Wikipedia:Reference desk/Archives/Science/2006 November 30

= November 30 =

Left and Right Side of the heart
What is the advantage of having the blood on the right side of the heart separated from that on the left side?


 * Perhaps there is a wikipedia article you could check ;) Nevertheless...as a start to the answer, blood in the heart is either received from the body coming back from use, or its been oxygenated and its coming back from the lungs...Now what do you think in terms of efficiency (so getting blood back to the body thats fresh - with oxygen as fast as possible) if you were mixing oxygenated and deoxygenated blood? 74.102.89.241 02:30, 30 November 2006 (UTC)


 * Apart from heart, the article about double circulatory system might be specifically relevant to this query, can someone nominate the diagram for PotD?? haha.. Vespine 02:50, 30 November 2006 (UTC)

BACTERIA.........
Which bacteria was the first one, to be named scientifically(binomial nomenclature)? -Thanking you,--Pupunwiki 02:48, 30 November 2006 (UTC)
 * We have someone work on getting the Bacteria article to featured quality. You might want to read that or, if it doesn't say, ask at Talk:Bacteria. - Mgm|(talk) 09:52, 30 November 2006 (UTC)

maximum RPM
What is the highest RPM ever recorded for a mechanical device with a diameter greater than an inch? 71.100.6.152 05:09, 30 November 2006 (UTC)
 * That's a bit vague, dude. You're gonna have to be a bit more specific.

Environmental Effects of Tobacco
Leaving aside health issues, if all the smoke from all the cigarettes, cigars, pipes etc that have ever been smoked throughout history was suddenly removed, would there be any appreciable effect at all on the climate or the environment? JackofOz 07:15, 30 November 2006 (UTC)
 * I'd say that the amount of carbon put into the air from smoking is utterly negligible compared to the amount added by industry, forest fires, etc. It'd be slightly higher if you factor in the production as well as the products, but I'm still not sure the effect would be appreciable. Of course, if you want to count factors arising from the butterfly effect, such as various scientists, politicians, and other key figures living longer as a result of not smoking, you might notice a difference. GeeJo (t)⁄(c) &bull; 08:31, 30 November 2006 (UTC)


 * Suppose a billion people smoke a thousand cigarettes per year (for easy calculation). A cigarette contains 1 gramme of tobacco. That's a billion kg. The Earth's total biomass is in the vicinity of 100 billion tonnes. So the yearly tobacco production and consumption accounts for one hundred thousandth of the total biomass. Or am I now comparing apples and oranges? We should be looking at the amount of plant matter that is renewed per year. Anyway, the tobacco plants are grown before the are burnt, so the net CO2 effect should be zero, if that's what you mean. DirkvdM 10:27, 30 November 2006 (UTC)


 * Amount of CO2 released smoking the tobacco is almost exactly equal to the amount of CO2 absorbed growing that tobacco. So the answer is no, no direct effect. An (indirect) effect of vast hordes of healthy but disgruntled former smokers roaming the planet can not be readily assessed, however. ;) --Dr_Dima.

They may die, but they won't care
Ignoring cost, legality, and common sense, would cocaine, either hydrochloride or freebase, work as an adequate rat poison if worked into their food? GeeJo (t)⁄(c) &bull; 08:37, 30 November 2006 (UTC)


 * It's got a lethal dose, so yes, of course. Do you mean to ask how much would be needed? DirkvdM 10:31, 30 November 2006 (UTC)


 * Hence the word "adequate" in the question. Ie. is the lethal dose so high that it'd be unlikely that the rat would consume enough in a normal meal? GeeJo (t)⁄(c) &bull; 11:39, 30 November 2006 (UTC)


 * The LD50 of cocaine when administered to mice is 95.1 mg/kg. (Bedford JA, Turner CE, Elsohly HN (1982). "Comparative lethality of coca and cocaine". Pharmacol Biochem Behav 17 (5): 1087–1088.). Assuming a rat has a similar LD50 as a mouse when it comes to coke, and it's a big rat, it would weigh in in at 500g.  You want to kill almost all the rats, not 50% of rats, so double the dose.  Then the rat would need to ingest (95.1 x 0.500 x 2 =) 95.1 mg of pure cocaine.


 * As coke's usually cut to around a 10% purity nowadays, you wouid therefore need to administer (95.1 x 10 =) 951 mg of cocaine to the rat, or about a gram. This would be around 0.5 mL of freebase (as the solubility of coke is 1800 mg/mL).  Entirely possible.  I suggest putting it in the middle of chips (fries) - rats love those!


 * Cheery reading on the effects of a lethal dose of cocaine (from the article) - toxicity results in seizures, followed by respiratory and circulatory depression of medullar origin. This may lead to death from respiratory failure, stroke, cerebral hemorrhage, or heart-failure. Cocaine is also highly pyrogenic, because the stimulation and increased muscular activity cause greater heat production. Heat loss is inhibited by the intense vasoconstriction. Cocaine-induced hyperthermia may cause muscle cell destruction and myoglobinuria resulting in renal failure. There is no specific antidote for cocaine overdose.


 * Incidentally, the lethal dose of cocaine for a human is around 150 grams, depending on your body weight.  Proto ::  type  12:50, 30 November 2006 (UTC)

Sell the critter a little coke cut with rat poison; that should cover all bases.Wolfgangus 12:58, 30 November 2006 (UTC)


 * Interesting. According to cocaine a gram costs between USD$40 and USD$80.  According to the above, it would take nearly a gram to kill one rat.  So I guess that's an expensive way to kill a rat!  192.168.1.1 7:51pm, 30 November 2006 (PST)

Energy Divided by Mass or Volume
Is there any such measuremnt that is "energy divided by mass" or "energy divided by volume"? The Anonymous One 09:34, 30 November 2006 (UTC)
 * For the former, going by E=mc2, E/m = c2. So measuring the speed of light is equivalent to measuring the square root of "energy divided by mass". For the latter, see Energy density. GeeJo (t)⁄(c) &bull; 10:02, 30 November 2006 (UTC)


 * This isn't entirely true, simply because "energy" is ambiguous. What you've said is true for the total relativistic energy of an object and its invariant mass (when it's at rest, or its relativistic mass in general).  But often we mean some other kind of energy: for instance, the specific energy (energy per mass, as Melchoir pointed out) of a battery should not be interpreted merely as $$c^2$$, but rather as the useful extractable energy of the battery divided by the mass of the chemicals inside (or perhaps the whole mass of the battery, for a practical measure).  These concepts (and realizing how to precisely define them) are extremely important for such things as modern automobile design; it makes a lot of difference if the energy you need to drive to the next town can be stored in 30kg of gasoline (taking up about 40 L), or a 300kg battery that might only take up 20L, or just 10kg of hydrogen but that takes 70L!  (Note: numbers fabricated.)  --Tardis 23:25, 30 November 2006 (UTC)


 * You mean 'is there such a unit of measurement'? Of course. 'Energy per mass' or 'energy per volume' might mean how much energy one could extract from a certain amount of fuel. Were you thinking of something in particular or just pondering on units in general? DirkvdM 10:35, 30 November 2006 (UTC)
 * Energy / volume would be Energy density. As is normal to name most things per volume, but yes I suppose for a fuel it might be different. I think the concept of energy density is used in electromagnetism and electromagnetic waves in particular.137.138.46.155 12:46, 30 November 2006 (UTC)
 * Isn't energy/volume related to pressure (for a gas)


 * It can be related to anything that has to do with energy per volume. So it's not as straightforward as a metre meaning one unambiguous thing. I don't know what it could mean in gas pressure, but in my example it could be the amount of energy that a typical engine can extract from a litre of fuel (in which case you'd have to specify the engine). Or it could be the amount of energy that a typical human body can extract from a certain amount of a certain type of food, something that can often be found on the packaging (confusingly usually also expressed in calories when the 'real' unit of of energy is Joule, but that's a different issue). DirkvdM 20:38, 30 November 2006 (UTC)


 * The internal energy of an ideal gas is $$PV$$, so its energy density is just $$P$$, yes. --Tardis 23:25, 30 November 2006 (UTC)

Specific energy. Melchoir 20:19, 30 November 2006 (UTC)

We also have Specific kinetic energy, another stub, and Specific orbital energy, a decent article. Melchoir 20:24, 30 November 2006 (UTC)

When I said "energy divided by mass" "energy divided by volume", I did NOT mean by a unit of measurement. I mean by a type of measurement, just like length, mass, or time. The Anonymous One 00:34, 2 December 2006 (UTC)

Sustainability of nuclear fission
I heard that the amount of uranium on Earth would be enough to satisfy the world's energy demands for ten years. I looked at the relevant Wikipedia articles, but there seems to be a lot of confusion about this. Is this figure reliable and is it based on today's energy demand and known reserves? DirkvdM 10:41, 30 November 2006 (UTC)


 * The reason you'll get so many different estimates is that there are a large number of variables involved, so there is no one 'straight' answer. For instance, it depends what kind of reactors we use, some designs use considerably less Uranium than others (as they use the fission products to generate further electricity). Then there is the key question of, much like with all fossil fuels, economic extraction. There is a stupendous amount of Uranium on the planet (it's about as common as zinc or tin ), the question is at what point does it become too expensive to extract. For instance, there is some Uranium in sea water, but the concentrations are very small, so a lot of seawater would need to be processed to extract it. So the question is not "when will Uranium run out?", but "when will Uranium become too expensive to extract?". The same problems dogs estimates of how much longer coal, oil and gas reserves will last - there is an awful lot of each left, but it's getting harder and harder (read: expensive) to extract. &mdash; QuantumEleven 11:45, 30 November 2006 (UTC)

I remember they were going to mine a low-grade uranium deposit near my cottage, but then the prices fell, and it was abandoned. There are a lot of these types of deposits. It's the same with oil; we are never going to run out of oil, just cheap oil. --Zeizmic 12:43, 30 November 2006 (UTC)


 * See Breeder reactor. These create nuclear fuel by converting non-fissile material into fuel. The problem is the products of reactor operation could be used to make bombs. So today most power reactors use a fuel cycle where the used fuel has to be stored in high tech repositories for many thousands of years. In the U.S, such a repository has been proposed but not placed in service, so used fuel is generally stored at the power plants indefinitely. With breeder reactors, fuel exhaustion would be a long, l-o-o-o-ng time in the future. Edison 16:35, 30 November 2006 (UTC)

So can a reasonable estimate be made? Politicians have to use this sort of info to decide if they should build new plants, so what assumptions would they make? Was that estimate of ten years reasonable or complete bull? Renewable_energy says some estimate was that we could use nuclear energy (fission?) for billions of years. Those estimates differ quite a bit, to put it mildly. DirkvdM 20:44, 30 November 2006 (UTC)


 * Where did you hear 10 years ? That seems absurdly low by any estimate.  Maybe that's how much uranium we have on hand without mining any more. StuRat 04:04, 1 December 2006 (UTC)


 * That would be silly. I heard it from someone who was supposed to know what he was talking about. I suppose he meant the known economically viable resources, but I wanted to be sure, so I asked. But the 'billions of years' really sounds absurd. DirkvdM 08:12, 1 December 2006 (UTC)


 * Not really. The Earth's core has been kept hot for billions of years, due to radioactivity, and that takes far more energy than people use. StuRat 08:35, 1 December 2006 (UTC)


 * Structure of the Earth says that is just one person's theory and that it is generally believed the heat is a residue. I thought it was a result of tidal forces. Anyway, for most of Earth's history most of the heat will have been a leftover of the initial heat, so your argument only holds true to a degree, if at all. Btw, that section also answers a similar question I had asked myself before - why the Uranium isn't all at the core. It seems it is mostly bound to lighter elements and therefore in the crust. But is also says a lot of it is in the innermost core. Confusing. DirkvdM 10:16, 2 December 2006 (UTC)


 * Due to volcanism, heavier elements are routinely spewed out onto the surface as a result of convection cells within the mantle. This mixes up the light and heavy elements, like stirring a drink with sugar at the bottom. StuRat 15:56, 2 December 2006 (UTC)


 * Yeah, I thought of that, but that's the mantle. The article speaks of the core. DirkvdM 07:23, 3 December 2006 (UTC)

Minaret construction
structural detail of minaret construction, step by step stage construction of minaret —The preceding unsigned comment was added by 41.204.224.130 (talk • contribs).


 * In what way is a minaret unique from other similar construction projects?


 * Atlant 16:01, 30 November 2006 (UTC)

Short dipole antenna
I guess I should know this, but still feel I need to ask. If now the current distribution on a short dipole antenna is triangular (as stated in the article), does that mean that the charge distribution is constant along each wire? Is this still the case as the frequency approaches zero? Thanks. —Bromskloss 19:32, 30 November 2006 (UTC)

Botulism
Is there some evolutionary advantage behind the development of botulinum toxin by Clostridium botulinum? Since it works by dicking around with acetylcholine, I can't imagine it having too much effect on its microbial competition, so is there some reason it might develop such an effective weapon to use against higher organisms? Given the toxin's complexity, it seems unlikely that it'd be produced as a random byproduct. GeeJo (t)⁄(c) &bull; 19:41, 30 November 2006 (UTC)
 * One can speculate that it may have some benefit as one way of obtaining an anaerobic food rich environment. There may be some trend in anaerobic bacteria to modify their environment to suit them, but I have not seen it described as such. Seejyb 21:08, 30 November 2006 (UTC)
 * According to Reinhard Jahn, "Protein toxins are highly sophisticated weapons that bacteria use to manipulate or kill eukaryotic cells or even entire organisms with minimal effort, thus providing a source of nutrients for their survival and proliferation," and "the purpose of the toxins: to block neuromuscular synaptic transmission and to kill the cell or organism that then serves as fermenter for bacterial proliferation" --JWSchmidt 23:08, 30 November 2006 (UTC)
 * Because the botulinum toxin genes remain unaltered in laboratory strains of Botulinum, it's likely that they have some function in addition to killing animals for food - probably multiple functions. But we don't know what they may be at this point. - Nunh-huh 00:18, 1 December 2006 (UTC)

Lovebird question
My pet lovebird has been behaving strangely recently. She's taken to chewing up my books, newpapers, telephone directory, etc into little strips and stuffing them into the feathers on her back. She does it with cigarette butts too. She's strutting around on the floor with these pieces of paper sticking out of her feathers, it looks absolutely hilarious. Sometimes she tries to fly with them, ends up losing most of them, then spends ages picking them up and positioning them again. Anyone else seen their birds doing this? What's the point of this behaviour? Just play that only makes sense to lovebirds? --84.64.164.71 19:46, 30 November 2006 (UTC)


 * You're lovebird sounds hawt! maybe I was one in a past life! ;) My completely wild guess is that it is some strange form of mating ritual, maybe she's just lonely? I thought lovebirds like living in pairs? Vespine 21:43, 30 November 2006 (UTC)


 * They do - but they don't have to. It's an urban myth that a single lovebird will die of loneliness. Like any parrot, they can make fine pets if given enough attention and intellectual stimulation (if not, they can go insane). I used to have one myself (lone bird) but she never did anything like that with her feathers. She did like to chew on anything chewable though (books, magazines, wallpaper, anything made of wood). She once excavated a cavity in the side of my sofa, I guess due to her nesting instinct kicking in when spring came around. --84.64.164.71 23:11, 30 November 2006 (UTC)

EDIT: No, I'm not answering my own question. The person who asked this is a friend of mine on the same network of PCs. --84.64.164.71 23:13, 30 November 2006 (UTC)

I suspect it's a short-circuit of two different instincts:

1) The urge to rip up suitable sized strips of soft materials and place them in the nest.

2) The urge to prune their feathers.

I've noticed that cats often have the instinct to scratch in the dirt after defecating, but don't seem to know that the whole object is to bury the feces, unless shown by a mother cat. Perhaps your bird can't quite figure out what it's instincts mean without training from it's parents. This also reminds me of the Star Trek episode where Nomad was a combination of two robots, one sent to seek out new civilizations and the other sent to sterilize soil samples. The resulting robot tried to sterilize new civilizations, LOL. StuRat 03:44, 1 December 2006 (UTC)


 * In a truly whack experiment, researchers found that in some species of bird, the females would choose a male who had a little chef's hat on his head, and the bigger the hat, the greater the preference of the females. Maybe your female lovebird's instinct is telling her that the additions will make her more appealing to potential mates. Edison 05:43, 1 December 2006 (UTC)


 * Ornithologists really must be a sad bunch to think of testing that out in the first place. GeeJo (t)⁄(c) &bull; 09:05, 1 December 2006 (UTC)


 * Agreed. If I had a little chef's hat, I'd never do that with it. StuRat 18:03, 1 December 2006 (UTC)


 * I believe it started with an observation that in the species the male with the most impressive crest or feathers sprouting from the head had the most luck with the ladies. Of course in the most intelligent species, nothing like that could occur, so thinning hair is no impediment, right? Edison 19:00, 1 December 2006 (UTC)

This is nesting behavior. My lovebird used to do the same thing, and then started laying infertile eggs. If your does too, just let her sit on them until she is bored. And please keep the cigarette butts away from her — they are very dangerous to birds. --Ginkgo 100 talk 20:52, 1 December 2006 (UTC)

breath
Why is your breath colder when you purse your lips?


 * If it is any colder, it is due to going from higher pressure in your mouth to lower pressure outside your mouth. Air gets colder when it suddenly drops in pressure.  The temperature difference should be very small compared to blowing without pursing your lips - though it may be measurable. --Kainaw (talk) 20:38, 30 November 2006 (UTC)


 * That would mean the temperature of the air in your mouth would also rise by the same amount, because it gets compressed, wouldn't it? And I don't feel that. Another possibility is that the wind chill factor increases when the airflow is made narrower. But I doubt if that is the only factor. Maybe a combination of the two? Plus a third one? Anyone? DirkvdM 20:54, 30 November 2006 (UTC)


 * I think I have this one. It has SOME to do with 'wind chill factor', but just on the 'surface'...pardon the pun. Your skin 'holds' a layer of 'skin-temperature-air' close to the surface of your skin. If that layer is 'blown away' by your breath, or otherwise, that thinner layer of warmer-than-ambient-air, is displaced, by relatively cool air, therefore feeling cooler. The temperature of the air of your breath cools-down fast! You can also get the same effect by blowing with your mouth 'wide open', if you blow hard/fast enough. The air from your mouth feels warm if you blow softly. So, this only 'works' if the temperature of the air, coming out of your mouth, is cooler than the air in the very proximity of your skin. A blow torch would still feel MUCH hotter if it were made to displace this 'said' air close to your skin, no matter how FAST the torch was 'blowing'. I hope this answers your question, and doesn`t beg for a dozen or so MORE! lol Dave172.163.70.157 21:48, 30 November 2006 (UTC)


 * I doubt it's really much colder, I'd like to know how the OP came to that conclusion. If it is just from blowing on their hand, then pursed lips create a more concentrated stream of air which is better at removing the ambient layer of warm air that is naturally created by your your skin, hence feeling colder. Vespine 21:40, 30 November 2006 (UTC)


 * The faster air from pursed lips causes more evaporation from the skin - giving a greater cooling effect?


 * I think it's measurably cooler. Try opening your mouth as wide as you can and blowing out as hard as possible.  Hot air!  But limiting the flow by pursing your lips makes the pressure difference greater... and you get a chill just like a discharging aerosol can.


 * Oh right, you mean like that! Well do this: cup both your hands around your mouth and nose so as to create an enclosed cavity around your mouth and then blow out as hard as you can with your lips pursed and you'll see that the air coming out of your pursed mouth is just as hot as when your mouth is opened, but if you let it travel over your skin with it will remove the ambient layer of warm air that your skin creates, like I said in my above post, and I agree that moisture evaporation will also be part of the effect. Vespine 22:24, 30 November 2006 (UTC)


 * I think you`re responding to MY response Vespine. If so, I`ll try to re-respond. Please note that I said blowing with mouth 'wide open', not with lips pursed. YOU try it. If you blow hard enough, it feels cool, regardless of humidity. I hope this doesn`t detract from the initial 'unsigned' questioner! Dave172.163.70.157 22:44, 30 November 2006 (UTC)


 * Believe its due to turbulence and mixing of the airflow at a short distance from the mouth. If you measure the gas temp right at the orifice (regardleass of shape) Im sure you will find it at about body temperature. Howver if you move the thermometer a few cm away from the orifice the static air temp will be that of the surrounding atmosphere. However this air is cuased to move by the hot air from your mouth and thus can show a chill factor on the hand etc. just like any moving air does. --Light current 23:04, 30 November 2006 (UTC)


 * Tough to follow what you`re trying to say here Light. Could you please make an attempt at clarifying? Dave172.163.70.157 23:11, 30 November 2006 (UTC)

Especially LAST sentence?


 * Im saying that
 * the air from the mouth is always hot,
 * it mixes with and moves the colder air
 * this mixture impacts the hand (or other body part)
 * the body part experiences a wind chill effect
 * hence the air seems cold
 * 8-)--Light current 23:40, 30 November 2006 (UTC)


 * I hate when people do this to ME but..."it mixes with and moves the colder air". Huh?
 * Nevermind. Gotcha. I still have to 'stick' with my conjecture that if blowing hard/fast enough, the air from the mouth will come out cool. I`ve tried it HERE! NOW! That`s not an arguement to YOUR 'findings' though Light. Dave172.163.70.157 00:12, 1 December 2006 (UTC)


 * No put your finger right in your mouth and blow. Is it hot or cold?--Light current 00:16, 1 December 2006 (UTC)


 * We`re not talking about the temperature IN your mouth Light, but outside. So, without being rude, I think yout arguement is invalid. No offense. Dave172.163.70.157 00:23, 1 December 2006 (UTC)


 * How do you manage to purse your lips when you have your finger in your mouth? GeeJo (t)⁄(c) &bull; 10:13, 1 December 2006 (UTC)


 * No, do my hand cupping experiment, if you blow with pursed lips into your cupped hands instead of letting the airflow wash over the surface of your skin you will see that the air coming out of your mouth IS warm. It's the washing effect that makes it seem cold. Vespine 00:31, 1 December 2006 (UTC)


 * A chilling explanation. BTW thats the way you can warm your nose in the winter.


 * Yeah, Vespine's experiment convinced me that it really is the wind chill factor, so my reservations were unjust. It really makes a huge difference. I once stood on a windy ridge and was shivering. I didn't have any more warm clothes to put on, just a plastic poncho, so I put that on. I was instantly warm because I had stopped the wind chill. DirkvdM 08:20, 1 December 2006 (UTC)


 * Just to get back so science vs speculation: The air exiting your mouth - ignoring respiratory dead space, which is valid for a resting respiratory pattern - is always body temperature, fully saturated with water vapour. You can rewrite the physiology books if you prove otherwise. What you perceive a few cm away from your mouth, and using your skin as a sensor is a different issue, which has been set out above (Bernoulli principle, Venturi effect, evaporative cooling). Seejyb 10:17, 1 December 2006 (UTC)

coal making
just wondering if it would be possible to make your own coal by: 1. getting dead plants 2. compacting at great pressure and heating massively 3. Coal!

would it work and if so you should try it thanks
 * Well, there is an artificial coal, produced by subjecting the peat to incremental increases in temperature up to 60°C and pressures to 14.48 MPa over a four-week period in the special installation. --Brand спойт 20:58, 30 November 2006 (UTC)


 * Maybe its possible, but I woulnd't really know what advantage it would give you 8-|--Light current 22:56, 30 November 2006 (UTC)


 * Agreed, you would likely put more energy into it than you would get out. Also, the dead plants may have uses as fertilizer (after composting), etc., which provides a better economic value for them. StuRat 03:29, 1 December 2006 (UTC)


 * However, if the point of the exercise is to get energy, you'd probably be better of just burning the biomass directly, or turning it into biogas and burning that, or making ethanol or biodiesel for high-value transport fuel rather than low-value stationary energy that is better supplied by nuclear power IMHO ;) --Robert Merkel 03:33, 1 December 2006 (UTC)


 * Unless it's been dried out first, it's likely to have too high of a moisture content to burn well, and wouldn't burn cleanly in any case. StuRat 08:25, 1 December 2006 (UTC)


 * After edit conflict:
 * Heating under pressure means no oxygen can get to it, so you get charcoal, right? Then again, part of the purpose of that is to get rid of humidity, so compression won't help there. DirkvdM 08:28, 1 December 2006 (UTC)

Water Scientific term
What is the scientific term that states that a drop water does not behave the same way for us as, for instance, an ant?
 * It does behave the same, but because the ant is smaller, there's a good chance he could walk over the water without disturbing the droplet because of the surface tension which people can't. Ants generally don't do water, so am not sure they can, but a lot of small animals can do this. - Mgm|(talk) 21:41, 30 November 2006 (UTC)


 * Scale (spatial)? Scalability? Or do you mean something specifically about water? DirkvdM 08:37, 1 December 2006 (UTC)

Also see Reynolds number If you make a tiny model of an airplane wing, you have to increase the air velocity many times to get the same flow. Insects live with the funny bits about this number. --Zeizmic 14:08, 1 December 2006 (UTC)


 * Yes, the viscous effects of the water start having more effect the smaller the scale you get down to. The phenomena keeping the small creature above the surface is known as surface tension.


 * Incidentally, if you get down to really small scales, such as bacteria, then you get a Stokes flow, which is reversible. The bacteria's tails have to move in a helical motion to propel it forward. But I digress. Readro 18:20, 3 December 2006 (UTC)

Molecules & Chemical Formula of Medicines?
I am wondering how people make up how the molecules of a medicine looks like? For example, Citalopram a popular anti-depressant known as Celexa, has the following image for the molecule:



& the formula is C20H21F1N2O1.

My question is how do they make an image of the molecule, they can't see the molecule via a microscope, and how do they make the chemical formula of the molecule?--Records 21:09, 30 November 2006 (UTC)


 * Have a look at our article on X-ray crystallography. That's one of the techniques used. - Nunh-huh 21:13, 30 November 2006 (UTC)


 * Also such compounds are made by chemical synthesis, assembled from smaller molecules by chemical reactions that have well understood and predictable behaviour; therefor when making a compound they will know what structure to expect because they knew what starting materials and reactions they used to make it.
 * The image (as in your picture) is a representation of the molecule (like a technical drawing or blueprint) - even if there was a microscope that could see molecules it would look different to the image.
 * The chemical formula will also be known in the same way the structure is known - because the scientists that make it know what smaller building blocks they used.
 * Even so the formula and structure need to be confirmed (in case an unusual reaction has happened) - typicaly the structure is confirmed by NMR, infrared spectroscopy and other methods. The chemical formula can be confirmed by chemical analysis.
 * Note the chemical formula can be got from the image of the molecule - in this case unmarked vertices (the points connecting the lines) represent carbon - so by just counting the number of each type of atom gives the chemical formula
 * I hope I've answered your question - apologies if any of it sounds condescending - It's not totally clear to me what you need to know so I've tried to cover most of it.83.100.138.110 21:41, 30 November 2006 (UTC)
 * Note - the formula seem wrong to me shouldn't it be C20H21F1N2O1 and not C20H22F1N2O1 ? Please check and correct.


 * I got the formula from Citalopram, why does it seem wrong?--Records 22:31, 30 November 2006 (UTC)


 * I just counted the hydrogens and only found 21 - maybe I missed one..83.100.138.110 23:13, 30 November 2006 (UTC)


 * Because it is! It was (sort of) vandalized a long time ago.  Part of it was fixed, but not all; I've just fixed the hydrogen count.  The molecular weight as given is correct; it was also broken, but was later fixed.  --Tardis 23:14, 30 November 2006 (UTC)


 * Corrected it in my question. Thnx --Records 05:50, 1 December 2006 (UTC)


 * Say we merged Citalopram, Bupropion & Clonazepam together. What would the new image look like for the molecule, and what will be the new chemical formula?

Citalopram:

+

Bupropion:

+

Clonazepam:

Citalopram: C20H21F1N2O1

+

Bupropion: C13H18Cl1N1O1

+

Clonazepam C15H10Cl1N3O3

--Records 22:54, 30 November 2006 (UTC)


 * That's an interesting question. We could add them together my making abitrary joins between the molecules, but I don't think that's what you're asking. There's no proceedure in chemistry for merging molecules (eg I'm assuming you mean something like merging a square and circle to make a square with rounded corners). Chemical structures have a set framework - there's no intermediate - it's like asking to merge a square and a triangle - I can't really give you a answer.83.100.138.110 23:17, 30 November 2006 (UTC)


 * Ooh...this is a very interesting!! This is addressed in the heart of organic chemistry, and organic synthesis. The pictures given in the articles are a rendition of the molecule - indeed, nobody has ever "seen" a molecule, but we can come up with a model that is consistent with a tremendous body of scientific knowledge. From this, we have confidence that the picture gives us something reasonable that summarizes all that data. You might take a look at our article on tamiflu - it gives two synthesis routes for that medication, and might give you a general idea of the sort of thinking involved with solving these problems. For a classic, see Nicolaou Taxol total synthesis. --HappyCamper 00:17, 1 December 2006 (UTC)


 * As someone who is currently waiting for my reaction to run (another two hours or so, YES!) before I go home...Most active chemists don't make a molecule out of nowhere, we build them slowly step by step. Thus, we know what we expect to get out of the next reaction, and know what to look for. Yes, X-ray is a technique that can be used but it is expensive and relies on you able to meake a solid crystal (not always possible). Most structure determination is done through a technique called Nuclear Magnetic Resonance Spectroscopy. This works by using the fact that in a magnetic field, all atoms in a molecule "resonate" at a different frequency of applied magnetic field. They do this because they are in different chemical environments due to thae shape of the molecule. This technique can give you information about how atoms are linked together, and about how they are arranged in space relative to one another. It is fast, cheap, and easy to interpret, despite what hordes of undergrads will tell you...---John

The starting material of Citalopram, (4-bromo-2-(hydroxymethyl)phenyl)-(4-chlorophenyl)-(3-dimethylaminopropyl) methanol was prepared in the following manner:

A Grignard reaction-solution prepared from 220 grams (1.15 mol) of p-chlorobromobenzene and 29 grams of magnesium turnings (1.2 mol) in 1500 milliliters of dry ether was added dropwise in the course of one hour to a suspension of 213 grams of 5-bromphthalide (1 mol) in 1500 milliliters of dry tetrahydrofuran. The temperature was not allowed to rise over 10 degrees Centigrade. After the addition was completed the reaction mixture was stirred for three hours at room temperature. The mixture was then poured into 2 liters of icewater and 100 milliliters of saturated aqueous ammonium chloride were added. The etherphase was separated and the water-tetrahydrofuranphase extracted once with 500 milliliters of ether. The etherphase was washed with water, dried over anhydrous magnesiumsulphate, filtered and evaporated in vacuum to yield 320 grams of 2-hydroxymethyl-4-bromo-4'-chloro-benzophenone in the form of a yellow oil which was not purified further but used directly in the next step. The 320 grams of oil were dissolved in 200 milliliters of dry tetrahydrofuran and added dropwise to a great excess of N,N-dimethylaminopropyl magnesium chloride in tetrahydrofuran under gentle reflux. After completed addition the mixture was refluxed over night. The reaction mixture was then poured into 5 liters of icewater and 200 milliliters of saturated aqueous ammonium chloride solution added. The mixture was extracted with a total of 2500 milliliters of ether. The etherphase was then extracted with 20% aqueous acetic acid to acid reaction, whereupon the acetic acid solution was made alkaline with 10 N sodiumhydroxide solution. After cooling, the oil, which separated out, was extracted twice with 500 milliliters of ether. The combined ether extracts were dried over anhydrous potassium carbonate, treated with active carbon and evaporated in vacuum. The remaining oil consists of somewhat impure (4-bromo-2-(hydroxymethyl)phenyl)-(4-chlorophenyl)-(3-dimethylaminopropyl) methanol which was used in the next step without further purification. Yield: 219 grams.

The 218 grams of oil from the previous step were heated for three hours on a steam bath with 1800 milliliters of 60% aqueous phosphoric acid while stirring vigorously. The reaction mixture was neutralized with saturated aqueous ammonia while continuously adding ice. The reaction mixture was then extracted with 1500 milliliters of ether, the etherphase separated, dried over anhydrous potassium carbonate, treated with active carbon and evaporated in vacuum. The residue was distilled in vacuum and 105 grams of 1-(4'-chlorophenyl)-1-(3-dimethylaminopropyl)-5-bromophthalan was obtained as an oil which boiled at 188-190 degrees Centigrade/0.1mm Hg.

1. Above they say "220 grams (1.15 mol)" how can they tell the number of molecules?

2. What equipment do chemsists use to perform the above experiment i.e. Test tube and?

'3. Say we took a Citalopram tablet, Bupropion tablet, and Clonazepam tablet. Crushed it. Add water. Mix it up and then dry it. The resulting mix would be new molecule?'

(and thanks for all help given so far)--Records 06:44, 1 December 2006 (UTC)
 * 1. They use the molar mass - each moleclue is assumed to have a molar mass - the sum of the mass of the parts. Dividing the mass used by molar mass gives the number of 'moles'. A 'mole' is a standard measure of number of molecules. 1mol contains a set number of molecules.
 * In the case above the molar mass of chlorobromobenzene is ~192 grams per mole. So 220 grams has 220/192 moles = ~1.15moles. See Mole (unit)
 * 2. Probably not a test tube. More likely a round bottom flask connected to a condensor see Laboratory glassware. A book on experimental organic chemistry should give you more details.
 * 3. No. The result will be a mixture of Citalopram, Bupropion & Clonazepam plus the tablet filler (usually chalk). In this case it is unlikely that any reaction will have occurred.
 * Hope that helps.87.102.8.53 15:42, 1 December 2006 (UTC)

Please can you give me the chemical formula and image of Citalopram, Bupropion & Clonazepam when mixed together?
 * The mixture doesn't have a formula.. The original chemical formulas remain the same on mixing.

If a chemist uses Laboratory glassware, what equipment do Pharma companies use for mass production of medicines? --Records 03:39, 2 December 2006 (UTC)


 * They use larger scale versions of laboratory glassware, and also probably some stainless steel vessels - imagine a cross between a science lab and industrial food processing equipment.

83.100.253.51 14:16, 2 December 2006 (UTC)

Achilles tendon
What is the best way to restretch an achilles tendon that has become shortened due to persistent wearing of high heels?--Light current 23:36, 30 November 2006 (UTC)
 * This is not medical advice, of course, but from what I know, from being very involved in sports in my earlier days, is to lean forward, agaisnt a wall, at about a 30 or so degree angle, with arms straight out, feet flat on the ground/floor, and gradually making a 'reverse' push-up, bringing face close to the wall you`re leaning against. You can 'straddle', and stretch one tendon out at a time, if you like. Gradually increase distance as long as comfortable. Dave172.163.70.157 23:56, 30 November 2006 (UTC)Side note...I`d choose a different shoe if I were you Light! lol


 * Im asking on behalf of a lady friend.--Light current 00:14, 1 December 2006 (UTC)
 * " I " knew THAT! Dave172.163.70.157 00:19, 1 December 2006 (UTC)


 * There are other ways to make a lady friend's toes curl up.. ;) Vespine 00:28, 1 December 2006 (UTC)


 * I know. But its her heels that are curling!--Light current 00:33, 1 December 2006 (UTC)


 * Her heels are CURLING? You KNOW what we`re about to say. She needs a doctor Light...really! No need for any of us to say anything more HERE! Dave172.163.70.157 04:35, 1 December 2006 (UTC)


 * Yeah she was walking on tippy toes last week!--Light current 21:42, 3 December 2006 (UTC)


 * See Stretching. For the achilles tendon, the stretch listed above is good, as is standing on a bottom stair tread or curb (kerb) and letting the heel drop. DO NOT BOUNCE! A program of stretching is preferred to a single stretching exercise. Cats appear to be the masters of a regular program of stretching. Edison 05:47, 1 December 2006 (UTC)

How about gradually moving to shorter heels and then flats ? StuRat 03:23, 1 December 2006 (UTC)


 * Shes gone straight to flats after injuring her toe. That could be the problem!--Light current 21:43, 3 December 2006 (UTC)


 * Agreed, don't go "cold turkey". StuRat 09:32, 4 December 2006 (UTC)


 * It appears to be 3" or 0" heels in her wardrobe/shoe rack 8-(--Light current 15:26, 4 December 2006 (UTC)

Humidex vs. heat index...
Can anyone tell me/us what the difference is, if any, between what Canadians call HUMIDEX, and what Americans call HEAT-INDEX? I don`t know if either of these terms is utilized in other countries. Is barometric pressure involved in either of their calculations? I`ve observed some reports of Heat-index being measured at temperatures BELOW the actual 'regular' temperature. This doesn`t happen with the Canadians` Humidex. anyone KNOW? I`m curious because I often travel between the two countries. Dave172.163.70.157 23:42, 30 November 2006 (UTC)


 * In hot weather, the humidity has a definite effect on how hot people (or any animal that sweats) actually are. This is because high humidity retards evaporative cooling.  However, unlike the wind-chill index, where the basis for comparison (no wind) is obvious, there is no obvious basis for comparing humidity.  Zero humidity could be used as a basis, but that's a condition that rarely exists anywhere on Earth, so seems like an odd choice.  100% relative humidity could also be used as a basis, but that is also unusually humid in many places.  So, choosing a basis somewhere in between means that humidity can be either above or below that basis, leading to either a higher or lower temperature felt by humans than the "usual".  I'm not sure what humidity the two indices use as their basis, however, or if they are the same. StuRat 03:14, 1 December 2006 (UTC)

See the links I added to the title for more info on each (the Humidex link has a comparison of the two). StuRat 03:17, 1 December 2006 (UTC)


 * Thanks Stu. Do you believe the formulae for those indices? All that for just a GUESS at how warm it FEELS! Sheesh! Dave172.163.70.157 15:09, 1 December 2006 (UTC)


 * Yea, what a mess. You'd think that if it was just going to be an approximation, that a much simpler formula would suffice. StuRat 15:22, 1 December 2006 (UTC)