Wikipedia:Reference desk/Archives/Science/2011 June 15

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June 15

Measurement Unit Of Malleability

What is the measurement of malleability?Curb Chain (talk) 05:00, 15 June 2011 (UTC)

Malleability is the ability of a metal to be hammered into thin flat sheets, see the article Ductility. An example of a very malleable metal is gold. Malleability is an example of non-linear behaviour of a material that is stressed beyond its elastic limit (below which many materials obey a linear Hooke's law). There are approximate mathematical descriptions of material plasticity, see here, but I think there is no standard measurement unit and only empirical data on how materials behave beyond their yield point. Cuddlyable3 (talk) 11:14, 15 June 2011 (UTC)

From what I remember of material science, percent elongation at fracture is the best measurement of ductility/malleability. FWIW 67.169.177.176 (talk) 09:34, 17 June 2011 (UTC)

Putting Humpty Dumpty back together again

In various medical dramas, I've seen doctors do everything from move intestines aside to get at something to basically scooping them out of the abdominal cavity and move them aside. Granted, these are works of fiction, so I don't think that they're always very accurate. What I'm wondering though is on the other end of things. When the patient has been saved and all their organs need to go back into their body, how much care needs to be taken to make sure the intestines aren't knotted up or laying incorrectly or something. Is there a process or procedure to putting them back in? Dismas|^(talk) 06:19, 15 June 2011 (UTC)

My Dad had such a surgery, where his intestines were pulled out, then put back in, and they seemed to think they would just "find their way back" to the right spot. They didn't. From then on he was noticeably lopsided, with a bulge on one side of his abdomen. StuRat (talk) 07:07, 15 June 2011 (UTC)

I wonder if it was possible that your dad had a slight incisional hernia which weakened part of his abdominal wall and the pressure of the abdominal contents pushed out rather more on one side than the other, not uncommon in major abdominal surgery. Within the abdomen where the intestines are is a single cavity which would exert even pressure against the whole abdominal wall. I don't believe there is a right spot for removed and replaced intestines. The most important factors are that when they are replaced they should not have their blood supply compromised and the intestine should not be twisted, stretched or knotted in a way that peristalsis would not be able to correct. Richard Avery (talk) 14:39, 15 June 2011 (UTC)

The way the body packs the contents of the abdominal cavity can vary. An embryo is a different payload than the OP talks about, but its positioning is sometimes unlucky, see for example Breech birth and Umbilical cord prolapse. Cuddlyable3 (talk) 09:45, 15 June 2011 (UTC)

I think the answer is, "with great difficulty" - my sense is that with intestinal surgery, if the surgeons don't do everything just right (and maybe even if they do) necrosis of the bowel can occur. Wnt (talk) 00:35, 16 June 2011 (UTC)

Reminds me of a story I read somewhere (can't remember where, for the life of me) in which someone got his abdomen slashed with a dagger, and the surgeons were forced to remove the damaged part of his intestines because they couldn't repair the damage properly (and then they had to perform a second operation because he had developed peritonitis). 67.169.177.176 (talk) 05:39, 17 June 2011 (UTC)

I am a mechanical engineer now i need a notes for the following topics

Specific requirements for automotive lubricants – Oxidation deterioration and degradation of lubricants – Additives and additive mechanism – Synthetic lubricants – Classification of lubricating oils – Properties of lubricating oils – Tests on lubricants – Grease – Classification – Properties – Test used in grease. — Preceding unsigned comment added by Vigneshvig88 (talk • contribs) 09:38, 15 June 2011 (UTC)

Your list of subjects looks like a whole course in lubrication. A place to start is the article Lubricant and move on to Lubricant#Application by fluid types. There are a number of e-books on lubrication fundamentalsthat I have not read but that may be helpful. Cuddlyable3 (talk) 10:01, 15 June 2011 (UTC)

Our article on tribology (the science of friction and lubrication) may also be useful. Gandalf61 (talk) 10:53, 15 June 2011 (UTC)

Respondents: I've started a discussion of this question here. --Sean 19:56, 15 June 2011 (UTC)

Multiple biopsy

Do doctors perform biopsy on a cancer patient several times to discover how the cancer is developing? Or is it a one time shot? 2.139.12.164 (talk) 09:50, 15 June 2011 (UTC)

As with most questions like this one, it depends on the circumstances. There are some scenarios where several biopsies might be employed to assess for distant metastases of solid tumors, or serial bone marrow biopsies might be used to follow leukemia. --- Medical geneticist (talk) 10:18, 15 June 2011 (UTC)

Clearly more than one measurement at different times is needed to determine how anything is developing. Cuddlyable3 (talk) 11:17, 15 June 2011 (UTC)

True, but it need not be a biopsy, per se... often the cancer will be followed by less invasive imaging techniques such as positron emission tomography. Again, it is an "it depends" kind of answer. --- Medical geneticist (talk) 11:33, 15 June 2011 (UTC)

Medical geneticist's response is spot on; it really depends on the circumstances. For a specific example, a prostate biopsy will often be performed in the event of suspected prostate cancer. Because these tumors are often very slow-growing and the patients who develop them tend to be older, low-grade tumors – those with a low Gleason score – can sometimes be left in place untreated. The risk of disease progression during a period of watchful waiting may be less serious than the risk of negative side effects caused by more aggressive therapy. (Indeed, four out of five men over the age of 80 probably have prostate cancer. Most will never even know about it, because they'll die of something else long before the prostate cancer gets them.) If the patient's symptoms become more severe (or there are other signs of disease progression like an increasing PSA score) then another biopsy may be performed to determine if the cancer has become more aggressive. TenOfAllTrades(talk) 14:14, 15 June 2011 (UTC)

Light's behaviour

Why light travel in straight light? — Preceding unsigned comment added by Ahsanshkh (talk • contribs) 11:27, 15 June 2011 (UTC)

Because everything that is not deflected travels in a straight line. But even light does not always travel in a straight line. See lenses, prism and also gravitational lens. 5BYv8cUJ (talk) 11:34, 15 June 2011 (UTC)

Also relevent in this case is Geodesic (general relativity). One needs to define what it means to be a "straight line" before one can decide how and why light travels that way... --Jayron32 11:55, 15 June 2011 (UTC)

The Poynting vector is not a simple explanation why light, an electromagnetic radiation, travels in a straight line, but it serves to show how light's behaviour relates to its constituent electric and magnetic fields. Cuddlyable3 (talk) 13:09, 15 June 2011 (UTC)

See conservation of momentum. Light has a relativistic mass which depends on the energy carried by the photon (by E=mc²), which in turn is equal to the frequency in cycles per second times Planck's constant (or the frequency in radians times Planck's reduced constant... same thing). So light of a given frequency has a proportional amount of mass, traveling at the speed of light. (Hmmm, on second thought, that's a bit mind boggling - see Momentum#Momentum in electromagnetism and even Abraham-Minkowski controversy. You know once the name Minkowski comes up, you're not in Kansas any more ;)) This momentum doesn't change unless something acts on it. Wnt (talk) 00:42, 16 June 2011 (UTC)

Fundamentally, because of the homogeneity and isotropy of space. The laws of physics have to be such that light in a flat vacuum travels in a straight line, because there's nothing that would enable the light to "choose" a new direction to go in. It's a matter of symmetry. Red Act (talk) 02:57, 16 June 2011 (UTC)

That's right. And that accounts for the deflections and refractions implicit in the first response above. Whatever direction it's going in, it will continue to go in that direction until and unless some external force (such as a lens, prism, mirror, reflective surface, etc) makes it go in a different direction. -- Jack of Oz ^{[your turn]} 13:17, 16 June 2011 (UTC)

Neutrino oscillations and CP violation

"Neutrino particle 'flips to all flavours'" (BBC News) says that the T2K experiment has announced provisional results that indicate that muon neutrinos can transform into electron neutrinos, and hence the θ₁₃ component of the neutrino mixing matrix is non-zero. I follow all of that (after a hand-waving fashion). The article then goes on to say that this type of neutrino oscillation would be an example of CP violation. However, it doesn't really explain just how these particular neutrino oscillations violate CP symmetry. Can anyone explain the connection in more detail, please ? Gandalf61 (talk) 12:27, 15 June 2011 (UTC)

Neutrino mixing is governed by the Pontecorvo–Maki–Nakagawa–Sakata matrix. In principle, this involves 9 complex numbers. However, after requiring the total amplitudes to remain constant over time, assuming that all neutrinos always have the same chirality (which is true as far as we can tell), and assuming neutrinos are Dirac fermions (like all other known fermions, but the Majorana fermion model is not experimentally excluded), this reduces the 18 nominal degrees of freedom to only 4 real numbers. In particular, CP violation occurs if and only if the imaginary part of $sin(\theta _{13})e^{-i\delta }\neq 0$, where $\theta _{13}$ and $\delta$ are numbers to be determined experimentally. A non-zero imaginary part would imply that nuetrinos and antineutrinos have different mixing rates, or in other words, in a CP-inverted universe neutrino mixing rates wouldn't look the same (hence CP-violation). $\theta _{13}$ is known to be small, but the current report suggests it is non-zero. Incidentally, $\delta$ is also unknown and could be 0, so $\theta _{13}\neq 0$ is a necessary but not sufficient condition to show where neutrinos oscillations violate CP-symmetry. Dragons flight (talk) 20:13, 15 June 2011 (UTC)

(ec) A non-real entry in the mixing matrix violates the C part of CP, which is complex conjugation. The standard parametrization consists of three Euler angles (θ₁₂, θ₂₃, θ₁₃) and one complex phase (δ₁₃). This article is about a new constraint on θ₁₃. If you look at CKM matrix#"Standard" parameters you'll see that all of the terms with δ₁₃ in them also have a factor of sin θ₁₃. So, one could say that a nonzero value of θ₁₃ "opens up the possibility" of CP violation, since the matrix is real if θ₁₃ = 0 regardless of the value of δ₁₃. But it's a stupid thing to say because (1) this parametrization is arbitrary and (2) there was never any reason to expect any of these parameters to be zero, and it would be very strange if they were, so the possibility has always been open and the only interesting result, in that connection, would be one that "closed it off". It's basically the same as saying "we have determined that we are not standing precisely at the North Pole, which opens up the possibility that we are not standing precisely on the Greenwich Meridian." -- BenRG (talk) 20:21, 15 June 2011 (UTC)

Thanks for the excellent responses. So, if I understand this correctly, CP violation will occur if both θ₁₃ and δ₁₃ are non-zero, but the provisional T2K results only establishes one of these conditions. So what sort of experiment would be required to measure the value of δ₁₃ and/or to directly demonstrate CP violation in neutrino oscillations ? Are there any such experiments ongoing or at the planning stage ? Gandalf61 (talk)

δ₁₃ is much harder to measure, but proposals have been made. see for instance this paper. Dauto (talk) 16:39, 16 June 2011 (UTC)

Problems topping up mobile

Does anyone know what a 'Error Code-91 System Error' means ? Because i have tried to topup my mobile (T-mobile) at three different stores today and the same thing happened in each case, on the recepts was: 'Transaction Failed' 'Error Code-91' 'System Error' Does this mean my topup card, SIM card or both have been cancelled, which the staff in the stores believe it could be. Help!!!109.145.108.36 (talk) 12:41, 15 June 2011 (UTC)

It may help to note that the OP's IP is in the UK OK! OK! Enough abbreviations! so their mobile operator is T-Mobile (UK). Cuddlyable3 (talk) 12:56, 15 June 2011 (UTC)

Just doing a few obvious checks: have you taken the battery out and reseated it? Have you taken the SIM out and reseated it? Switched off and on again? --TammyMoet (talk) 14:49, 15 June 2011 (UTC)

Does T-mobile not have some sort of help line or email you can contact? Nil Einne (talk) 15:36, 15 June 2011 (UTC)

Try topping up your mobile via their website, or by text.--Shantavira|^{feed me} 16:13, 15 June 2011 (UTC)

I tried topping up again today and it worked first go. The system must have been down or some thing.109.145.108.36 (talk) 12:09, 16 June 2011 (UTC)

Horticulture Nurseries

What is a nursery? What types of nurseries are there? What are the opportunities and challenges of nurseries? — Preceding unsigned comment added by 62.24.111.249 (talk) 13:57, 15 June 2011 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. You may find the Wikipedia articles horticulture and plant nursery may help you, though your best option is to read through the text book that your teacher gave you and/or read the notes you wrote down during in-class lecture. --Jayron32 14:11, 15 June 2011 (UTC)

If the OP's homework was assigned not in a Biology class but in something related to Paediatrics or Pedagogy, then Nursery might be more relevant :-) . {The poster formerly known as 87.81.230.195} 90.197.66.241 (talk) 18:11, 15 June 2011 (UTC)

Directions near the Poles

Is there a standard way of giving direction at or near the North or South Pole? At lower latitudes, "the wind is from the south-west" means something.

But if someone set up a weather vane at the pole, how could they tell someone else which way the wind was blowing?

Thanks, Wanderer57 (talk) 15:01, 15 June 2011 (UTC)

If you want the smartass answer... if you're at the North Pole, the wind is always from the south. Otherwise, see this page. -Atmoz (talk) 16:56, 15 June 2011 (UTC)

The link that Atmoz provides says "By international agreement (WMO Manual on codes v. 1, Code Table 878), within one degree of the North Pole, the Greenwich (0 degree) meridian is used...i.e. within about 60 nautical miles of the North Pole, winds are reported according to a compass face, oriented so the "North" arrow points toward the 0 degree meridian, and in this restricted area, "North" no longer refers to the North pole, but to the observatory in Greenwich, England." That means nobody can say which way the wind blows at a spot in the Arctic 89°N 0°E. Cuddlyable3 (talk) 08:38, 16 June 2011 (UTC)

On first reading the NOAA page pointed out by Atmoz seemed to make sense. Rereading it, I'm not sure. It seems to imply that, when setting up a weather vane near the North Pole (an activity I hardly ever do but want to be prepared for), the north pointer should point toward the 0° meridian. But the 0° meridian is a line, not a point. What does it mean to point toward a line? Maybe I've got this all backwards. Please advise. Thank you. Wanderer57 (talk) 20:37, 16 June 2011 (UTC)

It is a line, but technically at the north pole, you are standing on the topmost point of that line, so the entire line is the same direction from you. Googlemeister (talk) 20:51, 16 June 2011 (UTC)

Thanks. That's fine if you are on the prime meridian, But suppose you are 1 kilometer west of it, just for example? Wanderer57 (talk) 21:49, 16 June 2011 (UTC)

You mean 1 km south right? West at the pole does not exists remember? Googlemeister (talk) 20:34, 17 June 2011 (UTC)

My interpretation is that they are only really talking about the pole itself, presumably with the assumption that the wind will be blowing in the same direction at any point within 1 degree of the pole. So, if the wind is blowing along the 0° meridian, then we say the wind is at 0°. If it's blowing along the 75° meridian, then it's at 75°. --Tango (talk) 22:02, 16 June 2011 (UTC)

Aside from the direction of the wind, the question applies to other directional information. Eg, if a treasure is buried 5000 feet from the camp in a particular direction, how to express that direction, aside from pointing. Maybe this is not a practical concern? Wanderer57 (talk) 04:26, 17 June 2011 (UTC)

Obviously in most situations, the people who would ever get there would know how to use specific coordinates to indicate the treasure's position. But if not, then I guess they would use the Greenwich observatory as their new "North" (or GW-North) and so say it is 5000 feet "GW-West". This is because you could apply this rule: "North" no longer refers to the North pole, but to the observatory in Greenwich, England. even if you are not exactly on the pole.--Lgriot (talk) 07:52, 17 June 2011 (UTC)

At the South Pole they often use a local Cartesian coordinates grid, centered at the pole and aligned so that "grid-North" at the pole corresponds to the is the Prime Meridian. That gives a well-defined sense of "grid-North", "grid-West", etc. for everywhere within the grid. If one extends the Cartesian system too far, one would eventually run into problems with the curvature of the Earth, but I've only ever seen it used within a few miles of Pole. At that level it is adequate for most purposes. Dragons flight (talk) 20:51, 17 June 2011 (UTC)

A southwesterly wind at the North Pole could mean that there is an incoming wind and low pressure positioned over the pole. ~AH1 ^(discuss!) 15:50, 18 June 2011 (UTC)

Nose to the Brain

Is there any truth to the idea of there being straight access from the nose to the brain or is that just a myth? — Preceding unsigned comment added by 71.143.240.229 (talk) 15:07, 15 June 2011 (UTC)

I don't know what you mean by "straight access", but consider the top diagrams at nasal cavity and human brain. The brain image also shows the nasal cavity, which appears to directly adjoin the brain at some points. SemanticMantis (talk) 15:34, 15 June 2011 (UTC)

What does "straight access" mean? direct unimpeded access? in that case, no. There is 1-2 mm layer of bone between the top of the nasal cavity and the base of the brain. Richard Avery (talk) 15:55, 15 June 2011 (UTC)

Is there also bone from the top of the ear to the brain, blocking access to the brain? — Preceding unsigned comment added by 70.136.157.251 (talk) 16:01, 15 June 2011 (UTC)

The olfactory receptor neurons connect to the olfactory nerve which connects to the olfactory bulb which connects to other parts of the brain via the olfactory tract - see olfactory system. Doesn't seem very much like "straight access" to me - not more so than the other sensory systems, anyway. Gandalf61 (talk) 16:11, 15 June 2011 (UTC)

How does cocaine get to the brain when sniffed if there is a bone between the nasal cavity and the base of the brain? — Preceding unsigned comment added by 70.136.157.251 (talk) 16:40, 15 June 2011 (UTC)

Thru the bloodstream. 67.169.177.176 (talk) 17:31, 15 June 2011 (UTC)

This one I know the answer to. For almost all of the classical sensory systems, the pathway from sensory organs to the cerebral cortex has a way-station in the thalamus. The olfactory system is the only one of the "five senses" for which signals can reach the cerebral cortex without passing through the thalamus -- olfactory receptors in the nasal epithelium project to the olfactory bulb, which projects to the olfactory cortex. Looie496 (talk) 18:19, 15 June 2011 (UTC)

"Straight access from the nose to the brain" might also refer to the danger triangle of the face. -- BenRG (talk) 18:53, 15 June 2011 (UTC)

I'm pretty sure the idea the OP is referring to is the one I described -- it is very commonly discussed in books or articles about the sense of smell. Looie496 (talk) 19:08, 15 June 2011 (UTC)

The sense of smell is so critical to the survival and brought such evolutionary advantage to early complex animals, that one could almost say that the brain is an extension of the olfactory bulbs rather than visa versa. http://www.sciencemag.org/content/332/6032/955 You can't get more direct than that. Later, part of this neural complex became light sensitive and became eyes. These developments happened independently in several different lifeforms. Someone may also be able to find reference to the sense of smell in humans, still over-riding all one's other senses. --Aspro (talk) 19:53, 15 June 2011 (UTC)

I think that's an exaggeration. Yes, mammals were little burrowing things that put a high priority on the sense of smell, but olfaction is just one sense of, say, fish. Go back far enough and you get to Cnidaria such as Cubomedusae, which have tiny organs which feature a surprisingly complex eye, a sort of ear (well, at least, a balance sensing organ), and an open vestibule for sense of smell. In bilateral animals I think the most general model you can apply is that the brain is a combination of ganglia in each segment (dorsal in vertebrates, ventral in arthropods, but homologous) which each have sensory and motor functions controlling the limbs and communicate up and down a nerve cord. I think the sensory organs are just features of primitive appendages (antennae, ear joints, stalked -> socketed eyes) with specialized sensory equipment leading to particularly massive processing centers in the brain. Wnt (talk) 06:31, 16 June 2011 (UTC)

No, Looie496 is right, see below. μηδείς (talk) 01:57, 20 June 2011 (UTC)

I tried looking into this before at Wikipedia:Reference desk/Archives/Science/2011 April 7#Blood-brain Barrier. There is some exchange between blood flow in the nose and the brain, but the "blood-brain barrier" should be behind that - separating the brain from the blood vessels themselves. Yet there was one reference about a compound having better access, and I wasn't really sure why. Wnt (talk) 00:04, 16 June 2011 (UTC)

This reminds me of how the ancient egyptians removed the brain during the mumification process. How they have to tap the device with a small hammer to gain access to the skull. Plasmic Physics (talk) 02:26, 16 June 2011 (UTC)

Responding to Wnt, blood doesn't really come into play. The olfactory epithelium contains receptor neurons that are directly exposed to air, so they are capable of absorbing certain chemicals from the inhaled air and transporting them via the olfactory nerves into the brain. Looie496 (talk) 23:04, 16 June 2011 (UTC)

You might also want to read up on Egyptian mummies and the procedures involving disposal of the brain, yet there is no such Wikipedia article. ~AH1 ^(discuss!) 15:48, 18 June 2011 (UTC)

Looie496 is quite correct, chemoreception is the oldest sense, common to all single celled organisms and all animals, including sperm which use it to find the egg. Olfaction is not a power that mammals or fish developed in preexisting nostrils, but rather the nose and related organs evolved around olfaction, and to say the brain in craniates is an outgrowth of the olfactory lobe at its nexus with the locomotory nervous system is entirely justified ontogenetically. Light sensitivity is common to all animals, but the evolution of vision and eyes, rather than the ability to sense the direction of light and the day-night cycle is something that comes ages later than chemoreception. Neither lancelets nor tunicates possess eyes, but they do process chemoreceptive signals in what amount to their heads (at least while they have them). 01:57, 20 June 2011 (UTC)

spin current

An electrical current is generally unpolarized (consisting of 50% spin-up and 50% spin-down electrons); a spin polarized current is one with more electrons of either spin. By passing a current through a thick magnetic layer, one can produce a spin-polarized current. http://en.wikipedia.org/wiki/Spin_transfer

how come current is composed of half spin up and half spin down? is spin up magnetic north and spin down magnetic south? (apparently this is true is it correct Spin "up" would mean the electron is acting like a bar magnet whose north pole is pointing up; spin "down," the opposite.) — Preceding unsigned comment added by 82.38.96.241 (talk) 21:09, 15 June 2011 (UTC)

To be precise, half of them have the vertical component of the spin up while the other half has that component pointing down. The horizontal component being unknowable (which is not the same as unknown). Imporntant note: We talk about spin up and down by convention but we could just as well talk about spin left and spin right, or spin forward and spin backward if so we wished. Dauto (talk) 21:19, 15 June 2011 (UTC)

Personally, I prefer inside and outside. Plasmic Physics (talk) 00:28, 16 June 2011 (UTC)

so is there only really 2 directions of spin and they happen to provide the effect for the north and south magnet — Preceding unsigned comment added by 82.38.96.241 (talk) 21:22, 15 June 2011 (UTC)

It is more understandable to say that for unpolarized electrons the spin points in a random direction in space; however, the nature of quantum mechanics is that we can only ever measure one component of it's direction per electron. So we pick an axis in space (call it vertical), and see how many of them have a positive vertical component (up spin) and how many have a negative vertical component (down spin). Another aspect of quantum mechanics is that we can only really get positive or negative (not a magnitude). If you have a consistently polarized spin current you can get more information about the spin orientation by measuring many electrons, but you are strongly limited about the information that can get from any single electron because the act of measuring it changes it. Dragons flight (talk) 22:03, 15 June 2011 (UTC)

(EC) It's not really that there are only two directions of spin. Rather, it's a matter of no matter which direction you arbitrarily choose, if you measure the spin of an electron along that direction, there are only two possible values that the spin can be measured to be. So if you measure the spin along the z direction, for example, the spin will either be in the +z direction or the -z direction (the magnitude of the spin will be the same either way). The amount of spin in each of the x, y and z directions are not independent; after you measure the spin along one axis, you can't know anything about what the spin is along the other two axes. The measurement process basically messes up the spin along any orthogonal direction. For example, if you measure the spin in the z direction and it's in the +z direction, and then measure the spin in the x direction, and then measure the spin in the z direction again, it's a 50/50 chance as to whether the spin will be measured to be in the +z or -z direction in that final measurement. Red Act (talk) 22:08, 15 June 2011 (UTC)

Also worth pointing out that earth's magnetic field are believed to be produced by electric currents in its liquid core as opposed to electron's magnetism. Dauto (talk) 00:09, 16 June 2011 (UTC)

ADHD Medication Rankings

This question was removed [1]. I have restored it, because the remover was wrong, and it does not violate any of our medical advice guidelines. Note that I have not restored one response, as it may have violated our guidelines. See also the discussion on the talk page. Buddy431 (talk) 00:44, 16 June 2011 (UTC)

I can specifically find all of the ADHD medication and dosages. I can not find which one is stronger than the other. Like Adderall XR is the slow relsease, but is Vyvanse more powerful? Adding a section to list ADHD medications ranking them from the smallest (such as Adderall) to a more powerful or longer lasting medication (such as Concerta and Adderall XR) would be very helpful in my opinion. Thank you for any knowledge on this subject. — Preceding unsigned comment added by IT Zach P (talk • contribs) 21:55, 15 June 2011 (UTC)

I think discussion on the talk page favors retention of the question; in any case, in general it is not so simple to answer. While it can seem easy to say that one chemical is more potent than another, it's not like comparing 9 to 10. The dosage for either drug can be adjusted up or down. The affinity constant, bioavailability, and pharmacokinetics can differ in different ways. One compound might be a complete agonist or antagonist, while another has some mixture of these activities. One compound might be more potent, but have more serious side effects. To give a simple example, everyone knows that "heroin is more potent than morphine" - yet when a soldier has had a piece blown off on the battlefield, he still receives morphine, because it's the most potent all-around painkiller. You can evaluate which drug is "most potent" in that sense - what you would use to get the job done in a certain situation - and in general this is the basis of medical diagnosis and prescription. But the fact that all these drugs are still out on the market is a sign that there may no hard evidence to say which one is best for all people. Wnt (talk) 00:17, 16 June 2011 (UTC)

Monkey from Antalya, Turkey?

Sorry, if this is not the best place to ask this question. Can anyone tell me what kind of monkey this is? --Phagopsych (talk) 22:00, 15 June 2011 (UTC)

Maybe a Spider monkey? (Just a guess.) Bus stop (talk) 22:08, 15 June 2011 (UTC)

I think it's a vervet monkey, but there are a number of species that look pretty similar. Looie496 (talk) 23:07, 15 June 2011 (UTC)

...or maybe a grivet, which is very closely related to a vervet. Looie496 (talk) 23:17, 15 June 2011 (UTC)

Incidentally, this is exactly the right place to ask this question. StuRat (talk) 08:35, 16 June 2011 (UTC)

Thanks a lot. In the pic doesn't show very well but it has none or very little hair on the top of head (you know, that darker grey bit). Also it had a very long tail, like the Vervet monkey, but the head looks more like the grivet's. Lovely animal, by the way. Very friendly. I know they should not be kept as pets but it was really playful and affectionate, jumping to people's arms without much of a prompt :-) --Phagopsych (talk) 19:12, 16 June 2011 (UTC)

Yes, this is obviously a green monkey, but none of the various species is native to Turkey. μηδείς (talk) 01:58, 20 June 2011 (UTC)

Why no CO2 clouds high in the atmosphere?

Phase plot for carbon dioxide

Why doesn't CO2 condense into clouds where the temperature is low enough? Count Iblis (talk) 23:30, 15 June 2011 (UTC)

The minimum temperature in the atmosphere occurs at the base of the ionosphere, and is usually in the 250-300 Kelvin range. As you can see from the plot I have attached, CO2 does not have a stable solid phase in that temperature range at low pressures. Looie496 (talk) 23:49, 15 June 2011 (UTC)

There has been much speculation that polar mesospheric clouds, sometimes known as noctilucent clouds, are seeded by carbon dioxide crystals. Mesospheric clouds on other planets, especially Mars, have been observed to contain mostly carbon-dioxide ice. Other planets, like Jupiter and Neptune, also have mesospheres (of a sort); clouds in these planets can contain carbon dioxide, ammonia, and especially methane ice. Nimur (talk) 02:52, 16 June 2011 (UTC)

The difference is, the mesospheric temperatures on all those planets are much colder than on Earth. 67.169.177.176 (talk) 08:39, 16 June 2011 (UTC)

More importantly, the pressures of those planets are much higher than similar temperatured regions on earth. Phase is a function of both pressure and temperature; on Earth the coldest part of the atmosphere is of a pressure which is far to low to allow carbon dioxide to condense into crystals. On larger planets, like Juptier and Neptune, the lower levels of insolation means lower temperatures, while the greater mass means greater gravity, and thus greater atmospheric pressures. The OP appears to be considering only the temperature when questioning if CO2 should condense in the upper atmosphere of Earth. --Jayron32 12:15, 16 June 2011 (UTC)

Isn't it partial pressure, not pressure, that matters? High pressure doesn't necessarily mean high partial pressure. --Tango (talk) 12:34, 16 June 2011 (UTC)

Indeed, but there is no where on Earth where even the total pressure of the atmosphere exceeds the minimum pressure required to have CO2 condense. Logic would seem to dictate that a gas which makes up a fraction of that total cannot exceed the total itself, so rather self-evidently there is nowhere on Earth where CO2 should spontaneously condense. --Jayron32 15:26, 16 June 2011 (UTC)

I see, I forgot about the pressure :) . Count Iblis (talk) 17:01, 16 June 2011 (UTC)

Note that the graph at right only goes down to 200K however...at lower temperatures CO₂ will sublimate at Earth-like pressures and even lower; Mars has a surface pressure of around 10% of Earth's at most, and they have a large cap of CO₂ ice at each pole, as well as carbon dioxide clouds at several different layers of the atmosphere.-RunningOnBrains^(talk) 17:04, 16 June 2011 (UTC)

Sure, but below 200K isn't Earth-like temperatures (at any altitude), so what happens at Earth-like pressures at those temperatures isn't particularly interesting. --Tango (talk) 18:00, 16 June 2011 (UTC)

The mesosphere article says: "The upper boundary of the mesosphere is the mesopause, which can be the coldest naturally-occurring place on Earth with temperatures below 130 K." Count Iblis (talk) 19:51, 16 June 2011 (UTC)

Some places in Antarctica (e.g. the Vostok station) can get below 200 K in the winter. 67.169.177.176 (talk) 20:17, 16 June 2011 (UTC)

And as far as the mesosphere is concerned, note that the partial pressure of CO2 is many times lower than at sea level, which further hinders condensation. Also, at such high altitudes it's possible to start getting some UV-induced dissociation of CO2 into O1 (atomic oxygen) and CO -- which would further reduce the partial pressure. FWIW 67.169.177.176 (talk) 20:38, 16 June 2011 (UTC)

At levels of the lower stratosphere, temperatures and pressures are often low enough for water vapor and sometimes even carbon dioxide to freeze out of the atmosphere and reduce the greenhouse effect at those levels, especially considering that the greenhouse effect actually cools the stratosphere. See physical effects of climate change#Upper atmosphere. ~AH1 ^(discuss!) 15:43, 18 June 2011 (UTC)