Wikipedia:Reference desk/Archives/Science/2013 October 22

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October 22

Penicillin-producing fungi in the human body

According to its article, Trichophyton interdigitale is a species of fungus that's often responsible for causing fungal infections in humans and other species, and it's also one of the species known to produce penicillin. If wounded (e.g. punctures or cuts), are areas infected with T. interdigitale less likely to develop bacterial infections than areas not infected by the fungus? Or does the fungus produce such small amounts that it doesn't have a substantial effect? Nyttend (talk) 04:57, 22 October 2013 (UTC)

Well, the effect is apparently more just that the bacteria become resistant [1] but that does suggest there is some real antibacterial activity at some point. Wnt (talk) 05:25, 22 October 2013 (UTC)

House dust mite - Helping me with this could very well improve my life

Soon i am gonna move to a new place so it's kinda in late, but, is there any actually affective anti-House dust mite (Anti-HMT) Spray that i could buy from the net and spray upon my bed or in the room? something that'l really do the trick? thanks from all heart. Ben-Natan (talk) 09:10, 22 October 2013 (UTC)

I am not aware of any spray that will kill dust mites AND be harmless to humans. However, there are other things you can do:-

• Give the house a really thorough vacuuming with a high-suck vacuum cleaner like the 2kW Volta. Not one those useless litle round robot things. Deep pile carpets and matresses, especially matresses with a top wool layer per American practice, are nice to sleep on but they are dust mites' best friends.
• Then, get a commercial cleaning service in to wash all carpets.
• Wash the bedroom curtains. — Preceding unsigned comment added by 60.230.213.251 (talk) 09:40, 22 October 2013 (UTC)
• Use fine-weave cotton sheets on beds. You can get special fine weave sheets expressly for this purpose. They work, because the mites hide in the mattress during the day, then come up though the sheets to bite you when they sense your body warmth. With fine-weave sheets they have to walk the long way round.
• Before you move in, get a referral to an alergy specialist and have him test you for dust mite response. If you have no response, most likely with normal good cleaning stanards you won't have a problem. If you do have a response, you will need to be extra scrupolous in cleaning until the dust mite poulation falls.
• If you are moving into a furnished home, give the matresses away to the needy, and buy your own new. This is always a good idea anyway. All sorts of body oozes collect in matresses, even when they look clean.
• Wash the bedsheets each time you do so (should be once each week) with a small amount of eucalyptus oil added with the detergent. The smell's not at all overpowering, most people think its nice, but dust mites hate it. — Preceding unsigned comment added by 60.230.213.251 (talk) 09:43, 22 October 2013 (UTC)
• If you remain concerned, say by itching, have yourself tested again 3 months after you move in.

Lastly, the main problem with dust mites is that they make you itch. So do lots of other things - gardening in short sleaves without gloves, old age causing hormone levels to fluctuate (especially with females, but men too), taking certain presciption medications, alcoholism, and taking illicit drugs.

60.230.213.251 (talk) 09:37, 22 October 2013 (UTC)

Some of the information given above is bordering on medical advice which we are not supposed to give. You will find information from the professionals on how to deal with dust mites here and here. You will find lots more information if you google "dust mite allergy" Richerman (talk) 13:54, 22 October 2013 (UTC)

• I didn't think that dust mites caused itching - according to [2] there are other mites that do that. A search readily turns up resources like [3] that discuss both physical and medical approaches. Wnt (talk) 14:00, 22 October 2013 (UTC)

Which echoes my concern about some of the above being medical advice. I think the uncited advice from the anonymous editor above should be removed. Richerman (talk) 14:11, 22 October 2013 (UTC)

I want to make sure we are talking about dust mites and not bedbugs. Dust mites are microscopic and universal, and the best we can do is to reduce their numbers and the accumulations of their feces, by careful, frequent cleaning. Bedbugs, on the other hand, are large enough to see, and come out to bite people at night and suck blood, and need to be addressed by professionals, as they can cause medical problems. StuRat (talk)

Can dust mites be killed using radiation? It seems to me that irradiating your mattress with intense gamma rays would get rid of them. Count Iblis (talk) 15:48, 22 October 2013 (UTC)

Right -- just whip out your handy-dandy portable Tevatron and you're ready to go. Or would you prefer a tiny nuclear explosion? Or covering the bed with plutonium, maybe? Looie496 (talk) 16:06, 22 October 2013 (UTC)

The basic concept of sterilization by irradiation is sound (but men, don't try standing in front of the microwave as a "poor man's vasectomy"). However, home irradiation isn't practical, as it requires handling dangerous radioactive materials. I suppose somebody could offer a service where you bring your items in and they irradiate them, but just putting them in a chamber devoid of oxygen might be a lot safer. StuRat (talk) 16:15, 22 October 2013 (UTC)

You might say that radiation is used to kill bedbugs ... infrared radiation, as they are heated up. There's a whole little industry of tenting houses and heating them to 130 degrees F, and lesser expedients will apparently work: [4] Wnt (talk) 16:39, 22 October 2013 (UTC)

Ha, beat me to it. Yeah, insects are prone to dehydration. One way to ensure you're not carrying bugs from your old place to your new oine, for example, is just leave the truck wit all your junk in it parked in the sun for a day or more. So maybe if you just cranked up the heat in the new place as high as possible for as long as possible. This is all conjecture, of course, and note that these guys will probably breed back to the original level pretty quickly. 206.213.209.31 (talk) 17:19, 22 October 2013 (UTC)

Your thermostat goes up to 130°F ? Is that a Vulcan brand thermostat ? :-) StuRat (talk) 17:52, 22 October 2013 (UTC)

Damp clothes smell

After getting wet in the rain, I notice a musky smell on my clothes or body, that smells a little like clothes that have been forgotten in the washing machine. What causes this? Is it related to the same process for clothes left damp in the washing machine? --129.215.47.59 (talk) 10:05, 22 October 2013 (UTC)

See mildew. --Jayron32 11:04, 22 October 2013 (UTC)

Agreed. Clothes must remain wet for some time for mildew to grow. However, when they dry off or are washed with detergent alone, this doesn't kill the mildew, it simply remains dormant until the next time the clothes are left damp. I find using bleach in the laundry to be the most effective way to kill the mildew. StuRat (talk) 16:19, 22 October 2013 (UTC)

anaphilaxis and andrenaline

Why when someone needs to inject Epipen for elergy he needs to do it in her knee? why the other place of the body are not for that? If it needs the mussels there are a lot of them in the body, so what is the special in this place?176.13.29.148 (talk) 13:24, 22 October 2013 (UTC)

The muscles of the thigh (note—not the 'knee') are a large, easy-to-hit target, and one that is easy for most people to reach on their own body. The prinicipal concern with epinephrine autoinjectors like the EpiPen is that one might accidentally hit a vein, thereby allowing a single, concentrated dose of epinephrine (adrenaline) to be delivered straight to the heart. The outer thigh is an ideal injection site, as it contains no large blood vessels. From the manufacturer's web site [5]:

...The outer thigh is the safest site for IM injection as there is minimal risk of injection into major blood vessels or nerves in this area. Intravascular injection (which is possible on the front of the thigh) could lead to acute cardiovascular compromise. Injection into a major nerve (which could occur on the posterior thigh or buttock) can cause significant damage; also, injection into the buttock may not be effective for a severe allergic reaction. Accidental injection into the hand, particularly the digits, can cause serious injury and possibly gangrene....

So, the risk of Bad Things is higher with other injection sites. TenOfAllTrades(talk) 13:40, 22 October 2013 (UTC)

Looking for articles or references on epidemics due to lack of immunity

Hi all, when European colonists met indigenous peoples in the New World, Australia, and other places, my understanding is that many of the locals there were killed by smallpox and other diseases, diseases to which which the Europeans had an acquired immunity. The story then goes that contact between populations is inherently dangerous, because of this potential for epidemics. Yet as far as I am aware, the reverse did not happen, that is, the colonists did not in turn die of diseases contracted from the natives. Why did one side get sick and not the other? Or is the premise false? IBE (talk) 16:23, 22 October 2013 (UTC)

There is extensive discussion of this in Diamond's book Guns, Germs, and Steel. DES ^(talk) 16:28, 22 October 2013 (UTC)

Thankyou - exactly what I was after. I shall take note of the reference, and put it on the to-do list, but I won't be able to do this until well after the thread is exhausted. Can you or someone give me a very quick (three or four point) summary? I am primarily interested to know if the premise is true, and whether it is due to smallpox being a particularly contagious and virulent disease that just happened to be prevalent around at the same time as the contact between civilisations occurred. IBE (talk) 16:40, 22 October 2013 (UTC)

The article linked to summarizes his arguments fairly well. As to your question, it is generally agreed that there were a number of very widespread epidemics in North and South America after contact by Europeans, and that these were particularly severe because the local populace had little or no immunity to the imported microbes. Going the other way, it has at least been alleged that Syphilis migrated from the Americas back to Europe in a similar way, and that its initial outbreaks were very severe because of a lack of immunity. As to WHY this effect was so much larger in the Americas than in Europe, I don't think there is a general consensus. Diamond asserts that the previous history of Europeans had involved more encounters with initially separate groups, and a much wider East/west span (for all of Eurasia), and a larger variety of domestic animals (often a source of disease) all leading to a more robust set of immunities among the European population. Not all scholars accept his views. DES ^(talk) 16:49, 22 October 2013 (UTC)

I wouldn't think you'd need to look farther than the relative population sizes of the New and Old Worlds. With more people, there would be more diseases to evolve, and immunity to develop, in the Old World. The differences in population would, in turn, be due to the larger land area in the Old World, and the fact that it has been populated far longer. StuRat (talk) 17:46, 22 October 2013 (UTC)

According to this article indigenous diseases may have actually started to affect the indigenous population more at the time of colonization. Count Iblis (talk) 20:03, 22 October 2013 (UTC)

is space what we really see?

Is the outer space really what we know, like we see them in photos and movies? Or is it to human eyes? Will cat or chimpanzees have a different look at it? Is there anything invisible (to us at least) out there? -anand, chennai. — Preceding unsigned comment added by 122.164.37.214 (talk) 16:48, 22 October 2013 (UTC)

There's dark matter and black holes, although black holes become visible as they swallow matter. Also, all forces are invisible, including gravity, electromagnetism, and dark energy.

And the universe would look only slightly different to eyes that see ultraviolet or infrared. StuRat (talk) 17:36, 22 October 2013 (UTC)

Actually, no. For example galaxies look very different depending on the wavelength. Eyes can see only a tiny part of the electromagnetic spectrum. One can play with this e.g. with chromoscope. Various kinds of objects can be very faint at the visible wavelengths and very bright in X-rays or far-IR.

Photos, e.g. those colourful ones NASA proudly displays, also are generally different than what we could see with naked eye. The observations are (almost) always designed to solve some scientific problem... for example, a galaxy could be observed at three different wavelengths: 1) narrowband H-alpha 656 nm to probe star formation 2) some broadband observations at optical, like V-band 500 nm 3) infrared K-band at 2.2 micron. One then combines them into a RGB single image, which looks pretty but is very different than one would see with naked eye. The big telescopes do not even have eyepieces--at least normally. Telescope opening ceremonies and celebrations are a different matter, at least the first 8-m VLT had an eyepiece then. 88.148.249.186 (talk) 18:23, 22 October 2013 (UTC)

I'd call that slight difference. If there were galaxies which only existed in the IR or UV spectrum, I'd call that a major difference. StuRat (talk) 22:21, 22 October 2013 (UTC)

Cats see things a bit differently than humans do because (most) humans have trichromatic vision, whereas cats have dichromatic vision. Chimpanzees, however, have trichromatic vision similar to humans. Red Act (talk) 18:32, 22 October 2013 (UTC)

You might be interested in the qualia article. Sean.hoyland - talk 18:33, 22 October 2013 (UTC)

The qualia problem has bee solved. See Stephen E. Palmer's work. μηδείς (talk) 02:58, 23 October 2013 (UTC)

Thanks for the name because I don't think I've read anything of his, so I will. I didn't really mention qualia as "a problem", more as a response to the notion that "outer space" or anything is "really" like how animals or machines perceive or represent it. Sean.hoyland - talk 07:51, 23 October 2013 (UTC)

Palmer's research is in vision science and visual perception. I don't see how that than can "solve" the much wider philosophical questions about what qualia are, or whether they have any objective existence. Qualia (if they exist) are a component of all conscious experience, not just visual phenomena. Gandalf61 (talk) 09:09, 23 October 2013 (UTC)

Judging from this, Palmer apparently wouldn't disagree with that view. Sean.hoyland - talk 10:04, 23 October 2013 (UTC)

The Church–Turing–Deutsch principle implies that qualia are computational states. Intuitively this should be obvious from the brain in a vat thought experiment and then considering replacing the brain by a computer that simulates it. Count Iblis (talk) 17:18, 23 October 2013 (UTC)

But that's assuming a philosophical position, then offering it up as the answer. In other words, it's, essentially, "Assuming qualia are computational states, then qualia are computational states.", anyone who disagrees that that's what they are isn't going to accept any part of what you just said (nor will they find your intuitive/obvious conclusions to be intuitive/obvious). I'm not agreeing, nor disagreeing, just pointing out that most evidence is only evidence if you already assume the conclusion it is evidencing- hence the lack of positive results in philosophy.Phoenixia1177 (talk) 06:07, 26 October 2013 (UTC)

Feeding habits of the subterranean invertebrata

So... my yard is a thin coating of topsoil over the naturally occurring red clay, varying from dense to essentially rockhard. I've been attempting to improve drainage in one corner, maybe 30 foot square (10 meters square), which involved pulling up the sparse lawn there last fall and doing some digging. The point being that this area has been essentially vegetation free for about a year, baked pretty dry.

During the digging I notice two things. Firstly, down in the clay, maybe up to a foot deep which is as far as I dig, where there is no trace of any organic matter and it's pretty dense clay, I find quite a few earthworms of large size. Not monster movie size, but up there on the upper end of the normal earthworm distribution size. I don't find these guys in the more soil-like layer anywhere, although there are smaller earthworms there in reasonable number. I can see their tunnels horizontally in the clay, without any evidence of their going up into the soil layer. So, what do these big guys eat? You can't eat clay for a living, can you, even if you're an earthworm?

Secondly, back in the soil layer, there are a lot of chafer beetle grubs, the usual kind which infest lawns and eat the grass roots. Like a few per square foot, fat and happy. Mind you, this is bare soil, no turf, the occasional weed is all, and the grubs don't seem to associate with the weeds. There are a lot of maple tree roots in the soil, and they appear to be more numerous where there are roots, but I couldn't swear to it. They're not where the roots branch out into terminal little rootlets, just near the big solid inch thick roots. However, the rest of the yard where the grass is growing into a decently dense lawn, is essentially grub free. ??? Maybe the parents find it harder to lay eggs where the grass is thicker, but my question is, what are these guys in the bare area eating? They don't eat tree roots, AFAIK. I suppose they could eat whatever organic matter is in the soil, but again, I thought grubs didn't do that, they were consumers of grass roots. They're thriving quite well in the absence of any living plants other than the tree roots. ????206.213.251.31 (talk) 17:38, 22 October 2013 (UTC)

I'm not an earthworm expert, but from your description it seems likely that the large worms are in fact living in the topsoil and you're only noticing their tunnels in the clay because they can't break through and instead are worming along the boundary, perhaps looking for deeper crevices. In the normal topsoil their tunnels would probably collapse more readily and not be as noticeable. My "yard" runs from mixed to very clayey and it seems the ability of the clay to hold shape makes the worm trails there more long lasting and noticeable. Matt Deres (talk) 19:51, 22 October 2013 (UTC)

Clayey's not a word! You just made that up! μηδείς (talk) 02:56, 23 October 2013 (UTC)

To be honest, I was surprised when the Firefox spellcheck didn't redline it. Huh, it's redlining both "spellcheck" and "redline", but not "redlining" (or clayey). What a world. Matt Deres (talk) 15:44, 23 October 2013 (UTC)

The weird part is that what I remembered to be the correct word, clayvey, appears in only a handful of sites around the Internet and isn't coming up in dictionaries I see. Yet there are just enough hits to convince me it is real, hmm... Wnt (talk) 18:36, 24 October 2013 (UTC)

The mistake you're making is assuming that they stay in place. Both beetle larvae and earthworms are quite mobile. Is it getting colder in there? Those grubs are probably preparing to overwinter and are moving to deeper soil. They only really begin to feed in earnest in spring and summer before pupating and emerging as adults. Those "giant" earthworms are also very likely anecic earthworms (different from the smaller earthworms you found in the grassy soil area) which form permanent burrow networks and only emerge at night to find organic matter (usually dead leaves, but can be anything organic really) which they then drag back to their burrows to feed on. Have you noticed earthworm droppings (looks like a small pile of oozing or granular mud) in the bare area anywhere? If so, those are near the openings they emerge from. -- OBSIDIAN†SOUL 18:27, 23 October 2013 (UTC)

Cleaning from background radiation

By which means a human body can be completely cleansed from background radiation, including radon exposure? And what actions minimize their effect (perhaps water while taking a shower)? --93.174.25.12 (talk) 19:29, 22 October 2013 (UTC)

I'm quite confused. Background radiation is the stuff that is, like, everywhere, the radiation that exists as a baseline in all places. It cannot be avoided. See Background radiation which states that it is "ubiquitous". Excess radon exposure isn't really "background", if, for example, you have radon buildup in confined basement areas. If you wanted to minimize your exposure to background radiation, you could chose certain areas of earth to live on (the background radiation is ubiquitous, but not uniform). However, you cannot make yourself live your entire life exposed to literally no ionizing radiation ever. --Jayron32 19:40, 22 October 2013 (UTC)

Right - there is radiation coming from radon gas in the air, there is radiation from the food you eat and the water you drink, there is radiation from the rocks in the ground and from space in the form of cosmic rays. You could possibly reduce that somewhat by living in a lead-lined box in Antarctica *where atmospheric radon is at a minimum), eating food grown in another lead-lined box. That won't reduce the amount of radiation to zero - because you'd need an infinite thickness of lead to guarantee that.

But it's all a bit silly - we've evolved to live with a certain amount of background radiation - sure, there is a tiny increased cancer risk from background radiation - but eliminating it would come at such a high personal cost as to almost certainly make your statistical chances of dying early larger rather than smaller. There are better ways to spend money to live longer.

That said, if you live in an area with excessively high radon density, it does make sense to install good ventilation systems into your home and place of work.

SteveBaker (talk) 20:47, 22 October 2013 (UTC)

Is lead itself very slightly radioactive?  Card Zero  (talk) 21:39, 22 October 2013 (UTC)

Theoretically. But the observed isotopes of lead in nature do not show detectable levels of radioactivity. Someguy1221 (talk) 21:49, 22 October 2013 (UTC)

Not just theoretically but actually. We used to spend a fortune on special low radioactive lead for use in the lab. I think it came only from a few very deep mines but this is the only ref I can quickly fine to explain it. [6] Presumable the lead from these very deep mines formed so long ago that the radiation had reduced to very low levels. So yes, even lead give a slight radioactive signature -what ever its age and origin. Yet, to put it into context: my mom's apple pies are very much more radio-active – but too yummy to resist.--Aspro (talk) 22:07, 22 October 2013 (UTC)

...so they stay warm forever ? Yum. As for the lead, I don't think the lead from deep underground was formed earlier, if you are talking about the lead atoms themselves. However, there might be impurities in the lead ore (other elements) which have short enough half-lives that they significantly decay over millions of years. StuRat (talk) 22:17, 22 October 2013 (UTC)

What Stu said is right. The radiation is not coming from lead, but from contaminants. I hadn't thought of that wrinkle. Someguy1221 (talk) 22:25, 22 October 2013 (UTC)

@ StuRat. No, I am not talking about the formation of the lead atoms themselves but the age that they had crystallised and laid as Native metal in that deposit. Petrologist use the age of the overburden to help to attain and double confirm the latest age of the underburden. Thus, native lead from the deep mines exhibit lower alpha emitters – (or so the lead refiners that charged us an arm and a leg for just a few hundred weight told us). P.S. Mom's apple pies often got cold (when she was presumable able to keep them hidden from us long enough for the radiation (thermal?) to die down and they were just as good when cold. In which case I personally preferred a few cloves where as her hot pie benefited from a little aromatic cinnamon. Maybe a chief with a nuff (enough) culinary degrees to get a job as a cooks thermometer would like to comeback on this – as I am still experimenting to reproduce that elusive je ne sais quoi'' @Someguy1221 Now lets get to the 'term' lead. The post above said and I quote “living in a lead-lined box in Antarctica”. One assumes in this context... the common understanding of lead. forth definition. I.e., The stuff we come across every day. No mention, nor suggestion, intonation, et cetera, et cetera, of a practically unobtainable pure lead-lined box . Lets us now wave a 'red flag at a bull' . Tell me where I was wrong in my last post? --Aspro (talk) 14:35, 23 October 2013 (UTC)

No one was wrong. We were simply using different definitions. Someguy1221 (talk) 20:59, 23 October 2013 (UTC)

I believe almost all lead on Earth was formed in a supernova long before our solar system formed. Perhaps a tiny amount is produced as a decay product of other elements, but I can't imagine that being much of the total. However, if more radioactive lead isotopes are formed that way, it might be a significant amount of the radioactivity in lead. Can anyone confirm that this is what's happening ? StuRat (talk) 20:38, 23 October 2013 (UTC)

Oh Gosh! StuRat asks such good questions at times that I wished he concentrated on growing fluffy white butter flavoured pop corn ;-) Supernovas (as far as I understand) don't produce elemental lead. As far as I was taught, lead formation comes about in ordinary stars (think red giants but don't quote me on that). Earth might have arrogated from the detritus of a super-duper big bang but the heavier elements can have come from previous stellar fusion processes long, long, before the star went kapow. Come on Stephen Hawking's -where are you when I need you?--Aspro (talk) 21:47, 23 October 2013 (UTC)

Ah. As a sea mariner might say after he has thrown-up into the wind “it is all coming back to me now ”. The red giant/super giant forms elements up to the mass of lead. Heavier stuff is what super-dooper nouveau bright sparks are good at doing (they might -in this state- also create some more lead as well but I don't what to be around at such a time, to find out how much)”. [7]--Aspro (talk) 22:37, 23 October 2013 (UTC)

I don't think so. The longest lived radioactive isotope of lead is lead-205. Its half life of 15 million years is significant, but not enough for it to survive from any novas that provided significant amounts of material to the formation of the Earth. There are a number of papers on lead-205 [8] but I cannot access them at the moment. There are papers that discuss looking for the decay products of lead-205 in nature in order to determine whether it was present in the early solar system, and these papers seem to make the assumption that lead-205 is not itself present. Some groups claim that there is natural lead-205, but present as a contaminant in thallium ores, not lead ores (hypothetically produced by neutrino capture by a thallium nucleus). I suppose it's also possible that some lead-205 may be present as a decay product of more stable radioactive isotopes, but that's just a guess. Someguy1221 (talk) 06:49, 24 October 2013 (UTC)

A few weeks back I asked about ways to grow radiation-free food. Unfortunately, chemical elements like potassium, which we need for our survival, naturally include a significant amount of radioactive isotopes. The conclusion of the discussion was that it might be possible to produce foods using centrifuges and such to reduce the portion of radioactive isotopes, but it would be very expensive, and would only reduce the radiation somewhat. I do agree that, if it was possible to live a life free of ionizing radiation, then we should. Unfortunately, it doesn't seem to be possible. StuRat (talk)

It's not clear that living in an environment entirely free of ionizing radiation would be beneficial. Good data on the effects of human exposure to low (comparable to background) levels of ionizing radiation are very hard to come by, since the primary endpoints – overall lifespan, change in cancer rate, etc. – take a long time to assess (years to decades), and because any small effects of radiation exposure tend to get entirely swamped by the effects of more potent confounders (genetic and other environmental/behavioral). Moreover, there's obviously no data whatsoever on the effects of significantly-less-than-normal-background radiation exposure, just because it would be so difficult and costly to construct and maintain such an environment.

There is at least some laboratory evidence in model organisms suggesting that low levels of ionizing radiation exposure may be mildly beneficial, conferring some protection against certain types of damage. This stimulating effect, if genuine, goes by the name radiation hormesis; the thinking behind it is essentially that regular low-level challenges from background radiation serve to prime the cell's protective mechanisms and thereby make cells more resistant to additional radiation or other insults. TenOfAllTrades(talk) 22:26, 23 October 2013 (UTC)

First only use isotopical pure substances best the pure elements. Go and get carbon-12, .... only the non radiaktive ones. Buy the biosphere 2 disasamle it and bring it to a very deep mine building and clean it properly. Fill it with the isotopes you need and start introducing microbes to process the whole stuff to more complex chemical compounds. Algae would be best to start with. After some time you should be able to live in the biosphere 2. All the things you eat should come from inside the biosphere 2 and all what you want to get ride off should be dumped outside.After several years you should be fairly clean. To be 100% save wait one or two generations. A nealy non radioactive human will be at hand.--Stone (talk) 22:31, 22 October 2013 (UTC)

...and you'd better re-build you biosphere and all equipment using low-background steel. This could get very expensive :) Gandalf61 (talk) 08:28, 23 October 2013 (UTC)

Even then you're hosed, of course. Even if you start out with perfectly, ideally, absolutely pure stable isotopes, you're still going to get induced radioactivity from occasional interactions withneutrinos. You just can't win. TenOfAllTrades(talk) 21:22, 23 October 2013 (UTC)

Smog contest: Great Smog of 1952 in London versus today in Harbin, China

Did any scientists do air monitoring in the Great Smog of 1952 in London to see the level of particulates and pollutants?Has any reputable source at least estimated the actual pollution levels, beyond " blinding and deadly pea-soup?" I wonder how it compared to the present smog in industrial areas of China? Edison (talk) 22:49, 22 October 2013 (UTC)

Prob'ly not -- at that time, smog in London and other British cities was considered commonplace and not something to be too concerned about. It was only in retrospect, after examining the epidemiological data, that the actual harm caused by the Great Smog to the life and health of Londoners became apparent -- which led to clean-air legislation (which wasn't in place before the Great Smog). 24.23.196.85 (talk) 01:33, 23 October 2013 (UTC)

The CNN report on it says visibility was 100, and yesterday down to 20 - 30 meters. That's much more than during the Great Smog, according to our article visibility could be down to a metre or so... So, assuming similar composition, London was 20 - 30 times worse. They're both grey smog, not photochemical. Ssscienccce (talk) 08:43, 23 October 2013 (UTC)

My dad tells me that the worst day of the great smog was so thick that you could not see your feet while walking - but at as he travelled in to London by rail the visibility outside was only 50 feet or so because of fog. It surprises me that anyone would even try to travel in this, but evidently many people did by feeling kerbs and looking for lamp posts (road traffic had completely stopped). This makes a comparison of pollution levels difficult, it could well be that the thick natural fog meant that visibility was a lot less for the same pollution level. -- Q Chris (talk) 08:58, 23 October 2013 (UTC)

At any rate the article now says can't see a person so close that you can hold their hand. Sagittarian Milky Way (talk) 22:42, 23 October 2013 (UTC)

http://www.iapsc.org.uk/presentations/1206_P_Brimblecombe.pdf (page 7) shows some pollution measurements taken in London at County Hall and gives some interesting background information. Unfortunately, the London and Harbin measurements use very different types of measure making comparison difficult. I was a child in London at the time and remember smog being very frequent in winter. The Great Smog was unusual in its duration rather than in its thickness. The effect on health was well known but, still in the aftermath of the war, other things took priority. Thincat (talk) 23:25, 23 October 2013 (UTC)

"London-type smog is mainly a product of burning large amounts of high sulfur coal. Clean air laws passed in 1956 have greatly reduced smog formation in the United Kingdom; however, in other parts of the world London-type smog is still very prevalent. The main constituent of London-type smog is soot; however, these smogs also contain large quantities of fly ash, sulfur dioxide, sodium chloride and calcium sulfate particles. If concentrations are high enough, sulfur dioxide can react with atmospheric hydroxide to produce sulfuric acid." [9] BTW, I just about remember the last London smogs in the early 1960s - they don't make 'em like that any more. Alansplodge (talk) 23:34, 23 October 2013 (UTC)

What is this medical process called?

Be prepared for some extremely unscientific and vague descriptions here.

Step 1. Person has a disease.

Step 2. Person survives the disease, either through doctor intervention or just surviving it.

Step 3. The Doctors use something from his body to cure others in the future.

What am I describing? I feel I've heard of this before, but Google can't find anything of this description. 68.111.166.27 (talk) 23:58, 22 October 2013 (UTC)

Sounds like antibody therapy, or the related intravenous immunoglobulin therapy. The basic idea is that you take the antibodies that one person has developed against a disease-causing agent and use them to attack that same agent in other patients' bodies. In modern medical science, these therapeutic antibodies are not harvested from human survivors, but from genetically engineered lab animals. The sequence for the antibody is, however, often derived from a human survivor's immune system. Someguy1221 (talk) 00:32, 23 October 2013 (UTC)

Thank you! 68.111.166.27 (talk) 05:26, 23 October 2013 (UTC)

There's also polyclonal antibody therapy. Used more often for pathogens, venoms, and poisons. See Antiserum and Polyclonal B cell response.-- OBSIDIAN†SOUL 17:51, 23 October 2013 (UTC)