Wikipedia:Reference desk/Archives/Science/2011 July 4

Science desk
< July 3	<< Jun | July | Aug >>	July 5 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 4

Connection vagina - uterus

When a woman is pregnant, is this connection closed somehow? I suppose it has to be, to prevent the amniotic liquid to leek. Wikiweek (talk) 00:16, 4 July 2011 (UTC)

It is the placenta that keeps the amniotic fluid, and thus the developing fetus, in place; birth is imminent (relatively) when the placenta breaks and the amniotic fluid floods out. There is a good diagram in the placenta article. Bielle (talk) 00:25, 4 July 2011 (UTC)

See cervical effacement, cervical dilation. Wnt (talk) 01:54, 4 July 2011 (UTC)

The placenta most decidedly is not functioning to keep the amniotic fluid inside the uterus; that's the function of the amniotic sac, as Richard Avery notes. If the placenta is blocking the cervix, it's a dangerous and abnormal situation (the condition is known as placenta praevia; it can cause excessive bleeding at the time of birth and can result in both maternal and fetal death.) - Nunh-huh 06:35, 4 July 2011 (UTC)

Also cervical mucus plug. Dragons flight (talk) 06:14, 4 July 2011 (UTC)

See Amniotic sac which explains that the foetus is contained inside a membraneous sac along with the amniotic fluid. This sac is attached to the wall of the uterus by the placenta. When midwives or obstetricians (or anybody) talks about 'breaking the waters' in the final stages of pregnancy it is the rupture, deliberately or naturally, of this sac which occurs. Richard Avery (talk) 06:23, 4 July 2011 (UTC)

Big thanks to Ruichard Avery and Nunh-huh! That's the last time I post a "fact" I thought I remembered without checking first. It's a good job some people are paying proper attention. Bielle (talk) 06:43, 4 July 2011 (UTC)

To be clear, the amniotic sac is the watertight barrier - but so far as I know, once the cervix has ripened sufficiently, its breakage is almost inevitable. Note that the chorion, the outer layer of the amniotic sac, which is separated from the amnion in young embryos, is contiguous with the placenta (a tissue with both maternal and fetal components, including the chorion, formed wherever the chorion touches the implantation site of the placenta). Thus saying that the placenta forms part of the barrier is not far off from the mark, even in non-pathological cases where the placenta doesn't line the inside of the cervix. Wnt (talk) 09:01, 4 July 2011 (UTC)

:: Uhmm, what happened to my response then? Richard Avery (talk) 17:22, 4 July 2011 (UTC) Thank you whoever.Richard Avery (talk) 07:21, 5 July 2011 (UTC)

Badger page needs help

They are using badger as a paraphyletic page for anything with 'badger' in it's common name, but deceptively have a taxobox which implies something entirely less pathological in my mind. Anyways it screwed up all my region maps because I wasn't watching for insanity. There is probably a lot of mess in there and should be checked for correctness by an expert.Craig Pemberton (talk) 01:41, 4 July 2011 (UTC)

Futhermore the taxon Melinae is not listed at ITIS, so maybe there is some controversy over this point. Craig Pemberton (talk) 01:58, 4 July 2011 (UTC)

Why are you posting this here? Are you encountering some sort of unreasonable resistance when you attempt to fix this yourself? Please addres your concerns on the article page or attempt the edits yourself. μηδείς (talk) 23:21, 8 July 2011 (UTC)

Death, Undead, Zombie

I read the Problems of Definition of Death and we are now entering era where dead is hard to define. It used to be when heart cease beating, some one are prounounced death, but now by using artificial pacemaker, one can continue living. And then people who is braindead is considered dead, but this also challenged by Dr. Franklin Miller. So are these people considered undead? And also if some people with brain damage goes without care, they are neither alive or dead cause of the brain damage, and he still feels hungry and thirst but unable to cook or get descent food so they just ate anything that he found on his way. Can this people be called zombie? And if the people knowledge of medicine advanced, and many of these undeads were taken care, but if a sudden event like war made them untreatable, will we have a zombie apocalypse? roscoe_x (talk) 03:07, 4 July 2011 (UTC)

I think you are introducing a lot of speculation and unnecessary assumptions. "undead" is not a scientific term, so science would not recognise anyone as "undead". Also just because someone doesn't tick "all the boxes" we have created to define being either dead nor alive, does not mean they are "neither", it just means that our current definitions perhaps are not perfect, it's not impossible that the closer you examine it the line might be so fuzzy that perfect delineated definitions might not even exist, there might be a range, (death spectrum disorder, lol). But these new findings do not indicate that something NEW is happening to humans, it's purely what we're LEARNING about the process, i.e. if we haven't had a zombie apocalypse yet, we are no more likely to have one now just because we are learning more about consciousness and finding new difficulties in the diagnosis of what it really means to be dead. I think it's purely an artefact of looking at the subject on a finer scale then ever before. Vespine (talk) 03:53, 4 July 2011 (UTC)

An essay I found when looking for this [1] seems more philosophical than practical. A patient is deemed dead because it is well understood he is doomed, but his heart stops; but the transplant of the heart shows it can be started again. I think common sense tells us that someone who is "on the way out", who has passed the usual natural point of irreversible death, can be thought of as effectively dead, in order to save another. "Common sense" involves complex philosophical conclusions, which sometimes (as in this case) are more sophisticated than the theory of ethics to which people appeal. But it is true that with sufficient analysis, some cold-hearted decisions should be apparent. Wnt (talk) 09:10, 4 July 2011 (UTC)

In an abbreviated extract from The Mikado comic opera someone who was reportedly executed, but should not have been, comes to life to the consternation of the executioner who is thereby caught in a lie to the Mikado.

Enter Nanki-Poo

Nanki-Poo. The Heir Apparent is not slain.

Ko-Ko. Your Majesty, it's like this: It is true that I stated that I had killed Nanki-Poo. ... It's like this: When your Majesty says, "Let a thing be done," it's as good as done — practically, it is done — because your Majesty's will is law. Your Majesty says, "Kill a gentleman," and a gentleman is told off to be killed. Consequently, that gentleman is as good as dead — practically, he is dead — and if he is dead, why not say so?

Mikado. I see. Nothing could possibly be more satisfactory!

All sing the finale. Curtain.

Cuddlyable3 (talk) 13:36, 7 July 2011 (UTC)

Dehydration - overnight re-ocurrence

On a few occasions I have got dehydrated on a long hike, which gives me a headache, dry mouth, difficulty concentrating, dark urine, and of course a great thirst. During the evening I drink plenty of fluids and recover - symptoms go away and light urine. The next morning I find all the symptoms have returned, though not as bad!

I have wondered why this happens. My theory is that there is some tissue or organ that can only rehydrate water very slowly and that this is taking water from the rest of my body. Is this right? If so which tissue or organ is it? -- Q Chris (talk) 06:28, 4 July 2011 (UTC)

Yes, I believe that's it. It's most of the tissue in the body, mainly muscle, I think. I know that during dialysis, they have the opposite problem. That is, they can't take the excess fluid out too quickly, because it takes times to migrate from the tissue into the blood stream, where they can get to it. StuRat (talk) 06:42, 4 July 2011 (UTC)

The Reference desk isn't a suitable place to ask this question. As it has happened to you more than once I suggest you mention it to your doctor, as he will wont to excluded the early symptoms of something else. Let him then tell you how to rehydrate to avoid a rebound. There is also the potential problem of an increased risk of suddenly become incapacitated with heat stroke if you're getting this bad. --Aspro (talk) 12:02, 4 July 2011 (UTC)

This was not a request for medical advice. I know the medical advice would be "take plenty of water with you when hiking all day in hot weather". It just happens that a couple of times I have underestimated how much to take, i.e the weather has been hotter than I anticipated and/or the terrain more difficult -- Q Chris (talk) 15:05, 4 July 2011 (UTC)

I've noticed the same thing many times, having done a lot of hiking in the Arizona desert in hot conditions. I don't know the answer for sure, but my hypothesis is that the cause is the balance between sodium and potassium. These are the two main ions in the body, but when you sweat you lose a lot more sodium than potassium, because potassium is mainly located inside cells while sodium is mainly located outside. You restore sodium by eating salty things; you restore potassium mainly by eating fruits or vegetables (or drinking fruit or vegetable juices). If you sweat a lot, it can take a while to get the ions back into proper balance, and in the meantime, the water inside the body moves back and forth between the intracellular and extracellular spaces to maintain osmotic equilibrium. For what its worth, if you hike a lot in hot weather, taking Gatorade (or diluted Gatorade) instead of water will make it easier to stay in good shape. Looie496 (talk) 18:09, 4 July 2011 (UTC)

Note that there is also an "insensible loss" of water by breathing, etc., even while asleep, especially in desert conditions. Wnt (talk) 13:29, 6 July 2011 (UTC)

I just experienced exactly the same. This morning I felt kind of like my eyes was bulging out a bit in my head, and my urine was quite dark yellow, and then I came across this question and it all made sense. Yesterday afternoon I did a 45 min. moderate running exercise in sunny weather. Drank some fresh lemon water enroute - continued to drink a lot of water during the evening - feeling quite well hydrated - ate vegetables and eggs for dinner, a bun with mackerel for lunch. I hadn't been doing exercising for the last 3 months. 85.81.121.107 (talk) 06:52, 7 July 2011 (UTC)

Reccomendations of non-English sources on Evolution

I'm translating Evolution into Interlingua for ia.wiki, seeing as Evolution is a featured article here and we need more featured articles on our wiki. Due to the nature of the language, one of the criteria for being a featured article on the Interlingua Wikipedia is diverse sources: references from more than one source language, and from more than one nation. It's not make-or-break for becoming a featured article, but it'd make the case stronger.

For the Evolution article, I'd like recommendations as to non-English resources to use as primary references. References in languages I am able to read (Spanish, French) are preferred, but I can muddle through just about any language to find a reference if it's suitable. It's not a make or break when it comes to the article being featured, but it'd make the case much stronger.

Asking here because the Evolution talk page asks that only discussion related to altering the article takes place there. Almafeta (talk) 09:35, 4 July 2011 (UTC)

While a little piece of my scholar's soul cringes at the thought of adding footnotes to an article for the principle purpose of increasing the number of languages used in its references, I would suggest visiting the versions of the article which exist on other-language Wikipedias. While many of those articles do rely heavily on English-language sources, you should be able to find 'local' references as well. (In your preferred languages, see fr:Évolution (biologie) and es:Evolución biológica.) Those references should (in theory, at least) have undergone some measure of scrutiny by native speakers of those languages. TenOfAllTrades(talk) 14:00, 4 July 2011 (UTC)

I agree. There are some good overview-type sources in the fr article. Itsmejudith (talk) 21:03, 4 July 2011 (UTC)

Inertial mass

Suppose two positive charges are at rest (initially) close to one another. They'll repel, and begin to speed up. Will their masses increase? By $m={\frac {m_{0}}{\sqrt {1-v^{2}/c^{2}}}}$, I would expect that they should, but by E = mc^2 and conservation of energy the masses should be constant. How can the paradox be resolved? 74.15.136.219 (talk) 12:59, 4 July 2011 (UTC)

There is no paradox. The particles on their own do not form a closed system - you also have to take into account the potential energy stored in the electromagnetic field. It is this potential energy that is transformed into kinetic energy and (if the particles are travelling relativistically) increased mass. Gandalf61 (talk) 13:09, 4 July 2011 (UTC)

But if we viewed the situation in another reference frame moving relative to the first, wouldn't the momentum of the system appear to increase if the masses of the charges were to increase? 74.15.136.219 (talk) 18:00, 4 July 2011 (UTC)

The electromagnetic field, having energy, will also have momentum that must be included in the calculation of the total momentum from the point of view of that reference frame. Dauto (talk) 18:20, 4 July 2011 (UTC)

It is interesting to consider what happens if one charge is an electron and the other an antiproton; the electron should move roughly 1800 times faster and have 1800 times more of the final kinetic energy/relativistic mass. But it isn't actually surprising that the faster moving charge interacts and collects more of the mass-energy from an electromagnetic field. Though it still confuses me a bit to think of "where" the mass in that field originally resides, and what sort of particle it might be described as. Wnt (talk) 18:23, 4 July 2011 (UTC)

The particles are virtual photons. Dauto (talk) 20:29, 4 July 2011 (UTC)

Virtual photons with real mass...? Wnt (talk) 19:37, 5 July 2011 (UTC)

Yes. See the third paragraph of virtual particle. Red Act (talk) 19:50, 5 July 2011 (UTC)

I hadn't known what to make of that before. It says virtual photons can have mass; but here we see that they do have mass, and a specific mass. The potential energy stored in the field between two charges drops in proportion to the distance between them - because, I take it, the virtual particles going between them have some fixed mass-energy * lifespan that is a "fraction of Planck's constant". The longer the distance, the longer the time, the less mass is held within the field. And the mass is either positive or negative depending on whether the charges are same or different. Interesting. But what fraction of Planck's constant, and is it the same for all virtual photons mediating EM fields? Wnt (talk) 23:58, 5 July 2011 (UTC)

(I tried to work out this fraction for two electron charges assuming one virtual carrier, but came up with the peculiar result of 0.00116140962 s^2 = 8.9875517873681764E9 / (6.2415096516E18^2 * 6.6260695729E-34 * 299792458). I was thinking energy = FRACTION * Planck's / (X/c) = Coulomb's * charge * charge / distance. Sigh... Wnt (talk) 01:18, 6 July 2011 (UTC)

Okay great, thanks a lot, I think I understand. Sort of related question: rest mass is invariant, which means it is the same in all reference frames. But this doesn't seem to rule out the possibility that rest mass changes. Is there ever a situation where the rest mass of a fundamental particle changes? 74.15.136.219 (talk) 21:43, 4 July 2011 (UTC)

No, a fundamental particle of any type all by itself always has the same rest mass. (Some fundamental particles never appear by themselves; see color confinement.) However, a collection of multiple fundamental particles in close proximity won't in general have the same mass as the sum of the masses of the constituent fundamental particles; see mass defect. Red Act (talk) 22:53, 4 July 2011 (UTC)

In the other hand, if the particle is not by itself it might behave as if it had a different rest mass. see Effective mass (solid-state physics). Dauto (talk) 05:57, 5 July 2011 (UTC)

Okay, but if the potential energy can be defined up to an arbitrary constant, then isn't the mass created by the potential energy ill-defined? 74.15.136.219 (talk) 17:15, 6 July 2011 (UTC)

Specific Term Related to Ancient Anchors

What is the term used to describe baskets of stones or large sacks filled with sand that were used as anchors by the ancient Greeks? This is referenced under Anchor and the History of the Anchor, and I am looking for the specific word that describes it. The word begins with the letter "g." Egudmunsen (talk) 14:27, 4 July 2011 (UTC)

Gabions? Mikenorton (talk) 17:04, 4 July 2011 (UTC)

Maybe this should also be posted to the "language" reference desk. Michael Hardy (talk) 20:59, 4 July 2011 (UTC)

cables question

What is the difference among

-ropes
-cables
-tendons
-wires
-strands
-bars
-rods

in civil engineering(especially in case of prestressed concrete? — Preceding unsigned comment added by 113.199.241.79 (talk) 14:58, 4 July 2011 (UTC)

There are many differences, but perhaps the most obvious is that some of those are only useful in tension (like cables), while the solid objects (like rods) may also be useful in compression, bending, and torsion. StuRat (talk) 15:06, 4 July 2011 (UTC)

Making the assumption that this is for commercially available pre-stressed concrete products (pilings, structural members, light posts, etc) you may also find your choice of materials (plain steel, high-strength steel, corten, stainless, aluminum, etc.) will vary greatly. --Romantic Mollusk (talk) 19:46, 4 July 2011 (UTC)

Complicating StuRat's distinction between "useful only in tension" and "useful in tension and compression" is that sometimes they are distinguished by manufacturing technique instead: Wires are made by drawing through a die; cables are made by bundling a number of wires together. Bars and rods are made through extrusion, and sheets are made through rolling. When I worked in a mechanical testing lab, I occasionally tested wires that would make a decent club, and rods that had to be carefully handled to keep them from bending. --Carnildo (talk) 01:39, 7 July 2011 (UTC)

Rods and bars are intended to be rigid; ropes, cables, and wires are intended to be flexible. Michael Hardy (talk) 21:02, 4 July 2011 (UTC)

Opioids and hearing loss

By what mechanism do opioids cause hearing loss? Could one possible cause is excessive ear wax and a lack of ability to blow that ear wax out (and that that is somehow possibly to do with opioids, particularly in individuals that had conditions requiring them to have grommets when younger

So there are two questions here really. Firstly, by what mechanism do opiods generally cause hearing loss? Secondly, is there a plausible alternative mechanism that could be at work?

Re: difficulty in blowing out ear wax. What is really be referred to here is trouble performing the Valsalva maneuver

This is absolutely not a request for medical advice - the background info is provided for precisely that reason - background!

Cheers,

Egg Centric 18:50, 4 July 2011 (UTC)

When you discuss a medical problem in terms of a specific person and discuss ways of treating it, what you have is a request for medical advice, and asserting that it isn't doesn't change that. Looie496 (talk) 19:34, 4 July 2011 (UTC)

Perhaps I was unclear but there is absolutely no intent to ask for treatment advice whatsover. I'm interested only in mechanisms of action. Egg Centric 19:40, 4 July 2011 (UTC)

Nevertheless, I have extensively refactored the question. Hopefully it's clearer now too! Egg Centric 19:46, 4 July 2011 (UTC)

Hmmm, looking up heroin + deafness on PubMed gets a few papers about heroin causing bilateral sensorineural deafness in really obscure journals that won't even give a clue in the abstract what might be going on. I found another obscure article about oxycodone and hearing loss at PMID 19128688 - a pretty pathetic showing in the scientific literature considering the number of online discussions about people losing their hearing from Oxycontin. There's also a reference to this in the article on Rush Limbaugh. Someone have a PDR handy? Wnt (talk) 19:42, 4 July 2011 (UTC)

Just as an aside, Valsalva is a method of forcing open a dysfunctional Eustachian tube to aerate the middle ear, and nothing to do with ear wax Si1965 (talk) 20:36, 4 July 2011 (UTC)

I quickly scanned our ototoxicity article, but saw no mention of opioids. I will have a dig around at work tomorrow Si1965 (talk) 20:43, 4 July 2011 (UTC)

Ok, well it is theorised that it may feel much like the kind of ear condition that is solved by Valsalva, whatever they may be, as it appears to be found in people who haven't registered with a GP since boarding school or university or some equally distant time who had at least the sensation of blockages there resolved by Valsalva - but same sensation, no resolution after opioids (and definite hearing loss which incidentally is partly resolved by Valsalva) Egg Centric 21:30, 4 July 2011 (UTC)