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May 12

Eye of a hurricane question

I was not able to find the answer to this query in the article on Eye (cyclone). Anyway, I remember a movie from many years ago where one of the characters (it may have been Larry Hagman)was in his yacht and got caught up in a hurricane. Although he tried to out run it, alas, the hurricane caught up to him. However, he was able to ride out the hurricane and survived to find himself in the eye. While in the eye, he was rescued by a navy sub!

OK. I'm quite certain that this could not happen but am wondering about the physics of why not. I am sure that there have been boats, ships, etc. who have had to weather the storm and found themselves in the eys. What would prevent a sub from surfacing within the eye (to either affect a necessary rescue or to perform some scientific experiment/observation)? 99.250.117.26 (talk) 00:55, 12 May 2011 (UTC)

Nothing. Though, it would be risky. Plasmic Physics (talk) 01:18, 12 May 2011 (UTC)

I don't even see why it would be risky, except that there would be a certain amount of wave activity. Looie496 (talk) 01:57, 12 May 2011 (UTC)

A large amount of wave activity. Not only can there be waves over 100 feet high, but in the eye the waves are chaotic and coming from all different directions, since the wind which causes these waves is convergent towards the eye. I remember seeing footage from a hurricane hunter (I believe it was Hurricane Gilbert showing whitecaps around 50 feet high breaking over each other in all directions: not the kind place you'd want to have two water craft anywhere near each other. That said, how strong was this hurricane? In a weak one it might be plausible.

The question concerns the surfacing of the sub, ignoring interactions with the other vessel. Even subs are a risk of capsizing in such turbulance. I also say it's risky, because you have track the eye - you don't want to be caught outside of the eye. Plasmic Physics (talk) 03:22, 12 May 2011 (UTC)

Also notice that the yacht would have had to pass through the eye wall, which is absolutely the worst part of a hurricane. Perhaps in the story he did that while it was only Category 1, then it grew to something bigger ? StuRat (talk) 06:54, 12 May 2011 (UTC)

From a meteorological standpoint, it depends on the strength, direction, speed, and physical size of the hurricane, among other things (intensity trends, etc.). The eye wall is most severe in the northeastern quadrant, and slightly weaker as you get further south and west. Also, some hurricanes are lopsided, especially as they begin to transition into extratropical storms. In such a morphing cyclone, the northern semicircle may possess hundreds of miles of convection while the lower-level center of circulation is exposed on the southern side. Obviously, as noted above, waves probably wouldn't be all that high, even in the eye, where waves from all directions converge. A marginal Cat 1 may only have 15 or 20 foot waves, especially in the formative stages, and the 100-foot trough to crest monsters we hear about are exceptionally rare, and there's no way most vessels would be able to ride that out in the first place. Juliancolton (talk) 20:18, 12 May 2011 (UTC)

Hospital planning

questions are........1eqment planning for 3oo bedded hospital? 2-role of varius people involved in hospital project? 3-planning of various department like .... opd , casualty, blood bank , cssd ,i.c.u. cath lab ,it department, how to planning for 3oo beed hospital ans n brief detail.... 4-norms for operation designing in hospital? —Preceding unsigned comment added by Twinkeptel87 (talk • contribs) 06:25, 12 May 2011 (UTC)

This looks like a homework question. The Misplaced Pages Reference Desks don't answer homework questions - if we did you wouldn't learn anything! Tell us how far you have reached and what aspects are causing you trouble and we will give you some hints to help you on your way. Dolphin (t) 07:50, 12 May 2011 (UTC)

Our article Hospital has a section about Hospital#Buildings that may interest. This article and these guidelines give detailed planning information. Cuddlyable3 (talk) 10:30, 12 May 2011 (UTC)

Tips on building an LCD

I'm considering building my own Tiger LCD game, but this would require building an LCD from scratch in order to etch the correct patterns onto the electrode layer. I could use an off-the-shelf graphic LCD, but I'd like to stay true to the actual Tiger games.

I found a post that pretty much describes the way I thought of doing it at http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=40355 (ignoramus, Jul 17, 2006 03:06 PM), but the post is more of an overview than a guide.

My questions are:

What is the recommended liquid crystal for this purpose?

How exactly do you coat the glass with the liquid crystal?

For the polarizers, would this work if it is cut and both pieces are in the correct orientation?

And where can you buy the liquid crystal and ITO glass? I see Sigma Aldrich has both, but they are quite expensive. They sell ITO coated plastic film for cheap, but it is also very thin, and I'm not sure if it would survive etching (and it also couldn't be heated, I assume).

[Links to Sigma Aldrich pages :

ITO: http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=9548901

Liquid crystals: http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=16378837

Links to other sources are appreciated.]

I was unsure if this should go in computing or science, but since I am asking about chemical sources and the use of the chemicals, I decided it was more apt to be here.

Thanks in advance! —Preceding unsigned comment added by EEPROM Eagle (talk • contribs) 14:14, 12 May 2011 (UTC)

May I ask why you don't just use a standard LCD with a grid of pixels ? StuRat (talk) 19:04, 12 May 2011 (UTC)

No reason that I can't. The choice is basically for the accuracy of how mass produced LCD games usually work, and for learning and fun. I'd certainly be taking a much more difficult (and expensive) route this way. :) EEPROM Eagle (talk) 19:56, 12 May 2011 (UTC)

This is a very specific question, I think you'd be lucky to find someone here who has done specifically what you are looking for.. Why don't you join the avrfreaks board and contact the user? I've worked on a few AVR projects and was an active member there a few years ago, i have very fond memories of that board, probably the best support forum I've ever participated in. Some truly smart, helpful and funny folks there. Vespine (talk) 23:36, 12 May 2011 (UTC)

My partial understanding of Liquid crystal displays is that the pattern is not etched but deposited as a transparent conducting film of Indium tin oxide after painting a mask on the non-conductive areas. The liquid crystal is not painted on the glass, it is just a drop of fluid that is squeezed between the plates which are pressed together with thin spacers. Cuddlyable3 (talk) 13:26, 13 May 2011 (UTC)

I contacted him and he said he used an eyedropper to add the liquid crystal, so that makes sense with what Cuddlyable3 said. In addition to that post, I had read this wikiHow article about etching the glass, so I think it may work either way (etching the glass or creating a mask before the ITO is deposited onto it.

I still don't know where to find the supplies or what liquid crystal to get. I've looked on Alibaba for ITO glass, but am not sure about minimum orders or payment. I also checked there for liquid crystal but couldn't find much.

Thanks for all the help you've provided so far! EEPROM Eagle (talk) 22:34, 13 May 2011 (UTC)

This supplier may be what you seek. Cuddlyable3 (talk) 23:01, 13 May 2011 (UTC)

Hmmm, looks interesting, but they seem to list more uses regarding temperature sensitivity, and the article here for cholesterol, under "cholesteric liquid crystals", says that it "changes colour when its temperature changes." I could see that being an issue. :) EEPROM Eagle (talk) 01:31, 14 May 2011 (UTC)

Spy plane

I would like to know the name of the spy plane that have a large radar dome on top. Note: its not a turbo prop plane. Link to article appreciated. --Tyw7  (☎ Contact me! • Contributions)   → Gotta catch 'em all! 15:21, 12 May 2011 (UTC)

That would be AWACS (airborne warning and control) planes - they're not exactly "spy" planes, their role is monitoring air traffic for unauthorized flights or missile attacks -- Ferkelparade π 15:23, 12 May 2011 (UTC)

THanks. No wonder I couldn't find it. I was trying to search for spy planes. --Tyw7  (☎ Contact me! • Contributions)   Misplaced Pages, the 💕. 15:42, 12 May 2011 (UTC)

The E-1, E-2 and E-3 had large external radomes. A few other "nonstandard" American military aircraft have also had radomes mounted during testing and special operations. More recent advances in directional antennas, synthetic aperture RADAR, and phased array antennas have mostly obsoleted the need for an external radome. Nimur (talk) 19:43, 12 May 2011 (UTC)

I was looking for the Boeing E-3 Sentry. --Tyw7  (☎ Contact me! • Contributions)   → Do a good turn daily 21:39, 12 May 2011 (UTC)

mass of an atom in kinetic collisions

We note that electrons occupy most of the space in a molecule or an atom, but the nuclei have most of the mass. I am curious then, but the kinematics of a collision between two molecules or two atoms -- how exactly does an electronic collision lead to the movement of nuclei? We note that if a very small atom or molecule (like hydrogen) bounces off a very heavy one, the small atom cannot lose much of its kinetic energy, due to the law of elastic kinetic collisions base on the ratio of the two masses. How is this mass brought into play, if it is stored in the nucleus? Elle _{vécut heureuse} (be free) 19:48, 12 May 2011 (UTC)

The nuclei repel each other because they have similar electric charges. Dauto (talk) 20:25, 12 May 2011 (UTC)

This doesn't explain the Franck-Hertz experiment. I'm pretty sure the nuclei never come close to each other for nuclear-nuclear repulsion to be a significant force. Elle _{vécut heureuse} (be free) 20:50, 12 May 2011 (UTC)

(edit conflict)To answer the other question about mass distribution: for single atoms, a solid sphere with evenly distributed mass and a hollow, massless shell with a concentrated mass at the exact center will behave exactly the same. Atoms, however, only have one degree of freedom for its kinetic energy, that being translation, or movement through space. Molecules, depending on their shape, can have additional degrees of freedom, which include rotation and vibration. The organization of an atom certainly does have an effect on the results of collisions; however in the bulk substance, it makes MUCH more sense to think of these effects statisticly, rather than trying to treat them as a series of discrete events. Take something as simple as two gas-phase water molecules colliding, but from a classical mechanics sense. Depending on the angle, orientation, and incoming speed, such a collision could result in exhanges of kinetic energy between the water molecules which could result in either molecule changing its linear speed or trajectory (translation) or it could set one or the other molecule spinning (rotation) or it could introduce some bending and flexing within the molecule (vibration). It turns out that things like vibration and rotation are quantized at the molecular level, so treating them in a "classical, Newtonian" sense doesn't actually make much sense. Treating these motions in a statistical sense, as Ludwig Boltzmann's life work was about, makes more sense and quantum mechanical treatment of these modes of motion is how we actually make these calculations, see Rigid_rotor#The_quantum_mechanical_linear_rigid_rotor for a discussion of the mathematics behind calculating the rotational dynamics of a diatomic molecule. This is why temperature exists as a physical property in the first place; considering all of the multitude of motions involved in a substance on a individual molecular level isn't particularly helpful in understanding the behavior of the substance. --Jayron32 20:53, 12 May 2011 (UTC)

(edit conflict) Atoms and/or ions collide all the time; we have different names for various scenarios, because we use different physics and different equations to model them. If electrons are present on one atom, but not on the other, the phenomenon is called Rutherford scattering. If electrons are present on both atoms, the collision is described via chemical kinetics or "reaction kinematics" (a quantum chemistry treatment is needed for all but trivial examples). If electrons are not present around either atom, the result is nuclear scattering, whose effects can be dictated by either electrostatic or nuclear forces. Nimur (talk) 20:55, 12 May 2011 (UTC)

okay, it's just that I've been making these assumptions since forever. They tell me that hard spheres is a reasonable simplification -- I can believe that. But why should it behave like it has homogeneously distributed mass when most of it is in the centre? What about Franck-hertz -- which sounds more like electron-electron scattering, but instead the energy lost during elastic collisions is closer to a collision between a 0.000548 amu e- and a 200.59 amu mercury atom? Surely the electron is only encountering the electron cloud? Why does the electron cloud behave like it has so much mass? Elle _{vécut heureuse} (be free) 21:07, 12 May 2011 (UTC)

Because the electrons are so light compard to the nucleus, the electron cloud can adjust itself very fast when a charge approaches it. This is the rationale behind the Born-Oppenheimer approximation. The electron clouds at some given time are approximately the solution of the stationary Schrödinger equation, where you take the positions of the nuclei fixed. To a good approximation, the nuclei then interact with each other via an effective potential that you get when you add to the mutual Coulomb interaction the screening of the perturbed electron clouds.

You can exactly work out the case of two Hydrogen atoms in perturbation theory. If you take the two protons to be at fixed positions, then each electron is in the field of two protons and the other electron. If you treat the extra terms as a perturbation, you find that to second order in perturbation theory, the ground state energy is shifted. The ground state of this system drops in energy as the two atoms become closer to each other. Since this is the energy at rest of the atoms, this is the effective potential energy of the two atoms (this is the van der Waals interaction). So, atom-atom scattering at low energies can be described using this effective potential. But you see that this works precisely because the electrons are so light. Count Iblis (talk) 03:03, 13 May 2011 (UTC)

So is the hard sphere assumption (neglecting H-H bond formation -- just looking at a collision event) valid for this case? In the Franck-Hertz experiment, how does an energetic "free" electron feel the mass of the mercury nucleus? Elle _{vécut heureuse} (be free) 05:09, 13 May 2011 (UTC)

Well, what is de-Broglie wavelength of a 10 eV electron compared to the size of an atom? So, if such an electron interacts with the electron cloud, what you get is (with significant probability) a coherent interaction with the entire electron cloud that takes place on a time scale that is larger than the time scale on which electron cloud perturbations relax to new equilibrium states by transfering momentum to the nucleus.

So, you have a significant probability of an elastic interaction of the electron with the entire atom. You can compare this to how you have a significant probability that a neutron colliding with a nucleus in a crystal lattice will not produce a phonon, and instead the whole lattice will recoil as a whole. So, how can the neutron then feel the mass of the entire lattice instead of the single nucleus? Of course, this is all due to basic quantum mechanics, just compute the Debye Waller factor at zero temperature. Count Iblis (talk) 16:01, 13 May 2011 (UTC)

Identifying distant sources of light

A recent article (BBC News) noted that a gamma-ray emission (lasting six days), emanating from a small region of the Crab Nebula, had been detected in April. The article caused me to wonder about two questions:

1. Can scientists determine definitively whether the flare originated in the Crab Nebula or from a source behind (from our point of view) the nebula?
2. What process do scientists use to calculate, based upon observation of a distant light source, the distance from Earth of that distant object? Perhaps we can, if it will simplify the explanation, ignore considerations introduced by the metric expansion of space?

Thank you, -- Black Falcon 20:37, 12 May 2011 (UTC)

Nuclear processes do not emit light evenly over a broad spectral area, but emit light with the characteristic emission spectra of the involved elements. Astronomers can examine the spectral distribution of a light source, determine which elements are involved, and so measure the red shift of the received light. This allows them, by Hubble's law, to determine how distant the source is. -- Finlay McWalter ☻ Talk 20:46, 12 May 2011 (UTC)

Hubble's law would only apply in general, there are exceptions. So, you want to look at the red shift of the Crab Nebula and see if it matches the red shift of the gamma-ray source. If they match, chances are it's in the Crab Nebula. StuRat (talk) 20:49, 12 May 2011 (UTC)

Yes, that's true. Not only for cosmic oddballs that don't move away as one would generally expect, but particularly within gravitationally bound structures like galaxies. The Andromeda Galaxy article briefly discusses measurement of its rotation by observing the relative redshifts of the approaching and receding sectors of its disk, over and above the overall redshift of the whole thing. -- Finlay McWalter ☻ Talk 21:27, 12 May 2011 (UTC)

As a simple example consider the characteristic double-line emission spectrum of sodium (img). If you see a double-line, but at a different frequency, it's likely that you're seeing sodium, but red-shifted (or occasionally blue-shifted) due to its relative motion; you measure the distance between where you see the double line and where it should be (from your perspective) and that tells you the redshift. In practice things are more complicated, as there are many elements emitting, and some elements have much more complicated spectra (like iron). And some "sources" are really multiple things moving with different relative speeds, that happen to occupy the same piece of the sky (so, for example, you might see the sodium lines redshifted to two different places, because they're coming from two unrelated sources). But figuring out what's what is nevertheless tractable. -- Finlay McWalter ☻ Talk 20:58, 12 May 2011 (UTC)

Thank you both! Your comments and the articles to which you pointed—Hubble's law and Redshift, and from them Doppler effect—have clarified the issue quite a bit. Again, thanks, -- Black Falcon 21:49, 12 May 2011 (UTC)

This is not a new gamma ray source, but fluctuation in the brightness of a source that is always visible (and is, in fact, the brightest gamma ray source in the sky). Crab Nebula#Distance talks about how the distance to the Crab Nebula is measured. Cosmic distance ladder talks about the various methods of judging distances in astronomy. Hubble's law can't be used to find the distance to the Crab Nebula; it only applies at the scale of galactic superclusters and larger. -- BenRG (talk) 22:01, 12 May 2011 (UTC)

2011 Mississippi River floods

How many coal slurry ponds and how much coal slurry has been washed into the Mississippi River Valley so far in the 2011 Mississippi River floods? Can the Old River Control Structure keep most of Baton Rouge and New Orleans from flooding? 99.39.5.103 (talk) 22:35, 12 May 2011 (UTC)

For the latter, the ORCS is not primarily a flood control structure -- the Bonnet Carré Spillway and the Morganza Spillway are the two primary flood relief systems in Louisiana. The Bonnet Carré is already 2/3rds open and the US Army Corps of Engineers is readying the Morganza if needed. Current projections put the current floods below the Project Design Flood, the theoretical flood which these structures are intended to counteract. That said, even ideal operation of all structures along the Mississippi will not prevent Baton Rouge and New Orleans from flooding; indeed, the river gauge at Baton Rouge is already 3.5 feet into "major flood" level with New Orleans hovering at flood level. — Lomn 03:50, 13 May 2011 (UTC)

May 13

What is the role of the autonomic nervous system in uterine contraction?

129.78.32.21 (talk) 01:06, 13 May 2011 (UTC)

Try starting with Uterine contraction . Vespine (talk) 01:47, 13 May 2011 (UTC)

Hi. The page doesn't really specify the type of nervous system control over uterine contraction. 129.78.32.21 (talk) 01:55, 13 May 2011 (UTC)

in which case I have to ask is this a homework question? Were you assigned course text? Vespine (talk) 02:11, 13 May 2011 (UTC)

You could also try Google Scholar or our article on autonomic nervous system. ~AH1  18:40, 14 May 2011 (UTC)

Spider path

I just saw a spider walking around my ceiling, steadily moving inward in a spiral. I've seen them follow a similar pattern when making a web. So, what was it doing on the ceiling ? Does this particular spider lay web on a surface, in the hopes of catching crawling insects ? Or was it perhaps establishing supports from which it would next build a normal suspended web ? (Unfortunately, the spider is now a collection of guts and quivering severed legs, so I don't expect to finish the experiment anytime soon.) StuRat (talk) 06:26, 13 May 2011 (UTC)

If you'd only taken a picture of your spider before you squashed it, perhaps we could have determined the type of web that it produces. It sounds interesting behaviour. Could you not have waited an hour or two before succumbing to arachnophobia? It might now be too late to answer your question, but perhaps we have some spider experts ... ? Dbfirs 12:56, 13 May 2011 (UTC)

"And he that breaks a thing to find out what it is has left the path of wisdom" --Gandalf SemanticMantis (talk) 15:52, 13 May 2011 (UTC)

More seriously, several spiders do build horizontal webs, but usually these are across the top of a plant canopy. Did you actually see web filaments emerging from the spider? How fast was the motion? If it was quick, it might have been a hunting spider 'lassoing' prey (which may have been to small to notice in moment of giant spider panic). SemanticMantis (talk) 15:52, 13 May 2011 (UTC)

It was moving at top speed. It was maybe a half inch long, and it's color varied from clear to pale yellow. I didn't see a web filament, but I would expect it to be impossible to see that flat against a white ceiling. Why would it move in a spiral, if doing something other than web building ? StuRat (talk) 17:44, 13 May 2011 (UTC)

Usually body, leg, and mandible shape are the most useful characteristics for figuring out a spider's family. Species of wolf spider or jumping spider can rapidly run in circles around prey, stringing web to ensnare it. See an example here . The prey (if present) might have been easy to miss. If there was no prey, then 90.197 mentions some alternative strategies below. I suppose it could have been an anchoring mechanism, but all the web styles I know of use point contacts, not spirals. SemanticMantis (talk) 01:33, 14 May 2011 (UTC)

It was making a big rope in order to abseil from the ceiling. Count Iblis (talk) 22:53, 13 May 2011 (UTC)

Less alarmingly, some house-dwelling spiders actively hunt other insects rather than making passive web traps, and some of these lay loose networks of silk - usually invisible to humans until they build up enough and gather enough dust to become classic cobwebs - on walls and ceilings to provide them with surer footing. {The poster formerly known as 87.81.230.195} 90.197.66.60 (talk) 23:17, 13 May 2011 (UTC)

Nephrotic syndrome in children

Sir please provide me a simple flowchart on pathophysiology of nephrotic syndrome in children Jisaj (talk) 09:30, 13 May 2011 (UTC)

This search found many sources of information about nephrotic syndrome that may be useful to you. Cuddlyable3 (talk) 13:11, 13 May 2011 (UTC)

Waste of Mir Deorbiting

Please correct my admittedly limited understanding of orbital mechanics wherever necessary. I'm wrestling with why the russians chose to deorbit Mir, rather than either pushing it to a more stable orbit around earth from it's Low Earth Orbit, or use a Hohmann Transfer to a stable lunar orbit, to be used later as good space materials/metal for Moon colonization.

I get that Russia wanted it out of its current orbit which required regular orbital maintenance of about 25 m/s delta-v per year. It seemed they had to choose the deorbit path carefully as to not cause deaths, and had to launch up a module to dock with Mir to deorbit it. Even with this cost, they missed their mark and some remnants hit western Australia. From my calculations, it would require a little over half the power of a Space Shuttle Main Engine (there are three on any one space shuttle), which is roughly equivalent to the Soviet RD-0120 engine.

LEO - Lunar Orbit: 4.04 km/s delta-v Delta V Budget

Mir - 129,700 kg Mir

RD-0120 - 1.961 MN Thrust(vac), 3,449 kg, Isp(vac) = 455 seconds RD-0120

1.961 MN = 1,961,000 kg * m / s^2 * 455 s / (129,700 kg + 3,449 kg) = 6,701.176 m/s delta-v = 6.701 km/s delta-v

This means one RD-0120 could have set it in a nice lunar orbit - where at least if it crashed, big deal. However there are four inclinations about the moon where the orbit requires ZERO maintenance due to gravitational heterogeneity: 27deg, 50deg, 76deg, 86deg ( http://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/ ). This could have been useful after so many years of accumulating material in orbit for... the first moon base, or landed on the moon for 1/2 million pounds of building material for future colonization.

Was it not this easy? Am I missing something? —Preceding unsigned comment added by Ehryk (talk • contribs) 09:36, 13 May 2011 (UTC)

There are a million technical reasons why they couldn't do this, for example Mir's communications system would probably not work from lunar orbit, and the attitude determination system used Earth horizon sensors which would probably not work in lunar orbit either, and your SSME-sized engine would produce accelerations and vibrations that would tear Mir to pieces. But the main reason I'm sure is cost: It would cost millions of Rubles (maybe billions?) to design, build, and launch a system to send Mir to lunar orbit; and once there it would serve no purpose. There's simply no use for it, even as materials, in lunar orbit. So they did the economical and practical thing: Deorbited Mir into the Pacific Ocean. anonymous6494 20:20, 13 May 2011 (UTC)

You are forgetting the fuel consumption, 3449 kg is just the engine. Isp=455 s is not the maximum burn time but the ratio of lifting capacity in one g and the fuel consumption in kg/s.

The engine uses 1,961,000 (kg m/s/s)/(9.82 (m/s/s))/(455 s) = 425 kg/s

The engine normally runs 480 to 500 s in a launch but it can run in 1670 s, if we use your number 455 s then it need 425*455= 193 400 kg fuel.

This makes the spacecraft heavier and reduce the deltaV to 455 s*9.82 m/s*ln((193400 kg+129700 kg+3449 kg)/(129 700 kg + 3 449 kg)) = 4 008 m/s, very close to the needed 4040 m/s (1670 s burn needs 710 000 kg fuel and gives a deltaV of 8247 m/s)

To lift these 193 400 + 3 449 kg to LEO 25 times the fuel is needed so the start mass becomes 4 900 000 kg, almost two Seturn V (3,039,000 kg) would be needed. That is just to expensive. A Saturn V can take 45 000 kg to lunar orbit all the way from the earth's surface.--Gr8xoz (talk) 21:44, 13 May 2011 (UTC)

I made a mistake in the latest number it was 47,000 kg to translunar trajectory, to low lunar orbit it was probably about 30 000 to 35 000 kg.

--Gr8xoz (talk) 07:35, 14 May 2011 (UTC)

Bonding problem

I'm learning chemistry on my own from a free book on iBooks and it's good but the end-of-chapter problems don't have answers. One problem states: "Scientists in the lab are able to make the Cl₃ ion but not the F₃ ion. Give an explanation why this might be the case." My idea is that in the case of chlorine, the amount of energy needed to promote two electrons to make three half-filled hybridized orbitals is made up for by the energy released when the covalent bonds are made, but in the case of fluorine, it would take more energy to promote the electrons than would be released by the bonding, so it doesn't happen. Does this sound right? Thanks. 20.137.18.50 (talk) 12:14, 13 May 2011 (UTC)

I would say that it is related to the fact that unlike chlorine, fluorine does not have access to its d orbitals (or the 3s orbital in this case) to accomodate hypervalency structures. Plasmic Physics (talk) 12:38, 13 May 2011 (UTC)

I hate these sorts of problems because they are so often wrong (I'll WP:AGF and charitably say "authors did not consult the literature but rather wrote from their gut feeling or only superficial ideas"). F₃ was made and studied since the mid-1970s...see doi:10.1021/ic50174a040. One could say "why is it less stable" or something and not look as poor when someone finds it's already been done or become obsolete when someone does eventually do it. DMacks (talk) 14:18, 14 May 2011 (UTC)

d orbitals are not required for hypervalency. Consider FHF, for instance. I suspect that the instability of F₃ relative to Cl₃ can be explained in part by the same reasoning that explains the instability of F₂ relative to Cl₂.--Atemperman (talk) 07:10, 17 May 2011 (UTC)

Sodium silicate

Bronze casting: Is waterglass used in strengthening moulding sand for foundry work? Would it be suitable for small scale (5/6 kilo)bronze casting provided mould was completely dried?

It is a strong sand binder and OK for heavy alloys like bronze. It and the right type of sand with instructions should be obtainable from a hobby store. As a tip: you can speed up the chemical reaction with CO2 as shown in this video. http://www.youtube.com/watch?v=UPQmgeTFHEc&feature=player_embedded --Aspro (talk) 16:54, 13 May 2011 (UTC)

I should add, that if you haven't done any very high temperature casting before you really need to go on a course first, to learn about how to do casting safely.--Aspro (talk) 16:59, 13 May 2011 (UTC)

Cognitive bias relating to extrapolating from initial conditions

I've looked over List of cognitive biases, but I don't see the cognitive bias I'm looking for. I'm not sure it exists, but I hope so. Namely, it's the bias whereby a person generally assumes the initial conditions, or especially the initial trajectory, are indicative of future performance. e.g. think of price fluctuations, early childhood aptitude being extrapolated to genius, early athletic ability being extrapolated into the future, etc. That sort of thing. Does anyone know if this is an actual named bias? Thanks in advance! --Rajah (talk) 16:50, 13 May 2011 (UTC)

I'm not sure of the formal name, if any. When people give investment advice, it's common to say "Past performance does not guarantee future results", i.e. here, at the bottom, as a disclaimer, or even as the main topic. The phrase has also been adopted for uses not related to investment: in politics, for example, or sports. Unfortunately, I'm having trouble finding the origin of the term. Buddy431 (talk) 21:09, 13 May 2011 (UTC)

This could be the primacy effect or expectation bias, and possibly black swan theory, normalcy bias, or estimator bias depending on the context. 173.8.151.126 (talk) 04:52, 14 May 2011 (UTC)

A common effect when examining preliminary data. ~AH1  18:37, 14 May 2011 (UTC)

Try Confirmation_bias#Preference_for_early_information and elsewhere in that article. 92.15.1.9 (talk) 14:54, 17 May 2011 (UTC)

BIrds & Monarch butterflies.

I read that monarch butterfly caterpillars eat milkweed plants in order to build up toxins that will dissuade birds from eating them. Have the birds that prey on them now evolved to avoid eating the monarchs - or must each bird eat at least one monarch, dislike the taste/get sick, and then learn not to eat anymore? TIA smart guys! 216.136.51.242 (talk) 17:02, 13 May 2011 (UTC)

See Mimicry#M.C3.BCllerian. A bird may learn to not eat a Monarch because it had previously eaten a Viceroy. As for whether the avoidance is instinctual or learned, it could in principle be either, and likely depends on the species in question. SemanticMantis (talk) 17:59, 13 May 2011 (UTC)

Many thanks! That seems to answer it. They learn. 216.136.51.242 (talk) 19:05, 13 May 2011 (UTC)

There would need to be an evolutionary pressure in order for a species to develop an instinct to avoid eating another. Thus, the poison would need to be strong enough to at least occasionally cause death. If it only tasted bad, then, since those that ate the caterpillars would still live, they would continue to pass on their genes and instincts. StuRat (talk) 18:09, 13 May 2011 (UTC)

It wouldn't have to cause death surely? If the bird is simply too sick to mate for a day or two after eating the monarch, then over enough time, they might evolve. 216.136.51.242 (talk) 19:05, 13 May 2011 (UTC)

If the evolutionary pressure is low enough, then natural genetic drift will be the more powerful force. StuRat (talk) 21:52, 13 May 2011 (UTC)

Yes, apparently they have to learn from experience. However there is very strong evidence that rats and other animals can learn to avoid foods based on observing other animals's responses to them, so I'm not sure we can rule out that something of the same sort may happen in birds. Looie496 (talk) 18:13, 13 May 2011 (UTC)

One odd thing is that human babies don't do that. You'd expect them to only eat food provided by their parents, unless starving. But, in reality, they seem to try to eat anything that will fit in their mouths. StuRat (talk) 18:34, 13 May 2011 (UTC)

I remember hearing an explanation for this: babies are programmed from birth to consume food, it's the second thing they do after being born and it's the second most important thing (breathing of course being the most important thing). Their world is, therefore, defined by the sensations they receive through their mouth. A baby's eyesight is apparently extremely weak for about 6 weeks, and all the other senses have yet to fully develop. I suppose you'll want a reference for this. I'll have a look and be back later.--TammyMoet (talk) 08:03, 14 May 2011 (UTC)

That doesn't really say why babies evolved to behave like that. My own theory is that, back when most babies wouldn't survive, they could still help out the group if they did manage to find something new that was edible. Thus, the risk of this behavior causing them to not pass on their genes was relatively low (since they probably wouldn't, in any case), while the evolutionary benefit of increasing the chances of related individuals passing on their genes (by finding a new food source) was higher. StuRat (talk) 05:19, 16 May 2011 (UTC)

Rather than simply mimicry, it's likely that monarchs also use aposematism (the use of warning colours) to dissuade birds. Brightly coloured animals (especially involving bands of red/orange/yellow on black) are frequently poisonous or venomous; avoiding eating such things would be a very strong evolutionary pressure as it can be reinforced so frequently. As with most things in nature, it's probably a complicated combination of both these strategies where one strategy reinforces the other - and vice versa. Matt Deres (talk) 21:12, 14 May 2011 (UTC)

See https://www.monarchlab.org/Lab/Expert/AddExpertQuestion.aspx.

—Wavelength (talk) 22:17, 14 May 2011 (UTC)

Multiverses beginnings

Maybe I wasn't reading it properly, but the Multiverse doesn't seem to answer this query…

For the scientists who theorise about there being a Multiverse, is there a consensus about when constituent (parallel) universes began: did they all start when our Universe started at the Big Bang, or do they think some may have started before and some after?

Regards, -- PhantomSteve.alt/talk\ 19:30, 13 May 2011 (UTC)

"Multiverse" covers a huge number of different ideas, which have nothing in common except that there's more out there than the visible universe. Often, the other worlds are temporally disconnected from this one, meaning that you can't compare times in one to times in another to say which was "first". In traditional eternal inflation, there are a lot of independent big bangs one of which gave the cosmos that we see, and they are all "connected" inasmuch as they come from a common inflationary state, but I think the inflationary state is symmetric enough that you can't assign a time ordering to them (I may be wrong). In the many worlds interpretation of quantum mechanics, you start with one world which splits later into independently evolving parallel worlds, which then split again, etc. There will never be any consensus on the existence or properties of other worlds until we find some way to investigate them experimentally, which will probably never happen. -- BenRG (talk) 00:25, 14 May 2011 (UTC)

Other theories suggest that a multiverse is created/destroyed by black holes, during a quantum wavefunction collapse or during any scenario similar to Schrodinger's cat. ~AH1  18:35, 14 May 2011 (UTC)

Help identifying plant

Hi. There's a shrub in my back yard that I've been trying to identify for a while. In the past, I asked here, and was told that I should get pictures of it flowering, because it's easier to identify that way. What I've got now are the closest things I've seen to flowers on it. Here are some photos:

Thanks in advance if anyone can help me. If any more photos would be helpful please let me know; I can probably take them. I am in Denton, Texas, and the plant seems to grow wild here. -GTBacchus 21:01, 13 May 2011 (UTC)

Looks to me very like privet, probably Oval-leaved privet Ligustrum ovalifolium, or a close relative, which though of Japanese origin has been introduced worldwide as a garden hedging plant (and of course comes in many cultivated varieties - I have at least three in my own UK garden). As the article says, in the US it has escaped domesticity and become invasive. {The poster formerly known as 87.81.230.195} 90.197.66.60 (talk) 22:43, 13 May 2011 (UTC)

That's awesome; thank you very much! :) -GTBacchus 03:27, 14 May 2011 (UTC)

May 14

Increase voltage from batteries

Suppose you have 12 volt batteries, plenty of wire, and a piece of metal you need to pass an arbitrary voltage through, greater than 12. Is there any way to arrange the batteries and wires to do this? I don't know much (anything) about how electricity works, but it seems to me that if you put the batteries so that the negative end matches with the positive end of the next this should be possible. 24.215.229.69 (talk) 01:18, 14 May 2011 (UTC)

Yes, if you wire the batteries in series (which is what you're describing), you'll get a voltage equal to the individual battery voltage times the number of batteries. Two 12 volt batteries in series will yield (nominally) 24 volts. Acroterion (talk) 01:29, 14 May 2011 (UTC)

Batteries connected in series produce a voltage equal to the sum of the individual voltages. Batteries connected in parallel produce a voltage equal to the individual voltage. (Batteries connected in parallel should all have the same voltage.) See Series and parallel circuits. Dolphin (t) 05:34, 14 May 2011 (UTC)

Connecting batteries in parallel is inadvisable in practice. On the other hand, many bottery-powered electronic devices actually have up to six 1.5 volt batteries connected in series, so what OP asks for is actually done quite often. Just look at the battery holder of a remote control or wallclock etc you have, and you'll likely find an example for this. Further, some batteries you buy as a whole are internally composed of multiple batteries connected in series: for example the rechargable lead battery in your car is like this. – b_jonas 16:54, 14 May 2011 (UTC)

Using a large amount of wire to make an inductor, you can with an electronically controlled switch make a DC-DC converter that can increase the voltage considerably. Graeme Bartlett (talk) 10:58, 15 May 2011 (UTC)

...and without making an inductor you can also make a Charge pump DC-DC converter. Cuddlyable3 (talk) 20:01, 15 May 2011 (UTC)

Standard (North American) 9 V batteries are convenient for this, since the negative and positive terminals can be snapped together. I used to make ~50 V battery packs for lab use by snapping together 9 V batteries. I soldered a wire to the final + and – terminals (before snapping the batteries together), and then wrapped the whole assembly in electrical tape. This gives a nice sturdy higher-voltage battery.

Caution: connecting batteries in this way can produce voltages high enough to give you a painful shock. In principle, once you get over 50 V this could potentially be a lethal shock.--Srleffler (talk) 23:46, 16 May 2011 (UTC)

Leatherman

I guess this is loosely a "technology" question... My Leatherman multi-tool has a little nub on the screwdriver, as seen in this image on the right side of the "large screwdriver" about 3/4 of the way down. I searched "Leatherman diagram" until my eyes bled and none of them indicate what the heck that nub is for. Anyone? Thedoorhinge (talk) 02:28, 14 May 2011 (UTC)

Isn't it just there to give your finger something to grab onto when you want to pull out the screwdriver? Dragons flight (talk) 05:19, 14 May 2011 (UTC)

That's my guess as well. Note that unlike some of the other tools, the large screwdriver doesn't have a fingernail slot on the side of it, so some other means of grabbing onto it is needed. Red Act (talk)

Damn, I totally thought it had some obscure function. Well thanks for the info! Thedoorhinge (talk) 05:51, 14 May 2011 (UTC)

I have been told that an unidentified tool included in a Penknife is for getting stones out of horses' hooves. Cuddlyable3 (talk) 19:55, 15 May 2011 (UTC)

Infinity of infinite dimensional space

Cantor's diagonal argument shows that there is no Bijection between the real numbers and the integers. Therefore the infinity of the real numbers is greater than the infinity of the integers.

And for any finite number of dimensions, say N, the coordinates in the finite dimensional space (x0,x1,x2,x3,...,x(N-1),xN) can be bijected to the one dimensional real number line.

What happens when you have an infinite number of dimensions? (x0,x1,x2,x3,...) Where each coordinate x(i) is a real number. Is there a bijection between infinite dimensional space and the real number line? Hcobb (talk) 03:06, 14 May 2011 (UTC)

This would be better suited to the Math Refdesk, but the answer is yes, Cantor proved that the two cardinalities are the same. I'm not going to spell out the proof, but it involves arranging each infini-tuple of real numbers as a rectangular array by writing them in decimal form and lining up the digits vertically, then applying a pairing function to map the whole rectangular array into a linear sequence of digits. Any textbook on Cantor theory should include this proof. (The logic is very similar to the proof that the set of rational numbers is countable.) Looie496 (talk) 03:33, 14 May 2011 (UTC)

If x(i) is a real number, then x0 is a real number, so there's a bijection between (x0 in R, 0, 0, 0, ...) and R, but I don't know how to construct the full bijection between the infinite real vector and the reals, and I doubt it's very easy unless there's a diagonalization as Looie implies. Perhaps the more interesting question is if x(i) are in the integers or rationals instead of reals. In that case, I think the vector is still uncountably infinite, but again I don't know the bijection. Ask the Math Reference Desk. 173.8.151.126 (talk) 05:00, 14 May 2011 (UTC)

Electrons

Can electrons in rest may set to motion using a magnetic field? —Preceding unsigned comment added by 175.110.91.49 (talk) 10:23, 14 May 2011 (UTC)

Not with a fixed magnetic field. However, a time-varying magnetic field creates an electric field, which of course will exert a force on stationary electrons. See Faraday's law of induction#The Maxwell-Faraday equation. Red Act (talk) 10:50, 14 May 2011 (UTC)

Colour blindness

I've always assumed I have normal colour vision, but I just came across this, which is making me wonder. Can you read what this says? (There is actually a partial caveat on the associated explanation page, but that reveals the answer, and it's best to first try to read it without already knowing.) 86.181.206.103 (talk) 12:27, 14 May 2011 (UTC)

I can read it, but it is certainly not clear. I got the "right" answer, but I wasn't all that confident before I looked. And I know I am not color blind. --Jayron32 12:36, 14 May 2011 (UTC)

We don't answer medical questions. For what it is worth, you would need to look at a properly printed card anyway. Also, the color profile of your monitor may be way off giving a false rendition.--Aspro (talk) 13:14, 14 May 2011 (UTC)

Oh for goodness sake. —Preceding unsigned comment added by 86.181.206.103 (talk) 13:31, 14 May 2011 (UTC)

We do answer medical questions. We don't give medical advice, but that isn't the same thing. --Tango (talk) 16:43, 14 May 2011 (UTC)

Also keep in mind that there are numerous fake 'diagnostic' graphics that circulate. My WP:OR indicates this 'test' uses much less color contrast than the other tests I've seen. SemanticMantis (talk) 14:57, 14 May 2011 (UTC)

I can't read it and I'm colorblind. I've read that this may explain why my night vision is so good. Count Iblis (talk) 14:57, 14 May 2011 (UTC)

I think it's a psychological hoax to make us immagine we see something that's not there.190.56.112.55 (talk) 15:32, 14 May 2011 (UTC)

You can open the image in Photoshop or Gimp, and play with the Hue, Saturation, Contrast, and other parameters. Particularly, boost the saturation; then rotate the hue axis ("slide the hue bar") to rotate the red/green to a different axis in HSV space. This will assist the image in "popping out" perceptually. The image is very noisy and the purported "9" lacks a clean completion. That effect is independent of your ability to perceive red/green as separate colors. The image is therefore poor test of color-blindness; it conflates color-perception with outline-detection. Nimur (talk) 16:19, 14 May 2011 (UTC)

I could take a guess at why color blindness tests would deliberately use imperfect digits: a person who perceives the color contrast but only faintly (like me) could identify the greenest bits individually, then consciously fill in the connections, and figure out what the number is supposed to be. If the color contrast is perceived more strongly, an entirely different type of effortless edge detection is applied. Imperfections in the outline cause more difficulty for the "consciously working it out" method, thus ensuring that people who should fail the test do fail the test. I took the test with the big dots long ago, and they said I was color blind, and I remember that one of the numbers I failed on was a 6 that was pretty darn close to being a 5, which I figured out after it was too late to get credit for it. So apparently they've always been that way. 67.162.90.113 (talk) 05:34, 16 May 2011 (UTC)

Online color vision tests aren't all that great - not only is there issues with them sometimes being hacked up by amateurs, there's also issues with faithful color reproduction on computer screens, with CRT/LCD differences, differing color temperature settings, varying gamma correction, limited gamut, etc. I wouldn't trust a normal monitor to faithfully represent subtle color differences - there's a reason why imaging professional sometimes spend thousands of dollars on special color-correct monitors. That said, I was in a similar situation. I have glasses and so have been given Ishihara color tests a number of times without anyone mentioning anything, so I assumed I had normal color vision. However, like you I noticed difficulties with online color discrimination. It was only after I went to the eye doctor and explicitly asked for a thorough color vision assessment that I learned that I had slight red-green color blindness. The quick, several picture test they give you before they check your prescription is only intended to detect major, life altering color vision deficiencies (e.g. the "can't tell the red stoplight from the green stoplight" ones) - you have to use different plates to pick up the slight color vision issues (e.g. the "can't tell the difference between a bright yellow-green shirt and a bright yellow shirt" ones). Keep in mind that while many people go through life not realizing they have slight color vision issues, a change in color vision could be indicative of more serious eye problems. In my case, as I hadn't noticed any color vision issues until later in life, they scheduled me for additional tests with follow-ups a year later to check if the color vision was stable or if there was further deterioration. -- 174.31.219.218 (talk) 18:23, 14 May 2011 (UTC)

I was able to read the "49" very clearly. Maybe there is a continuum of near-colourblindness. ~AH1  18:33, 14 May 2011 (UTC)

We are all "colour-blind" in some respects. Human perception of colour varies considerably, even between individuals considered to have "normal" colour vision. No retina detects the full gamut of colours accurately, but just takes samples in (usually three) detection ranges, These ranges vary slightly between individuals and the relative sensitivity varies enormously. For most people, the brain adjusts perception so that we believe we are seeing "normal" colours, but this is really just because we adjust our interpretation to match what other people claim they see. If one detector is unusually weak then the person is described as "colour-blind" because they are unable to detect distinctions that most other people can make, but there is indeed a continuum, and the definition of "colour-blind" will vary between cultures and tests. Dbfirs 06:42, 15 May 2011 (UTC)

It will show up more clearly on some types of monitors than others -- it is intended as a pure contrast in hue, but some monitors will show it as a difference in brightness as well, which is much easier to detect. Looie496 (talk) 19:53, 14 May 2011 (UTC)

I found this much harder than the colour blindness test that I took when I tried to join the Royal Navy many years ago - it was made up of large dots 2 to 3mm across a bit like this. I passed easily (only I failed my A Levels!). Considering the exhaustive nature of the other medical tests they did, I don't think they would have given me an easy option. Alansplodge (talk) 20:21, 14 May 2011 (UTC)

A video series like Zimbardo's "Discovering psychology" (1990)

Additional time

Is there any information ava;lable on the subject? This is as opposed the the phenomenon of missing time. I'm sure that there is documentation on people having experiences where a sequence of events takes place in a period of time that is far too short to account for the experiences realized. Links to this phenomenon, specific or general would be of help. There must be an explanation out there. 184.211.105.250 (talk) 15:07, 14 May 2011 (UTC)

Time perception is our overview article. Before resorting to the paranormal, you should know that experimental psychology has repeatedely demonstrated that most humans are very poor observers of time. The "perceived" amount of time can deviate from the actual duration of an event by several orders of magnitude. Our article provides several good references on the subjective nature of human comprehension of duration. Nimur (talk) 16:10, 14 May 2011 (UTC)

(And for the uninitiated, "missing time" or "lost time" typically refers to the purported UFOology/abduction-related effect of unaccounted minutes or hours). Nimur (talk) 16:11, 14 May 2011 (UTC)

See Tevildo (talk) 16:23, 14 May 2011 (UTC)

There is an experiential phenomenon based around falling asleep, where whole scenarios seem to take place in the blink of an eye. I have had this for many years, and a doctor told me it was a sleep phenomenon, like lucid dreaming or the sensation of falling and waking up suddenly. However he didn't tell me the Latin name! --TammyMoet (talk) 16:33, 14 May 2011 (UTC)

See also flow (psychology) and deja vu. ~AH1  18:31, 14 May 2011 (UTC)

Chemistry

What is the product formed from the reaction of methyl alcohol and NaH? —Preceding unsigned comment added by 109.79.6.247 (talk) 15:28, 14 May 2011 (UTC)

See Alcohol#Deprotonation. I've added a section header to your question, as well. Tevildo (talk) 16:08, 14 May 2011 (UTC)

XLR specs

Hello! The US and Europe have different mains voltages, so will a microphone bought in the US work properly with recording equipment in Europe if they both have XLR connectors? I assumed that the XLR specification would require a specific voltage that the recording equipment would have to provide regardless of the mains voltage, but the article XLR connector isn't clear on the voltage specification, and I haven't been able to find online the EIA Standard RS-297-A that the article references. Thank you.--el Aprel (-_facienda) 18:48, 14 May 2011 (UTC)

To be clear, the recording equipment is manufactured in Europe, so it can handle the European mains voltage. I'm just concerned that it might pass a higher voltage to the US microphone. Thanks.--el Aprel (-_facienda) 22:35, 14 May 2011 (UTC)

It should be fine, the article you are after is Phantom power. Vespine (talk) 01:47, 16 May 2011 (UTC)

Colourful butterflys

I don't know why "Looie496" saw fit to remove this question as I'm not a "banned editor" as he/she claims, so here it is again. 92.28.246.151 (talk) 22:16, 14 May 2011 (UTC)

Why are some butterflys brightly coloured? Surely this would make them too visible to their bird predators? Thanks 92.29.120.214 (talk) 23:30, 13 May 2011 (UTC)

The colours advertise the bad taste. That's why you never see birds attack butterflies. --T H F S W (T · C · E) 23:32, 13 May 2011 (UTC)

This article is very interesting, and related to your question. Oops—I'm not sure if the whole article is available online. Bus stop (talk) 23:46, 13 May 2011 (UTC)

Well, not just bad tastes. Others use it for different purposes too - some have things that look like large cat's eyes, and other clever defenses. And some butterflies are dull coloured and use camouflage for defense. --T H F S W (T · C · E) 00:50, 14 May 2011 (UTC)

I thought it was only the nocturnal butterflies that have dull grey colors. – b_jonas 22:57, 14 May 2011 (UTC)

Editorial note: A geolocate on the IP says that this question was almost certainly posted by LightCurrent, who is banned from the reference desks and only asks questions because he enjoys bragging about getting people to waste their time answering them. Looie496 (talk) 23:39, 14 May 2011 (UTC)

Heh, joke's on him, I find the best way to learn is by answering others' questions. Gets me thinking about stuff I thought I knew.-RunningOnBrains 10:44, 15 May 2011 (UTC)

You are mistaken. I've never heard of "Lightcurrant". He or she is certainly not me. 92.15.25.241 (talk) 15:41, 15 May 2011 (UTC)

What's the largest object that can undergo diffraction?

Photons will diffract and interfere with itself if shot at slits that are of sufficient size. The same will happen for larger electrons, protons and atoms. According to a physics textbook, even Buckministerefullerene molecules will exhibit diffraction. When does this phenomenon stop? In other words, what is the largest object that will diffract and interfere with itself when shot at slits of proper size? How come I don't diffract and interfere with myself if I walk through two open doors? Thanks Acceptable (talk) 23:16, 14 May 2011 (UTC)

How can you tell that you're not diffracting? Dauto (talk) 23:24, 14 May 2011 (UTC)

The "Particle diffraction" section of our Diffraction article would be my first place to check. I think some virus-particles have been diffracted (but not mentioned there). But anyway, the article talks about the limits of size vs wavelength. You can calculate the value for any object and (as Dauto suggests) figure out what the effect would likely be. DMacks (talk) 23:27, 14 May 2011 (UTC)

The effect effectively stops when the decoherence rate becomes so large that a description of the system in terms of pure states always breaks down. You can formulate this problem as follows. If you have a superposition of an object being at position x1 and x2, how long does it take for the environment to "detect" the position of the object? You can find some formulas in e.g. this paper (formula 4.1 gives some times scales, figure 1 illustrates the intitial situation of the superposition). Count Iblis (talk) 01:13, 15 May 2011 (UTC)

You can walk through two doors simultaneously? That's one novel way to deal with the problem of The Lady, or the Tiger. Clarityfiend (talk) 03:17, 15 May 2011 (UTC)

A person can walk through two doors at once, but I think they each have to be less than about 10 nanometers wide for this to work. See de Broglie wavelength. Wnt (talk) 18:28, 15 May 2011 (UTC)

A person can walk through both these doors at once. Cuddlyable3 (talk) 19:47, 15 May 2011 (UTC)

May 15

the brain's Physical quantity of dwarfs and the fact they are smart just as any other human

thanks.

Please put this in question form. Plasmic Physics (talk) 02:56, 15 May 2011 (UTC)

There are over 200 distinct medical conditions which can cause dwarfism. Most people with dwarfism have normal intelligence, and in particular, achondroplasia, which accounts for about 70% of cases of dwarfism, is not associated with diminished intelligence. However, some of those 200+ medical conditions do result in mental impairment. See Dwarfism#Characteristics. Red Act (talk) 11:39, 15 May 2011 (UTC)

And I believe most dwarfs have brain (and head) sizes in the normal range, too. This makes the head disproportionately large. There are proportionate dwarfs, though, historically called midgets, where the brain would be smaller. I believe Gary Coleman from Diff'rent Strokes and Emmanuel Lewis from Webster (TV series) are examples (they are sometimes used on TV to play children, since they appear to "stay young" longer). StuRat (talk) 16:40, 15 May 2011 (UTC)

are there any scientifically proven FOODS there a long-term eating of them could improve\enhance the human vision\eye-sight system?...

thanks.

I don't know about improving your eyesight, but lutein and zeaxanthin, found in green leafy vegetables and other foods, are supposed to be good for protecting the eyes against macular degeneration and cataracts (see lutein#Role in human eyes and zeaxanthin#Relationship with diseases of the eye). At least, some studies show a connection, though the US Food and Drug Administration isn't totally convinced, according the the zeaxantin article. Clarityfiend (talk) 00:56, 15 May 2011 (UTC)

I've read that fish oils and Vitamin D can also prevent macular degeneration. Count Iblis (talk) 01:16, 15 May 2011 (UTC)

Likewise, Vitamin A and the related molecules known as the carotenes are vital to eye health. --Jayron32 01:25, 15 May 2011 (UTC)

During WW2 in order to conceal their invention of radar the British put out a myth that they were feeding their pilots carrots to improve their night vision. This claim is still heard but don't believe it (unless you are German and WW2 is on). Cuddlyable3 (talk) 18:01, 15 May 2011 (UTC)

Ice age Australasian straits

At the time when Australia was first peopled (~40,000 years ago or more), what modern strait would be/correspond to the widest sea gap faced by people coming from Southeast Asia (Sunda shelf) to New Guinea-Australia (then joined because of lower sea levels)? 98.194.39.132 (talk) 06:07, 15 May 2011 (UTC)

The Selat Lombok between Bali and Lombok would have been the first water encountered. But the widest part would have been the Timor Sea. Other possible routes may meet the Molucca Sea, Seram Sea or Halmahera Sea. You may also want to read Wallace Line which includes a map at the time you are interested. Graeme Bartlett (talk) 10:45, 15 May 2011 (UTC)

OK, thanks. I think the Timor Sea is what I'm looking for... 98.194.39.132 (talk) 16:33, 15 May 2011 (UTC)

As Graeme said, it's not that simple. There is really no way to understand the situation except by looking at a map -- I've appended the one from the Wallace Line article. Looie496 (talk) 17:07, 15 May 2011 (UTC)

UL or other agency approval or certification

In what situations a UL or other agency approval or certification is needed for electrified public structures? —Preceding unsigned comment added by Mustafa-900 (talk • contribs) 10:00, 15 May 2011 (UTC)

Public structures have to be approved by a Professional Engineer??

Is there a law, rule or a regulation that says:

"Public structures have to be approved by a Professional Engineer" or

"...drawings of public structures have to be evaluated and signed by a professional engineer" or

"no change to those drawings can be made without the approval of a professional engineer" —Preceding unsigned comment added by Mustafa-900 (talk • contribs) 10:04, 15 May 2011 (UTC)

It would be helpful if you said what jurisdiction you were worrying about? In general though, most jurisdictions in the developed world will require that some form of licensed and accredited individual (e.g. civil engineer, architect, building inspector) approve of any new construction that is intended for public use. Dragons flight (talk) 10:24, 15 May 2011 (UTC)

This is a question about law, not science. I believe the Humanites Refdesk is the correct place for it. Roger (talk) 10:34, 15 May 2011 (UTC)

I'm not so sure. Laws dealing with science could be handled here. StuRat (talk) 16:27, 15 May 2011 (UTC)

Minimum thread engagements

Is there a law, rule or a regulation about minimum thread engagements for load carrying bolts for public structures? —Preceding unsigned comment added by 24.229.140.47 (talk) 10:16, 15 May 2011 (UTC)

There are probably thousands of such laws: they are called building codes, and they delve into alarming levels of detail. The applicable laws and building codes will depend entirely on your country, state/province, and local jurisdiction. If you are in the United States, you could check with your local ASCE chapter for rough advice about applicable laws, as well as conventional industry-practice. If you are actually building a structure, you should have a Professional Engineer, an attorney (or several), and a building inspector involved in the process; one or all of those people will know where to get specific information on such details. Nimur (talk) 15:58, 15 May 2011 (UTC)

Does ISO 965 help? hydnjo (talk) 15:58, 15 May 2011 (UTC)

interference reason

I AM CONFUSED THAT IS PATH DIFFERENCE NECESSARY FOR INTERFERENCE ?CAN INTERFERENCE TAKE PLACE WITHOUT PATH DIFFERENCE? —Preceding unsigned comment added by Nikhil320 (talk • contribs) 11:48, 15 May 2011 (UTC)

According to Interference (wave propagation), a path difference is not necessary. If the paths are equal then you get 100% constructive interference (i.e. double the amplitude); if they differ by half a wavelength then you get 100% destructive interference (i.e. zero amplitude). For intermediate cases you get something in between. --Heron (talk) 12:13, 15 May 2011 (UTC)

A path difference doesn't always mean a phase shift. Two different paths can be of equal length or the difference can be an integer multiple of the wavelength, in which cases the phases will be the same at the receiver. StuRat (talk) 16:26, 15 May 2011 (UTC)

Also relevant: Optical path length is affected by index of refraction, so two optical paths may have different optical path lengths (for example, one may pass through a glass lens and the other passes through air), even if both distances are the same. Nimur (talk) 15:53, 15 May 2011 (UTC)

Sailing stones

what is the phenomena or reason behind the "SAILING STONES"? —Preceding unsigned comment added by 175.110.91.49 (talk) 18:24, 15 May 2011 (UTC)

We have an article Sailing stones which gives some ideas. The bottom line is that a desert is not always dry, and the winds in that area are quite strong. Wnt (talk) 18:31, 15 May 2011 (UTC)

It is still somewhat of a mystery though. No one knows for sure. --T H F S W (T · C · E) 21:29, 15 May 2011 (UTC)

I heard somewhere that this was fairly recently solved quite conclusively, trying to find a reference. Vespine (talk) 23:10, 15 May 2011 (UTC)

Sailing stones explains that ice, and ice floes, are also thought to play a part. Dolphin (t) 00:05, 16 May 2011 (UTC)

There are a few theories, but the three that have the most support are:

1. Ice is forming around the rocks and raising them, allowing them to "float" on a near frictionless bed of ice, and be pushed by the wind,
2. Rare but significant rains create a slick of water on the floor of Racetrack Playa, which wets the clay creating a very low-friction surface which the winds can then push the stones along, or
3. Some combination of these two theories.

I recently read this scientific article (at least, that's what I call it if my boss sees it) which suggested that the mystery had been solved, but a review of recent literature shows there is still no hard consensus among geologists.-RunningOnBrains 01:49, 16 May 2011 (UTC)

I am wondering if daily cycles of thermal expansion and thermal contraction can play a role here. If the rock was initially moved a bit by strong gusts, then that movement would create a clean track under the rock and behind it. On the front side, the ground would be a bit rougher. Then, it seems to me that the rock expanding and contracting could move it further forward. When the rock expands, the front side, which is very close to the edge where the rough ground starts, can move over the rough side a bit, due to different thermal expansion coefficents of the ground and the rock. It can then experience much more friction there, so that in the contraction cycle, it doesn't move as far back as it moved forward. Count Iblis (talk) 02:48, 16 May 2011 (UTC)

An interesting theory, but it doesn't fit observations. The stones don't move millimeters at a time, they sit still for years at a time and then suddenly move hundred meters overnight. The actual motion itself has never been observed. -RunningOnBrains 04:58, 16 May 2011 (UTC)

Correction, until very recently the movement hasn't been observed. There's a video on youtube now showing just that. It was linked to from a recent article about scientific "mysteries" that actually have really obvious answers HominidMachinae (talk) 07:55, 16 May 2011 (UTC)

I believe this is the video you are referring to. While they do observe water flowing across the valley floor, they do not observe the stones themselves moving. Also, all joking aside, I don't consider Cracked to be the most reliable of sources :) (I actually linked to that article above). -RunningOnBrains 08:16, 16 May 2011 (UTC)

graph in excel

(I posted this at the Computing desk, but it's probably more appropriate here)

I should be able to get my head around creating a graph in Excel 2007, but I can't. Please help me.

I want a line graph, and I want two lines on it, for, say, reaction with X and reaction without X. For each line there are five data points, I want v on the vertical axis and v/s on the horizontal axis (so ten figures to table for each line). It would be super simple to do this by hand but I need to do it in Excel, and I can't work out how to set up the table so that Excel has any clue what I'm after. How do I table this data so Excel's graphing function can make sense of it? Thanks a lot. Howie26 (talk) 19:00, 15 May 2011 (UTC)

Something like this?

v/s v (with X) v (without X) 1 4 3 6 5 8 6 9 8 11 2 1 7 3 8 5 9 6 10 8

The graph is a "scatter" graph style. DMacks (talk) 20:32, 15 May 2011 (UTC)

Just to use the opportunity to plug Openoffice.org, a free alternative to Microsoft (Actually the Go-oo version to be precise), I typed in your numbers, selected Insert -> Chart..., chose chart type Scatter, selected the appearance with lines, hit Finish, and dragged out the right side a little to make the perspective more like yours. The program is generally the equal of Excel, with the glaring exception that even the Go-oo version has a hard time handling more than about 20,000 of certain operations at a time, which IMHO is often the whole point of using a spreadsheet. Wnt (talk) 20:49, 15 May 2011 (UTC)

Precisely what I wanted!! Thank you both! Brilliant! Howie26 (talk) 21:40, 15 May 2011 (UTC)

DARAPRIM COMPOUND TAB. quinine dihydrochloride

Skullology or Skull-Osteology or what? - how should i say "skullology" in scientific terminology?

Thanks? —Preceding unsigned comment added by 109.67.5.122 (talk) 22:02, 15 May 2011 (UTC)

Unless there is an actual need for a defined "field", there may not be a name for it, especially if there isn't anything particularly unique to the field. I think it's unlikely there are people who study "skulls" in general, there would certainly be various osteologists (and probably palaeontologists) who specialize in skulls, but that's different, it doesn't mean they necessarily need their own distinct name. There used to be Craniometry and Phrenology but they were pseudo scientific. Vespine (talk) 23:04, 15 May 2011 (UTC)

My local hospital had a Cranio-Facial department, which dealt with the bones of the skull and face. I always thought that was the proper name for the medical specialism. --TammyMoet (talk) 12:17, 16 May 2011 (UTC)

Thanks.

i would like to have a good site \ FA which is dedicated to the differences between Male skull and Female skull, now, in the evolution, and some info about the etiology of the Difference.

thanks. —Preceding unsigned comment added by 109.67.5.122 (talk) 02:35, 16 May 2011 (UTC)

Gray's Anatomy has a section on Sexual Differences in the Skull which is quite technical.. I'm not sure you'll find much more then that. I wouldn't think there's anything evolutionary or etiologically unique about the differences in the skull as opposed to the rest of the skeleton in general. Vespine (talk) 03:54, 16 May 2011 (UTC)

May 16

Waterford Nuclear Generating Station

How is Waterford Nuclear Generating Station impacted by the 2011 Mississippi River floods? It looks like it might be under 20 feet of water, or fine depending on where one draws inferences. Can anyone tell for sure? Should we call the public affairs telephone number and ask? 99.39.5.103 (talk) 04:12, 16 May 2011 (UTC)

This CNN story says: "A nuclear unit in Louisiana may have to shut down if Mississippi River levels are too high, according to the Nuclear Regulatory Commission. The Waterford Steam Electric Station Unit 3, about 25 miles west of New Orleans, was back online Thursday after being shut April 6 to refuel and replace the main generator. Entergy Louisiana, which owns the plant, said flooding is not expected with the opening of the Bonnet Carre Spillway. But if the river exceeds 27 feet, the plant would be forced to shut down because a circulating water system that drives the turbine would not be able to operate." --Mr.98 (talk) 11:38, 16 May 2011 (UTC)

Thanks; added to article. 99.39.5.103 (talk) 18:28, 16 May 2011 (UTC)

being awake like a zombie

after get awaken by a family member in the middle of REM sleep... why is that?, and what can i do to cancel this zombie feelingness after that happened?.

THX —Preceding unsigned comment added by 109.67.5.122 (talk) 04:22, 16 May 2011 (UTC)

A normal person can be awakened from any stage of sleep. But it isn't REM sleep that gives rise to that "zombie" feeling, it's probably stage IV sleep, the deepest level. REM sleep is actually pretty light. People in it are hard to awaken because they are "cut off" from the world, but they pretty frequently awaken from it spontaneously. The best way I know to get rid of that drugged feeling is to go back to sleep. For me, if I can't do that, I generally feel shitty all day, or at least all morning. Looie496 (talk) 05:48, 16 May 2011 (UTC)

I'm curious about this also. Everything I read about sleep talks about cycles, but that's not how it seems to me. To me it feels like there are two different kinds of sleep, which I think of as "liver sleep" and "brain sleep". "Liver sleep" seems to have a lot to do with eating or sleep-conducive activities like nodding off in an audience or (God forbid) while driving, and is distinguished by my ability to sleep through noises like a TV going in the background that would immediately bother me in the other version. As a result, sometimes I doze off for an hour or two and then wake up from the background noise. I call it "liver sleep" because sometimes when I've been awoken from it, I've literally felt as if the "center of consciousness" is somewhere far down, even as far as my liver, and my head towers confusedly above it. The other kind, the brain sleep, is where I have all the good dreams. But I've never seen anything about two different kinds of sleep in the literature. Wnt (talk) 09:26, 16 May 2011 (UTC)

Because the literature is scientific, rather than just anecdotal. :-P There are volumes and volumes and volumes about sleep research being done; we don't have to make it up as we go along anymore... --Mr.98 (talk) 11:41, 16 May 2011 (UTC)

Hypnagogia includes a lot of different phenomena which affect people between sleep and wakefulness.--Kateshortforbob _talk 10:40, 16 May 2011 (UTC)

Plant survival

just wondering can a plant (given the appropriate conditions such as light,water etc) survive on the moon?

Let's see how the conditions differ. A day on the moon lasts about a month, so artificial light and dark may be required for some species - though there are multi-day and multi-month days and nights on the Earth too, near the poles, and many plants do just fine. There is no atmosphere (actually the Moon does have one, but it is so thin as to be hardly noticeable) so we'll need to give the plant some carbon dioxide and whatever gases the species in question needs. We'll need to give it soil that has the nutrients that the plant needs. Gravity is 1/6th of Earth gravity, and some plants might suffer, while others might thrive - if we insist, we could put the plant in a centrifuge for artificial gravity. The Moon is outside the Van Allen radiation belt, and therefore receives more radiation than the Earth's surface - we may need to build our greenhouse underground for protection.

I think we should be able to grow plants on the Moon. Not outside, though, as plants do need an atmosphere at the very least to get carbon dioxide for photosynthesis. And there are delicate species that require more carefully monitored conditions than more robust plants. 88.112.59.31 (talk) 13:52, 16 May 2011 (UTC)

The centrifuge suggestion seems rather impractical, especially in the case where we want to grow plants on the Moon to generate food. However, I'd think 1/6th normal gravity would be sufficient, although you might see different growth patterns (perhaps tall, gangly plants would result). StuRat (talk) 16:17, 16 May 2011 (UTC)

You have specify "appropriate conditions", because all inclusive conditions effectively renders the moon irrelevant to your question. It is like asking whether you can breathe (given the appropriate conditions such as a personal air supply) in a vacuum. Plasmic Physics (talk) 13:57, 16 May 2011 (UTC)

When do chlorine in a solution evaporate?

• Water that is heavily chlorinated (with NaOCl I believe)can be left in a bucket over night, letting the dissolved chlorine 'evaporate' from the water. Though the speed depends on the type of bleach and other factors .
• Saltwater, which contains dissolved NaCl can be left for as long as you like, the dissolved chlorine will not, to my knowledge, disappear.

What chemical effect is behind the difference? EverGreg (talk) 13:53, 16 May 2011 (UTC)

A solution emmanates chlorine gas when it contains chemically unstable, chlorine-containing compounds. These compounds decompose into free chlorine and other products. Hypochlorite in bleach is one example of unstable chlorine compounds, chloride is not, hence it does not decompose to chlorine. Plasmic Physics (talk) 14:10, 16 May 2011 (UTC)

Cl₂ + NaOH ${\displaystyle {\overleftarrow {\rightarrow }}}$ NaOCl + HCl

Since this reaction is reversible, if the Cl₂ is gradually removed from the equation by evaporation, the equilibrium will eventually lie fully to the left, leaving no NaOCl remaining. There is no comparable reversible reaction involving NaCl because it is so stable, as Plasmic Physics notes. —Preceding unsigned comment added by 148.177.1.210 (talk) 18:18, 16 May 2011 (UTC)

Space shuttle booster rockets

The booster thrust appears to be off-center, so what keeps the shuttle from rotating ? (I see that they also fire the shuttle engines, but those certainly appear to provide far less thrust than the boosters.) It occurs to me that the mass of fuel in the boosters must move the center of gravity towards them, when full. However, when nearly empty, this effect would be minimal. Do they steadily alter the relative thrust to provide more from the shuttle as the tanks empty out and the COG shifts ? StuRat (talk) 16:50, 16 May 2011 (UTC)

The SRB nozzles are gimballed through up to 8 degrees; the orbiter's engines gimbal too. As with any launcher (with gimballed thrust, which is almost all), the flight control system continually tweaks the direction of these to keep the spacecraft flying in the intended direction. Failure of this authority is typical of those "somersault into launchpad" accidents that fill space programme blooper reels. -- Finlay McWalter ☻ Talk 17:30, 16 May 2011 (UTC)

See space shuttle solid rocket booster#thrust vector control. It seems concievable that a constantly adjusted mass/thrust imbalance may be desirable to avoid a null control default situation.190.56.125.48 (talk) 17:49, 16 May 2011 (UTC)

The SRBs and external tank weigh about 20 times more then the actual shuttle, so there doesn't need to be nearly as much thrust under it. Vespine (talk) 00:12, 17 May 2011 (UTC)

How long does it take to test DNA?

In the case of bin Laden it took 6 hours, in the case of Dominique Strauss Kahn it will take 5 days.Quest09 (talk) 17:34, 16 May 2011 (UTC)

Our lengthy article DNA profiling discusses several DNA profiling methods, but nowhere discusses how long they each take — when someone finds the answer, please be sure to add the information to the relevant sections of that article. Comet Tuttle (talk) 18:14, 16 May 2011 (UTC)

(ec)And in the case of Alan Newton in New York City, it took 12 years. I think that for ordinary, non-"priority" defendants, it is typical to wait months for a result - probably in a cell because someone without the money for special consideration doesn't have money for bail either. Wnt (talk) 18:20, 16 May 2011 (UTC)

Any reason to think that article from 2005 indicates what's typical nowadays? The article itself mentions one crime lab so badly backlogged as apparently acknowledged by all involved, that people are now trying to use other resources and the lab themselves see the need to double their resources. Not exactly what you would expect if the situation is typical and accepted as the norm. Nil Einne (talk) 01:47, 17 May 2011 (UTC)

Eye color changing with mood.

My new g/f claims that her eyes change color with her mood. This seems spectacularly unlikely to me - but before I go stomping over this rather beautiful idea with big scientific boots on - I thought I should check with you guys. She claims her (normally brown) eyes turn greenish or golden depending on mood. My kinda suspicion is that her perception of herself changes with her mood and that her estimation of their color changes accordingly. But since this is a potential relationship minefield...yeah, exactly. 216.136.51.242 (talk) 18:09, 16 May 2011 (UTC)

See Iris (anatomy) — as one photo caption claims, the exact color of some eyes are "often perceived to vary according to its surroundings". You can either tell her "Pics, or it didn't happen", or you can arrange a carefully controlled scientific experiment, or you can agree, or you can tell her you need to closely examine her Crypts of Fuchs. Comet Tuttle (talk) 18:18, 16 May 2011 (UTC)

It is not uncommon for the appearance of eye color change to happen as the pupil dilates (or contracts). If you look very closely at your iris, you will see many different colors. Some people have uneven distribution of the color. She probably has a lot of brown near the pupil and more hazel around the edge. When the pupil dilates, the brown is dampened, allowing more of the hazel to appear. That is just a biological factor. Light sources also cause eye color changes. My eyes are a very different shade of blue under fluorescent lights compared to sunlight. Also, clothing/makeup can reflect off the eye, making the iris appear to change colors. Maybe she likes to wear green blouses when she's happy, making her eyes appear green. -- kainaw™ 18:19, 16 May 2011 (UTC)

I wonder if blood pressure, due to stress or anger or excitement, might make the eyes look more red. Also, does more oxygenated blood make them look redder, and less oxygenated blood make them look bluer ? StuRat (talk)

It is quite well documented that trauma to the surrounding area can result in the iris becoming brown because of the trapped blood leaking therein. See David Bowie as an example. (I also have a colleague who was in a RTA, and whose eyes went brown from blue as a result.) --TammyMoet (talk) 18:35, 16 May 2011 (UTC)

Mine also went from brown to blue after a severe motorcycle accident. -- kainaw™ 18:54, 16 May 2011 (UTC)

Really ? That's the opposite of the expected direction. StuRat (talk) 19:02, 16 May 2011 (UTC)

Eye color#Changes in eye color has some info, as does this "Ask a Geneticist" article and Snopes' forum. 99.39.5.103 (talk) 18:39, 16 May 2011 (UTC)

titration endpoint

I'm titrating solutions that contain two pH indicators, methyl red and bromocresol green. I'm not sure exactly what color I'm looking for as the end-point of the titration. I found a description of this indicator combination in an old paper (Stancil Cooper. Mixed Indicator Bromocresol Green-Methyl Red for Carbonates in Water, Industrial & Engineering Chemistry Analytical Edition 1941 13 (7), 466-470). It lists these color changes:

pH of Solution -- Color

• 5.2 and above -- Blue with trace of green

• 5.0 -- Light blue with lavender gray

• 4.8 -- Light pink gray with cast of blue

• 4.6 -- Light pink

• Below 4.6 -- Pink or rose

So which of these colors indicates the end-point? Thanks, ike9898 (talk) 19:23, 16 May 2011 (UTC)

Equivalence point says stop as soon as a color change can be seen, but for these particular indicators, "The endpoint of 2:3 methyl red:bromocresol indicator is light pink to light green. The complete transition is from light pink (sometimes tannish) to light green to light blue (acidic solution to basic solution). It is sometimes difficult to see the green endpoint since one-half a drop over will give the blue color without observation of the light green intermediate." Dualus (talk) 00:06, 17 May 2011 (UTC)

disease detection by dogs

A recent coversation triggered a years old memory of when I had badly injured my foot from a conflict with a power tool. The foot healed up fine but about a year later my little dog freind started insistently licking my foot close to the scar tissue. A couple of days later I noticed small points poking through my skin in the same place. It turned out that these were small chips of wood which were being expelled from my foot. My dog had clearly detected these before I could. Similarly I used to suffer migrain headaches and my little dog would come and lick my forehead and temples where the pain was. I've also heard stories about dogs being used to detect cancers. If I had not experienced this myself I might have poo-pooed it as misinterpretation, but my dog's unusual attention to the affected spots was undeniable. I'm not given to mystical explanations, and this should be scientifically verifiable. "Desease detection by dogs" only turned up deseases of dogs. Anybody know anything about this please?190.56.125.48 (talk) 19:39, 16 May 2011 (UTC)

"Dogs Smell Cancer in Patients' Breath, Study Shows", National Geographic (lung and breast cancer); Dogs 'sniff out' bladder cancer, BBC News (bladder cancer). The latter article also discusses self-reported claims of dogs detecting skin issues. But these news stories may just be the usual "a study says" stuff that popular science news coverage loves so much (much more than "a better study says that a previous exciting study was wrong, and in fact we know nothing"). -- Finlay McWalter ☻ Talk 19:47, 16 May 2011 (UTC)

Dogs can do a lot of very impressive things with their noses. There's a wonderful account in Temple Grandin's Animals in Translation about dogs that have been trained to detect when epileptics are about to have seizures and things like that. They have remarkably good rates at being able to be trained to sniff for cancers and other things. It's not mystical in the slightest — they have extremely powerful sensory organs and they are interested enough in humans to use them in ways that happen to be useful for us. --Mr.98 (talk) 20:56, 16 May 2011 (UTC)

The migraine example doesn't seem to match, though, because I see no reason for the affected area to release a smell through the skull. I suspect your dog either noticed a warm area or saw you were rubbing at it, and decided to give it "special attention". StuRat (talk) 21:04, 16 May 2011 (UTC)

We had a dog that was a brilliant early warning system if my brother and I were up past our bed time when our parents were out. When our dog would get really restless and run around the yard we knew we had a minute or two to kill the tv and lights and get in bed. It could obviously hear the car from a mile away. There was also a fantastic mythbusters episode on sniffer dogs, if I didn't trust mythbusters was genuine, i'd suspect foul play, it's almost unbelievable what they can do. Vespine (talk) 23:02, 16 May 2011 (UTC)

Aberration

According to http://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html, it is possible that a light from a star behind an observer can reach the eyes in front of the observer. How is this possible? 74.15.138.241 (talk) 20:32, 16 May 2011 (UTC)

It happens when the speed of the observer is higher than the component of the speed of light along the direction of the motion of the observer (The component can be smaller than c since it's only one out of three components). Dauto (talk) 20:55, 16 May 2011 (UTC)

(ec) The obvious answers are a reflection or being bent 180° around a massive object, like a black hole, but that article seems to be talking about the effects on a traveler moving at (near) the speed of light. StuRat (talk) 20:59, 16 May 2011 (UTC)

Our articles on this are relativistic aberration and relativistic beaming, and this external page has a good explanation. Red Act (talk) 21:02, 16 May 2011 (UTC)

Cervical spondylosis/hypertrophy, neural foraminal stenosis - parts of the body affected

C5-6 bilateral uncovertebral hypertrophy causing narrowing of neural foramen bilaterally.

C6-7 assymmetric right neural foraminal stenosis while left neural foramen preserved secondary to posterolateral osteophyte.

Upper discs and C7-T1 unremarkable. Facet joints and vertebral body alignment normal.

I am wondering what parts of the body might be affected by the compression of the affected nerve roots; and if this condition can cause compression of the spinal cord itself. Many thanks in advance. bcatt (talk) 22:02, 16 May 2011 (UTC)

It appears that you are asking us to interpret the results of an individual's imaging study, which would be inappropriate for us to do. This is really a situation where "clinical correlation is recommended," meaning that the person's doctor can explain what it means and whether any part of that person's body could be affected. We do have articles on spondylosis and cervical vertebrae that may help with general questions, but any specific information related to an individual's condition would violate our rules on giving medical advice. --- Medical geneticist (talk) 23:06, 16 May 2011 (UTC)

Nonlethal weapons for use on large animals

Are there any ? I suppose mail carriers have mace, etc., to deal with dogs, but I'm more concerned about rangers in animal reserves which occasionally have to shoot bears, wolves, tigers, lions, elephants, rhinos, etc, when they attack. This seems to run counter to their mission of preserving those species. Perhaps mace could still work, but you'd need the ability to spray it much further. Then there are stun guns which shoot electrodes at the subject. Loud sounds (air horn with a parabolic "cone" ?) and lights (lasers ?) might also work, but it seems like inflicting pain is important to teach those animals to avoid people from then on (both for the sake of the people and the animals). There are tranquilizer darts, of course, but those are too slow to stop a charging animal. So, I'd like to know if anybody is working on this niche market. StuRat (talk) 22:27, 16 May 2011 (UTC)

Brown bears can be repelled with pepper spray; that article says that spray cans designed for use against bears can be effective as far as 8m away. Personally I have my doubts about pepper spray, as in lower concentrations it seems more like a garnish than a deterrent, like a fish releasing a cloud of lemon juice and cream cheese to defend itself against humans. That article also talks about thwacking the bear's arse with wooden pellets from a slingshot (but do we really want to annoy it?) -- Finlay McWalter ☻ Talk 22:37, 16 May 2011 (UTC)

I agree. We need a method guaranteed to protect the human. StuRat (talk) 00:08, 17 May 2011 (UTC)

May 17

How old do you have to be a nurse in Japan?

How old do you have to be a nurse in Japan? Neptunekh2 (talk) 01:42, 17 May 2011 (UTC)

Can anyone recommend any books about Gynoid which are female robots with a human appearance.

Can anyone recommend any books about Gynoid which are female robots with a human appearance.

Thanks! Neptunekh2 (talk) 01:53, 17 May 2011 (UTC)

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