Wikipedia:Reference desk/Archives/Science/2012 November 22

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November 22

Freshwater Aquarium Parasites and Human Reactions

I'm trying to locate some sort of list of parasites that a human working in the water of a freshwater aquarium with an open wound might acquire, that would be severe enough that the parasite would actually not only destroy the flesh but conceivably the bone as well resulting in amputation if not diagnosed quick enough. I believe the specific parasite I'm trying to locate begins with the letter "M" - but I couldn't swear to it. I thought that if, perhaps, I could get a list of parasites that affected humans in the aforementioned conditions only (NOT the fish, they carry it), it just might jog my memory. Every search I've attempted, no matter how I word it, gives me FISH parasites like "ich", etc., which is not what I need. Can you please help me? 64.72.34.239 (talk) 02:10, 22 November 2012 (UTC)

Mycobacterium marinum, perhaps? -- Scray (talk) 02:23, 22 November 2012 (UTC)

That's a bacterium, not a parasite, but that's the first thing that came to my mind, too. I can't think of any possible parasite that would fit the description given by the OP, and I suspect he meant "pathogen" instead of "parasite". Dominus Vobisdu (talk) 04:11, 22 November 2012 (UTC)

Our parasitism includes bacteria, under the category microparasites. StuRat (talk) 04:37, 22 November 2012 (UTC)

The relationship of certain bacteria with humans can certainly be consider parasitism and so these bacteria can and are called parasites. However, human parasites generally does not include bacterium or viruses/virii probably following on from the general meaning of parasitic disease (as also reflects in our List of human parasitic diseases article). See for example [1] and [2]. Of course there's no reason to assume the OP know or follows this, so they could very well be including bacterial diseases when they mention parasites. Nil Einne (talk) 05:26, 22 November 2012 (UTC)

Fish TB (Mycobacterium marinum) usually just causes rashes or nodules, and like most other infections, usually only become serious in immunosuppressed individuals. The closest I could come to fish pathogens that enter through open wounds in humans and can result in septicemia and amputation if not diagnosed quickly enough are the various members of the genus Vibrio (of which cholera is part of).

Also for more accurate searching, the biological term for the interspecies transfer of diseases (usually animal -> human) is zoonosis. Adding that as a keyword can eliminate fish-only diseases. There are plenty of medical and veterinary papers on water-borne diseases which aquarists can come in contact with. Though note, that zoonotic pathogens do not really use fishes or other aquarium organisms as "carriers", they actually infect them too.

If you're looking for organisms which strictly only use non-human animals as vectors, then you may mean trematodes, which use them only as part of their life cycles. But like almost all highly specialized parasites, the diseases they cause (e.g. schistosomiasis) are rarely serious enough to kill their hosts.-- OBSIDIAN†SOUL 05:56, 22 November 2012 (UTC)

There are multiple reports of M. marinum infection requiring amputation even in people who do not have apparent immune dysfunction. Aeromonas is a pretty good fit, though my impression is that the OP is describing a chronic progressive process (i.e. M. marinum). -- Scray (talk) 06:47, 22 November 2012 (UTC)

Still, it's usually less serious than non-gastrointestinal non-cholera vibriosis. But yeah, agree, Aeromonas is a pretty good fit.-- OBSIDIAN†SOUL 09:56, 22 November 2012 (UTC)

Robotic Armor

I'm not sure if this question would fit in here, but is it scientifically possible to design robotic armor, say, like the ones that David Xanatos and Dingo from Gargoyles wear? Futurist110 (talk) 04:05, 22 November 2012 (UTC)

Could you describe that armor in a bit more detail for those of who haven't watched the show recently? Also, is your question answered in Powered exoskeleton? Thanks. Someguy1221 (talk) 04:07, 22 November 2012 (UTC)

I never noticed that article before, so maybe. Here's a description of the various robotic armors worn in Gargoyles--http://gargoyles.wikia.com/wiki/Exo-Frame. I'm specifically interested in robotic armors that cover the whole body with hard metal (or metal-like) materials, if you catch my drift. Futurist110 (talk) 04:12, 22 November 2012 (UTC)

Yes, it's possible. However, it's probably not a good idea. This is because there is no armor which can't be breached by some weapon, and thus it's usually better to keep your soldiers off the battlefield entirely or, if they must be there, have them be well hidden. A huge armored exoskeleton soldier would make an easy target. Of course, a powered exoskeleton can serve other purposes, like allowing you to carry more equipment, so might be more useful behind the lines. Remotely controlled robots on the battlefield would make more sense. StuRat (talk) 04:30, 22 November 2012 (UTC)

"This demonstrates the value of not being seen." ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:11, 22 November 2012 (UTC)

Is that from the Monty Python sketch ? StuRat (talk) 06:17, 23 November 2012 (UTC)

That would be the one! ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:04, 23 November 2012 (UTC)

Atomic/molecular blades

Various works of science fiction feature "atomic swords" or "molecular swords", which are described as swords with a blade that is, respectively, only a few atoms or a few molecules thick (some works go so far as to claim they are not just a few atoms/molecules thick but only a single atom/molecule thick) and thus so sharp they can cut through anything. There are also other similar variations, such as atomic/molecular whips consisting of a lash a few (or even single) atoms or molecules thick. I have some questions on this:

1. Are such weapons remotely constructable/viable, either the single- or few-atom/molecule varieties? (I suspect that even if they were constructable, they would not be viable because they would disintegrate on use.) If so, what types of atoms/molecules would they be constructed of, and how would they be constructed to keep them from disintegrating?
2. Suppose such a sword really existed and could be kept from disintegrating on use. Wouldn't the sword still be useless because the slices it makes are so thin that the separated molecules of whatever substance it was being swung through would just rebond? For example, if such a sword was swung through a wall, even though it cut the wall, it seems to me there would be no lasting damage because the molecules of the wall would just rebond.
3. What if the target is biological/living/organic? If such a sword was swung through your neck, would you really be decapitated and die? Or would no harm come to you because, since the slice was so thin, the separated molecules of your neck would just immediately rebond? Or would harm come to you, because the molecules of your neck wouldn't rebond correctly?

—SeekingAnswers (reply) 06:03, 22 November 2012 (UTC)

Not sure about a monomolecular wire, but a blade cutting through flesh would usually displace the two sides of the cut a bit relative to each other.

Cutting molecules, the ends will probably recombine in some way on both sides of the cut, so when the blade has passed the original parts of the molecules won't be available anymore for recombining.

It's very unlikely that cutting a molecule in an arbitrary position will result in two chemicals that react to form the original molecule. Chemical synthesis would be easy if that was the case. Ssscienccce (talk) 07:56, 22 November 2012 (UTC)

Spider silk is stronger than steel, not more than a few orders of magnitude away from the strongest nanotube imaginable and yet it breaks like cheese. I find it hard to believe those things could stay strong enough to work as even those bendy foil swords (and you might need a marker at the end to know where it is) and no idea how you'd make a single atom thick whip visible. Maybe one day they can figure out how to make molecules with nucleons and the strong force. Sagittarian Milky Way (talk) 08:15, 22 November 2012 (UTC)

Whether possible or not, the rebonding issue is indeed an interesting thought experiment. What precisely is a "cut"? My feeling though is that while you might pass it through a cell membrane without trace, nonetheless, a fiber of keratin or collagen would need to be broken somewhere, and once all such fibers are broken, the body really would be very weakly connected there. Of course, there is a certain amount of repair that occurs to some types of biological superstructures... it's not an easy thing to decide.

For a single set of covalent bonds to break an absurdly large number of other covalent bonds seems pretty far-fetched. I'd think some kind of "weird" matter would be needed for a decent handwavy chance at plausibility. Maybe compressed matter like the linear collection of ultra-dense deuterium, or a cosmic string, or something... but something so outside the realm of ordinary knowledge that it barely helps to name it. Wnt (talk) 10:31, 22 November 2012 (UTC)

The universe of Warhammer 40,000 has blades with "monomolecular edges"; but the impression I always got was that the blade got thicker away from the edge, forcing the separation of the cut substance. I don't know of other fictions with such edges, but might they not all work like this? A monomolecular edge is still unmaintainable, of course, but it addresses the rebonding issue. 146.87.49.176 (talk) 10:38, 22 November 2012 (UTC)

For reference, the TvTropes article on Sharpened to a Single Atom may provide some info, possibly even explanations, but I don't have time to read it. 146.87.49.176 (talk) 10:56, 22 November 2012 (UTC)

It's not quite what you're looking for, but see here. The article says an obsidian scalpel may only be 3 nanometres thick. Matt Deres (talk) 11:43, 22 November 2012 (UTC)

30 angstroms is still a pretty fair number of atoms, on the order of a medium sized globular protein. --69.113.197.155 (talk) 09:39, 23 November 2012 (UTC)

tvtropes.org, Monomolecular wire Trio The Punch (talk) 16:58, 22 November 2012 (UTC)

User:146.87.49.176 already earlier gave the same link above. It is interesting reading, though. :) —SeekingAnswers (reply) 21:50, 23 November 2012 (UTC)

I think it would rebond, much like when using a wire to cut through a block of ice, it refreezes on the other side. StuRat (talk) 06:15, 23 November 2012 (UTC)

I mentioned in my original post that I think so, too, with most inorganic materials, but what happens when cutting through something that is biological, given how complex organic molecules are? On the other hand, maybe many of these molecules are already in the state that requires lowest energy to be in, so they would naturally reform the same one. —SeekingAnswers (reply) 21:50, 23 November 2012 (UTC)

Blade edges a few atoms thick have been around since the stone age. 203.27.72.5 (talk) 02:05, 26 November 2012 (UTC)

Angler fish raised in aquaculture farms ?

Clearly delicious and not one of Cthulu's sperm.

Hello L.O. (Learned Ones) ! While we were enjoying a fish curry, one of the guests asked if angler fish was raised in aquaculture farms. Someone said "no, because it lives only in the great depths" (false : I've seen angler fishes in the Mediterranean no deeper than 10 m., 30 feet). And someone said "no, it catches little fishes by luring them with its bait near its mouth, and couldn't live on fish meat-balls" (but salmons, also originally predatory fishes, are commonly fed with those meat-balls) . Who is right ? Since angler fish is (here in France) one of the most expensive fishes, is it (or will it become) a product of aquaculture ? Thanks beforehand for your answers, T.y. Arapaima (talk) 08:30, 22 November 2012 (UTC)

The anglers most commonly used in cuisine are members of the genus Lophius (for France, it's likely Lophius piscatorius), more commonly known among fishermen as "monkfish" or "goosefish". You're correct in that they are [relatively] shallow-water and benthic (in contrast to deep-water pelagic anglers more commonly depicted in nature documentaries). They are not, however, cultured. I don't think it has anything to do with their being ambush predators though. Flatfishes, also ambush predators, are cultured quite extensively. They might become products of fish farms in the future, but AFAIK, there's no research being done on it now. Anglers are short-lived and fast-growers (a plus for possible captive raising); but they are also not social and can be cannibalistic. They are quite easily capable of eating individuals of the same size, which is obviously a problem. I do recommend you avoid them in the meantime though, they're overfished.-- OBSIDIAN†SOUL 11:34, 22 November 2012 (UTC)

Holy crap, I'd say you knocked that one out of the park with the first response. I dub thee the Ref Desks' official ichthyologist. Snow (talk) 14:20, 22 November 2012 (UTC)

Ha ha, Snow Rise, the caption on that image you added [3] is hilarious. Thanks for the laugh, lol. ;) —SeekingAnswers (reply)

;) Snow (talk) 23:56, 24 November 2012 (UTC)

<snort> The closest I come to being an ichthyologist is cleaning my aquarium. :P -- OBSIDIAN†SOUL 15:46, 22 November 2012 (UTC)

Wow, answer clear as an obsidian mirror ! Thanks a lot ! Next curry I cook 'll be from Molva molva , quite delicious, unexpensive, stands heat. But so many fidhbones ! T.y. Arapaima (talk) 17:23, 23 November 2012 (UTC)

Clinical Significance of Spike Frequency Adaptation

Hello. What is the clinical significance of spike frequency adaptation? What are some diseases associated with its malfunction? Sources would be greatly appreciated. Thanks in advance. --Mayfare (talk) 16:27, 22 November 2012 (UTC)

As far as I can see there is no solid evidence for anything of clinical significance. Adaptation is a basic property of neuron physiology, so one would expect defects in it to cause problems, but I don't think any serious ones have been pinned down yet. Looie496 (talk) 18:05, 22 November 2012 (UTC)

Fears and placebo

A few weeks ago entertainer Derren Brown made a programme in which he used the placebo effect to cure fears, claiming that all fears can be overcome by giving oneself permission to do so. In the next episode, he explored the idea of planting ideas in ones mind to convert an aetheist into a religious believer. However does any of his claims have any scientific basis? Has any research been done around these issues? 176.27.222.86 (talk) 20:51, 22 November 2012 (UTC)

Darren Brown is a magician, he uses tricks to acheive his effects, not science. His tricks are VERY convincing, but trust me, they're just tricks. One of the secrets is that in a lot of his tricks, he says he is doing one thing but in fact something else entirely is happening, it just appears to be what he's describing. Magicians call it "dual reality", it's an illusion. To give you a very simple example of a trick he uses, he says he will predict the letter someone will think of. He asks someone to think of a letter, then he pulls a piece of paper out of an envelope that has been in plain sight the whole time and reveals he had that letter written down. He explains with a convoluted story about how he used subtle "suggestion" and body language to "force" the participant to think of the letter, but in reality, he just switched cards using slight of hand. That's an extremely SIMPLE example, you might thing there's no possible way he could do something similar in a trick as complicated as the one you describe, but that's the whole point, that's why he's such a good magician. Vespine (talk) 22:11, 22 November 2012 (UTC)

I have little respect at all for "magicians" who have access to all the tricks available in a pre-recorded TV program. HiLo48 (talk) 22:17, 22 November 2012 (UTC)

See Derren Brown#Criticism. hydnjo (talk) 15:32, 23 November 2012 (UTC)

Is chemotherapy only against cancer?

What other illnesses also treated with some similar medicine? Comploose (talk) 21:31, 22 November 2012 (UTC)

You might try reading the first paragraph of the article chemotherapy. μηδείς (talk)