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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)[reply]

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

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)[reply]

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

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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

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

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

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:

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?
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.
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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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

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)[reply]

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)[reply]

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)[reply]

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

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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

Is chemotherapy only against cancer?

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

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

November 23

Ammo weight

How much do the following weigh: (1) an 8-round clip for the 22-cal Hi-Standard pistol; (2) a 5-round clip for the 7.92-mm Mauser 98 rifle; (3) a 32-round clip for the 9-mm MP-40 submachine gun; (4) 5 12-gauge shotgun shells; and (5) one German stick grenade? Thanks in advance! 24.23.196.85 (talk) 00:29, 23 November 2012 (UTC)[reply]

10 rounds of 9mm Luger (which is what the MP-40 would use) weigh ~120 grams. I can't help you though with magazine weight. So that's at least 0.8 lbs worth of ammunition alone, plus magazine weight. As for your others, you'd probably be better off finding some info about pack weight if that's what you're interested in, rather than individual components. Shadowjams (talk) 02:23, 23 November 2012 (UTC)[reply]

Well, thanks for your help, such as it is. I'm writing a World War 2 military thriller, and I want to make sure that my characters' ammo loads are not unrealistically heavy (as they are, for instance, in many computer games). 24.23.196.85 (talk) 03:34, 23 November 2012 (UTC)[reply]

Actually, I did some google searching for "weight of _____ cartridge" and I found a lot of forum discussions where this question is asked in various ways, and answered. Obviously differences in detail are going to matter... slugs will weigh different from shot and different from steel shot. The bullets will be more consistent, but even then certain differences may matter (steel versus brass cartridges). However, from a weight perspective, I don't think those tiny details will matter much. Just make sure you're finding the cartridge weight, and not just the bullet weight. It's quite easy to calculate bullet weight (grains is the customary measure of bullet weight, although our article is woefully deficient on talking about that usage). A grain is 64.8 milligrams. Sorry I don't have a more detailed answer, however that's a very specific list of items that I do not have. Shadowjams (talk) 05:49, 23 November 2012 (UTC)[reply]

Thanks! I've found the weight of the 22 LR cartridges -- 140 of them weigh only 1 pound -- and confirmed your figure of ~120 grams for 10 9-mm Parabellum cartridges, but still haven't found any info for the 7.92-mm Mauser. 24.23.196.85 (talk) 07:54, 23 November 2012 (UTC)[reply]

Follow-up: I've just found that 10 rounds of 7.92-mm Mauser ammo weigh about 250 grams. 24.23.196.85 (talk) 08:01, 23 November 2012 (UTC)[reply]

Well, I've done some figuring, and came out with a basic weapons + ammo load of about 30 pounds for most of the Maquis team, with Mike getting the heaviest load at 50 pounds (because he has to carry the Mauser), and the squad leaders (Francois, Blanche and Jacques) getting the second-heaviest at about 43-45 pounds (because they have the shotguns). These are on the heavy side, but not unreasonable. Of course, Alfred will also get to carry most (if not all) of the demolitions, which will bring up his total load as well... Anyway, thanks for your help, and clear skies to you! 24.23.196.85 (talk) 03:16, 24 November 2012 (UTC)[reply]

E-boats

What's the minimum number of crew needed to (A) navigate a German E-boat (not to be confused with a U-boat) from Harbor A to Harbor B without opposition; or (B) do the same while defending the boat against enemy attack? Thanks in advance! 24.23.196.85 (talk) 00:36, 23 November 2012 (UTC)[reply]

This account of the sinking of S-38 states that there were 23 crew members including 3 officers. It seems rather a lot. This report on the wreck of S-89 says 24 (there were different designs). The boats had reliable diesel engines, so I don't see why you would need more than 3 or 4 crew for a short journey in peacetime conditions. But that's just a guess; I may be missing something. Alansplodge (talk) 01:18, 23 November 2012 (UTC)[reply]

War ships are designed to be operable even when severely short-handed, in case of combat casualties. So, 3 or 4 for an unopposed journey seems about right -- and if they have to defend themselves, then probably somewhere around 7 or 8 (4 more than in the other case -- 2 per gun). If correct, this means for me that the Maquis group can indeed get away in an E-boat, but they will have to regroup prior to boarding the boat -- the infiltration team alone (Blanche, Mike and Alfred) would not be big enough to both sail the boat and defend it against attack, so the ambush team (everyone else) will have to rejoin them, probably by charging the base perimeter. 24.23.196.85 (talk) 03:25, 23 November 2012 (UTC)[reply]

If the journey was longer than one day, you would need to operate a watch system so that people get a break to eat and sleep. That's why the standard crew was more than twenty - there needed to be two men for every job. Alansplodge (talk) 12:50, 23 November 2012 (UTC)[reply]

Thanks! So if the journey is only a few hours (as it will be in my case), then only half that number is needed to keep the boat fully combat-operational during the journey (which won't even be needed in my case -- my characters will be escaping, not raiding, so they won't need the torpedoes). 24.23.196.85 (talk) 02:37, 24 November 2012 (UTC)[reply]

TQ

hi everyone I URGENTLY need to learn how thymoquinone acts within our body: does it pass through the cell membrane? does it have a receptor? how does it change cell responses to different proteins (hormones and ligands)? thank you all

kukubah 06:35, 23 November 2012 (UTC) — Preceding unsigned comment added by Kukubah (talk • contribs)

Is this a homework assignment? ~Amatulić (talk) 06:48, 23 November 2012 (UTC)[reply]

You just asked this a few days ago and were given some answers. But Amatulic is right. There is no time I can envision when asking an "urgent" question here indicates a valid use of the reference services (neither homework nor health are allowed here, and answers here are would require verification by you before being trusted). DMacks (talk) 06:57, 23 November 2012 (UTC)[reply]

We could take the lead of Dilbert's secretary, who, when told something is urgent, tells him, "Good, I'll start ignoring it immediately." ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:02, 23 November 2012 (UTC)[reply]

We could also reflect on the axiom that the urgent is rarely important, and the important is rarely urgent. -- Jack of Oz ^[Talk] 01:04, 24 November 2012 (UTC)[reply]

One exception to that is when some object is heading your direction at high speed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:25, 24 November 2012 (UTC)[reply]

What to do with this image

I was at Filoli a couple months ago and took this very detailed (click on it and zoom in) picture of two bees foraging on a flower. The flower was labeled "Party", so I figured I'd put the picture in the appropriate article about the plant, with the bees a useful reference to judge the size. Unfortunately, the identifier with which the Filoli caretakers chose to tag this flower doesn't seem to correspond to any article. Anybody have an idea what this is? I don't even know what category to put it in on Commons. ~Amatulić (talk) 06:48, 23 November 2012 (UTC)[reply]

Don't know about the flower, but another use could be in our article on bees. StuRat (talk) 06:53, 23 November 2012 (UTC)[reply]

I thought of that too, but the honey bee article seemed already saturated with images. ~Amatulić (talk) 08:06, 23 November 2012 (UTC)[reply]

There's a single-flowered dahlia cultivar named "Party" (another image) that resembles the flower in your photo. Can you remember what the foliage looked like and whether it matches that in the linked picture? Deor (talk) 12:36, 23 November 2012 (UTC)[reply]

Ah, that's the one, yes. Thanks. In the same patch was this other dahla picture I took. I guess that whole patch was dahlia. ~Amatulić (talk) 15:56, 23 November 2012 (UTC)[reply]

Vehicle propulsion name?

What is the formal name for this type of vehicle propulsion:

In contrast to continuous track ..? Electron9 (talk) 12:01, 23 November 2012 (UTC)[reply]

In contrast to continuous track they would be tires.--Shantavira|^{feed me} 12:16, 23 November 2012 (UTC)[reply]

In British military parlance, it would be "wheeled" as opposed to "tracked". See Combat Vehicle Reconnaissance (Wheeled) and Combat Vehicle Reconnaissance (Tracked). Alansplodge (talk) 12:46, 23 November 2012 (UTC)[reply]

Also, it would be described as "8x8" ("eight by eight") because the drive from the engine is distributed to all eight wheels. According to our Mowag Piranha article, there are 6x6 and 10x10 versions as well. We have an article, Four-wheel drive, which explains the principle. Alansplodge (talk) 14:23, 23 November 2012 (UTC)[reply]

Beryllium

Why is beryllium toxic? Double sharp (talk) 12:02, 23 November 2012 (UTC)[reply]

I don't know anything myself, but we do have a Beryllium poisoning article that does or should be edited to include what is known. DMacks (talk) 12:07, 23 November 2012 (UTC)[reply]

Apparently this was asked already in 2002(!), and still does not seem to have been answered with references (it's not in any Wikipedia article that I checked). Double sharp (talk) 13:58, 23 November 2012 (UTC)[reply]

A 2006 review article (PMID 16697706) in Clinical Immunology suggested that particular MHC class II alleles (in HLA-DP) have negatively-charged glutamic acid residues capable of complexing beryllium, resulting in the broad activation of CD4+ T cells (reminiscent of the recent report in Science explaining the mechanisms of silver "allergy"). This is plausible though the phenotype is variable and it's likely to involve more factors; for example, a 2010 report PMID 20075058 suggests additional contribution of polymorphisms in CCR5, a chemokine receptor that has been shown to be important in T cell migration. The HLA-DP polymorphisms may provide the trigger, and the CCR5 polymorphisms may determine severity. -- Scray (talk) 14:42, 23 November 2012 (UTC)[reply]

Diet Related to Mental Decline

I have gone to the google search engine and have turned up studies by Olivia Okereke, but nothing in the past few years.

I am searching for the recent, original source of this important information.

"In fact, a diet high in saturated fat seemed to speed up mental decline by five to six years, compared to a diet low in this kind of fat. The study was led by Olivia Okereke, MD, an assistant professor of psychiatry and epidemiology at Harvard. It was based on data from more than 6,000 women over age 65."Pacerjp4693 (talk) 14:52, 23 November 2012 (UTC) John P. Falchi[reply]

I wonder if they have carefully eliminated other factors. For example, I bet the same people who sit and eat potato chips tend to do so while "rotting their brain" watching TV. So, is it the chips, the lack of exercise, the TV, or some combo causing the mental decline ? StuRat (talk) 15:14, 23 November 2012 (UTC)[reply]

http://onlinelibrary.wiley.com/doi/10.1002/ana.23593/abstract Trio The Punch (talk) 16:05, 23 November 2012 (UTC)[reply]

Change in real mass or not

Suppose, a body is travelling at the speed of light, its real mass will change or it (mass) will remain same. I know the body's relativistic mass will change. I am confused between mass and relativistic mass. Sunny Singh (DAV) (talk) 15:17, 23 November 2012 (UTC)[reply]

First of all, strictly speaking, no physical mass can actually reach the speed of light (although it could approach that limit to any arbitrary degree, say 99.9999999%). Anyway, to answer your question, it's real (ie rest mass) remains unchanged. 66.87.126.233 (talk) 16:44, 23 November 2012 (UTC)[reply]

Despite the formula

M=m/{\sqrt {1-v^{2}/c^{2}}}

that I learnt more years ago than I care to remember, the concept of relativistic mass (

M

) is not used by those who work with relativity. They prefer to use just the "invariant mass" (rest mass,

m

). See Mass in special relativity#Relativistic mass for the momentum vectors preferred by mathematical physicists. The following quote from Taylor & Wheeler's Spacetime Physics reflects current thinking:

"The concept of "relativistic mass" is subject to misunderstanding. That's why we don't use it. First, it applies the name mass - belonging to the magnitude of a 4-vector - to a very different concept, the time component of a 4-vector. Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object. In reality, the increase of energy with velocity originates not in the object but in the geometric properties of spacetime itself."

Dbfirs 17:42, 23 November 2012 (UTC)[reply]

I want to know as the body's velocity will increase (reaching the speed of light, but not more than that), more matter will be added to its mass or its mass will always remain constant even if it travels at the velocity of 200,000km/s. Sunny Singh (DAV) (talk) 19:07, 24 November 2012 (UTC)[reply]

"Matter" and "mass" are easy to confuse, but they are distinct concepts, since mass is a property of matter. Matter is not added to the body, but when a body reaches very high velocities, its mass increases. This is because you need a greater force to accelerate it by the same velocity difference than you would need if its speed was lower. As noted above, "relativistic mass" is a confusing term, but, yes, it is valid to speak of relativistic mass, which (defined as the proportionality constant between force and acceleration) is given by:

m={\frac {m_{0}}{({1-{\frac {v^{2}}{c^{2}}})}^{3/2}}}

where $m_{0}$ is the rest mass (which, by definition, is a constant). You can see by the equation how mass tends to infinity as the velocity approaches the speed of light, meaning that it is impossible to accelerate objects so that they surpass c. Hope this clears things up. -Anagogist (talk) 23:47, 24 November 2012 (UTC)[reply]

Yes, the amount of matter remains constant (unless it is losing mass to accelerate), and the mass as measured by an observer on the moving body will not change from its invariant mass (rest mass) whatever the speed, but the apparent mass as observed by a "stationary" observer will seem to increase according to that formula (without the sesquipedal power?) The apparent increase can be thought of as an illusion caused by the distortion of space-time, especially when you remember that an observer on the "moving body" will observe a relativistic increase in the apparent mass of the observer "at rest" on the Earth (and of the Earth itself). Dbfirs 16:00, 25 November 2012 (UTC)[reply]

Diamond plate armor

Suppose there existed a full suit of plate armor made entirely out diamond rather than the usual iron or steel. Someone told me that this diamond plate armor would be useless in combat because it would be easily shattered. Is he correct? Diamond has higher hardness than iron or steel, so shouldn't this suit of diamond armor be less shatterable than ordinary plate armor? —SeekingAnswers (reply) 22:04, 23 November 2012 (UTC)[reply]

It's a common misconception that hardness and toughness are the same thing. They are not. See this video for a good real-world demonstration. AFAIK, a diamond plate would shatter in a similar way if you gave it a good whack with a sledgehammer. Not really sure how it would hold up against something like a sword - certainly it would be v. difficult, if not impossible to slice though the plate. --Kurt Shaped Box (talk) 22:24, 23 November 2012 (UTC)[reply]

Perhaps if a support structure were used such that even cracked diamond would stay in place any projectiles would be so dispersed that they pose very little danger? Electron9 (talk) 00:08, 24 November 2012 (UTC)[reply]

I've seen a funny seen in a movie, where a character tries to disprove an assertion that a particular gem is a diamond. He erroneously reasoned that since he was able to crush the diamond into pieces with a simple hammer, it must have been a fake, only to be embarassed by his naivity. Plasmic Physics (talk) 22:36, 24 November 2012 (UTC)[reply]

What kind of combat are we talking about here? European swords were heavier and less sharp which was for crushing armour. Asian swords were lighter and sharper for slicing. Then there are of course maces, arrows, pikes, cannon fire and a whole host of other things that you might find on battlefield in the middle ages. Then maybe you're actually talking about a modern battlefield with .50 calibre bullets, IEDs and laser guided bombs. Or maybe a battlefield with aliens from outer space with immensely powerful firearms, immortals who bring each other back to life by calling out their names, epic duels on flying skateboards, and a blatant disregard for anything logical or previously established. As noted above diamond is more resistant to cutting than say steel, whereas most weapons impact the armour and create a shock which is most easily survived with an optimum balance of ductility and strength. Diamond has essentially no ductility. 203.27.72.5 (talk) 07:06, 25 November 2012 (UTC)[reply]

What peak pressure from a explosion in joule and required ground depth?

What peak pressure will a ground surface be exposed to from an above ground explosion measured using the equivalent energy in joule and specifically how deep would an underground bunker have to be depending on soil or rock inertia and shear strength of said material etc? I assume that the explosion energy is the decisive factor not the type of explosion process. I didn't find any practical information in the relevant wp articles, specifically on the the occurring pressure. Electron9 (talk) 22:21, 23 November 2012 (UTC)[reply]

Gunshot

Is firing a 410 or 20 gauge shotgun 1 or 2 times a month while hunting, without hearing protection, enough to cause hearing damage? Apparently most hunters don't use hearing protection so they can hear the animals walking. --Wrk678 (talk) 22:30, 23 November 2012 (UTC)[reply]

Sorry, but questions about the functions of and effects on your inner ear do amount to a request for medical advice that should be related to a doctor. μηδείς (talk) 22:54, 23 November 2012 (UTC)[reply]

It most certainly does not, unless we have evidence that the OP is a hunter who uses a 410 or 20 gauge shotgun 1 or 2 times a month while hunting without hearing protection. Medical questions are perfectly acceptable unless they request a diagnosis, prognosis, or other personal advice. --140.180.246.185 (talk) 00:48, 24 November 2012 (UTC)[reply]

It's a borderline case. To answer it factually, you would have to determine the loudness and duration of the sound, and compare that to some table or another that indicates what levels and/or durations of noise are likely to cause hearing impairment. The OP could do that. OR, he could ask his doctor, who should either know the answer or know someone who would know the answer. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:26, 24 November 2012 (UTC)[reply]

So, while bullshit opinions will simply amount to opinion, only actual answers to this question would amount to medical advice? Get on with it then, where are the refs? μηδείς (talk) 02:28, 24 November 2012 (UTC)[reply]

I'm trying to subtly suggest to the OP that he do his own research. It's possible that info is even in wikipedia. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:59, 24 November 2012 (UTC)[reply]

As the OP didn't indicate they thought they were suffering from hearing loss or they were planning to do any shooting I fail to see how it can be a request for medical advice. Here is a list of how loud various shotguns are and if they would cause hearing loss. CambridgeBayWeather (talk) 15:29, 24 November 2012 (UTC)[reply]
This list isn't as comprehensive as the one CBW found, but makes clear that virtually all guns are loud enough to cause hearing loss. Matt Deres (talk) 19:35, 24 November 2012 (UTC)[reply]

Yes most hunters don't wear ear protection (in the old days many wouldn't even wear it at the range) and yes it causes hearing loss. Gunshots are exceptionally loud; the only reason they don't cause more damage is because their peak sound is so short. To what extent is difficult to determine. Our article on Earmuffs has some numbers about sound level and duration. There are modern earplugs that compress at a high pressure wave, which provide normal levels of hearing but protect somewhat against loud sounds. Some militaries provide these, and some hunters use them. They aren't basic foam, they look more like concentric cones of plastic. Shadowjams (talk) 03:50, 25 November 2012 (UTC)[reply]

November 24

Women nagging from a scientific or psychological point of view

I don't want this question to come out as sexist, since all I am asking are findings based on scientific studies, journals, and the like. Basically, from a scientific or psychological point of view, what are the reasons why women seem to nag so much? Is there anything in female psychology, something in their DNA, or other scientific factors that cause them to nag more than men? And is this trait common with other animals? I tried searching for scientific studies about the topic, but I couldn't find any. Narutolovehinata5 ^tccsdnew 00:53, 24 November 2012 (UTC)[reply]

It could be that women as a group is more about social interaction rather than about "things" for males. And in particular to change social behaviour by the means of repetition. Electron9 (talk) 03:21, 24 November 2012 (UTC)[reply]

Be careful. It is probably because males suck. 00:57, 24 November 2012 (UTC) p.s. On a more serious note: they talk more and some have periods.

Is the basis of your question, the claim that "women nag so much", supported by "scientific studies, journals, and the like"? Otherwise, the question certainly comes out as sexist. HiLo48 (talk) 01:02, 24 November 2012 (UTC)[reply]

I meant "seem to nag..." I'll add in those words right now. Narutolovehinata5 ^tccsdnew 01:04, 24 November 2012 (UTC)[reply]

I'm really not sure that helps. Presumably it's your opinion that "women seem to nag so much", but how much of the rest of the world feels that way? I don't. So that's 50/50 out of this tiny sample. Maybe the studies, if any, need to be on those that feel the same way as you. HiLo48 (talk) 01:10, 24 November 2012 (UTC)[reply]

See You Just Don't Understand: Women and Men in Conversation by Deborah Tannen.

—Wavelength (talk) 01:13, 24 November 2012 (UTC)[reply]

Deborah doesn't seem to be the brainy type:

“

I recall one discussion period following a lecture I gave to a group assembled in a bookstore. The group was composed mostly of women, but most of the discussion was being conducted by men in the audience. At one point, a man sitting in the middle was talking at such great length that several women in the front rows began shifting in their seats and rolling their eyes at me. Ironically, what he was going on about was how frustrated he feels when he has to listen to women going on and on about topics he finds boring and unimportant.

”

— Deborah Tannen

The article about Deborah contains the phrase "however, feminist linguists argue against Tannen's claims."...

Trio The Punch (talk) 01:30, 24 November 2012 (UTC)[reply]

The article about Dr. Tannen mentions two book awards that she has won.

—Wavelength (talk) 02:48, 24 November 2012 (UTC)[reply]

This page about one of Dr. Tannen's books has the following statement.

Women in managerial positions have embraced this book as an account and an explanation of their own experiences and a guide to making changes.

—Wavelength (talk) 02:54, 24 November 2012 (UTC)[reply]

I am not saying she is not successful, she is probably richer than I am, I said she doesn't seem to be the brainy type, a polite way of saying she is not very smart. I suspect feminists think her ideas are outdated and sexist. You forgot to mention the author of that quote... Is it Deborah herself? I googled "Women in managerial positions have embraced this book": 1 result, her own website. She either wrote it herself or the person who made her website did. Trio The Punch (talk) 03:00, 24 November 2012 (UTC)[reply]

This may or may not be helpful in answering the original questions. Dr. Tannen has videos on YouTube.

—Wavelength (talk) 04:12, 24 November 2012 (UTC)[reply]

Newton's Second Law

Ever since I have learned that Newton's second law is actually "force equals the change in momentum in time" instead of "F=ma" I have been curious about this but can't really find a good answer. I understand that in the second form, we assume that the mass is constant in time. The first form is more general because it allows mass to change in time such as a rocket being launched and its mass decreasing in time as fuel is being spent. My question is, is there any hint anywhere that Newton might have suspected relativistic changes in mass? Because the first form is general enough to allow increase in mass too as velocity increases. I realize that back in those days relativistic velocities were difficult to achieve and the relativistic effects were hard to measure with those instruments so no one had probably seen these effects in an experiment but you never know. Thanks! 184.96.226.214 (talk) 02:04, 24 November 2012 (UTC)[reply]

That's a later modification to Newton's second law. Newton's original text stated: "The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the straight line in which that force is impressed." 1729 English translation, for comparison here is Newton's latin original. It is quite clear he is talking about acceleration, "alteration of motion", as Newton's own explanatory notes after the statement of the law refer to acceleration rather unambiguously. Newton's original law makes no mention of mass at all; it is implied from context that he's refering to forces applied to the same object. --Jayron32 03:27, 24 November 2012 (UTC)[reply]

Mayans

Is it true the Mayans successfully predicted every solar and lunar eclipse up until current time and even when their own civilization would be overtaken by invading foreigners. This said they did http://voices.yahoo.com/will-world-really-end-2012-11075310.html --Wrk678 (talk) 08:04, 24 November 2012 (UTC)[reply]

Most of their writings were burned by the Spanish, as explained in Maya codices. Of the three surviving codices known to be authentic, the Dresden Codex has a table of times when eclipses could (but did not necessarily) occur.[4] It spans 11,959 days (405 lunar months or 32+ years), hardly "until current time". Plus, they weren't totally accurate ("The astronomers periodically corrected the eclipse tables, learning from their small mistakes and adjusting the calendars ..."[5]). As for the writer you cited, she also believes in "holistic healing" and makes an unexplained (and really hard to believe) claim that the Mayans knew "when their own civilization would be overtaken by invading foreigners". If they did, why didn't they prepare better? All in all, not exactly what we'd call a WP:reliable source, not by a long shot. Clarityfiend (talk) 11:13, 24 November 2012 (UTC)[reply]

We know very little about the Mayans. That hasn't stopped certain people from making a lot of money by exaggerating what we do know and adding some fiction. Extra-ordinary claims require extra-ordinary evidence. That Yahoo link was not written by an expert. The "voices" subdomain is the location of the Yahoo! Contributor Network, anyone can join by signing up here. If you want me to I can write a page about the fact that Justin Bieber is a shapeshifter and publish it on voices.yahoo.com. Would you believe me if I did? Trio The Punch (talk) 16:33, 24 November 2012 (UTC)[reply]

When there's little known, there's a tendency to want to fill in gaps, especially if one can make money from it. As the author of the book that debunked the Bermuda Triangle said, "Everybody loves a mystery." By contrast, there's not a lot written about how wonderful the Vikings were, because they were known all too well. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:24, 24 November 2012 (UTC)[reply]

Over time all historical people and groups of people turn into stereotypes. Many people use the same kind of stereotypes to describe modern people and groups of people, we use words like racism to describe that. People love these noble savages. BTW I hate Vikings and their repetitive singing. Trio The Punch (talk) 17:43, 24 November 2012 (UTC)[reply]

I think all intolerant people should be shot. -- Jack of Oz ^[Talk] 20:28, 24 November 2012 (UTC)[reply]

By shapeshifting Viking singers at long range with spam, spam, spam, spam, spam, spam, baked bean, spam, spam, spam and spam bullets. Clarityfiend (talk) 23:14, 24 November 2012 (UTC)[reply]

What is this formula depicting?

This tattoo on a person's foot looks like a really fancy chemistry thing. Could anyone enlighten me please? http://shechive.files.wordpress.com/2011/01/dork-nerd-10.jpg — Preceding unsigned comment added by 24.72.13.24 (talk) 08:11, 24 November 2012 (UTC)[reply]

Polypeptide 2HN-CO-Glycine-Leucine-Proline-Cystine-Asparagine-Glutamine-Isoleucine-Tyrosine-Cystine-NH2 with sulfur bridge between cystein and Cystine.--Stone (talk) 08:50, 24 November 2012 (UTC)[reply]

G-L-P-C-N-I-Y-C in short --Stone (talk) 08:53, 24 November 2012 (UTC)[reply]

Gly-Val-Pro-Cys-Asn-Gln-Ile-Tyr-Cys --Stone (talk)

It is Oxytocin, I think it is biochemists expression for love.

According to the article "it is sometimes referred to as the "love hormone"" (citation needed). Do biochemists give each other oxytocin chocolates?--Shantavira|^{feed me} 11:41, 24 November 2012 (UTC)[reply]

Such a tattoo could alternatively indicate a union booster, since oxytocin induces labor. Using such formulas as tattoos is about as sensible other things that one does not fully understand. -- Scray (talk) 16:45, 24 November 2012 (UTC)[reply]

"chocolate is packed full of glucose"

My textbook compares a chocolate bar to a baked potato; the baked potato releases energy slowly, the chocolate quickly, because one is starch and has to be broken down into glucose, and then quote: "whereas chocolate is packed full of glucose which is more readily absorbed..." My question is: have they taken a liberty here, by not clarifying that this is true of cheap milk chocolate bars? Or does this also extend to, say, an 85% Lindt chocolate bar? By saying just chocolate they are implying that cocoa itself is packed full of glucose. Would this be true? Howie.W.30 (talk) 09:22, 24 November 2012 (UTC)[reply]

All you need to do to answer this is look at the dietry information printed on the packet. It happens that I have a Cadbury "Old Gold" dark chocolate bar waiting for me to eat. This is not a cheap milk type. It says on the packet that the sugar content is 57.3 grammes per 100 g of chocolate. Delicous but perhaps not very good for you if not eaten in moderation. In World War 2 cholocate bars were issued to Australian soldiers to eat before battles, because it kept well in a convenient sealed packet, and when eaten would give you a fast energy boost - that's what sugars/glucose does. All that sugar won't come from the cocoa. Note that chocolate is made from milk without the water, and milk with its water is up to 8% glucose. I don't know if chocolate manufacturers add glucose/sugar but it seems likely. Googling glucose chocolate reveals that researchers have been trying to prove that cocoa reduces blood sugar level. Floda 124.178.154.224 (talk) 11:28, 24 November 2012 (UTC)[reply]

My bar of 70% Old Gold has 27.7g of sugars (which I take it to include lactose etc). I'm not saying this is low, simply that we have to be realistic, if a bar is 85% cocoa solids, it's not going to have 57.3 g of sugar. Nil Einne (talk) 11:55, 24 November 2012 (UTC)[reply]

I looked again. Yep, my (Australian made) bar of Old Gold says it has 57.3 g sugar per 100 g chocolate. The cocoa solids are listed as only 45%. I've tried other types with 85% cocoa solids - they are not to my taste. When I made my first post, I only thought to look at the detailed dietry info. If I had looked above that to the summary of ingredients, I would have seen that it says that sugar is added. Floda 124.178.154.224 (talk) 13:16, 24 November 2012 (UTC)[reply]

(EC) Well I question whether that's correct in general. Outside of countries where high fructose corn syrup is common, like the US, most chocolate bars even cheap ones will have sugar i.e. sucrose not glucose. (To be clear, I'm not saying that HFCS will have a worse effect on GI then sucrose, simply that something using HFCS will have a far amount of glucose as well of course as a lot of fructose.) E.g. I just confirmed this from a bar of Cadbury milk chocolate here in NZ. And the glycemic index of potatoes even baked ones is actually quite high whereas the glycemic index of even cheap milk chocolate AFAIK often isn't that high. E.g. [6] gives 49 for milk chocolate. It doesn't have baked potatoes but the lowest for potatoes is boiled at 56. Jacket potatoes which I presume were baked is given as 85. This source specifically mentions chocolate generally has a lower GI then potatoes [7]. This source [www.amsa.org/healingthehealer/GlycemicIndex.pdf] gives 85 for baked potatoes and 68 for chocolate bars (type not specified but I think it's resonable to assume we're talking about fairly normal cheap chocolate bars). This [8] gives 49 for chocolate bar, 68 for Mars Bar, no specific value for potatoes but it mentions it's normally fairly high. To perhaps further emphasise [9] gives 111 for a baked russet potato (82 for a boiled white potato), which may seem a little extreme but I'm sure this isn't the first time I've heard of a potato having a higher glycemic index (then glucose). Nil Einne (talk) 11:47, 24 November 2012 (UTC)[reply]

Besides the added sugar, chocolate contains both cocoa powder, which has some fat and a tiny bit of sugar (maybe 2-3%) [10] and cocoa butter, with all fat and no sugar [11]. My 85% cocoa Möser Roth bar has 8 grams of sugar per 50 gram serving, which would make it 16% sugar. Most chocolate bars add far more sugar. Why ? Because cocoa is quite bitter by itself.

You can buy baker's chocolate, without added sugar. You find it in the baking aisle, not with sweets, since the assumption is that it will be used in baking, along with added sugar, not consumed directly. Take a bite, if you dare, but be close to a place where you can spit it back out. StuRat (talk) 20:56, 24 November 2012 (UTC)[reply]

Dark chocolate has a rather low glycemic load, and diabetics who may need emergency sugar are aadvised to carry candy but not chocolate for that purpose. This website is quite incredible a resource for all your nutrition information needs: http://nutritiondata.self.com/facts/sweets/10638/2. μηδείς (talk) 21:27, 24 November 2012 (UTC)[reply]

Just a few comments on the above... sucrose is half glucose, half fructose. And while there's some small debate over the point, high fructose corn syrup is usually about the same nutritionally as sucrose (depending on concentration, but most are around 50%). There's very little difference in structure, or effect, between just sugar and HFCS. I'm baffled that your textbook would use a baked potato as an example of a low glycemic index food. Fiber tends to level out blood glucose levels more than anything else. Shadowjams (talk) 03:40, 25 November 2012 (UTC)[reply]

Drive shaft feature identification

What is that square cut out at the end of the drive shaft called [12]? What is its purpose?Dncsky (talk) 13:45, 24 November 2012 (UTC)[reply]

It is intended to allow the user to couple a generic part to the drive shaft. I'm not aware of a more technical term than "couple" or "socket" that's used in this sort of scenario: but I would label it a mortise socket if I were drafting a sketch for manufacturing a part to fit it. Nimur (talk) 14:13, 24 November 2012 (UTC)[reply]

But isn't there already a rotor attached? I can't see what else could be fitted on there.Dncsky (talk) 14:21, 24 November 2012 (UTC)[reply]

You linked to a photo of a very small engine, correct? It's plausible that one manufacturer can use this engine to drive a model or toy aircraft propeller; another manufacturer can use the same engine, unmodified, to power a small model car, and so on. Do you know the engine make and model? The image is somewhat small and blurry. Nimur (talk) 18:04, 24 November 2012 (UTC)[reply]

Assuming it is in fact machined into the crankshaft and not part of the propellor (I am very familiar with engines, but not engines of this type), its purpose may be for barring, and thus it could reasonably be called the barring socket or barring nut. Barring is the process of turning a piston engine over slowly and often to precise points such as top dead centre - something that mechanics must often do in the aseembly/maintenance/overhaul of engines. With the propellor fitted you would not need it - just grab the prop and turn. But the crankshaft may have a barring socket or nut anyway so you can work on the engine without the prop. The term comes from the history of engines - early piston engines were large and heavy, with big heavy cast iron flywheels. Holes were made around the periphery of the flywheel, into which you inserted a crowbar or just an iron bar of convenient length, to turn the engine over to check timing, adjust valve gear clearances etc. Modern large diesel engines such as types of 400 to 5000 horsepower have a geared mechanism that engages with the starting ring gear for this same purpose - to use it you attach a large wrench and push it in to engage with the flywheel and for every 100 turns or so of the nut you turn the crankshaft one turn. It is called the barring gear for the same historical reason. In very large engines of power staion and ship main propulsion size, an actual engine (non-mechanics and non-engineers sometimes incorrectly call it a donkey engine) is provided to turn the main engine over for maintenance/assembly/overhaul purposes - this is called a barring engine. (Not to be confused with a starter motor/starting engine, which is designed to turn the main engine over as fast as possible without any positional precision.) Keit 121.215.135.17 (talk) 15:40, 24 November 2012 (UTC)[reply]

It also could quite likely be just a retaining nut to affix the propellor, and not part of the shaft at all. Keit 121.215.135.17 (talk) 15:43, 24 November 2012 (UTC)[reply]

Why is the equator not a large desert?

Hi, I thought about the main theory of climate, and I haven't understood why is the equator not a large desert, and why the Sahara is. Exx8 (talk) 17:05, 24 November 2012 (UTC)[reply]

Most of the equatorial regions get rain. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:21, 24 November 2012 (UTC)[reply]

Desertification is caused by a variety of factors such as climate change and human activities but being close to the equator is not one of them. Trio The Punch (talk) 17:25, 24 November 2012 (UTC)[reply]

I'm curious what the "main theory" of climate is. Some topics, like algebra or calculus, have a central theorem that embodies the critical idea of study. Climate, however, is a very complex scientific topic. We understand climate through the methods of physics, chemistry, biology, ecology, meteorology,... but none of these profer a "main theory of climate." Nimur (talk) 18:13, 24 November 2012 (UTC)[reply]

Am I reading it wrongly, or does that map show East Anglia as being at a high risk of desertification? A visit to that part of the world at this time of year might be instructive to whoever drew it. Tevildo (talk) 18:21, 24 November 2012 (UTC)[reply]

According to the main theory, the most major factor to climate is the longitude .

Another oddity is that there seems to be a magical climate change right on the US-Canada border, in the Western plains. StuRat (talk) 22:10, 24 November 2012 (UTC)[reply]

The 50 degrees temperature differential across the border probably has something to do with it.Dncsky (talk) 23:30, 24 November 2012 (UTC)[reply]

East Anglia contains the areas of the UK with the lowest annual rainfall, so I guess it's nearer to being at risk of becoming a desert than, say, Manchester or South Wales or Cornwall. --Demiurge1000 (talk) 01:11, 25 November 2012 (UTC)[reply]

As you can see on the picture, the angle of which the sunlight hits the ground changes the amount of energy that cm^2 gets. By doing so the amout of thermal energy changes in the place. That why the poles are cold, and the equator is hot and Arabia and 20 to 30 longitudes are usually deserts.. But I don't got why the equator is not a desert!!! Exx8 (talk) 18:41, 24 November 2012 (UTC)[reply]

Heat is not the definition of a desert. Precipitation is. Precipitation is more complicated than longitude alone, because it is more complicated than temperature alone. --Mr.98 (talk) 19:07, 24 November 2012 (UTC)[reply]

Arabia,North Africa, Australia, Namibia all are near or between 20 to 30 longitude (south or north) and have vast areas of desert.

Exx8 (talk) 20:09, 24 November 2012 (UTC)[reply]

Substitute "latitude" for "longitude" and this discussion will make a lot more sense. Edison (talk) 20:18, 25 November 2012 (UTC)[reply]

Lack of rainful defines a desert, hence the largest desert is Antarctica. The reason certain latitudes are deserts is because of atmopheric cells. At the Equator heat evaporates and as it rises it cools and falls as rain. At 30 degrees the air cool and cirulates round by this time there is no water left in the air so it is dry and hence a desert. Also mountains and being landlocked causes desertifcation.Dja1979 (talk) 20:52, 24 November 2012 (UTC)[reply]

Rainfall patterns are strongly tied to prevailing winds. Places which lie on the windward side of mountain ranges tend to get more rain than those on the leeward side. This is called the rain shadow effect, and many deserts can be explained because the desert lies in the rain shadow of a mountain range. Also, wind that blows over the land for long distances doesn't gather any moisture, while wind that blows over ocean water (especially warm ocean water) does. Additionally, there are bands of the earth's atmosphere where there is a permanent state of high pressure that leads to very little rainfall, these are called the horse latitudes and you'll find much of the world's desert lying underneath these. When you combine many of these factors (rain shadow, land upwind, horse latitudes) you get the world's driest deserts (Sahara, Arabian, Atacama, Kalahari, etc.) --Jayron32 01:13, 25 November 2012 (UTC)[reply]

(oop, wrote this before seeing Jayron's response, pardon the duplicate links) Dja1979 has it right. Atmospheric cells are the big picture reason. Some additional links: The large cells create prevailing winds. The northern and southern trade winds meet in the Intertropical Convergence Zone, near the equator, which tends to be rainy and wet. In contrast around the Tropic of Cancer and Tropic of Capricorn the large-scale atmospheric circulation creates dry zones of high pressure called the horse latitudes, which is where the temperate deserts are located, more or less. It is also why very dry deserts can exist right next to oceans, like the Atacama Desert. Mountains and rain shadow effects can intensify the aridity, or cause aridity beyond the horse latitudes. The High Desert of Oregon, for example, is far north of the horse latitudes, well into the zone of the Westerlies, which, blowing off the Pacific Ocean create temperate rain forest along the coast and on the west side of the Cascade Range. But by the time the westerlies get over the Cascades they have lost most of their moisture due to orographic lift. Thus the east side of the mountains are very dry. Pfly (talk) 02:31, 25 November 2012 (UTC)[reply]

why is the desert strips are created around 30 degrees and not around 50 degrees for example?Exx8 (talk) —Preceding undated comment added 18:07, 25 November 2012 (UTC)[reply]

Based on this explanation, why don't the Rocky Mountains turn the northern Great Plains into an enormous rain-shadow desert?

Also, why does the map show much of the Canadian prairie as desert? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:35, 25 November 2012 (UTC)[reply]

Much of the Great Plains/Canadian Prairie is steppe, which can be "semi-arid" or pretty close to desert. True desert gets 250 ml or less of rain per year, a "semi-arid" or "semi-desert" climate gets between 250-500 ml of rain per year, and much of the Great Plains falls into this climate. The southeastern Great Plains gets considerable rainfall from warm, moist air flowing northward from the Gulf of Mexico; there's a feature called the "dry line" that roughly separates the drier great plains from the wetter great plains. The dry line defines tornado alley. Much of the Great Plains is at risk constantly from desertification; there are periods of extreme drought, whereby the plains are converted to desert land, see Dust Bowl for a time period when this happened in recent memory. Regarding the Rocky Mountains: there are lots of deserts in the rain shadow of the Rocky Mountains: Much of New Mexico, Colorado and West Texas lies within the High Plains, an area of desert or semi-desert conditions. Much of that area meets the literal definition of desert, or close to it. The really severe deserts in the U.S., however, lie between mountain ranges, where there is no inflow of moisture available from any direction. For example, the Mojave Desert lies between the Sierra Nevada and Rocky Mountains; it is part of the wider Basin and Range Province which is essentially all desert. --Jayron32 03:04, 26 November 2012 (UTC)[reply]

Human humerus

what does a broken human humerus at the head look like.18:14, 24 November 2012 (UTC) — Preceding unsigned comment added by 50.142.225.56 (talk)

This. Many similar images are available with a Google search on "Proximal humerus fracture". Tevildo (talk) 18:19, 24 November 2012 (UTC)[reply]

Sensor Array http://en.wikipedia.org/wiki/Sensor_array

In the Section on "Spectral Based Beamforming", there is a math equation for the "spacial covariance matrix" in which the "array manifold vector" V and it has a raised index or exponent "H" , but there is no explanation for what "H" stands for - that is my question? SnakeCasey (talk) 21:52, 24 November 2012 (UTC)[reply]

This is the Hermitian transpose, rows are turned into columns and complex conjugate is taken. Graeme Bartlett (talk) 22:04, 24 November 2012 (UTC)[reply]

~~That's what I guessed as well, but to be honest I was a bit stumped at first. Should it be changed? I don't think I've seen it elsewhere on Wikipedia. -Anagogist (talk) 22:06, 24 November 2012 (UTC)~~ Never mind, I'm an idiot. -Anagogist (talk) 22:08, 24 November 2012 (UTC)[reply]

micro wave shielding methods and materials

What particular materials are used to shield enclosed areas, like a small room? and where I might 0find them. — Preceding unsigned comment added by 75.6.143.24 (talk) 22:16, 24 November 2012 (UTC)[reply]

A metallic screen (much like a window screen). The actual spacing is critical, however, and depends on the frequencies you need to block. StuRat (talk) 22:21, 24 November 2012 (UTC)[reply]

See Faraday cage and Electromagnetic shielding for our articles on the subject. Tevildo (talk) 22:38, 24 November 2012 (UTC)[reply]

What is the current energy usage of the Internet

http://www.theregister.co.uk/2012/11/24/cudos_photonics_australian_institute_physics/ If we want to keep expanding the performance and the reach of the Internet, we need an inflection point: otherwise, its electricity consumption will become catastrophic.

Is it really that big a deal? Could we save a great deal of energy by turning the Internet off at night? Hcobb (talk) 23:23, 24 November 2012 (UTC)[reply]

Umm... what? It's not as easy as flipping a switch to "turn the Internet off," and even if it were I daresay people in other parts of the world will be rather cross with you for turning off their Internet at 9 in the morning. 24.92.74.238 (talk) 00:52, 25 November 2012 (UTC)[reply]

The Register is an amusing read, but it's important not to take anything it says too seriously. The word "catastrophic" is clearly an exaggeration here. The internet and internet industry and such, according to the article takes a few per cent of world energy demand; and as it continues to grow it will need more; so researchers are looking at ways to operate it more efficiently. That's about it. --Demiurge1000 (talk) 01:08, 25 November 2012 (UTC)[reply]

I've got a better idea. Just download the internet and print it off, then go through it one weekend, decide what to keep, and ditch the rest. I'm sure you'd save a massive amount of space. You can then use the scrap paper to mop up all that excess water in the Pacific Ocean. :) -- Jack of Oz ^[Talk] 07:55, 25 November 2012 (UTC) [reply]

Internet service is mostly carried by phone or cable lines so is not a huge added cost over the baseline signal. Servers are a new draw on electricity, and I understand it costs a lot to keep them from overheating. Computers cost money to run, but not so much more than running an old TV would have, one presumes. I'd look into the cost of running the servers. Imagine how big google's footprint must be. Probably not as bad as the machines in Terminator, yet. Once we get to Matrix stage they'll be feeding off us. μηδείς (talk) 02:53, 25 November 2012 (UTC)[reply]

Servers are computers, and the consistent trend has been that each new generation of servers can do more work while consuming less power. Also, servers are not "a new draw"... internet servers (in the modern sense) have been around for well over thirty years, web servers for well over twenty years.

Google and Amazon and similar hosting companies do indeed draw lots of power, but they do it by providing hosting facilities that mean power does not need to be used by smaller companies elsewhere. Such centralisation provides considerable efficiency (i.e. saves power) by allowing them to design their very large datacentres for best performance (solar panels on the roof, clever ways of using airflow and ambient temp cooling and so on.) --Demiurge1000 (talk) 03:13, 25 November 2012 (UTC)[reply]

Using power that wasn't used before efficiently is still using power. But I think Demiurge's overall point is obviously true, the internet saves an effload of power given all the efficiencies it introduces economywide. μηδείς (talk) 04:03, 25 November 2012 (UTC)[reply]

I wasn't discussing whether using the internet consumes more power than not using the internet (or not having an internet). I was discussing whether the ideas mentioned by the OP, and amplified by yourself, namely that the internet will progressively use more and more power to a "catastrophic" degree, are realisic. Current technology trends are to use less power to do more things. --Demiurge1000 (talk) 05:47, 25 November 2012 (UTC)[reply]

But, of course, increasing energy efficiency doesn't automatically mean reduced energy consumption. In many cases, increased efficiency may permit us to do more things economically, thus increasing the total workload. Consider that during WW2, code-breaking machines used a huge amount of power to do simple things, yet our total computer electricity consumption now is far more than then, despite massive increases in efficiency. StuRat (talk) 06:19, 25 November 2012 (UTC)[reply]

Same tasks, less power. Computers are not now used mainly for code-breaking. --Demiurge1000 (talk) 06:25, 25 November 2012 (UTC)[reply]

Which is my point, precisely. The more efficient they become, the wider their usage. StuRat (talk) 06:30, 25 November 2012 (UTC)[reply]

I see nothing that suggests a direct correlation between increased power efficiency of computers and more widespread use of them. --Demiurge1000 (talk) 17:07, 25 November 2012 (UTC)[reply]

They have both consistently increased over time, so the correlation is obvious. Whether there is a causal link or not is not as easy to tell, but I would be very surprised if there weren't. It's simple supply and demand - when something can be supplied cheaper, the price comes down, demand for it will increase and total consumption will increase. --Tango (talk) 17:38, 25 November 2012 (UTC)[reply]

If more of the economy is handled via the Internet, using more energy, then less of the economy is handled in old-fashioned ways, so that energy is conserved. For example, more teleconferencing means less driving and flying to meetings. More emails means fewer snail mails. More pics texted back and forth means less film needs to be developed and mailed. More movies viewed online means less driving to the video store to pick up movies or watching movies in theaters. It might all balance out, or even save energy overall. StuRat (talk) 05:25, 25 November 2012 (UTC)[reply]

More teleconferencing usually means more teleconferencing that generate more travelling for physical meetings ;) Electron9 (talk) 11:44, 25 November 2012 (UTC)[reply]

November 25

A question in biology of Retroviruses (physiology and ecology)

A cat scratch's a man and allegedly almost not even wounding him (the cat may have a also micronic level of blood on his nail). let's assume that this blood on the nail is infected with a retrovirus (like HIV). considering the fact that this virus could be destroyed with oxygen (which can be found on the air), if the blood on his nail will interact with air, how much time will it take that the air will destroy the virus which allegedly localized on his nail (when outside\inside is fur) ? Thanks !!! — Preceding unsigned comment added by 79.179.170.159 (talk) 00:20, 25 November 2012 (UTC)[reply]

Reactions on a molecular level such as oxygen destroying the envelope of a virus happen extremely fast when they do happen (miniscule fractions of a second) but there is no way for us to speculate on specific conditions like how tolerant any random virus is of air exposure, how much liquid the virus might be protected by, and how long it would take to for the liquid to evaporate or oxygen to dissolve into it. μηδείς (talk) 02:46, 25 November 2012 (UTC)[reply]

(edit conflict) If your question is primarily about HIV survival outside of a host, then this page has very good answers. Other than that, it would be speculation to give you any sort of time frame, as survival rates depend largely on exactly what kind of virus it is and exactly what kind of conditions it has been exposed to. Merely being lodged underneath nails can still expose it to a variety of conditions that can change its survival rate significantly.

It is important to remember that viruses are closer to self-replicating chemicals, von Neumann machines, rather than to other forms of life. They are incapable of initiating metabolic reactions on their own, and can survive indefinitely in any state that doesn't change their biochemical makeup. They can be frozen, crystallized, and even disassembled and put back together, and they can still be viable. That said, anything that changes their biochemical makeup can denature them (again like any other chemical). Factors that can influence virus survival rates include UV (including from sunlight), extreme temperatures, desiccation, acidity, the absence of host cells, the loss or absence of capsids and envelopes, etc. All these can affect the infected blood under cat's nails. See virus processing.

Lastly, as far as I know, the claim that "viruses are destroyed by oxygen" is pseudoscientific quackery associated with dubious use of oxygen therapy that can be outright dangerous in some cases. Dioxygen (O₂), the oxygen we breathe, is a relatively stable allotrope. That doesn't mean it does not have an effect (e.g. this study shows it can decrease or increase virus replication rates), but it's certainly not as simple as "oxygen kills viruses". Ozone (O₃), however, is quite effective in destroying bacteria, viruses, and other microorganisms and is used widely in industrial sterilization. It is, however, toxic to all living cells (like other reactive oxygen species), as its high reactivity makes it capable of literally tearing most organic molecules apart. It is also only present in significant quantities in the stratosphere. In order for it to kill the viruses under the cat's nails, the cat would probably have to be exposed to enough ozone to kill the cat itself.-- OBSIDIAN†SOUL 02:50, 25 November 2012 (UTC)[reply]

Obsidian, what you said in the last paragraph contradics all i have heard till now, i can't analouge it for what your said in the paragraphs before. if i understand right. — Preceding unsigned comment added by 79.179.170.159 (talk) 03:24, 25 November 2012 (UTC)[reply]

It might help if you provide a link to where you heard that oxygen (and I assume you mean oxygen in the air we breathe) destroys viruses. I'm betting it's one of those "miracle hyperoxygenated water" companies or a religious/New Age therapy site. Ozone does, as well as reactive oxygen species like hydrogen peroxide, but they also kill most of anything anyway. AFAIK, stable dioxygen does not. -- OBSIDIAN†SOUL 03:42, 25 November 2012 (UTC)[reply]

It's from no link. 2 doctors of medicine told this to me. — Preceding unsigned comment added by 79.179.170.159 (talk) 03:45, 25 November 2012 (UTC)[reply]

Then I'm sorry but I can not help. Perhaps someone else who knows their microbiology better can. As far as I can see though, there are no indications in sources I can find that dioxygen destroys viruses. There is a lot of research on ozone for the last couple of decades, but ozone is not the normal state of oxygen we find in the air we breathe. Perhaps your doctors merely meant it in a general way? As in by saying "exposure to air" they really mean exposure to environments outside of a host?-- OBSIDIAN†SOUL 03:58, 25 November 2012 (UTC)[reply]

A search for "virus destroyed by exposure to oxygen" at Google and Google Scholar seems to result in almost pure quackery or nothing. Yet I have heard the claim made in semi-respectable popular sources as well. I suspect exposure to ozone or O^- must be the culprit if there is an effect. Perhaps that or simple drying? μηδείς (talk) 04:00, 25 November 2012 (UTC)[reply]

Probably. Innocent confusion or deliberate synthesis.-- OBSIDIAN†SOUL 04:16, 25 November 2012 (UTC)[reply]

Radical species derived from oxygen cause protein to denature and damages nucleic acids. Virus are basically nucleic acids wrapped in protein. 203.27.72.5 (talk) 04:25, 25 November 2012 (UTC)[reply]

Reactive oxygen species have already been mentioned. -- OBSIDIAN†SOUL 04:34, 25 November 2012 (UTC)[reply]

Obsedian, they have talked on it's appearance without an host, i believe. i am but a layman, i can't really mediate, not more than listening. — Preceding unsigned comment added by 79.179.170.159 (talk) 04:41, 25 November 2012 (UTC)[reply]

Plant indentification in opening credits of Downton Abbey

What species are the two very large, spread-limbed, evergreen trees in the first three seconds of the Downton Abbey opening credits, as Lord Grantham (presumably) walks toward the manor house with his dog? See http://www.youtube.com/watch?v=v00bHK2C6kc. Thanks. μηδείς (talk) 07:32, 25 November 2012 (UTC)[reply]

They are apparently 18th century Lebanon cedars, according to this image from commons, and our Highclere castle article. Mikenorton (talk) 08:05, 25 November 2012 (UTC)[reply]

(edit conflict) There's more on the history of its origin in our article on Highclere Castle.-- OBSIDIAN†SOUL 08:10, 25 November 2012 (UTC)[reply]

Thanks. you can see why they'd put such a tree on a national flag. μηδείς (talk) 18:33, 25 November 2012 (UTC)[reply]

The first cedars were brought to England in the 1680s from Mount Lebanon where a small grove of trees tended by monks was said to have been planted by King Solomon. These were thought then to be the only cedars of Lebanon still in existence, so posession of one of their offspring was considered a prized asset. This was hightened by the number of times the cedar of Lebanon is mentioned in the Bible (in 48 seperate verses; Noah's Ark was made of it and it lined the Holy of Holies of the Temple in Jerusalem). They were wildly fashionable for large country houses throughout the 18th and 19th centuries, usually planted as a single specemin tree in a prominent place. It's difficult to think of an English stately home that doesn't have one. A lengthy diatribe on the subject is here. Alansplodge (talk) 19:21, 25 November 2012 (UTC)[reply]

Question about subwoofers

There is any obligatory relation (or a “most” range) or proportion in the diameter of the magnets of a drive and the diameter of the drive itself?

I’m don’t saying that have to be an exact same relation but… for example, there is a way of knowing (by simply seeing the size of the magnet and drive) that the magnet is not the original, and instead, that the original one was bigger?

Iskánder Vigoa Pérez (talk) 14:56, 25 November 2012 (UTC)[reply]

There are essentially two common types of speaker magnetic configuration: a) types with a cylinder-shaped magnet inside and the "return" magnetic circuit on the outside, and b) types with a ring-shaped magnet on the outside and the return magnetic circuit on the inside. For the first type, the magnet is always made to fit just inside the voice coil, allowing a small clearance distance to avoid fouling. For the second type, the overall diameter of the magnet is unimportant, so long as the magnet is big enough to supply enough flux to saturate the pole pieces. With ferrite magnets, the strength is not high, but they are cheap, so it is common for ferrite ring magnets to significantly overhang the rest of the magnetic structure.

What is more important in contributing a low distortion output is the ratio of the voice coil diameter to the cone diameter. Here, the short story is that the larger the voice coil diameter the better, but for any given realistic voice coil to cone ratio, a different set of harmonics are excited. In theory, the simplest issues with harmonic distortion occurs when the cone area inside the voice coil diameter is equal to the area outside, but no manufacturer makes voice coils that big, because of the cost. Lots of other factors influence frequency response and distortion. The whole story is too complex to explain here, especially without diagrams.

For an excellent series of easy to read articles discussing the design factors of loudspeaker driver design, see the US magazine AudioXpress for the last 6 months or so. If you can handle the math (senior high school standard), the classic and very comprehensive textbook on loudpeakers & microphones written by Olson in the late 1930's and reprinted up to the late 1950's is still the best. It was a standard work in its day - every State or university library of any merit should have a copy.

It would be very very unusual for a speaker magnet to be replaced. It cannot fail in service, and assembly of speaker magnet structures is a somewhat specialised job. What does get replaced or repaired is the cone and voice coil - these often fail if overdriven and a tech can learn how to do it in about half an hour. — Preceding unsigned comment added by 121.215.71.120 (talk) 15:47, 25 November 2012 (UTC)[reply]

Keit 121.215.71.120 (talk) 15:34, 25 November 2012 (UTC)[reply]

Wow… Thank you very much… that clarify all my doubts Iskánder Vigoa Pérez (talk) 16:14, 25 November 2012 (UTC)[reply]

Background photon emissions

So, I was reading this paper "Marked Increases in Background Photon Emissions in Sudbury Ontario More than One Week before the Magnitude > 8.0 Earthquakes in Japan and Chile", and it occurred to me that I don't really know what ground level background photon emissions that can be measured with a photomultiplier in a black wooden box covered with dark cloth in a windowless dark basement room are, despite knowing what all of those words mean. Although there is a bit more information in this earlier paper, I didn't have much luck via google. Do we have an article about this phenomenon ? I couldn't find one. Sean.hoyland - talk 15:23, 25 November 2012 (UTC)[reply]

As a scientist, I would be very reluctant to embrace the conclusions of any paper published in a SCIRP journal. Our article touches on some of that publisher's history, including instances where their peer review process seemed...less than rigorous: [13], [14]. (Speaking from personal experience, I know a number of graduate students who have been spammed with multiple invitations to join the editorial boards of various SCIRP journals—which doesn't inspire confidence.)

Meanwhile, Michael Persinger (the lead author of the two papers you found) has a history of publishing...interesting papers on fringe topics, and other groups have apparently had some difficulty reproducing some of his findings. Taken together, I see an awful lot of red flags. TenOfAllTrades(talk) 18:29, 25 November 2012 (UTC)[reply]

Agreed, I'm a geoscientist, but my only concern is that I really have no idea what background photon emissions are. Never heard of it. I'm assuming it's just one of those things I've missed i.e. everyone else has heard of it and knows what they are apart from me. Wouldn't be the first time. Sean.hoyland - talk 20:30, 25 November 2012 (UTC)[reply]

Even the most energetic gamma photons will not travel through more than a few metres of the ground. So any photons these fellows detected didn't radiate from Japan through the earth. Beyond that the only things coming up at these guys' basement photomultiplier are infrared, which is only an indication of how warm their basement floor is, and gammas from spontaneous nuclear decays in the few metres below them - again that's information only about the detector's environment, not about the whole earth or distant parts of it. Yes, there are background photons (coming down) from cosmic, galactic, and solar sources - but these won't make it into the basement (unless they left the basement door open). The only exception to that is radio frequency photons, which come from both astronomical and artificial sources - these can get in by diffraction and reflection (in the way that you might get a poor radio signal or bad cell phone coverage down in the basement). But you detect radio frequency photons with an antenna, not with an optical photomultiplier. So the claims in the paper are just aphysical - they're claiming they put an optical detector in a dark room, and that by some process it detected light; they then correlate that detection with some event (not exactly much data there) and then slyly imply a causation. So it's nonsense, at best. 87.112.97.202 (talk) 21:13, 25 November 2012 (UTC)[reply]

Well, here I go talking about something I know nothing about, but having read the earlier paper I provided a link for above in a futile attempt to learn what background photon emissions are supposed to be, I didn't get the impression that it was obviously aphysical or necessarily just visible light. The author says

"There is classic theoretical and empirical evidence that photon emissions can originate from the types of silicates contained within crustal structures."....okay, I guess this is supposed to be about mechanoluminescence
"Presumably the source of such emissions would be subtle mechanical pressures or electromagnetic stimuli."...so, I assume he's thinking about local sources, maybe including IR photons, I have no idea about his equipment, caused by local stress field variations coupled to global variations.....that somehow get into his black box....confused...but confused mostly about whether there actually is such a thing as ground level background photon emissions. Sean.hoyland - talk 22:12, 25 November 2012 (UTC)[reply]

It's pretty apparent from the references used in his paper that he (Persinger) is the first person (and probably the only person) who has claimed to detect these things. What he's calling 'ground level background photon emissions' are probably just the dark current from his photomultiplier tube. TenOfAllTrades(talk) 22:33, 25 November 2012 (UTC)[reply]

If you wanted to detect mechanical movement or stress in the local environment (which really means the cement floor of this guy's basement) then you'd use an ordinary stress sensor. Using a photo sensor is like using a thermometer to determine if your neighbour's TV is on. Ground movements strong enough to cause mechanoluminescence on the other side of the world would obviously show up on seismographs. 87.112.97.202 (talk) 22:52, 25 November 2012 (UTC)[reply]

Did the aborigines use dingoes as hunting dogs?

Does anyone know what benefit dogs brought humans in pre-invasion times? --Anthonyhcole (talk) 15:28, 25 November 2012 (UTC)[reply]

Our article (Dingoes#Present_day_distribution) says "possibly were used as food or eventually guard dogs" (without a source it seems) which sounds plausible but I assume no one really knows. There's this article. Sean.hoyland - talk 15:43, 25 November 2012 (UTC)[reply]

Another use, still today for bush aboriginals, is to keep warm at night - a sort of living heat providing blanket. A common expression in Australia for describing a cold night is to say someting like "Last night was a two dog night", or "Tonight will be a three dog night" due to its origins in using dogs to cuddle up to. Wickwack 120.145.26.49 (talk) 15:51, 25 November 2012 (UTC)[reply]

Final angular velocity after combining two disks

According the problem, two disks of equal masses are strung on the same rod. They are spinning with angular velocity $\omega _{0}$ but in opposite directions. The radius of one is $2r$ and the radius of the second is $r$ . My first answer was $1.5\omega _{0}mr^{2}$ which was obtained by adding the momentum of the larger disk ( $0.5\omega _{0}m(2r)^{2}=2\omega _{0}mr^{2}$ ) and the momentum of the smaller disk ( $0.5(-\omega _{0})mr^{2}=-0.5\omega _{0}mr^{2}$ ), and then dividing the result ( $1.5\omega _{0}mr^{2}$ ) by $mr^{2}$ . Since this was wrong, I divided by $2mr^{2}$ instead. it was wrong again. Where am I making my mistake? --Melab±1 ☎ 19:15, 25 November 2012 (UTC)[reply]

You need to divide by the combined moment of inertia, which is not

mr^{2}

nor

1.5mr^{2}

nor

2mr^{2}

. (Keep going ...) In rotational dynamics, moment of inertia plays the same role that simple mass plays in linear calculations. Our article on Moment of inertia might help. Dbfirs 21:07, 25 November 2012 (UTC)[reply]

I was able to find the solution. I have to divide

{\frac {1}{2}}\omega _{0}m(2r)^{2}-{\frac {1}{2}}\omega _{0}mr^{2}

by

{\frac {1}{2}}m(2r)^{2}+{\frac {1}{2}}mr^{2}

. But, seeing that either disk can be chosen to have the positive angular velocity, the solution could then be

\omega _{f}={\frac {{\frac {1}{2}}\omega _{0}mr^{2}-{\frac {1}{2}}\omega _{0}m(2r)^{2}}{{\frac {1}{2}}m(2r)^{2}+{\frac {1}{2}}mr^{2}}}=-{\frac {3}{5}}\omega _{0}

and that doesn't seem right. I also have to calculate the change in kinetic energy. --Melab±1 ☎ 22:31, 25 November 2012 (UTC)[reply]

Gas bubbles on side of plastic container filled by chlorinated water

Regarding Chlorinated Water ^[1]...

I pour water in a plastic water jug and let the water sit for a couple hours. Small semi-spherical bubbles appear sticking to the inside plastic side. Question: What gas is in these bubbles? Is it chlorine evaporating out of the water?

--InverseSubstance (talk) 19:51, 25 November 2012 (UTC)[reply]

Probably air - assuming that the water was significantly colder than the temperature of the room initially, small amounts of nitrogen and oxygen come out of solution as the water temperature rises, forming bubbles that nucleate at imperfections on the surface of the jug [15]. Mikenorton (talk) 20:59, 25 November 2012 (UTC)[reply]

According to the World Health Organisation, "chlorine is present in most disinfected drinking-water at concentrations of 0.2–1 mg/litre" [www.who.int/water_sanitation_health/dwq/chlorine.pdf]. With an atomic mass of 35.5g/mol, that's 0.000028mol of Cl or a maximum of 0.000014mol of Cl₂. Assuming chlorine is an ideal gas, that would have a volume of 0.315mL. At standard temperature, far more than that would stay dissolved in water. But let's say you could force it all out of solution. 0.315mL of gas could be contained within 100 bubbles 0.9mm in radius. The bubbles would be greeny-yellow. 203.27.72.5 (talk) 01:41, 26 November 2012 (UTC)[reply]

Is being HIV positive comparable to have diabetes?

Provided it's been treated. Comploose (talk) 23:52, 25 November 2012 (UTC)[reply]

Only in the almost irrelevant sense that both require lifelong treatment and monitoring, and both can kill you. As someone who spends so much time asking questions at the Ref Desk, Comploose, you surely know that your first stop for information should be the relevant Wikipedia articles. Do you have a question about the treatment and monitoring regimes associated with either condition that isn't addressed by Wikipedia? TenOfAllTrades(talk) 00:05, 26 November 2012 (UTC)[reply]

How can lifelong treatment and monitoring, and been killed be at the same time "almost irrelevant"? Comploose (talk) 00:29, 26 November 2012 (UTC)[reply]

Who said "almost irrelevant"? Trades is giving you good advice, and you respond with sarcasm and made up quotes? We don't do debate here, if you don't have a reference question this can be hatted. μηδείς (talk) 01:11, 26 November 2012 (UTC)[reply]

TenOfAllTrades said it. 4th and 5th words. 203.27.72.5 (talk) 01:16, 26 November 2012 (UTC)[reply]

Yes, my bad, I was looking for the irrelevant wikipedia article. He's right that the fact they are not curable is a rather minor similarity. μηδείς (talk) 01:22, 26 November 2012 (UTC)[reply]

November 26

stereo amplifier output impedance

How do I best go about calculating my amp's output impedance? Should put a given ohm resistor and than just differentiate the voltage drop there? Will this do it?

I need this to figure out its damping factor. — Preceding unsigned comment added by 77.35.20.143 (talk) 03:14, 26 November 2012 (UTC)[reply]

Which caulking should I use?

I have to caulk around a ceiling light fixture, I decide to use silicone caulk for the job, since it is high heat. I took a laser thermometer in the area I need to caulk and its 102° with the light on. I have previously used a particular type and brand of silicone caulk on many jobs and was happy with the results, it is the GE 2 silicone kitchen and bathroom caulk, it has a mold inhibitor and it but when I like most about it is that it has very little smell to it. When drying, some of the caulks have a horrible acetic acid smell to them which I want to avoid. My concern is that if I use this caulking, the mold inhibitor may get released into the air when it gets heated up. I looked into some of the "food safe" silicone caulk but it seems to be the type that smells like acetic acid, I'm concerned with the acidic acid type is that when it gets heated up, it may release that acetic acid smell again. I am going to link the MSDS sheets of both types of caulk I'm considering to use and I would like you to tell me which one I should use.

The Ge 2 kitchen and bathroom 3 hour dry http://www.homedepot.com/catalog/pdfImages/80/803b3b37-83d5-40b0-a182-9e5eba6d304c.pdf

The food safe one http://www.homedepot.com/catalog/pdfImages/a1/a12dd342-15df-4ca3-92fc-8204bdf74281.pdf?cm_mmc=seo%7Caltruik%7C100128841 --Wrk678 (talk) 03:37, 26 November 2012 (UTC)[reply]

^ Chlorination

[1] Chlorination

[1]