine are from Nalgene Outdoors, #2's, and I'd consider buying #4's. Does dishwashing liquid cause leaching from those? Thanks. (talk) 05:19, 28 April 2011 (UTC)

I don't see why they shouldn't cope with regular detergent, but read the instructions that came with the bottle and our article on Nalgene. Make sure you wash them out after your trip and that they're thoroughly dried before replacing the cap.--Shantavira|feed me 15:10, 28 April 2011 (UTC)
Yeah. I've only bought their LDPE bottles so far. Their shipping and constant availability of coupon codes are very affordable. (talk) 15:42, 28 April 2011 (UTC)

Hydrogen Sulfide[edit]

It is found in our bodies. Is it released? If so, how?

Is it found in air? The article says that in concentrations of more than 100 parts per million will produce a foul smell. Does that mean that it may or is found in air, but because it is so dilute, we cannot smell it?Curb Chain (talk) 05:35, 28 April 2011 (UTC)

Micro-organisms produce it in the guts under anaerobic conditions. Flatulence smells sometimes like H2S. doi:10.1016/j.jchromb.2009.05.026; [2] might be a good read. --Stone (talk) 07:23, 28 April 2011 (UTC)
The human nose is very sensitive to the presence of thiols, which is why ethanethiol is added to natural gas to give the otherwise odorless gas it's characteristic smell - so you can detect even small leaks. The article hydrogen sulfide says that 0.00047 ppm in air is the point where 50% of people can detect the odor (Hydrogen Sulfide#Toxicity). At 100 ppm eye damage can occur, and the olfactory nerve is paralyzed. (So, actually, at concentrations above 100 ppm, you *no longer* will smell anything.) When you're talking about "found in our bodies" you might be talking about the statement "The human body produces small amounts of H2S and uses it as a signaling molecule", rather than just gut bacterial production. The section Hydrogen Sulfide#Function in the body notes that "The gas is produced from cysteine by the enzymes cystathionine beta-synthase and cystathionine gamma-lyase." I can't find the figures at the moment, but the concentrations which are active in signaling are very low; lower than the nasal detection limit, if I recall correctly. -- (talk) 16:11, 28 April 2011 (UTC)

large bowel[edit]

What would be the weight of an empty adult human large bowel (colon)? —Preceding unsigned comment added by (talk) —Preceding unsigned comment added by (talk) 00:40, 29 April 2011 (UTC)

About 4 pounds. -- kainaw 01:29, 29 April 2011 (UTC)
Thank you. Thats all i wanted to know. Sorry if it was a wrong question to ask here.-- (talk) 07:12, 29 April 2011 (UTC)

What are the most dangerous jobs with positions available?[edit]

If anyone or myself decides that there's no more hope for their lives and that it's no longer worth living, perhaps it should end only by serving others. The military would detect suicidal tendencies long before the soldier hits the battlefield, so what civilian occupations could one hope to die on the job from trying to do exactly what the job entails? -- (talk) 10:59, 28 April 2011 (UTC)

Found an article that lists fishing as having the highest fatality rate: - Also mentions, amongst others, roofing and logging. Darigan (talk) 11:07, 28 April 2011 (UTC)
"Farming is one of the most dangerous occupations in the United States. More than 700 lives were lost in farm-related activities last year. Another 150,000 agricultural workers suffered disabling injuries from work- related accidents," per this article. --Halcatalyst (talk) 13:24, 28 April 2011 (UTC)
President of the US seems pretty dangerous. 8 out of 44 US presidents have died in office (about 18,000 deaths per 100,000), and any US citizen over the age of 35 can try for that job in 1.5 years (though it is not an easy job to get by any metric). A job with a roughly 100% fatality rate is Pope, but it is hard to predict in advance when that job will have an opening. Googlemeister (talk) 13:40, 28 April 2011 (UTC)
Dying while holding a job is not the same as dying because of a job. An accountant can die of cancer, and it doesn't mean that accountancy is what killed him. The cancer did. Contrawise, when a lumberjack dies because a tree lands on his head while working, it makes much more sense to say that he died of lumberjacking. As far as presidency goes, there have only been 4 assassinated presidents, rather than Presidents who died from health effects unrelated to being President. That's still a mortality rate of 9%, which is pretty high for any profession, however given that there have only been 44 presidents, that number has a fairly high margin of error. --Jayron32 14:06, 28 April 2011 (UTC)
Point taken. In any case, it is a very bad idea to take a dangerous job in the hopes that it will kill you because you would most likely putting others at risk. If you are a fisherman and go overboard, then someone might go into the water after you in an effort to rescue you and die because of it. As an additional question though, what if the stress of the job caused the accountant to have high blood pressure which was a contributing factor to a fatal heart attack? Would he count in the metric then? Googlemeister (talk) 14:40, 28 April 2011 (UTC)
An epidemiologist would call that the morbidity rate, not the mortality rate, to help keep the statistics straight. Nimur (talk) 17:09, 28 April 2011 (UTC)
Every fisherman knows not to go in after a man overboard, unless they want to die too! —Preceding unsigned comment added by (talk) 14:54, 28 April 2011 (UTC)
Ok fine, so maybe you make the Coast Guard diver go in after you. Googlemeister (talk) 13:00, 29 April 2011 (UTC)

If you are really serious about the " by serving others " part, there are numerous humanitarian aid organisations crying out for dedicated volunteers around the world. The Afrcan states. Sth. America, asia and many of those locations are quite dangerous. You might find something worthy of your last days, or heaven forbid, something worth living for. (talk) 18:08, 28 April 2011 (UTC)

Really? I thought for example the Peace Corps only takes a small fraction of applicants. Look up the details, and the "way you can help" always boils down to money. Capital is rare and precious, but humans are an unwanted waste product in any country. Wnt (talk) 19:12, 28 April 2011 (UTC)
The British charity Voluntary Service Overseas is only looking for "qualified professionals with at least two years’ post-qualification experience." Alansplodge (talk) 19:33, 28 April 2011 (UTC)
Astronaut or cosmonaut. I haven't done the numbers, but the fatalities rate - including the experimental phase - must be quite high. There might be experimental positions in teh future that benefit from someone willing to die. It is quite physically demanding, though, and as we know you can't just walk in. Depends what you mean by "positions available". Grandiose (me, talk, contribs) 18:19, 28 April 2011 (UTC)
Related is the one-way trip to Mars which, proponents say, is not a suicide mission but a colonization; there have been several hundred volunteers so far. Comet Tuttle (talk) 20:25, 28 April 2011 (UTC)

Or maybe you could do a tour of the blood donation centers (assuming your blood is usable). (talk) 20:37, 28 April 2011 (UTC)

What about applying as a journalist? Looks like there is a recent vacancy. (talk) 23:07, 2 May 2011 (UTC)

Brain to Body Mass Ratio[edit]

Wikipedia currently contains an article on this subject that lists a small number of species. Where can I find, or can you provide, a more complete list, from the smallest animal for which data exists to the largest?Markfriedman28 (talk) 18:48, 28 April 2011 (UTC)

This chart gives a more complete picture of the data, at least for vertebrates. I've seen more extensive tables in books, but not on the web. Note that because the brain increases in size at a lower rate than the body as a whole, the brain-to-body-size ratio is widely considered not to be very meaningful. The vertebrate with the largest value is the hummingbird; the one with the smallest value is the blue whale. Most scientists consider a parameter called the encephalization quotient to be the most meaningful measure of the relation between brain and body size. Looie496 (talk) 21:42, 28 April 2011 (UTC)

Unidentified Flower (or maybe Fungi?)[edit]

Hi folks. I've been going through my old photos trying to find images suitable for WP articles. I came across the below photo, but was not able to identify the plant. This bloom appeared in September in the Robson Valley of British Columbia. It was growing in the shade of a black Spruce. Would appreciate any help in trying to identify this little guy. The Interior (Talk) 21:06, 28 April 2011 (UTC)

What am I?
Wow, cool specimen! I can't help much, but I'm pretty sure I see pistils and stamens in the flower, which rules out fungus. The only thing I can think of vaguely similar is Monotropa_uniflora; maybe that will help get us started. SemanticMantis (talk) 22:59, 28 April 2011 (UTC)
Haha! The Corpse Plant! I think you might have nailed it SM. As the article says, it grows in deep shade: this one was almost right under a mature spruce. You're right about it being a flower, but it does have close relationship with fungi. Cool, thanks much. Unfortunately for me (but fortunate for WP) the article already has a lot of decent images. At least I can categorize the image at Commons now. The Interior (Talk) 00:12, 29 April 2011 (UTC)
I'd say your image would be a welcome addition to the article. It shows a slightly different growth habit and color than the current pics, and it's important to understand/see this variation of forms in plant ID. I'd also like to hear at least one other voice weigh in on the ID :) SemanticMantis (talk) 00:30, 29 April 2011 (UTC)

I'm always immensely impressed by the ability of wikipedians and botanists/biologists to recognize such a broad range of species, especially by pic alone. Perhaps it's the power of "the crowd", but it's still impressive! —Preceding unsigned comment added by Gogobera (talkcontribs) 04:51, 29 April 2011 (UTC)

Folklore from the indigenous people of the Pacific Northwest have it that those plants grow where a wolf has urinated. One of the favorite plants! Pfly (talk) 09:59, 1 May 2011 (UTC)
As for confirming the ID of Monotropa_uniflora, well, they look rather green to me, but maybe that is an artifact of the photography and lighting. The basic shape looks about right. I took some photos of some a couple years ago, from Deception Pass State Park, WA, a cluster, a close up. Pfly (talk) 10:08, 1 May 2011 (UTC)

Drug that removes the ability to resist[edit]

A while ago I read about a drug that "removes one's ability to resist". Someone affected by the drug will obey most commands. It's powder form, begins with C and is common in South America. I can't remember what it's called, does anybody know?-- (talk) 21:47, 28 April 2011 (UTC)

Scopolamine? (talk) 23:17, 28 April 2011 (UTC)
You're not thinking of cantharidin, are you? Extracted from the Spanish fly, it is a poison with an infamous past - for example, it was a poison of choice for the Marquis de Sade. Aside from being a false aphrodisiac, it doesn't fit your description because the fly is not indigenous to the Americas. -- Scray (talk) 02:22, 29 April 2011 (UTC)
Not a "C", but tetrodotoxin from a puffer fish is supposedly used to create a "zombie", although I believe that drug has more to do with the pseudo-coma than with the alleged lack of willpower. I'm not sure what drugs or combo is used for that effect, or if it's just the power of suggestion that does it. It's used in Haiti, which is rather close to South America, at least. StuRat (talk) 04:39, 29 April 2011 (UTC)
Ahh - StuRat's answer put me onto what you're likely thinking of - curare! It has no effect on cognition, so people won't become compliant with commands; however, they will become pliant! They'll also probably stop breathing, so it's not something to be trifled with. -- Scray (talk) 04:50, 29 April 2011 (UTC)
What a relief! I was really afraid you would be looking for Catholicism. Oh, excuse me, couldn't be it, it's not a powder. ;-) (talk) 17:13, 29 April 2011 (UTC)
But is in an opiate, at least according to Karl Marx. StuRat (talk) 21:38, 29 April 2011 (UTC)
Gunpowder is often used to force someone to obey your commands, is a powder, is common in South America, but it doesn't start with a C. – b_jonas 12:38, 1 May 2011 (UTC)
Does Truth drug help? Mitch Ames (talk) 14:02, 29 April 2011 (UTC)
Sodium Pentothal is the one most movies mention. However, it doesn't start with C and I don't believe it is particularly common in South America. Astronaut (talk) 15:29, 29 April 2011 (UTC)
See date rape drug (although there are many other types of drugs that reduce the ability to resist in one way or another). Looie496 (talk) 15:50, 29 April 2011 (UTC)