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December 1

Zygotes implanted in the wombs of other species

Has this ever been done in controlled experiments? I wonder how close the species have to be (if anything less than exact species matches can) for the fetus and mother to be able to create a compatible placental link without the mother's body seeing it as a foreign substance and killing it. 71.161.61.41 (talk) 01:06, 1 December 2009 (UTC)

I don't think the mothers body would see it as foreign. The problems are more likely in other areas. For example, a newborn has a special kind of hemoglobin which has a higher affinity for oxygen than the mother (so it can pull oxygen out of the mothers hemoglobin. So that has to match in a different species. The nutrition requirements must match, and the physical size of course. Possibly the most difficult is getting the placenta (which has the dna of the child) to embed in the mother. I have a vague memory of hearing about an extinct (or close to it) species being cloned, then embedded in a different, but similar, species (but I don't know if they did it, or just planned to). All that said, this is a very interesting question, and I don't know the answer. But I figured I'd post what I knew, since you didn't have any other replies. Ariel. (talk) 02:07, 1 December 2009 (UTC)

That would be the woolly mammoth in an elephant, I believe. 90.195.179.130 (talk) 06:37, 1 December 2009 (UTC)

Doesn't the blood get exchanged? Won't the blood cells be identified as foreign? 66.65.141.221 (talk) 03:47, 1 December 2009 (UTC)

No, unless there is a fetomaternal hemorrhage, the blood of the fetus and the mother do not mix. See Placenta#Fetoplacental_circulation. --NorwegianBlue ^talk 22:54, 1 December 2009 (UTC)

I'm pretty sure it would get rejected. Just look at how difficult it is to transplant organs between different humans. Or the fact that humans can form antigens even against their own fetuses. (e.g. Rhesus factor) Add to that different gestation periods and easily thousands of different factors that have to match up, most of which are probably unknown to us. I don't believe it's been attempted and I think it would be outright unethical to even attempt such a bizarre thing, given that there's zero probability of success. You're talking about literally millions of foreign proteins and compounds, every single one of which could possibly trigger an immune system response in the host/mother. --Pykk (talk) 06:45, 1 December 2009 (UTC)

As our article on Cloning#Cloning extinct and endangered species briefly mentions, it has been attempted before, obviously only in related species; with the zygote species usually being endangered. It obviously often comes up when discussing cloning extinct mammal species (for obvious reasons) and cloning or IVF reproduction of endangered mammal species (using mothers of the endangered species may be a bit risky and limiting). For example, this [1] shows some research in 1988 i.e. long before Dolly; this shows a horse mare and it's zebra surrogate child [2] [3]; and in fact this ref says the first case was in the 1970s [4]. Obviously for some of this stuff e.g. zebra/horse it's not that surprising it works since zebra/horse hybrids are possible; in the surrogate case the offspring does not have any genetic complement from the parent species unlike hybrids which have half, but on the other hand it doesn't have to cope with any problems arising from a mismatch (perhaps not the best word but can't think of anything else) of genes. I believe most research/interest now has been for cloning, probably because IVF likely still has some significant risk for the mother and because cloning is the hot thing nowadays. Or perhaps there's a fair amount of research ongoing with cases of non-cloned animals it's just harder to find refs since it isn't so 'hot'. [5] discusses the case of the Pyrenean Ibex (also mentioned there) which has so far been unsuccessful. There's also been discussion about panda cloning [6] and as that mentions and discussed here [7] there was some success with implanting panda embroyos in rabbits, obviously not with the intention of the rabbits carrying the pandas to term but to show implantation is possible (I believe using rabbits as temporary hosts is common so using them to attempt implantion would follow on). Obviously a better surrogate species would be necessary, what I'm not sure but presemuably some kind of bear. This perhaps raises one of the other issues. If you're using a cow, horse, sheep, goat, pig, etc as a surrogate that's easy since they're domestic animals and you can get large numbers. On the other hand if you're using a lion as surrogate for a tiger you may not be making things much easier then just using tiger surrogates while creating additional problems. Anyway although the last ref on pandas is from 2002, there doesn't seem to have been any significant new news I can find perhaps it was abandonded due to opposition [8] or was simply unsuccessful. There's also [9] which could be of interest altho I'm not sure if it discusses anything not in the other refs/our article and this [10] for a more scientific viewpoint. Interspecies surrogacy appears to be the common term but we have no article and while a useful search term you also get stuff like mother cats looking after puppies. Nil Einne (talk) 10:16, 1 December 2009 (UTC)

I guess that the surrogate mother could be heavily immuno-suppressed for the duration of her pregnancy using drugs - but this brings up another related question. How come there are not immune reactions to surrogate children (even of the same species) more frequently. IgG does cross the placental barrier - so why doesn't it attack foreign antigens that you would certainly find in either someone else's child, or even your own child?

Gene Therapy and Hormones

In theory, could gene therapy ever be used to replace or increase the estrogen and progesterone hormones, even if a woman's ovaries have been removed? —Preceding unsigned comment added by 71.156.167.121 (talk) 02:28, 1 December 2009 (UTC)

Gene therapy is in its very early infancy, so what all will ultimately be possible with it is really quite speculative at this point. So I think the sentence at the top of this page may apply here: "The reference desk does not answer requests for opinions or predictions about future events." Red Act (talk) 10:20, 1 December 2009 (UTC)

Perhaps your understanding of gene therapy is a bit misguided. All cells of the body have the theoretical potential to express all genes and produce all proteins. That being said, certain limitations exist for the vast, vast majority of cells in an organism such that they differentiate and lose totipotency/pleuropotency. Because all cells still retain the DNA to make all proteins, though, gene therapy, which works to supplant missing DNA (as in the case of a hereditary, genetic disorder) won't really accomplish what you are asking it to do. What your case would need is a de-differentiation/redifferentiation process by which another cell type would be able to produce ovarian hormones -- something that might work with a cloning-like procedure but is likely not happening anytime soon. DRosenbach ^{(Talk | Contribs)} 13:19, 1 December 2009 (UTC)

I have to disagree. There's no reason to think that, "in theory", gene therapy could not accomplish the production of estrogen and progesterone from a non-ovarian tissue. Gene therapy isn't about de-differentiating a cell type but rather adding back a normal copy of a mutant gene or adding some exogenous gene that will help to correct a disease (in this case, lack of ovaries). Each application of gene therapy is going to have a different target cell type and different approach. There may be some cases in which a small patch of muscle tissue (or other tissue) could produce enough of a certain gene product to reverse the symptoms of a disease. However, other disorders would require replacing the defective gene in a large proportion of the body's cells (which we currently can't do). The problem with the OP's question is that the gene therapy we have now would be like using a sledgehammer to try to cut the facets of a gemstone. It requires some really fancy tricks to mimic the endogenous switching between estrogen production and progesterone production in a fashion similar to the female menstrual cycle. Ideally, you would want your transgene to be under the control of the endogenous gonadotropins released by the pituitary gland, FSH and LH, which would be even more complicated. The answer to the question is that yes, it could probably be achieved using gene therapy, but in reality it seems unlikely that this type of therapy would ever be developed given the already existing (and relatively inexpensive) hormone replacement therapy or combined oral contraceptive pills. --- Medical geneticist (talk) 14:19, 1 December 2009 (UTC)

Air bubles in tap water

In modern tap water we see a lot of air bubbles, from where it comes and when we put our hands the splashing is very less compared to old taps?203.199.205.25 (talk) 09:31, 1 December 2009 (UTC)

The bubbles are there due to the faucet aerator, which not only reduces splashing, but also saves water. Unfortunately, the little stub article explains that the aerator breaks the stream into little droplets, but doesn't explain why that would help reduce splashing compared to a laminar flow of water. Red Act (talk) 09:50, 1 December 2009 (UTC)

Is everything energy?

As the subject line says. Is all matter made ultimately of energy? (Please excuse me for posting this. I should know the answer but I'm full of cold and my head is made of cotton wool.) --TammyMoet (talk) 10:16, 1 December 2009 (UTC)

That's basically correct. The mass of a body of matter is a measure of its energy content. See Mass–energy equivalence. Red Act (talk) 10:28, 1 December 2009 (UTC)

Thanks Red Act, I knew we had an article on it somewhere! --TammyMoet (talk) 11:45, 1 December 2009 (UTC)

Red Act is correct to point to mass-energy equivalence, but that does not mean that "all matter is made ultimately of energy". Energy is just our label for the quantity that is conserved in the conservation of energy law. Mass-energy equivalence establishes an "exchange rate" for converting between mass and energy. It means that conservation of energy and conservation of mass, which had origimated as two separate conservation laws, are now merged into a single conservation law. But the conversion does not have a preferred direction - we could just as easily say that the energy content of a body is a measure of its mass. From this point of view, we could, for example, assign a relativistic mass to photons, and add up the relativistic masses of colliding particles instead of adding their energies. But this is just a change of viewpoint - it does not mean that all energy is made ultimately of matter. There are several other conservation laws, and each of them gives us some information about which physical processes are possible and which ones are impossible (although when you introduce quantum mechanics, things are not as black and white as this, and possible/impossible becomes probable/improbable). But none of these conservation laws tell us anything conclusive about the ultimate constituents of matter. Gandalf61 (talk) 13:00, 1 December 2009 (UTC)

Mass-energy equivalence is one of the fundemental threads that actually shows up, in one form or another, in all of modern theoretical physics. It isn't that matter is a form of energy, or that energy is a form of matter. Its that the two are the same exact thing, but being observed under different conditions or in different environments. The same basic principle is at work in wave-particle duality, that is all of the universe can be said to behave in a wave-like (energy-like) manner, or as particles (matter-like) manner. That is, everything is both an object (particle) and a wave (energy), its not so much that anything "chooses" one form or another, its that the method of observation of something determines which properties of that thing you actually see; some methods of observation lead to wave-like properties being highlighted, while others lead to particle-like properties (see Double-slit experiment for a discussion of the principle at work in electrons and photons). For really big things, we only have observation methods that highlight the object-like nature of them, but when you get smaller and smaller, you can arrive at more and more wave-like properties comeing out. See also DeBroglie wavelength for the theoretical wave-particle duality in large objects, Schrödinger equation for the complex mathematics of wave functions of matter (there is even a possible Schrödinger equation which describes the entire universe as a single wave function), and Copenhagen interpretation for some of the philosophical implications of mass-energy equivalence. --Jayron32 20:57, 1 December 2009 (UTC)

Actually no. What it means is that mass and energy are the same thing! They are two words that mean the same thing. There is no test that can distinguish them, and no definition that discriminates between them. They are not interconvertable, they are the same. Note that "matter" and energy are not the same. But "mass" and energy are. Matter is energy plus quantum numbers, like charge or boson, spin, etc. And don't get confused by concepts like a photon being massless - it's actually that it has no rest mass, not that it's massless. All that said, I think the convention is that energy that is tightly bound in matter is called "mass". So the binding energy of an atom is called mass, but the heat, and velocity of an atom, it called energy, even though both contribute to it's gravity, and weight, etc. Heat is easy to remove from an atom, the binding energy is not. And to answer the question in the title, everything is not energy, because there are quantum numbers that are conserved, which also make up the universe. Ariel. (talk) 21:14, 1 December 2009 (UTC)

Regarding your last sentence, it depends on what the meaning of the word 'is' is. I would take the question "is everything energy?" to mean something like "within a closed region of flat spacetime, does what is contained within that region differ from a vacuum if and only if the total energy within that region differs from the total energy of a vacuum?". The answer to that question is "yes". You're taking the question "is everything energy" to mean something like "within a closed region of flat spacetime, is total energy the only conserved property of what's within that region?". The answer to that question is indeed "no", but I don't think that was the intent of the original question. Red Act (talk) 23:34, 1 December 2009 (UTC)

Regarding quantum numbers; don't quantum numbers all sum to zero when added across the whole universe anyways (i.e., the universe is neutral?). So there is nothing "extra" there that needs to be conserved once you have taken account of the energy/mass. Yes, they are conserved, but only to maintain the neutrality of the universe; there's nothing "left over" once you factor out the energy/mass! If so, then the singularity at the big bang would have had a net charge, and that doesn't make much sense... --Jayron32 00:41, 2 December 2009 (UTC)

Jayron32: That's the whole question of baryogenesis. Red Act: Your first question is also not what the op asked. You are basically saying there can be no quantum numbers unless there is also energy. A fine statement (is that really what you meant to say though?), but not what the op asked. The op asked is there anything else besides energy in the universe. And the answer is no, there are also other conserved quantities (as Gandalf61 said). In truth we are arguing over words, because the op's question is not well defined. But hopefully reading this will give him the answer anyway. And BTW, your answer to him was correct, I was arguing with Gandalf61 who implied that mass and energy were different, but they are not. They are not simply interchangeable - they are the same. Ariel. (talk) 01:36, 2 December 2009 (UTC)

Yes, loosely speaking, I was basically saying that there can be no quantum numbers unless there is also energy. Something physically exists if and only if it has energy. (I'm here ignoring vacuum energy and the complexity of the quantum vacuum.) So it works as a reasonable perspective to say that everything consists of energy, and quantum numbers are a way of describing some of the properties of that energy. I'm not saying that that's the only correct perspective, merely that it's a reasonable one. If you have a cubical granite rock, most people would say that it clearly consists of granite, and has a property of being cubical, rather than arguing that it consists of granite and cubicality. But the distinction between "consists of" and "has a property of" is a lot more arbitrary at small enough scales. That's ultimately not well-defined AFAIK. Red Act (talk) 07:29, 2 December 2009 (UTC)

I agree that energy and mass are indistinguishable and interchangeable - energy has mass, and mass has energy. And therefore we cannot say "everything consists of energy" without also saying "everything consists of mass". But the latter formulation sounds just wrong because it begs the questions "where does the mass come from ?" and "why do different bits of mass (i.e. fundamental particles) have different properties ?". You might as well say "everything consists of blue - but some of that blue appears to be green or red". Gandalf61 (talk) 12:01, 2 December 2009 (UTC)

Sell copyrights of my research work

Hi folks,

I have done a research work and project has come really well. My research paper has been chosen for publication in a Internatinal Journal in USA. I am basically from India. I was thinking like it would be better if I could give the copy rights for any of the research company so that my work (which I believe will cater the need of many doctor's world over) will get improved more. To be more specific My project is an Ophthalmology related one. Its not about drugs, its about diagnosing a device. So it will be a great help for me if any of you folks coul give me some information with regards to this (I don't have much knowledge in this field thats why asking).I am really sorry if I have posted in the wrong section.Thanks in Advance.

Thanks in Regards. —Preceding unsigned comment added by 202.54.176.51 (talk) 10:46, 1 December 2009 (UTC)

• Does copyright help? Also, if your research pertains to an ophthalmological diagnostic device, it seems like patent may also be a helpful article. However, we can't give you legal advice about copyrights and patents as they may apply to your specific case. Red Act (talk) 10:59, 1 December 2009 (UTC)
• (ec)You don't have copyright in the scientific results of your work - these could, if at all, only be protected by a patent. Copyright only protects the expression, not the ideas or the data. You do hold copyright to the actual text you wrote, but if you publish it in a journal, you almost certainly have to transfer copyright to the publisher - at best, you give him a fairly unrestricted license, but more typically you transfer it and receive some rights back. Sorry, that's how science works, and that's why scientists are rarely rich ;-). If you only want the results to be used (fame for you, better life for humanity), make sure you publish in a good journal and bring the paper to the attention of people who might be interested. If you want to make extra money, you need to apply for a patent, but a) it could be too late and b) its a fairly involved and none too cheap process, and there is no guarantee that you will recoup the money. --Stephan Schulz (talk) 11:07, 1 December 2009 (UTC)
  • One nitpick. In the US system you can't copyright scientific data, but in the UK and some other places one can claim a copyright over data. (Personally I think such copyrights are dumb, but I don't write the laws.) Dragons flight (talk) 01:47, 2 December 2009 (UTC)

If you publish your article in a traditional subscription journal you will be asked to transfer copyright to the journal as part of the process - and they won't pay you for it. See Scientific journal#Copyright. If you publish in an open access journal, i.e. a journal that is free to read and reuse, you will generally retain copyright, but you will usually have agree to release your work under a free license like the Creative Commons license. You need to pay to publish in many but not all open access journals,[11] and many open access journals will give full or partial waivers of the publication fees for researchers from countries like India. Fences&Windows 15:47, 1 December 2009 (UTC)

Size of processor dies

Does anyone know how large a typical processor die (I believe they're also referred to as wafers prior to assembly into a processor) would be? This [12] is exactly what I'm referring to - but I couldn't see a scale. 157.203.42.175 (talk) 13:19, 1 December 2009 (UTC)

First google hit has some numbers for recent chips: [13]. --Sean 13:32, 1 December 2009 (UTC)

FYI: I work in a fab where things such as that are manufactured. We refer to them as 'chips'. A 'wafer' is a round piece of silicon on which several to several hundred chips are built. See wafer (electronics). Dismas|^(talk) 14:14, 1 December 2009 (UTC)

Sean, thanks. Not sure how I missed that one. 157.203.42.175 (talk) 15:04, 1 December 2009 (UTC)

You can also look for pictures of naked cores, i.e. with the IHS removed. Extreme overclockers particularly those using water cooling sometimes do it (it's probably less common now then it was before because they are usually soldered) to improve cooling. The solder may confuse things a bit but if it's sufficiently removed you can usually see the size of the actual core. E.g. [14] [15] [16] [17] [18] [19] [20]. While these don't carry measurements (well one of them does and actually tells you the official size so you can see it's fairly close), you can work it out if you know the size of the entire processor (i.e. including circuit board) which probably isn't that hard to find out given that these are consistent within a processor socket for obvious reasons. Also [21] of a GPU (harder to find the dimensions but it helpfully includes a Singaporean coin). I'm not sure if all modern GPUs include an IHS anyway. I also came across [22] of a poor removal (of an already dead processor) which may be of interest because you can actually see some of the layers Nil Einne (talk) 23:46, 1 December 2009 (UTC)

Back before we had flash memory - lots of chips would have on-board UV-erasable, Programmable, ROM (UV-EPROM). In order to get the UV light into the chip to erase it - they had quartz windows over them - which handily lets you see the naked die inside. The processor in the photo to the right here is an ancient (and very simple) 8048. For scale, the pins on the side of the package are 1/10th of an inch apart. SteveBaker (talk) 00:36, 2 December 2009 (UTC)

the acidic group in aspartate/glutamate is COOH. what do you call the basic group in arginine?

That R-NH-(C=N)-NH2 motif. Why isn't this motif more common among organic compounds as carboxylic acids? It's kinda like the basic equivalent of COOH, isn't it? John Riemann Soong (talk) 15:48, 1 December 2009 (UTC)

It's a Guanidine group. I have to ask...did you actually look in the arginine article before posting the question about what its sidechain motif is called? It's stated in the first sentence of arginine#Structure. DMacks (talk) 17:00, 1 December 2009 (UTC)

I took a quick glance. I have to say, the phrase "the distal end of which is capped by a complex guanidinium group" isn't the most eye-catching sentence ever. Well anyway, why isn't the C+ carbocation resonance contributor shown? I would think it would be a major resonance structure, since with three electronegative nitrogens I imagine that that carbon is very positive. (In fact some 3-21 calculations show it to have over full positive charge!) Is a guanidine group much more reactive to nucleophiles than carboxylic acids, especially when protonated? Or does the delocalised positive charge, etc. make it react like amides? Basically why isn't this group hydrolysable under mild conditions (physiological conditions even) -- I imagine that hydrolysing a guanidine group on a protein (maybe converting it into an amide) would be potentially bad. John Riemann Soong (talk) 18:16, 1 December 2009 (UTC)

When you protonate the imine to make the guanidinium ion, this puts a + charge on a nitrogen. Basic rules of resonance will show that such charges are shared among alternate atoms; if you do the "electron pushing" to shift between resonance forms, there is no possible resonance form which puts a + charge on the carbon. Thus, there is no carbocation contribution to the resonance structure of guanidinium. The formal charge on the carbon is 0, and on each nitrogen is +1/3. Yeah, the electronegativity would indicate that having nitrogen at a higher formal charge would seem to be an intuitively backwards situation; but its just that there is no mechanism to have any charge on that carbon in guanidinium. --Jayron32 21:06, 1 December 2009 (UTC)

If the π electrons of C=N⁺H₂ are pulled into being a lone-pair on that N without another N lone-pair pushing it, you get C⁺(NH₂)₃ (for the parent structure). All this arrow-pushing would mean each N is sp² and the whole guanidinium is planar and highly resonance-stabilized, which is a common explanation for why guanidine is such a strong base. Of course, Nature is more clever than we are (once we actually study Her): turns out the NH₂ are actually rotated (propeller-like geometry around the C) and therefore there is not nearly as much resonance as simple arrow-pushing might predict. And that the high basicity is due to H-bonding of the added proton, not really enhanced electronic stability of the structure. See doi:10.1021/ja00059a035 for info. DMacks (talk) 22:51, 1 December 2009 (UTC)

In other words, it depends on whether the imine-N lone pair OR the imine C=N double bond is a better lewis base as to whether you end up with the carbon with a +1 formal charge OR you end up with the three nitrogens with a +1/3 formal charge. I'm pretty sure that in most cases, lone pairs are better lewis bases than π-bonding electrons are, which gives us the + charge distributed among the N's and not the C. --Jayron32 00:34, 2 December 2009 (UTC)

Putting cancer cells to sleep

I was reading about Kodiak bears' reproduction, specifically the part that says:

As soon as the egg is fertilized and divides a few times, it enters a state of suspended animation until autumn when it finally implants on the uterine wall and begins to grow again.

this made me wonder if any researchers are seeing if it would be possible to find out how to do that to other cells than Kodiak bear embryo cells by finding out how exactly it's done there (if that suspended animation functionality is a property of the Kodiak embryo cells themselves, an interaction in that specific kind of womb, or something else). The first application that came to my mind for stopping cell division of targeted cell types was cancer treatment. 20.137.18.50 (talk) 18:52, 1 December 2009 (UTC)

As I understand it - the difficulty isn't with killing or preventing subdivision of cancer cells - the problem is with finding ways to attack ONLY the cancer cells. If you have some way to direct a drug or other treatment to JUST the cancer cells - then there are any number of nasty things you can do to them to wipe them out. SteveBaker (talk) 00:30, 2 December 2009 (UTC)

Is there a medical term for this?

I think this might be closed-eye hallucination but I'm not sure...when I have my eyes closed when I'm about to go to sleep I sometimes see wallpaper-like repetitive patterns of leaves and flowers, or sometimes just ambiguous droplet-like dots. What is this called, if it isn't just CEH?--Editor510 ^{drop us a line, mate} 19:26, 1 December 2009 (UTC)

This seems to be a stage between consciousness and dreaming, akin to hypnogogic imagery. The mind may be perceiving the random sensory data as patterns. A higher level of dreaming would be perceiving the patterns as scenes rife with meaning, in vivid detail. If one attends to the incipient dream stage, the increasing level of consciousness causes the percept to revert to the original random patterns. See also the controversial Lucid dreaming. Edison (talk) 06:47, 2 December 2009 (UTC)

You may also find Prisoner's cinema interesting. cheers, 10draftsdeep (talk) 18:52, 2 December 2009 (UTC)

It may be related to Charles Bonnet Syndrome. -Craig Pemberton 02:06, 4 December 2009 (UTC)

It may be afterimages of whatever you were looking at that is, staring at, before you closed your eyes. Are you staring at leaves and flowers, or rain splashes on the window? --Janice Vian, Ph.D. (talk) 23:56, 6 December 2009 (UTC)

aspartame

I think saccharin is considered safe because it is broken down into non-toxic components in the stomach. What about aspartame? Is it broken down into non-toxic components during digestion or does it break down into toxic components during digestion which can be absorbed into the blood stream? 71.100.160.161 (talk) 21:38, 1 December 2009 (UTC)

Aspartame has some information pertaining to this. Unomi (talk) 21:42, 1 December 2009 (UTC)

Gums Bleeding

Before this question is dismissed as medical advice, please read carefully.

Why do one's gums bleed when there are a lot of bacteria proliferating on them? For instance, when someone avoids bruching their teeth for a while, and then brushes them, a lot of bleeding is observed. Why?130.127.52.67 (talk) 21:56, 1 December 2009 (UTC)

My understanding is this has nothing to do with bacteria at all. Gum tissue is simply sensitive, and if brushed regularly "toughens" against the assault of the bristles. The same can be said for flossing. If you don't floss for ages and then start, you'll look like you got on the wrong side of Mike Tyson. 61.189.63.183 (talk) 22:30, 1 December 2009 (UTC)

That would be a misunderstanding. DRosenbach ^{(Talk | Contribs)} 03:33, 2 December 2009 (UTC)

It is bacteria - see the link below. --Tango (talk) 22:38, 1 December 2009 (UTC)

See the two articles linked to from Gum disease. --Tango (talk) 22:38, 1 December 2009 (UTC)

There is a space between the gum and the tooth called the sulcus or gingival crevice. In health, the depth of the sulcus occurs where the junctional epithelial cells attach to the tooth. When the gum tissue is inflamed due to plaque, the depth of the sulcus no longer consists of fit, rigid junctional epithelial cells, but rather of flimsy, somewhat irregular epithelial cells. The epithelial barrier exists in an ulcerated state during gingival inflammation (otherwise known as gingivitis) and thus, bleeding from the underlying connective tissue occurs more easily, either when stimulated, or in cases of worse inflammation, even unstimulated. Plaque causes gingivitis and junctional epithelial ulceration because it is essentially minute food particles colonized by bacteria. Bacteria secrete all sorts of noxious and nasty chemicals, such as endotoxin and collagenase that stimulate a host response that induces inflammation via histamine and various interleukins and degrades colalgen, respectively. Let me know if there's anything else you'd like to know. DRosenbach ^{(Talk | Contribs)} 01:46, 2 December 2009 (UTC)

the economics of enantioselective chemistry

Are enantiotopically pure substances typically:

• Less than twice as expensive as a racemic mixture
• About as twice as expensive as a racemic mixture, with a little more to compensate for reagent consumption/workup
• More than 2x expensive as the racemic mixture?

Basically I'm wondering how price economics might convince companies whether to adopt an asymmetric process versus a chiral resolution process (where you discard half your yield). I imagine it might be variable for the substance involved (like if one enantiomer of a drug was particularly poisonous, for instance). John Riemann Soong (talk) 23:56, 1 December 2009 (UTC)

Depends on the source. Biologically derived molecules are usually provided in their enantiomerically pure state, and with the "unnatural" isomer being anywhere to slightly to ungodly more expensive (Because they have to be synthesized chemically). For example, L-phenylalanine from Sigma is about $390/kg, whereas D-phenylalanine is $2000/kg, and DL-phenylalanine is $430/kg (all for 98-99% purity, no extra testing/certification). For compounds which are both chemically synthesized, it depends on the starting materials. If chirally pure starting materials are available for reasonable prices and the chemical reactions to synthesize doesn't introduce/scramble any positions, entantiomerically pure compounds won't be any more expensive than the racemic mixture. The final case is where the stating compounds aren't chiral. If the synthesis incorporates entantioselective reactions/catalysts, the entantomerically pure compounds will be slightly more expensive than racemic, as entantioselective catalysts tend to be more expensive than the ones which give racemic products. If none of the previous points hold, the only practical way you can get entantiomerically pure compounds is by chiral column chromatography or by making a diastereomeric derivative. This makes the entantiomerically pure compounds ungodly expensive, as chiral chromatography columns are seriously expensive, and diastereomeric derivitization is a p.i.t.a. -- 128.104.112.95 (talk) 16:11, 3 December 2009 (UTC)

December 2

several questions

Here are two questions I that keep popping into mind and I have not had the chance to ask.

1. If you release a 100 pound mass from a geostationary orbit will it still be attracted to the Earth at the speed of 32 feet per second per second and if not what speed?

2. If you vibrate a magnet will it send out a magnetic wave at the frequency of vibration and if so will this magnetic wave in turn produce an electrical wave?

71.100.160.161 (talk) 00:13, 2 December 2009 (UTC)

For question 1, you need to specify at what height you are dropping from. The acceleration due to gravity should be (roughly) uniform at any given height, but will decrease with distance from the earth. However, if you drop such a weight from a geostationary orbit, it will not sink towards the ground; rather it will remain exactly where you let go of it, since it is in free fall with you when you release it, so unless you push it, it will remain in free fall right next to you. If you push it, it will move at whatever speed and whatever direction it was going when it left contact with your hand.

For question 2, electromagnetic waves are not seperable, they basically move together, orthogonal to each other. See this picture:

--Jayron32 00:29, 2 December 2009 (UTC)

(ec) If you release something while in orbit that something will also be in orbit and won't fall at all. If something started out at the altitude of geostationary orbit but with no horizontal momentum, then it would fall at a little under 1 foot per second per second (at first - it would increase as the object got closer to the Earth). Geostationary orbit is at about 36,000km above the centre of the Earth and the surface is about 6,000km above the centre. That's a factor of 6 different and, since gravity follows an inverse square law, that results in a factor of 36 difference between the gravitational acceleration. --Tango (talk) 00:29, 2 December 2009 (UTC)

For question 2, Jayron32, are you implying that if you move a magnet you make light (radio)? I guess it makes sense, since if you move a charge (electron in a wire) it makes light. Can you shake a magnet at kilohertz speeds? Ariel. (talk) 02:32, 2 December 2009 (UTC)

The OP implied that. I said nothing of the sort. I was dodging the question by merely noting that "magnetic" and "electric" waves cannot exist in isolation from each other; they are two sides to the same coin. His question is unanswerable as written because it presupposes something which is not true (the seperate nature of "electric" and "magnetic" waves). --Jayron32 05:02, 2 December 2009 (UTC)

"Fields and waves" was far from my strong point in school, but altering the current flow in a set of coils can create a rotating magnetic field, as was established by Nikola Tesla. Similarly, vibrating a magnet would cause induced voltage in a nearby coil, similar to varying current in a parallel coil. At least so far as "near field" effects are concerned, a moving magnet or a varying current in a wire or coil could have the same effect. Not so clear on antenna effects and radiated field. Electromagnetic waves have no lower frequency, and a charged particle or a magnet vibrating at 1 Hz or 100 Hz or 1000 Hz or 10 KHz should create an electromagnetic field, though at a lower frequency than what we usually consider "radio." Clearly a little horseshoe or bar magnet from the dime store, or a ceramic refrigerator magnet would fly apart or come loose from the moving thing if you attempted to rotate or vibrate it at megahertz radio frequencies, or microwave frequencies, or light frequencies. That is a material science problem and unrelated to the underlying physics. It should be possible to use a sound transducer to move a little neodymium magnet back and forth at 20 KHz, which is toward the upper end of the Very low frequency radio band (3Hz to 30KHz). I have doubts about the moving magnet acting as an efficient antenna or the actual emitted power. Edison (talk) 17:57, 2 December 2009 (UTC)

Evolution

http://www.jesus-is-savior.com/Evolution%20Hoax/devilution.htm

Is this a joke, or is that person serious? --70.250.212.43 (talk) 00:35, 2 December 2009 (UTC)

Sadly, he's probably serious. It doesn't make him correct, but I would fathom that the author of that bullshit actually believes it. --Jayron32 00:43, 2 December 2009 (UTC)

On the internet, if it looks crazy, it probably is. Hooray for democratization of communication channels—for every nut, a megaphone! --Mr.98 (talk) 01:48, 2 December 2009 (UTC)

It can sometimes be difficult to tell if a site or person is being serious or intended in as satire or parody. (Many people think Edward Current's work on Youtube is genuine/serious for example.) However that site appears to be genuine, I can find numerous discussions of it an evidentally it has had hosting problems Nil Einne (talk) 02:13, 2 December 2009 (UTC)

I'm beginning to be able to tell that a site is junk just by looking at the fonts, colors and centering of text on the page! It's truly incredible. Look at almost any site on perpetual motion, crystal healing, moon-landing conspiracies or anything like that - they all have the same basic look - primary colors, too many font sizes, centered text and pages that scroll on for dozens of screenfulls. It gets to the point where you don't even need to read the words anymore! SteveBaker (talk) 02:20, 2 December 2009 (UTC)

It's true that really amateurish/crazy sites stand out (e.g. Time Cube) in their embrace of vernacular web design... but looking good doesn't mean the content is any more sensible. Answers in Genesis has a wonderfully professional-looking site... but it's still full of junk. Looking bad doesn't necessarily mean that you're a crackpot, but I think most non-crackpots recognize that looking like a crackpot does not get their message across and change it. I think people who are 100% crackpots probably can't tell the difference. --Mr.98 (talk) 02:46, 2 December 2009 (UTC)

Mr.98, you only say that because you've been educated stupid by evil academia. :) A Quest For Knowledge (talk) 03:59, 3 December 2009 (UTC)

"primary colors, too many font sizes, centered text and pages that scroll on for dozens of screenfulls". Just like Daniel Brandt... Fences&Windows 03:31, 2 December 2009 (UTC)

Check out http://www.islamdenouncesterrorism.com/darwinism_materialism.html; it's even more ridiculous! They blame evolution for every societal problem since Darwin. Even things before Darwin are blamed on "Darwinism's" "materialistic roots". ----J4\/4 <talk> 17:58, 2 December 2009 (UTC)

The general principle of "If you sling enough mud - some of it will stick." definitely applies here! SteveBaker (talk) 19:28, 2 December 2009 (UTC)

I love a good comedy ;-). Falconus^{p t c} 21:15, 2 December 2009 (UTC)

There are lots of crazy sites out, and yes, some people really believe this crap. What gets me is that they think we're the naive ones. Add WP:FTN to your watchlist to get a sampling of the craziness. A Quest For Knowledge (talk) 05:01, 3 December 2009 (UTC)

BTW, we really could use some watchful eyes on the Fringe theory noticeboard, especially from editors knowledgeable about science. The fringe theorests were having a field day with the Climatic Research Unit e-mail hacking incident until we had to lock down the page. A lot of the time, it's hard to keep up with them because there are so many. A Quest For Knowledge (talk) 05:25, 3 December 2009 (UTC)

*wonders if anyone else thought of this Fringe when they first saw that board mentioned, and wondered how it managed to get so bad that we needed an entire noticeboard for one tv show...* :P J.delanoy^gabs_adds 05:42, 3 December 2009 (UTC)

The original link isn't nearly as funny as this one [23] where he claims that America is already communist (and so is every other Western democracy in the world). DJ Clayworth (talk) 20:25, 4 December 2009 (UTC)

greater permittivity than a vacuum?

Is it possible that there is something, perhaps an effected area of space such as in a pre-particle, (an area of space after the Big Band but before any particle has formed) where permittivity is greater than in a vacuum, allowing a particle to form? 71.100.160.161 (talk) 01:41, 2 December 2009 (UTC)

By Big Band, I assume you mean the big bang? Quantum mechanics states that even a vaccum has energy, so an absence of energy may indicate lower mass or permeability, but how the universe formed in the first place is probably beyond our scope of knowledge. ~AH1^(TCU) 02:35, 2 December 2009 (UTC)

By "vaccum," I assume you mean Vacuum. Edison (talk) 06:36, 2 December 2009 (UTC)

I assume that maximum permittivity is for a vacuum is determined by use of a perfect vacuum which would offer greater permittivity than a partial vacuum, So yes, is there the possibility of greater permittivity than a perfect vacuum such as an area in space so small it is too small to contain anything? 71.100.160.161 (talk) 15:39, 2 December 2009 (UTC)

I don't think this is an appropriate forum. There are several physics forums on the internet where you can discuss new theories and questions that are beyond the current scientific knowledge, but here our answear can merely be that no, there are no evidence nor generally accepted theories describing something like what you propose. (Which of course can be something exciting from one point of view :-) EverGreg (talk) 12:09, 2 December 2009 (UTC)

Such a variation has been proposed (published version requires payment) as an explanation for the Pioneer anomaly, but is far from being accepted. SpinningSpark 12:52, 2 December 2009 (UTC)

What's the permittivity of the space between two Casimir plates? --Tango (talk) 15:15, 2 December 2009 (UTC)

The same as a vacuum, the plates attract each other with an electromagnetic force. The difference is due to the plates. Graeme Bartlett (talk) 20:21, 2 December 2009 (UTC)

2,3-Dihydropyran as a protecting group

How do you take it off? I know you take it off with acid, but how do you guarantee that you get your actual alcohol back, with high yield? I would imagine the protected group might cleave in acid several ways ... John Riemann Soong (talk) 01:42, 2 December 2009 (UTC)

There are no guarantees in chemistry. You have to do the actual experiment using the actual reactants (and often screen several different times, temperatures, acids, reactant ratios, solvents, etc.) to find "what works best for intended reaction with minimum of unintended reactions". One reason there are so many different protocols for doing reactions is that every substrate is different, and (unlike in textbooks) every little thing may matter and may matter in totally unexpected ways. And the reason there are so many different protecting groups is because different substrates may have different sensitivies to various specific chemicals. Again, Nature is cleverer than the total of every journal article ACS has ever published.It's called research because you have to search over and over and over to find how to actually perform what seemed like an obvious and easy proposed idea:) DMacks (talk) 02:14, 2 December 2009 (UTC)

Well "guarantee" is a relative term. My prof mentioned it as a protecting group and now I am following up on it. According to design, is the ring oxygen supposed to be protonated sometimes? Or is the ring geometry making the ring oxygen act like an ethoxy oxygen on an anomeric carbon? Basically I'm worried the protected group will hydrolyse the wrong way. John Riemann Soong (talk) 02:29, 2 December 2009 (UTC)

In the real world, it doesn't matter which of the O is protonated first during acid-catalyzed hydrolysis deprotection. The acetal will fall apart either way, and eventually the ROH (deprotected alcohol) will detach—the product of acid-catalyzed hydrolysis of an acetal is ROH, R'OH, RCHO and you just happen to have "R' and R attached to the same molecular chain). On paper (i.e, not tied to the real world) you can do any and every possibility until you get to the one your prof wants:) But seriously, the reactions are reversible, and conditions are chosen to push towards the desired product by kinetics, thermodynamics, or concentration effects, etc. DMacks (talk) 21:14, 2 December 2009 (UTC)

Well I was wondering if the acetal cleaves (the non-product oxygen leaves), how is the product alkoxide ever supposed to leave? (It will create a primary carbocation...) John Riemann Soong (talk) 15:08, 4 December 2009 (UTC)

You asked about the "wrong way" cleavage and about whether it mattered which O gets protonated. I said (and you should know from learning about acid-catalyzed acetal hydrolysis) that both H get protonated eventually. And that it's not a primary carbocation, but is actually an oxonium-carbonyl (in resonance terms, the lone-pair on the "other" still-attached oxygen stabilizes the C⁺ attached to it (the original anomeric position). Once you protonate one oxygen, the whole hydrolysis reaction continues (and the other oxygen can come off under either acidic or basic conditions...hemi-acetals are not stable at all). DMacks (talk) 17:29, 4 December 2009 (UTC)

Also I have a question regarding the synthesis posted in that article. Do you dehydrate with alumina in neutral conditions? Is there a carbocation rearrangement involved? John Riemann Soong (talk) 01:50, 2 December 2009 (UTC)

Typhoon Nida

Hi. Please refer to the discussion topic I posted on Talk:2009 Pacific typhoon season. I am not forum shopping, just trying to incite quicker discussion. This seems a little disturbing, and the weather for the past few days has been unpredictable (just one example is that we've had black ice for the past two mornings). Thanks. ~AH1^(TCU) 02:43, 2 December 2009 (UTC)

If you wish to avoid accusations of "forum shopping" - then you need to ask us a specific question that you're unable to answer for yourself with the resources you have at hand. SteveBaker (talk) 12:46, 2 December 2009 (UTC)

Is the super typhoon responsible for all these ocean temperature changes, will this enhance El Nino, and could the pool of warm water actually cut of the Humboldt Current? ~AH1^(TCU) 00:32, 4 December 2009 (UTC)

ring opening/closure, reaction rates and entropy

I've been trying to organise the overload of reactions depending on some special entropy-reducing quality of rings or where two substituents are held in a conformed position next to each other ... can I get this straight:

Assuming enthalpy of the reaction is near zero (e.g. esterification <___---> hydrolysis), ring-closure reactions are slightly disfavoured (e.g. K will be a little less than 1) because of reduction in entropy. (Unless there is some weird effect where closure might actually relieve strain and increase the rotational degrees of freedom?) However, being in a ring will catalyse the reaction e.g. make both forward and reverse reactions faster.

Take the phthalic anhydride and pthalic acid. The enthalpy of forming the anhydride is positive (and the reduction in entropy hurts it further), but however kinetically, the rates of hydrolysis and anhydride-formation are both increased cuz of the ring effect. Distillation of water and heat will define the equilibrium point, but the ring proximity thing will make both reverse and forward reactions faster? I'm trying to frame this in terms of thermodynamics. John Riemann Soong (talk) 02:45, 2 December 2009 (UTC)

Speed at which levels of melanin in humans adapt to UV light

As I understand it, the varying levels of melanin in humans (and thus varying skin tones, and so forth) are believed to have evolved at least partly in response to differing levels of ultraviolet light — the high levels of UV light in equatorial areas prompt retention of melanin, while in places closer to the poles, there's less UV light and thus not so much melanin is kept. (I'm setting aside other contributing factors like diet, for now.) My question is: how quickly would changes in UV light be reflected in melanin? That is, if a group migrated from one place to another, how long would it take before there were noticeable changes in melanin levels (setting aside other factors) as a result? I don't expect this is the sort of thing that can be determined with any precision, but even rough figures would help. Ten thousand years? A hundred thousand? -- 203.97.105.173 (talk) 03:02, 2 December 2009 (UTC)

I recall being told that it would take ~10,000 years for black to go to white or vice versa. Dragons flight (talk) 03:05, 2 December 2009 (UTC)

To slightly side-step the question, some research suggests that light skin in Europe may have evolved as recently as 5,500 years ago:[24] Fences&Windows 03:28, 2 December 2009 (UTC)

In modern times, it may be never. Since everyone pretty much lives indoors now, theres little reproductive pressure to favor one skin tone over another, so there is little reason to suppose any such changes will occur in the future. Furthermore, there is little genetic isolation anymore, so there is little reason to believe that an isolated population would develop such uniform traits among themselves. --Jayron32 04:59, 2 December 2009 (UTC)

Jayron, you should come out sometime and enjoy the outdoors. Everyone does not pretty much live indoors. Your second point stands. Dauto (talk) 06:07, 2 December 2009 (UTC)

Do you work outside? Most don't anymore. --Tardis (talk) 15:59, 2 December 2009 (UTC)

Woman wearing a bikini

Who said anything about work? Dauto (talk) 01:42, 3 December 2009 (UTC)

Evolution can run pretty quickly when the genetic basis for the change is already in the population and the environmental change makes a significant dent in the ability of less useful genes to be passed on. It's likely that the genes for different skin colors are present in the general population - so if the UV levels changed suddenly and started to cause a dramatic change in birth rates and survivability then evolution might happen very rapidly. But that second point is the issue here. The disadvantage to light skinned people in sunny places or dark skinned people in less sunny places just isn't that dramatic. If there is only (let's say) a 1% chance of someone being so seriously disadvantaged by inappropriate skin tone that they failed to reproduce - then the rate of evolutionary change will be fairly slow. But if 90% of people with the wrong skin tone died before reaching child-bearing age - then we'd evolve in not too many generations. I don't know what the case was as mankind migrated around the world - or what it is today - but my gut feel is that this would be on the slower end of the scale in the past and essentially non-existant today in a technological world of sunblock, indoor living, clothing and vitamin Evitamin D(sorry!) supplements that allow anyone to live successfully in any climatic conditions. SteveBaker (talk) 12:44, 2 December 2009 (UTC)

That concept that skin tone evolution has stoped because we all live indoors, use cloth and sunblock and vitamin E (That last one is probabily irrelevant anyways) doesn't hold water. Those factors will make us evolve towards a lighter skin tone instead of a darker one. evolution still happens. 169.139.217.79 (talk) 15:54, 2 December 2009 (UTC)

Why would they make us evolve towards a lighter skin tone at all? What is the reproductive pressure to do so? Do darker-skinned people reproduce less effectively when they wear sunscreen and clothes and work in offices? The idea that people's skintone will change just because their environment changes smacks of Lamarckism, a thoroughly disproven idea. --Jayron32 18:56, 2 December 2009 (UTC)

People with dark skin tones at high latitudes do have an increased risk of rickets, but it is fairly minimal. --Tango (talk) 19:01, 2 December 2009 (UTC)

It's minimal in a modern world with good nutrition, vitamin-D supplements in milk and decent medical care - but when darker skinned people started to migrate into Northern Eurasia - none of those benefits were present - and that would have been enough of a problem to reduce reproductive success - and hence evolutionary benefit for people with lighter skin tones. The need to wear clothing as protection from the colder climate (thereby covering up yet more skin and making vitamin D production still less effective) probably added to the problem. Within enough generations - voila - lighter skin color. The benefit must have been substantial enough to offset the costs in terms of skin cancers and such caused by having a lighter skin on sunny days in the summer...which also isn't such a big deal in a modern world with people staying indoors much more and having clothing and sunblock. SteveBaker (talk) 19:23, 2 December 2009 (UTC)

Sorry, yes, I meant in the modern world. --Tango (talk) 19:43, 2 December 2009 (UTC)

Surely you mean vitamin D? --Tardis (talk) 15:59, 2 December 2009 (UTC)

Yes - I do, sorry! Vitamin D is produced in the skin when exposed to sunlight. Light skinned people need very little exposure to the sun each day to make all the Vitamin D they need. But dark skinned people who live in the extreme North or South of the planet - or in places where there is dense cloud cover for extended periods - don't absorb enough sunlight to make sufficient quantities of this vitamin - and that (presumably) is the main reason for the evolution of lighter skin colours as humans migrated away from the tropics. However, in our modern civilisation - this problem is easily overcome by eating an appropriate diet or (in extreme cases) taking vitamin supplements. Hence, there is unlikely to be any evolutionary pressure for lighter skin to continue to evolve in modern times. SteveBaker (talk) 19:15, 2 December 2009 (UTC)

Actually, there is a considerable body of opinion that vitamin-D deficiency (less serious than that needed to cause rickets) is a widespread problem even among light-skinned people. I remember this being in the news when I lived in Canada, where obviously it would be more of an issue than at my current California latitude.

The experts can't seem to agree on whether to recommend oral supplementation, partly because D, as a fat-soluble vitamin, is possible to overdose on. (Experts don't trust people much, as a general rule.) In any case I took D supplements during the Canadian winter. --Trovatore (talk) 02:02, 3 December 2009 (UTC)

Since going outdoors might involve disconnection from the internet and Wikipedia, could this be fatal?Trevor Loughlin (talk) 12:49, 2 December 2009 (UTC)

Wikipedia does not offer medical advice. Of course, if disconnecting yourself from Wikipedia could be fatal, we can hardly suggest that you go see a doctor either. Do you have an iPhone? --Tardis (talk) 15:59, 2 December 2009 (UTC)

The article Human skin color has a bit about all this. One gene which only arose between 5 and 12 thousand years ago accounts for about a third of the difference between black Africans and white Europeans. The previous ones in all likelihood spread even faster as they would have had a greater effect. So about 20 thousand years for most of the change would probably be quite reasonable. As to the amount of difference needed for genetic advantage to take effect I've read that a real advantage as little as one in a thousand will eventually spread throughout a population and not get swamped by random factors. This is why it always interesting to ask about possible advantages in some harmful genetic disease or predisposition to it to account for its existence. Dmcq (talk) 09:20, 3 December 2009 (UTC)

Thanks for all the answers. -- 203.97.105.173 (talk) 21:58, 5 December 2009 (UTC)

vitamin c chart at bottom of vitamin c article.

Is it possible to include kale in the vitamin c chart at the bottom of the vitamin c article? —Preceding unsigned comment added by 97.96.127.130 (talk) 10:13, 2 December 2009 (UTC)

Yes, it is possible. Be bold! Red Act (talk) 10:21, 2 December 2009 (UTC)

Remember to include your source for the information. SpinningSpark 10:25, 2 December 2009 (UTC)

You can get the vitamin c content for kale from the first of the three references cited for the table. If you get a value from that source, there's no need to cite a reference specifically for the new kale line that you add to the chart. All you need to do is add a new line in the table for kale, using the value you found in the reference. Red Act (talk) 10:36, 2 December 2009 (UTC)

GIS + ray-tracing algorithms = traffic noise estimation

I've put this here rather than in the Computing section as I think it is more likely to catch the eye of the appropriate people. I'd like to write a freeware program to predict the amount of traffic noise at various distances from busy roads, and display it in noise-intensity contours. Are there any freely available relevant algorithms or programming code that I could use rather than starting from scratch? Or does a free program already exist? The use of ray-tracing for sound rather than light was discussed in an earlier question on this page. Thanks. 89.242.106.49 (talk) 15:30, 2 December 2009 (UTC)

I see an immediate problem with this. First, assume that the entire world is perfectly flat - no trees, houses, fences, hills, etc... Noise is easily measured by the distance to traffic source(s) -- some places may get noise from more than one road. You can use something like Google Traffic to measure traffic density and simply reduce the noise the further from the road you get. Now, what if there is a large solid fence next to the road to block the noise? No online mapping service will map the fence. What if there is a large hill? You will need to overlay an elevation map to reduce sound quicker when going uphill. So, it seems to me that the first step is to create a map that has proper elevation based on land (hills/trees) and manmade objects (fences/buildings). Then, you can work on getting traffic data. -- kainaw™ 18:40, 2 December 2009 (UTC)

Please! I do have at least a double digit IQ and I'm well aware of all that already thanks. 89.242.106.49 (talk) 20:00, 2 December 2009 (UTC)

I think you may be making a mistake in fixating on ray tracing. That's an appropriate way to handle optical rendering - but it may not be the best way for audio. I would expect some kind of wave-front model to be better at handling your problems. As I explained in answer to your previous question on the computing desk - ray tracers (for light) presume light travels in straight lines without diffraction. If you employ that technique for audio then if the simulated microphone doesn't have "line of sight" to the cars on your virtual road - then it'll hear silence. But we know that in reality, a small rise in the ground does very little to cut out the noise of a nearby road (although it easily blocks 100% of the light coming from it!) - so you know, without doing very much deep thinking, that the problem you're trying to solve isn't a good fit for a classic raytracing solution. I typed "acoustics" into the search box at http://www.sourceforge.net (probably the largest repository of OpenSourced software in the world) and came up with several possible hits. One is FOAC - which claims to be: "software for calculating acoustic field by finite difference time domain method( FDTD )". It appears to be a plugin for Matlab. In the FOAC forums, there was a list of other opensourced acoustic packages: HERE. The language they use is completely foreign to a graphics guy like me - so I guess you just hit the limit of my expertise. Good luck! SteveBaker (talk) 18:53, 2 December 2009 (UTC)

I repeat my comment given to the previous poster. While a very simple program would suit settings in the countryside in a flat landscape - and that would be useful to many people including myself - a program suitable for an urban area would need to take into account reflecting off surfaces such as walls and being absorbed by other things such as vegetation as well. For an urban area I would need something which is capable of dealing with the equivalent of large scale maps that include buildings, and ideally being able to add ray-tracing capabilities to it. Doing it as a flat 2d plan would be the simplest case, but in some instances the differing elevetations would matter also. 89.242.106.49 (talk) 20:00, 2 December 2009 (UTC)

If you are going to start from scratch you will need something like Uniform theory of diffraction. I studied Geometric theory of diffraction before, and the formula's were huge, each filling up one complete page. This will account for waves of sound diffracting around obstacles. It will vary with frequency. Graeme Bartlett (talk) 20:10, 2 December 2009 (UTC)

A complex forumula may not be a problem, particularly if you can put it in a subroutine. 92.29.36.113 (talk) 23:37, 2 December 2009 (UTC)

El nino

Will it bring more snow to North Texas than usual?Accdude92 (talk to me!) (sign) 17:19, 2 December 2009 (UTC)

Take a look at NOAA's weekly El Niño status report -- the last few slides give an overview of the effects of El Niño on precipitation across the USA. Looie496 (talk) 17:53, 2 December 2009 (UTC)

I don't know whether El Nino caused it - but North Texas had some snow last night - and that's "more than usual" for early December. SteveBaker (talk) 18:22, 2 December 2009 (UTC)

There is a giant Gulf low currently in the Midwest, formed from a combination of at least five different low pressure systems, and it is travelling extremely fast. It looks to be worse than the 1993 Storm of the Century for those on the East Coast of the US and Southern Ontario, because the storm is drawing air and moisture from the Gulf of Mexico, the East Pacific, and the Caribbean, while the cold Arctic air extends to Hudson Bay and the northern reaches of Nunavut. Yesterday by this time, the low was still three separate systems, one in the Gulf later to acquire a classic tornado signature, another near New Mexico that resembled a hurricane on land, and yet another that was a cold front near the coast of Texas. Meanwhile in the western Pacific, Typhoon Nida recently weakened from a category five to a category one, but when it weakened to a category four it was perhaps briefly larger than Tip. Now a second system is starting to form behind Nida in the gap in the Subtropical High that the storm created. The warmest pool of water is now in the Central Pacific, and the Humboldt current is becoming choked by this warm pool as it moves east. Currently all the warmest water in the West Pacific is south of the equator. This could bring an early and extra boost to El Nino. Already, the warmer water in the south Eastern Pacific is affecting temperatures in the Gulf and Caribbean, and this was likely enhanced by the warmer water temperatures. Off Brazil, a zone of 26C+ water extends almost to Uruguay, and this is what happened in March of 2004 when Cyclone Catarina formed. ~AH1^(TCU) 23:42, 2 December 2009 (UTC)

Ok but what does that mean for North texas? More snow?Accdude92 (talk to me!) (sign) 14:02, 3 December 2009 (UTC)

This link seems to show more snow arriving in north Texas in the next week, probably two storms. ~AH1^(TCU) 00:30, 4 December 2009 (UTC)

Children on Wikipedia

I have a six year old daughter who I want to start using Wikipedia as a reference. However I'm afraid she'll click a few links and suddenly be staring at pictures I wouldn't want her to see for several more years. I believe this is a legitimate concern, for example, it only takes 3 clicks to go from Man to Human sexuality to Bondage (BDSM) where there's quite pornographic material. There must be near infinite similar examples. Is there a children's version she could use (not the Simple English wiki, I would like her to develop her vocabulary)? TheFutureAwaits (talk) 18:39, 2 December 2009 (UTC)

There are third-party ports of Wikipedia which have stripped out all of the "naughty bits". These are not actively edited versions of Wikipedia, so often they are not entirely as up-to-date as Wikipedia itself is, but if you are more concerned with protecting your children from pornographic material (a VERY legitimate concern) than it may be worth it to be dealing with a slightly out-of-date version of Wikipedia which has been cleaned up for the kids. Wikipedia for Schools is the one I recommend for others. Good luck! --Jayron32 18:52, 2 December 2009 (UTC)

A child of six shouldn't be left alone with an Internet connected computer - regardless of which site she uses. The way to have kids get the best out of the Internet (and Wikipedia) is to keep the computer in whatever room your family hangs out in - and for parent and child to surf together - just like you'd read a book together or (hopefully) watch TV together. Any of those things could potentially expose your kid to stuff you don't think is appropriate - so these activities need to be a "family time" kind of thing. That being the case - you can use Wikipedia with complete safety - with YOU deciding what's appropriate and not some anonymous (and fallible) Wikipedia-clone maker. If something difficult needs explaining - you are there to explain it. The computer is not a child-minder and shouldn't be treated as such. More importantly - you can also direct your child towards interesting/useful/appropriate things - not just away from inappropriate material - no amount of censorship of the content will help you there! A 6 year old is not able to make the connections that you can make - to find answers in an online encyclopedia that you can find. SteveBaker (talk) 19:39, 2 December 2009 (UTC)

I find it rather offensive that you're telling me how to raise my child. I simply asked if there was a children's version which Jayron was helpful in providing. It's a lot to assume I'm letting her on the internet unsupervised. It's good to know other people treat the issue with concern but please don't assume I neglect my children. TheFutureAwaits (talk) 19:57, 2 December 2009 (UTC)

I'm actually more concerned with truth than whether you might find it offensive or not. If you are supervising her then what do you have to worry about? Just use regular Wikipedia. What am I to assume from the nature of your question? The best way to increase her vocabulary is to read to her. When a kid doesn't understand a word - they just skip over it and guess the meaning (often incorrectly). SteveBaker (talk)

The suggestion to surf together is a pretty common answer to questions like yours. I don't think you should get offended, it's a good suggestion. It's not that anyone thinks you are negligent or that they're trying to tell you how to raise your child, it's just the fact that the internet, by it's very nature, is only a couple links away from content you might not want your kids to see. -- JSBillings 20:23, 2 December 2009 (UTC)

I had this problem a while back with a sequence which went Tudors>>Anne Boleyn>>Incest (which then was the wikilinked crime on her death warrant). If you do want to avoid being online at all the Schools Wikipedia also comes as a free download which we will mail you without charge if needed (yes, me). It is less popular compared to Wikipedia but a lot of schools intranets load it. As said it is currently mainly March 2008 content and Obama is still only a senator (there will be a big update in Q1 2010). --BozMo talk 20:38, 2 December 2009 (UTC)

It doesn't help the original poster, but I've experimented with creating filtered subsets of Wikipedia using categories and keywords to choose what material to exclude. My impression is that I can actually do a pretty good job at this. Not as good as hand-checking for obvious reasons, but the result I'd hope for would be a much larger collection of "good" articles while excluding most of what people find objectionable. I've thought about trying to finish this early next year. Dragons flight (talk) 20:48, 2 December 2009 (UTC)

Unfortunately, Wikipedia culture is such that we demand that our readers accept our "anything goes" policy as a price of using Wikipedia. You'll never get any prior warning of what the next click will bring you to; that's just not the way we roll here. However, Openmoko's Wikireader is a portable device for reading a static version of Wikipedia offline, and advertises itself as having parental controls. It might be the solution to the original questioner's problem (since Wikipedia resolutely refuses to provide a solution). - Nunh-huh 21:22, 2 December 2009 (UTC)

The wikireader parental controls are just a keyword based filter as I understand it. Dragons flight (talk) 22:29, 2 December 2009 (UTC)

We did make a request yonks ago for a hidden tag of "unsuitable for young children" be included in content so that a reader could switch it on or off but the community is for some reason extremely hostile to any concept of censorship. --BozMo talk 22:34, 2 December 2009 (UTC)

One problem is defining what is and is not "unsuitable for young children" on an international site. E.g. Europeans are pretty relaxed about children seeing non-sexualized female toplessness, but get an accidental 2-second "wardrobe malfunction" on US television, and you won't hear the end of it for months. -- 128.104.112.95 (talk) 23:09, 2 December 2009 (UTC)

Parental supervision while small children read Wikipedia is advisable, since a vandal can introduce any content into all but the few protected articles at any time, or can substitute an extremely obscene image for another image, with it typically taking several minutes or several days for articles few are watching to get reverted to the good version. Wikipedia is not censored, and content you might think inappropriate for a small child is only a couple of clicks away. Children doing unsupervised websurfing are also likely to be stalked by pedophiles. A School-appropriate version of Wikipedia as mentioned above would be useful, with staleness being the main problem. Edison (talk) 23:29, 2 December 2009 (UTC)

Lets not be silly children unsupervised websurfing are not 'likely' to be stalked by pedophiles. That is a ridiculous comment. They are clearly at more risk than when supervised with an adult, but the risk itself is still extremely low. 194.221.133.226 (talk) 10:13, 3 December 2009 (UTC)

I'd say the child is more at risk when they are supervised by an adult -- for every child molested by a pedophile they met over the internet, several thousand are molested by their parents. --Carnildo (talk) 02:40, 5 December 2009 (UTC)

You can get a huge reduction in simple vandalism by not serving any page unless it is at least a few hours old without further editing. That's another kind of automated filter one can use when collecting good versions. Dragons flight (talk) 23:41, 2 December 2009 (UTC)

The main trouble is that it's difficult for anyone else to anticipate exactly which images you would find unsuitable for your child, without knowing you or your child. One option is Internet filtering software, such as CyberSitter or NetNanny, which you can configure to suit your particular concerns. A conservative option is to turn off images altogether and browse text only. Dcoetzee 23:51, 2 December 2009 (UTC)

Exactly - there are widely differing opinions between parents about what is or is not appropriate at a whole range of ages. It's quite unreasonable to expect one filtered source to be appropriate for all parent's requirements, for all children (they are all different you know?!) over a wide range of ages. Then, we have three MILLION articles - nobody, no organisation, can possibly have checked them all. So we're left with some flaky keyword-based thing - which can't figure out what's in photos anyway. That will exclude some appropriate articles and fail to exclude some noxious ones. I simply don't believe this can work. But in any case - leaving a 6 year old alone with an internet-connected computer is just not reasonable. I'm sorry our OP objects - but it's true. Work with your kid - both you and she will be better off as result. SteveBaker (talk) 00:39, 3 December 2009 (UTC)

With keyword-based filters you also have the problem of the unmentionable British town. -- 128.104.112.95 (talk) 22:44, 3 December 2009 (UTC)

Buying the latest edition of Worldbook or just taking your child to the closest public library to read about things in that or similar encyclopedias is another great idea. Edison (talk) 00:24, 3 December 2009 (UTC)

Another question about visual phenomena...

When I close my eye and push hard on it, I see weird psychedelic greyness, like a swirly tunnel with RGB dots. What's that called?--Editor510 ^{drop us a line, mate} 18:52, 2 December 2009 (UTC)

Not sure that is a good thing to do, but I am no eye doctor... Googlemeister (talk) 19:47, 2 December 2009 (UTC)

Phosphene#Mechanical stimulation -- Finlay McWalter • Talk 19:48, 2 December 2009 (UTC)

Thank you, Finlay. Googlemeister, I asked for an answer, not medical advice. Keep that in mind for next time.--Editor510 ^{drop us a line, mate} 20:08, 2 December 2009 (UTC)

I guess this is a situation exemplifying the statement "There are no stupid questions... " Well, I am sure you can fill in the rest. Googlemeister (talk) 21:04, 2 December 2009 (UTC)

"...There are only stupid people who quote trite clichès and leave off the end for others to fill in themselves."--Jayron32 21:18, 3 December 2009 (UTC)

why do i feel hotter after a bath?

It gets cold where I live and I have no central heating. The house feels cold and the fire seems to not do much, however after a hot bath in the evening the house seems to be 50% hotter than it was. Is it my core temperature or something? —Preceding unsigned comment added by 89.242.173.139 (talk) 19:14, 2 December 2009 (UTC)

There's probably a couple of things at work here. First, to point out the obvious, after a hot shower or bath you are warmer. People typically have an internal temperature of about 37C, but it's much cooler than that at your extremities (feet, hands) and, to a lesser extent, any part of you exposed to the environment (i.e. your skin). A hot bath can raise the temperature of your extremities, making you feel warmer overall. Your core temperature changes very little except under rather uncomfortable extremes such as hyperthermia, so I doubt you've affected your core temp more than a tiny amount. The benefit to having your extremities warmed (to me) is that they stop acting like heat sinks for the rest of the body. Cold feet, by themselves, are no big deal, but on some chilly days it almost feels like they're draining the heat right out of you. When you add heat energy to your feet through hot water, rather than through your own efforts, it seems like you get paid twice - your feet are warm and you haven't had to freeze your hands (or your partner's back!) to do it. Matt Deres (talk) 21:33, 2 December 2009 (UTC)

Your temperature-detection equipment is in your skin; a hot bath raises the temperature of your skin, so there you are. As an aside, a simple fireplace will often cause a net heat loss in your house. You want some kind of wood stove or fireplace insert to make the fire put off more heat than it sucks up the chimney. --Sean 17:27, 3 December 2009 (UTC)

That point about fireplaces causing a net heat loss sounds bogus to me. Dauto (talk) 16:35, 4 December 2009 (UTC)

That's the common reaction, but it's true: a fireplace is very inefficient at transferring heat to the surrounding environment. Effectively all the hot gasses generated by the fire go up the chimney, most of the radiant heat is wasted heating up the fireplace bricks, and the room-temperature oxygen used up by the fire is replaced by sucking cold air in from the outside. --Carnildo (talk) 02:46, 5 December 2009 (UTC)

Children aargh

Ok, so I cannot always answer my offspring's question, here is one: "If you exclude a primary colour such as blue from the visual experience of a baby through to childhood we have been told they will not develop the ability to see and process that colour mentally, which I understand, but what if you exclude a secondary colour whilst allowing the separated components into their world: will their brain mix the colours and develop the secondary colour (say, green) via dreams etc or will they not develop a capacity to "see" the secondary colour in cognitive terms". Oh dear. Any help? --BozMo talk 20:43, 2 December 2009 (UTC)

Who said that excluding a primary color will prevent a child from being able to see it? I'm just curious, because I haven't heard that, and I am wondering how they managed to test it. Falconus^{p t c} 21:11, 2 December 2009 (UTC)

Who said it in this case was a biology teacher so it could be suspect although I suspect "see and process" should be taken together. There is lots of stuff around about lazy eyes and some eye conditions do selectively filter frequencies/colours so "testing it" I assumed was more "observing it" --BozMo talk 21:17, 2 December 2009 (UTC)

Firstly, green is a primary colour (it's additive or psychological primary colours that are relevant here and green is in both those groups, subtractive primary colours, which don't include green, are only relevant to painters). Secondly, could you provide a reference for your initial assertion? I'm not sure what would happen if you someone doesn't see a particular colour during their childhood. Under the opponent process theory, we perceive colour along two axes red-green and blue-yellow. I don't think you could exclude red, say, without also excluding green. That would mean you reduce colour to one axis. If the brain doesn't form the ability to see the other axis (and I don't know if it would or not) then you would essentially be colour blind (red-green colour blind or blue-yellow colour blind depending on which axis you exclude). If you exclude a secondary colour, it might be similar to the situation described in Opponent process#Reddish green and yellowish blue (which is about creating new secondary colours). In that case, people described it as a new colour that they couldn't recognise, but some were able to describe it as a combination of colours they knew. It would be reasonable to assume showing someone a secondary colour which is new to them would have a similar effect. --Tango (talk) 21:13, 2 December 2009 (UTC)

That's helpful thanks, and good enough I hope to keep my daughter thoughtful for a couple of hours. --BozMo talk 21:19, 2 December 2009 (UTC)

Google: Mancuso Hauswirth "color blindness" "hard-wired".—eric 01:21, 3 December 2009 (UTC)

Christmas lights

What is it that makes new-fangled LED Christmas lights look so harsh and cold, while old-fashioned incandescent Christmas lights look more warm? Something about the narrowness of their spectrum, prior life experience of them, or something else? - Nunh-huh 21:16, 2 December 2009 (UTC)

I expect it is the narrowness of the spectrum. --Tango (talk) 21:18, 2 December 2009 (UTC)

Color_temperature? --77.22.37.20 (talk) 21:37, 2 December 2009 (UTC)

I think it's because most LEDs are clear while the larger, older lights are usually frosted to an extent. If you've ever bought the wrong type of (regular) light bulb for your home, the difference should be immediately obvious. ~ Amory (u • t • c) 21:45, 2 December 2009 (UTC)

I suspect the answer is along the lines of what User:Tango said. Incandescent Christmas lights work by emitting white light, which is composed of all visible wavelengths, and then filtering it through a colored glass so that it appears colored, but light from the whole spectrum still gets through. LED lights, on the other hand, actually produce light of only one certain color, in a very narrow spectrum. It's this narrow spectrum that you're seeing as "harsh." Mildly Mad^T_C 21:53, 2 December 2009 (UTC)

I think the color temperature is a good answer, as 77.22.37.20 suggested. The retina is not a good spectrum analyzer to determine what wavelengths are present. The size of the source may also be a factor, since most incandescent Christmas bulbs are much larger than their LED rivals. Edison (talk) 23:21, 2 December 2009 (UTC)

It may also be that LEDs are typically strobed to work at maximum efficiency - i.e. they flash on and off very rapidly. This should be faster than the eye can detect, but may still cause an effect of harshness. You can check whether they flash by moving them quickly - you should be able to see the flashes that way. --Phil Holmes (talk) 09:48, 3 December 2009 (UTC)

I thought the strobing is due to plug-in LEDs running off AC current causing flickering at 50 or 60 Hz. I've never noticed the flickering when they operate under DC power. -- Flyguy649 ^talk 15:45, 3 December 2009 (UTC)

If you simply power an LED from a DC source, you're right - they don't strobe. However, LEDs are much more efficient at high currents, but running them continuously at such a current would make them too bright and probably too hot and they would fail. So the solution is to run them at high current for a short time, turn them off to let them cool and then switch them on again. So if you're a commercial manufacturer wanting to make your LEDs as efficient as possible, that's how you power them - and hence the strobing. Nothing to do with AC or DC. --Phil Holmes (talk) 10:00, 4 December 2009 (UTC)

Strobing LEDs definitely makes it look unnatural. If you slide your eyes quickly across a string of such lights you get a weird 'digital looking' trail instead of a smooth blur like you would with an incandescent

If you're thinking of white Christmas lights, then a big part of the issue is the actual color of the lights. They're not quite white. "White" incandescent tree lights are slightly yellowish which we mentally associate with warmth, candles, etc. Most "white" LED lights are actually slightly blue, maybe not enough that you notice consciously, but subconsciously you associate them with coldness, and metal, and artificial light sources. APL (talk) 16:47, 3 December 2009 (UTC)

Since most "white" LED's are typically ultraviolet LED's used to excite a phosphor coating - they could presumably fix that by reducing the amount of blue phosphor in the coating. However, because LED Xmas lights are not a vast market for white LED manufacturers - there isn't enough volume to justify making special off-white ones. I suspect that this will happen though - it's such a joy to have a string of lights actually work reliably after they've been pulled off a tree - stored in a garden shed for 340 days and then dumped back onto the tree again...when the prices fall by just a little more, the incandescent kind will go the way of the Dodo. I made my first set of LED Xmas lights myself - back before there were any that you could buy. I used 50 bi-color red/green LED's which can show any color in the red/orange/yellow/green range - all of which seem pretty Xmassy. They are still working - but the big DC power supply it takes to run them is a pain to deal with...so now I have store-bought ones. SteveBaker (talk) 18:39, 3 December 2009 (UTC)

But going through each bulb on a series circuit testing each one to see where the loose one is is part of Christmas tradition! --Tango (talk) 18:48, 3 December 2009 (UTC)

They'd better hurry up before our old lights need replacing: the decorations section of shops is horrible this year with the strings of strobing LEDs. Is it too much to ask for something that either flashes slowly or stays on? I'd even take a cold white if they at least avoided the headache-inducing throb. Or, instead of trying to be 'tasteful', they could just release strings of coloured LEDs: aren't the red ones cheaper? But either way, they have to stop that strobing. 86.166.148.95 (talk) 01:37, 4 December 2009 (UTC)

which element most toxic?

Which pure element is the most toxic if ingested? Natural elements only, don't worry about stuff heavier then Uranium. Is it arsenic? Googlemeister (talk) 21:41, 2 December 2009 (UTC)

How much and in what form are we talking about here? Chlorine gas is up there, but if you could figure out how to do it I imagine elemental Fluorine would be far worse. ~ Amory (u • t • c) 21:51, 2 December 2009 (UTC)

Well assume the natural state of the element at STP. So whereas drinking liquid helium would probably kill you, swallowing a bit of helium gas would not be lethal, so it is not that helium is naturally toxic. Googlemeister (talk) 21:56, 2 December 2009 (UTC)

Beryllium, Plutonium, Mercury, Arsenic, Cadmium are all pretty nasty.[25] Fences&Windows 22:27, 2 December 2009 (UTC)

But of lot of those are not as toxic as their salts, many of the heavy metals won't dissolve much in stomach acid, and small amounts will pass right through. Therefore one should consider things like sodium, potassium, bromine - not that you would ever be able to swallow them!  Ronhjones  ^(Talk) 22:35, 2 December 2009 (UTC)

Polonium isn't great - it was used to kill Alexander Litvinenko in the UK a couple of years ago. Brammers (talk) 23:15, 2 December 2009 (UTC)

But it didn't kill him via chemical toxicity, but by radiation. Polonium (any isotope) is so radioactive that there is probably no experiment that can measure its chemical toxicity, which is negligible in comparison. --Trovatore (talk) 00:28, 3 December 2009 (UTC)

Right... and if you are allowed to pick non-stable elements, you can find some reeeaaaallly nasty ones, albeit they have very short half-lives. Whether you count these as "natural elements" of course relies on different definitions of "natural". --Mr.98 (talk) 03:25, 3 December 2009 (UTC)

My objection was to the word "toxic". Radioactives will kill you, but they're not toxic, any more than a bullet is. Toxicity is a chemical property. --Trovatore (talk) 10:36, 3 December 2009 (UTC)

Hmm while I'm not disagreeing with you our article does toxic Nil Einne (talk) 15:30, 3 December 2009 (UTC)

I think toxicity means a bit more than you are claiming it does ("chemical toxicity" is one sub-variant of "toxicity"). I am fairly sure that highly radioactive substances are classed as highly toxic (ergo, Polonium#Toxicity). Where things get trickier are weakly radioactive but long-living substances (like, say, plutonium), which are not very acutely toxic (you will not keel over dead if you are exposed to it) but have long-term carcinogenic risks (you will get lung cancer in some number of years if you inhale a lot of it). --Mr.98 (talk) 17:51, 3 December 2009 (UTC)

Plutonium is toxic in addition to being radioactive, because it's a heavy metal. Not very toxic, though; supposedly about as toxic as caffeine.

I really think it's a misuse of the term to call radioactive substances "toxic" as a function of their radioactivity. Litvinenko wasn't poisoned, he was irradiated. Outcome is the same, of course, but it's a different thing. For that matter it strikes me as a bit off to call things poisons just because they are very acid or very alkaline — those are chemical properties but shading into physical ones. --Trovatore (talk) 21:01, 3 December 2009 (UTC)

I think toxicity is concerned less with mechanism than it is with measurements like LD50, which makes sense to me (otherwise you start getting into a lot of hair-splitting when all you really want to know is will it kill me quick). I find a basic benchmark for thinking about what toxicity means is, "what would make a good poison?" I think hair-splitting is useful when talking about acute toxicity or not (again, the radioactivity question, but for different substances), but not further down than that. --Mr.98 (talk) 14:34, 4 December 2009 (UTC)

I think beryllium (by far) is the most toxic element. The term you are looking for LD50. Try googling for LD50 and the names of some potential elements. I checked those that Fences posted, and beryllium easily beat the others. Also you have to distinguish between ingestion and inhalation (and injection possibly). Different things have different toxicity depending on the route of administration. Ariel. (talk) 01:23, 3 December 2009 (UTC)

Isaac Asimov's 1954 short story 'Sucker Bait' hinges on the realisation (by a non-specialist polymath whom Asimov terms a "mnemonic") that a higher than usual level of beryllium in the crust of a recently discovered planet is responsible for the death of its first colonists. 87.81.230.195 (talk) 14:10, 3 December 2009 (UTC)

Are you sure? In our article on Beryllium...

Ingestion

Swallowing beryllium has not been reported to cause effects in humans because very little beryllium is absorbed from the stomach and intestines. Harmful effects have sometimes been seen in animals ingesting beryllium.[41]

Googlemeister (talk) 16:20, 3 December 2009 (UTC)

Did you read the rest of the long toxicity section in the article? --Mr.98 (talk) 17:46, 3 December 2009 (UTC)

I admit, I only skimmed the rest since my question specifically was referring to ingestion and not inhalation or skin contact. Googlemeister (talk) 19:18, 3 December 2009 (UTC)

The most toxic element is anti-matter. Ingesting even 1/1000 gram of anti-matter is fatal. 139.130.57.34 (talk) 20:55, 3 December 2009 (UTC)

Possibly, but I don't see how you are going to get the antimatter (we will use antihydrogen since technically antimatter is not it's own element) into your mouth to swallow it before it annihilates. Googlemeister (talk) 21:14, 3 December 2009 (UTC)

This is not toxicity; this is vaporization. --Trovatore (talk) 21:17, 3 December 2009 (UTC)

--Jayron32 21:14, 3 December 2009 (UTC)

Solar panels

If you used a big magnifying glass to focus the sun's energy on one spot of a solar panel, could you therefore have a smaller panel while producing the same amount of power? What about a concave mirror? Dismas|^(talk) 22:15, 2 December 2009 (UTC)

Yes and yes. People often use reflectors and similar but there is a geometric problem that the sun moves so you have to move them or accept limited effectiveness. I have 11m2 of solar panel (water heating) on my roof plus a similar area of reflectors. It roughly doubles the measured output when the sun is in the correct position but not all day long. --BozMo talk 22:19, 2 December 2009 (UTC)

At some degree of concentration the solar energy would destroy the photovoltaic panel segment it was focussed on, like setting a piece of paper on fire with a magnifying lens. There is clearly a limit on the amount of concentration a panel can tolerate, and a maximum on the electricity it can generate. Edison (talk) 23:18, 2 December 2009 (UTC)

There's also a safety issue, as concentrating too much light can start fires, blind people, or burn them. Also, the "giant lens" might very well cost more than just having more solar cells. StuRat (talk) 07:16, 3 December 2009 (UTC)

A giant reflector is a lot easier to make than a giant lens, which is why this Australian company chose to use those instead. --antilived^{T | C | G} 10:31, 3 December 2009 (UTC)

On a related note, focussed sunlight is used to run concentrating solar power stations; there the sunlight generates heat to run a turbine (rather than using a solar panel). -- Finlay McWalter • Talk 01:34, 3 December 2009 (UTC)

Solar cell efficiency is directly related to temperature, the more you heat up a solar cell the less efficient it gets. A clever idea I saw on a tv show recently had like a raft of solar cells with large reflectors floating on water (like a lake or something) so as to dissipate the heat. Vespine (talk) 05:44, 4 December 2009 (UTC)

Even better, you can get solar cells combined with solar water heaters that keep the cells relatively cool and supply warm water as well. Mikenorton (talk) 23:42, 4 December 2009 (UTC)

December 3

Medical experiment that went terribly wrong

Resolved

I remember reading a news story from a few years ago about a medical experiment that went terribly wrong. My memory is foggy but I'll try as best I can to explain what I remember. The researchers were testing an experimental drug. It was the first trial on humans. The test subjects had a terrible reaction to the drug. I can't recall if any of the test subjects died, but a couple might have. I remember that part of the controversy was that the scientists administered the drug to the test subjects back to back, rather than waiting to make sure that the first person didn't have a negative reaction. They may have violated medical protocols. This happened maybe 2 or 3 years ago. It recieved some mainstream media attention. Again, my memory is foggy, but I think I read about it at BBC News. Does anyone know what I'm talking about? A Quest For Knowledge (talk) 05:16, 3 December 2009 (UTC)

Sounds a lot like the trials of TGN1412 — Zazou 05:34, 3 December 2009 (UTC)

• I think you've got it. It happened in England in March 2006; six patients got the drug at 10-minute intervals and it only took an hour before they began suffering one after the other. Nobody died, but they were all severely affected. --Anonymous, 08:28 UTC, December 3, 2009.

Presuming this is what you mean, and it sounds to me like it is, while the 10 minutes interval thing generated a lot of controversy amongst other things and did seem like a dumb thing to do to many, I don't believe it was a violation of protocols or particularly unusual. In fact, as this ref suggests [26] for example, giving sufficient time for a reaction to be observed is a new recommendation arising from the trial Nil Einne (talk) 10:40, 3 December 2009 (UTC)

They gave systemic doses of a previously untested drug instead of giving it topically to begin with. It was a drug designed to boost the immune system, they gave it to healthy patients, and it resulted in a cytokine storm. This was definitely predictable and as an immunologist noted "not rocket science". Fences&Windows 14:40, 3 December 2009 (UTC)

Maybe but that doesn't mean it violated the protocols of the time which was the point I was addressing. To put it a different way, they may have screwed up badly, but it doesn't mean they ignored established protocols, more that perhaps they didn't think properly whether the protocols were appropriate in the specific instance. On the other hand this [27] does suggest it's normal to try hazardous agents on one patient first so it may not have been uncommon as the earlier ref. However it isn't peer reviewed. There is of course still research ongoing as a result of the case. E.g. [28] [29] Nil Einne (talk) 15:44, 3 December 2009 (UTC)

The protocol-design issue is basically this: when you don't anticipate any problems, how long do you wait for problems to develop before you decide that it's enough? When they chose 10 minutes, they were probably imagining that the only possible rapidly manifesting problem would be something like anaphylactic shock, which comes on faster than that. In retrospect that was clearly a bad idea. But what if they'd waited an hour, only to find that after six hours people started getting sick? What if they'd waited a day, only to find that it took a week? With no data on the sort of problems to be expected, it really is a judgement call. Of course, if Fences is correct that this sort of reaction was to be expected, that's a different story. But that's not how it was reported in newspapers at the time, and I'm no immunologist, so I can't comment. --Anonymous, 08:55 UTC, December 5, 2009.

Perhaps the X-linked severe combined immunodeficiency gene therapy trial? Or less likely the gene therapy trial that killed Jesse Gelsinger. 75.41.110.200 (talk) 06:40, 3 December 2009 (UTC)

Yes, that's it. Thanks! A Quest For Knowledge (talk) 23:44, 3 December 2009 (UTC)

Butterfly sensation from infatuation.

There's a girl I've recently become infatuated with and I think she reciprocates my affections at least to some degree. Sometimes, I'll go many minutes without thinking of her and then suddenly, in a flash, I'll remember her-- infectious laughter, her supple contour, her stellar character, her daring wit, & her infinite, limpid, brown eyes... Accompanying these thoughts, I often experience a sinking sensation in my stomach or heart -- butterflies, I think it's sometimes called. What is the cause of this delicious sinking feeling? What are the biological and physical reasons for it? —Preceding unsigned comment added by 66.210.182.8 (talk) 05:41, 3 December 2009 (UTC)

Wikipedia has an article on everything. Looking at that article, it seems that the main component is due to anxiety, possibly due to adrenalin. Vimescarrot (talk) 09:52, 3 December 2009 (UTC)

and good luck! --pma (talk) 13:31, 3 December 2009 (UTC)

Well, we really ought to have an article on the neurobiology of love; there is enough of a literature. In the absence of an article, here is a pointer to a recent paper with a lot of information, a bit technical though. Looie496 (talk) 17:22, 3 December 2009 (UTC)

Also Esch, Tobias (2005). "The Neurobiology of Love" (PDF). Neuroendocrinology Letters. 3 (26). {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) Fences&Windows 23:25, 3 December 2009 (UTC)

And a video about how the key to love is oxytocin. Fences&Windows 23:29, 3 December 2009 (UTC)

This would somewhat overlap the existing article on limerence. 67.117.130.175 (talk) 06:58, 4 December 2009 (UTC)

Physical fallacies

Hi, I posted this question about speed of light calculations few months ago. Is there an article discussing such physical fallacies? If yes, can anyone volunteer to explain where the wrong use of physical laws was made in that website? I think such information should have the same interest as has been done to mathematical fallacy article.--Email4mobile (talk) 09:26, 3 December 2009 (UTC)

It seems to me you got a good answer last time. What else do you want to know? Second the paragraph "Variable Speed of Light" is not true. Not at all. It's completely contrary to the theory of relativity. And third scientists have NOT confirmed the existence of Dark Energy. Why do you want to learn anything at all from a website that does not understand science? If you want to theorize on changes to science go for it. But don't think for a second that what they say is correct by current theories. Unlike some, I don't mind speculating on changes to current thinking (historically the accepted scientific thinking of the day has been wrong quite often, I see no reason to believe we are in a unique period today) - but it's always important to note when your speculations differ from current understanding. Ariel. (talk) 11:07, 3 December 2009 (UTC)

I agree with Ariel, it is usually pretty pointless entering a scientific discussion with fundamentalists. The fundamentalist position starts from the premise that all truth emanates from their holy book (of whatever religion). It is intolerable to them that anyone else can obtain "truth" from another source, hence the strong desire to "prove" that their holy reference manual contains that truth, though it was previously somehow overlooked by everyone. I guarantee that no-one has previously interpreted that passage in the Koran as meaning the speed of light until long after science came up with an accurate measurement of it. Science starts from a radically different position, and mutually incompatible with the fundamentalist view. The scientific position is that truth (the laws of nature) is the simplest possible interpretation consistent with the experimetal results. This means that science will modify its laws in the light of new evidence. The fundamentalist can never do this, contradictory evidence will only cause the reasoning to become ever more contrived in order to make the holy book remain true.

I like the postulate on that site that Angels travel at the speed of light. If that is true, it means they are inside our own light cone and exist in our universe, not in some other ethereal existence. In principle then, they are scientifically detectable - but it is strange that no experiment, so far, has found them. SpinningSpark 14:03, 3 December 2009 (UTC)

Perhaps, but then we have never found any dark matter either. Googlemeister (talk) 14:22, 3 December 2009 (UTC)

Angels are photons, God is a singularity, and Satan is the heat death of the universe. Fences&Windows 14:31, 3 December 2009 (UTC)

That analogy doesn't work. In christian and jewish versions of the story, Satan is an angel who "turns to the dark side". I don't see how the heat death of the universe is also analogous to a photon. The information content of a singularity is restricted to it's mass and maybe it's spin...doesn't bode well for something that's supposed to be all-knowing and therefore containing an infinite amount of information!

Anyway - these kinds of websites are nonsense. It's very easy to come up with similar nonsense - it doesn't prove anything - the best you can do is ignore them. You can find approximate coincidences in ratios of numbers everywhere - it doesn't prove anything. Precise relationships are more interesting - but even then may not mean much. Let's look at one "fact" from that page:

"But 1400 years ago it was stated in the Quran (Koran, the book of Islam) that angels travel in one day the same distance that the moon travels in 1000 lunar years, that is, 12000 Lunar Orbits / Earth Day. Outside the gravitational field of the sun 12000 Lunar Orbits / Earth Day turned out to be the local speed of light!!!" - Well, how far does the moon travel in 1000 "lunar years"? What the heck is a "lunar year" anyway? If it's the time it takes the moon to orbit the sun - then that's almost exactly the same as a regular year - and the distance the moon travels over that time (relative to the earth) is 1.022km/s x 1000 x 365.25 x 24 x 60 x 60 = 32,251,000,000km - the distance light travels in a day is 1,079,000,000 km/hr x 24 = 25,896,000,000 km. So these supposed angels are travelling at about 25% faster than the speed of light. I'm not sure what the gravitational field of the sun has to do with it - the speed of light is constant and the sun's gravity can't change that, it can distort time a bit - but nothing like 25%. Now, you might consider the distance travelled by the moon relative to the sun...that's a bit tougher to calculate but it's got to be a lot more than it moves relative to the earth - so that just makes the situation worse. So this guy has an error of 25% in his calculations - that's simply not acceptable in any kind of scientific argument. The errors in our measurements of the speed of light and the speed of the moon are tiny TINY fractions of a percent. So this argument must be incorrect...period. SteveBaker (talk) 17:43, 3 December 2009 (UTC)

Not really related, but satan in jewish thought is NOT an angel that went to the dark side. Stan is more akin to a prosecutor, who works for god, has no free will! Ariel. (talk) 20:19, 3 December 2009 (UTC)

While I agree with Steve's overall sentiment, he is a bit overzealous with regard to numerical accuracy in astrophysics. For a lot of parameters, 25% error is acceptable in astrophysics... for example, look at some of the tolerances on the parameters of a typical exoplanet, CoRoT Exo B, as documented by the ESA. Its density is quoted with a 30% error bar. I've seen much more speculative numbers with worse uncertainty in other publications. Stellar physics publications are lucky if they can estimate some numbers to within a factor of 10. But these parameters are not the speed of light, which is well known to better than one part in a billion. In general, a "high level of accuracy" is context-specific. In any case, the above argument is making an outlandish claim, so a greater burden of proof is in order. While I can stomach a 50% uncertainty about whether an exoplanet is iron- or silicate-core, I don't have the same tolerance for the "angels are photons" argument. Because those claims are much more unbelievable, I would expect a much higher standard of accuracy before giving them even the slightest little bit of credibility. I guess my point can be summarized as follows: the above claims are false - but not simply because the numerical error is very large. Numerical error is acceptable, if the scientific claims are qualitatively correct. The above claims about "lunar years" are simply wrong, so it's useless to even bother analyzing their accuracy. Nimur (talk) 17:52, 3 December 2009 (UTC)

No, I'm not being overzealous. Errors that big are acceptable only when the data you're working from has error bars that big. The error bar on the speed of light is a very small fraction of a percent - and so is the speed of the moon, the length of a year and all of the other things that made up that calculation. The numbers I calculated for the distance travelled by the moon over 1000 years and the distance travelled by light in a day are accurate to within perhaps one part in a thousand. The discrepancy between them is 25%!! There is no way that those numbers back up that hypothesis - and no respectable scientist would say otherwise. Since our confidence in the speed of the moon, etc is very high - the hypothesis that the Koraan is correct about the nature of angels is busted. It flat out cannot be true. (Well, technically - the number "1000 years" has unspecified precision. I suppose that if the proponents of this theory are saying "1000 years plus or minus 50%" and therefore only quoting the number to one significant digit - then perhaps we have to grant that it is possible (not plausible - but possible). But I'm pretty darned certain that the proponents of this theory would tell us that when this holy book say 1000 - it means 1000.0000000000000000000000...not 803.2 - which would be the number required to make the hypothesis look a little more credible! Hence, probably, the necessity of muddying the water by dragging the sun's gravitational field into the fray - the hope being that anyone who tries the naive calculation above can be bamboozled into accepting the result as being 100% correct once general relativity has been accounted for...but sadly, that's not the case because none of the bits of the solar system involved are moving anything like fast enough relative to each other and the sun's gravitational field simply isn't that great.) SteveBaker (talk) 18:26, 3 December 2009 (UTC)

For the purposes of establishing the actual facts of this claim, I looked up the quoted passage and got;

He regulates the affair from the heaven to the earth; then shall it ascend to Him in a day the measure of which is a thousand years of what you count. (The Adoration 32:5)

I was going to post just the quote and leave it at that. However, I was intrigued by the lack of mention of the moon in the passage, or indeed, in the entire book (or chapter or whatever the Koran calls its subdivisions). Apparently we must read "the measure of what you count" as meaning a lunar year. So looking a bit further I found this;

To Him ascend the angels and the Spirit in a day the measure of which is fifty thousand years. (The Ways of Ascent 70:4)

Sooo, to be consistent we must interpret that the same way and now have angels travelling at 50C, and if the interpretation that angels travel at the speed of light or slower is to be maintained we must conclude that the Koran would have the speed of light to be at least 1.5x10¹⁰. I think that pretty much rules out the Koran as a potential reliable source for Wikipedia purposes. SpinningSpark 19:07, 3 December 2009 (UTC)

At the core of the issue, it's difficult/impossible to assess the scientific merits of an unscientific line of reasoning. This theory, and others like it, are very inconsistent, are not based on empirical observation, and do not draw logical conclusions from experimental data. Therefore any assertions that it makes are categorically unscientific. It doesn't matter what the error-bars are on its numeric results. A lot of numerology finds exact values via convoluted procedures. That "accuracy" does not mean the methods are sound or scientific. In the same way, the inaccuracy of the above numbers is irrelevant - the method is simply wrong. Nimur (talk) 19:09, 3 December 2009 (UTC)

Also, I object to SpinningSpark's comment, "that pretty much rules out the Koran as a potential reliable source for Wikipedia purposes." The Koran is a reliable source for information about Islam'. It is a very reliable source for Wikipedia's purposes when those purposes are related to Islam. It'd be hard to find a more reliable source for our article about Islam, for example. But, the Quran is not a scientific book, and sourcing scientific claims from it would be invalid. Since this is the science desk, we should never source our references from the Quran or any other "holy book;" nor should we source scientific claims from history books, poetry books, or other non-scientific references. However, that doesn't mean that these are unreliable sources - it's just the wrong source for the Science Desk or science-related issues. Nimur (talk) 19:16, 3 December 2009 (UTC)

Quite so, I had intended to qualify that with "...for scientific articles" or some such, but typed the more general "Wikipedia" instead. SpinningSpark 19:32, 3 December 2009 (UTC)

On second thoughts, no you cannot use the Koran as a reliable source about Islam, at least not on its own. The only thing it is a reliable source for is what the Koran says. SpinningSpark 09:03, 4 December 2009 (UTC)

The issue is not that people believe the Quran - that's entirely their own problem - it's that some people are attempting to portray what it says as somehow reliably relevant and applicable to modern science. Plainly, it's not...or at least not as that website explains it. But if he can't get his science right and he can't quote the Quran accurately then it's really no use to anyone. SteveBaker (talk) 19:44, 3 December 2009 (UTC)

A lunar year is 12 lunar months, which is about 354 days. That makes it a little closer than your calculation gave, but not by much. --Tango (talk) 22:37, 3 December 2009 (UTC)

Well, I'm an Arab and Muslim too; though I don't believe for any reason to connect between religion and Science. Unfortunately many Muslims believe. I'm afraid to say the one who tried to prove this fallacy was originally a professor as I heard. If I were just an engineer then how could I convince so may people who are spreading such information not only in that website but in the schools and universities. How can they believe me such information are totally mess unless I can verify that from reliable sources and I believe in Wikipedia because it either gives reliable sources or proofs. On the one hand, I still believe this problem is not just in Muslim countries but almost all religions have some extremist who would like to convince others by any means. Anyhow thank you very much for this wonderful interaction.--Email4mobile (talk) 20:38, 3 December 2009 (UTC)

I agree - it's certainly not just the Quran that makes these kinds of error. The Christian bible says that Pi is 3 and that bats are a species of bird. This is what happens when you try to take written material that's several thousands of years old and apply it to everything we've learned in the meantime. The fact is that we shouldn't expect this stuff to be halfway reasonable - the problem isn't the books - it's that people are still trying to apply it to modern situations. SteveBaker (talk) 00:53, 4 December 2009 (UTC)

Steve, I know you're not a big fan of the Bible, fine, but don't say nonsense about it. Nowhere does it say pi is 3. It says someone made a "molten of sea" that was 10 cubits across and 30 cubits round about. From there to "pi==3" there are a couple of large logical jumps. --Trovatore (talk) 00:59, 4 December 2009 (UTC)

The argument Steve mentions has indeed been made, but its main flaw (it seems to me) is to assume that exactly 10 and 30 (i.e. 10.0 and 30.0) cubits were meant. If the figures were actually rounded to the nearest cubit, which seems perfectly reasonable in the context, then the description is entirely consistent with the true value of pi: for example, 9⅔ and 30⅓ would come very close at 3.138. 87.81.230.195 (talk) 02:16, 4 December 2009 (UTC)

But that's the point! Did they mean 1000 lunar years or did they mean 1000 lunar years to one significant digit just like the "molten of sea" thing? If they really meant 803 lunar years - rounded to the nearest 1000...then this is indeed a valid "prediction" of the fastest speed anything can possibly move. But was it ever intended as a prediction of relativity? My bet is no. No more than the Bible is talking about geometry of circles. We're generally lead to believe that the words in these books are to be taken "as gospel". But we can't judge that by modern standards. Nobody measured the speed of an angel or the circumference of the "molten of sea" thing to modern precision levels. We must avoid dual-standard here. It's precisely as wrong to claim that the Quran predicts the speed of light as it is that the Bible predicts the value of pi - neither of those things were ever intended by the original authors - it's just modern hindsight trying to extract miracles where there is nothing but simple literary verbiage that's been blown out of all proportion. (Although it is pretty clear on that bat==bird thing - and on a whole bunch of other biological 'oopsies' in the dietary laws.) SteveBaker (talk) 04:08, 4 December 2009 (UTC)

What's the error with the bat bird thing? You define bird as creature with feathers. The bible doesn't, it defines the word in hebrew that is commonly translated as bird, as flying creature. During creation for example it even says flying creature[30][31]. And a bat flies, so what's the problem? And complaining about the basin is really stupid, since that part isn't even the word of god - it was a person recording what he saw - the basin was a physical object. You can't argue with that any more or any less than any other ancient document. And for the record the speed of light thing is nonsense. Ariel. (talk) 05:02, 4 December 2009 (UTC)

There seems to be some cherry picking going on here. My King James bible says,

And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. (Genesis 1:20)

The American Standard Version does not say flying creature either. SpinningSpark 13:58, 4 December 2009 (UTC)

Back to Steve: A Lunar year is a year in the lunar calendar, i.e. in this case likely the Islamic calendar. It consist of 12 lunar months, i.e. 354 or 355 days, depending on how the fractions work out. That's how the original author arrives at the 12000 (12 months times 1000 years). So the error is about 3 percentage points worse than your result. --Stephan Schulz (talk) 20:50, 3 December 2009 (UTC)

Yes, Stephan, I think I've already mentioned that in the previous discussion but not sure it SteveBaker noticed that. To me I've accepted this step of calculations but was surprised when he again used another kind of conversions to achieve cos(26.92952225^o) in order to reach 0.01% error. That was the point I wanted to swallow, but couldn't understand how (See the details here).--Email4mobile (talk) 21:02, 3 December 2009 (UTC)

Apart from that other verse talking about 50,000 years a day, let's first verify the 1000 years a day calculation, Spinningspark.--Email4mobile (talk) 21:21, 3 December 2009 (UTC)

Lines of little circles of light on camera

How come when a camera shoots something very bright like a brief shot of the sun, you often see little circles, usually as if they were strung together along a line? 20.137.18.50 (talk) 12:56, 3 December 2009 (UTC)

See lens flare. Gandalf61 (talk) 13:01, 3 December 2009 (UTC)

It's caused by light reflecting back and forth between the surfaces of the lenses. Cameras with high quality lenses don't do it nearly so much. The dots you see in the 'flare' aren't always circles - sometimes they are pentagonal or hexagonal. In this photo they seem to be 7-sided. SteveBaker (talk) 17:16, 3 December 2009 (UTC)

Fixed your link. APL (talk) 17:22, 3 December 2009 (UTC)

Almost certainly images of the leaves of the lens aperture. See bokeh. --Phil Holmes (talk) 09:54, 4 December 2009 (UTC)

Rainbow ham?

What I'm talking about

What causes the rainbow color that I sometimes see in ham and other cured meats? This says it's a "chemical reaction" (not telling much more), this says it's birefringence, which is a nicer word, but our article on birefringence doesn't mention this effect at all. (If it is birefringence, this is probably one of the most common effects of birefringence encountered in the typical life of citizens of the western world. Probably deserves a mention.) Staecker (talk) 17:35, 3 December 2009 (UTC)

A lot of cured meats are soaked in a brine, saline solution, or other liquid to add volume and flavor to them. The birefringence or other optical effects are often the result of these saline liquids suspended in the interstitial spaces of the meat. Nimur (talk) 17:46, 3 December 2009 (UTC)

There are several possibilities - one is that we're seeing an "oil on water" effect because oils from the meat are mixing with water - another is that we're seeing some kind of Dichroism effect - yet another is some kind of coherent scattering - similar to the thing that makes the colorless scales of a butterfly's wing show up in such vivid, iridescent colors. There are a lot of related effects and this could easily be any one of them - or even some complicated combination of them. Without some kind of expert study - I don't think we should speculate. SteveBaker (talk) 18:07, 3 December 2009 (UTC)

We can, however, point to prior research, e.g. Prediction of texture and colour of dry-cured ham by visible and near infrared spectroscopy using a fiber optic probe, Journal of Meat Science, 2005. Virtually everything that can possibly be observed, and many things that can't, has already been studied and published somewhere. Nimur (talk) 18:10, 3 December 2009 (UTC)

Darn! How did I miss that? I'm such an avid reader of the Journal of Meat Science! SteveBaker (talk) 19:38, 3 December 2009 (UTC)

Does such a disease exist?

Is there a disease where the neurons of the brain spontaneously form synapses with all their neighboring neurons at an accelerated rate, essentially forming one very deeply interconnected mess? 20.137.18.50 (talk) 18:27, 3 December 2009 (UTC)

Never heard of anything like that. If there were a mutation that did that, it seems likely to me that it would be fatal at a pretty early stage of embryonic development. Looie496 (talk) 20:41, 3 December 2009 (UTC)

Relevant articles are Synaptogenesis and Synaptic pruning. Landau–Kleffner syndrome and continuous spikes and waves during slow sleep syndrome, related to epilepsy, both involve too much synaptogenesis during childhood due to electrical activity that strengthens the synapses.[32] Fences&Windows 23:12, 3 December 2009 (UTC)

There is a great variety of proteins that participate in axonal guidance and/or affect synaptogenesis. See, for example, FMR1, Thrombospondin, semaphorins, and Amyloid precursor protein. I am not familiar with the specific pathology you refer to, though. --Dr Dima (talk) 00:48, 4 December 2009 (UTC)

cheesewring stones

It does not say in the article, but is the Cheesewring a natural formation, or is it man made like Stonehenge? Googlemeister (talk) 20:26, 3 December 2009 (UTC)

Looks natural to me. In southern Arizona there are hundreds of rock formations that look like that -- made of sandstone rather than granite though. Looie496 (talk) 20:37, 3 December 2009 (UTC)

The article states "Geological formation" which implies natural rather than man made source. In Southwestern Utah there are formations called Hoodoos (you've seen them in the old Wile E. Coyote cartoons). Geology + psychology is capable of some remarkable looking formations. I remember taking some college friends to Northern New Hampshire to see the Old Man of the Mountain (RIP), and they kept asking "No really, who carved that? Was it the Indians?" I kept trying to tell them it was just a natural formation. Other fun natural formations which have been mistaken for manmade include the Giant's Causeway in Ireland, the Pingos of northern Canada, the Badlands Guardian of Alberta, the Cydonia face on Mars, etc. --Jayron32 21:07, 3 December 2009 (UTC)

Apparently we are lucky that it still exists. Looie496 (talk) 21:22, 3 December 2009 (UTC)

For interest, there is currently an artist in the UK who makes somewhat similar, though smaller, piles of rocks on public beaches, often featuring apparently impossible balancing. Google-searching turns up the name Ray Tomes who has done something similar but I don't think he's the artist I have previously encountered. 87.81.230.195 (talk) 02:00, 4 December 2009 (UTC)

I think you might be referring to Andy Goldsworthy. Richard Avery (talk) 10:30, 5 December 2009 (UTC)

Idol rock

Speaking of apparently impossible balancing, I have seen a lot of amazing stuff in Utah, but nothing as amazing as the picture on the right. Looie496 (talk) 17:52, 4 December 2009 (UTC)

Yes, the strength of that Millstone grit at Brimham Rocks is remarkable. This shape is supposed to be a result of natural sand-blasting of the somewhat softer layer at the base. Mikenorton (talk) 13:26, 5 December 2009 (UTC)

The Cheesewring is a rather extreme example of a tor, a type of rock outcrop that typically forms in granite. They are a result of weathering, which has acted particularly on pre-existing sub-horizontal joints to produce the unlikely shape (see Haytor for a less extreme example). Mikenorton (talk) 11:06, 4 December 2009 (UTC)

North Korea's closed-circuit speaker system

In this article and at least one other at the Wall Street Journal, they say that the North Korean authorities notified the citizenry of the replacement of the North Korean won by means of "a closed-circuit system that feeds into speakers in homes and on streets, but that can't be monitored outside North Korea."

Speakers in homes? Really? Do we have a Wikipedia article on this system? Is this cable TV but without the TV? How many homes are equipped with this technology? I have a raft of questions. Tempshill (talk) 21:54, 3 December 2009 (UTC)

Is this science? Anyhow... from the New York Times: "Every North Korean home has a speaker on the wall. This functions as a radio with just one station -- the voice of the Government -- and in rural areas speakers are hooked up outside so that peasants can toil to the top 40 propaganda slogans. Some of the speakers are hooked directly into the electrical wiring, so that residents have no way of turning them off; they get up when the broadcasts begin and go to sleep when the propaganda stops. In some homes, however, the speakers have a plug, and people pull the plug when they want some quiet."[33] Just like in 1984. Something similar but less scary in Australia: "loudspeakers are sprouting like mushrooms on Sydney streets, peering down from the tops of traffic lights. The State Government has begun to put in place a permanent public address network that will, in some unspecified emergency, tell people what to do."[34] Fences&Windows 22:47, 3 December 2009 (UTC)

You might find this: [35] link interesting. It has a photo of a similar hard wired radio(?) in russia. Ariel. (talk) 00:03, 4 December 2009 (UTC)

Back in the 70s and 80s -- and probably well before that -- there was a ubiquitous contraption called "radiotochka" (radio spot) in the USSR households. IIRC the radio signal was transmitted via the electric wires of the power grid and not by air. I do not know how the signal was modulated, but I am pretty sure it was separated in frequency from the 50 Hz AC current the wires were carrying. There was only one station. Yes, it was government-controlled, but so was the TV, anyway; and it could be turned off or unplugged any time you like, of course :) . I doubt it that it transmitted anything back, but in principle I guess it could double as a bug for the bolsheviks to eavesdrop on you. --Dr Dima (talk) 00:08, 4 December 2009 (UTC)

(I haven't seen Ariel's post when I edited mine, but I didn't get the EC screen either. Weird.) anyway, Ariel, yes, that's it in the picture. It had one station only, though, not three; or maybe it had three in some places. Or maybe the other two were added after I emigrated :). --Dr Dima (talk) 00:13, 4 December 2009 (UTC)

Would you mind creating an article on it? It's ok if you don't know everything about it, just get it started and put in what you do know. (I know nothing about it. But maybe I can ask the person who posted the photo to contribute.) Ariel. (talk) 00:34, 4 December 2009 (UTC)

Last time I've seen a radiotochka was about 20 years ago. I do not think my memory from back then is accurate enough for me to write a Wikipedia article about it now. Sorry. --Dr Dima (talk) 01:07, 4 December 2009 (UTC)

I don't think it's that weird. The software is getting better and better at resolving edit conflicts. It's obviously fairly annoying for editors when you make extensive edits to a page (or even fairly minor but spread out ones) and have an edit conflict then have to resolve that then try again and have another conflict etc. Particularly a problem for high traffic pages. I'm not sure but it's also possible that this page is treated like an article and the software is more fussy on talk pages in recognition of the fact that edit conflicts could in some instances lead to confusing discussions. This is of course the kind of thing that people don't tend to notice since unless you actually get an edit conflict, you may not realise people have edited while you were editing. But to use an example I just encountered see [36]. I didn't actually look at the time when I started editing but I'm pretty sure it was before the 2 Madman2001 edits maybe even before the Derlinus. These where not that hard to resolve for the software, but I strongly suspect several years ago I would have gotten an EC Nil Einne (talk) 07:09, 5 December 2009 (UTC)

Incidentally, there was a similar device in use in the 1950's in the US. It was to be used for civil defense, and would also get the signal through the electrical wiring. It would be always left on to sound the alarm in an emergency (even if the homeowners had the radio and TV turned off). It never really caught on, though, and the plan was canceled after a few years. StuRat (talk) 05:44, 4 December 2009 (UTC)

That US device was on a History's Mysteries segment I saw a week or two ago. Clever device, tested and worked for transmitting an alarm. But the system was scrapped when they recognized that there was just the alarm, no ensuing instructions on how to respond to the situation. DMacks (talk) 07:34, 4 December 2009 (UTC)

Correction: History Detectives. The webpage for that segment might have some good information for an article about this type of system. DMacks (talk) 07:52, 4 December 2009 (UTC)

For example, National Emergency Alarm Repeater. DMacks (talk) 07:54, 4 December 2009 (UTC)

In some places in the U.S. the emergency sirens can broadcast announcements as well as their really annoying screech. Which would be useful if that tornado ever happens to come at 1 o'clock on the first Saturday of any month (monthly system test time). Rmhermen (talk) 14:44, 4 December 2009 (UTC)

Thanks for the responses - I'll add "radiotchka" to Wikipedia:Requested articles. Tempshill (talk) 07:25, 5 December 2009 (UTC)

Environmental Impact of ebooks vs paper books

I've seen some e-book distributors advertising ebooks as environmentally friendlier than the 'dead tree' version. On the face of it this seemed reasonable; no trees, no chemicals for paper and ink making, no distribution of heavy books, no bricks and mortar stores (and all the energy to run them), but then I started thinking about the computing required to deliver ebooks. So, which is more environmentally friendly? I'll leave it to you to decide how much of the production / distribution / consumption chain to include, also what constitutes 'environmentally friendly'. Scrotal3838 (talk) 22:02, 3 December 2009 (UTC)

Hmm well this page and this page outline some perceived problems with paper. See also Pulp (paper). On the other hand Electronic waste is often portrayed as being bad fairly serious, and factories that produce Kindles or computers or whatever of course also pollute. On the balance, however, I'd say that electronic distribution is much more environmentally friendly. It could (theoretically) replace a huge amount of printed material, and I just don't think there's any way the pollution generated making a kindle could add up to the pollution generated making a piece of paper for every page a kindle electronically displays. As far as energy to run servers and the devices themselves, I really doubt you could quantify ebooks as being anything but a marginal energy use. I don't see why ebook distribution would take up any more energy than a regular website, which on an energy per unit of information basis is extremely efficient.

However, the argument should be taken with a grain of salt, in my opinion. People were predicting similar improvements with the advent of email replacing memos. But paper use over the period when email became widespread increased, due to it being much easier to produce documents with modern printers and (ironically?) people printing out their work emails to have a paper copy. I forget where I read that last bit, I think it was in the Economist. Regardless, I think ebooks could be portrayed as better for the environment if it can be demonstrated that the user in fact uses less paper, and doesn't just use the same amount of paper and an electronic device that has an environmental impact in its creation, operation and disposal. TastyCakes (talk) 23:26, 3 December 2009 (UTC)

To read an ebook you need to turn your computer on (assuming it was off), and that requires electric power which consumes energy producing CO2, CO, NO, NO2, SO2, etc... Dauto (talk) 01:50, 4 December 2009 (UTC)

Well first, you might live in an area that gets its electricity from hydro or nuclear or some other generator that doesn't produce pollution. And second, turning wood into paper requires significant electricity as well, along with chemicals and the logging of forests. And then you have to fuel the trucks that distribute books and other paper to stores or distribution centres, which also uses energy and produce pollution. I don't think anyone would argue that ebooks have zero environmental consequences. But again, taking everything in account it looks like they have less impact that printed books, which was the question. TastyCakes (talk) 02:43, 4 December 2009 (UTC)

I don't think there is much doubt that this is not a question of energy use. After all, the Kindle runs for a heck of a long time on battery power - and the 60 watt light bulb you are reading it by is consuming at least 100 times more energy than the eBook itself. It's more a question of environmental damage during manufacture and ultimate disposal. That comes down to how long books and eBook readers last. Books seem to be almost immortal. I don't think I know anyone who throws them away...it seems almost sacrilegious to do so - and burning a book is just such a taboo (especially for Ray Bradbury fans!) that I doubt anyone does it routinely. However, if eBook readers are going to be regularly obsoleted like laptops and fancy phones are - with a lifetime of just a few year - then dumped onto landfills - then we can probably say that the eBook is doing more environmental damage. Paper books lock in carbon - and if you dump them into landfill, the compost nicely and their carbon is sequestered - that's a net win if the manufacturing process wasn't too nasty. Most books are read by many people before they eventually go wherever it is they go. Since an eBook player has no moving parts (well, except, perhaps for the switches) - it could last a long time. If they aren't obsoleted, then all likelyhood, the battery will be the thing that finally kills them. Most batteries die because their lives get shorter and shorter over the years - and that's a real problem for an eBook which really needs to be cable-free and to run for MANY hours without a recharge. If things settle down enough technologically - and the battery life is good enough - then perhaps there is a chance of the eBook being a better choice - but I kinda doubt it right now.

(Dear Santa: Steve would like a Kindle for Xmas please - I have carefully sequestered the lump of carbon you sent me last year.)

SteveBaker (talk) 03:49, 4 December 2009 (UTC)

Who uses a 60 watt light bulb to read? A 15W or even 12W or heck even 8W CFL does fine Nil Einne (talk) 08:23, 4 December 2009 (UTC)

OK - even an 8W CFL uses vastly more power than a Kindle. The beautiful thing about ePaper is that the image stays there when you remove the power source. Hence a well-designed ePaper based eBook reader can turn itself completely off and consume literally zero power while you're actually reading. You wake it up by pushing a button to turn the page or something - the on-board computer grabs the next page, formats it, sends it to the ePaper - then turns itself off again about a tenth of a second later. They use truly microscopic amounts of power when you are using them as intended. Of course if you surf the web with them using the wireless link or continually flip back and forth between pages - then it's going to eat more power - but for simply reading a novel or something - their power consumption is almost completely negligable. SteveBaker (talk) 19:18, 4 December 2009 (UTC)

Also, how many of us read ebooks with the Kindle? I had never even heard of it. Most people will use a desktop computer or a laptop and these consume more energy than the Kindle. Most people don't turn the lights off when using a computer either so there realy isn't any savings. Finally, the environmental cost for the production of a paper book happens only once while the power consumption for reading an ebook happens every time you read it. 169.139.217.77 (talk) 14:27, 4 December 2009 (UTC)

See Amazon Kindle and electronic paper. It is true, at this point Kindle and other electronic paper readers have a negligible share of the overall book market. But the real question is whether the average Kindle owner's paper "usage" goes down enough to offset how much environmental damage the Kindle does through its creation, use and disposal. I don't know the numbers (I'm not sure anyone does), so I'll make them up to explain. Say the production of a kindle produces the same "environmental impact" or "environmental footprint" or whatever as 1000 books. I don't know if that's an accurate number or not. But if the owner of the Kindle only reads 100 books on the Kindle over the course of its life, the Kindle has not been better for the environment than the paper equivalent. If, however, they read 5000 books, it is a great improvement. As I state above, I suspect, on average, the Kindle is better for the environment than its paper equivalent over the course of its life, but that is just from a vague feeling of how much damage the paper industry causes compared to the electronic industry. TastyCakes (talk) 17:41, 4 December 2009 (UTC)

I'd like to agree with you - but the niggling problem I have is that paper books are often read by multiple people - when I'm done reading with my books, I either lend them to other people to read - or take them to my local "Half Price Books" store and sell them - or I give them away to some local charity or something. I can't ever recall tossing a book into the trash. Most of the books I read are second hand anyway - so I think it's possible that a typical book is read maybe a dozen times before it finally falls apart or something. That skews things in favor of paper books. If we assume that an average Kindle is used to read 1000 books (that seems like a very high number to me) - then if paper books are each read by 10 different people (or even by the same person 10 times) - then the Kindle has to be more environmentally friendly than 100 paper books - not 1000. I can't help suspecting that the average Kindle will only last at most maybe 10 years...probably more like 5. SteveBaker (talk) 19:18, 4 December 2009 (UTC)

Hmm that's true, multiple readers are left out on my simplistic calculation. And there is the added complication that the Barnes & Noble Nook allows users to lend e-books to others and this capability could become the norm. I guess the easiest (and fairest?) way to measure it would be if electronic readers became more commonplace (say, 10% of the market for new books) and then measure how much paper production per capita decreases in the same market over the same period. Then if you could get a reasonable estimate of how long the average Kindle will last (or how long until its obsolescence) you could estimate how much paper the average Kindle displaces over its lifetime. Of course that's making the big assumption that ebook readers are the only thing affecting paper sales per capita over that period, and it seems likely that a greater percentage of people will read a greater percentage of things on phones, computers and PCs over the same period... TastyCakes (talk) 01:27, 5 December 2009 (UTC)

Why would it so bad to take the carbon from trees and store it in a form (paper) that won't contribute to CO2 percentage for probably hundreds of years? I never understood why transforming trees to stored carbon should be bad, as long as trees are grown again afterwards. ----Ayacop (talk) 18:07, 4 December 2009 (UTC)

Oh that's not bad - it's good. But the environmental impact of printing a paper book is a lot more than just the wood pulp it's made from (which - as you say - is a positive benefit to the environment because it's sequestering carbon). But making paper from wood pulp requires diesel fuel to power the lumber trucks, gasoline for chainsaws, electricity for the pulp-making machine, water (lots of it). Most paper is also bleached - presumably with some nasty toxic chemicals. The ink is laced with antimony and other nasty heavy metals. There is glue in the binding. Many paperback thrillers have the title embossed and coated with a thin metal foil. More gasoline is burned in getting the book from the printer to the bookstore - and for the eventual purchaser to go to the bookstore and back. So paper books certainly do have an environmental footprint. We just don't have the information to compare the size of that footprint to an eBook reader. Gut feel says that a single book is much less destructive than a single eBook reader - but then we don't know how many books are replaced by that reader over it's lifetime - maybe it's a lot - maybe very few because books are so well recycled across many readers. That makes this a tough question to answer. SteveBaker (talk) 19:18, 4 December 2009 (UTC)

Stars

How are we able to see stars if they are so far away? jc iindyysgvxc (my contributions) 22:02, 3 December 2009 (UTC)

They are bright. --Jayron32 22:09, 3 December 2009 (UTC)

There's not a lot in the way. Light doesn't just fade away over long distances -- it has to go through plenty of interstellar dust before becoming indiscernible. Vranak (talk) 22:12, 3 December 2009 (UTC)

It does spread out, though. The brightness of nearby stars is determined more by the inverse square law than extinction. --Tango (talk) 22:15, 3 December 2009 (UTC)

A more interesting question might be: "How are we able to look at any of the night sky and not see stars?" See Olbers' paradox. Dragons flight (talk) 23:22, 3 December 2009 (UTC)

The previous answers are missing a critical point - and (sadly) it's a somewhat complicated explanation.

The sun is a star - a pretty normal, boring kind of star just like many others in the sky. It's so bright that you can't look at it for more than the briefest moment without wrecking your eyesight. Most of the other stars out there are at least that bright - and space is pretty empty - interstellar gasses and dust make very little difference. So the only real effect is that of distance.

As others have pointed out, that's driven by the "inverse square law" - when one thing is twice as far away as another similar thing - it's four times dimmer - four times further away means 16 times dimmer and so on. The sun is only 93 million miles away - that's 8 light-minutes. The nearest star is 4 light-years away. Let's consider Vega (which is one of the brightest stars in the sky) - if you were 93 million miles away from it - it would be about 37 times brighter than our sun and you'd need some pretty good sunglasses and a good dollop of SPF-50! But fortunately, it's 25 light years away. So, Vega is 25x365x24x60/8...about one and a half million times further away. Which means that even though it's 37 times brighter when you're up close, it's 1.5Mx1.5M/37 times dimmer from where we're standing (73 billion times dimmer) because of that inverse-square law thing.

Our eyes are able to see a range of brightnesses from the maximum (which is about where the sun's brightness is) to a minimum of about 10 billion times dimmer than that. On that basis, Vega ought to be about 7 times too dim for us to see - but it's not. It's actually pretty bright. So you can tell right away that that inverse square law that everyone is going on about ISN'T the whole story.

There is obviously something else going on - and that is that the total amount of light from the sun is spread over that large disk you see in the sky - and while Vega is 73 billion times dimmer, all of that light is collected into one tiny dot. It gets hard to calculate the effect that has - but it's actually rather significant because the apparent size of the sun compared to that of Vega is gargantuan. In fact, the apparent area of an object obeys the same inverse-square law as the brightness does - so when you double the distance to something, it looks four times smaller (in area, that is). That concentration of light from a perceptually large object into progressively smaller areas of our retina exactly counteracts the inverse-square law.

Someone's going to complain about that - but think about it...that's why you can see something quite clearly when it's 200 feet away and it's not 40,000 times dimmer than when it's 1 foot away!

That means that until you are so far away that the sun is just a speck that's comparable to the resolution of your retina - it's not really any dimmer to look at than it is up close. The total amount of light is much less - but the light coming hitting each cell in your retina is exactly the same - until the projected image of the sun on the back of your eye starts to get smaller than the size of a single cell. So if you were out at the orbit of (say) Pluto - where the sun casts almost no heat and very little light - staring at the sun's tiny disk would still ruin a very small patch of your eyeball.

But still, 73 billion is a big number - Vega is still a heck of a lot dimmer - as you'd expect. However: remember that the sun is bright enough to literally blind you - and that your eyes are really sensitive - we can see things that are 10 billion times dimmer than the sun - so it's actually quite easy to see Vega even in very light-polluted cities. Much dimmer stars are also visible to the naked eye.

SteveBaker (talk) 23:54, 3 December 2009 (UTC)

I understand that an interesting question is why the night sky is not bright white rather than black, as an infinite number of stars would lead to the former. 89.242.105.246 (talk) 01:13, 4 December 2009 (UTC)

I believe the answer to that question, known as Olbers' paradox (which remarkably was first hinted at by Edgar Allen Poe in his essay Eureka: A Prose Poem), is that the Universe is not infinitely old, so light from the more distant stars has not yet had time to reach us. Attenuation due to red shift may also play a part. 87.81.230.195 (talk) 01:44, 4 December 2009 (UTC)

The Olbers' paradox article is pretty good - it lays out all of the possible reasons for this. SteveBaker (talk) 03:32, 4 December 2009 (UTC)

Aha. I've actually caught the most excellent SteveBaker in a misstatement. In his first response to the OP, refering to brightness of the Sun, he stated, "Most of the other stars out there are at least that bright." In reality, the vast majority of stars are far dimmer than the Sun. They are, in fact, so dim that we don't see them. So what was meant was that of the stars we see, most are at least as bright as the Sun. (Just a tiny correction) B00P (talk) 08:17, 5 December 2009 (UTC)

Indeed - I believe about 90% of the stars in the galaxy are red dwarfs, few (if any) of which can be seen with the naked eye. --Tango (talk) 11:49, 5 December 2009 (UTC)

The most useless particle

Say you had to choose one type of subatomic particle to be completely rid of: every single particle of that kind would completely disappear and no process would ever produce them ever again. Which would make the least difference to the Universe? Vitriol (talk) 22:37, 3 December 2009 (UTC)

I strongly suspect there is no answer to this - they are all absolutely 100% necessary. Take any one away (if that's even possible - string theory says "No") then the universe would be a dramatically different place - probably life as we know it wouldn't exist. But there is no "marginally less useful" particle. SteveBaker (talk) 23:04, 3 December 2009 (UTC)

String theory in its current form doesn't say anything useful about the Standard Model. The current thinking that there are a huge number of string theory vacua with different effective physical laws in each one. There might be one that looks like the Standard Model with a particle missing. -- BenRG (talk) 02:46, 4 December 2009 (UTC)

Oh, I don't know. A universe without a top quark might not differ much. Top is very hard to create and decays in ~5×10⁻²⁵ s. Now there might be secondary effects on the rest of the standard model if one removed the top, and I'm not sure how to predict what modifications to the larger theory might be necessary, but the top by itself seems of little importance. Dragons flight (talk) 23:14, 3 December 2009 (UTC)

There is no particle that could be removed from the Standard Model without either making it inconsistent or making life impossible. However, we could remove a whole group of particles, such as the third generation of the standard model (which comprises the tau, tau neutrino, top quark, and bottom quark) This is the only of the three generations with no practical applications. 74.14.108.210 (talk) 23:13, 3 December 2009 (UTC)

Not to hijack the question but could you elaborate on that a little? Why would it be inconsistent or non-life sustaining if, for example, the top quark didn't exist? Maybe not so many pleasing symmetries would exist but where are the serious effects? 129.234.53.144 (talk) 23:56, 3 December 2009 (UTC)

In physics the math always balances. If the top quark was missing, some physical interaction would not balance which is impossible. So some other particle or effect would, nay MUST, happen instead. Which would then have implications, etc, etc. Make any change, and everything else changes too. Ariel. (talk) 00:01, 4 December 2009 (UTC)

The up-type and down-type quarks couple via the weak interaction, and I think there's a loss of unitarity if you don't have the same number of particles of each type. On the other hand, there are preon theories with nine quarks, four of one type and five of the other, that don't have unitarity problems as far as I know. The story is the same on the lepton side. I don't think there's any known reason why there have to be the same number of quarks as leptons, though, so you can get rid of just two quarks or just a charged lepton and a neutrino without trouble. (This is not quite "getting rid of the top and bottom" or "getting rid of the tauon and tau neutrino" because you would also have to rejigger the CKM matrix or PMNS matrix, which alters the nature of the leftover particles as well.) One problem with dropping a generation is that there can be no CP violation in the weak interaction with two generations, and CP violation of some kind is needed to explain why there's more matter than antimatter. But I don't think the CP violation in the weak force can be used to explain that anyway. My vote for the most useless particles goes to the right-handed neutrinos, unless they turn out to be an important component of dark matter. -- BenRG (talk) 02:46, 4 December 2009 (UTC)

BenRG, the symmetry between the number of leptons and quarks is necessary in order to cancel the gauge anomalies that would otherwise destroy gauge symmetry and spoil renormalization. Dauto (talk) 07:13, 4 December 2009 (UTC)

Oh. Oops. -- BenRG (talk) 17:53, 4 December 2009 (UTC)

More importantly, per Murray Gell-Mann, "that which is not forbidden is mandatory" in particle physics. The existance of the top and bottom quarks is necessitated by the symmetry in the Standard Model. The entire system predictes the existance of said particles, therefore they are ALL equally vital. We have a pschological sense that particles like electrons are more vital because we tend to work with them more often, but the entire system of particles is not seperable; you must take them all, because the laws that created the top quark also created the electron; you could not create a universe with one and not the other. You can think of the Standard Model like a house of cards. If you remove any part of it, the whole system does not stand. See also anthropic principle for more on this. --Jayron32 00:16, 4 December 2009 (UTC)

Here's an interesting article for you Weakless Universe, they imagine a universe where something is missing. But as you see they had to change various other things too to make it work. Ariel. (talk) 00:31, 4 December 2009 (UTC)

Excuse me, but that's totally nonsense answer. If there were no top quark, the standard model would be seriously broken, I agree. But that's still just a human model of physical reality. If the universe had no top quark, then that would imply physicists need to discover a theory of particle physics that is different from the standard model, and one in particular where top quark formation is forbidden. However, because the top quark is almost never involved in interactions at human scales, more likely than not one could invent a new theory (perhaps much less elegant) that still gave the same predictions for human life as we have now. The Standard Model might be a "house of cards", but physical reality need not adhere to your sense of aesthetic beauty in determining its laws. For another example, the Higgs boson has but long sought after and not yet found. Most physicists seem to believe the Higgs will eventually be found, but one can just as well replace the Standard Model with one of several Higgsless models and our physical reality would look the same. Dragons flight (talk) 00:35, 4 December 2009 (UTC)

The Standard Model doesn't predict the number of generations; there's no known reason why there should be three. I don't know of any anthropic reason either. "Everything not forbidden is compulsory" is not about particle content. It's a statement that any interaction or decay that's not forbidden by a conservation law has a nonzero probability of occurring in quantum mechanics (classically forbidden transitions can happen in quantum mechanics because of tunneling). -- BenRG (talk) 02:46, 4 December 2009 (UTC)

If string theory is to be believed - then all of these particles are just modes of vibration on a string - getting rid of one mode of vibration is an entirely unreasonable proposition - so it's very possible that these things are no more removable from the universe than the color yellow or objects weighing exactly 17.2kg. SteveBaker (talk) 03:29, 4 December 2009 (UTC)

Strings have vibrational modes (harmonics), and those vibrational modes are particles, but the modes are quantized in multiples of roughly the Planck mass. All observed particles have masses far smaller than that, so they all belong to the ground state of string vibration. They're supposed to be distinguished by their behavior in the extra dimensions, but there's no reason to believe that the shape of the extra dimensions is unique. You can say a similar thing about quantum field theory. "Particles are just vibrational modes of the vacuum" is an accurate enough statement about QFT. It doesn't make sense to get rid of one vibrational mode, so you're stuck with a certain set of particles—for a given vacuum. But this doesn't answer anything; it just rephrases the question about the particle content as a question about the vacuum.

There was some speculation in the earlier days of string theory that it would turn out to have a unique vacuum which would have the Standard Model as a low-energy approximation, but the current thinking is that there are lots of vacuum states and only some of them match the Standard Model. Whether there are vacuum states corresponding to slight variations of the Standard Model isn't known. It isn't even known that there's a vacuum state corresponding to the Standard Model, though obviously they hope that there is. -- BenRG (talk) 05:13, 4 December 2009 (UTC)

I could definitely do without [fat electrons] being sent down the electricity supply and clogging up my computer:) Dmcq (talk) 06:43, 4 December 2009 (UTC)

December 4

Storks

Why do you get storks in places like Germany and Holland but not in Britain? Germany has a more severe winter than Britain, so that cannot be the reason. 89.242.105.246 (talk) 01:08, 4 December 2009 (UTC)

Storks are seen in UK [37], occasionally. However, UK is rather far west and north-west from their habitat (Central and Eastern Europe). They migrate south by one of three routes, AFAIK: western route over France, central route over Italy, or eastern route over Israel. If they were to spend the summer in UK, they would have to fly east to France and then south, which, I guess, they usually don't. --Dr Dima (talk) 01:42, 4 December 2009 (UTC)

name of physics book

What is the name of the physics book depicted here? In case you are wondering, that is Tiger Woods's car. Thanks. 67.117.130.175 (talk) 01:24, 4 December 2009 (UTC)

See this. hydnjo (talk) 01:42, 4 December 2009 (UTC)

It is “Get a Grip on Physics” by John Gribbin. Edit: the above link does not work for those of us for whom Google automatically redirects to Google.co.uk, so here is a UK version of it: [38] 78.149.192.188 (talk) 11:24, 4 December 2009 (UTC)

Took a minor liberty and Wikilinked the name in your post, 78.149, as I'm a fan of Gribbin. 87.81.230.195 (talk) 12:55, 4 December 2009 (UTC)

Cat and dog ear fold.

What is the function of the small pleat on the ventral/posterior exterior margin of a cat or dog auricle? Presumably other Carnivora have this feature as well. It looks like this: ----==-===--- where the skin doubles, and the interior fold is divided. The structure is visible in this image: http://en.wikipedia.org/wiki/File:Terrier_mixed-breed_dog.jpg. -Craig Pemberton 01:43, 4 December 2009 (UTC)

I'm going to go out on a limb and say that this fold has no appreciable function. My guess is that it is a vestigial trait left over from some other ancestral characteristic. I also have to admit that I am not at all qualified to make such an assumption so if someone else has evidence to the contrary you can safely ignore my answer. Presumably since some bats have quite gnarly ears, the folds play some role in sensing direction or attenuating certain sound, but a lot of bats also have smooth ears and hear just fine so it seems to suggest that this characteristic doesn't play a major role. Similarly it's hard to imagine the folds in human ears play a significant "functional" part of our hearing, if any part at all. Vespine (talk) 05:26, 4 December 2009 (UTC)

I've always assumed that it has to do with turning the ears. That is, the fold is present when the attached muscle is relaxed, while it's straigtened out and the ear turns when the muscle tenses. StuRat (talk) 05:28, 4 December 2009 (UTC)

Rechargable Batteries

Just curious: which is faster? Draining a battery OR charging it? or can they be completed in roughly equal periods of time? I'm thinking draining a battery could potentially be faster because (I think?) batteries don't heat up when they lose power, only when they're charged, so the absence of a thermal consideration would allow for a faster rate of flow? Thanks! 218.25.32.210 (talk) 02:00, 4 December 2009 (UTC)

I guess you've never used a smart phone or semi smart phone then. Draining a battery can definitely result in it heating up. This happened even with my Panasonic VS2 which wasn't a particularly fancy phone, when using GPRS or when taking many photos nearly continously. In fact from some quick Googling I see it can happen with continous talking too which makes sense so I wonder if you could probably notice this even with completely non smart mobile phones in some circumstances so you may be able to try this yourself if you have a mobile phone (although it's obviously going to cost money in such circumstances). I'm thinking here of Lithium-ion batteries obviously but I'm pretty sure this would apply to most rechargable batteries. Obviously when it comes down to it, it's depends under what conditions. You could discharge or charge a battery at a very high rate but it may damage the battery or in some cases particularly lithium-ion batteries result in explosions. For example, you can get 15 minute fast chargers for NiMH batteries that are supposed to charge in about ~15 minutes but as the batteries get hot and it isn't particularly good for them to be charged so fast, many have a switch to allow slower charging. (Which would still be faster then most traditional chargers and I suspect even extremely fast charging is probably significantly better for the battery then overcharging that can happen with old unsmart chargers). Similarly most lithium-ion batteries have temperature sensors I believe and these help limit the rate of discharging and charging to prevent the battery getting too hot Nil Einne (talk) 02:39, 4 December 2009 (UTC)

Though I own a smartphone, 99% of my usage is text messages, so I had indeed never experienced what you relate. In terms of my original question, I'm really more interested in laboratory/theoretical conditions and the physics behind the results - though I thank you for your long and detailed response! :-) 218.25.32.210 (talk) 02:55, 4 December 2009 (UTC)

The question is relevant to designing an electric bus to run a fixed urban route. The goal is to have two busses, one always charging and the other always in motion. My assumptions are that the bus design sets no limit on the battery size or weight, the battery type (to be defined) cannot accept charge as fast as it discharges in use, and that any charging arrangement can be made available at the bus terminus. It seems that if the bus is equipped with battery capacity X times as much as needed to complete its route until the busses swap at the terminus, then the battery can be charged at 1/X times the current at which it discharged. That will be achieved by switching the battery cells from parallel for driving, to series for charging. Am I am right? X must be a smallish integer. Cuddlyable3 (talk) 14:33, 4 December 2009 (UTC)

What's the use of a bus if it's always in motion? Also are we talking a dedicated busway here or something? Or just completely empty roads? Nil Einne (talk) 15:59, 4 December 2009 (UTC)

There are services for swapping car batteries, you might want to look at something similar:[39][40]. Fences&Windows 16:06, 5 December 2009 (UTC)

Hair

Why do girls typically have longer hair than boys? jc iindyysgvxc (my contributions) 05:34, 4 December 2009 (UTC)

For the same reasons they wear lipstick when most men don't - cultural norms. Note that men having shorter hair than women on average is not universal to all cultures. In societies in which men traditionally wear turbans, their hair will be very long, perhaps even perpetually uncut such as with Sikhs. In those situations you may very well have most women, even with "long" hair, walking around with less hanging off their skulls than men! 218.25.32.210 (talk) 05:44, 4 December 2009 (UTC)

No, I'm pretty sure that girls are capable of growing longer hair than boys. It's not just a matter of how they cut it. So the OP's question stands. Some google found that estrogen and androgen have an effect on how long hair says in the anagen phase. Google for hormone and hair. Ariel. (talk) 06:32, 4 December 2009 (UTC)

Can you point to any WP:RELIABLE sources for your claim, or just a Googled bunch of blog entries from random Internet people? Tempshill (talk) 07:55, 4 December 2009 (UTC)

I don't see any reason to expect Sikh men to have more hair then Sikh women. Both are expected to observe Kesh (Sikhism) AFAIK. Women may not wear turbans but unless that increases hair growth or reduces it falling out or something then it's fairly irrelevant. Now if you include facial har and body hair and perhaps because men tend to be slightly larger on average you could argue that all that means men would on average have more hair but a more sensible interpretation wouldn't include those factors IMHO so it seems they would have roughly equal amounts of hair. Also since no one has done so yet, I might as well link to Long hair Nil Einne (talk) 08:14, 4 December 2009 (UTC)

(after ec) Rate of hair growth does not differ significantly between men and women, but telogen (easily detached) hair does: PMID 11531795 (they studied both Africans and Caucasians). -- Scray (talk) 08:22, 4 December 2009 (UTC)

As anecdotal evidence contradicting Ariel's contention, consider that I (a British white male) have in two separate periods of my life (ages ca 19-23 and 45-50) grown to and maintained my hair at near waist length with no difficulty: I've also encountered plenty of other adult males with hair as long or longer. There may be weak statistical trends in 'hair-length potential' attributable to sex, but the overwhelming bulk of the generally observed length differences is purely down to fashion. 87.81.230.195 (talk) 12:51, 4 December 2009 (UTC)

I found some data from the 1950s that suggests that women's head hair grows ever so slightly faster than men's - though only by about 0.02mm/day.[41] Fences&Windows 15:25, 4 December 2009 (UTC)

This may be a crazy idea, what if the reason females grew hair faster was because the hormones that signal hair growth in the body were spread out over more places in the male body than the female? Mac Davis (talk) 16:36, 5 December 2009 (UTC)

Green Laser Pointer

Recently I bought a green laser pointer thinking of high power etc. but when switched it on I saw that it does NEVER foucus single point but in nearly fifty or so points dividing the power all over. I thought that there should be some adjustment that could be removed but no. There is a lens type thing on front that can be slightly rotated ( causing points to dance here and there ) but no way I can foucs it to single point. What I should to it to make it SINGLE point ?

 Jon Ascton  (talk) 07:56, 4 December 2009 (UTC)

You need to hold a suitable (separate) convex lens in front of it. MER-C 11:39, 4 December 2009 (UTC)

See the image in the article Speckle pattern. Cuddlyable3 (talk) 14:07, 4 December 2009 (UTC)

Restyl tablets

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activation energy and pri/sec/tert advantages

On paper (resonance structures), the benzylic / allylic site looks quite reactive, but from the bond energies table I see that a benzylic and allylic C-H bond is only about 15 kcal/mol weaker than a "normal" C-H bond. Same goes for C-X bonds (halide). Are there other effects at play (besides I guess bond weakness?) In fact choosing iodide as a leaving group over chloride seems to give a much bigger energy advantage than benzylic/allylic!

Btw, is iodide catalysis "true catalysis"? (Where in an alkyl halide SN2 substitution reaction you put some iodide in solution to speed it up.) What I understand is that iodide is a good leaving group but iodide is not that solvated (so you start out with higher energy, allowing it both to react and leave), but chloride is more solvated (so it ends up in lower energy) so in fact you've increased the energy gap between the reactants and the products, altering the equilibrium. John Riemann Soong (talk) 15:17, 4 December 2009 (UTC)

Organizing chemicals (practical)

I have been tasked with organizing the chemical room of a foodservice D.C. The chemicals are those you'd expect retaurants and other institutions to order - cleansers, chafing fuel, de-greasers, detergents, sanitizers, de-limers, soaps, etc. While they've never had a serious spill, there's no harm in taking some extra precautions, so I'd like to organize the room in such a way to minimize the risks associated with the accidental mixture of chemicals. For the first order of business, I've separated the strong alkalis, acids (of which there's only a few), and flammables (again, only a few) away from each other, keeping more innucuous items like soaps in between. What else ought I keep in mind? Should oxidisers like sodium hypochlorite be given special treatment? Would it be better to have the oxidisers near the alkalis or the acids - or completely separate? Let me emphasize: the actual risk of accidental mixture is very low, the substances are securely packaged and carefully stacked, and we're talking about commercial and light industrial mixtures here, not weapons grade stuff :). Matt Deres (talk) 16:14, 4 December 2009 (UTC)

Follow the normal rules of H&S, i.e. keep heavy items on lower shelves if not on the floor: items which are frequently used closer to hand than items which are infrequently used. Make sure the shelves are properly labelled with the item which is to be kept in that position, so all your plans are not set to nought by people who think they know better! --TammyMoet (talk) 16:24, 4 December 2009 (UTC)

I'm not worried about that stuff (though I appreciate the advice); I organize and design distribution centres as part of my job. I just want to make the room as safe as it can be, keeping potential chemical reactions in mind, as well as the normal stuff. And, to be honest, you don't necessarily want heavy stuff on the floor; something around hip height is best - would you rather pick up a frozen turkey from floor height or from counter height? Matt Deres (talk) 16:43, 4 December 2009 (UTC)

(ec) Even with "low grade" or light commercial chemicals, serious hazards may exist. For example, never mix bleach with ammonia or acid. Be sure to check the MSDS safety sheet for any chemicals - these safety sheets will have storage guidelines that will outline any safety issues associated with storage. Typically, acids and bases are stored in separate cabinets. Oxidizers are never stored near fuels. Pressurized gas falls into its own category, and gas cylinders have entirely separate safety requirements (often mandatory outdoor storage, depending on conditions). Above all, consult the MSDS sheets - these are very informative and will spell out any potential hazards in plain english. Some "benign" chemicals may have storage details that you did not know about. Nimur (talk) 16:44, 4 December 2009 (UTC)

The MSDS's are, of course, the ultimate guide. The problem there is that when you're dealing with hundreds of chemicals, it may be more useful to start with general guidelines and then work your way down, so to speak. It's a shame that the word "bleach" has more than one meaning; hydrogen peroxide is both a bleach and an acid so according to that poster, I should keep it away from itself :-). Matt Deres (talk) 18:12, 4 December 2009 (UTC)

As important as the location is the manner of storage: Flammables in a fire cabinet, liquid acids on a spill tray, gas canisters behind chains, etc. On the other hand, my local supermarket keeps liquid acid drain cleaner right above the liquid base drain cleaner and right near the bread! Rmhermen (talk) 19:20, 4 December 2009 (UTC)

December 5

causes of internal ache and chokeness along the throat

Removed request for medical advice. The only advice Wikipedia can give is to call a doctor and have a face-to-face meeting with him/her. Only a medical professional can give responsible medical advice.

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Pyruvic Acid vs. Pyruvate as end product of Glycolysis

Most sources I've seen (incl. wiki) say that pyruvate is the end product of glycolysis. Except I was reviewing some biology in the Schaum's Outlines and it said pyruvic acid. According to wikipedia the formual for pyruvic acid is C(3) H(4) O (3) (I don't know how to do subscripts) and pyruvate is C (3) H(3) O(3), which makes sense given that pyruvate is the ionized form. In the glycolysis article it says pyruvate is the end product but if you look at the picture (glycolysis overview) then end product is has 4 hydrogen, which would make it pyruvic acid, not pyruvate. This makes more sense because after glycolysis if fermenation occurs the end product, supposedly pyruvate, is reduced twice by the two NAHDH to make a 6 hydrogen compound, which doesn't make sense because pyruvate reduced twice would only have five hydrogens. So my question is: is the end product of glycolysis pyruvate or pyruvic acid? Thanks, 76.95.117.123 (talk) 02:19, 5 December 2009 (UTC)

They are the same thing. Pyruvic acid is C₃H₄O₃, and pyruvate is the anion C₃H₃O₃^-. If you read the article on pyruvic acid, the second sentence of the lead tells you just that. Pyruvate is the form used by the Citric Acid Cycle. ~ Amory (u • t • c) 02:50, 5 December 2009 (UTC)

They are the same thing, and which form prevails basically depends on the pH in the cell. In this case it's most likely pyruvate - any pyruvic acid generated would have dissociated into pyruvate and proton anyway. Tim Song (talk) 02:59, 5 December 2009 (UTC)

So I could say either as the answer to the question? But if the pyruvic acid disassociated into pyruvate then fermentation wouldn't produce a 6 H compound. The only reason I'm curious is that I do Science Bowl and the question sometimes comes up. Which answer would be more correct? I kinda said that pyruvate is the ionized form of pyruvic acid in my question btw...66.133.196.152 (talk) 03:09, 5 December 2009 (UTC)

Say pyruvate because that is the form it will be in given the conditions. Also, pyruvate and H⁺ are among the reactants in anaerobic respiration. I saw you said that about the ions, apologies if you felt slighted. I just wanted to set up the proper subtext and background. ~ Amory (u • t • c) 03:25, 5 December 2009 (UTC)

If they say it's wrong based on that grounds you can always appeal. Pyruvate may be temporarily protonated in an enzyme at the active site, but usually what happens is that the COOH group has to be deprotonated. This gives the COO- system the electron it needs to expel the weak carbonyl-carbonyl bond and cleave as carbon dioxide. It can't cleave if it's protonated. ;-) The two-carbon molecule remaining (acetaldehyde) is further oxidised is attacked by the sulfur thiol of CoA to become acetyl CoA. John Riemann Soong (talk) 03:28, 5 December 2009 (UTC)

You can think of it like this: The proton of pyruvic acid helps supply protons to the proton pump in the electron transport chain. Note that NADH (reduced form of NAD+) carries 2 electrons but only one proton. The other "lost" proton has to come from deprotonating pyruvic acid. ;-) (As you might know, carboxylate is a weak base so it's not very good at taking back the lost proton.)

Decarboxylation (loss of CO2) donates a pair of energetic electrons (to NAD+) that will be used for the electron transport chain. The thermodynamic stability of CO2 helps drive the donation.

Acetyl-CoA is a useful anabolic building block (if you want to build sugars or fatty acid]]), but if you want to oxidise it all the way (use all its energetic electrons) it's kinda hard to oxidise and pull electrons (via evolving CO2) out of a molecule to nothingness (converting acetaldehyde to formaldehyde and formic acid would be a pretty bad idea), so it goes through the citric acid cycle. John Riemann Soong (talk) 03:57, 5 December 2009 (UTC)

Ok thanks John Riemann Soong! The first explanation you gave helped me alot. And if I challenge I say the wiki ref desk told me :-)

66.133.196.152 (talk) 04:11, 5 December 2009 (UTC)

heat modelling

this code has come as an outcome of modelling of spot modelling process.i have arrived at eqation (1).If we take initial heat (due to atmospheric conditions) in each point as unity.this in coded in initialisation section. Now dq is sent to ode45 for solving in a prescribed time domain and with initial condition y0=0.

function dq = heat(t,q)
p=5;%number of variables
%--------------------------
% generation of const matrix
%---------------------------
A = [5 4 3 2 1]';----------------------------------------arbitrarily chosen constant A,B,C,D
B = [5 4 3 2 1]';------------------------------------------------
C = [5 4 3 2 1]';------------------------------------------------
D = [5 4 3 2 1 ]';------------------------------------------------
%----------------------------------
dq = zeros(p,1); 
%-----------initialisation-----------------
for i=1:p
   q(i) =1;
end
%----------------------------------------
    dq(1) = A(1)*q(2) + B(1)*q(1) + D(1);
for i=2:p-1
    dq(i) = A(i)*q(i+1) + B(i)*q(i) + C(i)*q(i-1) + D(i); -----------------(1)
end

here 'i' represents the weld number.code has considered the contribution from a point before ,a point after the point 'i', and contribution of heat added in next point.now my problem is that i want to optimise this process i.e. minimize dq.i.e.i need the welding to be cooled fastly.so what parameter should i consider for optimisation and what method should i adopt. SCI-hunter (talk) —Preceding undated comment added 03:01, 5 December 2009 (UTC).

See this duplicate inquiry at WP:RD/Math. Takes your pick but not both. You are in a little maze of twisty passages. hydnjo (talk) 03:49, 5 December 2009 (UTC)

I have formatted the code for readability. Nimur (talk) 04:45, 5 December 2009 (UTC)

The code seems rather nonsensical - the first 'for' loop sets all members of q(1..p) to 1. So surely the second loop sets every element of dq(n) to A(n)+B(n)+C(n)+D(n) ? Why so much complication? You don't say what language this is written in - but what C-like programming language has arrays that start from index 1? This suggests that whatever this code is intended to do...it's not doing it. SteveBaker (talk) 16:16, 5 December 2009 (UTC)

It was subtly implied that it was Matlab code; between the syntax and the reference to ode45; the OP might want to read our guide on asking for help with code. Nimur (talk) 19:11, 5 December 2009 (UTC)

its written in matlab and its approxmately functioning correctly.please help now 220.225.98.251 (talk) —Preceding undated comment added 16:28, 5 December 2009 (UTC).

What do you mean by "minimize dq" ? dq is a function (vector in your code).

More broadly, try following the following steps:

1. Formulate a clear mathematical statement of the physical problem you are trying to solve.
2. Derive (or pick) a mathematical solution/algorithm for the problem (or its discretized/approximate version)
3. Write Matlab code for the algorithm. Test and debug it.

Right now, you seem to be at step 3, and it is not clear (at least to us) if you have followed the previous steps. As such, your code does what it does, but we cannot determine if it actually implements the algorithm derived in step 2, and if the algorithm solves the problem in step 1 (remember GIGO).

PS: You should consult fellow students for tips on better Matlab coding; your current code is pretty poor. For example, the function takes in inputs t and q, and then doesn't use either. Instead it simply defines q. Also your first loop can be replaced by q = ones(p,1). Note that this review is intended to guide, not criticize. Hope it helps. Abecedare (talk) 16:52, 5 December 2009 (UTC)

Abecedare, dq is not a function. That is the syntax for declaring a return value. The function, heat(t,q), returns a vector whose local name is dq. This is standard MATLAB code style. What is unclear is why the code overwrites q, which is an input; and why it does that overwrite in such an inefficient and convoluted way. I suspect the OP used "pseudocode" or dummy assignments instead of writing a comment or actually implementing the correct physics. If the OP reviews Abecedare's and others' suggestions, and our software help guidelines, it will greatly help us answer the problem. I'm also going to posit that the simulated annealing article may be conceptually helpful, as well as the heat equation article. Nimur (talk) 19:40, 5 December 2009 (UTC)

I meant to indicate that dq is not scalar valued, so it doesn't make sense to try and minimize it. My language was ambiguous though; thanks for pointing it out. Abecedare (talk) 19:54, 5 December 2009 (UTC)

Bohr Magneton Number for Copper Sulphate.

I'm currently trying to calculate the dimensionless Bohr Magneton number p_eff for CuSO₄·5H₂O. The formulae I have are:

$\mu _{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}}}\right)^{\frac {1}{2}}$

$p_{eff}={\frac {\mu _{eff}}{\mu _{B}}}$

and $\mu _{B}={\frac {eh}{4\pi m_{e}}}$

Where all the symbols have usual meanings and values. From this, p_eff should be:

$p_{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}\mu _{B}}}\right)^{\frac {1}{2}}$

However, the formula I have been given for the dimensionless Bohr magneton number is:

$p_{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}\mu _{B}^{2}}}\right)^{\frac {1}{2}}$

Where the fundamental constant of magnetism of an electron is squared in the denominator, how can this be? Thanks for any help 188.221.55.165 (talk) 13:32, 5 December 2009 (UTC)

Does rice water has chemical reaction with mineral water's plastic bottle?

I had collect some rice water after washing rice for watering plants.
Because of keep raining these few days, I kept the rice water in plastic bottles to watering plants later.
But I found that after about two weeks, the plastic bottles had been harden and bloat.
The base of the bottle also bloat until hardly to stand on a flat surface.
I'm wondering is there any chemical reaction between rice water and mineral plastic bottle?
I'm curious and wish to know more about this condition, and also the reason why the bottle becomes like this.
Can anyone helps to find out the reason?

There is some problem statements i wish to know:
1. What is the fators affecting the bottle to bloat and harden?
2. What is the effect (positvely and negetively)
2. Does the chemical reaction brings harm to human?
3. Does it brings harm to plants if i watering plant with the rice water in it?

This is the condition i kept the rice water for about 2 weeks:
1. Date I kept the rice water in plastic bottles: 21/12/2009 to 5/12/2009 (I discovered out the condition on 5/12/2009)
2. Temperature: about 27 degree celsius to 33 degree celsius (sometimes in air-conditioned of 24 degree celsius)
3. Place I kept it: in a cupboard in my room
4. Not exposed to sunlight.

And these are few of the pictures of the bottle's condition:

• 
  This picture shows the difference of the base of original plastic bottle and the plastic bottle with rice water inside.
• 
  This picture shows that the plastic bottle with rice water inside hardly stand on a flat surface.
• 
  This picture shows the upper part of bottle also had bloat.
• 
  This picture shows that I kept the bottles with rice water inside in a book shelf with glass windows.

--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)

---

We can't look at the pictures unless you put them somewhere that we all have access to - upload to Commons or somewhere equally accessible. Mikenorton (talk) 17:14, 5 December 2009 (UTC)

Your links are inaccessible as well. bibliomaniac15 18:00, 5 December 2009 (UTC)

Thanks, that's much better. Mikenorton (talk) 18:51, 5 December 2009 (UTC)

I'm sorry about previous condition. I'm still a newbie in wikipedia, that's why I'm keep finding the instructions and ways to fix those problems. And thank you for your help to guide me. Just now, I'm still finding the ways to reply.--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)

Perhaps you are inadvertantly making rice wine? 75.41.110.200 (talk) 18:06, 5 December 2009 (UTC)

I have to agree that fermentation of rice starch in the water, creating carbon dioxide, is a likely cause of this. Mikenorton (talk) 18:58, 5 December 2009 (UTC)

But I just kept the rice water after I wash the rice. At first my motive is just to watering the plants later because the past few days were raining. Until yesterday only i found out that the shape of bottle had change and had harden. Err..does it means that I'm accidentally make of rice wine which produce carbon dioxide, and the carbon dioxide had harden the bottle?--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)

Eye water

What is the substance composed of that wets and lubricates the human eye? Mac Davis (talk) 16:26, 5 December 2009 (UTC)

See tears. The standard "wetness" is referred to as "basal tears" and according to the article it contains contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Matt Deres (talk) 16:38, 5 December 2009 (UTC)

classical music and emotions

I find it very strange which songs trigger strong emotions in myself — e.g., I get flushing waves of "tingles" whenever I hear Pachelbel's Canon, even though I can't recall having any strong memories associated with the song. Bits of Wagner hit me similar. I would probably generalize that it is probably only classical music that affects me in this particular way (the waves of "tingles," whatever that is), but I'm not a particularly big fan of classical at all (and haven't spent long amounts of time listening or playing it or anything along those lines), and generally do not think of myself as a terribly sentimental person (nor someone who is unusually appreciative of or interested in music). What causes this? Is it just some sort of long-lost association to music playing in stores around Christmastime when I was a child? Some property of this type of music itself—mathematical "problems" being proposed and solved? Just a sign of how complicated and weird the human brain is? I know there has been a lot written and researched on music and the brain, but I'd love a summary, if someone out there has thought about it much. --Mr.98 (talk) 16:45, 5 December 2009 (UTC)

Anything in the music psychology article give you any clues? Between cultural conditioning and a biological predisposition to perceive rhythm, tonal scales, and harmonics, music can inspire a strong psychological response. It's pretty much impossible to pinpoint what exactly triggers this response for you, but a lot of research has been done on music and psychology. Nimur (talk) 19:15, 5 December 2009 (UTC)

Showering with contact lenses

Why do most manufacturers of soft contact lenses warn against showering with them in or using tap water to rinse out the lens case? What negative effects could showering with them in have on the lenses? Thanks! --98.108.36.186 (talk) 20:27, 5 December 2009 (UTC)