Wikipedia:Reference desk/Archives/Science/2006 December 18

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[edit] December 18

[edit] trismus &faciculations of upperlimb during menstrual cycle

married women aged 29yrs with h/o subserosal fibroid (4.5*2.3cms ) (primary infertility )h/o trismus& fasiculation during menstrual cycleon &off episodes -2yrs .Are these symptoms related to menstrual cycle 0r there might be systemic cuase —The preceding unsigned comment was added by 202.54.91.201 (talk) 03:56, 18 December 2006 (UTC).

Not enough info, and probably too individual a case to give a general answer. Obviously, see a doctor for a better answer. alteripse 04:02, 18 December 2006 (UTC)

[edit] Sexual abstinence

What are the biological effects of prolonged male sexual abstinence?141.161.34.125 05:43, 18 December 2006 (UTC)

You'll probably find the information you're looking for at Go Ask Alice!, which can be found here. --HappyCamper 13:14, 18 December 2006 (UTC)
I believe that a British study last year concluded that there are no negative effects in your average male -- for about five days. After that... you do the math. :) Vranak 16:42, 18 December 2006 (UTC)
See also Blue balls.  --LambiamTalk 16:57, 18 December 2006 (UTC)
If I not mistaken, 'blue balls' traditionally refers to the condition where a male has been excited by his partner, but not to the point of *******. Not simple abstinence. Vranak 17:41, 18 December 2006 (UTC)
Maybe the user is looking for specific information, along the lines of this: Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables. Perhaps there are effects on blood serum of various hormones as well? Effects of that? Any specific, scientific information? This is a science reference desk, correct?141.161.98.108 21:43, 18 December 2006 (UTC)

See also this: Prostate Specific Antigen Levels: Effect of Sexual Activity. "Determine whether six lifestyle factors (dietary fat, smoking, sleep, alcohol consumption, physical, and sexual activities) associated with non-prostate cancer-related, elevated prostate specific antigen (PSA) levels" "Men who were more sexually active at time T1 were at higher risk of a falsely elevated PSA level >4.0 ng/ml at time T2."141.161.98.108 21:50, 18 December 2006 (UTC)

Does abstinence in this case include masturbation, or sexual intercourse only? I can't imagine how they would be different in health benefits. (Excluding those old ideas like blindness) Crisco 1492 07:53, 21 December 2006 (UTC)

[edit] Human Adaptations

I had a weird train of thought, and then thought of this -- I tired looking for answers but I couldn't find anything:

When the species Homo Sapien evolves, what new key characteristics will it possess (micro or macro evolutionary changes)? —The preceding unsigned comment was added by 68.15.52.92 (talk) 06:51, 18 December 2006 (UTC).

I saw an article on this in the newspaper a few weeks ago, I think it was adapted from a reputable source like Nature. But the reality is any prediction for how something may evolve in the future is simply guesswork, whether it be humans or anything else. Organisms will adapt to their environment but we can't predict what the environment will be like, or what adaptations may be favoured, especially as other organisms are also evolving. The best guesses tend to continue on the main trends in human evolution over the last few million years - e.g., further increased brain size, continued hair loss, etc. But as I said above, no one can really say. That's one of the interesting things about historical processes like evolution - they're perfectly explicable after they happen assuming you have enough details, but can't be predicted beforehand. Of course, there's also the possibility that we will be able to use our technology to control our own evolution, such as through genetic engineering, nanotechnology implants, etc. Try a Google search on something like predictions human evolution, you'll find stuff like this--jjron 07:21, 18 December 2006 (UTC)
Arent we,like all other animals, evolving slowly all the time?--Light current 13:36, 18 December 2006 (UTC)

Resistance to disease would be one major adaptation. For example, those who live in Africa and are resistant to AIDS, either based on their behavioral drives or immune system, have a substantial evolutionary advantage over those who aren't. In the developed world the evolutionary pressure is less, because fewer people die, and are thus unable to pass on their genes, due to AIDS. StuRat 13:59, 18 December 2006 (UTC)

The evolutionary pressure is certainly not "less" in the developed world, just different. There would be no pressure only if every person had exactly the same chance of reproduction. Please can we stamp this notion out? alteripse 20:17, 18 December 2006 (UTC)

My post was on resistance to disease. Since disease has less of an effect on reproductive success in the developed world, there is less evolutionary pressure to increase resistance to disease there. However, there is likely more evolutionary pressure in other areas of human biology, yes. StuRat 02:29, 19 December 2006 (UTC)
Which means simply that the factors favoring or impeding reproduction in the developed world are different than those in the underdeveloped world, not that they are less-- that is the misconception suggested by your assertion and re-asserted explicitly by the uneducated author of the next comment. alteripse 15:27, 19 December 2006 (UTC)
Saying the factors are different is essentially the same thing as saying that some factors (like disease resistance) are more important in certain regions (like Africa) than they are in other regions (and, symmetrically, other factors are more important in the reverse regions). We aren't disagreeing here, just using different terminology for the same thing. StuRat 15:46, 19 December 2006 (UTC)
(Edit conflict) Nonsense. In the first world, modern medicine and civilisation has dramatically increased the chance of a human being surviving from conception to reproductive age. It hasn't removed selection pressure entirely (that's basically impossible) but it has decreased the evolutionary drive by a huge amount. Maelin (Talk | Contribs) 02:34, 19 December 2006 (UTC)
You are simply and utterly wrong on this. Modern humans have not transcended reproductive selection, just altered the major factors. Your message suggests you lack a basic understanding of natural selection. Educate yourself. alteripse 15:27, 19 December 2006 (UTC)
I would suggest precisely such a lack of understanding on your part, except that I try not to be so rude in debates. Selection pressure is strongest when it is hard for an organism to survive from conception to reproduction. In such a situation, every biological advantage is precious and every disadvantage is severe. For humans in the first world, it's now quite easy to survive to adulthood - which is obvious from the recent (last few hundred years) increase in human populations. Where once a child born blind would almost certainly not survive to adulthood, now they are marrying happily and having children of their own. Where once susceptability to disease would have likely killed a person during childhood, now modern medicine saves their life - and on they go. We aren't altering the major factors, we're eliminating them. Some new ones may arise as a result of our new lifestyles, but there is no reason to believe they will be as strong as the ones we are steadily working to remove. Maelin (Talk | Contribs) 02:12, 20 December 2006 (UTC)
You really don't understand reproductive selection, do you? Any heritable characteristic that is not universally present in all human beings and is associated (just asssociated, not even causally) with more less reproductive success than average for the population is subject to natural selection. This can be skin color, by a dozen putative direct and indirect mechanisms, it can be susceptibility to environmental chemicals that affect the estrogen receptors, it can be metabolic efficiency and tendency to gain fat or defend fat in food-abundant or food-sparse environments, it can be a differential social habit like breastfeeding or age of first childbearing that is associated with a host of heritable ethnic factors, it can be ability to detoxify environmental chemicals, or the fashion of underwear (affecting sperm count) if the underwear choice has a statistical association with any genetic/ethnic factors, or it can be personality tendencies like libido, shyness, or risk-taking, or cultural practices that delay childbearing like valuing education and women's rights, or genetic susceptibility to addictive substances in the environment that might impair bearing and protecting an infant. You have absolutely no evidence whether or which of these factors might be as important as the genes associated with susceptibility to cholera, or rotavirus, or measles, or malaria, or tuberculosis, or AIDS. You have far too narrow an understanding of possible selection pressures. And yes, ignorance that stubbornly defends itself against evidence and education does strain my civility. alteripse 02:37, 20 December 2006 (UTC)
Please do not post in this thread again until you can do so in an adult fashion. I have not attempted to belittle your intelligence and I'd appreciate the same courtesy. Debate can not continue in the face of outright aggression. Now, I find your assertion that things like choice of underwear and support for the women's rights movement pose as much of a selection pressure as things like susceptability to tuberculosis to be difficult to swallow at best. Sure, there are still selection pressures operating on humanity. I never disputed that. My claim is that existing pressures are insignificant in comparison with those of the past. Obviously there are still external factors that affect whether a child will grow up and procreate. However, I dispute that those selection pressures that exist today have as strong an effect as those that existed before we began to alter our environment to suit ourselves. Maelin (Talk | Contribs) 02:53, 20 December 2006 (UTC)
There are several factors that determine if a person or other animal passes on it's genes. Surviving to reproductive age is one, yes, but there is also the number of offspring produced and the portion of them which survive to reproductive age. While the first and third factors are now less significant in the developed world, due to the high percentage of survivors, this makes the second factor, number of children produced, an even more important measure of reproductive success. StuRat 15:53, 19 December 2006 (UTC)
Remember that survival means nothing to evolution if one does not reproduce. So while medicine has reduced mortality and increased potential fecundity remember natural selection is only relevent if an indvidual reproduces. Beckboyanch 06:52, 21 December 2006 (UTC)
Humans in the future will smell better. —Pengo talk · contribs 08:02, 28 December 2006 (UTC)

[edit] A drop of water in space

I wonder what would happen to a drop of room temperature water when suddenly released into space (or into a vacuum chamber with a temperature of nearly absolute zero). Would it just freeze to a small block of ice, or it wouldn't have time to freeze and it would boil (or possibly explode) first because of the extremely low pressure? Is it the same thing that happens to water when released from the captivity of pressure and the plasma in a particle accelerator when it is no longer contained by the electromagnetic field? --V. Szabolcs 09:03, 18 December 2006 (UTC)

It would slowly evaporate. A vacuum has no temperature; only matter can have a temperature. In space there is nothing to conduct heat away from the water.--Shantavira 09:26, 18 December 2006 (UTC)
It might freeze (cold) and then sublime (low pressure) - I doubt it would explode - a large piece wood be so cooled by any evaporation that the process would stop until it is warmed by some external source, this is the case with comets which are mostly ice..83.100.250.252 09:38, 18 December 2006 (UTC)
As for the plasma/ice comparison - it's similar - but I don't know enough to say more.83.100.250.252 09:38, 18 December 2006 (UTC)
Let me first talk about something I know. If you put water in a vacuum system, at room temperature, and pump the air away, parts of it will boil while other parts freeze. (If the water contains much dissolved air, the boiling will be violent.) Presumably it is evaporative cooling that causes some parts of the water to get cold enough to freeze. After a short time while, you have only ice left, and then, if you wait for many hours, the ice will sublimate away. Now for your actual question. If the water drop was in zero gravity and not in a container, the boiling would probably break it into pieces. (If the water had a lot of dissolved air, this would be many tiny pieces.) After a short time you would have a few ice shards. Eventually these would sublimate away. Cardamon 09:51, 18 December 2006 (UTC)
Shanti is correct in that there is nothing to conduct heat one way or another. However the mechanism at work must be that of radiation. Every body above absolute zero will radiate electromagnetic energy (heat) into space. The maount radiated will depend onthe emissivity and temperatureof the body according to [1] I think. Also every body that is not completely refelective or transmissive at all wavelengths must, by definition, absorb energy. Now we have the dileema: does it freeze or does it boil?
The temperaure of such an object can be calculated by using an energy balance equation such that the radiated enegry is equal to the absorbed energy. In this case the temperature must be stable. In the case of a blob of water, it is highly unlikely to recieve more radiation than it emits (unless near a star) and therfore would probably end uo as ice (like some comets).However, to be sure one would have to do the energy balance calculations 8-)--Light current 12:58, 18 December 2006 (UTC)
OTOH See [[2]] and an interesting question is: what would happen if you threw a small lump of ice into space? Would it sublimate?--Light current 13:23, 18 December 2006 (UTC)
During the Mercury program, and the Gemini program when the astronaut dumped urine from a container out into space, or when water vapor was vented, it froze into little crystals of ice, which reflected sunlight in a sparkling pattern. They referred to it as the "Constellation Urion." [3] Granted, ammonia isn't water, but an ammonia leak on the International space station left an astronaut covered with an inch thick layer or ammonia crystals. He was instructed to brush off what he could, then just stay outside an extra orbit, sightseeing, while more of the crystals sublimated. So I would go with the answer that is would quickly freeze into crystals, then sublimate in a matter of hours. Edison 15:56, 18 December 2006 (UTC)
OK well we cant deny the facts, but what would you say actually cuases the sublimation. Is it just the low (zero) pressure?--Light current 16:01, 18 December 2006 (UTC)
Yes the low pressure (and the vast emptiness of space) - if a water molecule evaporates it's very unlikely to find it's way back - space after all is pretty much the opposite of a closed system.83.100.250.252 17:40, 18 December 2006 (UTC)
Hmm the phase diagram [[4]] for water shows that at low pressure and temp, water could be either solid or gaesous. —The preceding unsigned comment was added by Light current (talk • contribs) 16:17, 18 December 2006 (UTC).

Thanks for the explanations. As I understand now, maybe it boils for a very very short period of time, after which its fill freeze quickly and after that, sublimate. --V. Szabolcs 20:38, 19 December 2006 (UTC)

Or maybe not 8-)--Light current 04:50, 27 December 2006 (UTC)

[edit] Formation of a comet

The above question reminded me of another question: How do comets form (or reform) ? That is, they have been described as "dirty snowballs", so the ice should sublimate at a low rate all the time, and at a high rate as they near the Sun (shown by the trail). So, how do they replace this lost mass ? Is it just by ramming water molecules found in space ? They don't appear to be large enough to have a very substantial gravitational field which would be sufficient to pull in water molecules at the speeds they move through space. And, if they don't replace this mass, I would expect comets to have lost all their mass by now, if they are as old as the solar system. StuRat 13:54, 18 December 2006 (UTC)

Why should the ice sumblimate without heat? I dont believe its does. I believe that comets do get some of their ice sublimated as they approach the sun. THis results in the famous comet tails which always point away from the sun due to the solar radiation/particles etc. Since most of the time the comets are a long way from the sun, their icy shells do not sublimate most of the time. Also the amount of ice necessary to give those tails is probably minimal. So Halleys comet should have its tail for a few more million years hopefully. 8-)--Light current 14:00, 18 December 2006 (UTC)
Comets are short-lived (cosmologically speaking). They lose 0.1-1 percent (some sources say even more) of their mass each time they enter the central solar system. They may gain some insignificant amounts of mass back when they are far away from the Sun (at perihelion any collisions with external particles are more likely to reduce mass than increase it.) Eventually what's left is an asteroid, or simply nothing if the comet had no rocky nucleus to begin with. Better hurry if you want to see Halley's Comet; some estimate it is going to lose its volatiles in just another 5600 years. The good news is that the Oort cloud has a good supply of fresh comets; as old comets evaporate, new ones are hurtled towards the inner solar system when they randomly destabilize each others' orbits. Weregerbil 14:19, 18 December 2006 (UTC)
They do not replace their mass if they are in a orbit close to the sun. They slowly desintegrate and after some cycles (depending on course mass and composition) they break apart and are absorbed by the planets of the solar system as meteors, you see in the night, or like the ones which hit Jupiter. I never heard of a comet with a rock as nucleus so thea desintegrate to near nothing. The question how comets form is unsolved. The ice and carbondioxide and the organic materials need low temperatures to form solide bodies, this indicates low temperatures. The minerals detected by stardust and deep impact indicate temperatures above 1000°C at their formation. This gives a slight difference and a monstrous headache for some comet scientists. Rosetta (spacecraft) will give all answers you want in 2014!--Stone 14:49, 18 December 2006 (UTC)
There is speculation that at least some comets have enough mass to end up as asteroids: [5]]. But much of this is indeed conjecture. Btw, the 5600 year remaining lifetime for Halley's comet I quoted above is something I found on one web site; can't say how they came up with that figure. Another site says it loses 0.1% each pass, giving it of the order of ten times that long. Who knows. Weregerbil 15:12, 18 December 2006 (UTC)
Yeah thanks Weregerbil. Thats why i 'vaugified' my previous answer.--Light current 15:15, 18 December 2006 (UTC)

[edit] Decaffinated coffee beans

Can someone explain how coffee beans are made 'decaffinated'?

At what point, and how is the caffine removed from the beans?

thanks

81.129.212.135 12:07, 18 December 2006 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see Decaffeination. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. --Shantavira 12:58, 18 December 2006 (UTC)

Then what do we do with the unwanted caffeine? To make billion tons of Red Bull? -- Toytoy 13:50, 18 December 2006 (UTC)

Put still this is not enough. They make artefical one, because the demand is high for coke and pepsi!--Stone 14:52, 18 December 2006 (UTC)

Very good question!

The word 'decaffinated' is a massive fraud.

Beans are not decaffinated: they are caffeine-free by default. Only by roasting beans do you develop caffeine. Vranak 16:39, 18 December 2006 (UTC)

That's contradicted by Caffeine, Decaffeination, Coffee processing, and Coffee. DMacks 17:21, 18 December 2006 (UTC)
Yes, I can't find anything that supports it either. Vranak, what chemical do you think is present in raw coffee beans that is turned into caffeine by roasting? —Keenan Pepper 17:24, 18 December 2006 (UTC)
It is easy to extract caffeine from green coffee beans! Water is good enough! So there is caffeine already in green beans!--Stone 17:34, 18 December 2006 (UTC)
I believe I read this off a placard in Starbucks. However, if this is contradicted across numerous articles in Wikipedia, what I said earlier should be regarded as suspect and wrong until I can check back. Cheers Vranak 17:37, 18 December 2006 (UTC)

Caffeine, like many other plant alkaloids, is the weapon created by plants against insects and other plant eaters. Humans have big livers, therefore, we can break down many plant alkaloids. We even enjoying taking some of them. Anyway, caffeine exists in live plants. Roasting only makes coffee beans taste better. End of story. -- Toytoy 22:30, 18 December 2006 (UTC)

[edit] Drying out silica gel

Can I revive a sachet of silica gel beads (dehydrate them again) in the microwave? --Username132 (talk) 16:03, 18 December 2006 (UTC)

Of course once the gel is dry, the water will be gone and it wont heat so efficiently, will it? What happens if it overheats? --Username132 (talk) 16:24, 18 December 2006 (UTC)
If it gets very hot - it could sinter (possibly) or fuse (ie melt together - unlikely) - this would reduce the ability of the gel to absorb the water next time.83.100.250.252 17:42, 18 December 2006 (UTC)

[edit] Walking

what is the right amount of walking i should do weekly? —The preceding unsigned comment was added by 82.167.47.141 (talk) 16:14, 18 December 2006 (UTC).

It will depend upon:
  • Your current physical condition
  • Your end goal (for example, weight control, desire to become a long-distance race walker, etc.)
Perhaps you want to tell us more? And, of course, only your doctor can tell you whether a given amount of walking will be good for you, personally.
Atlant 16:30, 18 December 2006 (UTC)

Couldn't agree more -- it's totally dependant on how you feel. Weather plays a huge factor here. I find that even if I'm full of energy and the temperature outside is nice, if there's a lot of glare through the clouds, I don't like being outside much.

That said, I walk many kilometers each day (usually), and I consider it to be the second most vital factor in my continuing well being. The first of course is a healthy diet.Vranak 16:37, 18 December 2006 (UTC)

Well assuming you are in good health (the recommendation is to always check with your doctor before embarking upon a fitness routine), IIRC the documentary Supersize Me said 4-5 kilometres a day of walking (including just getting from A to B) was the threshold between healthy and not so much. I don't know if that info is any use to you. Anchoress 16:41, 18 December 2006 (UTC)

Walking alone isn't enough to keep you fit and healthy. You need to do some sort of exercise that will get your heart rate up 3 times a week to lower your risk of heart disease and otherwise stay healthy. Walking is probably better than nothing though, especially if you live in a hilly area. You need to check with your doctor if you plan NOT to do exercise ever in your life. —Pengo talk · contribs 20:54, 18 December 2006 (UTC)

Pengo, that information isn't consistent with my recent reading; do you have refs for your assertion? I know that used to be the belief, but I've seen a lot of recent data that suggests close to VO2 max exercise isn't necessary for heart health. Anchoress 21:01, 18 December 2006 (UTC)
Walking 'not enough to get fit' (bbc news). My claims likely misrepresenting this study, but it doesn't look like it's out of date as yet. It compares a 10,000-step exercise programme (as mentioned by Chairboy+Rmhermen below) with a more traditional fitness regime of moderate intensity. —Pengo talk · contribs 01:40, 19 December 2006 (UTC)
Yeah, but the walking participants in that study were working 'at their own pace', and (contrary to the description), the article doesn't say that walking cannot provide the health benefits of a moderate exercise program, but specifically the 10,000 steps program of light exercise apparently does not. It's possible for a lot of people to walk quickly enough to, as the article describes, be winded but able to speak a couple of sentences at the end of the workout. Anchoress 07:20, 19 December 2006 (UTC)
Mmm, I would say that broadly speaking, walking 10-30 kilometers per week will be quite enough to keep you in shape. That said, I do favor more vigorous exercise, say, once a week. I find jogging to be terrible for your joints over the long term. Sports like hockey and soccer that demand lots of moving, turning, flexibility, and overall robustness will really get you in good shape, as long as you don't over-do it. Vranak 21:59, 18 December 2006 (UTC)

A common figure used to describe a healthy amount of walking is 10,000 steps a day. The distance this would cover would be dependent on your stride, of course. - CHAIRBOY (☎) 21:33, 18 December 2006 (UTC)

Link to 10,000 Steps Program Rmhermen 22:39, 18 December 2006 (UTC)

[edit] books

How do I go about obtaining printed books from Wikipedia

I don't think that Wikipedia sells books.--Azer Red Si? 16:36, 18 December 2006 (UTC)
If you read German, there's de:Wikipedia:Publikationen, but I don't know of similar projects for any other languages yet. —Keenan Pepper 17:14, 18 December 2006 (UTC)

[edit] Video games a cure for ADD?

I heard somewhere a while ago that video games actually help to relieve the symptoms of ADD/ADHD by stimulating the areas of the brain that are underdeveloped because of ADD, and that people with ADD have a higher tendency to become addicted to them because their brains unknowingly crave that stimulation that they provide. Is this credible or no?--Azer Red Si? 16:36, 18 December 2006 (UTC)

Without having any field-specific knowlege, I'd say it is quite doubtfull. General sonsensus is that videogames may increase the occurance of ADD/ADHD becuase they reward a short attention span. If you can find the source that you heard this from, it may be easier to evaluate credibility. 216.254.24.10 19:10, 18 December 2006 (UTC)
But maybe the argument will work on your parents... alteripse 01:40, 19 December 2006 (UTC)

[edit] Quantum Mechanics

Hello,

I recently started studying Quantum Mechanics and find the mathematical beauty of this theory quite exceptional. But I haven't really had the opportunity of working with real example, and am still baffled by many animations I find on the net (e.g. http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/104_18a.html or http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/107_12c.html). I would have liked a little link or explanation on how it would be possible to obtain these results (for example, being able to find the curve in the second example as a function of time and position to be able to reproduce a similar graph). And generally, what is the method to obtain such visualizations (e.g. http://winter.group.shef.ac.uk/orbitron/, which obviously depends on isosurfaces, but how would one obtain the equations corresponding to the wave functions ?) ?

In general, I would like to know how one obtains such visualisations (are numerical methods important ? etc...).

Thanks --Xedi 17:22, 18 December 2006 (UTC)

Yes, the topic is very beautiful...it's sort of tricky to answer your question, so let's see if this is good enough to keep you interested. There are a small number of quantum mechanical systems which can be solved exactly, so for those, generally, the plots are based on analytic solutions. The hydrogen-like atom is an example. For more complicated systems, you'll need to resort to more advanced methods such as density functional theory. Numerical methods are at the heart of advanced approaches (and also where all the neat research is taking place today), so in a sense, it's good to know. However, to understand the general concepts, typically, small systems which can be solved with pencil and paper give plenty insight into quantum mechanics. --HappyCamper 20:05, 18 December 2006 (UTC)
Thanks for the hydrogen-like atom link, it's very helpful ! But then, what about the rest ? I mean, for the tunnel effect, for example, where does that visualisation comes from (I mean, mathematically) ? --Xedi 20:18, 18 December 2006 (UTC)
There's some stuff at Quantum tunnelling...but isn't so clearly written. Finite potential barrier (QM) has better information. Essentially, what you do is solve the Schrodinger equation for a system with a step potential, and the one of the solutions that comes out of the calculations is this "tunneling". It depends on the energy of the step and the incident particle. There's a nice drawing at the bottom of the article too. --HappyCamper 21:45, 18 December 2006 (UTC)
Personally I think the best bet is to go through it historically - start with the failings of classical mechanics at the turn of the 20th century (the UV catastrophe and such) and work forward from there. If you can get a cheap second-hand copy, there's a chapter of Atkins' Physical Chemistry which has an excellent introduction. As it's an undergrad chemistry text there's a decent balance between the maths and the actual qualitative effects. Sockatume 05:12, 20 December 2006 (UTC)

[edit] Weight Fluctuations

I watch my weight on a daily basis, and note that it fluctuates by as much 2Kg on successive days, eg. 94Kg, 92Kg, 93Kg, 94Kg. Measurements taken at the same time each day on a fully functional scale, with a pretty much regular exercise, eating , drinking, toilet habit. The question then is how can one account for these wide weight fluctuations over such a short period ? Does atmospheric pressure perhaps vary sufficiently from one day to the next to create the effect of "more atmosphere pressing down on my shoulders ?" --Dr snoobab 17:52, 18 December 2006 (UTC)

Water retention. Anchoress 18:00, 18 December 2006 (UTC)
I have had similarly-anomalous weight fluctuations, that I cannot account for merely by thinking about water retention or defecatory diminishment. I am inclined to say that atmospheric conditions can indeed affect weight measurements, in the order of a kilogram or two.
However, I will not say this. I will instead ask: on what surface are your placing your weigh scale? Carpet will not do! Vranak 19:18, 18 December 2006 (UTC)
How on earth can atmospheric conditions affect body mass? Actually, fluid retention is a much more likely explanation. If Mick Jagger, who's 145lbs of solid bone and muscle, can lose 5 pounds during a concert, you or I can gain or lose a pound or two of water weight in a day, due to excess carbohydrate consumption, excess salt consumption, or the reverse. Anchoress 20:49, 18 December 2006 (UTC)
How about temperature effects? I'm sure the reading on the scale depends on ambient temperature, although it might take very large temperature swings to make that much of a difference. -anonymous6494 20:57, 18 December 2006 (UTC)
Well, atmospheric conditions will affect your skin, flesh, and pores, of course. Mick may lose a few pounds of fluid during a concert via evaporation and perspiration. So I guess we're saying the same thing: fluid retention or fluid loss will account for the difference. I'm merely adding that atmospheric conditions will affect how much fluid you retain, or lose. Vranak 21:55, 18 December 2006 (UTC)
Type and quantity of food you eat, water retention (or excretion), bowel movements, swaeting, loss of moisture overnight all have a part to play.--Light current 23:59, 18 December 2006 (UTC)

What type of scale is it ? A balance scale ? StuRat 02:15, 19 December 2006 (UTC)

Normal Bathroom Scale in good condition on a solid flat tiled floor. Thanks for the answers so far !--Dr snoobab 03:54, 19 December 2006 (UTC)
When you say 'normal' scale, I assume you mean the ones with a dial and needle setup rather than say the digital ones. These are a bit notorious for minor fluctuations in measurements, especially the cheaper ones. When using these you must also be wary of parallax errors. These are very easy to make and are independent of the device (i.e., they're an error of the user). Can I suggest you do a little experiment. Weigh yourself say ten times over a ten minute period where the other factors suggested above will have no effect, and see if you get identical results. Try a similar experiment over a longer period, say five times over an hour (without eating, drinking, going to the toilet, or moving the scales) but go away and do something else between measurements and again compare results. See if you get any variations, and if so, whether the variations show a trend. --jjron 14:38, 19 December 2006 (UTC)

I had a "normal" bathroom scale which would tend to stick when the air was moist, like right after a shower. Thus, it would either read high or low, depending on where it decided to stick. StuRat 16:44, 20 December 2006 (UTC)

[edit] How does panting reduce heat?

I've been wondering this from some time. According to your article, "Animals with a body covered by fur have limited ability to sweat, and rely heavily on panting to increase evaporation of water across the moist surface of the tongue and mouth". Apparently it has something to do with evaporation of water, which I'm guessing is a release of heat. But this makes no sense; how does increased evaporation in the mouth help cool off the entire body? Much help appreciated ! Xhin 20:41, 18 December 2006 (UTC)

Just like any other cooling mechanism (sweating, elephant ears, etc). The cooled blood flows through the body, distributing the cooling properties. Anchoress 20:51, 18 December 2006 (UTC)
Also, evaporation and radiation have an effect. Evaporation has a cooling effect from any membrane that's wet, and radiation comes into play: By breathing, you're effectively increasing the available surface area for heat to be transfered to. Before breathing/panting, you only have your skin. When you breathe, you pull cool air into your lungs, it is heated by the radiated heat of your internal surfaces, and when you breathe out, the air carries heat with it. Panting would increase the airflow that this cooling method uses, much like blowing a fan over something carries heat away faster, assuming it is suspended in a medium that is cooler than the object. It's all about entropy in the end. - CHAIRBOY (☎) 21:31, 18 December 2006 (UTC)
Panting gets outside air into the body, and inside air out of the body, so to speak. As internal body temperatures are hotter than outside temperatures (unless you live on Venus), panting is an expediant way of swapping hotness for coolness. Vranak 21:52, 18 December 2006 (UTC)

Thanks for your help! As a follow-up question, how does it help when the external temperature is hotter than the internal temperature? (say, a hundred and five or so degrees.) Again, much help appreciated ! Xhin 22:13, 18 December 2006 (UTC)

It is not just a matter of heat being "carried away". Evaporation does actually absorb heat from the environment, thereby cooling it. That is also how the refrigeration of most fridges works, by the evaporation of the refrigerant, thereby achieving temperatures way below the external temperature.  --LambiamTalk 22:26, 18 December 2006 (UTC)
Evaporative cooling has the potential to lower the temp of a damp object relative to the surrounding temps. StuRat 23:55, 18 December 2006 (UTC)
I reckon than an overheated dog will cool down faster if he's panting in a freezer than panting in a sauna. In fact, I'm quite certain of that.
That said, your body has to put some effort into 'warming up' frigid air, so keeping comfortable when overheated is not a trivial linear equation by any stretch of the imagination. Vranak 00:01, 19 December 2006 (UTC)

Think of evaporative cooling this way: the temperature of water is the average amount of energy its molecules have. If you evaporate some of the water, the hottest molecules escape, because only the hottest molecules can escape. What are left are cooler molecules, so the temperature goes down.

If you pant in 40-degree weather, evaporative cooling will cool down the blood in your tongue, which will cool down the rest of your body. However, the hot air itself will warm up the blood in your lungs, which will warm up the rest of your body. So I think panting in 40-degree weather will actually make you hotter. --Bowlhover 01:42, 19 December 2006 (UTC)

I disagree. It would be a zero-sum gain, meaning the air is warmed up no more than the tongue is cooled down. However, the heat in the air will mostly not go back into the dog's body. Instead, mostly 40 degree air would be drawn into the dog's lungs, cooling it further. (Note that I was assuming 40 F, which is just over freezing temp, you probably meant 40 C, which is just over body temp. Still, evaporative cooling might work up until something like 50 C.) StuRat 02:01, 19 December 2006 (UTC)
Yes, I was talking about 40 degrees Celsius (that's the world standard, isn't it?). Of course evaporative cooling still works at that temperature, but even if it cools the tongue as much as the air itself heats the lungs, the lungs have more blood and will therefore have a greater effect on body temperature. --Bowlhover 03:12, 19 December 2006 (UTC)
Did anyone find a reference in Wikipedia for panting? I do not find a description of the physiology of panting. --Seejyb 12:06, 19 December 2006 (UTC)
The energy lost from panting when external tempature is hotter than internal tempature do to the energy lost due to phase changes. Q=ml where q is in joules m is mass and l is the latent heat of vaporization. for water that number is 2.26x10^6 j/kg so for every kilogram of water vaporized one loses 2.26x10^6 joules even if the external temp is hotter than the internal. compare this to the energy lost by the change in temp. the equation is heat supplied or removed in changing the heat of a substance is Q=mcΔT where q is the the heat supplied or lost (in joules) m is mass c is the specific heat of the substance and ΔT is the change in temp (in C) waters specfic heat is 4186 j/kgC. so for a ten degree C change in temp for 1 kg of water is 41860 J about 2% of the erngy lost due to phase change. (feel free to check my math i did it all in my head) Beckboyanch 07:17, 21 December 2006 (UTC)

[edit] Gargle salty liquid

Why does gargling with really salty water help sooth a sore throat? I've been doing this whenever I have a sore throat for years and it works like a charm! Dismas|(talk) 21:31, 18 December 2006 (UTC)

According to Gargling, " Gargling with a solution of table salt is known to provide relief for a sore throat because as a natural dehydrator, salt draws water from the inflammations in the throat by osmosis, killing the bacteria which cause the sore throat." Friday (talk) 21:33, 18 December 2006 (UTC)
Generally speaking, swimming, washing, frollicking in, bathing wounds in, and even gargling with unpolluted sea water is wonderful for just about any ailment -- except thirst. Vranak 21:44, 18 December 2006 (UTC)
I don't think the question has been answered. Killing bacteria should not cause INSTANT pain relief, but this salt water method does, at least for 30 minutes or so. --Username132 (talk) 09:33, 23 December 2006 (UTC)
Through the process of osmosis, the swelling is nearly instantaneously eradicated. The swelling causes pain; thus, instant pain relief. —The preceding unsigned comment was added by 70.114.249.248 (talk) 22:48, 23 December 2006 (UTC).

[edit] How dangerous, if ingested, is shampoo?

I have swallowed a small amount of shampoo about an hour ago (around 0430 at +8 GMT, malaysia) containing the following: Water, Sodium Laureth Sulfate, Lauramidopropyl Betaine, Sodium Cocoamphoacetate, cocamide MEA, laureth-4, Fragnance (That's all it says), Glycerin, Sodium Benzoate, Polyquanternium-10, alchohol, sodium citrate, PEG/PPG-20/22, Butyl ether Dimethicone, Bis(C13-15 Alkoxy), PG Amodimethicone, Quaternium-33, Citrus Aurantium Bergamia (Bergamo) Fruit extract, Butylene Glycol, propylene glycol, Cl 42053, Methylcloroisothiazolinone, Mentha piperita (peppermint) leaf extract, methylisthiazoline, and eucalyptus globulus leaf extract. The product was Feather® Nature Plus Fresh & Lively Shampoo.

Since I'm feeling fine now my question is: "Is the shampoo really dangerous and, if it is, how much of it would it take to cause permanent and/or fatal consequences?"

—The preceding unsigned comment was added by 219.95.43.30 (talk) 21:41, 18 December 2006 (UTC).

Seek immediate medical attention. Hipocrite - «Talk» 21:43, 18 December 2006 (UTC)
Simply call your GP, or the GP on duty. They know the proper way to get toxicity information. Wikipedia is hardly the place for this. Arakrys 02:40, 28 December 2006 (UTC)
Where I live, in North America, it's common for phone books to list emergency numbers at the front, and they often have free, 24 hour poison control phone numbers that people can call for advice. Does something like that exist in your region? If so, call them. If not, I agree with the previous posters about medical attention. Anchoress 21:51, 18 December 2006 (UTC)
I have removed two comments which attempted to diagnose the severity of the poster's medical condition, prescribed a course of action, or offered a prognosis. I ask that people remember that we can't diagnose or prescribe here on the Reference Desk, that we definitely don't do so in emergent cases, and that we absolutely don't do so for minors. TenOfAllTrades(talk) 23:05, 18 December 2006 (UTC)

I feel almost completely fine now though except for the headache-nausea thing which could be easily explained by 10 hours at the computer. What I've been reading so far about Sodium Laureth Sulfate so far has me still a little worried, stuff like this that I know are biased but still put me into minor panic mode when I read stuff like "can't be metabolized by the liver" and "male fertility loss". Since there's no more need to diagnose and offer prognosises my latest query would then be on the severity of the shampoo in question or any shampoo. I've edited the top with links and the relevant query.--219.95.43.30 23:43, 18 December 2006 (UTC)

Check out some of these links. Anchoress 23:19, 18 December 2006 (UTC)
Did you swallow the actual liquid shampoo or the lather? I can understand accidentally getting lather in your mouth. --24.249.108.133 23:19, 18 December 2006 (UTC)

Actual lather but a while ago I used some liquid soap as mouth wash with no ill effects. I'll check the contents in a moment. It had Sodium Laureth Sulfate, too. And formaldehyde! Hmm. I never swallowed, though. Anyway could you guys tell my how much of the Feather® Nature Plus Fresh & Lively Shampoo would it take to kill a person please? It'd make an awesome opening for conversation (Did you know if you somehow ended up drink x amount of shampoo you'd suffer x horrible symptoms and die?!)--219.95.43.30 23:43, 18 December 2006 (UTC)

Now that you're all well and nothing I say could be construed as medical advice, here goes. I would venture to say that a healthy adult would not be able to kill her or himself by ingesting regular shampoo. Is it a good idea? -absolutely not, it will make you terribly sick, detergents tend to cause violent diarrhea, but this actually helps the stuff pass through you more rapidly. There were a lot of chemicals in that bottle you had, but probably in pretty small amounts; ingredients are listed by weight, and you need very little perfume to smell up a bottle, so probably anything listed after "fragrance" is not too copious. Anyway, even if it smells good, shampoo probably tastes awful, and the near instant vomiting reflex will prevent too much from getting into you anyhow. Also, I would recommend very strongly against getting medical information from the internet unless you are very confident in the source. The web site you linked has no credibility in my book. And neither does much of anything here. If you want medical advice, ask a physician. If you want information on chemicals, look up the MSDS. If you want to settle a bet or are just mildly curious, that's when to consult wikipedia. Tuckerekcut 00:40, 19 December 2006 (UTC)
The MSDSs often go way over the top though, just look up sodium chloride for a good example of this. Plugwash 00:59, 19 December 2006 (UTC)
Haha, the first hit for "MSDS sodium chloride" gives the M. musculus intracervical LD50. (It's 131μ, in case you care). Remember girls, cervical dilators and the dead sea don't mix.Tuckerekcut 01:54, 19 December 2006 (UTC)
Keep in mind that SLS is also an ingredient in most toothpastes and shaving gels. Formaldehyde is usually found in ultra-cheap generic brand shampoos, at least in the USA. It's a cheaper preservative than parabens (but even $2 Suave shampoos are formaldehyde free). --24.249.108.133 23:34, 21 December 2006 (UTC)
For future reference the National Poison Centre [6] would probably be your best bet if your unsure. If you don't know the number, call up Telekom directory services. In some cases, the product may have a number on the back which you can dial. With fairly toxic substances, there will usually be emergency medical instructions as well. Of course, you could either head to hospital or dial 999 if you're genuinely concerned or unsure. If you do head to hospital, make sure you bring the product with you. I would say in many countries, arguably Malaysia as well, if the product doesn't have specific warnings you're probably okay if it's a small amount. You might get sick, but it's unlikely to be anything serious enough to require hospitalisation or emergency medical treatment IMHO. But I can't guarantee this and would urge anyone who ingests something to seek help just in case Nil Einne 14:35, 21 December 2006 (UTC)

[edit] Creation of the VCR internal clock

I read the article regarding video machines and it gave very good information regarding the history of vcr's.

I am trying to determine who the inventor of this aspect of the vcr machine is.

Can you help? —The preceding unsigned comment was added by Dedele34 (talk • contribs) 22:56, 18 December 2006 (UTC).

Good question. The VCR article discusses the evolution of the timer mechanism throughout the article, but the word "clock" is never even used. —Pengo talk · contribs 01:50, 19 December 2006 (UTC)
I remember the older style VCR machines that had an inbuilt clock (I think usually LEDs) which you could also program your shows by, but a separate mechanical counter for the tape. The mechanical counter didn't give you an indication of the actual time taken, just like the tape counters in the old audio tape decks. So which aspect of the clock do you mean, the clock, the program timer, or the counter? Really, all of these were adapted from earlier devices as mentioned, they weren't actually invented for the VCR. Setting the timer to record a show is really just a modification of what alarm clocks do. --jjron 07:46, 19 December 2006 (UTC)
IIRC, some very early Sony U-matic video cassette recorders actually used an analogue clock mechanism; I think I owned one once. I'm not sure the idea of putting a clock in a VCR was ever really "invented"; I think it would have to count as being "obvious". Even a pretty old audio cassette recorder of mine has a switch you can flip that will cause it to automatically enter either record or play mode when power is first applied. Combined with an external timer switch, even it can record programs in your absence.
Atlant 12:30, 19 December 2006 (UTC)

[edit] Sense of touch

I often have a very unpleasant feeling while touching some kinds of textiles (something like a combination of formication and kicking by current), and the feeling remains some time after. What's going on (and eventually how to avoid this, except wearing gloves). :) Bisley

The obvious first question: what type of textiles? Man-made fibers (polyester, acrylic, nylon, spandex etc), I am guessing? Vranak 23:55, 18 December 2006 (UTC)
Wool and acrylic, may be some other types used for pullovers in particular. --Bisley —The preceding unsigned comment was added by 83.142.184.86 (talk) 00:32, 19 December 2006 (UTC).
Hyper sensitivity to electrostatic discharge? That's my guess. I don't even know if that's a condition. —Pengo talk · contribs 01:41, 19 December 2006 (UTC)
I have no idea how to explain this or what to recommend. I think reading about reiki might help though. Vranak 02:36, 19 December 2006 (UTC)
Maybe you have hyperesthesia. - Cybergoth 05:14, 19 December 2006 (UTC)
Quite a few people cannot touch a peach, and even the idea of touching one makes them shiver. If you have the same, it has something to do with the fuzziness. Spandex should be fine, but velvet is sheer torture. It is a tactile equivalent of what other people have with the sound (and the idea) of a nail scratching the blackboard. There is almost certainly a word for this condition, but I don't know it. For eating a peach, it may help to wet it, but wetting is usually not practical and also possibly not helpful for textiles. Other than avoiding it, there seems to be little choice but enduring it.  --LambiamTalk 09:12, 19 December 2006 (UTC)
Interesting that our article formication redirects to anogther page ... --HappyCamper 16:35, 19 December 2006 (UTC)
Another name may be paresthesia. That does not explain your sensation, simply labels it:-) --Seejyb 23:23, 19 December 2006 (UTC)
Perhaps a bit OT, but I know someone who can't stand wool. Personally, I don't really have a problem with any fabric but I absolutely can't stand the sound of polystyrene. Nil Einne 14:38, 21 December 2006 (UTC)