Wikipedia:Reference desk/Archives/Science/2006 November 14

= November 14 =

Bismuth-213
When the isotope bismuth-213 emits an alpha particle, what new element results? what if it emits a beta particle? Thanks!!

You're gonna have to make this homework question less obvious if you want it answered. Consider: Bismuth is element 83, yours has a mass of 213, find out how many neutrons and protons it has, then subtract the number of neutrons and protons in an alpha particle, and recalculate the element number of the result. Repeat for a beta particle. Tuckerekcut 01:03, 14 November 2006 (UTC)


 * Elementary! --Light current 01:07, 14 November 2006 (UTC)


 * By the way, bismuth-213 is a ficticious isotope. --Bowlhover 01:11, 14 November 2006 (UTC)


 * So is the question a trick?--Light current 01:33, 14 November 2006 (UTC)


 * What do you mean, it is fictitious? According to Isotopes of bismuth, it has a half-life of around 46 minutes. — Knowledge Seeker দ 03:13, 14 November 2006 (UTC)


 * I wonder why the article Bismuth doesnt link to Isotopes of Bismuth?--Light current 03:27, 14 November 2006 (UTC)


 * It does, at the bottom of the element box, on the right side. StuRat 04:24, 14 November 2006 (UTC)


 * I've been very careless lately; I looked at the list of 3 isotopes in the Bismuth article, and assumed that they were the only ones. I don't think I saw the "isotopes of bismuth" link.  --Bowlhover 04:34, 14 November 2006 (UTC)


 * Isotopes never really become "fictitious", they just become more and more unstable. You might say oxygen-24 is the heaviest isotope of oxygen, but my colleague Calem Hoffman is writing a paper on oxygen-25. It's unbound to neutron decay, so its lifetime is so short that its energy has a large range because of the uncertainty principle between energy and time. Still, it's a legitimate state that has objective reality. —Keenan Pepper 06:08, 14 November 2006 (UTC)


 * Yes, but O-9999 is still rather fictitious. StuRat 06:43, 14 November 2006 (UTC)


 * Maybe on Earth, but what about inside a neutron star? —Keenan Pepper 21:39, 14 November 2006 (UTC)


 * I wouldn't think even the most stable atoms would stay intact in such an environment. StuRat 02:55, 15 November 2006 (UTC)


 * A neutron star is by definition a star made entirely of neutrons! 8-)--Light current 03:04, 15 November 2006 (UTC)


 * How naïve! —Keenan Pepper 05:54, 15 November 2006 (UTC)


 * Only the central part of a neutron star is made up entirely of neutrons, not all the star, AFAIK. However, that depends to a significant extent on how you define a surface of a star (not a trivial task). Anyway, I don't think that you would find O-9999 at any depth inside a neutron star; rather, just a "soup" of neutrons, protons and electrons. However, if a catastrophic event involving a neutron star would happen (for example, a collapse to a black hole if the mass exceeds the limit, or collision with another star / black hole), some of the matter will be ejected. Most of it would still be neutrons I suppose, at least for an hour or two (neutron, when left alone, has a lifetime of about 15 minutes; it can be longer if it still has other particles to strongly interact with). Then maybe there is a chance to find something like a highly excited O-9999 nucleus, namely, a nucleus of a stable Oxygen isotope with a cloud of neutrons around it. --Dr_Dima.

irradiated food
When food is irradiated with gamma rays from a cobalt-60 source, does the food become radioactive? why is this?

Probably the easiest way to explain this is to think of atoms as tiny bombs. Radioactive atoms are bombs which are liable to blow up at any moment, whereas most atoms are relatively stable unless hit in exactly the right place and with exactly the right amount of energy. So consider Co-60 a insidious bomb. When this bomb explodes, it sends a shard of shrapnel hurling through space. Chances are, that shrapnel will never hit anything (space is actually pretty empty), but a very small percentage of the time, the shard will hit something. When the shard does hit something, a few things can happen: most of the time, everything probaly just snaps back into place, no harm done. Sometimes, however, a molecule will get knocked out of whack. If, by some wild chance, that molecule happens to be DNA, and that part of the DNA happened to have two cysteine residues next to each other, then the DNA will end up pretty messed up at that point, and if this dimer in the DNA happens to cause a mutation, and if that mutation happens to be bad (you see where this is going), then death or some other pathology can result (please note that death and pathologies can result from a lot of other molecular bombardment mishaps, but this is a popular one). This is how the radiation kills whatever is in the food. However, very rarely, the bomb shard hits another molecule in such a way that that molecule becomes "armed" up to blow up itself. The reason irradiation doesn't tend to make other things radioactive is because this secondary "explosion" is very unlikely in the first place, and exposure is limited in such a way to decrease this possibility even furthur, ensuring that irradiated food is no more radioactive than, say, brazil nuts (actually, probably much less so...).Tuckerekcut 00:53, 14 November 2006 (UTC)


 * No. Gamma rays are high energy light.  It doesn't change atomic structures.  It can change chemical bonds and that kills bacteria but to be radioactive the atomic structure changes.  Usually, neutron radiation is required to make something radioactive IIRC.  --Tbeatty 03:01, 14 November 2006 (UTC)


 * Gamma_rays has some similiar info -- Wikicheng 04:47, 14 November 2006 (UTC)


 * My bad, I probably shouldn't try to answer chem problems in the future, I didn't even look up the decay process for Co 60.Tuckerekcut 12:28, 14 November 2006 (UTC)
 * See Induced gamma emission, however, for info on how gamma rays can make some substances temporarily radioactive. Rmhermen 15:42, 14 November 2006 (UTC)

Atoms
Can you tell me how many types of atoms can you expect to find in a pure sample of any element?


 * Depends on your definition of "pure", and "type", which element you're talking about, and where you got your sample from.


 * In the real world, most samples of elements, no matter how pure, contain very small traces of contaminants. Ignoring that, for the moment, most elements come in more than one isotope, though the number varies greatly between the different elements.  Gold, for instance, has only one stable isotope, whereas tin has 10.  --Robert Merkel 03:26, 14 November 2006 (UTC)

A have a feeling this is a high school chem question. In which case, the answer is 1. "pure sample" of any one element means it contains only atoms of that one element. -- `/aksha 03:49, 14 November 2006 (UTC)

Right. In high school you learn that a sample of each chemical element consists of atoms of only one type (namely, atoms of that chemical element). If you are preparing for a chemistry exam, follow `/aksha's advice. In college or university you learn that atoms of a chemical element are actually not all alike. the electric charge of the nucleus of all the atoms of a given chemical element is the same, and the chemical properties of all the atoms of that chemical element are very, very similar. However, the number of neutrons in the nucleus of an atom need not be the same, look at isotopes in Wiki.

Another year passes, and you learn that the protons and the neutrons in the nucleus may be arranged in different quantum states. Again, even in a single-element single-isotope sample not all atoms are the same. You open Wiki, and here it is, an article on nuclear isomers.

A few months go by, and you suddenly learn that when you put a magnet to your sample, for elements/isotopes with net electron and/or nuclear magnetic moment, some atoms have higher energy than the others. Again, even in single-element single-isotope single-nuclear-isomer sample not all atoms are the same. Fascinating, as Spock used to say. Wait, there is more.

Now you take a basic plasma science course. You heat up your atoms to a few thousand Kelvin or more, and - surprise surprise - again, not all atoms are the same. Some have excited electrons in them, some have lost one or more electrons altogether and became positive atomic ions. Now you have a variety of atoms in your single-element single-isotope single-nuclear-isomer sample! The punchline is simple. If you want good grades at school, know what the teacher expects you to say. If you want to succeed in science, read books and talk to scientists. And, using Wiki ref desk also helps ;-) --Dr_Dima

Molecule
How many atoms are there in one molecule of H3PO4 ? and how many atoms of each element are there in this molecule?


 * See chemical formula for a description of what the formula above means, from which you can figure out the answer to your question. --Robert Merkel 03:28, 14 November 2006 (UTC)


 * 3 hydrogen atoms, 1 phosphorous atom, and 4 oxygen atoms. (you should go read chemical formula anyway, this isn't meant to be a place for homework questions). -- `/aksha 03:43, 14 November 2006 (UTC)


 * Then don't encourage the behavour by answering homework questions. --BluePlatypus 07:35, 14 November 2006 (UTC)

Are there Infinite Possible Futures? or just a lot?
A piece of semi-spiritual philosophy hold "We live in a universe of infinite possibilities". But is this actually true, according to our best guesses of the laws of physics? Are there an infinite number of states this galaxy could be in 10 minutes from now? or just some arbitrarily large yet finite number? --Alecmconroy 03:57, 14 November 2006 (UTC)

In 10 minutes it will be in one state. Therefore, the answer is 1. :) --Tbeatty 04:30, 14 November 2006 (UTC)


 * Nice answer. If I may interpret, Tbeatty means it all depends on what kind of "possibilities" you're talking about. For more information, I recommend Norman Swartz's book The Concept of Physical Law, specifically the chapter Potentialities, available online free of charge. —Keenan Pepper 06:18, 14 November 2006 (UTC)
 * Also see many-worlds interpretation. --Wooty Woot? &#124; contribs 06:36, 14 November 2006 (UTC)


 * Since there are a finite number of particles in the universe we inhabit, I would say that the number of possible futures is finite. However, there may be an infinite number of universes... Clarityfiend 07:55, 14 November 2006 (UTC)


 * There are, however, apparently an infinite number of possible positions and momenta for each particle, unless space is quantized. So the answer, really, is that we just don't know. -- SCZenz 16:17, 14 November 2006 (UTC)

Earliest sound recording (possibly pre-Edison)
Is anyone familiar with any attempts to record sound prior to Edison's famous 1877 invention of the phonograph? Our article on Sound recording and reproduction says "the first practical sound recording and reproduction device ..."

The reason I ask is this: Talk:Fr%C3%A9d%C3%A9ric_Chopin. It was posted by a new user earlier today, and you can see my answer to him there. While I know quite a bit about Chopin, I know less about early attempts at sound recording. Is what this user suggests even possible? (You can tell from my reply what I think.) Yet perhaps there were attempts to record sound before Edison which we haven't covered in Wikipedia. Thanks! Antandrus (talk) 04:44, 14 November 2006 (UTC)


 * The code for the cd is XOHA CDO10491. Most likely, XOHA stands for 'hoax' and O10491 for 1 April 1991. DirkvdM 09:58, 14 November 2006 (UTC)


 * There is a good article about it here (scroll down until you see "hoax"). --Kainaw (talk) 14:03, 14 November 2006 (UTC)


 * No one before Thomas Edison is known to have even made the attempt to record and play back sound. Scott built the phonautograph whcih had all the elements needed to record sound: a diaphragm to respond to sound waves, a stylus to record them, and a smoked glass plate to receive the tracing. But obviously you could not operate a playback stylus from the smoked glass. In theory, such a smoked glass tracing could have been photographically copied and used to etch a playable record. The technology to practically do that did not exist in the 1860's. That was the basis of the Chopin recording hoax. Yet there exist a few pre-Edison sound wave tracings, by Scott, and from 1868 by the physiologist Donders (Donders, F. C. (1868/1969).On the speed of mental processes. Acta Psychologica, 30, 412-431.) These are clear black and white photo reproductions of words and phrases recorded by Donders with a phonautograph while doing reaction time experiments. I know of no one having done the obvious task of translating these phonautograph traces to wave files. There would be a need for equalization of different parts of the frequency spectrum, and perhaps controlling for geometric distortions but I would expect some sound could be recovered. Ideally, the phonautograph would be modelled and its resonant frequencies and distortions "subtracted out" in the reproduction, but it would be cool to hear at least a raw playback of the tracings. Edison 14:37, 14 November 2006 (UTC)

What does it mean when your Monocytes decrease..
What does it mean when your Monocytes decrease..


 * A decrease in monocytes could mean you are immunocompromised. A more detailed explanation would depend on the context. Rockpock  e  t  06:33, 14 November 2006 (UTC)
 * It's not particularly meaningful to look at monocyte percentage as an isolated number, because (obviously), if something (like a bacterial infection) increases your neutrophil count, your monocyte % will decrease, and that won't really mean anything, it's just the result of the increase in polys, which is the significant thing. The WBC differential count provides the greatest amount of information when it is looked at as a pattern, in terms of both changes over time, and the relative quantities of the various cells. A low monocyte count in isolation isn't usually particularly significant - though of course if this occurs in a clinical situation, it should be reviewed by the clinician and clarified by him or her with the patient. - Nunh-huh 07:21, 14 November 2006 (UTC)
 * Compromised? Makes it sound like your immune system was paid-off for a back door. X [' Mac Davis '] ( DESK | How's my driving? ) 17:14, 14 November 2006 (UTC)

Naming a Diels-Alder product
I am attempting to name of the following product of a Diels-Alder reaction:. I have found the name of a similar molecule, but cannot determine exactly how to translate the change from O to N. Thank you in advance; any help is greatly appreciated. --ChunkySoup 07:03, 14 November 2006 (UTC)


 * the dienophile in the similar compound is maleic anhydride, which leads to a succinic anhydride derivative. the dienophile in your DA reaction is methyl maleimide, which leads to a succinimide derivative. Xcomradex 08:05, 14 November 2006 (UTC)


 * Chemical Abstracts names it as cis-3a,4,9,9a-tetrahydro-2-methyl-4,9[1',2']-benzeno-1H-benz[f]isoindole-1,3(2H)-dione and lists as an alternate name cis-9,10-dihydro-N-methyl-9,10-ethanoanthracene-11,12-dicarboximide. --Ed (Edgar181) 19:10, 14 November 2006 (UTC)

microalgal bioreactors
hello, ive been doing some research and i cant find anything on microalgal bioreactors. i need to know what a microalgal bioreactor is, what its used for, whats its uses and its effects on the surrounding envionment? And who uses microalgal bioreactors such as organisations etc...

thanks heaps guys, graham


 * Have you read Biochemical engineering? It's primarily composed to material related to bioreactors. I'm only familiar with tissue-related bioreactors, but I'd assume a microalgal one would be used to grow algae, with primary uses by whomever would be studying algae. I don't think the reactor has an effect on the surrounding environment, since it's designed to be a completely in-vitro system. 16:27, 14 November 2006 (UTC)

alternating magnet
Is there a permanent magnet that alternates its poles withut any supply of energy


 * It is not likely that you'll find one. If this exists, all you need to do is to wind a coil of wire around it. The changing magnetic field would produce alternating current without spending any energy ! -- Wikicheng 11:07, 14 November 2006 (UTC)
 * Erm, not quite. You need a power source. There won't be any alternating current if you don't put any current in the wire to start with. You can't get energy from nothing. - Mgm|(talk) 11:17, 14 November 2006 (UTC)


 * A changing magnetic field passing through a wire creates electrical current. You don't need to put current in the wire to get it going.  You can try it yourself.  Attach the ends of a coil to a volt meter and wave a magnet back and forth past all the coil.  You'll see the volt meter bounce. --Kainaw (talk) 14:00, 14 November 2006 (UTC)


 * Also, the alignment and re-alignment of the magnetic dipoles would need energy. Frankchn 11:10, 14 November 2006 (UTC)
 * Well, if we get a permanent magnet which changes it's polarity without using any energy (wow !), the we can get AC from the magnet by simply winding a coil of wire around it ? If effect, such a magnet does not exist.-- Wikicheng 13:15, 14 November 2006 (UTC)
 * But wait! That means that if the earth were surrounded by a giant coil of wire, then every time it flipped its magnetic pole (every few million years) it would generate a half cycle of electricity. Cool! 14:42, 14 November 2006 (UTC)Edison


 * Yes but the frequency would be rather low beacuse the flipping actually seems to take thousands of years. THe induced voltage would therefore be very low. 8-)--Light current 16:23, 14 November 2006 (UTC)


 * I didn't know that earth flips its magnetic poles (albeit once in a million years). I am assuming that the change would not be instantaneous but would be gradual. So does it mean that in the middle of this cycle, there will be a period when there are no North and South poles ?(because the N pole is slowly becoming S pole and vice versa) -- Wikicheng 11:32, 15 November 2006 (UTC)


 * To some degree yes (though the other non-magnetic sets of poles would still exist in their same location, see e.g. North pole), but it's not as if the Earth's magnetic field is as simple as that of a bar magnet. It fluctuates quite a bit and during the course of a flip (if I recall correctly), it's sort of a general weaking of the polar poles compared to fluctuations all over the Earth and eventually the magnetic poles re-establish themselves, potentially reversed. That is a very simplified version of the story, of course. digfarenough (talk) 20:34, 15 November 2006 (UTC)


 * Good info. Geomagnetic_reversal has more details. Thanks -- Wikicheng 04:50, 16 November 2006 (UTC)

organ transplantation
What are the sources available for organ transplantation?Are such sources effective?Are they ethical?How may the government improve its healthy system to make organ transplantation more effective? —Preceding unsigned comment added by 210.195.36.143 (talk • contribs)


 * This is a too broad a question for a full treatment here. You might like to start at organ transplantation and see some of the many links from there.--Shantavira 11:50, 14 November 2006 (UTC)
 * Why would organ transplantation be unethical unless you "stole" the organ, or got it from the black market? Unless you believed one should leave God's creatures how they were born. X [' Mac Davis '] ( DESK | How's my driving? ) 17:12, 14 November 2006 (UTC)
 * I believe they were asking if the sources were ethical. On top of stolen organs, some question the ethics of paying for organs, for example. Skittle 22:36, 14 November 2006 (UTC)

Anomalous compounds/substances
What are the examples of such compound which show anomalous behaviour?

Why do water show anomalous behaviour?Explain in short.

maheshwor


 * See our articles on physics and chemistry of water and hydrogen bonding. Gandalf61 13:25, 14 November 2006 (UTC)


 * In short, anomaly. The fact that water expands as it freezes might be considered an anomaly.--Shantavira 13:27, 14 November 2006 (UTC)

Which types of painkillers does caffeine enhance?
The caffeine article mentions, in the "effects" section, that caffeine is sometimes used in conjunction with painkillers; I've heard elsewhere that caffeine enhances the action of analgesics. My question is, which classes of analgesics does caffeine enhance? Does it affect NSAIDs, narcotics, gabapentin, and/or local anesthetics? Thanks. -- Creidieki 13:42, 14 November 2006 (UTC)


 * Caffeine is matabolized by cytochrome P450, and thus may potentiate any other drug which is metabolized through this pathway. You'll have to be more specific for the other compounds (these things you have listed are grouped by mechanism of action, not mechanism of catabolism), but I will tell you that gabapentin isn't even metabolized in the body (and get this: the bigger a dose you take, the less of it is bioavailable, isn't that weird?), so it is not contraindicated with caffeine. However, there are other interactions (because a certain isoform of cytochrome p450, CYP2A6, is slightly inhibited by gabapentoin) in your list. Gabapentoin should not be taken with naproxen (an NSAID), hydrocodone or morphine (these are narcotics), unless your doctor specifically is aware of the interplay between these drugs (its, um, complicated, and needs vigilant monitoring). Gabapentoin has other contraindications too, but not, as far as I remember (which is not very far), in the drug classes listed above. This is not medical advice, see your physician if this question is anything but hypothetical, mixing drugs can have potentially lethal effects. Tuckerekcut 19:28, 14 November 2006 (UTC)
 * Thank you for your response; I've been bouncing around between physicians a bit. I'll corner one of them about some questions I have now.  -- Creidieki 21:20, 14 November 2006 (UTC)
 * Some unorganized, general info...Excedrin & other brands of headache medicine contain acetaminophen, aspirin & caffeine -- which apparently provides "significantly superior efficacy and speed of onset compared with" ibuprofin. Codeine is often given with caffeine, according to this site, but it's not clear that it helps with the opiate effects or the acetaminophen that often accompanies it. This paper suggests that caffeine consumption increases headache risk. According to this paper, "acute, but not long term, caffeine intake reduced neuropathic pain state in nerve-injured rats, but only at very high doses." -- Scientizzle 19:41, 14 November 2006 (UTC)
 * The last abstract I linked to explains "The potential hyperalgesic effect of chronic A(1) adenosine receptor blockade [by caffeine] may have been compensated for by an antinociceptive effect of caffeine through antagonism of A(2A) receptors and tolerance development." Drugs that work through adenosine receptor systems may be particularly affected by caffeine. -- Scientizzle 19:45, 14 November 2006 (UTC)

An innovative application of laser?
Hi all! Could you help me out and give me a really innovative thing you could/would like to do with lasers? Thanks in advance. PS: This aint for school. And I need it as fast as possible.--202.88.231.147 14:11, 14 November 2006 (UTC)
 * Use a laser to levitate an object. Edison 14:43, 14 November 2006 (UTC)


 * I heard on the radio yesterday that the only reason supermarkets still put plastic wrap onto cucumbers is that the label doesn't stick to the cucumber properly. So I'd laser-etch the label info (including the barcode) into the skin of the cucumber.  Hopefully some tweaking of the laser frequency and power could produce a mark that noticeably changes the colour of the cucumber skin (ideally bleaches it white) without really damaging the skin (affecting its shelf life and customer acceptability).  As cucumbers are mostly eaten in little slices, the mark shouldn't be off-putting to the final consumer. -- Finlay McWalter | Talk 14:48, 14 November 2006 (UTC)


 * Believe it or don't it's been done! I read a blurb about laser-etched food items a few years ago; sorry, no link.


 * Atlant 18:50, 14 November 2006 (UTC)

A means of propulsion for spacecraft. A powerful stationary laser in Earth orbit aims a laser at the spacecraft. The beam then reflects off the craft, accelerating it away from the laser. StuRat 15:01, 14 November 2006 (UTC)


 * Make three lasers: red, blue, and green. Each one will be fine-tuned to a specific frequency. Use them to project HD television on a screen. Then, make the screen out of three fibers: red, blue, and green. When meshed together, they will appear to be nearly black. But, the fibers are made so that they reflect one and only one frequency of light - the one the lasers produce. So, when all 3 lasers hit the fabric, it produces crisp and clear white light. When they don't, it is black - even in a completely lit room. So, you can have super-mega-huge projection television without having to shut off all the lights. --Kainaw (talk) 15:07, 14 November 2006 (UTC)
 * It's not precisely related, but this might interest you: Tunable crystals] 16:14, 14 November 2006 (UTC)


 * Optical computers 16:14, 14 November 2006 (UTC)


 * Burn a marriage proposal to your loved-one onto the surface of the Moon? --Kurt Shaped Box 20:48, 14 November 2006 (UTC)


 * Sinc the current best focussed lasers produce a spot one mile wide at the moons surface, the power density would probably not be enough to boil a cup of tea!--Light current 21:43, 14 November 2006 (UTC)


 * What if you cranked it up to 11? ;) --Kurt Shaped Box 21:53, 14 November 2006 (UTC)


 * I think the problem is one of the atmosphere tending to defocus the beam due to turbulence; so the power is a secondary issue-- Its how fine you can focus it on the moons surface. --Light current 22:00, 14 November 2006 (UTC)


 * Wouldn't a wide beam be the most suitable choice for carving a message into the moon anyway? If you wanted to be able to see it from earth, this is... --Kurt Shaped Box 22:54, 14 November 2006 (UTC)


 * No because as I said before you cant get enough power per sq cm to actually burn anything!--Light current 23:07, 14 November 2006 (UTC)


 * Could George W. Bush? --Kurt Shaped Box 01:02, 15 November 2006 (UTC)


 * Yes, if you give him a blowtorch and a rocket to get to the Moon. And a $9.99 laser pointer to apply to the freshly burnt surface, as it must be an "application of laser" after all. --Dr_Dima.


 * Could you set a soapbox on fire with a laser?Edison 15:24, 15 November 2006 (UTC)


 * Yes, but that's arson. --Dr_Dima.


 * That's just great. The first grafitti on the Moon. Speaking of which, does anybody actually "own" or have any legal rights to any part of our neighbor (somebody who could sue you for defacing his or her property)? Clarityfiend 00:32, 15 November 2006 (UTC)


 * The Outer Space Treaty says that the Moon or anywhere else outside earth can't be claimed by any particular country. Until there is actually an attempt to economically exploit some extraterrestrial body, however, it's really not an issue. --Robert Merkel 00:39, 15 November 2006 (UTC)

the liver
To whom this may concern, I tried to get a clear copy of your "view from below" the liver and I am unable to. It down loads fuzzy and prints illegible. Is there any possible way that you can send me a clear copy or fix the one on the page so that it is more functioning. As a user of your site I am always excited to see all your wonderfull illustrations but when they are unreadable, it is frustrating. I am a homeschooler doing a unit on the digestive system with my two children so this particular illustraion would be wonderful to have since it labels all the liver parts.

Thank you in advance for your help. With much appreciation Christine Blamire

My email:(removed)
 * Those images from Grey's anatomy are kind of hard to read and fuzzy. Does it look different on the internet to you? X [' Mac Davis '] ( DESK | How's my driving? ) 17:10, 14 November 2006 (UTC)


 * I had some free time, so I emailed her a response, which I've included below:
 * Hi! I'm Creidieki (please excuse the weird name), and I'm one of the volunteers answering questions at Wikipedia's Reference desk.


 * I should note first that we don't usually reply via email. In general, putting your email in a public place on Wikipedia is an easy way for spammers and other impolite folk to find it.  We've hidden your email address on the page.  For the reference desk, you should check back at the same reference desk page you asked on to see answers to your question.


 * It looked like you hadn't realized that, so I thought I'd send you an email; other people may also respond to your question on the reference desk, and you should look for those responses over the next several days, at http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#the_liver . (Or you could go to Wikipedia, type "Wikipedia:Reference desk" into the search box, go to "science", and then scroll down to find your question).


 * Anyway, on to answering your question. Wikipedia is a free encyclopedia, which means a couple of things.  It's put together by volunteers, and we only accept material that can be freely redistributed (under a license called the GFDL).  That's really good, because it means that schools and universities and people can use Wikipedia's material under very generous terms.  Unfortunately, it's also difficult to find trained medical illustrators who want to draw complicated diagrams for free.  It looks like the liver picture you were asking about was scanned from a 1917 book copy of Grey's Anatomy; it's probably accurate, but we're not going to be able to find a better copy of that specific diagram for you.


 * So, if you want a good image of the liver, you're probably going to have to look elsewhere. I searched google for a bit, and came up with a few candidates for better images.  Frankly, I have no idea how authoritative these images are; all I can say is that they claim to be diagrams of the liver.  You may want to go to a local library and see if they have an updated copy of Grey's Anatomy, or other similar books.


 * http://www.ariess.com/s-crina/liver-anatomy.htm -- claims to use Grey's Anatomy as a source.


 * http://medicalcenter.osu.edu/patientcare/healthinformation/otherhealthtopics/LiverBiliaryPancreaticDis4540/TheLiverAnatomyandFunctio4542/ -- from a university medical center.


 * I hope those two links help. Again, you should check at the reference desk for other answers.

-- Creidieki 17:29, 14 November 2006 (UTC)


 * THe image in question is a plate from an old (out of copyright) edition of Gray's Anatomy. You can get a bigger version of the same image here. -- Finlay McWalter | Talk 17:35, 14 November 2006 (UTC)

Tai Chi hand postures
What is the meaning (purpose) of the hands in the closing posture of Yang style Tai Chi. Right fist in palm of left hand or left fist in palm of right hand. Thank You Mike Woodside


 * It's a salute. It's typically found at the end of wushu sets, though its origin probably predates competitive kung fu.


 * If I understand you correctly, you are basically covering your fist with the other hand (usually the left covering the right). I was taught that this is symbollically "covering your weapon" and saying that you mean no harm, although since your fist is still there, it means that you will defend yourself as necessary. We use it as a sign of respect at the beginning and end of class and forms (Shaolin Wushu Kung Fu). At least that's what we were told, I have no idea if it is correct. But it sounds reasonable. --Bennybp 01:45, 15 November 2006 (UTC)

Kashi
According to this article, Kashi products cause "excessive gas". Is there any truth to this (perhaps from the ingredients) or is this edit vandalism? | A ndonic O  Talk 19:44, 14 November 2006 (UTC)


 * The claim seems somewhat unlikely given the ingredients, and after having eaten Kashri cereals I've never noticed any untoward effects. A radical change of diet may initially cause extra gas as the flora adapts to it; perhaps that is the origin of the complaint, but then it is not specific to Kashri. The anon's IP address has no history of vandalism and is assigned to the Detroit Medical Center, but the statement is depreciative of a commercial product, completely unsourced, and in this form ("may") unfalsifiable. Altogether I've found it best to remove this claim. --Lambiam Talk  20:28, 14 November 2006 (UTC)


 * There might be a basis for the claim in that high fiber foods can cause gas, and Kashi cereals tend to have a higher dietary fiber content than more mainstream cereals.--Mabris 21:24, 14 November 2006 (UTC)

Natural logarithm units
When taking the natural log of a number in a given unit, would the result be in the same unit? That is, would the following statement be true?

$$\ln\left(10m\right) \approx 2.3m$$

My thinking is that it would be false, as:

$$\ln\left(10m\right) = \ln\left(10\right) + \ln\left(m\right) \ne 2.3m \mbox{ in general}$$

Any comments would be appreciated. --132.194.13.121 20:24, 14 November 2006 (UTC)


 * Mathematical functions do not change units. Taking the log of a number is no different than multiplying by a constant.  For example: 10 * 10m = 100m.  Your example of proving it wrong would be: 10 * 10m = 10 * 10 + 10 * m.  That makes no sense, just as ln(m) makes no sense. --Kainaw (talk) 20:31, 14 November 2006 (UTC)


 * Thanks for the reply, although I think you might be mistaken here. Mathematical functions frequently change units, provided they are not linear functions. As an example, consider (10m)2 = 100m2. I believe a simplified version of the 'correct' answer here is that the natural log function results in a unitless number. Comments? --132.194.13.121 20:40, 14 November 2006 (UTC)


 * The issue here is that the natural logarithm only takes unitless numbers as arguments. Thus physical quantities that involve natural logs of numbers with units always have some "scale" in the argument to cancel out the units.  Otherwise there would be exactly the problem you describe. -- SCZenz 20:42, 14 November 2006 (UTC)


 * (after edit conflict) A more appropriate spot for this question is the Mathematics reference desk, but in any case the statement is false. If 0 < m < 1/10, ln(10m) < 0, while 2.3m > 0. When you graph ln(10m) against m you get a curve that has the same shape as the green curve in the article Logarithm, whereas graphing 2.3m gives a straight line. There must be a relationship between the "2.3" in the question and the fact that ln(10) = 2.302585..., so someone may have mistakenly thought that log(a×b) = log(a) × b for the case a = 10. --Lambiam Talk  20:44, 14 November 2006 (UTC)


 * I think m is supposed to be a unit here, perhaps meters. -- SCZenz 20:47, 14 November 2006 (UTC)


 * (after another edit conflict) Now I understand the question, the "m" is supposed to be metres, and not a variable. Then indeed ln(10m) is meaningless. (By convention, units are not set in italics.) --Lambiam Talk  20:51, 14 November 2006 (UTC)


 * Thanks for all the responses. This came up in a Chem lab project measuring vapor pressures at various temperatures. (Hence the post in the Science desk.) When this is done, a plot of lnP vs. 1/T yields a straight line, the slope of which is of interest. Now, the average slope of this plot would be m = &Delta;(lnP) / &Delta;(1/T). So in this sense the unit for pressure isn't important as it is subtracted out as I showed above. In other words, what SCZenz said above. Sorry for the confusion Lambiam - I did mention "When taking the natural log of a number in a given unit". --132.194.13.121 21:03, 14 November 2006 (UTC)


 * Right, the slope will be independent of the "scale" (i.e. unit) of pressure being used in the argument, so it often isn't specified. -- SCZenz 21:06, 14 November 2006 (UTC)


 * If you treat the log of a unit as an unspecified constant, then they should all cancel out at the end. By itself, ln(10 m) is meaningless, but ln(10 m) – ln(5 m) = ln(10) + ln(m) – ln(5) – ln(m) = ln(10) – ln(5) = ln(2) = 0.693. It works out that way because the difference of the logs is the log of the ratio, which is dimensionless. If you end up with the log of a unit in your final answer, that means you made a mistake. —Keenan Pepper 21:15, 14 November 2006 (UTC)


 * THe log of a number is the power to which you raise the base to get that number. Does a power have units? 8-)--Light current 21:48, 14 November 2006 (UTC)


 * Answer : NO!--Light current 22:09, 14 November 2006 (UTC)


 * For instance consider the problem of changing nepers into dBs. THe bases are different but the net difference between the two units is only one of multiplication by a certain constant that relates the two bases (base e and base 10 -- cant remember what it is and too lazy to work it out). Is this comment relavant?--Light current 21:54, 14 November 2006 (UTC)

I think the best answer is there is a unit ln(P) where P is in pascals, but there is no special name for this unit. Indeed, I can't think of any unit with a special name that is the result of taking the natural or common logarithm of a quantity expressed in some other unit. --Gerry Ashton 02:41, 15 November 2006 (UTC)


 * Sorry, that doesn't work either. In dimensional algebra, the numbers are conceptually multiplied by their units of measure. Thus 2 m &times; 3 m = 6 m&sup2;: you're just multiplying the 2, the 3, and the two instances of "meters" all together.  In fact it works just like 2m &times; 3m = 6m&sup2; where m is a mathematical variable instead of being meters.  But if it was meaningful to take ln(20 Pa), you would get ln(20) + ln(Pa), not ln(20) times anything.  It simply is a fact that taking the logarithm is something you can only do with a pure, dimensionless number.


 * What may confuse the issue is that something like "pressure in pascals" is a dimensionless number, and so it's safe to take its logarithm if you want. Think of the word "in" here as indicating division. You are dividing the actual pressure, 20 Pa, by the unit Pa to get the pure number 20. So as soon as you work with something like "pressure in pascals" or "length in meters", you are using dimensionless numbers.


 * --Anonymous, 07:05 UTC, November 15.


 * Logarithmic scales always have an implicit reference value - the value of the underlying that corresponds to a value of 0 on the logarithmic scale. For example:
 * The reference value for the decibel scale (in the acoustics definition) is 20 µPa.
 * The reference value for the decibel watt scale is 1 W.
 * The reference value for the pH scale is 1 mol/litre.
 * The reference value for the Krumbein scale of grain size is 1mm.
 * By assigning a value of ln(10) to "ln(10m)" you are implicitly using a reference value of 1m. If you use a different reference value, you add or subtract a constant amount from the values in the logarithmic scale. Gandalf61 13:02, 15 November 2006 (UTC)


 * Strictly, one should only take logs of a dimensionless scalar, so in the original question you shouldn't really ever have ended up with an expression like $$d \ln(p) / d(1/T)$$ because you're taking logs of a dimensional quantity. It's algebraically equivalent to $$d \ln (p/p_0) / d(1/T) $$ (with $$p_0$$ constant), which is a valid expression because here you're taking a log of a dimensionless quantity.  Given that this equivalence holds regardless of the value of the reference value $$p_0$$, it's convenient to simply write $$\ln(p)$$ as a lazy shorthand, provided that you interpret it as "$$\ln(p/p_0)$$, for some $$p_0$$ which had better turn out to cancel out or otherwise something has definitely gone wrong". Arbitrary username 00:24, 17 November 2006 (UTC)

Saltwater
What chemicals are in saltwater?


 * Salt, and water. Philc  TECI 23:16, 14 November 2006 (UTC)


 * Perhaps you mean seawater? Vespine 23:18, 14 November 2006 (UTC)


 * (edcon)
 * Plus a few other things probably. Sea water--Light current 23:19, 14 November 2006 (UTC)


 * Heck, even saltwater itself would tell you. DMacks 23:22, 14 November 2006 (UTC)