Wikipedia:Reference desk/Archives/Science/2009 December 13

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December 13[edit]

Bleach Reactions[edit]

Ive had a mouse(or mouses) crawling around my room lately and i didnt really notice untill i saw one of the buggers the other night. Theres mouse excretions all over the carpet and places where it could hide where its especially concentrated.

Is it safe to spray the carpets with bleach or will this have some kind of reaction with the (presumably small?) amounts of ammonia in the mouse waste and ultimately kill me?

Cheers, kp —Preceding unsigned comment added by (talk) 06:28, 13 December 2009 (UTC)

Urine + bleach --> chloramines, which are toxic. Probably it will be a small amount if you're cleaning a small spot, but it's still not the approach you should take. Go for an enzymatic cleaner (you can find it in pet stores, as it's used to clean up litter boxes and dog and cat urine or poop stains.) It is more likely to remove the smell, and won't turn your carpet white. - Nunh-huh 07:29, 13 December 2009 (UTC)
Bleach will oxidise ureas? Ureas already seem oxidised to me ... what will bleach do, convert urea to nitrogen dioxide, carbon dioxide and water? :S John Riemann Soong (talk) 01:02, 14 December 2009 (UTC)
I thought that since people have been putting bleach down toilets for years, this wouldn't be a problem, but it seems I was wrong. The Chlorine institute says not to mix chlorine bleach with urea or ammonia, and this NJ health factsheet warns about cleaning cat litter trays or diaper pails with it. You could try using borax, which is recommended by many for removing urine[1][2] --Pleasantman (talk) 13:34, 14 December 2009 (UTC)

Nitrogen Trichloride IED?[edit]

Would it be possible to build an improvised explosive device using urine and chlorine based cleaning products? —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 13:28, 13 December 2009 (UTC)

  • I'm not going to look up how to make a bomb, but: "[NCl3 is] formed in swimming pools when the chlorine gas used to disinfect the water reacts with nitrogen compounds found in urine, and can be a health risk to people like lifeguards who work continuously around the water. NCl3 can be formed when chlorine reacts with nitrogen compounds in wastewater treatment plants. The particular danger associated with the formation of NCl3 under these conditions is that a combination of its sensitive nature and low solubility in water leads to explosive droplets of NCl3."[3] It's also very unstable, so don't try to make any: Nitrogen trichloride#Safety. Fences&Windows 17:04, 13 December 2009 (UTC)

Autophagy in bacteria[edit]

In eukaryotes specialized organelles - lysozomes - are used to mediate autophagy. Since bacteria lack organelles, they obviously can not take that approach. Even so, are there processes comparable to autophagy that occur in bacteria? Specifically, can a bacteria that finds itself in a low nutrient environment break down it's own proteins and structures to provide a temporary emergency supply of energy? Dragons flight (talk) 13:45, 13 December 2009 (UTC)

As you said, prokaryotes do not possess membrane-bound organelles. It's a great question. DRosenbach (Talk | Contribs) 14:21, 13 December 2009 (UTC)
Yes. Under starvation conditions bacteria will break down, or lyse, their macromolecules, and then many form resistant endospores. Fences&Windows 16:59, 13 December 2009 (UTC)
Don't suppose you can back your assertion with a reference? I specifically want to know about the consumption of macromolecules as a food source, which I'm having trouble finding references to for bacteria. Simply breaking down macromolecules wouldn't be interesting to me unless they can also utilize the associated energy for other activities. Dragons flight (talk) 21:28, 13 December 2009 (UTC)
There are tons of research studies on it, just Google "bacteria starvation proteolysis". Here's a recent study: [4]. Fences&Windows 20:42, 14 December 2009 (UTC)

on average how many pounds of fish are under a square meter of ocean?[edit]

On average, how many pounds of fish are under a square meter of ocean? (talk) 14:30, 13 December 2009 (UTC)

Ocean biomass has some aggregate total mass of marine fish for the entire ocean; you can divide that by an estimate of total ocean surface area. However, fish are not uniformly distributed, so the merit of this average value, at least constructed in such a simple way, is dubious. Nimur (talk) 16:18, 13 December 2009 (UTC)
Google tells me that in January of this year a team estimated that the total mass of bony fish in the ocean is between 812 and 2050 million tons, therefore between 1.6 and 4 trillion pounds (1.6x1012—4x1012 pounds). Our ocean article gives the surface area of the ocean as 3.6x1014 square meters. Dividing, you get somewhere around a hundredth of a pound per square meter. The distribution is extremely inhomogeneous though -- the vast bulk of fish are found on continental shelves. Also note that the figure leaves out squid, which might boost the number by 25% or more if included. Looie496 (talk) 16:35, 13 December 2009 (UTC)

what if you include the mass of all living things in the sea, including single-celled organisms? Then how much is under each square meter of water? (talk) 16:57, 13 December 2009 (UTC)

[5] gives several estimates for the total mass of living things in the ocean - but the bottom line seems to be between 3 and 4x109 metric tons - so let's split the difference and go with 3.6x1012kg - dividing that by the 3.6x1014 square meters of ocean surface gives us a handy 0.01kg/m2. Given the size of the likely errors in our assumptions - this is a very similar kind of a number to the one Looie496 gives above - so you could assume that about half of that mass is fish and the other half algae, plants, etc. SteveBaker (talk) 17:22, 13 December 2009 (UTC)

Europe and Asia[edit]

Where does the boundary between Asia and Europe between Ural mountain and Ural river meet each other? —Preceding unsigned comment added by (talk) 16:06, 13 December 2009 (UTC)

There is no fixed boundary. See Europe-Asia border and Borders of the continents#Europe and Asia. PrimeHunter (talk) 16:16, 13 December 2009 (UTC)
There are also several politicized slants on where the border is and where it should be, in both a political and cultural sense. The Caucasus has no shortage of conflict over this - see Dagestan (Invasion of Dagestan (1999)), Ossetia (2008 South Ossetia war), Chechnya, (First Chechen War and Second Chechen War). With such a disputed cultural and political boundary, and in the absence of a clear geographical barrier like a river or coastline, the boundary is very poorly defined and its location depends on who you ask. I think the Ural region has had less conflict over the boundary, historically, but the line is similarly ambiguous. Nimur (talk) 17:09, 13 December 2009 (UTC)
The border of Asia and Europe is not a political issue.It has nothing to do with the politics.It is purely an issue of geographical nature.So my question was also of geographical nature. —Preceding unsigned comment added by (talk) 03:22, 14 December 2009 (UTC)
As explained in numerous articles including those linked to I presume, geographically the concept of Europe and Asia is questionable or even meaningless Nil Einne (talk) 11:54, 14 December 2009 (UTC)
The late Isaac Asimov once referred to "Afro-Eurasia." (existing before the Suez Canal)
Civic Cat (talk) 19:55, 17 December 2009 (UTC)


How do I test for radon in water? I would prefer something I can find in a basic laboratory, if not something I could find in a store. I'm doing a science fair project on it. THX --Richard —Preceding unsigned comment added by (talk) 16:18, 13 December 2009 (UTC)

[6][7][8] Fences&Windows 16:52, 13 December 2009 (UTC)
It's a shame that F&W provided no description of those links - the second one is highly applicable and contains an excellent discussion of air/water partitioning of radon, with a method of on-site radon testing of water. -- Scray (talk) 17:35, 13 December 2009 (UTC)

Hmmm - tricky. Radon is a nobel gas - like Neon or Argon - so simple chemical tests are unlikely to be available. It does form a compound with fluorine to form Radon difluoride - but that sounds like a tough thing to do.
Radon is radioactive - and decays with a half-life of 3.8 days - so you could instead test for the decay product. Unfortunately, the commonest isotope of Radon decays to Polonium - perhaps you could detect the polonium instead - but sadly, the test for Polonium requires fancy spectrographic techniques - which are almost certainly beyond your "basic laboratory". So I think you have to test for radiation. If you can get a hold of one - I'd start testing the water with a geiger counter - if that indicates that the water is radioactive to a higher degree than background radiation - then the odds are very high that it's radon rather than some other radioactive substance. I don't know whether a gieger counter falls within your definition of a "basic laboratory".
Our article on Radon says that tests for radon in air are done using a Lucas cell - but again, that's measuring radiation, not a direct test for the chemical element itself. Our article says that radon test kits are cheap "and in some cases, free" - so perhaps you should talk to the manufacturers of the test kits and see if they'll send you a freebie - if you get a hold of the right person and explain what it's for, they'll probably be very helpful (it's free advertising!). However, I suspect that they are talking about radon in the air - not in the water. Also - if you're doing a science fair - remember that the half-life of Radon is just a few days - so you'll need to get a fresh sample on the day of the fair if you need to demonstrate the testing 'live'. SteveBaker (talk) 17:04, 13 December 2009 (UTC)

Decay chain(4n+2, Uranium series).PNG

It's not chemically difficult to purify extract and purify polonium, even at very small amounts (isolated microgram quantities from several liters of urine!). Once it's pure, it's easy to quantify by measuring the radioactivity. But it's α, so you need a scintillation counter not a Geiger-counter. If you've got a scintillation counter already though, easier to just monitor radon directly with it instead of waiting for its daughter-nuclei. DMacks (talk) 18:08, 13 December 2009 (UTC)
Yes - but the radon only hangs around for a matter of days to weeks. The polonium that it decays into is much less radioactive and stays around for years. Hence, if you could easily do a chemical test for polonium, that would be a good thing to do because radon is a noble gas and will be extremely hard to test for chemically. But evidently, you can't chemically test for polonium either. So you're back to testing for radioactivity - and if you're going to do that then you might as well try to deduce how much radon is present from that.
You could presumably take a fresh water sample - measure the radioactivity - then wait (say) 3.8 days (the half-life of the most common radon isotope) - then measure the radioactivity of that same sample again. The amount by which the radiation levels have dropped would be an measure of how much radon was present in the original sample. Doing it that way, you're more directly measuring the radon content because (if present) it's radioactivity should completely dominate all of the other potential sources in the water.
Test kits for radon are easily obtainable - and cheap ( for example!) - but the problem with that is that the test kits only test the air - not the water. That makes our OP's task kinda tricky. I suppose you could boil away the water and somehow separate out the radon gas (it's really heavy) and then use an airborn test...but it's not clear whether you'd get enough radon from a small enough sample of water to make that feasible on an amateur scale (boiling away even a couple of gallons of water is TOUGH!). The second and third of the links that User:Fences and windows linked to seem to say that there are direct tests one can do on water - but since both are pay-to-read pages, I can't tell what the actual tests entail.
So - our OP has to measure radiation - not attempt difficult chemical or spectroscopic tests. Using the "test, wait 3.8 days, retest approach", you'd get a pretty good idea of the amount of radon in the sample...but that requires that our OP can find either a scintillation counter or a geiger counter or something similar.
I suppose - if you didn't have access to a geiger counter - you could try to McGyver a radiation counter somehow. Maybe get a household smoke detector and (carefully!) remove the Americium radiation source from it - then use the alpha particle detector to measure the radioactivity from the water. If you could pull it off - it would be an amazingly cool science fair project! Googling "homemade Geiger counter" produced a bunch of interesting pages. SteveBaker (talk) 19:26, 13 December 2009 (UTC)
Again, you can isolate incredibly minute amounts of polonium quantitatively. The problem isn't "no chemical test" (you just weigh the recovered material) but actually doing it on such a small scale. The amount of radon in the air (even dangerously-high levels in a poorly ventilated basement) is really a very small number. See Radon#Concentration units. But isn't polonium's half-life very short also? DMacks (talk) 19:50, 13 December 2009 (UTC)
Oh - you're right. 222Rn (the commonest Radon isotope) decays to Polonium - but all of the commonly found isotopes of Po are long-lived. What I didn't check was exactly which isotope of Polonium you get. Our article says: 218Po - which has a half-life of just a few minutes. Decay chain says that the first stable decay product is 210Pb - lead. Darn. You can't find that chemically because there will be plenty of regular lead in the water anyway. OK - so definitely you're going to need a radiation counter. SteveBaker (talk) 02:01, 14 December 2009 (UTC)

5' Cap and Poly-A Tail[edit]

Hello. If the 5' cap of mRNA is indigestible by nucleases since it resembles the 3' end, then why is the poly-A tail at the 3' end digestible? Thanks in advance. --Mayfare (talk) 19:36, 13 December 2009 (UTC)

What is your source for the 5' cap being indigestible and the 3' poly-A tail being digestable? In essence, they need not be digestable beyond being able to be cleaved from the mRNA at their points of attachment, which I am sure they are, or else they would remain indefinately. On second thought, does it really matter if it stays indefinately? The AUG "primer," so to speak, is the point at which translation will begin either way, but I do think the 5' cap is cleaved. DRosenbach (Talk | Contribs) 21:18, 13 December 2009 (UTC)
The 5' cap doesn't mimic the poly-A tail, the cap is simply a methylated guanine attached in an odd way. Together they prevent digestion, but there are decapping enzymes (names escape me) which can remove the cap. ~ Amory (utc) 01:28, 14 December 2009 (UTC)
Aaaaand of course there's an article. 5' cap ~ Amory (utc) 01:28, 14 December 2009 (UTC)

According to the 5' cap article, "the 5' cap looks like the 3' end of an RNA molecule (the 5' carbon of the cap ribose is bonded, and the 3' unbonded). This provides significant resistance to 5' exonucleases." According to the polyadenylation article, "in eukaryotic somatic cells, the poly(A) tail of most mRNAs in the cytoplasm gradually get shorter, and mRNAs with shorter poly(A) tail are translated less and degraded sooner." --Mayfare (talk) 10:30, 15 December 2009 (UTC)

Identify species from unusual shell[edit]

left-handed shell

I found this shell on the east coast of the US (Atlantic Ocean). It is the only one I've found that opens on this side - all others I've found go around the other way and open on the other side. Can anyone identify it? Bubba73 (Who's attacking me now?), 22:14, 13 December 2009 (UTC)

Are there some species that are left-handed? Or is this one a mutation or something? Bubba73 (Who's attacking me now?), 23:43, 13 December 2009 (UTC)
It may be a Lightning whelk. Bubba73 (Who's attacking me now?), 00:00, 14 December 2009 (UTC)
We appear to be missing our article on the chirality of shells, but taking Gastropod shell as an example, most "are dextral (right-handed) in their coiling, but a small minority of species and genera are virtually always sinistral (left-handed), and a very few species (for example Amphidromus perversus[) show an even mixture of dextral and sinistral individuals." --Tagishsimon (talk) 00:37, 14 December 2009 (UTC)
The times had an article about this a little while ago. Again, snails. ~ Amory (utc) 01:24, 14 December 2009 (UTC)
And sex. And snakes. Excellent article. --Tagishsimon (talk) 01:55, 14 December 2009 (UTC)
Stephen Jay Gould has written an essay titled 'Left snails and right minds' about that subject in chapter 16 of his book 'Dinosaur in a haystack: reflections in natural history'. Dauto (talk) 01:49, 14 December 2009 (UTC)
Thanks, these pretty much tell me what I wanted to know (except for the specific species). (And I've ordered Gould's book.) Bubba73 (Who's attacking me now?), 01:51, 14 December 2009 (UTC)

Identified as a Lightning whelk. Bubba73 (Who's attacking me now?), 16:07, 14 December 2009 (UTC)


Hunter-gatherer societies (such as Africans) were largely peaceful and in touch with nature. They only hunted what they needed to survive, and as a result they didn't cause any extinction. Then the Europeans came with technology and changed everything. Now, as a result of European technology, Africa is one of the most violent regions on the planet, with constant extinction, attempted genocide, etc. Other hunter-gatherer societies were largely peaceful as well, but then they turned violent and destructive once technology arrived. Why is it that technological societies have so much more problems than "primitive" hunter-gatherer societies? -- (talk) 23:03, 13 December 2009 (UTC)

I just feel the need to say citation needed! Who told you hunter gatherers were peaceful? Were Africans hunter gatherers? Were they peaceful? Where did you get that they only hunted for survival? Have technological societies mopre problems with violence? Citation needed! Dmcq (talk) 23:19, 13 December 2009 (UTC)
There is little evidence that hunter-gatherer societies are necessarily more peaceful or more sustainable. You might, for example, take a look at John Keeley's War Before Civilization: The Myth of the Peaceful Savage. There are also some good books (the titles evade me at the moment) on the ways in which indigenous societies in the Americas often did agricultural and earth-works projects that had vast effects on their ecosystems. The overall premise that technological societies have more problems than primitive societies is fairly unsustainable. The problems are often different, to be sure. And we lack much record of much of life in a pre-modern period. But social problems hardly seem to be new, nor would one necessarily expect them to be. --Mr.98 (talk) 23:34, 13 December 2009 (UTC)
Try also Jared Diamond's Guns, Germs, and Steel: The Fates of Human Societies. While I won't go into details, the gist of the author's thesis is that the differences between societies (especially those which made the transition from hunter-gatherer societies to intensive agriculture versus those which did not) can be laid almost entirely at the feet of differences in the availability of domesticable plant and animal species in various regions. He makes a very persuasive argument that the innate character or characteristics of each region's native peoples had no appreciable effect.
On the issue of the relative peacefulness of hunter-gatherer societies, Diamond notes that in areas with low population densities, if your more powerful neighbour wants your land or hunting grounds, then you can just move further away. In small groups (family groups of hunter-gatherers, or small villages of early agricultural societies) it is possible to every person to know every other person in the group; any violence is directed solely at 'outsiders' and there is a vested interest in (indeed, an evolutionary imperative for) getting along. As you move to higher population densities and larger groupings, there's no way to escape your neighbors, and you have to deal with strangers even within your own society. Both factors lead to increased conflict not due to a change in the nature of the individuals involved, but due to a change in circumstance.
On the issue of extinctions, technologically-primitive peoples lacked the tools to efficiently eradicate entire species or (in general) to generate significant change in the environment. Hunter-gatherer populations were generallly very low-density, making it difficult for them to exceed the carrying capacity of the land. In other words, they lacked the numbers and the tools to render (many) species extinct; it had nothing to do with being 'in touch with nature'. They raped and pillaged as best they could, though they probably didn't succeed in wiping out entire species very often. (One very big exception may be the mammoth and other Pleistocene megafauna. See Quaternary extinction event#Hunting hypothesis.) TenOfAllTrades(talk) 00:58, 14 December 2009 (UTC)
We have Guns, Germs, and Steel, btw. so watch out... --Tagishsimon (talk) 01:02, 14 December 2009 (UTC)
(ec) There is evidence that Hunter-gatherers caused the extinction of several sub-species of the Mammoth - so, yeah - they probably caused extinctions. Tribes of modern hunter-gatherers have wars - there is no reason to believe that this didn't also happen back in prehistory. Were they in touch with nature? Probably. So this kind of wishful thinking really isn't true - which means that we can't answer your question because it's based on an obviously false premise. SteveBaker (talk) 01:37, 14 December 2009 (UTC)
What does "in touch with nature" even mean in this context? APL (talk) 01:40, 14 December 2009 (UTC)
The Native Americans managed to keep bison alive and thriving for millennia. The Europeans showed up and bison were nearly extinct in a matter of years. That shows that the Native Americans were more in touch with nature than the Europeans. -- (talk) 01:53, 14 December 2009 (UTC)
It's certainly true that they didn't destroy the buffalo. On the other hand the Indians had neither economic incentives nor technological means to accomplish the eradication of the buffalo. So it doesn't really tell us anything. I have never killed a T-rex, but that's not proof I love and respect them. I think a good case can be made that many Native Americans did in fact treat living things with greater respect than the typical European settler, but to make that case one needs to look at legitimate lines of evidence and behavior and not impossible counter-factuals. For example, their religious and cultural traditions, their (small-scale) hunting practices, and their response to different hunting practices introduced by Europeans. Dragons flight (talk) 02:19, 14 December 2009 (UTC)
What does "in touch with nature" mean? You have to define it before you can use it in any sort of arguments at all. As far as I can tell it's nothing more than a feel-good phrase. APL (talk) 17:53, 14 December 2009 (UTC)
It's also commonly believe that humans were the ultimate cause of extinction of much of Australian megafauna possibly both due to hunting and their use of fire. Our article briefly discusses this and the evidence available and this appears to be even more recent [9]. In any case, it is well accepted that the Māori are responsible for the extinction of the Moa and indirectly therefore of the Haast's Eagle which preyed on Moa and also the Adzebill and other species, although of course they weren't necessarily all hunter-gathers. Holocene extinction may also be of interest. In terms of this 'in touch with nature' thing there is IMHO some suggestion that recent human arrivals were commonly not particularly in touch with nature and it was only with the development of more sophisticated culture and in some cases agriculture that they began to realise they should take more care with what they killed to avoid wiping out species in the area they were living in (which was generally a disadvantage to them). Even then, their limitations in tools etc was also likely a limiting factor. Those humans who were completely inept at taking care of nature were likely to make themselves extinct Nil Einne (talk) 03:28, 14 December 2009 (UTC)
Head-Smashed-In Buffalo Jump shows that Indians did everything they could to kill buffalo and probably harvested more than they could use at time. (talk) 03:37, 14 December 2009 (UTC)
And the Easter Islanders were sufficiently "in touch with nature" that they made every tree on their island extinct...two for the price of one! SteveBaker (talk) 05:05, 14 December 2009 (UTC)
There is evidence that the settlement of polynesia, 3000 years ago, caused mass-extinctions and depletion of resources. From recent archeological studies of the island Vanuatu, east of Australia, we know that giant tortoises and many other species disappeared within the first century after human settlement. Excavated household waste also showed that seashells got progressively smaller over the years, indicating that the harvesting of the seashell population was done in a non-sustainable way. Consider for a moment that these ecological catastrophes were brought on not by consumerism or extravagant cultures but simply by people collecting food to eat. EverGreg (talk) 08:00, 14 December 2009 (UTC)
The Nazca cut down all their best trees. [10] Then again, they were farmers, so this doesn't count. I note though that the reason for farming is to solve the problem of not having enough food. This leads (without foresight) to the problem of deforestation, but the alternative (population control by letting people starve) is still a problem. Also, problems come in two kinds, those which cause heartache and pain and those which cause interest and fulfillment, depending I think on the learning curve or the condition of flow (psychology). Happy states of flow are I suppose more likely to be found in technological societies, where the idea that "nothing is impossible" is present, while hunter-gatherers are presumably stuck behind a kind of learning cliff which they haven't even thought about scaling, and are highly vulnerable to famine and flood and disease (and war). (talk) 09:11, 14 December 2009 (UTC)
The reasons for the "primitive people were in touch with nature, modern people are not" fallacy are pretty easy to see. They come from our own deep-seated reservations about modernity, about a desire to see our own problems as part of a kicked-out-of-Eden story. But there is not much evidence for this view at all—it is more poetic and literary than it is historical and literal. What we can take away from this, I think, is not that Native peoples were bad, or that the European way of dealing with life is "the same" as theirs. It is more a deeper quality about how humans interact with their environments in general, and in this sense, the technological ability does have real importance—technology allows us to amplify our more exploitive side quite a bit. "Pre-civilized" nations definitely lacked the MEANS to be as destructive to either themselves or their lands on a scale comparable with the Europeans, for the most part, even if they did not actually lack the WILL to do so. In such an analysis, it is a problem of quantity and not quality of difference. --Mr.98 (talk) 14:58, 14 December 2009 (UTC)
We had almost this exact discussion last week, here. I suggest you read that. Once again, the question is based on a false assumption. There is plenty of evidence that hunter-gatherer societies caused mass extinctions, usually when moving to a new place where the native large animals weren't used to humans and thus made easy prey. You don't need any technology beyond a spear to kill an animal that doesn't know to run away from you. --Tango (talk) 15:03, 14 December 2009 (UTC)
Note that Polynesians were not hunter-gatherers, strictly speaking--they practiced agriculture. Same for nearly all Africans. Also for the majority of Native Americans at the time of European contact--at least the contact of European diseases. Pfly (talk) 06:16, 16 December 2009 (UTC)

I would suggest that when one thoroughly examines oral histories as well as the archeological and other such records, that humans are humans no matter the continent or the society. Tehecnology only allows us to be more efficient in what we do . . . without guns and the like, it may have taken longer to over hunt or over gather, but in the end, we are what we are. Some individuals and some communities may be a bit more sensitive, but at risk of over generalizing, we are what we are. Perhaps there is an element of globalization (i.e. awareness and eco friendly marketing) that can be used to alter our naturally destructive path . . . just some thoughts . . . .

Didn't our hunter-gathering ancestors wipe out the Neanderthals: the first race war?Civic Cat (talk) 20:04, 17 December 2009 (UTC)