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April 28

The new "Xi_b^*" baryon

Is http://www.sciencedaily.com/releases/2012/04/120427095621.htm trying to write "$\Xi _{b}^{*}$"? Whose fault was it that the TeX got put into a press release?

More importantly, what will the Wikipedia article on the new particle be named? 70.58.10.111 (talk) 04:24, 28 April 2012 (UTC)

See Xi baryon for more information and further reading on this class of particles. --Jayron32 04:49, 28 April 2012 (UTC)

The new particle is not yet included in our article. The quark content of the new particle is said to be up/strange/bottom. With the naming convention described in our article, this should be called $\Xi _{b}^{0}$, but this is already a known particle. I don't know what the asterix is supposed to indicate, high energy unstable state perhaps? SpinningSpark 11:18, 28 April 2012 (UTC)

To quote the original reference's abstract (arXiv:1204.5955v1), "the $\Xi _{b}^{*0}$ baryon, the J^P = 3/2⁺ excitation of the $\Xi _{b}^{0}$." DMacks (talk) 16:56, 28 April 2012 (UTC)

What is this black substance ?

http://img804.imageshack.us/img804/7756/image1os.jpg and http://img4.imageshack.us/img4/9763/size2k.jpg what is black substance in these photos ? — Preceding unsigned comment added by 182.185.194.68 (talk) 10:44, 28 April 2012 (UTC)

I'm guessing from context that it's cannabis resin, but these photos are awful, and you need to give us better context. AlexTiefling (talk) 11:08, 28 April 2012 (UTC)

I can't convince myself the black object in the first picture is the same as the brown one in the second. The first one looks like it might be wrapped in black plastic - maybe the pictures didn't specify it was unwrapped between shots? From context I'm thinking the second one is a brownie, but that's just my stomach talking. ;) Wnt (talk) 13:05, 28 April 2012 (UTC)

I think you are right these seems to be two separate objects. I have added more images, http://imm.io/nvhd, http://imm.io/nvj3, http://imm.io/nvk7, http://imm.io/nvkV, http://imm.io/nvlG, http://imm.io/nvoM, http://imm.io/nvpx, http://imm.io/nvpU, http://imm.io/nvqu. Some have been cropped and some are in original size. Hopefully these will be of help. — Preceding unsigned comment added by 182.185.194.68 (talk) 14:35, 28 April 2012 (UTC)

I don't know if any of these things is the same as any other. There are certainly more than two or three different objects. There might be a second one of the same "brownie" as the second original image ([1]). I still keep picturing brownies, also brownie batter [2] - if these pictures are from a medical marijuana user I'd believe it, since many of them prefer to avoid smoking for health reasons. Wnt (talk) 16:45, 28 April 2012 (UTC)

Never heard of hash brownies? --TammyMoet (talk) 17:30, 28 April 2012 (UTC)

Well this is certainly not marijuana for medical use, as too many cigarettes can be seen in the photos. Can it be Charas, where taken in Pakistan. — Preceding unsigned comment added by 182.185.194.68 (talk) 19:37, 28 April 2012 (UTC)

Sure, it could be. It could also be many other things. These photos are not enough for a positive identification of any sort. Perhaps if you could touch it, smell it, taste it, or burn it, you could narrow down the possibilities. Charas should behave rather differently than e.g pitch under a few of these basic tests. 96.235.227.66 (talk) 00:50, 29 April 2012 (UTC)

Presence of Joint (cannabis) confirm marijuana smoking, is charas quite plastic ? I mean it's shape can easily changed ? — Preceding unsigned comment added by 182.185.194.68 (talk) 01:59, 29 April 2012 (UTC)

Freezing

Why does hot water freeze faster than cold water? --108.206.4.199 (talk) 13:54, 28 April 2012 (UTC)

Mpemba effect#Causes has some explanations - which pertain depends on the specific experimental setup. -- Finlay McWalterჷTalk 14:01, 28 April 2012 (UTC)

... and, of course, the statement, as given, is false in many circumstances. Dbfirs 15:36, 28 April 2012 (UTC)

As with several other of the OP's ref desk questions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:10, 29 April 2012 (UTC)

This is User:Tango's favorite subject. :) Count Iblis (talk) 15:38, 28 April 2012 (UTC)

Fortunately, the photos didn't come out very well! --Tango (talk) 02:21, 29 April 2012 (UTC)

Permanent marking of stolen clothing

IMHO there is a red color, which marks stolen clothing permanently. --84.61.181.19 (talk) 17:00, 28 April 2012 (UTC)

Could you phrase that as a question? SpinningSpark 17:26, 28 April 2012 (UTC)

Who says there is a red color, which marks stolen clothing permanently? —Tamfang (talk) 17:36, 28 April 2012 (UTC)

Someone with kleptomania and chromatopsia ? Sean.hoyland - talk 18:02, 28 April 2012 (UTC)

What is the name of the red color, which marks stolen clothing permanently? --84.61.181.19 (talk) 18:55, 28 April 2012 (UTC)

Dye pack, which is mostly about banks, lists Disperse Red 9 as commonly used in money packs. But I don't know about clothes. --Mr.98 (talk) 20:30, 28 April 2012 (UTC)

Do we truly not have an article on dye tags, as described in this HOWTO on removal of the tags (should the clerk fail to do so)? I thought that we had an article on everything. -- ToE 03:37, 29 April 2012 (UTC)

There are a couple article sections on the topic, but neither of them say anything about the type of ink or dye that's used: Retail loss prevention#Ink tags and Electronic article surveillance#Occasional vs. informed shoplifters. Ink tag just redirects to the latter article. Red Act (talk) 04:10, 29 April 2012 (UTC)

I just changed the redirect target to the former which seems more relevant. SpinningSpark 10:13, 29 April 2012 (UTC)

It doesn't answer the question, but this book has a lot of interesting information. The first ink tags were made by Colour Tag and were quite vicious, using a toxic dye and a tendency to explode when removed due to being filled under pressure. Modern versions use a non-toxic and non-flammable dye but the book does not name the chemicals. I imagine that each manufacturer has their own recipe - note that they come in a variety of colours, not just red. SpinningSpark 10:28, 29 April 2012 (UTC)

What a strangely crude device! Every retailer must have a tool to get the tags off, so any serious organized shoplifting gang must have them. And as shown in the "howto" site it apparently isn't rocket science even for the random person to defeat them. I haven't seen anything I recognize as similar to that in the U.S. Wnt (talk) 11:25, 29 April 2012 (UTC)

Sensormatic is/was another major vendor. I remember seeing various sorts of these things all over the US even within the past few years, usually looking like a large opaque off-white clothes-pin or 2-inch square. DMacks (talk) 11:43, 29 April 2012 (UTC)

It's not meant to be rocket science, it's meant to be a deterrent up to a certain amount of effort, and nothing more. Most shoplifting is not done by high-tech ninjas with portable (and I suppose they would have to be silent) dremels. (Anecdote: I worked at a Barnes and Noble many years ago, and we had those little RFID inventory control stickers. It wasn't actually worth the price or effort to put them into all inventory, though, so they only had us put it on things that cost more than $50, and every 10th book, or something like that. Someone, somewhere, had done the math on what the cost of the system was versus the cost in saving inventory and the deterrent value. We of course did have some "loss", but that's expected with such stores and is factored into the pricing schemes.) --Mr.98 (talk) 00:43, 30 April 2012 (UTC)

Aquifer drawdown and cloud cover.

I was about to mark a statement in the groundwater article as dubious, but then I noticed that the same statement can be found in a lot of related articles. The statement conflicts with my understanding of phase equilibrium. Here are the articles I checked:

Groundwater

Aquifer drawdown or overdrafting and the pumping of fossil water increases the total amount of water within the hydrosphere subject to transpiration and evaporation processes, thereby causing accretion in water vapour and cloud cover, the primary absorbers of infrared radiation in the Earth's atmosphere. Adding water to the system has a forcing effect on the whole Earth system, an accurate estimate of which hydrogeological fact is yet to be quantified.

Overdrafting

Aquifer drawdown or overdrafting and the pumping of fossil water increases the total amount of water within the hydrosphere subject to transpiration and evaporation processes, thereby causing accretion in water vapour and cloud cover, the primary absorbers of infrared radiation in the earth's atmosphere[citation needed]. Adding water to the system has a forcing effect on the whole earth system, an accurate estimate of which hydrogeological fact is yet to be quantified.

Water crisis

Aquifer drawdown or overdrafting and the pumping of fossil water increases the total amount of water within the hydrosphere subject to transpiration and evaporation processes, thereby causing accretion in water vapour and cloud cover, the primary absorbers of infrared radiation in the earth's atmosphere. Adding water to the system has a forcing effect on the whole earth system, an accurate estimate of which hydrogeological fact is yet to be quantified.

Water cycle

Aquifer drawdown or overdrafting and the pumping of fossil water increases the total amount of water in the hydrosphere[18] that is subject to transpiration and evaporation thereby causing accretion in water vapour and cloud cover which are the primary absorbers of infrared radiation in the Earth's atmosphere. Adding water to the system has a forcing effect on the whole earth system, an accurate estimate of which hydrogeological fact is yet to be quantified.

Hydrosphere

Aquifer draw down or over drafting and the pumping of fossil water increases the total amount of water in the hydrosphere[4] that is subject to transpiration and evaporation thereby causing accretion in water vapor and cloud cover which are the primary absorbers of infrared radiation in the Earth's atmosphere.
I could add a dubious template to all of them, but how many more are there? And is my doubt justified? Ssscienccce (talk) 17:34, 28 April 2012 (UTC)

Not only dubious, but poor English. This is a pretty serious problem you've stumbled on, as it appears to be on many pages for over a year, I'm gonna see how deep the rabbit hole goes... -RunningOnBrains^(talk) 19:15, 28 April 2012 (UTC)

Just another four I think, Fossil water, Drawdown (hydrology), Water table & Aquifer. Mikenorton (talk) 19:22, 28 April 2012 (UTC)

I was able to track it down to a single IP in February 2011, using this article as a source on some pages. Seems pretty dubious to me, but it has been postulated by some scientists (now that I actually know what the IP was TRYING to say). Still, per WP:UNDUE, it doesn't belong in most if not all of these articles, so I'm going to remove it. -RunningOnBrains^(talk) 19:23, 28 April 2012 (UTC)

Just a note, I did end up leaving a sentence about sea-level rise in most of the articles, as that part is backed up by the cited study. All that stuff about extra water vapor/etc. is pure original research, and was removed. -RunningOnBrains^(talk) 19:41, 28 April 2012 (UTC)

Thanks for taking the trouble :-). Ssscienccce (talk) 10:36, 30 April 2012 (UTC)

sodium metasilicate

my understanding is when sodium metasilicate comes into contact with water it becomes especially caustic kind of like calcium oxide does. My question is when it contacts with water does it react to produce a less caustic chemical kind of like calcium oxide becomes calcium hydroxide? Or does it stay as sodium metasilicate. If it does react how long does it take?--64.38.226.88 (talk) 19:38, 28 April 2012 (UTC)

No, sodium silicate readily dissolves into 2 Na⁺ + SiO₃^-2 and the evaporation residue will mostly be the Na₂SiO₃·9H₂O hydrate. It's a very strong caustic base when saturated, and dangerous as such. 70.58.10.111 (talk) 01:36, 29 April 2012 (UTC)

SiO²⁻
₃ + H
₂O ←→ SiH
₂O²⁻
₄

SiH
₂O²⁻
₄ ←→ SiO
₂ + 2HO⁻

Plasmic Physics (talk) 08:42, 29 April 2012 (UTC)

News to me. I wonder what proportion of the ion ends up as SiO
₂ in solution? 70.58.10.111 (talk) 00:00, 1 May 2012 (UTC)

I would imagine a large proportion, as the equilibrium constant for the reaction of silica with water is much less than one, substituting hydroxide for water in the reaction sequence should not have a very large effect on the constant. Plasmic Physics (talk) 00:29, 1 May 2012 (UTC)

It would still be less than one, I guess. Plasmic Physics (talk) 00:32, 1 May 2012 (UTC)

April 29

How do I mimic static over the cellphone?

In some situations, I feel the need to mimic increasing static on a phone before disconnecting. It needs to sound convincing, so what are the best methods? Thanks. --68.102.29.129 (talk) 02:26, 29 April 2012 (UTC)

Stand outside, hold phone into wind. --Mr.98 (talk) 02:53, 29 April 2012 (UTC)

This isn't always convenient when the day is calm, and when I'm in a bad position to go outside and hold the phone into the wind. Are there other methods just as good? --68.102.29.129 (talk) 03:36, 29 April 2012 (UTC)

Modern digital communication rarely injects Gaussian noise into the audio channel. A dropped call often occurs without warning, and the call simply disconnects. If you're seeking to realistically simulate a call interrupted by poor reception, simply disconnect at a random time. If you actually want to play "static" over the microphone for some other reason, consider recording some white noise and playing it in the background using an audio player. Nimur (talk) 04:10, 29 April 2012 (UTC)

Well, there is comfort noise. DMacks (talk) 09:01, 29 April 2012 (UTC)

I don't know about cell phones in particular, but in general simply blowing directly onto a microphone tends to produce a surprising amount of noise, unless you're using a dead cat or something. Red Act (talk) 04:40, 29 April 2012 (UTC)

The best trick might be to hang up while you yourself are talking, reducing the possibility that the other party will think you hung up on them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:52, 29 April 2012 (UTC)

I agree - digital cellphones don't often get noisy before dropping out, but what they often do is chop up / interrupt your voice a few times before disconnecting. You could simulate this by rapidly placing and removing your finger over the microphone hole while continuing your talking. On most modern phones, it's only a single hole 0.5 to 1 mm diameter. If you do this more than once or twice to the same caller, they'll will catch on to what you are doing though. Wickwack121.221.228.248 (talk) 05:34, 29 April 2012 (UTC)

A Fibres in Frog Sciatic Nerve

Hello. Are the A-alpha fibres of the frog sciatic nerve the only component of A fibres that are myelinated? Thanks in advance. --Mayfare (talk) 18:20, 29 April 2012 (UTC)

I don't know the answer but a google snippet suggested that this paper might have some information. SpinningSpark 10:54, 30 April 2012 (UTC)

Gravity

Physicists variously talk about gravity as an element of space-time, as gravity waves, and as gravitons. Are these related in some way or are they three different views of gravity? — Preceding unsigned comment added by Gstrom47 (talk • contribs) 20:19, 29 April 2012 (UTC)

Gravitational waves and viewing gravity as the curvature of spacetime are part of the same model of gravity, general relativity. Gravitons are an attempt to extend quantum field theory to gravity, which is a different approach in that general relativity doesn't deal with quantum mechanics at all. Red Act (talk) 21:02, 29 April 2012 (UTC)

On the other hand, I don't want to give the impression that general relativity and gravitons are completely unrelated. Two ways in which gravitational waves and gravitons are related are that both travel at the speed of light, and they both have the same symmetry: if you rotate either a gravitational wave or a graviton by 180 degrees, it will wind up looking the same as before the rotation. It's just that one involves a quantum field and the other involves a classical (nonquantum) field, very similar to the relationship between electromagnetic waves and photons. Red Act (talk) 21:53, 29 April 2012 (UTC)

They are all closely related. A graviton is a quantum of gravitational wave energy, and Feynman diagrams with virtual gravitons are mathematically related to the field equations of general relativity in much the same way that a Taylor series is related to the function it approximates. -- BenRG (talk) 00:48, 30 April 2012 (UTC)

Agree with all of the above. General relativity is a classical field theory and so gives rise to gravitational waves which are analagous to electromagnetic waves in classical electromagnetism. If you try to develop a quantum field theory version of general relativity (which is one of the possible routes to a quantum theory of gravity) then gravitational waves are replaced by gravitons, in the same way as photons replace electromagnetic waves in quantum electrodynamics. So gravitational waves and gravitons are two different ways of describing the same phenomena - one classical, one quantum. However, in contrast to electromagnetism, we have not yet directly detected gravitation waves (although there is some indirect evidence for their existence) or gravitons. Gandalf61 (talk) 10:53, 30 April 2012 (UTC)

Both you and Red Act suggest that gravitons replace gravitational waves in quantum field theories. That seems very misleading to me. "Graviton" is just another word for "gravitational wave" in quantum field theory. It's equally true that in quantum theory sound is replaced by phonons. Anything involving vibration gets quantized. That's no call to invent new terms for everything, much less to treat them as new concepts. -- BenRG (talk) 17:29, 30 April 2012 (UTC)

Your QFT knowledge is much stronger than mine, but my understanding is that assuming that gravitons exist, then gravitational waves of the strength for example being searched for by LIGO et al can basically be viewed as a coherent state of many gravitons. However, although the existence of gravitons would imply the existence of gravitational waves, the converse is not true; gravitational waves are predicted to exist (by GR) independently of whether gravity actually quantizes into gravitons. To put it another way, if LIGO and even more powerful detectors continue to fail to find gravitational waves, that would be a blow to GR in a way that, say, a theoretical result in QFT showing that gravitons can't actually exist would not be. So gravitational waves and gravitons are at least different in that regard. Would you agree with that assessment? Red Act (talk) 18:48, 30 April 2012 (UTC)

Actually, I stand by "replaced". A classical wave is a solution to a system of PDEs such as the wave equation, Maxwell's equations or the Einstein field equations. It assumes that space, time and other properties of the system such as energy and momenta are continuous and take on definite values, and our knowledge of their values is limited only by the sensitivity of our instruments. A quantum model is fundamentally different. It involves probability waves that are superficially similar to the waves in the classical model, but we cannot observe them directly due to wave function collapse. What we observe are quanta. Only when a large number of quanta are observed does the classical wave picture emerge at a macroscopic level. Gandalf61 (talk) 14:05, 1 May 2012 (UTC)

Why were the X-15 rocket-powered aircrafts retired?

Why were the X-15 rocket-powered aircrafts retired? 82.31.133.165 (talk) 21:09, 29 April 2012 (UTC)

As the X indicates, they were experimental aircraft, never intended to be useful for any practical purpose. They were intended to test a concept, and once that concept was proven, there was no longer much point in flying them. Looie496 (talk) 21:19, 29 April 2012 (UTC)

Indeed. Compared with other experimental aircraft, X-15 had a remarkably long career (over 10 years, 199 flights, on three airframes). X-15 research fed directly into the space shuttle's glide phase design (and I imagine into classified hypersonic control projects like MIRVs). -- Finlay McWalterჷTalk 21:24, 29 April 2012 (UTC)

As for rocket-powered aircraft, in general, they suffer from a rather short flight time, which makes them less flexible (you can't circle the runway for long, waiting for a chance to land). A large turn radius is another problem. StuRat (talk) 21:31, 29 April 2012 (UTC)

The X-15 was a military research vehicle. The USAF's plan was to incrementally develop space transport - there should have been a successor to the X-15. However, the response of the US Govt to the success of Sputnik and other Russian space projects was to decide that a) a "space race" was necessary, and the USA must win it, and b) it must be done with a civilian effort. This was so that that orbiting altitudes and space did not becaome a military domain. Thus the military programme was terminated, and NASA created, with von Braun in charge. von Braun was partial to large "brute force" vertically launched disposable rockets, rather than re-usable flyable planes. Ratbone58.170.164.197 (talk) 14:58, 30 April 2012 (UTC)

That makes for a nice story, but the first X-15 flights didn't occur until after NASA was created, and the last of the 199 flights was more than a decade after Sputnik started the space race. Of the 12 people to ever fly an X-15, five were NASA personnel, including the first man on the moon Neil Armstrong. Yes, the successor vehicle was terminated in favor of the heavy lift rockets that came to represent the space race; however, it is too simplistic to say that X-15 was killed simply because it was military. The X-15 was originally proposed and created as a joint operation between the USAF and the civilian NACA program, which later became NASA. As a joint USAF / NASA project, it enjoyed a far longer life than most X- series experimental flight vehicles. Dragons flight (talk) 15:25, 30 April 2012 (UTC)

Nowhere did I say the X-15 was killed off - I only said the military programme (ie X15B, Dynasoar etc) was terminated and there was no successor when there should have been. It is misleading to say the X15 did not fly until NASA was created, without further qualification. It takes much much longer to design and build a air/space vehicle than it does to create a govt agency. Planning for the X-15 goes back to at least 1955, probably even further in meetings, discussions and the like not in the public domain. Nobody thought of creating NASA until 1958. Pres Eisenhower did not sign the enabling law into effect until late 1958, and Russian space achievements were the driver. Ratbone124.182.4.180 (talk) 02:55, 1 May 2012 (UTC)

Preventing water damage when building a building

Is it necessary, since the building still doesn't have roof, or is it not, since it's just concrete? XPPaul (talk) 22:12, 29 April 2012 (UTC)

If the builders get to the point where there are things inside the building that would be damaged by water before the roof is finished, then can cover the top with plastic sheeting or something similar (I have seen that on building sites). I think it's normal to finish the roof before you start to work on the interior, though, so it would just be concrete and bricks - a bigger problem is if you are working on the roof of an existing building, then you some kind of temporary protection. --Tango (talk) 22:34, 29 April 2012 (UTC)

Just to make things clear, a bare reinforced concrete frame of a building in construction won't get damaged by direct water contact?XPPaul (talk) 23:09, 29 April 2012 (UTC)

Well, the concrete needs a dry period to set. After that, the concrete itself should be OK, but if there's no drainage, water could accumulate and undermine the foundation, causing it to fail. Rebar can also rust, if sitting in water. This could also cause the concrete to fail. I seem to recall a walking bridge over a highway failing that way a few years back. Then filler in low-quality concrete may also be damaged by water. Chunks of iron, for example, will also rust there. Most of these effects would require a lot of time and water, though, so one or two rainstorms won't be a problem. StuRat (talk) 23:51, 29 April 2012 (UTC)

There can be a problem with timber that has too much moisture if it is going to be enclosed and unable to dry out. SpinningSpark 23:23, 29 April 2012 (UTC)

Niagara falls into dam

Is it theoretically possible that the Niagara Falls could be turned into a hydroelectric dam? Also, how long will it take until the Great Lakes drain into Lake Ontario? 64.229.204.143 (talk) 22:46, 29 April 2012 (UTC)

Anywhere with a significant flow of water could be turned into a hydroelectric generator. They don't usually use waterfalls, though - it's easier to create your own drop using a dam. There would be a lot of engineering problems with using the Niagara falls, and they would also lose all the tourism. I'm not sure what you mean about the Great Lakes - they aren't draining out, there is always water being added from rivers that drain into them. --Tango (talk) 23:04, 29 April 2012 (UTC)

I don't think a flow of water is sufficient. You also need a canyon, so your dam can be like the plug in a bathtub. To build a dam on flat ground would require that you build the entire "bathtub", which would cost more than it would be worth. In the case of Niagara Falls, I believe the part above the falls is fairly flat. StuRat (talk) 23:42, 29 April 2012 (UTC)

No canyon necessary, but a slow flow (at low pressure) would not generate electricity very efficiently, so a reasonable height difference is usually preferred. The advantage of using a canyon (or similar geographical feature) is that a large reservoir can be maintained at reasonable cost, so that generation can continue in dry weather. Dbfirs 06:52, 30 April 2012 (UTC)

If you mean no canyon is necessary for hydroelectric power generation, I agree, since this is currently done at Niagara. However, if you mean that a large dam can be constructed economically without a canyon, which is what this question is about, then I disagree. StuRat (talk) 15:13, 30 April 2012 (UTC)

No, I wasn't suggesting that a large dam would be economic without some sort of natural valley, so we are in agreement, except on what the question is about. My point was that only a height difference is important, not a dam or canyon. Dbfirs 07:25, 1 May 2012 (UTC)

The title and first sentence would seem to indicate that the question was about a dam, not other forms of hydroelectric generation. StuRat (talk) 07:30, 1 May 2012 (UTC)

... but it doesn't say "large dam". Anyway, we agree on the essentials, and that generation is separate from damming. Dbfirs 07:10, 2 May 2012 (UTC)

The land around Niagara Falls is pretty flat, although there are escarpments, like the Niagara Escarpment, which is why there's a waterfall there at all. Also there is a canyon, or at least a gorge, below the falls, extending to about Lewiston, NY (Google Maps terrain shows it here, [3]). It would probably be possible, in theory anyway, to build a dam near Lewiston, creating a reservoir backing up to the falls. It's easy to think of various reasons why this hasn't been done, and won't be. Instead they built "off-river" reservoirs. Pfly (talk) 01:33, 1 May 2012 (UTC)

Also, for more on hydroelectric dams with minimal reservoirs, see Run-of-the-river hydroelectricity. Pfly (talk) 01:41, 1 May 2012 (UTC)

One final tidbit I can't help but mention--there have been some very grand plans envisioned for Niagara Falls. One of the wildest was described in The Human Drift by King C. Gillette--the guy who founded the Gillette company. He pictured a giant utopian city built right on top of Niagara Falls, rectangular in shape, 135x45 miles large, built out of porcelain, the only city on the entire continent, powered with electricity from the falls, and run by a "world corporation". Pfly (talk) 01:56, 1 May 2012 (UTC)

Kinda like Fallingwater, only much bigger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:03, 2 May 2012 (UTC)

Niagra Falls is used for hydroelectric power generation - see Niagra Falls#Power. So much so that the amount of water the power plant uses is limited by treaty for fear of the Falls drying up to a trickle. SpinningSpark 23:28, 29 April 2012 (UTC)

According to our Niagara River page it was the very first river used for hydroelectricity in North America. There's a monument to Nikola Tesla on Goat Island right at the falls. In satellite imagery, like File:Niagara Falls SPOT 1314.jpg, you can see the two large reservoirs used for hydroelectricity generation (one in the US and one in Canada). Water is diverted from the river above the falls into the two reservoirs and then returned to the river below the falls, falling through large turbines to make electricity. In short, not only is Niagara Falls already used for making electricity, it is one of the most famous and historic examples of hydroelectric power. Pfly (talk) 23:36, 29 April 2012 (UTC)

As has already been noted, the Great Lakes are continually refilled with rain and snow melt. However, even if all precipitation in the Great Lakes watershed ended, the lakes still wouldn't "drain", as the lakes are deeper than the rivers connecting them (Detroit River, Saint Clair River, Niagara River, Saint Lawrence River). So, each lake would only drain to the depth of it's outlet river. From there, it would eventually evaporate. StuRat (talk) 15:19, 30 April 2012 (UTC)

(psst, also the St. Marys River!) Pfly (talk) 04:15, 1 May 2012 (UTC)

Thanks, couldn't remember the name of that one. There's also the Straits of Mackinac, although I'm not sure if that's shallower than Lake Michigan. StuRat (talk) 08:40, 1 May 2012 (UTC)

Also don't forget the Chicago River which was canalized from an inlet river to an outlet river. It is technically feasible to get from New Orleans to the mouth of the St. Lawrence via boat. Another way to put that is that the entire eastern portion of the U.S. is technically an island, as it is completely surrounded by water (though not all natural sources). --Jayron32 23:20, 1 May 2012 (UTC)

Kinda like Cape Cod, only much bigger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:04, 2 May 2012 (UTC)

What are typical Power capacities for suburban Distribution Substations??98.225.64.151 (talk) 23:13, 29 April 2012 (UTC)

I live in Arizona, with major summertime Air-Con loads. I do know that my own neighborhood substation was built in 1985 on about 1 acre of land, and is fed by a 138kV line. I've asked my Utility for that substation's Power rating, but they won't tell me because of "security reasons." Thanks in advance to you Power engineers.

You are asking the wrong question and/or are asking a question, which if you had the answer, the answer would have no meaning for you. 138kV lines would generally be used to supply power at levels exceeding 20 MW (megawatt), up to 600 MW or more. This is a power level that is appropriate for entire districts up to significant cities. A substation requiring 1 acre is a huge substation. If you want to know if what feeds your house is adequate, you need to focus on the distrubtion transformer and/or RMU (Ring Main Unit, a type of switch) that feeds your street. This is typically about the size of one or two domestic fridges. In most countries, these are mounted up on poles if you have open wire distribution, or in roadside cabinets in underground cabling is used. In the USA, with undertground street cabling, the transformers & RMU's are often underground as well. Instead of asking what is the power rating, you coukld ask something like what is the site design power capacity, and what has been the load growth over (say) the last 10 years. But even this will be pretty meaningless, because there is a lot of substation reconfiguration, load transfer, and other upgrade work the power company can do, so that even if a substation appears to be at 100% capacity, there is likley nothing electricity consumers should be concerned about. In any case, substations at the level you are talking about are usually fully redundant - if there is a fault, the power company can changing switching and feed the loads from somethwere else, and they can switch loads as required to even up the loads on various interconnected substations. Wickwack121.221.89.56 (talk) 03:08, 30 April 2012 (UTC)

It is a very reasonable and sensible question, but not one easily answered based only on the area of the substation and the incoming transmission voltage. 138kv lines differ in their current capabilities, based on conductor size, for instance. To figure out the answer to your question, one would need to know the transmission capability of the 138kv line or lines entering the substation, and the capabilities of the power system (generating stations or substations) supplying those 138kv lines. That represents the maximum power could be supplied to transformers at the distribution substation. The next questions is how many transformers of what megawatt rating are located at the distribution substation, to step the 138kv transmission down to 34kv, 12 kv or 4kv distribution. Other elements which could limit the power are any other things the current might pass through, such as current transformers, inductors, bus bars, switches, circuit breakers and wavetraps. A utility strives to make sure that some cheap element is not the limiting factor. Then one could consider the capabilities of the distribution lines leaving the substation. In the end, a maximum power capability could be computed, based not on the strongest but on the weakest link in the chain. One utility I am familiar with can have up to four 40 MVA (megavoltamp) transformers stepping down 138kv transmission from two incoming transmission lines to about 30 12 kv distribution lines, for a total of 160 MVA. I know of other substations in urban areas with four 50 mva transformers. Other utilities might have varying ultimate designs for their substations. (The megawatts would be somewhat less than the MVA due to the power factor of motors etc being less than one). A utility might start with one 30 mva 138kv-12kv transformer transformer in a substation. Edison (talk) 01:50, 1 May 2012 (UTC)

I agree with Wickwack - the "power rating" is not a question meaningfull or relavent to a consumer. However the rest of what Edison says is valid and supports Wickwack. It should also be noted that the effective power (or (VA) capacity of a substation may depend on its' switched configuration: E.g., due to internal bus limitations, if power is drawn from incomming feeds A and B and switched to supply distributions X and Y, while feed C supplies distribution W, the total capacity might be different if say distribution B is switched on to feed D. Particular distributions may be feed from more than one substation. Sometimes large consumers with critical functions (eg satelite tracking stations, hospitals) have feeders from two or more substations so that they have power no matter what accident or fault happens in either feeders or substations. Ratbone124.182.4.180 (talk) 03:10, 1 May 2012 (UTC)

Also, a utility typically builds in a LOT of redundancy, so that one or more transmission lines, transformers, bus ties, bus sections, and distribution lines can be out of service without having to drop load. They are not so optimistic as to assume everything will be working perfectly on a peak load day. A substation might be expected to serve only half the load it is nominally capable of, to allow for contingencies. Additionally, the "stiffness" or available fault current from a substation might have an impact on the amount of flicker all the other customers from a substation see when some industrial load such as a steelmaking arc furnace, or a very large motor is switched on and off frequently. This is one aspect of the power available besides the issue of how much current it could supply without burning something out (transmission line, transformer, etc). Edison (talk) 03:33, 1 May 2012 (UTC)

Leftover rabies?

So it seems 2 animals of some sort had a fight in my back yard last night. Bits of fur and whatnot laying about. So: IF one or more had rabies, AND IF said animal bled or drooled or whatnot on the ground, what danger would there be of being exposed by being in that area? Obviously I didn't roll around in the grass, but I'm just curious. Thanks in advance. — Preceding unsigned comment added by 71.62.103.2 (talk) 23:31, 29 April 2012 (UTC)

Pretty low, unless you intend to use the drool-covered fur to make a bandage for a cut on your arm. Even then you probably wouldn't get rabies (but might get some other infection). StuRat (talk) 23:39, 29 April 2012 (UTC)

This website has a fairly detailed description of what counts as exposure, and surprisingly (to me at least) it states that contact with blood of an infected animal does not count as exposure. Of course in your case there might be some saliva mixed in with the blood, so I still wouldn't go touching it. Vespine (talk) 23:54, 29 April 2012 (UTC)

I don't believe you can get rabbies by touching contaminated saliva or blood. Bites are obviously a different ball park. XPPaul (talk) 00:11, 30 April 2012 (UTC)

Actually you can should you have exposed wounds or get it on mucous membranes. See this from the CDC which gives nonbite criteria. Our article, Rabies transmission, mentions cave explorers being infected, although TTBOMK the route of transmission such as aerosols IMO was somewhat speculative although not unreasonable. To safeguard other scavenging animals such as pets from getting into the mess, I'd use a shovel to remove any large pieces and rinse the area down with a garden hose. Plus, avoid not tracking any of it in with your shoes. --Modocc (talk) 01:05, 30 April 2012 (UTC)

Yes the website I linked does explain that it is possible to be infected through "non-bite exposure" to saliva or CNS tissues, such as brain matter. As the above states, you would need to contact mucous membrane (which can be as simple as rubbing your eye) or a wound such as sa cratch or abrasion. Vespine (talk) 01:28, 30 April 2012 (UTC)

April 30

Fibrosis

Do all infections and inflammations cause scar tissue to form in the area affected? — Preceding unsigned comment added by 138.253.210.6 (talk) 08:17, 30 April 2012 (UTC)

I don't think so otherwise the common cold would scar nasal tissue, and that's obviously not true. I stand to be corrected though. --TammyMoet (talk) 09:30, 30 April 2012 (UTC)

No. Small areas of damage to the body are fixed by regrowing the original tissue, with a few exceptions, like nerve cells. Thus, no damage should be apparent once this process is complete. However, this is too slow for large areas of damage, so scar tissue is used, instead. Unfortunately, we lack the ability to gradually replace scar tissue with normal tissue, so scars become permanent. StuRat (talk) 15:30, 30 April 2012 (UTC)

Kinased oligonucleotides

Hello. What's a "kinased oligonucleotide", and how does it differ from a "normal" oligonucleotide? Thanks! Leptictidium (mt) 10:25, 30 April 2012 (UTC)

Does protein kinase have the information you need? SpinningSpark 15:48, 30 April 2012 (UTC)

Kinases are enzymes that facilitate the addition of phosphate groups to other molecules; a 'kinased' oligonucleotide is therefore one to which a phosphate has been added (generally to the 5' end) through the use of an enzyme (most often T4 or T7 polynucleotide kinase). TenOfAllTrades(talk) 15:49, 30 April 2012 (UTC)

Why it's not just called a phosphorylated oligo is beyond me..... Fgf10 (talk) 17:01, 30 April 2012 (UTC)

Probably historical accident. I'm guessing that the T4 PNK method was either the first, the cheapest, or the most popular method for some period of time (and may still be—I've never done much work in the area) and it has just stuck. The term phosphorylated is definitely also used; it is slightly broader in its meaning, however, in that it can also cover oligos that were phosphorylated using other mechanisms (that is, not with a kinase) or at the other (3') end of the strand. If it makes you feel better, Google suggests that phosphorylated oliogos outnumber their kinased brethren on the web by about three to one. TenOfAllTrades(talk) 13:12, 1 May 2012 (UTC)

How many neurons can fire at once?

I've read the average neuron in the human brain can fire 200 times per second. How many neurons can actually sustain this rate simultaneously? How many usually do? Is this limited by physical constraints (e.g. ability to feed in and dissipate energy) or by neurological bottlenecks? NeonMerlin 12:11, 30 April 2012 (UTC)

I suspect that while the (limitted) supply of nutrients will enforce an upper limit of how many many neurons can simulataneously fire at maxiumum rate, electric disturbance will impose a lower limit. Every neuron that fires creates an electric field that propagates out through the bulk of the brain. If you get enough firing simultaneously and rythmically, the electric fields will add, perhaps creating a field strong enough to fire more neurons. This could avalanche thru the brain causing loss of functioning until nutrients and/or neurotransmitters are finally expended. Any comments from those who have studied epilepsy? Ratbone58.170.164.197 (talk) 14:49, 30 April 2012 (UTC)

the high Amplitude of Delta wave production indicates synchronized firing of many neurons (at low frequency). I believe Exploding head syndrome and Life review are other examples of simultaneous activity of large percentage of neurons. --Digrpat (talk) 22:00, 30 April 2012 (UTC)

Does this mean that EHS or seizures could (at least in theory) result if the executive functions were somehow artificially accelerated too much? (The idea of such acceleration was what motivated the question, because I've read about the "executive bottleneck" hypothesis and am interested in cognitive enhancement.) NeonMerlin 12:17, 1 May 2012 (UTC)

200 Hz is a rate you only see in brief bursts, usually not more than 5 or 10 spikes. There are areas of the brain where most of the neurons run constantly at 50 Hz or more, but those areas only make up a small fraction of the total brain. In the cerebral cortex, the great majority of neurons fire at overall time-averaged rates of 10 Hz or less, although individual neurons can ramp up quite a bit from that for brief periods when they are active. During an epileptic seizure the rates go up substantially, but I don't have any figures -- I'm pretty sure the max rate is far below 200 Hz, though. Looie496 (talk) 04:20, 1 May 2012 (UTC)

Hydraulics/Pressure question

I have a box with a shaft passing through it. The box (completely insulated of course) is filled with a hydraulic fluid maintained at a certain pressure (say, 10 bar). When the shaft rotates (say, at 1500 RPM), will the pressure acting on the walls of the box change? If so, how? 117.216.154.47 (talk) 12:39, 30 April 2012 (UTC)

Somewhat irrespective of the pressure within the box, as any practical fluid will have a finite viscosity, the rotating shaft will tend to drag round the fluid with it, the the thereby rotating fluid will try to drag round the box as well. If the box is not externally constrained, then it will rotate at the same speed as the shaft. If the box is externally prevented from rotating, then there will be power dissipated in the fluid. If viscosity is sufficient, the power absorbed in the fluid will raise its' temperature. All practical fluids expand slightly with temperature, so if the box is trulely rigid, and the seals perfect, infinite pressure could in theory be attained. In practice, at reasonable speeds like 1500 RPM, things will be different. Practical fluids show a marked decrease in viscosity with temperature, and (usually) a very slight decrease in viscosity with pressure. This means that in practice, you are likely to have the fluid temperature settle at a slightly raised temperature with little change in pressure (depending on the box & shaft dimensions, perhaps not even measurable), as it will settle at a temperature just great enough to reduce the viscosity so as to absorb just enough power to maintain that temperature. See http://en.wikipedia.org/wiki/Viscosity Ratbone58.170.164.197 (talk) 14:38, 30 April 2012 (UTC)

I know this is a stupid followup question, but here goes. Due to the rotation of the fluid, won't there be any "centrifugal force" acting on each fluid particle, and hence, won't the pressure in the radial direction increase? — Preceding unsigned comment added by 117.216.154.47 (talk) 18:34, 30 April 2012 (UTC)

It's not a stupid question at all. I should have thought of it myself. However, for centrifugal force to result in pressure on the walls of the box, there must be sufficient centrifugal force to overcome internal cohesive (atomic) forces within the fluid, added to the static pressure, forming tiny pockets of vacuum. This could be achieved by making the radial size of the box large enough with respect to the given RPM. If the box is externally constrained from rotating, it may be difficult to get the fluid rotating fast enough. Below the critical speed, there will be no pockets of vacuum and no increase in pressure due to centrifugal force at all. Ratbone124.182.4.180 (talk) 04:17, 1 May 2012 (UTC)

fever to being cold

If someone went from a fever to being cold constantly and very fast would it be enough to kill (I am asking this out of curiosity). --86.41.70.125 (talk) 14:57, 30 April 2012 (UTC)

Not sure what you mean:

1) If they go from feeling hot to feeling cold, this can be a sign of disease, but how they feel won't directly effect their health.

2) If the temperature in the environment suddenly changes, this can cause shock, and potentially could kill you do to a heart attack. However, lots of people do just that, like the Polar Bear Club and those who go from a hot sauna to rolling naked in the snow.

3) If you mean your core body temperature suddenly changes by a large amount, that certainly would be unhealthy, perhaps shattering bones and teeth, but this isn't possible. StuRat (talk) 15:39, 30 April 2012 (UTC)

No I mean if one was to from fever to being cold and then get a fever again and being cold again then it gets repeated over and over again would it be enough to kill them. --86.45.153.97 (talk) 16:13, 1 May 2012 (UTC)

You just repeated the same thing again. If I didn't understand the first time, then repeating it won't help. Which of the 3 I listed do you mean ? If you mean something else, try explaining it using different words. Specifically, please tell me precisely what is making them hot or cold, and whether they really are hot and cold or merely feel that way. StuRat (talk) 18:26, 1 May 2012 (UTC)

I mean is someone going from being hot to cold repeatly for a period of time. --86.45.153.65 (talk) 19:57, 1 May 2012 (UTC)

You still haven't said what is causing them to get hot and then cold. Without knowing that, I can't answer. Is the temperature around them changing rapidly ? StuRat (talk) 20:12, 1 May 2012 (UTC)

Parasitic pepper twin ?

Bell peppers often have something "extra" inside. It looks like a small pepper, itself, and is often tadpole shaped (but curled up). They are usually attached at the stem, but other times are not attached at all, rather rattling around inside. Is this a parasitic twin ? StuRat (talk) 16:11, 30 April 2012 (UTC)

It's known as an "internal proliferation" and is a form of Parthenocarpy according to this - see also this. Mikenorton (talk) 16:15, 30 April 2012 (UTC)

OK, thanks for the info. I'll mark this resolved. StuRat (talk) 18:12, 1 May 2012 (UTC)

Resolved

Engineering at university

At most universities, are engineering modules taught by a wide range of schools/departments e.g. Maths department, environmental sciences department etc or is it all taught by an engineering department? 80.195.94.171 (talk) 16:26, 30 April 2012 (UTC)

This is very much school-specific. My undergraduate university, which offered accredited degrees in Electrical Engineering and Computer Science, (and many other engineering and non-engineering fields), had certain mathematics courses that could be taken via the math department or via the computer science department. Certain classes were considered "interchangeable," and others required specific departmental course codes. In my graduate program, specific modules were recommended to be taught by individual professors, irrespective of their department. Many professors officially sat in multiple departments, e.g., the physics and computer science and the mathematics department, for reasons of academic politics - so I had the option to list a few courses as either a physics, or as a math, or as a computer science class - even though it was the same material and the same classroom. It's difficult to get statistics for "most" universities, but a good place to begin checking is the accreditation requirements for universities in your region.

For example, my undergraduate institution's accrediting board was the ABET. Here's an overview of what that exactly means: Proud to be an ABET Accredited Program. Roughly, this means that an independent board of academic experts, not affiliated with the university, has certified that our required mathematics and engineering courses are "very rigorous," and meet exacting standards, which-ever department actually is responsible for delivering the instruction. Nimur (talk) 16:55, 30 April 2012 (UTC)

Here in the UK you'll see an engineering department at most universities, but undergrads can be expected to have to trot to the maths department (and others) for the occasional lecture. LukeSurl ^{t c} 23:27, 30 April 2012 (UTC)

Ex-UK lecturer here: my old department used to provide modules for other departments so we used to have to teach our subject area in other departments. Sometimes this meant I'd have to teach in places such as art studios, machine rooms or draughting rooms. So it's not the case that the students would have to move around: lecturers also moved. I guess it depended on what was easiest to timetable. --TammyMoet (talk) 02:00, 1 May 2012 (UTC)

When I did my Bachelor of Engineering course, not only were math subjects taught by the Math Department, physics subjects taught by the Physics department, and the one solitary chemistry unit taught by the Chemistry department, in the fisrt two years of the (4 year) course, the university compelled you to do what they called "broadening units" with the stated intent of making you a more balanced man. For broadening units, you could pick whatever units from any uni course you liked, subject to timetable conflicts and subject prerequisites. I chose psychology and journalism units - and never regreted it.

At least here in Australia, universities providing engineering and certain other degrees considered to have academic significance (eg medicine) have for many years compelled undergrads to first do a "common first year", the first year of an Arts degree, or even a whole Arts degree. This is driven because the standard of education in Australian high schools has been slowly dropping for years - I believe the USA also has this problem. High school graduates used to be well equiped to tackle a solid degree, but they are not now.

At the Uni I went to, the allocation of rooms was another matter. I think the central administration used some sort of computer program to allocate rooms, and to the computer a room was a room was a room... We were continually walking from one end of campus to the other. It kept us fit.

Ratbone124.182.4.180 (talk) 03:34, 1 May 2012 (UTC)

Mechanical engineers often need computer science subjects (for control systems), management is a common topic on engineering courses (for project management etc), and some civil engineers study architecture, as well as the usual mathematics courses. There's a lot of potential subjects, and they may be taught by lecturers from other departments, or on courses run by other departments, or even by engineering faculty/department lecturers. --Colapeninsula (talk) 08:50, 1 May 2012 (UTC)

In the U.S., at least, I am pretty sure it is similar to the Australian example above. At most universities in the U.S., one would only take the engineering specific courses in the Engineering department. Thus, while a Chemical Engineer would need to take calculus and organic chemistry and fluid dynamics, it would be usual to take the calculus class from the Math department, the organic chemistry from the Chemistry department, and the Fluid Dynamics class from the Chemical Engineering department. This may be more efficient for the university, as Calculus is going to be the same whether it is used by a Chemical Engineer or an Economist, so they can sit in the same room and learn about integrals and differentials next to each other, so there's no real need to teach a sepetate "chemical engineer only" calculus class. --Jayron32 18:14, 1 May 2012 (UTC)

At my (American) university that I attend now, we do have an engineering section of calculus, with TAs who are engineers, that focuses towards applications of calculus in engineering. At a different school I have attended, they had two sets of chemistry classes, one in the liberal arts school, and another in the engineering/hard science school. In general though, I think Jayron32 is correct, at least in my experience. Buddy431 (talk) 18:40, 1 May 2012 (UTC)

At my undergrad school, the main required calculus course was taught by the math department and from a "pure" viewpoint. The engineers probably didn't think they needed quite so many proofs, but it was considered important to teach them to them anyway, for culture. --Trovatore (talk) 18:45, 1 May 2012 (UTC)

It's part of the long and continuous debate in education on the value of a liberal arts education versus a vocational education. The former aims to train a "complete citizen" by giving them the tools they need to do many jobs, and also to be a more complete citizen, fully engaged with the culture, history, and society. The latter focuses purely on skills that train one for their job, ignoring the rest. --Jayron32 23:32, 1 May 2012 (UTC)

A further comment on something touhed on by Nimur above - a reflection on the adminstrative/political/acreditation quirks of universities - Australian ones at least. I did my bachelor degree in electronic engineering - comprising a common first year - a mix of just about anything, then 3 futher years specialising in electronics with significant amounts of Math from teh Math Dept and some physics from Physics dept. In third year, us electronics students got programmed to do a unit called "Control Systems 304". In Uni nomenclature, the 3 in "304" means a third year unit, the 0 means its supposed to be of only moderate intellectual and workload challenge, and the 4 means the 4th revison of the unit since the degree was acredited. Electrical students got programmed to do a unit called "Feedback Modelling 316". The "1" in 316 means that the unit is of higher intellectual and workload challenge. Mechanical engineers got to do a unit called something else again. We all went to the same room and got taught the same thing by the same lecturer! Each subject unit was allocated so many points. The points for C304 were different to FM316. To be awarded a degree, you needed a total of x many points. At exam time, we got to do the same exam papers labelled with all three subject names and codes. So the same subject, actually about various forms of negative feedback, is supposedly easy or difficult depending on what degree your are doing! What utter nonsense. Keit120.145.52.89 (talk) 04:07, 2 May 2012 (UTC)

highest decibel rating of any fling insect.

i asked this question in the entertaiment section but i hope i can get also answers here. Wich insect has the loudest decuibel rating when the insect flies? — Preceding unsigned comment added by Saludacymbals (talk • contribs) 20:23, 30 April 2012 (UTC)

Considering "loudest" to mean the highest decibel rating, I think you are looking for a massive insect that is also in some sense a poor flyer. Echoing some comments from the other Q: As Alansplodge pointed out, a dragonfly can be large, but are amazing fliers and quite quiet. Bumblebees are loud, but are not so loud as a cicada or cicada killer, perhaps in part due to mass differences. I have never heard a Hercules beetle or Goliathus goliatus in flight, but I would think the latter could easily be louder yet, perhaps the loudest. One interesting aspect of your question is that it would be relatively straightforward to gather some big bugs and do some audio testing, but somehow I think nobody has :) SemanticMantis (talk) 00:11, 1 May 2012 (UTC)

Since none of our photos give a good sense of scale, check out G. goliathus here [4]. SemanticMantis (talk) 00:16, 1 May 2012 (UTC)

so is even a cicadfa when it flyes loud?(article edited) Secmantimantis i meant any insect! — Preceding unsigned comment added by Saludacymbals (talk • contribs) 10:11, 1 May 2012 (UTC)

Yes, cicadas are loud flyers. In the USA, it is the loudest insect flight I commonly hear. green fruit beetles are also loud, but I think cicadas are louder. (This is all original research). Among all insects, I guessed the large beetles that I listed above might be loudest. I've looked through the scientific literature, and the only relevant material I found comes from bat research. For example, this paper [5] discusses how insect wing beats reflect sonar signals. This is not the same as loudness, but it's a start. SemanticMantis (talk) 13:12, 1 May 2012 (UTC)

May 1

Entangled Qubits as Polarized Light

I'm trying to find a way to visualize entangled states, as might be used in a quantum computer. The various articles I can find, and my physics textbook, make vague references to polarized light as a simple model for a qubit. I can understand the one-qubit case, since the components of the electric wave in two orthogonal axes for a coherent beam of light or a single photon will consist of two phasors, represented as two complex numbers, where overall amplitude and phase can be ignored. What's left is the two dimensions of polarization, representing angle and eccentricity. Gates are passing through eg a fluid that rotates polarization, and measurement is passing through a polarizing filter. So a two-qubit register should be two beams of light, or perhaps a beam of light with two colors. I haven't found anything that specifies which it is. Where I get lost is understanding how these bits can become entangled, and where the process can go from there. Black Carrot (talk) 00:30, 1 May 2012 (UTC)

Size of the cat's eye nebula

Our article says that the core is 0.2 ly. Obviously it doesn't burn like a star, so what defines the core? And how large is the entire nebula? Even a ballpark figure would help me. Thanks, --T H F S W (T · C · E) 05:19, 1 May 2012 (UTC)

The angular diameter is about 5 arcmin, which corresponds to roughly 5 ly at that distance. The planetary nebula itself corresponds to the bright inner core, so that is material that was ejected at once when the star entered its PN phase. The larger fainter nebula is material that was ejected over a longer period before that, when the star was a red giant. --Wrongfilter (talk) 08:35, 1 May 2012 (UTC)

So the core is the part we see in all those classic pictures? --T H F S W (T · C · E) 16:16, 1 May 2012 (UTC)

Air in submerged car

Assuming a normal family car was submerged without it being smashed about, and there was one adult inside, roughly how long could they survive on air trapped in the vehicle?

If they inflated the air bags and punctured them, would that help, and if so, to what extent? --Dweller (talk) 09:36, 1 May 2012 (UTC)

Airbags don't contain air - they contain the output of gas generators, which are essentially little rocket engines. You wouldn't want to be breathing that. -- Finlay McWalterჷTalk 09:42, 1 May 2012 (UTC)

I did wonder! OK, how about the air naturally in the car? --Dweller (talk) 10:37, 1 May 2012 (UTC)

Since cars are far from airtight the air would remain "trapped" for only a short time. It would probably take only a matter of seconds rather than minutes for the cabin to fill up with water as the air escapes through the door "seals" and other gaps. Roger (talk) 10:46, 1 May 2012 (UTC)

Interesting. The engine is the heaviest part of the car, so I guess it would nose-dive, leaving whatever air there is against the back window. In a saloon car with no hatchback, there's no door seals there. Would there be as much as a minute's worth of air, or more? --Dweller (talk) 10:49, 1 May 2012 (UTC)

Chappaquiddick incident#Testimony and cause of death contains some supposition on this subject. -- ToE 11:22, 1 May 2012 (UTC)

Mythbusters did a number of submerged car escape myths (you can google for videos). Based on their videos the engine pulls the car down nose first and it seems to take about 30-40 seconds for the front to fill and 60-75 total seconds for the air to also escape from the back seat. Of course, the precise time will vary with the make of the car, etc. Dragons flight (talk) 11:50, 1 May 2012 (UTC)

Have a look at [6] for a practical demonstration. The accompanying notes are interesting. Bazza (talk) 13:37, 1 May 2012 (UTC)

It's also important to note that you normally do not want to stay as long as possible in the car. Quite in contrary, you should try to open the windows to let water flow inside (so you can open the doors. 188.76.235.0 (talk) 13:49, 1 May 2012 (UTC)

If car does drop to the point where you can't open the door and your power windows are shorted out and you are in shallow water, then waiting for the car to fill with water so you can open the door may be your only option. Hopefully you could use that time to unbuckle, get into position, calm down and take deep breaths, for your break for the surface once the pressure equalizes. StuRat (talk) 18:10, 1 May 2012 (UTC)

Googling for something like cubic meter breathe air suffocate suggests that for a person in rest, one cubic meter of air should last about two hours until it has too little oxygen and too much carbon dioxide. Heavy physical activity can cut that time by a factor of ten; I imagine the stress of being in a submerged car will cause you to breathe heavily. If your car's interior volume is, say, three cubic meters, that would be of the order of a couple of hours. If partially filled with water, adjust accordingly. If your head is barely above surface, in a bubble of a couple of bucketfuls of air, let's call it one minute per bucket tops. 88.114.124.228 (talk) 16:13, 1 May 2012 (UTC)

This formula from an atmospheric sciences course is pretty fascinating. --Sean 20:59, 1 May 2012 (UTC)

What does this mean? Gravitational waves should penetrate regions of space that electromagnetic waves cannot.

165.212.189.187 (talk) 13:04, 1 May 2012 (UTC)

As far as I know, electromagnetic waves, or radiation, can penetrate any region of space. So, the statement does not make sense to me either. Plasmic Physics (talk) 13:16, 1 May 2012 (UTC)

Well, light can be blocked by solid materials, whereas gravity cannot. That must be what they are referring to. Goodbye Galaxy (talk) 13:35, 1 May 2012 (UTC)

Electromagnetic waves of frequencies up to up to microwaves are dramatically attenutated by magnetic shielding and by faraday cages - see http://en.wikipedia.org/wiki/Faraday_cage. It is quite simple to make a faraday cage to reduce incident radiation to levels too low to measure. The next thing after microwaves is infrared thru to light - which is blocked by all sorts of things including metals. Gravitational waves are predicted to penetrate all these things. Keit58.164.230.165 (talk) 13:46, 1 May 2012 (UTC)

Could it be worded better?165.212.189.187 (talk) 14:12, 1 May 2012 (UTC)

But do faraday cages block ALL radiation?165.212.189.187 (talk) 15:47, 1 May 2012 (UTC)

Since you can see into a Faraday cage, obviously not. Gandalf61 (talk) 15:52, 1 May 2012 (UTC)

The blocking of radiation depends on the scale of the mesh. A tighter mesh blocks more ranges of radiation. OsmanRF34 (talk) 15:59, 1 May 2012 (UTC)

EM radiation is not blocked 100%, it decays at an exponential rate, but never reaches zero completely. Plasmic Physics (talk) 22:08, 1 May 2012 (UTC)

Touche. I was particularly thinking of a solid one to rule out the light issue. Then the word "should" should be removed bc we know it DOES, right?165.212.189.187 (talk) 17:17, 1 May 2012 (UTC)

No, we don't know that yet. Gravitational waves have not been successfully detected. Various theories predict that it could penetrate regions impervious to EM waves, but we don't know that for sure yet. 173.32.168.59 (talk) 17:49, 1 May 2012 (UTC)

Ok I get it. SVT is the best theory so far.165.212.189.187 (talk) 18:06, 1 May 2012 (UTC)

Faraday cages are not perfect. The scale of the mesh is not the only factor. Since the wires or mesh (or even solid sheet) must in practice have electrical resistance, there will be an excess voltage within the walls and the attenuation imperfect. However, by suitable choice in wire/mesh weight, and double screening if necessary, any required attenuation can be achieved. But the attenuation is not an exponential decay. Exponential decay of EM waves occurs in dielectrics, however, and gravity waves are thought not so attenuated. Ratbone120.145.52.89 (talk) 02:10, 2 May 2012 (UTC)

Amputating limbs of quadriplegics

Do quadriplegics need to have their limbs amputated sometimes? Why doesn't the blood clot, if they necessarily won't be moving their limbs? — Preceding unsigned comment added by 188.76.235.0 (talk) 13:22, 1 May 2012 (UTC)

Bones make blood. I think they would want to keep limbs where possible. Zzubnik (talk) 14:33, 1 May 2012 (UTC)

Not sure if that's a valid reason. After all, fewer limbs also mean less blood is needed, so less red-cell generating capacity is OK. Some reasons to keep the limbs might be psychological considerations and the hope that they might one day be cured of their quadriplegic condition, say by use of stem cells to regenerate the nerves. StuRat (talk) 17:59, 1 May 2012 (UTC)

And they do have problems with blood clots, see Tetraplegia which notes that such people have high rates of Deep vein thrombosis. --Jayron32 16:23, 1 May 2012 (UTC)

wasp

A few months ago I noticed a wasp in a cupboard in my house. I don't know how long it had been there, but it looked pretty dead to me. I didn't get rid of it because, well, I couldn't be bothered to and it wasn't affecting me. A few weeks later I go in the cupboard again and it's still there, exactly the same as before, it hasn't moved at all. So I am now certain it is dead. Again I just leave it because I'm really lazy. Today, I noticed a wasp buzzing around the house so I opened a window and let it go. Then I thought.. no way, it couldn't be the wasp in the cupboard, could it? I checked and it's gone. So.. do wasps hibernate or something? I'm assuming it was the same wasp, although I can't be certain. It looked like a normal wasp to me and not a big queen wasp. — Preceding unsigned comment added by Waspgirl03 (talk • contribs) 20:32, 1 May 2012 (UTC)

I doubt if it's the same wasp. It might have been cleaned up by somebody else, blown out of the cabinet when somebody opened the door, or perhaps some other critter dragged it off to eat it. (After it dehydrated, it would be far lighter and more prone to blowing around.) StuRat (talk) 20:43, 1 May 2012 (UTC)

Nobody else is here but me, and I am certain I didn't accidentally move it. I looked around nearby I didn't find it. Also, it wasn't on it's back it was actually hanging onto a cardboard box in a pose which seemed like it could have been alive if I had seen it outside and moving Waspgirl03 (talk) 21:16, 1 May 2012 (UTC)

Social insects will routinely "bring out their dead" in order to keep their place tidy. Perhaps you saw the pall bearer leaving. --Sean 21:02, 1 May 2012 (UTC)

I don't understand. Bring out the dead wasp from my cupboard to somewhere else? For what purpose? And why did it wait several months to do it? Waspgirl03 (talk) 21:16, 1 May 2012 (UTC)

According to various web pages wasps do hibernate, usually in warm sheltered places, and at least in the UK tend to emerge somewhere around mid-April -- so all that seems consistent, but it would have to have been a queen. Looie496 (talk) 21:57, 1 May 2012 (UTC)

I'm in the UK, so I guess it must have been a queen then. Do the queens look very similar to normal wasps? I assumed they would be a lot bigger Waspgirl03 (talk) 22:01, 1 May 2012 (UTC)

They're _noticeably_ bigger, but not a _lot_ bigger. This site has a picture of a (very dead) worker and (equally dead) queen next to each other for comparison. See Vespula vulgaris for our article on the beasties, incidentally. Tevildo (talk) 22:21, 1 May 2012 (UTC)

I figure I should know the answer to this kind of question, since my user name is vespine, (it's not because I'm an expert, I just like wasps, and the word vespine) .. So after reading the wasp article, I think I found the answer: In most species of social wasp the young queens mate in the vicinity of their home nest and do not travel like their male counterparts do. The young queens will then leave the colony to hibernate for the winter once the other worker wasps and founder queen have started to die off. So a YOUNG wasp might not even be fully grown yet, making it probably indistinguishable from any other wasp. Vespine (talk) 02:22, 2 May 2012 (UTC)

May 2

Meditation and Sleep

I read somewhere many years ago that someone had done a study on meditation and sleep, and found that if you meditate for half an hour every day, you can get by on four hours of sleep with no ill effects. (My numbers may be wrong. It has been years since I read this, after all.) It seems like everyone has heard something like this, but I've never been able to find the study.

I've taken several Vipassana courses, and Goenka says that anapana meditation can completely replace sleep--but he also says that he can feel his sub-atomic particles vibrating, so I don't consider him a very reliable source. It's the same on Google--many of the people talking about meditation also talk about developing psychic powers and the like, and almost never cite any experiments.

So did any such experiment ever occur? 67.142.166.24 (talk) 00:25, 2 May 2012 (UTC)

I can see meditation, like any form of rest, slightly reducing the amount of sleep needed at night, but not eliminating it. StuRat (talk) 00:40, 2 May 2012 (UTC)

It's probably not the study you are thinking of, but http://www.biomedcentral.com/content/pdf/1744-9081-6-47.pdf is a very recent study that addresses the issues and also gives pointers to the earlier literature (not that there is much of it). This is unfortunately an area where many practitioners make wild claims not backed up by solid evidence. Looie496 (talk) 00:41, 2 May 2012 (UTC)

One of the largest proponents of this must be Transcendental Meditation, some of those loons claim they can fly! Vespine (talk) 01:56, 2 May 2012 (UTC)

It would take an excedingly well designed and carefully conducted experiment to prove anything anyway, because anyone can train themself to reduce the amount of sleep required. During Word War 2 in the Pacific, soldiers got used to months on end with very little sleep. I enrolled at university when I was working full time - the boss let me take time off during the day to attend lectures providing I came back later in the same day to get my work done. In order to get all the assignments done, I reduced my sleep from 8 hours per night to 6 hours per night without any problems other than feeling sleepy for the first month or so only. I kept this up for 7 years until I had the enginering degrees I wanted. It took about another 3 years until I drifted back to 7 hours per night. I have also found that when changing careers, which I have done 4 times, the amount of time I sleep increases temporarily. So I would think that if you avoid mental stimulation (perhaps by doing too much meditation), you will need less sleep. I know some old retired folks who complain they onnly can sleep 4 hours or so each night. Given that they mostly spend their days sitting around watching television, I'm not surprised. Ratbone120.145.52.89 (talk) 02:23, 2 May 2012 (UTC)