Wikipedia:Reference desk/Archives/Science/2006 September 13

=September 13=

Blood-brain barrier
I was thinking about how the Blood-brain barrier prevents polar molecules from entering the brain (e.g. glucose have to be transported to the other side). But how can then red blood cells reach the brain to deliver it's need for oxygen? Is there a way for these cells to circumvent the BBB? I cannot believe that oxygen is diffusing from the BBB to reach all areas of the brain, it's not likely. /80.217.232.217 14:00, 13 September 2006 (UTC)
 * A good question. -- DLL .. T 19:14, 13 September 2006 (UTC)
 * Perhaps a clarification of the BBB is in order: the barrier isn't really some wall at the bottom of the brain or something. Blood-brain_barrier has more, but here's some info...There are numerous blood vessels and capillaries throughout the brain, but the capillary beds are a little different than elsewhere in the body--the capillaries in the body are relatively "loosely" surrounded by cells and there is a lot of easy passage of fluids, large proteins and cells between the blood and the lymph/interstitial fluid; in the brain, the endothelial cells are packed very tightly together, forming an effective barrier against anything of moderate size or polarity. Oxygen still freely diffuses accross the cell membranes of the endothelial cells and beyond, and it really doesn't have to diffuse that far. Additionally, the brain uses something like a quarter of the oxygen taken in by the lungs, so there's a hefty concentration gradient that allows diffusion to happen quite easily; and since the brain receives a large share of the body's blood circulation, there's no shartage of oxygen availability, either. This should provide some handy graphical representation, too. -- Scientizzle 19:46, 13 September 2006 (UTC)

How do you define Pica?
I read the article about Pica and I want to know more about this disorder. I know a lot of people who like to eat stuff that normally would be considered gross, like raw potato and powdered milk. Is it always a disorder when you eat things like that? I like to eat paper, in little bits at a time. Is this Pica? Should I stop doing it? Even if it is Pica, is paper dangerous to eat? --Jonathan talk 00:06, 13 September 2006 (UTC)


 * Does it decrease your quality of life? If not, don't worry about it. But please, stay away from bleached paper. Paper itself is pretty much just insoluble fiber (cellulose) but the chemicals they use to bleach it include some pretty nasty species (most famously, members of the dioxin family).Tuckerekcut 01:48, 13 September 2006 (UTC)

Crayon eaters... http://www.southcoasttoday.com/daily/02-05/02-07-05/zzzadann.htm - R_Lee_E (talk, contribs) 03:51, 13 September 2006 (UTC)


 * It's not always a sign of an underlying disorder such as iron deficiency anemia, etc. It can be a manifestation of a psychiatric disorder, though. Or, it can just be that a person likes to eat a certain thing, such as paper. If it bothers you, stop. If not, I wouldn't worry. InvictaHOG 10:05, 13 September 2006 (UTC)


 * Eating real foods in preparations you consider "gross" is not necessarily pica. There is a cultural component for starters. For instance, many Westerners would think it "gross" to eat raw fish, while many Japanese consider it "gross" to eat greasy-gravy foods like chicken fried steak. True pica is actually pretty rare. I can't say whether your paper eating qualifies. --Ginkgo100 talk · e@ 22:09, 13 September 2006 (UTC)


 * What's gross about raw potato? User:Zoe|(talk) 02:38, 14 September 2006 (UTC)

Thanks again for the answers. --Jonathan talk 12:06, 14 September 2006 (UTC)

Psychology and Human Viruses
I am in the 12th grade and I am very interested in Human Viruses. Now i need to write a paper in Psychology about theories such as Gestalt Theory, Psychology of Lieing "Why people lie" and "Nature vs. Nurture" and such. It can basicly be anything that involves psychology. Now I wanna tie in Psychology and human viruses such as I dont know, How they form or the affect of the human body from human viruses. I believe I need a theory that I need to disprove/prove. As long as it involves human viruses and I can write a paper about it im fine with it. So basicly my question is, Is there any psychological theory about human viruses? and what is it?

Thanks in Advance for any help.

--Coolguy 1175talk 00:22, 13 September 2006 (UTC)


 * One of my favorite psychologists, Claude Steele, once did a study on alcohol and safe sex. Basically, he was trying to show that alcohol, rather than being simply a disinhibitor, more accurately serves to narrow one's attention.  Narrowing one's attention generally has a disinhibitory effect, but not always.  Steele showed that if you put an card with warnings about HIV in front of a drunk, they'll actually be less likely (at least according to their own predictions) to have unsafe sex that night than a sober person presented with the same card.  (HIV being a virus. :-))


 * Another angle: even though almost all medical scientists are sure that the benefits of immunization (against viruses) far outweigh the risks, a lot of parents won't allow their children to be immunized. What motivates these anti-vaccinationists? --Allen 00:56, 13 September 2006 (UTC)


 * Other articles I should have linked to (it seems we have relatively poor organization on this topic): Vaccination, Vaccine controversy --Allen 01:04, 13 September 2006 (UTC)

You might be interested in Torrey & Yolken's theory ("Could schizophrenia be a viral zoonosis transmitted from house cats?" Schizophr Bull. 1995;21(2):167-71) that at least some cases of Schizophrenia are caused by a parasite (not a virus) carried by house cats. see also: Toxoplasmosis, Toxoplasma gondii & Pete.Hurd 03:19, 13 September 2006 (UTC)


 * People live with bacteria and viruses all their life. Psychology could tell plenty of things, viz. -


 * When you're unhealthy and those little beasts attack you, instead of living peacefully within or outside, it is because you're in a bad mood.
 * If the great idea in our societies is to cure people, is it better to cure the mind by psy means, to build healthy houses and towns, or to attack our mini friends and destroy a little our bodies ? (I'm not 100% of an antivaccin', I'm writing this for the general idea). -- DLL .. T 19:12, 13 September 2006 (UTC)
 * The most human viruses are called memes. Thet are very interesting, psychologically speaking. --193.56.241.75 07:14, 14 September 2006 (UTC)

Sinusitis vs. Migraines
Following up on my question from the other day, Wikipedia's article states that a significant portion of migraines may be misdiagnosed as sinusitis. Migraine patients often perceive pain in the sinuses and migraines themselves may be accompanied by increased mucus production. So...how would I determine the difference? I do experience severe headaches that last 4-72 hours, often accompanied by nausea (although not actual vomiting) and have a family history of severe headaches - which might have been migraines misdiagnosed as sinusitis? I'd always thought my headaches were due to airborne allergens (dust or pollens) but the worst episodes seem to occur without any relation to seasonal weather. I'm thinking of trying the "ice cream headhache" treatment the next time I feel one coming on - just to test whether that helps. Is there any other way to test the hypothesis? Durova 02:19, 13 September 2006 (UTC)
 * See a migraine/headache specialist. It's really, really difficult to self-diagnose types of headaches and causes. Particularly since some causes of severe headaches are life-threatening problems (like tumour, stroke, meningitis, etc). But there are classes of drugs (triptans, vascular constrictors, etc) that will relieve migraine symptoms but not those of other types of headache, so get yourself a prescription for Imitrex and try it out. Anchoress 07:12, 14 September 2006 (UTC)

Preserve human tissues
I'm getting some organs surgically removed, and I may consider the option of preserving them. What is the easiest and best way to preserve them? Should I buy 95% pure alcohol, something like Everclear_(alcohol)? Or where would I buy formaldehyde? Maybe at the university? I hear it's toxic though? What are the pros and cons of various methods of preservation in a jar? I wish I had the equipment for plastination, LOL. --Sonjaaa 03:11, 13 September 2006 (UTC)


 * Formalin (37% aqueous formaldehyde) would be the gold standard, talk to a local university biology department nicely and see how much luck you have. Alternatively ask the doctors at the hospital. its generally used as a 2% formalin solution in ethanol. it is also rather toxic, so don't spill it on yourself, or try to have the organ put back in. You could have a peek at embalming chemicals too.Xcomradex 04:21, 13 September 2006 (UTC)
 * I'm sure the university would give you some. — [ Mac Davis ] (talk) ( Desk | Help me improve )
 * I really doubt any University would give you anything toxic. I can't buy fix, or anything for that matter, from my University stores without having the appropriate paperwork in hand.  Initial fix in formalin, then store in paraformaldehyde, just guessing. Pete.Hurd 05:35, 13 September 2006 (UTC)
 * Well it is a fairly special case here, c'mon. I know several guys that just go ask for some liquid nitrogen to take home from their University. — [ Mac Davis ] (talk) ( Desk | Help me improve )

Avoid preserving tissues in ethanol. Just Google "Nelson's Blood" and see what might happen.Maybe your local undertaker would give you a little jar of embalming fluid, to build good will against the day all your organs need a bit of preserving. Then you could put the little jar in the casket so you will be all in the same place and require less reassembly on judgment day. Also having your removed organ handy will lessen the tendency to fulfill the campfire ghost story of the thumping sound coming up the stairs and a voice asking "WHERE'S MY GOLDEN ORGAN?" http://www.evboard.com/archive/index.php/t-33740.html Edison 15:09, 13 September 2006 (UTC)


 * Patient rights vary by country, but if you're in the United States you have the right to demand your own organs back. It helps to state your intentions in advance (or as soon after the surgery as possible) and it helps to have a relative act as an advocate.  I did get a relative's body part from a hospital in formalin, but in practical terms the pathologist was very concerned to make certain there were no children in the home - it's highly toxic stuff.  Hospitals legally have to comply with the demand, but they might "accidentally" dispose of the organ before they process the request. Durova 17:04, 13 September 2006 (UTC)


 * Last week in my anatomy lab some techs came in and made us wear exposure badges which measured ethanol, formaldehyde and phenol concentrations in the air, so I would guess that those are the main chemicals used in preserving semi-dry bodies (it may differ from the solution used for liquid-suspended preservations). You mentioned in passing that you were having some organs removed, dare I say how many, or even which ones?Tuckerekcut 21:41, 13 September 2006 (UTC)

Why do you want to preserve the material? If you want to preserve it for cultural or religious reasons (e.g. you want it buried with you later), you may have more luck convincing someone (embalmer, someone at the hospital) to provide you with what you need. Failing that, you could simply request the unpreserved item(s) and use any of the usual methods people use to preserve meat - freezing, canning, smoking, salting, pickling, etc., although none of those will perfectly preserve it for (hopefully) decades to come. If you just want a keepsake, then the suggestions above sound good. Matt Deres 03:48, 15 September 2006 (UTC)

'Sulfisomezole Sodium'
Hi In front of me I have eye drops. On the bottle I see that it contains, 'Sulfisomezole Sodium'. I can't find it here (or anywhere else). So I went to the request page but can't figure out how to go about making a request. I am assuming that by making a request it is meant, that I would like someone who knows anything on it to hopefully provide info on it and put this info on this site.

Thanks


 * You've tried google? That exact phrase didn't get me much that seemed useful, but just searching for "sulfisomezole" taught me a lot. DMacks 04:42, 13 September 2006 (UTC)
 * You put this on the help desk, and I asked you to leave me a message on my talk page. I'll write the article (stub) tomorrow (unless somebody else wants to first!), which is faster than making a request. Good idea for asking here though. — [ Mac Davis ] (talk) ( Desk | Help me improve )
 * Isn't sulfisomezole covered in sulfamethoxazole? Is the problem that we need a redirect for sulfisomezole sodium?- Nunh-huh 19:37, 13 September 2006 (UTC)

Why isn't a Kerr ring singularity a string?
I wrongly posted this elsewhere: Just a question. A black hole singularity is an infinitesimally small, two dimensional ring that spins at the speed of light and its surface wiggles with quantum foam. Wouldn’t this pretty much describe a closed string as well? Especially since closed strings describe fermions and the shorter the wavelength at which they oscillate, the greater the mass of the particle of matter they represent. Wouldn’t this prove that strings do exist? To which I got this: A black hole's singularity is 0-dimensional, and its event horizon is 2-dimensional. Strings are 1-dimensional. So there certainly isn't a direct analogy. Brian Greene does discuss the relationship between strings and black holes in one of the later chapters of The Elegant Universe, though. (A caveat for my own piece of mind: Mr. Greene is a little bit overenthusiastic about the prospects for proving/solving string theory in the near future. Regardless of what impression you're left with if you do read his book, nobody has a clue if string theory is real, and there are no clear prospects for resolving the matter anytime soon.)

However: "When a spherical non-rotating body collapses under its own gravitation under general relativity, it is usually supposed to collapse to a single point. This is not the case with a rotating black hole (a Kerr black hole). With a fluid rotating body, its distribution of mass is not spherical (it shows an equatorial bulge), and it has angular momentum. Since a point cannot support rotation or angular momentum, the minimal shape of the singularity that can support these properties is instead a ring with zero thickness but non-zero radius, and this is referred to as a ring singularity, or Kerr singularity." (from the Wiki)

"A closed string looks like a small loop." (from anyone)

I know that particles have zero dimensions and strings have one, still, a really small ring and a really small loop have nothing in common? Just intuitively, shouldn't gravity crush the contents of a black hole into a string? --208.15.6.162 05:53, 13 September 2006 (UTC)Arch Little
 * Hurray for good questions. Who said a black hole was two dimensional? The mathematical singularity exists there because what we know of physics breaks down, because things get so extreme. There may or may not be actually an infintesimally small piece of matter there. The black hole does not spin at the speed of light, because a mass just can't do that. Then again, I guess physics breaks down because of the extremes, and we don't really know. The event horizon is three dimensional, as far as we know. — [ Mac Davis ] (talk) ( Desk | Help me improve )


 * What you seem to have hit upon is the very reason string theory can include GR where quantum mechanics can't. In string theory, the smallest any object can be is the size of a string (~the planck length) whereas in QM objects can be of zero size.  If ST is correct then the singularity would not be a string, but it would be string size. An event horizon is two dimensional - it is a surface.  The black hole itself is three dimensional, but its surface is two dimensional.

Thanks, but if a string is the building block for everything and the ring singularity is shrunk to the size of a string, then the ring singularity is its own building block and it must be a string. That's just geometric logic. NASA has found proof of Kerr ring singularities by observing matter in acretion disks. The matter could only be falling into a singularity that was spinning. Such a ring singularity would be proof for the ST.208.15.6.162 03:59, 14 September 2006 (UTC)Archie


 * The least wrong way to think about the singularity in a black hole is "the place where everything inside the event horizon is going". In GR, the coordinates become degenerate at the event horizon -- in particular the forward time direction is a spatial direction.  In a non-rotating black hole (q.v. Black hole, Schwarzschild black hole, Kerr black hole, and Charged black hole) the forward time direction is towards a point.  Thus, anywhere inside the event horizon, waiting will result in moving toward that point.  This point is a singularity because, for instance, the forward time direction is discontinuous there.  In a rotating black hole, the forward time direction points slightly outward from the center (centrifugal force) and inward from everywhere else.  This "extrudes" the singularity into a ring -- i.e. there is a set of points homeomorphic to a circle where the forward time direction is discontinuous.  Waiting around in this event horizon causes inexorable motion towards this ring.
 * As an interesting side note, from the point of view of an observer far away from the black hole, it takes an infinitely long time for an object to follow those forward in time vectors all the way to the singularity. Of course, from the object's point of view, the time to arrive is finite.  This is one of those wacky consequences of trying to compare clocks at places where the forward time directions aren't parallel.
 * Equivalently, there's no physical thing at the singularity. It's just where all the time vectors point.  Since it's not a physical thing, it would not be composed of strings in ST.  A successful ST may also encompass a loop quantum gravity, but this is by no means currently clear.  So we can't currently say that there are special forms of loops near the singularity (and thus we cannot say that there are special strings there).  -- 66.103.112.140 04:14, 14 September 2006 (UTC)  a.k.a.  Fuzzyeric 02:48, 15 September 2006 (UTC)

No physical thing at the singularity? Well something has a great many solar masses at the singularity. Hawking radiation converts this mass slowly as this very real physical thing melts away. (BTW, strings also make up non-physical things, like forces.) I'm saying that the ring singularity is a string loop. Closed strings that represent fermions vibrate in correlation to the mass of the particle they represent. A ring singularity spins near the speed of light (thanks Mac), which should cause some pretty good vibration related to its extreme mass. If its the size of a closed loop string and it behaves like one, maybe it is a special looped string. It doesn't take a lot of hand waiving to look at a drawing of a ring singularity and a closed loop string to see the similaities. 208.15.6.162 09:41, 14 September 2006 (UTC)Archie


 * Remember also that Hawking radiation has a problem if all the interior mass is at the singularity. The probability of mass tunnelling from the singularity to the surface (i.e. backwards in time and several meters) is so low that the universe wouldn't last long enough to let any non-microscopic black hole evaporate.  The external pair production event has to interact with matter frozen just inside the horizon, which is fine because it is as far as the external observer is concerned.  For matter to reach the singularity, it would have to never escape as Hawking radiation, implies that so much of the mass doesn't evaporate that the black hole is never microscopic, implies that Hawking radiation is strongly inhibited for that black hole for a very long time, (seems to) imply vacuum pair production has been turned off near the horizon.  How does one turn the vacuum off
 * Also, if it's spinning so fast, then from the point of view of an observer not at the singularity, its vibrational frequencies are extremely retarded by special relativity. The local gravity is doing that also.  So it's not observably vibrating. -- Fuzzyeric 03:00, 15 September 2006 (UTC)


 * The explanation given by 66.103.112.140 is very good from the point of view of GR. A singularity in GR is a slightly abstract notion in exactly the way the above user explained.  I evidently didn't make my point very well.  I was trying to say that it is impossible to compress anything down below the size of a string.  The GR singularity would be at the (mean) centre of this string sized lump of matter.  GR can't really tell us what happens at this point - it just doesn't work when gravity is not the dominant force.  My explanations are based on what we know about ST (we know that according to ST no actual thing can be smaller than a string), assuming it is correct.  I suppose this wouldn't really clash with the GR  version of a singularity - perhaps a new word is needed. If (big if) ST is correct and there is this string sized thing round a singularity, we wouldn't be able to see it to prove ST because of cosmic censorship.

We already know what a ring singularity would look like and we know what a closed string would look like. We know a lot of other details about them, too, many of which coincide. GR describes a ring singularity without too much argument. Independently, ST has described something very similar as the basic building block of everything. The size of a string was arrived at intuitively from QFT. Nothing can be smaller than the Plank length because of the Heisenberg uncertainty principle. Thus anything smaller than a string would supposedly explode to the size of a string. Also, this puts a bottom limit on what gravity should do to a singularity. Detective work isn't about seeing the crime, its about recognizing the evidence.208.15.6.162 11:11, 14 September 2006 (UTC)Archie


 * Having seen the article on ring singularities, it all seems far too definate. I find it hard to imaging we really know that much about them.  From my understanding, a ring singularity would be a one dimensional circle, whereas (it string theory is correct) the matter would form a two dimensional surface around a singularity.  A colleague of mine did a lot of work on Kerr black holes some time ago.  I'll ask them for more information next time we meet.


 * I've finally remembered the name (Samir Mathur) and therefore the whimsical name they gave to their ST model of a black hole. Fuzzballs.  In their model, using the language I introduced in the GR answer above, the strings are extruded into the positive time direction, with one end at the event horizon and the other end at the singularity.  The theory didn't explain in detail how a heterotic string was suddenly cleaved into an open string, but this may be the route to understanding the ST prediction of the boundary conditions of the universe.  Of course, one can add a one-point compactification and attach the two ends of the string (one at the Big Bang and the other at the singularity) together, incidentally creating a new non-self-interference condition.  Anyway...
 * So even under the current best guess of ST black holes, there is no physical object at the singularity; it's still just a place where the normal rules don't work and there's no ultra-condensed mass there, it's distributed around the interior of the event horizon (from the point of view of an external observer) or reached its final condition in finite time (from the point of view of an internal observer). -- Fuzzyeric 02:48, 15 September 2006 (UTC)

Hi Fuzzyeric. A star bulges at its equator and spins. When and if it collapses into a singularity the mass collapses around the bulge and forms into a ring. It spins ever faster to conserve angular momentum. This initial mass makes it to the singularity. That's what creates the event horizon. That's when time dialation kicks in. In a Schwartzschild singularity a non-spinning mass collapses uniformly into an ever smaller point that rips through space time. I think that a lot of people have the misconception that the singularity must always vanish because of this. However, a ring singularity should be crushed down to the size of a string (Plank's length) by gravity and then stop for the reasons I've mentioned. NASA released info over a year ago that matter observed in an acretion disk could only be falling in to a spinning singularity. If it is spinning, then it is still there. You seem to be stuck on what is happening in between the inner and outer event horizons and not the singularity itself.208.15.6.162 04:25, 15 September 2006 (UTC)Archie


 * From Black hole: "From the viewpoint of a distant observer, an object falling into a black hole appears to slow down, approaching but never quite reaching the event horizon. As the object falls into the black hole, it appears redder and dimmer to the distant observer, due to the extreme gravitational red shift caused by the gravity of the black hole. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon." and "At the center of the black hole, well inside the event horizon, general relativity predicts a singularity, a place where the curvature of spacetime becomes infinite and gravitational forces become infinitely strong."  Thus, from the point of view of an external observer, no matter added to an existing black hole can ever reach the singularity.  It can't even reach the horizon.
 * Gravitational collapse collapse describes the formation of the black hole both from the point of view of an observer on the star and from a remote observer. Note that the two stories need not appear compatible becuase one observer's forward time direction becomes orthogonal to the other's.  The article describes a scenario similar to the above: "As the free falling observer (in his time) falls faster and faster toward the Schwarzschild radius, the stationary observer sees him progressing slower and slower towards the Schwarzschild radius and will never see him passing that stage."
 * I fully understand the idea that the mass collapses into a singularity. This is just incompatible with any observable history.  In fact, the time dilation caused by the stupendous curvatures near the singularity ensure that no test matter can ever arrive in finite time, even from the point of view observers inside the event horizon (and "above" the test matter).  So there is no hypothetical observer that ever sees matter reach the singularity.  (Well, okay... an observer already at the singularity, who necessarily has nonphysicality problems, can see material falling to himself in finite time, but only because his clock is stopped.)
 * Ultimately, the problem is that the singularity is a problem of coordinate charts. Outside the event horizon, our atlas contains a chart that's flat except near the black hole.  Then it's progressively non-flat as it approaches the event horizon.  At the event horizon the coordinates "break", similar to the problem of Mercator projection necessarily omitting two points (classically the north pole and south pole).  However, much like analytic continuation, we can augment our atlas with the charts local to observers falling through the event horizon.  These have to be constructed to provide compatibility with the chart inside the event horizon.  My copy of  describes these "Novikov coordinates" in section 31.4 (p. 826, et seq.).  Every atlas for this manifold has a common feature: the charts can't cover the entire interior of the event horizon.  There is always a singularity (q.v. hairy ball theorem for an example) somewhere in the interior and for some atlases, this singularity is not of measure zero.  Thus, there is no coherent sequence of local coordinates that allow anything to reach the singularity.
 * Really. It is very fundamental that nothing ever reaches the singularity.  Also, nothing ever has to.  Collapsing the star to the event horizon will produce an object externally indistinguishable from the one you're imagining.  The only difference is in the interior.  The coordinate systems in the interior are so unfamiliar that it is easy to draw incorrect conclusions without careful analysis.  -- Fuzzyeric 02:46, 16 September 2006 (UTC)


 * Arch Little, you wrote "A black hole singularity is an infinitesimally small, two dimensional ring that spins at the speed of light". I don't know where you got that, but in classical gtr, this is not right.  As Fuzzyeric suggested somewhere above, I think, in gtr the singularity cannot be easily treated as if it were part of spacetime or as if it had a well defined dimension.


 * Be careful in reading too much into popular books, even those written by competent physicists. Physics can be pretty subtle and often resists translation into non-mathematical language.  I'd go further: generally, almost everything is lost in the translation.  I've seen dozens of popular books on relativity, and think only three are of any value at all.  I like the way Fuzzyeric put it: "The least wrong way to think about the singularity..." :-/  The right way is of course to bite the bullet and learn the math.  In the long run this also turns out to be the easy way, for those of you who can't stop banging your head against the weird-sounding claims you read about in popular physics book :-/


 * In the interests of ridiculously complete disclosure: I went to the same high school as Brian Greene, but am not acquainted with him.---CH 04:24, 18 September 2006 (UTC)


 * Be careful in reading too much into popular books, even those written by competent physicists. Physics can be pretty subtle and often resists translation into non-mathematical language.  I'd go further: generally, almost everything is lost in the translation.  I've seen dozens of popular books on relativity, and think only three are of any value at all.  I like the way Fuzzyeric put it: "The least wrong way to think about the singularity..." :-/  The right way is of course to bite the bullet and learn the math.  In the long run this also turns out to be the easy way, for those of you who can't stop banging your head against the weird-sounding claims you read about in popular physics book :-/  Well said, sir!

science
1.why the rainbow is bow-shaped ?

2.How does the rain cease to fall ?


 * Try our articles on Rainbow and rain. - Mgm|(talk) 07:58, 13 September 2006 (UTC)


 * 1. It's a circle that is cut off at the horizon.


 * 2. It hits the ground. DirkvdM 08:36, 13 September 2006 (UTC)


 * Or, y'know, the sea. Or a puddle... or me. Vitriol 13:02, 13 September 2006 (UTC)

If the observer is on or near the ground, a circular rainbow will be truncated where it appears to hit the ground. If the observer is at a high altitude, however, it will be seen as a full circle. StuRat 14:20, 13 September 2006 (UTC)


 * The rain within the bow is continuing to fall. But as droplets pass through that region of space that forms the correct solid angle with your eyes and the sun, they contribute, for just an instant, to that part of the rainbow. And each rain droplet, of course, gets to contribute to the full spectrum as it falls into different angles with your eyes and the sun.


 * And furthering StuRat's point, you can see a fuly circular rainbow if you're willing to stand on a ladder while spraying downwards with a garden hose.; the (primary) rainbow always occurs at a certain angle from the sun (and the secondary rainbow, if present, always occurs at another, different angle).


 * Atlant 15:27, 13 September 2006 (UTC)


 * I saw an OU prograqmme once on tv about how rainbows form. It was quite a complex phenomenon and mind bendingly difficult to understand at the time. Im afraid my brain glazed over!--Light current 19:42, 13 September 2006 (UTC)


 * I once saw a double full rain circle when standing behind a waterfall. Alas I didn't bring a camera. DirkvdM 09:02, 14 September 2006 (UTC)


 * I saw a quadruple rainbow once (and the gay coalition wasn't even having a parade that day). :-) StuRat 09:42, 14 September 2006 (UTC)

How thumb drive work?
Can anyone tell me how do computer read the data from the thumb drive (or pen drive) we use daily?Unlike the CD, VCD, DVD even the hard disk have the driver or ROM to read the data from the them, the way of the data read by the computer is confusing.
 * USB flash drives are basically just containers for a chip of flash memory. As far as drivers are concerned I'm not totally sure, but I think the operating system has a default driver for such purposes. - Dammit 09:58, 13 September 2006 (UTC)


 * Particularly USB flash drives implement the USB mass storage device class protocol - which means the OS is responsible for knowing how to talk to a generic USB-MSD but it's the responsibility of the flash drive's onboard controller to implement that interface. It's a nice division of labour - the OS doesn't need to know all the horrid complexities of working with flash memory, and by implementing one simple interface the drive can work in any compatible OS without the need to author device drivers for each one.  -- Finlay McWalter | Talk 12:00, 13 September 2006 (UTC)


 * Have you read thumb drive? It's fairly comprehensive.--Shantavira 09:58, 13 September 2006 (UTC)


 * Indeed. --Proficient 05:48, 15 September 2006 (UTC)

Circular motion
A girl standing at the equator is in circular motion about the earth's axis .Calculate the angular speed of the girl. The radius of the earth is 6400km .the girl has a mass of 60kg .Calculate the resultant force of the girl necessary for this circular motion If the girl were to stand on eighing scales calibrated in newtons,what reading would it give?
 * The top of this page states Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. This sounds awfully close to a homework question so try it yourself first. We will however, be glad to help you should you encounter any problems. - Dammit 09:53, 13 September 2006 (UTC)


 * <--rant-->Why do teachers think up these ridiculous questions? How about preparing kids for the real world? She got hold of some eighing scales calibrated in Newtons??? And surely angular speed should be angular velocity.<--end rant-->--Shantavira 10:05, 13 September 2006 (UTC)


 * I suspect it does mean angular speed. It sounds like a GCSE question and they probably don't need to know about vectors.


 * Everybody loves the GCSE! Nobody is going to help? Ok well I will have to than, because the three people above me couldn't ...wait, what are eighing scales? — [ Mac Davis ] (talk) ( Desk | Help me improve )


 * "Eighing scales" are used to determine how much you "eigh", which is directly proportional to the size of your "ass". :-) StuRat 14:12, 13 September 2006 (UTC)


 * Eh?--Light current 14:46, 13 September 2006 (UTC)


 * Which in turn is proportional to how many Marse ® bars you eat. DirkvdM 09:11, 14 September 2006 (UTC)


 * Yuk, I just realised an alternative meaning for that. DirkvdM 09:16, 14 September 2006 (UTC)


 * Eh, I mean, I just realised there is an alternative meaning for that. I didn't realise it in the sense that I did it. DirkvdM 09:21, 14 September 2006 (UTC)


 * Am I the only one having this conversation? (No wonder if I claim to eat Marse bars.) DirkvdM 09:21, 14 September 2006 (UTC)


 * Yes, eating "arse" bars will increase the size of your "ass". :-) StuRat 09:37, 14 September 2006 (UTC)
 * So will eating lard. Hence the term 'lard ass'--Light current 02:59, 15 September 2006 (UTC)

Obviously, eighing scales measure how much Tim Horton's coffee you can drink in a blizzard, while waiting for the roads to be opened up. --Zeizmic 15:24, 13 September 2006 (UTC)


 * See also above.  &#x2013; b_jonas 07:13, 14 September 2006 (UTC)

Questionable stuff in Endoplasmic reticulum
Our Endoplasmic reticulum article has been getting a lot of edits recently, many apparently from silly schoolkids. The section on "smooth ER" says "The smooth ER has functions in several metabolic processes, including synthesis of lipids, metabolism of carbohydrates, and detoxification of drugs and poisons" (my emphasis). That last part sounds very strange to me: it sounds like a vast oversimplification of a highly complex physiological process, and something that one wouldn't expect would be so easy to locate to a specific structure. Unfortunately the article, while quite elaborate, is entirely unsourced, so it's hard to check this. Thoughts? -- Finlay McWalter | Talk 12:06, 13 September 2006 (UTC)
 * That's terrible. I agree with you and will do some work in the article. — [ Mac Davis ] (talk) ( Desk | Help me improve )
 * Look better? — [ Mac Davis ] (talk) ( Desk | Help me improve )
 * Much, thanks. Expect future revisions, however, to note that the primary function of the Golgi apparatus is Steven is Ghay :) -- Finlay McWalter | Talk 16:52, 13 September 2006 (UTC)


 * Maybe a lot of sixth graders are learning about organelles and such. --Proficient 05:49, 15 September 2006 (UTC)

Gold-xenon compound
I've been reading about how one can make a compound of gold and xenon, two apparently unreactive elements. Do we have an article on this? What's its chemical name? It could be AuXe4 or Xe4Au, or something much more complicated. Is there a picture anywhere? And there's no point in asking me to look it up, I've been looking at gold and xenon and their compounds pages and have no idea where to begin, and looking up 'gold xenon compound' on Google yields nothing that can help me (I'm a cripple when it comes to chemistry). Help plz? Vitriol 13:01, 13 September 2006 (UTC)


 * I've only heard of that as a divalent cation, AuXe42+, not a proper compound itself, and never seen a name for it. For some "food for thought", here's an overview of some recent noble-gas chemistry. DMacks 13:34, 13 September 2006 (UTC)


 * See, I don't know what a cation is at all. Vitriol 13:37, 13 September 2006 (UTC)


 * A cation is a positive ion, a molecule lacking one or more electrons, thus giving it a positive charge. StuRat 13:51, 13 September 2006 (UTC)


 * From the ion article (I didn't know what it was either): "a positively-charged ion, which has fewer electrons than protons, is known as a cation (pronounced cat-eye-on), for it is attracted to cathodes."


 * By the way, Googling for auxe4 gives some interesting results, such as the mention of a darkred AuXe42+ crystal. - Dammit 13:53, 13 September 2006 (UTC)


 * Can you say it has electron holes? Or is that in semiconductors? — [ Mac Davis ] (talk) ( Desk | Help me improve )


 * I suppose you can, if you want to. StuRat 14:09, 13 September 2006 (UTC)


 * No, but the concepts are similar. A hole is a missing covalent bond in a crystal lattice which causes that particular atom to become a cation.  But a cation itself is just a positively-charged atom, and it need not have any bonds, nor be in a crystal lattice.  If a cation is sitting alone in solution, it is NOT a hole.   And if a cation is in a crystal lattice with equal numbers of anions, they are bonded by electrostatic (ionic) bonds and not by movable covalent bonds, so we still wouldn't call the cations by the name "hole."  --Wjbeaty 18:28, 13 September 2006 (UTC)


 * A small addition to answer the rest of the asker's questions, mentions Tetra Xenono Gold(II) as the name for the ion. The molecular configuration is pictured here. - Dammit 14:11, 13 September 2006 (UTC)

Forgive me if I am outside of my expertise, but I don't think it is completely accurate to polarize (snicker) the issue with respect to ionic versus covalent bonds. I have been taught to think of these types of bonds as extremes on a spectral scale, rather than opposites on a quantal one. That is, "ionic" and "covalent" describe attributes of a bond, but not the bond itself (and that there is indeed a middle ground). As such, ionic:covalent::velcro:glue, as opposed to ionic:covalent::velcro:magnetic attraction (if that was confusing, ignore it...)Tuckerekcut 21:33, 13 September 2006 (UTC)


 * Obviously the crystals aren't of the isolated AuXe42+ ion, they are of one its salts. one salt containing the ion is [AuXe4][Sb2F11]2. And the other partner isn't just sitting there, gold-fluoride interactions stabilise the whole assembly. If you have acess to more traditional (non-free) sources of information, see: Angewandte Chemie, International Edition (2002),  41(3),  454-456. i could post an image from this paper if you guys think it falls under fair review in copyright terms, showing the arrangement of atoms. and if someone shows me how to upload an image. Xcomradex 22:14, 13 September 2006 (UTC)


 * never mind, worked it out. the diagram is here. Xcomradex 22:47, 13 September 2006 (UTC)
 * As a sidenote, I've started an article about Tetra Xenono Gold (actually a substub, but feel free to change that). Maybe you can include the photo there if it falls under fair use. You can upload via - Dammit 23:00, 13 September 2006 (UTC)


 * Might want to add a note in the Noble gas compound page (or at least a link) too. DMacks 23:06, 13 September 2006 (UTC)

Bacteria question
My mother-in-law has had chronic chest congestion for many years. She was recently advised by her physician that the results of a sputum test shows she has congestion due to the presence of "sutomonus" bacteria (or virus?) in her lungs, and that it is untreatable. I do not know if this is the correct spelling of the bacteria, and I am unable to find any information about it using this phonetic spelling. Any information on this subject would be appreciated. Thank you.Spokaloo 16:27, 13 September 2006 (UTC)


 * It's probably Pseudomonas. -- Finlay McWalter | Talk 17:06, 13 September 2006 (UTC)
 * Unquestionably Pseudomonas, probably Pseudomonas aeruginosa. The organism is often found colonizing the sputum of people with chronic lung disease, such as bronchiectasis. There are instances where prophylactic treatment of the organism (by such means as aerosolized antibiotics) can be helpful in preventing further lung damage; if your mother-in-law has not consulted a lung specialist (pulmonologist), it might be useful to obtain another opinion as to the advisability of treatment. - Nunh-huh 19:29, 13 September 2006 (UTC)

dna
i think you guys might remember me i was the one who asked the question about the extraction of dna from pea soup, even after i tried it with my father's help i couldn't get it right , so i have decided to make a model of the structure of dna or a working model on dna , since the topic given to me was dna , therefore  could u help me witha few ideas on what to make so that i can expand on that .forgive me for my naiveity but is it possible to make a working model on dna , im not talking about an experiment or activity, thank you Mightright 19:34, 13 September 2006 (UTC)


 * Sorry the extraction didn't work out for you. There are lots of DNA-modeling kits available from science education stores; just do a google search on "DNA model" and poke around.  This website on about.com has instructions for building your own without a kit, although they look like they might be rather crude.  A good simple physical model of DNA "works" in the sense that you can see why the molecule has a double helical shape, you can compare the major groove to the minor groove, you can see why A pairs with T and G with C, and you can see how an accidental pairing of A with G can create a bulge in the molecule.  I don't know if there are models that can easily demonstrate replication and transcription and things like that, but at least with a physical model in hand you can point to things while explaining those processes to people. --Allen 20:29, 13 September 2006 (UTC)


 * If you're interested in spending some money, you might check out this page from sciencekit.com. I've ordered a couple things from them; they're kind of expensive, but at least they cater to individuals interested in buying just one or two things, rather than teachers ordering in bulk.  --Allen 20:32, 13 September 2006 (UTC)

Hold on: you tried to get DNA out of pea soup!? I think I remember your original question, and if you did say "soup", I misread it. As I remember (im sure somebody with a little more skill in wikipedics can link it...) I briefly described the marmur technique (which I called the marburg technique, sorry), in which DNA is extracted with cold EtOH. This would not have worked for pea soup. To make pea soup, one must cook the peas for a long time to get a proper consistency, and canned varieties are also flash heated or irradiated to avoid spoilage. This processing would destroy, or at least severely fragment all of the endogenous DNA material. The metals in the can would do a number on it too. In order to get macroscopic amounts of genetic material, you really need to start with fresh or flash frozen cells. Tuckerekcut 21:23, 13 September 2006 (UTC)
 * You can make a really nice DNA model with some spare Knex. Forget about the pea shoup, sounds messy! --Zeizmic 22:07, 13 September 2006 (UTC)

i just called the goo like liquid, soup (pea soup !yuck), actually these projects are supposed to be hand made not ordered from amazom because threr is every chance that my bio teache could flunk me for that 212.72.0.190 03:52, 14 September 2006 (UTC)

Woman/man physiological difference in body structure and movement
Is there a verified exemple of a woman/girl beating a boy/man in a fight without any weapon or it's just another urban legend? Don't get me wrong, I'm no mysoginist! This is a REAL (amateur) quasi-scientific inquiry based on an hypotesis that :women/men physiological differences(like better height ,better muscles,more grey matter in brain cells)are not innate but acquired via "darwin natural selection"-type genetic mutations throughout the years of human evolution. As a counter exemple of man superiority,you can check the "black widow" spider case. --SamiKaero 19:59, 13 September 2006 (UTC)


 * It is very hard to determine which components of observed sexual differences in humans are "caused by" genes or by social circumstances. (I use quotes here, because in a certain sense everything is caused by both genes and the environment.)  Determining which characteristics are a result of selection pressures would be even harder because that study would require more detailed understanding of human evolution than we are ever likely to have.  (For conflicting views, see evolutionary psychology and sociobiology).  Your question suggests, however, that you over estimate the actual sexual differentiation in humans.  Although, ON AVERAGE men may be stronger than women, there are certainly many women who are stronger than most men.  I feel confident that in all of human history many women have defeated many men in hand to hand fighting.  --best, kevin [kzollman][talk] 20:34, 13 September 2006 (UTC)


 * Yeah, I get beat up by girls all the time. AEuSoes1 20:41, 13 September 2006 (UTC)


 * It's hardly scientific, but some of the most formidable sparring opponents at my kung fu school are women. (Alas, I am not among these Amazons, but I hold my own.) --Ginkgo100 talk · e@ 20:46, 13 September 2006 (UTC)


 * Spousal abuse notes that a significant minority of cases involve women wacking their mates. More authoritatively, on the Bob Newhart Show, Mr. Peterson (an ex-Marine no less) is regularly abused by his wife. If Bob treats it, it must be so. Clarityfiend 20:54, 13 September 2006 (UTC)
 * Katie Sandwina ---Sluzzelin 21:05, 13 September 2006 (UTC)


 * Martial arts do not rely on strength --Light current 21:47, 13 September 2006 (UTC)


 * There's a book (probably long out of print) called Her Wits about Her that documents instances of women who successfully fought away violent assailants. Durova 22:13, 13 September 2006 (UTC)

How about last week's news: alteripse 22:21, 13 September 2006 (UTC)
 * How about two weeks ago's news? It is possible for a woman to beat a man in a fight, just look at it as if the woman was just a smaller man. In this situation we can approximate it. A more skilled fighter can win a fight over a larger fighter. — [  Mac Davis ](talk) ( New!  SUPERDESK | Help me improve ) 22:43, 13 September 2006 (UTC)

photo review
recently i returned from the phillipine islands on a diving trip. part of my objective was to photograph sea slugs or nudibranches. i have many photos that i feel would enhance the articles to sea slugs. all are of large format size and excellent quality. my question is and understand that i am a first time visitor to this site, who do i send the photos to for evaluation? i am not certain after reading the section on photos excatly what the process is. your help is greatly appreciated as i feel i can add to a small section of this site. the photos i have may prove to be useful for a student doing research or some other worthy cause.

thank you for your assistance Golfdog
 * Scientifically, this sounds interesting. You really have to go through the whole Wikipedia bag, starting with the general help, and editing information.   You can donate extra pictures in their general archive (you have to find out how!)  This is a fun hobby, and I was generally proficient in a few days.  Good luck! --Zeizmic 22:03, 13 September 2006 (UTC)


 * There isn't really an evaluation process at all. If you think your photos can help an article, add them. If you think they're considerably more helpful than an image already there, then replace it. It might be more helpful to ask (in the talk page, probably) if others agree before you do this, though.


 * If you want to upload all the pictures right away but are unsure if all or any of them should eventually be included in the Wikipedia, then try uploading to the Wikimedia Commons, which is a sister project of the Wikipedia. You can display pictures from the commons here, so you only have to upload the images to one site. -- Consumed Crustacean (talk) 22:04, 13 September 2006 (UTC)
 * How many pictures do you have? Do you know what species each is of? If you feel very uncomfortable (uploading was difficult for me the first few times), you can read the guide on it (which someone else will hopefully supply), or I can do it for you. — [  Mac Davis ](talk) ( New!  SUPERDESK | Help me improve )  18:53, 13 September 2006 (UTC)


 * Here we go: Uploading images - Dammit 22:53, 13 September 2006 (UTC)
 * It was hard because I didn't have a guide. :) Good luck. — [  Mac Davis ](talk) ( New!  SUPERDESK | Help me improve ) 01:16, 14 September 2006 (UTC)


 * To clarify why it is a good idea to upload to Wikimedia Commons, there are several Wikimedia projects, such as the different language Wikipedias, which can't use each other's photos, so they would have to be uploaded to each separately. That's why this central repository was made. You can place the photos here at the English Wikipedia like this: [[Image:DirkvdM green on blue plant.jpg|right|thumb|100px|A nice photo by me]] (check the source (click 'edit' to the top right) to see how I placed the photo). For an upload manual see http://commons.wikimedia.org/wiki/Commons:First_steps/Upload_form. If you need help identifying what's on the photos, see http://commons.wikimedia.org/wiki/Category:Unknown_species and follow the links to as specific a category as you can find. DirkvdM 09:49, 14 September 2006 (UTC)


 * That's a really nice photo, you should add it to the Yucca article, if you are so inclined. Gary 02:43, 17 September 2006 (UTC)

Help with Science Fair Project Topic
My question is one regarding my science fair project topic (obviously). I am looking for a science fair project related to or with computers. Why? I guess because I think computers are so interesting, but anyways, I'd like to know if you could kind of help me find some computer science fair projects also please let it be one that an 8th grader is capable of doing.


 * Thank You
 * Sincerely,
 * Raoul Frere


 * Get yourself some educational software intended for little kids (say first graders). Figure out what each one is supposed to teach them (reading, arithmetic, colours, whatever).  Then persuade the first-grade teacher to lend you some of her little charges, and let them loose on a computer with the educational software.  Watch what they do, and after a time (say 15 minutes) talk to them and ask them about the program - did they enjoy it?  did they learn how to do the thing the program was supposed to be helping them with?  could they work it themselves, or did they need someone to help them?  Then you can analyse your findings and present your results,and say what kinds of educational software actually work and which (hint: it's most of them) are really just junk.  But make sure to have a proper hypothesis and a scientific way of measuring your results (otherwise you're just doing market research, which sure ain't science). -- Finlay McWalter | Talk 21:28, 13 September 2006 (UTC)
 * I like that idea! Get some behavorial science/psych in there too. — [   Mac Davis ](talk) ( New!  SUPERDESK | Help me improve ) 22:39, 13 September 2006 (UTC)


 * I've always thought it would be cool to build a family of logic gates from basic components, but I've never done it so I don't know how much time and money it takes. Finlay's idea is probably a lot better, but I thought I'd mention mine in case you're more into the technical side of things.  Another idea might be to learn how to use a programming language to do simple image processing with bitmaps.  When I was in college, I took an intro course in C, and really simple image processing turned out to have a pretty high impressiveness-to-difficulty ratio.  --Allen 22:21, 13 September 2006 (UTC)


 * No no! Get the computer to control some moving thing! Thatll grab everyones attention.--Light current 22:42, 13 September 2006 (UTC)


 * Attention catching? Why don't you buy some old dead computers for $5 and annihlate them with thermite or napalm? Chemistry/Computer science! — [  Mac Davis ](talk) ( New!  SUPERDESK | Help me improve ) 22:45, 13 September 2006 (UTC)


 * It's cynical, but science-fair stuff should be attention catching - pity the poor judges who have to thole endless papier-mache volcanoes and potatoes/fungus/cress growing crudola. My next-door neighbour (who is about Raoul's age) was going to do a rotting-sandwiches experiment (yawn) but I suggested chucking eggs out of windows wrapped in various kinds of packing materials (and with a nice naked egg as a control).  He made a bunch of different packages (bubblewrap, newspaper, polystyrene beads) and took photos of the results of each droptest.  He had fun doing it (especially the smashing parts), much more so than he'd have had watching sandwiches rot. Better yet (well, worse for him, 'cos he's shy) he won the fair and had to present it at some regional fair (much to his excruciation).   I had worse luck persuading his older brother, however. Said teen was scheduled for medical school, and his bio project was something dull involving the nitrogen metabolism of soil bacteria.  My idea was altogether more fun (and more attention-grabbing-science-fair-ey) - buy a sheep's heart from the butcher and (armed with some plumbing supplies, a fishtank aerator, a bottle of lucozade and a car battery) see how many beats we can get out of the old ticker. For some odd reason that idea was decried as "sick". -- Finlay McWalter | Talk 23:00, 13 September 2006 (UTC)

You cannot be Sirius--Light current 22:47, 13 September 2006 (UTC)


 * It's fairly trivial to build the basic logic gate types using one or two transistors each. One such circuit is even linked directly from the logic gate article. I've seen articles from back in the 80s (perhaps in the "Amateur Scientist" column in Scientific American?) in which logic gates were constructed using ropes/struts/pulleys, and using billiard balls on pool tables with specially-arranged bumpers. DMacks 22:54, 13 September 2006 (UTC)


 * Not a debunk, but the Apraphulian computer (near Pullleg Mountains...) was an April Fools' joke ("Computer is unearthed in the jungle of Apraphul, An ancient rope-and-pulley.", Scientific American, April 1988, p. 96). 1 2 3 . Despite this, it could make a good science fair project, especially if you use the logic to *do* something. -- Fuzzyeric 03:52, 15 September 2006 (UTC)


 * I don't know how it could be made into a science experiment (and it might be outside your realm of computer experience), but something that is not nearly well-enough known, and it always of interest, is how easy it is to get data off a supposedly cleaned or erased disk. I'd suggest going to a 2nd hand computer store or a big second hand store (where they often have old hard disks at $1 a pound or $1 a gig), and show how the data can be retrieved despite the previous owners' erasure efforts, or your own. Anchoress 00:11, 15 September 2006 (UTC)

KW Vs HP
Car engine power here in Australia is normally measured in KW. How do I convert that figure to horse power?Downunda 00:01, 14 September 2006 (UTC)


 * 1 kW is abou 1.34 hp. Google will also do all kinds of conversions for you, including this one.  TenOfAllTrades(talk) 00:12, 14 September 2006 (UTC)


 * 746 W = 1 hp--Light current 00:15, 14 September 2006 (UTC)

Thanks folks! Downunda 00:16, 14 September 2006 (UTC)


 * I once learned a simple mnemonic for this: "In Fourteen-hundred and ninety-two / Columbus sailed the ocean blue / Divide that son of a bitch by two / And that's how many watts are in a horsepower". You're welcome.  -- Plutor  talk contribs  19:05, 14 September 2006 (UTC)
 * That's priceless!!! I usually just round this in my head by figuring 100HP is 75KW, you can rough out numbers either way pretty easily.   --Jmeden2000 20:42, 14 September 2006 (UTC)