Wikipedia:Reference desk/Archives/Science/2006 November 29

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[edit] November 29

[edit] Valence Electrons

Hello:

I was wondering how one could find the amount of valence electrons in a particular element, and how valence electrons are different from just normal electrons.

Thanks,

--Vikramkr

Valence electrons fill the Valence shell of an atom, that article may clear up your queries. Vespine 00:56, 29 November 2006 (UTC)
--Thanks Vikramkr 04:50, 30 November 2006 (UTC)

[edit] Can one be 'left-eared'?...

Most people are left or right handed, legged, eyed, etc...Can a person really have a prefered EAR? Of course, I`m presuming no pathology is involved here. And, I don`t mean 'prefered' as a regular preference. I mean 'prefered' in the sense that the person truly, consistently UNDERSTANDS things better, not hears better. Remember, no pathology present. Nothing like earwax, or proximity, anything like that. Personally, I have a very difficult time following instructions, remembering numbers, and such, when holding the telephone to my right ear during telephone conversations. No such difficulties while using my left ear. To the best of my knowledge, each of my ears is equally 'sensitive'. I don`t think I favor one over the other for things other than "close" hearing. i.e. phone. Is anyone aware of any study/ies having been conducted that has/have produced any palpable and/or meaningful results? Could there be a 'left-brain right brain' thing happening here? Thanks for listening! Dave172.129.2.55 00:15, 29 November 2006 (UTC)

The vestibular nerves, the nerves that convey auditory information from the ear to the brain, actually split in two with one branch going to the ipsilateral and one to the contralateral side. Thus the only difference between hearing things in one ear as opposed to the other is the timing of the impulse to either side of the pons, where the auditory cortex is. Therefore, unlike most other senses (the sense of balance is the same as with hearing, but vision, smell, touch, and probably taste are conveyed slightly differently to either side of the brain), hearing is essentially sensed the same on both sides. If you feel that your understanding of sounds is better in one ear than the other, you are probably imagining things, unless you have some sort of signal conduction block in the midline of your pons (very unlikely). Either way, it's in your head. --This is not intended as medical advice or a diagnosis. If you feel you have a medical problem, see a physician.-- Tuckerekcut 01:00, 29 November 2006 (UTC)
It was recently found that one of the ears is statistically slightly better at hearing certain sounds better than the other. X [Mac Davis] (DESK|How's my driving?) 01:01, 29 November 2006 (UTC)
...it`s in your head." Good one! Perhaps I didn`t 'spell it out' properly: I have no problem understanding the SOUNDS of the words, it`s more like I have difficulty understanding the MEANING. Maybe an exemple will clarify: Suppose I was given a test to repeat a 7-number sequence. Despite hearing every number perfectly well, I would succeed in remembering much better while sounds were isolated to left ear only vs. right ear only. I hope this clears things up. And no, I don`t believe I have any medical problem. Thanks for your responses so far. Dave 172.129.2.55 03:40, 29 November 2006 (UTC)
You may have an undiagnosed problem. The portion of your brain which processes input from one ear may not be working properly. I believe, after certain types of brain damage, people can only recognize objects with one eye. You may have something similar, but with the ears. Have you done testing to establish the difference in memorization, or is it just a casual observation ? StuRat 07:07, 29 November 2006 (UTC)
(Edit conflict !) I suppose that it is natural that one organ of a pair is better than the other? We can't expect both our ears / eyes / kidneys etc to be tuned perfectly. I have noticed that one of my eyes sees colours (very) slightly differently from the other. For example, if I look at something red with each of my eyes, I can make out that the shade of red seen by the right eye is slightly different from the shade seen by the left eye. I have heard this from others too. But the preference may be a matter of taste, or may depend on your handedness. I being right handed, when I need to close an eye, tend to close by left eye though I don't have any problem with the left eye.-- WikiCheng | Talk 07:11, 29 November 2006 (UTC)
What I was trying to point out in my earlier edit was that whereas the eyes (actually, the left and right fields of vision) go to opposite sides of the brain, the ears both send nerves to the same part of the brain. Thus accounts of being left or right eye dominant make sense to even an amateur neurologist. However since this sort of hemispherical separation does not occur for the auditory tracts, one cannot apply the same logic to hearing. The brain knows what is being seen by what part of the eye by actual localization on the cortex, but sounds are distinguished from side to side only by the time at which they reach the pons. Even the location of the auditory cortex, in the pons instead of the higher parts of the brain, confers very rapid signal transduction between the two sides (no corpus callosum to go through). What is important in all this is that sound is not "decoded" into language until after it leaves the auditory cortex. Because of this, the information is packaged in such a way that it effectively loses its designation of right or left. Take home point: the processes of comprehention and understanding occur after the sides are merged. If two highways merge together, one cannot tell which car came from which highway by standing miles downstream from the intersection.Tuckerekcut 14:43, 29 November 2006 (UTC)
Thanks so much folks. To Stu, just casual observation, as you put it, albeit somewhat troubling at times. To Tucker, very educational. Your 'merging' analogy really 'drove things home' for me. I might just mention this to my doctor...who knows? Thank you all again! Dave172.129.2.55 16:26, 29 November 2006 (UTC)
While the analogies and ideas expressed are more or less right, one can be left-eared, as you call it. Technically it is referred to a ‘minor ear’ and a ‘major ear’ (the allusions to music may or may not be intentional).
First, while information for one ear does travel to both sides via the pathways described, both timing and the amount of information sent to either side varies (see this website, for example). This system, like other modalities, tends to be contralateral: where right ear maps to left hemisphere etc. Like Tuckerekcut said, this system is less hemispecific than other modalities, but it still has contralateral properties.
Secondly, the dominance of one ear over another was first described using dichotic listening tasks in the 1960s. Specifically, when playing two different stimuli in both ears at the same time, one ear tends to have an advantage. No one is sure as to the exact cause of this phenomenon, some speculate that since language is specialized to the left hemisphere, the right ear may perceive language better (where individual difference in gender and handedness may strength, weaken, or reverse the effect (i.e. 15%-25% of left-handers have language on the opposite side). A good resource for more information on this is a paper by Bruce Morton:

"Dichotic listening was introduced in its present form by Broadbent (1956), popularized by Kimura (1961a, 1961b, 1967), and has been the subject of thousands of publications regarding its relationship to brain laterality. In the dichotic listening paradigm, each ear is simultaneously supplied with a different auditory stimulus, such as a simple number (Broadbent, 1956) or consonant–vowel (CV) syllable (Studdert-Kennedy & Shankweiler, 1970). Most people have a ‘‘major ear’’ through which they are able to report input of dichotic stimuli more accurately. Thus, they are said to display either a right-ear advantage (REA) or a left-ear advantage (LEA) as the case may be. The REA or LEA response of an individual appears to be a personal characteristic. It was stable for months for about 90% of subjects tested (Wexler & King, 1990). When the dichotic stimuli are separated in delivery time, commonly by 90 ms (Studdert-Kennedy, Shankweiler, & Schulman, 1970; Berlin, Lowe-Bell, Cullen, & Thompson, 1976), ear advantage disappears and most individuals are able to correctly report the separate stimuli with either ear."

(Brain and Cognition 45, 229–237 (2001) doi:10.1006/brcg.2000.1240, available online at http://www.idealibrary.com)
Whether or not this is the source of your perceptual experience remains to be seen. Does the effect present itself more often when there is background noise? Also, I suspect you’re left-handed. And finally, I highly doubt your experience is outside the range of normal, and you most likely have no cognitive defect. --Cody.Pope 21:13, 29 November 2006 (UTC)
Very, VERY interesting Cody.pope. If by 'background noise' you mean a noisy telephone, where I mention I notice the 'effect' most, then yes. If background noise in general, then no noticeable difference: both ears are equally 'bad'. Not to be mistaken for the above-mentioned 'understanding the meaning of' problem with the right ear. Finally, how astute of you! I am indeed left-handed! Thank you all very much for the 'enlightenments'...if that`s a word. Dave172.163.70.157 02:09, 30 November 2006 (UTC)

I thought I was satisfied but, upon re-reading the 'results' of the studies/tests mentioned above, I think the results are quite possibly skewed. Had the testing taken into account 'attentivity'? Maybe the 'conclusions' of 'major ear' were simply that the subjects were LISTENING HARDER with that ear. Ever listen to music through headphones, and try to analyze it by say, counting the number of instruments that are playing, in some specific passage? You`ll no doubt 'jump' from 'listening' with one ear, then the other, probably not prefering one over the other. While counting in one speaker, are you NOTICING what`s happening in the other? Another qualm I have with these studies is that I don`t think it has anything to do with my 'problem'. They`re not testng the 'understanding of the meaning of' what they might or might not have heard in one ear or the other. They`re only testing preference. Well, I guess that`s enough. I just have this little quirk and I thought there might have been a simple answer/description/solution... Sorry for carrying-on for so long. Thanks again to all for listening to my ramblings. Dave172.163.70.157 03:07, 30 November 2006 (UTC) AHH! I just re-read again. In Bruce Morton`s paper, he says, "...through which they are able to report input of dichotic stimuli more ACCURATELY." I think I can accept that as 'understanding the meaning of'. That certainly settles it: one CAN be 'left-eared'. I got it, finally! Thanks for your collective patience. Dave172.163.70.157 03:34, 30 November 2006 (UTC)

[edit] Castor bean

I decide to eat a castor bean, will I die? X [Mac Davis] (DESK|How's my driving?) 01:01, 29 November 2006 (UTC)

Look it up at linked word --Light current 01:17, 29 November 2006 (UTC)

I meant to ask if I swallowed one whole then I would feel sick or die? It says that the ricin in one-two castor beans can kill an adult, but does it need to go through any processing or extraction to kill? Because ricin talks all about that. X [Mac Davis] (DESK|How's my driving?) 02:35, 29 November 2006 (UTC)
You have to chew the seed to die. If you don't chew it, it passes through your body. -THB 04:15, 29 November 2006 (UTC)
My advice is not to test that theory.  --LambiamTalk 13:16, 29 November 2006 (UTC)

[edit] Trapezius

I decide to artifically strengthen my trapezius muscles, how should I go about doing this? X [Mac Davis] (DESK|How's my driving?) 01:01, 29 November 2006 (UTC)

Attach a steel cable running through the muscle, anchored well into the bone near each ligament. That should create artificial strength in the weakest muscle. --Kainaw (talk) 02:14, 29 November 2006 (UTC)
Duh, look at the article, I am an idiot. It probably says that for the abs too. Trust me, rarely don't look at articles. I feel like deleting these. Embarrassing. X [Mac Davis] (DESK|How's my driving?) 02:37, 29 November 2006 (UTC)
I just found the phrase "artificially strengthen" to be funny. I don't consider excercise to be artificial. However, feel free to delete your own questions. --Kainaw (talk) 02:40, 29 November 2006 (UTC)
Sorry! Nothing on RD is allowed to be funny anymore 8-(--Light current 02:11, 30 November 2006 (UTC)
What? I think weight lifting is rather artificial. As in, going to the gym to go pick up pieces of metal so that you will strengthen your muscles for later uses. X [Mac Davis] (DESK|How's my driving?) 05:38, 30 November 2006 (UTC)

[edit] Abs

I decide to artifically strengthen my abductor muscles, how should I go about doing this? X [Mac Davis] (DESK|How's my driving?) 01:01, 29 November 2006 (UTC)

Abs usually refers to the rectus abdominis muscle, not to the abductors. (Abduction means "to move away from the midline", and there are many muscles that do this -- eg, abductor pollicis longus, deltoid muscle, tensor fascia lata.) So which do you mean? And what do you mean by "artificially strengthen"? --David Iberri (talk) 01:33, 29 November 2006 (UTC)
You might also want to check where that article you linked to goes.
No I linked that! Mac obviously used the wrong word.--Light current 02:21, 29 November 2006 (UTC)
I concurr. Abs. And I meant all that exercise you people do. I'm happy with a sendentary lifestyle until I become twenty and start gaining mass like a black hole in a McDonald'sX [Mac Davis] (DESK|How's my driving?) 02:33, 29 November 2006 (UTC)
Well, situps are pretty decent for strengthening the abs, but I'll ask again: what does it mean to artificially strengthen a muscle? --David Iberri (talk) 02:39, 29 November 2006 (UTC)
Also it may be worth adding because it is a common misconception: strengthening your abs does not necessarily help to reduce the fat accumulating on your stomach region, it doesn't work that way. Weight loss and strength training are two different things. Vespine 03:05, 29 November 2006 (UTC)
  • Gee. I work out my abductor and adductor muscles a couple times a week -- it's quite possible the questioner was asking about the hip abductors (gluteus medius muscle and gluteus minimus muscle). There are machines at the gym for this (which mostly consist of spreading your legs against resistance), and you can also do it with free exercise; single leg quad and glute exercises will work the hip abductors. (Though, given the title, I imagine he does mean abdominals, in which case, never mind.) --jpgordon∇∆∇∆ 20:42, 29 November 2006 (UTC)
Well, whatever I meant, pretty much everything you guys say here is very interesting. X [Mac Davis] (DESK|How's my driving?) 05:36, 30 November 2006 (UTC)

[edit] Sticky notes

What is the adhesive on sticky notes? X [Mac Davis] (DESK|How's my driving?) 01:01, 29 November 2006 (UTC)

Glue--Light current 01:16, 29 November 2006 (UTC)
There is a link at the bottom of the Post-it note article to the patent on the adhesive. -THB 02:05, 29 November 2006 (UTC)

[edit] urine fertilizer

How much water would have to be added to human urine (or any urine) to allow it to be used directly as a lawn fertilizer? 71.100.6.152 03:33, 29 November 2006 (UTC)

None. 202.168.50.40 03:51, 29 November 2006 (UTC)
Then why does pure urine make brown spots on a lawn? 71.100.6.152 04:10, 29 November 2006 (UTC)
Depends what you want to fertilise, obviously the lawn cannot take it at that concentration. I don't know if anything would like it, as it removes water from the plant. Next time you pee on the lawn, give it a good water when you get over the hangover :). --liquidGhoul 04:16, 29 November 2006 (UTC)

I have an idea for dealing with weeds; train your pets to pee on them. The urine will kill the weeds. Then, once diluted by rain, it will fertilize the rest of the lawn. StuRat 06:56, 29 November 2006 (UTC)

Neat urine is too acidic to be an effective fertilizer. Far better to pee on the compost heap, where it will be valuable in breaking everything down.--Shantavira 09:45, 29 November 2006 (UTC)
LOL @ "neat urine" ... as opposed to served on the rocks with a lemon twist ? Also, the acidity is reduced when it's diluted by rain. StuRat 10:39, 29 November 2006 (UTC)
Which reminds me that lemon trees love human piss. They really do thrive on it. JackofOz 03:39, 30 November 2006 (UTC)
  • Lemon tree: very pretty
  • And the lemon flower is sweet
  • But the fruit of the lemon
  • Is impossible to eat
Now we know why!--Light current 03:46, 30 November 2006 (UTC)
I'd better not tell you about all the vegetables that are fertilised with manure, then. (and that ain't horse shit)  :) JackofOz 03:59, 30 November 2006 (UTC)

Marge Simpson: "The farm plants aren't doing very well, maybe we should add more fertilizer ?"

Homer Simpson: "Geez, Marge, I'm only one man !" StuRat 10:48, 30 November 2006 (UTC)

What... Did you get locked out of the house after a long night of drinking or is your toilet clogged or do you just want to 'piss' (pardon the pun) off the neighbors?
I heard that nettles can make use of the nitrogen in neat urine also. --Username132 (talk) 15:42, 3 December 2006 (UTC)

[edit] B12/Cyanocobalamin

What meats often have the highest amounts of B12? Does the B12 found in sports drinks and other artificial products have the same effect as more natural or direct sources of the vitamin? Thank you.

Liver, yes. See cyanocobalamin. Please sign your posts using four tildes (~~~~). -THB 04:25, 29 November 2006 (UTC)
Sardines have high amounts of vitamin B12 in them, more than meat. Plus calcium, Omega 3. I've read that sardines have less mercury in them than other fish because their small size (and presumebly young age) means they have had less time for the mercury to accumulate in them. Drawbacks: they are canned with a lot of salt, and those little tins keep breaking my tin openers or can openers. 81.104.12.10 01:04, 30 November 2006 (UTC)

[edit] ph scale

I was wondering wat is the most acidic liquid and what is the ph level. THank you Dragonfire 734 03:47, 29 November 2006 (UTC)

See Fluoroantimonic acid. -THB 04:22, 29 November 2006 (UTC)

[edit] Finance / SEC question: How much is MySpace founder Chris DeWolfe worth?

I'm trying to figure out how much MySpace founder Chris DeWolfe is worth. I found these SEC documents:

http://www.secinfo.com/dSEyn.zFa.htm?Find=dewolfe#16thPage

The above SEC filing states that Chris DeWolfe owns 114,825 of InterMix, which is less than 1% of the company. InterMix was bought for $580M in cash (or the equivalent of $12 per share of InterMix shares) by News Corp as specified in this document:

http://www.secinfo.com/d141Nx.z17Xe.d.htm?Find=dewolfe&Line=79#Line79

So is it accurate to assume Chris DeWolfe made $1.3M from the MySpace deal?

WinCon 04:23, 29 November 2006 (UTC)

Closer to $1.4 gross. Did he have costs associated with acquiring the shares? If so, you would have to deduct them to get the profit. And don't forget about taxes. -THB 04:28, 29 November 2006 (UTC)

[edit] Reverse polarity and antimatter query

Is antimatter made by reversing the polarity of subatomic particles? and I slightly understand the geomagnetic reversal for the earth. But are other particles or objects of polarity reversed often, if yes what is an example?...and can you reverse the polarity of a person if they are charged with static electricity, if yes, what would occur?69.150.209.13 06:20, 29 November 2006 (UTC)

Antimatter is only made in pair production with matter. Mathematically it is equivalent to matter with its charge and parity flipped, or with time reversed, but it cannot be created in this manner. Polarity is a different phenomenon, refering to the alignment of atoms; reversing polarity would result in the electromagnetic field produced by those atoms being reversed. Hopefully that's a start at least. -- SCZenz 06:50, 29 November 2006 (UTC)

[edit] repulsive quantum vacuum

This page says they were going to measure it http://www.quantumfields.com/AIAA2001.pdf, this page says that it was measured at 0.5 micronewtons http://arxiv.org/ftp/quant-ph/papers/0511/0511179.pdf, the first report was filed at NASA and the other seems to come from a respected physics institute. So does this mean we have an anti-casimir effect then, a force that can push outwards instead of pull inwards? Greg

This isn't my area of physics, so I'm not able to read the papers very well or to vouch for their reputability, but... As I read the first paper, it states that they're working on an experiment to see if configurations producing a repulsive force due to the casimir effect exist. (The second paper seems more narrow, and I'm not sure exactly how it relates to your question.) But yes, it would appear that, in theory, some scientists expect that what you describe is possible. -- SCZenz 08:15, 29 November 2006 (UTC)

Look more closely at the section on the paper that is called " repulsive vacuum fluctuations, it claims that they were measured at o.5 micronewtons, i assume that means that they have been measured right? Greg

The two papers you'll want to track down are these:
  • J. Maclay et al., AIAA/ASME/SAE/ASEE, AIAA-2001-3359.
  • J. Maclay, Phys. Rev., A61, (2000), p. 052110.
I hope this helps, --HappyCamper 17:55, 29 November 2006 (UTC)

These papers show that scientists as a whole beleive the repulsive quantum vacuum waves are real, But i would like to know if they have actually been measured and how strong the think they will be, will they be, in there best state, as strong as the casimir effect [1 atmosphere of pressure]? Greg

[edit] Photon Duality

An Old subject but could someone please explain the current theory of partical duality. I thought I had it figured out, "Transformes from energy to matter for a brief instant durring an interaction by the equation E=mc^2. Durring the interaction I thought that when it existed as matter is speed was <<C then back to energy propegating through space time at C. Like the particles in a accelerator that result from a smash, these particles exist as mass and in an electromagnetic field spiral and pop into energy. Likewise in space-time particles are continually popping from energy fluxuations to matter, then back to energy. I have a head ach,, any replies??~--Aaron hart 09:29, 29 November 2006 (UTC)

dunno what you're thinking, and I dunno about photon duality but this is a simplification of what I was taught about particle duality: particles can either be described as probability functions (probability waves) - they don't exist anywhere, there're just chances that they exist at a particular place. Or they can exist as actual particles with definitive locations. The odd paradox of the particle duality and quantum mechanics is that there is experimental evidence for both the probaility wave and particle!!
ignore that complicated rigamarole shit unless you're applying for a job at fermilab or your'e a euro and looking at CERN -Steve
The wave-particle duality is usually not approached from the perspective of E=mc^2...the latter deals with the equivalence between mass and energy. --HappyCamper 17:43, 29 November 2006 (UTC)
You are probably confusing wave-particle duality with 'vacuum fluctuations'. I.e. a photon can produce a particle-antiparticle pair, and even a vacuum can borrow the energy to do this if it is repaid (i.e. the particles annihilate) in a short enough time. But the particle nature of the photon is not related to forming these pairs (pair production). It is maybe best thought of as a wave sets the probability of finding the particle, but is (of course) more compicated than that with particles as quantised fields! Photons are always massless and always travel at c. Electrons for example have mass and travel always at <c but still have wave-like properties. 137.138.46.155 12:39, 30 November 2006 (UTC)
Steve, there are plenty of Europeans at Fermilab and plenty of Americans at CERN. Particle physics is a worldwide community137.138.46.155 12:39, 30 November 2006 (UTC)

As I understand it, duality doesn't mean they turn from on to the other but rather the observable will be what it needs to be to satisfy the physics using both wave and particle descriptions. The photon observable has a duality but the photon itself is what it is and doesn't pop back and forth. Just my laymen $0.02. --Tbeatty 02:43, 4 December 2006 (UTC)

Has it been proven that photons always travel at c, is it possible that durring an interaction velcity is <C and transforms into mass, then imidiatly back??? Just wondering I mean is anyone really sure at this time??--Aaron hart 10:14, 27 August 2007 (UTC) and i did intend to relate e=mc^2, energy of the wave to mass of the particle, are you people 100% sure that I am incorect as far as I know this is still open, we just don't know. we do know what we observe but we all know that is incorrect!!!--Aaron hart 10:32, 27 August 2007 (UTC)

[edit] science help

Hello, here is my problem "Apply Euler's theorem to A = A(T,V,n). Do you recognize the resulting equation?"

using my book and Thermodynamic_potentials I have done this:

I have applied used Euler's theorem to get A = T(dA/dT) + P(dA/dV) + n(dA/dn)

Then I have applied the equations of state to get dA/dT = -S , dA/dV = -P and dA/dn = u

so, A = -TS - PV + u*n

now what is this supposed to be?!? It looks like internal energy U (except the TS term is positive). But it doesn't make sense because in the article, A = -PV + u*n

help? Thanks. -Steve

ok update:
A = -TS - PV + un
U = TS - PV + un
A = U - TS + un
therefore, A = -PV + un
yea that makes absolutely no mathematical sense, but I think it's the right answer. And technically, all the statements are correct...just not correct when they are coupled together perhaps.
throw me a bone! Thanks -Steve
I'm not sure what the question is...the logic is not clear. So, let's see if this is what we want: If we start with A = A(T,V,N), the full derivative is dA = (dA/dT) dT + (dA/dV) dV + (dA/dN) dN in which you can make all those substitutions to get
dA = -SdT - PdV + μdN
Now, to get your final answer, you would have to have an isothermal situation where T is held constant. Integrating both sides gives you A = - PV + μN. Hope this helps! --HappyCamper 17:32, 29 November 2006 (UTC)

[edit] avoidant personality disorder

In your fine article on the above, you state that "Psychologists suggest that their rejection can be due to a highly superior intellect and/or physical appearance than that of the general public." I am researching the topic so would very much like to know if you can give me a reference for this contention - espcially since it appears to contradict the more general assumption that sufferers from APD will have low self-esteem.

Thanks for any help you can offer.

Bob

it's possible APD people frequently have another disorder (who knows if it's cause or effect) such as Narcissistic Personality Disorder derived from their superior intellect. Have you researched how often vaguely defined disorders like these overlap? -Steve
btw, how is this different than the eponoymous Asperger's syndrome? -Steve
Being Aspergic myself I would contend that it is possible to have poor social skills and be unaware of the fact, or, if you are, not care. Vitriol 15:03, 29 November 2006 (UTC)

Unfortunately you have found one of the (enormous number of) unsourced statements that aren't supposed to exist in Wikipedia, but do all the same. If you do find a source for it, please add it. On the other hand, if you are knowledgeable on the subject and believe that the claim contradicts the current consensus, then please delete it and improve Wikipedia thereby.

If you are knowledgeably suspicious of it, but do not feel confident to excise it completely, please remove it, but add a section to the article's Talk page explaining what you have removed and why.

Oh, and please sign your contributions (here and on a talk page) with four tildes (~~~~). --ColinFine 00:00, 4 December 2006 (UTC)

[edit] Tuning fork

what happens if one of the prong is cut ?

If you mean cut off completely, the tuning fork will still work just fine, but not be as loud, since you will be left with only one vibrating prong. The number of prongs is not important. You can make a standard four-pronged fork vibrate too. Of course, if one of the prongs is shortened, the two prongs will vibrate at different rates and give different notes, so it will no longer be of much use as a tuning fork.--Shantavira 15:38, 29 November 2006 (UTC)
"The two prongs will vibrate at different rates and give different notes" — That doesn't make sense. The fork has an unlimited number of normal modes and associated resonant frequencies, not one for each prong. A fork with prongs of different lengths would still give one strong fundamental and several weak inharmonic overtones. —Keenan Pepper 20:57, 29 November 2006 (UTC)

Tuning fork has more info. I'd like to find out if the two prongs automatically become in-phase, thus amplifying the signal. I would think that air pressure, or the sonic waves going down the main shafts would bring this about. --Zeizmic 16:58, 29 November 2006 (UTC)

I think the tuning fork necessarily vibrates with the two ends in phase. Imagine a system where the handle of the fork is missing. Then, the tuning fork is simply a bar that has been bent. For simplicity sake, we imagine that this bar is just completely flat. It would not be possible for this bar to vibrate with the ends out of phase. I think Wikipedia would have an article on this somewhere, perhaps in a mechanical engineering article dealing with damping. In that area, they can consider the situation where a wooden plank is free, fixed or supported on both ends. A bunch of differential equations result, and it is this which govern the dynamics. --HappyCamper 17:40, 29 November 2006 (UTC)
Actually, I believe they are exactly anti-phase, so that they both pull out together and both push in together. This nulls out the motion in the handle of the tuning fork thus allowing more energy to go into vibrating the air. Dragons flight 17:59, 29 November 2006 (UTC)
(Continuing Dragons flight's point) ... so a tuning fork with only one bar will lose energy through the handle to your hand much more rapidly than a tuning fork with two counterbalancing bars. See Q factor.
Atlant 18:09, 29 November 2006 (UTC)
Oh yes, you two are precisely right! My error. --HappyCamper 19:06, 29 November 2006 (UTC)
Anyone noticed how yuo only strike one prong, and the other one vibrates as well?--Light current 00:12, 1 December 2006 (UTC)
See Acoustic resonance, aka "sympathetic vibration". As we've discussed above, mechanical energy is coupled through the portion of the fork near the handle from one bar to the other.
Atlant 13:16, 1 December 2006 (UTC)

[edit] How are radioactive materials mined? Where do they occur naturally?

In light of the recent news articles, how are radioactive materials mined? I can't imagine walking in the forest and tripping over polonium. Thanks!

South Africa has tons of uranium mines. Raul654 19:44, 29 November 2006 (UTC)
And apparently so does canada. See Uranium mining Raul654 19:44, 29 November 2006 (UTC)
However, polonium-210 is generally created in a nuclear reactor by exposing bismuth to radiation. It can be purchased in very minute quantities for industrial uses, but would need to be concentrated to levels not readily available to be an effective poison. Dragons flight 19:56, 29 November 2006 (UTC)

Most naturally occurring radioactive elements aren't all that radioactive (because, if they are, they quickly decay, so the 4.3 billion year old Earth doesn't have many left) and are often diluted by non-radioactive materials. Thus, they can typically be mined with simple precautions, like breathing masks. They are later refined and possibly put through a breeder reactor to produce the highly radioactive materials used in nuclear reactors and nuclear weapons. At that point, much more elaborate safety precautions are needed. StuRat 21:37, 29 November 2006 (UTC)

Australia is a major exporter of uranium too. As for occurring naturally, pitchblende was the first substance in which radioactive material was found, firstly uranium by Martin Heinrich Klaproth and later polonium and the much more radioactive radium by Marie Curie for which she eventually payed the highest price. Vespine 22:18, 29 November 2006 (UTC)
Actually polonium is much more radioactive than radium. Radium-226 has a half-life of about 1600 years, whereas polonium-210 is only about 138 days. (And they're both alpha emitters of comparable energy, so it's an apples-to-apples comparison.) --Trovatore 04:22, 1 December 2006 (UTC)
In the US during the 1950s, when there was an artificial market for uranium which created a "rush" for it, prospectors would go around areas thought likely to have uranium deposits (geologists spent a lot of time trying to figure out what types of areas those were in the 1940s) with geiger counters, sometimes drilling holes deep into the ground and seeing if there was any residual radiation there. --24.147.86.187 01:45, 30 November 2006 (UTC)
Just a thought - if toxicity is a matter of concentration, then wouldn't it make more sense to get rid of the waste the same way? Just pump it into the atmosphere so it will get spread evenly all over the world? Of course, the waste products are much more radioactive (yes?) and presence in the (breathable) air is not the same as being in the ground. Ok, bad idea. Lateral thinking doesn't always give the best solutions. :) DirkvdM 10:46, 30 November 2006 (UTC)
It would immediately settle out on the ground right round where it was released in the air, and the people there would get an excessive radiation dosage. However, one serious suggestion was to dump radioactive waste into the deepest oceanic trenches. It would eventually leak out, but would be so diluted by the oceans that it wouldn't pose a problem. However, the risk exists that terrorists of the future might be able to retrieve the waste and use it to make dirty bombs. For this reason, the waste might be intentionally leaked out more quickly, to dissipate it immediately. I believe the Russians already have used this method, scuttling old nuclear subs in the ocean with the reactors and fuel rods intact. This is the type of thing environmentalists just hate and monster movie buffs just love, certain that the radiation will mutate a giant tube worm that will then attack Tokyo. StuRat 13:52, 30 November 2006 (UTC)
But isn't the output (waste) of a fission plant much more racio-active than the input (fuel)? DirkvdM 20:28, 30 November 2006 (UTC)
I would expect it to much less radioactive, like depleted uranium. StuRat 04:11, 1 December 2006 (UTC)
Nuclear waste is much more radioactive because the fission process generates fission fragments (light, unstable nuclei) that are highly radioactive. Dragons flight 04:38, 1 December 2006 (UTC)

[edit] History of Gears

This New York Times articlementions that

  • A geared computing device existed in the 2nd century B.C.
  • According to Dr. François Charette of the University of Munich museum, "It seems clear [that] much of the mind-boggling technological sophistication available in some parts of the Hellenistic and Greco-Roman world was simply not transmitted further... The gear-wheel, in this case, had to be reinvented."

When and by whom, prior to such discoveries as this, was the gear considered to have been invented? (No historical info at Gear. Question cross-posted to Talk:Gear.) Wareh 21:48, 29 November 2006 (UTC)

There was a mechanical geared clock called the Salisbury cathedral clock which was built at Salisbury Cathedral before 1386 AD. It was about as complicated as any device of that era. It had an escapement mechanism and no clockface. It struck a bell on the hour. I have seen it in operation. There were more primitive mechanical clocks a hundred years earlier. Edison 22:41, 29 November 2006 (UTC)
I think the problem with a question like this is that what we now know as gears have gone through many subtle stages of evolution. Gears are a form of transmission, looking at it that way, I would say someone like Archimedes probably kicked things off by inventing the block and tackle, but even that is based on the pulley which was around for a long time before then, sometime since the wheel was invented. From that to a modern gear is a very gradual evolution and a lot of the in between was so subtle that what was done by who and when is not really well known. My guess that the next big advance would be the mill quite a long time after Mr medes, and then after that probably the clock, but neither of those things can really be attributed to a person or a specific time. Modern gears as in clock work are said to date back to the 12th or 13th century, but can not be attributed to a person. Vespine 22:54, 29 November 2006 (UTC)
The problem is that in the ancient world, few inventors of anything were recorded. There is no justfication for grabbing the only name that come to your mind, like Archimedes. This is especially true of a basic mechanism like a gear. Gearboxes have been discovered in ancient shipwrecks, but not with a nice "JohnDoeius fecit" label. alteripse 11:25, 30 November 2006 (UTC)
There is a conference on the Antikythera mechanism on today and tomorrow. One can look forward to some interesting findings. Seejyb 20:26, 30 November 2006 (UTC)

[edit] banana "strings"

Can anyone help with the technical term for the "strings" that often appear on a banana when its skin is removed? Thanks, George

Fibre(s) - plant fibre?
Seems they might be bundles of phloem. See [1] and [2]. --David Iberri (talk) 23:28, 29 November 2006 (UTC)
I don't agree with the pronunciation given at these links; I think it is two syllables, like "poem".  --LambiamTalk 07:06, 30 November 2006 (UTC)
It is 'flO-"em according to http://www.m-w.com/dictionary/Phloem -- WikiCheng | Talk 11:21, 30 November 2006 (UTC)

[edit] nail varnish

Can people who paint people's finger nails for a job get sick inhaling all the fumes? Haldane Fisher 22:37, 29 November 2006 (UTC)

The article acetone says that it is not that toxic. The stuff gives me a headache, though. --Zeizmic 23:37, 29 November 2006 (UTC)
Most nail polish (and nail polish removers) are based on ethyl acetate now, rather than acetone. (Ethyl acetate is both less toxic and less flammable than acetone.) Still, the MSDS[3] indicates that you shouldn't be breathing it for extended periods at a concentration above 400 ppm (parts per million). Exposure to high concentrations may have a narcotic effect, and may cause lung, liver, and kidney damage. In principle long-term exposure could cause problems in sensitive individuals, or people who work in poorly-ventilated spaces. TenOfAllTrades(talk) 00:12, 30 November 2006 (UTC)

[edit] How do they make Liquid Nitrogen?

Hi, I was wondering how exactly they make liquid nitrogen beyond (I'm assuming) the general idea of pressurizing the gas. Furthermore, do they use the same method for liquid helium? Thank you very much! Andromeda321 00:02, 30 November 2006 (UTC)

Liquid air is a good place to start. DMacks 00:05, 30 November 2006 (UTC)
The Linde process is probably the start of it--Light current 00:06, 30 November 2006 (UTC)
I don't know but I do know that liquid oxygen is very difficult to get hold of because it's dangerous, but you can make it using liquid nitrogen because oxygen has a higher boiling point than nitrogen. Haldane Fisher 09:40, 30 November 2006 (UTC)
...which makes an interesting danger for liquid nitrogen too:) Keep those Dewars (mostly-)closed, kids. And those goggles on[4]. DMacks 13:49, 30 November 2006 (UTC)