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December 26

rare and hazardous research chemicals

Name a few chemicals that are hazardous, used rarely and applied for novel research purposes (ex:certain toxins that are researched in very few laboratories against deadly unusual microbes). — Preceding unsigned comment added by 213.120.141.254 (talk) 06:07, 26 December 2012 (UTC)

Is that what your teacher asked you to do on your homework? -- Jack of Oz 06:58, 26 December 2012 (UTC)

nope. I am aware that advise and homeworks are not discussed here. — Preceding unsigned comment added by 213.120.141.254 (talk) 09:14, 26 December 2012 (UTC)

If it looks like homework, sounds like homework, smells like homework, it probably is homework. You've asked a question in a way that probably 1000's, even millions, of chemicals, toxins, virus particles, and other substances might qualify. And it should be easy to think of a few if you give it a moment's thought - a few more moments' thought might suggest some words to google. Why don't you just run your eye over the periodic table and look up a few promising elements? Some of the high weight elements have only been synthesied in one or two labs at considerable effort just to get a few atoms. If you narrow it down a bit what you want to class as rare, and tell us what steps you have taken so far to find out, i.e., show us you are not just lazy, we might feel more inclined to do a bit of digging for you. Floda 58.164.226.231 (talk) 11:11, 26 December 2012 (UTC)

Except that those superheavy elements are not really used for what your question seems to classify as novel research purposes – there's not much time to do much with them before they decay, given their short half-lives. Pure research is more like it. Double sharp (talk) 13:49, 26 December 2012 (UTC)

• my favorite Brevetoxin --Stone (talk) 11:27, 26 December 2012 (UTC)

This blog is a source of wonderful stories about chemicals that no sane person would handle, usually because they're explosive, corrosive, or incredibly smelly - all backed up with references to actual research that has used them. AlexTiefling (talk) 10:14, 27 December 2012 (UTC)

Of these chemicals, the only one I've ever had to work with is anhydrous hydrogen fluoride (we used it, and still use it, in the alkylation unit at the refinery). 24.23.196.85 (talk) 20:01, 29 December 2012 (UTC)

Bacterial infection before antibiotics

I know before the discovery of antibiotics, herbs were used to treat bacterial infection. Is there any information available about the success rate of this treatment? --PlanetEditor (talk) 09:24, 26 December 2012 (UTC)

I'm not aware of any quantitative information, but the basic answer is: dismal. No herbal treatment comes anywhere close to penicillin. For superficial infections, the most effective primitive treatments are probably either licking the wound (saliva is a pretty potent antibiotic) or spreading honey on it. Looie496 (talk) 16:18, 26 December 2012 (UTC)

Or Maggot therapy. Ruslik_Zero 18:53, 26 December 2012 (UTC)

Or putting a poultice of moldy bread on it, as the ancient Greeks had done (but that is actually a primitive form of antibiotic treatment, they just didn't know it at the time). 24.23.196.85 (talk) 01:08, 27 December 2012 (UTC)

Researching it takes me to links about how we are almost back to the pre-antibiotics era (due to superbugs). Maybe we will have to use greatpa's antibiotics again. OsmanRF34 (talk) 22:09, 26 December 2012 (UTC)

Train related engineering questions

1) Is it possible to increase train speed by doubling current train width?

2) Why China reduce its train speed from 350 to 300km/h, does reducing the speed by 50km/h also increase the train safety? Why?

3) What's the main propulsion inside fast train? Electric motor?

4) With current technology, is it cheaper to build a bridge or a tunnel below sea? roscoe_x (talk) 14:51, 26 December 2012 (UTC)

I numbered your Q's for ease of response:

1) Doubling width does not automatically allow for an increase in speed. In fact, you want to minimize cross sectional area (≈height×width) to reduce drag.

2) Any decrease in speed increases safety, since it reduces the chances of a crash and also the severity.

3) There are a variety of propulsion systems used, but the best choice, IMHO, is to not have any engine on-board, and instead deliver energy using the tracks, as in a mag-lev train.

4) A bridge is cheaper in shallow water, and a tunnel in deep water (due to the height of the supports needed for a bridge). StuRat (talk) 21:42, 26 December 2012 (UTC)

1) Widening does indeed allow for faster turning.

2) Operating below maximum speed is standard practice, as it allows trains to make up time following delays.

3) High Speed Trains generally use electric motors. Delivery of propulsion from the track, as is proposed above, would incur absurdly large infrastructure costs and is not a sensible proposal for a large network.

4) A bridge is cheaper for crossing water. Building a tunnel under deep water requires a deep tunnel which is also absurdly expensive. A tunnel is used for going under mountains or the like. — Preceding unsigned comment added by 92.11.76.114 (talk) 23:38, 26 December 2012 (UTC)

1) Perhaps, if you mean wider and shorter. But wider and proportionally taller doesn't help.

3) You need to read up on maglev trains: .

4) The cost of building tunnels under deep water rises more slowly with additional depth than the cost of bridges does. Hence the Chunnel, as opposed to a bridge. StuRat (talk) 23:43, 26 December 2012 (UTC)

Indeed, "chidge" just doesn't have the same ring to it. Evanh2008  11:12, 29 December 2012 (UTC)

2) Per High-speed rail in China#Corruption and concerns, the official line is that "This was in response to concerns over safety, low ridership due to high ticket prices, and high energy usage." Suspicious people (like me) speculate that it is because of corruption in the construction that may compromise safety. Clarityfiend (talk) 22:21, 26 December 2012 (UTC)

1) The main problem with doubling width is that it would necessitate a change in loading gauge, and almost certainly in track gauge. High speed trains run on regular tracks at least part of the time, if only to be taken for servicing and so on. And I understand that the Chinese authorities are trying to increase the adherence to Standard Gauge throughout Eurasia, to try and let their own network link up with other nations', and thus enable truly transcontinental trains. As Russia currently uses Russian Gauge, as do many ex-Soviet nations, that's quite a challenge. Introducing a variant gauge just for high speed would certainly over-complicate the task. AlexTiefling (talk) 00:08, 27 December 2012 (UTC)

I remember that according to one of Albert Speer's books, Hitler had a plan for trains twice as large in every dimension which his underlings, citing similar concerns, politely convinced him to defer until after he won the war. Wnt (talk) 00:17, 27 December 2012 (UTC)

Stalin had no such inhibitions - see 4-14-4. Tevildo (talk) 00:43, 27 December 2012 (UTC)

1) I recommend you read up on Brunel's seven-foot gauge.

4) Unless built over very shallow water, a bridge is very limited in its maximum span compared to a tunnel, due to requirements for intermediate supports.

24.23.196.85 (talk) 01:33, 27 December 2012 (UTC)

One of the practical limits on the speed of passenger trains on existing track is the lateral g-forces exerted on them in corners. Hence the two ways to increase speeds are:

1. To use larger radius curves - which results in difficulties with using existing track - or even with upgrading existing track without a lot of land purchasing.
2. To attempt what British Rail did with tilting Advanced Passenger Train...which was notoriously unsuccessful.

SteveBaker (talk) 03:55, 27 December 2012 (UTC)

Is it the lateral forces on the passengers or train that's the problem ? StuRat (talk) 04:07, 27 December 2012 (UTC)

On the passengers -- they get thrown sideways. Hence the use of "pendular suspension" in many high-speed trains like the aptly-named Italian Pendolino or the Swedish X 2000. 24.23.196.85 (talk) 06:31, 27 December 2012 (UTC)

Seems like a much simpler fix for that is putting the backs of the seats against the windows (perhaps slanted with the feet forward and head back) and requiring people to remain seated when going through curves. StuRat (talk) 22:17, 27 December 2012 (UTC)

That's supposed to be a joke, right? 24.23.196.85 (talk) 00:48, 28 December 2012 (UTC)

No. Also, looking out the windows at 300 kph can cause nausea even if there's no lateral g's. StuRat (talk) 00:55, 28 December 2012 (UTC)

And just how do you stop people from getting up and walking around, or get them to reseat themselves every time the train approaches a curve? Also, not being able to look out the window on a curve can cause worse nausea than in the scenario you describe. 24.23.196.85 (talk) 01:41, 29 December 2012 (UTC)

The same way you get them to sit on airplanes when they encounter turbulence. StuRat (talk) 04:13, 29 December 2012 (UTC)

Turbulence on an airplane happens much less frequently than curves on a railroad line. 24.23.196.85 (talk) 19:58, 29 December 2012 (UTC)

Yes, but it's also less predictable. Being able to plan the exact times people need to remain seated is quite helpful. And airplane passengers also need to remain seated during take-off and landings. StuRat (talk) 23:27, 29 December 2012 (UTC)

Well, I don't think the pax would appreciate being forced to sit in their seats more than half the time, which is what would happen on most lines if this solution was adopted. 24.23.196.85 (talk) 01:08, 1 January 2013 (UTC)

That certainly is the case on airplanes, where they encourage people to stay seated the entire time, except for when using the bathroom. If making the train tilt correctly doubles the price, I, for one, would rather save the money. StuRat (talk) 06:54, 1 January 2013 (UTC)

Regarding question #4, bridges need not be rigidly anchored to the sea bed. A pontoon bridge design similar to the Lacey V. Murrow Memorial Bridge may be an economic option. Likewise, a tunnel need not be embedded in the sea bed. See submerged floating tunnel. A combination of the two or a bridge-tunnel may be needed to balance shipping and cost considerations. See also transatlantic tunnel. -- Tom N (tcncv) talk/contrib 16:55, 28 December 2012 (UTC)

You can't send a bullet train over a pontoon bridge or through a submerged floating tunnel -- it would break apart. And a bridge-tunnel crossing can only be built in shallow water -- it needs intermediate islands (natural or artificial) for the transition between bridge and tunnel or vice versa. 24.23.196.85 (talk) 01:50, 29 December 2012 (UTC)

Couldn't mechanical resonance be defeated by good engineering (or even by some kind of computer controlled active compensatory mechanism)? Wnt (talk) 18:51, 31 December 2012 (UTC)

Not for such an inherently flexible structure as a pontoon bridge or floating tunnel -- not over the full range of vibrational frequencies produced by a fast train, anyway. Hell, it's not even possible to drive a fast train over a suspension bridge, for the same reason -- so why would a pontoon bridge be any better? 24.23.196.85 (talk) 01:04, 1 January 2013 (UTC)

Roche limit for black holes

where is Roche limit for any black hole?Akbarmohammadzade --78.38.28.3 (talk) 16:29, 26 December 2012 (UTC)

Black holes do not have Roche limit. They are essentially inviolable. Ruslik_Zero 18:51, 26 December 2012 (UTC)

I think that answer is true, at least in a sense, but it is a bit unsatisfying to me. The Roche limit is a point where part of an object is going to fall away from it. How could something inside an event horizon fall away from the center? To illustrate, the Roche limit article says that a satellite can only be torn apart if its density is less than twice that of the primary, because otherwise the limit is inside the primary - so anything that could bring a black hole to the Roche limit would be darn near one already. And so my assumption is that the black hole + primary become a big rotating black hole. But note that a rotating black hole has a ring singularity, and so one can argue that you have disrupted the innards of the black hole and turned them into an "orbiting ring of debris" in some very, very loose sense. I'm not really giving you an answer with this, just making an appeal for an imaginative consideration by one of the experts. :) Wnt (talk) 20:32, 26 December 2012 (UTC)

This is an interesting question that I've never thought about before. There are a bunch of papers/preprints about it on the arXiv. According to arXiv:0705.1570 (which has pictures), the event horizon is distorted by the tidal force into a cigar shape. This actually surprises me, because the event horizon of a rotating black hole is not distorted: it's a sphere with no equatorial bulge. The singularity remains a point/line (I think), but the Planckian region, where the curvature exceeds the Planck curvature and therefore general relativity is presumably wrong, is flattened like a pancake. The paper mentions that there's a threshold tidal force beyond which the pancake extends outside the event horizon, giving you a naked singularity (more or less). This might imply the existence of a (mass-dependent) maximum tidal force analogous to the maximum rotational speed of a rotating black hole (beyond which you get a naked singularity). I'm not sure how this force could actually be achieved, though, since it seems to require another black hole essentially touching the first.

arXiv:0910.4311 mentions that a black hole orbiting another body will gain mass from tidal friction, and I assume (though it doesn't say so) that it would eventually become tidally locked to the other body. This isn't directly relevant to the question, but it's interesting. -- BenRG (talk) 01:34, 27 December 2012 (UTC)

thanks all. It might be two Roche limit for any black hole .One of them outer than event horizon and other inner it as we know all objects elongate infinitive there. — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 08:52, 27 December 2012 (UTC)

It would be useful to frame the question properly. The Roche limit for a body applies in relation to another, and depends upon properties of both (the mass of the primary, and the density and configuration of the secondary). Thus, the Roche limit of a (normal matter) body orbiting a black hole (the primary) will be the radius from the black hole where the object will disintegrate under the influence of tidal forces, and this will typically be far outside the event horizon of the black hole for smaller black holes, but inside the event horizon for supermassive black holes such as in the centre of the galaxy. The radius of a black hole's event horizon is proportional to its mass. The Roche limit is proportional to the cube root of the ratio of the black hole's mass and the orbiting body's density. The previous answers assumed that the black hole is the secondary, orbiting an even larger primary. Here the (infinite) density of a non-rotating black hole makes the Roche limit zero radius from the primary's centre, though the rotating case (a Kerr black holes as the secondary) might be interesting, since the singularity presumably differs non-trivially from a spherical configuration. — Quondum 09:35, 27 December 2012 (UTC)

When we talk about black holes we imagine some thing absorbing and destroying all around it .This is not reality about them. If it is so that any black hole has infinitive mighty and effect at all distance , this has contraction with nature laws. I want to say (as said last about planets round black hole )that the black hole with mass M and rotating properties , has as gravity field as last star .we say if any black hole was any star which had planets , its members will rotate round it safely . if our sun was able to be black hole ,our earth was rotating round it ,without any difference later and after . why we do such mistake ? black hole sun cannot destroy not only low density Saturn but also near mercury ,then we give some hypothetical properties to it, of absorbing all the things? can any black hole absorb its neighborhood star?never .

have you never calculate Roche limit of any black hole?

excuse me --Akbarmohammadzade (talk) 10:47, 27 December 2012 (UTC)<

Hmmm, there's another problem: there are no stable orbits very close to a non-rotating black hole. See photon sphere. But black holes in such relationships might be rapidly rotating, so sometimes I suppose it is possible... (but I'm out of my depth on this) Wnt (talk) 15:38, 27 December 2012 (UTC)

Shwartz child radius for any star 10 times massive than sun is about 5kilo meters Akbarmohammadzade — Preceding unsigned comment added by 2.187.90.105 (talk) 17:08, 27 December 2012 (UTC) 1.5 times further it will be about 8 kilometers--Akbarmohammadzade (talk) 17:32, 27 December 2012 (UTC)

Past article from the Lancet medical journal.

I require a specific article from a past Lancet journal. The article if from 2005 volume366 pages 29-36.IT IS specifically about the ABCD criteria after a TIA (transient ischemic attack). — Preceding unsigned comment added by 24.185.248.186 (talk) 16:32, 26 December 2012 (UTC)

The article is titled A simple score (ABCD) to identify individuals at high early risk of stroke after transient ischaemic attack. If you search for the title at scholar.google.com, you can get access to several downloadable online versions, including this one. This way of finding things works pretty frequently. Looie496 (talk) 17:23, 26 December 2012 (UTC)

Misplaced Pages:WikiProject Resource Exchange/Resource Request is the place to request articles that aren't available free online. -- BenRG (talk) 17:52, 26 December 2012 (UTC)

How does it come that this is legal? OsmanRF34 (talk) 21:48, 26 December 2012 (UTC)

We don't give legal advice. But you might want to read fair use. 208.102.63.50 (talk) 23:04, 26 December 2012 (UTC)

December 27

measuring in a hypodermic syringe

How does one accurately measure small amounts of medicine in a hypodermic syringe? Is there medication left in the needle after the injection?Tmary (talk) 01:07, 27 December 2012 (UTC)

(1) The hypodermic syringe usually has markings on the side showing the volume of medicine to be delivered. (2) Yes, there is a small amount of medicine left in the needle after the injection, but it's unusable because it cannot be expelled from the needle, and also because it's mixed with the patient's (possibly infected) blood. 24.23.196.85 (talk) 01:16, 27 December 2012 (UTC)

2) I think what they are asking about is if the unused portion remaining in the syringe is accounted for in the markings. I'm not sure, but guess that this amount is insignificant, either way. StuRat (talk) 01:26, 27 December 2012 (UTC)

(2) All the syringes I've seen are calibrated "to deliver" -- which means that the markings show the volume actually injected. 24.23.196.85 (talk) 01:41, 27 December 2012 (UTC)

also, a standard amount of medicine is in solution by weight per volume in the liquid matrix. So one simply measures a volume of a usually pre-made solution to be injected, rather than measuring some miniscule weight. μηδείς (talk) 01:25, 27 December 2012 (UTC)

Seems like the graduations measure the amount in the barrel - so when you suck the liquid inside, you're getting a little extra inside the needle...then when you do the injection, that exact amount is left inside the needle at the end - so the reading on the barrel should be exactly correct no matter the volume inside the needle. I suspect that the limitations on precision are more to do with the skill and eyesight of the operator than anything else. SteveBaker (talk) 03:46, 27 December 2012 (UTC)

There is a small dead volume in many sorts of equipment. One quick way to avoid it being a problem is to keep its contents constant. That is, if you keep the syringe needle-down, pull the syringe barrel from the 0.0 mL marking to 0.2 mL and then push it out to 0.0 mL, you have picked up and squirted out 0.2 mL. The needle (and the inner part of the Luer lock and other areas) started empty and wind up empty. Or else you could pull to 0.3 mL, invert and push down to 0.2 mL (expelling the air that had been in the needle, etc.). Then when you push to 0.0 mL, you are still ejecting "0.2 mL to 0.0 mL", now indeed wasting the drops in the needle. Either way, you keep the same material in that space, whatever it is does not interfere when the barrel moves a certain number of volume-markings (standard laboratory practice when titrating by volume from a burette). DMacks (talk) 03:48, 27 December 2012 (UTC)

Note that having a constant 'dead volume' in a syringe depends on the contents being liquid (and specifically aqueous, as water is practically incompressible), i.e. the syringe is commonly tapped to bring any air bubble(s) to the top, and the uppermost contents, liquid and gas alike, are expelled down to the desired precise quantity. Wnt (talk) 04:40, 27 December 2012 (UTC)

Something else I should add is that the syringe should be chosen for the amount of med to be given. You wouldn't use a 100 ml syringe to administer 5 ml of meds, as it would be less accurate at that dosage than a 5 or 10 ml syringe. StuRat (talk) 04:43, 27 December 2012 (UTC)

The smallest-measuring syringes in common use are insulin syringes. The smaller ones are 0.3 ml or 0.5 ml, and graduated in units that are equivalent in volume to 0.01 ml. The imprecision of delivery has been studied. With careful technique the error of delivery is 0.003 ml or less, but can be higher with poor technique. alteripse (talk) 06:34, 30 December 2012 (UTC)

decline of space expansion and exploration

I came across an old (pre-70's) transcript of an Earl Nightingale radio broadcast in which he spoke of Seaborg's predictions for the year 2000. Seaborg predicted that moon trips would be commonplace by 1992, and people would be able to go around the world in 2 hours, and that we would be visiting nearby planets by the year 2000. Interesting that he also predicted the 'internet'... he said that people would be able to use radio technology to read books from remote libraries :) Now my question is - why is mankind not devoting resources into space expansion and exploration? Surely, with the large number of extinction events possible, that we would need a 'backup' of mankind in space bases on the moon and beyond? Yes I know the traditional response to this is that it's 'prohibitively' expensive, but surely there's got to be more to it than this? What's the use hoarding or misusing funds if a comet can wipe us out tomorrow? Sandman30s (talk) 09:51, 27 December 2012 (UTC)

Is the transcript of this Seaborg interview available online? Nimur (talk) 18:16, 27 December 2012 (UTC)

No, they were "Defy" (South African electrical brand) transcripts of the radio show that my grandfather collected. Email me and I will scan and send to you. I should probably make them all available online as there some real gems there and I don't believe there is any copyright. Sandman30s (talk) 20:57, 27 December 2012 (UTC)

There almost certainly won't be any comets wiping us out tomorrow because we're constantly monitoring for any nearby objects of sufficient size to do serious damage. Launching anything into space is ridiculously expensive, even for low-earth orbit. Creating a fully autonomous offworld base (in orbit or on another body) is an extremely difficult task by itself; there's an absolutely vast number of ways in which it could go wrong. The combined cost of developing the necessary equipment and launching it into space would be outrageous. The chances of an offworld colony being wiped out would be much greater than the chances of the entire human race being wiped out. If we really wanted to protect the human race from mass extinction events, I'd imagine building underground cities would presently be a much better choice than colonising space. As for space exploration, we are doing that, except we're using robots instead of humans, because it's just that much cheaper and easier. --Link  11:01, 27 December 2012 (UTC)

Yes I know about monitoring near-earth objects, but we currently would not be able to prevent a large object (kilometres in diameter?) from crashing into earth. What's the use having underground cities (or even cities on the ocean bed) if a comet hits or supervolcano erupts? These events would wipe out all surface life as well as all crops, so how would the subterranean dwellers get food? I would also imagine that creating underground cities would be just as expensive as cities on the moon. Yes I do agree that a space base would be far more dangerous, but that's the whole point of creating backup(s)... if your primary source is gone then at least you do have a backup. Sandman30s (talk) 11:17, 27 December 2012 (UTC)

The ocean would be hard to disrupt, especially not quickly. Yes, if an event leads to the whole ocean boiling you're screwed in the long run, but no dinosaur killer or Snowball Earth event ever did that. (A full fledged runaway greenhouse, maybe...) There is actually extensive military-oriented regulation of trading in even a camera that can see things more than a mile deep, so there must be something down there, though the usual explanation involves crashed nuke sub(s). I don't think we can rule out that one or more such bases to shelter elites haven't already been constructed, though I know of no evidence. Wnt (talk) 15:33, 27 December 2012 (UTC)

Can you provide a link to where I may read more about the trading limitations on such cameras? Are you talking about pressure resistant cameras and housings? -- 41.8.83.148 (talk) 05:30, 28 December 2012 (UTC)

You could move underground during the most turbulent period, and then return to the surface once things start to stabilise again. Getting food would be problematic, but it's not quite easy to do in space either. You seem to be underestimating how incredibly inhospitable space actually is. Once you're out of the protective shell of Earth's atmosphere and magnetosphere, you're constantly pelted by radiation. No planet or moon in the solar system beside Earth has a breathable atmosphere. There's nowhere other than Earth where leaving the protection of a spaceship or space suit is survivable for even a minute or so. It would probably still be easier for humans to survive on Earth in the aftermath of a global disaster than it would be on Mars in the most favourable conditions. Sure, it would be useful to have an off-world colony, but the launch costs alone make it utterly infeasible (a space elevator would alleviate that problem, but we're not quite at the point where we can build one yet). Putting a permanently manned base on the moon is just about at the limit of what we could reasonably do right now. Creating a completely autonomous (i.e. capable of surviving indefinitely even if the Earth were to go kaboom) colony for a minimum viable population of humans is very far out of reach for the time being. Ensuring a few thousand humans could survive a global disaster on earth is easier, cheaper, and likely more effective than creating an offworld colony that can repopulate the Earth later. --Link  16:49, 27 December 2012 (UTC)

You could get by the minimum viable population problem by keeping thousands of frozen embryos (or sperm and eggs), so you'd only need a "caretaker" population. StuRat (talk) 21:23, 27 December 2012 (UTC)

Thank you for your thoughts. Let's say terraforming became viable and feasible in the distant future. Would you still say that underground cities would be better than colonies on a terraformed Mars? Sandman30s (talk) 21:07, 27 December 2012 (UTC)

Well, except the runaway greenhouse. If the oceans actually boil and the water vapor greatly enhances the greenhouse effect, so that the whole planet gets a proper steam cleaning, then anywhere, even underground, will eventually be uninhabitable. Getting the energy to run enough air conditioning to live in an oven when you can't go anywhere seems like a long shot, though I suppose in such a thick atmosphere amazing things can be done with wind power (a little late, tho) Wnt (talk) 17:02, 27 December 2012 (UTC)

I am currently looking at tens of thousands of perfect tomato plants sitting on a cement floor while a foot of snow is on the roof above, so getting food while living underground really would not be a problem so long as one has continuous energy (likely nuclear) and a one time supply of water, seed, fertilizer, and growing equipment. 50.101.153.9 (talk) 21:40, 27 December 2012 (UTC)

Right at this very moment people ARE going round the world in two hours (less actually), in the International Space Station. HiLo48 (talk) 22:14, 27 December 2012 (UTC)

Yea, if you don't count the take-off, landing, prep time, etc. Actually getting from the ground in Australia to the ground in the US takes a lot longer. StuRat (talk) 05:33, 28 December 2012 (UTC)

Link: Glenn T. Seaborg - 41.8.83.148 (talk) 05:44, 28 December 2012 (UTC)

quantum effects in processors

How, specifically, do modern processors use quantum effects? (i.e. "don't work without it", etc). This is not homework. 91.120.48.242 (talk) 11:49, 27 December 2012 (UTC)

If nothing else, transistors depend on quantum effects. It's hard to give a definitive answer, because really every property of matter is a quantum effect if you look deeply enough. Looie496 (talk) 15:47, 27 December 2012 (UTC)

But that's not what I mean. When they're designing a processor, they have modeling software (to lay out the circuits). Does this modeling software include quantum effects? 91.120.48.242 (talk) 15:54, 27 December 2012 (UTC)

No. Looie496 (talk) 16:33, 27 December 2012 (UTC)

Thank you, Looie. Is there a size where it would? I found a stackoverflow answer to the question "Is Quantum Physics used in manufacturing CPU's" (June '11). It says they mostly avoid it: "As component sizes have gotten smaller, tunneling has become an increasingly important limiting factor in the design and layout of chips." Is there some kind of size where you could no longer avoid these effects, but, for example, have CPU modeling software (for laying out new CPU's) that actively includes the quantum effects for you to include in the design? I am not talking about a quantum computer per se, just at what point traditional CPU design will directly work with (use) quantum effects, if indeed there is such a size. 91.120.48.242 (talk) 16:56, 27 December 2012 (UTC)

Modern off-the-shelf processors do not, but see http://en.wikipedia.org/Quantum_computer#Developments. The article states that, "In 2009, researchers at Yale University created the first rudimentary solid-state quantum processor." It goes on to summarize other state-of-the-art developments. --Modocc (talk) 17:06, 27 December 2012 (UTC)

This also depends on what you mean when you say "designing a processor." In modern engineering practice, a computer architect (or a whole team of them) designs a system architecture, including a low-level digital logic representation/implementation of the instruction set architecture. At this layer of abstraction, transistors are "guaranteed" to work. One could say that we build in a sanity-check any place we use an error correction code, because we handle any generic type of bit error without regard to the source of the bit-flip. That bit error could be due to thermal noise, or analog electromagnetic interference, or a timing error due to imperfect trace length, or a cosmic-ray alpha particle striking the transistor, or a quantum fluctuation... but it just doesn't matter. The computer architect doesn't care why the analog circuit might fail; at this layer of abstraction, we just have ones and zeros. Now, usually it is "someone else's job" to make sure that the bit-error rate is as low as possible. An entire team of engineers worries about each source of error: a layout crew makes sure the traces on the silicon get designed properly for minimum clock skew and best signal integrity. A packaging engineer (or a team of them) worries about using the right type of plastic encasement to minimize RFI and EMI and alpha particle strikes.

And finally, somebody - usually not just one engineer, but an entire company full of engineers - worries about what we calll very large scale integration. These guys don't care at all whether the system architect designed a billion transistors that comprise a processor, or a radio demodulator, or a giant billion-transistor no-op. It's their job to ensure that all billion silicon transistors get built right - as designed. This is sometimes called the "Process." Each manufacturer of silicon has their own process, and distribute large complex computer aided design tools that automatically translate a digital design into the correct number of photolithography masks - one mask for each layer of semiconductor, insulator, and conductor layer. It is the job of the fabrication process company to make sure that their masks properly convert a digital design into the analog world. They worry about such things as the optical resolution of their lithography masks; if they choose to use quantum mechanics to analyze the optical path, it may improve their yield. In fact, current semiconductor processes are so small that it's uncommon to use light during photolithography; the wavelength of light is larger than the features being etched. So, they may use x-rays, or ultraviolet light, or any other strange proprietary technique to get around the wavelength limitation. This method can be called a "quantum" effect: you cannot build a single transistor if the uncertainty principle dictates that your photon is larger than the transistor. Another team of engineers - chemists, electrical engineers, material scientists, and so on - worry about etching. They worry about how many seconds of exposure to various etching chemicals are required to remove photomask, and etch away the undesired parts of the semiconductor structure. Now that nano-layer fab processes have such a small number of atoms, the process of acid dissolving solid surface atoms can be modeled quantum-mechanically. This is a molecular physics problem, or a statistical problem. If a quantum-mechanical analysis of this chemistry helps the engineers etch better transistors, it will affect the yield.

The design of an electronic circuit in semiconductor requires accurate knowledge of the dynamic electrical properties of a material. In semiconductors, things like electrical resisitivity and free electron count and even thermal constants are dictated by atomic processes. In very small transistors, such as the ones in a modern process, these properties might require analysis of atomic physics, because there are so few atoms that we can't "average" everything out (as we do in conventional thermodynamics or large-scale statistical physics). An entire field of quantum mechanics analysis - semiconductor physics - is useful in analyzing the electrical and other properties of structures that are built from just a handful of atoms or molecules.

Finally, we can consider the statistical methods of quantum mechanics - independent of their applications to atomic physics. Quantum mechanics helps scientists speak definitively about uncertainty. It helps analyze quantized (countable) effects while also working with analog (continuously varying) phenomena. So, at very low levels of analysis, or at very abstract levels of analysis, we can use methods of QM to analyze things like defect count per wafer, and use that knowledge to guide and modify our designs.

Now, I often hear the pure physicists say things like "quantum mechanics makes the transistor possible." As a former physicist, turned silicon-engineer, I can say my piece: this is utter baloney. It's physicist-talk. Engineers have historically designed, and will continue to design in the future, without understanding the absolutist view of "fundamental processes" that phyicists continually strive for. Engineers are able to work with problems, analytically and quantitatively, while abstracting away the irrelevant details - any detail that doesn't directly affect the current problem. Most engineers in the semiconductor industry - even the ones down low in the process stack - never ever ever use QM or its techniques. Some engineers do. Unlike pure physics research, where scientists use the most sophisticated analysis possible, engineers only use the analytical tools that are needed to get the job done. When designing computer processor logic, QM is almost totally irrelevant. When working with the implementation of that processor as an analog circuit, QM is often irrelevant. But, there are cases where QM improves the process. And there are probably some areas where methods of QM are absolutely essential to the correct design and analysis. But on the whole, what you should recognize is that QM is a method of analysis, not a physical fact. Like all physics, quantum mechanics is a best-effort to accurately model the world as we observe it. It happens to be the best method we have for analyzing atomic physics, and many similar problems. When atomic processes affect analog circuits, we must use QM. But again, let me reemphasize: engineers work by abstracting problems and worrying only about the details that directly affect them. Only half-in-jest, I say that QM analysis is "always" somebody else's job; everyone knows that somewhere in the machine, QM rears its ugly head, but as long as each engineer can make her/his contribution work right, he/she doesn't need to do any extra mathematical juggling. Nimur (talk) 17:51, 27 December 2012 (UTC)

Thank you. I read all this (in a few sessions :). Basically, you are saying that the part that I am interested in - chip architecture design - does not and probably will not use QM, which is more like "noise" that has to be removed by error checks and carefully embodying the abstract design: it is literally at a lower layer and does not make it into chip design. Thus if I understand you correctly, my question is similar to the question "do Internet Protocols like TCP/IP or UDP make use of the fact that light is both a wave and a particle?" and the answer is "No, not at all", and double not for quantum entaglement. That fact has been abstracted away long before they see it. TCP/IP or UDP doesn't even know if it is going over fiber optics, over copper, or over radio. All it gets is the 1's and 0's. You are basically saying the same thing about QM effects: they are abstracted away long before the chip designers see them. Thank you for your detailed answer, Nimur! --91.120.48.242 (talk) 12:58, 28 December 2012 (UTC)

I too found Nimur's exposition an informative read. There are of course things at the lower layers that do not get entirely abstracted away: simulations of implementations can result in high-level logic design choices, e.g. differences at higher design levels may make a difference to the highest clock frequency at which a circuit implementation will function correctly. At times there are low-level aspects that are exploited at a higher level, e.g. in true random number generators, where noise (sometimes of a quantum nature) is the basis of the functionality required. — Quondum 13:28, 28 December 2012 (UTC)

hair/fur, not pelt

Please list the characteristics of squirrel fiber, squirrel tail fiber, and raccoon fiber.Curb Chain (talk) 12:28, 27 December 2012 (UTC)

Please do your own homework. Your quetion reads like it has been copied straight out of an assignment. If not, show us why not. Wickwack 58.169.234.153 (talk) 13:50, 27 December 2012 (UTC)

They tend to grow outward from the skin, and are long and slender. Does that help? ←Baseball Bugs carrots→ 04:34, 28 December 2012 (UTC)

Thanks but can you give more distinguishing charactersitics?Curb Chain (talk) 06:24, 28 December 2012 (UTC)

Hydrogenated Polyisobutene in cosmetics

The entry on Polyisobutene makes it sound like something I wouldn't want to rub on my skin. But I've seen "hydrogenated Polyisobutene" as in ingredient in a number of hand lotions. What properties would make it appropriate for that? --71.189.190.62 (talk) 17:59, 27 December 2012 (UTC)

Let's provide a link to the article in question: polyisobutene. While our article doesn't talk about the hydrogenated version, it sounds like it can be used as a thickening agent to keep the oils from readily evaporating, and doesn't have much of a smell. So, it makes the hand lotion last a long time and not stink. The fact that it's used in chewing gum also makes it clear that it's not toxic. StuRat (talk) 18:07, 27 December 2012 (UTC)

As the article notes, PIB and many related compounds are common synthetic rubbers. I bet you've handled, used, and maybe even worn many things made out of it. We also have an article about hydrogenation. DMacks (talk) 18:39, 27 December 2012 (UTC)

If your cosmetic ingredients gross you out, don't think too much about the urea they frequently add. StuRat (talk) 18:58, 27 December 2012 (UTC)

Daily Comet Ison pic?

I'd like to rig up a picture on my computer's desktop to be a current image of Comet Ison, the one that could become a Great Comet in about a year. Is there a "live" image somewhere on the net I can link to? (By "Live", I mean "taken this week or so".)

Even better would be a time-lapse showing the motion of the comet from its discovery until now, but I'd be delighted just to find a weekly-updated image of what the comet looks like now. TIA - Tarcil (talk) 19:12, 27 December 2012 (UTC)

Mystery mineral

I've had this item for a number of years, having purchased it from a rocks and minerals gift shop, but have unfortunately forgotten what it was called and have long since lost the handy little label describing it. This may have said something about it being an industrial by-product, perhaps from Eastern Europe or Russia, but I could be misremembering. It's certainly very pretty - the picture doesn't really do it justice. It's iridescent, and the edges are rather sharp. It wasn't too expensive either, around £20 I think, if that helps to narrow it down. Any ideas what it could be? the wub "?!" 21:41, 27 December 2012 (UTC)

Looks like slag. Graeme Bartlett (talk) 21:49, 27 December 2012 (UTC)

Could be schist. --Jayron32 22:19, 27 December 2012 (UTC)

Reminds me a bit of Bismuth crystals.--Gilderien Chat|List of good deeds 22:59, 27 December 2012 (UTC)

Might be silicon carbide. -Modocc (talk) 23:49, 27 December 2012 (UTC)

It seems flat. Is one side different from the other side? If so, how? Also, does it seem especially light or especially heavy for its size, or just of expected weight? I don't know what it is, but I think this information may help more knowledgeable editors to take a guess. Also—is it strong—or would it break very easily if you for instance applied manual pressure to it? Bus stop (talk) 00:04, 28 December 2012 (UTC)

The sides are all similar. I would say that it's quite light, and it's easy to break flakes off it.

Silicon carbide / carborundum definitely seems like the right answer. It looks very like this example, and the fact that it's found on the inside of blast furnaces sounds like what was on the card. Thanks everyone! the wub "?!" 01:04, 28 December 2012 (UTC)

Is it hard? Does it scratch glas? --Stone (talk) 12:11, 28 December 2012 (UTC)

It looks to me like quenched pyrite or galena, both being a sulfide mineral. Plasmic Physics (talk) 02:41, 28 December 2012 (UTC)

To tell some of the above options apart you can do a streak test. Use one of the broken off bits to scratch the rough back of a porcelain tile. bismuth galena and pyrite will give dark streaks, silicon carbide will just scratch the tile. Schist will probably leave a brown or grey mark and slag may leave a gray line of broken glass fragments. Graeme Bartlett (talk) 10:37, 28 December 2012 (UTC)

From what I remember of building up a rock collection when I was younger, the important part is that it's got a titanium coating on it - as someone else said, possibly just slag with the coating. It goes under a trade name because "worthless chunk of stuff with titanium coating" doesn't sell as well. 67.212.112.183 (talk) 08:33, 31 December 2012 (UTC)

Woops, wasn't logged in Lsfreak (talk) 08:36, 31 December 2012 (UTC)

December 28

Mr Edelweiss type of bird

In the film Nanny McPhee Returns, she has a bird named Mr. Edelweiss. What type of bird is he? — Preceding unsigned comment added by Donmust90 (talk • contribs) 02:05, 28 December 2012 (UTC)

he is a Jackdaw, from what I can ascertain via Google. AndyTheGrump (talk) 05:06, 28 December 2012 (UTC)

Name that fish (Halfbeak -- ballyhoo?)

I was snorkelling in Cuba last week (near Playa Jibacoa, roughly halfway between Havana and Varadero). Lurking just under the water's surface near the reefs not far off shore, I saw a number of interesting fish, including the character pictured at right. My best guess is that it was roughly a foot long, including the 'beak'.

I'm pretty sure it's some sort of Halfbeak, and I think it might be a Ballyhoo. Is there anyone who knows their saltwater tropical fish who can confirm/narrow that identification? And is there an article that could use the picture? Thanks, KevinHadley (talk) 03:06, 28 December 2012 (UTC)

The ballyhoo article only contains a low-res drawing, so an actual pic would be a definite improvement. StuRat (talk) 05:40, 28 December 2012 (UTC)

It's a Ballyhoo. Darkness Shines (talk) 10:45, 28 December 2012 (UTC)

Can a tunnel flood?

Like a major one like the Lincoln Tunnel or the Channel Tunnel. ScienceApe (talk) 07:32, 28 December 2012 (UTC)

I fail to see why wouldn't it be possible. It must have a draining mechanism, which probably stops when everything is flooded. OsmanRF34 (talk) 13:17, 28 December 2012 (UTC)

The Holland Tunnel just flooded in Hurricane Sandy. You can even watch it

Lincoln Tunnel was the only one that wasn't closed in NYC. --jpgordon 20:03, 28 December 2012 (UTC)

The Midtown Tunnel between Norfolk and Portsmouth, Virginia flooded in 2003 when maintenance crews were unable to completely close the floodgates in time due to (IIRC) a drainage grate or cover plate that had been welded in place. -- Tom N (tcncv) talk/contrib 00:23, 29 December 2012 (UTC)

(YouTube link: How to Knit * Knitted Hat Top Down * How to increase)

The vid shows knitting with 3 or 4 needles. Is it possible to knit with say 7 needles?Curb Chain (talk) 08:18, 28 December 2012 (UTC)

See Circular knitting - no obvious reason why you couldn't use five or more double ended needles (they are sold in sets of four or five apparently), although these days you would most likely use circular needles. Mikenorton (talk) 09:06, 28 December 2012 (UTC)

As someone who always knits with circular needles, I can tell you they are not practical for smaller items such as socks, and 4 or 5 needles are the norm for knitting socks. No reason why 7 needles couldn't be used but it would be very complicated. I wouldn't want to try it. TammyMoet (talk) 09:52, 28 December 2012 (UTC)

Not without a knitting machine, anyway. --jpgordon 15:55, 28 December 2012 (UTC)

Those use hooks or latch hooks, not needles. Rmhermen (talk) 18:22, 28 December 2012 (UTC)

Or, as they commonly called, "latch hook needles". --jpgordon 19:50, 28 December 2012 (UTC)

Not by me. But they aren't knitting needles whatever their name. Rmhermen (talk) 20:08, 28 December 2012 (UTC)

Can curing of paints change tensile properties

We are painters doing powder and pvdf coatings on aluminum. Normally, aluminum alloy 6063 is used for door, window sections. However, in one specific case, we have got alloy 6082 T6 for pvdf coating job. PVDF coatings need to be cured at a temp of approx 230-240 degree C for 8 to 10 minutes, which, in general is specified by the paint manufacturers.

Would curing at this temperature and time bring some difference in the Fy or elongation/ tensile properties of the metal 6082? If so, to what extend. The mill finished extruded material received by us has a Fy 255 mPa.

Your opinion is awaited.

Regards, Sanjay — Preceding unsigned comment added by 122.161.52.208 (talk) 13:14, 28 December 2012 (UTC)

If you have a look at Steel#Material properties, you can see that heating may cause Recrystallization (metallurgy) of the alloy. Whether or not that will happen at that temperature is entirely dependent on the particular alloy's thermal behaviour. Considering the relatively low melting point of the alloy (555 °C), that does not seem unlikely to me.

For those who are looking for more information on the alloy: . Plasmic Physics (talk) 19:08, 28 December 2012 (UTC)

telling if we are in a Virtual Machine

Suppose the universe might be emulated, just as we might emulate a few atoms of it once we have all the laws figured out. Propose strategies that we can follow to determine whether the physical universe is in fact being emulated in this sense or not. This is not homework. 91.120.48.242 (talk) 14:50, 28 December 2012 (UTC)

Similar questions have been asked here several times before, I recommend a search of the archives. Our most relevant article on the concept is Simulation hypothesis, which gives an overview of the problem and its history. From there you can jump to articles that seem relevant to you or follow the references. I notice that there is an original research tag at the top of the article, so you should be aware that some portions may be user speculation instead of being based entirely on reliable sources. 209.131.76.183 (talk) 15:54, 28 December 2012 (UTC)

If this is not a homework question, why is it worded like one? Propose strategies that we can follow to determine whether you are doing your own work. However, for the record, we can help with your homework, so long as it is in the manner of a library reference desk, ie. pointing you in the right direction. From the link by 209, you want reference 28, which I suppose is obvious since it is under the section "testing the hypothesis". The article is quite advanced, so try to pick up the gist. You may be interested in chaos theory, in particular Chaos theory#Distinguishing random from chaotic data. If the universe were a numerical simulation, there would presumably be limits on chaotic behaviour, since it involves intractable complexity. So your answer could propose ways of testing the universe based on subjecting chaotic processes to tests that determine if they are, in fact, truly chaotic. You will have to do this bit yourself. IBE (talk) 17:53, 28 December 2012 (UTC)

I'm curious what you think of these contributions (left-hand side) - http://en.wikipedia.org/search/?title=Misplaced Pages:Reference_desk/Science&diff=prev&oldid=530148333 - the part that has been removed from the question. is it the same as what you propose? 178.48.114.143 (talk) 21:33, 28 December 2012 (UTC)

Very interesting, but I'll wait to see what someone smarter suggests. I think it's clear that we are dealing with a fairly bright person who hasn't got his ideas sorted out very clearly, or at least doesn't know how to express them. It is certainly along the same lines, however. IBE (talk) 21:43, 28 December 2012 (UTC)

I would also add that there are many possible configurations of the question itself - does it allow quantum computers, for example? It seems clear from the post you linked that the OP is not considering such possibilities, because quantum computers could definitely generate random numbers. If pseudorandom processes occurred in reality where science expects random ones, then yes, you have some hard evidence of a VM reality. Absence of them could indicate a quantum computer VM, however. I don't know how quantum computers might influence chaos calculations, but I would have thought not on a fundamental level. Please anyone who knows this stuff well, tell us about it. IBE (talk) 21:48, 28 December 2012 (UTC)

OP, have you read Stephen Wolfram's A New Kind of Science? It proposes that the universe is a just a very, very big cellular automaton. To tell if the universe is such a system could prove problematic of course, because if it's true then we are all part of it.. --hydrox (talk) 06:47, 29 December 2012 (UTC)

This question is very similar as the test for reality above. When I see such repetitions I get a feeling of deja-vu that let me thinking if the simulation we are immerse is saving in computational power by repeating stuff. OsmanRF34 (talk) 11:13, 29 December 2012 (UTC)

Ok, but this is much more empirical than the one above - just look at the difference in length of the discussions. Longer discussions here are usually traceable to unanswerable questions. Not that my own contribution here is any kind of exact answer - rather I was hoping to get someone to clarify/ refute my suggestions. IBE (talk) 15:06, 29 December 2012 (UTC)

I should note that if someone specifically wanted to rule out that that we are living in The Matrix, that is relatively straightforward. The rules of 'The Matrix' specify that the laws of physics and so on only apply as long as you expect them to, and that firm belief that (for example) you can jump really far or run really fast will allow you to do so. Put your hand up if you've ever 'missed a step' or taken an extra step when going up or down stairs. You were absolutely certain that your foot was going to move in a certain way, even support your weight where there was no step, and yet reality asserted itself and did not warp to match your expectations. Therefore, we cannot be in The Matrix.

All of which simply goes to show, as others have said, that in order to properly assess anything like this, you need to narrow down and be specific. Take and develop a theory of reality and work out how you would expect it to behave. Don't just go with vague general ideas. 86.129.14.69 (talk) 23:55, 29 December 2012 (UTC)

But "The Matrix" isn't quite what most "simulated universe" proponents are describing. In the movie, the human minds aren't "simulated" - they are actual humans. What I think we're discussing here is where our brains are also being simulated. You could test for being in a "Matrix" by looking carefully at (for example) brain scanners. You could perhaps make a sound in someone's ear - and look on the brain scanner to see when the neural pathways "lit up" in response to the sound. There would have to be a substantial delay between sound and response if the simulated sound had to travel along miles of wiring into the real human's brain and back again to the simulation computer. Other tests like deliberately destroying a part of a living brain and seeing how it affected the victim would also exhibit strange resuls in the matrix that would be completely different compared to (for example) animal brains. When you think about the level of scientific research amongst people in the matrix - it's rather surprising that they wouldn't have figured it out yet! However, in a "fully simulated" universe, there would be no such artifacts visible...so you couldn't prove a thing. SteveBaker (talk) 04:18, 31 December 2012 (UTC)

See this and this. Shadowjams (talk) 00:46, 30 December 2012 (UTC)

The trouble with both of those links is that they both assume that simulation has to happen in fixed time steps in a regular lattice. That's a naive view of how computer simulations work. We can do event-driven simulation where there are no fixed time steps - and we can do simulation in a continuum rather than a lattice and easily bypass the mechanisms that those articles rely on for their testing. Certainly most simulations aren't done that way for efficiency reasons - but there is no proof possible by showing the lack of a "grid" or a "time step" in our universe. SteveBaker (talk) 04:03, 31 December 2012 (UTC)

The point that most people who think about this forget is that the laws of physics in the "parent" universe (where the computer that's simulating us resides) don't have to be identical (or even remotely similar) to the laws of physics inside the simulation. Our computers are limited in speed by the speed of light - in power by the ability to dissipate heat - in size by the sizes of atoms and the nature of quantum mechanics - and the scale of a gigantic computer is limited by resources of the planet earth and our human ability to mass-produce parts.

Consider this: If our "parent" universe had no speed of light limitation, didn't even have things like atoms as fundamental particles - then computers could be made of logic elements billions of times smaller and trillions of times faster than ours - and be assembled into vast computers that could be trillions of lightyears across (remember - no speed of light limitations in the parent universe!)...in such a crazy place, it might easily be possible to simulate every last detail of every particle in our universe to precisions far higher than we can (even fundamentally) measure - and it could do it on a machine as commonplace (to them) as laptop is to us. Once you unshackle your thinking from the parent universe being in any way like ours - then all bets are off.

The "universes" that we make simulations of (computer games, for example) have plenty of restrictions that our universe doesn't have - in computer games, there are no full-spectrum colors - an inhabitant of the "Grand Theft Auto" universe (assuming his AI software would permit such a thing) would be able to take a spectrogram of the color of any object in his universe and discover that color is made up of a mixture of three distinct frequencies - Red, Green and Blue. He might formulate a complicate "physics" to explain this - and he'd imagine that anyone who was simulating him would have the same restriction. Well, guess what, the "parent" universe of the Grand Theft Auto universe has full-spectrum colors. Ha! SteveBaker (talk) 04:03, 31 December 2012 (UTC)

A drug meant specifically to induce pain

There are plenty of drugs to create a recreational experience, but are there any drugs that cause acute pain after injecting, swallowing or inhaling them?

I was wondering if such drugs could be used to turn recreational drug use into a painful experience via classical conditioning, by mixing the original drug with the pain-inducing one and giving it to the users. (Just to be clear, I didn't ignore the serious disadvantages, and possibly illegality, of this method, and don't expect to see it being applied to rehabilitate drug addicts.)

Thanks, 82.166.216.211 (talk) 23:49, 28 December 2012 (UTC)

Well, there are lots of drugs that cause pain upon being injected; I'm thinking that the vast majority of things you could possibly push into your bloodstream would probably hurt quite a bit. The problem is that drug dealers don't typically try to rehabilitate their users. I also doubt it would work, even if you got by the staggering legal and logistical hurdles. If watching yourself waste away, spitting out all your teeth, and slipping into the occasional coma don't do smarten people up, I'm not sure what will. :( Matt Deres (talk) 00:27, 29 December 2012 (UTC)

Because acute pain is more persuasive than those other things. That's why torture became so popular. Whoop whoop pull up 06:57, 29 December 2012 (UTC)

That's pretty much the way Disulfiram (Antabuse) works in the treatment of chronic alcoholism. Tonywalton  00:35, 29 December 2012 (UTC)

(e/c)You may find this interesting. Not quite what you were looking for, but very similar. Matt Deres (talk) 00:37, 29 December 2012 (UTC)

Ooh! Spooky! Tonywalton  00:38, 29 December 2012 (UTC)

Platypus venom would be a wonderful candidate for the drug you seek.--Digrpat (talk) 00:46, 29 December 2012 (UTC)

This has been in the news, see the sadistic suggestions made about oxycontin and capsaicin. μηδείς (talk) 03:54, 29 December 2012 (UTC)

See poison. If they cause pain, they never get as far as being called drugs, which by definition are intended to have a beneficial or enjoyable effect. Most household chemicals don't get to be called drugs for that reason, but many of them will cause pain.--Shantavira| 12:20, 29 December 2012 (UTC)

Actually, a drug can be something that primarily or as a side effect causes an adverse effect. A common lay use is to indicate an adverse effect, as in "He gave the victim a stupifying drug and then raped her". As far as scientific or medical use goes, we were taught in 1st year university the following: A nutrient is a substance that enables body metabolism; the effect of nutrients is made apparent when they are absent. In contrast, a drug is a substance that affects body metabolism; the effect of drugs is seen in their addition. In other words, you can't do without nutrients - but you can do without drugs.

In the hospital/asylum treatment of severe mental disease, various forms of treatment have been used over the years to stimulate correct behaviour by "treatments" that cause pain or distress. In general, such treatments may be dressed up or genuinely thought to have some beneficial effect. A well known (non drug) example is electro-convulsive shock therapy (now discredited but replaced by magnetic induction therapy - the same thing slightly disguised). Clozapine and similar drugs, which are thought to reduce schizophenia symptoms, get used by the less ethical practitioners to cause pain or distress which may cause patients (not necessarily schizo patients) to suppress their undesirable, difficult, or non-co-operative behavior in order to avoid getting it again. In strong enough doses it causes pain, from intestinal and heart infarction, which is pretty scary, and distress from uncontrolled slobering and other problems.

When I was working (as avolunteer) at a drug adict support center, we would sometimes get folk presenting themselves and claiming they were addicted to heroin when they were not (it was one way to get methodone for a friend or to sell - there were other more bizare reasons). What the doctor did was give them an injectable narcotic agonist. If the person had not been on the claimed drug, the agonist would have little or no observable effect, and they would be told to nick off. But if the person was actually consuming heroin (or whichever), they would go into immediate full on withdrawal symptoms - pain, shakes, shock, etc, for a short time. Then we knew they were genuine, and needed our help.

It would be very difficult to cure hard addicts of their addiction by classical conditioning. Severe pain may be the least of their problems (Whoop Whoop is quite incorrect in this); you can be as high as kite while in severe pain and not mind the pain; in any case narcotics suppress pain.

Floda 58.170.169.255 (talk) 16:15, 29 December 2012 (UTC)

December 29

meteorites from EARTH to Mars, rather than vice versa

Hi, what i read is that about a ton of meteorites of mars origin land on earth every year. How often would the reverse happen given Earth's stronger gravity? Less often I'm sure but how less often? Is there an approximate formula based on gravitys and distance from sun etc? Thanks68.65.169.66 (talk) 01:20, 29 December 2012 (UTC)

When was the last time a meteorite impact on Earth was storng enough to eject material into space? This is not just a matter of stronger gravity -- it's also a matter of Earth having a dense atmosphere that all but prevents any Earth material from being ejected into space as meteors. 24.23.196.85 (talk) 01:37, 29 December 2012 (UTC)

I don't know when the last one was, but a meteorite impact on Earth, if it did bang stuff off of earth, even many millions of years ago, could be a continuing source of meteorites to Mars. Also, i wonder about (Earth)volcanoes shooting material away from Earth.68.65.169.66 (talk) 02:09, 29 December 2012 (UTC)

No volcano has ever been powerful enough to launch stuff into space -- the rocks fly thousands of feet into the air at most, while the volcanic ash usually goes up into the stratosphere and just hangs there for some weeks. 24.23.196.85 (talk) 02:51, 29 December 2012 (UTC)

No volcano on Earth. There have been (water) volcanoes that launched material into space. Some of Saturn's rings are from one (see Enceladus (moon)). StuRat (talk) 04:05, 29 December 2012 (UTC)

No volcano in historical times has come anywhere close to achieving an orbital launch. Large modern eruptions send volcanic bombs (i.e. large rocks) up to 500 m or so above the volcano. However, we have good evidence of volcanic explosions 10-100 times larger having occurred over geologic times. This makes it likely that at least occasionally volcanic eruptions might send rocks miles into the sky, and just possibly the very largest eruptions might approach escape trajectories. Back in the early twentieth century, there was a theory in geology that large, suborbital volcanic ejecta was responsible for creating impact craters (e.g. verneshot). We now know that most impact craters have a extraterrestrial origin (i.e. meteors), but I don't think one can completely rule out the possibility of an extremely large, extremely rare (e.g. 1 per 100 million years) volcanic eruption being capable of launching some rocks off the planet. If it has ever happened though, it certainly doesn't happen often. Dragons flight (talk) 05:12, 29 December 2012 (UTC)

What about meteorite impacts?64.9.234.141 (talk) 05:58, 29 December 2012 (UTC)

It would require a pretty big meteorite impact. Still not very common, since big impacts are themselves rare—maybe once every 10 million years or so at most. Whoop whoop pull up 06:59, 29 December 2012 (UTC)

I thank you for your answer. I'm not sure how you get your estimate, or even if your estimate is at least from intuition gained from experience and study. My original question was how much Earth material gets to mars relative to the reverse process, (which hopefully the scientists who claim about 1 ton/year have their reasons). But if you are correct that such meteorite impacts are on average 1 every 10 million years, how much transfer would we expect to mars? Is it likely or unlikely that there been in the last 100million years meteor impacts that ejected millions of tons of matter from Earth?(I ask the large amount of a million tons because I bet the odds of any given particle of it ever getting to mars, let alone in a given year, are small.) Could we say perhaps then that extremely tiny amounts of Earth end up on Mars, like a teaspoon per year?Thanks again.64.9.234.141 (talk) 08:02, 29 December 2012 (UTC)

• Terrene meteorites in the moon: its relevance for the study of the origin of life in the Earth Here somebody wants to look what the earth meteorites look like to search for the beginning of life on earth.
• doi:10.1016/0012-821X(94)00232-N Here somebody wants to know how life spread from earth with meteorites.
• Testing interplanetary transfer of bacteria between Earth and Mars as a result of natural impact phenomena and human spaceflight activities Bacterial transfer in the solar system. --Stone (talk) 09:06, 29 December 2012 (UTC)

I don't see how anything ejected from Earth could make it to Mars -- Mars is tens of millions of miles farther from the sun, and the ejected material would have to overcome the sun's gravity for that great distance. Duoduoduo (talk) 13:57, 29 December 2012 (UTC)

It takes an enormous amount of energy to get off the Earth. The amount of energy to get from Earth to Mars is only about 4 times larger than the amount required to escape the Earth. If you have any scenario that can get you off the Earth, it isn't hard to imagine a scenario with a few times more energy that gets you to Mars. Dragons flight (talk) 15:23, 29 December 2012 (UTC)

While the escape velocity from the surface of Earth is more than double that of from Mars (11.2 km/s vs 5.0 km/s), I believe that Duoduoduo is mistaken if they think that once the object has escaped from the planet, then somehow the sun's gravity makes it much easier to travel from Mars to Earth than vice versa. Can someone more familiar with orbital mechanics speak to this point? -- ToE 18:18, 29 December 2012 (UTC)

Well, if you just put an object with no initial momentum just outside Mars's gravity well, it will fall toward the sun, crossing Earth's orbit on the way. But if you put an object with no initial momentum just outside Earth's gravity well, it will also fall toward the sun, hence not crossing Mars's orbit. Duoduoduo (talk) 22:10, 29 December 2012 (UTC)

Hmmm, but a rock that falls from near Earth orbit should return near to the same distance over and over again... and if so, is there a chance that it will interact again and a gravitational slingshot will get it out some distance? (but then again, it shouldn't be moving very fast relative to Earth, so it shouldn't slingshot very far... I think...) Wnt (talk) 23:16, 29 December 2012 (UTC)

But that "no initial momentum" (relative to the Sun) assumption is wrong. Anything starting from Earth will have about the same initial momentum as Earth, and anything starting from Mars will have about the same initial momentum as Mars. Therefore, it would take just as much energy, but in an opposite direction, to force an object from an Earth orbit to a Mars orbit as vice-versa. StuRat (talk) 23:21, 29 December 2012 (UTC)

"No initial momentum" was just intended as an unnecessary simplifying assumption to focus on the issue at hand -- the sun's gravity. This seems simple to me -- from Mars to Earth the sun's gravity is helping, while from Earth to Mars you're working against the sun's gravity. Duoduoduo (talk) 13:09, 30 December 2012 (UTC)

No, no, StuRat is correct. The "No-Initial-Momentum" assumption is not a good first approximation. Look at Delta-v budget#Delta-vs between Earth, Moon and Mars for an good picture on that topic. It takes about 10 km/s to go from Earth to Low Earth Orbit, and much less than that to reach a Mars Transfer orbit. And the Earth slingshot idea seems quite viable to me. Dauto (talk) 15:55, 30 December 2012 (UTC)

Forget the "No-Initial-Momentum" assumption -- as I said, it has nothing to do with my point, and I already retracted it. You say that it takes a positive boost to get out to Mars. Part of that boost is needed because you're fighting against the sun's gravity. My point is that it doesn't take that same boost to get from Mars to Earth, since the sun's gravity is helping rather than hurting. In other words, my point was simply that the sun pulls things toward the sun. Or can you get from Earth to Mars without overcoming the sun's gravity?? (And I too like the Earth slingshot idea.) Duoduoduo (talk) 16:48, 30 December 2012 (UTC)

What we're trying to explain is that it takes just as much energy to force an object in orbit about the Sun, at Mars, down to an Earth orbit, as to do the reverse. Think of the kid's experiment where you swing a ball on a string around your head. It wants to go outward, and it takes an active force to pull it inward. If this wasn't the case, then everything would have fallen into the Sun long ago. And the size of the object doesn't matter (much). Jupiter can orbit the Sun just as a speck of dust can.

Now, you are correct that an object with no initial momentum relative to the Sun would fall into it, but this just won't be the case with either Mars or Earth meteorites. StuRat (talk) 00:20, 31 December 2012 (UTC)

Please bear with me, as I'm trying to learn something here. What I'm saying is I think analogous to the following from Delta-v budget#Near earth objects:

The delta-v to return from them are usually quite small, sometimes as low as 60 m/s....However, the delta-v to reach near earth objects is usually higher, over 3.8 km/s

Duoduoduo (talk) 17:04, 30 December 2012 (UTC)

From an earlier post: When was the last time a meteorite impact on Earth was storng enough to eject material into space?

Well, I doubt it was the last, but there's at least one big one, though it obviously didn't make it to Mars. — The Hand That Feeds You: 00:08, 31 December 2012 (UTC)

Even though we haven't had any large impactors here on Earth very recently - my "gut feel" wonders whether it might be the case that the velocity of the debris will follow some kind of (gaussian?) velocity distribution? While the average velocity might not be enough to reach escape velocity - wouldn't it be possible for a freak particle out on the far end of the distribution to make it out? The energy equation ought to allow it - providing the piece of debris is small enough. SteveBaker (talk) 04:28, 31 December 2012 (UTC)

Confusion in article Atomic mass and bond order greater than 6

1. While reading the article Atomic_mass#Mass_defects_in_atomic_masses, I read in the linked section "deviation is positive or negative". What does deviation and positive/negative mean in the context ?
2. No two elements in the periodic table can form a bond with greater order than 6. Why ? Sunny Singh (DAV) (talk) 13:51, 29 December 2012 (UTC)

One atomic unit of mass is 1/12-th of the mass of Carbon-12 atom. Hydrogen-1 (proton+electron) has mass higher than this unit. So, the mass deviation is positive. Atoms heavier than carbon (up to nickel) generally have negative deviations. Ruslik_Zero 15:37, 29 December 2012 (UTC)

For your second question, see this article. Septuple bonds are not possible between two atoms of any elements with atomic numbers 100 and below. They might be possible in the early superactinides, but their half-lives may not be enough for chemical characterization (except, possibly, for a few elements around the magic number Z = 126). Double sharp (talk) 07:17, 30 December 2012 (UTC)

We have a Sextuple bond article that includes that ref. DMacks (talk) 20:45, 30 December 2012 (UTC)

Biochemistry of Seizures

What are the biochemical processes involved in a seizure. Is it different for every cause I.e.for low blood pressure, transplant rejection, high fever, allergy etc. — Preceding unsigned comment added by 176.27.208.210 (talk) 16:39, 29 December 2012 (UTC)

Don't know, but in the case of an epileptic seizure, dogs can apparently predict them, which points to a chemical odor, which means there must be chemical reactions leading up to it. StuRat (talk) 23:24, 29 December 2012 (UTC)

I think you're probably correct about chemical odors. But it seems to me there some chance that dogs detect it by other means instead. Their eyes are very sensitive to motion, perhaps especially of human motion, and they hear at some frequencies humans can't.199.33.32.40 (talk) 00:25, 30 December 2012 (UTC)

Thanks for your answers. Im pretty sure that every biochemical process in the human body involves chemical reactions and that most symptoms of illnesses are also caused by biochemical reactions. My question is specifically which biochemical processes/reactions cause seizures. 176.27.208.210 (talk) 02:48, 30 December 2012 (UTC)

I don't think that's true. A heart attack can be caused by a blockage, and a stroke can be caused by a break in a blood vessel. Neither requires any chemical reactions immediately leading up to it. StuRat (talk) 03:13, 30 December 2012 (UTC)

True but surely there's chemical processes which lead to blockages or burst vessels. 176.27.208.210 (talk) 13:23, 30 December 2012 (UTC)

Seizures have many causes (e.g, hyponatremia, hypoglycemia, hypocalcemia). The muscle activity and alterations of breathing can produce some common post-ictal chemical changes (e.g., elevated prolactin). Doctors pay more attention to the chemistry of possible causes than to the chemistry of the consequences. alteripse (talk) 06:27, 30 December 2012 (UTC)

• Rather than writing a long response I'm just going to give a pointer to our article on epilepsy. Looie496 (talk) 14:32, 30 December 2012 (UTC)
• The OP seems to be asking for an explanation at the wrong level of causation. Seizures are neurological events, and have to do with malfunctions of neurons and their signalling of each other and the body. See action potential and neurotransmitter for relevant articles. There isn't some sort of general chemical reaction going on like combustion that causes a seizure as such. All the normal sorts of chemical events that are going on in normal functioning will be found during seizures, but in the circumstance of improperly coordinated actions of the cells. Asking for a chemical explanation as such is about as relevant as it would be to ask what sort of chemical reactions are going on during a senate filibuster or a ferry capsizing. μηδείς (talk) 20:39, 30 December 2012 (UTC)

One intriguing piece of the puzzle has to do with a fall in the carbon dioxide tension before a seizure, particularly in patients with fever or hypoxic-ischemic encephalopathy. A fall in pCO2 is thought to lower the seizure threshold. The relationship between CO2 and seizures has been studied since at least the 1920s, but specific clinical interventions (like supplemental CO2 administration) have only been investigated in the last few years. I wish I understood it better on a biochemical level, but the potential clinical applications are exciting. EricEnfermero 23:30, 30 December 2012 (UTC)

December 30

Morse code

Two questions in one: (1) How many chars/min can a skilled operator transmit in Morse code (assuming that he/she has already encrypted the message beforehand)? (2) On average, how long did it take for the Gestapo to locate a radio operator using direction finding? Thanks in advance! 24.23.196.85 (talk) 05:19, 30 December 2012 (UTC)

2) This will depend on whether they are smart enough to send the message from a moving vehicle, or at least restrict themselves to short messages, each broadcast from a new location. StuRat (talk) 05:38, 30 December 2012 (UTC)

(2) I meant how long can an operator "safely" transmit continuously from one location and not have the Gestapo kick in the front door. 24.23.196.85 (talk) 05:45, 30 December 2012 (UTC)

Question 1 is answered in the Morse Code article. Zoonoses (talk) 07:00, 30 December 2012 (UTC)

Depending on what you want this answered for, you may need to take into account some additional facts not covered in teh Wiki article:-

1. While good operators can send and recieve at 40 word per min or more, that is for a perfect link. In a shortwave or medium wave radio link, fading and noise may interfere with reception - the operators will then send as slow as required. With good narrow band recievers, slow enough morse can be copied accurately at signal stengths far below the noise level (hiss, static, machine noise etc) that would obliterate voice. That is the advantage of morse - you can almost always get through when nothing else will, and it nees only simple low tech equipment.

2. Military operators have always been trained in "short codes" - combinations of 3 or 4 letters coresponding to entries in a list of common messages often sent. For example in the NATO code used by navies in and after WW2, to transmit from a flagship the message "I am going to turn right onto magnetic course 290 degrees" could be transmitted as something like "XDEX90".

3. For WW2, German operators were trained to send and recieve in moving noisy environments using specially built rigs closely simulating the noise, vibration, and shock as would be experienced in aircraft and vehicles & tanks under way and under attack. Other forces probably had similar training.

In France, the Gestapo & regular German forces had a simple way of tracing a covert transmitter located in a town somewhere. Back then, a radio transmitter either needed big batteries (the size of a car batteries) or were powered from house current power mains. Usually, house current was the choice. Upon detecting a transmitter and getting a rough direction in seconds they would go to the substation and cut the power for just as long as it took to move the switch up and down - say a fraction of a second. If a matching break in transmission was detected, they knew they had the right area. If transmission continued, they would then race to a likely pole switch feeding a street and do the same. Repeat as required. In this way they could identify the correct street and sometines the correct block of flats within minutes. Then they would just block the street off and thoroughly search every dwelling.

Wickwack 58.167.246.100 (talk) 07:38, 30 December 2012 (UTC)

There was a 1960's spy movie where they did the power cutting to determine which apartment in a building the spy was transmitting from, but in WW2 they used direction finding rather than cutting the power to parts of a city to locate a spy. Any sensible spy would suspend transmitting when the power went off and back on. It would be very time consuming to drive around a city and climb poles to cut power for transmitter locating, and the message would likely be complete before you could achieve more than one such cut. Spy transmitters of WW2 were generally made to work off batteries, in any event. A WW2 US radio operator I know said she could operate at 40 WPM, She had no trouble transmitting encrypted as opposed to plaintext. That is what she was trained on. Edison (talk) 22:28, 30 December 2012 (UTC)

Hmmm, can't tell you the history but just thinking about this it might be worth reconsidering. The point is though that the spy has no way to know that the power is about to be cut, and if the spy depends on electricity, or perhaps even electric light, then once the power is off the transmission will stop. In theory you could have people shut off power to a different little part of a city every ten seconds and figure it out to some high level of precision. I suppose one appealing aspect of the scheme is that if the spy is transmitting by some kind of link or mechanism you can't detect, then you might track where the spy himself is located rather than coming up with the triangulated position of a walkie-talkie taped to a telephone or whatever. Wnt (talk) 00:28, 31 December 2012 (UTC)

Also, if the message is in code, then it's likely to be much slower to transmit than plaintext for a couple of reasons:

• Try using handwriting or typing to copy an English sentence - then try writing or typing a random string of letters or numbers of the same length. It's much harder. If I ask you to type "The cat sat on the mat" - 22 characters, you can do it in probably a couple of seconds. If I ask you to type "RKA VXL ZQG SFG OGH KS"...it'll take you much longer. You can read "The cat sat on the mat" almost instantly, hold it in your mind and just type it out as fast as your fingers can move. "RKA VXL ZQG SFG OGH KS" is probably something you can only read three or maybe six characters at a time.
• If you make a mistake typing English text ("The cat sqt on teh matt") - then the guy at the other end can still read it. But if you make a mistake with some kinds of code - then you're probably going to produce gibberish when it's decoded. So much more care is needed. The message may need to be sent more than once so that the decoders can be sure you didn't make any mistakes.

So this isn't so much about morse code proficiency as about the way the code is handled. Many codes were simple English sentences: "The aardvark sees the mountain" might mean "I need you to attack the weapons depot north of Berlin at the time we previously agreed two nights from now".

SteveBaker (talk) 17:50, 30 December 2012 (UTC)

I disagree with Edison on the effectiveness of the power cutting method. I think he has missed that it was used in conjunction with rapid direction finding. Back then covert transmitters were MF of HF. In a city of well developed suburb, sufficiently accurate direction finding on HF to be used on its' own is not possible. Now, in WW2, if you were a French peasant, and a truck full of German soldiers comes down the street at speed, you didn't hessitate, you got out the way.

Another aspect to consider is that back then electricity distribution was open wires on poles, not underground cable. In open wire distribution, the occaisonal short from wind blown debri or birds happens from time to time, so electricity companies use reclosers. Reclosers are a circuit breaker that trips on overload same as a normal circuit breaker, then waits a predetermined delay, then reconnects. If the overload is still there it trips out again. But often the overload has gone, saving the electicity company manual intervention. So folk get used to short breaks and think nothing of it. Aslo, there was a war on. Short breaks in power happens in war.

However, Edison is quite correct in saying operators have no difficulty is transmitting (or recieving) coded messages or random sequences of characters as compared to plain text. This is partly due to training, and partly due to the nature of morse code. When keying, you think letter by letter, not word by word, as 40 words per min (about one letter per second) is actually a slow process.

Lastly, when transmitting an encrypted message, you NEVER re-transmit just because the recieving end didn't recieve all the characters. You compromise the coding security if you do. It was the (actually quite rare) mistakes like that that enabled the British to read vast quantities of German military traffic. What you do is leave the recieving end to make the best of it, or if necessary, wait a bit and encrypt a different text that has the same ultimate effect.

Wickwack 60.230.218.203 (talk) 02:28, 31 December 2012 (UTC)

You and I know that you shouldn't retransmit (well, not for some classes of code) - but back in WWII, it's likely that only a few people in Bletchly Park knew that...evidently the entire German military was unaware of this particular decryption exploit! SteveBaker (talk) 04:34, 31 December 2012 (UTC)

Perhaps. But I have a copy of Alan Turing - The Enigma, by Andrew Hodges, and some textbooks on encryption. These all make it clear that:-

1. The Germans were properly trained, but never the less made mistakes.

2. On of the less common mistakes that they made was to re-tramsit messages, and that did occiasonally help Bletchly chaps.

3. Their navy had separate encription/coding schemes for habour comms, fleet operations, and weather reports. The British could sometimes pickup habour comms and decript the relatively simple code. Then, match it up with the same thing transmitted using Fleet Ops encryption. They also matched up decripted weather reports also repeated on Fleet Ops. Big, big mistake. Once the British cracked a weather report and matched it to a same length message on Fleet Ops that day, they had the day's key to all the other Fleet Ops messages.

4. A few German operators, if they were not busy with official messges, would send common nursery rhymes (of the Mary had a little lamb sort), both to practice and maintain speed, and to ensure the radio link was available at all times. Big mistake. Once Bletchly realised that was what they were doing, they looked in light traffic periods for messages matching the length of common German rhymes and concentrate on those to get the day's key.

5. German operators did have one aspect of faulty training. They would commonly send messages with polite preamble, as in: TO General Berkhead FROM Captain Nichtwhitt SUBJECT Seizure of Town. Heil Hitler Blah Blah Blah ... Blah. Bad mistake. Never use standard forms in encrypted radio messages in a war. And never never use salutations like "Heil Hitler" in lots of messages.

6. The biggest mistake of all is that the German top brass, when faced with too many coincidences (as in British depth charge equiped aircraft intercepting German submarines far too often, or British merchant convoys diverting just after an order to submarines to intercept them), assumed that the British could not be reading the encrypted radio messages becasue a) the enigma encryption method was unbreakable (it essentially was, if used correctly every time) and their operators were properly trained. So instead of looking at procedures, they wasted a lot of time looking for harbour spies. And they assumed that Bristish radar was a lot better than it was, and better than was and is technically possible.

So, don't rule out that British operators were trained and did know not to re-transmit messages. Wickwack 120.145.54.24 (talk) 05:20, 31 December 2012 (UTC)

Thanks for the info, everyone! So, 40 words/min on average, huh? That means that the transmissions can be kept very short indeed -- the one radio message I have so far in my novel has only 26 words (including agent ID, security tag and so on, but excluding the commas, stops and the final "over"), so it would take Blanche only about 40 seconds to transmit. I don't think even the best DF team can home in on something this short. (Francois will get to transmit the next message, but I intend to keep it similarly short.)  :-) 24.23.196.85 (talk) 05:45, 31 December 2012 (UTC)

No sweat. Note that punctuation was not normally sent. The word "over" only occurs in 2nd rate TV shows and novels. The reciever knows you've stopped transmitting anyway. Wickwack 120.145.145.21 (talk) 10:48, 31 December 2012 (UTC)

Lorcaserin and what else? - FDA approved Obesity medication

i'v heard that except Lorcaserin, there's gonna be another Med', what is it's name? thanks. — Preceding unsigned comment added by 109.65.115.101 (talk) 06:32, 30 December 2012 (UTC)

Orlistat. OsmanRF34 (talk) 16:40, 30 December 2012 (UTC)

No. Orlistat was taken out. it gotta be something else. 109.65.115.101 (talk) 06:13, 31 December 2012 (UTC)

What kind of chemicals would be produced when a Polyethylene plastic bag is burnt? How?

Sometimes I can smell a bit odor, so I guess it is not burnt into just carbon dioxide and water.--Inspector (talk) 09:54, 30 December 2012 (UTC)

First the long polymer chains can be broken down into alkenes and alkanes. These may give the waxy smell. There may also be partial oxidation of these to an aldehyde or primary alcohol. Graeme Bartlett (talk) 11:58, 30 December 2012 (UTC)

Combustion#Reaction mechanism suggests it starts with a hydrogen atom being stripped off by oxygen. The radical part of the polymer is highly reactive and can then further react with O₂ to form a peroxyl radical, which in turn can steal another hydrogen atom to make another radical and a peroxide. Graeme Bartlett (talk) 12:14, 30 December 2012 (UTC)

Of course, if you're just burning plastic bags - there is a good chance that it's not polyethylene anyway - there are lots of other materials used in plastic bags these days. Plastic film lists Polypropylene, Polyester, Nylon and Vinyl - along with various bioplastics. There are also things like dyes, plasticisers, release agents and who-knows-what involved in the combustion processes here. SteveBaker (talk) 17:41, 30 December 2012 (UTC)

For what it's worth, PVC and polyurethane are particularly nasty -- the former releases hydrogen chloride during burning (and often some chlorine gas as well), while the latter releases such highly toxic gases as prussic acid and formaldehyde. NOT a good idea to EVER burn those two! 24.23.196.85 (talk) 05:49, 31 December 2012 (UTC)

Does infrasonic results resonance in human body?

My physics teacher, as well as many Chinese websites , says that infrasonic results resonance in human body, thus 'infrasonic weapon' can be made. But Chinese Misplaced Pages says infrasonic doesn't damage human tissues, and English Misplaced Pages says it just cauese pain in the ear drums. I can't find anything about 'infrasonic weapon' which work by making resonance to human body on English websites, can anyone provide any information about it, please?--維基小霸王 (talk) 12:24, 30 December 2012 (UTC)

There's something in the Vladimir Gavreau article, but the article seems to think that it may have been imaginary. 71.79.67.209 (talk) 13:05, 30 December 2012 (UTC)

It seems diffrent because the frech imaginary one doesn't kill people by resonance.--維基小霸王 (talk) 15:00, 30 December 2012 (UTC)

There is a real lack of good research on this topic. To give a fairly bad example, the only recent paper I found in NCBI for infrasound and nausea is a review at that deprecates the idea, though the authors very reluctantly cite (Leventhall G, Pelmear P, Benton S. A Review of Published Research on Low Frequency Noise and its Effects. Department for Environment, Food and Rural Affairs, London, UK; 2003. Yuan H, Long H, Liu J, Qu L, Chen J, Mou X. Effects of infrasound on hippocampus-dependent learning and memory in rats and some underlying mechanisms. Environ Toxicol Pharm. 2009;28:243–247. doi: 10.1016/j.etap.2009.04.011. Leventhall G. Infrasound from wind turbines - fact, fiction or deception? Can Acoust. 2006;34:29–36.) that loud infrasound does cause symptoms similar to those reported by subjects.

As someone who simply hears "infra"sound, some of the unquestioned assumptions of these researchers are very annoying - for example, they point out that infrasound "is emitted from road vehicles, aircraft, industrial machinery, artillery and mining explosions, air movement machinery including wind turbines, compressors, and air-conditioning units," without recognizing that indeed each and every one of these things is also annoying for the same reasons (but most of the other sources are mobile or intermittent). They furthermore fail to appreciate that infrasound "from natural sources like meteors, volcanic eruptions and ocean waves... Indeed, many mammals communicate using infrasound" is the reason why infrasound can be disturbing - because it is a warning of movements of substantial amounts of mass. They fail to appreciate that natural infrasound from wind, made up of multiple frequencies and ever-changing, can have a soothing quality. They also fail to appreciate the chief annoyance of infrasound, which is that unlike high-pitched sound that will not penetrate a window, or low-pitched sound that won't penetrate a wall or a pillow, infrasound seems to penetrate absolutely everything (except water). Now, to give them some credit, windmills I've encountered actually do produce mostly sound in high-pitched frequencies, but if you had a house next to one all you'd hear indoors would be the infra part, however large or small that may be.

Most crucially, however, their paper illustrates the absurdity of some of the sound figures given, because it actually makes use of measurements in dBA, a scale which is based on the idea that infrasound is inaudible and therefore is not even considered in taking sound measurements! All other scales either do not "normalize" sound to exclude those frequencies, or do so to a lesser degree. Wnt (talk) 19:56, 30 December 2012 (UTC)

The type of resonance that could occur in this case would be an acoustic standing wave. This requires a structure that is some multiple of a quarter of a wavelength (see e.g. Acoustic_resonance#Resonance_of_a_tube_of_air). Since the speed of sound in the human body (mostly water) is about v = 1500 m/s (speed of sound#water) and infrasound has frequencies below f = 20 Hz the body would need to have a length of at least ${\displaystyle {\frac {v}{4f}}\approx 20{\text{ m}}}$ to resonate. At high enough powers anything will be dangerous, but for ultrasound it will not be due to resonance. Ulflund (talk) 20:15, 30 December 2012 (UTC)

Not correct. A mass suspended in an elastic medium will resonate if the frequency is equal to 1 / (2Π (m.c)) where m is the mass and c is the elastic compliance. Consider a loudspeaker: Quality loudspeakers as made with cone resonances as low as 20 Hz even with a cone diameter of only a few hundred mm. Thus it is quite possible that internal organs in the body could resonate at low frequencies. Wickwack 60.230.218.203 (talk) 02:37, 31 December 2012 (UTC)

I don't know about resonance, but I do know that at high volume, a particular frequency range may cause lethal cavitation to occur in the body. Plasmic Physics (talk) 06:28, 31 December 2012 (UTC)

Lethal cavitation is a process where the compression and decompression within the body (soundwaves travelling through it), causes soft body tissue to liquefy. There is at least one recorded death from lethal cavitation, where a person experimented with infrasound, and unknowingly found the correct range and generated a sound at elevated volume for only 3 seconds. He was paralysed and killed within that time. He was found intact, albeit with liquid brain matter exuding from his ears, burst bladder, basically if it was not for his skin, he'd have to be taken away in a bucket. Plasmic Physics (talk) 06:47, 31 December 2012 (UTC)

, if you please --Jayron32 06:54, 31 December 2012 (UTC)

About that, I saw it on a documentary on the C.I. Network or Dicovery Network. I don't remember what it was called, perhaps "A strange way to die"/"Strange ways to die"? Apparently, there is this underground social group who exploit the wellknown euphoric effect of infrasound, this person was experimenting with generating specific soundtracks to harnass this effect, with intention to sell. He found that 7 Hz was a good frequency... Plasmic Physics (talk) 07:29, 31 December 2012 (UTC)

No, it definitely was "10 Bizarre ways to die." Plasmic Physics (talk) 08:02, 31 December 2012 (UTC)

Resonance is most effective (or dangerous, depending on your POV) on perfectly rigid bodies, with crystals being about as close as we can come. Softer materials, like people, tend to absorb any vibration before it can build up. So, while it still might be possible, it would require far more energy than the proverbial opera singer shattering a champagne glass. StuRat (talk) 08:22, 31 December 2012 (UTC)

Properties of blood

From my understanding, blood is a shear thinning fluid. So it acts like a liquid when you apply shear to it, I.e. when flowing but when the flow rate is reduced it behaves like a solid and that this is the property of blood which helps with clotting and recovering from injuries. My question is how does this property interact with platelets etc to help with this process? Is it the fact that platelets work better in more viscous fluids? 176.27.208.210 (talk) 13:31, 30 December 2012 (UTC)

why do doctors tell women not to douche

Women have been douching for thousands of years, in fact before modern medicine, Women used to cure infections in that area with douching. Now they tell people not to douche because it may disrupt Flora, as an experiment I tried not washing my skin for a month and got numerous staph infections. There is Flora on our skin, so I don't think there theory Is correct. Although they claim the vagina is self-cleaning, They also claim the ear is self-cleaning, however it is only self-cleaning to an extent, and it should be cleaned at least periodically inside. For example, if a man were to ejaculate into the vagina without a condom in my opinion it should be douched out with plain water. This also used used to be recommended in the olden days, because the sperm (which is a living thing) that does not leak out will basically rot in there.--Mk651117 (talk) 13:35, 30 December 2012 (UTC)

The Reference desks are a forum for asking questions, not a forum for expressing your own personal opinions about things. Looie496 (talk) 14:26, 30 December 2012 (UTC)

(e/c)You've phrased your question in such a way that it appears you're asking for medical advice, which we cannot give. If you have questions about your own habits, you should consult your family doctor. I can point out that our article on douche leads to this Science News article which goes over many of the downsides associated with the practice. Your separate claim of getting multiple staph infections simply by not washing an area of your skin sounds frankly incredible. If true, you should definitely seek medical attention. Matt Deres (talk) 14:28, 30 December 2012 (UTC)

I'm not a female so I don't douche I'm not asking for medical advise. --Mk651117 (talk) 16:56, 30 December 2012 (UTC)

Well this is a reference desk, so here is a reference. Alansplodge (talk) 20:24, 30 December 2012 (UTC)

An interesting quote from that study "In a 1997 meeting of the Nonprescription Drug Advisory Committee of the Food and Drug Administration (149), Dr. Andrew Onderdonk presented data looking at women with abnormal vaginal ecology, such as women with culture-positive vaginal yeast infections (32). His group treated women with either sterile water, a vinegar and water douching solution, or a povidone-iodine solution. Twenty-four hours after treatment with the various douche solutions, the only women whose vaginal microflora returned to normal were the women who used the povidone-iodine douche. This suggested that, in women who have an abnormal vaginal ecology, perhaps due to a vaginal yeast infection, douching with povidone-iodine may be beneficial and may help to return the vaginal ecology back to normal values. "

It would appear that that study says that a vaginal yeast infection can be cured with a single application of an iodine-based douche. It seems to me like the drug companies are trying to discourage douching so they can sell expensive drugs to treat vaginal infections when douching is a cheap alternative option.--Mk651117 (talk) 20:59, 30 December 2012 (UTC)

Sorry, I have no reference aside from my experience as a married male, but "rotting sperm" is definitely not generally a problem for women who do not douche. The problem with your skin experiment is that for your whole life you HAVE disrupted the flora on your skin by washing with soap every single day. By not washing you are not immediately returning your skin to it's "natural" state all of a sudden. There are millions of people around the world who do not wash with soap every day and apart from probably being a bit smelly to our sensibilities, do not suffer from constant staph infections. Vespine (talk) 00:22, 31 December 2012 (UTC)

Just one more note, your opening premise is a logical falicy known as appeal to tradition. Vespine (talk) 00:25, 31 December 2012 (UTC)

Vespine If someone disrupts their flora on their skin by washing It with soap every day that would make them more likely to get staph infections and if they stopped washing with soap for a month It should make them less likely according to the logic doctors have regarding vaginal flora. If this person stopped washing for a month their flora should return to normal by then and and make them more resistant to staph infections if anything. The irony of this is that if you read about staph infections as well as things like folliculitis and cellulitis one of the causes is poor hygiene, which rules out the fact that flora plays much part in infections. --Jason677 (talk) 01:02, 31 December 2012 (UTC)

I don't follow your logic. Flora is a balance, besides, we're talking about internal and external which are probably quite different from each other. But in any case, if you wash your skin with soap, you are removing the bulk of the flora on your skin, so staph infections are not more likely, because the WHOLE balance is too low, when you stop washing, the "bad" bacteria have less "good" bacteria to fight and can end up winning, that's how you get an infection. The bacteria is always there, but the balance has been thrown out. You can't say a month is enough time for the balance to return, it may never return. A similar thing happens when you undergo heavy duty antibiotic treatment, such as chemo therapy, the balance in your gut is thrown out, initially ALL the bacteria are affected, but when they start to recolonise, some bacteria can grow back faster then others and that's what can cause issues. Fecal transplant can be used as a treatment by giving the patient back the colonies of bacteria they previously had to re-establish their previous balance. I'm also not sure about the logic in your last sentance, a lot of infections are caused by bacteria present in the flora, so im not sure how you can deduce that flora doesn't play much part in infections. Vespine (talk) 03:08, 31 December 2012 (UTC)

Add indicator lamp to heater

I have a question about electrical circuits. I have an electrical heater at home, powered by mains electricity (220V AC), which I use when changing my baby's diapers so she doesn't get too cold. Many models have a feature where they automatically turn off after a certain period of time (eg 10 minutes), but my heater does not have this feature. I only turn it on to change diapers, but occasionally I forget to turn it off, which is annoying as it uses a fair amount of power.

I would therefore like to add some kind of indicator light/lamp to remind me that the heater is switched on. Is there anything you can suggest which would accomplish this? I thought about wiring a light in series with the heater, but I only have 220V lamps, which wouldn't work in series with another 220V device. Any tips would be appreciated! — QuantumEleven 15:03, 30 December 2012 (UTC)

If you need to ask a question this basic, you are obviously not qualified to work on mains voltage cicuits. Therfore I suggest you take a different tack, which is simpler anyway. Purchase an multi-output extension lead. Typicall units have 4 outlets on a small box about 40 x 150 x 30 mm dependiong on style and country. These incorporate a neon light that indicates the power is on. Plug the extension lead/board into the wall outlet and teh heater into the lead/board. Get into the habit of switching on/off at the wall, and then the light will warn you that you have the heater powwered up. Wickwack 124.182.143.91 (talk) 16:41, 30 December 2012 (UTC)

Neon light ? I've never seen one of those on a power strip. They typically have an LED light (often in the power switch): , although older ones might have an incandescent light. If you don't have a wall switch on your outlet, be sure to get a power strip with a power switch on it, then turn the heater on and off there (I use my foot, since it's on the floor). In addition to a switch and indicator light, some also act as a surge protector, but that's more for protecting delicate electronic equipment, so you could skip that feature here, to save some money. StuRat (talk) 21:31, 30 December 2012 (UTC)

LEDs in a power strip??? StuRat, do you have any idea of the nonsense you talk? The Belkin unit you linked to has a neon light in the switch. In most countries, a wall outlet without a switch would be illegal, as the ability to switch off an appliance broken or on fire is an important safety requirement. Keit 120.145.54.24 (talk) 02:44, 31 December 2012 (UTC)

LED is correct. Not neon. I can only imagine the waste of energy. And wall sockets almost never have switches in the U.S. Where are they required? Rmhermen (talk) 03:34, 31 December 2012 (UTC)

? you guys must be young; i'm old enough that my stock of power strips, switches and GFCs with pilot lights, etc. antedate the wide availability of LEDs and rely on the once ubiquitous NE2 bulb, a handy item with a current draw of a few milliamps whose availability at every Radio Shack I miss, due to a lifelong habit of wiring them (with a current-limiting resistor) across the after-the-switch power leads of all appliances such as the OP's heater which did not come with an indicator. Of course, that parallels the general switch from things relying on 110 volts (in America) to ones that run on batteries.  :::Gzuckier (talk) 04:39, 31 December 2012 (UTC)

Don't worry, those NE-2's are still readily available, and will be for years to come. For things that run on AC without any internal conversion to DC, and a myriad of applications that use the special characteristics of a gas discharge, there's nothing better than a small neon tube - cheap, simple, and yes, more energy efficient than a LED. Not as long life as a LED though. Just about every electronics hobbyist shop and trade supplier has them. We had RadioShack/Tandy in Australia for a while. I don't miss them. They stocked a small weird combination of odd bits and pieces at inflated prices. Firms like Dick Smith, Altronics, etc left them for dead. Keit 120.145.54.24 (talk) 05:01, 31 December 2012 (UTC)

Keit, are you going to admit you were once again wrong by saying power strips never come with LED indicator lights ? And how about not accusing me of talking nonsense (when it's you who doesn't seem to know squat about electronics, at least outside of your home country). StuRat (talk) 06:10, 31 December 2012 (UTC)

SuRat, put a sock in it. Not only am I a fully qualified professional electrical/electronic engineer, I have over 50 years experience, mostly in design and senior roles, and while I am not familiar with the US National Electrical Code (as it applies only in the USA) I am fully familiar with practices in countries whose standards are based on European standards, which is most countries in the World, Japan and the USA excepted. And I do know darn well what's in power boards and the like, and its never LEDs for the reasons given by Gzuckier and myself. Stop trying to defend the indefensible. Think before you post, check your facts, and you won't be picked on by me or anyone else (they do squawk now and then don't they?), because you won't be posting such bulldust. Keit 121.215.132.62 (talk) 10:41, 31 December 2012 (UTC)

I have seen perhaps one outlet per room controlled by a switch by the door, and that outlet is typically used for a lamp. Controlling all outlets with switches would inevitably lead to having clocks switched off, etc. StuRat (talk) 03:40, 31 December 2012 (UTC)

My current house has multiple outlets per room controlled by wall switches, in lieu of ceiling light fixtures. And yes, it is incredibly annoying; I have mostly put those little covers over them that prevent me from absentmindedly switching them off. Gzuckier (talk) 04:39, 31 December 2012 (UTC)

Better still, get a timer. You see those ones that will turn lights on and off at specific times of day. If you set that machine to turn on and off for just one hour in every 24 hours (say, on at midnight, off at 1am) - then, when you need to use the heater, rotate the dial to "midnight" - until it just turns on - then if you forget, the heater will turn it off again, automatically one hour later. Of course if you don't use the heater then it'll turn on again 24 hours later...but if it's a changing table, it's unlikely that you won't use it at least that often! By all means use a extension cord with a neon indicator too...but this would be a good back-stop. Since heaters use a lot of current, make sure that both extension cord and timer can handle that amount. SteveBaker (talk) 17:29, 30 December 2012 (UTC)

There's a couple of countdown or boost timers which you set and timeout and they're fairly cheap, but in fact the 24 hour timers tend to be even cheaper and all you need do is set only the switch off time and not the switch on time and you've got a good adjustable countdown with them. Dmcq (talk) 19:19, 30 December 2012 (UTC)

You might have trouble finding an appliance timer rated for the wattage used by a space heater. In the US, they typically draw 1500 watts, and those small outlet timers can't handle that. StuRat (talk) 21:27, 30 December 2012 (UTC)

The OP said their voltage is 220 V. Appliance timers rated for either 8 A or 10 A are quite common in 220 V and 240 V countries - that corresponds to 1760 to 2200 W. Keit 120.145.54.24 (talk) 02:44, 31 December 2012 (UTC)

Why do some carbon compounds burn and others not?

Why don't granite, diamonds, limestone CO2 burn? But, methane and other do? OsmanRF34 (talk) 16:30, 30 December 2012 (UTC)

A chemical will only burn if it is in an environment that allows an exothermic reaction to take place. Looie496 (talk) 16:37, 30 December 2012 (UTC)

And why is an ignited match an environment that allows an exothermic reaction to take place in the case of paper, but not in the case of granite? OsmanRF34 (talk) 16:50, 30 December 2012 (UTC)

It's down to how tightly the carbon is bonded to the other elements in the compound (and to itself). If you burn some methane (CH4 - carbon and hydrogen) in oxygen, you get CO2 and H2O - carbon dioxide and water. The oxygen in the CO2 and H2O is bound more tightly to the Carbon and Hydrogen than those the carbon and hydrogen were bonded to each other in the methane. Put in terms of energy - the amount of energy it took to pull the methane molecules apart was far less than the amount that was released when the carbon and hydrogen bonded with the oxygen - so that reaction happens very easily. The reverse reaction would require massive energy input - lots of energy to pull the carbon and hydrogen away from the oxygen and very little (if any) regained if the carbon and hydrogen could somehow be turned back into methane. SteveBaker (talk) 17:23, 30 December 2012 (UTC)

Your premise is wrong. Diamond#history talks explicitly about combustion of diamond. --ColinFine (talk) 17:30, 30 December 2012 (UTC)

In fact a demonstration of burning a diamond in oxygen was shown in the Royal Institution Christmas Lectures only the other day. You can see it at http://www.bbc.co.uk/programmes/b01pp6bq but you may only be able to watch it from a UK ip adress. Richerman (talk) 18:02, 30 December 2012 (UTC)

It requires a LOT of heat though - the energy input to break apart those strong lattice bonds in order that combustion can occur. You can't just wave a match over it and expect it to catch fire. SteveBaker (talk) 18:26, 30 December 2012 (UTC)

Yes, he used a blowtorch in the RI demonstration. Richerman (talk) 19:07, 30 December 2012 (UTC)

Sorry, I just watched it again to check. He used a hydrogen flame light it and then after a few seconds he removed the flame and the diamond kept glowing as the carbon carried on combining with the oxygen to form CO2. Richerman (talk) 19:25, 30 December 2012 (UTC)

To be clear, carbon dioxide (CO2) is the product of burning, so it doesn't itself burn (it's the most stable combination of carbon and oxygen). Limestone is made up of CO2 which has dissolved in water and reacted reversibly to form carbonic acid (H2O+CO2=H2CO3) and then given up a hydronium (proton) because of alkaline conditions to yield bicarbonate HCO3-, which interacts with calcium ion to produce limestone (CaCO3). Since limestone is made from CO2 interacting by further (non-burning) means that don't require energy in, it doesn't produce energy out by burning. Lastly granite doesn't contain any carbon that I'm aware of. Wnt (talk) 19:21, 30 December 2012 (UTC)

Carbon dioxide can burn (or at least can provide an environment for something to burn). Set light to magnesium ribbon in a CO₂ atmosphere and the magnesium will burn quite happily, stripping the O from the CO₂ and generating a lot of soot. By the way that's probably graphite rather than granite. Tonywalton  00:26, 31 December 2012 (UTC)

The OP may be confusing granite with graphite. --NorwegianBlue 19:54, 30 December 2012 (UTC)

Ah, of course. And that's interesting because graphite is actually used as a refractory. Looking into this, there seems to be some sophistication involved - the graphite might be treated with phosphates, or it might be intended to oxidize before silicon carbide components ... I don't presently really understand the industrial uses. "Graphite does not burn or support combustion. If ground to sub-micron sizes, graphite may ignite spontaneously in air." Hmmm.... Wnt (talk) 00:16, 31 December 2012 (UTC)

Strictly speaking graphite does not burn; no solid does. What happens is that the heat (either initial applied heat, or heat of combustion) causes the graphite (or other substance) to sublimate to gasseous carbon, which burns very readily. It takes a lot of heat to sublimate graphite, you it is difficult to get started. In complex substances, ege wood, coal, pyrolisation occurs - the local heat causes the wood, coal, etc to break down into gasseous components that burn, and solid components (the ash) that will not.

The fact that graphite will burn if the temperature is high enough to sublimate it is why graphite moderated nuclear reactors are inherently dangerous, and there have been some serious accidents in England and elsewhere. If the control rods get stuck, up she goes. Keit 120.145.54.24 (talk) 02:55, 31 December 2012 (UTC)

Actually, the reason why graphite-moderated reactors are dangerous is because of their positive void coefficient -- which essentially means that when the reactor temperature increases, the nuclear reaction self-accelerates, possibly leading to a dangerous runaway reaction, (although we Americans have operated just such a reactor at Hanford Site for decades without any serious trouble). 24.23.196.85 (talk) 06:01, 31 December 2012 (UTC)

That may be so, but it's more complicated than that. And I do mean the graphite can catch fire and has done. Windscale UK 1957 is an example. A graphite moderated reactor at Windscale had an unexpected temperature increase with control rods inserted for which the reason was not understood at the time, due to a defective design and the technicans took the wrong action, trying to correct it with emergency fored air cooling thru the graphite channels, which led to locallised very high temperatures, which set the uranium alight which set the graphite alight. The positive reaction coefficient was understood at the time and had little or nothing to nothing to do with it. It is thought that failure to fully aneal the graphite, as required regularly in graphite moderated reactors was the initial cause. Graphite moderated reactors are cheap and simple to construct, but are full of tricks in operation. Keit 121.215.132.62 (talk) 10:27, 31 December 2012 (UTC)

Article on energy effects of direct sunlight?

Do we have an article that discusses the effect caused by direct sunlight on a surface? I'm looking for something to describe what's going on in this picture, where sunlight has melted all the snow off the roof except for the area that's shaded by one of the chimneys. Shade doesn't help enough, its parent Category:Shading is actually a graphics thing, and Insolation may be useful, but it appears to be on a global or continental scale instead of something small enough to be measured in feet or metres. Nyttend (talk) 18:01, 30 December 2012 (UTC)

How about Solar gain? Richerman (talk) 18:05, 30 December 2012 (UTC)

Thank you. I've added the photo to the article; is the caption accurate and relevant? "Solar gain is illustrated by the snow on the roof of this house: sunlight has melted all of the snow, except for the area that is shaded by the chimney to the right". Nyttend (talk) 18:18, 30 December 2012 (UTC)

Sounds about right to me but I'm no expert. Richerman (talk) 19:00, 30 December 2012 (UTC)

December 31

Light illumination?

Why does red light produce less illumination than blue or green light? NealCruco (talk) 01:01, 31 December 2012 (UTC)

Misplaced Pages doesn't have a good non-technical article on it (the closest I could find was Luminosity function), but the human eye is most sensitive to green light, and more sensitive to red light than to blue light, but more sensitive to variations in blue than in red, giving the appearance of greater sensitivity to blue. --Carnildo (talk) 01:34, 31 December 2012 (UTC)

The technical term (and the main article) is photometry, the field of study that deals with human perception of photons and illumination. Strictly speaking, a red light source and a blue light source and a white light source can all shine with the same luminous intensity, and yet still be perceived at different apparent brightnesses when viewed by the human eyeball (and the brain, which is usually attached, that processes the vision stimuli). This is because your eyeball is not the standard eyeball that was used to define luminous intensity. And of course, if you read and understand luminous intensity, it will be obvious why a blue, red, and white light-source might produce the same number of watts of visible light, yet vary significantly in perceived brightness: because brightness is perceived in a wavelength-dependent way by the human visual system. Everything from the photochemical response of retina cells, to the brain's psychological interpretation of color signal, is wavelength-dependent, and this ensemble must be approximated by one of the many common luminosity functions, or by one you create for yourself for your own purposes. Our photometry article elaborates on the subtleties of measuring "brightness" and related quantities; depending on your application, you may want to measure incident energy, or incident photon-count, or perceived luminous intensity, or some other specific quality/quantity. Many standard units and methodologies exist that cover most common use-cases. Compare radiometry, which avoids the messy bits of perception and instead deals exclusively with physical quantities like number od total incident photons, or watts. Nimur (talk) 04:11, 31 December 2012 (UTC)

Also, Purkinje effect may be relevant. Gzuckier (talk) 04:55, 31 December 2012 (UTC)

And any number of other contextual effects applied by various other modules in the visual system, as in edge and shape detection. Here are some optical illusions illustrating just a few of these forms of post-optic nerve processing of the raw luminosity/wavelength information provided by the eye: 1, 2, 3, 4, 5. Snow (talk) 06:30, 31 December 2012 (UTC)

Eating meat from a venom-killed animal

Would it be safe to eat the meat of a creature that has been killed by the venom of another animal, say a chicken bitten by a rattlesnake or a fish stung to death by jellyfish? Or would that depend on the individual animals involved? 69.111.189.155 (talk) 02:06, 31 December 2012 (UTC)

We can't answer medical questions here. Hot Stop (Talk) 02:10, 31 December 2012 (UTC)

We can't give medical advice, but hopefully no one is being advised here. Our article venomous snake says something I didn't know: "It is, for example, harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. The two exceptions are: the Rhabdophis keelback snakes secrete poison from glands they get from the poisonous toads they consume, and similarly, certain garter snakes from Oregon retain toxins in their livers from the newts they eat." In general, every toxin is different, so it is impossible to make any general statement with accuracy - I don't know if those are the only two exceptions. Wnt (talk) 02:19, 31 December 2012 (UTC)

Just to clarify, I didn't intend for this to be medical advice. I was just curious. Thanks for the responses anyway! 69.111.189.155 (talk) 03:50, 31 December 2012 (UTC)

Our article snakebite points to a paper "Riggs BS, Smilkstein MJ, Kulig KW, et al. Rattlesnake envenomation with massive oropharyngeal edema following incision and suction (Abstract). Presented at the AACT/AAPCC/ABMT/CAPCC Annual Scientific Meeting, Vancouver, Canada, September 27 October 2, 1987." which (the article claims) indicates that people have gotten poisoned by sucking snake venom from other people's wounds...so I suppose it's not impossible for you to get into trouble by eating venom-killed meat. But the size of the dose from eating a pound or so of the meat from an animal seems like it would be rather small in a 100lb+ human provided you didn't eat the part of the animal close to the actual bite site. Tough question though...I wouldn't want to bet my life on anyone's answer here! SteveBaker (talk) 05:01, 31 December 2012 (UTC)

How can i Make a Ligand substance be SELECTIVE on specific receptor areas ?

Let's say i create a new general material which inhibits all types of Gaba receptors, but i want it to be selective to a very particular area of the brain. in other words, while the substance can influence all brain areas with Gaba R, I want it to focus on a particular one.

what are the princilpals of making a particular molecule Selective? what things should i take for granted? when constructing this molecule.

THIS IS NOT HOMEWORK !, i ask because i want to know about the principles. i understand that lately, some new info was discovered about this. thanks. 109.65.115.101 (talk) 06:20, 31 December 2012 (UTC)

Well, I suppose you could make something which reacts more with grey matter or white matter, or perhaps with areas that are more active (use more glucose), but I don't know how you could make it only react with, say, areas storing memories of cats. There has been some study on applying electromagnetic fields to the brain, and perhaps you could make something that would only be activated in the presence of a strong electromagnetic field, and thus you could control which regions of the brain are affected, by altering the field strength and shape around the head. StuRat (talk) 07:10, 31 December 2012 (UTC)

if i understand you correctly what you say is: after a ligand is given, we could "Navigate it" to a specific brain regions by external methods? — Preceding unsigned comment added by 109.67.131.95 (talk) 09:57, 31 December 2012 (UTC)

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