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March 11

Tongs Cause Illness!

Tongs must cause illnesses to be spread. Think about it: if I reach my hand into a bucket of rolls, I may contaminate 2-5 rolls, i.e. the ones that my hand comes directly in contact with. However, if I use a tong, I am touching the same surface that dozens of others have touched, giving me their germs, and spreading my own to all future users of the tongs. The same goes for any food I can think of, given that eventually one's hands will reach the mouth. Why do people insist on using tongs when five seconds of thought reveals they are a BAD thing? 169.229.75.128 (talk) 00:25, 11 March 2009 (UTC)

NOoooo! The tongs have two ends - the end you touch and the end that touches the bread. The bread touches the parts of the tongs that (in theory) no human hand has gone - so it stays clean. Sure, your hand gets fractionally dirtier - and if you use the same hand to pick up your bread - then it gets a fraction-of-a-fraction dirtier. However, at least it's all under your control - you can go wash your hands - or pick the bread up with a napkin - or cut and eat with knife and fork - it's all your choice. If the bread is already covered with who-knows-what when you get it, there is nothing you can do. SteveBaker (talk) 00:41, 11 March 2009 (UTC)

Also to consider... How long does some bacteria/virus that you have on your fingers last on the tongs as compared to the food - especially when the food is on a warmer. Personally, I do not eat at buffets because I find it overpriced and disgusting - no different than eating from a trough. If I did, I would prefer the people touched the tongs and not my food. I can wash my hands, but I can't wash all the food. -- kainaw™ 01:10, 11 March 2009 (UTC)

No, you're both missing the point. To Steve: you touch the tongs with the germs, then you eat your food. It doesn't matter if there are two ends! No one I see at the buffet actually washes their hands IN BETWEEN getting their food and eating, they might wash before the whole process but not after getting the food. It's not "fractional", germs are germs are germs are germs. And to Kainaw: you ask about time? When 100's of people are touching the tongs each hour, how long does it matter? 169.229.75.140 (talk) 01:27, 11 March 2009 (UTC)

I won't argue your point regarding rolls (I'm not sure you're right, but I can't conclusively say why.) However, let's look down the buffet table a bit past the bread and see what else we have... Any ideas on how to serve spaghetti without tongs? - Eron^Talk 01:49, 11 March 2009 (UTC)

Since this is the Science reference desk and not the Wild Speculation Reference Desk, take a look at Survival of foodborne pathogens on stainless steel surfaces and cross-contamination to foods, from the International Journal of Food Microbiology (2003) [1]; and, The survival and transfer of microbial contamination via cloths, hands and utensils, in the Journal of Applied Bacteriology (1990) [2]. "Gram-negative species survived for up to 4 h, and in some cases up to 24 h. Where contaminated surfaces or cloths came into contact with the fingers, a stainless steel bowl, or a clean laminate surface, organisms were transferred in sufficient numbers to represent a potential hazard if in contact with food." Evidently, utensils can and do spread bacteria. Of course, a more relevant question is: do tongs decrease the risk of bacteria propagation compared to handling food without them? Nimur (talk) 01:58, 11 March 2009 (UTC)

The spaghetti issue is ONLY a messiness/convenience issue. My original point is about cleanliness and germs. I was scolded by a buffet manager for not using the tongs for the rolls, that's what started this thread.169.229.75.140 (talk) 02:12, 11 March 2009 (UTC)

See also Five-second rule. -- Wavelength (talk) 03:32, 11 March 2009 (UTC)

You're mistaken about the fractional thing. The number of pathogens you come in to contact with makes a big difference in how likely you are to be infected. If you still don't get it, to use a simple example, there's a big difference between frenching someone who has a cold and the same person coughing onto their hand which they then use to open a door and the door is then later opened by person B and then person B later shakes hands with person C who then opens another door which you person D opens. And the reason why restaurants insist on tongs is because they don't want you contaminating their food (indeed it may be a legal requirement). Person you're not aware of this but your exposted to 'germs' probably every minute of every day unless you live or work in some sort of ultra clean room. Contaminating their utesils is a different matter and realisticly is to be expected. Do you object when the waiter doles out utesils with their hand? What about when the waiter doles out food with their hand? The key point as SB mentions and we discussed later, you can choose not to eat with your hands (or wash/sterilise them after they've been contaminated). But once the food has been you have to either throw it out or cook it again. Nil Einne (talk) 06:25, 11 March 2009 (UTC)

Another point... Assume some heavily diseased imbecile is trying to infect everyone at a buffet. In scenario 1, he uses tongs. I touch the tongs and my hands have some bacteria on them. Most bacteria will not absorb into your skin easily. They must get into your body (usually through ingestion). But, it is on my hands and I use a fork, spoon, and knife while I eat. So, I'm not infected. In scenario 2, he shoves his hands into all the food. Everything he touches gets infected. As others shuffle the food around, the infection spreads. The food is infected so, regardless of if I use utensils or not, I will get infected. Which scenario is more sanitary? -- kainaw™ 03:43, 11 March 2009 (UTC)

If plasitc surfaces worked just as well for breeding bacteria as food, why then don't we use empty petri dishes instead of Agar plates to grow cultures? Since we do the latter, one assumes pathogens grow better when they have lots of stuff they can eat.76.97.245.5 (talk) 03:57, 11 March 2009 (UTC)

As a final point to Kainaw's scenario, the same diseased person opened the door to the restaurant that you also opened. If you touched the door, you got the same germs as you would have from the utensils... The whole thing is that this is more about ritual uncleanliness with regards to the psychology of eating more than any real risk of increased disease. Disease spread by contact with tongs would just as likely spread through any of a thousand other mechanisms throughout the course of your day. If you want to avoid infection at that level, your probably better off not leaving your clean-room of a house... --Jayron32.talk.contribs 05:57, 11 March 2009 (UTC)

I think Kainaw has an excellent point. Just use utesils to eat the food (yes you can use a fork to eat a roll) and don't touch your mouth or nose (which is something you shouldn't be doing anyway). Unless you wear rubber gloves everywhere you go, you pick up way more germs in regular contact with the environment anyway so it's pointless worrying about the germs that do get on your hand, just avoid consuming them. Nil Einne (talk) 06:17, 11 March 2009 (UTC)

Two other related points, the vast majority of bacteria are harmless. If you do not get exposed to infectious organisms you will never build up a useful immunity. Richard Avery (talk) 07:25, 11 March 2009 (UTC)

The point everyone seems to be making is basically this: who cares because you will get the germs anyway. In that case, AGAIN I ask why have tongs if you're gonna get the illness anyways. And to respond to legal questions, that's my point! Why are tongs required by law? And finally, NO ONE doesn't touch their mouth at some point. Somehow, someway, your hand (or something you touch) will make it to your mouth. I do not object to waiters because I have some trust that they wash their hands because their job depends on it. Regular buffet-goers, I am almost sure, do NOT wash their hands. I would rather they just grab the food, infect one or two or three rolls than touch the tongs and infect everyone who touches it in the future.128.32.78.189 (talk) 17:12, 11 March 2009 (UTC)

I think the distinction is between what is possible and what is likely. It is possible that people will get sick if everyone uses tongs. It is likely that people will get sick if everyone uses their hands. SDY (talk) 17:21, 11 March 2009 (UTC)

I still can't see how that's true. If dozens of people touch the tongs, while only a handful of rolls (or whatever) are contaminated if there are no tongs, then even if the odds of contamination are a dozen times more likely for the no-tongs, the number of infections will still be EQUAL either way (at most).128.32.78.176 (talk) 17:37, 11 March 2009 (UTC)

You are not considering the fact that just as everyone uses the tongs to select bread, without tongs everyone would use their hands. So multiply that 2 to 5 rolls you suggest might be contaminated by hand contact by every person who takes a piece of bread. You reach in and touch four rolls. I reach in and touch three different ones. The next guy reaches in and touches five different ones. Pretty soon the whole bin would be contaminated, wouldn't it? Given the choice between surface contamination of a utensil, which might be transferred to my hand, and surface contamination of food, which will be transferred to my mouth, I'll take my chances with the tongs. (If you are really worried about this, may I suggest using a napkin to hold the tongs?) - Eron^Talk 17:44, 11 March 2009 (UTC)

You won't object if a waiter hands out food with his/her hands? Really? Also it's easily possible to minimise contact with your mouth and nose (no one said never touch). Personally I don't actually bother but I don't get sick much so I guess it doesn't matter. But since you are so worried about getting sick from touching tongs, you really need to change your practices rather then getting worked up over nothing. I do hope you already wear a face mask whereever you go. P.S. As has already been stated, touching tongs which have been contaminated is unlikely to be sufficient to infect you. If you get 'infected' then it's really your own fault due to poor practice in handling food. On the other hand there's little you can do once some jerk has contamianted your food other then not eat it. Nil Einne (talk) 19:45, 11 March 2009 (UTC)

What about things besides bacteria? I can think of any number of substances (bodily fluids, engine grease, mud...) that might be on someone's hands that I would much rather get on my hands than in my food.-- Mad031683 (talk) 20:25, 11 March 2009 (UTC)

If you are careful, I would think you could reach in and only touch the roll you were taking. 65.167.146.130 (talk) 20:46, 11 March 2009 (UTC)

Of course you could, and I made that point to the buffet manager too, he thought I was insane I think. And I'm not doing this because I personally get sick a lot, I don't, I'm asking this because I'm curious about common practices and the reasoning behind them.169.229.75.140 (talk) 03:55, 12 March 2009 (UTC)

But not everyone will do that. I'm sure you've noticed that a certain number of people don't seem to have a very good understanding or belief in the Germ Theory of Disease. So the question is : which is worse? A Hands->Tongs->Hands->Food transfer that happens 100% of the time? Or a Hands->Food transfer that happens happens (let's say) 10% of the time. APL (talk) 18:06, 18 March 2009 (UTC)

The questioner has made it very clear that he will not accept any statements that may imply that a person can get his or her hands contaminated and, from that point on, avoid spreading the contamination to his or her mouth. Apparently, the questioner spends all his time with his hands in his mouth and has never heard of things like forks and spoons. With that lifestyle and limited knowledge, no amount of explanation will allow this argument to progress. -- kainaw™ 03:59, 12 March 2009 (UTC)

Disinfecting a Chicken Wing

So I have a lab where I have to 'remove all surface bacteria from a chicken wing'. I've thought about it, and my best ideas are:

1) Microwave it for a few minutes (but that would make the room smell bad..) 2) Boil it 3) Soak it in Listerine for 5 minutes (which has the added bonus of making it minty fresh)

I'm looking for something easy, but effective, so my lab report can have both a short procedure section and a minuscule errors section. Any materials I can get my hand on are fair game. In fact, there's not many restrictions at all, except that I have to be able to explain it. Any ideas? -Pete5x5 05:46, 11 March 2009 (UTC) —Preceding unsigned comment added by Pete5x5 (talk • contribs)

And there is no requirement for being able to eat the chicken wing after this cleaning? Dismas|^(talk) 05:48, 11 March 2009 (UTC)

I wouldn't recommend microwaving or boiling as those would effectively cook the chicken wing, which from a lab perspective would make it less useful for future experiments. You might get some ideas at Sterilization (microbiology). - Eron^Talk 05:51, 11 March 2009 (UTC)

Does the chicken wing have to be recognizable as a chicken wing even? You could simply incinerate it, and then test the ashes for bacteria. If not, then what is wrong with simply frying the wing in hot oil for 5 minutes or so? Then you can coat it in hot sauce, dip it in blue-cheese dressing, and enjoy. If the wing must remain raw after disinfection, then a sufficiently concentrated salt solution or brine should do the trick, or a hefty spray with Lysol or another surface disinfectant may work as well. --Jayron32.talk.contribs 05:54, 11 March 2009 (UTC)

This is probably a useless answer. Using food irradiation is an effective method of killing pathogens present on food without significantly affecting the taste, composition or appearance of food. However it's unlikely you have access to an irradiation chamber and I'm pretty sure you need to be well qualified and trained to use such things Nil Einne (talk) 06:11, 11 March 2009 (UTC)

Take off the skin? DMacks (talk) 06:11, 11 March 2009 (UTC)

Incidentally I would take care with microwaving it too long. Things can catch fire in a microwave Nil Einne (talk) 06:19, 11 March 2009 (UTC)

Just catch fire if you're lucky! DMacks (talk) 06:25, 11 March 2009 (UTC)

Going with more impractical ideas very high pressure would work. It would also reduce much of your chicken wing to pulp. "All" bacteria is quite a tall order because there are some rather hardy bugs out there. Plus any chicken wing you'll encounter in a lab will already have encountered a lot of processing {http://attra.ncat.org/attra-pub/poultryprocess.html#washing]. It may even have been frozen and thawed. What is on the outside of your wing comes from 4 sources: seeping out or migrating from the inside, introduced through the air, introduced through surface contact and those that survived previous processing. The latter are the most difficult to get rid of. Since some bacteria can form endospores any of those might survive most of the methods suggested above. Our article suggests Ethylene oxide. Nasty stuff, and not for your average lab assignment. To get rid of "most if not all" surface bacteria you could go with a multiple step process. I'd try in no particular order: washing in an acid, rinsing in a base, dipping in alcohol, dumping it in in boiling distilled water, shock frosting, trying to avoid exposing the surface to contact with air as much as possible. Putting it in a bag you pump full of pure oxygen should get rid of a couple of the surviving bugs. If your following assessment doesn't include doing anything with the bacteria not on the outside of the wing, you could try breeding some "easy to kill" variety in large quantity and use them to crowd out other bugs. That method is not foolproof either, because bacteria swap genetic material. Good luck. 76.97.245.5 (talk) 10:02, 11 March 2009 (UTC)

Certainly there are a lot of ways of doing this - but which you choose has to depend dramatically on what you intend to use the chicken for afterwards. If you are going to examine the structure of the wing by dissection - then the answer has to not physically disrupt the shapes and textures. But if you are going to feed it to lab animals - then that doesn't matter at all and instead you have to be sure you're not introducing other substances into the food. So the answer is "it depends". SteveBaker (talk) 11:16, 11 March 2009 (UTC)

All excellent ideas. We definitely don't have to eat the chicken wing after, seeing as they intentionally infect it with bacteria beforehand so that might be a little dangerous. And I would imagine it would have to still be recognizable at the end because we're supposed to let it sit for a day once we're done then come back and see how 'clean' it is (hopefully somewhere relatively sterile, or all that work will be for nothing). My favourite idea is to incinerate it and test the ashes, but not only would it be difficult for me to find a way to incinerate it (I pretty much only have access to a Bunsen burner or a microwave, unless I'm going to bring something else in) but it would be very hard to swab afterward. The strong acid/base thing is probably also unacheiveable, as I think we're only provided with stuff normally found in our particular lab room, which in this case is disinfectants. Other than that, I'd have to bring it in. -Pete5x5 11:32, 11 March 2009 (UTC) —Preceding unsigned comment added by Pete5x5 (talk • contribs)

For surface treatment, look into using iodine compounds such as Povidone-iodine which is commonly used in medical purposes. It's the brown liquid that surgeons swab people with before making their incision. That would probably do the trick nicely and avoid harming the rest of your chicken. Failing that, I'd go with a simple 70% ethanol solution which is typically what is used in a lab for disinfecting things. --- Medical geneticist (talk) 13:48, 11 March 2009 (UTC)

Soak it in alcohol for a few seconds, put it in a (fire proof) container, set it on fire, let it burn for a while, close the container to extinguish the fire. Dauto (talk) 14:49, 11 March 2009 (UTC)

I love the idea of setting it on fire. I'm always looking for excuses to burn things. -Pete5x5 16:20, 11 March 2009 (UTC) —Preceding unsigned comment added by Pete5x5 (talk • contribs)

There are commercial anti-bacterial washes for fruit and vegetables[3]. I don't know how well they would work on chicken (does chicken have more germs?) Alcohol and vinegar as already mentioned would have a similar effect. --Maltelauridsbrigge (talk) 16:54, 11 March 2009 (UTC)

Chicken in general does have more germs. They don't test chicken for C. jejuni, they just assume it's there. No one in the real world expects that it is possible to get "all" bacteria off of a piece of food. The standard used for things such as pasteurization is generally a 5D reduction (5 logs or 99.999%) because of the concept of an infectious dose-one bacterium is rarely enough to cause an actual infection, though for things like Salmonella it may be a very low order (ten is the number I hear, but ten in one bite, one 8 oz serving, one day, it's not so clear so the number isn't helpful). SDY (talk) 17:31, 11 March 2009 (UTC)

A brief complete submersion in 95% ethanol, plus 2 minutes of constant agitation in 10% bleach solution and then 70% ethanol solution sterilizes with practically 100% efficiency all surface bacteria and fungal spores from sections of leaf while leaving interior fungi and bacteria intact. For a chicken wing, you may need to lengthen the agitation step if there are feathers or other air-trapping surfaces on the skin. 152.16.144.213 (talk) 21:52, 11 March 2009 (UTC)

Well the experiment has been performed, and by soaking the wing in vinegar for 5 minutes then boiling it in a brine solution I removed almost all of the bacteria from the wing. The agar plate showed only 11 small colonies of bacteria after being spotted with a wash from the chicken wing, as oppose to the group beside me, who had over 280 colonies. Thanks everyone!

Resolved

-Pete5x5 (talk) 18:06, 13 March 2009 (UTC)

How does cancer kill people?

Just what the subject says. Is it something to do with the body's available resources diverted to feed all these cells? Or does the cancer release toxins? Please note this is not a request for medical advice, it's just that having been with someone who died of cancer, I'm curious to find out what happened at the end. --TammyMoet (talk) 10:14, 11 March 2009 (UTC)

See this archive entry of the Science Reference Desk. —Preceding unsigned comment added by 173.49.15.165 (talk) 12:28, 11 March 2009 (UTC)

Thanks for that reference - I'd searched the archives myself but failed to find it! I'm still not clear, though. Is it that there are more cancer cells than normal cells, and once the tipping point is reached, the cancer is incurable, you've just got to wait until you've been taken over completely?

--TammyMoet (talk) 18:49, 11 March 2009 (UTC)

I should note that I'm not particularly well educated in this area, it's just speculation on how I think this would work. Unfortunately it's a very, very broad question because different cancers damage different organs. Most simply, it's that eventually the number of cancer cells makes it too hard for an organ to work efficiently, or even at all, and this is what would kill you. For example, cancer of the pancreas eventually stops sufficient enzyme secretion (as cancerous cells in this case cannot synthesize enzymes, at least I think) and this prevents digestion of certain foods, especially proteins and lipids. But of course, cancer can then metastatize (a.k.a. spread to other areas) and then you start getting multiple issues with multiple organs. Cancer essentially overwhelms the body, but you'd get a better explanation from a textbook. —Cyclonenim (talk · contribs · email) 20:20, 11 March 2009 (UTC)

The problem with pancreatic cancer is that its symptoms are often vague until the disease has metastasized, and/or has invaded into adjacent tissues. The pancreas itself is not necessary for survival if the patient is given insulin and digestive enzymes. Otherwise, Cyclonenim is correct in that the mechanism of death may be dependent on local conditions. A brain metastasis may lead to increased intracranial pressure, which may result in fatal brain herniation. A cancer may invade into large blood vessels, which then may rupture and result in fatal massive hemorrhage. Often, metastatic cancer leads to a condition called cachexia (loss of appetite, loss of weight and muscle tissue, fatigue, weakness). The patient then becomes susceptible to infections, which often are the direct cause of death. --NorwegianBlue ^talk 22:50, 11 March 2009 (UTC)

Hygiene without soap

Is it possible to clean the skin without soap? I was thinking that perhaps using something like a salt or seawater could replace soap.--Mr.K. (talk) 13:15, 11 March 2009 (UTC)

Alcohol rub perhaps? It would depend on why you wanted to avoid using soap. Fribbler (talk) 13:23, 11 March 2009 (UTC)

Aqueous cream? I believe that is used by people allergic to soap. --Tango (talk) 13:34, 11 March 2009 (UTC)

Soap is used because it easily carries away oils and residues which harbor bacteria. This is because soap is chemically soluble in both water and oil (polar solvents and nonpolar solvents). If you want to remove the same quantity of oil and residue, you will need to use a chemical which can dissolve them, or mechanical scrubbing to remove them by brute-force. It's not necessary to remove all the oils from the skin to be "clean" (in fact, this may agitate some people's sensitive skin). Ideally you just want to eliminate harmful bacteria; sometimes effective washing with plain water is sufficient. Nimur (talk) 14:40, 11 March 2009 (UTC)

In some cultures, they use urine to clean skin, since it's mildly antiseptic. StuRat (talk) 15:25, 11 March 2009 (UTC)

The Romans were well known for bathing every day, and are not known for using soap. They used a scraper to remove sweat and dirt and oil from the skin. Edison (talk) 15:30, 11 March 2009 (UTC)

I see that there are alternatives. But what about what I suggested above? Would seawater do the trick? I feel that my skin is clean after I bath at sea.--Mr.K. (talk) 16:09, 11 March 2009 (UTC)

Shower gel is not soap, as it has not been saponified. --Sean 16:18, 11 March 2009 (UTC)

When I bathe in seawater, I come out covered in salt crystals, which does not leave me feeling clean at all. // BL \\ (talk) 22:56, 11 March 2009 (UTC)

Seawater is a habitat for many species. If you'd like to wash away dead skin cells and body oils it might do the trick. If you'd like to remove the flora and fauna that has established itself on your skin since your last bath, you might end up just changing the population figures. The CDC has a couple of pages that describe some of the entities living in seawater in various holiday locations. I decided they came under "way too much information." Filtering seawater through a couple of layers of cloth would make it more usable. 76.97.245.5 (talk) 11:02, 12 March 2009 (UTC)

There are places in the world where people bathe in seawater, mainly due to a lack of fresh water. Whenever possible, they still rinse in fresh water to remove the salt and other residue left from the seawater. StuRat (talk) 15:05, 13 March 2009 (UTC)

Is my head younger than my feet?

We all know that if you take two ridiculously sensitive clocks, perfectly calibrated to one aonther, leave one on earth and take another up in an airplane, time will be shown to have passed slightly slower for the 'airplane clock'--less gravity. So, taking the premise that I do not spend an equal amount of time standing on my head as a I do upright, does this mean (on a ridiculously tiny scale) that since my head is farther from the earth's gravitational force than my feet, my head is slightly younger?—70.19.64.161 (talk) 13:20, 11 March 2009 (UTC)

A four-week old fetus, with head but no feet

Any such effect would be utterly negligable compared to the fact that (if I'm reading Prenatal development correctly) your head developed at least two weeks before your feet. Algebraist 13:27, 11 March 2009 (UTC)

Your head probably moves around more, too (think about sitting down in a chair - your feet basically don't move while your head moves quite a lot), so there is a contribution from that too. So, yes, I think your head probably is younger than your feet (assuming you start timing both at the same time), but by an immeasurably short amount of time. (I'm taking something of a leap of faith saying it's immeasurable, but considering it takes one of our best atomic clocks to measure the difference from a plane ride [incidentally, I think it's the motion rather than the gravity which causes most of that difference], I think it would take something even more precise to measure the difference between your head and your feet, even over your entire life.) --Tango (talk) 13:32, 11 March 2009 (UTC)

If your head is moving about a lot relative to your feet, then your feet are also moving about a lot relative to your head, so that effect would tend to make both your head and your feet younger than the other. I have no idea how significant these effects would be compared to the gravitational effects (of course, in absolute terms, all these effects are tiny). Algebraist 13:36, 11 March 2009 (UTC)

Have you read Twin paradox? It explains that problem - the short answer is that the one accelerating is the one that ends up younger. --Tango (talk) 14:33, 11 March 2009 (UTC)

Isn't that something to do with the fact the accelerating one changes inertial frame of reference? —Cyclonenim (talk · contribs · email) 14:44, 11 March 2009 (UTC)

Sort of - accelerating means you don't have an inertial reference frame (inertial basically means "non-accelerating"). Special relativity says that all inertia reference frames are on an equal footing, it doesn't say anything about non-inertial frames (you need general relativity for that, but that doesn't affect the Twins paradox). --Tango (talk) 17:21, 11 March 2009 (UTC)

Er, I used to know all that stuff, but apparently no longer. I'm not at all sure my head does more accelerating than my feet, though, what with walking and so on. Algebraist 18:50, 11 March 2009 (UTC)

Gravitational redshift would make your had a tiny bit older (not younger). Dauto (talk) 15:14, 11 March 2009 (UTC)

You don't mean redshift, you mean time dilation, but you're right. Time goes slower nearer a massive object, not further away. --Tango (talk) 16:29, 11 March 2009 (UTC)

No, I mean redshift because that's what it is usually called. Time dilation is fine as well. Dauto (talk) 17:07, 11 March 2009 (UTC)

No, gravitational redshift is where light it shifted towards the red end of the spectrum by gravity. That can be viewed as being caused by time dilation. The slowing of time is called "time dilation". --Tango (talk) 17:18, 11 March 2009 (UTC)

Gravitational time dilation is often called gravitational redshift wheather you like it or not. Dauto (talk) 18:47, 11 March 2009 (UTC)

Can't we all just get along? - Eron^Talk 18:57, 11 March 2009 (UTC)

Thanks for the link. It explains better than I could why reshift is indeed the correct term. Dauto (talk) 19:06, 11 March 2009 (UTC)

Kind of related comment/question: what's the theory/law that states that the faster something moves, the less it is affected by time? And doesn't that mean that if you could somehow move at the speed of light time wouldn't affect you at all? -Pete5x5 (talk) 16:39, 11 March 2009 (UTC)

That's time dilation, referenced above. It doesn't mean that time doesn't affect you; it means that to an observer who isn't moving as fast, time doesn't appear to be affecting you. (More correctly, time is affecting you more slowly.) Within your own personal frame of reference you would still experience the passage of time. - Eron^Talk 16:57, 11 March 2009 (UTC)

Special relativity#Time dilation and length contraction also has relevant info about your question. Dauto (talk) 17:07, 11 March 2009 (UTC)

One thing worth considering is also that tissue in the brain tends to be turned over (=replaced with new cells) move slowly AFAIK. So most of the cells in your feet might be a lot younger than most of the ones in your head. This fact will likely vastly outweigh any time dilation/ gravitational effects. 76.97.245.5 (talk) 11:12, 12 March 2009 (UTC)

Finger and toenails

This didn't happen to me and is a subject of mere curiosity, so I hope it won't be construed as seeking medical advice; however: can a fingernail or toenail, entirely removed (at the root) ever grow back? And if so, will it be deformed? 99.245.92.47 (talk) 13:28, 11 March 2009 (UTC)

It's unusual, but possible. See "Ingrown nail#Nail avulsion". The new nail usually has some deformity. Axl ¤ [Talk] 15:28, 11 March 2009 (UTC)

Oh, ugh! I wish you would have put a disturbing picture warning on that. When you say "unusual", does that mean it's unusual for the nail to return? 99.245.92.47 (talk) 15:35, 11 March 2009 (UTC)

I thought it was dependent upon whether you take the nail plate out or not. If you do, it can't regrow. —Cyclonenim (talk · contribs · email) 16:14, 11 March 2009 (UTC)

Perhaps of interest: one of my goats had his horns burned off as a baby, and now only sad and deformed little nubs grow back. Horns and nails are anatomically similar. --Sean 16:31, 11 March 2009 (UTC)

Removing the nail plate alone is usually not enough. It is necessary to remove the nail matrix as well. Most doctors use phenol to ablate the nail matrix. The quoted recurrence rate is 16–28%. [Sorry for not placing a warning about my previous message.] Axl ¤ [Talk] 17:52, 11 March 2009 (UTC)

As an aside, if a nail "falls off" due to a subungual hematoma, does it grow back? Also, Wikipedia is not censored, so sometimes we have disturbing images. ~AH1^(TCU) 21:39, 11 March 2009 (UTC)

Wikipedia isn't censored, but that doesn't mean it isn't thoughtful to warn when you post something that is highly likely to disturb the unwary. That isn't even nearly censorship. Good manners :) As to a subungal hemotoma, surely that would depend on how it was treated? The comments above certainly suggest that if it just 'fell off' (i.e., the nail plate is still there, but the hard bit has dropped off) it would grow back. OR: people I've known who slammed their fingers in doors and subsequently lost the nail had the nail grow back. 79.74.17.24 (talk) 22:35, 12 March 2009 (UTC)

A few years ago, I lost an index fingernail after a momentary lapse of attention with a barbell. That fingertip was naked for a couple of weeks, but it grew back completely normally. Dobermanji (talk) 02:49, 12 March 2009 (UTC)

I once lost the nail of my index finger after an accident with hot (well, boiling) cooking oil. It eventually did grow back. Aside from a few shallow vertical grooves on the nail's surface, it looks pretty much as it did before too. --Kurt Shaped Box (talk) 03:18, 12 March 2009 (UTC)

I once slammed my big toe in a door. The nail fell off, then grew back very strange, sort of a big amorphous lump of nail material rather than a nail per se. I resigned myself to having it that way permanently, but eventually the big lump grew past the end of the toe, and from that point on the nail was normal.

This took a couple of years, I think. I didn't exactly keep records. The long time frame seems to have been occasioned just by how slowly toenails grow. "Toenails, on the other hand, never grow at all" --Rosencrantz, or was it Guildenstern?

--Trovatore (talk) 21:05, 16 March 2009 (UTC)

dark matter 2 questions

1. Is there any circumstance where dark matter interacts with regular matter? has an attractive of repulsive effect on it for example?

2. Is dark matter only theorized to exist in space or could there be some in the room with me right now? —Preceding unsigned comment added by 79.68.243.251 (talk) 15:03, 11 March 2009 (UTC)

Dark matter will defnitaly interact with normal matter gravitationally and attract it. That's how we know about dark matter to begin with. Under the WIMP (Weakly Interacting Massive Particles) model for dark matter, those particles also interact with normal matter through very weak interactions. WIMPs are considered the best candidates for dark matter nowadays. If the WIMP model is right, those particles are zipping through your body right now completely unoticed. Dauto (talk) 15:31, 11 March 2009 (UTC)

As regards q2, we can make a guesstimate of the hypothetical density of dark matter. Assuming a typical dark matter particle has a mass of about of 10^-25 kg - around the mid-range of WIMP models - and the total mass of dark matter in our galaxy is the same as that of visible matter - about 10⁴¹ kg - then our galaxy contains about 10⁶⁶ dark matter particles. But these particles are distibuted evenly throughout the galaxy - they do not clump together into atoms, molecules, dust clouds and ultimately stars and planets as ordinary matter does. And the volume of the galaxy is about 10⁶⁰ m³. So the density of dark matter is about one million particles per m³. So yes, there could be several million dark matter particles in the room with you now. But that is not a very high density in particle physics terms (for comparison, our neutrino articles says "Every second, about 65 billion (6.5×10¹⁰) solar neutrinos pass through every square centimeter on Earth that faces the sun") and dark matter particles are really hard to detect. Gandalf61 (talk) 13:19, 12 March 2009 (UTC)

Gibb's free energy of a reaction

We know that delta G of a reaction being negetive then the reaction occur to considerable extent but revers is possible in a reaction which I know as nonspontenous reaction.Supriyochowdhury (talk) 17:53, 11 March 2009 (UTC)

Did you forget to ask a question? Dauto (talk) 19:26, 11 March 2009 (UTC)

My question is that any sponteneous reaction is possible though the delta G of the reaction is posetive?Supriyochowdhury (talk) 18:05, 12 March 2009 (UTC)

Yes, there will be some spontaneous reactions due to random fluctuations, but those reactions will quickly reverse themselves leading to equilibrium. See Stoichiometry. Also remember that Gibbs free energy should be used when the system is kept at constant pressure. Helmholtz free energy should be used instead if the system is kept at constant volume. Dauto (talk) 19:59, 12 March 2009 (UTC)

Poison Ivy Tolerance

Going camping soon and my friends are loading up on poison ivy treatments. I never got that rash so I must be immune to it. My friends said it is because I am Native American. They are assuming that Native Americans are immune to this. While all the NA's I know also do not develop this rash, I think that it doesn't have anything to do with race. Before I leave, I want to be able to spit out some proof. Is it possible to NA's to be naturally immune to poison ivy/oak/sumac?--Emyn ned (talk) 17:53, 11 March 2009 (UTC)

Wait, there isn't gonna be any ivy now at this time of the year, right? --Emyn ned (talk) 18:09, 11 March 2009 (UTC)

To answer your second question first, if there is poison ivy out there it will still be able to cause a reaction. This reference notes that "the leafless vines can cause a reaction in winter because all parts of the plant, with the possible exception of the pollen, contain urushiol." Urushiol is the component that causes the rash, which is formally known as urushiol-induced contact dermatitis. Some 15 to 30 percent of people have little or no reaction to uroshiol but I've found no reputable source suggesting that Native Americans are any more likely to be in that group. Sources also suggest that repeated exposure can sensitize people such that they start to develop a reaction. So the fact that you have never had a reaction does not mean that you never will; with repeated exposure you could become susceptible.

This reference notes that "some cultures, including certain Native American cultures, have used homeopathic treatment for poison ivy, oak, or sumac as a means of preventing the rash." I would assume that if they needed to treat the rash, they probably were not immune. Some people claim that eating poison ivy leaves can help produce immunity but this isn't supported by research. As the reference states, "stories of successful prevention of rash through eating the leaves are common, but research studies have failed to reproduce these results without the people involved in the studies developing mild to serious side effects." - Eron^Talk 18:37, 11 March 2009 (UTC)

I seriously doubt that native americans have traditionally used homeopathy given that it was created in europe little more then 200 years ago. Dauto (talk) 19:02, 11 March 2009 (UTC)

I would assume that the reference means homeopathic-type remedies, given that it goes on to discuss eating poison ivy leaves as a means of developing immunity to the rash. - Eron^Talk 19:06, 11 March 2009 (UTC)

But that's not homeopathy. Dauto (talk) 19:24, 11 March 2009 (UTC)

Perhaps you should take your concerns up with the good people at WebMD who posted the article I linked to. In any case, whether or not Native Americans practiced homeopathy or whether their treatments could be described as being like homeopathy is beside the point. The OP wanted to know if Native Americans are immune to poison ivy. I suggested that as there is evidence they developed treatments - of some kind - for the poison ivy rash, it is unlikely they were immune to it. - Eron^Talk 19:28, 11 March 2009 (UTC)

More likely than not they're talking about something akin to Desensitization (medicine), which is not homeopathy per se. SDY (talk) 22:00, 11 March 2009 (UTC)

Being immune to Poison Ivy is relatively common. This Straight Dope article says about 15%, but they don't cite a source. APL (talk) 19:50, 11 March 2009 (UTC)

As I recall, they tested a bunch of poison ivy cures on Mythbusters, and that proved to be surprisingly difficult for them because of a statistically unlikely occurrence: they had trouble finding a cast member who wasn't immune to it, and ended up having to use one of the crew members as a test bed. -- Captain Disdain (talk) 22:37, 11 March 2009 (UTC)

Anectodal experience: you can build up an immunity to poison ivy / poison oak. My father used to react to poison ivy when he was young. Then one day he had to wade through a field of the stuff, cutting and pulling the plants, etc. Naturally a horrible rash ensued. However, after that incident, poison ivy never bothered him again. I remember growing up, the rest of the family had to be careful not to touch him after a walk in the woods, because he had stopped paying attention to the poison ivy. ~Amatulić (talk) 01:52, 12 March 2009 (UTC)

While I'm willing to believe that can happen (allergies being notoriously fickle), the more common experience is that urushiol dermatitis gets more severe with each succesive exposure. I very much do not recommend that anyone try this approach. --Trovatore (talk) 01:58, 12 March 2009 (UTC)

I'm not recommending it either, just saying what happened with my Dad. In his case, he had a few exposures followed by an unavoidable huge massive exposure, equivalent to rolling naked in a pile of poison ivy. Whatever his body had to do to deal with that, seemed to have resulted in a permanent immunity. The thought of doing this deliberately makes me quail. I certainly wouldn't assume one man's experience is applicable to anyone else, especially me. ~Amatulić (talk) 02:04, 12 March 2009 (UTC)

nearsighted from reading?

do kids who read all through adolescence (and end up professors) end up nearsighted as a result, needing glasses to see far away, and kids who play outside all day end up needing no glasses normally as adults but reading glasses to see things up close, for example to read their utility bills? Or is there no correlation... —Preceding unsigned comment added by 92.230.65.185 (talk) 19:10, 11 March 2009 (UTC)

As a kid who read all through adolesence and as an adult requires no glasses of any kind, and I have better eyesight than my friends who played outside all day, I'd say there's no correlation, but that's OR -- Mad031683 (talk) 20:00, 11 March 2009 (UTC)

This is OR as well, but I've spent a good portion of my time as a child and early adoloscent reading, watching TV, or using the computer. Nowadays, I have glasses but only use them occasionally. I've heard that wearing glasses will cause eyes to become accustomed to the glasses and less so to the naked-eye vision, but I don't think this is proven. ~AH1^(TCU) 21:30, 11 March 2009 (UTC)

See Myopia#Etiology_and_pathogenesis. --98.217.14.211 (talk) 11:50, 12 March 2009 (UTC)

what is the most false thing generally accepted in science as true?

What is the most false thing generally accepted in science as true? Thank you. —Preceding unsigned comment added by 92.230.65.185 (talk) 22:34, 11 March 2009 (UTC)

Isn't that a bit of a contradiction? If it's "most false", i.e. very not true, then it wouldn't be accepted as true in science. —Cyclonenim (talk · contribs · email) 22:43, 11 March 2009 (UTC)

Many physical "laws" fall apart on a certain level and could be considered "false" on that account. One doesn't always equal one, for example in the amount of energy needed for acceleration at relativistic speeds. Many things in science are just "best guesses" or "good enough" because they are consistent with experimental data. There are many assumptions made for the sake of simplicity, usually because the simplification is not expected to affect results. I agree that the original question is far too broad and vague to be answered, but "not true equals not science" is misleading. SDY (talk) 22:53, 11 March 2009 (UTC)

Science doesn't really have "false things accepted as true". The closest thing would probably be "useful approximations": for example, Newtonian mechanics isn't correct, but it's commonly used because the math is much easier than that of general relativity, and the answers are usually close enough. --Carnildo (talk) 23:30, 11 March 2009 (UTC)

Do you mean what was accepted by scientists as true that was later proven false? 12.216.168.198 (talk) 23:48, 11 March 2009 (UTC)

That happens on a semi-regular basis. See T. Kuhn's The Structure of Scientific Revolutions, probably the best known work on how science changes. It gave us the expression "paradigm shift." Usually those changes are incremental and are a refinement of previous thinking on the subject, but every so often someone like Einstein comes along and makes a bit of a ruckus. Sometimes it's someone like Galileo coming out and saying what's already been said even though it's unpopular and uncomfortable, sometimes it's someone like Freud asking questions that previously would have been considered inappropriate (Freud's answers to those questions have since fallen victim to the same phenomenon, but the questions were good). SDY (talk) 00:11, 12 March 2009 (UTC)

The fact that 2 + 2 = 5 is false is generally accepted in science to be true. 219.102.220.90 (talk) 03:43, 12 March 2009 (UTC)

What about for really large values of 2? DMacks (talk) 04:42, 12 March 2009 (UTC)

2+2 does not equal 5, but 2. + 2. does equal 5. for large values of 2. That's more of a programming joke though. SDY (talk) 04:56, 12 March 2009 (UTC)

However, 1 + 1 = 10. arimareiji (talk) 19:41, 12 March 2009 (UTC)

"You can get tenure." :-) 76.97.245.5 (talk) 11:16, 12 March 2009 (UTC)

Best answer by far. ^_^ arimareiji (talk) 19:40, 12 March 2009 (UTC)

"Armstrong and Aldrin landed on the Moon on 20 July 1969". (I'm not saying they didn't get to the Moon. I'm saying that no calendar has ever been created to apply to the Moon, and that "20 July 1969" is a terrestrial date that has no application beyond Earth.) -- JackofOz (talk) 11:37, 12 March 2009 (UTC)

What's wrong with using Earthly calendars when off Earth? Algebraist 11:45, 12 March 2009 (UTC)

Yeah, the guys on the ISS use the same date as us! Zain Ebrahim (talk) 13:27, 12 March 2009 (UTC)

There's nothing wrong with it; it's a handy and useful way of pinpointing (for people on Earth) when this event occurred (on the Moon). But it lacks the precision that scientists normally crave. Our calendar is a "model", if you like, of a celestial object (the Earth) that revolves around its parent object (the Sun) in c. 365 days; the "day" being defined as 24 hours ("hour" has its own separate definition), and is roughly equivalent to the Earth's rotational period. The Moon has a different rotational period than Earth does, and a different revolutionary period around its parent object (the Earth) than Earth does around the Sun. A calendar for the Moon would not be divided into months (of 28-31 Moon-days, for example) because the Moon-year and the Moon-day are identical (they're both equivalent to c. 29 Earth-days), so "month" would be meaningless in such a calendar. You could have "Moon-hours", though, where the Moon-day/year is divided into some useful sub-divisions. So, it would be more precise to say that Armstrong and Aldrin landed on the Moon at a moment in time that corresponded to a moment that occurred during 20 July 1969 UTC on Earth. -- JackofOz (talk) 20:33, 12 March 2009 (UTC)

That's a really weird usage of precise. And if you're going to oppose scientists using a time-measuring system that isn't properly attuned to the movements of the body they're talking about, then you should start by demanding that they stop using our ludicrous month system. Algebraist 20:50, 12 March 2009 (UTC)

Weird? Maybe. I don't have a problem with being considered to have weird ideas, but I prefer to think of them as "individual" or even "unorthodox". But they are defensible. I'm not making any demands of anyone, I was simply responding to the question. I don't oppose anyone using Earth dates to refer to non-terrestrial events, because it makes common sense to do so, and it would be absurd to expect people to use the formulation I came up with above. I don't deny any of that. I'm simply saying that it's not scientifically precise to the degree that many other details are routinely distilled to their nth degree of precision. Months? There was never anything scientific about their unequal lengths, and nobody's ever suggested there was. Months are purely a social construct, not a scientific one, even if they were originally roughly correlated to the lunar period (hence the name "month"). Weeks are also a purely social/theological construct, although there's somewhat more regularity with them. -- JackofOz (talk) 22:57, 12 March 2009 (UTC)

How would we know? If science incorrectly accepts something as true, how would we know they were wrong? And why wouldn't scientists know? APL (talk) 13:10, 12 March 2009 (UTC)

The question really doesn't make sense - if we know something is false - why would it be a part of science? The closest things I can think of are when one branch of science holds on to an antiquated view of how things work while the rest strides ahead. But even in those cases, the proponents of the antiquated view will generally maintain that the older ideas simply make doing what they do easier - and that they fully understand what's 'really' going on.

But if I'm forced to come up with an example - it would be friction. Everyone is taught in school and probably in college-level general science that the force due to friction is the coefficient of friction multiplied by the force with which the two surfaces are pressed together. Notably that the area of contact doesn't matter. This is so wildly wrong in many real world situations that I find it hard to believe it's ever taught...but it is. The first, second and THIRD times I mentioned this on this very science ref desk, a lot of pretty expert scientists complained bitterly and said that I was wrong. Well, I'm not - and there are a ton of day-to-day experiments you can do to show that. The one I currently like best is the business of taking two telephone books - stacking them one atop the other and trying to slide one off of the other. It's easy - you can do it with your little finger. Now, interleave the pages of the two books so that page 1 of the first book lies between pages 1 and 2 of the second book...all the way up to page 1,000 (or whatever) being between pages 1000 and 1001 of the second book. The total 'normal force' hasn't changed - and in fact, the normal force on the upper pages is much less than when they were simply stacked - but no matter what - you can't pull those two phone books apart! The Mythbusters did the experiment - and even chaining the spine of each phone book to a car and driving the two cars in opposite directions wouldn't pull them apart. Eventually they used to rather impressive tanks (!) and finally did manage to separate them. The difference between the force exerted by your little finger and the force exerted by two very large tanks is a measure of just how far wrong this "law" is.

But even in this case, scientists who actually need to deal with friction (eg the ones who design tires for your car) know full well that the standard law they teach in schools is nonsense - it's only the ones who don't actually use this obscure branch of physics who are (typically) ill-informed. So to say that science as a whole is ignorant of this is quite false.

SteveBaker (talk) 15:56, 12 March 2009 (UTC)

Your mistake here is to state that the total 'normal force' hasn't changed. Each contact surface has its own normal force (which should not be vectorially added prior to calculating the friction), and each surface has its own friction force (fairly well described by the standar formula). These friction forces add up to a very large force (all in accordance with the standard formula). While it is true that the standard formula used to calculate friction forces is not an exact principle, it is not wildly wrong either. Dauto (talk) 16:18, 12 March 2009 (UTC)

So what you are saying is that if I dismantled the two books into individual sheets - then taped them together to form two (enormous) flat sheets and stacked one onto the other then I could move the top one relative to the bottom one with more or less the same amount of force as when I put one book on top of the other? That's what's implied by the contact area not being a factor in the standard equation...and it's flat out not true. Trying to drag 1000 square feet of paper along (whose total normal force is exactly the same as a telephone book) requires an enormous amount of force. So the standard formula is not merely a somewhat inexact principle - it's flat out WRONG! Your point about vector sums wasn't clear enough for me to understand...the standard equation is linear - so...well, look - it doesn't matter...a simple thought experiment is enough here. I guess this will be the FOURTH time we've had to debate whether the standard formulation is right (approximately) or wrong in most cases! When I was taught this in physics classes back in the late 1960's - we were given an experiment with a block of wood whose width, height and depth were not equal - and various lead weights to place on top of it to change the normal force - and a spring balance to pull it along the bench to measure the frictional force. None of use believed that we'd get the same results when the block was laying 'flat' versus being on it's side - we dutifully plotted two graphs of the weight of the lead+wood versus the force measured with the spring balance. The teacher insisted that the results would be the same regardless of the orientation of the block and that the graph would be linear - and (no surprise in retrospect) not ONE person in the class came out with experimental results that came even close to supporting either of those conclusions! The fact that people continue to defend this as if it were essentially true (when it obviously isn't) is perhaps the exact kind of thing that our OP wishes to learn about. My understanding is that the standard equation works moderately well for things like lubricated steel plates and other "engineering" applications - but for practical day-to-day stuff, it's worse than useless! But just look at the real world. What do you notice about the tires on a dragster? They are BIG and SMOOTH...why? To increase the contact area of course! But this equation that we're all taught says that the contact area doesn't matter...that it has NO EFFECT WHATEVER on the frictional forces?!...How can such a theory be even remotely tenable?! SteveBaker (talk) 19:31, 12 March 2009 (UTC)

We have an article on creation science (which implies that it is a science) . There is also the story of this man musing "dass der Alte nicht würfelt" (which translates as "the old Geezer does not play dice"). --Cookatoo.ergo.ZooM (talk) 16:09, 12 March 2009 (UTC)

Our article is called "creation science" because that is what the people that practice it call it. That doesn't make it science. (My uni department is called "Mathematical Sciences" - that doesn't make mathematics a science, it just sounds better when you apply for funding!) Einstein didn't believe Quantum Mechanics when it was first proposed, but once there was substantial evidence for it he changed his mind, as any good scientist would - I'm not sure how that is relevant anyway. --Tango (talk) 16:24, 12 March 2009 (UTC)

Also, the original question implies degrees of falseness. In science, we construct our ideas so that they are either true, or false, not "halfway". While the concept of "partially correct" may apply in some philosophy (and a lot of school homework sets), scientists like to use falsifiability as the criteria for including an idea as "scientific." So, there is nothing in science which is "more false" than other half-way false things. It's a binary "true" or "false", because that is how we construct the problems we are interested in. Nimur (talk) 16:49, 12 March 2009 (UTC)

One thing about science which is "generally accepted" as in high school science books, but is really false in the case of many published studies, is that scientists follow a "scientific method" with some sequential stages, such as observation, hypothesis formation, predictions from the hypothesis/hypotheses, experimentation, rejection of disproved hypotheses, formulation of general theories or laws. In practice, it is often the case that the hypothesis formation follows the data collection. A scientists stumbles on a robust and reproducible phenomenon because he has access to a new gadget, creates some neat graphs, then someone else comes up with an explanation for the neat graph, and it is written up as if the hypothesis had preceded the experimentation. Sometimes the experiments are done and presented in an order other than the published one, which is written up so as to make it look like a series or well organized experiments cutting down to the gist ofthe new phenomenon, but "Experiment 1" was often run last, perhaps at the suggestion of an editor at the journal, who said it was unpublishable without it. The two orders relate to the "Logic of discovery" where semirandom tinkering produces a neat phenomenon, and the "Logic of justification" whereby it is written up for publication. Edison (talk) 17:17, 12 March 2009 (UTC)

One thing which was always taught to me as true (and I only discovered otherwise by my own reading) was that light always travels in straight lines. They never told me about the 'except in the presence of a strong gravitational field...' exception. --Joe^Talk_Work 02:03, 16 March 2009 (UTC)

Friction

I respectfully disagree with both Steve and Dauto regarding friction between the two books.

"Everyone is taught in school and probably in college-level general science that the force due to friction is the coefficient of friction multiplied by the force with which the two surfaces are pressed together."

— SteveBaker

I was taught that limiting friction is defined in that way. In Steve's first example (books, one on top of the other), the coefficient of static friction is (relatively) low, so only a low force is required to overcome the limiting friction. In the second example (interleaved books), the coefficient of static friction is high, so a high force is required. Indeed the limiting friction between the two books will exceed the limiting friction between the "lower" book and the surface on which they rest. Therefore pushing the upper of the interleaved books actually pushes both books together.

In both situations, neither book moves vertically. Therefore the normal force must be same — exactly equalling the weight of the books (if the books are on a flat horizontal surface). Axl ¤ [Talk] 17:22, 12 March 2009 (UTC)

You're confused. The total normal force doesn't chage. But in the second case This force is the vector sum of many normal forces, and a friction force must be calculated for each one of them. Those friction forces add up. The friction coefficient doesn't change. Dauto (talk) 17:46, 12 March 2009 (UTC)

Without commenting on this discussion, our article says "Friction is distinct from traction. Surface area does not affect friction significantly because as contact area increases, force per unit area decreases. In traction, however, surface area is important". If this is wrong, it would IMHO be good if it is revised (with references of course) Nil Einne (talk) 08:20, 13 March 2009 (UTC)

Yes, it's wrong. The statement should be removed. Dauto (talk) 17:53, 13 March 2009 (UTC)

Quantum mechanics? [4] 216.239.234.196 (talk) 18:05, 12 March 2009 (UTC)

the relevance of a citation index? --dab (𒁳) 09:11, 13 March 2009 (UTC)

Dauto, I understand that the interleaved books apply numerous additional forces upon each other, both up and down. However our disagreement is in the definition of the terms "normal force" and "coefficient of static friction". My understanding is that "normal force" is defined as the net force applied. The coefficient of static friction is a derived number, dependent on the limiting friction and the normal force. I have tried looking on the internet and in my local library for clear definitions, but have been unsuccessful. I would appreciate it if you could quote the definitions from one of your hefty tomes. ;-) Thanks. Axl ¤ [Talk] 09:41, 13 March 2009 (UTC)

"When I was taught this in physics classes back in the late 1960's ... the teacher insisted that the results would be the same regardless of the orientation of the block."

— SteveBaker

I was taught in the 1980s and 1990s. I don't recall being told that by my teacher. Axl ¤ [Talk] 09:50, 13 March 2009 (UTC)

Well, then perhaps things are getting better...but slowly and patchily. Just 3 years ago, my son was taught the same bogus equation as I was (although because this is the US school system, there was no time for doing the experiment...so we had to do it at home in order that I could explain that the equation he was taught was of limited - if any - use). It's useful to read the section of the The Feynman Lectures on Physics relating to this very topic. I was taught physics at university using the Feynman books (they WERE the physics curriculum for science majors who were not studying physics directly!) - and it was really like a breath of fresh air compared to high-school physics. SteveBaker (talk) 11:28, 13 March 2009 (UTC)

It's worth noting the difference between "empircal law" and "physics" here. (Friction is a perfect example which highlights this case). The distinction is that the "empircal law" is an approximate equation based on observations for a particular experimental setup. It is not attempting to explain the root causes of the observations. As such, it is inapplicable in situations with different setups. Sometimes, applying it will yield dramatically wrong values! Nearly every equation of friction is I have seen used in real engineering problems is an empircal law, and as such it could give horrible results in other situations. But that doesn't make the equation wrong - it's just inapplicable! On the other hand, the purist/theorist can spend a lot of hours trying to generalize the geometries and material properties with quantum-electro-whatever theories of surface-interaction. Often, (friction being a case-in-point), their horrible (but correct) derivation is untenable, and it won't stick around in the real world for very long at all. Nimur (talk) 16:11, 13 March 2009 (UTC)

Nimur, the friction law is indeed an empirical law as you pointed out (that doesn't mean it's not physics!), but that fact has little bearing on the discussion at hand. Dauto (talk) 17:58, 13 March 2009 (UTC)

Axl, Your understanding is incorrect. If you have more then one contact surface between two bodies, A friction force has to be calculated separately for each contact surface before the normal forces are added to obtain the net normal force. Think about how you would solve the problem of a block that is sliding down a v-shaped ramp . There are two contact surfaces, each with its own normal and friction force. If you first (vectorially) add the normal forces and then compute the friction from that net normal, you get the wrong answer. The friction coefficient depends on the surface's proprieties (chemical composition, roughness, lubrication, etc...). If the coefficient of friction depended on the configuration of the blocks in the problem, as you seem to imply, It would be a completely useless concept and SteveBaker would be right. He isn't. Dauto (talk) 16:24, 13 March 2009 (UTC)

SteveBaker, You said "Trying to drag 1000 square feet of paper along (whose total normal force is exactly the same as a telephone book) requires an enormous amount of force" I can only assume you haven't done the experiment, since your conclusion is wrong . You said "I guess this will be the FOURTH time we've had to debate whether the standard formulation is right (approximately) or wrong in most cases! ". That shold be a hint to you that you may be wrong . You said "The teacher insisted that the results would be the same regardless of the orientation of the block and that the graph would be linear - and (no surprise in retrospect) not ONE person in the class came out with experimental results that came even close to supporting either of those conclusions!". There was likely some sort of systematic error in the experiment design. Not an uncommom thing at all. You said "What do you notice about the tires on a dragster? They are BIG and SMOOTH...why? To increase the contact area of course! But this equation that we're all taught says that the contact area doesn't matter...that it has NO EFFECT WHATEVER on the frictional forces?!...How can such a theory be even remotely tenable?!" read that for an answer. Note specially when they say "(remember, the big tire is relative to heat dispersal and not directly to traction)". Report back after you're done eating humble pie. Dauto (talk) 16:46, 13 March 2009 (UTC)

"Report back after you're done eating humble pie?" That's really an unnecessary comment. Even if we don't agree with another editor, we should try to keep things civil, please. - Eron^Talk 18:08, 13 March 2009 (UTC)

There's nothing wrong with eating humble pie. I've done it my self quite a few times. It's actually a healthy thing to do when it's waranted. SteveBaker asked for it by making statements such "Trying to drag 1000 square feet of paper along (whose total normal force is exactly the same as a telephone book) requires an enormous amount of force. So the standard formula is not merely a somewhat inexact principle - it's flat out WRONG!" when he obviously doesn't really know that such an enormous force is needed, or when he said "What do you notice about the tires on a dragster? They are BIG and SMOOTH...why? To increase the contact area of course!" when he assumes that his explanation is the only possible explanation. He's is being guilty of doing science by gut feeling (again) and ought to acknowlege the possibility that he's wrong. Dauto (talk) 19:32, 13 March 2009 (UTC)

In Google Books, I can look through a book called Nonlinear dynamics of a wheeled vehicle by Jan Awrejcewicz (not sure that a link would work right). A series of figures in this book shows the variation of the frictional force with several parameters; for example, Figure 3.13 on page 83 shows the dependence of the circumferential and lateral coefficients of friction on the vertical load. The variation, at least for certain slip parameters, is substantial. (Keep in mind that during maneuvers, the tire load on one side of the car can be very different from the other side.) I would agree with Steve that the friction of real systems, like car tires, is more complicated than was presented in my HS physics class. -- Coneslayer (talk) 19:40, 13 March 2009 (UTC)

Yes, the standard friction formula is simplistic and things can be more complicated in the real world. But it is still a usefull first order approximation. SteveBaker caims that the formula is so out of whack to be completely useless in most pratical situations. He's wrong. Dauto (talk) 20:04, 13 March 2009 (UTC)

Regarding Stevebaker's phone book example: suppose the phone book contains 1000 sheets of paper. Suppose the highest possible friction when the books are stacked is "f". When the books' pages are interwoven, the 999th sheet presses down on the 1000th sheet with a normal force equal to the weight of two books, minus that of a single piece of paper. The frictional force this contributes is of course greater than f. The 998 sheet applies roughly the same force on the 999th sheet; the resulting friction is thus roughly the same. The 998th and 997th, 997th and 996th, and 996th and 995th sheets, and the rest of the books, behave the same way. Thus, the total friction should be much larger than f, regardless of whether f=μN is valid.

Note that I am not saying Stevebaker is wrong, just that his example does not support his claims. --Bowlhover (talk) 22:38, 13 March 2009 (UTC)

Dauto, I understand your point. As I stated before, our disagreement lies in the definitions of "normal force" and "coefficient of static friction". Please provide specific (sourced) definitions. Thanks. Axl ¤ [Talk] 23:34, 13 March 2009 (UTC)

Axl, What happens if the net normal force between to objects is zero (A pair of tweezers picking up a block)? Infinite friction coefficient? Dauto (talk) 05:32, 14 March 2009 (UTC)

Then you should be able to stand the two interleaved phone books on their short edges with their spines pointed vertically upwards. Now there is no gravitational force pushing down on the pages at all...if you are right then the two phone books will slide apart easily. If you watched the Mythbusters show where they tested this - you'd know that nothing could be further from the truth. The orientation of the books didn't make ANY noticable difference to the effort needed to pull them apart. Then - what about the thought experiment I challenged Dauto with above (which he's carefully ignoring) - what do YOU think would happen if you cut all of the 1000 or so ~1 sq.ft pages out of each of two phone books and taped them together to make two ~30'x30' sheets of paper. Now lay one on top of the other on some nice large flat floor. Now we have PRECISELY the same normal force between the two sheets as we did between two non-interleaved phone books simply stacked one atop the other. But now we have a 1000 times bigger contact area. Do you think it would be as easy to slide those two sheets over one-another compared to sliding one phone book over the other? I don't think that anyone would claim that.

What's wrong with the 'standard' equation is not that it's an approximation. We all understand that friction is a complex matter and isn't likely to be 100% accurately defined with a simple equation. The problem is that it doesn't include the term for contact area AT ALL - and in cases like when two 30' square sheets of paper are sliding across one-another the area term totally dominates the equation. So it's not just that the equation isn't quite exact - it's that it's entirely missing an exceedingly important term altogether. When you entirely miss out terms - the 'form' of the equation is wrong. That's bad because not only do you get inaccurate numerical answers from it - but you also lead people to conclude that the area simply doesn't matter. That's a qualitative error - not just a minor quantitative inaccuracy. What you have is not an approximation because taking sufficiently extreme values for that missing term can produce arbitrarily large errors in the result. That's why it's an error - not an approximation. There are undoubtedly cases where the effect of the area on the frictional force is negligable - and there are equally undoubtedly cases when it totally dominates the result. So what is needed is a more honest approximation for the friction force - that perhaps multiplies the frictional coefficient by the normal force and then multiplies THAT by the contact area raised to the power of some number that ranges from 0 to 1 depending on the material...then, for objects like sheets of paper and car tires where the frictional force is roughly proportional to the area, you'd have this new constant be close to 1.0 and for objects that behave more like the traditional equation, the constant would be close to zero - but sadly, it would leave the equation dimensionally incorrect...so...no. SteveBaker (talk) 23:47, 13 March 2009 (UTC)

Please read again Dauto's responses in this thread. Your example of the interleaved phone book vs. the large sheet of paper fails on at least two counts. One, you continue to add the force normal vectors between each sheet in order to claim "we have PRECISELY the same normal force". As Dauto has pointed out, this is an invalid approach to the problem. You must find the normal force acting between each pair of surfaces of the interleaved books, apply the formula, then perform the addition. Another error is to assume that gravity is the only thing exerting a normal force between the surfaces. As you attach the two phone books to your separate vehicles and apply tension (and undoubtedly compression and torque as well) what are all the resulting mechanical forces present?—eric 00:56, 14 March 2009 (UTC)

OK SteveBaker, I tryed the experiment (well, I used two of my books with approximately 130 pages). Here's what happened: When I tryed pulling the books apart I noticed that the pages started squishing together. That happens because the pages are not exactly parallel to each other, being closer together at the spine and further apart at the oposite end where the other book's pages are interlacing. That means that a small component of the force I am applying on the paper (may be a few percent of the total force itself) is actually being used to produce the normal force (An effect similar to the one you can get with aChinese finger trap). The more you pull, the tighter the pages get. To test that I tryed pushing the books together instead of pulling them apart. I put one of them lying down on its spine and lightly tapped the other one. It moved further in! (try it). That shouldn't have happened if your theory that the larger area produces larger friction was right. What do you have to say about that? I quote your other point: "what about the thought experiment I challenged Dauto with above (which he's carefully ignoring) - what do YOU think would happen if you cut all of the 1000 or so ~1 sq.ft pages out of each of two phone books and taped them together to make two ~30'x30' sheets of paper. Now lay one on top of the other on some nice large flat floor. Now we have PRECISELY the same normal force between the two sheets as we did between two non-interleaved phone books simply stacked one atop the other. But now we have a 1000 times bigger contact area. Do you think it would be as easy to slide those two sheets over one-another compared to sliding one phone book over the other? I don't think that anyone would claim that." Well, that's exactlly what I am claiming. Dauto (talk) 01:41, 14 March 2009 (UTC)

I tried the experiment too, with two 140-page books composed of A4 paper. When completely interwoven, I could not pull them apart no matter how hard I tried, and saw the same effect Dauto was referring too. Of course, then I had the problem of separating the books. I stuck my finger into the pages so that a quarter was on one side and the rest on the other. The quarter of the pages could be separated effortlessly, and so could the rest of the pages after I divided them. When I laid the books down so that the broadest surfaces faced up and down, the normal force came into play and it took a force a few times larger to pull the books apart, but as I showed above, this does not imply f=μN is invalid. If there is a positive correlation between surface area and friction, and if we assume friction alone can explain what my results, the dependence between the two would have to be extremely strong to account for what I saw (i.e. that reducing surface area by a factor of 4 apparently turned friction from something I couldn't overcome to a negligible effect). I don't think such a heavy dependence fits everyday experience. Again, I am not claiming that friction doesn't depend on surface area, just that the phone book example doesn't prove that it does.

About the friction on a giant sheet made from the phone book's paper: I don't know what will happen, but f=μN is not meant to for extreme scenarios like this. It clearly doesn't apply to extremely small surfaces, and I suspect it's invalid for very large ones as well. That in itself does not prevent the equation from being useful for the possibly-limited physical conditions it was meant for. --Bowlhover (talk) 05:17, 14 March 2009 (UTC)

Dauto, again I understand your point. Again I ask for precise definitions from a reliable source. [I suspect that the concept of the "normal force" is a simplification used to model effects on an object resting on a single surface.] Axl ¤ [Talk] 18:19, 14 March 2009 (UTC)

Axl, that definition can be seen on any elementary book of mechanics. Normal is the component of the contact force perpendicular to the surface and friction is the component parallel to the surface. You need a clearly defined surface for the definitions to make sense. But that's not the issue here. The issue is wheather the linear relationship between (maximal static or kinetic) friction and the normal is an approximately valid priciple in many practical situations or not. Dauto (talk) 21:09, 14 March 2009 (UTC)

Let's do some math to settle the phonebook issue down. Let the weight of one sheet of paper be $m{\vec {g}}$ and the coefficient of friction between two papers $\mu$. Let's interleave two books' pages, both consisting of $n$ sheets. Looking at one sheet of one book the total force acting upon it is the sum of friction forces applied to its top and its bottom. Let's say the sheet has $i$ sheets of the same book above it. The maximal static force of friction that may be applied to its top side equals $2img\mu$ while the analogue for its bottom side is $(2i+1)mg\mu$ (we added the weight of the sheet in question). Some force is generated at every contact surface and to get the total force, we must sum over all the surfaces, equivalenty all the sheets (which can be done algebraically, because the forces have the same direction):

$F=\sum _{i=0}^{n-1}[2img\mu +(2i+1)mg\mu ]=\sum _{i=0}^{n-1}(4i+1)mg\mu =(2n^{2}-n)\mu mg{\text{.}}$

As the force scales as $n^{2}$, there's nothing surprising in the fact Mythbusters needed a tank to pull the books apart for $n\sim 1000$. When they turned the books vertical there wasn't any qualitative change to be expected: $mg$ was then replaced by an elastic force applied by the binding (which turned out about similar in size), which sums up analogously. — Pt _(T) 22:36, 14 March 2009 (UTC)

Pancreatic cancer

This is kind of a follow on question from someone else's above. Why aren't pancreatic transplants a suitable form of treatment for pancreatic cancer that has not metastasized elsewhere? I know it's sometimes hard to tell how malignant a cancer is, but caught early enough and being low enough grade, isn't this cancer treatable via transplant? —Cyclonenim (talk · contribs · email) 23:28, 11 March 2009 (UTC)

From Pancreas transplantation:

"Patients with pancreatic cancer are not eligible for valuable pancreatic transplantations, since the condition has a very high mortality rate and the disease, being highly malignant, could and probably would soon return."

--Carnildo (talk) 23:35, 11 March 2009 (UTC)

Just to add to the above. Pancreatic cancer is particularly nasty in it's silence. It grows and metastasises without symptoms. Lung cancer gives you haemoptysis, bowel cancer gives you bloody stools, brain tumours cause neurological symptoms. Pancreatic cancer causes little visible signs or symptoms until it's too late, and then it's everywhere. Fribbler (talk) 23:39, 11 March 2009 (UTC)

I had read the above quote which is what sparked my question. I'm aware that it has a high mortality rate and malignancy. However, thanks Fribbler, it's merely a case of "you just can't be sure if it's spread", then? —Cyclonenim (talk · contribs · email) 23:57, 11 March 2009 (UTC)

"Merely" is a dangerous word in the multi-faceted world of medicine :-) , but that is the basic idea. It's what makes testicular/breast/skin cancer so curable (the lumps are obvious) vs. pancreatic, liver, kidney tumours etc. that silently metastasise without outward notice. Fribbler (talk) 00:14, 12 March 2009 (UTC)

Transplantable organs are always in short supply. They need to figure out where they're going to do the most good. APL (talk) 01:41, 12 March 2009 (UTC)

The major functions of the pancreas can be achieved with medical treatment: enzyme supplements (Creon) and insulin. Whipple procedure usually involves just the head of the pancreas, although is sometimes extended to full pancreatectomy. Pancreas transplantation, like other organ transplants, requires immunosuppressive drugs to prevent transplant rejection. Therefore pancreatic transplant is usually reserved for diabetic people who have very erratic blood sugar control despite insulin. Often, these people also have kidney transplantation as well (for renal failure) so they would require immunosuppressants anyway. Axl ¤ [Talk] 08:14, 12 March 2009 (UTC)

Also, the immunosuppressants can help the progression and spread of some cancers. I'm not sure how specifically this applies to pancreatic cancer, but that's a general argument used by transplant specialists to justify not transplanting any solid organ into someone with cancer. Mattopaedia ^{Have a yarn} 12:37, 12 March 2009 (UTC)

Pancreatic cancer rarely lets people survive longer than 4-6 months. —Cyclonenim (talk · contribs · email) 18:45, 12 March 2009 (UTC)

March 12

Chemical reaction writing programs

Anyone here know of any good (preferably free) programs for drawing chemical reactions, with lewis bonds, electron pushing, etc? (PS: I use Windows). Thanks. Someguy1221 (talk) 04:51, 12 March 2009 (UTC)

I recommend ISIS/Draw and MarvinSketch to my organic students. DMacks (talk) 05:02, 12 March 2009 (UTC)

One way or another ISIS/Draw was acquired by Symyx (I think when Symyx bought MDL for their electronic notebook). In any case ISIS/Draw doesn't appear to be freely available anymore. Molecule editors appears to have a few example of open source programs.--OMCV (talk) 05:52, 12 March 2009 (UTC)

There is a Symyx Draw no-fee version. Obviously not free-as-in-speech, but still no-cash-outlay-to-use. DMacks (talk) 06:05, 12 March 2009 (UTC)

Thanks, with ChemDraw move to a license model I might end up moving back to ISIS someday soon.--OMCV (talk) 06:08, 12 March 2009 (UTC)

Heat in the human brain

Does the human brain, like a computer's CPU, produce heat at a rate proportional to the rate of processing it performs? NeonMerlin 05:10, 12 March 2009 (UTC)

Increased blood flow is very well correlated with increased neural activity (see Functional magnetic resonance imaging) but it's not clear what the purpose is. It'd be awesome if we could say that increased firing rates of neuron's caused an increased use of oxygen (and by extension, an increase in heat, not that that's what neuroscientists care about, to my knowledge). But as the article explains, it's not nearly that simple, and is still being actively researched. Someguy1221 (talk) 05:59, 12 March 2009 (UTC)

this may help I don't have a pubmed access card anymore (but if you go to university, it is free to get one. 71.54.173.193 (talk) 10:57, 12 March 2009 (UTC)

Furthermore, it doesn't have to do with "processing", it simply has to do with brain metabolism. I asked that question several months ago and is an active area of research. I am not an expert, just a hunter-gatherer of knowledge. When the brain oxidizes glucose, heat is released. When your brain is active in say the PFC, then that area uses more glucose. If you want to get your brain hot, perform an activity that is in your rote memory (i.e. you can do it without thinking about it), and do that while trying to do 4d maze puzzles online. The physical activity should be something very light, such as spinning a poker chip in your fingers. If you try to "light up" all the areas of your brain, you can feel very sleepy afterwards. however, its not something that can be measured. If you want a really long post of the subject, its actually one of my favorite interests in neurology, just let me know. I always liked the idea of brain analogies to computers. You seem to be coming from the computer side, while I'm coming from the opposite side (biology major). I'm just a noob, but I know how to use google-scholar, which has tons of technical stuff that is a lot to digest. Most of the stuff is talking about neuroactive drugs; rarely do you find a purely purposeful article written about a fun, interesting topic. —Preceding unsigned comment added by 71.54.173.193 (talk) 11:06, 12 March 2009 (UTC)

OK - I'll bite! I'd like a really long post on the subject please. It seems relevent to this question - and it's certainly of more general interest. (Besides - I need to point at someone else when people complain that my posts are too long to read!) There is a rather fundamental relationship between information flow and thermodynamics. Ties between the dual concepts of "Entropy is about heat" and "Entropy is about order and randomness" seem to be fundamental. Hence, I would certainly maintain that it's impossible for "thinking" or "computing" to happen without generating heat. However - computers get hot when their transistors are switching - so if your computer just sits there idly flipping registers and memory between 10101010 and 01010101, it'll get hot without actually doing anything meaningful. It's interesting that instructing your hand to spin a poker chip over and over does the same thing in humans. SteveBaker (talk) 15:39, 12 March 2009 (UTC)

See Landauer's principle for the minimum amount of heat generated from computation. Also, see Reversible computing for getting around that problem by never actually deleting anything. I'm pretty sure it would still generate some heat because something would have to move and leave gravitational waves, though. — DanielLC 17:14, 12 March 2009 (UTC)

Rhesus incompatibility

Why is it that hemolytic disease of the newborn only occurs when a mother is rhesus negative and her baby is rhesus positive? Why does the same thing not occur if the mother is Rh positive and the baby is Rh negative? Many thanks in advance. —Preceding unsigned comment added by 139.222.241.23 (talk) 12:24, 12 March 2009 (UTC)

If an Rh -ve mother gives birth to a Rh +ve baby, it is relatively common for a small amount of the fetal blood to enter the mother's circulation at around the time of separation of the placenta. This causes the mother to manufacture antibodies to the Rh factor. If she gets pregnant again, those antibodies she made last time can cross the placenta and enter the fetal circulation, and if that baby is RH +ve also, the reaction of the mother's antibodies to the baby's Rh factor causes HDN. So that's why all Rh -ve new mums are given Anti-D - to prevent those antibodies forming. If the mother is Rh +ve she is essentially already immune to the Rh factor and so no antibody forming process occurs, so no problem for the baby. Mattopaedia ^{Have a yarn} 12:46, 12 March 2009 (UTC)

A Rh -ve baby could come into contact with a Rh +ve mother's blood and develop the antibodies, which I guess would increase the chance of haemolytic disease of the newborn occurring if that baby grows up and have a Rh +ve baby. The original baby wouldn't be at any risk, though. --Tango (talk) 13:49, 12 March 2009 (UTC)

Are you sure about that? Wouldn't the baby's immune system be to immature for that to happen? Dauto (talk) 16:00, 12 March 2009 (UTC)

No, I'm not sure. If it does happen, the risk is probably very low. I know there are other ways to become sensitised to the Rhesus D antigen than just during childbirth (mistaken transfusions, for example), but I don't know if during your own birth is one of them. Newborn babies certainly have a working immune system - they wouldn't last very long without one - they need help from their mother's immune system (via the placenta and breast milk) because they haven't been exposed to anything yet so don't have their own antibodies, but I think they are capable of making their own when they are exposed to something. --Tango (talk) 16:13, 12 March 2009 (UTC)

Looked at another way (very simplistically), the Rh-neg baby lacks the antigen, so there is nothing for the mom's immune system to attack. --Scray (talk) 15:45, 12 March 2009 (UTC)

Dauto is correct. Rhesus disease is modulated by the adaptive immune system, notably B cells and T cells. B cell function doesn't mature for at least several months after birth, possibly up to two years. Memory B cells are required to maintain long-term immunity; these are absent in the fetus and new-born. Similarly, T cells develop in the thymus which matures during childhood. Colostrum, a form of breast milk, contains antibodies that assist immunity in the new-born infant. Axl ¤ [Talk] 16:29, 12 March 2009 (UTC)

Thanks to all who helped! —Preceding unsigned comment added by 139.222.241.23 (talk) 20:55, 12 March 2009 (UTC)

There are two "rhesus molecules". The one with the D epitope, which is highly immunogenic, and the one with the c or C and e or E epitopes, which are less immunogenic. Persons who are Rh(D) negative lack the entire Rh(D) molecule. Antibodies against all of these five "rhesus epitopes" may cause HDN, but anti-D immunization is much more frequent than the others, and is a much greater problem (with anti-c as number two in the Rh-system). HDN is caused by maternal immunization against fetal antigens. The hypothetical immunization of an Rh(D) negative baby against Rh(D) positive maternal blood that Tango suggests may cause problems later in the life of the baby, is not something that is seen in clinical practice. If anything, the entry of maternal blood cells into the circulation of the fetus or newborn would lead to tolerization, not immunization. --NorwegianBlue ^talk 22:29, 12 March 2009 (UTC)

"Reese's incompatibility" = not liking peanut butter in your chocolate. StuRat (talk) 05:44, 13 March 2009 (UTC)

What is the usefulness of hESC compared to Adult stem cells

We're soon going to have a speaker at our school speak on ESC research and related topics. He is a theology professor and I have a nagging feeling that the information he gives at the talk won't be the full, or the accurate, picture. This is one issue which frequently comes up in the discussion and I'm wondering how stem cell research rates these two types of stem cells (feel free to include information on umbilical cord stem cells as well) in reference to their potential usefulness. I do understand that adult stem cells have already been used for some purposes, but my question is on the expected utility of these two types of cells. I have no interest in any analysis of what "should" be done, just what those who are in the field realistically believe "could" be done by each of these two sources.

If I didn't have such a large amount of work on my plate I would do a thorough look into this myself, but I imagine someone here already can cite numerous journals and studies without too much effort.

Thank you :)

Chris M. (talk) 17:43, 12 March 2009 (UTC)

Try HESC and Induced pluripotent stem cell. Kittybrewster ☎ 20:49, 12 March 2009 (UTC)

Tomentella Fungus and Dicrocoelium dendriticum

Dicrocoelium dendriticum causes the ant (forgot which species) to climb a grass blade every night and climb down at day. And the Tomentella Fungus causes the ant to perch high on a blade of grass and the fungus grows out of its head into a spike which then spits out spores to infect other ants (ew!). Could this ever happen to humans? or has it?--Emyn ned (talk) 18:21, 12 March 2009 (UTC)

I meant more of the mind-controlling like. Or whatever else... --Emyn ned (talk) 18:25, 12 March 2009 (UTC)

I think there's a parasite that makes you want to touch your mouth after going to the toilet. —Preceding unsigned comment added by 124.176.181.108 (talk) 19:00, 12 March 2009 (UTC)

See Toxoplasmosis#Behavioral_changes for one example. -- Coneslayer (talk) 19:05, 12 March 2009 (UTC)

Oh, that's a good example! --Emyn ned (talk) 19:34, 12 March 2009 (UTC)

I think rabies has some neurological symptoms in humans that might fit your mind-controll description, depending on how broadlly you define mind-controll. Dauto (talk) 19:27, 12 March 2009 (UTC)

So, do you think that anytime soon, we will witness someone climbling a tree, have a cone grow out of his head and ooze out spores to other people below? --Emyn ned (talk) 19:35, 12 March 2009 (UTC)

Probably - Eron^Talk 19:49, 12 March 2009 (UTC)

I would say no, because those microbes are likely only able to activate existing programming in the brain. I suspect that those ants already had a "program" to climb a blade of grass, perhaps to view the surrounding area or communicate with distant ants. Similarly, animals with rabies already had a program to bite other animals. People do have such basic "instinctive" functions, but they tend to be for very simple things, like coughing, vomiting, hiccups, etc. Therefore, things like this could indeed result from a brain parasite. However, climbing a tree isn't instinctive for us, it's a learned behavior. This means it's learned differently, if at all, for different people, as opposed to a simple program that can be easily activated by a brain parasite. StuRat (talk) 05:40, 13 March 2009 (UTC)

So, it is possible that someone with "chronic hiccups" could actually have a brain parasite? Is it possible that it could have gone undetected by doctors looking for a diagnosis? Maybe everyone's brain is infected by millions of different types of parasites responsible for altering specifc behaviors?! --Emyn ned (talk) 13:23, 13 March 2009 (UTC)

I don't know of any cases where a parasite causes hiccups, but star fruit can do this in people with kidney failure: Star_fruit#Health_risks. StuRat (talk) 14:57, 13 March 2009 (UTC)

Thanks everyone. Was hoping to find some human zombies via parasite. I think my older bro is one cuz he drools when he sees girls at the mall.--Emyn ned (talk) 18:18, 13 March 2009 (UTC)

Surgery

Hi. I've always wondered how surgeons access the brain through the skull, the heart and lungs through the ribcage and the abdominal cavity through the abdominal muscles. Could anyone tell me what happens, ie is the bone just cut away and then somehow replaced later and do you cut through the abdominal muscles? Or if not, how is it done? Thanks. 92.0.253.238 (talk) 20:32, 12 March 2009 (UTC)

May I suggest the article on Minimally invasive surgery? It has a good wealth of info and some external links that can answer your question. Livewireo (talk) 20:45, 12 March 2009 (UTC)

However, minimally invasive surgery is not available for all procedures. When it's not, in general the idea is to minimize the amount of cutting by cutting between structures and spreading them apart, but yes, bones and muscles are cut as necessary. For open-heart surgery they the cut the sternum lengthwise and spread open the rib cage, then when they're done they fasten the parts together with wire so the bone will heal. (Do a web search on "heart surgery" and "sternum".) --Anonymous, 20:56 UTC, March 12, 2009.

[1] for brain surgery, portions of the skull are indeed cut away and later replaced.

[2] for chest surgery, the ribs are spread (as Anonymous indicated) with a rib spreader

[3] for abdominal surgery, an incision is made and abdominal muscles are pushed to the side. - Nunh-huh 20:59, 12 March 2009 (UTC)

(Just a grace note, but don't look too closely into what this entails unless you have a strong stomach. It'll hurt just seeing it.) arimareiji (talk) 21:51, 12 March 2009 (UTC)

When you've seen your wife have a Caesarean section - NOTHING like that will surprise you again! SteveBaker (talk) 23:32, 12 March 2009 (UTC)

In general, they try to cut with the grain of the muscle fibers rather than against it -- things heal much better and faster that way. --Carnildo (talk) 00:14, 13 March 2009 (UTC)

As far as brain surgery: the abdominal muscles are left alone :-) but my neurosurgeon says that a small area of skull was removed when I had to have surgery on the surface of the brain; it was taken away and replaced with titanium plates. Not a large amount of skull is always removed; in my case, the surgeon told me that, if we arranged all the plates together in a rectangle, they still wouldn't cover a normal-sized postage stamp. Nyttend (talk) 03:59, 13 March 2009 (UTC)

And I read once of a child whose skull was malformed; the top of it was taken off, ground to goo and troweled back in place to harden in a less distinctive shape. This account is likely oversimplified. —Tamfang (talk) 07:33, 13 March 2009 (UTC)

Katrina Firlick's Another Day in the Frontal Lobe is a very readable account of the work of a brain surgeon. For a lay person, this will tell you as much about modern brain surgery as you ever want (or, hopefully, ever need) to know. Gandalf61 (talk) 10:53, 13 March 2009 (UTC)

Many areas of the brain which commonly have tumors or CSF leaks can be accesses through the nose or mouth. Endoscopic surgery via the nose can access pituitary tumors, for instance, as opposed to opening the skull and damaging brain tissue to get to the tumor. An approach through the mouth and palate can access additional areas. Talk about building ships in bottles! 17:30, 13 March 2009 (UTC)

Orchid Species

I am trying to locate a particular orchid species, but I can't remember the Latin name, and I'm hoping someone here does. The species is unusual in that the plant produces a single, broad leaf. It has a white flower. Unfortunately, I do not know anything else about it and I don't have a photograph. Can anyone tell me the species name?130.127.99.54 (talk) 22:50, 12 March 2009 (UTC)

Nevermind; I've answered my own question. It was Nervilia aragoana.130.127.99.54 (talk) 23:00, 12 March 2009 (UTC)

Resolved

StuRat (talk) 05:22, 13 March 2009 (UTC)

Genetic traits split across continents

I was just watching Andrew Marr's brilliant programme about how Darwin's ideas have had various political effects over the decades, and I missed some deatils about something. He was talking about a recent theory involving DNA and genetics which claimed that a divide in the type of genes that people have can possibly be connected to brain size. The genes thought to relate to smaller brain sizes are dominant in sub-Saharan Africa and larger brain sizes are supposedly linked to the genes from Europe/Asia. He had his own DNA tested and found that he falls into the gene pool common in sub-Saharan Africa. They stressed that although the genetic difference is real, it's relation to brain size is hotly contested. I've no doubt got some of these details a bit wrong but can someone fill me in on what I've missed. Do we have an article on this? And before anyone points out that the page I've linked to gives me the option to 'watch again', I can't do that at the moment. Thanks.91.111.86.221 (talk) 22:51, 12 March 2009 (UTC)

We have a brain size article, which references one paper on genetics. We also have Race and intelligence, which is the very definition of "hotly contested". Mimetic Polyalloy (talk) 23:10, 12 March 2009 (UTC)

Not having read either article, my kneejerk reaction is say it sounds like an attempt to resurrect some pseudoscientific Nazi eugenics bullshit to me. Astronaut (talk) 23:37, 12 March 2009 (UTC)

then maybe you should read the article, shouldn't you. There is a reason that Race and intelligence article and Nazi eugenics are treated as distinct topics. --dab (𒁳) 09:09, 13 March 2009 (UTC)

Yeah - they don't sound to be in any way related. Eugenics was (effectively) selective breeding of humans in order to 'improve the species' - which is perhaps a not entirely stupid idea if done right. Of course the Nazi's didn't do it right - which has gotten eugenics a bad rap - from which it may never recover. But (for example) if we continue to promote artificial reproductive methods for couples who can't have children for some genetic reason - then we are removing the evolutionary pressure on our species that ensures that we are able to reproduce naturally. If, in the future, the genes that prevent sufficient sperm production - or which cause kinked up tubes in the ladies - become much more prevalent, then only people with lots of money or comprehensive health insurance will be able to have children. That is something, I'm sure we all agree is clearly a bad thing - and perhaps a little (and I'm going to use the 'E-word') eugenics may be called for to fix that - limiting the availability of artificial reproductive techniques, for example. It's not like there aren't tens of thousands of children without parents who would benefit from adoption by childless couples. That's a far cry from hauling people off to death camps. Rationally - it's hard to argue against SOME controls here - but the Nazi's have made even the discussion of this somewhat taboo - and I'm sure that what I just wrote is already raising some hackles.

The other side of this is the race and intelligence thing. And again, it's not unreasonable to study the impact of genetics on human intelligence - and if in the course of that study, you discover that one "race" (already we're slipping into dangerous territory) - implying some specific mix of genes - has a strong correlation with some measure of intelligence - then that is a valid thing for science to study. However, the racially-prejudiced nut-jobs out there - and the history of the slave trade (esp. in the USA) have made publishing such studies difficult and (again) almost taboo. But it's valid science - and the results might turn out to be exceedingly important in understanding what makes us tick. A correlation between (say) length of middle toe of left foot and intelligence would be an interesting (and perhaps even useful) scientific discovery - but a correlation between skin melamine content and intelligence is likely to cause rioting in the streets. Although, if the findings were that white males are genetically stupid - then I imagine the results would be widely published (if only by white females - who have long known this)!

But there is really no relationship between these two topics UNLESS one uses the results of one's genetic studies on intelligence to push for a eugenic "solution" to improving human intelligence by herding one group of people into death camps. That seems a most unlikely coupling for a rational science-based civilisation (which, of course, we aren't even close to having). As scientists we'd have to be MUCH more concerned that by tampering with the evolutionary pressures on humanity, we'd do something catastrophic.

However, the whole topic is moot because every time one attempts to bring up these perfectly reasonable lines of inquiry - one is immediately stamped as a Nazi (even if you were thinking in terms of limiting future suffering for millions and had no thought of setting up death camps) - or as a white-supremacist (even if your findings are that the Bushmen of the Kalahari are the smartest people on earth and that white guys are the stupidest).

SteveBaker (talk) 11:17, 13 March 2009 (UTC)

Minor correction. A correlation between skin melamine content and intelligence is not going to concern anyone too much (except, perhaps, consumers of Chinese sourced milk). A correlation between skin melanin content and intelligence would be controversial, however. Rockpocket 00:42, 14 March 2009 (UTC)

Oh - you thought I was discussing the horribly non-pc concept of relating skin color to IQ...no, no - it was the milk thing. :-) OK, my bad. SteveBaker (talk) 23:16, 14 March 2009 (UTC)

Thanks. I guess it's my fault for mentioning brain size and race in the same sentence but what I'm looking for is a specific, genuine, recorded, proven difference in DNA that has been discovered (I think). According to the programme, it was just one letter (GTC or A) that was different and it was fairly clear cut that the divide was across Africa.91.111.85.208 (talk) 13:33, 13 March 2009 (UTC)

It's ok, I've found it. It's the work of Bruce Lahn, who apparently states that a gene variant evolved around 6000yrs ago and some of us have the old ancestral type and some of us have the new variant.91.111.85.208 (talk) 13:58, 13 March 2009 (UTC)

Regarding race and intelligence, it should be noted that there is a difference between race (read: genetics) and culture (read: learned behavior and values). It is entirely possible that a difference in IQ is the result of culture and not genetics. The graph found here [5] shows that Asian Americans have higher IQs than other races in the US. But is that because Asian Americans really are more intelligent than other races living in the US or that they simply place a greater emphasis on education and as a result score higher on IQ tests? If the latter, that's a difference in culture, not race. As someone who lives in the US, it seems as if Asian Americans spend more time studying than other students. In order to eliminate culture from the equation, you would basically need to take kidnap children at childbirth, raise them identically (which probably means keeping them isolated from the rest of the world lest the world influence their behavior and values) and then perform IQ tests. Since such an experiment is obviously unethical, there really isn't any accurate way to determine the relationship between race and intelligence. A Quest For Knowledge (talk) 14:47, 13 March 2009 (UTC)

First off, before people get in too much of a huff over this (is it too late?), please do NOT conflate brain size and/or head size with intelligence. They are not interchangeable or even necessarily related. There are brilliant people with smaller-than-average head size and not-so-brilliant people with larger-than-average head size and everything else in between. Second, it is inescapeable that genes play a role in the development of bodily structures, including the brain. We know this because many genetic disorders affect brain development, and can lead to microcephaly or macrocephaly. In many of these cases, abnormal head size is associated with cognitive deficits, but these are in pathogenic situations, not the normal range of human variation. Third, there are any number of physical characteristics that differ between various geographic groups in the world -- why not head size or brain size? If there is a clear association between a gene that is more prevalent in one population than another, that correlates with differences in a given physical characteristic between populations, and has a biological function that supports the conclusions drawn by the association study (as is the case for microcephalin) then why should this information be problematic? The problem comes in people ascribing undue importance to the genetic and physical differences.

On the other hand, the controversy over a genetic contribution to "intelligence" is a completely different subject. There is an intense discussion about this going on in the journal Nature right now [6][7][8][9][10][11][12][13][14][15] that really sets out two sides of the discussion. Recommended reading before we continue what is an inherently visceral argument. --- Medical geneticist (talk) 14:53, 13 March 2009 (UTC)

I've got 'em. Email me if you want copies (not you MG, you obviously already have them). They are good stuff. Franamax (talk) 23:34, 14 March 2009 (UTC)

Yes, indeed. And it's definitely not helped by the fact that there is no solid definition or test for intelligence. IQ tests really only measure how good you are at IQ tests and there enough cultural biasses in them to make testing of people of widely different cultural backgrounds an exceedingly touchy matter. Unless the differences are enormous, there are any number of experimental slip-ups that could annihilate the very small differences that are claimed in what few studies have been done. SteveBaker (talk) 22:49, 13 March 2009 (UTC)

March 13

Name of a test

What's the test called in Psychology where you give a group of people the same sheet of paper where there is a character description. People are supposed to rate on the scale of 1 to 10 how much it applies to them, but the point is that everybody gives it a really high rating because it includes such generic qualities (like being lazy sometimes, wanting to do good, being pretty smart in relations to some things etc.)? I went to a lecture at the local university when I was around 13 and they performed this test on all the audience and I've been trying to find out what it's called ever since. --BiT (talk) 00:50, 13 March 2009 (UTC)

It's the basis of most palm-reading, tarot card readings and astrology predictions. Cold reading, the Forer effect (also called the "Barnum Effect"), Subjective validation, Cognitive bias...these are all related to this effect. I don't know which particular term psychologists use. SteveBaker (talk) 01:06, 13 March 2009 (UTC)

No, it's not related to palm reading or tarot cards. What you're talking about is the Myer-Briggs test. The test is dependent on how self-aware or honest the test-taker is so some people argue the validity of the results, but the theories independent of that are pretty interesting. --75.34.179.39 (talk) 18:39, 17 March 2009 (UTC)

You might also be interested in Barnum effect. --ReluctantPhilosopher (talk) 13:55, 20 March 2009 (UTC)

Worms in face

Hi,

Just saw a video [16], showing tiny worms crawling out of someone's face.

Just what is this worm?

Thanks PrinzPH (talk) 01:21, 13 March 2009 (UTC)

Bloody hell. It looks like all the guy's whiteheads are trying to crawl out of his face and escape. One of the comments on the video suggests that this condition may be related to eating parasite-ridden seafood - and several others suggest that it is best treated by rubbing cockroach juice into the skin. I'd really like to know more about this myself. There's just something incredibly compelling about videos of other people having parasites removed, isn't there? --Kurt Shaped Box (talk) 02:28, 13 March 2009 (UTC)

My dad knew someone with untreated worms, which he would occasionally pull out of his arm as a form of entertainment. For some reason, that man didn't have a wife or girlfriend. StuRat (talk) 05:19, 13 March 2009 (UTC)

_{Really? I would have thought the man would have had plenty of bait for catching women...} —Cyclonenim (talk · contribs · email) 07:43, 13 March 2009 (UTC)

Stuff like that makes my skin crawl.91.111.85.208 (talk) 13:36, 13 March 2009 (UTC)

The skin does not look inflamed, and the "worms" (and I do think that is what they are) do not seem to be erupting in any consistent way with regard to pores or lesions. The way the gloved hand keeps rubbing the skin just before the worms appear makes me suspect the worms are being applied rather than being brought out from deeper tissue. I'm not familiar with any human parasite that would appear in this way, nor would I expect one to affect the face so diffusely without skin changes. I think it's being misinterpreted. Just my sense of it, not enough info to be dogmatic, but I think Worms on face would be a more accurate heading. --Scray (talk) 00:51, 14 March 2009 (UTC)

I decline to view that video, but aren't there some sorts of flies that lay their eggs on an animal's skin that burrow under the surface, and the maggots feast on the fresh flesh when they hatch? -- Deborahjay (talk) 22:19, 21 March 2009 (UTC)

Pressure ridges in ice

Reading about pressure ridges, I was curious: does this involve strictly cracks, or does it include other phenomena also? The picture to the side I took yesterday at a lake that exhibited pressure ridges (see another picture for what I mean), but it also had an extremely bumpy surface at one edge. Could this be related to the pressure ridges? Nyttend (talk) 01:36, 13 March 2009 (UTC)

This sounds like a question for CambridgeBayWeather. Deor (talk) 01:59, 13 March 2009 (UTC)

I would think that bumpy ice is formed when water leaks up through cracks out onto the smooth ice surface and freezes there. StuRat (talk) 05:10, 13 March 2009 (UTC)

Yes, I've seen that before. Also, especially on the edges while the ice is still forming there tends to be a layer of water on top of the ice, and the movement of the water from wind and currents can cause the ice to form in less than perfect sheets. 219.102.220.90 (talk) 06:35, 13 March 2009 (UTC)

I added to the Pressure ridge article that they are also found on sea ice, probably more common due to the larger expanse of ice, added an image and a link to Commons. Google has some good pictures as well. The effect in the picture is probably created in the way that StuRat and 219.102.220.90 describe. It could also be caused by an stream where the inflow is going over the top of the ice and then freezing as per 219. Strangely enough the effect in the picture is not that common up here. Enter CambridgeBayWeather, waits for audience applause, not a sausage 16:23, 13 March 2009 (UTC)

Perhaps because the freezing process occurs quicker? I'd love to time researching the languages up there some day. 219.102.220.90 (talk) 23:36, 13 March 2009 (UTC)

Formula Unit vs Empirical Formula (Ionic Compounds)

Hello. What is the difference between the formula unit and the empirical formula for ionic compounds? Thanks in advance. --Mayfare (talk) 01:59, 13 March 2009 (UTC)

Aren't they the same? Formula unit and empirical formula seem to be the relevant articles. I think there might be some pathological chemicals which are exceptions, where the ratio of atoms does not seem to make sense based on electronegativities or "expected" ionization states; in those cases, the empircal formula would be the measured ratio of atoms as determined by elemental analysis (e.g. by mass). Nimur (talk) 04:30, 13 March 2009 (UTC)

Something like that, yes - perhaps look into Mercurous chloride or similar. 78.151.212.201 (talk) —Preceding undated comment added 10:31, 13 March 2009 (UTC).

Is there a theoretical maximum upper limit to handgun size?

Recently I've heard about people building revolvers that can fire .600 Nitro Express, .700 Nitro Express, .50 BMG and 20 mm caliber rounds. Most of them have been one-off custom jobs, but the former is actually being mass-produced by at least one company.

So, is there actually any sort of upper limit to how large we can make a handgun? --90.240.240.251 (talk) 05:20, 13 March 2009 (UTC)

Well, how much can you lift with one hand? It's mostly a question of weight and recoil, I would think. The gun has to be capable of being aimed and fired without knocking the wielder off his feet. This would be affected by both the size of the projectile and the amount of propellant. A related factor would be capacity - how many rounds should it carry? More rounds, more weight. Hm. Turns out I have more questions for you than answers! - Eron^Talk 05:27, 13 March 2009 (UTC)

Yes. The limiting factor would probably be human lift strength. If you dispense with niceties like ammo and reloading, and focus on projectile diameter, you could theoretically launch a light-weight bullet the size of a dinner plate. Such a bullet would be of negligible actual use, being severely limited in range, accuracy, and damage, but hey, you'd have the biggest gun. As far as practical guns are concerned, you'll probably find the upper limit already available for purchase in one form or another, depending on your particular value of "practical" (0 = dinner plate). In handgun size, like many other things, bigger is not necessarily better. – 74  07:53, 13 March 2009 (UTC)

Yeah, with these 'big guns' it sounds as though we're already getting into the realms of pistols that could only really be fired repeatedly with any accuracy by a Terminator. Sure, if you needed to take down a fully-grown, angry African Elephant or Rhino at close range before it flattened you, then something like the above might be useful - but a pistol that weighs six kilos is a heck of a lot to lug around in the wilds, on a 'just in case' basis (I think that the standard, tried-and-tested elephant rifles are actually lighter than this!). --Kurt Shaped Box (talk) 19:44, 13 March 2009 (UTC)

According to The Rifle and Hound in Ceylon, which is a bit outdated of course, the obvious solution is to exploit some natives as the carriers for each British man's armament:

• 4 Double-barrled No. 10 bore, "of such power in metal that they weigh fifteen pounds each"
• A No. 10 twelve-grooved rifle (rifled preferred for elephant shooting over smooth-bores, though much disputed)
• A four-ounce single-barrel rifle weighing 21 pounds
• One long two-ounce (bullet) rifle weighing sixteen pounds
• Several smooth bores and fowling pieces (which do not count toward the total armament count)

It's hardly a fair fight for the elephant, with that armament. But a fair fight - "this is a foreigner's notion of the chase; he hunts for the pot; and by Englishmen alone is the glorious feeling shared of true, fair, and manly sport." Nimur (talk) 20:26, 13 March 2009 (UTC)

Hey, it sounds a heck of a lot more sporting than one of those canned hunt jobs. Yep, you can now go to South Africa and shoot semi-tame elephants at point-blank range from the comfort of a Jeep or your favourite hunting chair without having to hump the heavy ordnance around (five shot .600 Nitro revolver - five elephants for the bag?). I can't help but feel that we've lost something along the way. --Kurt Shaped Box (talk) 21:07, 13 March 2009 (UTC)

That sounds really awful. Canned hunting? Where's the sport? "Who would shoot a hare in form? who would net a trout stream? who would hit a man when down? A Frenchman would do all these things, and might be no bad fellow after all. It would be HIS way of doing it." Nimur (talk) 21:20, 13 March 2009 (UTC)

Funnily enough, that quote reminded me of something one of the S.African canned hunt operators said when interviewed by a disapproving Louis Theroux. Basically, he said that this (canned hunting) was something that worked in a South African context, stating that the proliferation of CH ranches in the last decade has been beneficial from a conservation standpoint in the country - as the hunters' considerable incoming funds have allowed tens of thousands of acres of natural habitat to be purchased and protected (by armed guards and 50ft fences!), in a pristine state (as opposed to say, being razed for intensive farming) and also, that by breeding endangered species to be put to the foreign gun and (literally) putting a high price on their heads, a tangible financial interest in ensuring the proliferation of the various species has been created (yaknow, give something a value and The People Will Take An Interest). It's an interesting argument, at least. --Kurt Shaped Box (talk) 03:47, 14 March 2009 (UTC)

I'd think the recoil would be the bigger issue. It would depend on both the caliber and "load". Firing too much bullet would cause a recoil which would make the gun move out of position for the next shot. This would make such a gun less effective than one with a more reasonable size. StuRat (talk) 14:50, 13 March 2009 (UTC)

There are widely varying theories of lethality for various calibers (it seems to amount mostly to situational needs and personal preference). I would posit that the mainstream available guns are manufactured in sort of a "bell curve" of available calibers because those dimensions are best-suited for their lethality. For example, although a Desert Eagle may pack a punch with a single round, as a weapon overall it is probably less "effective" than, say, a Beretta 92 (with a dramatically smaller bullet). As such, few organizations use Desert Eagles (and those who do very likely use it for intimidation-factor, rather than combat effectiveness). This is of course a judgment call based on a lot of estimated factors; but the US Army seems to agree - when it comes to caliber, smaller is better. Nimur (talk) 15:30, 13 March 2009 (UTC)

When it comes to a (non sniper) battlefield situation, the difference in tactical terms between killing and merely wounding the enemy is not particularly great. Either way, you've just shot a man, who has fallen over in the mud and now has two or three of his comrades kneeling around him, trying to plug the holes and stop him from leaking (and also not pointing their guns at you). If he lives, he won't be up and fighting again for a while, if ever again. So, if you don't strictly *need* to kill your enemy with one shot to take him and his cohorts out of the fight, then why not use a smaller, lighter round and benefit from the decreased recoil and increased capacity? --Kurt Shaped Box (talk) 20:01, 13 March 2009 (UTC)

That sounds like a reasonable analysis of conventional warfare, but I'm not sure if it applies as well to the modern terrorist. That is, if they are able to move, a suicide bomber will likely still detonate his explosives, and nobody is likely to attempt a rescue of a suicide bomber, in any case. StuRat (talk) 23:41, 13 March 2009 (UTC)

Kurt: I would expect that armies want more stopping power from a more powerful round. bibliomaniac15 04:00, 14 March 2009 (UTC)

Take a look at the articles on Punt guns and on recoilless guns. Especially the latter, as it explains how to deal with the recoil problem. --Dr Dima (talk) 22:37, 13 March 2009 (UTC)

Traditional "recoilless" techniques are of very limited use in a handgun, where discharging anything behind the gun would prove rather hazardous for the wielder. Still, recoil can be managed by trading off against a different parameter: increasing gun mass, reducing powder load, reducing bullet mass, etc. – 74  02:11, 16 March 2009 (UTC)

The Gyrojet of Man from UNCLE fame fired a rocket propelled slug. It came out of the barrel at quite low velocity, so no recoil to speak of. At least in the Man from UNCLE version, the gun itself was very lightweight (didn't need much strength) and could be mistaken for a toy. 75.62.6.87 (talk) 22:10, 14 March 2009 (UTC)

Toilet seat warmers

Sorry, two questions! The first is about the toilets we have here with seat warmers on them. I've heard in the past about bacteria and parasites that can survive x amount of time after initial contact on places like toilet seats (but probably more often on door handles and the like), and I'm just wondering if seat warmers wouldn't have a significant effect on that, possibly keeping these things alive until the next guy comes. 219.102.220.90 (talk) 06:27, 13 March 2009 (UTC) I've taken the liberty of splitting your double-question into two separate questions because otherwise the answer thread(s) will be horribly confusing! SteveBaker (talk) 10:47, 13 March 2009 (UTC)

Bacteria on things like a toilet seat probably don't die through lack of warmth over a period of hours. But what the warm seat MIGHT do is allow them to multiply - which might be more serious. However, there is unlikely to be much in the way of nutrients - so I suspect there is no great risk. At any rate - as careful (and a little obsessed) as the Japanese are about safety in general - and about toilets (we British would NOT want our toilets to talk to us!) - I'm sure they've tested these things for safety. SteveBaker (talk) 10:47, 13 March 2009 (UTC)

Don't worry; my toilet doesn't talk to me. It has a power freshener, makes a waterfall sound when I sit on it, and sprinkles my anus with warm fluid. 219.102.220.90 (talk)

On a dry, nonporous surface, I suspect that warming will have little effect — and may actually shorten the viable lifespan of any pathogens by hastening evaporation. As well, in addition to warmth and moisture, growth of pathogenic organisms will require a food source — and there's very little for a bacterium to eat on a toilet seat.

In practice, the bacterial counts on a toilet seat are usually quite low, and most pathogens aren't capable of entering your body through the firm barrier of your intact posterior. Surfaces in your home that generally host more bacteria than your toilet seat include: your refrigerator door; kitchen countertop; sinks and faucets throughout the home; kitchen sponge or cloth; dish towels; the typical child's toy...[17]. TenOfAllTrades(talk) 13:44, 13 March 2009 (UTC)

This is slightly tangential, but it's worth saying. In this supposed "era" of energy-awareness and conservation, while everyone is converting incandescent lightbulbs to cold-cathodes to save thirty or fifty watts, people are still finding amazing ways to spend fifty or a hundred (or fifty-thousand) extra watts "warming" toilets and roadways. This reflects dismally on our prospects for energy conservation. Nimur (talk) 15:37, 13 March 2009 (UTC)

Yeah, it's pretty sad, I know. There is a button for "energy conservance mode", but it doesn't seem to change the temperature of the seat at all, so I can't imagine how much energy it saves. Maybe it just turns it off during the wee hours. *cough*. 219.102.220.90 (talk)

Nothing feels more refreshing than sitting on a toilet seat that is actually cold. A warm seat just serves to remind you that other people use the bathroom too. Livewireo (talk) 15:58, 13 March 2009 (UTC)

But it's not quite as refreshing a second later, when you realize that it only feels cold because it's wet. :-) StuRat (talk) 01:43, 14 March 2009 (UTC)

Ah - I understand - so you heat the seat so you can be sitting in a puddle of someone else's pee without noticing that it's wet. Got it. Thanks! SteveBaker (talk) 02:33, 14 March 2009 (UTC)

You get used to it after a while. :) 219.102.220.90 (talk)

Thanks!219.102.220.90 (talk) 03:24, 14 March 2009 (UTC)

Donating bodies

The second question is about body donation. I assume that the laws vary a lot depending on where you live; as you can probably tell from my IP I'm in Japan, but I'm Canadian. I have no idea if they have a body donation program in Japan, but I'm pretty sure they do in Canada. Most of the information on the web is about American medical schools so I'm not even sure about that. Also, if I were to want to donate my body to an institution that was outside of my country of citizenship (assuming I was Canadian, or American if there's no information), would that be possible? Thanks! 219.102.220.90 (talk) 06:27, 13 March 2009 (UTC)

Many countries won't even allow you to donate blood if you have lived overseas in the last (say) 10 years - so there is no doubt that organ donation for medical purposes is going to be impossible in some places. However if you are donating it for research, then I don't see why that would be a problem. You're going to have to find out what the laws are where you live because it's highly unlikely that they'll be the same everwhere. SteveBaker (talk) 10:47, 13 March 2009 (UTC)

• Donating your body to science may be possible, but expect to pay for the transport yourself. The University of Tennessee Body Farm has such a clause.[18] - Mgm|^(talk) 11:30, 13 March 2009 (UTC)
  • The body farm issue has came up before Wikipedia:Reference desk/Archives/Science/2008 October_22#UK BOD. If you just want to donate your body to science (be it for research or practice) I'm quite sure there will be progrms available in Japan. If you wan't find anything you may want to check with universities particularly those involved in medical research and attached to teaching hospitals. Nil Einne (talk) 11:36, 13 March 2009 (UTC)

Are psychological illnesses contagious?

If you spend too much time with aggressive people, for example, does this make you aggressive?--80.58.205.37 (talk) 12:17, 13 March 2009 (UTC)

Well, aggressiveness isn't technically a psychological illness, so the answer to your question below is that it depends on the personality. The human mind has a tendency to mimic others and try to fit in with its situation. OTOH, there are people whose personalities are such that they can at least minimize the aggressiveness of some. (Take, for instance, a good counselor who helps violent youth to try to get turned around all day.)

Psychological illnesses, OTOH, aren't contagious int he sense you can actually catch bipolar disorder, for instance. Being around poeple who are totally bipolar all day can wear one down and cause anxiety-related disorders, though.

But then,t here's also the joke that someone will repeat, so it may as well be me - "Insanity is hereditary - you get it from your children." :-)172.131.176.22 (talk) 12:54, 13 March 2009 (UTC)

Depending how one reads your questions, there are a couple of answers. To the general are psychological illnesses contagious?, I suppose one could point to something like mass hysteria for an instance of a bona fidepsychological condition.

The second question – on aggressiveness – could be rephrased as, are modes of social interaction learned? The biggest part of that answer is almost certainly yes. We tend to pick up and internalize cues for appropriate interpersonal conduct from those around us. TenOfAllTrades(talk) 13:28, 13 March 2009 (UTC)

Yes, I expressed myself poorly. I mean both - are some illnesses - like depression or anxiety - 'contagious'? And are character or behavior traits 'contagious'? —Preceding unsigned comment added by 80.58.205.37 (talk) 13:34, 13 March 2009 (UTC)

I would expect that the more common effect would be that people would attempt to keep their mental illness hidden if they receive negative feedback and not keep it hidden if it is "accepted". This wouldn't apply to severe psychoses, but only to those conditions which are somewhat controllable. For example, someone with OCD who needed to repeat some phrase every time a door is opened could probably repeat it in their mind if they were laughed at whenever they said it out loud. On the other hand, if they were around others with OCD or others who were more accepting of OCD, they might say the phrase out loud. This could give the appearance of "OCD being contagious". StuRat (talk) 14:14, 13 March 2009 (UTC)

I haven't read any research on your question, but it would not surprise me. I have worked in psychiatric hospitals and it was really tough for me to spend so much time every working day with people who feel really bad, who suffer from deep depression or deep anxiety. I think it would have been detrimental for my own mental health if I would have stayed there. Of course, this only goes for those of us who are vulnerable in that way, but that is usually the case with contagious diseases. Lova Falk (talk) 17:11, 13 March 2009 (UTC)

The following article might be helpful, you might not be able to read the whole thing if you aren't a new scientist subscriber, but I seemed to be able to get most of it even when I was logged off.

http://www.newscientist.com/article/mg20126881.600-how-your-friends-friends-can-affect-your-mood.html?page=1

131.111.8.97 (talk) 18:24, 13 March 2009 (UTC)

Well, I suppose that psychological conditions could be passed via power of suggestion, but contagious implies that there is a contagion, i.e. a substance which could carry the dissease with it. I mean, if you get depressed being around depressed people all day, that doesn't mean that there was a germ or virus or something that carries the depression, it just means that the emotional state of the people you hang around with can effect your own emotional state... --Jayron32.talk.contribs 00:06, 14 March 2009 (UTC)

I've heard the word "contagious" used in a more general way quite often, as in "laughter is contagious". Then there are a small percentage of mental disorders which may be directly caused by a contagion. On the other hand, general diseases, some of which are contagious, may also cause some mental problems, such as depression, in some people. StuRat (talk) 00:56, 14 March 2009 (UTC)

See Borna disease. --Arcadian (talk) 05:23, 15 March 2009 (UTC)

UV light to reveal body fluids // cat spray

Two part question: -Use of UV light to highlight body fluids on surfaces as seen in crime dramas: Is there a name for this and do we have an article on it? If not, is there any trick to it, or do you just need a UV lamp and dark conditions? -Would this technique work to highlight "cat spray" (not urine, but the oily, stinky stuff they use to mark territory)?

Maybe you can guess -- a cat sprayed in my basement, and I can't find the exact spot, so I can't do much to clean it up! ike9898 (talk) 14:07, 13 March 2009 (UTC)

That's photoluminescence, and specifically fluorescence, although I didn't locate an article specifically about your application of finding bodily fluids. Another way to find the cat pee is to bring a cat or dog down there, which will immediately locate it for you. Just make sure you don't bring an intact male, or he will feel the need to add his own contribution to the spot. And, while we're at it, why not get the cat in question neutered to prevent a repeat ? StuRat (talk) 14:24, 13 March 2009 (UTC)

Using a dog is a great idea, which I think I'll try tomorrow! As to the neutering, this is what everyone I talk to brings up. Both my cats (males) are neutered and have been since they were adopted as kittens. I have caught one of them spraying a few times over the years. So I don't think it's impossible for a neutered male to spray, just a lot less likely. ike9898 (talk) 14:58, 13 March 2009 (UTC)

A quick skim of some fairly reliable sources supports the notion that neutered males can spray. ike9898 (talk) 21:38, 13 March 2009 (UTC)

Yea, I guess that happens if they are too old when neutered. Another factor in animal spraying is that they all feel the need to spray whenever they smell the spray from another animal. Having two males makes them particularly likely to try to best one another. If you can get all the smell out and use a powerful deodorizer, you might stop a recurrence. StuRat (talk) 23:36, 13 March 2009 (UTC)

See luminol. --Sean 16:32, 13 March 2009 (UTC)

Cat urine definitely fluoresces under a blacklight. No luminol needed, no special tricks: just turn the lights out and the blacklight on, and make a basement sweep. I'm pretty sure that "spray" is just a special case of urine. The lights are fairly cheap, so I would definitely give it a try. - Nunh-huh 16:45, 13 March 2009 (UTC)

Does the urine fluoresce after drying? And, does that happen with dog or human urine as well? -hydnjo (talk) 19:48, 14 March 2009 (UTC)

Yes and yes. The components which fluoresce aren't liquid, so can't evaporate. StuRat (talk) 04:23, 15 March 2009 (UTC)

Update I tried two different UV lamps. Both effectively revealed the location of the urine spots, but one of the lamps made the spots glow much brighter (at least one of these two lamps emits UV in a different range that a "Blacklight" does). Anyway, I cleaned the spots, the smell went away, and then two days later the cat did it again! ike9898 (talk) 21:39, 16 March 2009 (UTC)

That's a cat for you.... Try it one more time: clean it, then crinkle up some tin foil and spread it over the previously affected area. Apparently peeing on tin foil isn't quite so much fun for kitty. Some folk also put double-sided tape on the floor near the area (cats don't like to walk on it) and use citrus scented spray, which cats tend to avoid. - Nunh-huh 21:45, 16 March 2009 (UTC)

I've ordered some pheromone diffusers that supposedly have a calming effect on cats. And some enzyme based cleaner. Wish me luck. ike9898 (talk) 13:50, 17 March 2009 (UTC)

Uranian axis tilt > 90 degrees?

The axis of the planet Uranus is said to be tilted about 98 degrees, i.e., it is essentially on its side and "rolling" through its orbit. Cute simplistic imagery aside, why is it that this value is not rather given as about 82 degrees, that is, less than a right angle? As a somewhat absurd analogy, the axis of the Earth is not said to be tilted at 157 degrees.

I thought it might be because the pole found on the south side of the ecliptic was actually closer to the planet's North magnetic pole, but the diagram in the article suggests otherwise, if I read it correctly.

Why is this convention held? Baccyak4H (Yak!) 15:01, 13 March 2009 (UTC)

I'm wondering if it has anything to do with the polarity of the rotation ("clockwise vs. counterclockwise"). I have to think about this for a while to see whether this actually makes any sense (as the planet revolves around the sun); but it may be a greater-than-90-degree tilt to preserve the correct rotation direction as most of the other planets. Nimur (talk) 15:42, 13 March 2009 (UTC)

Also see IAU/IAG Working Group on cartographic coordinates and rotational elements[19], which explicitly lays out the justification for picking which pole is "north", while acknowledging that this is a matter of preference. "The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system. The direction of the north pole is specified by the value of its right ascension α0 and declination δ0." They do not seem to give the "97.77°" number. Note that the description of Uranian rotation is sometimes given as "retrograde" and sometimes not - so it seems like there is not a total consensus on which pole is "north." Nimur (talk) 15:50, 13 March 2009 (UTC)

In other words, the issue is whether you view the direction of rotation as defining which end of the axis is north. In my opinion that is the sensible thing to do and it means that the axis is inclined by 98°. The IAU/IAG group has the opposite opinion. In that case the axis itself does not carry an orientation so it is natural to refer to it as inclined by an angle less than 90°, i.e. by 82°. You then have to add that the rotation is retrograde. By the way, the same issue arises for Venus and Pluto. --Anonymous, 19:38 UTC, March 13, 2009.

Nimur and Anonymous explanations are correct. I just want to point out that the description of Uranus motion as "rolling through its orbit" doesn't make sense and should be avoided. Dauto (talk) 19:45, 13 March 2009 (UTC)

Looking southward onto Uranus from the north side of the ecliptic, the planet would look more like it's rotating in retrograde motion than not. Venus has an axial tilt of nearly 360 degrees, due to its retrograde motion, but that likely depends on the convention used. ~AH1^(TCU) 22:34, 13 March 2009 (UTC)

I think you were turned the wrong way when you said 360°; it should be 180°, right ? StuRat (talk) 23:29, 13 March 2009 (UTC)

Likewise, many sources list the axial tilt of Venus as a more absurd 177 degrees. The convention seems to be that the "north pole" is that pole which, if you call it north, will present a planet that rotates the same direction as Earth. So basically, depending on your perspective, Venus is either spinning "backwards" (if you accept that it's north pole is the one closest to the orientation of the Earth's north pole) or "upside down" (if you accept that north is defined by the direction of spin). The same logic applies to Uranus, and it really doesn't matter which you pick. Either Uranus has an 82 degree tilt, and turns backwards (i.e. retrograde) or it has a 98 degree tilt, turning in the same direction as Earth... --Jayron32.talk.contribs 00:00, 14 March 2009 (UTC)

Many thanks for the replies. The parity of the rotation makes sense. Baccyak4H (Yak!) 03:56, 14 March 2009 (UTC)

Any difference between brush with a dry or wet toothbrush?

I've noticed a few habits when people brush their teeth. Some put toothpaste on a dry toothbrush and proceed to brush. Others put toothpaste on, then wet the toothbrush with water. And still others wet the toothbrush, put toothpaste on, then wet it again. Is any method "better" than others? I would tend to think the dry brush would have a more abrasive effect since it's not being diluted by water (at least initially before its mixed with saliva). --70.167.58.6 (talk) 16:27, 13 March 2009 (UTC)

A clinical comparison of three powered toothbrushes found that the toothbrush filaments on some toothbrush models may bend slightly when wet. There did not seem to be any effective change in the resulting cleaning capability. Nimur (talk) 16:44, 13 March 2009 (UTC)

Keep in mind that, as our toothbrush article indicates, abrasive is not really what you want while brushing your teeth, as it can damage the enamel. --140.247.250.160 (talk) 19:59, 13 March 2009 (UTC)

I'm one of the wet-brushers (I wet it after, but I'll attribute that to laziness), and there is a clear reason for that, or at least there is to me. Putting a dry toothbrush into your mouth instantly lowers the average saliva level in your mouth (because loose saliva will attach to the brush head) and since most gel toothpastes foam better when mixed with water (as with soaps) wetting the brush keeps the inside of the mouth salivized and facilitates the toothpaste foaming process. I find brushing with a dry brush makes it difficult to distribute the toothpaste evenly among my teeth, as it clumps up and gets pushed to the side when it should be getting mixed into the bristles. 219.102.220.90 (talk) 23:51, 13 March 2009 (UTC)

Volunteering extra information: I have in my possession books published about thirty or forty years ago that were against brushing teeth with toothpaste. Using a dry brush was recommended, and for tough cases, brushing your teeth with salt was deemed the best solution. --Ouro (blah blah) 17:26, 14 March 2009 (UTC)

Breathing dust from cat litter, unhealthy?

When I clean my cat litter, it produces an awful amount of dust. I'm wandering whether it can be unhealthy to breath that dust? --Phenylalanine (talk) 16:48, 13 March 2009 (UTC)

Yes. Don't you know we have an article on everything? See here and also here. Matt Deres (talk) 20:04, 13 March 2009 (UTC)

Virtually any type of dust can cause pneumoconiosis. Certain chemicals (notably asbestos and coal soot) are so problematic that they have special medical terminology just for them. However, the sorts of occupational exposures are usually daily interactions over many years. Short-term exposure to small quantities of dust is probably not harmful, but if you find it aggravating, you can consider wearing a disposable dust mask (our article focuses mostly on respirators, but I'm thinking of simpler cloth or fiber masks like this). They are very cheap, and you can get a lot of uses out of them. Nimur (talk) 20:07, 13 March 2009 (UTC)

It may not be unhealthy but it's definitely smelly!!--TammyMoet (talk) 21:09, 13 March 2009 (UTC)

Thanks to all for the useful information! --Phenylalanine (talk) 22:44, 13 March 2009 (UTC)

Wait, wait! There's more about the smell. -hydnjo (talk) 23:41, 13 March 2009 (UTC)

Adding on to what that article notes, the pine-based cat litter is, unlike the silica or clay, nearly dust-free. It alone has earned the Nunh-huh seal of approval. -Nunh-huh 01:35, 14 March 2009 (UTC)

So how do they get rid of the formaldehyde? Or do they? AFIK pine naturally emits formaldehyde. It's part of the "piney" smell. I googled but there seems to be no mention of that. BTW> There's also recycled paper litter and wheat based litter if you don't want to go with clay. Printing ink has some very nasty chemicals in it, so the ink free varieties should be better. Baking soda helps against the smell. 76.97.245.5 (talk) 08:18, 14 March 2009 (UTC)

Baking soda also fizzes when urine is sprayed on it, and the result of that is that kitty point blank refuses to use the litter tray and pees elsewhere! --TammyMoet (talk) 14:27, 14 March 2009 (UTC)

Re the formaldehyde question: From this site "According to the manufacturers, pine-based varieties are made from recycled shavings, which are kiln dried to remove aromatic oils, and then compressed into pellets." And from the Feline Pine site "Feline Pine® is 100% natural, biodegradable pine that has been heated and pressurized to remove any harmful wood oils." -hydnjo (talk) 19:27, 14 March 2009 (UTC)

Thanks, that explains it. Re.: Baking soda Tammy, cats have preferences. We had one who insisted on a particular brand of cat litter and you can imagine what happened when we moved to a place where that wasn't available! If you mix it in with the litter and don't use too much I haven't had one yet who refused to use the box then, but you never know. 76.97.245.5 (talk) 09:39, 15 March 2009 (UTC)

Toxoplasmosis is aerosolized. --Arcadian (talk) 05:16, 15 March 2009 (UTC)

Molecular bio technique: protein expression?

I'm new to protein expression, and I could use a little starting out advice. I have a human gene that has already been cloned into a pCMV-SPORT6 mammalian expression vector under a CMV promoter; the vector also contains an AmpR selectable marker. The protein involved is a very hydrophobic ER membrane protein that is also post-translationally modified, so bacterial expression isn't really an option. My questions are:

1. Since the vector has AmpR, is there some mammalian (or other eukaryotic) selection agent I can use, or do I have to subclone the gene into another vector that can be used for selection?
2. What types of cell lines are usually used for expression of intracellular membrane proteins?
3. Are there any particular pitfalls, gotchas, or other horror stories that I should know about before I begin? —Preceding unsigned comment added by 69.127.231.186 (talk) 16:54, 13 March 2009 (UTC)

Ampicillin resistance will only be useful for bacterial selection (i.e. propagating your clone). For selection in mammalian cells you'll need something like G418 selection, which will require you to subclone into another vector. You could also try expression using baculovirus-infected insect cells. Choice of cell line probably depends on what's available at your institution (it's usually easy for someone to split some cells for you to start growing) but you may want to find the most physiologically relevant cell type. Lots of people just use chinese hamster ovary (CHO) cells, but if you know what cell type your protein is expressed in, you could try to pick a cell line from that tissue. The ATCC website has tons of info about different cell lines (http://www.atcc.org/Portals/1/Pdf/CellCatalog/Tools_Models.pdf) that you can sift through. The major "gotchas" are going to come in the protein purification step, especially if you have an integral membrane protein that is hydrophobic and post-translationally modified. Good luck! --- Medical geneticist (talk) 18:54, 13 March 2009 (UTC)

M.g.'s response is excellent as always, but I'd add that this answer illustrates the utility of being able to move your gene from one vector to another until you find the right system, and the Gateway system can be your best friend in this situation (no conflict of interest to report!). The "destination" vectors they offer (for a wide variety of host cells) include N- and C-terminal extensions that increase solubility and/or offer tags (like 6His, myc, etc) for purification. Of course, they offer all sorts of selectable markers. Transfers among vectors are isothermal and nearly 100% efficient. Getting it into the Gateway system can be tricky but their tech support is helpful. Hope this helps. --Scray (talk) 00:30, 14 March 2009 (UTC)

It looks like a great system, but the costs are... prohibitive. Unfortunately, we're limping along financially as it is. 69.127.231.186 (talk) 03:18, 14 March 2009 (UTC)

Understood, but don't underestimate the savings one realizes when an experiment works. --Scray (talk) 03:27, 14 March 2009 (UTC)

Need information from an Icarus article

I'm hoping someone here has access to this journal article:

• Zellner, B (March 1985). "The eight-color asteroid survey: Results for 589 minor planets". Icarus. 61 (3): 355–416. doi:10.1016/0019-1035(85)90133-2. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

If you do, I'd like to know if it provides a classification of asteroid 243 Ida, when the spectroscopic measurements were taken, and what pages of the article the information appears on. Thank you. Wronkiew (talk) 17:55, 13 March 2009 (UTC)

Not an answer, but you could always try WP:WRE. —Cyclonenim (talk · contribs · email) 22:35, 13 March 2009 (UTC)

Thanks for the tip. I posted this request at WRE as well, maybe someone has access to the paper there. Wronkiew (talk) 17:13, 14 March 2009 (UTC)

Article obtained, thanks again. Wronkiew (talk) 16:06, 16 March 2009 (UTC)

Evaporation of methanol/water mixture

Hi,

If I have a solution of about 50% methanol in water (plus salts etc), is it possible to differentially evaporate only the methanol, leaving only water? For a bit of background, we're trying to remove this from a frozen cell culture pellet in a lypholyser/freeze drier.

Any physical chemists or anyone know anything about this topic?

Thanks!!!

77.12.3.80 (talk) 18:17, 13 March 2009 (UTC)

Since ethanol methanol has a boiling point of 78.4 64.7°C and water has a boiling point of 100°C, heating it to a temp between those two should cause the ethanol methanol to boil off and leave most of the water. This assumes that nothing else is present, but you said some salts are present, which could alter the boiling point of the water. Also, be careful when boiling off ethanol methanol, as it is flammable. That is, don't let it vent into a lab where there are open flames, but rather do this under an exhaust fan. You did ask about evaporation, though, not boiling. This would work, too, but could take a very long time. The colder the sample, the longer it will take. StuRat (talk) 23:19, 13 March 2009 (UTC)

The OP is asking about methanol, not ethanol. As far as ethanol/water, nuh-uh, it forms an azeotrope. Franamax (talk) 23:30, 13 March 2009 (UTC)

Thanks for the correction, I've updated my post accordingly. As for the azeotrope issue, the next poster seems to have addressed that. StuRat (talk) 00:52, 14 March 2009 (UTC)

Azeotropes generally only occur at certain concentrations and pressures, for example with ethanol-water mixture, the azeotrope forms at a 95% ethanol/5% water mixture (hence, the maximum proof of liquor is usually 190 proof). We do have an article on Azeotropic distillation which discusses special techniques for seperating azeotropes. However, this forum post: [20] indicates that methanol and water do not form azeotropes at atmospheric pressure, which means that you should be able to get pure seperation using simple distillation techniques. this data table of azeotropic data indicates the same; that methanol forms no azeotrope with water. So if you heat the mixture to above the boiling point of methanol, which at atmospheric pressure is about 65 deg C, then you will be able to drive off all of the methanol and leave all of the water (as an aside, due to the fact that water still has a sizable vapor pressure at those temperatures, meaning that while you can leave behind pure water, if you cool and collect the methanol vapor, you will still have water in it... --Jayron32.talk.contribs 23:52, 13 March 2009 (UTC)

There's also membrane separation from what I looked ar earlier trying to find a solution. I think the problem here though is that the OP wants to keep the cell culture frozen, so 65 degC wouldn't do it. If the pellet can be thawed, then wouldn't dilution be simplest? Put the pellet on a filter and pour water on it, eventually there will be cells and water, with all the methanol flushed through the filter. (Just don't shake it at the same time, the methanol will get stronger!! :)

To do it in a frozen state, I think you would need something like a getter for methanol, i.e. some substance that would adsorb or fix the methanol and give it a lower vapour pressure. Perhaps enclosing the pellet in a separation membrane, with a drying agent on the other side? Then the methanol would sublimate and pass through the membrane, while the water stayed in vapour equilibrium on the pellet side. Franamax (talk) 03:35, 14 March 2009 (UTC)

banded krait bite

If bitten on hand by a banded krait snake, would it save life if hand was cut off soon after bite? —Preceding unsigned comment added by 72.160.181.221 (talk • contribs) 18:50, 13 March 2009

Let's hope this is not a medical advice question. If the venom has already entered the bloodstream, it will spread within a few seconds, so amputation is useless. If the krait venom is only in the tissues, it will spread diffusely, and so it's possible that an amputation may actually help. Field Manual 21-76 states clearly that in snakebite situations, amputation is commonly a result of too-late treatment, but it does not mention it as a precaution, in the event of snakebite.

“ The primary concern in the treatment of snakebite is to limit the amount of eventual tissue destruction around the bite area.

A bite wound, regardless of the type of animal that inflicted it, can become infected from bacteria in the animal's mouth. With nonpoisonous as well as poisonous snakebites, this local infection is responsible for a large part of the residual damage that results. Snake venoms not only contain poisons that attack the victim's central nervous system (neurotoxins) and blood circulation (hemotoxins), but also digestive enzymes (cytotoxins) to aid in digesting their prey. These poisons can cause a very large area of tissue death, leaving a large open wound. This condition could lead to the need for eventual amputation if not treated. Shock and panic in a person bitten by a snake can also affect the person's recovery. Excitement, hysteria, and panic can speed up the circulation, causing the body to absorb the toxin quickly. Signs of shock occur within the first 30 minutes after the bite.

”

I can find no references to "preventative" amputation. Amputation is not to be taken lightly, and should certainly not be performed by an amateur; this may cause collateral damage far worse than the original injury. Nimur (talk) 19:12, 13 March 2009 (UTC)

Well it certainly helped Hannibal at his time of need ;-) -hydnjo (talk) 22:59, 13 March 2009 (UTC)

I don't know about preventative amputation for snakebites, but preventative amputation is sometimes used in other cases, such as cancer. StuRat (talk) 23:12, 13 March 2009 (UTC)

In that case, a trained surgeon is present and has a little time to prepare - a krait bite's neurotoxin can kill a bull in under half an hour. A human, weighing an order of magnitude less than a bull, probably has an order of magnitude less time. That's not a lot of time to prep an OR! Nimur (talk) 23:44, 13 March 2009 (UTC)

Our article states that, "There are no authenticated records of human beings having been bitten." Not sure this is the snake one should worry about most. --Scray (talk) 02:05, 14 March 2009 (UTC)

Corneal diseases of less severity than Fuch's Dystrophy

Is there a corneal disease of less severity than Fuch's Dystrophy which has the similar effect of poorly regulating fluid transfer in the endothelium and can result in a reduced cell count in the endothelial layer? I heard of something like "Haltata" but could not find anything on the web or in Wikipedia. For symptomatic relief, I understand this condition can be aided by lubricative moisturizing drops as opposed to actually drying out the eyes with a hair dryer as suggested by Wikipedia's article on Fuch's Dystrophy. —Preceding unsigned comment added by Jaysfive (talk • contribs) 19:55, 13 March 2009 (UTC)

Why the location of the new Russian spaceport?

Russia is planning to construct Vostochny Cosmodrome in the Russian Far East, to reduce its dependence on the Baikonur Cosmodrome for low inclination or geostationary launches. They're planning on locating it in the Amur Oblast (although they don't decide as to where until next year). You would think that the primary criterion for a Baikonur-replacement site would be as low a latitude as possible (Baikonur is at 45°N). The Amur Oblast ranges only as far south as 49°N. On looking at the Russian Far East, there seem to be some rather nicer places to put such a facility: somewhere like Khabarovsk (which is at 48°N and which is near Komsomolsk-on-Amur, Russia's capital of aviation) or the flatlands north of Vladivostok (at about 44°N). Both are well connected to Russia's mainline railway network, and seem to be better situated with regard to weather, power, and supporting industry. The launch tracks from either would still largely pass over water, Sakhalin, and maybe the sparsely inhabited parts of northern Hokkaido. Surely every degree south would save fuel or afford more orbital flexibility. So my question is - what technical characteristic favours the inland Amur basin over these two maritime options? (or is there a political angle I've not considered?) 87.115.143.223 (talk) 20:25, 13 March 2009 (UTC)

Far be it from me to speculate, but there may be some ugly politics associated with launching spacecraft eastbound into the Pacific? Nimur (talk) 20:35, 13 March 2009 (UTC)

That's true, but missile/launcher capable powers are very careful to tell each other when they launch anything even slightly suborbital. No-one is going to mistake a Russian sat launch for a missile. Plesetsk is a former ICBM base (firing over the pole at the US) and no-one gets upset when they see a planned launch (often in a polar orbit) from there. 87.115.143.223 (talk) 20:47, 13 March 2009 (UTC)

I guess my point is not about true operational problems (as you describe, it is easy to avoid those). Most civilians have very little trouble cooperating internationally and making sure that their expensive rockets don't accidentally land where they are not supposed to. However, any civilian space-program always carries an implicit, public declaration of military missile capability for the nation it represents - and so there is a subtle, ugly undertone to any civilian launch (even if it carries the most benign and friendly scientific satellite). The act of launching the rocket is sort of a reminder to everyone: "We can launch something (wink wink nudge nudge) and fly it near/over your territory. By the way, this one is harmless." So, even though the construction of a civilian cosmodrome may truly have no sinister intent (conspiracy theories aside, and ignoring military-civilian collaboration projects) - there can still be political thunderclouds associated with it. Nimur (talk) 22:08, 13 March 2009 (UTC)

(Take a look at Poker Flat. A lot of awesome science is done there. It's about as far from "military" as I've seen, and I've been through my fair share of missile ranges). "The whole idea of tipping a rocket on its side was brand new," said Geophysical Institute Assistant Professor and HEX Principal Investigator Mark Conde. An 800 mile-long horizontal rocket-track on a civilian range which points northward from Alaska? Sure it was, Dr. Conde, sure it was. Nimur (talk) 22:13, 13 March 2009 (UTC)

And (as it's surely scarier to be on the receiving end) there wasn't a tizzy when they fired a Bulova missile from the White Sea at central Kamchatka [21] in November. 87.115.143.223 (talk) 20:59, 13 March 2009 (UTC)

Incidentally I think I've discounted some political issues:

1. invasion from China: both Vladivostok and Khabarovsk are of huge military significance to Russia: they'll defend them long after a dump like Amur has fallen
2. proximity to China (wherein countries get unnerved when rockets get launched very near their borders): the same is true for southern Amur - to get a decent distance from China in Amur they'll have to be at about 51°N - it doesn't seem worthwhile to build so far north, when they have Plesetsk.
3. flooding of the upper Ussuri River (for the Vladivostok option) - well, they're not cheap british housebuilders, so they're smart enough to find a big flat hill :)

87.115.143.223 (talk) 20:39, 13 March 2009 (UTC)

When governments build big things in the middle-of-nowhere provinces, it's often to create jobs where they're badly needed. So that's my guess --Pykk (talk) 20:51, 13 March 2009 (UTC)

Pykk's idea is reasonable. However, I'd think that a priority would be to ensure that no launch tracks passed over any other country, even "sparsely-populated" areas. Rockets leave toxic residue from the fuel downrange; Hokkaido is home to the minority Ainu people of Japan, so sparse population doesn't necessarily count; Russia and Japan are still arguing about those four islands from WWII; and I'm not a launch expert, but wouldn't the launch track tend to head a bit southwards anyway? I'd imagine the priority would be to ensure that you can get the payload into orbit entirely over your own territory and international waters. If that takes a little more boost, so be it. The Russians already have pretty powerful boosters anyway, the biggest in the world I do believe. Franamax (talk) 23:50, 13 March 2009 (UTC)

Rockets don't always go where you want them to either, and not hitting people when a booster fails is an important consideration. SDY (talk) 00:08, 14 March 2009 (UTC)

Thanks everyone; I think Franamax has it. Frankly I really doubt the Russians care very much about the nerves of South Korean and Japanese air defence officials, or the feelings of the people of Hokkaido, but I think they don't want to have to fly through Japanese airspace (and thus have to ask permission, rather than just give notice). As our airspace article notes, there's no real definition of how high a country's airspace goes, but I bet they're factoring in some possible future international agreement that puts it at the Karman line, and they need a few hundred miles of setback to make sure they're above that before they pass over Japan. That's essentially the arrangement at Baikonur; they'd still be ascending when they passed over China and Mongolia, but clearly high enough to be (or to claim to be) out of those countries airspaces. 87.115.143.223 (talk) 12:34, 15 March 2009 (UTC)

X-Z motorized stage

I am looking to buy or build a small motorized stage that can move a small, light weight object vertically ~3 cm and horizontally ~6 cm. This will be part of a micro imaging system. An interface for computer control would be a big plus, but manual toggle switches might work too. I have $1000+ budget, but a short time frame, so it needs to be something that can be bought or assembled off-the-shelf in a hurry. Anyone have any ideas of suppliers for this sort of thing? In the absence of something commercial, I've also been considering hobby items and toys that might be repurposed (e.g. Lego Mindstorms), so that kind of suggestion might work too. Dragons flight (talk) 23:52, 13 March 2009 (UTC)

Lego Mindstorms could EASILY do that - and at a couple of hundred bucks would be well within your budget. If you need to move in X, Y and Z then you'll need three motors (I forget how many you get with the standard set - so you may need to buy an extra. The motors come with 'rotation sensors' so you can figure out how far they've moved. There are also 'bump sensors' that you could place at one end of each 'track' so the computer can wind the motors in that direction until the sensor triggers so it knows where they are at the start of the run. There are 'rack and pinion' gears to translate rotary motion into linear motion.

The biggest issue is going to be precision. You have not said how precise or how smooth it has to move...and that's a HUGE deal. You can gear the system WAY down so it moves very slowly - but there is a limit to precision because Lego gears do not mesh particularly tightly - and there is a certain amount of backlash. There are a few tricks to help that - which we can discuss if you'd like. But if you are expecting (say) 1/10th millimeter precision - then it's going to be hard. 1mm precision is more do-able...but that's the critical factor here. There are HUGE numbers of online resources for Lego enthusiasts (they call themselves "AFOL's" - Adult Fans Of Lego) and there are a lot who have much mechanical/robotics expertise.

Interfacing to the Lego computer is very easy - there are lots of libraries out there to help you do that. It has a bluetooth interface should you want to interface things like keyboards - you can drive it with the keypad on any bluetooth cellphone! It can be hooked to the computer with a USB cable. The programming "language" it comes with is a graphical thing where you essentially draw a flow-chart of sorts. However, the AFOL's have written a C-like programming language called "NQC" (Not Quite C) that enables experienced programmers to work with it and feel right at home.

You'll probably find that the kit you get will be missing some parts you'll need for this project (although you might get lucky). If so then I strongly suggest you go to the http://www.bricklink.com/ site - where AFOL's will sell you any number of super-rare and specialised parts for pretty low $$$. That's MUCH less frustrating than scanning the shelves of Toys'R'Us hoping to find a kit with just the right gear wheel - and then finding you need to buy 20 sets to get the number you need!

SteveBaker (talk) 02:26, 14 March 2009 (UTC)

I have a target speed of ~0.5 cm/s horizontal and discrete steps of 0.5 mm vertically. Bricklink seems quite helpful. I was concerned that the parts in the default set didn't go all that far towards covering my needs. Dragons flight (talk) 04:04, 14 March 2009 (UTC)

I would probably take too long for you, but using a printer or scanner might work neatly. I haven't tried to control a modern printer precisely, but the older dot matrix epsom printers could be sent commands to nudge the roller or print head a bit at a time. Polypipe Wrangler (talk) 21:25, 14 March 2009 (UTC)

This is one of those problems that you can solve quickly or solve cheaply - but quickly AND cheaply is harder. I agree that you could certainly do a MUCH better job by repurposing other mechanism or having custom parts made...but that's either expensive or time-consuming. With Lego, you get cheap AND fast - but at the price of not being able to make a really powerful or really precise mechanism. However, you'll certainly be able to gear down a gear train so where you can reach the horizontal speed and the vertical 'step' size - but the problems will come if (for example) you command the system to go 2cm up and then 1cm down - and if you then expect to be 1cm up from where you started to a precision of within 0.5mm - that's tough because of gear backlash. However, if you've driven 1cm up and now you want to drive another 0.5mm up - I don't think that's a problem because you're going in the same direction.

Because the teeth don't mesh precisely - there are little gaps between the teeth of one gear and that of the next. When you keep driving in one direction, this isn't a problem because everything stays in contact. But when you reverse the motor, it has to revolve a little bit to move the first gear tooth backwards across that little gap. This is 'backlash'. If you have to use a 'train' of (say) six gearwheels to get the speed low enough - each pair of wheels has to move across that gap. Worse still, with really low gearing you have to turn the motor much more in order to cross the gap in the last set of gears. So the computer can't naively just assume that if it turns the motor 100 revolutions in one direction then 100 revolutions in the other - that the output will actually move at all.

Backlash is present in all geared systems - but it's worse with lego because the manufacturing tolerances of plastic wheels isn't very good to start with - and the nature of the geometry of lego (with fixed spacing for the 'studs' that is different from the vertical spacing of the 'bricks'), it's necessary to allow for very loose gearing in order that little kids can make things that actually work! Using a nice set of brass gears would get you much better precision - but making it all work on-time and in-budget would be much harder.

There are some tricks (both hardware and software) to get around the problems to some degree.

Re-purposing some other mechanism is possible - but the effort to integrate it into a system is vastly harder. Sure, the positioning mechanisms on old-style printers is pretty good - but you have to figure out (without documentation) how to drive the motors - and you have to machine custom brackets and stuff. You could even use things like the head positioning motors from an old CD drive - which will get you SPECTACULAR precision - but you'll need to fritz around experimenting because they can't move much of a load. (Incidentally - you didn't tell us how much weight you want this gizmo to move...that's important too!) But the beauty of Lego is that it's all there...the parts all fit together - you can build any geometry you want - and you can have something working in a couple of hours. If there is a problem with it - you can tear it apart and do it again some other way and be done in another hour.

Lego has a lot of parts that you'd find hard to get other ways - things like a clutch gear that slips if it's asked to deliver too much torque - very handy to avoid wrecking things if you're trying to drive something against a hard end-stop - there are pulleys with rubberbands for drive belts - drive chains (like a bicycle chain with plastic chain links that you can snap in and out to change the length) - rack & pinion gears, etc. Lego also has pneumatic cylinders, valves, pumps and reservoirs. There are 3rd party Lego-compatible temperature, pH, pressure and ultrasonic ranging sensors.

SteveBaker (talk) 22:29, 14 March 2009 (UTC)

March 14

Soundwaves

How do soundwaves travel from a radio or TV? —Preceding unsigned comment added by 71.31.106.65 (talk) 01:59, 14 March 2009 (UTC)

The same way they do when you speak or make any other sound. The electrical signals inside the radio (or whatever) cause an electromagnet coil to pull or push a small magnet that's glued onto the back of the loudspeaker cone - when the cone moves forwards, it pushes a higher pressure "wave" of air ahead of it - and when it moves backwards it creates a region of lower pressure. It does this hundreds or thousands or even tens of thousands of times per second depending on the pitch of the sound it's producing. The waves travel outwards through the air like ripples when you toss a pebble into a pond (well, kinda) and those ripples eventually reach your ears where the waves of high and low pressure alternately push and pull your eardrum. That in turn causes pressure waves through fluid inside your ear - which wiggles some tiny hairs that are connected to nerve cells that turn those vibrations into electrical signals for your brain. SOund waves are a little bit different from waves in a pond because they push and pull at the air rather than moving it up and down like the water waves. That allows them to travel in three dimensions instead of just along the surface as water waves do. Hence the sound 'ripples' move outwards in spherical patterns instead of circles as water waves do. Sound waves move at somewhere around 700 miles per hour - so the sound waves seem to travel pretty much instantaneously. SteveBaker (talk) 02:09, 14 March 2009 (UTC)

Were you asking how they travel from the radio or TV to your ear, or how they get to the radio or TV in the first place, 71.31.106.65? --Chetvorno^TALK 06:25, 14 March 2009 (UTC)

In what year in firearms history was antimony first added to lead in the manufacture of bullets?

I would like to know in what year in the developmen of firearms was antimony first added to lead in bullet manufacture to cut down on lead deposits in the bore. —Preceding unsigned comment added by 76.29.75.202 (talk) 05:53, 14 March 2009 (UTC)

This page says: "Antimony has been used in shot since the 1800s, but did the Spanish use it in musket balls in the 16th century? I don't know." Given that antimony-lead alloys have been known about since ancient times ["The Elements of Murder: A History of Poison" by John Emsley], it's likely that antimony-lead was used right from the beginning of firearms. --Heron (talk) 14:19, 14 March 2009 (UTC)

Orbits of moons

As far as I know, all the planets orbit the sun in (almost) the same plane. Do the moons orbit their planets in the same plane ? Are there moons whose orbital plane makes a wide angle (say > 45 deg) to the plane in which the planets orbit the sun ? WikiCheng | Talk 06:05, 14 March 2009 (UTC)

All of the planets orbit the Sun in roughly the same plane (now that we don't count Pluto as a planet). And most of the planets have moons (and maybe rings) which orbit in approximately the same plane. However, the "moon planes" are often different from the "planet plane". StuRat (talk) 06:50, 14 March 2009 (UTC)

See Irregular moon. Dauto (talk) 06:57, 14 March 2009 (UTC)

Longer answer:

It depends on how the moon is formed. If it is a body that originally orbited the Sun and which was later by captured by the planet (such an event must involve the influence of a fourth body), then its orbit can be inclined at any angle. According to the articles on these irregular moons and the Kozai mechanism, inclinations above about 55° are unstable in the long term. One moon with an inclination above 45° is Margaret.

Larger moons that are formed with the planet or broken off it by a giant impact will be regular moons, with low orbital inclination (with respect to the planet's equator, not the ecliptic).

--Anonymous, 06:59 UTC, March 14, 2009.

Take a look at Uranus. The whole planet, rings and moons are tilted at about 98° to the plane of Uranus' orbit round the Sun. Astronaut (talk) 11:06, 14 March 2009 (UTC)

Which is why I said "with respect to the planet's equator". See also the item above about whether that description is appropriate. --Anonymous, 20:04 UTC, March 14, 2009.

Solutions

What do you get if you mix a liter and a quarter of 2.2 % alcohol and the same quantity of 4.6 % alcohol? The answer at first glance would seem to be the average of the two, but I'm doubtful of that (seems too easy). Could you guys help me out? Thank you so much in advance. Killiondude (talk) 07:19, 14 March 2009 (UTC)

Think of it this way: if you have one liter of mixture at 2.2%, how many liters of alcohol is there? Ditto for the 4.6% solution. Combine the two, you have two liters of which X+Y liters is alcohol; how many percent is that X+Y of two liters. (Yup, taking the average does work.) 88.112.62.225 (talk) 09:48, 14 March 2009 (UTC)

When you mix, say, 1L of 100% ethanol and 1L of water, you get something less than 2L of the solution. However, as you've only got small alcohol amounts (look like beverage-ballpark concentrations?) the volume should not change very much, so yes, you can just take the average. 77.12.9.104 (talk) 10:40, 14 March 2009 (UTC)

Okay, thanks! Killiondude (talk) 19:16, 14 March 2009 (UTC)

Cataract surgery

Cataract#Cataract_surgery says that operations have been happening since 600BC. It also says that local anaesthetics are used. What would have happened to 600BC patients? And does anyone have any idea how the idea of operating on an eye to cut out milkiness might have come about? -- SGBailey (talk) 08:34, 14 March 2009 (UTC)

Nothing? Well they may have used opium or something but I suspect in many cases nothing was used. I'm not sure but I don't think cataract surgery is the extremely bad when it comes to pain (but I'm not volunteering to try it). You might be interested in surgery and anaesthesia which discusses this (surgery very briefly although it does say "Before the advent of anesthesia, surgery was a traumatically painful procedure and surgeons were encouraged to be as swift as possible to minimize patient suffering") Nil Einne (talk) 13:25, 14 March 2009 (UTC)

Jaundice

Hi all I would just like to make it clear I am not requesting any medical advice from anyone, I am merely rearching the diagnosis and treatment of jaundice. After hours of research, there are a few things which still confuse me, I hope someone can help. First of all, are doctors looking for elevated concentrations of bilirubin in the bloodstream when taking the full blood count? I read somewhere that elevated conjugated bilirubin suggests obstruction of the common bile duct and elevated unconjugated (insoluble?) bilirubin means that there has been excessive destruction of red blood cells. If it is suspected that hepititis is the cause of jaundice I believe doctors use 'viral markers' for heptititis A,B and C to try and ascertain whether or not this is the case. What are viral markers and how is this test conducted? Presumably a blood sample taken to search for the presence of either of the hepititis viruses? When a gallstone obstructs the common bile duct I believe removing the gall bladder is an option - but I thought - upon removing the gall bladder would not the gall stone still be there causing an obstruction? Also does anyone know what causes the dilation of the bile duct when it is obstructed? Sorry to ask so many questions - I am not expecting one person to answer the whole lot if you can answer just one it would help a lot. Many thanks. —Preceding unsigned comment added by 139.222.240.117 (talk) 15:35, 14 March 2009 (UTC)

As you suggest we can't provide medical advice here, but it seems that your questions can be answered fully without providing medical advice. Our Jaundice article does contain a great deal of relevant information and links to more, including answers to many of your questions.

• Not sure what you mean by "full blood count", so I don't know how to answer the first question. The total and direct bilirubin levels are included in many blood chemistry panels, but are not included in the cell-counting tests often referred to as a complete blood count.
• Our article on Hepatitis has information on the various causes, and links to each of those with info on the markers. The markers are generally measured in a blood specimen as you surmise. There are many markers, so recapitulating that content here might not be sensible. If you have specific questions, just ask and I'm sure people here can answer.
• A gallstone in a bile duct can result in increased pressure behind the obstruction, resulting in dilated ducts. There are a variety of ways to remove the stone, addressed here. You're correct that removing the gallbladder would only remove a stone in the gallbladder itself or in the removed portion of the cystic duct.

I hope this helps. --Scray (talk) 16:15, 14 March 2009 (UTC)

(After EC) A complete blood count (CBC) is really only measuring blood cells (red blood cells, white blood cells, platelets) and some other indices that are useful in some circumstances). Measurement of serum bilirubin is a separate test, although it is also performed on blood sample.

Before answering the rest of your questions, here's a quick blurb: Bilirubin is a degradation product of heme compounds, among which the most abundant is probably hemoglobin in the red blood cells. When a red blood cell is lysed, the hemoglobin is converted to (unconjugated) bilirubin and transported to the liver, where it is enzymatically conjugated to become more water soluble. The conjugated bilirubin then makes its way through the bile canaliculi into the gall bladder, where it is stored before being ultimately excreted into the small intestine for disposal in the feces.

Hemolysis will result in a temporary increase in uncongugated bilirubin. The liver is usually functioning normally, however, so any bilirubin that is conjugated there will be disposed of normally through the gall bladder. The consequences of a gall stone blocking the bile duct depends on its location. Since new bile is being continuously produced by the liver, a blockage will create distension of the bile system upstream of that location (like damming a river or an accident on a highway). Depending on the location of the stone, you might just get distension and inflammation of the gall bladder (cholecystitis), or it might block the flow of bile from the liver and therefore cause conjugated bilirubin to "spill" into the bloodstream, since there's nowhere else for it to go. Surgeons can sometimes use endoscopic surgery (ERCP) to pluck a stone out of the bile duct but if the gallbladder is inflamed, a cholecystectomy is performed. Note that because of the anatomy (see bile duct), there is still flow of bile from the liver through the common bile duct even after the gall bladder is removed.

In acute hepatitis there is damage to the liver cells, such that when they burst open they release their contents (including liver enzymes and conjugated bilirubin) into the bloodstream. Chronic hepatitis that leads to cirrhosis might eventually reduce the enzymatic capability of the liver such that unconjugated bilirubin predominates. It depends on the situation. The tests that are usually done to detect viruses (including those that cause hepatitis) are blood tests based on either the patient's antibodies -- which can indicate current or past infection -- or detection of the viral nucleic acid using polymerase chain reaction (PCR) or other such tests. The advantage of the latter molecular tests is that if properly calibrated they can give information about viral load. Does this help? --- Medical geneticist (talk) 16:40, 14 March 2009 (UTC)

1. The "full blood count" does not test for bilirubin. Bilirubin is part of the screen called liver function tests.
2. The article "Jaundice" answers your next questions.
3. Markers of viral hepatitis are blood tests for specific antigens and antibodies.
4. Cholecystectomy removes stones that are already present in the gallbladder. It also prevent new stones from arising. If a stone is blocking the common bile duct, the commonest procedure is ERCP to remove the stone.

Axl ¤ [Talk] 18:05, 14 March 2009 (UTC)

light in context with black holes

It has been observed that the path of light turns in the presence of black holes. But there can not exist any gravitational force as light has no mass. Please explain.--Lightfreak (talk) 16:58, 14 March 2009 (UTC)

See gravitational lens. The mass bends spacetime, while light takes the shortest path through spacetime. There is no "gravitational force" in General Relativity—just warping of spacetime and associated accelerations. --98.217.14.211 (talk) 17:04, 14 March 2009 (UTC)

While 98.217.14.211's explanation is ideed correct, it is good to point out that even within newtonian approximation a light ray trajectory would bend. In newtonian mechanics the path of a particle under a gravitational field is independent of the particle's masss, depending on the particle's initial velocity alone. Dauto (talk) 17:59, 14 March 2009 (UTC)

True, true. Indeed, the question is not whether the light is bent by gravity, but by how much. GR and Newtonian physics predict different values for it and are thus distinguishable experimentally along this line (among a few others). --98.217.14.211 (talk) 18:06, 14 March 2009 (UTC)

Photons (which make up light) most certainly do have mass - but only by virtue of their speed. Their 'rest mass' is zero. Also, the path of light is bent by much more ordinary objects than black holes. In fact, Einsteins theory of relativity predicted this - and the scientists who verified his theory did so by carefully measuring how starlight is bent by the mass of our sun. (They had to wait for a total eclipse to be able to do this - so it took a few years.) As others have said, gravity bends space - so the photon (in a sense) is travelling in a straight line through space that has been bent - hence it APPEARS to be travelling along a curve to outside observers. Anything with mass bends space to some degree or other...it's just that the amount of the bending is so small that it's not really noticable for things like stars(!) unless you have some pretty sophisticated equipment...but around a black hole, it's very noticable. SteveBaker (talk) 21:31, 14 March 2009 (UTC)

thanks!--Lightfreak (talk) 08:11, 15 March 2009 (UTC)

domestic turkeys

How many domestic turkeys are there in the world? We have numbers for most domestic livestock, shhep, pigs, cattle, but not turkeys and I would like to know. 12.216.168.198 (talk) 17:00, 14 March 2009 (UTC)

:Here are the 2000 US production figures. [22] You'd have to go country by country and need a lot of time and a calculator. This site has an overview. [23] Good luck. 76.97.245.5 (talk) 17:56, 14 March 2009 (UTC)

The UN agriculture estimates are available at: [24]. The database includes the ability to search by individual country, by region or by world total. Turkeys are one of the tracked products. They have the figure of 636,000,000 turkeys slaughtered in 2007[25] giving 5,885,012 tonnes of turkey meat. They do not, however, tell howe many animals are alive in total, only how many are harvested. And this entry includes the code A which means "May include official, semi-official or estimated data" Rmhermen (talk) 15:58, 16 March 2009 (UTC)

Why is it that bullets often don't have nice round numbers for their calibers?

The article on firearm cartridges lists many types of cartridges. Many of them seem to have strange values for their calibers. For example, in the case of the .308_Winchester, 0.308 inch is not a nice round number either in metric or in U.S. customary units. Is there a reason for choices like that? —Preceding unsigned comment added by 98.114.146.54 (talk) 19:17, 14 March 2009 (UTC)

I kinda suspect this relates back to when bullets were simple spherical lead balls. They would probably have specified the bullets by weight - so the weight may have been a nice round number - but the resulting caliber would have turned out to be some inconvenient number. But that's a guess - I don't know for sure. Alternatively, our article caliber discusses bullet sizes but about the only thing that sheds any light on this is the confusion between measuring the diameter of the barrel to the outsides of the grooves or the inside. I suppose that a nice round-number 0.3" internal diameter might grow to 0.308 measured to the bottoms of the grooves. I'm sure someone here will know better. SteveBaker (talk) 23:26, 14 March 2009 (UTC)

The article on the Winchester links to its "parent case", the .300 Savage, though that's a bit confusing because both the .300 savage page and the winchester page list the actual bullet diameter as .308. Could one of those be a mistake? 219.102.220.90 (talk) 23:31, 14 March 2009 (UTC)

Right - but the 0.008" (eight THOUSANDTH's of an inch!) difference sounds like just the right amount to account for the 'rifling' - the spiral grooves inside the barrel. The bullet has to 'take the rifling' - meaning that it has to squash into those grooves. Eight thousandths of an inch sounds about right to me. SteveBaker (talk) 01:03, 15 March 2009 (UTC)

OK, but my issue was that although both have the same diameter (and presumably a 0.008" rifling), one is called a .300 and the other a .308. Is it reasonable to think that they may have chosen to brand the Savage with its base diameter, but the Winchester with its diameter + rifling thickness, perhaps to distinguish them or for some other marketing purposes? If so, that would imply that the "not nice" caliber of the Winchester was, at least in part, a marketing choice. 219.102.220.90 (talk) 04:12, 15 March 2009 (UTC)

According to caliber: "In firearms, the caliber is the approximate diameter of the bullet used. In a rifled barrel, the distance is measured between opposing lands or grooves; groove measurements are common in cartridge designations originating in the United States, while land measurements are more common elsewhere."...does that explain it? 8 thousandths of an inch sounds like a believable difference between land and grooves. SteveBaker (talk) 04:50, 15 March 2009 (UTC)

No, the caliber names are not this precise. They are historical names, often, and the physical diameter, rifling or not, is not precise to the "name" of the bullet. What's more, there are some rounds that have roughly equivalent sizes (7.62mm and .30-06, for example), but are not precisely the same size or round. Rifle rounds and their caliber should be understood as rough approximations of their size, but not precise measurements. This makes sense too when you realize that many of the most widespread rounds were invented over a hundred years ago (the 30-06 is the -06 because it was invented in 1906). Shadowjams (talk) 10:47, 15 March 2009 (UTC)

The rifling is important because without it the bullet could 'roll' around some random axis and the magnus effect would deflect the bullet reducing acuracy. Dauto (talk) 01:48, 15 March 2009 (UTC)

Well...yes...but what does that do to explain the dimensions people choose for bullets? SteveBaker (talk) 04:50, 15 March 2009 (UTC)

The answer to this question is not scientific. It's more a consequence of history, marketing, and randomness. A number of rounds were made in imprecise diameters for unknown reasons. But once they were established, it was an issue of relative changes. More critical, the secondary number on many cartridges, after you get past the ".30" or "7 mm", are purely issues of powder, marketing, or historical significance. To make it even more complicated, many calibers are not what they seem to be. A number of bullets have "calibers" that are very different from their actual fractions of an inch measurements. For a little bit of background check out Gregg Lee Carter, Guns in American Society, isbn 1576072681, page 102-03. It's available on Google books. There's a small section that will explain a little bit of the insanity. If you want a historic reason why a particular cartridge is why it is, I don't know it, but if you find it out, please add it to the appropriate article. Shadowjams (talk) 10:42, 15 March 2009 (UTC)

Why do some ducks quack constantly?

Having observed a lot of mallard ducks recently, I've noticed that the males in particular seem to quack almost continuously when just walking or swimming around(especially if they're with females). Is there any reason for this constant noise-making? 69.224.37.48 (talk) 21:07, 14 March 2009 (UTC)

Same reason some young man need noisy motorcicles, I suppose. Dauto (talk) 21:11, 14 March 2009 (UTC)

Er, are you sure it is the male that is quacking? As far as I know it is only the female that quacks. Here is what Steve Madge and Hilary Burn say about Mallards in their reference book Waterfowl (p. 211): "Voice. Quite vocal, especially female. Male utters a soft, rasping 'kreep'. Female's most obvious call is a series of quacks, quite mocking or laughter-like in delivery, descending towards the end, 'QUACK-QUACK-QUACK-quack-quack-quack...', heard mostly in late summer and autumn. Similar descending series of quacks are uttered by several other females of the genus." Possibly the mallards you are observing are hybrid or feral domestic ducks that haven't read the book I quote. This still doesn't answer your question as to why they quack so much, regardless of whether they are male or female.--Eriastrum (talk) 22:50, 14 March 2009 (UTC)

Certainly our article duck says that only the females quack. Bird vocalization says that short 'calls' like quacks are used to keep the flock together and to alert fellow flock members to danger. Perhaps they are only quacking when you are nearby and posing a danger to them. You might not think you are a danger but...mmmm...crispy duck with orange sauce. SteveBaker (talk) 22:51, 14 March 2009 (UTC)

Your answer may be overpopulation. "Duck territories" on ponds and in public parks are much closer together than they ought to be. That has led to lots of unfavorable behavior changes. Things like a bunch of juvenile ducks getting together and gang-raping a female, females getting drowned by a bunch of males trying to mate, juveniles of both sexes getting killed by older ducks; all that has been described as a result. Apparently experts have some special terms for male quacking. (All male ducks in the poll refused to quack when questioned :-) OR: Male Mallards have been observed to issue a variety of calls/quacks for different purposes: food call (cascading downwards), mating call, attack/retreat calls (the Donald Duck like enraged screams), "ranging quack" issued while a pair is together to keep the female close, particularly in uncertain situations. (This is a sort of under his breath grumble and may be what you have heard.) Although it may seem counterproductive to get noisy when a predator is near, lots of birds making noise in different directions actually confuses most predators because they find it harder to decide which one to go chase. Eriastrum's explanation that what we see most often are actually some hybrids might have something to do with it, too. Particularly interbreeding with domestic species, because the above behavior has been observed in public parks on 3 continents. (Does our KurtshapedBox do ducks, too, or just gulls and doves?)76.97.245.5 (talk) 10:26, 15 March 2009 (UTC)

The "ranging quack" sounds about right; the male mallards I've seen usually make this (fairly quiet and nearly constant) sound when with a female. 69.224.37.48 (talk) 16:21, 16 March 2009 (UTC)

CO2 in an aquarium

Hi. Let's say a small aquarium has an abnormally high pH level. Would blowing in one's breath through a straw help to lower the pH? Or would this have too small an effect or would it be more harmful than helpful to the occupants? Thanks. ~AH1^(TCU) 21:37, 14 March 2009 (UTC)

So your theory is that dissolving CO2 from your breath will create enough carbonic acid to make a measurable difference? Well, you're right that there is CO2 in your expelled breath and that when you dissolve CO2 in water it makes carbonic acid...but the question is "how much?". Gut-feel says not enough to make a difference. Only 5% of your exhaled breath is CO2 - and only a tiny amount of that will actually dissolve in the water because it's not under enough pressure and you're probably making quite big bubbles where the interface between water and gas doesn't have enough area to allow much of that CO2 to meet the water before the bubble reaches the surface of the tank. When they carbonate fizzy drinks, they use pure CO2 at a pressure of 100 to 150 psi. SteveBaker (talk) 22:49, 14 March 2009 (UTC)

I agree, especially as it's a "small aquarium" with an "abnormally high pH level". You're better off giving small, regular water changes with more stable pH water.91.111.85.208 (talk) 23:41, 14 March 2009 (UTC)

The effect you may be looking for is dispersing more oxygen in the tank and thus encouraging aerobic rather than anerobic entities to thrive. This would allow ammonia from fish waste to get broken down. The problem is twofold: You'd stir up sediments from the bottom or your aquarium, thus severely decreasing water quality until the population has changed. Your exhaled air contains less oxygen than the ambient air. (Not sure how big an effect that would have). Incremental water change suggested above sounds good. Also ask at your local aquarium supplies store. They usually have several products available to counteract acute ph imbalance. (like e.g. tablets, "green sponge" filter, powder etc.) Which product you need depends on a lot of things including what fish, plants and other creatures you keep, temperature, size of your aquarium. etc. So either call ahead and ask or bring as much data on your aquarium as you can. This page might also be useful. [26] - 76.97.245.5 (talk) 06:19, 15 March 2009 (UTC)

March 15

Melatonin activity and the human eye

hi guys... do you know where i can find info on melatonin and race/ eye colour? i mean, it definitely has something to do cause melatonin depends on light, since for example blue eyes are more sensitive to light i imagine melatonin in the pineal gland is different in diferent races.

also, does the sensitivity of the melatonin receptors in the eye have anything to do with eye colour? like for example, are the melatonin receptors more sensitive in blue eyes than they are in brown eyes?

thank you! hopefully I can find some info.

oh and also haha, does eye colour affect eye sight? like does a really light blue eyed person see things 'differently' than a brown eyed person?

—Preceding unsigned comment added by 75.69.27.198 (talk) 01:10, 15 March 2009 (UTC)

Have you read eye color? That will probably answer most of your questions. --Tango (talk) 01:21, 15 March 2009 (UTC)

Seems like you're confusing melatonin with melanin. Dauto (talk) 01:25, 15 March 2009 (UTC)

Or may be you're not confusing them, but why should eye color play a role in the circadian regulation? Dauto (talk) 01:37, 15 March 2009 (UTC)

I'm not confusing melatonin with melanin...i know they are different but they are both related and affect each other. and why would eye color play a role in circadian regulation? because colour is related to light 'intake' and circadian rythm is also. —Preceding unsigned comment added by 65.183.130.151 (talk) 16:20, 15 March 2009 (UTC)

No, they're not related. One is a pigment, the other is a hormone. Melatonin itself isn't affected by light, melatonin levels in the blood are, through a complex set of mechanisms, which are not related to your eyes. Even blind people have lower melatonin levels in daylight. And eye color doesn't change 'intake' of light one bit. The light you see is passing through your pupil, not the colored portions of your eye. --130.237.179.182 (talk) 20:47, 15 March 2009 (UTC)

Pain in the...eye

So after reading arc eye, snow blindness and flash blindness, as well as perusing through eye disease, I'm still in the dark as to how bright lights cause pain and permanent loss of vision. Why do our eyes hurt when we see very bright lights? The retina allegedly has no pain receptors...is it strain on the iris dilator muscle trying to contract very hard? Or an interpreation by the brain of intense light? And aside from UV damage to the cornea, what is the mechanism by which very intense light (I'm talking nuclear flash or laser in the eye kind of intense) can blind a person, or is that just hollywood dramatization? Thanks. Someguy1221 (talk) 07:14, 15 March 2009 (UTC)

Retina has many light receptors. These receptors never grow in number, but instead, may deplete over time. this is why older people have weak eyesight. Intense light may destroy these light receptors and may cause blindness. the pain in the eye is because of the fact that iris, that controls the amount of light entering the eye, tries to reduce the amount of intense light entering the eye.--Lightfreak (talk) 08:27, 15 March 2009 (UTC)

A nuclear flash - at a distance where it's not going to kill you - won't blind you. Richard Feynman was the only person to watch the world's first nuclear explosion with his naked eyes (well, actually, 'eye' - he closed the one eye just in case he had a slipup in his math). In several of his autobiographies - he explains why he knew that was a safe thing to do. On the other hand, even a relatively small laser (such as a laser-pointer) will damage your eye if you stare at it for more than a half second or so. The iris is intended to shrink to exclude harmful amounts of light - but there is a limit to how small it can get. A laser beam can easily get through that hole. In addition to the pain from the iris muscles contracting - there definitely is a pschological element to it. If you use computer graphics to display all of the artifacts of a bright, blinding light on a computer screen - in a situation when they are 'immersed' in the on-screen action - you can convince people that the light is painfully bright, when in reality even if the entire screen were lit up at maximum brightness, it would not give you a moment's thought. SteveBaker (talk) 13:10, 15 March 2009 (UTC)

Just a reality check on the supposed devastating amount of energy a laser pointer could pout through the iris. A laser pointer says "Class 3a laser product. Max output < 5 mW. Wavelength 630-680 nm." How many mW of solar energy would be reflected through the pupil if you looked at a white surface large enough to fill the visual field illuminated by full sunlight, which would be bright but would not be expected to cause blindness? Pupil (eye) says it can narrow to as small as 3 mm. Solar energy issaid to be about 1 kilowatt per square meter. White paper is said to reflect about 85% of the light hitting it. So how many mW of energy would enter hit the 3mm pupil when you look at a white painted house, or car, or white paper, or snow (albedo 96% per [27]) in full sunlight? Woul'nt it be somewhat more than 5 mW? Edison (talk) 15:13, 15 March 2009 (UTC)

According to the US laser health and safety guidelines: a class 2 red laser will damage your eye with less than a quarter second of exposure. The concern is that this can be less than your blink response. Hence all legal laser pointers (in the US at least) are class 1 or (at most) 1M. Those can still do bad things to your vision - but not if you know to quickly close your eyes and turn your head away because you have more time to react. With a class 3 or above - you have no chance. Pretty much any exposure is enough to blind you...these things are dangerous! SteveBaker (talk) 01:27, 16 March 2009 (UTC)

And thus the question, how do they blind you? Someguy1221 (talk) 05:45, 16 March 2009 (UTC)

I think the key detail is that light scattering off a piece of paper spreads out, a laser doesn't (significantly). I'm not sure how to calculate how much light would getting into the eye from those things, but there is a simple reality check - compare with looking directly at the sun. If solar energy is 1kW/m² then a 3mm diameter disc would receive 7mW. Comparable to shining a Class 3a laser at your eye. However, I was having a discussion over dinner just last week with a physicist and a chemist who each use big lasers (Class 3 and 4) and apparently how dangerous a laser is doesn't just depend on its power. A powerful laser in the visible part of the spectrum will make you blink and look away very quickly, so the danger is minimal (still not a good idea to try, though!). A slightly less powerful IR laser will burn straight through your retina before you realise what is happening. (At least, I think the key detail was wavelength, I don't remember everything they said - the bit about power not being all important is definitely true, though.) --Tango (talk) 15:34, 15 March 2009 (UTC)

Tango - Yow. Both interesting and shudder-inducingly informative; nice response.

Edison - from a couple of different tacks, explaining the same principle of why concentrated low energy may have a lot more effect than diffuse high energy:

"Sharpness" represents the fact that when you concentrate force into a very small area, it has a much greater effect. Look at the tip of a pin, or the edge of a razor blade - they have very tiny surface areas. One pound of force concentrated into a square 0.1 mm wide (100 lb/mm²) may easily cut through something, while 100 pounds of force may have no effect whatsoever if dispersed over a comparatively "huge" square 1 cm wide (1 lb/mm²).

Similarly, consider a space heater that puts out 10,000X amount of energy per second into a cubic 10 m wide room (10 X/m³). It keeps the room warm, but never comes close to burning you, because the energy is diffused into a large volume. But if you touch a spot on the heater for one second, absorbing a tiny 1X fraction of the energy into a "cube" of flesh 1 cm wide (1,000,000 X/m³), you get burned.

Does this make it any clearer, or just more confusing? arimareiji (talk) 20:22, 15 March 2009 (UTC)

Incidentally, the US government did do many studies on how much light and at what distances from a nuclear explosion would be needed to do eye damage. --98.217.14.211 (talk) 15:34, 15 March 2009 (UTC)

Back to basics: explain why solar energy reflected from a snowbank or white painted wall filling the visual field is so much less dangerous than the 5 mW laser pointer. I scent mumbo-jumbo. Edison (talk) 02:20, 16 March 2009 (UTC)

Short answer: Because it is more spread out. (Long answer, see above!) (Although, I'm not actually sure it is more dangerous - snow can cause temporary blindness and I'm not sure a 5mW laser pointer is going to cause much more than that unless you are really stupid with it.) --Tango (talk) 12:12, 16 March 2009 (UTC)

One factor that has been missing from this discussion is how "spread out" (more technically, collimated) the light is. This factor is important because the eye is not just a single large photoreceptor with some area; it has a focussing system - a lens. A perfectly collimated light source shining on a perfect lens would focus the light to a single point, which would burn anything on that point regardless of the irradiance (power per unit area) of the light. Of course no light source or lens is perfect, but laser light is much more collimated than sunlight. The relevant unit here is radiance, sometimes referred to as brightness. The higher radiance of a laser is why even a low power laser is much more dangerous than sunlight. Someone42 (talk) 12:19, 16 March 2009 (UTC)

That's been missing from the discussion? I'm sure I mentioned it about half a dozen times... --Tango (talk) 15:32, 16 March 2009 (UTC)

Death

Here is the first scenario. A healthy person is "locked away" in a room, with no chance for escape or outside assistance/intervention/communication. The room has an infinite supply of air/oxygen pumped in ... and the room has an infinite supply of good drinking water available. Would that person be expected to die? Or can he live like this indefinitely (up until his inevitable and expected "natural death")? If the former, how long would it take to die? And what would be his cause of death? The second scenario is exactly as the first, minus the water. Same questions. In these scenarios, both the person's physical body and mind are completely healthy ... so that he would not die of any (pre-existing) disease, nor commit suicide, etc. Also, the room is perfectly comfortable, so that heat/cold/etc. is not an issue. If it makes any difference, we can also throw in good working plumbing/toilet facilities in the room to remove waste. Thanks. (Joseph A. Spadaro (talk) 18:40, 15 March 2009 (UTC))

He would die of starvation in a few weeks in the former and of thirst in about three days in the ladder. — DanielLC 19:24, 15 March 2009 (UTC)

1. Yes. No. Depends on a wide variety of factors, including how much fat and muscle he has. Starvation.
2. Yes. No. Generally, one to two weeks. Dehydration.

This PDF may shed more light on the subject. arimareiji (talk) 19:38, 15 March 2009 (UTC)

The Scottish used to wall enemies up like this in cupboard sized spaces in their castles, although they may in some cases have left a small hole to allow food and water in. 84.13.169.19 (talk) 22:10, 15 March 2009 (UTC)

In some of the above replies, you have answered that the person dies of starvation / dehydration / etc. I know that that is what happens to the person's body (i.e., he becomes starved and/or dehydrated) ... but is that what he actually dies of? In other words ... does he really die of, for instance, "multiple organ failure" (or some other medical terminology) ... if indeed the starving leads to vital organs failing, that is? Thanks. (Joseph A. Spadaro (talk) 01:06, 16 March 2009 (UTC))

Multiple organ failure is an option, sure. Our article on starvation outlines the various effects of starvation pretty well. It's impossible to say what exactly would kill the person in such a situation, but it could be a heart attack, or it could be the result of an infection, or scurvy, or... there are lots of things, but the point is that if the body runs out of energy, it will eventually break down one way or another. (Also, you mention that they wouldn't commit suicide, but psychological symptoms -- including depression -- are generally associated with starvation, and a person trapped in a room with nothing to eat might well commit suicide.) Likewise, dehydration can be fatal pretty quickly (and can also be associated with starving, which can cause diarrhea). Dehydration tends to result in kidney failure, but other internal organs will also stop working. Regardless of whether the problem is starvation or dehydration, if you take away the body's fuel, it'll start to shut down. The exact order this happens in probably varies, depending on the patient. -- Captain Disdain (talk) 02:07, 16 March 2009 (UTC)

A friend who went through "survival school" said that they teach the rule of "threes:" you can survive three minutes without oxygen, three hours without shelter, three days without water, and three weeks without food. Your scenario suggests death in about three weeks if food is denied while air, shelter and water are provided. Milage may vary. Edison (talk) 02:17, 16 March 2009 (UTC)

Why would three hours without shelter kill anybody except under extreme weather conditions? Dauto (talk) 03:28, 16 March 2009 (UTC)

The sky is falling! Clarityfiend (talk) 03:40, 16 March 2009 (UTC)

I'd like to second Dauto's question, this seems interesting... could you elaborate, Edison? --Ouro (blah blah) 07:33, 16 March 2009 (UTC)

Indeed, how long you can last without shelter depends on the circumstances. It could vary from anywhere between a few minutes (you're in the Arctic and your tent blows away while you aren't wearing your Arctic clothing) to pretty much indefinite (in the tropics, say, as long as you have a decent hat). Shelter was probably included in there because that is the order you are generally taught to deal with your primary needs in. Obvious, if you don't have air, you need to sort that out pretty quickly! After that, you worry first about shelter, then water, then food. Unless you are already seriously dehydrated, that will pretty much always be the best order. Even if you don't need shelter in order to live it has massive psychological benefits. --Tango (talk) 15:30, 16 March 2009 (UTC)

I'd just like to add that one morbidly obese person who was quoted on the BBC lived for over a year on water and vitamins - so this might suggest someone could live longer than three weeks (until the vitamin part took effect, in which case a disease like anemia or scurvy would kill them). One source suggests eight to twelve weeks. - Jarry1250 ^{(t, c)} 20:47, 16 March 2009 (UTC)

Tesla's wireless electricity

According to this article, Tesla tried to create a world-wide, aerially-broadcast energy network. Would this have had health or environmental implications? Would the electricity mess anything up, or would we be safe? 86.8.176.85 (talk) 18:53, 15 March 2009 (UTC)

It would mess _everything_ up. The amount of RF interference would be ridiculous. --130.237.179.182 (talk) 20:44, 15 March 2009 (UTC)

RF interference with what? Modern technology, certainly, but the question asked about health and environmental issues. I'm not aware of any proven RF hazards in that area until it gets so intense as to directly cause heating (like in a microwave oven). --Anonymous, 21:20 UTC, March 15, 2009.

Some people have expressed concern about the health effects of high-voltage pylons near homes. But there seems to be no basis for their apprehension.

For significant distances and significant amounts of power, there is no known method of transferring electrical power without the use of wires.

A transformer will do it by employing a magnetic field. But that involves only an extremely short distance.

I once read a newspaper article about a farmer who had a metal fence that ran alongside an overhead power line. The farmer was picking up and using electrical power from the fence. He was taken to court for it! I don't know how much power he picked up, or what the voltage was, but the distance was small.

However, a crystal radio set does receive a tiny amount of power from a rather distant transmitting station and put it to use (legally!) to actuate headphones. It is amazing that such a small amount of power will do it. The power must be in the microwatts.

In Wikepedia, the article Crystal radio, (in the section "Attempts at recovering RF carrier power") says that claims have been made that power from a radio station carrier wave can be used to amplify the output of a crystal radio. But no details or circuits are given. (A crystal radio itself does not amplify.) The "Construction and operation" discussion which follows is also interesting.

However, the obvious problem with sending significant amounts of power through space is that anyone can pick it up for free (like a radio signal) unless some means can be devised to make it available only to paying customers. – GlowWorm. —Preceding unsigned comment added by 98.17.37.175 (talk) 22:31, 15 March 2009 (UTC)

For anything but very short distances (less than WiFi can transmit), it would be wildly impractical using current technologies. If we can focus and recapture extremely coherent EMR that's minimally absorbed by intervening matter, it may be possible, but if you promiscuously radiate energy in all directions, you lose the overwhelming majority of it. Entropy's a bitch. arimareiji (talk) 23:05, 15 March 2009 (UTC)

In some cases, radiated power that is not expended externally is periodically returned to the source. A coil with AC flowing through it exhibits that property. The collapsing magnetic field returns energy to the source unless a conductor intercepts the field. The conductor would need to be part of a complete circuit for any appreciable amount of power to be taken by it. Obviously, an AC magnetic field cannot be used to transmit power for any great distance - every conductor in its path would absorb some of the energy. At present there is no known method of transferring a significant amount of electrical power broadcast (as Tesla planned) or by a directional beam. – GlowWorm. —Preceding unsigned comment added by 98.17.37.175 (talk) 01:19, 16 March 2009 (UTC)

Tesla claimed that electromagnetic radiation consisted of longitudinal waves of compression and rarefaction, rather than transverse waves as called for by Maxwell. He built a tower which was intended to send energy to great distances, but which was not shown to do so. He made some major contributions to electrical technology, but also made periodic wild claims. Edison (talk) 02:13, 16 March 2009 (UTC)

I agree with GlowWorm; as far as I know, it has never been proven that radiation from those huge electrical pylons right over your head is harmful, but somehow I think a huge amount of wireless energy traveling through someone wouldn't be good for people (it's like the previously mentioned radiation, except ALL of the energy traveling through the pylons being transmitted), especially for those with pacemakers and such. Not to mention the ridiculous amount of interference and possible damage to anything electrical that passed in it's range. -Pete5x5 (talk) 17:57, 16 March 2009 (UTC)

Many normal items can act as a (rather inefficient) antenna. This can include metal clothes hangers, wire fences, even dental work. Normally the amount of energy received is insignificant (although, in rare cases it's enough to hear a radio station on these items). However, if you had a billion times as much energy in the air, you would then get a billion times as much received by all these accidental antennae, causing fires and exploding people's heads from time to time. StuRat (talk) 02:37, 17 March 2009 (UTC)

Roses: meaning of "perpetually" or "repeat" flowering

The gardening book I'm looking at distinguishes between perpetually and repeat flowing roses. What is the difference, and which is better? I have read the Rose article, and the gardening book does not define the difference. 84.13.169.19 (talk) 22:05, 15 March 2009 (UTC)

The perpetual flowering roses will have a small number of flowers all through the growing season, spring, summer and autumn. The repeat will come out in a second burst with a blank period in between. Better is hard to say as each kind will be more attractive at different times. Graeme Bartlett (talk) 02:53, 16 March 2009 (UTC)

Thanks. 89.243.72.130 (talk) 20:49, 16 March 2009 (UTC)

Remember to deadhead the roses after the first bloom. (cut off the dead flowers), so that energy goes into new flowers rather than rose hips.

When is certain pet article content a "How To"

I'm pretty new, so I'm sorry if this is something that would be common sense for more established wikipedians.... I am looking at small animal pet articles such as house rabbit, syrian hamster, fancy mouse, fancy rat and so on... some of these contain information on the care of the species as a pet (caging, feeding, handling, bedding etc). At what point does go from being informative about the article's subject to being How To? If these topics are appropriate, what would be best way to address the somewhat controversial issue of what kind of bedding(s) are safe vs toxic. Currently, the topic is avoided in some articles, and presented one-sided in others. Should each species' article be edited to have the different POV's supported with article references, and then watch every article to make sure that edits are reflected across all of them; or should "pet bedding" be made into an article, and each pet species article then point to that article? (I'm leaning towards this being too much of a How-To that should be deleted, or if it is appropriate to the articles, then I'd rather see "pet bedding" being its own article..., but I don't want to step on any of the many toes of the different small pet article editors!) --6th Happiness (talk) 23:16, 15 March 2009 (UTC)

Your best bet for questions of this nature would be to run them by folks at either the Help Desk (if you're trying to find the relevant policy pages) or the Village Pump (if you're looking for a more free-ranging discussion about what the policy should be or how it ought to be applied). TenOfAllTrades(talk) 23:45, 15 March 2009 (UTC)

Thanks, will do that. --6th Happiness (talk) 23:47, 15 March 2009 (UTC)

Just a couple of suggstions, if you see them before leaving: At least in the hamster article, there are a few sentences that are too close to How-To and a few that are just downright regrettably-shallow advice. That type of info can and should be pulled out of the articles. Specifically wrt bedding, I would think it's completely appropriate to briefly note in specific animals' articles why certain bedding types are bad based on biology - but not to go on at length about how often to change it, or whether your hamster likes paper or hemp bedding, etc. As to whether a longer article on pet bedding would be viable, I would think it can be. But I'm also a lazy bum, so I'll leave the researching and writing to you. ^_^ arimareiji (talk) 23:54, 15 March 2009 (UTC)

Thanks for your input arimareiji (I've reposted to Wikipedia:Help_desk if you want to see if there are any further replies there) —Preceding unsigned comment added by 6th Happiness (talk • contribs) 00:11, 16 March 2009 (UTC)

March 16

Turning a clear LED light bulb into a frosted one

Is there an easy DIY method to convert the clear plastic shell of an LED light bulb into a frosted one (without significantly reducing the light output)? —Preceding unsigned comment added by 173.49.9.243 (talk) 02:41, 16 March 2009 (UTC)

It would depend on the type of plastic used. Dipping the bulb quickly in Acetone and letting it air-dry will likely accomplish your goal, though if you're trying to compensate for the extreme directionality of the light from most LED bulbs, a simple bulb frostover isn't going to get the job done. —Scheinwerfermann ^T·_C03:43, 16 March 2009 (UTC)

(ec)I've used various organic solvents (takes some experimentation with solvent and time depending on the plastic) to get frosted effects on clear plastic parts. Could also try sand-paper or steel wool to get a brushed surface effect. Never tried it on LED lightbulbs. DMacks (talk) 03:46, 16 March 2009 (UTC)

OR try little dabs of superglue. Use pin to apply. 76.97.245.5 (talk) 07:33, 16 March 2009 (UTC)

Most people just sand the plastic envelope slightly. It does lose a little light. There are wideangle leds you can buy if that's what you want. 75.62.6.87 (talk) 10:07, 16 March 2009 (UTC)

Optimum sizes/shapes for ice cubes

What would be the best (including practicalities like glass sizes) sizes and shapes for ice cubes to make them melt faster or slower? I'd have thought that a big ice cube would melt more slowly, but would a sphere or cube or any other shape be best? 86.8.176.85 (talk) 03:15, 16 March 2009 (UTC)

My anecdotal observation has been that a long, cylindrical form works better than any of the more traditional cube variants. In my experiments carried out using different rubber ice moulds from IKEA, I found that the cylindrical ices froze fastest and were quickest and most efficient at cooling down drinks. The fast freezing and drink cool-down are probably due to the large surface area of the cylindrical form, while the perceived efficiency is probably because the ice cylinders cool the whole height of the drink. Cubes, on the other hand, float on top and supercool the upper portion of the drink while leaving the lower portion largely uncooled. —Scheinwerfermann ^T·_C03:41, 16 March 2009 (UTC)

The surface area of the ice determine the rate at which heat gets in--the larger the area, the faster the heat transfer. With a certain rate of heat transfer, ice cubes with less volume obviously melt faster. If you want the ice to melt (and cool the surrounding fluid) as quickly as possible, you'd want a high surface-area-to-volume ratio. A sphere has the lowest ratio, so definitely don't use one.

If this is a practical question, I think the best solution is to grind up the ice cubes, whatever shape they happen to be, and dump the pieces into whatever has to be cooled. If you want to have the ice melt faster, just grind it into smaller pieces. Even minimal crushing will increase the surface-area-to-volume ratio to a value much higher than any single ice cube can realistically have. --Bowlhover (talk) 04:58, 16 March 2009 (UTC)

This assumes that the main goal of the ice cubes is to cool the drink quickly. In some circumstances, you might prefer ice cubes that cool slowly, over a long period, in which case spheres might be more desirable. jeffjon (talk) 14:03, 16 March 2009 (UTC)

About the optimality of the spheric shape: it is true that a ball has the surface of minimal area among all bodies with the same volume (that is, solves the three dimensional isoperimetric problem), but, to be precise, what matters here is that a ball has the minimal thermal capacity among all bodies with the same volume; the two variational problems being not directly connected. pma--79.21.30.83 (talk) 16:44, 16 March 2009 (UTC)

Crushing will certainly generate the best surface-area to volume and for practical purposes will undoubtedly cool your drink faster than any other shape. But it's kinda cheating if you're trying to build a single lump of ice. What you need is some kind of fractal surface - a sierpinski sponge perhaps - pleasing because it's so much like a regular ice cube - but able to dissolve in an arbitarily short amount of time. If course constructing such an object in your refrigerator might be a bit of a challenge! SteveBaker (talk) 00:05, 17 March 2009 (UTC)

Having infinite area, the sierpinski sponge would indeed melt instantaneously. Having zero volume, it would do no cooling at all. :) Dauto (talk) 04:39, 17 March 2009 (UTC)

If your point is to cool your beer cooler fast and keep it cold, You might want to try adding some salt to the ice. That will reduce the melting point of the ice several degrees making the ice melt fast. Make sure you wash the beer bottles before opening them. Dauto (talk) 04:45, 17 March 2009 (UTC)

Animal olympics

If there were an animal Olympics, which species would win which events? What would win 100m, weightlifting, any of the events where an animal could sort of compete. 86.8.176.85 (talk) 05:47, 16 March 2009 (UTC)

Are you looking for absolute numbers or would you figure in relative body sizes. Have a look, we probably have a couple of lists somewhere. (Sorry but I got to turn in so can't/ won't be more help. Speed record's a start.76.97.245.5 (talk) 07:32, 16 March 2009 (UTC)

I think what you really want to know is which of the animals is the strongest, fastest, etc... right? Or maybe you just dig crazy animal Olympics. Hell, why not! But honestly, that's a problematic theme, because it's kind of hard to figure out how to measure or even compare these animals. In a lot of cases, this would involve guesswork: for example, gorillas are really, really strong, but it's hard to make them do bench presses, so the scientific data on how strong they precisely are tends to be sketchy. In fact, the definition of strength can also be iffy: an elephant can haul amazing loads, but I'd bet that a blue whale is still stronger. So how do you measure that? And then again, surely proportion has to count for something: all of these animals are pretty much lightweights compared to ants, which can lift many times their own body weight... To switch tracks a little, speedwise, a cheetah can pretty much beat anything on land on a 100m sprint -- they can sprint at up to 120 km/h. And yet a peregrine falcon will leave it in the dust; they've been clocked at 250 km/h when diving. We'd definitely need some ground rules here -- in addition to ridiculously cooperative animals... -- Captain Disdain (talk) 10:41, 16 March 2009 (UTC)

I think the animal Olympics would need to borrow a page from the Paralympic Games and institute a classification system, where the various animal athletes would be grouped for competition according to their physical function. So we could have the 100m for biped, quadruped, avian, aquatic (mammal), aquatic (non-mammal), invertebrate, etc. - Eron^Talk 14:31, 16 March 2009 (UTC)

Solar cooker

why is glass plane/cover used in a solar cooker? —Preceding unsigned comment added by Pratimap (talk • contribs) 07:39, 16 March 2009 (UTC)

The glass cover allows sunlight to enter the device unimpeded, but upon entering, some of the sunlight's energy is converted into heat within the cooker. The cover then traps the heat by blocking the escape of hot air. This is the "heat trapping" type of solar cooker, and other types exist as well. Read more at Solar cooker. Someguy1221 (talk) 08:32, 16 March 2009 (UTC)

Glass is also pretty opaque to infrared, so it stops heat escaping as radiation, as well. (This is how the greenhouse effect works in the case of actual greenhouses.) --Tango (talk) 15:22, 16 March 2009 (UTC)

Glass is transparent to IR, or else thermographic cameras won't work. Greenhouses trap heat by preventing warmed air from mixing with the surrounding atmosphere or rising to high altitudes, as explained by Greenhouse effect#Real greenhouses. --Bowlhover (talk) 21:06, 16 March 2009 (UTC)

You really can't lump the entire IR spectrum together like that. Glass has transmission/absorption peaks and valleys throughout the IR range, which is why, simultaneously, 1) IR cameras can use glass lenses, and 2) glass bending and laminating operations can use IR to heat the glass efficiently. jeffjon (talk) 13:12, 17 March 2009 (UTC)

Watch one of those police programs on TV where they have thermal imaging - the windows of houses look like solid white squares, you can't see inside the houses through them. That's because IR is pretty much opaque at the relevant wavelengths. I'm not sure how the glass lenses in such cameras work - perhaps it's a different type of glass? --Tango (talk) 14:29, 17 March 2009 (UTC)

Killer cancer

I'm not seeing this in our articles. What are the most common proximal causes of death associated with cancer? Metastatic growths in the brain or heart would obviously be good candidates, but probably not the only major ones. What do tumors typically do to people that cause the body to cease functioning? Obviously with a group of diseases as diverse as cancer there are probably many possible ways it can kill you, but I just looking for the common ones. Dragons flight (talk) 08:18, 16 March 2009 (UTC)

It varies significantly between types of cancer. I found a number of reviews of the precise question on PubMed: [28] [29] [30] [31] [32]. I recall from some or another doctor that infection is in general the single most common cause of death amongst cancer patients. Someguy1221 (talk) 08:48, 16 March 2009 (UTC)

Measurement of breast size by water displacement

Hi I was wondering if anyone had any idea where I could find some information regarding this please:
Basically sometime around 1985-1990, James Owen Drife led a study where they measured women's breast size through submersion in water, (and presumably its displacement), which caused a far bit of newspaper controversary, at least in the UK.
Does anyone know where this was published? Or even in which newspapers it was reported? Or just some more information on it??
Many thanks Duke Of Wessex (talk) 08:45, 16 March 2009 (UTC)

He wrote an article on what you describe in 1975 (available free here) in the British Medical Journal. Drife has published 20 articles on various issues relating to breasts, but I'm not sure any of the ones contain what you described based on their titles. But they are available for free from pubmed, except for one which I have read but is a review and not a research paper. Someguy1221 (talk) 09:02, 16 March 2009 (UTC)

Thanks for those links, (and in super-fast time!), I think the 1975 one is what I'm after, but have you (or anyone) any idea if it was mentioned in the newspapers at the time? Or more recently? Thanks! Duke Of Wessex (talk) 16:11, 16 March 2009 (UTC)

The obvious problem with this method is that breasts are generally attached to someone, so you can't determine the displacement of the breasts alone. Deciding where the breasts end and the rest of the person begins is not an easy or precise task. StuRat (talk) 02:22, 17 March 2009 (UTC)

Why doesn't clingfilm / plastic wrap cling to Parmesan?

In my fridge, once opened, all the cheese are covered in clingfilm. For the vast majority of the cheese the film does what it's supposed to and clings tightly to the cheese, wrapping it up. With parmesan, however, it doesn't - it's almost as though it loses its static, and instead of clinging to it, simply covers it loosely. Why? It's not a case of the same piece of film being opened and closed multiple times, as it will happen with a fresh piece of film - after a certain period of time, when I go back to the fridge to get it out, it's given up the ghost and gone all loose... pushthebutton | go on... | push it! 09:55, 16 March 2009 (UTC)

Parmesan cheese (Parmigiano-Reggiano to purists) has a slightly oily surface; you can feel the difference when you pick up a wedge of the stuff. The film just slides off. (The fats in most other cheeses tend to stay quite solid at refrigerator temperature, so there's less sliding.) TenOfAllTrades(talk) 13:56, 16 March 2009 (UTC)

I put a section in Plastic wrap on how it works. To elaborate a bit on Ten of all Trade's "oily" explanation: the wrap will bond lightly with the fat molecules on the cheesy surface, but those molecules are not tightly bonded to the cheese. In butter or American cheese there is enough of a smooth surface that is tightly bonded to the rest of the block so the wrap will stick. 76.97.245.5 (talk) 14:15, 16 March 2009 (UTC)

Transmission line simple problem

Hi, I'm trying to solve Problem 1 at [33], but I'm not sure, any help will be appreciated. What I do is apply Ohm's law at t=0, so that the voltage wave is -1 volts towards de open circuit. That way I'll get a series of -1 and 0 voltage levels at the short circuit and 1,0,1,0 at the open circuit. Is this correct? Thanks! --62.57.238.224 (talk) 10:49, 16 March 2009 (UTC)

error in lorentz transformation

I think there is a contradiction between the formula of the lorentz transformation and the length contraction in special relativity. In the formula $\mathbf {x={\frac {x'+vt'}{\sqrt[{}]{1-{\frac {v^{2}}{c^{2}}}}}}}$, suppose a coordinate system K' is moving with a relative velocity to K equal to v. Then if we solve the formula for t' = 0, x' = 0 and a v less than c, we will surely get a value greater than 1. So what will happen is that a rod measuring 1m in K' will appear to be longer as seen from K. But this is in contradiction with the length contradiction formula, $L'={\frac {L}{\gamma (v)}}=L\,{\sqrt {1-v^{2}/c^{2}}}$ which states that the length will decrease. Please explain. (if this is really a discovery, please guide me to get a patent for it because i don't know the procedure as i am only 14).--harish (talk) 11:57, 16 March 2009 (UTC)

If you put t’=0 and x’=0 in the formula for the Lorentz transformation, according to me the result would be x=0. This just means that the origin of both systems K and K' (i.e. the points x and x’) are coincident at the moment t=0 (i.e. before the system K' has moved relative to K at all). This is just a trivial result, really... Or are you doing something else? MuDavid 12:17, 16 March 2009 (UTC)

A similar question was asked last month (but with the co-ordinate systems swapped). See Wikipedia:Reference_desk/Archives/Science/2009_February_28#contradiction_between_lorentz_transformation_and_length_contraction. The core of these sorts of problems are that, even though the Lorentz transform is symmetric, observers in different reference frames will disagree on lengths and times. Remember that you have to account for relative lengths as well as times and that length measurements are presumably made at simultaneous times, where Relativity_of_simultaneity needs to be accounted for. Someone42 (talk) 12:37, 16 March 2009 (UTC)

The question was asked by the same person, which means he reamains unconvinced. Dauto (talk) 13:10, 16 March 2009 (UTC)

Simple explanation is that if you measure the distance between two space-time events that are simultaneous in K' (i.e. have the same value of t') then you are measuring length from the point of view of K'. And from the point if view of the K' frame of reference, L' is indeed greater than L. But if you want to measure length in the K frame of reference then you need to measure the distance between two space-time events that are simultaneous in K (i.e. have the same value of t), in which case in turns out the L is greater than L'. As a general principle, the difference between the space co-ordinates of two points in space-time that are separated by a space-like interval is maximised in the frame of reference in which they are simultaneous. Gandalf61 (talk) 14:21, 16 March 2009 (UTC)

Gandalf, from the expression for the invariant 'distance' $(dS)^{2}=(dl)^{2}-(dt)^{2}=(dl')^{2}-(dt')^{2}\,$ (where $dl\,$ and $dl'\,$ are the space coordinate distances between the two events and $dt\,$ and $dt'\,$ are the time differences between the two events) we see that if the primeless frame is the one where the two events are simultaneous $(dt=0)\,$, then $(dl')^{2}=(dl)^{2}+(dt')^{2}>(dl)^{2}\,$, which makes $dl\,$ minimal (not maximal as you stated). —Preceding unsigned comment added by Dauto (talk • contribs) 19:27, 16 March 2009 (UTC)

Yes, indeed. And, now I think again, my final point was not relevant to the original question anyway. Gandalf61 (talk) 13:17, 17 March 2009 (UTC)

Yes, I agree - for the second time around, our OP is incorrect. ...And as for a patent...it varies under the laws of different countries - but in most places, you can't patent an equation - even if it's correct. SteveBaker (talk) 23:36, 16 March 2009 (UTC)

I've always thought patents were for commercially useful inventions, and that scientific and mathematical discoveries go in academic journals. --Bowlhover (talk) 14:40, 17 March 2009 (UTC)

Perchloric acid

What is the oxidation state of Cl in Perchloric acid?--Abhishek Jacob (talk) 12:47, 16 March 2009 (UTC)

+7, i.e. chlorine(VII).

Ben (talk) 13:01, 16 March 2009 (UTC)

Just in case this was a homework question, please keep in mind that the guidelines suggest that we should try to avoid answering homework questions (though we're happy to give a helpful nudge in the right direction if the OP shows that an effort has already been made. --Scray (talk) 23:09, 16 March 2009 (UTC)

nutrition

at what temperature a body starts to feel in coldness and a temperature out side his body is 22???thank you —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 14:26, 16 March 2009 (UTC)

Moving the following from the mathematics desk, posted by the same user under an identical header. —JAO • T • C 14:29, 16 March 2009 (UTC)

how can i organize my food per a day? how many calories i'm suposed to include in my daily meals?? what are the most important kinds os food i may eat in order to make a 'diet'? i'm 12 years old and am 72kg that is so bad:S

please help me by answering i need it!! —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 14:22, 16 March 2009 (UTC)

Specific advice should be provided by a medical professional. We have an article on the US Dietary Reference Intake, but that's provided for adults aged 40-50. As our dieting article notes, dieting in youth can be extremely hazardous. Consult a professional to develop a plan that is safe and healthy. — Lomn 14:49, 16 March 2009 (UTC)

If your school has a School nurse she can help answer your questions. She's there for students' health and should have relevant information available. 76.97.245.5 (talk) 15:07, 16 March 2009 (UTC)

why?who?when?what? (questions)

why do a person cry? why do a person cough? why do a person laugh? why do a person shout? how do a person feels when he sneeze ?why? who can help by answering these questions?ineed them am doing a project just any umm inf.about it i hope findung please help !! without details!!bye —Preceding unsigned comment added by Nisreen mansour (talk • contribs) 10:35, 16 March 2009

Onion or Emotion, Cough,Laughter, Vociferation, Sneeze. There's a search window in your side bar. Type in your word and click on "Search". 76.97.245.5 (talk) 15:01, 16 March 2009 (UTC)

Supermassive black hole collisions...again.

Hi. OK, so I remember asking a question about the merger between Andromeda, the Milky Way, and Triangulum a while back, and whether their black holes might collide. They might miss, but now it looks like collisions between supermassive black holes as a result of galaxy mergers might not be so rare after all: [34][35][36]. If two black holes collide in this manner, could the ensuing explosion have effects on Earth? Remember that explosions such as this may travel at close to the speed of light, so the explosion itself would not take much longer to reach us after the light from the explosion has reached us. Could a similar scenario occur between Milky Way, Andromeda, Triangulum, and possibly a few other galaxies? Thanks. ~AH1^(TCU) 15:54, 16 March 2009 (UTC)

As far as I know, the details of black hole mergers is still an open question. However, I don't know of any reason for a massive explosion. There would be lots of gravity waves gravitational waves oops! emitted, but they would have to be really powerful to cause any harm to Earth from such a big distance - I would be surprised if they were that powerful. --Tango (talk) 16:10, 16 March 2009 (UTC)

Well, you'd get a big mess from the black holes becoming active feeders, and their accretion discs interacting would likely result in a big mess. As I recall, Death from the Skies discusses this in one chapter. I believe the odds tend to favor minimal effect on the solar system (there's a good chance it gets ejected from the galaxy entirely) unless it happens to be along the polar axes of the SMBHs, which is fairly unlikely. — Lomn 16:17, 16 March 2009 (UTC)

See gravitational wave (not gravity wave!), which says "even waves from extreme systems like merging binary black holes die out to very small amplitude by the time they reach the Earth". Presumably if we were in the line of fire for any resulting relativistic jet it would be a lot more noticeable. --Sean 17:01, 16 March 2009 (UTC)

Oops! Fixed. --Tango (talk) 17:06, 16 March 2009 (UTC)

VERNIER CALLIPER

HOW TO MEASURE WITH DIAL VERNIER —Preceding unsigned comment added by VIVEK MENON89 (talk • contribs) 16:33, 16 March 2009 (UTC)

See Caliper scroll down to dial caliper. Be sure your dial is set to zero before you start and don't forget to add the readings from the slide. 76.97.245.5 (talk) 17:25, 16 March 2009 (UTC)

With proper care, such a measurement is very near accurate. Edison (talk) 14:17, 17 March 2009 (UTC)

German toilet

Why do German toilets have a little shelf?--80.58.205.37 (talk) 17:47, 16 March 2009 (UTC)

Far greater minds than mine have pondered (and probably solved) this question, but I think it is simply an excuse for German women to insist that men sit down to pee, because (with the shelf) they argue that pee splashes out of the toilet creating a mess worse than death. Why they need to emasculate men so badly they have redesigned the toilet, I do not know. 77.12.50.107 (talk) 19:15, 16 March 2009 (UTC)

Apparently it's designed to facilitate examination of one's feces. --Sean 21:52, 16 March 2009 (UTC)

For those like me who had no idea what this was talking about but are curious, here's a helpful link. Maybe I'm just being culturally insensitive, but ew. arimareiji (talk) 22:11, 16 March 2009 (UTC)

The last Vespasienne in Paris

I have observed similar - but much smaller - shelves in French toilets. Fortunately, us boys are able to negotiate these smaller devices from our lofty peeing posture...and of course there is always the pissoir or vespasienne (WHAT! We have no articles on these magnificent monuments to male urination?)... But sadly, I have yet to visit any country (the US included) who have reached the pinnacle of success of The Great British Loo. US toilets come close - but the failure to master the simple concept of the siphon dooms them to dribble and leak and need all manner of careful tweaks and adjustments. The worst I've encountered is certainly on some of the Greek islands where the diameter of their sewer pipes are mathematically guaranteed to block for any human of normal 'caliber'. They insist that you deposit used toilet paper in a small basket provided for this very purpose (cue ungodly smells and health hazards). One 'safari lodge' in Kenya was particularly lacking. "Where is the toilet?"..."Everywhere" (accompanied by a sweeping gesture across the entire landscape outside the hut). Sigh. SteveBaker (talk) 23:22, 16 March 2009 (UTC)

The original reason had more to do with flushing. 2 Systems used to be common in Germany: a thing called "Druckspüler" which basically produced a high pressure jet of water. The second is a cistern mounted near the ceiling. (About 2 yds. above the commode.) Both created a significant amount of water pressure when flushing. Reportedly an American style flushing toilet then could create a whirlpool effect that let the "item to be flushed" stay in the bowl. Most Germans answering to online questions stated that they preferred the German system (called Flachspüler), because with the flush toilet water from the bowl may spray up onto one's butt (following the equal but opposite reaction principle). (If you can read German google the topic. Lots of toilet humor.:-) 76.97.245.5 (talk) 23:31, 16 March 2009 (UTC)

To get splashed on the butt while flushing, you'd need to flush while seated. I always stand up before flushing; doesn't everyone else ? StuRat (talk) 01:44, 17 March 2009 (UTC)

Nope, they're talking about water splashing back up when solid feces drop into the bowl. Not while flushing. People did say it was easier to get a stool sample with a "Flachspüler" but that was not cited as the major advantage. It seems merely a side benefit. There seem to be quite a number of well established urban myths circulating. 76.97.245.5 (talk) 14:16, 17 March 2009 (UTC)

Of course Wikipedia also writes about German toilets. See Flush toilet#Cultural variations. PrimeHunter (talk) 04:11, 17 March 2009 (UTC)

bladder removal

Does bladder removal surgery effect male verility and what other side effects 66.53.123.127 (talk) 18:29, 16 March 2009 (UTC)

Bladder removal? Is that even possible? The bladder is a vital organ. Do you mean gall bladder? --Tango (talk) 18:39, 16 March 2009 (UTC)

cystectomy 77.12.50.107 (talk) 20:24, 16 March 2009 (UTC)

The bladder isn't a vital organ, perhaps you're thinking of the kidneys, which filter waste from the blood and produce urine. The bladder only stores urine. As long as a path exists from the kidneys to the outside of the body, the waste can still be eliminated. Of course, without either an internal or external bag of some sort, urine will just drip out continuously, which is a major quality of life issue, though not fatal (unless it leads to death by suicide or some other cause). StuRat (talk) 01:16, 17 March 2009 (UTC)

Bladder removal surgery (cystectomy) has a number of complications, including a small number of men who require an inflatable penis prosthesis. Axl ¤ [Talk] 10:18, 17 March 2009 (UTC)

"Examples of complications include cardiovascular (myocardial infarction, bradycardia, atrial flutter, congestive heart failure), diversion-related (urinary leak, afferent/efferent limb malfunction or stenosis, stomal stenosis, urinary fistula, ureteroenteric anastomotic stricture), gastrointestinal (small bowel obstruction, gastrointestinal bleed, enteric fistula, hepatic failure, diarrhea), infectious disease (sepsis, pneumonia, pyelonephritis, abscess, urinary tract infection, clostridium colitis), lymphatic (lymphedema, lymphocele), neurologic (cerebrovascular accident, seizure, nerve palsy, psychosis), pulmonary (respiratory failure, pneumothorax, asthma exacerbation), renal (calculous disease, hyperchloremic metabolic acidosis, renal failure), vascular/thrombosis (deep venous thrombosis, pulmonary embolus, mesenteric thrombosis), wound/incision/hernia (superficial wound infection, incisional hernia, fascial dehiscence, parastomal hernia) or other (gout, drain migration, hydrocele)."

— Clark et al.

Axl ¤ [Talk] 10:32, 17 March 2009 (UTC)

Lice

Do lice have parasites that live on them? Thanks for info. --AlexSuricata (talk) 21:06, 16 March 2009 (UTC)

I'm not sure about on them (ectoparasites), but a few Rickettsia and Anaplasma species exist as parasites in lice (intracellular parasites). If lice have not yet been shown to carry Wolbachia (endosymbionts), they probably will. --Scray (talk) 22:49, 16 March 2009 (UTC)

Yeah - and if you're ever inclined not to panic over a few lice - check out the impressive list of human diseases that are attributed to Rickettsia's. Our article lists: typhus, rickettsialpox, Boutonneuse fever, African Tick Bite Fever, Rocky Mountain spotted fever, Australian Tick Typhus, Flinders Island Spotted Fever and Queensland Tick Typhus!! Sadly the ticks don't seem to mind them at all. Yikes! SteveBaker (talk) 23:05, 16 March 2009 (UTC)

C'mon now Steve, be fair. I've voted for a few lice, and some companies give 'em big bonuses. --Scray (talk) 23:12, 16 March 2009 (UTC)

Don't you mean you've voted for ticks ? "Politics" = poly + ticks, meaning many blood-sucking parasites. StuRat (talk) 01:02, 17 March 2009 (UTC)

No - you have the wrong derivation of the term. Politician is a mispronounciation of the french polyteteian - specifically a person with two or more faces. Traditionally, most politicians are, to this day, two-faced. SteveBaker (talk) 01:38, 17 March 2009 (UTC)

Hmm... perhaps it's the invertebrate parasites that we're treating unfairly. --Scray (talk) 02:13, 17 March 2009 (UTC)

Glad you provided the link, because otherwise I wouldn't have known which set of spineless bloodsuckers you meant. arimareiji (talk) 04:28, 17 March 2009 (UTC)

That was vicious. Nice one! --Scray (talk) 04:35, 17 March 2009 (UTC)

Some little parasites suffer from smaller parasites: "Great fleas have lesser fleas upon their backs to bite'em, and little fleas have lesser fleas, and so ad infinitum." Edison (talk) 14:15, 17 March 2009 (UTC)

Euclid's Elements

At the end of the opening of the article Euclid's_Elements it states "Not until the 20th century, by which time its content was universally taught through school books, did it cease to be considered something all educated people had read." Who/what/why/where/when did this happen? I find it interesting and perplexing to note the swift roundhouse kick delivered by Euclid_and_his_Modern_Rivals to its competitors in the late 19th century, and also Einstein's first words in his book on special relativity: "In your schooldays most of you who read this book made acquaintance with the noble building of Euclid's geometry, ..." If the Elements was so deeply entrenched in most education systems, what or who was the driving force behind getting rid of it? —Preceding unsigned comment added by 99.255.228.5 (talk) 21:46, 16 March 2009 (UTC)

We haven't gotten rid of it - we teach the same principles - just without the archaic language and old-fashioned terminology. I was certainly taught geometry from the axioms and theorems of Euclid...just not from that exact book. As a work, it's really remarkable in being probably the first book to approach mathematics methodically. Define some "obvious" axioms - then use the axioms to prove some simple stuff - then build proof on proof until you have things coming out of the system that are truly NOT obvious. It's what mathematics is all about. It's almost incidental that it teaches us the basics of geometry - although that's why most people would have been taught it. Furthermore, huge, interesting and (above all) useful areas of mathematics have been opened up by methodically pursuing what happens if you deny one or more of Euclid's axioms and follow where that leads you. Non-Euclidean geometry has come about (ironically) because of Euclid - where the Euclidean stuff was pretty much already known - but just not proven so rigorously. SteveBaker (talk) 22:59, 16 March 2009 (UTC)

I had a reasonably good math education in high school in Ontario, Canada, in the late 1960s / early 1970s, and we certainly did not learn Euclid's axioms. I never learned them in school, although I did read the Elements for fun later. We learned how to do formal proofs in geometry in high school, I think in grade 10, but they were not founded on an explicit set of axioms. On the other hand, in grade 13 we did some group theory on abstract operations, and that involved what amounted to reasoning from axioms. --Anonymous, 03:45 UTC, March 17, 2009.

Painful bumps in Inner Lip

About four days ago, I started feeling a tiny bump on my bottom inner lip and in a matter of hours, it got bigger and painful (about the size of a bell pepper seed). It was flesh-coloured and had a little red dot. I went to bed that night and by the next day, it had disappeared. Today, I'm feeling the little tiny bump again and I'm afraid it's going to happen all over again. I'm freaked out because I don't know what it is. Has anyone experieced anything like this or have any information that might help? Many thanks. AC —Preceding unsigned comment added by 189.216.26.199 (talk) 22:44, 16 March 2009 (UTC)

I'm sorry but we are not allowed to answer this sort of medical question here on the reference desk. If you are concerned - you should consult a doctor. Sorry. SteveBaker (talk) 22:49, 16 March 2009 (UTC)

To expand on that, anonymous advice from random people on the internet is worse than useless when it comes to your health. Go see a doctor, tell them what you told us, show them, etc. 79.74.9.81 (talk) 22:54, 16 March 2009 (UTC)

Sorry, I didn't know that. Thanks to both. AC —Preceding unsigned comment added by 189.216.26.199 (talk) 22:57, 16 March 2009 (UTC)

This question's medical advice request status is being discussed here: Wikipedia_talk:Reference_desk#Possible_medical_advice_question:_.22Painful_bumps_in_Inner_Lip.22. StuRat (talk) 15:08, 17 March 2009 (UTC)

March 17

Trachelospermum jasminoides

what would happen if u consumed the leaves,flower...ect. of this plant? would the effects of ibogain be felt? or is the plant poisones? —Preceding unsigned comment added by 76.14.124.175 (talk) 00:48, 17 March 2009 (UTC)

According to this reference, "the whole plant is poisonous." - Eron^Talk 00:59, 17 March 2009 (UTC)

piperazine

beacause Piperidine and piperazine are very similar, do they have the same effects on the brain? —Preceding unsigned comment added by 76.14.124.175 (talk) 01:00, 17 March 2009 (UTC)

I'm not aware of human therapeutic uses of piperidine or piperazine. Both of those articles do list derivatives, among them antipsychotics. --Scray (talk) 02:10, 17 March 2009 (UTC)

(post e.c.) Neither article mentions psychotropic functions for either Piperidine or Piperazine, although some of their derivatives are psychoactive as Scray mentioned above. I'm not sure about the metabolites. Although they have similar functional groups and are fairly close in shape and size, that does not always translate to similar behavior biologically. Docking (molecular) describes the basic idea: small differences in shape can have major effects on the ability of a compound to bind to an enzyme's active site (or other relevant portion). Sifaka ^talk 02:33, 17 March 2009 (UTC)

Both piperidine and piperazine block nicotinic cholinergic receptors. Piperidine is more potent than piperazine. [By the way, piperazine is used to treat parasitic infections in people.] Axl ¤ [Talk] 10:47, 17 March 2009 (UTC)

Theory of Chemical Emotions: Pointless to Pursue Happiness?

Since most of our emotions are chemical reactions in the brain, and while the events of our lives do trigger the release of those chemicals, they do not increase or decrease production (apparent from exercise, stress, eating habits, and drugs). So two genetically identical twins with similar exercise, stress, and eating habits should experience the same total amount of happiness, right? Regardless of what is happening to them? (assuming they can keep themselves from getting stressed out about the events). One of the twins might have events that trigger lots of happiness in short bursts while the other has a more constant rate of happiness, but they should both experience the same total amount.

If this is true, doesn't this completely undermine the point of perusing things that make us happy if we will inevitably experience the same amount of happiness regardless? Thus we should foremost pursue good eating habits, exercise habits and controlling our stress levels and not worry about anything else (especially since worrying lowers our Serotonin production)? Also if this were true it would redefine what services we need to provide to 3rd world countries as charity as they will find their own happiness in their poverty as long as they can be well fed and control their stress levels, correct?

Something seems really wrong about this theory but I'm not sure where the hole is. It does readily explain why people who have everything find sadness in small details (like being spoiled) and people who have nothing still find happiness in the small details, though to say that we each have an amount of happiness specifically determined by genetics, stress, eating, and drugs seems a little much. What am I missing? Thanks. Anythingapplied (talk) 01:53, 17 March 2009 (UTC)

I don't see how any of this changes the way we should treat the less fortunate (including what we call the third world). Actually the whole thing about people having "nothing" being just as happy as others is bunk. In case you've never tried it being poor is really stressful. Wealth makes people happier until they reach some place around middle to upper middle class, additional wealth after that point doesn't do anything for happiness. Since what it means to be middle class changes over time I imagine this response ties to our evolved sense of justice which is tied into the chemical system you mentioned. Anyways I'm not going to offer a well wrapped answer but I will say that Walt Disney said something to the effect that "for every smile there must be a tear" and XKCD make a good point about arboreal rodents.--OMCV (talk) 02:17, 17 March 2009 (UTC)

I'm not at all familiar with this particular topic but I have a feeling that part of the problem may lie in your premise: happiness is not the same as the level of neurotransmitters. The interactions in the brain that translate out to one's state of mind are not necessarily correlated with the simple total amount of particular neurotransmitters. I'm not a neuroscientist but my guess is that there is a good spread of natural variation in global neurotransmitter levels and that two people with rather different neurotransmitter level profiles can report similar moods while people with similar profiles can report very different moods. If it was clearcut, scientists would be reporting conclusive findings to that effect long ago (and wikipedia would have the info in the relevant articles). I think it's fair to say that scientists pretty much don't know how biochemical interactions in the brain scale up to things like mood although there are some decent theories as to what factors are relevant. Sifaka ^talk 03:19, 17 March 2009 (UTC)

While I'm far from an expert on this, I'm pretty sure your premise "do trigger the release of those chemicals, they do not increase or decrease production (apparent from exercise, stress, eating habits, and drugs)" is incorrect. When neurotransmitters are released they are eventually replaced. It's not like you can use up all of your neurotransmitters in the long term and never have them again (in the short term obviously the level may get low). In any case there is also the fact there is bound to be some natural turnover (it's all very well having the neurotransmitters but there's clearly a big difference between when they affect you and when they don't) and I'm pretty sure some studies have shown you can get an increase in the baseline level with things like exercise etc. Also I don't think it makes much sense to say "One of the twins might have events that trigger lots of happiness in short bursts while the other has a more constant rate of happiness, but they should both experience the same total amount" for starters how the heck do you quantitise hapiness like that and secondly why can't one of the twins have events that trigger lot of happiness while also having a high constant rate? Nil Einne (talk) 11:18, 17 March 2009 (UTC)

There is some research that indicates a persons "happiness" measured by a variety psychological tests is rather resistant to most environmental influences. People who are happy are happy despite what happens to them and people who are sad are sad despite what happens to them. This is also true for self-confidence and a number of other moods/personality traits. This means regardless of what people do they won't be substantially happier. So the levels of neurotransmitters might fluctuate but they keep a steady average, a baseline. Grounding this phenomenon to biological/chemical basis is only reasonable. I wouldn't know how to cite any of this.--OMCV (talk) 11:44, 17 March 2009 (UTC)

Anyway what's the point of pursuing happiness? You might as well drug yourself up as do something so pointless with your life is my feeling. Though I guess I'm fairly happy anyway so it's no great deal to me. Dmcq (talk) 12:24, 17 March 2009 (UTC)

Flashbangs

How do flashbangs work? How can they make a person temporarily blind and make the ears go numb?