Wikipedia:Reference desk/Archives/Science/2006 November 21

= November 21 =

DNA Models
I need to make a DNA model for a project, what would be the most cost effective yet original things i could use to make it?

THANKS!!!


 * How about using Legos ? StuRat 01:48, 22 November 2006 (UTC)


 * As someone who has professionally played with Lego, let me point out that 'Legos' is a dilution of the trademark. :) DirkvdM 08:06, 22 November 2006 (UTC)


 * If you're going to cry over the use of genericized trademarks, I'll just have to hand you a Kleenex. StuRat 08:35, 22 November 2006 (UTC)

Plasticine may also work for you ! --Pupunwiki 03:05, 22 November 2006 (UTC)


 * Matchsticks?--Light current 03:16, 22 November 2006 (UTC)


 * Plasticine+matchsticks? If the matches are not long/thick/strong enough for the size of model you're aiming at, you can use those wooden or bamboo skewers you can find in supermarkets. --Lambiam Talk  13:42, 22 November 2006 (UTC)

Better Bio Gas Yeild?
I would like to know the yields of bio gas by anaerobic digestion of Food Wastes(fruit juice,Souce & Jam industry waste) Vs. Brewery industry waste (using malt)...?? Need methane to CO2 ratios (Approximate values) in both cases...!!

Thank You... Malinda

Picture permissions
if I would like to use the figure (not text) on page "endothelium" in a PHD thesis how do ask for permission ?
 * If you click on the figure, it will take you to the image page, where we find that the picture was an overview of a human artery made for PhD project. Maastricht, november 2005. Stijn A.I. Ghesquiere www.applesnail.net, and it's licenced under the Creative Commons Attribution ShareAlike License v. 2.5.  You could use it under the CC-SA provisions, or write to Stijn to secure special permission. (You could ask on his talk page here, but he doesn't seem to have been around for six months or so and might not see it.) - Nunh-huh 13:36, 21 November 2006 (UTC)
 * Under the provisions of the CC Attribution-ShareAlike 2.5 license, you may you are free:
 * to copy, distribute, display, and perform the work
 * to make derivative works
 * to make commercial use of the work
 * Under the following conditions:
 * You must attribute the work in the manner specified by the author or licensor.
 * If you alter, transform, or build upon this work, you may distribute the resulting work only under a license identical to this one.
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 * Any of these conditions can be waived if you get permission from the copyright holder.
 * In short, you can use it without explicit permission, just give credit where credit is due. – ClockworkSoul 17:20, 21 November 2006 (UTC)

Fridge mice
Am I completely insane, or do I remember seeing a nature documentary years ago, about some mice which had evolved adaptations to living inside the giant freezers at meat processing plants? It had much longer hair than normal mice and walked on tiptoes to reduce heat loss.
 * Sounds like the type of thing people tell you when you're very very stoned. Of course fridge mice exist.
 * Seriously I think this sort of thing happens long before the pink eyed ones have chance to evolve into an artic version [Warning - Dead mouse image! http://www.geocities.com/fsims2002/fourmice.jpg]
 * Rats have fur coats and can manage low temps to get food. Per they survive at -30 °C.  Mice also live in cold climates, even the arctic, perhaps hibernating or digging burrows. So if they had a food source and air to breathe in a freezer they might survive, and if they had a hole to get in the freezer(like a dilapidated cold storage warehouse) while they lived outside, it is likely they would do so. Edison 22:38, 21 November 2006 (UTC)

composition of pH buffers?
What is the composition of the pH buffers used to caliberate the pH meters(pH4.0,pH7.o,pH9.2)? why are these specific buffers used and are there any alternatives?


 * Yes, there are many alternatives. Take a look at Good's buffers to see a list of reasons why some buffers are prefered over others. --HappyCamper 16:43, 21 November 2006 (UTC)

Conductivity
How can I order these compunds in order of conductivity? CoCl3*6(NH3)   PtCl2*4(NH3)     RhCl3*5(NH3)   CrCl3*4(NH3)    Thanks!
 * Find the number of dissociated ions produced by dissolution. For instance CoCl3*6(NH3) produces Co(NH3)63+ and 3 Cl-, wheras CrCl3*4(NH3) will produce Cr(NH3)4Clundefined2- and Cl-. As the first one produces 4 ions and the section 2 the former will have a higher conductivity.87.102.16.174 20:14, 21 November 2006 (UTC)
 * The alternative is to find the answer experimentally...
 * Note that here I've assumed that Cr and Co are forming octahedral complexes (coordination numer 6) if they form for instance cubic complexes the answer will be different.
 * Note the number of dissotiated ions can be assumed to give a measure of conductivity - though different ions may give different conductivities and the effect vary with concentration etc.
 * Note: This is a simplified answer.87.102.16.174 21:40, 21 November 2006 (UTC)

Cheap helium
First of all, let me say I'm definitely not planning to go cluster ballooning without the necessary training and experience, because that would be foolish and dangerous. That said, where can I get lots of pressurized helium for a reasonable price? I'm talking like 20 kilograms of helium here. Is there any way I can get that much for a few hundred dollars? It's okay if I have to return the cylinders. 128.186.232.32 20:11, 21 November 2006 (UTC)


 * According to, ballon grade helium from a DIY store costs $50 for 300 cubic feet, which a quick and ugly Google calculation prices at 33 U.S. Dollars / kg or $660 altogether . The US government has set helium prices far lower than this , at $37.50/1000 ft3, which works out at a much more reasonable $7.41 per kilo , but commercial helium has such a massive markup on it. Mind you, standard ballon companies are much worse;  this company works out at $1000 per kilo!   La  ï  ka  22:06, 21 November 2006 (UTC)


 * I imagine that for the "party rental" places you are really just paying for the overhead, not the helium, which is likely in such small quantities that it really doesn't matter for the overall business costs. I bet if you found where the balloon companies get their helium, you could find it for a pretty decent price. --Fastfission 23:59, 21 November 2006 (UTC)


 * i'd suggest BOC Gases. Xcomradex 03:12, 22 November 2006 (UTC)


 * It would help if you specify in whic country. DirkvdM 08:09, 22 November 2006 (UTC)

The Black Sea
my science teacher was talking about the black sea and she would give any extra credit to who found out why it go its name I want to know if you can tell me if the Black Sea got its name from black cyanobacteria or if it got its name from something else?? please help!! —Preceding unsigned comment added by 24.62.129.188 (talk • contribs)


 * Have you considered looking at the article Black Sea. You'll probably get an answer a hell of a lot faster than waiting for someone to read the article for you. --Kainaw (talk) 21:36, 21 November 2006 (UTC)

i could care less can you tell me —Preceding unsigned comment added by 24.62.129.188 (talk • contribs)


 * The answer is contained in our article on the Black Sea. JBKramer 21:42, 21 November 2006 (UTC)


 * That's just rude, are you an only child? You sound like a spoiled brat, sign your posts and learn some manners and someone may be kind enough to help you. Vespine 21:44, 21 November 2006 (UTC)


 * Why would you bother asking a question if you don't care if someone would answer it? DMacks 22:14, 21 November 2006 (UTC)


 * You can care less? How much less? This is an encylopedia you know, all you have to do is type in "Black Sea" and look it up yourself to save us the time. X [' Mac Davis '] ( DESK | How's my driving? ) 22:39, 21 November 2006 (UTC)


 * Please dont attack the newbies, even if they are a bit impolite!--Light current 23:04, 21 November 2006 (UTC)

The expression is "couldn't care less". If you "could care less", that means you must care, at least a bit. This is perhaps the most misused expression by kids today. StuRat 01:41, 22 November 2006 (UTC)


 * I just dont care! 8-)--Light current 02:13, 22 November 2006 (UTC)


 * stares* just give the guy an answer, how hard can it be? It's a hw question but there's no need to BITE even if the person's being a little rude. "The motive for the name may be an ancient assignment of colors to the direction of the compass, black referring to the north, and red referring to the south....[...]...Another possible explanation comes from the color of the Black Sea's deep waters. Being further north than the Mediterranean Sea and much less saline, the microalgae concentration is much more rich, hence the dark color." (from Black Sea) -- `/aksha 03:51, 22 November 2006 (UTC)


 * Remember, it's not our policy to give homework answers. We want them to learn how to find answers themselves, not just go and ask somebody to do their homework for them. StuRat 04:58, 22 November 2006 (UTC)


 * Yes, i know. Which is why we should tell them to go and find their own answers. But in this case, it really doesn't take much effort to edit on an answer. Comments like "are you an only child? You sound like a spoiled brat" are really not all that productive. -- `/aksha 05:04, 22 November 2006 (UTC)


 * The purpose of the no homework policy isn't to keep us from having to do work, it's to enable the students to learn how to find answers on their own. They never learn this if we spoon-feed them the answers. StuRat 08:20, 22 November 2006 (UTC)


 * Can you please comment on my suggestion at Wikipedia_talk:Reference_desk/Science ? -- WikiCheng | Talk 07:20, 22 November 2006 (UTC)


 * This would seem appropriate to describe all comments after the forth one (by JBKramer).--hydnjo talk 14:44, 22 November 2006 (UTC)

Polarization filters
I was wondering if there's any way I could make a polarizing filter myself (or get it for free!). I live in the middle of a technological nowhere in Brazil, so this stuff is hard - if not impossible - to find around here. Filters for cameras are very expensive, and won't work with what I want (they need to be flexible and easy to cut in any shape)

The thing is, whenever I get my hands in some electronic junk with a LCD screen, I remove their LCD screens and take the polarizing filters on them. They are little, flexible pieces of plastic, exactly the kind of material I want. The problem is that they are never big enough (I need at least one 10cm x 10cm piece).

Is there any way I could fabricate this material myself? Or is there any place I could get such a thing for a reasonable price? (or even for free - as a free sample and such?)

Thanks for any help. ☢  Ҡ i∊ ff   ⌇  ↯  22:08, 21 November 2006 (UTC)


 * It kind of depends on the application you have in mind. Making the stuff yourself is a nonstarter, but sheets of plastic polarizing film – often under the trade name Polaroid – can be had for relatively little money.  The first site I came across which ships to Brazil was here, which sells a 21x30cm polarizing film for about nine U.S. dollars.  (They also appear to have monster sheets of 63x90cm, plus some other specialty stuff.)  Shipping to Brazil looks to be $5 for a single sheet, but that price goes down if you buy more.  Note that I'm not affiliated with that seller, and I haven't purchased from them so I can't endorse their stuff.  Hope that gets you started, anyway.  TenOfAllTrades(talk) 22:43, 21 November 2006 (UTC)


 * Well, my plan is some sort of cross between scientific experiment and art project. On an important note, it can't be those thin adhesive films since they're usually too flexible and well, adhesive. That P120 on that website seems to be just right. I'll try to look for it somewhere nearby. Any more ideas? ☢  Ҡ i∊ ff   ⌇  ↯  00:01, 22 November 2006 (UTC)


 * Sounds interesting! If the problems are "too flexible" and "too sticky", why not use the stickiness to stick it to something stiffer? DMacks 03:19, 22 November 2006 (UTC)


 * Actually, the problem is finding ANY polarizing film around here.
 * On an additional question, what's the name of those filters that when sandwiched between two polarized filters, they present a particular hue? These can also be found inside LCD screens (and apparently they're the source of the rainbow effect when you press them - but I could be wrong). They don't behave the same way as the other filters, and they have no effect at all if not between two polarizing filters. ☢  Ҡ i∊ ff   ⌇  ↯  04:53, 22 November 2006 (UTC)


 * I can't guarantee this is right/will work but if you want to make your own polarising filter you need a optically active substance that absorbs light. One possible solution if iodised starch (the starch is chiral) - make a starch solution (dilute) filter it to get it free of undissolved starch. Now add iodine (can you get iodine tincture from a chemist ? - it's a disinfectant comes in small bottles). The solution should turn black/dark blue. Now all you need to do is cover a glass plate or otherwise with the solution - I'd suggest using a mist sprayer or airbrush to spray on a thin film - let the water evaporate then spray on some more.. I hope this will work. (Maybe someone else knows of a suitable compound - I've also heard than quinine salts can work - can you get quinine?)87.102.36.82 13:46, 22 November 2006 (UTC)

Psychologist
Say I had a psychological problem, how would I go about finding a therapist for me? X [' Mac Davis '] ( DESK | How's my driving? ) 22:38, 21 November 2006 (UTC)


 * See your doctor first.--Light current 23:02, 21 November 2006 (UTC)


 * If you are in Britain, make an appointment to see your GP and explain your worries. They are supposed to work out who you need to see and help set it up. If it were more urgent, you could: go to the local A&E and explain the problem or, if you can find a contact number for them, call your local mental health crisis team. Skittle 23:28, 21 November 2006 (UTC)


 * Mac not be from these here parts! Arrr! I think he's American or something 8-)--Light current 23:42, 21 November 2006 (UTC)


 * I feared as much. I did look for clues on his userpage, but answer came there none. Skittle 23:44, 21 November 2006 (UTC)
 * Ah. When I go to England I was speak as such. French fri... err chips give there me to please? X [' Mac Davis '] ( DESK | How's my driving? ) 01:04, 22 November 2006 (UTC)


 * In the US: if you have health insurance, check with your provider. They will have a list of what sorts of therapy they support and a list of therapists they will pay for. If you don't have health insurance: check the yellow pages, there are lots in there. If you need it to be cheap and don't have insurance, look for therapists who advertise having a "sliding scale" fee policy. --24.147.86.187 03:05, 22 November 2006 (UTC)
 * Then again you might want it to be good, over cheap? X [' Mac Davis '] ( DESK | How's my driving? ) 06:16, 22 November 2006 (UTC)
 * You know the drill: we do not and cannot give medical or psychological advice. But a regular doctor, General Practitioner, Family Doctor can prescribe drugs to treat mental illness, but might refer you to a Psychiatrist, who can do psychotherapy as well as prescribing drugs to treat anxiety, depression, psychosis, etc. The G.P. or psychiatrist might refer you to a psychologist or other practitioner (clinical social worker) who could do talking therapies. Some medical plans have the psychiatrist do only the medication management and have the psychologist or clinical social worker do the talking therapy. Some plans want you to call for approval in advance to get full coverage. Edison 06:33, 22 November 2006 (UTC)

coordination compounds
What would the possible isomers of Co3+ coordinated to the tridentate ligand DETA be? I'm more interested in the geometric isomers, but would there be optical isomers as well? I'm most interested in structure... would there be trans and cis for these? Thanks ~ Mike 130.207.180.50 23:14, 21 November 2006 (UTC)


 * Just to be sure, you do mean cobalt, not carbon trioxide, right ? StuRat 01:36, 22 November 2006 (UTC)


 * try building it out of models. i'm trying to picture it in my head, and i think i can see an optical isomer in this octahedral complex (N and n represent the donors from two different DETA's, numbered along the chain 1-3):

N3 N2 |  n1   \ | / Co     + mirror image / | \ N1 |  n2     n3


 * --Xcomradex 02:16, 22 November 2006 (UTC)


 * There are many isomers including the two above, Note in the above example there are 2 more pairs of optical isomers resulting from 'rotating' one ligand 120 degrees e.g

N3 N2 |  n2   \ | / Co     + mirror image / | \ N1 |  n3     n1

OOPS DID YOU SPOT MY DELIBERATE MISTAKE - the image below is the mirror image of the one above.. Actually not deliberate - just a mistake.87.102.36.82 N3 N2 |  n3   \ | / Co     + mirror image   IGNORE THIS / | \ N1 |  n1     n2

also non chiral:

n3 N2 |  N3   \ | / Co      / | \ N1 | n1     n2 Maybe there are others - again this is assuming only octahedral mononuclear complexs are formed...So it is a simplification87.102.36.82 13:35, 22 November 2006 (UTC)

Opposite effect of Helium on voice...
Almost everyone knows how Helium affects the voice but, is there another gas that can make the opposite affect? i.e. make the voice deeper? Please note that if such a gas/mixture of gases exists, I certainly do not wish to attempt it. I`m just curious. Thanks, Dave


 * Lighter than air gases, like helium, make you squeak. Heavier than air gases make you sound deep.  Krypton and sulfur hexaflouride are examples of relatively safe substances that could be used this way.  Dragons flight 00:18, 22 November 2006 (UTC)


 * To round out the list, Xenon is another. Interesting that you thought of sulfur hexafluoride though... --HappyCamper 00:34, 22 November 2006 (UTC)


 * Xenon is not safe to breathe; even though chemically inert, it is a general anesthetic!! --Anonymous, 07:00 UTC, November 23.


 * Would carbon dioxide work? --Kurt Shaped Box 00:45, 22 November 2006 (UTC)


 * Yes, but breathing it in sufficient quantities is potentially quite dangerous (i.e. deadly) because of the way your body reacts to high levels of carbon dioxide in your blood. Only a minute or two exposure above a 10% concentration will knock you out.  It can also form carbonic acid in your mucus membranes which I imagine would be quite unpleasant.  All together, I would strongly recommend not trying to breath high concentrations of carbon dioxide.  Dragons flight 01:27, 22 November 2006 (UTC)


 * Thank you so much Dragons flight, so precise and concise. I love it, but, this begs a follow-up... I clicked on both links, and found their respective 'speeds of sound', but SF6(sorry, I don`t know how to do a subscript) gives 2 results for 'speed of sound'. Not NECESSARILY important, just a note. 340m/s versus 120m/s? Why? I`m an amateur audio/studio technician and wonder if 'breathing-in' these gases, and, if safe to do so, could 'allow' a 'singer' to achieve a note he/she couldn`t do so otherwise? Would 'achievable' frequencies be proportionel to 'speed of sound' of THAT other gas? I find this MOST interesting! Thanks again, Dave 172.132.147.26 00:58, 22 November 2006 (UTC)


 * If a singer wants to change the pitch of their voice, that's easy enough to do with electronics, even in real time, if needed. StuRat 01:32, 22 November 2006 (UTC)


 * These gases affect the resonant modes of your vocal cavity, and so they affect the timbre of your voice but not the pitch. Helium causes high frequency overtones to be emphasized (at the expense of low frequencies), hence the squeak, and heavy gases do the reverse.  However, neither case significantly affects the fundementals of how fast your vocal cords can vibrate, so a trained vocalist would still produce the same range of notes, just with a greatly altered suite of accompanying harmonics.  Dragons flight 01:47, 22 November 2006 (UTC)


 * Agreed StuRat, but that always sounds fake/artificial. How would it actually SOUND if utilizing one of those OTHER methods?...I just read your last edit Dragons flight...are you saying that one couldn`t actually get a 'deeper' voice?...just that the 'highs' would be subdued? Thank you, Dave 172.132.147.26 01:54, 22 November 2006 (UTC)


 * Don't you think helium voices sound fake ? They always make people laugh, after all. StuRat 08:16, 22 November 2006 (UTC)


 * i've heard a rumor that argon does it, never tried it though. its much cheaper than xenon too, if you're considering trying this. Xcomradex 02:08, 22 November 2006 (UTC)


 * An interesting application of this idea (beyond the trivial) is that of using a gas in which the speed of sound is less than it is in air. The idea is to fill the inside of a loudspeaker cabinet with a bag full of the gas. THis would make the cabinet seem bigger to the drive unit and could also cutdown the size of those massive transmission line speakers. I think CO2 would be suitable. I'm not sure if this idea has ever been incorporated into commercial speakers.--Light current 02:24, 22 November 2006 (UTC)


 * A co-worker once started a discussion with me on that subject- we had access to dewars of liquid nitrogen, and practically unlimited supplies of gaseous nitrogen. Being heavier than air, we assumed it would deepen one's voice and so have the opposite effect of helium.  However, being heavier than air, it would also tend to settle in the lungs and not come out, thus displacing oxygen and potentially asphyxiating the experimenter.  After realizing that, neither one of us was willing to try it out.  192.168.1.1 8:15pm, 21 November 2006 (PST)


 * Unlike CO2, the body doesn't react like it's asphyxiating with Nitrogen. If you displace oxygen with CO2, you will start breathing faster to try to get more O2.  If you displace oxygen with nitrogen, you won't react at all.  Nitrogen is inert but very dangerous in a confined space.  --Tbeatty 04:45, 22 November 2006 (UTC)


 * Jesus God, we are careful to tell people about the limitations of our advice for medical and legal, and then people are telling other people about breathing fluorine componds??? Or CO2? Or liquid nitrogen? Do nothing without adequate adult supervision and follow all safety advisories includind MSDS sheets. Edison 06:38, 22 November 2006 (UTC)
 * Not to mention xenon -- see above. --Anon.
 * To be fair, 192 suggested gaseous N2, not liquid. GeeJo (t)⁄(c) &bull; 08:01, 22 November 2006 (UTC)


 * LOL. How stupid would one have to be? DirkvdM 08:18, 22 November 2006 (UTC)


 * I remember reading about a case a while back in which a chemistry student, after being shown the trick of sipping a tiny amount of liquid N2 (fairly safe if you're careful, since it forms an evaporating bed of gas before it hits your tongue. Lets you blow smoke at people!), tried to glug some as a party trick thinking it'd work the same way. When she swallowed, her epiglottis held the stuff close enough to freeze the surrounding tissue, and ended up causing a fair amount of damage. GeeJo (t)⁄(c) &bull; 11:41, 22 November 2006 (UTC)
 * Wasn't there a couple of guys who died after getting the bright idea of putting on oxygen masks and hooking them up to a tank of nitrous oxide whilst searching for that extra-special high? --Kurt Shaped Box 22:46, 22 November 2006 (UTC)
 * Couldn't you just hang upside down to let it out? DirkvdM 08:17, 22 November 2006 (UTC)


 * A couple of thoughts. First, nitrogen gas (molecular weight: 28) is lighter than oxygen gas (molecular weight: 32) and slightly lighter than air (average, effective molecular weight near that of nitrogen).  Nitrogen gas produced from boiling liquid nitrogen tends to sink because it's cooler (and consequently denser) than the surrounding room air; if you were to inhale the gas, it would be very quickly warmed to your body's temperature and be slightly less dense than normal air.  Of course, the difference is small enough so as to be almost negligible in terms of the sound of your voice.
 * With respect to heavier-than-air gases 'settling' in the lungs and becoming trapped, you have nothing to worry about. Exhaling compresses the lungs and forces much of the gas out.  Inhalation creates sufficient mixing that residual gases will be diluted and flushed out on during successive breaths.  (If this didn't happen, then carbon dioxide would sit in the bottom of your lungs and kill you, yes?)  The inhalation of heavier-than-air gases has been used for valid (albeit highly specialized) medical purposes for decades.  Xenon, for example, has been tested as a contrast agent for lung imaging in certain x-ray and MRI methods.  TenOfAllTrades(talk) 00:30, 23 November 2006 (UTC)


 * I seem to remember that the Exploratorium had a balloon of CO2 that functioned as a lens for sound. &mdash;Tamfang 05:57, 24 November 2006 (UTC)