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January 15

Piggyback IC picture?

Could anyone photograph a piggyback circuit like MK38P70 with a suitable commons license? Electron9 (talk) 00:46, 15 January 2013 (UTC)

I perused the archives but . . . anal sex question

Within the porn industry, there is an increasing amount of (unprotected) anal sex. In reading the wikipedia artical on anal sex and reviewing quite a few archive responses, I am still unsure of something (or a few things).

As I understand the wiki artical, one of the problems is a lack of sufficient lubrication in the anal area that can cause pain and increases the risks of harm. With this in mind, how do porn actresses manage to perform so "vigoriously?" Some of the participants seem to be going at it quite roughly. While I am sure that there is lubricant being used, of course the application of such is not shown. So, how does it get applied and to whom? How can the actresses perform with such "enthusiasum?" Do they mentally block out the pain? How do they reduce the potential harm/injury their "enthusiasm" may cause?

Another related question is how the actors/actresses keep mthemselves safe. The vast majority of scenes do not show the use of condoms. Also, there are many scenes where the penis is removed and the female performs oral sex (sometimes the penis was in her own anus while at other times it was in another woman's anus). So, how do they keep themselves safe?

My apologies for so many queries in one post; I know this is poor form.

99.250.103.117 (talk) 01:16, 15 January 2013 (UTC)

For your first question, they edit out the application of the lube. Which probably causes some people to try it, find it unpleasant and wonder how the actors could do it so easily. The actresses (speaking from a hetero viewpoint, insert various genders as you see fit) who perform so, as you say, vigorously not only have the aforementioned lube but are also often used to performing the act in their own private lives or on camera previously. They're also more comfortable in front of the camera than many people trying it for the first time at home would be. The relaxation helps the men penetrate and keeps the women from feeling (as much) pain. To reduce the potential harm, the actress can have fingers or a toy slide in to again increase the amount of relaxation and start things a bit more slowly. As to whether this is included in the final film is up to the director.

As far as keeping themselves safe from infections and such, some states require porn actors to be tested for STDs every so often. I don't know the specifics but California has laws on the books for such things. Also, the more reputable production companies will encourage testing since it keeps their actors safe and keeps the money flowing in. And as for the Ass to mouth, before doing an anal scene, most if not all actresses perform a enema on themselves to clean out their rectum. Dismas|^(talk) 02:21, 15 January 2013 (UTC)

Stoya did an AMA on Reddit about eight months ago and was asked a question by someone "sorta curious about how anal sex works in porn". Her response mostly had to do with cleanliness/prep so I don't know if it really answers your question, but it's all I got. Braincricket (talk) 02:52, 15 January 2013 (UTC)

iPhone 5 Vibration in Response to Rubbing

When my iPhone 5 is resting on a flat hard surface (a wooden desk), and I rub my finger across the top silver-colored metal edge of the phone (just above the ear speaker), I feel a very faint vibration in response. For comparison it reminds me of the vibrations felt from singing bowels bowls. It does not vibrate if I do the same thing while holding it in my hand other hand, nor if I use my other hand to hold the phone in place on the desk. While it seems to be easiest to elicit this vibration from the top silver edge, I've also gotten it from the right edge too indicating to me it might be possible to do this on every edge (though I have been unsuccessful in my attempts to do so). My question is, what is responsible for the vibration? I originally thought it must be a part or parts within the phone vibrating, perhaps even the mechanism that causes vibration during text messages and other alerts. Then I thought it might simply be a reaction between the surface of the metal and my finger. Any help in solving this mystery will be appreciated! Lord Arador (talk) 03:46, 15 January 2013 (UTC)

See sympathetic vibration. μηδείς (talk) 03:50, 15 January 2013 (UTC)

Thanks, that clears the basics up for me. I'm still wondering though, why certain surfaces or objects (like my phone) will vibrate in response to rubbing while others do not seem to. What differentiates objects on their ability to vibrate so? The references weren't particularly helpful. Lord Arador (talk) 04:14, 15 January 2013 (UTC)

It's not really possible to give a specific answer without physical specifics. I can tell you I have had phones that have and have had phones that have not vibrated when rubbed. But I never got to the point of dissecting one. (Old rotary phones, which I did disect, actually had bells inside!) The relevant fundamental is that these phones are meant to vibrate, so its not surprising that they do. There is probably some tech type here who will tell you there's an internal vibrating plate. I'll retire at this point. μηδείς (talk) 04:26, 15 January 2013 (UTC)

"Singing bowels"? like this guy? Mingmingla (talk) 05:53, 15 January 2013 (UTC)

Wow, although that's surprisingly somewhat relevant, I of course meant singing bowls. Lord Arador (talk) 06:43, 15 January 2013 (UTC)

You might also want to check out friction idiophones, such as Ben Franklin's armonica. ~E: 07:02, 15 January 2013 (UTC):modified:74.60.29.141 (talk) 09:12, 15 January 2013 (UTC)

Evolution (type)

 Scientists believe that these two species evolved from a common ancestor which was forced to North America's southeastern and southwestern corners by advancing glaciers.
 Separated for centuries by vast ice sheets, the survivors evolved into two species which are still separated by a wide gap across the continent's midsection.

From the Chimney swift article →

Which would best describe this as an example?

1. Common descent
2. Adaptive radiation
3. Evolutionary radiation
4. Divergent evolution
5. Other?

(Note: the above articles should do a better job explaining distinctions and commonalities.)
~Thanks, ~Eric 74.60.29.141 (talk) 03:58, 15 January 2013 (UTC)

Is this homework? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 04:22, 15 January 2013 (UTC)

Actually, I'm assisting with editing the Chimney swift article, and was thinking about clarifying, or at least linking to the proper place. ~E:74.60.29.141 (talk) 05:03, 15 January 2013 (UTC)

(EC with all prior below) I'm still somewhat unclear what you want to do. Common descent will obviously describe the relationship between these two species but it also describes the relationship between you, me and the two chimney swift species as well as with all those and the human and chimney swift microbiome. Since we're only describing two species and from the information provided I don't know that Evolutionary radiation or Adaptive radiation are great descriptors of what happened (which is not to say they're wrong presuming the changes are adaptive, simply that AFAIK they normally primarily used for larger scale speciations). Without reading the article, there's a fair chance Divergent evolution as I suspect Allopatric speciation can be said to be involved, and a bunch of other things besides. A lot depends on how similar the species even are, it may be that the amount of change is actually limited anyway (are we sure the changes are even primarily adaptations as opposed to genetic drift?) if the environments were similar and these species haven't actually seemed to diverge that far despite the separation for a long time in which case for some of these terms, while they are not necessarily wrong, may not be great descriptors. In other words, while I appreciate your desire to help, I'm not sure just throwing in a bunch of key words to every article in which they apply is really necessary (is this the norm in FAs?). But if you really want to put something, probably just mention Allopatric speciation if it's correct and leave it at that. Nil Einne (talk) 05:47, 15 January 2013 (UTC)

Y'know, the way you placed this really makes my (prior) suggestion seem redundant. You could've just placed your addition in temporal order, like the rest of us do (ec's are common for us all). -- Scray (talk) 07:04, 15 January 2013 (UTC)

How about Allopatric speciation? -- Scray (talk) 05:18, 15 January 2013 (UTC)

Sounds like an effect of isolation, like with Galapagos tortoises, due to biological dispersal to the various islands. StuRat (talk) 05:23, 15 January 2013 (UTC)

The similarity between the two species is a result of common descent; the differences between them are a result of allopatric speciation, which is a type of divergent evolution as well as a type of evolutionary radiation, and may be a type of adaptive radiation as well (if the differences are adaptive rather than merely random). Looie496 (talk) 05:43, 15 January 2013 (UTC)

That sounds about right. May I quote you on that?   ;)   An {{efn}} might be the best option for this, since it is tangential to the article, and a bit more complex than expected. Btw: "A picture is worth [several] words."

~Thanks again, ~Eric F 74.60.29.141 (talk) 05:59, 15 January 2013 (UTC)

...or, how about simply linking:   ...[evolved into two species] → [Allopatric speciation] ? ~E74.60.29.141 (talk) 06:13, 15 January 2013 (UTC)

Made the link for you -- check it out! :-) 24.23.196.85 (talk) 06:26, 15 January 2013 (UTC)

That does the trick! ~E:74.60.29.141 (talk) 06:52, 15 January 2013 (UTC)

Chimney cleaning

Hello all, I've been meaning to ask this question for some time now: When cleaning chimneys, how exactly can the sweep tell if substantially all the soot and creosote has been removed? In the article Chimney sweep, it says that back when they used climbing boys, they would determine by feel whether the chimney walls were smooth (which meant that the chimney was clean) -- but how did they know when to stop cleaning after this practice was (rightly) outlawed and they changed over to using a telescopic brush? Also, while it's pretty easy to remove loose soot and creosote, how did they manage to remove baked-on gunk without anyone actually going inside the chimney? 24.23.196.85 (talk) 06:23, 15 January 2013 (UTC)

It's a rather gnarly wire brush, capable of scraping it off. StuRat (talk) 16:17, 15 January 2013 (UTC)

Thanks! So one pass through the chimney is all it takes to get all the gunk out? 24.23.196.85 (talk) 00:45, 16 January 2013 (UTC)

I suppose multiple passes are better. Here are some pics of the brushes: [1]. BTW, are you familiar with the creosote sweeping log: [2] ? Using that first would make the creosote more brittle, and thus easier to remove (they claim it will fall off all by itself, but that might be a bit overly optimistic). StuRat (talk) 02:26, 16 January 2013 (UTC)

When I had my chimney inspected last year, creosote and soot buildup was checked simply by shining a rather bright flashlight up the chimney and seeing what the sides looked like. --Carnildo (talk) 02:18, 16 January 2013 (UTC)

With coal fires, as far as I know, you don't get the creosote deposits that you get with burning conifer logs. When I was a child in 1960s London, my memory of the chimney sweep (who used to arrive on a bicycle equipped with a large box to carry the soot away with) was that he used to run the brush up and down the flue until the soot stopped falling out. I remember being asked to stand in the back garden and yell when the brush appeared out of the chimney pot. Those who didn't employ a sweep would have to call out the London Fire Brigade when the accumulated soot in their chimneys caught fire, a fairly regular occurrence. The firemen would use a stirrup pump to squirt water into the flue, making a terrible mess in the process. Alansplodge (talk) 15:15, 16 January 2013 (UTC)

Thanks for the info, everyone! You see, I'm writing a military thriller that takes place during World War 2, and one of the important characters has a day job/cover job as a chimney sweep (whereas his work in the Maquis is as a demolitionist and a spotter) -- so naturally I'm trying to find out as much as I can about that trade.  :-) 24.23.196.85 (talk) 01:04, 17 January 2013 (UTC)

You're welcome. May we mark this Q resolved ? StuRat (talk) 17:46, 18 January 2013 (UTC)

If you want -- but if anyone else wants to chime in, they're welcome to do so. 24.23.196.85 (talk) 02:47, 19 January 2013 (UTC)

Gender differences in autism spectrum disorders

Why are autism spectrum disorders so much more common in males than females? --168.7.238.100 (talk) 06:57, 15 January 2013 (UTC)

"This could be because of genetic differences between the sexes, or that the criteria used to diagnose autism are based on the characteristics of male behaviour. However, our understanding is far from complete, and this will remain the case until we know more about the causes of autism."

References

~E:74.60.29.141 (talk) 07:20, 15 January 2013 (UTC)

I'd endorse that reference strongly. It's not at all clear that the large gender imbalance in cases of autism is not an observational artefact. AlexTiefling (talk) 11:08, 15 January 2013 (UTC)

There is some suggestion that autistic females exhibit different symptoms (such as Anorexia nervosa...see especially: Anorexia_nervosa#Relationship_to_autism) than autistic males who have the same underlying disorder. If anorexia and autism are merely different sides of the same coin then perhaps there is no gender disparity in the underlying disorder at all - but rather in the way those symptoms are presented and the outcome of the resulting diagnosis. It doesn't help that autism is a "spectrum" disorder with victims going all the way from near normality to people who are totally cut off from humanity - and even people who are nominally at the same point in the spectrum often have wildly different symptoms. That fact might be a reflection of there being multiple underlying disorders with similar outcomes that science has bundled under the "autism" term - or it might reflect any number of other environmental, developmental or genetic differences amongst victims that might change the way the disorder presents itself - which would lend credibility to the anorexia nervosa connection in females.

That said, the research work surrounding autism is very difficult and solid results are hard to come by.

This might be a time when the best answer for our OP is "Nobody knows".

SteveBaker (talk) 15:37, 15 January 2013 (UTC)

Our article Autism mentions the "extreme male brain theory", but I'll decline to say much about it because of my skepticism of such a simplistic idea. I think of it more as a question of whether genes on the sex chromosomes could be involved (see [3] for example). Though one can argue that this is sort of the same concept, the point is, a few genes being in a more extreme form - even SRY - are not I would think of as "hyper-maleness", plus, the fact that autism is seen more often in males means that genes which make someone male should naturally turn up as involved, so there's something a little circular about it. Still... trace that linkage back far enough, and it's got to be connected to something. Wnt (talk) 16:49, 15 January 2013 (UTC)

There are lots of other odd gender-linked conditions surrounding this. For example consider that:

1. Left-handed people are more often autistic than right-handed people (or to put it the other way around, autistic people are more often left-handed than the general population).
2. Dyslexia is a common co-morbid condition of Autism - ie more people have both conditions than statistically likely if they are completely unrelated.
3. Dyslexia is much more common in left handers.
4. Males are more often left-handed than females are.
5. Males are also more often dyslexic than females.

...and so, again, we see a gender-related difference. Is this because left-handedness and dyslexia are caused by mild forms of autism - or because autism, dyslexia and left-handedness are all separately related to maleness and therefore there will be a statistical correlation between them even though they don't share a common cause?

Which is cause and which is effect? This is truly insufficiently well studied.

SteveBaker (talk) 17:23, 15 January 2013 (UTC)

Perhaps the strangest sex-linked trait is sexual orientation. That is, a disproportionate number of males seem to be sexually attracted to females. :-) StuRat (talk) 01:08, 17 January 2013 (UTC)

K in KCl

How much (in gram) elemental potassium is there in 1 gram of potassium chloride? --PlanetEditor (talk) 07:17, 15 January 2013 (UTC)

Sounds like homework. What are the proportions (as percentage of total, based on atomic weight) of potassium and chloride in KCl? -- Scray (talk) 07:48, 15 January 2013 (UTC)

74.55g of KCl contain 39.10g of potassium and 35.45g of chlorine. I hope I did it right.--Stone (talk) 09:07, 15 January 2013 (UTC)

Ok, thanks. --PlanetEditor (talk) 14:16, 15 January 2013 (UTC)

Acceleration of acceleration

Student me, please help. How do we find the d covered if we have acceleration of acceleration rate. For eg: A train starts from rest, and starts acceleration. Each second the acceleration rate goes up by 1m. What will the distance covered and velocity after 10 secs? How will we dot it? [Not a homework, please tell me, its just intuition of an 11 year boy.]— Preceding unsigned comment added by 117.226.159.194 (talk) 11:05, 15 January 2013 (UTC)

The rate of change of acceleration is called Jerk (physics). They even have to consider the change of jerk when designing roller coasters. Dmcq (talk) 12:01, 15 January 2013 (UTC)

First get a formula for the acceleration. From what you describe it sounds like a(t) = t, where t is seconds. Then take the antiderivative (twice) which is quite easy for a function like this, in order to get the velocity and displacement. See Polynomial#Elementary_properties_of_polynomials for the antiderivative of a polynomial. Staecker (talk) 12:47, 15 January 2013 (UTC)

The answers can be obtained using the algebraic equations for uniform jerk given in the article which Dmcq linked to, in the section here: Jerk_(physics)#Equations Modocc (talk) 13:15, 15 January 2013 (UTC)

How can we derive the formula? 117.226.159.194 (talk) 14:07, 15 January 2013 (UTC)
$s=ut+{\frac {1}{2}}a.t^{2}+{\frac {1}{6}}jt^{3}$

By definition, $u(t)={\frac {\mathrm {d} s(t)}{\mathrm {d} t}}$, so $s(t)=\int _{0}^{t}\!u(t)\,dt\,+s(0)$

and likewise, $a(t)={\frac {\mathrm {d} u(t)}{\mathrm {d} t}}$, so $u(t)=\int _{0}^{t}\!a(t)\,dt\,+u(0)$

And $j(t)={\frac {\mathrm {d} a(t)}{\mathrm {d} t}}$, so $a(t)=\int _{0}^{t}\!j(t)\,dt\,+a(0)$

If $j(t)=constant=j$, then we can start solving the integrals, using the rule $\int _{0}^{t}ct^{b}\,dt=c{\frac {t^{b+1}}{b+1}}$.

We get $a(t)=\int _{0}^{t}j\,dt+a(0)=jt+a(0)$, so $u(t)=\int _{0}^{t}jt+a(0)\,dt+u(0)={\frac {1}{2}}jt^{2}+a(0)t+u(0)$

And finally, $s(t)=\int _{0}^{t}{\frac {1}{2}}j.t^{2}+a(0)t+u(0)\,dt+s(0)={\frac {1}{6}}jt^{3}+{\frac {1}{2}}a(0)t^{2}+u(0)t+s(0)$

And this is essentially the formula that you wanted to derive. - Lindert (talk) 15:05, 15 January 2013 (UTC)

milliequivalent

I have purchased a potassium citrus tablet. In the ingredients section the following is written:

• "Potassium Citrate IP 1000 mg (10 meq potassium per tablet)"

So how much elemental potassium is there in 1000 mg potassium citrate? How could I convert meq into mg? --PlanetEditor (talk) 14:20, 15 January 2013 (UTC)

I do wonder if you're working homework here, in which case it is useful to realize that we have an article milliequivalent which explains the relationship with millimolar (Note K+ and H+ carry the same charge, but there's more than one K+ in the formula of potassium citrate). We also have an article on potassium citrate in which the molecular weight can be looked up. (For serious homework you should double check our figures in case someone's having a prank...) You may find it easiest to determine how many moles of potassium citrate are in 1000 mg, then how much that many moles of potassium weighs, but you could also figure out the ratio first by the ratio of weights if that's what you prefer. Wnt (talk) 16:40, 15 January 2013 (UTC)

Pluto and Neptune collision

From the images below and since Neptune and Pluto cross paths about every 200+ years, is it likely the two will ever collide? Are there any theories on this? Thanks ツ Jenova20 ^(email) 14:31, 15 January 2013 (UTC)

Pluto's orbit and the ecliptic.

Orbit of Pluto—ecliptic view. This 'side view' of Pluto's orbit (in red) shows its large inclination to Earth's ecliptic orbital plane.

Their paths do not cross. They path of Pluto at times takes it closer to the sun than Neptune, but it does so without ever crossing the path that Neptune takes in its orbit. --Jayron32 14:34, 15 January 2013 (UTC)

This animation shows the relationship of the orbits of Neptune and Pluto over time. It's plotted relative to Neptune, which makes it (the blue blob) stationary in this view. Note the loops of the orbit of Pluto, where it dips closer to the Sun than Neptune. But the resonant character of their orbits means the two aren't ever very close. I can't find an estimation based on modern data, but a 1965 paper "Libration of the close approaches of Pluto to Neptune" by Cohen & Hubbard puts the closest approach at a massive 18AU.[4] -- Finlay McWalterჷTalk 15:43, 15 January 2013 (UTC)

Ahhh...very interesting. Thank you very much for that. I suppose if they could collide on their paths then they would have done it by now anyway. Thanks again guys ツ Jenova20 ^(email) 16:13, 15 January 2013 (UTC)

See Stability of the Solar System#Neptune–Pluto resonance says "Although the resonance itself will remain stable in the short term, it becomes impossible to predict the position of Pluto with any degree of accuracy more than 10–20 million years (the Lyapunov time) into the future" -- Finlay McWalterჷTalk 16:19, 15 January 2013 (UTC)

I'm rather confused watching the simulations on Pluto. It looks to me like it hits the little blue dot, which I assume to be Neptune, both on the top and side views, at the same time. It doesn't look like it is "furthest" from Neptune in the plane of the ecliptic at that time, but like that's when it is crossing the ecliptic. Is there an error in the graphic or am I just somehow looking at it wrong? Wnt (talk) 16:26, 15 January 2013 (UTC)

I agree that those two animations don't help much! At right, I've uploaded the last frame of the top-view animation for clarity (it's still not a great diagram - but it'll have to do!). The problem is that you need to visualize the two orbits in three dimensions. Look carefully at the top-view diagram. The red line showing the path of Pluto is "beneath" the white grid lines (ie, the white lines block your view of the red line) when the planet is below the plane of the ecliptic (on the left side of the diagram) and "above" those white lines when the planet is above that plane (on the right side). From that, you can tell that the point where Pluto crosses upwards through the plane of the ecliptic (and the red line switches from being drawn below the white lines to being drawn above them) is at about 6 o'clock on the diagram. and goes back down again somewhere around 12 o'clock on the diagram. Now look at the dark blue dot, representing Neptune and the circle representing that orbit. At 6 o'clock, it's about two grid lines inside the orbit of Pluto - and at 12 o'clock, it's about one grid line outside of the orbit of Pluto. So at the two points where Pluto is at the same "height" as Neptune, it's far away "horizontally". So it doesn't matter where the two planets are along their orbits - they still cannot possibly collide because one orbit never comes remotely close to touching the other. SteveBaker (talk) 16:59, 15 January 2013 (UTC)

So if we said the universe was a flat plate, then Pluto is usually above or below Neptune in height because it orbits the sun at a different degree right? Thanks ツ Jenova20 ^(email) 17:11, 15 January 2013 (UTC)

Yes, exactly. (Well..."If the universe solar system was a flat plate...". The universe is far from flat!) And more importantly, the two places where pluto's tilted orbit passes through that "flat plate" are nowhere near where neptune orbits. FYI: That "flat plate" is called "The Plane Of The Ecliptic" - and most of the moons, planets, asteroids and such like orbit more or less exactly in that flat disk. That's because Jupiter's giant gravity tends to pull orbits into that nice, flat, organized disk. The reason why Pluto's orbit is so whacky is a subject of considerable debate. SteveBaker (talk) 17:57, 15 January 2013 (UTC)

No,no, Jupiter didn't create the ecliptic and it doesn't force other objects into the ecliptic. In fact Jupiter interactions with other planets over time - noticeably Saturn - has driven their orbits away from the ecliptic. The ecliptic exists because the planets were formed from a disk of gas and dust that formed around the young sun. Pluto has a different origin. Dauto (talk) 00:37, 16 January 2013 (UTC)

Also see Pluto#Relationship_with_Neptune. StuRat (talk) 17:48, 15 January 2013 (UTC)

You've answered all the questions i had on the subject. Thank you very much ツ Jenova20 ^(email) 11:24, 16 January 2013 (UTC)

Ah, one more. Everything just repeats every 3 Neptune years, about 5 centuries. They only pass each other once (at least in this eon), at almost the furthest possible point. Sagittarian Milky Way (talk) 21:45, 16 January 2013 (UTC)

is this correct?

I made what is my understanding based on what you've said so far for volume of gas/pressure stored inside a fixed-size container. Here:

http://i.imgur.com/Ga1j1.jpg (note: feel free to inline it)

I would like to know if it's correct. Basically, as x goes to the right greater and greater amount of gas is put inside.

Thank you. 86.101.32.82 (talk) 19:00, 15 January 2013 (UTC)

There are a few qualitative issues. Firstly, let us assume we choose a constant temperature that is below the critical temperature of the substance (i.e. a temperature at which it will liquify). As we add mass (taking away heat to keep the temperature constant), at fist the pressure rises close to linearly. As it starts to liquify, the graph then will go exactly horizontal, assuming that it is not supercooled (cooled below its condensation temperature without condensation occurring), where part of the contents of the container will be gas, part liquid. When we have added enough that it is all liquid, the pressure will rise very sharply, nearly vertical but not quite. At some pressure it will probably solidify, most likely creating a tiny horizontal plateau in the steep climb. Further transitions between different phases of solid may occur. Hydrogen, for example, may become metallic at sufficiently high pressures. Eventually, the primary source of pressure will be degeneracy pressure of the electrons, such as occurs in white dwarfs. As the pressure increases the electrons will combine with the protons to from neutrons (with the emission of electron neutrinos, which escape). This is the type of matter expected in the core of a neutron star. By this stage, the substance can not longer be considered to be hydrogen (or whatever we started with). Further compression may lead to a black hole, but that assumes that the substance in localized, so this should not be considered as part of the process without a clearer specification of the context. — Quondum 19:53, 15 January 2013 (UTC)

Thank you for taking the time to describe this curve to me. Is there any way you could draw it (even in paint), you can label the points 1 2 3 4 5 6 with the text tool and explain it here. I would be interested in the values (to rough orders of magnitude) of these things, if you could kind of demonstrate it for me. Thank you!!! 86.101.32.82 (talk) 20:07, 15 January 2013 (UTC)

The science of hydrogen (and other substances) under extreme pressures is not exact, since there are limits to the pressures that can be reached experimentally. You can look at diagrams such as this, which gives density versus temperature but not pressure, or this, which gives pressure versus temperature. Answering your question semi-realistically would require a lot of hunting, reading and probably synthesis of results such as these, so the qualitative description will have to do unless someone else with more direct knowledge in this area can add to this. — Quondum 21:35, 15 January 2013 (UTC)

Note that adding material to a fixed-size container is (in the continuum approximation) equivalent to reducing the size of the container with a fixed amount of material. It is this latter process that is usually discussed, and quantities like specific volume are used that dispense with the irrelevant size of the container. For the vapor-liquid transition, I found an MIT resource with several related figures; many of the lines are exactly the path you're interested in (an isotherm, since you specify a constant temperature). We even have one neat 3D figure here at Saturation Dome. Quondum's description is quite good. If you're really interested, I have some of the appropriate simulation tools (at least for very simple materials). From memory, I've calculated hydrogen to achieve pressures upwards of a TPa at water density with a temperature of $10^{5}$ K (which is not an unreasonable temperature if you compress it quickly rather than isothermally). --Tardis (talk) 03:05, 17 January 2013 (UTC)

January 16

File:Unknown hairy creature on stump.jpg

Can anyone find the name of this cute beast in latin and edit for rename on commons for me? Thanks in advance.--Canoe1967 (talk) 03:02, 16 January 2013 (UTC)

It's a gibbon or siamang, but there are some 16 species and I don't know which this is. It may be a juvenile given the coloring. Do we usually use images with copyright stamps on them? μηδείς (talk) 03:08, 16 January 2013 (UTC)

Kind of looks like a Yeti, presumably due to lack of clues as to the scale. StuRat (talk) 03:28, 16 January 2013 (UTC)

Gibbons are the smallest of apes. μηδείς (talk) 03:33, 16 January 2013 (UTC)

Images on commons are either copyright or public domain. Copyright ones need a free licence for use though. They can insist on attribution (credit) for every use of the image including derivatives. They can insist on name, company, and website displayed by every image if they wish. If someone wants to use it without credit near the image they may have to pay big bucks though.--Canoe1967 (talk) 03:39, 16 January 2013 (UTC)

I guess my point is that I don't ever remember having seen any image at wikipedia with a copyright watermark. I am wondering if such images are deprecated. μηδείς (talk) 03:50, 16 January 2013 (UTC)

The graphics volunteers remove them if they are really ugly and need to be used in articles. See: http://commons.wikimedia.org/wiki/Category:Images_with_watermarks Close to 3,000 now that have been put in the cats and probably far more that haven't.--Canoe1967 (talk) 04:08, 16 January 2013 (UTC)

Thanks, guess you're one o' them guys? μηδείς (talk) 05:00, 16 January 2013 (UTC)

According to the photographer, the photo was taken in São Paulo Zoo. So I guess the monkey is native to Brazil. Does it look like a female black howler? --PlanetEditor (talk) 04:51, 16 January 2013 (UTC)

No, it's definitely a gibbon, a south-east Asian/Indonesian ape of some sort, not a monkey. μηδείς (talk) 04:55, 16 January 2013 (UTC)

I agree it is a 'lesser ape'. I moved it to a more specific unknown category that I think is correct. It is probably harmless until someone wants a quality image of one with proper name. I see there are many unknown in the primate categories.--Canoe1967 (talk) 05:21, 16 January 2013 (UTC)

How about a White-handed Gibbon, (hylobates lar), which the São Paulo Zoo shows pictures of <re-dacted, site has viruses>. Richard Avery (talk) 08:27, 16 January 2013 (UTC)

Fantastic observation. There external features include black face, a white ring surrounding the face, white hair in hands. So it is likely a white handed gibbon. --PlanetEditor (talk) 08:38, 16 January 2013 (UTC)

Seems some admin over there got trigger happy. It is now called File:Something in latin sitting on a stump over water.jpg. I had prepped the re-name template waiting for a latin name and someone went and activated it. I hope they won't be mad when I ask for another re-name. Are we safe to call it: File:Hylobates lar sitting on a stump over water.jpg then? They like latin names for images over there, I think.--Canoe1967 (talk) 18:20, 16 January 2013 (UTC)

I can't open the link Avery has given; it gets a webkit failure in Safari and crashes Internet Explorer. It does seem likely by process of eliminating the other species by their images that this is Hylobates lar. 19:00, 16 January 2013 (UTC)

I'd go for it Canoe. They like latin names because they work in lots of languages and it avoids local names. Richard Avery (talk) 19:50, 16 January 2013 (UTC)

• 'WARNING!' The above link to the zoo lit up my anit-virus as trojan in it. I am going to redact it above.--Canoe1967 (talk) 20:00, 16 January 2013 (UTC)

Resolved

Thanks all for your help. I think I will ask a primate project if they want the watermark removed for articles.--Canoe1967 (talk) 21:06, 16 January 2013 (UTC)

Mars may get humid and muggy?

I never knew Mars may hit 100 F /38 C. However this source said Mars near equator at summer can hit 90 F. I thought Mars for most of the globe is colder than the coldest place on the Earth. Does mid-latitude ever get above 0 C/32 F or mid-latitude is colder than Antarctica and Greenland even on the summer days. Is the polar regions on Mars always cold. Is 70 F of Mars rare or it gets 70 F quite routinely. Is equator or tropical regions of Mars usually bone-chilly or it often gets 70s and 80sF?--69.228.25.10 (talk) 04:09, 16 January 2013 (UTC)

The very sparse Martian atmosphere has a very low heat capacity so its reaching higher temperatures due to insolation is not that surprising. μηδείς (talk) 04:59, 16 January 2013 (UTC)

Warm it may sometimes get, but "humid and muggy" requires atmospheric moisture, not common on Mars. HiLo48 (talk) 05:14, 16 January 2013 (UTC)

Yes, muggy implies a high humidity relative to human comfort, which you are simply not going to get in a CO2 atmosphere with 1% of the Earth's atmosphere's density. μηδείς (talk) 05:30, 16 January 2013 (UTC)

You have two main factors changing temperature on Mars relative to Earth:

1) The increased distance from the Sun makes it cooler, on average.

2) The thinner atmosphere and lack of oceans doesn't transport the heat as well, making it hotter where the sunlight hits, and cooler elsewhere.

Those two factors work in opposite directions at the equator, resulting in daytime temperatures similar to Earth. However, at the poles, both those factors move Martian poles towards being cooler than Earth, resulting in permafrost in areas permanently in shadow. Other minor factors affecting the temperature on Mars relative to Earth are it's reflectivity (albedo), lack of significant greenhouse effect (also due to the thin atmosphere), and tilt.

Also note that the temperature extremes result in migration of moisture towards the poles, in that any moisture at the equator evaporates on the hot days, then blows around until it gets someplace cold enough to precipitate/redeposit as ice. This happens on Earth, too, but here we have countering effects, like glaciers flowing from Antarctica into the ocean, melting, and returning the water to the equator. StuRat (talk) 05:27, 16 January 2013 (UTC)

The greenhouse effect is not at all minor. As our article says, Earth would have an average temperature of -18 degrees if it had no atmosphere, whereas its current temperature is 14 degrees. That's a difference of 33 degrees. --140.180.240.178 (talk) 06:34, 16 January 2013 (UTC)

Which degrees are those? Real Celsius ones, or those tiny American ones? HiLo48 (talk) 08:26, 16 January 2013 (UTC)

Why the Wedgwood scale of course. Who needs those newfangled new-age hippie temperature units anyway? --Guy Macon (talk) 09:01, 16 January 2013 (UTC)

One good thing about Fahrenheit is that you almost never hear it expressed as something-POINT-something (other than maybe 98.6) as it's finely-graded enough to give sufficient information as-is. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:01, 16 January 2013 (UTC)

That's a great argument. When are you getting the speedometer in your car recalibrated into inches per decade? SteveBaker (talk) 16:45, 16 January 2013 (UTC)

Not a good counter-example, since speedometers don't need to include decimal values in either MPH or KPH. Now, if in either system the top speed of a car was about 2, then we would need decimal values. StuRat (talk) 17:44, 16 January 2013 (UTC)

The better example of the latter is the Tachometer, which is typically divided into gradients. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:36, 17 January 2013 (UTC)

Rather than just reading the entire source, I just look at Mars as it has seasons because it is tilt at 25.5 degree axis, so its pole will be colder and equator will be hotter because at planetary equator the sun is more direct than at poles. At equator I estimate 70-90 is rare, at 35 degree latitude, same latitude as Los Angeles on Mars I will say above freezing is rare, the further you move poleward on latitude on Mars, it will get colder. Mars doesn't have oceans or greenhouse gas so I know the temperature fluctuates greater than earth will.--69.228.25.10 (talk) 22:36, 16 January 2013 (UTC)

Hamiltonian

Is it an over-simplification to say that the Hamiltonian describes the wave-function; or is that just part of it? Lighthead ^þ 06:03, 16 January 2013 (UTC)

The Schrödinger equation describes the wave function. The Hamiltonian is the most important thing in the equation, but it is not the whole equation. Looie496 (talk) 06:17, 16 January 2013 (UTC)

Thanks a lot. That article is a lot easier to understand, at least from that vantage point. Thanks. Lighthead ^þ 06:28, 16 January 2013 (UTC)

(ec) It's not an over-simplification; it's simply wrong. The Hamiltonian represents the energy of a state, and is not specific to quantum mechanics. In fact, it originated in classical Hamiltonian mechanics, and that's the context under which most physics students know about it. I think it's rather confusing that our article specifically talks about the Hamiltonian in quantum mechanics without ever mentioning that it's the same, conceptually, as the classical Hamiltonian. --140.180.240.178 (talk) 06:30, 16 January 2013 (UTC)

Hmm... that's interesting. Hey! You should have an account on Wikipedia... unless you already do. Thanks. Lighthead ^þ 06:34, 16 January 2013 (UTC)

The Schrödinger equation article does specify, however, that the Hamiltonian is the total energy of the wave function. It doesn't describe it as exclusive to the wave function. Lighthead ^þ 06:42, 16 January 2013 (UTC)

Hamiltonian: This article needs improvement; and YOU can improve it! Lighthead ^þ 07:14, 16 January 2013 (UTC)

What needs improvement, specifically? Have you read our article on the interpretation of the Hamiltonian formulation? The application of these techniques to wave mechanics, or to atomic physics, builds on that prerequisite knowledge. Nimur (talk) 15:48, 16 January 2013 (UTC)

Harmful effect of excessive masturbation - Cortisol production

I came across an interesting piece here. According to the article, excessive masturbation results in increased production of cortisol. (Other sources support this fact) This cortisol in turn increases blood pressure, blood sugar, and results in insulin resistance. The website I cited is an alternative medical source, but their argument seems to be logical. On the other hand, mainstream medicine has always claimed masturbation does not have any negative effect. How does mainstream medicine refute their argument? --PlanetEditor (talk) 08:17, 16 January 2013 (UTC)

I suspect mainstream medicine would ignore their argument. There is no evidence it is based on any properly conducted and peer reviewed research, as medical science must be. Instead, it appears to be a commercial story used to promote the use of a particular herbal product. HiLo48 (talk) 08:24, 16 January 2013 (UTC)

... no doubt some marketing bright spark trying to capitalize on the deep-seated insecurity some people still have about masturbation, considering how strongly it was stigmatized in some Western countries until quite recently. If the argument applies to masturbation, it applies equally well to many other normal, healthy activities such as sex, sport, excitement etc. — Quondum 11:04, 16 January 2013 (UTC)

What a brilliant website. Although failing to define what "excess" means, their research clearly concludes that orgasm results in fatigue. Who'd a-thunk? Sounds kind of like General Ripper's discussion of "loss of essence". ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:43, 16 January 2013 (UTC)

Apparently "Most men limit the activity to three times a week", so maybe more than that is "excessive", making you one of the "others [who] tend to go overboard". AndrewWTaylor (talk) 14:01, 16 January 2013 (UTC)

Notice the weasel-wording there, based on some unsupported "most men" claim. Reminds me of this, from Annie Hall... Doctors: "How often do you have sex?" Annie Hall (Diane Keaton): "All the time. Three times a week." Woody Allen's character: "Almost never. Three times a week." ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:38, 16 January 2013 (UTC)

Yeah - this is junk science at it's worst. There is no consideration whatever of the magnitude of the effect - or of possible beneficial effects from other changes this behavior might bring about (Oxytocin, for example, is produced in orgasm, and it has lots of beneficial effects). Certainly, the herbal remedies suggested there are guaranteed not to have been adequately tested for safety and effectiveness. Junk, junk, junkity-junk. Ignore it. SteveBaker (talk) 14:05, 16 January 2013 (UTC)

They have another article claiming over-masturbation results in increased production of DHT which in turn causes hair loss. Some other source does support this claim.

I remember once I masturbated more than 15 times in a single day after which I had headache, muscle weakness, fatigue and other symptoms of postorgasmic illness syndrome. --PlanetEditor (talk) 19:52, 16 January 2013 (UTC)

Use less strong porn the next time you masturbate for the first time in your life. I started with old women and only masturbated 10 times in single day.

• Do we have an article someone can link to about this masturbation? I have never heard of it before. μηδείς (talk) 23:11, 16 January 2013 (UTC)

• • You could start your investigation by locating a copy of Portnoy's Complaint. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:14, 17 January 2013 (UTC)

I don't think we give medical advice. Don't risk it. --DHeyward (talk) 04:28, 17 January 2013 (UTC)

Please help (weight of air)

I am a student. How do we take out the weight of air an object, say of 100 cm^2, is carrying? 115.253.44.234 (talk) 10:24, 16 January 2013 (UTC)

The weight of the air in the column above an object is equal to the atmospheric pressure multiplied by the cross-sectional area of the column. If this were 100 cm², this would be roughly 1000 newtons. If you want to know the net effect on the weight of an object due to atmospheric pressure, you need to take into account the upwards pressure underneath the object, which closely balances that from above. The overall effect is a slight reduction in weight equal to the bouyancy of the object in air, which comes to roughly 12 N/m³, which is the specific weight (weight density) of air. In most instances, this is so small compared to the specific weight of normal objects (roughly 1/800 of that of water) that it can be neglected in everyday contexts. — Quondum 10:51, 16 January 2013 (UTC)

If a box were a rectangular solid with the area of the face as the OP stated, and it were evacuated, would the pressure tending to crush it be only a function of the 100 sq cm of the top, or would the area of the sides matter? It seems like a hollow evacuated metal can 1 meter tall would need thicker walls than one 1 cm tall, both with 100 sq cm tops, to withstand atmospheric pressure. Being crushed is one "net effect" of atmospheric pressure, as is bouyancy. Edison (talk) 21:57, 16 January 2013 (UTC)

Crushing is a very complicated process, which depends on many things such as the geometry, internal structure, construction techniques, and so on. To a spherical cow approximation, crushing from pressure can be modeled as acting independently on each surface of the box. --Carnildo (talk) 02:46, 18 January 2013 (UTC)

Weight or mass? 1 mole of gas takes up 22.4 litres at Standard temperature and pressure. You would need to know the atomic mass of air and then figure out how many moles are contained in 100 cm^2. I think you need to compensate for the diatomic elements as well at 2x mass per mole.--Canoe1967 (talk) 23:32, 16 January 2013 (UTC)

Nitrogen is the main gas in air. Its article states density at 1.251 grams per liter.--Canoe1967 (talk) 01:54, 17 January 2013 (UTC)

I changed title to make it useful. StuRat (talk) 02:01, 17 January 2013 (UTC)

Yes there is a diffusive force the gas would exert on all sides of an evacuated vessel. The diffusive force is a function of the relative density inside the vessel and outside. This in turn is related to gravity and temperature of the gas. The force becomes a function of the surface area of the vessel but the "weight" of air is really just a function of the mass of molecules in a gravitational field. You can actually take a vessel, evacuate it, weight it at empty and then begin pressurizing it to 1 atmosphre pressure, 2 atmospheres, 3 atmospheres, etc while weighing it and you will see the "weight" of the air. As an aside, diffusive forces are also prominent in cell biology and creates osmotic pressure. It is also important in semiconductors and is a primary physical property on P/N junctions. --DHeyward (talk) 04:43, 17 January 2013 (UTC)

Vitamin K2 in ((Vitamins)) nav-box

Hi all,
At present, the vitamin K2 link in the nav-box points to Menatetrenone, which would appear to me to be a proprietary synthetic version of the naturally-occurring forms of K₂. I'm usually WP:BOLD, but in this case don't want to be WP:ALLTHEWRONGKINDOFBOLD.
Your thoughts and help as always sincerely appreciated. --Shirt58 (talk) 10:58, 16 January 2013 (UTC)

I'm not an expert, but the article does not seem to substantiate your conclusion about what the name Menatetrenone means (although the juxtaposition of the first two sentences in the lead of Menatetrenone is bad and they should be separated). The link pointing to a specific K₂-vitamin rather than to the general article does seem wrong (and misleading). It should evidently be changed to Vitamin K2, with the associated visible name changed from Menatetrenone to Menaquinones. — Quondum 11:46, 16 January 2013 (UTC)

Agreed, the link is wrong. Your reasoning is correct. Fgf10 (talk) 13:03, 16 January 2013 (UTC)

Okay, I did the deed. — Quondum 16:16, 16 January 2013 (UTC)

Thank you!--Shirt58 (talk) 10:23, 17 January 2013 (UTC)

Animal behaviour

Are humans the only animal who seek long term relationships for love and not just for reproducing? — Preceding unsigned comment added by 176.250.205.226 (talk) 11:24, 16 January 2013 (UTC)

'Love' is a product of human culture and society. I'm not sure we'd be able to recognise it in other animals. But bonobos and dolphins are well known to have non-reproductive sexual contact. AlexTiefling (talk) 11:30, 16 January 2013 (UTC)

Love is a product of biology caused by hormones and maybe influence a little by culture and society. I'm still incredulous that kissing was invented by the Romans. Doesn't it just happen when your faces get very close? Sagittarian Milky Way (talk) 22:28, 16 January 2013 (UTC)

There's also the common phrase about Swans mating for life and dying of depression if their partners are killed. The Swan article on Wikipedia confirms some truth to the mating part of it. Thanks ツ Jenova20 ^(email) 11:33, 16 January 2013 (UTC)

You could rephrase it a little to make it a question that can be answered with less speculation: Are there any examples of animals (except humans) where a male and a female form a pair and continue as a pair even when the female isn't fertile anymore? Sjö (talk) 12:50, 16 January 2013 (UTC)

There is considerable evidence that human females may be unique (or nearly so) in losing fertility before death. This paper suggests the possibility of non-human primates undergoing menopause (the end of female fertility) - but perhaps only in captive animals with enhanced lifespans compared to the same species in the wild. I was unable to find any studies that show menopause in other mammals or any other kinds of animal for that matter. Male fertility is even less likely to spontaneously end - even in humans, most men are fertile for their entire lives. So this question could only reasonably pertain to animals who lose fertility due to injury or disease. Under such circumstances, it would be hard to know whether that individuals' mate actually understands that fertility has been lost. Without modern medical advances, even a human would probably not know for sure except in very obvious cases.

So looking for species of animal that stay paired even after fertility has ended due to age or injury doesn't offer an answer here.

Perhaps a better answer is Homosexual behavior in animals - if such behavior produces pair-bonding between same-sex animals where reproduction is clearly impossible from the outset - then perhaps we can use this to form a reasonable answer.

So to pick just one example from Homosexual behavior in animals: "An estimated one-quarter of all black swans pairings are of homosexual males"...and from Black swan: "...the Black Swan is largely monogamous, pairing for life...". So if "pairing" is "love" then there are black swans who "love" despite no possibility of reproduction - then answer to our OP's question is "YesNo". But it's hard to attribute emotion to animals - especially non-primates - so whether pairing is "love" will probably never be known...it may not even be a meaningful question. Even humans are sometimes uncertain about whether what they feel is "love" or "lust".

On balance, I'd have to say that the answer is "YesNo" - but it's not a simple question. SteveBaker (talk) 13:31, 16 January 2013 (UTC)

Elephants, some whales and a few other animals seem to have a menopause, see menopause#In other animals. Dmcq (talk) 14:14, 16 January 2013 (UTC)

Yeah, there are a few - but many of them are in dispute (eg because the effect has only been seen in animals in captivity who live longer than they would in the wild) - and in any case, I didn't see that in species that exhibit long-term pair-bonding. SteveBaker (talk) 14:42, 16 January 2013 (UTC)

It's not just animals in captivity that have their lifespan "artificially" extended by having no predators, a steady supply of food, and by medical attention. All of those apply to humans as well. Our paleolithic ancestors living "in the wild" usually didn't live long enough to experience menopause either. --Guy Macon (talk) 18:14, 16 January 2013 (UTC)

Animals don't necessarily live longer in captivity, it fact it has been hard to ensure some live a normal lifespan. And it's quite likely our paleolithic ancestors lived much longer than people in poor places nowadays once they got past childhood - they often were nowhere near so poor. The article Life expectancy indicates they on average they lived long enough to have a menopause if they got past childhood. Dmcq (talk) 22:43, 16 January 2013 (UTC)

Exactly. It's a common idea that people died very young back then because the average life expectancy in the paleolithic was just 33 years. But averages are deceptive. There were a hell of a lot of deaths in childhood - which pulls the average life expectancy way down. According to our life expectancy article, anyone who managed to survive past the age of 15 had a life expectancy of 54 years - which is plenty enough to pass menopause (which in modern women typically happens between 42 and 58 years). By far the majority of adult females would have lived well past menopause even in the paleolithic. SteveBaker (talk) 16:28, 17 January 2013 (UTC)

The revised question is well-answered. It can however not be considered to be "rephrase[d] it a little": it is a very different question, with a very different answer. The answer to to the first, I think, is an unequivocal "no" (many species form long term pairing), though I realize some might object that we can't prove that any other animals feel "love" or that this is the basis for the pairing, to which I'd say a strong case should be possible that several do. — Quondum 14:36, 16 January 2013 (UTC)

From the lede of our article on Love: " "Love" may refer specifically to the passionate desire and intimacy of romantic love, to the sexual love of eros, to the emotional closeness of familial love, to the platonic love that defines friendship,[4] or to the profound oneness or devotion of religious love,[5] or to a concept of love that encompasses all of those feelings. This diversity of uses and meanings, combined with the complexity of the feelings involved, makes love unusually difficult to consistently define, compared to other emotional states."...it's clear that we cannot say whether any or all of those things are present in any non-human animals. Heck, we can't reliably show whether a human is honestly or consistently exhibiting this emotion according to that definition.

Our article Biological basis of love describes a whole slew of chemical signatures of human "love" - we could ask whether those chemical signatures are present in pair-bonded animals. Oxytocin is a major signature indicating long-term love - but it has other roles in the body. Our article says: "Virtually all vertebrates have an oxytocin-like nonapeptide hormone that supports reproductive functions". You can follow the same papertrail for vasopressin (another "long-term-love" hormone in humans) and arrive at the same conclusion. So that suggests that other vertebrates might also feel the emotion...but perhaps not invertebrates.

Biological basis of love also says that the Limbic system (a structure in the brain) is heavily involved in the emotion - and that system was present in the common ancestor of mammals and reptiles - so perhaps vertebrates who lack a limbic system might not qualify as passionate lovers.

SteveBaker (talk) 14:57, 16 January 2013 (UTC)

I posted the other day on WikiProject Biology asking if anyone could improve our article pair bond. No answers there yet, would be good to get some attention tithe article Itsmejudith (talk) 22:15, 16 January 2013 (UTC)

• Without reading the whole discussion, I think bald eagles mate for life if that is any help.--Canoe1967 (talk) 23:36, 16 January 2013 (UTC)

Hmmm. Mushroom spores produce primary mycelium; these primary mycelia fuse and form secondary mycelium in which the two individuals join as one to go about their lives (See Plasmogamy). One might argue this is a more profound relationship toward certain religious notions of marriage merely aspire. Of course, you can say "is that love?" because mushrooms don't think the way humans do; and you ask that of any animal. For now, lacking a proper theory of consciousness, it is a matter of semantics/definitions, I suppose. Wnt (talk) 00:10, 17 January 2013 (UTC)

Here is a link about animals that mate for life. On the other hand, this paper claims humans are genetically polygamous. --PlanetEditor (talk) 02:02, 17 January 2013 (UTC)

More specifically, the claim is that humans are more polygynous than polyandrous in terms of reproductive success, or at least that they have been (though I suspect that nothing has changed in this regard). — Quondum 13:34, 17 January 2013 (UTC)

There is no argument whatever that many other species pair-bond for life. Finding more examples of that doesn't advance our answer here...it's a given...similarly, it's pointless to ask whether humans are genetically polygamous or not...it's known that a significant majority of us do in fact pair-bond for life and that most will experience the emotion that we label as "love". It's also known that the majority of us continue to pair-bond beyond female menopause. There is really no debate about those things.

The two difficult parts of the problem are:

1. Can pair-bonding in non-human animals be equated with the human emotion called "love"?
2. Do any non-human, pair-bonding species lose fertility as they age?

The first is ridiculously difficult to answer - the definition of "love" is very broad and the question of "do members of species X love each other" is unfalsifiable - in fact "does anyone other than me exhibit this emotion" is unfalsifiable too! We have to guess that the chemical signatures of human pair-bonding (which generally includes feelings of love) are a close match for those found in other vertebrates - and the brain structures involved are present in at least mammals and reptiles. If that's enough to satisfy the conditions of the OP's question - then we have some sort of an answer - but "love" is a very vague term and a rock-solid answer is impossible, even in principle.

The second seems to be almost always "no" - but there are a few exceptions (elephants, whales) - but even those have patchy evidence, may only apply to animals in captivity who outlive their natural lifespans. We currently have no examples of animals that are thought to lose fertility as they age that are also known for pair-bonding - which means that this question of whether "love" ends at menopause in other pair-bonding species is meaningless because they never have menopause.

I was able to show that there are several species where same-sex pair-bonding is common...and in that case, "love" (if we accept #1) is occurring where there is no chance of producing offspring...but that's not the same thing as "losing fertility with age"...so I'm not sure it counts.

On balance, we should say that humans are indeed the only species who do this...but not because we're the only ones who'd care about their mates after fertility has ended - it's because fertility simply doesn't end in most other species, so the question of what would happen if it did is moot.

SteveBaker (talk) 16:19, 17 January 2013 (UTC)

Sudden blindness

can sudden blindness occur even when you get frequent follow up eye exam or would the exam reveal progression of nerve damage to the eye retina — Preceding unsigned comment added by 69.141.51.81 (talk) 14:11, 16 January 2013 (UTC)

alternative (natural means)for treating eye pressure without eye drop medication — Preceding unsigned comment added by 69.141.51.81 (talk) 14:13, 16 January 2013 (UTC)

WARNING: We're not allowed to give medical advice here. That said, Blindness#Causes suggests that some causes of blindness (eg methanol poisoning) might be too sudden to show up with frequent eye exams...where others (eg cataracts) should be detectable long before they cause significant vision loss, so frequent eye exams might discover the cause before significant blindness results from it. So the answer to your first question depends on the cause of blindness.

For your second question: Our article Ocular hypertension suggests that acetazolamide is a common treatment for excessive "eye pressure" that does not require eye drops - but, again, it all depends on the cause of the eye pressure. Some causes might require drops.

These are complicated and difficult matters - and nobody can know what's right for a particular individual without a careful medical examination. SteveBaker (talk) 14:39, 16 January 2013 (UTC)

Regular eye examinations are only going to show the progress of degenerative conditions. Oddly the article on blindness and specifically the section on causes does not mention retinal thrombosis which can, without warning, cause complete loss of sight in the affected eye within hours. Richard Avery (talk) 16:19, 16 January 2013 (UTC)

(You should probably dive in and fix the article! Finding and fixing such errors is a part of the function of the reference desk.) SteveBaker (talk) 16:41, 16 January 2013 (UTC)

• Is it coincidence that that section is just below a section on harmful effects of excessive masturbation?--Canoe1967 (talk) 23:42, 16 January 2013 (UTC)

The second question may be addressed by Glaucoma#Research ("Natural compounds"). Marijuana has had longstanding use for the condition, occasionally even being preferred by some patients who say that it is more effective than other medications. Of course, on an individual case basis a person would need a clear medical diagnosis of the exact type, and discuss drug options (though I suspect the physician's recommendation natural vs. non would often be less a matter of individual diagnosis than which drugs he is permitted to push in his state...) Seriously though - if your interest is more than academic, you need more help than random Wikipedians responding to a vaguely worded sentence. Wnt (talk) 23:51, 16 January 2013 (UTC)

ImageJ macro for batch merge of images

I have image files named in the format:

Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 2 ul Lipofectamine 2000 - 15x - Field 1 - Brightfield - 2012-12-16.tif

Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 2 ul Lipofectamine 2000 - 15x - Field 1 - UV red - 2012-12-16.tif

Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 2 ul Lipofectamine 2000 - 15x - Field 2 - Brightfield - 2012-12-16.tif

Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 2 ul Lipofectamine 2000 - 15x - Field 2 - UV red - 2012-12-16.tif

etc

I would like to merge each "Brightfield" image with its associated "UV red" image using ImageJ. Can anyone help me put together a macro to do this?

I tried using the built-in macro recorder but it doesn't pay attention to how much I increased the contrast of the red images and it also uses specfic file names which is useless when each file is named differently (obviously; you can't have two files with the exact same path!) 129.215.47.59 (talk) 14:23, 11 January 2013 (UTC)

Maybe better to ask this at the Computing Desk. - Lindert (talk) 14:39, 11 January 2013 (UTC)

Computing people probably don't deal with ImageJ. ImageJ is an NIH application. 72.229.155.79 (talk) 19:21, 11 January 2013 (UTC)

One can always try, and most people here on the science desk don't work for the NIH either (if there are any at all). Also ImageJ is open-source and has many useful functions, so maybe some 'computing people' have used it. Anyway, if you still think this is the best place, just forget I said anything. I'm afraid I can't be of much help, but good luck finding an answer. - Lindert (talk) 20:38, 11 January 2013 (UTC)

It would help if you could upload the actual images. What exactly would this merge do ? Are you talking about combining the red from one image with the blue and green from another ? Are the images of the same size and already properly aligned ? StuRat (talk) 23:16, 11 January 2013 (UTC)

Hi. The images look like this.

Bright field

UV red

Merged

Precedure to merge one pair of images

Open brightfield image. Image>Type>8-bit

Open UV/red image. Image>Adjust>Brightness/Contrast and increase contrast five clicks

Image>Type>8-bit

Merge channels - set C1 (red) as UV/red image and set C4 (gray) as brightfield image.

Save new image with name: Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 2 ul Lipofectamine 2000 - 15x - Field 1 - Merged - 2012-12-16.tif

Macro as recorded by ImageJ during above procedure

open("B:\\Sean Smith\\M\\DF1\\Ex.SS.4.4.170 - 2012-12-13\\Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 4 ul Lipofectamine 2000 - 15x - Field 1 - Brightfield - 2012-12-13.tif");

run("8-bit");

open("B:\\Sean Smith\\M\\DF1\\Ex.SS.4.4.170 - 2012-12-13\\Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 4 ul Lipofectamine 2000 - 15x - Field 1 - UV red - 2012-12-13.tif");

//run("Brightness/Contrast...");

//run("Brightness/Contrast...");

run("8-bit");

run("Merge Channels...", "c1=[Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 4 ul Lipofectamine 2000 - 15x - Field 1 - UV red - 2012-12-13.tif] c4=[Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 4 ul Lipofectamine 2000 - 15x - Field 1 - Brightfield - 2012-12-13.tif]");

saveAs("Tiff", ""B:\\Sean Smith\\M\\DF1\\Ex.SS.4.4.170 - 2012-12-13\\Exp.SS.4.4.170 - DF1 - MSTN HDR donor candidate 1 - 4 ul Lipofectamine 2000 - 15x - Field 1 - Merged - 2012-12-13.tif");

129.215.47.59 (talk) 14:42, 14 January 2013 (UTC) — Preceding unsigned comment added by 78.144.207.252 (talk)

I can't help, but you could also try asking at a forum specifically for imageJ. This one [5] seems to have some good answers. SemanticMantis (talk) 15:39, 16 January 2013 (UTC)

The only general advice I can give for this sort of thing is to use entirely keyboard shortcuts or command line commands when recording a macro. Often the mouse-y bits get lost, but the other methods will successfully record. SemanticMantis (talk) 15:40, 16 January 2013 (UTC)

effect of touch

how does a touch such as a pat on the back make you feel good? what happens in the brain to register this as a pleasurable sensation? thank you.24.27.44.43 (talk) 23:12, 16 January 2013 (UTC)

Being touched is not universally something that "makes you feel good". Humans and animals both will respond positively or negatively to being touched, depending on whether they are "used to it" and whether they trust the one doing the touching. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:29, 17 January 2013 (UTC)

i understand that and am interested whether positive or negative. i would like to know where in the brain, what neurotransmitters, etc. i have not been able to find much information on the science of touch.24.27.44.43 (talk) 00:52, 17 January 2013 (UTC)

Two sources. --PlanetEditor (talk) 02:12, 17 January 2013 (UTC)

The article Physical intimacy says "A hug or touch can result in the release of oxytocin, dopamine, and serotonin, and in a reduction in stress hormones." These are all linked to positive perceptions. — Quondum 07:45, 17 January 2013 (UTC)

Certainly oxytocin is produced during prolonged hugging - and that definitely makes you feel good. I don't know that a pat on the back would also have that effect though. It's more likely that there is a psychological feeling that the other person appreciates you or something. I wonder if there are cultures in the world where back-patting isn't a gesture of support or appreciation? SteveBaker (talk) 15:56, 17 January 2013 (UTC)

How hot?

How hot would the air get if you put a car in the center of a house (some disassembly may be required), found an alternative source of air, and then ran the engine till everything reached thermal equilibrium?

Of course it would depend on a number of factors, like where on the scale from F1 car to Corolla, idling or full throttle, your insulation, outside temperature, whether you're measuring outside the vehicle or inside with doors and windows closed, and whether it's is in neutral or running on rollers. Would it even run that long before something breaks? Maybe coolants and lubricants not reccomended by the manual could let it last longer, possibly at the expense of extensive damage? Sagittarian Milky Way (talk) 23:28, 16 January 2013 (UTC)

I have reformatted this and closed it. Anyone who has sources can give them outside the hat. μηδείς (talk) 23:33, 16 January 2013 (UTC)

I've reopened this question because although the exact temperature obtained depends only on fuel consumption, the amount of space heated and heat loss to the outdoors, precision isn't needed to answer this question, only accuracy. --Modocc (talk) 01:10, 17 January 2013 (UTC)

This can't be estimated with R-values of walls, horsepower, and the 25-30% efficiency of internal combustion engines? Sagittarian Milky Way (talk) 23:37, 16 January 2013 (UTC)

Hmmm. In brief an internal combustion engine is not a steam engine - there's no fundamental reason that I know of why it can't work without cooling. Yet I can't think of one that really does work without a radiator (engine cooling) functioning. So I'm not sure if the limit here is something that can be worked out from first principles or if it's a matter of engineering. Also there are some aspects of the question left unspecified, i.e. whether there is free input of cool outside air, what happens to the exhaust and so forth. The simplest version is that if you put a very good insulated enclosure around a car engine (but preserve normal engine cooling functions!) then you'll have the enclosure at the same temperature as the engine. You might want to take a step back and think if there's a simpler way to express what you're actually wondering about. Wnt (talk) 23:59, 16 January 2013 (UTC)

If you try to run an internal combustion engine without cooling, the oil breaks down, and combined with the expansion of metal parts this causes the cylinders to seize, which causes the engine to come apart. Looie496 (talk) 00:16, 17 January 2013 (UTC)

Practically speaking, it would be basically just an overly complicated gasoline furnace, unless you have some mechanical work for the engine to perform, because the moving parts are unnecessary (these parts will store a fairly small amount of kinetic energy as long as these are in motion). [Note that gasoline is not generally used for heating purposes though due to its high volatility]. In addition, carbon monoxide from the exhaust is a danger and must be vented to the outdoors. This is best done with a heat exchanger that brings in fresh air which gets heated (these heat exchangers can be over ninety percent efficient). If vented properly, the space would get just as hot as with a regular gasoline furnace consuming the same amount of fuel. For a fictional version of a machine that was morphed into a furnace, see Mike Mulligan and His Steam Shovel. -Modocc (talk) 01:00, 17 January 2013 (UTC)

If the question is serious, the OP should ask at the mathematics desk for an equation that would address all the relevant variables. As it stands the question is fatally ill-formed (what's the heat capacity of the house, for example) and the answers more like random wall spaghetti than links to references that will actually answer what's asked. μηδείς (talk) 01:16, 17 January 2013 (UTC)

Meh, I disagree that this belongs elsewhere. Its an applied science or engineering problem. Perhaps I'm being presumptive, but the question seems to be more along the lines of how practical it is to use a car engine for heating, as in can it heat a given space (maintaining an equilibrium). There does exist resources for various furnace capacities and recommendations for such purpose. -Modocc (talk) 01:32, 17 January 2013 (UTC)

We've still got not question and no referenced answers, but we do have a single-purpose account reopenning trolling by another single-purpose account. Discuss this at talk before reopenning. μηδείς (talk) 02:24, 17 January 2013 (UTC)

It seems like a fine thought experiment. —Steve Summit (talk) 03:28, 17 January 2013 (UTC)

Due to gasoline's high volatility, it is not generally used in space heaters (or furnaces for that matter) here in the USA (but gasoline can be used in outdoor camping gear and it seems I recently read about it being used for space heating elsewhere, furthermore it was at one time used in cars and aircraft, see the article on gasoline heaters). Kerosine heaters used to be somewhat common (its similar to gasoline, but is considerably less volatile). Because of this, gasoline should not be used in a home. In any case, that said, power for space heaters and furnaces are rated in BTUs per hour. For homes, recommended furnace BTUs start at 60,000 BTU/hr: [6]. Gasoline engines that are running at idle speed, consume roughly between .4 and 1.2 gallons per hour: [7]. At one gallon per hour, according to Onlineconversion.com, converting the energy content of a gallon of gasoline to kilocalories, this yields 31,470 kilocalories/hr or 124,883 BTU/hr which is more than enough heat. I'm sometimes prone to dumb errors though, so someone should double check my figures. -Modocc (talk) 06:27, 17 January 2013 (UTC)

Looking into the energy content of these fuels a bit more, I found a useful tabulation of gasoline gallon equivalents. The GGE of kerosine, which would be safer to use, is 0.9000, thus it has more energy per gallon than gasoline. -Modocc (talk) 08:35, 17 January 2013 (UTC)

There have been various proposals and even some working engines that are adiabatic -- engines made out of ceramic that require no cooling. So far nobody has solved the lubrication/wear problem to make one last as long as a conventional engine. Now of course any IC engine loses heat from the fact that exhaust is hotter than the intake, and with the adiabatic engine the incoming air is really quite cold compared to the engine, while the exhaust is still very hot. the thermodynamics of IC engines are such that whatever energy from the burning fuel that doesn't result in power output needs to be removed somehow or the temperature will increase without limit. --Guy Macon (talk) 06:53, 17 January 2013 (UTC)

There are indeed some modern home heating units that use a Stirling engine to produce electricity that is fed into the grid, and only use the "waste heat" for heating. That seems like a very good concept, at least in principle. --Stephan Schulz (talk) 13:21, 17 January 2013 (UTC)

Oh come on Ref.Deskers...we can do better than that! Obviously our OP isn't looking for a precise answer - this is a highly "back-of-envelope" calculation with lots of assumptions built into it to get a rough idea of what would happen.

It seems to me that once equilibrium has been attained, 100% of the energy in the gasoline either turns up as heat (one way or another) or as heat and unburned gasses in the exhaust. For now, let's assume that the pipe that takes the exhaust outside is long enough to act as an efficient heat exchanger - and we'll ignore unburned fuel in the exhaust and assume that that the car is just a complicated way of turning the energy in the gasoline into heat. We'll assume that nobody is revving the engine here. A google search reveals that a typical modern 4 cylinder engine burns about a quarter of a US gallon of gas per hour at idle (infinite miles-per-gallon!). The energy density of gasoline is 36.6 kWh/USgal - so the car is at best a 10kW heater...probably worse because we're ingoring fuel/heat coming out of the tailpipe - which is significant at idle.

A "typical" 2000 sq.ft US home (not in Alaska or Nevada) needs a 40kW heater to keep the place comfortable through the year - so right off the bat, we know that this car is a pretty poor heater. If that's your only source of heat then the house is going to be pretty cold in winter! The effect of adding a car into your heating system would have a similar effect to cranking up your thermostat until it increases your heater's energy consumption by about 10kW - which is about 25%. Well, the common advice on saving energy is that you add 1% and 3% to your heating bill for every degF you crank up the thermostat...so the car would likely increase the temperature within the house by between 8 and 25 degF.

How big are the "error bars" on this calculation? Huge, obviously. We don't know the kind of car, whether it's being revved, how big the house is, how well insulated it is, what the outside temperature is, what the exhaust losses are. But what we can ascertain from "typical" numbers is that your house would get quite a bit hotter - but the car alone couldn't replace your heating system.

SteveBaker (talk) 15:50, 17 January 2013 (UTC)

Very good, except for the last part. If you do indeed rev up the engine, you can easily get up to 10 times the fuel consumption (based on 10 l/100 km just to spite the imperialists ;-). So you can turn it into a 100 kW heater. Also, the result very much depends on the quality of the isolation. In Germany, we now have so-called passive houses which are so well isolated that they normally need no extra heating. For very cold situations, the have a 2 kW heater integrated into the controlled ventilation system. So there is another order of magnitude ;-).--Stephan Schulz (talk) 16:11, 17 January 2013 (UTC)

Yes - I agree. As I said, the error bars are huge. But for a "typical" idling US car, US house, US insulation, mid-US winter day - I'd stand by the 8 to 25 degF temperature rise. If you did the experiment with a Toyota Prius, you'd get almost no heating at all (the tiny gasoline engine shuts off automatically when the car is stationary, so it runs on batteries until the digital clock runs them down enough for the engine to kick in and recharge them - that probably takes a hundred years to happen!). If you did it with a hard-revved Ferrari 612 Scaglietti (which has probably the worst fuel economy of any production car) in a "passive house" during a heat-wave - then you're going to get really hot, really fast! We don't have enough information to answer the question in general - but I believe that in the spirit of how it was asked (a back-of-envelope thought experiment) - the answer is as I've suggested. SteveBaker (talk) 16:43, 17 January 2013 (UTC)

I will trade you a top-of-the-line home heating/cooling system for that Ferrari Scaglietti you have there. No need to thank me. :) --Guy Macon (talk) 16:49, 17 January 2013 (UTC)

Sadly, the '06 Scaglietti has a clutch sensor that malfunctions in excessive heat and Ferrari say that it "may render the vehicle inoperable and possibly result in a crash" - I'm sure you wouldn't want it crashing while it's parked in the middle of your basement with all of those heating ducts wrapped around it. :-) SteveBaker (talk) 17:51, 17 January 2013 (UTC)

I've mentioned this before, but I've devised a machine which can put a stop to our reliance on fuels altogether and with any luck, I've every intention on completing it soon too. The idle speed fuel consumption data I linked to is old, from the early 70s, but is still important, for it shows that sufficient fuel can be burned to produce enough heat for a small home within a moderate climate without over-revving many engines, especially the larger and older ones. Even newer engines could be put under a load such as an electric generator to crank out more heat at fewer RPMs. I just spoke with my friend whose grandfather sold Model-Ts and he tells me their engines (which could run on petrol, kerosene or ethanol) were more efficient than later engines because of a cleaner burn (I haven't found any data to support that though), but today's fuel injected cars are even more efficient and I do not think waste huge amounts of unburnt or incompletely burnt fuel to the exhaust. So other than matching the engine or engines (lets say two of them if needed) with the space and loads, there is no reason these cannot be used to provide heat (as with the OP's thought experiment) and electric power. I'll add that where I live, heat pumps are better, but it would be nice to have an electric generator installed too. -Modocc (talk) 18:32, 17 January 2013 (UTC)

"I've devised a machine which can put a stop to our reliance on fuels altogether" - So what does it run on? AlexTiefling (talk) 22:37, 17 January 2013 (UTC)

Modocc has previously claimed to have found a loophole in the 2nd law of thermodynamics - and hence is presumably building an over-unity perpetual motion machine of the second kind (a machine that can reverse the direction of entropy or some such). So...um...well. What does one say to that and remain within the bounds of WP:AGF? Er..."Good luck"? SteveBaker (talk) 23:52, 17 January 2013 (UTC)

That almost sums up my position, but "over-unity" is incorrect because that would be a violation of the perfection of the first law or the conservation of energy. Of course, the second law is very useful and seemingly ubiquitous, but, yes, I've figured out a way to completely defeat it. Modocc (talk) 00:28, 18 January 2013 (UTC)

Well, you better patent it before you talk about it too much here, then. Especially now that the US uses (the idiotic) first to file rule. --Trovatore (talk) 00:47, 18 January 2013 (UTC)

[8] As per the previous discussion Modocc needs to build a working model first since the idiotic US now uses the idiotic 'need a working model if it violates basic physics' rule. Well you can submit a working model later possibly but as with all applications you're SOL if your patent application is incomplete, the idiotic US has more idiotic rules limiting people from adding stuff they forgot or 'forgot'. Unfortunately their physical limitations make building a working model of this ground breaking work difficult. P.S. As per the article you linked to, ignoring the idiotic constitutional issues, the idiotic US does not actually currently use idiotic first to file rule but instead uses the idiotic first to invent rule so the OP still has time. Nil Einne (talk) 02:54, 18 January 2013 (UTC)

Given that the US patent office probably rejects any kind of perpetual motion patents, he's probably got all the time in the world. Vaguely related: I wonder where the patent office stores all those working models? Maybe in the Smithsonian? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:06, 18 January 2013 (UTC)

The rule on perpetual motion machines is that there has to be a working model. That's not true of most other patents. Where would the patent office store all of these fully-working perpetual motion machines? Well, I guess they'll cross that bridge when they come to it. :-) SteveBaker (talk) 16:11, 18 January 2013 (UTC)

If the only models they require are for perpetual motion machines, then they probably store them in Shangri-La. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:18, 18 January 2013 (UTC)

They get sent to The Museum of Unworkable Devices. They have a secret cellar where they stow away all devices that actually work. It's all part of the same cover-up, you see.

Now, in a more serious tone. Modocc, nobody will believe you until you have a workable device. And then you will have to get it tested by independent teams. --Enric Naval (talk) 22:48, 19 January 2013 (UTC)

Perhaps, because believability would certainly be an issue if I were to choose to make it public before I complete it. I'm not infallible of course, but unlike the nonsense of cranks that you might be more familiar with, my invention is not difficult to comprehend or to implement. Yet because of strong prejudices and the possibility of missteps in any publication, I am working on simply building the device. -Modocc (talk) 02:08, 20 January 2013 (UTC)

January 17

Nickel replacing magnesium in geoporphyrin

The geoporphyrins - see Abelsonite - have formed from chlorophyll in fossils of plants. However, the Mg ion is replaced by Ni or V ion. What is the mechanism for Mg replacement with Ni or V? Namely, did this somehow happened after fossilization (how?) or did the original plants have Ni or V ions in their photopigments? Or maybe only the few porphyrin molecules that had Ni or V ion at the center of the ring survived until present, and the ones with Mg (or Fe) ion did not? Our article Porphyrin#Organic geochemistry seems to suggest that Ni- and V- containing porphyrins in oil and oil-shale came from bacteria and not from plants. Indeed, corphin has Ni ion at the center of its porphyrin ring. On the other hand, this paper suggests that the plant chlorophyll is the origin of the porphyrin in oil, and does not explain how Mg was replaced by Ni. So what`s the answer? Thanks in advance, --Dr Dima (talk) 00:43, 17 January 2013 (UTC)

It could be post depositional ion replacement, if Ni or V ions have radii compatible with the porphyrin ring, then given the right chemical conditions, it will replace the magnesium. This would explain the rarity of the mineral, the conincidence of porphyrin and soluble Ni or V salts. Plasmic Physics (talk) 09:00, 17 January 2013 (UTC)

Atomic/Ionic Radii

Why is it that the atomic radius of fluorine (64pm) is less than the ionic radius of the sodium ion (98pm on the IB Chemistry data booklet, various values around/over 100pm in wikipedia articles, but in any case, still far greater than the atmoic radius of fluorine)? Applying a Bohr-Rutherford diagram (which I understand is a simplistic/somewhat inaccurate representation), it would appear that the sodium ion has a greater nuclear charge than fluorine, and the same number of electron shells. The nuclear charge, as I've been taught, overcomes the repulsion created by increased electron-electron repulsion, which should therefore lead to a smaller radius (neon illustrates this trend, as its radius, 58pm, is smaller than that of fluorine, and it has the same differences with fluorine as the sodium ion does (although neon does have 1 fewer proton)). I've asked around, and someone suggested it may have something to do with sub-levels (which I have not learned but sort-of understand through my own reading), although I do not see how this explains it. Could someone offer an explanation? (all group 1 ions appear to be smaller than group 17 and 18 atoms). Brambleclawx 02:09, 17 January 2013 (UTC)

You're likely measuring apples and oranges here. Atomic radius is a fuzzy concept (because atoms are fuzzy concepts) and there can be a great varience in how radii are measured or defined from one method to another. The Van der Waals radius of an atom derived the Van der Waals equations of state for a gas-phase atom is not going to be a compatible measurement to the Ionic radius, which is measured empirically from the crystal lattice via X-ray crystallography. Different measurements measuring different things in different ways cannot be compared quantitatively. --Jayron32 02:59, 17 January 2013 (UTC)

Thank you. I guess I was just focussing too hard on there being a definitive boundary, hm? Brambleclawx 00:54, 20 January 2013 (UTC)

You should be measuring the ionic radius and not the atomic radius for F to compare this. Currently you are comparing the radii of F and Na⁺. Shannon ([9]) gives r_ion(F⁻)=119 pm and r_ion(Na⁺)=116 pm. Double sharp (talk) 15:34, 18 January 2013 (UTC)

As a matter of fact, I fully intended to compare F and Na⁺. I am aware that F^- is indeed larger, but I was hoping to understand why sodium ion was bigger than fluorine atom, with a basis in what I've learned supposedly affect these things: "nuclear charge", "electron shell shielding", "electron-electron repulsion" and "number of shells". Brambleclawx 00:54, 20 January 2013 (UTC)

Olive-colored matters in cooked crabs and crayfish

When you peel open the shell of a crab, you'll see some soft olive-colored matter in the shell, mostly on the sides. What is that? Is it supposed to be edible?

When you pull the head of a cooked crayfish off its tail, it'll expose some olive-colored matter, soft and perhaps runny—something that seems to be in the head before. Again, what is that? Is it supposed to be edible? — Preceding unsigned comment added by 71.185.166.208 (talk) 04:33, 17 January 2013 (UTC)

I think what you are talking about crab is hepatopancreas, also known as tomalley. --PlanetEditor (talk) 04:45, 17 January 2013 (UTC)

And I've eaten them (in lobster, crayfish, and blue crabs) and suffered no ill effects. Eating crayfish has a bit of a ritual associated with it ("suck the head and pinch the tail"). this video shows the procedure, the "suck the head" portion of the procedure involves extracting the tomalley from the crayfish. Being essentially liver, tomalley/hepatopancreas has the same sorts of health risks associated with eating liver; if you consumed a bowl of the stuff every day for breakfast, it may be unhealthy, but in moderation (which is how often most people eat these foods; they aren't every day staples) you'd be fine. The Wikipedia article on tomalley notes that there have been health warnings against eating the tomalley of specific shellfish at specific times, but this is often associated with red tide; that makes sense as the liver is basically a filter organ, and thus when there are higher-than-normal levels of toxic substances in the water the lobster is living in, there's going to be more of that stuff in the tomalley as well. --Jayron32 05:28, 17 January 2013 (UTC)

Perception of time between age groups?

I recall watching a tv show where Michio Kaku introduced an experiment that tested the perception of time under duress (does time really slow down during an accident, for example). But I'm wondering if there have been any experiments on the perception of time between different age groups? For example, as a child, I clearly recall getting up, going to school—which dragged on forever—but then in the afternoons, you cram in as much adventure as you can, and you were able to do so. Decades later, I notice I'm getting ready for bed every day, but it feels like I just did that, even though it was 24 hours ago. Adults are always saying how fast time flies. Is it simply due to a difference in, say, stress? I'm very curious, though, if there've been actual (and good) studies on this. – Kerαunoςcopia^◁_galaxies 06:31, 17 January 2013 (UTC)

Original research: When I was a child, half an hour would seem like forever, but now it doesn't seem like a long time at all. And paradoxically, back then I wasn't able to read the seconds on a digital watch because they'd flicker too fast for my eyes, but now I can do it easily. 24.23.196.85 (talk) 06:45, 17 January 2013 (UTC)

Wikipedia has an article named Time perception which may provide an interesting launching point for the OP to research the answers to their question, and to other related topics. --Jayron32 06:58, 17 January 2013 (UTC)

I have observed that the main reason is that any given period of time, say 24 hours, as a percentage of total life experience decreases as time passes, or I should say as the total time of your life experience increases. This has been cited many times here. Example is 24 hours to a 1 day old is double the total life experience for that baby but to a one month old is 1/30 of total life experience.165.212.189.187 (talk) 15:30, 17 January 2013 (UTC)

Tangerine peel oil and styrofoam cup

I am drinking tea in a styrofoam cup (I know, I know shame on me, but in my defense i usually have a mug) and I have a bit of a cold. So I took the peel of my tangerine and ripped it into small pieces over top of the cup of tea. I could see the oils make film on the surface of the tea and got a good amount of it in my tea. a few minutes later I noticed that the styrofoam cup above the water line has been eaten away! What happened? Is this safe to drink? I wont but just wondering. not necessarily medical advice but if the reaction has leached certain chemicals into the tea the it is just lain facts.165.212.189.187 (talk) 15:22, 17 January 2013 (UTC)

I recommend you don't drink it but take it to a toxic waste facilty for proper disposal. Didn't your mother teach you about mixing chemicals? If you pour it down the sink we may end up with mutant marine animals that may take over the world.(kidding)--Canoe1967 (talk) 15:40, 17 January 2013 (UTC)

I only know that acid can eat away at aluminium foil. You can't use it to envelope food that carries tomato, lemon, etc. In Catalonia it's traditional to use tomato in all sandwiches. It is still traditional that mothers prepare sandwiches for the their kids, and they have to add a layer of paper between the foil and the sandwich, or switch to plastic films. --Enric Naval (talk) 15:42, 17 January 2013 (UTC)

I think you have probably rediscovered Limonene recycling. Sean.hoyland - talk 15:43, 17 January 2013 (UTC)

I remember using a styrofoam cup full of petrol to prime carburetor once. The cup turned to oobleck very quickly. It was probably some type hydrocarbon in the peel.--Canoe1967 (talk) 15:51, 17 January 2013 (UTC)

We're not supposed to give medical advice, but I think we should be allowed to say that styrofoam is not a food, even when dissolved in a hydrophobic oil. Wnt (talk) 16:15, 17 January 2013 (UTC)

To enlarge and clarify what Wnt is saying - it is entirely possible for quite a range of oils and related organic chemicals to dissolve or corrode polystyrene. This has nothing to do with acidity, and everything to do with the propensity of non-polar solutes to dissolve in non-polar solvents. Tea is mostly water, which is very polar, with some emulsified fats, which are mildly polar and also not good solvents. On the other hand, vegetable oils are quite good solvents, and mostly non-polar. So they dissolve polystyrene. And no, the resulting mish-mash is not good to drink. AlexTiefling (talk) 16:30, 17 January 2013 (UTC)

Boeing 787 manufacturing locations of windshields and fuel tanks

Didn't see those in the summary at Boeing_787_Dreamliner#Manufacturing_and_suppliers 20.137.2.50 (talk) 16:22, 17 January 2013 (UTC)

The Boeing 787 cockpit windows are made by PPG Aerospace Transparencies.

http://www.ppg.com/coatings/aerospace/transparencies1/B787_tb_v9.pdf

The Boeing 787 fuel tanks are manufactured by Boeing. --Guy Macon (talk) 16:42, 17 January 2013 (UTC)

Which article is this?

I failed to jot it down. Thanks in advance. [10] 65.88.88.71 (talk) 22:20, 17 January 2013 (UTC)

That site requires a password, which I do not have. Sorry. If you don't have one either, then WP:REX may be able to help you. --Jayron32 22:26, 17 January 2013 (UTC)

I'm not sure exactly how I found it, but I think the article is: Melinda Wenner Moyer (November–December 2012). "You are what you eat: food can affect your behavior--even when you just look at it". Psychology Today. 45 (6): 43.{{cite journal}}: CS1 maint: date format (link). Looie496 (talk) 00:04, 18 January 2013 (UTC)

Thank you! 65.88.88.71 (talk) 21:20, 18 January 2013 (UTC)

January 18

V-engine with unequal stroke lengths on different banks

Soviet's V-12 Diesel model V-2 engine has a stroke of 180mm on the left cylinder group and 186mm right cylinder group.

1. Is there a name for this configuration? Googling "unequal stroke length" got me nothing related.
2. What's its purpose?
3. Is there any other engine with this setup?

Dncsky (talk) 02:00, 18 January 2013 (UTC)

It does seem odd. A quick google search found this [11], which states that "The V-2-34 features an aluminum alloy body and is meant to be mounted lengthwise in the vehicle hull. Two cylinder banks with 6 cylinders each were placed in an angle of 60 degrees. The pistons are linked to the central crank shaft by wrist connecting rods, which means that only six rods are directly connected to the crank shaft. This special design also results in a slightly lower stroke in both sides of the engine. The right side has a stroke of 186.7 mm and 180mm in the cylinders on the left bank". From the description, the unequal stroke may be a side-effect of the design, rather than an intended feature. The photo of a cutaway V-2 here [12] seems to show a connecting rod (on the left) which is connected to something other then the crankshaft - from the look of it to an extension lug on the side of a conventional connecting rod big-end. This would fit the description, and if it works the way it appears, the reduced stroke for the secondary connecting rod may be a simple consequence of the geometry. AndyTheGrump (talk) 02:28, 18 January 2013 (UTC)

Thank you!Dncsky (talk) 02:34, 18 January 2013 (UTC)

Resolved

Looking further, it may be the other way round: using Google translate on one of the sources that the Russian-language article on the engine [13] cites [14], It appears that the secondary connecting rods have the longer stroke - and in consequence, the cylinders have a higher compression ratio. AndyTheGrump (talk) 02:49, 18 January 2013 (UTC)

That would be a physical impossibility, unless the secondary conrod connecting point was very displaced, on a spur off the primary conrod. That would have very severe weight and strength penalty - you wouldn't do it. If you visualise a connecting point on the primary conrod, inline with its logitiudinal axis, that point must, as the crankshaft rotates, describe a circle just above and at smaller diameter than does the big end. Hence the stroke produced by the secondary conrod must be less than that produced ny the primary conrod. If I was the designer of this engine, adn for some reason wanted this conrod arrangment (I can't think why I would, although it does allow a large bearing area), I would doctor the intake valve timing so that the effective compression on both sides was equal. This would enable smooth running while using the greatest commonality of parts. The impact on power output (rather arbitarily set in a diesel engine) and fuel economy would be negligible.

As for other engines using this configuration, radial aircraft engines have been made with one master conrod and several secondary conrods attached in a ring around the master bigend. In a radial engine, there is not the room for separate bigends for each rod to be on the crankshaft.

Ratbone 124.178.174.189 (talk) 03:05, 18 January 2013 (UTC)

Looking at the cutaway photo, I'd say that the secondary conrod connecting point was displaced, on a spur off the primary conrod, though it is hard to tell. In any case, even with the secondary conrod connecting to the primary on the centreline of the primary, the thrust from the secondary conrod is going to create a bending force, due to the cylinder V configuration. As for the exact geometry, without further information there is no way to be sure. AndyTheGrump (talk) 04:28, 18 January 2013 (UTC)

A longer stroke does not imply a higher compression ratio. If you double the stroke and you move the piston down far enough to double the volume at top dead center the compression ratio is unchanged. --Guy Macon (talk) 04:30, 18 January 2013 (UTC)

God point, Guy. Anyway, I've found a diagram of the engine here (about 20% down the page): [15] - note the way the secondary conrod 'wrist pin' is offset from the centreline of the primary. As for which cylinder has the longer stroke, I'll leave it for someone else to figure out. AndyTheGrump (talk) 04:41, 18 January 2013 (UTC)

A longer stroke with the same compression ratio means that something else has to change, either pistons, and/or cylider head height, remembering that the piston must at top dead centre just about touch the head, or piston squish will not work properly, leading to poor compustion, fuel and combustion products forced past the rings, etc. Cheaper and easier to keep everything the same on both banks, and tweak the intake valve timing as I said. However, all this appears to be not relevant. I printed out the cross section view linked by AndyTheGrump, and found by carefull measurement that:-

• Pistons, and cylinders on both banks are the same; So are the heads, except for being mirror images of each other;
• The secondary conrods are indeed attached on a spur on the primary rods;
• The spur is positioned such that, at left bank TDC, the spur bearing is positioned just slightly to the right of crankshaft centre and just slightly below the point at which a line to the spur bearing centre would make 120^o to a line from spur centre to crank centre. This means that the stroke for both banks is the same!.

Where did the 180 mm / 186 mm dimensions in the Wikipedia article come from? There is no reference for the dimensions cited - it's probably wrong, even though the refrences [16] and [17] (Russian Wikipedia) provided by AndyThe Grump clearly state it's the case. [16] clearly states each bank has a different stroke, but not for all versions of the engine, which does not seem likely.

Ratbone 124.178.147.222 (talk) 05:08, 18 January 2013 (UTC)

This reference - http://translate.google.com/translate?sl=ru&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&eotf=1&u=http%3A%2F%2Fru.wikipedia.org%2Fwiki%2F%25D0%2592-2, states that the secondary rod side has greater stroke and compression (look at table at bottom), "due to kinematic reasons". Presumably that means to statically balance the engine - which is weird and makes no sense to me. The spur arrangment would indeed introduce balancing issues, but a difference in stroke will not fix that. Ratbone 124.178.147.222 (talk) —Preceding undated comment added 05:39, 18 January 2013 (UTC)

Seismic morse code

Let's say I was a Soviet spy in Washington, DC, and I wanted to send an SOS message to a seismometer monitored by my contact in Moscow. How large a bomb would I need to use for each dot or dash, and what sort of transmission rate could I get? --Carnildo (talk) 03:08, 18 January 2013 (UTC)

You'd need a nuclear weapon for each dot and dash, and your transmission rate would be maybe one character a day (due to the need to travel to a new site and bury the weapon prior to sending each new dot or dash). Of course, with that many nukes, you won't need to send an SOS -- you could just blow up your pursuers (along with anyone else who happens to be within a country mile) and be done with it. (Of course, doing so will probably lead to a nuclear war between the USA and the USSR, and also setting off nukes on US soil without authorization from the Soviet Prime Minister will most likely get you executed as an "enemy of the state".) Now can we PLEASE have some SERIOUS questions?24.23.196.85 (talk) 03:28, 18 January 2013 (UTC)

Not necessarily. It is a classic question in information theory, sometimes set by lecturers in the subject. In any communications channel, radio, sound in air, seismic, or whatever, there is a tradoff between information rate, transmitter power, and noise level. Noise level is in this case set by interference at the receiving site by vibrations from vehicles on roads, construction site works, etc. For a given noise level, how much transmitter power (i.e., size of explosion) you need is proportional to how fast you want to send the message. Real communications systems generally require more power than is predicted by the theorry - one has to design a encoding system to make the best of the channel. If you wanted to transmit "SOS" and could accept taking months to send it, you could perhaps employ a building site pile driver, using a code that translates the three letters into a vast number of bangs. But if you could accept only seconds, you'd probably need a nuclear bomb. See http://en.wikipedia.org/wiki/Information_theory Ratbone 124.178.174.189 (talk) 03:31, 18 January 2013 (UTC)

Absolutely not -- the magnitude of the seismic wave drops off as the SQUARE of the distance, so by the time it travels from Washington DC to Moscow, any seismic wave less powerful than that made by a nuclear explosion will have dropped to below detectable levels. This has nothing to do with information theory, this is straight physics. 24.23.196.85 (talk) 03:38, 18 January 2013 (UTC)

Sorry, but this is no different to any other communication medium. For example, in radio comms, where information theory has a major application, received power also falls as to the square of the distance. Info theory tells us why, for example, shortwave broadcast radio requires hundreds of kilowatts of transmitter power to send AM music, but radio hams can communicate around the World using only a few watts using morse code. The square law makes the transmitter power required much greater than it would be for a linear-with-distance loss system (which never occurs in practice), but the info theory math still applies. You do need a filter mechanism at the receiver tuned to the coding system in use, so that the noise is discriminated against. I suggest you read up on info theory before talking about things you are not aware of. Ratbone 124.178.174.189 (talk) 03:50, 18 January 2013 (UTC)

On the contrary, YOU should read up on physics -- a seismic signal simply WILL NOT make it halfway around the world without dropping to undetectable levels. Do you even know WHY a radio signal can be detected at such a distance? It's NOT because it's so powerful, but because it's focused in just one narrow frequency channel, and because the receiver can efficiently filter out the broadband noise and amplify ONLY the selected frequency -- which is NOT the case with a bomb and a seismometer! Also, like ALL big cities, Moscow has such a high background seismic noise level on ALL frequencies (from construction work, trucks, buses, trains, trolleys, the Metro, etc.) that even if a weak seismic signal does make the distance, it will be drowned out by the noise and undetectable! 24.23.196.85 (talk) 05:33, 18 January 2013 (UTC)

You've sunk your own argument. Yes, indeed radio works by filtering. But you can filter a mechanical transmission system (eg seismic) too. There is more than one way to filter. You can filter on frequency, as in traditional analogue radio, or you can filter on digital coding (as in cellphones and some types of military comms - termed "spread spectrum", although this is only one type of spread spectrum). Comms systems can, and do, share the same frequency if the digital coding is different, and share the same coding if the frequency is different. A simple example: Say the agent makes a thump every 32 hours for a month to send a morse dash, and every 40 hours for a month to make a morse dot. Moscow could then filter for these thump rates and exclude much noise. (it would not be smart choosing an integer multiple of 24 hours, or a sub-multiple, for obvious reasons) There are much better coding schemes but this will do for a simple example.

Your bit about Moscow being noisy is of no importance, for two additional reasons: a) it just means the transmitter has to be a bit more powerfull than otherwise, and b) who said the reciving site has to be at Moscow? They can do the same as is done with Embassy radio coms: set up a reciving site at a quiet location, and pass the message on to Moscow via phone or courier etc.

I strongly suggest you read up on the subjects of information theory, coding, messaging systems before you goof again. Electronic and comms engineers spend much time studying this very same field in undergraduate courses.

Ratbone 124.178.147.222 (talk) 05:57, 18 January 2013 (UTC)

I strongly agree - even a small source is not 100% undetectable - even if the amount of signal that reaches the detector is amazingly tiny. If the pulses are regular enough - and at a known frequency - then you can detect it given enough time. Suppose we have a hypothetical pile-driver that thumps (or does not thump) at PRECISELY one second intervals and does that (or doesn't do it) continuously to send one bit of information every 32 years. Let's suppose that the effect of one of those thumps is a signal that appears at the detector that is one part per billion of the 'background' vibrations due to distant volcanoes, cars, footsteps of the experimenter, etc. Let's have the recieving seismograph be monitored every half second for all of that time and separate out that data into the odd-numbered half seconds and the even numbered half seconds. (Technically, you'd need to sample a little faster than that...but let's keep things simple for a moment!)

• If the transmitter sent a "0" bit (the pile driver didn't thump for 32 years) then the difference between the average of the odd and of the even half-second readings measured over 32 years will be very, very close to zero.
• If the transmitter sent a "1" bit (by thumping once a second for 32 years) then the average vibration at all of the odd-numbered values (when the pile drivers' hammer was being lifted ready for the next thump) over 32 years will be significantly less than the average of the even-numbered half-second values when the pile-driver hit the dirt. The amount of difference in the measurement was one part in a billion - but added up a billion times and divided by a billion - the result should be that the even-numbered reading will be about twice that of the odd-numbered readings...easily noticeable...quite distinctive!

The difference between the two is perfectly adequate to receive a one bit signal at a billionth of a Hertz transmission rate. Even if the detector isn't accurate enough to receive that signal, the errors in the detector will average out over enough time - and the signal will show through. Even if the detector has only one bit of precision - showing a '0' for less-than-average amounts of ground displacement and '1' for greater-than-average, the presence of background "noise" around that cutoff point will result in the pile driver producing a statistically greater-than-average number of 1 bits over 32 years...even if the detector is inherently crappy and noisy - the resulting noise produced in the signal will average out eventually. There are entire areas of science and mathematics in "communications theory" that relate signal strength, noise ratios, bit rates, detector precision and so forth.

Of course this might fail if there is interference from other sources at the same frequency. So if you picked once-per-second (1Hz) as your signalling rate and there is a mechanical clock in the room with the detector - then the clock is a transmitter "broadcasting" on the same frequency and that could easily wipe out the signal that you're trying to detect. The frequency of our pile-driver clock would also have to be pretty solid - if it was "off" by a bit, or drifted compared to what the detector is expecting, then that would be difficult. A smart pile-driver-transmitter designer would pick a frequency that's not polluted by noise from man-made sources. You'd want to avoid 1Hz transmission rates for sure! Maybe also avoid rates close to that of the footstep-frequency of a typical adult human...avoid rates similar to the density of road traffic near where the receiver is located.

The practicality of averaging the results from a seismometer for a billion seconds and getting one bit of information every 32 years is going to be problematic...but it's not impossible.

To pick a "real world" example, consider how hard it is to detect a planet orbiting a star that a few hundred lightyears away by the tiny amount of light that's blocked by the planet as it crosses in front of the star for a few days once a year. The amount of variation in the brightness of the star as a tiny planet crosses in front of it's disk is vanishingly small...but analyse the light over a long enough time and you can pull that tiny variation out from all of the background noise in the telescope. Science does these kinds of amazing tricks routinely. It's just a matter of technique and time. SteveBaker (talk) 15:48, 18 January 2013 (UTC)

All this still won't help the KGB if the signal is so weak as to be below detectable levels (which will be the case for a Washington DC to Moscow seismic signal that uses anything less than maybe a 100-kT nuclear bomb). 24.23.196.85 (talk) 01:04, 19 January 2013 (UTC)

Didn't you read anything that Ratbone and SteveBaker wrote? Information theory, as both have outlined, is a well established branch of science, applying to any communication medium, radio, communication by light beam, mechanical systems, seismic communication, etc. A standard textbook used in many information/communication theory courses for some years is Modern Digital and Analog Communication Systems, B P Lathi, pub: Holt-Saunders. Chapter 8 covers in depth the principles discused by Ratbone and SteveBaker here. Coding is covered in other chapters. If you have good high-school level math, you can study this or similar books and realise you are wrong - given enough time and a good coding system, there is no lower limit on transmitter power. The subject of information theory, which can be regarded as the science of sending a mesage as fast as possible in a finite bandwidth in the presence of noise with the least transmitter power, was established by C E Shannon, R V L Hartley, and H Nyquist papers in the Bell System Technical Journal, in the 1920's. Keit 121.215.159.209 (talk) 01:44, 19 January 2013 (UTC)

I have been poached! μηδείς (talk) 12:30, 18 January 2013 (UTC)

You are wrong. Given enough time and a repetitive signal, the concept of "below detectable levels" does not exist. Repeat it enough times on a regular enough basis and you can send a Washington DC to Moscow seismic signal with the power of a firecracker. Of course you will die of old age long before it is received... I haven't run the numbers but I suspect that it would take longer than the current age of the universe. Go back and read SteveBaker's comment again. --Guy Macon (talk) 01:35, 19 January 2013 (UTC)

Of course the concept of "below detectable levels" exists -- if the signal is weaker than the seismometer's sensitivity limits, then the instrument won't pick it up no matter how many times it repeats! YOU are the one who's wrong here! 24.23.196.85 (talk) 02:09, 19 January 2013 (UTC)

I'm transmitting a "1" with a dim LED in a sealed safe 1km underground at .0187534019265 Hz. The reciever is a silver halide camera on the other side of the Earth. :) Sagittarian Milky Way (talk) 03:28, 19 January 2013 (UTC)

I am totally clueless here, but doesn't transmission require a channel or a medium? The earth will conduct vibrations. But in Sag.'s example, does the 10,000 degree core of the earth count as a channel for the transmission of light? μηδείς (talk) 04:02, 19 January 2013 (UTC)

There is another issue with Sag's example: Silver halide detection requires the received energy to exceed a threshold - below the threshold for each sliver halide crystal nothing happens. However, this is not important wrt the OP's question, as a linear transducer can be used to detect seismic waves. Ratbone 121.215.34.98 (talk) 04:09, 19 January 2013 (UTC)

The Sun can be seen through thin enough gold leaf. Let's say the sunlight is made at least 10 million times dimmer by passing through the gold leaf (100000 is used for visual filters). The Earth is I don't know a 100 trillion times thicker? If the Sun could be bought, the box would say 35,700,000,000,000,000,000,000,000,000 lumens. Adjust for inverse square-law of the distances. So at least 260000000000000000000x10000000^{100000000000000} times dimmer than visual detectability. And if you say the halides won't be activated and there's a bright core in the way, then information theory! (make sure the photos are near the threshold, though) Sagittarian Milky Way (talk) 17:21, 19 January 2013 (UTC)

And even a linear transducer will have a certain detection threshold below which it will not detect a signal. If nothing else, the Heisenberg uncertainty principle puts an ABSOLUTE limit on the accuracy of ALL measurements and precludes the detection of an "infinitely small" signal. 24.23.196.85 (talk) 07:04, 19 January 2013 (UTC)

But you don't need to detect individual pulses to detect the message. The signal is superimposed on the background noise. Sometimes the sum of noise and signal pulse will breach the detection threshold, and sometimes it wont. But if the signal pulse is there, this sum will breach the threshold more often than if it isn't. You can collect data over a long enough time to get to an arbitrary certainty for distinguishing the "pulse" from the "no pulse" case, no matter how small the difference. Heisenberg does not affect this. --Stephan Schulz (talk) 09:59, 19 January 2013 (UTC)

Honestly, all the discussion is coding theory is largely academic, while the original question was phrased in practical terms. A system that takes 100 years to transmit a signal is of no practical value. So far, no one has really looked at the problem in practical terms. We would need to know what the transmission efficiency of seismic waves from DC to Moscow actually is. And we need a frame of reference for how much seismic energy you can generate from an explosive (or any other method). Till one has those details in hand, you can't figure out if the initial signal to noise ratio is 10:1, 1:1, 1:1000, 1:1000000, 1:10³⁰ or what. Without such basic details you can't figure out what is needed to build a practical system for seismic communication. Coding theory can dig you out of the noise, but if you are starting many orders of magnitude below the noise floor then it is unlikely the system can ever be built in a practical way. Dragons flight (talk) 04:04, 19 January 2013 (UTC)

The original question was deliberately posed as an absurd one on the talk page--hence my obscure reference to being poached. Carnildo is having a little joke on us by posting it here. But I do think the question of a medium which follows from subsequent comments is an interesting one. For example, "In space, no one can hear you scream." I take that to mean that ordinary sound waves simply cannot propagate through a vacuum. (Although supernova shockwaves can through near vacuums, if I understand correctly.) Doesn't information theory require a suitable medium, and aren't claims for infinite transmissabilty (again, a term I am making up) based on assumption like the perfect gas that don't hold in reality? μηδείς (talk) 04:19, 19 January 2013 (UTC)

I reckon I showed that it is not a system you would use in practice in my first post. Using radio is the tried and tested way and is vastly cheaper and more convenient. The agent could also simply phone and use a coded message. We used to phone our family in East Germany from time to time, business calls were made, and who is to know that a certain pre-arranged number (not necessarily in any particular country) will be answered by someone trained to react to a certain secret code word by forwarding it on. However, the OP asked how large a bomb is required for seismic signalling, and what sort of transmission rate could be achieved. That's a good question to ask, and we've answered it - the transmission rate and bomb size need to be traded off against each other, and the trade off will not be of practical use as you say. Ratbone 121.215.34.98 (talk) 04:21, 19 January 2013 (UTC)

Yes, information theory requires a medium by implication, as the system bandwidth is one of teh calculation inputs. For electromagnetic waves (radio, light), the medium can be a vacuum. Sound can travel in anything that is not a vacuum. The medium in this case is the earth propagating seismic waves - essentially low frequency sound travelling in an elastic solid the same as it does as a result of geologic disclocations i.e., earthquakes. Radio waves and light travelling in a vacuum is a lossless system - the strength of the falls of with the square of the distance purely because of the ever increasing volume per unit energy. In the case of sound (or seismic waves) travelling in a solid, there is a loss above this - because there are frictional losses converting some of the sound energy to heat along the way. That does not mean a total loss after some distance x though - you just need to increase the transmitter power (bomb size) to compensate.

I don't see the question as necessarily absurd or silly - in part because this is a classic assignment question sometimes asked by lecturers in information theory and coding, as I stated in my first post. By specifically asking about bomb size and signalling rate, the OP has displayed some ability to think beyond what many lay people can do (and clearly better than poster 24.23.196.85). Or he might be just being silly and fluked a good question - I don't know the guy, so I cannot know. We shouldn't be too ready to judge a question silly - many of us ask questions of an unusual scenario in order to test or increase our understanding of physics. I've done it myself - it is a very effective technique.

Ratbone 121.215.34.98 (talk) 04:39, 19 January 2013 (UTC)

The silliness lay in my original talk page suggestion that a spy would send an sos signal by nuclear bomb, not in the pure physics aspect. As a physics question it could simply be reworded as what TNT equivalent would be necessary for a regular signal to be detected on the other side of the Earth. (I also understand at the antipodes the signal would be focused and hence magnified.) μηδείς (talk) 05:09, 19 January 2013 (UTC)

I should point out that Moscow and Washington DC are not geographical antipodes (though they can be considered political antipodes) -- in fact, the distance between them is approximately 5000 miles (8000 km) on a great circle route. As for calculating the size of the bomb needed, the most important piece of info is the seismic wave absorption coefficient of oceanic basalt -- this absorption, along with the inverse-square decrease in intensity I mentioned earlier, will account for most of the signal attenuation over this distance. (In practice, even this prediction will be overly optimistic, because the seismic waves will be scattered and partly retroreflected back toward Washington DC every time they encounter a geological fault or a boundary between different rocks -- in particular, there will be major attenuation at the Mid-Atlantic Rift, which will mean the signal will arrive in Moscow even weaker than what this theoretical model predicts.) 24.23.196.85 (talk) 07:17, 19 January 2013 (UTC)

The same thing happens with any wave propagating through a medium. Electromagnetic waves suffer a degree of attenuation above the square-law-with distance rule in non-vacuum media due to a degree of conversion into heat, and portions get reflected backwards when any change in media offreing different dielectric and/or magnetic properties is encountered. In all cases, the intensity at some distance x is non zero, and as it is non-zero, it can be used to communicate by means of frequency filtering or pattern filtering. Indeed, in seismic testing to determine geology for earth resistivity calculations, filtering is used to reduce the size of the bang/thump to that of striking a plate with a sledge hammer a few times - the detection equipment knows when you hit the plate and triggers its signal storage and timing from it. Ratbone 121.215.17.194 (talk) 09:54, 19 January 2013 (UTC)

What kind of seismic testing you are referring to ? I'm not aware of seismic being used to determine resistivity, although I guess it's sometimes used to constrain the earth model for an inversion based on well log data. I don't understand "filtering is used to reduce the size of the bang/thump to that of striking a plate with a sledge hammer a few times". A lot of steps are involved in processing seismic, but I don't recognize that one, although I guess you might be referring to compressing the wavelet via decon. If anything, the opposite of reducing the size of the bang is done to try to minimize the effects of absorption and geometric spreading from the data. The recording equipment for marine streamers and onshore/ocean bottom cables certainly needs to know when the airgun arrays/vibrator sweeps happen or else you will be burning through hundreds of thousands of dollars in acquisition cost with nothing to show for it in no time. Sean.hoyland - talk 12:29, 19 January 2013 (UTC)

We have a real-world example of a chemical explosion in Wyoming that registered on seismographs as far away as Europe. --Guy Macon (talk) 09:18, 19 January 2013 (UTC)

That had "only" about 40 tonnes of (unspecified) explosives - or about one large truck full of the stuff, so it gives us an upper bound. And it wasn't focused to produce a seismic shock, but set of by accident, so much of the blast probably dissipated into the air. One should be able to do better. --Stephan Schulz (talk) 09:52, 19 January 2013 (UTC)

Reason for glass being transparent face on but opaque edge on

My understanding of why transparent materials (at least SiO2) are transparent (which is informed by what I remember from a semiconductor physics class I took in college) is that the energy difference between the constituent atoms' base state and next available excited state is larger than the energy that photons (of visible light frequencies encountered in everyday life here on Earth) have, so they pass through the material. But I was just thinking about this as I looked at a piece of glass that was transparent when viewed face-on but green when viewed edge-on. And it's not because of thickness: a piece a quarter-inch wide and a quarter-inch thick is still highly transparent through its face and nearly opaque green through its side. Who can explain in as SIMPLE terms as possible what key features of the crystal structure (though I thought glass was often amorphous) cause high transparency at one angle and high opacity at another? 20.137.2.50 (talk) 14:44, 18 January 2013 (UTC)

In a word: thickness. Consider that a cube of glass won't have any preferred direction of "transparency": it will be equally transparent in all directions. Differences in transparency only become apparent in big sheets of glass, which are basically large retangular prisms. The shortest side is dramatically shorter than the two longer sides, so the amount of material that the light has to pass through is significantly more edge-on. If the index of refraction of the glass is such that a light beam traversing the glass in a particular direction gets deflected before it reaches the other side, you can't see clearly in that direction. Picture light going through a piece of glass 1/4 inch thick and 3 feet wide, edge on. Any light that strikes that edge even at a slight angle will be deflected by refraction enough to never reach the opposite side. This doesn't happen when you view the pane of glass from the front. --Jayron32 14:51, 18 January 2013 (UTC)

I don't have a cube of glass handy to check, but I'm pretty sure it will be equally transparent through all faces, if they are finished the same way. Note that many types of window glass have a different type of finish on the edges, and this can contribute to the thickness effects Jayron describes above. SemanticMantis (talk) 14:59, 18 January 2013 (UTC)

(ec) The key bit there is 'if they were finished the same way'. If you're looking at pieces cut from flat sheets of glass (like panes of glass used for windows) I can think of (at least) three reasons why the appearance of the glass might be different from the cut sides/edges as it is from the originally-manufactured flat face.

1. Most plate glass is made using the float glass process. This process produces faces that are extremely smooth and uniform—and the opposing faces will be very nearly perfectly parallel. The other surfaces of the glass cannot be subjected to this process (obviously).
2. Cutting the edge of the sheet of glass can (will!) introduce microscopic and macroscopic defects, fractures, and other light-scattering features to the cut edge. Even if polished, these surfaces will not be identical to the float-glass faces. Opposing cut faces are also unlikely to be quite as parallel as the opposing faces of the float-glass pane.
3. Surface coatings may have been applied to the exposed surfaces of the plate glass. Some may be deliberate and permanent, for reducing visible reflections or heat leakage, others may be incidental, such as adhesive residue left behind from the protective paper often applied to glass for shipping.

Any or all three of these factors can and will affect the way that light scatters and reflects (internally and externally) from the surfaces of the piece of glass, and thereby affect the appearance of the light transmitted through the glass. If you were to take a larger lump of glass, and cut and polish it into a cube, I suspect that you would find its properties are pretty isotropic: the same in all directions. TenOfAllTrades(talk) 15:21, 18 January 2013 (UTC)

Then I would like to know the details of how finish affects transparency. This picture captures my observational rationale. About in the middle horizontally and at the bottom quarter vertically, for instance, you'll see a fairly trapezoidal piece that closes to a triangular point at its right. So though its width is at or less that of its thickness, it is still green edge on but is transparent face on. 20.137.2.50 (talk) 15:09, 18 January 2013 (UTC)

In that image, the camera is at an angle of (let's guess) 60 degrees to the "horizontal" surface of the glass. Light from the ground beneath is refracted going into the bottom of the glass, then again as it emerges from the top and heads towards the camera. The light is attenuated by maybe a quarter inch of glass. But the "vertical" sides of the glass are more like 30 degrees from the camera. The light that emerges from that angle at the sides has been subject to "total internal reflection" and bounced around perhaps dozens of times within the sheet before emerging towards the camera - the total distance travelled through the glass could be a dozen times more than the relatively straight path taken on the horizontal sides. Hence more attenuation - and it looks green. If you look at some of the smaller chunks (especially the ones just to the left of the stone column), the horizontals and verticals look about the same color. SteveBaker (talk) 15:19, 18 January 2013 (UTC)

Jayron gave you the right answer. You may like to read up on optical fibre. Optical fibre is used by phone companies to send information via very thin glass strands dozens of kilometers long. The glass used is essentially quite normal silica glass, equally transparent in all directions. However, it is thousands of times more transparent than standard silica glass due to extreme purity, so that the signal can go end to end. Ratbone 120.145.29.226 (talk) 15:31, 18 January 2013 (UTC)

More reading: See Total internal reflection, which is exactly what occurs when you view a pane of glass edge on. Light simply can't escape in that direction. --Jayron32 15:56, 18 January 2013 (UTC)

That was nice. Sunny Singh (DAV) (talk) 13:18, 19 January 2013 (UTC)

12cm

is a man with 12cm wide feet (at the widest point, the ball of foot) a 4e, 5e or 6e wide width shoe?--Shoes15151617 (talk) 17:12, 18 January 2013 (UTC)

That's impossible to know without knowing the length as well. Per the Wikipedia article on shoe size Shoe widths are relative to the length of the shoe, so a size 10/4E width foot will be a different width than a size 14/4E shoe (assuming U.S. measurements, as the "4E" width designation is usually a U.S. designation). If you have a question, you should visit a shoe store and get measured; most shoe stores have a Brannock Device to measure your foot, and that can give you an idea of your correct size. --Jayron32 17:26, 18 January 2013 (UTC)

I hate that device, since it doesn't measure height. As a result, they always recommend normal width for me, when I really need wide shoes to accommodate the additional height of my feet. StuRat (talk) 17:39, 18 January 2013 (UTC)

As with any tool, it just gets you started. You, for example, know that your feet run wide from what the device tells you. So, you're going to tend to find shoes sized somewhat wider than it recommends. The idea is that, if you know absolutely nothing about your shoe size, it gives you a ballpark to start from. You should always try on the shoes in question, and several sizes for each style, because styles and manufacturers will all vary somewhat, so even though you're a 10.5/4E in Nike sneakers, you may find you're an 11/D in Timberlands. The device is useful, but only if you're not unwise in how you use it. Try the shoes on regardless... --Jayron32 18:30, 18 January 2013 (UTC)

The device doesn't seem to help. Since I need to try them on to see if they fit anyway, and know my approximate size, why bother with the device at all ? StuRat (talk) 19:07, 19 January 2013 (UTC)

I am a 11 1/2 shoe length with 12cm wide feet. Is that a 4e , 5e or 6e?--Shoes15151617 (talk) 19:52, 18 January 2013 (UTC)

Neurotransmitters - if someone is being hard with dancing in clubs

This is not a medical advice, just a theoretical case to evaluate.

someone go to lot's of dance clubs, and dance very genteelly, he\she could be with someone who "knocks out" in dancing, he\she could sit and the partner will dance near him - but when he\she dances, it's always have to be clumsy, absent, slow, gentle, he/she being hard with this because it potentially hearts him/her - hearts the experience. the one do fell the need to do dancing but something just blocks it from it. alchaol seems to worsen it (by upgrading neural inhibition?)

i think it have to do with levels on neurotransmitters, what do you guys think of such matter? maybe the individual lacks dopamine?, maybe it needs caffeine/xanthins? — Preceding unsigned comment added by 79.176.113.107 (talk) 17:44, 18 January 2013 (UTC)

The question is hard to understand because of poor English, so I have to guess at what you mean. If you are asking whether slow and clumsy dancing can be caused by altered neurotransmitter levels, the answer is yes. But there are other possible causes too. Looie496 (talk) 18:02, 18 January 2013 (UTC)

poor english? excuse me?, what neurotransmitters could play a role?, sure that a neuro-informative level could be another option (the individual doesn't have neural information about how to dance), but, i am interested to hear opinions about the neurotransmitters that has to do with dancing. — Preceding unsigned comment added by 79.176.113.107 (talk) 19:04, 18 January 2013 (UTC)

Dopamine is the most obvious possibility. A person with Parkinson's disease (caused by loss of dopamine cells) will have great difficulty dancing. But also a person who is depressed (low levels of norepinephrine and serotonin, among other things) will often be uninterested in dancing. Looie496 (talk) 21:44, 18 January 2013 (UTC)

What do you mean by "knocks out" in dancing? What do you mean by "potentially hearts him/her - hearts the experience"? Do you mean "potentially loves him/her"? Do you mean "potentially gives him/her a heart attack"? It's not that your English is poor, it's that there's too much slang in it for those of us with more experience (OK and who are older) to be able to give you a proper answer. --TammyMoet (talk) 09:53, 19 January 2013 (UTC)

I think Developmental dyspraxia is probably as good as you'll get from Wikipedia about such problems. We can't give medical advice or diagnosis of individual cases. As to neurotransmitters there's a large number of them and people aren't at all certain what they all do. Dmcq (talk) 20:00, 18 January 2013 (UTC)

Being able to dance requires a sense of rythm. Our sense of rythm arises from certain neural structures - timing neurons. It is a brain wiring configuration thing, not just an adequate supply of neurotransmitters. It is also highly variable between individuals. I was always unable to dance. At one time I got involved in electronic music, and from there got interested in playing guitar. That was terribly difficult at first, as a sense of timing/rythm is required for that as well. But, by persistence, after a while things "clicked" and I was able to play. I was then able to dance as well. So dancing skill can be acquired. Floda 121.221.210.234 (talk) 00:18, 19 January 2013 (UTC)

Alex Hum

please either consider creating such an article yourself or clarifying your question regarding references, if you have one
The following discussion has been closed. Please do not modify it.
Alex Hum is making revolutionary discoveries in the field of intelligence clothing such as sunglasses that one can watch television. I have found very little on this pioneer, and many around college campus' are calling him the next Steve Jobs. Below is a link from ScienceDirect.com. Alex Hum, voted as one of the outstanding people of the 20th century by the Cambridge International Biographical Centre, Cambridge, England, has achieved much of his world-wide attention because of his aim and vision of infusing wireless technologies into everyday high-tech devices and, now into, haute-couture. Dr. Hum is managing the international i-Wear consortium (sponsored by Adidas, Energizer, Seikon–Epson, France Telecom, Levi's, Samsonite, Bekintex, Recticel, Philips, Siemens, WL Gore, Courreges, Vasco Data Securities, and more). i-Wear is a multi-disciplinary research and industrial consortium to invent the deep future of intelligent clothing. In addition, he is the Chief Scientist in Starlab Research Laboratories nv/sa in Belgium. He was a scholar and obtained a direct Ph.D. in RF/Microwave Engineering. He was a Member of Technical Staff at the Centre for Wireless Communications, with experience in project management and industrial collaboration with top technology companies. His specialities are RF/microwave circuit and system design, wireless technology, 3G cellular systems, antenna systems, and the design of RFIC and MMIC integrated circuits. A member of IEEE and IEE – Dr. Hum publishes regularly in internationally-refereed journals and frequently addresses international conferences. He holds several patents. Dr. Hum is listed in Who's Who in Science and Technology as well as Who's Who in the World. — Preceding unsigned comment added by 199.120.31.20 (talk) 19:11, 18 January 2013 (UTC)

mrsa

I heard if someone gets a mrsa infection they carry mrsa for life is that true? Is that also true for non mrsa staph?--Shoes15151617 (talk) 19:54, 18 January 2013 (UTC)

Do you mean MRSA?--Shantavira|^{feed me} 20:15, 18 January 2013 (UTC)

yes--Shoes15151617 (talk) 20:53, 18 January 2013 (UTC)

In general, "going dormant" only to emerge later and cause more problems, is more a behavior I associate with viruses than bacteria. StuRat (talk) 02:45, 19 January 2013 (UTC)

• Bacteria can colonize people; for example, MRSA can colonize the nose without causing disease for long periods of time, then under certain circumstances it can cause disease in that same person. Example: PMID 23290578 and PMID 18374690 -- Scray (talk) 03:08, 19 January 2013 (UTC)

• Staph aureus is very often found on the skin, and as Scray said, also in the nose. MRSA is just a strain of Staph aureus which is resistant to methicillin. So if someone has had lots of S. aureus infections which have been treated with antibiotics (note that minor issues such as boils and sinusitis can be caused by S. aureus infection) it is likely that there will be some bacterial cells on the skin or in the nose which are methicillin resistant, and they can happily stay there without causing any issues. douts (talk) 13:54, 19 January 2013 (UTC)

heatwave?

can anyone tell me why this http://www.bbc.co.uk/news/world-asia-21072347 says it was a "heatwave" in sydney today of 46C but this http://www.weather.com/weather/today/Sydney+ASXX0112:1:AS says it only reached 24C ? --Shoes15151617 (talk) 20:59, 18 January 2013 (UTC)

The 46C reading is reiterated by the Sydney Morning Herald here, by the Nine Network here, and by Weather Underground here. -- Finlay McWalterჷTalk 21:14, 18 January 2013 (UTC)

The cooler temperature is for the 19th - the BBC story (from the 18th) mentions the expected sharp drop in temperature "However, meteorologists have forecast a dramatic change in weather overnight in Sydney, with thunder storms expected to bring a rapid drop in temperatures". Mikenorton (talk) 21:31, 18 January 2013 (UTC)

Yes, it's a forecast for the 19th. It says "Today" but that's local time where it's already the 19th. The "Yesterday" link for the 18th says "115°F High". That's 46°C. PrimeHunter (talk) 21:36, 18 January 2013 (UTC)

Incidentally, the fire in Victoria that killed one man at Seaton yesterday (the same one that's cut off Licola) was only 20km from where I live, and day was like night here (Maffra) yesterday from all the smoke. The imminent danger has passed but we remain on high alert, because the fire's predicted to spread up into the high country where there's even more abundant dry fuel, gather a great deal more energy, and possibly turn back this way. Australia has been enduring its worst heatwave and bushfire season on record, with almost no part of the country untouched, and temperature records falling like flies. See 2012–13 Australian bushfire season. -- Jack of Oz ^[Talk] 21:54, 18 January 2013 (UTC)

And it's not just the heat. An absence of rain for over a month hasn't helped. My vegie garden is very sad. But it's worth noting that fatalities from the fires so far have been very low. Just luck? Not sure. HiLo48 (talk) 21:58, 18 January 2013 (UTC)

We learnt a lot from the Black Saturday bushfires in 2009, which killed 173 people. -- Jack of Oz ^[Talk] 22:30, 18 January 2013 (UTC)

True, but we still have opposing opinions on what's the safest approach when fire is on its way, and whether fuel reduction burns are a good idea, and how and when to conduct them, with the proponents of each view 100% certain that their view is correct. Still, the ongoing debate keeps the issue of fire safety in peoples' minds, and that can only be a good thing. HiLo48 (talk) 04:13, 19 January 2013 (UTC)

January 19

About AHL

Is AHL special for each kind of bacterium? — Preceding unsigned comment added by Viacoha (talk • contribs) 02:06, 19 January 2013 (UTC)

What does the American Hockey League have to do with bacteria? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:12, 19 January 2013 (UTC)

[16] Gzuckier (talk) 08:50, 19 January 2013 (UTC)

AHL → acyl-homoserine lactones (enables many gram-negative bacteria to engage in quorum sensing) — Preceding unsigned comment added by Viacoha (talk • contribs) 02:16, 19 January 2013 (UTC)

Yes, different bacterial species generally have different AHLs. 24.23.196.85 (talk) 02:38, 19 January 2013 (UTC)

Astronauts in talking space

You know that sound just needs only medium to travel. So, if two astronauts touched their helmet together and are talking, will they be able to listen each others voices?27.62.9.222 (talk) 12:31, 19 January 2013 (UTC)

Yes, that should work if the helmets touch at points that are made of some hard material (glass, plastic, metal, etc - rubber would likely work poorly). 88.112.41.6 (talk) 14:02, 19 January 2013 (UTC)

Also, if they only touch at a single point, that might not be enough. That is, the volume level might be too low to hear. StuRat (talk) 19:02, 19 January 2013 (UTC)

Aurora

Are auroras harmful? What will happen if any flying object entered in it, e.g. a plane?27.62.9.222 (talk) 12:42, 19 January 2013 (UTC)

No. Auroras are caused by energetic charged particles (solar wind) colliding with atoms in the Thermosphere, far above the heights that most planes fly at. Even if the space shuttle were to fly through it, it's very unlikely that any harm or damage will occur due to the interaction being at the atomic level. douts (talk) 14:05, 19 January 2013 (UTC)

Two bar magnets tied together

If two bar magnets are tied with a string such that one is placed over other, and North pole of first lies above South pole of second, and S pole of first lies above N pole of second. Both magnets are tied for a long time, e.g., for one month. Their poles will interchange or the poles will remain same as initially they are. Britannica User (talk) 13:13, 19 January 2013 (UTC)

If not heated they are likely to remain the same. Ruslik_Zero 18:31, 19 January 2013 (UTC)

Gas from posterior side of body

Please, don't take this question as funny one. What is the common term for gas released from posterior side of our body ? It has foul smell. Why ? It also produces sound sometimes. Why ? Sunny Singh (DAV) (talk) 13:32, 19 January 2013 (UTC)

See Flatulence. Mikenorton (talk) 13:34, 19 January 2013 (UTC)

Please don't take this answer as a funny one, but the common term is a fart. This, however, is somewhat rude, so don't go round saying it to people you don't know. A common, more polite term is just "gas", as in "I can't eat chillies, they give me gas". Again, it's not something that people discuss much, unless needed. IBE (talk) 15:14, 19 January 2013 (UTC)

I think "gas" can either mean farting or burping. That is, how the gas escapes the body isn't specified. StuRat (talk) 18:59, 19 January 2013 (UTC)

The medical term for gas generated in the digestive tract is flatus. Gandalf61 (talk) 17:32, 19 January 2013 (UTC)

One of the stranger medical devices is the flatus bag, designed to collect farts: [17]. Apparently the flatus gases are sometimes analyzed [18], while at other times they are just collected to prevent the patient and medical staff from being exposed to unpleasant and potentially toxic levels of flatus gas. StuRat (talk) 19:15, 19 January 2013 (UTC)

One can find almost anything on the Internet. http://www.fartnames.com/ has a list of euphemisms, including Trouser trumpet, Message from the Interior, Under-thunder, and my favorite, Step on a Duck. --Guy Macon (talk) 18:09, 19 January 2013 (UTC)

Semiautomatic cook off

As the article on Cooking off mentions, it can potentially happen with semiautomatics that fire from a closed bolt position. If a magazine was loaded with the first cartridge being full of a pyrotechnic such that it heated the chamber intensely, could it then just unload the rest of the rounds as if by fully automatic fire? 210.210.129.92 (talk) 16:29, 19 January 2013 (UTC)

If the following conditions are met, it could happen:

The chamber would have to be hot enough but not the magazine. If, for example, the entire firearm is in a fire, it is likely that the rounds in the magazine will cook off first (less thermal mass, so they get hot first).

As you mentioned, the firearm would have to fire from a closed bolt.

The action would have to be able to cycle at that temperature despite parts expanding and lubrication burning off.

There would be a delay as each new round heats up. This delay would have to be shorter than the time it takes for the chamber to cool down enough so that it doesn't set off a round.

The trigger mechanism would have to be such that an unpulled trigger or the safety (if on) only stops the firing pin from engaging. If it is designed so that an unpulled trigger also locks the cycling, the second round would not make it into the chamber. I don't know if any actual firearms are designed this way. See Trigger (firearms). --Guy Macon (talk) 17:29, 19 January 2013 (UTC)

If the chamber is hot enough it doesn't matter why it's hot enough. But that said, Guy's last point is kind of interesting... I don't know enough to answer that offhand, but I'll pay attention to that point in the future. Shadowjams (talk) 20:58, 19 January 2013 (UTC)

Is there relation between yank and work ?

Is there relation between yank and work ? Is there any formula involving both yank and work ?Sunny Singh (DAV) (talk) 18:35, 19 January 2013 (UTC)

Well, "yank" is the derivative of force with respect to time, "work" is force moved through a distance. How "related" is that? Not much - a force can vary over time without producing any motion - so the work done is zero. (Imagine a battery powered electromagnet stuck to your refrigerator...as the battery runs down, the force changes (a "yank") - but no actual mechanical work is produced. I'm sure there are plenty of formulae that incorporate both terms - nothing immediately comes to mind though. SteveBaker (talk) 19:12, 19 January 2013 (UTC)

How images of galaxies are taken?

I want to know that how astronomers take images of galaxies ? For example, how do images of Milky Way are taken although we are inside it ? It is just like taking the image of a house by sitting in a room inside that house.Parimal Kumar Singh (talk) 19:09, 19 January 2013 (UTC)

Photographs of other galaxies are taken with cameras (or comparable sensors) attached to telescopes. If you see a "photo" of the Milky Way galaxy that looks complete, like this, it's either a photo of some other galaxy (that hopefully is similar to the Milky Way galaxy) or it's a simulation. -- Finlay McWalterჷTalk 19:16, 19 January 2013 (UTC)

Or more accurately, it is like making a world map without a satellite: [19] --140.180.253.61 (talk) 20:40, 19 January 2013 (UTC)

That's a great example. It wasn't until 1972 that we had an actual photograph of the earth as opposed to smaller photos stitched together. --Guy Macon (talk) 20:56, 19 January 2013 (UTC)

That is not what our article claims ("The Blue Marble was not the first clear image taken") Rmhermen (talk) 23:40, 19 January 2013 (UTC)

This photo from 1967 is described as the first one. File:ATSIII_10NOV67_153107.jpg RudolfRed (talk) 00:50, 20 January 2013 (UTC)

if light is just electromagnetic spectrum, why don't we have electric web cams with equal precision?

What is the exact reason that I can't replace a web cam with an electric version (that works in the electric part of the spectrum) and replace a light source with a source of electrons. Do electrons not bounce off people etc the same as light does?

Basically, other than color (due to the research into it), what's so special about light versus electricity when it comes to cheap 'imaging'? 178.48.114.143 (talk) 21:51, 19 January 2013 (UTC)

Electrons will interact with the air, not travel through it, which is why tubes like TV tubes are evacuated. If you up the energy enough to get through the air, you make a particle beam weapon. -- Finlay McWalterჷTalk 21:56, 19 January 2013 (UTC)

Fair enough. And if we imagine a room without air, then can a web cam work over the electric part of the spectrum just as well as light, as long as we 'illuminate' the room with a source of electrons? Or, in addition to not traveling through air, do they also not bounce off of objects nicely? 178.48.114.143 (talk) 22:23, 19 January 2013 (UTC)

You mean one of these, only larger? No reason why that wouldn't work. A bit like killing a fly with a bulldozer, but it should work. --Guy Macon (talk) 22:29, 19 January 2013 (UTC)

For the ordinary things you'll find in a room, the electrons will be absorbed by the surfaces of many of them, yielding no picture. When you see a picture of an object like a fly imaged with an electron microscope, it has probably been plated with a thin layer of gold so that it reflects the incoming electrons - see Electron microscope#Sample preparation. If you did that, you'd still only get a monochrome image. -- Finlay McWalterჷTalk 22:37, 19 January 2013 (UTC)

Do you mean I would get a monochrome image because I've just plated everything with gold? (after sucking all the air out). But, yeah, question answered. 178.48.114.143 (talk) 23:10, 19 January 2013 (UTC)

I think one thing should be clarified first. Light is an electromagnetic wave, or, alternatively, a stream of photons - see Wave-particle duality. Photons are uncharged particles with zero rest mass, and hence travel at the speed of light. They typically only interact with matter by being absorbed or emitted whole. Electrons, on the other hand, are charged particles with a rest mass of roughly 1/1800s u. As a result, electrons can travel at any speed, are influenced by electric and magnetic fields, and can interact with other charged particles in ways photons cannot. I'm not aware of any material that is transparent to electrons in the same way glass is to visible light. While electron beams are also called beta rays, they are not part of the electromagnetic spectrum, and have quite different properties from electromagnetic waves. In particular, beta rays are ionizing radiation, and hence quite unhealthy. --Stephan Schulz (talk) 23:27, 19 January 2013 (UTC)

That's interesting. Could you explain where radio itself (like am/fm, wifi, bluetooth, etc) falls here? Is it like light, but goes through stuff? Is it (as the name implies) part of the electromagnetic spectrum? If so, why doesn't light go through stuff the same way? I probably had more this in mind than electrons, I didn't realize that electrons are so different from radio waves - I thought they were similar, thanks for explaining. 178.48.114.143 (talk) 00:26, 20 January 2013 (UTC)

You need to read electromagnetic spectrum which puts all of the various types of light into relation with each other. Radio is the term for a range of wavelengths of light (colors, if you will) which are significantly lower in energy than light which our eyes are tuned to see. All light interacts with some matter, but different light interacts with different matter. For example, glass is generally transparent to most light in the visible range, but it is opaque to most wavelengths in the ultraviolet range. Also, radio doesn't just "go through stuff". Radio can be blocked if it lacks a straight path to reach the receiver (known as a line-of-sight path). Radio is reflected by parts of the Earth's atmosphere, so it can be reflected around smaller objects and hills and things, but many places exist in a "radio shadow", especially in mountainous areas where large mountains can block effective line-of-sight to radio sources. The article Radio propagation covers some of this. --Jayron32 00:43, 20 January 2013 (UTC)

What happen to helium in our sun

I know the Sun fuse Hydrogen into Helium and after billions of years eventually it ran out of hydrogen then started to fuse helium into bigger atoms and eventually collapse. What happen to helium in those billions of years? Is it just stay somewhere inside the sun? Or is it broken down to hydrogen again to start out the fusion cycle? 184.97.244.130 (talk) 00:18, 20 January 2013 (UTC)

Eventually it will become carbon through the triple alpha process.--Gilderien Chat|List of good deeds 00:25, 20 January 2013 (UTC)

why is this not used in air?

http://en.wikipedia.org/wiki/Modulated_ultrasound

why isn't this used for near-field communications (like bluetooth etc). is it because radio is so much easier? But radio requires licenses and has limited spectrum, not that this doesn't but i would imagine while no one else thinks to use it it does!  :) 178.48.114.143 (talk) 00:22, 20 January 2013 (UTC)

Lol, I found this: http://www.theregister.co.uk/2012/11/08/ultrasonic_bonking/

“ A Singapore firm is punting ultrasonic sound as an alternative to NFC for short-range wireless communications, pointing out that it works with existing hardware and provides a demo app to prove it.

The software, which is on Google Play and iTunes (search for SSCconnect) in both free and ad-supported versions, allows devices to exchange contact details, URLs, and clipboard contents at the breakneck speed of 275 bytes per second.

”

But in fact this is just iphone hardware. couldn't specialized hardware be a bit better? 178.48.114.143 (talk) 00:24, 20 January 2013 (UTC)

Take a look at these:

http://alumni.media.mit.edu/~wiz/ultracom.html

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA499556

http://www.cs.ou.edu/~antonio/pubs/conf059.pdf

In particular, look at the data rates they have been able to achieve.

--Guy Macon (talk) 00:53, 20 January 2013 (UTC)

I suspect one problem would be interference. In other words it would work fine if you were the only one using it, but what happens if you were in a crowd with many people using it. There could also be a problem with phase diffraction from multiple sources. (See also Superposition principle and Convolution) ~ It would probably be okay if by "short-range" you mean "a few inches". ~E:74.60.29.141 (talk) 01:17, 20 January 2013 (UTC)

--41.203.67.133 (talk)mkm~== oligomers and monomers ==

what are the differences between oligomers and monomers using equations and mechanisms as a basis for the differentiation — Preceding unsigned comment added by 41.203.67.133 (talk) 01:08, 20 January 2013 (UTC)

polymerisation

what is the difference between the average degree of polymerization and the extent of a reaction using equations and reaction mechanisms to distinguish between them — Preceding unsigned comment added by 41.203.67.133 (talk) 01:12, 20 January 2013 (UTC)

chemistry [polymer chemistry]

what is the difference between number average molecular weight and weight average molecular weight — Preceding unsigned comment added by 41.203.67.133 (talk) 01:17, 20 January 2013 (UTC)