Wikipedia:Reference desk/Archives/Science/2006 November 24

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November 24

Mechanism of voice deeping due to testosterone

How exactly does this work? What happens to the vocal folds? X [Mac Davis] (DESK|How's my driving?) 00:37, 24 November 2006 (UTC)

They get thicker and change their movement characteristics. Differential growth of the chest and trachea at puberty result in differences in the size and movement of the air column, and also contribute to adult male:female differences of voice timbre. alteripse 01:06, 24 November 2006 (UTC)

Testosterone increases the size of the voice box thus deepening the tone! It also increases other things!--Light current 01:39, 24 November 2006 (UTC)

Carpal Tunnel Syndrome

How does one prevent it. Exercises? I have been playing a lot of piano lately, and am freaking out. Thanks. 71.252.11.5 02:25, 24 November 2006 (UTC)

As always, the answer is : See your doctor!--Light current 02:27, 24 November 2006 (UTC)

The usual response is to consult a doctor, but I've found that consulting a GP isn't necessarily illuminating. Have you read the carpal tunnel article? From personal experience, I find that regular stretches and range-of-motion exercises are important, but not just for the wrists, for shoulders too, and maintaining proper posture. This means two or three times a day stretching your fingers and wrists (the fingers back and thumbs to the front and back of wrist), as well as the wrist circle exercise, at least 10 each way. Also the finger wiggling and clenching/flexing exercises. They're so simple people don't bother doing them, but they really help. Also, shoulder rotation (carefully) and stretches, including stretching your biceps. Also shoulder shrugs and rolls, and careful neck stretches.

I've found that if I do get a bit of a sore wrist, ice helps. And once you do get sore, stretches and exercises can actually irritate it, so just take a few days off whatever you were doing, and ice for 10 minutes 3 times a day. BUT I'm not a doctor, giving you advice based on personal experience. Also, if you find you're having problems despite good posture and stretching (and hand position, obviously), try adjusting your stool height. Anchoress 02:36, 24 November 2006 (UTC)

No, you consult the doctor and insist (s)he refers you to someone who knows aboout the problem!--Light current 02:39, 24 November 2006 (UTC)

Of course, taking a break from any activity which causes you pain is almost always a good idea, to allow your body time to heal. StuRat 08:22, 24 November 2006 (UTC)

The right position at the piano might help, but I don't follow that advise myself. Instead I take a (stiff) walk every day for half an hour or so, letting my arms swing freely. It takes a week or so for that to start to help. Of course you should do this before you feel any effects, but then you'll never know if it would have been necessary. Very frustrating. But it's a good idea in general to go for a walk every day (get some fresh air, meet the neighbours). Another thing I noticed at the computer is that when something doesn't go my way I tense up and that sometimes causes pangs of pain (note that this doesn't happen anymore since I sewitched from msWindows to Linux). So it's better (again, also in general) to not get upset or tense up. The tensing up may happen when practising too much, so don't do that for too long. I noticed that when I keep on practising a specific bit and it doesn't seem to improve, when I play it the next day, it goes a lot better. So practise a difficult bit daily, but don't take it too far and give it some time to improve. DirkvdM 10:00, 24 November 2006 (UTC)

Ibuprofen and wrist braces both help a lot for minor repetitive strain injuries (in my experience). If you are really suffering though there are other approaches which can be taken, too, such as operations and things of that nature. Adjusting your posture when typing or playing is probably a first step, though — it seems to me that most repetitive strain injuries are often due to poor orthopedics. --24.147.86.187 15:24, 24 November 2006 (UTC)

Decomposition on the moon and in outer space?

Let's say a whale corpse is laying on the moon would it decompose differently without the oxygen? Would it decompose at all? How about in the middle of space, orbiting a star, and always warm but not cooking in the sun?

Without bacteria, and without weathering, I would expect decomposition not to occur at all. Now, whether the bacteria already inside the whale might survive in some capacity in space, I'm not 100% sure about, although I suspect it's too cold for them to do anything at the very least. -- SCZenz 05:12, 24 November 2006 (UTC)

The average temperature of a whale in near-Earth space would be roughly equal to the average surface temperature of Earth, or a bit less for lack of the "greenhouse" – let's say a bit above freezing. Anaerobic microbial activity should therefore continue so long as enough water has not yet sublimated and outgassed. Next comes weathering: no wind or rain, of course, but there's thermal stress (assuming the whale does not always keep the same side to the sun) and the slow sandblasting of micrometeors. —Tamfang 05:39, 24 November 2006 (UTC)

I think you underestimate the greenhouse effect. I'd say that all of the whale, in space, would remain frozen except for perhaps an inch deep on the side facing the Sun. StuRat 08:27, 24 November 2006 (UTC)

Don't be silly. The Moon's surface reaches temperatures above 100°C during the two weeks of daytime, before dropping far below freezing during the two weeks of night. Daytime heat would propagate deeply into the corpse by conduction. Now, water cannot exist in liquid form at zero pressure, but the cell walls will retain pressure for a while (a person can survive a few seconds' exposure to vacuum — the movie 2001: A Space Odyssey got it right). I would guess that the the cell walls will break down when the water starts boiling or freezing, whichever comes first (did the whale arrive by lunar day or lunar night?), if not sooner. --Anon, 22:45 UTC, Nov. 24.

Are we sure that there are no bacteria on moon (and other planets / satellites)? http://www.panspermia.org/bacteria.htm and http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=200 seem to suggest otherwise. Is it not possible that moon does have some micro-organisms and we don't know about it? -- WikiCheng | Talk 06:31, 24 November 2006 (UTC)

Wikicheng, I would say it is certainly possible there are bacteria on the Moon, but we have no actual evidence afaik. Absence of evidence is not necessarily evidence of absence; but equally, we can't assume it is evidence of presence. JackofOz 06:56, 24 November 2006 (UTC)

And even if there were bacteria, they would be so unfamiliar with whale biology that they wouldn't likely be able to decompose it. StuRat 07:53, 24 November 2006 (UTC)

Willzyx's corpse must have dried out before any significant biological decomposition could take place. Drying is an excellent technique for food preservation; think beef jerky, pemmican, and stockfish. It will take a long time before other forms of deterioration compromise the structural integrity. The next Moon expedition may be in for quite a shock.  --Lambiam^Talk 06:40, 24 November 2006 (UTC)

So ... if the whale is on the Moon, where is the bowl of petunias ? Gandalf61 10:56, 24 November 2006 (UTC)

Even down on the earth's surface, the sun provides about 1 kilowatt of energy per square meter. The sun side of the whale will get hot. The shade side will get cold. Exposed tissues will be hit by ultraviolet radiation from the sun inhibiting bacterial growth on the surface. Anerobic bacteria should be able to decompose the interior tissues. Moisture will evaporate or sublimate. Outgassing might produce enough spin to put it in rotisserie mode. It should shrivel and desicate. Mmmm, whale jerky! Edison 05:31, 27 November 2006 (UTC)

Weird, weird anatomy question (not medical advice)

I'm wondering (not for the purposes of criminal action or medical advice) what effect the removal of certain upper body bones would have on arm mobility. I'm mostly curious about the scapula, collarbone, sternum, and upper ribs. Would the complete removal of any of those bones result in the inability or significantly reduced ability to move one's arms? Anchoress 06:16, 24 November 2006 (UTC)

Have a look at the muscles attached to the scapula, and note that the glenoid is part of the scapula. Without the joint and muscles, the shoulder and upper arm would function only as a floppy hanging base for movement of the forearm and hand. Come to think of it, I do not know of a situation where someone would have a missing scapula but otherwise normal arm - the glenoid, coracoid or acromion may be missing, but total absence must be exceedingly rare. Assuming the shoulder glenohumeral joint and the capsule and muscles around it are intact, the other bones can all be removed without major problems relating to the degree of mobility of the arm as such. Ability to use normally - as opposed to ability to move, as in range of active motion - is a different issue, since strength and stability may be affected. The reduced stability and rigidity of the chest and shoulder girdle has to be compensated for by increased muscle strength and fibrous tissue growth. The difficult one is the sternum. Since there are no muscles which traverse it, its function would have to be taken over by fibrous tissue, but a wobbly chest and ribs that are not fixed anteriorly is a poor base for use of the arms. Seejyb 12:41, 24 November 2006 (UTC)

Thanks for the answer, Seejyb. I really appreciate the effort and detail. :-)) Anchoress 05:56, 25 November 2006 (UTC)

I knew somebody who lacked a clavicle, and I believe she said her mother did as well. She had no immediately obvious impairment from this, but I think her ability to lift with her arms was limited. --ColinFine 11:46, 26 November 2006 (UTC)

masturbation

does it really make you weak, fragile, skinnier and blinder?

I would say no, and why would it? Lol. Splintercellguy 09:55, 24 November 2006 (UTC)

Well, it's a form of exercise, so it should help getting skinnnier and stronger. You'd have to do it quite often for any such effect to be noticeable, though. Then again, it's less boring than most other forms of exercise. :) DirkvdM 10:05, 24 November 2006 (UTC)

It can do the opposite. Allegedly. A Sid the Sexist story, when he took delivery of satellite television (and thereby access to European porn channels) led to Sid developing enormous muscles on his right arm. Mind you, it was a cartoon. --Dweller 10:09, 24 November 2006 (UTC)

On a serious note, see Masturbation#Medical_attitudes which mentions that it is a myth -- WikiCheng | Talk 10:59, 24 November 2006 (UTC)

Perhaps. --Proficient 05:31, 27 November 2006 (UTC)

Question in Chemistry

please say me what is the products when NH₃ reacts with MnO₂,MnO₃ ,FeO,Fe₂O₃

DY⁺OH^-, better known as DoYourOwnHomeworkite. Laïka 15:26, 24 November 2006 (UTC)

That aside it would also help if you could be more specific as to the physical state of the reactants - e.g. solvent (if any), temperature. The reactivity of the solids you mention also varies with the method of preparation and history of the sample.

The state of NH₃is aquoes and others are solid

E=mc2 ... innovation?

I've read Wiki's page on Einstein's famous equation but I need to isolate something about it for an article and I can't: What, if anything, is it about the way he related matter to energy that can be regarded as an innovation independent of all the work leading up to its publication? Wolfgangus 10:12, 24 November 2006 (UTC)

Well, basically, everything. In short, Einstein came up with the revelation that matter and energy are essentially just different forms of the same thing, as the formula suggests - the speed of light squared in the formula is just a constant that relates them together. To put it simply, you can think of matter as condensed energy. Nobody else had come close to this idea. --jjron 12:09, 24 November 2006 (UTC)

That's not totally true, of course — people had been trying to relate matter to energy for a long time. It is not even that E=mc^2 is that revelatory in and of itself, but that such a simple (and accurate) relation would flow from his theory of special relativity. E=mc^2 did not become "the" equation until after it was touted as being behind the atomic bomb. (nothing illustrates that sort of deliberate connection made more than this cover from 1946, IMO) --24.147.86.187 15:21, 24 November 2006 (UTC)

Thank you so much for the answer. One follow-up: if matter is condensed energy, can it be accurately stated that energy is just a form of dissipated matter? Wolfgangus 12:40, 24 November 2006 (UTC)

That is accurate enough. As an example, in a nuclear reaction, such as a nuclear bomb, the massive amount of energy released comes from converting (or dissipating as you say) a tiny amount of mass directly to energy according to E = mc². BTW, you're welcome. --jjron 13:02, 24 November 2006 (UTC)

Er,.. what was E equal to before Einstein?--Light current 15:59, 24 November 2006 (UTC)

It's not a question of what E was equal to before Einstein; E=mc2 just expresses a relationship, and previously there weren't an (correctly expressed) relationships between energy and mass (to simplify things greatly—many tried to unify all matter through electromagnetism in the time before Einstein, but none of it worked out well). --24.147.86.187 16:17, 24 November 2006 (UTC)

Pardon? What about E = 1/2 mv²--Light current 16:19, 24 November 2006 (UTC)

Kepler's laws refer to something quite different and are not an attempt to unify energy and matter at all. --140.247.240.219 19:55, 24 November 2006 (UTC)

This has the answers you're looking for, as audio! Droud 16:24, 24 November 2006 (UTC)

Those are scientific explanations of the equation, not historical ones. I doubt anyone in that list, great physicists than they are, have much of an idea of the details behind the history that they didn't get out of physics textbooks. --140.247.240.219 19:55, 24 November 2006 (UTC)

Thanks to all for the spirited response. PS - that Time cover is brutally sublime, but he probably felt he deserved it. Wolfgangus 17:10, 24 November 2006 (UTC)

The Fundamental thing that Einstein related was that Mass and Energy are the same thing. That additional Kinetic energy acts as if more mass were added and that the amount of mass is related to the kinetic energy through his equation. --Tbeatty 23:48, 24 November 2006 (UTC)

Iron's role in the human body

I know that iron's the metal in hemoglobin, but what I'm curious about is this: Does it have to be iron that performs this function? Could another metal do it? CameoAppearance ^orate 12:03, 24 November 2006 (UTC)

Sure it could be a different metal, and in fact is in some animals. Refer to Hemocyanin where this function is performed by copper. Incidentally these creatures are true 'blue bloods', i.e., if you see their blood it looks blue rather than red. --jjron 12:14, 24 November 2006 (UTC)

Let's not forget about the iron's role in the cytochromes, or in electron transport, or in iron sulfur centers, since most of this is in the mitochondria, and they're pretty much the same in all animals, I'd say electron transport is pretty much an iron only function, no substitutions possible. That's not to say that iron is the only metal involved, just that it can't really be replaced in these roles, any more than you could swap the copper in an oxygen splitting complex with any other metal, and have it still work out--66.65.104.195 15:07, 24 November 2006 (UTC)

pure water

In comparison to pure deionised, distilled water what is the amount of dissolved undesirable elements, ions, compounds, gases etc in freezer ice.

Undesirable in what sense? Toxic? Dangerous? Bad tasting? Or simply unnecessary? Laïka 14:59, 24 November 2006 (UTC)

unnecessary - contaminents making it inpure..

This is a good place to start. This has details on allowable contaminant limits for the USA. Droud 16:31, 24 November 2006 (UTC)

were not interested in tap water, but distilled water from the freezer! --Light current 20:33, 24 November 2006 (UTC)

You meant the frost buildup in a refrigerator/freezer? Odors are volitile compounds, and they tend to condense on sufficiently cold surfaces. Frost in the freezer grows as water vapor condenses (sublimes) directly from gas to solid. So as frost grows, it becomes filled with all the concentrated odors from food in the fridge (as well as odors in the kitchen and house.) Melt the frost and the volitile compounds are released. Put some freezer frost in your hand and take a whiff. Whew! Fridge-stank! --Wjbeaty 22:38, 25 November 2006 (UTC)

What if you have no food in the freezer? And how impure would the melt water be?--Light current 22:50, 25 November 2006 (UTC)

Integrated circuits

hi, i wanted specific information on IC 7473 FOR SOME important work. It would be helpful if i got sone info...Thanking you, Eby

Here [1]--Light current 15:41, 24 November 2006 (UTC)

rounded screw heads

It's well known that philips screw heads can get rounded off with use.. Can someone say what type of screw head socket (or bolt head socket) is most resistant to rounding - preferable from personal experience? Thank you87.102.33.100 15:23, 24 November 2006 (UTC)

Don't know about screw type but make sure you use the correct screwdriver, with size and with type (bear in mind there is at least one other type that looks a bit like Philips). Don't overtighten. Pay attention. Once a screw starts rounding or the driver slipping, stop and look and try and work out what's wrong. I once had a screw, think it was TORX. Someone told me it was allen key type (hex) so I was using an allen key and didn't look properly it started rounding. I stopped but it then happened with another screw. I was wondering what the heck since the it seemed to be fit properly. It was only when I looked carefully I realised my mistake but a bit late... BTW, Screw#Types of screw drive may help Nil Einne 15:44, 24 November 2006 (UTC)

I prefer Posidriv screws which seem to have overtaken Phillips as the most common crosshead screw. Then of course there are hex bolts which I have never seen rounded unless abused with the wrong tool. I would think it impossible to round a hex socket using the correct size key. I think the key would bend first IMO> 8-)--Light current 15:48, 24 November 2006 (UTC)

Robertson screws (sometimes called "square recess" in the US, I think) are popular in Canada; the screwdriver likes to stay in the screw and there isn't the behavior that the least bit of overtorquing tends to destroy the screwhead. --Anon, 22:58 UTC, November 24.

If a srew head gets rounded off you're screwed. :) Plain old slotted heads are a whole lot better. I never understood the change to philips screw heads and the like. But one type, of which I don't know the name (anyone?), that does not round at all is a hexagonal hole, with a screwdriver that is just a bent hexagonal bar. An extremely simple solution (the way I like them) which works a lot better in most ways (the bent bar is also easier to operate because it gives you leverage). Why hasn't this completely taken over the screw world? DirkvdM 08:29, 25 November 2006 (UTC)

The plain old slotted head doesn't keep the screwdriver centered the way Philips and Robertson heads do. The name I know the bent hexagonal screwdriver by is Allen key; that article lists other names. --Anon, 11:55 UTC, Nov. 25.

I've always wondered that as well! Phillips are so terribly easy to wear out and have such an awful contact area... They're completely inefficient. I'm very fond of square (Robertson) and hex heads, though, but they're nearly impossible to come across here in Brazil. Simple polygonal slots seem to be the most logical solution to me, but my biggest issue is how most screwheads have shallow slots, and this is usually the biggest problem that causes wear.

Anyway, I'm pretty sure there are some white-collar hot-shots who dictated this stuff solely on money contracts. I can even picture these 60 year-old rich guys smoking their cigars and laughing at the world struggling to get those damned worn-out Phillips screws out. Damn them! ☢ Ҡi∊ff⌇↯ 08:48, 25 November 2006 (UTC)

Thanks for all your answers - actually I've had loads of problems with those hex head screws you all seem to like so much - mostly due to poor tolerances in the tools and cheap metal used for the tools. The reason philips screws are so bad (they are it's true) is that they are designed to cam out - it's useful in mass production with electric screwdrivers - they're really just a tighten once screw, not designed for repeated use. Lets work together to rid the world of these evil fastening devices. Thanks/83.100.138.7 15:16, 25 November 2006 (UTC)

I work in manufacturing and in my experience the phillips screw doesn't deserve all the bad press it is getting in this article. The biggest advantage of phillips over flat is that they keep the screwdriver centered by nature. Another advantage is that one can turn a phillips screw from a moderate angle without slipping out or sacrificing significant torque. Yet another advantage is that a correctly sized screw will fit snugly enough into a good phillips screwdriver well enough to stay put long enough to get it started in an inaccessible spot (without the need for magnetism, which doesn't work on stainless, brass, or aluminum anyway). Allen head screws do share some, but not all of these advantages. Although it is true that one can usually get a bit more torque into a flat head screw without damage, one can generally work with phillips with confidence and without damage if one always uses a well-made screwdriver in good condition and of the correct size and drives it with sufficient pressure to keep the screwdriver seated in the screw head. Benbrilling 06:53, 26 November 2006 (UTC)

another problem I've had with phillips is guessing what size head to use - for instance when assembling a table I found that 1,2 and 3 size worked.. I still don't know what the correct size was - no such problem with other screws.83.100.138.7 19:47, 25 November 2006 (UTC)

Don't complain that any size fits. That's a benefit. Actually the one that fits best gives the best torque. If it's too small it gives poor torque and if it's too big, don't worry, it won't go in at all. And it's an advantage that there are only 3 sizes. With a bit of practice you will find it easy to guess which size screwdriver to use, and with a perfect fit. On the other hand, with a slotted screw you have to not only get the right width but also the right thickness to fit perfectly, thus getting the best torque. I have seen thousands of screws in my day and far more of the chewed up ones have been slotted. --Benbrilling 06:53, 26 November 2006 (UTC)

Torx screws are very good.

Meanwhile, I think Phillips screws are probably popular because the self-centering nature of the screw/driver relationship makes semi-automated assembly very simple (as compared to a flat-slotted screwhead). And they're probably cheaper than Allen (hex-recess) screws and Torx srews, although Torx is becoming very popular in American high-end electronics and most American-designed automobiles.

Atlant 16:58, 27 November 2006 (UTC)

Calculating Conductivity

Ok, I'm doing a report on silicon's semiconductivity properties. One thing I'd like help with is calculating conductivity, I'd like to acheive a value for the silicons conductivity in siemens with and without phosphorous doping at room temperature, and I'm not quite sure how to go about this. Even if there is a value listed on wikipedia (or anywhere else) for there conductivity I still need to know how to calculate it. I dont know how to calculate it, so heres what I've gathered so far. Please also help me verify the info I have got, as I'm not sure how factually accurate it actually is.

• In standard silicon the energy recquired to free an electron from the higest level in the electron shell in order to conduct is approx 0.75eV
  • Therefore approx 1 in 10¹⁰ electrons is free at room temperature
• In doped silicon (1 part in 10⁶ is phosphorous) each phosphorous atom contributes four electrons which are approximately as difficult to remove (0.75 eV) as silicon ones (as they have entered into covalent bonds with silicon), and 1 electron that does not bond, which recquires approx 0.01eV to free.
  • Doping increases the number of free electrons from approx 1 in 10¹⁰ by a factor of 10⁴ at room temperature (roughly)

I hope this is enough info to calculate conductivity, if not, I hope there is sufficent explanation to collect other neccesary information, thank you very much for your help in advance. Philc _T^E_C^I 16:18, 24 November 2006 (UTC) I hope this is enough info to calculate conductivity, if not, I hope there is sufficent explanation to collect other neccesary information, thank you very much for your help in advance. Philc _T^E_C^I 16:18, 24 November 2006 (UTC)

I'll try to start you off - take 1 cubic meter of silicon - calculate its mass (multiply by density), then calculate the number of moles (divide by Si atomic mass), calculate number of atoms (multiply by avogadro's constant). Now multiply by number of electrons contributed by each Si atom to the conduction band (don't know what this is possibly 8?).Now multiply by fraction of free electrons. This gives you the number of free electrons in the cubic meter sample. ("A coulomb is then equal to exactly 6.241 509 629 152 65×1018" electrons from coulomb). Now you need the drift velocity. The current will be equal to drift velocity times total free coloumbic charge(please check this..). The conductance is the current divided by voltage. Hope this helps - 87.102.33.100 16:56, 24 November 2006 (UTC)There are probably other and better ways to do this..87.102.33.100 16:59, 24 November 2006 (UTC)

So if I have 4 valence electrons per atom, multiplied by avogadros constant, divided by 10¹⁰ (1 in 10¹⁰ is free) that will give me free electrons per mole;

${\frac {4\times 6.0221415\times 10^{23}}{10^{10}}}=2.4088566\times 10^{14}\ \mathbf {e} _{free}\,mol^{-1}$ in pure silicon

so this added to the 1 electron contributed by 1 part in every 10⁶ when doped gives;

${\frac {4\times 6.0221415\times 10^{23}}{10^{10}}}+{\frac {6.0221415\times 10^{23}}{10^{6}}}=6.02455036\times 10^{17}\ \mathbf {e} _{free}\,mol^{-1}$ in phosphourous doped silicon.

I think this is right.

Your method for obtaining the conductance while im sure works, needs experimental data which I dont have, I'm sure there must be a way of calculating conductance, as I have given all of the factors that affect (or atleast I think I have) Philc _T^E_C^I 18:18, 24 November 2006 (UTC)

Looking back at what I suggested - it seem that all I did was to convert your request for conductance into a request for drift velocity..

Thinking about it some more I notice that as conductance is the reciprocal of resistance - and the resistance of a sample will cause a voltage drop across the sample - and hence with current flowing - a power loss: it must be true that the resitance/conductance must be caused by power/energy dissapated in the silicon when current flows. I can't suggest an easy way to calculate this.. Any energy required to 'ionise' an electron would surely be regained on the other side as it leaves the sample? Totally stumped - someone else please suggest..87.102.33.100 19:55, 24 November 2006 (UTC)

Too complicated. For doping, you need to know N_AN_D = n_i². Then you can plug these into the standard resistance equation which I believe uses both acceptor and donor concentrations for resistance. --Tbeatty 04:19, 25 November 2006 (UTC)

Is there an article or link where N_AN_D = n_i² is explained? Philc _T^E_C^I 11:15, 25 November 2006 (UTC)

Couldn't find it on WP but S.M. Sze "Semiconductor Physics" will have it. It's the classical reference. --Tbeatty 21:59, 25 November 2006 (UTC)

All I remember from my semiconductor physics class is that is you put in a bit more dopant then the required amount, the semiconductor is said to be "doped into total degeneracy" which is a most memorable phrase. Edison 05:22, 27 November 2006 (UTC)

Iron Ingestion

I remember hearing somewhere that iron should not be taken alongside foods/tablets containing vitamin C, since iron prohibits vitamin C from being absorbed and hence makes it pretty useless. Or it might be the other way around - maybe vitamin C stops iron from being ingested. It might not even be vitamin C which does this - my memory is hazy on this subject.

Either way, I've seen some multi-vitamin tablets which contain both iron and vitamin C. Are these effective? If so, how do they manage to get around the effect one of the ingredients has on the other? RevenDS 16:54, 24 November 2006 (UTC)

Actually, Vitamin C is necessary for iron absorption. It prevents the formation of insoluble and unabsorbable iron compounds and reduces ferric to ferrous iron, which seems to be a requirement for the uptake of iron into the mucosal cells. (Just in passing, and just because it darts through my head, I note that iron poisoning is very common in children, and occurs mainly after ingestion of vitamins containing iron....) - Nunh-huh 16:59, 24 November 2006 (UTC)

So would that mean that it is necessary to have vitamin C with iron? Therefore, you should not have iron without vitamin C if you want it to be effective? RevenDS 19:10, 24 November 2006 (UTC)

No, necessary was a bad word for me to use. My point was that Vitamin C increases iron absorption, rather than decreases it, as postulated by the questioner. But if you are taking iron you presumably want to absorb what you're taking, and vitamin C will help you to do it. - Nunh-huh 19:53, 24 November 2006 (UTC)

Just ferritin around I found it! 8-)--Light current 19:48, 24 November 2006 (UTC)

I use ferrous gluconate with a vitamin C tablet. It's very powerful, and you have to be careful to watch for effects. Most likely the first effect is that it bungs you up. --Zeizmic 20:50, 24 November 2006 (UTC)

Yes, Vitamin C promotes iron absorption. Perhaps you were thinking of caffeine, which inhibits iron absorption? EdC 23:28, 24 November 2006 (UTC)

So if youre anaemic, its better to go decaff?--Light current 23:29, 24 November 2006 (UTC)

While I am certainly not giving medical advice here, I personally would not take iron supplements unless I had been specifically diagnosed with an iron deficiency. Too little iron is not good, but too much can be very bad indeed. There was a hypothesis floating around for a while that excess iron is a major cause of heart disease. I don't know how much acceptance it has these days. Partly it was based on the observation that heart disease is more common in men (who don't lose iron every month), post-menopausal women (ditto) and red-meat eaters. --Trovatore 05:12, 25 November 2006 (UTC)

Crystal structure affecting properties of Group 2 metals

I'd be very grateful for any helpful pointers you have here, even if it is a just a link to a site with the answer. I've found out that Be and Mg are Hexagonal Close Packed crystal structures; Ba is Body Centred Cubic and Sr and Ca are Face Centred Cubic. However, I can't find anywhere telling me how this crystal arrangement can affect the physical properties of a pure metallic sample of the substance. Any guidance would be greatly appreciated! Thanks, --86.139.127.29 17:28, 24 November 2006 (UTC)

One immediate impact is the co-ordination number. HCP and FCC are close-packed structures with a co-ordination number of 12, but in BCC it is only 8.--G N Frykman 19:15, 24 November 2006 (UTC)

The physical properties (strength, melting point etc) of a HCP or FCC structure would be very similar all other things being equal.. So in your case atomic radius amongst other factors would be a big factor in the physical properties. As for Ba I can't see any logical reason why it would be BCC when 12 coordiantion is clearly easily attainable - are you sure it is body centered cubic?87.102.33.100 19:31, 24 November 2006 (UTC)

So crystal structure has little effect on physical properties? I was told that the fact that Calcium has a higher melting temperature than Be is because of the crystal structure of Ca. Why is this? As for the structure of Ba being body centred cubic, I got that information from the barium page... Is it incorrect? --86.139.127.29 21:26, 25 November 2006 (UTC)

(Be/Ba typo? above?)

Going down the group 2 metals (data from wikipedia)

m.p.: Be 1560 Mg 923 Ca 1115 Sr 1050 Ba 1000 (Ra 973?) (in kelvin)

Ignoring Mg for now, the melting point decreases going down the column.

(at least) Two factors contribute here; the mass of the atom - heavier things melt and boil higher (as in the flourine, chlorine, bromine, iodine series).

The other factor is the strength of interaction between the atoms - which will probably decrease going down the column. It seems that the interatomic interactions have the upper hand here.

I can't explain the 'blip' at magnesium..

Note that otherwise the harder elements melt higher (hardness is also a measure of interatomic interaction strength).

As for the crystal structure of Barium I haven't verified its structure but as I mentioned above - is there any reason why it would not be 12 coordinate close packed.. 83.100.138.7 22:51, 25 November 2006 (UTC)

Removing a wart

A wanted to remove a wart that I got (it's not viral). Pls don't tell me to go to the doctor, because I won't. It is too small. Would it be a good idea to burn it with a hot iron? I could also connect a wire to the oven to keep it hot and put the other extreme of the wire on it. Is it a good idea?132.231.54.1 20:09, 24 November 2006 (UTC)

Probably not. Don't pharmacists sell little patches you can just stick on the skin than slowly burn it away or am I thinking of something else?

Not a good idea to burn it. Get some wart solution from the chemist. Salicylic acid--Light current 20:31, 24 November 2006 (UTC)

I think "freezing" it away is a better idea. Either physically, with dry ice, or chemically, with salicylic acid that is sold as wart remover.

Yeah but freezing reqiures the use of liquid nitrogen and it hurts like hell! BTW ALL warts are caused by a virus! --Light current 20:35, 24 November 2006 (UTC)

Why would salicylic acid work here? I suppose it is only good against viral warts, not natural ones.Mr.K. 20:37, 24 November 2006 (UTC)

Wharts a non viral wart? Look at the page on warts!--Light current 20:39, 24 November 2006 (UTC)

Do you believe everything that wikipedia tells you? Cysts are a kind of non viral warts.Mr.K. 20:49, 24 November 2006 (UTC)

No! I must insist: Cysts are cysts!--Light current 20:50, 24 November 2006 (UTC)

In medicine yes. But, coloquially you are probably wrong. Some people use the word wart, cyst and fibroma for the same purpose. See the [1b] meaning. Mr.K. 20:52, 24 November 2006 (UTC)

'Sigh'. Let the guy remove his "wart" if he wants to. --Russoc4 21:05, 24 November 2006 (UTC)

Yes but burning is not a good idea! Is there a doctor in the house? 8-(--Light current 22:09, 24 November 2006 (UTC)

But this is supposed to be the science reference desk. If people use terms inaccurately, we should correct them. More significantly, if question ansker doesn't know the difference between a wart and a cyst, he/she might not be able to tell whether his/her "wart" is non-viral Nil Einne 06:19, 25 November 2006 (UTC)

I once burned off a wart with a cigarette. Yes, it hurt. Yes, I was drunk when I did it. Yes, it got rid of the thing. There's much better ways of doing it, though. See your doc - he can refer you to the liquid nitrogen people. --Kurt Shaped Box 23:24, 24 November 2006 (UTC)

Well, my doctor used a laser to burn it off (with some anathestic) on my hand of course. 61.14.88.77 03:52, 25 November 2006 (UTC)

When I was a kid my parents told me I could get rid of warts by putting the juice of some plant on it. And it worked. Later I heard that that is just make believe (a placebo). You can think warts away, so if you believe something (anything) will work it will. Hmmm, have I spoilt it now? DirkvdM 08:58, 25 November 2006 (UTC)

Last time I had one the pharmacist sold me some special ice spray to remove it. I think it was the same kind as the cooling spray the is used in to treat sports injuries but with a special "applicator" nozzle. And there is of course all kinds of fluids and tinctures which actually work. Just find a competent pharamcist and ask. 85.124.48.161 22:29, 27 November 2006 (UTC)

Hydrazone

Where might I be able to find a drawn out mechanism for the creation of a hydrazone from an aldehyde and hydrazine? Or is it as simple as drawing an arrow from the oxygen on the aldehyde to the nitrogen on the hydrazine? --Russoc4 20:19, 24 November 2006 (UTC)

Scheme 1 here http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/1991/56/i04/f-pdf/f_jo00004a016.pdf gives mechanism - in general it's nucleophilic attack by hydrazine N on carbonyl C followed by proton transfer and elimination of water.87.102.33.100 20:35, 24 November 2006 (UTC)

You have been most helpful. Thanks :) --Russoc4 20:53, 24 November 2006 (UTC)

toxicology

I am doing a school science project about ricin and its potential as a biological weapon. The guidelines stated that I had to do a project about ecology or life science, but I'm not sure if this counts as life science. I asked my teachers and friends, but they've all said different things. Please help!

Ricin if anything is a product of the vegetable oil industry - it comes from the 'husks' of de fatted castor beans (see of course ricin) The main product is castor oil (hence the tradename Castrol) If your project extended to the castor bean in general and included ricin as an aside then this would just about fit into the ecology/lifescience remit.. But that would reduce the amount of stuff about ricin itself to a small fraction of your project.. If you were to extend your project to include mode of action, possible other uses etc then i guess that is in life science. However as it stands your project 'Ricin and its potential as a biological weapon' sounds like military topic to me. I think it's close enough to go ahead with if you really want to.

It doesn't sound like "ecology" to me. "Life science" is pretty vague, though, and if you talked about the effects of ricin on the human anatomical system it would probably count as a "life science" project. Talking about it in political or military terms though would quickly move you out of the realm of "life science," though. --140.247.240.219 22:07, 24 November 2006 (UTC)

The study of the plant synthesis and biological effects of ricin would be life science, but an isolated discussion of a delivery system probably not. The latter subject may nevertheless be appropriate if it were described in relation to the requirements for absorption of the poison, which would be the study of the living target (e.g. life science says you have to inhale it, therefore the delivery system needs to address this). I think you are on life science ground. Seejyb 00:33, 25 November 2006 (UTC)

It would seem to me that the opinion that matters is the opinion of your teachers, specifically the ones who would be grading this project (I assume it's graded). If they don't agree, depending on how things work in your school you might be able to convince them if you can back up your view sufficiently but it would seem to me it would be far better to just accept their opinion even if others don't agree with them Nil Einne 06:03, 25 November 2006 (UTC)

Death is part of life. DirkvdM 08:59, 25 November 2006 (UTC)

Well, I'm going to discuss how the biological and chemical properties of ricin would make it an effective biological weapon. I mean stuff like how its toxicity and how easy it is to make, and how that affects its effectiveness as a biological weapon.

Silly, perhaps, anatomical question.....

Are blood vessels 'alive'? If blood vessels are alive, how do they get 'fed'? Do they retrieve nutrients/oxygen from the blood they`re 'carrying'? That would make sense for arteries, but how about from the depleted blood flowing through veins? Is there still enough 'stuff' left for the veins to be nourished? Do blood vessels feed themselves? Thanks, Dave 172.144.28.171 23:27, 24 November 2006 (UTC)

As for your first question, yes. Blood vessels are alive in the sense that they are made of living cells like everything else in the human body. However, due to their specialization, neither the blood vessels nor the cells that make them up could survive independently except under contrived, laboratory conditions, so this may be why they do not seem as if they are alive. Dar-Ape 00:38, 25 November 2006 (UTC)

To expand slightly: the endothelial cells, which are in direct contact with the blood, and cells to a depth of several layers, do quite nicely on what can be obtained by direct contact. The small vessels are able to obtain nutrients and oxygen via direct diffusion. Larger vessels require an actual blood supply: vessels that supply vessels are vasa vasorum - Nunh-huh 00:45, 25 November 2006 (UTC)

Thanks so much for your answers but I`ll tell you what prompted me to ask it/them. Maybe I should have just asked what I wanted answered in the first place. To the point...I was thinking about by-pass surgery. I knew that surgeons often 'recruited' blood vessels from the legs and such for this purpose. I`ve seen surgeries on TV, and have watched 'new' arteries being connected, but the surgeons, from what I could observe, never connected any blood vessels to these 'new' arteries. How are these 'new' arteries fed? Sorry if I wasted anyone`s time with my first post. Thank you, Dave 172.144.28.171 02:13, 25 November 2006 (UTC)

In coronary artery bypass surgery the radial artery or saphenous vein are often used to connect the aorta or left internal mammary artery to the coronary arteries. These 'new arteries' are fed by the blood flowing through them.Mmoneypenny 18:57, 25 November 2006 (UTC)