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April 25

What's inside a snooker ball?

Are they solid plastic all the way through, or is there something else in the middle? --Kurt Shaped Box (talk) 00:42, 25 April 2008 (UTC)[reply]

See Billiard ball. DMacks (talk) 02:21, 25 April 2008 (UTC)[reply]

Billiard balls today are solid polymer, often a phenolic resin, polyester, or acrylic. This site has a cutaway picture. TenOfAllTrades(talk) 02:27, 25 April 2008 (UTC)[reply]

According to that site, the momentary "instantaneous" impulse, or collision, of stick against ball, has a "resulting friction temperature between ball and cloth can easily reach 250°c". What does this mean? I am not familiar with the term "friction temperature"; it seems like any heat would be absorbed by the relatively large heat-sink that is the mass of the billiard ball. Also, I was always taught that a billiard-ball is about the best example for a perfectly elastic collision, with virtually no energy lost to the impact deformation due to material stiffness. Comments? Is "friction temperature" just marketing-ese to sell more billiard balls? Nimur (talk) 05:42, 25 April 2008 (UTC)[reply]

When the ball skids across the felt the temperature on the surface of the ball would be 250C. The ball is a poor conductor of heat so any heat generated will not be transmitted will throughout the ball, thus the temperature at a local point can get quite hot. When the ball is skidding it is not elastic, when they are rolling and collide then it is close to an elastic collion.--Shniken1 (talk) 06:58, 25 April 2008 (UTC)[reply]

So the stripe goes all the way through? Interesting. I'd always thought that it was just a surface feature... --Kurt Shaped Box (talk) 22:54, 25 April 2008 (UTC)[reply]

Looks like it. Just like Blackpool rock —Preceding unsigned comment added by 79.76.217.249 (talk) 03:27, 26 April 2008 (UTC)[reply]

So, Snooker ball now redirects somewhere useful. Who was it that said that the Reference Desk did little to improve the encyclopedia? ;) --Kurt Shaped Box (talk) 19:50, 26 April 2008 (UTC)[reply]

Derivore

What is a derivore? 99.226.26.154 (talk) 00:43, 25 April 2008 (UTC)[reply]

Are you sure you don't mean detrivore? —Keenan Pepper 02:00, 25 April 2008 (UTC)[reply]

Or maybe an hors d'œuvre? Nimur (talk) 05:44, 25 April 2008 (UTC)[reply]

IDing Tanzanian termite-raiding ant

I know trying to ID insects from s.o.'s description can be an exercise in futility, but I hope I can provide enough details to narrow it down to the family at least.

I have come across colonies of similar, perhaps the same, large black ant in Tanzania, both near the coast on sandy riverbanks in forest reserves in Dar es Salaam, and upcountry in acacia scrub in the Rift Valley, within sight of Ngorongoro and the Serengeti. They're ~~1cm long, not particularly numerous (one colony a hundred or so, another maybe a thousand), and they emit a noise that sounds like rain when disturbed. Although I've never been stung, I've seen the effect on others, and it's clearly painful, though even a 4-yr old will stop crying after 5-10 minutes, and there's no swelling (from a single sting, anyway). However, they have one of the more painful ant stings in the area. They're diurnal hunters, and hit harvester termites on their forays. (Prob'ly other things, but termites is what I've seen.) In Swahili they're known as sungu-sungu, though there's so much regional variation in species and names that that might not be much good for an ID. They're larger than the siafu.

Anyone have any ideas?

Thanks, kwami (talk) 01:29, 25 April 2008 (UTC)[reply]

Hi Kwami, Sungusungu gets this: (Tanzania) they are (Kiswahili) "biting ants" and "In Swahili, Sungusungu denotes a highly cooperative and aggressive type of ant; in the Sukuma language, it means poison." in an article on vigilante groups[1]. Hard to find anything on them in entomology, except vaguely that they are meat-eating and get this, "small ant"[2]. Only the Carpenter ant is termite specific and widespread but nothing about origins. (addn) PS have you seen this[3]?Fwiw, Julia Rossi (talk) 09:18, 26 April 2008 (UTC)[reply]

Thanks. Carpenter ants are formicins, which makes sense since they may nest in the walls of houses, but it doesn't fit their sting — but then, I've never been stung, so maybe I'm wrong on that. They are the right size.

When you say 'termite specific', do you mean in nesting, or raiding?

kwami (talk) 10:13, 26 April 2008 (UTC)[reply]

Had in mind raiding. Julia Rossi (talk) 12:22, 26 April 2008 (UTC)[reply]

More Quantum Theory

According to Zeno's paradox#Does Quantum Theory solve the paradox?, it states that Planck length and Planck time are the smallest mesurable units of their respective dimensions. It then implies that space may be discontinuous and not infintely divisible, having the Planck length as the smallest unit of traversable space. How could this be? Where could I find more information about this? Furthermore, why is it (Planck length) the smallest mesurable unit of space, the Planck time the smallest mesurable amount of time? Why can nothing smaller be meaured? Thanks, Zrs 12 (talk) 02:50, 25 April 2008 (UTC)[reply]

Planck units are expressed in terms of relations between fundamental constants; our theories which use such constants don't make any sense if you start talking about units smaller (or in some cases larger) than Planck units. When you're thinking about things that small you can't let yours intuitive concepts interfere—length, time, matter, etc. don't operate on those scales the same way they do on more macroscopic, human scales. The easiest way to make sense of Planck units is to start by understanding the importance and implications of a quantum of energy (quantum), and then think about what it would mean to establish that sort of thing for other measurements. It's pretty unintuitive when you first come across it but there are pretty unimpeachable experiments that support it. --68.125.224.4 (talk) 03:54, 25 April 2008 (UTC)[reply]

Why can nothing smaller be meaured?. What are you going to measure it with? If the smallest measuring rod that can be constructed is a planck length and the smallest clock tick is the planck time, then it is not possible to construct a measuring instrument that can measure anything smaller. SpinningSpark 09:22, 25 April 2008 (UTC)[reply]

It does not automatically follow that you can't measure something smaller than the smallest measuring stick you can construct. It's easy to measure beyond the resolution of your measuring device. You can introduce some random noise known to average to zero and then measure the signal plus the noise and average over a large sample. The great part is that the noise can be several times larger than the signal, as long as it averages to zero you still get a measurement at greater precision to your measuring stick.

I'm not qualified to comment on this in regards to the Plank length, though. I imagine there are other difficulties that go beyond simple resolution restrictions on a measuring stick. APL (talk) 13:25, 25 April 2008 (UTC)[reply]

You assume that there exists something smaller to measure. If no such thing exists, it is impossible. For instance, if the charge on an electron were the smallest possible charge (I know about quarks, but am going to ignore them for this discussion) then your charge meter can only go up and down by whole electrons at the very best resolution that can be constructed. This is not some deficiency in my skill at constructing the meter. It is because the meter itself must necessarily use electron charge in the parts from which it is constructed. If you then add noise, you can only add noise in +/- whole numbers of electrons. You might get an average that is not a whole number but that does not mean that there is a fractional number of electrons in the box. It just represents the statistical error due to a less than infinite sample. SpinningSpark 10:02, 26 April 2008 (UTC)[reply]

You might want to read Heisenberg uncertainty principle, Planck length#Physical significance, and Planck time#Physica significance. The last section brings up some possible evidence to challenge this theory, but information is sketchy; you might want to follow up with the references. --Prestidigitator (talk) 18:34, 25 April 2008 (UTC)[reply]

Type of spider in Spider fighting

Can anyone identify the spiders in the article? These spiders are orb-weavers, roughly .5 to 1 cm long. They live in trees, power lines and tall grasses. They are found here in the Philippines. I posted this question on WP:SPI on August 2007 but didn't get any replies.--Lenticel ^(talk) 05:58, 25 April 2008 (UTC)[reply]

Hi Lenticel, I get a type of Argiope and there's one here[4] close-up. Addn: Aka a type of garden orb weaver[5]. Julia Rossi (talk) 01:37, 26 April 2008 (UTC)[reply]

The spiders looks more like Araneus (dull colored) than Agriope (larger and strikingly colored). I read List of Araneus species and found out that there are many species of Araneus in the Philippines. Well at least we narrowed it down to the genus level. Thanks Julia!--Lenticel ^(talk) 07:11, 26 April 2008 (UTC)[reply]

Ah, found it confusing colorwise especially sinceboth g's have their less vibrant types -- the Araneus I found looked highly coloured and ball shaped. Do they also like to web around power lines? happy searching, : ) Julia Rossi (talk) 07:46, 26 April 2008 (UTC)[reply]

PS You've got a few Argiopes in the Philippines too – those spiders get around! Julia Rossi (talk) 07:51, 26 April 2008 (UTC)[reply]

Yes they do spin webs in power lines. Kids prefer these spiders as fighters as they are "brave" enough to show themselves openly to predators. Yes we do have Argiopes here which we call gagambang ekis (X spider) due to their X like decorations--Lenticel ^(talk) 11:13, 26 April 2008 (UTC)[reply]

A tip from an arachnidologist: that the size of a web shows how powerful a spider is – poor spider, Julia Rossi (talk) 13:06, 26 April 2008 (UTC) PS Thanks for the link to decorations - didn't know we had that article. JR[reply]

Shells

Hi, What is actually the shape of each shell of an atom ? Is it a 3-D spherical shape, or an ellipse like that of the planets, or something else? Thanks. 116.68.70.51 (talk) 10:37, 25 April 2008 (UTC) A 15 year old.[reply]

See Atomic orbital. It differs between difference subshell types. s-orbitals are spherical, but the others aren't as simple. 83.253.253.166 (talk) 10:59, 25 April 2008 (UTC)[reply]

The shapes are usually modeled as Legendre polynomials in spherical coordinates, because these forms are solutions to the governing equation of an electron. The easiest solution is of course the sphere, or s orbital. However, the higher order shells are very complex and may exhibit weird geometries (e.g. quantum effects) - for example, the electron's distribution function may be finite on both sides of a node and zero in between. Nimur (talk) 14:32, 25 April 2008 (UTC)[reply]

Thank you! 116.68.71.144 (talk) 13:12, 26 April 2008 (UTC)A 15 year old[reply]

Eyes

Hi! This is the same 15 year old again.........What I want to ask is, when an eyelash falls in the eye, somewhere in the white portion, I might not even notice it, but if it falls on the pupil, I would get a prickly stinging sensation immediately, even if it touches only a small portion of my iris and doesn't interfere with vision. Why is it so? I thought that the conjunctiva covered the front of the eye evenly. How should I know precisely when something touches only a certain portion?? (The conjunctiva doesn't have nerves, does it??) 116.68.70.51 (talk) 10:45, 25 April 2008 (UTC) A 15 year old[reply]

My understanding as someone who hasn't studied the eye, but has worn contacts for a very long time, is that the eye itself has no sensory nerves and doesn't notice anything on it. Your eyelid, on the other hand, is very sensitive and notices immediately if there is anything disturbing the smoothness of the eye. An eyelash "in your eye" is only noticed as it gets "run over" by the lid. -SandyJax (talk) 15:03, 25 April 2008 (UTC)[reply]

However, if you see the eyelash fall, that may trigger the "I've got something in my eye" feeling, too. So, lashes which fall in your field of view are more likley to cause a reaction. StuRat (talk) 15:27, 25 April 2008 (UTC)[reply]

There are no nerves (motor or sensory) in the sclera (white of the eye) so nothing can be felt on it. The pupil doesn't have any nerves either, but (as StuRat mentioned) I believe when the eye visually notices something on the pupil, it triggers a response; namely, pain to help you know it's there and the eye starts to secrete tears. Regards, CycloneNimrod^Talk? 16:43, 25 April 2008 (UTC)[reply]

I have difficulty believing that there are no sensory nerves on the sclera or ~~pupil~~cornea. If I hold my eyes open to let them dry out, they begin to sting, and that sensation is definitely on the surface of my eyes. If I take a tissue paper and poke it into different places on my eye, it tickles or even hurts. This also happens in the dark if I can't see what's happening. I'm skeptical that a visual cue will trigger a physical pain response localized on the eye surface. ~Amatulić (talk) 18:53, 25 April 2008 (UTC)[reply]

The pupil isn't part of the surface of the eye. Think of the surface of the eyeball as consisting of two parts: the white part, the sclera, and the clear part (which overlies the iris, lens, and pupil), called the cornea. The sclera has very little in the way of neuroreceptors, but the cornea is one of the most sensitive and densely innervated tissues in the body. Corneal abrasions are exquisitely painful. - Nunh-huh 20:07, 25 April 2008 (UTC)[reply]

The entire surface of the eye has sensory nerves that are used to trigger tear formation. I've done work on two studies involving sensory nerves on the eye. One found reduced sensation and reduced tears in patients who had LASIK. Another found that lack of sensory nerves on the surface of the eye correlated with early onset of glaucoma. -- kainaw ™ 00:42, 26 April 2008 (UTC)[reply]

Cellphone signal

Someone told me today that numbers like 911, 112 and 999 (emergency numbers) can be called without any signal. I doubt very much that this is possible, but if it is, someone please explain how it can be? Thanks! Regards, CycloneNimrod^Talk? 16:54, 25 April 2008 (UTC)[reply]

Perhaps what was meant was that emergency numbers can be called without a service plan; since a cell phone is, at a very basic level, a radio transceiver, a signal is necessary to make it work. --LarryMac | Talk 17:07, 25 April 2008 (UTC)[reply]

Agreed, they had the terms mixed up. Or you do. Either way, cell phones can call emergency numbers without any service plan. In fact, many communities have charities for abused women that give away old cell phones for free. They give them to women who may be in danger from their ex-husbands and so forth, so that if the need arises they can call 911 without having to pay for a service plan. see this, this, and this. Dismas|^(talk) 17:17, 25 April 2008 (UTC)[reply]

From a user point of view it can seem as if they operate without any signal, and if you define 'signal' as the thing that your phone tells you it has (as is the way many lay people use it), then it does. Often when I don't have any 'signal' (I have no bars lit up) my phone says 'emergency only', meaning it can only be used to call 999 or 112. This is because there is no signal for my network, but other transmitters for other networks can be reached if necessary. 79.66.99.37 (talk) 17:33, 25 April 2008 (UTC)[reply]

QI tells us that on Christmas Day, lots of Americans call 911 to test their new phones because they have no network. -mattbuck (Talk) 14:53, 26 April 2008 (UTC)[reply]

That seems highly unlikely, due to the nature of the cell phone business in the US; i.e. phones and plans are tightly coupled and purchasing a phone without having it already set up with a carrier is not the norm. I'd like to know where QI sourced that factoid. --LarryMac | Talk 15:18, 28 April 2008 (UTC)[reply]

The phones probably were already associated with a carrier, but not activated and thus couldn't be immediately used. - Pureblade | ^Θ 17:58, 29 April 2008 (UTC)[reply]

NAV (Anatomy)

I've been cleaning up the NAV disamb page and I just want to check whether the following is correct:

In anatomy, NAV stands for nerve-artery-vein, when all these follow a common pathway.

Zain Ebrahim (talk) 17:05, 25 April 2008 (UTC)[reply]

True, a useful mnemonic for the order of vessels and nerves on the front of the upper thigh, for example. A fuller version is NAVEL - (lateral to medial) Femoral nerve, femoral artery, femoral vein, empty space with lymphatics. I tidied up the NAV (anatomy) page a bit. -- Flyguy649 ^talk 01:47, 26 April 2008 (UTC)[reply]

And yes in shortform, writing "Femoral n.a.v" would mean all three. -- Flyguy649 ^talk 14:38, 26 April 2008 (UTC)[reply]

What causes dark circles under the eyes?

What causes dark undereye circles? --70.167.58.6 (talk) 18:54, 25 April 2008 (UTC)[reply]

The eye circle article has an answer, although it isn't cited with reference. ~Amatulić (talk) 20:30, 25 April 2008 (UTC)[reply]

The two explanations in the article for dark circles resulting from lack of sleep or fatigue seem utter bollucks. How would lack of sleep "make the skin pale" to the extent that the underlying blood vessels become more visible, but nowhee elso on the body? What layer of the skin would "become pale?" I thought pallor is more often associated with a decrease in peripheral blood flow. The other explanation is that "when one lies down since gravity can cause fluid to collect in the lower eye lid" again unsatisfactory because when I have stayed up all night, by definition I have not been lying down, and this assuredly results in dark circles. Edison (talk) 01:27, 26 April 2008 (UTC)[reply]

I think you've misunderstood the second explanation (though it still seems dubious to me). The article seems to state that lying down allows the blood to circulate more freely and it's standing (or sitting) up that causes the blood to be trapped, thus agreeing with your experience. By extension, that should mean that lying down, even without sleeping, should be enough to prevent the formation of the circles, but that hasn't been my experience. Matt Deres (talk) 20:09, 30 April 2008 (UTC)[reply]

cockateils

moved from Village Pump -- Kesh (talk) 21:44, 25 April 2008 (UTC)[reply]

We have questions about weird things our bird does. what size are their hearts? our bird will look straight ahead at us and we can barly see his eyes...can he see us? also...he does this weird thing with his mouth. It looks like he's yawning, but he'll do this over and over again. & whats the best way to start petting him? He's used to us, but he doesnt like us touching him. Whats he doing? Thanks email removed —Preceding unsigned comment added by 209.33.106.106 (talk) 17:09, 25 April 2008 (UTC)[reply]

Guess you've seen our article Cockatiel - it's a start, especially about getting to know your little bird. Julia Rossi (talk) 12:26, 26 April 2008 (UTC)[reply]

Maybe by putting User:Kurt Shaped Box's name here, he will notice this question. Kurt is the resident bird/gull/budgie expert and may have useful insights. Nimur (talk) 14:36, 26 April 2008 (UTC)[reply]

This site [6] has lots of good information on bird behavior and training.--Eriastrum (talk) 16:12, 26 April 2008 (UTC)[reply]

Just saw this topic. WRT your Cockatiel's repeated 'yawning', it could be one of a few things - but it *may* mean that there's something wrong with him. It could be the case that he's actually gasping for breath, for instance. You should probably take him to an avian veterinarian and get him checked out, just to be on the safe side. Birds are *very* good at hiding illness - they often don't appear to look sick at all until they're almost at the point of keeling over, so you do need to keep a close eye out for any behaviour that appears to be out of the ordinary. Pet birds are also generally prone to respiratory problems, be they environmental in cause or due to an infection. --Kurt Shaped Box (talk) 23:14, 27 April 2008 (UTC)[reply]

April 26

Famciclovir or Acyclovir

Are there any instances in the literature of where short doses of fam/a/ciclcovir induced herpes zoster without prior infection? Also, adverse events such as peripheral neuropathy? Thank you.

75.73.61.30 (talk) 01:55, 26 April 2008 (UTC)Jonathan[reply]

Herpes Zoster is caused exclusively by the varicella zoster virus. Infection with VZV is necessary for herpes zoster, and thus neither aciclovir nor its derivatives (or anything, really) can induce this syndrome in an uninfected person. Peripheral neuropathy is not listed, per se as an AE in my dated (2004) PDR for acyclovir, though parasthesia is. Tuckerekcut (talk) 05:04, 26 April 2008 (UTC)[reply]

Thank you for answering. Kind of worded it wrong, inducing shingles in previously unshingled participants. I am aware dormant VZV is required. —Preceding unsigned comment added by 71.195.4.244 (talk) 20:12, 26 April 2008 (UTC)[reply]

Space and time as emergent phenomena

Kindly point out any references (books, webpages, etc.) on space and time as emergent phenomena. --Masatran (talk) 07:45, 26 April 2008 (UTC)[reply]

Michael Lockwood's book The Labyrinth of Time (ISBN 978-0-19-921726-7) is a survey of the role of time in modern physics.
Roger Penrose's The Road to Reality contains a good explanation of the links between the arrow of time, thermodynamics and cosmology.
Julian Barbour's The End of Time: The Next Revolution in Our Understanding of the Universe - a radical and non-mainstream treatment - questions the objective nature of the concept of time. Gandalf61 (talk) 08:32, 26 April 2008 (UTC)[reply]

this sounds suspiciously like homework...hell, it's not even a question, jsut a demand for others to do research. GO TO A LIBRARY. If you can get to a college campus, try running a database keyword search, like on JSTOR or something. --Shaggorama (talk) 17:26, 26 April 2008 (UTC)[reply]

Please don't bite the questioners. This question is exactly what a reference desk is here for. --Sean 20:13, 26 April 2008 (UTC)[reply]

Science Without Numbers by Hartry H. Field or something similar?

I'm looking for Hartry H. Field's Science Without Numbers: A Defence of Nominalism in which, apparently, he describes physics without the use of any mathematics. It looks like it is out of print, and the used copies are rare and expensive. Since I'm in Brazil, a scientific and philosophical desert, this sort of thing is not really available in any place I've checked.

Is there any other way I could possibly get my hands on this book, or at least something similar? I'm very curious about this sort of approach. Thanks! — Kieff | Talk 08:58, 26 April 2008 (UTC)[reply]

Sorry, I don't know the book, but I always found Michael Faraday very inspiring. He achieved a high degree of scientific proficiency without much math. (Not that I hate math, just shows that it can be done.) Lisa4edit--71.236.23.111 (talk) 10:12, 26 April 2008 (UTC)[reply]

WH Smith in the UK claim to have it available [7] for £24.95 (that's about $50). Cheapest I've seen, the second hand copies seem to be selling for up to $200. I rather suspect though, that if you actually try and purchase the book from Smith's, it might turn out they don't actually have any. Other suggestions: you could try listing it on eBay as an item wanted - never know your luck; you could also ask here WP:Library. SpinningSpark 12:18, 26 April 2008 (UTC)[reply]

I don't think Faraday is the same thing by the way. Faraday was not actually against mathematics. Field apparently wants to expunge it from science. SpinningSpark 12:18, 26 April 2008 (UTC)[reply]

He's not trying to expunge mathematics as such, but rather mathematical objects (numbers, functions and such). In that book he shows how one can develop physics (he uses Newtonian gravitation as an example) with essentially its usual mathematical structure, but with all talk of dodgy non-existant objects replaced by talk of points in physical space and suchlike. A caveat to the OP: a JSTOR review has 'It should be added that this is not a popular work for the general reader; it is a technical work presupposing familiarity with current efforts to axiomatize physical theories by means of mathematical logic'. Algebraist 12:57, 26 April 2008 (UTC)[reply]

This may not help, but it may be worth a try:

Hartry Field, Silver Professor of Philosophy; Professor of Philosophy

Department of Philosophy / 5 Washington Place / New York, NY 10003

Phone: (212) 998-3795 / Fax: (212) 995-4179 / Email: [email protected]

He is the author of Science Without Numbers (Blackwell 1980), which won the Lakatos Prize, of Realism, Mathematics and Modality (Blackwell 1989), and of Truth and the Absence of Fact (Oxford 2001). Current interests include objectivity and indeterminacy, a priori knowledge, causation, and the semantic and set-theoretic paradoxes.

Amazon has an offer for $145 plus a review which you may find interesting.

--Cookatoo.ergo.ZooM (talk) 12:49, 26 April 2008 (UTC)[reply]

Where in Brazil are you? There's an excellent book store in a lot of the larger cities called 'Livraria Cultura' that has a surprisingly good philosophy section, books in MANY languages, and will also order books for you. [www.mercadolivre.com Mercado Livre], Brazil's response to eBay might giv eyou some options too. Does amazon not deliver to Brazil? --Shaggorama (talk) 17:38, 26 April 2008 (UTC)[reply]

According to Worldcat, the university of Sao Paulo has a copy. -Arch dude (talk) 18:38, 26 April 2008 (UTC)[reply]

Yeah. Guess that's the best chance I have. I don't live in São Paulo, though, so it'll be tricky. Thanks, tho. — Kieff | Talk 19:02, 26 April 2008 (UTC)[reply]

Do they have interlibrary loans in Brazil? --Anon, 00:12 UTC, April 27, 2008.

Amazon do delivers to Brazil. 217.168.1.93 (talk) 12:14, 28 April 2008 (UTC)[reply]

I'm not gonna pay that much for a single book I'm merely curious about. — Kieff | Talk 23:04, 28 April 2008 (UTC)[reply]

Osmolarity and Cells

Hi, I'm a beginning student to this field, and I just have a quick question. Actually I'm wondering if my understanding of this is correct.

Imagine you have a cell which you place in a solution. If the solution is: Isotonic = no change in cell size
Hypertonic = cells shrink BECAUSE water flows to dilute higher solute concentration outside of cell
Hypotonic = cells expand BECAUSE water flows to dilute higher solute concentration inside of cell

Is this correct? It's just that my textbook says that the solutes diffuse and that the water follows them, but this makes no sense (in the hypertonic solution, wouldn't particles flow into the cell, causing it to expand?). Thanks Guycalledryan (talk) 10:33, 26 April 2008 (UTC)[reply]

See our article on tonicity which explains this. The solute will not pass through the cell membrane if the membrane is impermeable to that solute. If the solute cannot be exchanged, the concentration can only then be equalised with an exchange of water. SpinningSpark 12:42, 26 April 2008 (UTC)[reply]

The whole idea is that the cell membrane prevents some particles from diffusing. Due to Entropy, particles concentrated in a small area tend to disperse until the area they can inhabit is homogenized. The deal with cells is that they let some particles cross their membrane (like water) but they don't let others pass through. So, if you put a cell in a concentrated solution (HYPERtonic to the cell) water flows OUT of the cell in an attempt to equalize the concentration outside with the concentration inside, and the cell loses volume (i.e. shrinks). Conversely, if you put a cell in a HYPOtonic solution (like pure H20) water flows into the cell in an attempt to dilute the concentration inside the cell.

The general rule is that systems move towards equilibrium, which in this case is isotonicity. When your book says water follows solute, they're saying that in general the water well go where it can find the highest concentration of solute, because the tendency of the system is to dilute the high concentration. --Shaggorama (talk) 17:34, 26 April 2008 (UTC)[reply]

FUNDAMENTAL ATTRIBUTION ERROR

Am seeking someone who might have participated in a FAE study and /or an individual(s) whom have done some research in this area and has some stimulating theories as to our assumptions that a person's social and enviornmental influences a persons actions vs the kind of individual they are. How often do we find ourselves sliopping int those tendencies to judge?

And are we the Kind of person because of our social and eviornmental influences? ZLAW —Preceding unsigned comment added by Zeldawong (talk • contribs) 14:58, 26 April 2008 (UTC)[reply]

I don't know about research into FAE itself, but I encountered a recent example. First some stats were presented which showed that recent black immigrants from Africa to the US were as healthy as whites in the US, but that after a generation the African-Americans were less healthy than the white Americans. They then concluded that this was due to racism. I concluded that it was possibly due to diet and other factors, but that more research would be needed to be sure. They seemed to have a goal of proving something and interpretted the data accordingly. In any case where somebody "sets out to prove something", the results should be questioned. Instead, they should "set out to find the truth, whatever it is". StuRat (talk) 07:15, 29 April 2008 (UTC)[reply]

Check the authors of some of the recent sources cited on our Fundamental attribution error page? DMacks (talk) 07:32, 29 April 2008 (UTC)[reply]

StuRat, do you think it could have been regression to the mean? ie, if immigrants are self-selected to be healthier than average. --MagneticFlux (talk) 02:56, 1 May 2008 (UTC)[reply]

Are you sure that's an example? Doesn't really sounds like it to me at least from Fundamental attribution error. If anythimn, they're overattributing the situational explanation (since surely racism is a situational explanation, it's not that the authors were suggesting the second generation Africa-Americans were doing something that resulted in racism towards them is it?) while under-estimating the dispositional explaination but even that isn't necessarily true since diet for example can be a situational factor. In any case, the healthy immigrant effect doesn't seem to be limited to blacks [8] & Immigration to the United States (this is also rather interesting [9]) Nil Einne (talk) 11:35, 1 May 2008 (UTC)[reply]

Nuclear Testing on GIs

Can anyone direct me toward a good site that has interviews from GIs used as "guinea pigs" in the Nuclear Test sites during the Cold War. I keep coming up with some site about Guinea pig retinas and medical revolutions. :( —Preceding unsigned comment added by EWHS (talk • contribs) 15:56, 26 April 2008 (UTC)[reply]

The term for this, oddly enough, is Atomic veteran. (Wow, something WP doesn't have an article on! You can even get a license plate with it on it if you were one, in Alabama.) Here's a website all about interviews with veterans who participated in nuclear tests: Atomic Veterans History Project. --Captain Ref Desk (talk) 17:15, 26 April 2008 (UTC)[reply]

Outside of the US, "nuclear test veteran" or "nuclear veteran" seem common Nil Einne (talk) 18:33, 26 April 2008 (UTC)[reply]

Will they ever invent a microwave that wont freak out if I accidently leave my fork in there?

I heard this asked by Adam Corolla and it's always bothered me too. I figure there must be a reason why this happens. Bill Nye said it would be like trying to design a mirror that doesn't reflect. But there are mirrors that dont reflect. Two way mirrors. One side you can see thru. Microwave-safe cans still reflect (though,fainter), and there seems to be no problem there. What is the science here that explains why they cant invent an everything safe microwave?--Sunburned Baby (talk) 21:04, 26 April 2008 (UTC)[reply]

A lot of people misunderstand two-way mirrors -- what they do is reflect some of the light, and let (most of) the rest of it through. Works the same from either direction (hence the name two-way mirror). The apparent directionality comes from the fact that, when one side is lit much brighter than the other, the intensity of the reflection is so much greater than the intensity of the light coming through from the other side, that the eye can't make out the transmitted signal.

However I don't see why a microwave couldn't be developed that would detect that there's a fork in it, and turn itself off so that you don't get the arcing. But you would have to take the fork out before cooking the food. --Trovatore (talk) 21:33, 26 April 2008 (UTC)[reply]

See Two-way mirror. hydnjo talk 23:48, 26 April 2008 (UTC)[reply]

Microwaves are electromagnetic radiation, so they push around electric charges. A water molecule is like a little electric dipole (the oxygen side is negative and the hydrogen side is positive), so when microwaves hit water molecules they move around faster, and this motion of molecules is manifested as heat. Metals are conductors of electricity, which means electric charges can flow through them. When microwaves hit a metal, electric currents flow across the surface of the metal. (It's only the surface and not the whole volume of the metal because the surface currents cancel out the electric field of the microwaves; the waves only penetrate a microscopic distance into the metal.) The problem with putting a fork in the microwave is not simply that it's made of metal, the problem is that it has sharp points. As the electric currents flow across the sharp points, the charge builds up and creates a large electric field; much larger than the field of the microwaves themselves. If the field gets too high (3 kV/mm), the air undergoes electrical breakdown and turns into a plasma, which conducts electricity and makes the microwave oven "freak out".

I actually leave spoons in the microwave all the time, because I understand the physics and know that it's safe. As I said, it's not the metal itself, it's the sharp points act as focal points for the electric field.

So to answer your question, it's impossible to invent a microwave oven that doesn't do this, because it's just the way electromagnetism works. If you have strong electromagnetic waves hitting a sharp metal point, there's going to be a large field there no matter what. —Keenan Pepper 21:41, 26 April 2008 (UTC)[reply]

Understanding these focal points, are there ways to manipulate the arrangement of sharp points so as to prove different mechanics of electrics and electromagnetism? Say, for instance, to put in some forks arranged in a particular formation, along with the traditional ferromagnetic materials organized around a magnet of some kind? 81.93.102.185 (talk) 21:51, 26 April 2008 (UTC)[reply]

It would be far simpler to just use plastic forks. -- Hi Ev 02:59, 27 April 2008 (UTC)[reply]

I think the solution to this problem would be to create some sort of metal-polymer alloy that is metallic enough to stand up to dishwashers and years of use, but plastic enough not to create sparks in a microwave. Vranak (talk) 22:03, 26 April 2008 (UTC)[reply]

Or maybe the microwave could rearrange its field inside to makd a null at the pointy bits on the fork, so that no sparks are generated, but enough microwaves still heat up the food. You are unlikely to see such a machine though as it would cost more to make. Graeme Bartlett (talk) 22:13, 26 April 2008 (UTC)[reply]

You may not be able to leave a fork in the microwave, but how about making one along with cooking your dinner? (See http://www.nature.com/nature/journal/v399/n6737/full/399668a0.html or http://www.sciencedaily.com/releases/1999/06/990622055733.htm) It would make your TV dinner rather costly and wasteful, though.--Lisa4edit (talk) 02:14, 27 April 2008 (UTC)[reply]

there must be more to the phenomenon then "points:" this only explains fork arcing. what about aluminum foil and cd's? And split grapes? microwaves do some weird stuff, consult youtube. --Shaggorama (talk) 08:30, 28 April 2008 (UTC)[reply]

Aluminum foil and cds are to thin to handle the currents that microwaves put through them. The same process that cooks the food is what causes the microwave to freak out with metal objects. They can't be made to do one and not the other, that's a bit like saying you want your mirror to reflect the room you're in but not you, it just doesn't work that way. Mad031683 (talk) 15:02, 28 April 2008 (UTC)[reply]

Do microwaves put current thro conductors? Or do they just induce a voltage> —Preceding unsigned comment added by 79.76.217.249 (talk) 00:42, 29 April 2008 (UTC)[reply]

Moment of Inertia

I was given a moment of inertia problem that went somewhat at follows. We are considering a trebuchet, with a 60kg mass .14meters from the axel, and a .12kg rock 2.86meters from the axel. We are then asked to find the max speed of the rock. The question itself I answered, getting something close to 25m/s, and I did it using conservation of energy. But I have a few questions. First, is there another method of answering the question? Second, when doing conservation of energy, would the potential energy be mgh? Finally, if we wanted to determine whether the big or the small object fell, would we see which mass times distance was greater, or would we calculate which moment of inertia was greater, and why? —Preceding unsigned comment added by 76.69.240.138 (talk) 21:30, 26 April 2008 (UTC)[reply]

I remembered a TV program a few years back (History channel I think). They built a trebuchet and found that the wheels were not just for rolling the siege engine into position, but also figured into the equations of firing the missle. I tried to find a link for you, but I only found s.o. else who had seen the program mentioning it in a physics forum. Our page says the fact is disputed among scientist, but unfortunately doesn't have a reference link. --Lisa4edit (talk) 03:02, 27 April 2008 (UTC)[reply]

I saw that program, too. I thought the conclusion was that the wheels are needed for the recoil, to prevent forces from building up in the frame which would otherwise shake it apart. StuRat (talk) 06:00, 27 April 2008 (UTC)[reply]

I think I know what program you're talking about. I remember seeing it on Discovery Channel. Two competing groups built an English (fixed weight) and a French (hanging weight) trebuchet. It was pretty cool, but I couldn't find its name last time I checked. — Kieff | Talk 11:50, 27 April 2008 (UTC)[reply]

Conservation of energy is a good approach. Potential energy lost by counterweight - which is mgh - is equal to potential energy gained by rock and arm plus kinetic energy gained by rock, arm and counterweight. You could work out the net torque on the trebuchet arm at each point in its motion, then divide by the moment of inertia of the arm, rock and counterweight to find the angular acceleration of the system, then integrate this to work out the angular velocity and hence linear velocity of the rock at point of release - but you should get the same answer.

Calculating the net torque (which is how you know that the counterweight is heavy enough to move arm and rock) just involves multiplying weight x distance from pivot for rock, arm and counterweight - if the arm is a uniform beam then it can be treated as a point weight at its geometric centre. Don't confuse torque with momement of intertia - that is like confusing force and mass.

Note that both approaches neglect energy lost due to friction, air resistance, deformation of the terbuchet frame, and linear motion of the trebuchet if it is on wheels - so in real life your trebuchet performance will not be as good as your calculation suggests. You are also assuming that the trebuchet is a simple lever. More sophisticated trebuchets - see right - had the rock in a sling and the counterweight in a pivoted cage, so they were not just a simple lever. The mathematical anaylsis of a sling trebuchet is much more difficult, because of the complications introduced by the rotations of rock and counterweight about the additional pivots. Gandalf61 (talk) 08:32, 27 April 2008 (UTC)[reply]

April 27

Flower name

Does anyone know the name of this flower? I don't know what it is and I would like to add this image to the appropriate article. --AutoGyro (talk) 02:31, 27 April 2008 (UTC)[reply]

Looks like a Narcissus (a.k.a. a "daffodil") of some sort to me. -- Hi Ev 02:50, 27 April 2008 (UTC)[reply]

Concur with daffodil. But as there are thousands of different cultivars it would take a narcissophile of some expertise to put a varietal name to it. Richard Avery (talk) 11:55, 27 April 2008 (UTC)[reply]

That's an interesting word: "narcissophile" (someone who loves loving themself ?). StuRat (talk) 07:06, 29 April 2008 (UTC)[reply]

This is almost certainly the most commonly grown daffodil: King Alfred [10].--Eriastrum (talk) 15:04, 27 April 2008 (UTC)[reply]

Hampster who injured his mouth with too long teeth

My name is Popeye. I am a Teddy Bear Hamster. I have been in misery for the last 7 hours, I haven't left my bed and I am making choking noises. I cut the roof of my mouth with my very long teeth. My master took me to our friend at the pet store who cut off about 1 millimeter of my bottom teeth. But I am still making the choking noise and I won't leave my bed. My master is afraid I am going to die. Please help----Popeye, I am about 6 months old. —Preceding unsigned comment added by 68.164.84.9 (talk) 03:11, 27 April 2008 (UTC)[reply]

Popeye's master should have given Popeye some things to gnaw on that wear down teeth. See Tooth (animal)#Rodent. I am not sure what can be done now except wait for the damage to heal, if possible. If I were Popeye's master, I would immediately call a vet and ask for advice. The vet may have some liquid food to drop in Popeye's mouth to feed him while he recovers. =Axlq 04:18, 27 April 2008 (UTC)[reply]

We are as forbidden to give veterinary advice as to give medical or legal advice. See a vet. Edison (talk) 00:50, 29 April 2008 (UTC)[reply]

Quantum: Potential between the Electrons

Suppose there are two electrons in an one-dimentional spatial space (imaging two electrons in the same wire of infinite length). And the wave function of two electrons is $\Psi =\psi (x_{1},x_{2})$ where $x_{1}$ and $x_{2}$ are the postions of the respective electron. Then $|\psi (x_{1},x_{2})|^{2}$ should be the probability density function for finding the first electron at $x_{1}$ and the second electron at $x_{2}$ . And the normalization condition of the wave function $\Psi$ should be

\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }|\psi (x_{1},x_{2})|^{2}\,dx_{1}\,dx_{2}=1

(1)

And the potential $V$ of the electron should be

V={1 \over 4\pi \varepsilon _{0}}{\frac {q_{1}q_{2}}{r}}

(2)

according to Coulomb's law and the fact that $F=-\nabla V$ . Where $r$ is the distance between the two electrons. For two electrons in one-dimensional space, it should be

r=|x_{1}-x_{2}|

(3)

Replace (3) into (2), the potential $V$ becomes

V={1 \over 4\pi \varepsilon _{0}}{\frac {q_{1}q_{2}}{|x_{1}-x_{2}|}}={q_{1}q_{2} \over 4\pi \varepsilon _{0}}{\frac {1}{|x_{1}-x_{2}|}}\equiv v(x_{1},x_{2})

(4)

Because of the Uncertainty Principle, we can not make sure the position of each electron. But we know the probability of finding them by $|\psi (x_{1},x_{2})|^{2}$ . (one way to find out the potential $V$ of the electron is to introduce quantum electrodynamics according to Gandalf61's suggestion in the discussion Determine the Force between the Electrons which, however, seems too complex to me) Then my idea to find out the effective potential $V_{d}$ in discrete form is simply to calculate the weighted sum

V_{d}=P_{1}V_{1}+P_{2}V_{2}+P_{3}V_{3}+...

where $P_{1}$ , $P_{2}$ , $P_{3}$ ,... are probabilities of finding the two electrons at different positions and $V_{1}$ , $V_{2}$ , $V_{3}$ ,... are the potentials at the corresponding positions. So

V_{d}=\sum _{x_{2}}\sum _{x_{1}}P(x_{1},x_{2})v(x_{1},x_{2})

V_{d}=\sum _{x_{2}}\sum _{x_{1}}P(x_{1},x_{2})\left({q_{1}q_{2} \over 4\pi \varepsilon _{0}}{\frac {1}{|x_{1}-x_{2}|}}\right)

V_{d}={q_{1}q_{2} \over 4\pi \varepsilon _{0}}\sum _{x_{2}}\sum _{x_{1}}{\frac {P(x_{1},x_{2})}{|x_{1}-x_{2}|}}

where $P(x_{1},x_{2})$ is the probability of finding the first electron at $x_{1}$ and the second electron at $x_{2}$ . Or, the effective potential $V_{c}$ in continuous form

V_{c}=\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }|\psi (x_{1},x_{2})|^{2}\,v(x_{1},x_{2})\,dx_{1}\,dx_{2}

V_{c}=\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }|\psi (x_{1},x_{2})|^{2}\,\left({q_{1}q_{2} \over 4\pi \varepsilon _{0}}{\frac {1}{|x_{1}-x_{2}|}}\right)\,dx_{1}\,dx_{2}

V_{c}={q_{1}q_{2} \over 4\pi \varepsilon _{0}}\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }{\frac {|\psi (x_{1},x_{2})|^{2}}{|x_{1}-x_{2}|}}\,dx_{1}\,dx_{2}

and my question is can I determine the potential of the two electrons by the equation $V_{c}={q_{1}q_{2} \over 4\pi \varepsilon _{0}}\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }{\frac {|\psi (x_{1},x_{2})|^{2}}{|x_{1}-x_{2}|}}\,dx_{1}\,dx_{2}$ ? - Justin545 (talk) 03:16, 27 April 2008 (UTC)[reply]

I don't mean to be disrespectful or denegrating, but honestly, this looks suspiciously like a homework problem to me. =Axlq 04:12, 27 April 2008 (UTC)[reply]

It appears they've done prior work, indicating that they require assistance on something researched. Wisdom89 _{(_T / ^C)} 04:16, 27 April 2008 (UTC)[reply]

I am neither doing a homework nor writing a paper. Studying things about quantum is just one of my hobbies while I am free. - Justin545 (talk) 05:15, 27 April 2008 (UTC)[reply]

You have the right form for the expectation value of the potential between the electrons, however, you have to use

v(x_{1},x_{2})

in solving the Schrodinger equation (written below) by which you determine the wave function. Until you solve the Schrondinger equation you won't know the form of Ψ and hence you couldn't compute the expectation value anyway.

(-{\hbar ^{2} \over 2m_{1}}{\partial ^{2} \over \partial x_{1}^{2}}-{\hbar ^{2} \over 2m_{2}}{\partial ^{2} \over \partial x_{2}^{2}}+v(x_{1},x_{2}))\Psi (x_{1},x_{2},t)=i\hbar {\partial  \over \partial t}\Psi (x_{1},x_{2},t)

Here I've included the explicit time dependence because your proposed boundary condition (two electron on an infinite wire) would not admit any non-trivial time independent solutions. Dragons flight (talk) 08:30, 27 April 2008 (UTC)[reply]

Does that mean I can know the form of

\Psi

by solving the following Schrondinger

\left[-{\hbar ^{2} \over 2m_{1}}{\partial ^{2} \over \partial x_{1}^{2}}-{\hbar ^{2} \over 2m_{2}}{\partial ^{2} \over \partial x_{2}^{2}}+\left({1 \over 4\pi \varepsilon _{0}}{\frac {q_{1}q_{2}}{|x_{1}-x_{2}|}}\right)\right]\Psi (x_{1},x_{2},t)=i\hbar {\partial  \over \partial t}\Psi (x_{1},x_{2},t)

? Thanks. - Justin545 (talk) 09:43, 27 April 2008 (UTC)[reply]

Yes, that looks correct to me. If you extend this to three spatial dimensions, you have the hydrogen-like atom, which is perhaps the most useful exactly solvable model in quantum mechanics. Make sure to work in the center of momentum frame and use the reduced mass; then the problem separates nicely into a center-of-mass motion part (whose eigenstates are plane waves), and a relative motion part (whose eigenstates are atomic orbitals). —Keenan Pepper 18:04, 27 April 2008 (UTC)[reply]

Name of material

Does anyone know what kind of material is this (the uniform)? Is it the same material worn by professional StarCraft players on competitions? Looks similar at least --217.14.103.168 (talk) 07:38, 27 April 2008 (UTC)[reply]

The uniform would be called a "flight suit", but that won't get you much closer to the material I'm afraid.--Lisa4edit (talk) 09:49, 27 April 2008 (UTC)[reply]

It looks to me like the sort of suit that Formula One drivers wear and is probably a composite of several layers, the key one being Nomex for fire resistance. This site has some information. SpinningSpark 10:54, 27 April 2008 (UTC)[reply]

I found this mail address: [email protected] They might be able to help you. The racing suit family looks likely, because "Marathon Racing Inc." runs the site. That suit had some extra "waste product disposal" features though. I don't think that's standard for racing suits. He wore a fire resistant suit during his glider flight, but there's no mention of this one except that it was silver. --Lisa4edit (talk) 11:01, 27 April 2008 (UTC)[reply]

BTW, I've never seen Starcraft players but I'm somewhat doubtful they usually wear anything like that. I've looked at a few pictures including the one here StarCraft professional competition and although none of them are that good, I would suspect it's more likely some kind of simple & cheap somewhat shiny synthethic, perhaps Lycra Nil Einne (talk) 19:45, 27 April 2008 (UTC)[reply]

Cyclic carbonates ?

In this article (http://www.sciencedaily.com/releases/2008/04/080424103217.htm) they mention cyclic carbonates. Wikipedia doesn't seem to have an article on them and my chemistry is a couple of decades old. I seem to have a faint memory though that says most of them are toxic?? --Lisa4edit (talk) 09:03, 27 April 2008 (UTC)[reply]

We have an article on carbonates and individual cyclic carbonates such as ethylene carbonate but apparently no article for them as a group. Here is the Material Safety Data Sheet for ethylene carbonate. Not very pleasant stuff. SpinningSpark 11:22, 27 April 2008 (UTC)[reply]

Also, the article Carbonate ester names a few more of them (individual articles as well), but without actually calling them cyclic carbonates. SpinningSpark 11:27, 27 April 2008 (UTC)[reply]

Thanks. So the murky old memory wasn't that far off. Not really the stuff to look forward to having in the neighborhood. Hope they'll take adequate safety precautions. --Lisa4edit (talk) 11:54, 27 April 2008 (UTC)[reply]

Fortunately even the simplest cyclic carbonate is a liquid (ethylene carbonate, bp 260 °C), so it's not going to create a cloud of toxic gas if there's a leak from a storage tank. DMacks (talk) 18:59, 27 April 2008 (UTC)[reply]

medical

how to control trigylcides —Preceding unsigned comment added by 60.243.25.44 (talk) 09:13, 27 April 2008 (UTC)[reply]

Presumably you mean triglyceride. If so hypertriglyceridemia discusses the medical aspects of excessive levels of triglycerides in the blood. -- Alan Liefting (talk) - 11:02, 27 April 2008 (UTC)[reply]

This may be of interest to you: Hypolipidemic agent. Also see Statins and fibrates. Wisdom89 _{(_T / ^C)} 18:12, 27 April 2008 (UTC)[reply]

Humans and ability of interactions with others

There is a law that says humans are only capable of dealing with about 150 people. WP has a page on it. Any ideas? -- Alan Liefting (talk) - 09:36, 27 April 2008 (UTC)[reply]

Never heard of that one before. Could you give us a clue or link where you've encountered that. I checked the "social interaction" and "Interpersonal Interaction" pages briefly, but nothing stuck out, except that they still seem to need a lot of work. --Lisa4edit (talk) 09:48, 27 April 2008 (UTC)[reply]

It's called somebody's number and it's extrapolated from the size of a part of our brains (the cerebral cortex?) relative to other primates. I have read the article here; I will try to remember the person's name. moink (talk) 11:23, 27 April 2008 (UTC)[reply]

Got it. Dunbar's number. moink (talk) 11:29, 27 April 2008 (UTC)[reply]

Yep, I had also just found it from what you said, but it is a hypothesis at first glance and the 150 are an estimate. Worth further reading though. --Lisa4edit (talk) 11:40, 27 April 2008 (UTC)[reply]

The original paper on Dunbar's number was published in 1992 (according to the wp article), just at the beginning of the popularization of the itnernet and certainly well before the proliferation of social netwroking websites. Dunbar's number was estimated based on anthropological observations of social networks. The nature of social networks in developed countries has since changed; our capacity to keep stable relationships has expanded significantly due to the communicative and mnemonic assitance provided by websites such as facebook and myspace. The only times i've ever heard Dunbar's number mentioned it was in the context of how the itnernet has changed society (and the number was always mentioned with a degree of contention). Quite frankly, I was surprised to learn how recen the study was, given I have yet to meet anyone who feels the study is pertinent to modern society. --Shaggorama (talk) 08:44, 28 April 2008 (UTC)[reply]

Why is frozen milk yellow?

Why is frozen milk yellow?--Shantavira|^{feed me} 11:12, 27 April 2008 (UTC)[reply]

I've been dealing quite a bit with frozen milk of late, though not cow's milk. I don't find that the frozen milk is any different colour from the liquid milk. It does have a slight yellowish cast, either frozen or liquid, which is true of any "whole" (full-fat) milk. Skim (non-fat) milk often seems bluish. moink (talk) 11:21, 27 April 2008 (UTC)[reply]

The fat in the milk freezes at a lower temperature than the other watery part and rises to the top when that part freezes (compare ice from the freezer to ice cream). According to milk, the yellow colour comes from fat globules. Skim milk won't turn yellow, according to this (which isn't very encyclopedic, I admit).

Zain Ebrahim (talk) 11:26, 27 April 2008 (UTC)[reply]

Ah, I have been freezing milk in transparent containers and looking at it from the side, so I see all the milk. Shantavira, have you been looking at your frozen milk from the top? (thus seeing the cream?) moink (talk) 11:34, 27 April 2008 (UTC)[reply]

Liquid milk appears white not because it is white but because the particles (fat, protein) scatter the light equally across the spectrum. My guess is that when you freeze the milk, you see the actual colour of the milk (the fat part will probably be yellow).--Shniken1 (talk) 12:04, 27 April 2008 (UTC)[reply]

That's an interesting distinction. I would have said that's the definition of something being white... --Tango (talk) 21:26, 1 May 2008 (UTC)[reply]

I believe it is fat, which, for some reason, finds it's way to the outside of the container, not just the top. The freezing process causes the fat to seperate, and fat is lighter than milk, but it doesn't seem to exclusively rise to the top until the ice thaws, but rather it sticks to the container. I would guess that this is because the density of frozen milk (being mostly water) is less, so that fat is no longer significantly lighter. Why it sticks to the inside of the container must have something to do with relative surface tensions. StuRat (talk) 15:46, 27 April 2008 (UTC)[reply]

Milk is an emulsion. That makes the process of freezing a whole lot more complex. You have a transport problem where part of the material follows fluid dynamics while the other is solid. I have no reference, but the observed separation of fat might be similar to frost heaving. With the fat behaving like the soil. Whether the fat is yellow or more whitish depends to some degree on what the cow ate (see here http://jds.fass.org/cgi/reprint/7/2/146.pdf?ck=nck). See one can turn something simple like frozen milk into something rather complex. Thanks for asking this question. I had fun looking for answers. ;-) Lisa4edit (talk) 17:17, 27 April 2008 (UTC)[reply]

Keep in mind that milk, being a natural product, varies slightly in color from place to place and location to location. Something as simple as breed of cow which produced the milk, or the type of food fed to the cow (e.g. silage versus pasturage) can change the color and/or flavor of the milk. Color can vary based on the amount of carotenes in the cows' diets. You tend to see differences happening in the Northern Hemisphere at about this time, as cows which have been kept inside all winter (and fed silage) make a transition outside to graze on pasture. -- 128.104.112.85 (talk) 17:24, 27 April 2008 (UTC)[reply]

Spherical coordinates

Hi, If the motion of a body is traced in cartesian and spherical coordinate systems, what is the basic difference, other than the method of representing the points?? Will the shape differ?? 116.68.71.144 (talk) 14:06, 27 April 2008 (UTC)A 15 year old.[reply]

The shape wouldn't differ. The mathematical equations describing them would be different. Which coordinate system gives you the easier equation depends on the motion you want to describe. --Lisa4edit (talk) 15:03, 27 April 2008 (UTC)[reply]

Agreed, any path can be represented in spherical, cylindrical, or cartesian coords. However, since it's far easier to show straight line motion with cartesian coords and far simpler to represent near-circular motion, like orbits, in spherical coords, which system is chosen to represent the motion may tell you something about the expected motion. StuRat (talk) 15:23, 27 April 2008 (UTC)[reply]

Thanks for answering ! 116.68.69.231 (talk) 12:28, 28 April 2008 (UTC)A 15 year old[reply]

Condition name

Is there a name for a condition where people can not remember the name of an object such as a fruit? For instance they me be able to remember the name of a strawberry because the eat strawberry jam almost every day but can not remember the name of a mango after a few weeks or months when handed the fruit, calling it a guava? 71.100.11.39 (talk) 14:09, 27 April 2008 (UTC) [reply]

Aphasia seems to be what you're looking for. At least one type of it. --Lisa4edit (talk) 14:21, 27 April 2008 (UTC)[reply]

I would have answered, but I can never recall the name... :-) StuRat (talk) 15:16, 27 April 2008 (UTC)[reply]

There is also agnosia, where a patient fails to recognise an object and therefore can not apply a name to it. A strawberry would be perceived as a roundish red object with small pimply kernels and some green squashed bits on one end, but you would have no idea about its use.

Forgetting little used terms is quite common in a variety of neurological disorders (dementia or Alzheimer´s). Actually, It is quite normal for anybody to confuse terms which are infrequently used. I am sure that I would mix up terms for tropical fruit, different types of pasta and the names of various names of sausages if there was not a label in front of it. --Cookatoo.ergo.ZooM (talk) 16:23, 27 April 2008 (UTC)[reply]

Knew there was another one that I had forgotten ;-) The interesting thing is that they found that the brain seems to store stuff by category. That's why you are more likely to name a vegetable with a wrong vegetable name rather than that for a sausage. You might still do that if the sausage name has a similar "sound pattern" or you ate it at the same time you ate that fruit.--Lisa4edit (talk) 17:32, 27 April 2008 (UTC)[reply]

This link [11] to a book by Oliver Sachs might be relevant. Richard Avery (talk) 06:49, 28 April 2008 (UTC)[reply]

Specifically what you are describing sounds like plain old bad memory. If it were taken to a much stronger extreme, then it could perhaps be considered Visual agnosia, which happens to be one of the topics covered in the Sachs book cited above. From Neurophilosophy, by Patricia Churchland:

"Patients unimpaired visually may be unable to identify by vision common objects, though they can name them if allowed to touch, hear, or semll them. They can faithfully copy a line drawing but remain unable to say what the object is." (224)

--Shaggorama (talk) 08:55, 28 April 2008 (UTC)[reply]

dinasours

how dinasours relates to the environment —Preceding unsigned comment added by 70.23.173.57 (talk) 18:05, 27 April 2008 (UTC)[reply]

I'm a little perplexed as to what your question means..could you elaborate pleas? Wisdom89 _{(_T / ^C)} 18:09, 27 April 2008 (UTC)[reply]

Our Dinosaur article mentions a couple of factors:

However, by the late Cretaceous, the environment was changing dramatically and

...no closely related species exist to provide zygotes or a suitable environment... --hydnjo talk 18:30, 27 April 2008 (UTC)[reply]

Unfortunately, our environment article doesn't mention the word "dinosaur". :) Zain Ebrahim (talk) 10:29, 28 April 2008 (UTC)[reply]

I believe our good friend Dana Rohrabacher can fill us in on the relationship:

"We don’t know what those other cycles were caused by in the past. Could be dinosaur flatulence, you know, or who knows? We do know the CO2 in the past had its time when it was greater as well. And what happened when the CO2 was greater since then and now? There have been many cycles of up and down warming."

— Æµ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 17:05, 29 April 2008 (UTC)[reply]

"They smoked". Julia Rossi (talk) 08:31, 30 April 2008 (UTC)[reply]

A few questions on drugs

I'm filling out a general health test, completely open-book, open-note, open-person (talk to anybody), and I've done just about all of it. I have a few questions though:

What is it called when alcohol is consumed faster than it can be processed by the body?
The use of alcohol with GHB can produce so much sedation that your brain stops telling you to — ? (think/eat/breathe/move)
As prescription drug — has increased with direct-to-consumer advertising, there has been a parallel increase in prescription drug use.
— cannot write prescriptions for themselves, but they do have considerable influence over what physicians do.
Some people are using GHB every two to four hours because if they don't use it, they cannot sleep, and get extremely anxious to the point of becoming —.
As the brain adapts to the hyper-release of dopamine with — drug use, lack of the drugs causes severe craving and addiction.

The last four are fill-in-the-blanks and seem rather vague to me to narrow it down, but then again, I don't know too much about drugs. Thanks in advance for your help! --Fbv65e del — t — c // 19:58, 27 April 2008 (UTC)[reply]

I may as well give some a go, but I can't be certain.

What is it called when alcohol is consumed faster than it can be processed by the body? Getting drunk?
The use of alcohol with GHB can produce so much sedation that your brain stops telling you to — ? breathe
As prescription drug (This could be any number of things, from antibiotics to paracetamol) has increased with direct-to-consumer advertising, there has been a parallel increase in prescription drug use.
(Patients/psycologists) cannot write prescriptions for themselves, but they do have considerable influence over what physicians do.
Some people are using GHB every two to four hours because if they don't use it, they cannot sleep, and get extremely anxious to the point of becoming (suicidal?).
As the brain adapts to the hyper-release of dopamine with (chronic/prolonged?) drug use, lack of the drugs causes severe craving and addiction.

Luxosus (talk) 04:16, 28 April 2008 (UTC)[reply]

"completely open-book, open-note, open-person (talk to anybody). " Are you kidding? Why did your teacher even give you a test? Are they testing your understanding of the material or your capacity to do research? I've never heard of an "open-person" test. What school do you go to? --Shaggorama (talk) 08:59, 28 April 2008 (UTC)[reply]

(Mildly off-topic...)I've had many such tests which are intentionally "open to any resource or person"; although rarely in the so-to-speak "introductory" level courses. It's really a philosophy of education; why bother testing knowledge solely through an exercise of memorization? What's the important skill - learning information, or retaining it for a short time? This philosophy places a certain level of trust on the student; similarly, the student must acknowledge that there's no point in "cheating" and must have a certain level of responsibility/maturity to gain anything from the class. I also know several professionals whose universities did not use grades or marks at all; upon graduation, they were given "summaries" written by their professors (like an open letter of recommendation). Sometimes this scheme makes it harder to quickly assess an individual ("3.2 out of 4.0" is easy to digest but is actually really not a very effective way to judge a person's ability, skill, dedication, intelligence, or much else). Nimur (talk) 13:30, 28 April 2008 (UTC)[reply]

Well, the point of it is not to memorize the answers but learn the information. I agree, it's kind of pointless, which is why I'm handing it in late and still not completely finished, but the course is more of an educational course in the sense that it's meant to teach us this information, rather than having us cram and study it. But as it turns out I am basically cramming to get this test in anyway, thereby defeating the purpose. :) Thanks for your help -- I don't really care what I put, so long as something's there. --Fbv65e del — t — c // 16:30, 28 April 2008 (UTC)[reply]

Nimur, I'd contend that the concept of cheating is meaningless in a test as open as this. "Ask anyone" seems to be inclusive of the option: "ask your classmate who already found the answer." --Shaggorama (talk) 07:00, 1 May 2008 (UTC)[reply]

and getting drunk fast is Binge drinking. Julia Rossi (talk) 10:21, 28 April 2008 (UTC)[reply]

Many of those questions seem not so much designed to test your general knowledge as your ability to regurgitate whatever the teacher or book said. I'd look through your notes and the book to see if the answers are there. StuRat (talk) 05:33, 29 April 2008 (UTC)[reply]

Poteries

Peut-on enregistrer les bruits aux potteries? —Preceding unsigned comment added by 99.237.101.48 (talk) 20:21, 27 April 2008 (UTC)[reply]

Est-ce que c'est une plaisanterie? What noise? And I guess the translator got "potteries" wrong. --Lisa4edit (talk) 21:02, 27 April 2008 (UTC)[reply]

Well, there was that X-Files episode where Jesus' command to Lazarus got recorded on a pot being spun in the vicinity, and when it was played as a record, it brought dead people back to life (or at least undeath, which seems a bit odd). --Trovatore (talk) 21:08, 27 April 2008 (UTC)[reply]

C'est "poteries", pas "potteries". Trovatore: Pourquoi penses-tu que c'est une plaisanterie?

Est-ce que l'épisode est réaliste? Merci. --99.237.101.48 (talk) 21:41, 27 April 2008 (UTC)[reply]

In theory one could record noise on pottery, just like one can record noise on a vinyl surface. The principle is the same but one would need either a very large pot, or extreme precision to be able to record a significant amount of sound and play it back. If anyone knows that it actually has been done (I mean outside X-files) please let us know, I am interested. --Lgriot (talk) 21:54, 27 April 2008 (UTC)[reply]

Mythbusters tried this. They couldn't get it to work really at all from what I remember. Dismas|^(talk) 04:42, 28 April 2008 (UTC)[reply]

Cette histoire des enregistrements faits sur la poterie n'est pas vraie ; il s'agit d'un vidéo canularesque fait pour le 1er avril en Belgique: [12]. Si vous comprenez l'anglais, vous pouvez lire ici une explication de la farce: [13].

P.S. : Si vous voulez poser des questions en français, vous aurez plus de succès ici: Wikipédia:Oracle.

(In English: the story isn't true; it has been an idea in science fiction for many years and was recently brought to attention by a April Fool's video made in Belgium (1st link). The second link explains the history of the hoax.) Lesgles (talk) 22:03, 27 April 2008 (UTC)[reply]

Pas de lieu Rhône que nous. Edison (talk) 02:56, 28 April 2008 (UTC)[reply]

(If it makes no sense, say it aloud. The less well you speak French, the sooner it will make sense.) Edison (talk) 00:48, 29 April 2008 (UTC)[reply]

This idea also was the key to the solution of one episode of CSI. Apparently, it works a lot better in fiction than it does in practice ;-).

Atlant (talk) 14:03, 28 April 2008 (UTC)[reply]

See Archaeoacoustics or this link as well. Also, I read Gregory Benford's short story, Time Shards, based on this idea, and it was pretty entertaining. -- Hi Ev 11:30, 28 April 2008 (UTC)[reply]

Est-ce qu'il y a des personnes qui peuvent faire une traduction? Les "traductrices" en ligne ne sont pas très utiles...

Merci pour les réponses!

Are there people who can make a translation? The "translators" on line are not very useful... Thank you for the answers! --99.237.101.48 (talk) 06:46, 29 April 2008 (UTC)[reply]

Translate what, exactly? Are you asking for the responses to be translated into French? Given that (a) you seem to be able to compose in English and (b) your IP address traces to Richmond Hill, Ontario, squarely inside Anglophone Canada, I have to wonder why you would want that. --Trovatore (talk) 01:25, 30 April 2008 (UTC)[reply]

A drug called APO 300

My 86 year old forther is taking a small blueish coloured pill with the letters APO 300 on one side. I would like to know what this drug is, and what it is for. He takes it at lunch hour

Thanks

Tom —Preceding unsigned comment added by 24.36.232.146 (talk) 20:22, 27 April 2008 (UTC)[reply]

The drug is called Apo-ranitidine (unfortunately, we have no article on this drug) and serves to reduce the production of stomach acid. This drug can be used in the treatment of various conditions, including heartburn, gastroesophageal reflux disease, and Zollinger-Ellison syndrome. It's intended purpose is usually to reduce pain from these conditions, although it can also prevent ulcers in some circumstances. It is from the general family of drugs called H2 antagonist. You can find more information about the drug here. Someguy1221 (talk) 21:16, 27 April 2008 (UTC)[reply]

Ranitidine, commercially known as Zantac. -- Kesh (talk) 21:25, 27 April 2008 (UTC)[reply]

Why did that completely not occur to me...Someguy1221 (talk) 22:22, 27 April 2008 (UTC)[reply]

Norepinephrine

It says that norepinephrine is both a stress hormone and a neurotransmitter. Does that mean when you are really stressed out you can think better, because you have higher levels of norepinephrine, or something like that? --131.215.166.126 (talk) 21:34, 27 April 2008 (UTC)[reply]

It means that norepenphrine functions and behaves both as a hormone (circulates in the blood) and a neurotransmitter (communication between neurons). It is secreted from the adrenal medulla along with epinephrine and trace amounts of dopamine, in addition to being present in the central nervous system that acts as a stimulatory neurotransmitter. Wisdom89 _{(_T / ^C)} 21:36, 27 April 2008 (UTC)[reply]

And yes, in a manner of speaking, norepinephrine does improve cognition as it is essential for maintaining alert and wakefulness, in addition to a slew of other functions. Wisdom89 _{(_T / ^C)} 21:37, 27 April 2008 (UTC)[reply]

In response to your question specifically, no, being stressed does not make you think better. The Blood brain barrier prevents large molecules in the blood stream from entering the nervous system, protecting it from most infections. Although norepinephrine can be found in the brain and in the body in general, the norepinephrine produced by the adrenal glands doesn't reach the brain. Norepinephrine in the brain is produced by neurons and stays in the brain.

Besides, think pracitcally: when you're stressed, don't you find that you are more grumpy, unstable and more prone to making bad decisions? Do you personally think that you or those around you "think better" when you're stressed? Faster maybe, but better?

Moreover, although drugs that boost norepinephrine availability have been useed to treat ADHD, the general idea that having alot of neurotransmitter in general makes you think better is a little confused. Having alot of a neurotransmitter may sound good but it's usually not and often can result in psychiatric disorders of chemical imbalance. Dopamine is commonly used as an example: dopamine deficiency results in Alzheimers, and dopamine excess can cause Schizophrenia. --Shaggorama (talk) 09:24, 28 April 2008 (UTC)[reply]

I was referring to norepinephrine as a neurotransmitter, not as a hormone. However, your response is not entirely correct as the locus coeruleus in the brain stem is indeed activated during periods of necessary vigilance when an individual is stressed and anxious, but this is just a minor point. The fact of the matter is the adrenergic afferents from the LC that release norepi stimulates the prefrontal cortex. Wisdom89 _{(_T / ^C)} 15:19, 28 April 2008 (UTC)[reply]

Agree with Wisdom99. Also, dopamine deficiency is associated with Parkinson disease, not Alzheimer disease. The latter is usually associated with acetylcholine deficiency. --David Iberri (talk) 16:32, 28 April 2008 (UTC)[reply]

April 28

Website with yellow text on a black background (and some blinking elements)...

Man, why does that hurt my eyes and screw up my vision so much? I can only look at it for maybe ten seconds before my vision is completely screwed up (blurry and wobbly with 'stars' and intrusive afterimages) and my eyes start watering. --Kurt Shaped Box (talk) 00:13, 28 April 2008 (UTC)[reply]

Funny, I heard the same thing the other day from someone whose work essentially requires staring at a computer screen all day long...It has never bothered me, personally. Someguy1221 (talk) 00:25, 28 April 2008 (UTC)[reply]

I never usually have problems myself. I do occasionally see afterimages (a bit like if you've been staring at the sun - but less so) if I've been reading bright-on-black text on my screen for a long time - but this was the first page I've ever seen in a long time that actually, literally *hurt* me to look at it. Red-on-navy-blue text (for some reason, that used to be a quite popular choice for personal websites a few years back) is not much fun for me either... --Kurt Shaped Box (talk) 00:42, 28 April 2008 (UTC)[reply]

Hi. Black text on white background leaves an afterimage in my eyes too, even if I turn the computer's brightness and contrast to the lowest possible. Also, I think a developer might have changed Wikipedia's background colour from purple-white to blue-white a couple of months ago. Most websites don't *hurt* my eyes, but if I use the computer for too long then sometimes I will get a headache. Thanks. ~A H 1^(TCU) 00:55, 28 April 2008 (UTC)[reply]

Look at Action potential. I'm no expert, but as far as I understand it the chemicals (e.g. electrolytes) in your cells get out of whack and that may cause pain. There are also effects of nerves firing electrical impulses at certain intervals. Photosensitive epilepsy is probably over-reported, but migraines and headache fall well within the spectrum. (Oops had my desks mixed up.) Lisa4edit71.236.23.111 (talk) 04:47, 28 April 2008 (UTC)[reply]

Virginian Tree Identification

Do basswoods grow in Virginia? I'm trying to identify a tree that has heart-shaped leaves with ridged edges, and that narrow into a thin stinger-like point at the pointy end of the heart.

It looks very similar to the picture of the leaf under the basswood article:

http://en.wikipedia.org/wiki/Image:Lisc_lipy.jpg http://en.wikipedia.org/wiki/Basswood 71.174.18.26 (talk) 00:44, 28 April 2008 (UTC)HotSpringsMonkey[reply]

According to my Audubon guide, Virginia is at the southern limit of American Basswood and the northern end of White Basswood aka Linden aka Basswood. In my (Ontario) experience, the leaves are quite large, 3-5" across, and the mature trees are often hollow, though still lively. They're kind of a messy-looking tree, unlike, say, a beech or oak.

"Leaves alternate in 2 rows...3 or more main veins from base, often toothed...Flowers in branched clusters...5 petals (sometimes none)". Best I can do! Franamax (talk) 22:21, 28 April 2008 (UTC)[reply]

What will happen if scientists ever see the beginning of time?

Is this possible? Every once in a while I read in the paper that scientists, using telescopes, have went back a few more million years and now see the universe in it's infancy. Is there a limit here? And if they ever do see the beginning of time, can thier minds handle it? Will thier minds shut down, or will it be like peering into subatomic realms, where they know they've seen something but cant explain it? --Sam Science (talk) 02:34, 28 April 2008 (UTC)[reply]

Scientists do not see time. They see electromagnetic radiation (of which visible light is a part). When you see that they are seeing far back in time, it means that the particles (or wavicles if you want to be weird) originated a long time ago and are just now making it to Earth so scientists can see it. So, is it possible to see the very first particle ever emitted? Yes. Will we see it? That is a math problem. The particle travels at the speed of light in basically a straight line. Once it passes Earth, it is too late to try and catch it. Of course, this assumes that space doesn't wrap around on itself giving the particle another chance to swoop by Earth. As for your odd pondering about melting minds and whatnot... It is not reasonable to assume that seeing an electromagnetic particle will melt anyone's mind. It is just a little speck of energy. The importance of the speck (being the first one created) is placed on it by those doing the research, not the speck itself. -- kainaw ™ 02:58, 28 April 2008 (UTC)[reply]

So no face melting?--Shniken1 (talk) 05:25, 28 April 2008 (UTC)[reply]

There is a limit of electromagnetic viewing, as the universe was originally opaque. -mattbuck (Talk) 11:16, 28 April 2008 (UTC)[reply]

The cosmic neutrino background gets you back much further, if we ever manage to detect it. Algebraist 11:23, 28 April 2008 (UTC)[reply]

The universe is the same everywhere, and there will always be light from any era that was emitted at just the right distance away to be reaching us right now. The reason we can't see the earliest photons is not that they've passed us but simply that they were long ago reabsorbed. As mattbuck said, the universe was opaque (to electromagnetic radiation) until about 375,000 years after the big bang. We've already seen light from that era (the CMBR), and we'll never see any earlier light because unlike the CMBR it didn't survive to the present era. -- BenRG (talk) 12:08, 28 April 2008 (UTC)[reply]

"The very first particle ever emitted" implies a level of synchronicity which is not currently consistent with theory of space-time. See our article on relativity of simultaneity for an introduction to this sort of mind-bending topic. Briefly, "the first particle ever emitted" is a different particle for two different observers, in different reference frames (depending on where you are and how you're moving). This sure does make it difficult to define how the universe started! There are some limits, imposed by causality, though, so some particles are definitely precursors to other particles; nonetheless, the "first event in the universe" is probably not the best way to think about the early universe. Nimur (talk) 13:39, 28 April 2008 (UTC)[reply]

Actually in cosmology there's no congruence of different notions of simultaneity the way there is in special relativity. There's a privileged time coordinate called cosmological time which can be used to order events that aren't causally connected. The special relativistic notion of "observer" doesn't really carry over to general relativity. People do use the word "observer" in general relativity, but they mean something completely different by it (in special relativity it's usually a global inertial reference frame, in general relativity it's usually a worldline). I agree that "the very first particle ever emitted" doesn't make much sense, but that's for quantum mechanical and quantum gravitational reasons. -- BenRG (talk) 19:38, 28 April 2008 (UTC)[reply]

The article Cosmology says the universe is ~13.7±0.2×10^9 years old. Age of the universe says "13.73 billion years, with an uncertainty of about 120 million years," which overlaps the other article but is a more precise claim. The Hubble space telescope has reportedly [14] "seen" ancient white dwarf stars which are 12 to 13 billion years old. We non-astronomers get the impression that astronomy is creeping closer and closer to the "first light" of the universe, emitted some time after the "big bang." In 2001, astronomers said [15] that after the big bang the universe was too hot for complete atoms to form, but that after 300,000 years hydrogen atoms could form, and that half a million years later, light-emitting objects could form. By subtraction, 13.73 billion -.8 billion yields 12.93 billion years (+/- yadda yadda) as the oldest light emitting objects. Is there any reason one might not read in science news one day that we have now observed these first light emitting objects? Is it possible that Hubblle's light from 12 to 13 billion years ago includes some of the first light emitting objects? Edison (talk) 00:44, 29 April 2008 (UTC)[reply]

I found a 2003 article which seems to say the Hubble 'scope saw these first light emitting objects. The light was emitted when the hydrogen atoms filling the universe was ionized enough to permit light to propagate. The estimated there weree 400 million "proto-galactic objects" in the universe at that time, when the "dark ages" of light absorption by hydroegn atomes ended, which the Arizona State University scientists estimated to be about 1.3 billion years after the big bang. The numbers seem rather imprecise from various sources. Edison (talk) 00:59, 29 April 2008 (UTC)[reply]

Simplified timeline is as follows:

Recombination - approx 300,000 years After Big Bang; universe has cooled enough for neutral hydrogen and helium atoms to form; photons that we now see as cosmic microwave background were last scattered at this time; these are the "oldest" photons that we will ever see.
Dark ages - approx. 300,000 - 100m years ABB; universe is filled with neutral hydrogen and helium; photons that will form CMB propogate freely; no stars/quasars have yet had time to form.
First quasars and Population III stars form - approx 100m years ABB; Spitzer Space Telescope may have captured photons emitted by these objects; Keck II telescope has captured images of proto-galaxies from 500m years ABB.
Reionization - starting approx. 150m years ABB; photons emitted by first stars and quasars ionise neutral hydrogen atoms in inter-stellar space; universe is filled with low-density plasma; most CMB photons are unaffected, but some Thomson scattering can be detected; plasma absorbs light from first stars and quasars at hydrogen line wavelength. Gandalf61 (talk) 10:00, 29 April 2008 (UTC)[reply]

Day on Mercury

How long is "day" on Mercury? Night? How long does it take for Mercury to rotate around its axis? —Preceding unsigned comment added by 24.7.54.224 (talk) 06:56, 28 April 2008 (UTC)[reply]

Have you seen our article on Mercury (planet)? If the article doesn't answer your question, feel free to come back here and provide some more detail on what you're looking for. Thanks, Confusing Manifestation(Say hi!) 07:32, 28 April 2008 (UTC)[reply]

Mercury rotates around its axis, relative to the fixed stars, once in about 58.7 Earth days. It revolves around the sun exactly 2/3 as fast, or once in about 88 Earth days. To an observer on Mercury, the Sun moves across the sky with the difference of these rotation rates, resulting in a day (sunrise to sunrise) of 3*58.7~176 Earth days. "Day" (sunrise to sunset) and "night" are of course each half as long. --mglg_(talk) 00:26, 29 April 2008 (UTC)[reply]

The relative length of day and night would depend on where on the planet you stand when. --Lisa4edit (talk) 00:55, 29 April 2008 (UTC)[reply]

See Mercury (planet)#Spin–orbit resonance for an explanation of why the day and year have an exact 3:2 ratio. Also see the last paragraph in Mercury (planet)#Orbit and rotation for a description of an interesting phenomenon (the Sun sometimes "turns around and goes the other way" when viewed from Mercury). StuRat (talk) 05:08, 29 April 2008 (UTC)[reply]

Generational LEDs

I was looking into emergency lighting for my car and came across the LED lit ones being listed as "Generation I LEDs" or "Generation III LEDs". I've never heard of different generations of LEDs before, is there any difference between them? -- MacAddct  1984 ^{(talk • contribs)} 15:02, 28 April 2008 (UTC)[reply]

Are you sure your not getting confused by something like [16]? This is referring to the generation of the device given by the flashlight company, not the LED per se. Generally speaking, LEDs, as with most electronic devices are getting all the time. LEDs in particular are getting more efficient (which I believe includes brighter for a given voltage level, brighter overall and better luminous efficacy) as well as cheaper to produce. IIRC the Colour Rendering Index is also being improved as well as different Colour temperatures so they are suitable for people with different preferences (both probably not that important for a flash light) Nil Einne (talk) 17:44, 28 April 2008 (UTC)[reply]

That's what I had thought at first, but the descriptions certainly seem to imply different models of LEDs. Compare: [17] and [18]. "66 Hyper Bright 5mm Generation I LEDs" vs "Generation III LED's" -- MacAddct  1984 ^{(talk • contribs)} 18:03, 28 April 2008 (UTC)[reply]

It seems to be mostly a marketing term. Manufacturers group their products by specs like operating voltage, color, composition and light output. Generation III is usually used for LEDs that produce bright "white" light and are used to replace lightbulbs. Generation II seems to be a company specific term (http://compoundsemi.com/documents/view/generic.php?id=709). This http://olla.ichf.edu.pl/lect/SS2005/H_Boerner.pdf may contain an explanation or may refer only to a specific type. --Lisa4edit (talk) 21:48, 28 April 2008 (UTC)[reply]

Medical explanation.

Is there a medical explanation for as to why someone is obsessed with religion and philosophy? I have been studying "Biology and human behavior" and the man lecturing claims that it has to dd with an imbalance in the brain. Could someone please elaborate on this for me? Thanks. —Preceding unsigned comment added by 72.40.54.255 (talk) 20:31, 28 April 2008 (UTC)[reply]

Mixing science and religion is always a recipe for murky results. What your lecturer might have been referring to is Obsessive-compulsive disorder. But the phrase "obsessed with religion" is usually not understood as referring to the medical disorder, but more to a psychological state (or disorder) Obsessive love is an article that could shed light on some of the issues involved, but I wouldn't call it a collection of well established facts. As with most psychological issues there is a fine line between common and accepted and harmful and pathological. If someone spends all their free time meditating on the deeper sense of being that's o.k. If they can't sleep because of it and skip work or don't eat and don't socialize, that's reason for worry. If they start harming others or themselves that's pathological. There may be a "chicken and egg" causality though. E.g. if you don't sleep you can develop symptoms that are indistinguishable from bipolar disorder, but bipolar disorder can/does cause insomnia. Chemical imbalances in the brain can be caused by the system not being set up correctly or by it being knocked out of order.--Lisa4edit (talk) 21:17, 28 April 2008 (UTC)[reply]

There are two uses for the word "obsession": the clinical disorders mentioned by Lisa4edit above, plus the more general layman's term to refer to preoccupation or fascination with a subject. Neither are restricted to religion and philosophy: clinical obsessive disorders can vary in subject and severity. As for the second, it is perhaps difficult to ally with specific scientific reasons. We all have interests and things we enjoy thinking about: science, philosophy, sport, archeology, Wikipedia, stamp-collecting, bird watching, and so on; some of us are more "obsessed" by our interests than others. An elite sportsman, for example, is extremely single-minded. Would you class that as a pathological imbalance in the brain? Or just a response of natural talent and application? An academic scientist is driven to investigate, observe, study, research and develop ideas and natural phenomena. Some people spend much time considering metaphysical matters. It is entirely natural. Gwinva (talk) 05:31, 29 April 2008 (UTC)[reply]

LHC

When in May does the LHC start up. Is is midnight May 1 or later? Thanks *Max* (talk) 21:14, 28 April 2008 (UTC).[reply]

Judging by this http://cerncourier.com/cws/article/cern/33789 looks like it'll be June. They have to cool the ring before they can inject the first beam. I guess that would be what you call start up. --Lisa4edit (talk) 21:31, 28 April 2008 (UTC)[reply]

...But that doesn't mean they start collecting data in June. According to Peter Woit's blog they're planning a physics run at 5 TeV starting in September, and at 7 TeV in April 2009. I'm not sure where he got those dates (he cites two sources, but I can't find them in either one). -- BenRG (talk) 21:56, 28 April 2008 (UTC)[reply]

You're right. That's when it starts getting interesting. (Remember though that LHCb already got nice data from cosmic rays during the equipment testing.) But things don't usually happen when they are supposed to. I could get at the sources but they had nothing really interesting on dates, except that the June date for injection might be "late" June. They plan to run it at 5TeV and then shut down around X-mas to get it ready for 7 TeV. I'd say keep and eye on the Cern Courier and that blog but don't hold your breath. boredom - anticipation - frantic exhilaration, repeat :-) —Preceding unsigned comment added by Lisa4edit (talk • contribs) 22:28, 28 April 2008 (UTC) oops--Lisa4edit (talk) 22:30, 28 April 2008 (UTC)[reply]

Helium: Lewis Structure

Hello. Why are helium's valence electrons paired to the right in the Lewis dot diagram? Can helium's valence electrons be paired to the top? Thanks in advance. P.S. May you please name some ionic compounds in which carbon is a cation? --Mayfare (talk) 22:50, 28 April 2008 (UTC)[reply]

I vaguely remember there's a rule about where the pair goes, but you'll rarely find a high school teacher and never find a professor and/or chemist who actually cares. The point is that there are two valence electrons in the same orbital, so as long as that's clear...As for carbon being a cation, there is the general class of molecules called carbocations. Most of these that you find in chemistry are merely reactive intermediates, but some can be isolated, especially certain aromatic carbocations, such as many salts cotaining tropylium. Someguy1221 (talk) 23:00, 28 April 2008 (UTC)[reply]

Aurora borealis from space?

Is this photo (from WikiCommons) real or fake? According to its deletion request page, it cannot be real because of the location of the sun and where the aurora seems to be over. Kreachure (talk) 23:18, 28 April 2008 (UTC)[reply]

According to the info sheet it was taken from Atlantis. Maybe you could ask NASA for more details (http://www.nasa.gov/help/contact/index.html). Science photos are often "enhanced" to show details or make a point. There was quite a bit of shouting back and forth about red tints in photos of some planets while back. There are instruments/cameras that collect "image data" outside of the human visual spectrum. If you assign a color we can see to that information and overlay it over a visual spectrum image that would not be a "fake", but humans would not get the same image if they looked at it. --Lisa4edit (talk) 00:34, 29 April 2008 (UTC)[reply]

The thing is that the image has a delete proposal because it's not certain that it's from NASA. I was expecting aid that didn't involve contacting a U.S. government agency :P. Their contact page says that they're not too worried about answering inquiries such as this one; so maybe someone here can help? Kreachure (talk) 15:03, 29 April 2008 (UTC)[reply]

I'll see if my astronomer can help out, but that will take a while and he may not be able to say anything definitive. Meanwhile since NASA is up to it's usual "impressive efficiency" because they have to shovel all their "leadership", you might have more luck e-mailing these guys with your picture and question: [email protected] I've met a couple and they are nice folks and helpful. Just tell the deletomanicas to hold their horses. --Lisa4edit (talk) 22:07, 29 April 2008 (UTC)[reply]

Follow the "see also" link from the deletion request page and you'll see a message from NASA saying why the picture must be a composite. The aurora is too bright, the wrong color, and probably in the wrong place. --Anonymous, 00:22 UTC, April 30, 2008.

Well, apparently NASA did send a response. (I'm impressed ;-) I think there is a way to move the image to your user page. That way it would not be "lost". Since NASA confirmed it to be a composite why not label it as such. With a title like "artist rendering of an aurora viewed from space" or "composite modeling aurora effects above the atmosphere" people would know what it is. I don't think you'll be able to put it back into commons until you've found the "copyright owner" though. BTW it might well not be NASA but ESA or one of the others. --Lisa4edit (talk) 03:59, 30 April 2008 (UTC)[reply]

April 29

Relation between isospin and up and down quark content

I wrote the following in the List of baryons

Up and down quarks each carry isospin 1⁄2. Due to Pauli's exclusion principle, quarks of the same flavor must have their isospin aligned. Three aligned up and down quarks would make a particle with isospin 3⁄2, while two up quarks (who must be aligned) and a strange quark would make a particle with isospin 1.
— Headbomb

And then I go on and detail explicitely what particles go with what isospin etc... Check it out if you want List of baryons#Isospin and up and down quark content.

I'm not 100% sure of myself, and I can't find reference on it. So if you can confirm that I understood things correctly, that would be great, and if you could provide me with a reference for this that would be even better (preferably a specific passage within a book, or an article specifically about this. [[::User:Headbomb|Headbomb]] ([[::User talk:Headbomb|talk]] · [[::Special:Contributions/Headbomb|contribs]]) 00:01, 29 April 2008 (UTC)

Carbonyl chemistry

To be straight up: It's a homework question. But I have been trying to do it, to no avail. Can someone at least point to a correct direction? Here is the problem [19] Will the alkyne be the nucleophile? But surely the alpha carbons of CN and/or the ester would form the enolate/nucleophile. I'm also suspecting that it's intramolecular. Then there's also the methyl group that could form an enolate. So, I'm not even sure which is the nucleophile and electrophile. Any suggestions?128.163.224.47 (talk) 00:57, 29 April 2008 (UTC)[reply]

:My organic chem is a bit rusty but I don't think this is an enolate reaction. An enolate could not form on either molecule here. Could you give some info on what context this question was asked? What type of chem? Type of questions before and after? --Shniken1 (talk) 02:46, 29 April 2008 (UTC)[reply]

You could form enolate (or similar resonance-stabilized α-carbanion) at methyl of ketone or at CH between the two nitriles or at CH between the two esters. Or you could deprotonate the alkyne CH. Which is most acidic (especially remember to consider resonance stabilization)? Once you have a nucleophile (something that is not present until you deprotonate something here), gotta figure out what it could attack. What electrophile(s) are present and which are most electrophilic? Do enolates have a preference for certain types of electrophilic structures? Is there a reasonably good ring-size available by intramolecular attack? Shniken1's got a good point (and a good crutch for problem-sets:)...what similar problems have you already seen? DMacks (talk) 03:10, 29 April 2008 (UTC)[reply]

Matrix of structural similarity of proteins

Where can I get a matrix of structural similarity of proteins? CATH is probably what I want, but I am not sure how to proceed, probably because my background is Computer Science, not Biology.

What I actually want is a list of proteins IDs with their amino acid sequences, and a matrix in which cell i,j gives the structural difference between protein i and protein j, as a real number. --Masatran (talk) 10:11, 29 April 2008 (UTC)[reply]

Defining the 'difference' between two proteins in a biochemically-meaningful way is a nontrivially difficult problem. If you're interested in the primary structure only (just the amino acid sequence), you could adapt the protein-protein BLAST (blastp) algorithms to your task. They will boil your sequence-sequence similarity down to a real number, at least.

If you want to compare secondary or tertiary structure, you're in for a world of hurt. Determining how proteins will fold based only on their amino acid sequence is still an open problem in computational biology, and if you can do it successfully you will be showered with glory, riches, and possibly a Nobel prize. If you limit yourself to known 3D structures in a curated database (like the Protein Data Bank), you will still have to decide a basis for comparison. Are two alpha helices 'similar' if they have the same length and charge distribution, even if they contain completely different amino acids? TenOfAllTrades(talk) 12:32, 29 April 2008 (UTC)[reply]

Someone else asked the same question a while back. Check out http://folding.stanford.edu/ Folding@Home. As tenofalltrades explained folding is the key to understanding how proteins work. These guys are using computer time donated by people to do the computing of various folds for them. They've adapted their program to run on some game machines now and that helped a lot. Look at the "science" page for some basic info. --71.236.23.111 (talk) 13:02, 29 April 2008 (UTC)[reply]

Unknown animal: very tiny snake-like black thing.

I live in Minas Gerais, Brazil, and today I've found a very, very tiny snake-like thing in my room. It's not a worm, it has scales and everything, no legs, but it just very tiny. The scales are black, btw. It's about 7-8 cm long and 3mm thick, and moves like a snake. I guess it's an reptile of some sort. Any ideas? 189.15.70.185 (talk) 12:53, 29 April 2008 (UTC)[reply]

Sorry snakes freak me out, so I'll forego looking through the Wikipedia snake pages. As to the size, it's spring. That makes it highly likely that your tiny snake is a baby snake. I'd not wait to find out what it'll grow up into. --71.236.23.111 (talk) 13:13, 29 April 2008 (UTC)[reply]

I've seen snakes that small before Nil Einne (talk) 13:48, 29 April 2008 (UTC)[reply]

[20] & Leptotyphlops bilineatus for two examples of claimed to be smallest snakes in the world (I don't think they're the same thing). BTW neither have pictures. Nil Einne (talk) 13:53, 29 April 2008 (UTC)[reply]

Given the locations cited neither of those two seems likely in Brazil, but it makes the point that it might possibly be a full grown specimen. Have you tried this: http://pt.wikipedia.org/wiki/Lista_de_cobras_pe%C3%A7onhentas_do_Brasil ? If you can't read Portugês you can look at the "Nome binomial" in the boxes and then look up the description on the English pages. --Lisa4edit (talk) 16:00, 29 April 2008 (UTC)[reply]

Well no, my point was more that such tiny snakes to exist (and apparently in several places). It may be some other kind of Leptotyphlops, they appear to be quite small in general although the others that I could find lengths for were 20-30 cm when full grown, not 8cm Nil Einne (talk) 22:43, 29 April 2008 (UTC)[reply]

Whistling teakettle

Why, just before it whistles, a teakettle suddenly becomes less noisy than before? It's as if fewer molecules are hitting the sides of the kettle. Thanks. Imagine Reason (talk) 13:21, 29 April 2008 (UTC)[reply]

I would guess that as the pressure builds up it retards boiling, then, as the steam escapes, the pressure lowers and rapid boiling continues. StuRat (talk) 16:42, 29 April 2008 (UTC)[reply]

Actually, the same thing happens when you boil water in an open vessel. See the explanation at The Straight Dope. --Rallette (talk) 16:49, 29 April 2008 (UTC)[reply]

Name of muscles on either side of the lower spine?

Today the results of an X-ray on my spine came back, and the doctor who examined the results told me that the "muscles on either side of the spine in my [lower] back" were spasmodic. I am going back some time next week to discuss further with my GP, but I was wondering, as the doctor never told me, what are the names of the muscles surrounding the lower spine? (I don't think this qualifies as asking for medical advice, as I am not asking for advice, merely the name of certain muscles) 88.104.246.77 (talk) 13:22, 29 April 2008 (UTC)[reply]

There are quite a lot, but they are listed here: Table of muscles of the human body#Back -- MacAddct  1984 ^{(talk • contribs)} 13:27, 29 April 2008 (UTC)[reply]

Thank you. It's quite a confusing list for someone who doesn't understand most medical terms, but it should help. I'll probably just ask my GP for what specific muscles are affected. 88.104.246.77 (talk) 13:32, 29 April 2008 (UTC)[reply]

(ec) There are a number of muscle groups in the lower back; balancing and walking erect take a fair bit of tweaking. Your best bet is to pull out a copy of Gray's Anatomy and have a look around. (Bonus—the entire 20th editing of Gray's is in the public domain and online: [21].) You'll want the myology section, perhaps starting with the deep muscles of the back and the muscles and fasciæ of the iliac region. Scroll down to the figures. (Many of our articles also use Gray's figures.) TenOfAllTrades(talk) 13:35, 29 April 2008 (UTC)[reply]

(ecII) Gray's Anatomy in online at Bartleby. The deep muscles are here, and the iliac are here. --Milkbreath (talk) 13:38, 29 April 2008 (UTC)[reply]

Interesting factoid: I was interested in getting higher-res scans of Gray's for Wikipedia and contacted Bartleby.com and got a curt response from the owner saying that Wikipedia was using the scans without his permission and that he held copyright over them (presumably because he colored in the 1918-edition pictures, or perhaps for doing the scans (which would not be legit)). I didn't pursue it any further, but I do have in the back of my mind that some day I'd like to get hold of a copy and do really nice scans of it. --Sean 17:55, 29 April 2008 (UTC)[reply]

Spinal erectors. Vranak (talk) 16:54, 29 April 2008 (UTC)[reply]

Time of Unconsciousness

How long does a person typically remain unconcious after being knocked out from head trauma? --Think Fast (talk) 15:07, 29 April 2008 (UTC)[reply]

There's no 'typical' length of time. It can range from 'a few seconds' to 'forever'. Even after consciousness is restored, the victim may be disoriented, nauseated, and headachey—the Hollywood picture of the hero leaping back to his feet to chase down the bad guy and defuse the bomb is very misleading. The trauma may also rupture blood vessels in the brain, leading to bleeding that requires surgical intervention. Permanent damage may also have occurred, with a wide assortment of neurological sequelae. TenOfAllTrades(talk) 15:51, 29 April 2008 (UTC)[reply]

Spin

Can someone explain to me what spin (physics) is? There is what most people would think of as spin, like what a basketball has when you put it on the end of your finger and spin it around with your hand and, apparently, there is another kind but the linked article does an poor job of explaining it to non-physicists. Maybe it is just too technical to explain to non-physicists but hopefully someone here can try. Recury (talk) 17:24, 29 April 2008 (UTC)[reply]

I think you might be looking for the Spin (physics)#Spin and magnetic moments section. If you take a spherical shell with a uniformly distributed surface charge density (or maybe it is a sphere with uniformly distributed volume charge density; can't remember) and spin it, characteristics of the magnetic field you get looks similar to that of a particle with spin. Even for neutrally charged particles like the neutron, the magnetic field looks similar to a spinning charge distribution (imagine perhaps two spherical shells with equal but opposite charges, one inside the other). I don't believe it is known (and perhaps it doesn't matter) whether or not the particle is actually spinning in the classical sense of the word; it simply looked like it to someone studying the electromagnetic properties of the particle, and that was the inspiration for using the name for that quantum number. --Prestidigitator (talk) 18:03, 29 April 2008 (UTC)[reply]

Wouldnt the net curl of such a field be zero? I had the vague impression that diamagnetic and paramagnetic properties required that the curl be non-zero. I havent studied it mathematically. thats just my intuition speaking.Em3ryguy (talk) 20:48, 29 April 2008 (UTC)[reply]

No, I suppose not. Thinking two dimensionally, each particle would be a sort of curl dipole and the whole material would be a sort of curl dielectric. If all the particles align then it would be as if there was a net curl on one side and the opposite curl on the other and any applied magnetic field would be either strengthened or weakened. Why didnt I see that before? Em3ryguy (talk) 00:57, 30 April 2008 (UTC)[reply]

Cross points on star/galaxy photographs

In many astronomy photographs, stars and galaxies will often have 4 points coming out of the star/galaxy. These points go up, down, left and right. What are these lines/points and what causes them? e.g. http://antwrp.gsfc.nasa.gov/apod/ap070516.html Thanks. --Rajah (talk) 18:36, 29 April 2008 (UTC)[reply]

Those are most commonly diffraction spikes from the internal structure of the telescope. — Lomn 19:01, 29 April 2008 (UTC)[reply]

Awesome. Thanks! --Rajah (talk) 19:58, 29 April 2008 (UTC)[reply]

Hot-tub - Spa - Water treatment options.

Briefly - I bought this brilliant Hot Tub for use in our garden in Scotland - and we love it - made in Carlsbad Calif. But the water treatment chemicals are Chlorine based - expensive - and they antagonise my skin - badly - so much so I don't use it as much as I would like. So, the manufacturers suggested I use their "Non-Chlorine" water treatment - but it still contains chlorine based chemicals - so that's a non-starter. Question - can I use a splash of ordinary household liquid bleach before each use, and then change the water every couple of weeks or so - I know that won't harm my skin, but could it harm the Tub/Pumps/Filters etc? You will understand that the manufacturer isn't keen as they want me to keep on purchasing their "product specific" (expensive) chemicals. Thanks. 92.10.186.2 (talk) 18:47, 29 April 2008 (UTC)[reply]

The non-chlorine chemicals I use in my spa are bromine-based. The other alternative I've heard of is an "ozonator", although last I checked those were out of my price range. --LarryMac | Talk 19:06, 29 April 2008 (UTC)[reply]

"Ordinary household liquid bleach" is often the same chlorine-based chemical as pool chlorine, just diluted more. So on the one hand, it would certainly not harm the pool equipment, but on the other hand, by the time you add enough to have any substantial effect on the water, you're at the same point as if you'd chlorinated the pool as normal. The reason people use "pool chlorine" is because it is more concentrated, so it takes less of this chemical than of laundry bleach to get the same chlorination level in the pool (no effect on the result) and/or because it also contains stabilizers that keep the chlorine active for longer (less chlorine needs to be added overall). There are lots of other pool-water sanitizing products...bromine is often used in hot-tubs (it's similar to chlorine but more stable at higher temperatures), ozone or silver are more expensive alternatives. DMacks (talk) 20:45, 29 April 2008 (UTC)[reply]

I would strongly recommend an ozonator. If you don't have wild crowds in your hot tub every night, the ozonator may be all the sanitizer you need routinely need (although you may still want to "shock" the tub occasionally). Some ozonators use germicidal lamps to make ozone; these will last several years and then need to be replaced. (Intheory, the lamp alone ought to be replaceable but in practice, it usually isn't.) Others use a corona discharge and they allegedly last a lot longer.

Atlant (talk) 22:55, 29 April 2008 (UTC)[reply]

Another option might be to just change the water more often. This might be a good choice if you can use the waste water to water your lawn, which should work if it's not full of nasty chemicals. One downside, for an outside hot tub the water you add is likely to be ice-cold if added by hose, requiring time and money to heat it electrically in the hot tub. On the other hand, for an indoor hot tub you may have a hot water supply line from your water heater which can provide cheaper preheated water using natural gas to heat it. However, getting the waste water from an indoor tub to the lawn could be tricky, requiring a siphon hose out the window.

Also, if you haven't yet experimented with reducing the quantity of chemicals in the water but still using the same ones, try that. Showering before you use the tub will also reduce the quantity of bacteria you introduce each time. StuRat (talk) 17:02, 30 April 2008 (UTC)[reply]

Alcohol consumption causes hiccups?

It is an established phenomenon in humorous comic books that excessive alcohol consumption causes hiccups. In real life, I have experienced it very seldom. I am experiencing it right now, but this is the first case in over half a year. My question is, how and why does this happen? JIP | Talk 19:38, 29 April 2008 (UTC)[reply]

There doesn't appear to be a solid explanation, but this page has some informed speculation. TenOfAllTrades(talk) 20:08, 29 April 2008 (UTC)[reply]

Drinking anything that has been chilled can cause hiccups. I think this is more likely the cause than alcohol.--Shantavira|^{feed me} 07:19, 30 April 2008 (UTC)[reply]

It might have some relation with spicy/hot food that's consumed along with it (at least that's the practice in India). Also, may be, alcohol could be making the whole respiratory control less coordinated. But, both the explanations I gave are pure guesses.

Regards.

Ketan Panchal, MBBS (talk) 07:25, 30 April 2008 (UTC)[reply]

Oh, so now we're editing wikipedia whilst drunk, are we? ;) Ziggy Saw dust 17:05, 30 April 2008 (UTC)[reply]

Ostrich egg in microwave

Is this real or fake: http://www.youtube.com/watch?v=IMM7s5RRqT4 ? Has anyone else tested this and can we calculate what the egg/bomb's explosive force would be? Thanks. --Rajah (talk) 20:00, 29 April 2008 (UTC)[reply]

I don't understand why the entire oven would burst; if the egg were to explode, the shell would crack and the liquidy insides, (possibly boiled / gasified) would make a mess... but it seems very unlikely that the egg could detonate the oven. This is especially unlikely because microwaves are really not designed to be airtight; so the pressure would easily seep out, rather than building up and exploding. Many microwaves even have exhaust fans and vents to help air circulate. Nimur (talk) 04:43, 30 April 2008 (UTC)[reply]

I've "done the experiment" with a chicken egg, and they do have an amazingly high amount of explosive force when microwaved. In addition to the shell being able to contain a high force when equally distributed, the egg also cooked from the outside in, meaning the solid egg also contains and evenly distributes the force. Once a crack does develop, all of the force built up from the steam releases at once. It blew the door of the microwave open and made a mess, in my case, but no permanent damage was done. StuRat (talk) 16:44, 30 April 2008 (UTC)[reply]

HIF alpha expression

Is the HIFalpha protein consitutively expressed? I know ARNT is, but I can't seem to find out if HIFalpha is! Thanks 163.1.214.119 (talk) 21:51, 29 April 2008 (UTC)[reply]

This pubmed abstract seems to imply it is: http://www.ncbi.nlm.nih.gov/pubmed/11292861 and that is it normally degraded, but hypoxia induces it action. --Rajah (talk) 04:17, 30 April 2008 (UTC)[reply]

in fact, wikipedia's own article Hypoxia-inducible factors implies it's constitutively expressed. (citation needed, of course) --Rajah (talk) 04:20, 30 April 2008 (UTC)[reply]

Implosion bomb

Would it be possible to generate a powerful implosion by using a dust made from a material that binds with nitrogen? If so, what material could be used? This is just idle curiosity, and I don't plan on actually building one. — DanielLC 22:00, 29 April 2008 (UTC)[reply]

The times when I could remember how to reformulate shoe-polish are definitely over, but why would you want to have an implosion. The reason you have that in nuclear bombs from what I read is to get the material to critical stage. For nitrogen you could just use an explosion. (Bat-cave and cigarette-lighter should not be mixed!). If you want a dust explosion, there are very few things that won't do. Just depends on how fine and the right mix. Flour's a well-known one. Sugar has recently been sadly demonstrated by a sugar plant in Georgia. Lots of bang for supermarket buck. Don't try any of this at home or in "interesting" places like Iraq!!! --Lisa4edit (talk) 22:25, 29 April 2008 (UTC)[reply]

An implosion would be cooler, if only because it's not the way it's normally done. I forgot to mention, all products would need to be solid or liquid, rather than gas. The idea is that it spreads out trough the air, then is heated to a critical temperature and "explodes", but absorbs gas rather than releasing it. I think the dust staying solid might prevent it from working, as the middle of the dust wouldn't be able to oxidize. — DanielLC 22:52, 29 April 2008 (UTC)[reply]

As far as I can make out that would depend on the relative particle distribution in the dust-cloud and the ignition point. But even imagining the math behind that gives me a headache. Your best bet would probably be mixing an "accelerant" type chemical with the actual explosive agent. Given that you want to direct the explosive force inward (which makes it an implosion) you'd then have to add "projectile" material to redirect it outward again, unless you want to use all the force to compact material in the center; sort of like creating a glass drop or diamond depending on the oomph. If you could get your liquid component to form a bubble that would confine the dust and then have most of the force of the dust explosion go toward the center which is the math headache with relative velocities and energy transfer, that should work. You might run out of oxygen in the middle though. That means that one of your chemicals also has to release some. As basis for thought experiments you could visualize an old TV tube. Gas or liquid mist isn't that big a difference. Sorry, I'm more of a "trial and error" kind of person than a "what if", this is about as far as I can take it without going in to major research. --71.236.23.111 (talk) 23:41, 29 April 2008 (UTC)[reply]

I'm not trying to make an implosion with an explosive force around the center like they do with nukes. I'm trying to decrease the pressure in the center by turning the air into a solid, and letting the normal air pressure do the rest.

When I mentioned the products being solid or liquid, I meant the stuff that was produced by the reaction. If you get a reaction like 2Xx(s) + N₂(g) -> 2XxN(s), it will make a dramatic decrease in pressure. 2Xx(s) + N₂(g) -> 2XxN(g), on the other hand, will increase it. 24.7.180.224 (talk) 01:12, 30 April 2008 (UTC)[reply]

Nitrogen (N₂) is one of the most stable molecules; you'd have a hard time getting a rapid reaction which consumes it. It is more often a stable by-product of other chemical reactions. Nimur (talk) 04:48, 30 April 2008 (UTC)[reply]

I think what he means is some sort of nitrate compound. I still don't really see how you'd get the implosion though. You'd need to do something that produced a rapid and very localized decrease in pressure if you were going to have it be even noticeable. I can't think of an easy way to do that with explosives but maybe I'm not very chemically imaginative. --69.110.41.71 (talk) 09:03, 30 April 2008 (UTC)[reply]

You could burn some kind of reactive metal in nitrogen. Magnesium, or Calcium dust can burn in nitrogen, and oxygen, just leaving the noble gases behind. But a lot of energy will be produced in the reaction. Graeme Bartlett (talk) 11:24, 30 April 2008 (UTC)[reply]

Rabbit.jpg

Now I have my own picture issue. Could a biologist please have a look at the Rabbit page or the Rabbit.jpg picture. I may be off, but that looks like meeting way too many criteria for Hare to be a rabbit. --Lisa4edit (talk) 22:11, 29 April 2008 (UTC)[reply]

The face-shape and ear-length certainly look more hare-like to me, but I am only familiar with British rabbits and hares, and I'm not an expert, so I can't say for sure. Do we have any experts? 78.32.74.31 (talk) 01:53, 30 April 2008 (UTC)[reply]

Well, it certainly isn't a European rabbit, seeing as the original caption says it was taken in Louisiana. Not being familiar with North American lagomorphs, however, I've no idea what species it might be. It probably should be removed from the Rabbit infobox (as I've just done) until it's been properly identified, though. —Ilmari Karonen (talk) 05:02, 30 April 2008 (UTC)[reply]

I see we are "just splitting hares" again. :-) StuRat (talk) 16:36, 30 April 2008 (UTC)[reply]

what's going on with evolution?

will there ever be a point at which evolution finds the perfect traits and all species become one single species with every evolutionary advantage given to it? —Preceding unsigned comment added by 86.139.48.3 (talk) 23:09, 29 April 2008 (UTC)[reply]

No, evolution is contantly occuring and the environmental pressures are always changing. Although we may wipe out all species on Earth--Shniken1 (talk) 23:24, 29 April 2008 (UTC)[reply]

No, the environment constantly changes and creatures should evolve to adapt to it. Besides having one species is not possible as species have diverged to different evolutionary pathways (I don't think a plant will evolve to a humanoid very soon). We might get a single species if we wiped out everything on the planet as Shniken1 says but I'm pretty sure that humans do not have the perfect traits.--Lenticel ^(talk) 23:44, 29 April 2008 (UTC)[reply]

will all niches become one niche?Em3ryguy (talk) 23:49, 29 April 2008 (UTC)[reply]

A common misconception that evolution moves towards the optimum. It moves toward the most suitable average. And every species had a lot of baggage that was once useful, no longer is, but doesn't harm that much either. Then there are the selection prinicples for mates. Those are a sea-saw between "new and adventurous" and "tried and true". Moreover environments are changing constantly. Yesterday resistance to bird flue and drug resistant TB wasn't interesting. Tomorrow it might single out the ones that keep standing. We could always head for becoming cockroaches though :-) --71.236.23.111 (talk) 23:53, 29 April 2008 (UTC)[reply]

Well really it's beyond the capacity of anyone (scientist or otherwise) to speak definitively about the eventual long-term course of biological evolution; but based on a lot of logic and observations, it stands to reason that there is no "optimum" organism which we are evolving towards. Sometimes evolution can even yield undesirable traits (e.g. short-term benefits with long-term repercussions) so it's really not accurate to say we're making consistent steady "improvement". Nimur (talk) 04:52, 30 April 2008 (UTC)[reply]

A really interesting question – perhaps it already exists as an organism – maybe the biome is it. Julia Rossi (talk) 05:10, 30 April 2008 (UTC)[reply]

An ecosystem or biome is not really an organism (under the non-Gaia hypothesis) but several different plants and animals that share a certain habitat. And that's neither ideal nor final in any way. There are plant successions. Invasive species and competitive, dominating plants (sorry forgot the word for that type, weed's not it.) Same with animals. And ecosystems are never stable. The most extreme ones include bromeliads in tall trees in the rainforest and hydrothermal vents one storm or an earthquake and the entire community is gone. Bogs gather leaf-matter that gathers and builds up the soil until it's higher than the water table. Then all the bog plants and animals go and the "dry ground" plants and animals move in. Citizens of Pompei were pretty well adapted to their environment until Vesuvius erupted. Then all of a sudden being a Thermophile was a much better suited organism. I hope my examples are clear enough. This is a very broad topic. Put very bluntly there is no such thing as an "optimum". --Lisa4edit (talk) 06:07, 30 April 2008 (UTC)[reply]

Nimur, could you give an example of such an evolutionary misstep? Thanks. --Sean 12:08, 30 April 2008 (UTC)[reply]

The simplest example I can think of is a predator-prey model where the predator develops a sufficient upper-hand. Maybe the wolf becomes faster than the rabbits; then, over-predation occurs, and the food source is exhausted. If the wolves evolve sufficiently fast, they can extinguish the rabbit population before a new equilibrium can be established. Here, a "positive" evolutionary step (faster wolves, better hunters) results in a negative outcome for their species (over-predation). Nimur (talk) 15:01, 30 April 2008 (UTC)[reply]

I'd say Giant panda. Their almost-exclusive diet of bamboo (which is not a very good food source) is really detrimental to their survival, especially with human encroachment on their territory. -- Kesh (talk) 23:11, 30 April 2008 (UTC)[reply]

As noted above the environment is constantly changing, which leads to more evolution. However, if we started with the given of a permanently fixed environment, I think we would eventually either get a stable situation or an oscillating system (say the prey becomes nocturnal, then the predator follows, then the prey becomes diurnal, etc.). StuRat (talk) 16:33, 30 April 2008 (UTC)[reply]

Sorry I'd disagree unless we're talking in a different hypothetical universe. If you have a stable system you get stagnation. (Funny we don't have a relevant page, non of the disambiguation links fully illuminates the concept. Work for future editors) The idea you proposed hits walls in so many places. Our universe is built on dynamic processes. At no level is there anything stable, from the smallest particle to the big wide whole. Earth is the way it is, rather than a barren rock, because it depends on dynamics. Think of rotation and revolution, plate tectonics, weather, water cycle, tide, ocean flow etc. etc. If you get dynamics you get change and change is never predictable. Uncertainty principle. Game theory describes some mathematical aspects of the predator - prey relation. Ignoring for the sake of the argument the processes required that lead to there being a predator and prey; any of the dynamic processes on earth cited above could throw a serious lug wrench into your oscillating process and that is if you don't get a large rock thrown at it from elsewhere. (Meteoroid) For stable oscillation your predator and prey would only be allowed to move in certain strictly defined patterns. Otherwise you'd automatically introduce chaos. The basic flaw with the idea in the OP's question is the concept that there is an "optimum". In a chaotic dynamic system that is impossible as far as I know. Anything that can be defined as an optimum can only be so temporarily. Remember what Feynman said : Complex problems have simple, easy-to-understand, wrong answers. :-)Lisa4edit (talk) 22:25, 30 April 2008 (UTC)[reply]

nitrogen again

could i get the price of nitrogen per gram? —Preceding unsigned comment added by 76.14.124.175 (talk) 23:47, 29 April 2008 (UTC)[reply]

At this point I'd suggest either google or refining dove droppings. What's the science in a price quotation? Several people have suggested links before. Although I usually am all in favor of being helpful and giving people a break, there is a limit and repetition gets tiresome. Even the most wide-flung definition of an encyclopedia would not include "commodities exchange information board". --Lisa4edit (talk) 03:33, 30 April 2008 (UTC)[reply]

And, you'll have a hard time purchasing nitrogen in units of grams. You'll usually buy it by the cylinder or by the ton. You should probably talk to a vendor to see if they have regulations about who they will sell to, as well; nitrogen is safe, but any compressed gas is potentially hazardous, since it is under pressure. Nimur (talk) 05:02, 30 April 2008 (UTC)[reply]

Nitrogen is not safe in quantity: if your supply talk contains enough of it to displace the air you're breathing, you can fall unconscious before you realize something's wrong, and suffocate to death in minutes. The reason you don't realize anything's wrong is that instead of a "low oxygen level" sensor, your body is equipped with a "high carbon dioxide level" sensor. The one is as good as the other if you're not getting oxygen because you're not breathing, but if you're in an oxygen-free atmosphere, you can exhale the CO2 normally. See nitrogen asphyxiation. (For essentially the same reason in reverse, CO2 in quantity is also not safe. See Carbon dioxide#Toxicity.) --Anonymous, 22:05 UTC, April 30, 2008.

April 30

Eyelids

The purpose of eyelids is to clean the surface of the eye. But I know some animals don't have eyelids so I was wondering how do they keep their eyes clean? Astronaut (talk) 04:09, 30 April 2008 (UTC)[reply]

Nictitating membrane (caution-graphic chicken eye imagery) is one other option; this is usually in addition to "normal" eyelids. Nimur (talk) 04:55, 30 April 2008 (UTC)[reply]

Geckos use their tounges.--Lisa4edit (talk) 05:45, 30 April 2008 (UTC)[reply]

I'd say eyelids have several purposes. Besides cleaning the eye, they also:

1) Keep the eye moist, especially when sleeping.

2) Protect the eye from debris, especially when sleeping.

3) Reduce bright light, by squinting. StuRat (talk) 16:22, 30 April 2008 (UTC)[reply]

Backpack helicopter

What are the problems for making a backpack helicopter? 217.168.4.83 (talk) 04:28, 30 April 2008 (UTC)[reply]

Efficiently storing enough energy in a light, portable environment would be one problem. You'd need a lot of fuel or electricity or some other energy source to provide enough power to lift a (presumably) full-sized human. Batteries that are powerful enough to power a large motor would be huge and heavy. Gasoline is a possible option, but it could be very dangerous to strap to your back. Control and stability would be difficult hurdles, but the problem is not insurmountable (especially given the effectiveness of modern computerized control and a huge body of research in unconventional flight stability). Safety is a significant concern in any aircraft, and if you intend to put the engine, fuel, or rotors near a human with minimal protection, you would have to devise a pretty good and reliable safety mechanism. Surely if you just brainstorm a bit, or sketch out a few diagrams, you'll see a lot of hurdles. You might be interested in ultralight aircraft; this could give you some idea of more realistic vehicles. Nimur (talk) 04:59, 30 April 2008 (UTC)[reply]

Amazingly, we have an article on backpack helicopters. Nimur (talk) 05:05, 30 April 2008 (UTC)[reply]

MythBusters did an episode on this, IIRC. Ziggy Saw dust 17:12, 30 April 2008 (UTC)[reply]

Fixed your link. Presumably the specific episode you mean is this one, but the designs tried were not helicopter-style. --Anon, 22:07 UTC, April 30, 2008.

Thermodynamic feasibility of converting creatine to phosphocreatine

I got this doubt reading the 25th edition Harper's Biochemistry (the latest is the 26th edition), which I couldn't get resolved even after searching on the internet including Wikipedia. There is a mitochondrial creatine kinase (miCK) present between the inner & outer mitochondrial membranes, which phosphorylates creatine to phosphocreatine at the cost of an ATP molecule (ATP-->ADP), which is exported out the mitochondrion through the pore protein 'P' (pages 147-148). What is the need for such an enzyme if any way cytosolic creatine kinase can carry out the same reaction? My guess, is that it must be faster to transport phosphocreatine out of the mitochondrion than ATP, but I do not know for sure (as such a thing is not WRITTEN in the text); then, once in the cytosol, the phosphocreatine must be getting converted back to creatine, phosphorylating ADP to ATP in the process. But, an even bigger doubt is how is the reaction creatine-->phosphocreatine (requiring 43.1 kJ/mol)--carried out between the two mitochondrial membranes thermodynamically feasible if ATP-->ADP releases only 30.5 kJ/mol (page 126; table 12-1)? Looking forward to replies--answers/guesses/just about anything.

Regards.

Ketan Panchal, MBBS (talk) 06:58, 30 April 2008 (UTC)[reply]

Ring finger

Why is the ring finger hard to move by itself? Interactive Fiction Expert/Talk to me 10:16, 30 April 2008 (UTC)[reply]

"It is the weakest of the fingers on the hand, as it shares a flexor muscle with the middle and little fingers. It is the only finger that cannot be fully extended by the majority of people, in itself separately." On the bottom of the wikipedia article. Kingpomba (talk) 11:02, 30 April 2008 (UTC)[reply]

I thought it was because of the extensor, actually - extensor digitorum - but I could be wrong, it's been a while since first-year anatomy --131.111.135.84 (talk) 12:07, 30 April 2008 (UTC)[reply]

Cheese

What happens if you sneeze while eating cheese? I am asking this because it says something about this in a book I have. Interactive Fiction Expert/Talk to me 10:16, 30 April 2008 (UTC)[reply]

Is this a riddle or a limerick? Perhaps you will get cheese spray. Or shall we say a breeze of cheese? Graeme Bartlett (talk) 11:33, 30 April 2008 (UTC)[reply]

Is that what spray cheese really is? DMacks (talk) 16:18, 30 April 2008 (UTC)[reply]

Is there water in a virus

Most life needs water, but do viruses? Are they wet? Obviously they need the host body and that has water in it, but does the virus itself have any water because it is so simple? xxx User:Hyper Girl 10:16, 30 April 2008 (UTC)[reply]

I am going to guess that there is water in little pockets between the protein and DNA molecules. Graeme Bartlett (talk) 11:26, 30 April 2008 (UTC)[reply]

Viruses do not contain water in the way that living cells do. They are simply genetic material DNA or RNA packaged in a protective protein coat. You could say viruses "need" water, though, because they are inert until their genetic material inserts itself into an ordinary, water-filled, living cell.

Atlant (talk) 13:11, 30 April 2008 (UTC)[reply]

It depends on how you define 'wet'. Virtually all protein molecules will have water molecules associated with them—proteins pretty much can't fold without the presence of water. Hydrogen bonding between the protein and surrounding water molecules is often a significant contributor to protein stability and structure, as is the preference for hydrophobic amino acid residues to be buried away from the bulk water solvent. (There are many, many, many papers and books written on these topics; I'm dramatically simplifying.) When proteins are crystallized for x-ray crystallography, the protein crystals contain large amounts of bound water.

The amount of water in different viruses varies, but all will contain some water. Exactly how much can be estimated by various means; the most straightforward essentially rely on centrifugation to 'wring out' virus particles. By these sorts of measurements, the influenza virus is about two thirds water (link to PDF), while the vaccinia virus is nearly ninety percent water (abstract).

The necessity of this intrinsic water explains why many viruses don't remain viable for long periods when left out on otherwise clean, dry surfaces. Viruses like HIV are rather flimsy, and are inactivated by drying. Other viruses will survive dehydration and rehydration much more effectively—though even after air drying many will still contain at least some amount of bound water. TenOfAllTrades(talk) 13:44, 30 April 2008 (UTC)[reply]

Electrolysis of solution

I cant exactly remember because it was a week or two ago but it interests me. In chemistry class we were testing if solutions were ionic bonded or covalent bonded by passing a mild electrical current supplied from a battery cell through them. Im not sure if it was saline or not but once the current was applied it turned yellow(i think my teacher might of said something about the sodium). Does this sound like saline? if it does why did it do this? Kingpomba (talk) 10:22, 30 April 2008 (UTC)[reply]

Sodium ions do not usually cause visible coloring in solutions (a glass of common table-salt dissolved in water is just a bunch of sodium and chloride ions, and you can see it's colorless). Usually when one thinks "ions that make colors in water", one is talking about the transition metals. Putting two electrodes in solution can electrolyze the solution, but it can also electrolyze the electrodes themselves. This process results in one electrode actually dissolving into the electrolyte a little. DMacks (talk) 16:17, 30 April 2008 (UTC)[reply]

Indeed Sodium ions do not usually cause visible coloring in solutions-in water that is. Ionic Sodium is of course bright blue to metallic in liquid ammonia. But in this case are you sure you meant water? Or when you said solutions did you mean liquids? Also isn't the big difference that ionic solutions conduct a lot but covalent ones don't? There wasn't a light bulb in a circuit lighting stuff up yellow you forgot to mention is there? --BozMo talk 18:28, 30 April 2008 (UTC)[reply]

Just an idea. This might have been an effect of impurities / additives in either the salt or the water. We once had a series of experiments go seriously wrong until we had a look at all the stuff that was in our "table salt". Turned out it didn't have enough sodium chloride in it. Red coloring would indicate iron. Green's copper most likely. Iodine might cause the yellow coloring, although usually it'd be more brown from what I remember. --Lisa4edit (talk) 23:33, 30 April 2008 (UTC)[reply]

Is it statistical "insignificance" or "nonsignificance"?

As title - I know it's a stats question, but it's intended for use in a psychology paper so, um, think it's probably better in this section. I was told it was "nonsignificant" but Google Scholar gives far more results for "insignificant" (though that may reflect its use as a normal word) - any advice? Thanks! --131.111.135.84 (talk) 11:58, 30 April 2008 (UTC)[reply]

When in doubt, it is always acceptable to say that the differences were not statistically significant. TenOfAllTrades(talk) 12:11, 30 April 2008 (UTC)[reply]

elements

How many elements are there as most site say approximately 115 but I want the exat answer (if thereis one) —Preceding unsigned comment added by 78.149.107.50 (talk) 15:04, 30 April 2008 (UTC)[reply]

There isn't really. 94 elements occur naturally on Earth, and a further 23 have been created artificially in laboratories, but there might be others elsewhere in the universe (possibly in some alien's lab), and someone'll synthesize another before too long, so there's no clear answer. Algebraist 16:10, 30 April 2008 (UTC)[reply]

Then there are some that are so unstable they decay in a millionth of a second, so do you count that as "an element" ? StuRat (talk) 16:15, 30 April 2008 (UTC)[reply]

Petrol consumption

How is a car's fuel consumption (per metre) related to speed? If I travel a certain distance at 100km/h I'd spend more time travelling than if I were going at 120km/h and thus the car would be using petrol for longer but at a lower revolution rate (if that's the right term). So what's the trade-off? I'm sure there's a non-linear relationship somewhere that I'm missing. Thanks, Zain Ebrahim (talk) 16:53, 30 April 2008 (UTC)[reply]

Air resistance increases non-linearly with speed. That's probably what you're missing. See Drag (physics). The drag force on an object increases with the square of the velocity, but the power required to overcome the drag increases with the cube of the velocity. ~Amatulić (talk) 17:00, 30 April 2008 (UTC)[reply]

That makes fuel consumption inefficient at high speeds, but it is also inefficient at low speeds, as internal combustion engines need a certain amount of fuel just to idle. The ideal "cruise speed" varies by car, due to factors such as gearing and the coefficient of drag (which measures how stream-lined it is), but something like 90 km/h is typical (until you strap a mattress on top, that is). StuRat (talk) 17:08, 30 April 2008 (UTC)[reply]

Thanks, guys. From the article I see why power increases with the cube of velocity but how does consumption relate to power (if it is trivially related)? Also, I don't quite understand why the energy required to idle causes inefficiency at low speeds. Does it have something to do with gears? Zain Ebrahim (talk) 17:27, 30 April 2008 (UTC)[reply]

As for the inefficiency at low speeds, the issue is that a certain minimum fuel is used all the time, even though you don't theoretically need that much to move at low speeds. So, essentially, you are wasting gas just to keep the car running. This is one advantage to electric vehicles, they don't need to waste fuel to keep running. This makes them better for low speed, city, stop-and-go driving, where gasoline engines are worst. Gasoline-electric hybrids also take advantage of this. StuRat (talk) 17:37, 30 April 2008 (UTC)[reply]

Fuel consumption is trivially related to power. Fuel contains potential energy realized by burning it to drive an engine. Power is simply energy expended per unit time. Needing more power means you need to expend more energy in a given time increment, which translates to expending more fuel. The fuel consumption vs power graph should theoretically be linear, but as StuRat pointed out above, there are wastes to contend with at low speeds. ~Amatulić (talk) 17:45, 30 April 2008 (UTC)[reply]

Thanks a lot, guys! Zain Ebrahim (talk) 17:52, 30 April 2008 (UTC)[reply]

Melting plastics

As a hobby, I sometimes get a bunch of junk plastic (drink bottles, packaging, old baby toys, etc.) and put it in a pot, and then melt it over the stove. I've been attempting to pour it into a Play-Doh mold with little success. I need:

A material that is malleable with your hands or tools (like clay), can withstand high temperatures, and is structurally strong enough to have some pressure put on it without deforming (the play-doh is too soft and the plastic deforms the cast, turning into a blob).
Information about the safety of melting plastics and the fumes created by doing so. I have a gas mask that I wear whilst melting, but I do this in my kitchen and don't want it to smell like ass-and-a-half for the next 3 days. Also, my dog can't wear a gas mask.
To be able to tell the difference between different types of plastics; thermoplastic/thermoset, hardness, melting temperature, etc. And a way to find this out from the source of the plastic and its appearance.

Thank you in advance... Ziggy Saw dust 17:11, 30 April 2008 (UTC)[reply]

Of course you should be warned that molten plastic is quite dangerous. Aside from the fumes there's the danger of getting some on your skin, where it will be impossible to remove until you are severely burned. Softer plastics will also tend to have lower melting points. Completely avoid hard plastics, as they are likely to be thermoset plastics that just smoke and burn when heated. Try using metal molds sold for cookies.

I suggest doing this all outside at a fire pit or on a bbq (although the neighbors will likely complain about the fumes either way). If it catches fire you will essentially have an oil fire, so have an extinguisher nearby rated for that, and also have a bucket of water to submerge your hands if they get small bits of molten plastic on them. Better yet, wear thick leather gloves. Also, consider bringing an extension cord outside with a cheap microwave so you can heat the plastics that way. This may enable you to heat them more evenly.

The recycle number on the plastic may also give you a clue as to which will work best. It's written inside a triangle with arrows pointing clockwise.

Another suggestion, instead of plastics use crayons, which melt at a lower temp yet, and are nice and colorful, allowing you to indulge both your creativity and pyromania. StuRat (talk) 17:26, 30 April 2008 (UTC)[reply]

Yep be very careful. Polyurethane in particular gives off cyanide gas when heated which your dog is not going to appreciate. Getting a candle making kit or similar seems a safer hobby. --BozMo talk 17:48, 30 April 2008 (UTC)[reply]

I partially disagree with some of the above. I've encountered some soft plastics that don't readily melt (teflon for example, a thermoset toy-mold plastic from the 1970s called plastigoop, and I think some silicone polymers) whereas some hard plastics such as polystyrene melt readily.

To pour something molten into a mold, it helps to heat up the mold to the melting temperature of what you're pouring into it. You may be experiencing the problem of your mold sucking out all the heat from the plastic before it can flow fully into the mold. ~Amatulić (talk) 17:55, 30 April 2008 (UTC)[reply]

If you had a metal mould, could you melt your plastic in the mold itself? Then you wouldn't have to pour it at all and you wouldn't have to be anywhere near it except for a short while you remove it from the BBQ with a pair of tongs. Astronaut (talk) 18:34, 30 April 2008 (UTC)[reply]

Note that it isn't just a problem with the smell for 3 days. If there is a smell for 3 days then there is a good chance some of the potentially toxic or carciogenic fumes are around. (While cyanide may be a concern, IMHO it's only a minor one since if I'm not mistaken and supported by the Cyanide poisoning cyanide may kill you or make you weak and sick for a few days but if you're carefully, I think that unlikely and the chronic effects of a minor acute exposure to cyanide which is readily metabolised are probably less concerning then the chronic effects of some of the other stuff you will produce which may hang around in your body or the environment for years.) Unless you are planning to wear a gas mask for the next 3 days or whatever (I presume you live alone) the gas mask may not solve the problem. You could do it outside of course or at least make sure your kitchen is very well ventilated. But other then your poor dog, depending on what kind of quantity we're talking about here, how close your neighbours are, the wind, etc others could be affected. Then there is the issue of whether it may be illegal. Personally I wouldn't recommend it. Some science experiments are fine to do in the home. Some are not. Generally speaking, any science experiment where you produce a significant amount of nasty fumes which may affect you and perhaps more importantly, innocent bystanders, should be avoided. Melting plastics, except by accident, is one of them. If you really want to do this, I suggest you at least go to an isolated area without anything that's likely to catch fire. Nil Einne (talk) 19:38, 30 April 2008 (UTC)[reply]

I'd say you should find another hobby before you find out in a couple of years that this was a really bad idea. Plastic recycling will give you the material code. That does not mean that that's all that's in there. There are things like plasticizers that are also really nasty. Plastics are polymers and if you split those chains (or circles) there's no telling what they'll react with and where they break and link up again. It's all a game of ratios and probabilities. The problem is that some of the possible results are toxic, mutagenic or carcinogenic at very low concentrations and effects can be delayed and cumulative. It's like hitting your head, if you do it occasionally that's within the usual "life is detrimental to your health" limits. If you make a regular and repeated habit of it, it will eventually kill you. Since the more heat you put in the more broken links you get and the more fumes develop, using an counter-top oven at lower temperatures and reshaping the plastic rather than melting the stuff in a pot is safer by a sizable margin. You can use oven safe ceramic cake molds. Make sure your vent is on at full tilt and you use the highest grade filter in it you can lay your hands on (I've seen some pretty high grade composite ones in Europe). Exchange filter after you're done and dispose of the old one. (Environmentalists will hate you forever). Open every outside door and window you have after you are done to reduce relative concentration of airborne residuals. This gets you from running into the wall at full tilt to bumping your head from a standing position going with the above analogy.Lisa4edit (talk) 21:12, 30 April 2008 (UTC)[reply]

Do not assume that your gas mask protects you. It should have a rating on it and it probably allows cyanide through it.--Shniken1 (talk) 00:14, 1 May 2008 (UTC)[reply]

Well, as far as safety goes, I do it outside, wearing a gas mask/goggles/chemical gloves/apron as well as setting up a leaf blower, shop vac (set to blow), and a fan blowing into the wind... Ziggy Saw dust 01:23, 1 May 2008 (UTC)[reply]

Chemical Name

In the 1960's there was an insecticide commonly known as C40. What is the chemical name for this compoundTraudt1 (talk) 18:46, 30 April 2008 (UTC)[reply]

This? DMacks (talk) 18:55, 30 April 2008 (UTC)[reply]

Colours in Transition Metal Complexes

Hi all. From what I understand of the reason for colour in compounds like hydrated copper (II) sulphate, it's caused by the promotion of d electrons. My question is, why does this promotion then mean that light is absorbed over a range of frequencies? I've been told that this is because of collisions with other atoms or molecules (essentially Brownian motion) meaning that the energy gap varies a bit. I'm puzzled though, as that implies to me that if you cooled copper sulphate to near absolute zero, it would become colourless as the range of -frequencies- (edit - I meant wavelengths)absorbed by the energy gaps would become so small as to be insignificant to the naked eye when you pass white light through it. Does copper sulphate really become colourless near absolute zero, or is there something I have wrong here? Thanks Trebor27trebor (talk) 18:50, 30 April 2008 (UTC)[reply]

How did you conclude that "light is absorbed over a range of frequencies"? DMacks (talk) 18:53, 30 April 2008 (UTC)[reply]

I've seen diagrams of light being absorbed across a range of wavelengths (not frequencies, sorry) in transition metal complexes. Sorry, my dopey mistake. They look a bit like [22]. Trebor27trebor (talk) 19:33, 30 April 2008 (UTC)[reply]

Er, light is absorbed over a range of frequencies – and wavelengths, since frequency is just c divided by wavelength – when you're in any sort of condensed phase. (At least) two factors contribute to the broadening of the absorbance peaks. First, molecules at room temperature may be a variety of different rotational and vibrational energy levels, and may be excited to different rotational and vibrational levels; this means that the difference between the ground and first excited electronic energy levels is slightly shifted. Second, there are constant interactions with adjacent molecules (water if you're in solution; with other hydrated copper complexes if in the solid phase) that act to slightly shift the effective energy levels of both ground and excited electronic states—again broadening the absorbance range for the compound.

You only get nice sharp absorption lines if you're working with gases at not-too-high pressures. Under those circumstances, individual molecules are effectively not interacting with each other, so they don't mess up each other's energy levels. TenOfAllTrades(talk) 21:37, 30 April 2008 (UTC)[reply]

This image shows the energy levels involved in a rovibrational transition. Each line will appear in a gas phase spectra as a sharp peak. In the condensed phase these will all broaden because of intermolecular interactions to give a broad peak. Similar, but more complex, transitions are seen in electronic transitions.

An energy level diagram showing some of the transitions involved in the spectrum of a linear molecule: P branch (where $\Delta J=-1$ ), Q branch (not always allowed, $\Delta J=0$ ) and R branch ( $\Delta J=1$ )

HIV/Antibodies

Upon contact in the bloodstream with the HIV virus, (which are part of the retrovirus family so seem to have virus envelopes, from what I can make out from the article) why can't antibodies attack this virus and render it useless? Thanks, 86.159.224.183 (talk) 20:04, 30 April 2008 (UTC)[reply]

I think, but i'm not certain, that the HIV virus attacks T cells which are the cells, amongst others, which attack invaders in the body. This means that the body cannot fight off HIV since it has nothing uncompromised to fight it with. That's almost certainly wrong, just my assumption. Regards, CycloneNimrod^Talk? 21:23, 30 April 2008 (UTC)[reply]

The other half of the answer is that the infected T-cells and cetain other cell types will not be eliminated by the rest of the immune system once infected (so far as I'm aware, at least not too many of them, certainly), so some HIV will always survive the onslaught of the immune system while simultaneously wearing it down. As some evidence of just how hard HIV is for the body to fight off, recent studies that attempted to vaccinate individuals against HIV by promoting deveopment of HIV antibodies prior to infection have shown absolutely no effectiveness. Someguy1221 (talk) 22:21, 30 April 2008 (UTC)[reply]

Antibodies do attack the virus, and Cyto-toxic T cells do destroy virally infected cells. However, helper T cells are absolutely essential for the proper functioning of the immune system, both humoral and cell-mediated via secretion of cytokines and clonal expansion. This is one of the subtypes of immune cells (in addition to dendritic cells and macrophages) that become infected by HIV via the CD4 receptor protein. At first the virus is kept at bay, but decreased T cell count creates a derangement in cell-mediated immunity and consequently the development of AIDS. Wisdom89 _{(_T / ^C)} 00:09, 1 May 2008 (UTC)[reply]

Electron microscopes

Certain particles, such as electrons and protons, exhibit wave-particle duality, correct? If this is the case, and protons too act like waves, why can we not use protons in a microscope like we do with electrons? Surely with their shorter wavelength they could allow us to visualise things like atoms? Regards, CycloneNimrod^Talk? 21:26, 30 April 2008 (UTC)[reply]

They are called nuclear microscopes, although our article on them is unfortunately short. Someguy1221 (talk) 22:23, 30 April 2008 (UTC)[reply]

They contain much more energy, and cause more damage to it item irradiated by them. Graeme Bartlett (talk) 22:25, 30 April 2008 (UTC)[reply]

Neutrons are used in similar ways see Neutron scattering and links therein.--Shniken1 (talk) 23:58, 30 April 2008 (UTC)[reply]

Is it common for doctors to be unable to dress/bandage a leg?

So, I took my grandma to the doctors' the other day for a checkup on the healing of her leg ulcer (which is getting better, thankfully). We sat down and reminded the doctor (not my nan's usual GP) that we were there to get the leg looked at, at which point she stopped me and said that she'd better go have a look to see if there were still any nurses in the building (this was late afternoon), as if she were to remove the bandage and dressing to examine the ulcer, she would be unable to put a new one on - because she didn't know how!

This wasn't a case of "a nurse could bandage a leg better than me" or "it's a nurse's job to put the bandages on, not mine", she literally told my nan and I that she'd never put a bandage on a patient before and that she had no idea how to do it. As it turns out, all the nurses had gone home for the day, so she was going to send my nan home and make her come back early the following day (which would be quite a slog for her, in her current state of health). Luckily, *I've* dressed my nan's leg several times and know exactly how it's done (it's not particularly complex), so we managed to get it looked at in the end.

So, when training, are doctors in the UK not taught how to do basic treatments such as this, with the assumption that there will always be a nurse on hand to do it for them, or is this an isolated case? This particular doctor is far, far from being young and inexperienced (I'd be able to understand it more if she had been newly-qualified). Any UK medical-type people here?

My nan is currently in a care home (not permanently, I hope) and we were having a laugh about it tonight with an African nurse that looks after her - she was gobsmacked when she heard the story and told us that where she was from (I forget where exactly), it would be unthinkable for a doctor not to know how to change a simple dressing. --Kurt Shaped Box (talk) 23:58, 30 April 2008 (UTC)[reply]

May 1

Using LC-MS to test purity of water

Hello. If I obtain LC-MS or GC-MS machine, and learn to use properly, can I accurately test the purity of my tap water and filter water? Thanks you. Applefungus (talk) 00:26, 1 May 2008 (UTC)[reply]

Yes and no. You may be able to detect some impurities in the water but not others. Why do you need to test it? What are you testing for? These machines are expensive so it is probably not worth paying for one just because of your curiosity.--Shniken1 (talk) 01:25, 1 May 2008 (UTC)[reply]

Bird Identification

I'm trying to identify this bird. I saw it in Boston, MA, along with another bird that was also unusually colored (orangeish, I believe). You can't see it very well in these pictures, but both had feathers on their feet. Both were very disoriented, flying into the wall when chased by some children (I couldn't get a picture of the other one, because the children had chased it away), suggesting that they might have been bred in captivity. Is this a domesticated pigeon, and if so, what kind?

Thanks, --MagneticFlux (talk) 02:32, 1 May 2008 (UTC)[reply]