Wikipedia:Reference desk/Archives/Science/2007 August 12

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August 12

Need help with another link - hair pulling obsession

I'm looking for an article or reference for an assertion that in some instances, the syndrome (pathology? mental illness?) that causes an irresistible urge to pull out head hair may be caused by or related to food sensitivities (allergies). However, I don't even know the name of the syndrome. Any help is appreciated. Also interested in any studies or articles that correlate this syndrome to Demodex or other microbe/spore/parasite infestation. Anchoress 00:52, 12 August 2007 (UTC)

Trichotillomania is strictly an obsessive compulsive disorder, to the best of my knowledge. StuRat 01:33, 12 August 2007 (UTC)

Oh, thanks for the link to the name of the disorder, I can do some searching now. I don't know if the associations with the outside contributors I mentioned have been proven or are mainstream, but I'd like to see any documents on the topics if they exist. Anchoress 02:11, 12 August 2007 (UTC)

Silicate Lattice - edges?

So... theoretically, we have an infinite array of Si-O-Si bonds. But realistically, a crystal will end. So.. what happens at the end? Do we have OH or O(1-), with what sort of cation, and so on?

Yes - OH or even Si-O-Si bridges can happen, and the H in OH can be replaced by a cation as well as you suggest, in fact the OH groups can be reacted with compounds such as Me₃SiCl to give O-SIMe₃ terminal groups etc.

Actually, now that I think about it.. what happens in diamond? I suppose CH3 groups or even vinyl groups are possible at the edge.

It's a similar situation - what you find on the edges depends on how the diamond was made/ it's history - in air C-OH groups or C=O groups are most likely.

If you cleave a diamond to get two new surfaces - there will be Radical (chemistry) at the new edges - these will react with air (or water) to form C-O bonds - reaction with N2 in air can also happen/

If you make diamond from chemical vapour deposition of say methane then yes - CH3 or vinyl end groups are likely.87.102.66.187 10:43, 14 August 2007 (UTC)

The topic is known as surface science more specifically surface chemistry see surface functionalization - we don't seem to have a lot on it. A web search might turn up more info..87.102.66.187 10:46, 14 August 2007 (UTC)

Concentrated acids - definition, calculations?

how are concentrated acids defined?... I know pure sulfuric acid is impossible to have, since it combines with itself to form pyrosulfuric acid and water, so is 98.5% sulfuric acid the highest concentration you can have?... What about other concentrated acids, like nitric, hydrochloric, and phosphoric? And finally... how would one do calculations involving mass equations (I suppose the H20 term in the acid dissociation equation is no longer negligible)

The concentrations of laboratory conentrated acids usually comes from the composition of the free distilling azeotrope - in the case of nitric this is 68%, in HCl the figure is about 20% but more HCl can easily be dissolved in water - the usual conc. is about 35-38% see Hydrochloric acid

Other acids such as acetic acid can be obtained esily pure 100%.

You can have 100% sulphuric acid - by adding a small about of SO3 to 98.5% sulphuric. As you know there is an equilibrium between sulphuric acid, pyrosulphuric acid and water - in the case of 100% sulphuric acid most of the substance will be in the sulphuric acid form.

(See also oleum) and look at Sulfuric acid for more info on the equilibriums.

I'm not sure about phosphoric acid - see Phosphoric acid "Pure anhydrous phosphoric acid is a white solid that melts at 42.35 °C to form a colorless, viscous liquid."

As for calculations you would need the equilibrium constants (see also Chemical_equilibrium) of the various species present in the liquid. Ask if you need more info etc.87.102.1.234 10:28, 12 August 2007 (UTC)

Fear of reading text books

Im doing mbbs..i cant study anything before the exams..because of this i've failed many exams...as soon as i start reading,my heart starts pounding..ill get precordial pain..this is since 4years

I would suggest consulting your medical practitioner; I don't believe there's much that we can do. Seriously, if this has been a long-standing issue for you, perhaps you need to consult? Splintercellguy 12:06, 12 August 2007 (UTC)

Certainly we cannot give medical advice, and you should consult a doctor about any chest pains. That aside, to get started doing something which seems odious and unbearable, such as reading your assigned textbook, try establishing a time when you are going to do it (initially) and a place and a duration. Try setting a kitchen timer for 15 minutes (you can endure the agony of reading for that long, right?) then open the book at the assigned start page and start reading. Next time, set the timer for longer, to build up your tolerance. Possibly, you will find after the 15 minute timer dings that it isn't as bad as you expected. Edison 03:06, 13 August 2007 (UTC)

See panic attack. This is a rather common problem that I've seen. Each year that I was teaching, I'd find many students suffer from panic attacks due to various things such as taking an exam or being required to give a presentation. One girl fainted every time she'd be asked to answer a question. The article suggests treatments, but they will only work if a medical professional diagnoses you with this specific disorder. Do not assume that an article on Wikipedia can diagnose your specific problem. I only mention the disorder (and frequency of it) to try and reduce your anxiety that is must be something severe. -- Kainaw^(what?) 03:44, 13 August 2007 (UTC)

I know quite some students who failed year after year due to problems of this kind, and this is so unnecessary given that these are medical problems that can be treated suprisingly well. So, please, go and seek professional advice, it could change much. There are lots of mental techniques to overcome such fears, and even drugs that support the process. It may, however, be not the best idea to only ask a general practitioner. Overcome any bad feeling you may have about it and ask a psychiatrist and/or a psychotherapist -- they are much more experienced with such problems. Simon A. 06:36, 17 August 2007 (UTC)

mitosis

i'm just wondering..what do you guys think will happen if a cell undergoes nion-stop mitosis? and what do you think will happen if a cell can't undergo mitosis? thanks! :)

What kind of cell? Any single celled organism could be said to be undergoing non-stop mitosis (although mitosis might not be the exact correct word for it). A single celled organism that can't divide is one that is going to die. For multicellular organisms, let's just look at humans. Cells that can't undergo mitosis are in a state called senescence. Cancer is a disorder in which cells in humans or other animals mitose uncontrollably. There are some cell types that naturally mitose constantly, however (Some cancer treatments indiscriminately target all dividing cells, resulting in loss of hair and compromised immune systems, as some of the cells related to these naturally divide near constantly). Someguy1221 06:25, 12 August 2007 (UTC)

That was a great explanation. You might also want to read section 9.5 of this page [1]. Cells can labile, stable or permanent, and permanent cells only very rarely replicate. Recurring dreams 09:36, 12 August 2007 (UTC)

Recharging batteries

I've heard that one has to fully charge a rechargeable battery in a new appliance, otherwise it'll not be fully charged in future charges...is this true? or is it a myth?

Do you mean using old batteries in another appliance? Or do you mean new batteries? I recently bought some and it stated on the package that the first time they should preferably be left in the charger for a whole day. Is that what you were thinking of? Don't know the reason, but if the manufacturer advises it, it'll be for a reason. DirkvdM 09:25, 12 August 2007 (UTC)

I mean the new batteries. But why does the manufacturer advise so? won't the battery get overcharged?

The manufacture does not want a flat battery to give the impression that the appliance does not work. Followed by a return of the product. Batteries can take a bit of overcharging with out destroying them. Batteries sitting around for a long time self discharge. Your statement is mostly myth, unless you chuck them in the bin thinking they are dead! Graeme Bartlett 11:02, 12 August 2007 (UTC)

At any rate, a proper battery charger will not overcharge. —Steve Summit (talk) 11:40, 12 August 2007 (UTC)

The first couple of charges with a new rechargeable battery help to "condition" the battery for use. These batteries have a memory of sorts, as it will remember how much it was charged and recharge to that point again. That is why it is important to fully charge and fully discharge before charging again the first few times. It is also helpful to fully discharge and charge your battery every so often, say once every month or so. This link gives a small amount of information regarding the first battery charge. You can also do a google search for "first battery charge" and get a wealth of information on it. http://www.cellpower.com/FAQs.cfm#How%20should%20I%20charge%20my%20battery

thx!

Overcast Days

Why do I feel so lazy and tired on overcast days even when I know I have had enough rest? my guess would be that the weather slows my metabolic rate...thus the lack of energy...but why does it slow my metabolic rate while it doesn't seem to affect anyone around me?

Seasonal affective disorder? --antilived^{T | C | G} 10:10, 12 August 2007 (UTC)

This helps, thanks!

Fractional charges on quarks

we know that charge has a QUANTIZED property,meaning that it exit in discrete packets rather than continuous amounts then why QUARKS has charge values in fraction? ..........usman

I don't really understand your question. It's not like they can have any fractial charge. It has to be be either 1/3 or 2/3. So it seems to me that the "quanta" of charge is 1/3 the charge of en electron. We choose the electron charge as a convention. We could just as easily choose the d quark. Then that would have charge -1 the u would have charge 2 the e would have charge -3. Theresa Knott | The otter sank 14:18, 12 August 2007 (UTC)

But quarks don't wander around by themselves - they come in threes - and I believe that the combinations always have a charge that adds up to a whole number. (Someone may want to correct me on that - this is not my subject.) SteveBaker 23:10, 12 August 2007 (UTC)

Pseudocodes, DFDs and Flowchart

Guys, its ADIDS.

Well i have another problem.

My Computer Studies teacher can't give detailed diagrams for how DFDs work and for diagrams for it. I dont also have flowchart examples. I am just doing my O levels so all I want is a non technical examples. Can any one post a link here for me?

PSEUDOCODES

Well. I had a problem writing a pseudocode/algorithm (formal) for i)finding out the avg,highest,lowest no.s from a set. ii) using various loop constructs (like for-next, loop-until,while-do,etc)

Can any one find me a review about such pseudocodes.

Wikipedia gives a much more difficult technical overview on such topics. SO HELP ME!!!!!!!!!!

ADIDS

Please don't spam questions across sections. Check computing :). Splintercellguy 14:35, 12 August 2007 (UTC)

Magic cleaning liquid

A 'magic' substance is called "sugar soap" in de Commonwealth countries. I could not find any information on a bottle as to its chemical contents. Is it farfetched to call it a Trisodium phosphate solution, considering what is written in the "sugar soap" article? VanBurenen 15:43, 12 August 2007 (UTC)

Good question. It appears that Liquid Sugar Soap is a TSP based. But to confuse the issue more, I found an article that suggests adding sugar (sucrose) to your homemade soaps to make them lather more. I've also seen "sugar scrubs", which are sugared oils which soften skin. this article might be the best answer, though. "It is sodium carbonate and sodium phosphate, and sometimes sodium silicate as well."

Note that phosphorus-based cleansers are difficult to find in America due to their environmental problems. Many cleansers NAMED "TSP" may actually not contain any trisodiumphosphate. --Mdwyer 17:56, 12 August 2007 (UTC)

I rewrote the sugar soap article. I think it is safe to say, "If you are in the US and are looking for something to clean your paint, then you are looking for TSP." --Mdwyer 18:11, 12 August 2007 (UTC)

Hmmm - that's really interesting. Being a Brit, I've always use 'Sugar Soap' to clean paintwork prior to repainting it. Here in Texas, I've never been able to buy any - and nobody seems to have heard of it, so it's been hard to find an equivalent. When I buy it in UK, it always came in a gallon tub filled with small granules of this soapy stuff. Being granulated, it dissolves quickly in warm water. I had always understood it was called Sugar Soap because it has the texture of sugar crystals. But that doesn't make much sense if it's available in liquid form too. SteveBaker 22:52, 12 August 2007 (UTC)

The double pendulum...

does the double pendulum have a time period as such....and if so...how do we practically find it out...and if so then the time period is dependant on the intermediate mass or the main bob?

It's common to use a Lagrangian mechanics approach; this will allow you to solve the system in a straightforward way via conservation of energy. Depending on the arrangement, the double pendulum may be stable, and may even be well-approximated by a simple harmonic oscillator, but since it has two degrees of freedom, you must generalize what you mean by the "periodicity," as many types of complicated oscillations may have periods that do not return to identical initial conditions. Nimur 16:19, 12 August 2007 (UTC)

We even have an article about the double pendulum, which mentions that it can exhibit chaotic motion (in the technical sense, not the colloquial "wow, that's crazy":). DMacks 19:05, 12 August 2007 (UTC)

Since you specifically asked, both the stability and any form of periodicity would depend on both masses and both pendulum lengths; but the equation for the period would probably not yield a simple relationship with these values. Nimur 21:31, 12 August 2007 (UTC)

But nimur, how do i derive or get to this equation and what is this equation.....could you please elucidate?

The math is given in Double pendulum (of course). But what you are asking for is impossible. A double pendulum doesn't have a 'period' - a period implies periodicity. ie The object is at some position, moving at some speed - then sometime later, it's at the same exact position, moving at the same exact speed - the "period" being the time elapsed between those two events. A double pendulum may move in such a way that it will NEVER return to the exact same position and speed - no matter how long you watch it for. Without periodicity, there can be no equation for the period. It's a classic example of a 'chaotic' system. You can't predict a double pendulums' motion over the long term - except under the simplest of starting conditions. This seems amazing because it's such a simple thing to look at - and that's why they are officially "cool"! SteveBaker 18:57, 14 August 2007 (UTC)

Urinal etiquette

Could someone explain the various rules of 'polite urinal use' in the mens' room to me? Thanks. I know the obvious 'never use the urinal directly next to another guy' thing. Thanks. --84.64.182.39 23:11, 12 August 2007 (UTC)

1) Don't splash.

2) Unzip and zip back up facing the urinal, not facing other men.

3) Don't look at anyone while urinating, stare at the urinal or wall in front of you.

4) Flush after.

5) Wash your hands after.

6) No snacking on the urinal cake. StuRat 23:46, 12 August 2007 (UTC)

If there are (say) ten urinals in a row, go 1-3-5-7-9 (i.e. keep one urinal between each user). In an empty three-urinal mens' room, *never* got straight to the middle one (effectively, it means that you're bogarting all three and causing other users to wait until you've finished). Never use a urinal next to another man, or between two other men. If you have a choice, use the urinal furthest from the door (to avoid other men walking behind you whilst you're urinating). Do not use the urinal for solid waste. --Kurt Shaped Box 23:56, 12 August 2007 (UTC)

And, perhaps, most important of all: Dont try doing any George Michael impressions while you're in there (an I don't mean singing). You never know who's in the next stall. BTW, whats scientific about this query? —Preceding unsigned comment added by 88.109.93.168 (talk • contribs) 00:29, 13 August 2007

Hmmm. The psychology behind it might be interesting to discuss, come to think of it. I'm in the UK and it (the urinal spacing thing, that is) seems to be a pretty universal, unspoken thing. I don't remember anyone ever explaining it to me either - it's just something that guys 'do'. --Kurt Shaped Box 07:43, 13 August 2007 (UTC)

Some may disagree with me, but I say don't talk in the men's room, even to your friends. It can wait until you're finished. Talking in the restroom is something girls do. —Keenan Pepper 00:46, 13 August 2007 (UTC)

The disturbing part is what girls talk about when they're in the bathroom. Someguy1221 02:39, 13 August 2007 (UTC)

http://www.drinknation.com/urinaltest.php - I got a perfect score! Yeay me! ←Ben^B4 00:52, 13 August 2007 (UTC)

Why not use the urinal next to one in use? What is it there for then? Sure, if there is enough room I usually observe some spacing too, but if the only available urinal is between two other guys, I'll use it. If I weren't 'allowed' to, it shouldn't be there, right? And why not talk? That's actually one of the few times I engage in small talk, just to pass the time. I haven't noticed anyone being bothered by either breaking of the 'taboos'. I suppose this is a cultural thing (I'm Dutch, btw). DirkvdM 08:53, 13 August 2007 (UTC)

Yeah, it must be cultural. I've found myself in situations where someone is using the middle urinal of three and bunch of grown men are hanging around at the back of the restroom (that's another 'unwritten rule', I guess - 'don't stand directly behind your fellow urinal users') waiting for him to finish before they can go forth and pee. It sounds really lame when you write it down... :) Perhaps the most important rule of all, as yet unmentioned - is that you must never, ever attempt to use a urinal that is already in use. Breaking this rule *may* get you stabbed. --Kurt Shaped Box 09:32, 13 August 2007 (UTC)

Additional etiquette rule: 7)"Stand close. The man behind you may be barefoot." Edison 15:07, 13 August 2007 (UTC)

• Dave Barry's Complete guide to guys has a good section on this. The real deal is just Leave each other alone - as any Nervous peer can attest. WilyD 15:20, 13 August 2007 (UTC)

Speaking of different cultures, I once ended up in a gay bar. When I went to the toilet it was pitch black - suppose that was the 'dark room'. I walked a few paces, felt 'splash splash' under my feet and decided to relieve myself there. Go with the flow, so to say. :) DirkvdM 17:28, 13 August 2007 (UTC)

O_O I would burn those shoes. Anyway, I agree with all the above but want to add that it's not really as necessary to observe spacing if there are nice big privacy barriers between the urinals. But if there's no barrier the spacing becomes extremely important- with no barriers I for one am completely incapable of relaxing enough to "go" if there's not more than 2 urinals between me and the next guy o_O --froth^t 20:07, 13 August 2007 (UTC)

I believe that's a sign of inadequate beer intake. If you really have to go, you can probably manage it under almost any circumstances. Friday (talk) 20:12, 13 August 2007 (UTC)

What the heck do you scared boys do when confronted with a place that has only one big trough? Or at a sports venue that is packed with guys trying to go during a break in the action? Or even better, the combination of the two? Heck, it's only a penis. Roughly half of all humans have one. --LarryMac | Talk 20:14, 13 August 2007 (UTC)

Easy. The users space themselves appropriately at the trough. In the case of a sports game, they patiently wait in line (they really do!). There is *no* excuse for poor urinal etiquette. --Kurt Shaped Box 20:55, 13 August 2007 (UTC)

What about changing rooms at sports parks? Do you guys use them in turns, or what? Or does the fear of same-sex nudity not apply there for some reason? DirkvdM 07:46, 14 August 2007 (UTC)

Honestly, I think you should as at the Humanities desk. ←Ben^B4 03:41, 15 August 2007 (UTC)

Huh? DirkvdM 14:57, 17 August 2007 (UTC)

Dirk, I don't think the posters above worry about same-sex nudity. This is rather a question of personal space -- a concept in psychology that there is a minimum distance (depending on relation of the people) that people need around them to feel comfortable. Well, and urinals are a rather striking violation of this principle because they are commonly spaced closer than people who don't know each other would stand even in normal social situations. Simon A. 06:58, 17 August 2007 (UTC)

Then there are those of us who prefer not to be so close that we get splashed with each other's tinkle. StuRat 06:40, 18 August 2007 (UTC)