Wikipedia:Reference desk/Archives/Science/2009 September 18

= September 18 =

Water and the Human Body
If there was a video camera which could only film the movement of water inside people's bodies what would the footage look like of people going about their daily lives? Would it look like fluid sloshing all over the place or would it be mostly static except for arteries and veins? TheFutureAwaits (talk) 08:20, 18 September 2009 (UTC)
 * Given that most of the water is contained in individual cells and the bloodstream, the only "sloshing" would be water that has just been consumed or has gathered in the bladder. In the bloodstream, it would be "flowing" rather than "sloshing". Baseball Bugs What's up, Doc? carrots 14:04, 18 September 2009 (UTC)


 * Sloshing is generally a Bad Thing. To get 'sloshing', you need to have free liquid and open air in the save cavity within the body.  Usually this doesn't happen (or happens rarely and is quickly remedied).  You can get a mixture of gas and liquid in the upper gastrointestinal tract by swallowing air with your food or drink, or by consumption of carbonated beverages; either way, this gas is released through belching.  Gas further down in the system (generated by the action of digestion) usually comes out the other end.
 * You can accumulate air/fluid mixtures in the digestive system if there is some sort of obstruction or bowel perforation, and in the lungs due to inflammation or inhalation of liquids.  shows a person with a bowel perforation.  The description is on this page.  The pelvic bone is visible at the bottom of the frame, the lower edge of the lungs is at the top, and the spine runs up the center.  Arrowheads indicate multiple air-liquid interfaces in the bowel.  TenOfAllTrades(talk) 14:31, 18 September 2009 (UTC)

Okay....um why don't we steer away from the bowels. The water in people's cells, is it moved around when someone is walking, jumping or falling? TheFutureAwaits (talk) 14:43, 18 September 2009 (UTC)
 * There should not be any air bubbles in cells, and the interior of cells is partly water and partly other stuff, as I recall from biology class, so you might get smooth motion of the cells themselves, in response to body movements, but no "sloshing" as such. In fact, the same presumably should hold true of the bladder and stomach - there should be no air at all in the bladder, and not much in the stomach - so you would see "rolling" as a result of change of position of the containing organ due to body movement - but no real "sloshing" in the bladder and not much in the stomach. And the rest of the body, I think, would be smoothe motion. Baseball Bugs What's up, Doc? carrots 14:46, 18 September 2009 (UTC)


 * In Cells tehmselves the Cytoskeleton keeps things from moving around. Or even keeps them moving. The liquid just flows around them. Even though cells are somewhat flexibile, human cells (except for a few kinds) are pretty rigid things. --212.6.123.204 (talk) 16:47, 18 September 2009 (UTC)

There are other places where fluids move around besides the circulatory system, though. Besides the contents of the digestive tract there's also bile, lymph, tears, urine, semen (for some of us), and probably others I've forgotten. However, in all cases these things are produced in small quantities and normally move slowly (with obvious exceptions), so they'd hardly be noticeable in the original poster's scenario. --Anonymous, 18:43 UTC, September 18, 2009.
 * Don't forget cerebrospinal fluid. As you say, though, all of those are generally small volumes, moving quite slowly relative to blood.  (For CSF, you make about 500 mL (two cups) per day, and the brain and CNS hold about 150 mL (a little over half a cup).  It's a modest trickle.)  TenOfAllTrades(talk) 22:32, 18 September 2009 (UTC)

Technically there would be constant movement within intra and extra-cellular fluids as there is constant movement of micro-particles in the body. Be it minerals/lipids/protein you name it. Water goes where particles go, specially saline. It would be a bit complicated to explain here. But you should read on hypertonic and hypotonic solutions within the human body and the fluid shift it causes and that might give you a better idea on the subject. The marieb or Tortora physiology manuals are quite thorough on the subject.

Energy eigenfunctions of a free particle
If someone could help me with this it'd be much appreciated - the more help I can get the better.

"Find the energy eigenfunctions ψE(x) for a free particle of mass m subject to the periodic boundary condition

ψE(x) = ψE(x + L).

What are the allowed values of E? What are the degeneracies of the energy levels? Comment on the limit L → ∞."

For the eigenfunctions, I think they're the f satisfying -(h2/2m)$$\nabla^2$$f(x) = E * f(x) - working in 1 dimension.

This means our functions have to be of the form Asin(kx)+Bcos(kx) with k^2=2mE/(h^2), and the periodicity implies kL=2npi, right? In which case we can find the values of E in terms of n,L etc.

I'm not really sure if I'm at all right on this, or what the 'allowed values' are, and I'm clueless about the degeneracies too.

If anyone could walk me through some of it i'd really appreciate it!

Thanks :) Spamalert101 (talk) 12:54, 18 September 2009 (UTC)
 * If the boundary condition is periodic then the function (solution) must be periodic too, as you guess. But shouldn't you consider higher harmonics as part of the function. eg Function = Sum over n ( Ansin(knx)+Bncos(knx) ) maybe that's implicit and you already have
 * Your equation for k looks right.
 * Don't you also need to state the nature of the boundary to get a solution eg the potential energy that relates to the boundary

(h2/2m)$$\nabla^2$$f(x) = (E-boundary energy function) * f(x) maybe you are expected to ignore this and just assume an approximate solution?
 * With that you can then attempt to get a full solution. But as far as you have got what you have written seems basically not wrong.83.100.251.196 (talk) 13:08, 18 September 2009 (UTC)
 * You've already got allowed values - these are values - from kL=2npi gives k=2npi/L so you have a range of solutions to try with n=1,2,3,4 etc - these will be your allowed values - solving for Efunction for each n gives the allowed values of E (these are called the eigenvalues I think)83.100.251.196 (talk) 13:16, 18 September 2009 (UTC)


 * You're most of the way there. n has to be an integer, and it follows (using the equations you wrote above) that E can only have certain discrete values for a given L. The degeneracy comes from the fact that different values of A and B with the same k give different solutions with the same energy. (Only the ratio of A and B matters, since the overall scaling factor on the wave function is irrelevant.) -- BenRG (talk) 13:16, 18 September 2009 (UTC)

Does it tend to a continuous function as L goes to infinity, or something else? Spamalert101 (talk) 14:16, 18 September 2009 (UTC)
 * Assuming that the boundaries are potential barriers, and do not dissapear - I think part of the solution would be to make the assumption that the wavefunction goes to zero at +/- infinity. Maybe I'm missing something, but I think a little more info about the boundaries is needed...83.100.251.196 (talk) 14:28, 18 September 2009 (UTC)
 * 83.100.251.196, you are missing the fact that there are no boundaries (Or rather the boundary condition is just periodicity and nothing else). The problem is perfectly fine the way it is stated whithout any other conditions at +- infinity os anywhere else. Dauto (talk) 15:21, 18 September 2009 (UTC)

Incinel, inkinel, ...?
I was watching an episode of World's Toughest Fixes where they were working on an aircraft. The vertical fin was attached with bolts made of a metal that sounds like inkinel ("a metal harder than steel, harder than titanium"). I tried a couple of spellings but found little on google. What is that metal? Do we have an article on it? 62.78.198.48 (talk) 18:01, 18 September 2009 (UTC)
 * Inconel ? 83.100.251.196 (talk) 18:16, 18 September 2009 (UTC)
 * Inconel is used for high temp applications. I would question why the bolts on the vertical stabilizer of an airplane would need that (unless perhaps it was supersonic), but it sounds like 83.100 might have it.  Googlemeister (talk) 18:43, 18 September 2009 (UTC)
 * It seems like inconel has similar properties to Kovar (which is a brand-name, I believe, for particular nickel-iron-cobalt alloys). Kovar is a useful alloy because its coefficient of thermal expansion matches that of glass.  It's possible that Inconel's thermal expansion matches that of the carbon-fiber, fiber-glass, or other synthetic or composite material that the vertical stabilizer is made of.  It would be extremely undesirable if the metal tail portion thermally expands at a different rate than the vertical stabilizer - potentially leading to cracking, fissuring, and other disaster scenarios for an airframe.  I would guess that Inconel is used for this reason, rather than its high melting point.  One of the most complicated mechanical challenges in a modern airframe is making all the exotic materials (carbon fiber, phenolic paper, fiber-wrap, exotic metal alloys, plastics and other synthetics) play nice together.  Remember that hardness used in lay-person-speech may not be the correct usage - they may actually be referring to a wide variety of material properties - toughness, ductility, hardness, impact strength, compressive strength, etc.  Nimur (talk) 21:27, 18 September 2009 (UTC)


 * This search seems to confirm it http://www.google.co.uk/search?hl=en&q=inconel+boeing+767&meta=&aq=f&oq= it looks like they had problems with the standard stainless steel bolts (as well as some other parts), so went for the 'best alloy' they could get for bolts - it's probably not a specific design requirement for inconel - they just will have wanted an alloy that would be trouble free.83.100.251.196 (talk) 21:53, 18 September 2009 (UTC)
 * ".. replacement of all H-11 steel alloy barrel nuts and bolts with Inconel nuts and bolts, which ends the repetitive inspections. " 83.100.251.196 (talk) 21:56, 18 September 2009 (UTC)


 * Inconel is used for three reasons: 1) it's very strong, 2) it retains its strength at high temperatures better than other metals, and 3) it's resistant to chemical attack. --Carnildo (talk) 01:05, 23 September 2009 (UTC)

remove reproductive organs
I'm writing a book about a woman who hates her reproductive organs and wants them gone. She absolutely hates the idea of pregnancy, sex with men or any implication that her body could produce a child if she was raped or something. What scientific things could she do to either remove or destroy her reproductive organs without causing damage to herself? What medical procedures would be most efficient and safe for her to undergo to achieve this? Any and all suggestions are welcome, this book is a wacky tale so weird and wonderful ideas are welcome, as long as they actually work in real life. Thanks.


 * For starters, you want to read hysterectomy. --Anonymous, 18:46 UTC, September 18, 2009.


 * Oh, you already posted about that on the Miscellaneous Desk. Okay, it's not the same question, but... --Anon, 18:52 UTC, Sep. 18.
 * Yes, similar question although I thought this aspect of the question would be better suited to the science desk


 * Also look at Oophorectomy - remove the ovaries and there are no eggs, just like spaying female cats and dogs.  Ron h jones (Talk) 20:40, 18 September 2009 (UTC)
 * You can sterilise a women without removing the ovaries - you just need to cut/partially remove the fallopian tubes. --Tango (talk) 01:30, 19 September 2009 (UTC)
 * True, but if she hates her reproductive system so much, then ovary removal will also stop her periods - which if left might remind her about her sexuality.  Ron h jones (Talk) 18:49, 19 September 2009 (UTC)
 * Phalloplasty? Presumably without the other aspects of gender reassignment. Not sure about efficient, but it's certainly wacky. 84.12.138.49 (talk) 22:09, 18 September 2009 (UTC)
 * Tying the tubes is the way to go. The female equivalent of vasectomy. You don't want to mess around with innards too much - the more you do, the more risk of complications. Tie the tubes and leave everything else intact. Especially leave the ovaries, as the source of female hormones and such - unless you want your protagonist to develop a mustache. Baseball Bugs What's up, Doc? carrots 02:15, 19 September 2009 (UTC)
 * This seems like a good option. Is there a specific name for female phalloplasty or cutting the fallopian tubes which I could look up? Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)
 * Yes, it's called Tubal ligation. Baseball Bugs What's up, Doc? carrots 09:22, 19 September 2009 (UTC)


 * People's feelings change over time - it would be a serious mistake to do something irreversible even if it seemed like a good idea today. SteveBaker (talk) 02:21, 19 September 2009 (UTC)
 * Since the book is supposedly a fantasy, maybe instead of having them tied she could have a valve installed in each tube, which could be turned open or closed under certain circumstances. Baseball Bugs What's up, Doc? carrots 02:32, 19 September 2009 (UTC)
 * No, she wants any possibility of becoming pregnant gone for good. This will NEVER change. Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)
 * Then tying the tubes is the best bet, as it's the least invasive and traumatic to the body and is fully effective in preventing pregnancy. Baseball Bugs What's up, Doc? carrots 09:19, 19 September 2009 (UTC)

Thanks everyone! I'm going to read up on this, if I have any more questions I hope it will be ok to ask again.

1,2 diketones and ascorbic acid
I know 1,3-diketones rapidly convert into their enol forms because of hydrogen bond stabilisation. But what about ascorbic acid? Why is it predominantly in enol form? Here, the inductive effect seems more important than any hydrogen bonding effect (you'd have to form a four-membered ring for the alcohol proton to hydrogen bond with the ketone.) Is it carbonyl-carbonyl repulsion and also the fact that the alkene bond stabilises the carbons next to the alcohol groups? John Riemann Soong (talk) 20:20, 18 September 2009 (UTC)
 * very short answer - enol form includes a conjugated pi system: an enone - which gains additional stabilisation from interaction of the C=C and C=O pi systems. (also see diketone)
 * 1,3 diketones are predominately in the enol form for this reason eg 1,3 dioxocyclohexane (cyclohexane-1,3-dione) has increased acidicity too, despite being unable to form the hydrogen bond. For unconstrained 1,3 diones the potential for hydrogen bonding (or coordination to a metal) is 'icing on the cake'.83.100.251.196 (talk) 23:45, 18 September 2009 (UTC)
 * Why is diacetyl found predominantly as a diketone though, and not in enone form? Is it because the terminal alkene is destabilised? (Wow, hyperconjugation gives a large enough stabilisation to determine whether something is found in enone form or not?) John Riemann Soong (talk) 15:23, 19 September 2009 (UTC)
 * Um, anyone? John Riemann Soong (talk) 01:29, 22 September 2009 (UTC)

Natural walking speed?
Hi. I know that I swing my arms while walking, kind of like a pendulum. The swinging of my arms is coordinated, more or less, with the speed of my gait. (The right arm goes forward as the left leg steps forward.) I also know that a pendulum has, at least at a decent first approximation, a natural period that depends on the pendulum's length. Therefore, since my arms are of fixed length, they must have a natural period. Therefore, I have a natural walking speed determined by the lengths of my arms.

Does that make any sense? If so, do people tend to walk at this pace, or not? Would it be more efficient if we did? -GTBacchus(talk) 23:38, 18 September 2009 (UTC)
 * yes it makes sense - but I don't think that the arms are free oscillators - specifically consider the rotating motion of the hips (and to a lesser extent torso) as you walk (eg think about those 'speed walkers' at the olympics) - so the motion of the arms, can serve also to provide a small amount of additional thrust or drive to the walking motion. I'm sure a human locomotion expert will be along soon>.83.100.251.196 (talk) 23:50, 18 September 2009 (UTC)
 * Clarify - it's not clear to me whether the arm motions helps thrust, or serves to reduce impulse or control balance when walking.. It does seem that the movement of the arms is related to walking motion and is muscular in nature, nor is it clear whether this reflex muscle motion of the arms is helpful, or an evolutionary throwback to quadrupeds , or a safety mechanism, or a bit of all. 83.100.251.196 (talk) 00:37, 19 September 2009 (UTC)
 * This seems convincing to me:"During rhythmic movement, arm activity contributes to the neural excitation of leg muscles. These observations are consistent with the emergence of human bipedalism and nonhuman primate arboreal quadrupedal walking."
 * This seems to confirm that swinging arms is beneficial to reducing impulsive forces: Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it. Walking with opposite-to-normal arm phasing required minimal shoulder effort but magnified the ground reaction moment, causing metabolic rate to increase by 26 per cent. Passive dynamics appear to make arm swinging easy, while indirect benefits from reduced vertical moments make it worthwhile overall.
 * Also from the same place "The shoulder muscles contribute to active swinging (Fernandez-Ballesteros et al. 1965)" see link above.83.100.251.196 (talk) 00:45, 19 September 2009 (UTC)


 * After all that sigh see  "..A vast majority of people exhibited an actual angular velocity exceeding the expected theoretical angular velocity calculated for a virtual pendulum of similar mass and length characteristics.."
 * This suggests that people swing their arms faster than that expected from a pendulum, but doesn't answer if it would be more efficient to walk slower.83.100.251.196 (talk) 00:50, 19 September 2009 (UTC)
 * You might find the graph: figure 8.19 page 212 "Muscles, reflexes, and locomotion" by Thomas A. McMahon helpful - note that at below 5mph (a good walking speed) that energy use is not linear with speed (ie not E=k x Speed ) - but that the energy use remains almost constant for motion between 1 and 5 mph - though it does decrease a little at lower speeds - the obvious conclusion to this is that it is not more efficient to walk slower than a standard walking pace (assuming a power=force x velocity law).83.100.251.196 (talk) 00:58, 19 September 2009 (UTC)


 * Try walking while holding your arms stiff at your sides, and you'll see the value in arm motion. It's not like a pendulum, it's fully-body coordination. Baseball Bugs What's up, Doc? carrots 11:54, 19 September 2009 (UTC)
 * Sure, I think that's clear enough, but I don't see why that full body coordination can't be reinforced by (or alternatively have to work against) something inherent about the swinging arm. I don't think the value in arm motion has been brought into question, just whether or not there might be a most natural period for it. If arm motion weren't an important part of walking, the question would be meaningless. -GTBacchus(talk) 01:33, 22 September 2009 (UTC)