Science desk
< January 21	<< Dec \| January \| Feb >>	January 23 >

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

January 22

how do i get taller

now i'm over 20 and my height is 5'4" so i want to more tall than before so how can i do?

00:28, 22 January 2008 (UTC)~ — Preceding unsigned comment added by 68.161.204.136 (talk • contribs) 00:28, 22 January 2008 (UTC)[reply]

Wear platform shoes? Either that or HGH. Paragon12321 (talk) 01:39, 22 January 2008 (UTC)[reply]

Viagra then lie down :D —Preceding unsigned comment added by Shniken1 (talk • contribs) 02:22, 22 January 2008 (UTC)[reply]

The questioner might not be male... —Keenan Pepper 02:24, 22 January 2008 (UTC)[reply]

The HGH suggestion seems perilously close to (bad) medical advice, but let me just point out that it probably wouldn't work anyway. As I understand it, once the ends of bones like the major ones in your arms and legs close off, which I think they do by the age of 20, hormones will not make the bones larger. What it might do is expand certain other bones, like ones in your face, which could distort your appearance in ways you wouldn't like. This is my personal non-expert understanding and is not meant as advice of any kind.

There is a procedure that we probably have an article on but which I don't know the name of. It involves cutting through the leg bones and holding them apart a small distance via some sort of adjustable metal rigging, then slowly increasing the distance as the bone grows to fill the gap. It's supposed to be terribly painful. Whether it will work on a 20-year-old I don't know. I mention it solely for academic interest--I don't think you'll find a reputable practitioner willing to do it on someone of normal height who just would prefer to be taller. --Trovatore (talk) 02:40, 22 January 2008 (UTC)[reply]

(Edit conflict): There is such thing as limb lengthening surgery Distraction_osteogenesis#Cosmetic_lengthening_of_limbs. (You may recall this from the film Gattaca.) But, as far as I can see, you'd have to be insane to go for it. Even if everything goes well you'll be off your feet for the better part of a year. (And if things go wrong, potentially the rest of your life.) That's a high price to pay for a few inches of height.APL (talk) 02:43, 22 January 2008 (UTC)[reply]

Perhaps you could try picking clothing that causes an optical illusion of extra height. For females, vertical stripes and a narrow v neckline might help add some apparent height. If your a male perhaps try solid colors. Picking some appropriate shoes could easily add an inch or more, guy or girl. Have a look at human height, you may not be as short as you think compared to everyone else. 152.3.44.183 (talk) 03:03, 22 January 2008 (UTC)[reply]

I would urge you to not worry about your height. Yes, I know this is easier said than done, but really: since there's nothing you can do about it, taking it easy and living with it and not worrying about it is the only approach there is.

I'm not saying there aren't people who will disrespect you for being shorter than average. There are such people. But there are also people who will disrespect you for being too tall, or too fat, or too skinny, or too old, or too young, or too smart, or too stupid, or for being male, or female, or white, or black, or just about anything. Don't worry about them, either. Their prejudices are their problem, not yours.

Most people -- and the people who matter -- will respect you for being who you are. There's no surer way to look like a nincompoop and earn people's disrespect than by trying to be someone you're not.

I know several people who are short, and who are self-conscious and defensive about it, and they're real jerks. (There's even a name for this: Napoleon syndrome.) I know several other people who are short, and who don't care at all, and they're perfectly normal people; I don't even notice that they're shorter than average. —Steve Summit (talk) 03:38, 22 January 2008 (UTC)[reply]

Hey, I'm 5'4" and I didn't know I was supposed to be short! Julia Rossi (talk) 07:24, 22 January 2008 (UTC)[reply]

I should point out that Napoleon syndrome is actually a misnomer. Napoleon wasn't that short. That's a misconception. 64.236.121.129 (talk) 14:41, 22 January 2008 (UTC)[reply]

Move somewhere with poor general nutrition. China used to be a good bet, but they're getting taller. Failing that, you should listen to Steve Summit above. What can be offputting about short men is not their height but the rat terrier attitude that sometimes accompanies it. If you're a woman, there's no stigma to being 5'4", so you needn't give it another thought. --Sean 14:20, 22 January 2008 (UTC)[reply]

You can become a famous actor and force all the extras on the set to be shorter than you. For example, I was in Camp Pendleton when one of the Rambo movies was filming. They put out a casting call for Marines to play extras. The only qualification was that you had to be under 5'7". -- kainaw ™ 15:19, 22 January 2008 (UTC)[reply]

Consider travelling in India, Japan, Mexico or the Philippines, see here [1] for human height averages. ; ) Julia Rossi (talk) 04:36, 23 January 2008 (UTC)[reply]

What is your reason for wanting to be taller? If it is not for cosmetic reasons then you might be interested to know that Sumo wrestlers who are just a fraction off the height requirement (yes, there is one, but I don't know what it is) have an implant placed in the top of their head above the skull. SpinningSpark 14:58, 23 January 2008 (UTC)[reply]

I'm 165-168 cm and I don't consider it a problem. Sure now that I live in New Zealand, I'm probably considered on the short side but who cares? Nil Einne (talk) 17:20, 23 January 2008 (UTC)[reply]

Woman care.217.168.4.225 (talk) 00:15, 28 January 2008 (UTC)[reply]

leg stab

I remember reading The Island of Dr. Moreau like 10 years ago.. Moreau stabbed his leg with a knife in a specific spot that he said has no nerves, so it doesn't hurt. Does this really exist? --f f r o t h 03:03, 22 January 2008 (UTC)[reply]

I'd expect not but I'm also certainly not an expert on anatomy. Bellum et Pax (talk) 03:51, 22 January 2008 (UTC)[reply]

Consider it from an evolutionary perspective. Having a point on the body where you could stick a knife in without feeling any pain would represent a survival disadvantage—you could be seriously injured and bleeding heavily and not realize it. Different parts of the skin have different degrees of innervation; your fingertips are more sensitive to touch than the middle of your back. There is no part of a healthy person's skin surface devoid of pain receptors (nociceptors).

Disease or injury can sever or disable the nerves to a part of the body, however. The canonical example is the disease leprosy, where the bacterium involved can kill off peripheral nerves in the body. Injuries to the affected extremeties frequently go unfelt and unnoticed, ultimately leading to the loss of limbs. TenOfAllTrades(talk) 04:38, 22 January 2008 (UTC)[reply]

Leprosy only kills nerves? How would incidental injuries going unnoticed make your extremities fall off? Getting punched in the nose would hurt, but even if you notice the pain there's nothing you can do about it and it just heals on its own. Same with nicking your shin on the coffee table or something. I mean, fall off? You'd have to have wire cinched tight around it for hours, or get hacked to pieces with an axe.. --f f r o t h 04:55, 23 January 2008 (UTC)[reply]

Things spinning really fast

Why is it that things that spin really fast look like they're going backwards? Like car tires. Bellum et Pax (talk) 06:57, 22 January 2008 (UTC)[reply]

They don't, except in movies/TV or under certain types of artificial light. See wagon-wheel effect. --Anonymous, 07:45 UTC, January 22, 2008.

This was here half a year ago, check it out. --Ouro (blah blah) 07:46, 22 January 2008 (UTC)[reply]

Western blot

I'm kind of discomforted by the fact that I've done these before, but I can't understand why they work. The primary antibody used in a western blot is typically created (initially) in an immune reaction to the protein of interest. The protein of interest is also denatured and (often with stuff attaching to it as well) in the course of the western blot. And so I'm perplexed that the primary antibody actually binds to the protein at all. I'm hoping someone can correct my confusion. Someguy1221 (talk) 10:10, 22 January 2008 (UTC)[reply]

You're quite correct in that many of the antibodies generated against the intact, non-denatured protein won't bind to SDS-denatured, linear protein from a western blot. Usually, however, at least some epitopes present on folded protein are preserved in the denatured protein. Consider a beta sheet, for example. An antibody that recognizes an epitope that runs perpendicular to the strands in the sheet (across several strands) won't work on denatured protein, whereas an antibody that binds to an epitope parallel to the strands in the sheet (following a single strand) may.

In practice, many antibodies are no longer prepared using the whole protein as the immunogen. Instead, short polypeptides (ten amino acid residues, give or take) corresponding to sequences from the protein of interest are synthesized and injected into the animal to generate antibodies. (The peptides are chemically 'decorated' in various ways to make them more attractive to the immune system.) These peptides generally have a 'look and feel' that's much closer to the denatured, extended protein seen during a typical western blot.

In any case, many (polyclonal) antibodies are also affinity purified. Essentially, you coat a column with the denatured protein or peptide of interested and flow the antibody mixture over it. Only the antibodies with the desired binding properties will stick; these antibodies can be eluted (collected) by washing in a slightly more aggressive buffer.

As for the 'stuff attach[ed]' to the protein, I assume that you mean the SDS (or other detergent) used to denature and solubilize the protein. Again, you're correct that high concentrations of detergent would definitely interfere with antibody binding. If you check your buffer recipe for the primary antibody, it will contain little (if any) detergent—perhaps just a dash of Tween to discourage nonspecific binding of the primary antibody. TenOfAllTrades(talk) 16:03, 22 January 2008 (UTC)[reply]

Location of spleen (in humans)

Can you help resolve an apparent ambiguity?

In the article Spleen, it is shown as being about level with the liver, just below the left lung.

But in the article Gallbladder is a diagram which also shows the spleen (number 8), which shows it as being a bit lower down.

Thanks. — Alan^✉ 13:46, 22 January 2008 (UTC)[reply]

Dare I suggest putting the word "spleen" into Google images? The top graphic, whose source is a US government health agency, seems more likely to be correct than the hand-drawn lower one, just on the face of things. And Google seems to agree. I mean, it doesn't take expert knowledge to figure that one out, is all I'm saying. --24.147.69.31 (talk) 16:18, 22 January 2008 (UTC)[reply]

The upper drawing is correct, the lower (which in fact shows the spleen lower than the liver!) is misleading. A normal spleen is palpable in only about 3% of thin people; in the remaining 97% it's above the level of the lowest rib. In contrast, the liver extends much more frequently below the rib cage (a minimum of 5cm in 51% of patients in one study). - Nunh-huh 18:18, 22 January 2008 (UTC)[reply]

If the image is misleading, perhaps it should be removed from the six articles it is used in (and the dozens of additional articles in other language projects). 96.227.63.251 (talk) 23:10, 22 January 2008 (UTC)[reply]

It would probably be better if it were simply redrawn, and the new version uploaded over the old one. - Nunh-huh 00:41, 23 January 2008 (UTC)[reply]

The spleen and liver are lower in children than in adults. Thought that might be interesting.--TreeSmiler (talk) 02:53, 23 January 2008 (UTC)[reply]

Or is the rib cage higher? :) - Nunh-huh 05:14, 24 January 2008 (UTC)[reply]

Thanks for the replies. — Alan^✉ 19:42, 24 January 2008 (UTC)[reply]

Testing an electric fence

In the movies they sometimes throw a piece of wood at a fence to see if it is electrified. Would this work in real life? If not, how can you test it to see if it is electrified? 64.236.121.129 (talk) 14:36, 22 January 2008 (UTC)[reply]

Depends on the type of electric fence. Are you planning on breaking into a North Korean prison camp or just crossing a field with cows? --BozMo talk 14:44, 22 January 2008 (UTC)[reply]

For cattle-type fences, just tap it. If it shocks you, it works. (NOTE THIS IS AT YOUR OWN RISK --BozMo talk 15:41, 22 January 2008 (UTC)) They are designed to shock cattle, not kill them. For lethal electric fences, that much electricity will charge the air around it. There are many things you can do to check for high amounts of static electricity in the air - such a holding a sheet of paper near the fence. The static electricity will bend the paper. You can experiment easily with a balloon. Rub it on the carpet to get it all charged up and see what various items do when they get close to the balloon. -- kainaw ™ 14:53, 22 January 2008 (UTC)[reply]

I would not count on being able to identify a lethal electric fence by the electric field in the air around it. According to the electric fence article, "modern low-impedance" electric fences wait until something touches them before delivering the jolt. I don't think the point of this is to defeat detection -- electric fences aren't usually intended to murder the unsuspecting traveler, but rather to deter passage. It's probably more a question of reducing the electric bill. --Trovatore (talk) 23:18, 22 January 2008 (UTC)[reply]

How would the fence know when any thing was touching it before delivering high voltage, and why would it wait?--TreeSmiler (talk) 23:32, 22 January 2008 (UTC)[reply]

How: it would keep a small potential difference (AC or DC? I don't know) between the fence and ground, and monitor the current. When the current starts to flow, it lowers the boom. Why: That way, you don't have to supply large amounts of power continuously. --Trovatore (talk) 23:43, 22 January 2008 (UTC)[reply]

I really wouldn't bother with all that if I was designing the shocking device (and Im sure neither would other electronic engineers). I would just create short duration HV pulses every 500 ms or so. Generation of high voltage at low current does not imply large electrical power input anyway. You could do it, if necessary, from a small 9v battery feeding an inverter.--TreeSmiler (talk) 00:43, 23 January 2008 (UTC)[reply]

Well, that would be one approach, but you still need more power than with the detection methodology, so why do you want to waste it? Just to have a slightly simpler design? Plus you'll be putting out an RF signal that might cause interference somewhere. (And I'm sorry, but I don't buy that you can lethally electrify a prison camp with a single 9V battery -- I'd have to see the design.) --Trovatore (talk) 00:55, 23 January 2008 (UTC)[reply]

Any voltage can simply be transformed up to a voltage that will cause a lethal current to pass through the human body. The amount of energy required is not that great either (I didn't specify the electrical capacity in Ampere-hours of the battery). See BSI publication PD6519 Part 1. [2]--TreeSmiler (talk) 02:11, 23 January 2008 (UTC)[reply]

Well, you said it was a "small 9v battery" -- it's reasonable to assume you're talking about an ordinary one. And you're talking about putting lethal pulses through a whole fence twice a second. I still don't buy it. There's a minimum amount of energy needed to overcome the parasitics to bring the fence up to that voltage, even for an instant, and you're not going to be able to draw enough power to do that twice a second. If you could, of course, you'd drain the battery almost at once, but you can't. Granted that I haven't done the actual calculations here, but come on. --Trovatore (talk) 02:35, 23 January 2008 (UTC)[reply]

I didnt say how long the battery would last did I? In fact I emphasized this in my last post by saying 'I didn't specify the electrical capacity in Ampere-hours of the [[battery]'--TreeSmiler (talk) 02:40, 23 January 2008 (UTC)[reply]

Dont forget that if there is no load on the high voltage side, there is essentially no energy used there.--TreeSmiler (talk) 02:44, 23 January 2008 (UTC)[reply]

You still have the RLC to overcome every time you bring the fence up to the lethal voltage. And actually it had better be a really super-lethal voltage if it's going to fry the target without some sort of circuit that detects the load and provides extra energy. And if you're going to do the latter then I don't think you're saving much complexity over the scheme I was talking about. --Trovatore (talk) 02:56, 23 January 2008 (UTC)[reply]

Neither capacitors nor inductors absorb/dissipate any energy. Resistance is not a factor until current is drawn. You dont want a lethal electric current- you want something that is going to deter, not kill or maim.--TreeSmiler (talk) 03:02, 23 January 2008 (UTC)[reply]

You don't have to keep wikilinking "energy"; I know what it is. The point about capacitance as a parasitic is that you have to supply a certain amount of charge to get the desired voltage; the actual energy will be dissipated resistively or as RF emissions, or maybe in corona discharge (I can't see how this can possibly work without voltages that will cause arcing). Similarly for inductance. As for your last sentence, you may not have looked back at the context of this thread. We are indeed specifically talking about lethal fences. --Trovatore (talk) 03:08, 23 January 2008 (UTC)[reply]

I link not for your benefit, but for others following this thread (sorry). I think you are misguided about the voltages at which corona discharges etc appear. We are actually talking about they sometimes throw a piece of wood at a fence to see if it is electrified. The word lethal is not in the original question.--TreeSmiler (talk) 03:16, 23 January 2008 (UTC)[reply]

No, we're talking about For lethal electric fences, that much electricity will charge the air around it. There are many things you can do to check for high amounts of static electricity in the air - such a holding a sheet of paper near the fence. The static electricity will bend the paper. --Trovatore (talk) 03:20, 23 January 2008 (UTC)[reply]

OK--TreeSmiler (talk) 03:32, 23 January 2008 (UTC)[reply]

In no case will a piece of wood tell you anything. I am not convinced that a sheet of paper will, either. The proper method would be using a volt-ohm meter to test for a high voltage potential between the wire and the ground. MilesAgain (talk) 15:08, 22 January 2008 (UTC)[reply]

Not true. A damp walking stick will tingle on a cattle fence. I use that all the time. --BozMo talk 15:41, 22 January 2008 (UTC)[reply]

What about a piece of metal? 64.236.121.129 (talk) 15:26, 22 January 2008 (UTC)[reply]

Only if it's firmly connected to the ground/earth and not at all connected to you.

Atlant (talk) 15:32, 22 January 2008 (UTC)[reply]

What is the possible voltage level, and how much current can it supply? I would want to know both of these things, at least in a qualitative sense. before testing whether it was live. Throwing a piece of wood would be a very poor test. Wires could be at a pretty high voltage before the piece of wood did anything dramatic. A common voltmeter such as you might have in a typical household shop would be unsafe for high voltages (480 V and up) since it could flash over and electrocute the user. Labs and utility workers have used a variety of testing devices such as a "statiscope" or equivalent [3] as well as high voltage digital meters on a long insulated handle. A rule is to test the tester before and after testing the conductor. A "live wire" result shows that the conductor is energized, but a FAILURE TO FIND IT ENEREGIZED DOES NOT MEAN IT IS SAFE TO TOUCH. Utility crews would test it dead, then ground it via approved grounding means, before touching it without high voltage gloves and other protective gear. Edison (talk) 18:08, 22 January 2008 (UTC)[reply]

So, peeing on the fence would be a *really* bad idea then? Do people actually do that? --Kurt Shaped Box (talk) 01:44, 23 January 2008 (UTC)[reply]

Yes. It was tested on Mythbusters. It was not possible to create a stream steady enough to get electrical current to travel from the fence to the human. -- kainaw ™ 01:53, 23 January 2008 (UTC)[reply]

Peeing on a low voltage electric fence may be ok, but I certainly would not try it on an 11 kv cable or overhead line (if you can project that far!). The resulting current would, shall we say, smart severely! --TreeSmiler (talk) 02:15, 23 January 2008 (UTC)[reply]

Look there are many ways I could advise people to kill themselves with even very low voltage sources, like 1.5 v batteries. Its not difficult. But Im not about to publish that sort of info here (or anywhere).--TreeSmiler (talk) 02:21, 23 January 2008 (UTC)[reply]

To try to answer the original question, depending upon the voltage on the fence, I would probably use a voltmeter. If the current was sufficient to light a small (bicycle lamp) electric lamp, you could use that.

I would always use insulated probes tested to withstand the maximum voltage that could possibly be there. I would also use an approved fused meter (or lamp) that could break the maximum fault current that could be supplied by the fence. (Safety warning over)--TreeSmiler (talk) 03:29, 23 January 2008 (UTC)[reply]

Also back to the original, my trusty electrical multimeter goes everywhere with me professionally, but I would not normally take it out on country walks (its not sealed against mud and cowshit). I find the best practical indication of electrification is if the fence/wire has been fixed to the posts with insulators, commonly glass or ceramic.

But thats not the reason I posted, I wanted to comment on the first two replies "Are you planning on breaking into a North Korean prison camp . . " and ". . . with a balloon. Rub it on the carpet . . .". Why do the North Koreans carpet around their prison camps? SpinningSpark 14:16, 23 January 2008 (UTC)[reply]

Just a note on one thing I've been told (by farmers & hunters) - if you do test an electric fence by touching it, use the *back* of your hand. If it's live, muscle contraction will close your hand and move it away from the wire, as opposed to palm towards the wire, where muscle contraction will tend to close your hand around the wire. I've never had an opportunity to try this, though. -- 128.104.112.34 (talk) 18:00, 24 January 2008 (UTC)[reply]

Chemistry: molarity vs. normality

How to convert molarity to normality? —Preceding unsigned comment added by 117.193.226.200 (talk) 15:34, 22 January 2008 (UTC)[reply]

Normality is just the ratio of two molarities. See Concentration#Molarity and Concentration#Normality. If you have 2 molar of X, and 3 molar of Y, then Y is 1.5 normal to X. Note that it is not an absolute unit: a concentration is always normal to some other concentration. MilesAgain (talk) 16:14, 22 January 2008 (UTC)[reply]

There is a discussion of this in the archives (here) --Bennybp (talk) 17:43, 22 January 2008 (UTC)[reply]

Which better to go after if being sexually assaulted (not for the squeamish)

Okay, you all remember when Lorena Bobbitt cut off her husband's...well, you can follow the link, I checked. Anyway, that was just a normal fight - well, it wasn't normal, but what I mean is, it wasn't a sexual assault. If it had been, or if she really wanted to get him, would it have been better to cut off the testicles? Because, then the guy couldn't do anything with his penis anyway. And, furthermore, if a woman is being sexually assaulted, you can't squeeze that off, but wouldn't it be pretty easy to squeeze the testicles not only till the guy fled in extreme pain (I knew someone who had one of those get twisted around and had a lot of pain) but even till they popped? Can they pop? Like I said, not for the squeamish. —Preceding unsigned comment added by 4.68.248.130 (talk) 21:16, 22 January 2008 (UTC)[reply]

[4] Let me just say, "oy." Someguy1221 (talk) 21:27, 22 January 2008 (UTC)[reply]

Isn't it astonishing that a woman who rips off a man's testicle and tries to eat it can write "I am in no way a violent person?" !!!! That takes balls...but I suppose she has them to spare... - Nunh-huh 22:05, 22 January 2008 (UTC)[reply]

Actually someone without testicles can potentially be sexually aroused as it may not eliminate the sex drive completely. I would presume the use of hormone replacement therapy in particular helps to reduce the effects (although the human mind is a amazing thing). See castration for some details. You may want to consider people who have orchiectomy as part of a sex reassignment surgery for male to female intersexuals. Or for that matter, female to male intersexuals who obviously don't and never hard testicles. Many of these people do have sex to some extent I believe. There would I presume be studies into the sex drive and info one how they may improve their sex drive for these people. Even ignoring these sort of cases, there would I presume be some info into ways it can be improved for people who have both testicles removed because they are cancerous or by accident (may not be that common but probably enough that there is some info). You may also want to consider the debate about the efficacy of castration to stop sex offenders (this usually revolves around chemical castration but I'm sure there has been some discussions related to physical castration). Incidentally, castration does mention castration play as a BDSM practice, which stimulates it without actually doing it. I'm not quite sure what this means and being male I'm not sure if I want to know. I presume it isn't talking about chemical castration. Your best bet is probably to cut off the penis after castration Nil Einne (talk) 17:09, 23 January 2008 (UTC)[reply]

N.B. it may also be useful to look into spinal cord injuries. These can greatly impair the connection penis and the brain (so to speak). The testicles are still there and so are producing hormones but their ability for arousal is clearly going to be greatly affected. But people with such injuries have ways they can have sex. While obviously this is the opposite of what were are speaking about, there's probably some lessons that can be learnt Nil Einne (talk) 17:14, 23 January 2008 (UTC)[reply]

I recall but don't particularly feel like looking up a post on BMEzine's Modblog in which a eunuch described how happy he was with his amputated testicles and replacement testosterone--he was quite adamant that the women loved his empty scrotum. grendel|khan 06:56, 27 January 2008 (UTC)[reply]

I suppose for accuracy's sake, we should point out that there was no "fight" involved when Lorena Bobbitt lopped off her husband's penis: he was sleeping on the couch when she mutilated him. In such a situation, Lorena's logical choice was: put the knife down, and go home to mother. - Nunh-huh 05:13, 24 January 2008 (UTC)[reply]

Having trained in martial arts classes with both sexes for a number of years, the advice that I have usually heard given is, yes, the testicles are a good target but do not assume your attacker will drop immediately or even react - adrenaline has amazing effects and could easily block or delay the pain reception. Also, they may not be available to you, for instance if the attacker has your arms pinned and control of your legs. There are plenty of other "squishy" targets available which can be effective with minimal strength and training, for instance eyeball gouging, fish hooking, pulling the attackers head in close and biting the ears/nose. If the testicles do present themselves, I have read on self defense forums that a sharp downwards pull and twist is most effective, apparently rendering some victims unconscious but I have (thankfully) never had to test this theory. 78.32.138.240 (talk) 23:46, 28 January 2008 (UTC)[reply]

Snap crackle pop

Before I ask this question, I'd like to assure the overzealous reference desk patrollers that this is not a request for medical advice. It is a request for information on human anatomy.

Last night, I was looking upward and turning my head from side to side when I felt a rather odd "pop" in my neck. I assume this was bumps on two of the vertebrae rubbing against each other; which two would it have been? --67.185.172.158 (talk) 21:29, 22 January 2008 (UTC)[reply]

This Cracking joints article seems pretty complete. --Mdwyer (talk) 22:24, 22 January 2008 (UTC)[reply]

Glass dust?

http://www.youtube.com/watch?v=YD4quOf0n6E&feature=related

^Harry Potter. At 2:31, wouldn't that glass dust still hurt them? 64.236.121.129 (talk) 21:43, 22 January 2008 (UTC)[reply]

Of course not, because Dumbledore protected them with magic. The shield pulverized the glass projectiles, maybe it also slowed them down, or turned them into candy, or completely destroyed them and replaced them with an illusion of dust, or toughened everything on the other side so it would resist the impacts. It's magic, applying physics and common sense won't help you explain what is going on. gnfnrf (talk) 22:03, 22 January 2008 (UTC)[reply]

You could go with literal explanations instead. Maybe the writer/director thought it looked cooler that way, or just didn't think about what glass dust would do to a person. Someguy1221 (talk) 22:11, 22 January 2008 (UTC)[reply]

Ignoring magic, if glass dust were moving towards a person at that around that velocity, would it be dangerous? 64.236.121.129 (talk) 17:01, 23 January 2008 (UTC)[reply]

To counter the impact of any projectile, you want to spread the force out over as large of an area as possible to reduce the impact pressure and you also want to spread the impact out over as long of a time period as possible. Turning a few shards of glass into a powder would help on the first count and possibly also on the second. The shape of the glass dust particles would also be important. Sharp particles would be far more dangerous than rounded particles, which are essentially "sand". Of course, sand is still an irritant in the eyes. StuRat (talk) 05:18, 23 January 2008 (UTC)[reply]

Thanks, but that's not really related... Interesting though. 64.236.121.129 (talk) 16:58, 23 January 2008 (UTC)[reply]

I guess my point was that things below a certain size aren't sharp. --Sean 01:13, 24 January 2008 (UTC)[reply]

I'm afraid that's not correct. 64.236.121.129 (talk) 19:23, 24 January 2008 (UTC)[reply]

Or at least the size has to be very small, like individual atoms, for objects to no longer be "sharp". StuRat (talk) 17:16, 27 January 2008 (UTC)[reply]

Post-coital urticaria in a penicillin-sensitive patient

Female being treated with amoxicillin. Within minutes post-coitus (with condom), (male) penicillin-sensitive patient developed urticaria around genitals but not on penis. Treated by (somewhat doubtful) GP for drug reaction, and urticaria healed (so this is a science question, not a medical advice question). What I want to know if there are any reported cases of this in the literature? I could not find any. --196.210.102.113 (talk) 21:43, 22 January 2008 (UTC)[reply]

If they are, they would be in MEDLINE, but that is probably where you looked. MilesAgain (talk) 13:32, 23 January 2008 (UTC)[reply]

Forgive me if it appears that I'm dumbing this down. I am. Maybe it will pull in a better response:

Have you ever heard of someone getting an alergic reaction -- hives -- from something their sex partner was taking? --Mdwyer (talk) 05:33, 24 January 2008 (UTC)[reply]

Melonized Steel

We received a specification from a customer for a marine steel part; after machining the part needs to be "melonized". I assume it refers to some sort of heat treating or chemical processing that is required to prevent oxidation. I couldn't find anything on the web except for a Chevrolet melonized gear, but it didn't really show any useful information about what the specification is. I also checked ASTM site and found nothing. —Preceding unsigned comment added by Delriodave (talk • contribs) 21:49, 22 January 2008 (UTC)[reply]

'Melonized' appears to be typo for 'melanized', steel which has gone through 'melanization'. I'll guess that by analogy to melanin, this process creates a black oxide layer on the steel. Note that our iron oxide article describes black oxide as follows:

"Magnetite (under the name Black Oxide) is used for coating steel tools [2]. This protects them from corrosion and gives a pleasing appearance.

Atlant (talk) 22:23, 22 January 2008 (UTC)[reply]

Could the customer be referring to Melonite processing? In any case, why not ask them? --169.230.94.28 (talk) 22:34, 22 January 2008 (UTC)[reply]

Circular motion/ conservation of energy.

Hi all. This question is from an A-level physics exam I took a couple of days ago. I'm posting it here because I got an answer which is quite pleasing if I'm right, so I'd like to know if I am.

It concerns a ride at a theme park which basically consists of a swing with a rigid pole instead of a chain, the length of which is 18m. The question asks: What is the ratio of the force from the seat on the rider to the rider's weight when the swing is at its lowest point, if it is released from a horizontal position?

My working is as follows:

Net force on rider (in upwards direction): $F_{NET}=F_{SEAT}-mg={\frac {mv^{2}}{r}}$

By conservation of energy, ${\frac {mv^{2}}{2}}=mgr$

So $v^{2}=2gr\,$

Substituting into the force equation, $F_{SEAT}-mg={\frac {m(2gr)}{r}}=2mg$

Therefore, $F_{SEAT}=3mg\,$

What we are looking for is ${\frac {F_{SEAT}}{Weight}}={\frac {3mg}{mg}}=3$

Which seems to work out quite nicely, apart from the fact that a friend got $\pi$ , which makes me think I've missed something. Can anyone confirm the answer or find a flaw in my working? Thanks Seth Bresnett • (talk) 22:29, 22 January 2008 (UTC)[reply]

Your calculation looks OK to me. That means you are feeling an "effective gravity" of 3 g at that point. Which is pretty cool because 3 g is about the maximum effective gravity you would feel in a space shuttle launch. --169.230.94.28 (talk)

If this is correct, then the force at the bottom is independent of the length of the bar. Can that be correct? -Arch dude (talk) 00:42, 23 January 2008 (UTC)[reply]

Yes, given standard assumptions. That includes assuming the mass of the rod is negligible compared to the mass of seat+rider, however, which seems unlikely, especially for long rods. [[User talk:Algebraist|Algebraist]] (talk) 00:57, 23 January 2008 (UTC)[reply]

isn't it mv^2/2 = mvr, not mgr--155.144.251.120 (talk) 03:00, 23 January 2008 (UTC)[reply]

No. Algebraist 10:25, 23 January 2008 (UTC)[reply]

Creatine

Sorry for the re-post, but due to the incompetency of some users on wiki I had to repost.

Do creatine phosphate and creatine monohydrate turn into the same thing by the body? —Preceding unsigned comment added by 76.167.156.92 (talk) 22:49, 22 January 2008 (UTC)[reply]

Your last question was not lost to "incompetency", it was removed because it appeared to be asking for specific medical advice, which is forbidden on the reference desk. I suppose you can debate whether or not you were asking for medical advice or asking a general question, but please Assume Good Faith. APL (talk) 23:58, 22 January 2008 (UTC)[reply]

See phosphocreatine (the name of creatine phosphate). As explained to me, the natural process is that phosphocreatine is made in your liver and transported to the muscles for storage. Then, as needed, it is converted to ATP for short-term energy bursts. Creatine monohydrate is one of many creatine supplements. It will increase the creatine in your body, which should lead to more phosphocreatine production, which should lead to more phosphocreatine storage, which should lead to the ability to have more short-term energy bursts. I use should because I do not know of any proper tests on introducing creatine to the body through supplements. -- kainaw ™ 17:37, 23 January 2008 (UTC)[reply]

Thanks Kainaw —Preceding unsigned comment added by 71.105.67.123 (talk) 08:42, 24 January 2008 (UTC)[reply]