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Revision as of 13:27, 3 November 2010
of the Wikipedia reference desk.
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October 30
Carbonated drinks and digestive health?
This is a bit speculative here and there might not be a definitive answer:
If it's true that neurotransmitters are reduced in reaction to a receptor being stimulated... So, for instance, capsaicin which normally causes pain and inflammation can also be a treatment for reducing pain and inflammation...
And if there is something like pressure receptors somewhere in the GI tract (mechanoreceptors?? osmoreceptors?? some other name??)...
...Then, in the long-term, couldn't carbonated drinks lead to digestive problems (in the short-term, carbonated drinks can lead to borborygmus, right? In the long-term, couldn't they cause GI pressure to be poorly regulated?) ☯ Zenwhat (talk) 01:24, 30 October 2010 (UTC)
- My anecdotal experience is that excessive CO2 can lead one to feel a little gassy, but it is usually vented pretty quickly. I'm not sure I see things hanging around enough, or having significant physiological effect, to have long-term effects of the sort you're describing, but I'm no anatomist. --Mr.98 (talk) 02:59, 30 October 2010 (UTC)
uakari fruits
What is the name of the fruit that Bald Uakaris eat in order to produce more babies? —Preceding unsigned comment added by 70.31.22.155 (talk) 01:38, 30 October 2010 (UTC)
- Our Bald Uakari article says: "The overall diet of a uakari consists of 67% seeds, 18% fruit, 6% flowers, 5% animal prey, and buds. They will also eat insects that happen to be cross their path, however they do not specifically pursue this type of food." It also says: "Their powerful lower jaw forms a pseudodental comb, which allows the uakari to open the hard surfaces of unripe fruits and eat the nuts that most other primates would not be able to open," but it doesn't say specifically what they might eat that would affect their reproductive behavior. WikiDao ☯ (talk) 01:59, 30 October 2010 (UTC)
Time dilation? Time speeding?
Dear friend, I have difficulty understand the beginning of the section {Time dilation and length contraction} in Special Relativity, Could some one tell me what should I say to respond the LAST suggestion from DVdm in the following conversation? Please help.
Regards, John
Discussion at Talk:Special_relativity#Time_dilation_and_length_contraction.
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== Time dilation and length contraction == THE BEGINNING OF THIS SECTION IS NOT CLEAR. PLEASE REVIEW WITH THE CAPITAL CHARACTERS.
Writing the Lorentz transformation and its inverse in terms of coordinate differences we get △t’=γ(△t-(v△x/c^2))
△x’=γ(△x-v△t) and △t=γ(△t’+(v△x’/c^2)), △x=γ(△x’+v△t’) Suppose we have a clock at rest in the unprimed system S. Two consecutive ticks of this clock are then characterized by Δx = 0. If we want to know the relation between the times between these ticks as measured in both systems, we can use the first equation and find: △t’=γ△t (for events satisfying Δx = 0)
This shows that the time Δt' between the two ticks as seen in the 'moving' frame S' is larger than the time Δt between these ticks as measured in the rest frame of the clock. This phenomenon is called time dilation.
Regards, John Huang Jh17710 (talk) 05:37, 24 October 2010 (UTC)
Thanks for your note, JRSpriggs. It is really hard to stay posted in Wikipedia, but, I will try to follow their regulations.Jh17710 (talk) 15:43, 24 October 2010 (UTC)
Thanks a lot, DVdm. You are the person I need to talk to. I thought that some thing wrong in this short paragraph, from "Writing..." to "...is called time dilation." because I was unable to explain the "△t’" mathematically to fit in the "Two consecutive ticks of this clock". I asked for help.
Regards, JohnJh17710 (talk) 19:54, 24 October 2010 (UTC)
Thanks DVdm. As you can tell, I just try to make this section more reader friendly. My main point is that, the usage of a popular symbol △t in this section is very different from popular definition. As I know, △t is for the difference of two times, △t=(t2-t1), so that I hope someone can bridge the gap.
Especially, when you think about the popular time equation of SR, t'=t/γ, which is also true for △t'=△t/γ with regular definition as (t2'-t1')=(t2-t1)/γ; don't you think this section needs some modification? Regards, JohnJh17710 (talk) 00:32, 25 October 2010 (UTC)
Thanks DVdm. Now, we have △t for the difference of two times, △t=(t2-t1). In this paragraph, t1 will be the time of the first tick in S and t2 is for the time of the second tick in S. If we arrange the clock to stay in S, we will derive △t'=γ△t like in the current paragraph; if we let the clock to stay in S', like what Einstein did in his paper dated 6-30-1905, then we will derive △t'=△t/γ, like what Einstein had derived before. That is why JRSpriggs said {This is the reverse of way that I would have chosen to do it, if it were up to me.}
However, if we use 1s' to represent the length of <time unit> in S', and 1s to represent that in S, then the definition of 1s' and 1s will make them not compatible with Lorentz equation. Then, we need to figure out some other way to use the symbols 1s' and 1s to explain time dilation.
Regards, JohnJh17710 (talk) 04:09, 26 October 2010 (UTC)
You are right about the setup, {Δt' would then mean the "length (t2'-t1')Ut' as measured in S' for one unit of time 1*(Ut) in S}. But, in that setup the equation Δt' = γ Δt expresses time speeding, not dilation, because for all |v|<c, we have γ>1 and Δt'>Δt. Assume that γ=5, we will have Δt=1 and Δt'=5, that means {the event of two ticks in S} is measured as 1*Ut in S and measured as 5*Ut' in S'. That means Δt'=5*Ut'=1*Ut=Δt, Ut'=Ut/5; the clock in S' is running faster. But, Einstein wanted it the other way. Isn't it?Jh17710 (talk) 02:21, 27 October 2010 (UTC)
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Thanks. JohnJh17710 (talk) 04:04, 30 October 2010 (UTC)
- I see you haven't had any luck so far in getting your question answered. As a suggestion, perhaps you'd have better luck getting an answer if you repost your question as a paragraph that's as brief as possible, while still containing all the information that's essential to understanding what it is that you're asking. A question is a little less daunting to the volunteers if the question can be understood by just reading one brief paragraph, rather than having to read through an entire lengthy conversation to see what's going on. Red Act (talk) 02:29, 31 October 2010 (UTC)
Stained glass
Is there any way of finding out when a particular stained glass window was made and by whom and as a result determine if the artist died more than 70 years ago?
During what has turned out to be a successful GA review of St James' Church, Stretham the reviewer drew my attention to a potential Freedom of Panorama issue with the image I took of the church's stained glass window, File:St James Church Stretham window 06-09-2010.jpg, licensed as {{cc-by-3.0}} i.e. my own work. I raised the issue at the media copyright questions forum here. The church plans website ("Stretham, St James' (1874-76)". Church plans online. Lambeth Palace Library. Retrieved 26 August 2010.) indicates that the church was restored between 1874 and 1876 by architect J. P. St Aubyn. Heavily restored, according to VCH (T.D. Atkinson, Ethel M. Hampson, E.T. Long, C.A.F. Meekings, Edward Miller, H.B. Wells, G.M.G. Woodgate (1953), Pugh, R.B. (ed.), The Victoria History of the Counties of England: Cambridge and the isle of Ely, vol. IV, Oxford University Press, pp. 151–159{{citation}}
: CS1 maint: multiple names: authors list (link)). Indeed, VCH records "The chancel has an east window of five lights with modern geometrical tracery, and there is a hood-mould terminating in heads". Does this mean modern in the 1953 (VCH) sense or modern in the not medieval sense? Pevsner is no help either.
- The VCH was originally published in the first decade of the 20th Century, so IMHO Victorian would probably be "modern". Alansplodge (talk) 14:33, 30 October 2010 (UTC)
Short of going down to the Cambridgeshire Archives (hard but not impossible for me) or the Lambeth Palace Library (nearly impossible for me) I am not sure how I can determine who made this stained glass window and when. In any case, would such trips constitute OR? Just for completeness, I have asked the church's team vicar and one of the church wardens; neither can help
--Senra (Talk) 11:17, 30 October 2010 (UTC)
- I've always found Cambridgeshire Archives most helpful by phone, could you try ringing them? --TammyMoet (talk) 11:24, 30 October 2010 (UTC)
- The image you took, second pane from right, bottom - "AD MDCCCLXVIII" = 1868? I would guess that dates the glass though it could refer to an event portrayed in the image - however the image appears to be the Ascension of Christ so I think it's the date - there's also a name "Henricus Herveius Baber" on the second pane from the left - is this the artist (or benefactor)? I would guess the date refers to a commisioning date rather than installation - which would fit with a 1870s restoration. (maybe) Sf5xeplus (talk) 11:40, 30 October 2010 (UTC)
- Ha ha. I'm an idiot. Every artist signs their work don't they? Well then Shylocke (aka Sf5xeplus), I am going to agree with you on the date, thank you. However, Henry Hervey Baber was a vicar of Stretham serving from 1827–1869. Also reading my way through British and Irish stained glass (1811–1918) at the moment too --Senra (Talk) 11:48, 30 October 2010 (UTC)
- (Concievable was my bad spelling and Shylocke was a freudian slip as I know someone called Shylocke) --Senra (Talk) 12:03, 30 October 2010 (UTC)
- According to our article this Henry Hervey Baber popped his clogs in 1869 - maybe it's a memorial? (or paid for by him as part memorial?)Sf5xeplus (talk) 12:05, 30 October 2010 (UTC)
- Out of curoisity, how did you get such a straight image (no parallax) - special lens, ladder or photoshop ? Sf5xeplus (talk) 12:12, 30 October 2010 (UTC)
- (Concievable was my bad spelling and Shylocke was a freudian slip as I know someone called Shylocke) --Senra (Talk) 12:03, 30 October 2010 (UTC)
- Following your above question and assuming no parallax in this image, I have just measured the two images. The window in this view measures 8.9 x 8.25 whilst the window in this view measures 70 x 68 which is 3.3 mm too short - not bad for mark one eyeball! --Senra (Talk) 12:33, 30 October 2010 (UTC)
- Just some general background on English church stained glass. Surviving medieval stained glass is quite rare, as much of it was destroyed during the English Civil War in the 17th Century. Stained glass depicting religious scenes didn't really re-appear until the second half of the 19th Century, when the Oxford Movement co-incided with the Arts and Crafts Movement. Before that, it would have been considered "popish" except if it showed secular subjects - family crests were common. They became the most popular sort of memorial for parishoners (by late Victorian times, grand memorial tablets were considered a bit vain). The windows would often carry the name and dates of the deceased - "the dedication" - or it might be on a small plaque underneath, usually "To the Glory of God and in Memory of...". I've never seen a church stained glass with the artist's name on it. The east window of my church has the name of a local builders' merchants on it; apparently you could pick one out of a catalogue. I'm certain this would have been a memorial to Henry Hervey Baber commissioned soon after his death. Alansplodge (talk) 13:02, 30 October 2010 (UTC)
- Following your above question and assuming no parallax in this image, I have just measured the two images. The window in this view measures 8.9 x 8.25 whilst the window in this view measures 70 x 68 which is 3.3 mm too short - not bad for mark one eyeball! --Senra (Talk) 12:33, 30 October 2010 (UTC)
- Just a note that although church windows are traditionally not "signed" by the artist, many of them will bear the designer's monogram. You can see one here.--Shantavira|feed me 14:35, 30 October 2010 (UTC)
- I stand corrected. There's rather a good index of makers' marks here[1], mostly quite inconspicuous. This one - Comper, J Ninian - has a strawberry plant as their mark[2]. Thanks Shantavira, I'll look more closely in future. Alansplodge (talk) 16:23, 30 October 2010 (UTC)
- Just a note that although church windows are traditionally not "signed" by the artist, many of them will bear the designer's monogram. You can see one here.--Shantavira|feed me 14:35, 30 October 2010 (UTC)
Facinating. Makers marks; memorials; arts and crafts; and all despite my bad spelling!
I have sent an email to Cambridgeshire Archives. In the meantime, I am not certain this window is a memorial to Henry Hervey Baber as he died in 1869 and the date on the glass is 1868. Additionally the restoration was later (1874–1876). I have also carefully examined every inch of the image without finding any marks although the highlights are a little blown making it hard to see a makers mark if it is there. I guess I need to make another visit to the church whilst hoping Cambridgeshire Archives can help too. Thank you to everyone who has taken the time to reply above.
--Senra (Talk) 18:48, 30 October 2010 (UTC)
- Issue resolved by Elen of the Roads (talk · contribs) at Wikipedia:Media copyright questions#Stained glass window .28UK.29 Panoramafreiheit.3F
“ | Stained glass windows are considered works of artistic craftsmanship and therefore subject to UK freedom of panorama. Stained glass in a building which is open to the public (which churches have to be in the UK to get exemption from the rates) can be photographed without breach of copyright. | ” |
Is it possible to create an exotic atom with antiprotons instead of electrons?
With the antiprotons in a stable orbital shell around the nucleus. Can this be achieved? ScienceApe (talk) 14:36, 30 October 2010 (UTC)
- "Massive particles in cloud around nucleus" doesn't sound anything like an "atom" at all (would it be possible to condense a bunch of antielectrons into a dense enough core to form a "nucleus" of your thing)? There sure is antimatter, but it's still got the same particle masses in the same "places". DMacks (talk) 14:52, 30 October 2010 (UTC)
- I'm no physicist but it strikes me that if you couldn't do it with regular protons, you couldn't do it with antiprotons. The charge is not what makes them act like protons or electrons in the sense you mean here (which can form nuclei, which form clouds); they have fundamentally different properties and constituent parts separate from their charge. --Mr.98 (talk) 15:13, 30 October 2010 (UTC)
- (ec)Have you read Muonium, and Positronium? It doesn't look like antiprotons are easy to create; so there is little experimental work with even short-lived antiproton species. Nimur (talk) 15:21, 30 October 2010 (UTC)
- I think the proposition was that you'd have a nucleus full of antielectrons surrounded by a cloud of antiprotons — maintaining the charge locations of a standard atom (positive nucleus, negative cloud), but with antiparticles. I don't think that will work — electrons/antielectrons are just not going to work in a nucleus, and protons/antiprotons are not going to behave like an electron cloud. It's not the same thing as nucleus of antiprotons surrounded by a cloud of antielectrons, which is certainly possible (antihydrogen). But I'm no physicist. --Mr.98 (talk) 16:03, 30 October 2010 (UTC)
Ok what about anti-neutrons instead of neutrons in what would otherwise be a normal atom? Would they annihilate with the normal protons? ScienceApe (talk) 15:19, 30 October 2010 (UTC)
- Yes, the anti-quarks will combine with quarks to form pions which will then decay. But, as far as the original question is concerned, you can actually form a short lived "atom" consisting of a proton and an anti-proton. When a proton and an anti-proton meet they will actually form a bound state at some high lying energy level. Then the system makes transitions to lower lying levels, eventually making the transition to the final state where the proton and anti-proton have annihilated. Count Iblis (talk) 15:56, 30 October 2010 (UTC)
- I see we have articles on antihydrogen, which has been made; antideuterium hasn't been. Antiprotonic helium is an antiprotonic atom for which an article has been started; I suppose you can mix an antiproton into anything. Wnt (talk) 18:53, 30 October 2010 (UTC)
- Isn't what prevents the proton from "annihilating" the electron (to form say, a neutron) is that the electron has much too fast to be absorbed? John Riemann Soong (talk) 23:24, 30 October 2010 (UTC)
- No, Protons don't spontaneously abosorb electrons to form neutrons because neutrons are heavier them the sum of the masses of an electron and a proton so that there is an energy gap that would have to be bridged in order for the reaction to occur. 76.123.74.93 (talk) 03:52, 31 October 2010 (UTC)
- That process - adding an electron and a proton to "yield" a neutron, is called Electron capture. It can only occur in certain circumstances. It is in some sense the time-reversal of β− decay. Nimur (talk) 21:41, 1 November 2010 (UTC)
- No, Protons don't spontaneously abosorb electrons to form neutrons because neutrons are heavier them the sum of the masses of an electron and a proton so that there is an energy gap that would have to be bridged in order for the reaction to occur. 76.123.74.93 (talk) 03:52, 31 October 2010 (UTC)
The ground state of the electron in an atom is far from the nucleus. The antiproton is much heavier and so it will radiate photons and drop down until contact with the nucleus and boom. Hcobb (talk) 21:55, 1 November 2010 (UTC)
Woodchip bug
Anyone know what species this insect is? It's camouflaged to look like a woodchip=P.Smallman12q (talk) 16:32, 30 October 2010 (UTC)
- Try asking whatsthatbug.com. SmartSE (talk) 23:39, 30 October 2010 (UTC)
- Go on, give us a clue. Whereabouts on the planet did you see it? Alansplodge (talk) 11:52, 31 October 2010 (UTC)
- I saw it amongst some shrub trimmings in New York. Almost crushed the poor critter... My camera phone had a hard time focusing on it. I'll give whatsthatbug.com a try if Wikipedia doesn't come up with an answer (these ref desks are usually quite good=D).Smallman12q (talk) 13:57, 31 October 2010 (UTC)
- I'm pretty sure its a moth, but being in the UK I don't know enough about (or have references on) American lepidoptera to try narrowing it down much further. You might also try asking on the appropriate forum at Ask a Biologist. 87.81.230.195 (talk) 02:35, 1 November 2010 (UTC)
- I saw it amongst some shrub trimmings in New York. Almost crushed the poor critter... My camera phone had a hard time focusing on it. I'll give whatsthatbug.com a try if Wikipedia doesn't come up with an answer (these ref desks are usually quite good=D).Smallman12q (talk) 13:57, 31 October 2010 (UTC)
- Go on, give us a clue. Whereabouts on the planet did you see it? Alansplodge (talk) 11:52, 31 October 2010 (UTC)
volcanic tropical cyclones
If weather conditions are just right when a volcano erupts and causes an ash cloud to blow over tropical waters is it possible for a tropical cyclone to form. --213.94.238.235 (talk) 18:19, 30 October 2010 (UTC)
- Probably not. Tropical cyclone formation requires evaporation from the sea surface, and the ash would block sunlight from reaching the water. In the Atlantic, there are sometimes surges of dust that blow from the Sahara, and they suppress cyclone formation while the dust is in the air. Looie496 (talk) 19:42, 30 October 2010 (UTC)
Pure energy
What does pure energy look like? --75.33.217.61 (talk) 18:52, 30 October 2010 (UTC)
- Either "nothing", "it does not exist", or "it depends on its wavelength"--take your pick. DMacks (talk) 19:04, 30 October 2010 (UTC)
- To answer that question, you'd have to define what you mean by "pure" energy. If by "pure energy" you mean a form of energy that has no properties other than energy, then the answer is that we can't see pure energy. The only thing our eyes are capable of seeing is light. And the photons of which light consists not only have energy as one of their properties, but also have nonzero spin, so they wouldn't count as "pure energy" according to the above definition. On the other hand, if you define "pure energy" as massless forms of energy, then light would count as "pure energy", so everything that your eyes are capable of seeing is pure energy, since ultimately, all you can see is light. Red Act (talk) 19:21, 30 October 2010 (UTC)
- By the way, if by "pure energy" you mean a form of energy that has no properties other than energy, then pure energy doesn't even exist. All of the elementary particles that everything in the universe is ultimately made out of have one or more properties other than energy. Red Act (talk) 19:30, 30 October 2010 (UTC)
- And as far as what Pure Energy looks like, the cover art looks rather comic book-y, and the band members themselves consider it to look "dreadful"[3] and "like some 10-year-old's school notebook drawings"[4]. Red Act (talk) 19:43, 30 October 2010 (UTC)
- Choose any picture here. Cuddlyable3 (talk) 22:39, 30 October 2010 (UTC)
- (re RedAct) I'm fairly certain an answer is light .. sure photons have spin - but that is the handle by which the photons 'carry' the energy - eg a photon with 0 energy doesn't exist.87.102.72.130 (talk) 13:05, 31 October 2010 (UTC)
- Yes, that's a perfectly reasonable answer. "It doesn't exist" is also a perfectly reasonable answer. "Pure energy" doesn't have any standard scientific meaning, so the question as posed is ill-defined. Unless and until the OP provides a definition for what "pure energy" is to be taken to mean, there is no one "correct" answer. Red Act (talk) 01:17, 1 November 2010 (UTC)
- (re RedAct) I'm fairly certain an answer is light .. sure photons have spin - but that is the handle by which the photons 'carry' the energy - eg a photon with 0 energy doesn't exist.87.102.72.130 (talk) 13:05, 31 October 2010 (UTC)
DC Circuits - resistors
O.K., so this is homework, but I'm totally bewildered on a particular point. We've been asked to calculate the current in a branch of a circuit where there is a resistor which has resistance 'approaching zero and infinite ohms'. I'm fine working out the currents / voltages if there are numbers involved - loop rule, junction rule etc, but the infinite bit??? Is it anything to do with moving a charge from infinity, i.e. potential difference? ThanksSophiepuss (talk) 19:35, 30 October 2010 (UTC)
- The exact text of the question would help. Is it two cases "(1)resistance approaching zero; (2) resistance approaching infinity," or is it a single impossible circuit element whose resistance approaches both zero and infinity at the same time? It sounds like if it is two cases, a single pole single throw switch would be the circuit element to consider, since it could be close to zero or close to infinite resistance. Edison (talk) 20:02, 30 October 2010 (UTC)
- (EC) If a resistor has infinite ohms, it's basically the same as if the resistor was completely removed from the circuit. There is zero current flowing through a resistor with infinite ohms. Red Act (talk) 20:07, 30 October 2010 (UTC)
- A zero resistance element will have zero voltage dropped across it, and other resistances as well as the voltages in the circuit will determine the current through it. Edison (talk) 00:53, 31 October 2010 (UTC)
- A teaching/learning note for the OP. Part of the reason for asking this type of question is to take you beyond the "I'm fine working out the currents / voltages if there are numbers involved..." stage. Your formulae may not work with zero/infinity, but they will work with numbers approaching those figures. So do your calculations using 0.1, 0.01, 0.001... and see what happens; this will point you towards what happens as you approach zero, and from that you should be able to extrapolate to what will most likely happen at zero. Then do the same using very large numbers for the case of approaching infinity. (And a slight warning - with some physical situations zero and/or infinity may be special cases with quite unexpected results, but if that's the case questions usually won't be framed in this way unless you've been taught the special cases). --jjron (talk) 04:06, 31 October 2010 (UTC)
- A zero resistance element will have zero voltage dropped across it, and other resistances as well as the voltages in the circuit will determine the current through it. Edison (talk) 00:53, 31 October 2010 (UTC)
- If the resistance approaches 0, replace the resistor with wire and think about what happens. If it approaches infinity, remove the resistor and see what happens. --99.237.232.254 (talk) 21:17, 1 November 2010 (UTC)
What is the average age of onset of Alzheimer's disease?
Abdbdba (talk) 22:10, 30 October 2010 (UTC)
Wikipedia has an article on Alzheimer's disease and its section Epidemiology is what we can offer. Note that "onset" of Alzheimer's disease is hard to quantify. The data is for diagnosed cases. Cuddlyable3 (talk) 22:33, 30 October 2010 (UTC)
- I couldn't see an average age of onset in that section. DuncanHill (talk) 22:35, 30 October 2010 (UTC)
- Wikipedia also has an article about Early-onset Alzheimer's disease which notes that the majority of sufferers are in their 50's, or early 60's.Cuddlyable3 (talk) 22:46, 30 October 2010 (UTC)
SECIS element
The SECIS element causes UGA stop codons to encode selenocysteine instead of stopping translation. But if it occurs in the 3' untranslated region of the mRNA in eukaryots, how does it effect this change in translation? If it binds to the ribosome in some way, couldn't the SECIS element bind to a ribosome while it is translating a totally different mRNA? Icek (talk) 22:40, 30 October 2010 (UTC)
- The present article is woefully incomplete. From [5] it appears that what SECIS binds is still being investigated, though some proteins are known; in fact it appears different SECIS binding elements will interact with different "spectrums" of proteins. (In reality what that means is that the authors found that SECIS elements bind nucleolin with widely varying affinity, but then again, they don't know where nucleolin binds it) Also see SECISBP2.
- The present guess from the above article (which may not cover all ideas) is that the SECIS element leads indirectly to the binding of the elongation factor and thereby holds the SeC tRNA in the general neighborhood of the ribosome while the SECIS-containing mRNA is attached. Alternatively they suggest there might be a different initiation event from the 5' end ... I can't say exactly how that leads to recruitment of the SeC tRNA. Wnt (talk) 21:11, 31 October 2010 (UTC)
does citric acid actively mask the taste of ethanol?
It's well-known that citrusy fruit (lime, oranges, etc.) will mask the taste of alcohol, but I see none of our biochemistry articles cover this phenomenon. At what level does the masking occur?
Does it occur at the nervous system level (i.e. citrus reception inhibits ethanol bitterness signals?) or the receptor-chemistry level (citric acid binds competitively to ethanol receptors, or ethanol's affinity for ethanol receptors is downgraded by citric acid?). Is it ionic citrate or the neutral citric acid that does the masking? John Riemann Soong (talk) 22:53, 30 October 2010 (UTC)
- From my perspective, almost anything (except water) added to alcohol masks (changes) its taste. I've never heard (to contrast with your contention that it is "well known") that "citrusy fruit" did a more pronounced job than, say, cola. As for how any soda or fruit juice effects such a change is a question I will leave to the scientists here. Bielle (talk) 23:32, 30 October 2010 (UTC)
- Cola doesn't mask it really well -- it simply dilutes or masks it with the taste of sugar (which isn't that good of a masker). I take it there's a reason that "hard lemonade" and adding lime to drinks are popular practices. John Riemann Soong (talk) 00:20, 31 October 2010 (UTC)
Taste and smell receptors are limited in variety. It does not seem unlikely that those which are sensitive to one kind of solvent (alcohol) might be limited by another (acid). Ginger Conspiracy (talk) 03:43, 31 October 2010 (UTC)
- I do not know their full diversity, but as I recall, taste receptors have to number several dozen in type, and smell receptors several hundred. (The "five taste" model is vastly oversimplified of course.) John Riemann Soong (talk) 04:53, 31 October 2010 (UTC)
- Taste receptor mentions 25. 75.41.110.200 (talk) 05:47, 2 November 2010 (UTC)
Difficulty in differentiating actors and actresses from the fictional characters they portray?
Is there a specific term for this? Not necessarily in the creepy, obsessional way (though it could be the same thing) but more along the lines of when fans of long-running dramas and soap operas approach the actors and actresses when they see them in the street and talk to them as though they were the same person as the character they play in the show, refer to them by the character's name, etc. Sometimes when you read interviews with the actors, they tell stories about 'this guy/woman who came up to me this time and...'. Things like people who play doctors being asked for medical advice, or being dragged over to help because someone is having a heart attack/seizure/baby - or actors and actresses being insulted or threatened by members of the public for the actions of their characters (say if the character was a rapist, or murderer, or wife-beater), or being praised for being strong enough to overcome rape/wife-beating/cancer/grievous injury - or actors in sci-fi shows being asked questions as though the fictional universe of the show was real, etc... --Kurt Shaped Box (talk) 23:19, 30 October 2010 (UTC)
- Are you describing an extreme case of typecasting (acting)? -- 119.31.121.89 (talk) 00:29, 31 October 2010 (UTC)
- That is the word, but it's actually less extreme. Just having a few audience members confuse an actor or actress with a character is far better than when casting decision makers start doing it. That could be why casting professionals are often been kept separate by studios from producers and directors. By the way, this question would probably get a better answer on WP:RDH the humanities reference desk, because the theatrical branch of forensics (public speaking) is an art, not a science. Ginger Conspiracy (talk) 03:52, 31 October 2010 (UTC)
- I'm no psychology expert, but it seems to be almost a type of Transference. --jjron (talk) 03:55, 31 October 2010 (UTC)
Theory?
I can remember seeing a program on teleportation. One (of the many) drawbacks of teleportation was that some theory said it was impossible to know the exact position of every sub-atomic particle all the time. What's the theory called? Albacore (talk) 23:57, 30 October 2010 (UTC)
- The Heisenberg uncertainty principle indicates that we may know the exact position of a subatomic particle, or the speed at which it is moving, not both. (This also applies on the macro level; you can know the location of e.g. a car, or its speed, but cannot discern both at the same time, as speed is dependent on knowing the car's position in at least two places and calculating how fast it got from one to the next.) → ROUX ₪ 00:00, 31 October 2010 (UTC)
- I often find myself driving around in my car and knowing both where I am and how fast I am going both at the same time (and I've noticed that even more since the advent of GPS navigation technology). WikiDao ☯ (talk) 00:08, 31 October 2010 (UTC)
- In that case, it is actually two different observers. Your odometer is observing your speed (and does not know your location), while your GPS knows your location (but not your speed). → ROUX ₪ 00:11, 31 October 2010 (UTC)
- (I'm not often aware of my momentum and my location at the same time, though, it's true). WikiDao ☯ (talk) 00:13, 31 October 2010 (UTC)
- (In practice, your GPS can figure out your speed pretty easily. I think it is probably known on here — but worth stating for such a basic question — that HUP only applies to very small scales, e.g. things smaller than atoms. --Mr.98 (talk) 00:14, 31 October 2010 (UTC))
- There is some uncertainty for an object the size of my car, though, right? It's just that it is indistinguishable from zero because of the value of ħ in
- if I recall the explanation for that correctly. Is that right, or what is a better way to understand that? WikiDao ☯ (talk) 01:07, 31 October 2010 (UTC)
- Exactly right:
- and you are not able to measure the velocity of even a half kilo particle with an accuracy of 10-17 m/s nor its position with an accuracy of 10-17 m. -- 124.157.254.112 (talk) 04:54, 31 October 2010 (UTC)
- Oops -- just reedited the equation as I had dropped the 2. -- 124.157.254.112 (talk) 05:09, 31 October 2010 (UTC)
- I wasn't trying to imply you couldn't calculate HUP for your car — just that it was so small as to be meaningless on a macroscopic scale, and thus the car's position/momentum could easily be treated classically for really all but the most silly purposes. --Mr.98 (talk) 15:36, 31 October 2010 (UTC)
- Oops -- just reedited the equation as I had dropped the 2. -- 124.157.254.112 (talk) 05:09, 31 October 2010 (UTC)
- As far as the uncertainty principle is concerned, it doesn't matter if there are two different observers; it only matters what information is measured, not who knows it. (And GPS devices do measure your velocity.) I'm not sure if plugging the mass of your car into ΔxΔp ≥ ħ/2 makes sense. Quantum behavior only shows up in systems that are thermally isolated, which a car certainly is not. Emitting blackbody radiation is effectively the same as being measured. It might make more sense to plug in the mass of the "car plus environment" (leading to even less practical uncertainty), but I'm not sure how big that environment would be.
- In that case, it is actually two different observers. Your odometer is observing your speed (and does not know your location), while your GPS knows your location (but not your speed). → ROUX ₪ 00:11, 31 October 2010 (UTC)
- I often find myself driving around in my car and knowing both where I am and how fast I am going both at the same time (and I've noticed that even more since the advent of GPS navigation technology). WikiDao ☯ (talk) 00:08, 31 October 2010 (UTC)
- Going back to the original question, there are a lot of reasons why teleportation is impossible, but the uncertainty principle is not one of those reasons. It is potentially a problem if you encode your vital statistics as classical bits, but you don't have to do that; you can use qubits. If you manage to solve all of the other unsolvable problems of teleportation, quantum computing hardware should be child's play. -- BenRG (talk) 06:49, 31 October 2010 (UTC)
October 31
Artificial reefs
After reading this article, I still remain with the question as to how long such reefs take to become populated with any life considerable enough to make it a bona fide reef -- I guess that definition as a factor of time can be debated, but assuming a range could be established, the article didn't seem to give one -- so when sinking ships or doing something like this, how long after construction does it take for a reef to appear? DRosenbach (Talk | Contribs) 00:05, 31 October 2010 (UTC)
- Technically a reef doesn't have to contain any life, so by definition as soon as the artificial reef is put in place it is a bona fide reef. But since you ask about the life, colonisation would begin almost immediately, but the time until you would define that to be a 'bona fide reef' would not be so clear cut as there's probably no hard and fast rules, at least not that I know about, for how much life is required. It would also be highly variable depending on where the reef was being established. For example, put in an artificial reef around the Great Barrier Reef and it will probably be teeming with sea-life within a week, put one up in under the Arctic sea ice and you're probably looking at considerably longer. Coral_reefs#Formation may also be helpful. --jjron (talk) 03:36, 31 October 2010 (UTC)
- If you want to pursue this question further, you may wish to search some fishing message boards which will presumable contain some discussion of fishing conditions at newly created artificial reefs. -- 124.157.254.112 (talk) 04:58, 31 October 2010 (UTC)
- This 2009 article[6] is about the reef formed by sinking HMS Scylla (F71) near Plymouth in the UK. The National Marine Aquarium, Plymouth which organised the project, says "the scuttled former Royal Navy frigate is now home to about 260 sea species" in the course of 5 years. It also added £25 million to the local economy, because 42,000 divers had visited the site. Some more scientific information here[7] and here[8]. Alansplodge (talk) 17:18, 1 November 2010 (UTC)
Earthworms
How much of an earthworm is protein? I'd like my oscars and dinosaur bichir to grow at a more rapid rate than they are apparently doing now, and would a diet richer in live earthworms provide me with success? I figure that crickets have too much exoskeleton and wings to give me a good bang for my buck, seeing how earthworms are free from my backyard. Any comments? DRosenbach (Talk | Contribs) 00:14, 31 October 2010 (UTC)
- Well I really think you could type http://www.google.co.uk/search?sourceid=chrome&ie=UTF-8&q=earthworm+protein+content .. and take my word for it every article on the first page of results is a gem!
- Anyway, nagging aside, we are here to serve: http://www.jstor.org/pss/2396435 - by dry weight well over 60% protein, <10% fat, variable carbohydrates
- I know that earthworms are considered excellent food for other carnivorves eg salamanders, and are used as bait by fisherman - so I guess you are on to a money saving winner.
- Excluding the usual warnings about fish overfeeding, and overloading filter systems with high nitrogen content waste.. which I'm sure you've already read or heard.77.86.42.103 (talk) 00:45, 31 October 2010 (UTC)
- oh hang on . parasites and diseases - I don't recall ever having heard that earthworms are a parasite source, but diseases are a possibility .. I suppose. 77.86.42.103 (talk) 00:55, 31 October 2010 (UTC)
- A good rule of thumb: diversify food! No single source of food can have it all. And, since oscars are serious predators, you should give them something more substantial than earthworms. They need fish flesh! East of Borschov 10:50, 31 October 2010 (UTC)
- My 2 oscars are about 2 inches long, so I don't think there are many fish that I can feed them. I have two mollies in the tank with them for over a month and I suppose they are way too big because they are fine. DRosenbach (Talk | Contribs) 12:57, 31 October 2010 (UTC)
- If you keep the mollies (or guppies etc) in a separate tank they will rapidly breed - producing fry for the other fish to eat . I shouldn't really be promoting icthycide, but if you enjoy a bit of un-balanced 'gladiator style' fishkeeping it's the way to go.87.102.72.130 (talk) 13:02, 31 October 2010 (UTC)
- Not necessarily live fish. The breeders that I know make their own frozen food from minced raw fish (the common supermarket white fish) with some cereal and vitamins. East of Borschov 22:53, 31 October 2010 (UTC)
- My 2 oscars are about 2 inches long, so I don't think there are many fish that I can feed them. I have two mollies in the tank with them for over a month and I suppose they are way too big because they are fine. DRosenbach (Talk | Contribs) 12:57, 31 October 2010 (UTC)
Optical computing
Why haven't optical computers become widespread? The technology exists and it has many advantages over electronic computing. --75.33.217.61 (talk) 00:26, 31 October 2010 (UTC)
- Have you read Optical computing#Misconceptions, challenges and prospects? The simple answer is that the technology is still in its infancy, and many problems have to be solved first. Clarityfiend (talk) 01:26, 31 October 2010 (UTC)
why do plants use so much more potassium than animals?
Almost all the biochem taught to me so far has been systemically biased towards animals ... I think my professor is biased in favour of his own race. Anyway...I can't seem to find an explanation. Do they use the potassium to bring water into the cells? Do animals not do this because their cells lack cell walls? I'm really curious why potassium is a micronutrient in animals but a macronutrient in plants. Furthermore, plants usually lack sodium. Do terrestrial rocks have more potassium than sodium? John Riemann Soong (talk) 00:40, 31 October 2010 (UTC)
- First sentence in Potassium in biology: "Potassium is an essential mineral macronutrient and is the main intracellular ion for all types of cells." Furthermore it goes on to say: "Potassium is the major cation (positive ion) inside animal cells, while sodium is the major cation outside animal cells." This would seem to suggest an error in your premise that it's more important in plants than animals. Is this what you're looking for? (And BTW, animals are not a 'race'). --jjron (talk) 03:47, 31 October 2010 (UTC)
- Potassium is a micronutrient, not a macronutrient for animals. Extracellular sodium concentration as I recall >>> cytosolic potassium concentration. Is it potassium a micronutrient because animal cells are usually close to isotonic? John Riemann Soong (talk) 04:51, 31 October 2010 (UTC)
- Macronutrient#Types_of_nutrient and Micronutrient both agree with the Potassium in biology article that potassium is a macronutrient. Micronutrient says the distinction is at 100 micrograms/day (though that sounds very low and seems to disagree with the list it gives later - maybe it's meant to be 100 milligrams/day; I've added a citation needed tag), while dietary mineral says the dietary requirement for potassium is 4700 mg a day. And yes, as suggested above, sodium concentrations are greater outside the cells. See also Sodium#Biological_role. --jjron (talk) 05:48, 31 October 2010 (UTC)
- I meant that sodium usage >> potassium usage, sorry. In the potassium article, it is cited as a micronutrient. John Riemann Soong (talk) 07:02, 31 October 2010 (UTC)
- Macronutrient#Types_of_nutrient and Micronutrient both agree with the Potassium in biology article that potassium is a macronutrient. Micronutrient says the distinction is at 100 micrograms/day (though that sounds very low and seems to disagree with the list it gives later - maybe it's meant to be 100 milligrams/day; I've added a citation needed tag), while dietary mineral says the dietary requirement for potassium is 4700 mg a day. And yes, as suggested above, sodium concentrations are greater outside the cells. See also Sodium#Biological_role. --jjron (talk) 05:48, 31 October 2010 (UTC)
- Eh, to be honest I would have instinctively said it was a micronutrient, but overall the articles seem to be calling it a macronutrient - however there seems to be no clearly defined cut-off and it could just be playing semantics. To put it another way, you'd undoubtedly say that carbohydrates, protein and fats were macronutrients for animals, but this is not the case for plants as they largely manufacture their own, which means something like potassium could be considered relatively more important. So to compare fairly you really need to look at elements and talk about the macronutrients being carbon, oxygen, hydrogen, nitrogen, etc. On this list potassium now ranks considerably lower for plants and the key elements for plants and animals are more similar. Regardless of this, yes it's true that plants require/use far more potassium than sodium, and less sodium than animals. The main point is that animals use a lot of sodium and potassium in the sodium-potassium pump. In plants, a similar 'pump' system utilises hydrogen and potassium rather than sodium. Additionally, some plants require considerably more sodium than others, halophytes for example, and some plants can substitute sodium for potassium in some functions if necessary. --jjron (talk) 14:31, 31 October 2010 (UTC)
- I think this is simply a matter of growth -- plants grow much more rapidly than animals. Animal cells require very large amounts of potassium, but we don't lose it very rapidly because almost all of it is intracellular, so we don't need a large intake. If we were growing rapidly, we would need a lot more, to supply the new cells we are creating. Looie496 (talk) 18:00, 31 October 2010 (UTC)
- Mammals also use sodium for excretion: the sodium is actively pumped across a membrane towards the outside world, and the water follows it by osmosis. In urination, this helps to prevent the organic contaminants from crystallizing out of the urine; in sweating, it allows water to be "pumped" onto the surface of the skin to evaporate and cool it. Potassium cannot be used for this purpose, because it has other physiological roles as described above. Physchim62 (talk) 18:08, 31 October 2010 (UTC)
Contradiction in the solution to a Physics question?
Read Question 10 (c) here: http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003139/RND01/PH866_paper99.pdf
The solution can be found here: http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003068/RND01/PH866_report99.pdf
The solution for part i) has the red light going below the blue light, but the solution to part ii) shows it going above the blue light. Can someone explain this apparent contradiction?-220.253.253.75 (talk) 00:48, 31 October 2010 (UTC)
- Simple. Your brain automatically assumes the light came in a straight line. If you project the red and blue rays straight back, it looks like the
redblue one came from a higher point. Clarityfiend (talk) 01:24, 31 October 2010 (UTC)- Oh OK. However, that still poses a contradiction between that question (Question 10 (c) (i), 1999 paper), and Question 4 (f) (i) from the 1997 paper found here:http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003429/RND01/PH866_paper97.pdf whose solution can be found here: http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003378/RND01/PH866_report97.pdf Could someone resolve this contradiction as well?-220.253.253.75 (talk) 03:10, 31 October 2010 (UTC)
- The solutions are AFTER all of the examiner's comments by the way (i.e. scroll down).-220.253.253.75 (talk) 03:18, 31 October 2010 (UTC)
- I thought that first answer looked a bit odd, but I was too lazy to pursue it. It's wrong, as shown in the colorful picture in Prism (optics). Clarityfiend (talk) 07:27, 31 October 2010 (UTC)
- The solutions are AFTER all of the examiner's comments by the way (i.e. scroll down).-220.253.253.75 (talk) 03:18, 31 October 2010 (UTC)
- Oh OK. However, that still poses a contradiction between that question (Question 10 (c) (i), 1999 paper), and Question 4 (f) (i) from the 1997 paper found here:http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003429/RND01/PH866_paper97.pdf whose solution can be found here: http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/003378/RND01/PH866_report97.pdf Could someone resolve this contradiction as well?-220.253.253.75 (talk) 03:10, 31 October 2010 (UTC)
Solar cells, dark current and current direction
Hi, a little knowledge is a dangerous thing and I have tangled myself trying to understand current in PV cells.
Light strikes the depleted (middle) region of the p-n junction, creating electron/hole pairs which are separated by the electric field established by bringing doped semiconductors into contact with each other, leading to accumulation of electrons (and negative charge) at the p-side and holes/positive charge at the n-side. Got it. Now my questions are:
1) Is the potential difference between the n- and p-sides that drives a working current through an external circuit *the same as* the potential difference that drives the dark current back through the cell? Or are those two currents driven by different phenomena?
2) More fundamentally, I can see that (negatively charged) electrons accumulated at the p-side would be attracted to flow through an external wire to the (positively charged) n-side. But doesn't this mean we have a current flowing from a negative terminal to a positive terminal? A positive current flows from a positive terminal to negative, right?
I hope I've explained my confusion and appreciate any help untangling myself. —Preceding unsigned comment added by 146.23.212.21 (talk) 12:20, 31 October 2010 (UTC)
- I think you've got that backwards. The electrons produced by the photoelectric effect accumulate on the n-doped side of the p-n junction, and the holes accumulate on the p-doped side. See the arrows in this diagram. That diagram is used at Theory of solar cell#Photogeneration of charge carriers, which unfortunately doesn't use words to provide support for the direction of the arrows in the diagram. Red Act (talk) 16:36, 31 October 2010 (UTC)
Thanks Red Act, yes you're absolutely right, sorry for that silly mistake. I've actually done quite a lot of reading today and think I understand my original confusion: it is not the built-in electric field that drives the external current; rather it is better to think of a solar cell as a current producer that happens to create a potential difference across the cell when it's connected to an external load. Indeed the n-side does wind up as the negative "terminal", and the p-side the "positive", which neatly describes the direction of current and electron flow through the circuit (embarassingly, I forgot they are opposite!) —Preceding unsigned comment added by 146.23.212.21 (talk) 13:43, 1 November 2010 (UTC)
Creature in Thailand
There is a bunch of similar images, but I became specifically interested in these ones from Thailand. What's the hell is that? A mock-up or some underdeveloped baby? —Preceding unsigned comment added by 85.222.86.130 (talk) 21:31, 31 October 2010 (UTC)
- Here's a previous thread on the topic, with a link to a Snopes discussion. Deor (talk) 21:58, 31 October 2010 (UTC)
Curious phenomenon
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --TenOfAllTrades(talk) 16:15, 1 November 2010 (UTC)
Birefringence
Can someone tell me what exactly the x,y, z axes in a uniaxial crystal are? The article birefringence fails to identify them in any images, making me highly confused. Is the z-axis the optical axis? John Riemann Soong (talk) 22:29, 31 October 2010 (UTC)
- It's somewhat arbitrary, but usually the standard 3 dimensional cartesian coordinate system has the x axis going in-out, the y-axis going left-right, and the z-axis going up-down. --Jayron32 01:33, 1 November 2010 (UTC)
- Thanks, but that doesn't help me so much because I still don't know where the optic axis and the anisotropy or any of the relevant properties are defined! Which axis is on the optic axis on? Does the table match the image? John Riemann Soong (talk) 02:01, 1 November 2010 (UTC)
- In the calcite images -- which axis are the letters being seen through? John Riemann Soong (talk) 02:02, 1 November 2010 (UTC)
November 1
PETA video
In this video of trappers killing their fur-bearing animals, aren't the animals being either killed instantaneously or being knocked unconscious? It just seems to me much ado about nothing -- sort of like fooling people with statistics that they don't understand. Sure, it looks spooky to see these raccoons kicking a bit, but that happens after severing the carotids/trachea of a chicken, too? DRosenbach (Talk | Contribs) 01:30, 1 November 2010 (UTC)
- Our article on the animal in the video is at Raccoon Dog. -- 119.31.126.67 (talk) 13:07, 1 November 2010 (UTC)
- In a sense, the video is a purely objective demonstration. It's up to individuals to decide whether this activity is ethical or justifiable. In terms of scientific analysis, it is probable that the raccoon is capable of feeling pain; I think the consensus is that a quick blow to the head is among the less painful lethal techniques. See pain in animals for starters. As far as the movements - I can't tell from the videos whether we're seeing a reflex, rigor mortis, or conscious squirming - in my opinion, it is not possible to discern conclusively from these videos. Nimur (talk) 01:43, 1 November 2010 (UTC)
- (edit conflict) (haven't watched the video btw)
- PETA's position is:
according to co-founder Ingrid Newkirk."If anybody wonders 'what's this with all these reforms?', you can hear us clearly. Our goal is total animal liberation, and the day when everyone believes that animals are not ours to eat, not ours to wear, not ours to experiment [on], and not ours for entertainment or any other exploitive purpose."
- How "well" they may be euthanized to harvest their fur does not change the fact that they are being raised in captivity and then killed solely to harvest their fur. Some consider that to be unethical, or feel a sense of empathy for the animals. Others do not. But the objection for some of those who do is not that they are being tortured to death (which presumably everyone would object to), but just that "we" are ill-using them for a clearly unnecessary and purely vanity-driven purpose. WikiDao ☯ (talk) 01:57, 1 November 2010 (UTC)
- Just watched the video. I have no idea how anyone could not have a problem with that. What exactly is the point of your "question", DRosenbach? Could you please clarify exactly what it is you would like to know? Thank you. WikiDao ☯ (talk) 02:27, 1 November 2010 (UTC)
- Why should he clarify his question? He states it very clearly. He wants to know if this video depicts cruelty on a still-conscious animal. I don't think there's a way to know, but personally it looks to me that the raccoon was completely 'out' after the first blow. If true, the video shows no more cruelty than a slaughterhouse, probably less cruelty than many types of fishing.
- In any case, while they sometimes do good investigative work, their motives are not to educate, and I absolutely would not trust a video being distributed by PETA without third party verification. APL (talk) 03:30, 1 November 2010 (UTC)
- Did you watch the entire video? If the animal was "out" after the first blow, how do you explain the squirming? Humans certainly don't move their limbs around frantically after being knocked out.
- I think DRosenbach explained it in the question - personally I've seen a goat beheaded (also in China as it happens) - so it was definately dead - but it kept 'spasming' similar to what was seen in the video - we probably have an article on the phenonoma - but I don't know what it is called.Sf5xeplus (talk) 05:54, 1 November 2010 (UTC)
- No. I'll admit that I only watched about half of it. Does something dramatically different happen in the second half? I don't have a reference handy, but I'm pretty sure that humans do sometimes twitch after crushing blows to the head. Hollywood doesn't portray it that way for reasons that should be obvious after watching the video. (Notable exception : "The Rock").
- If you want to feel bad for those animals, feel bad that they grew up on a farm, probably in cages. Not because they died from a sudden blow to the head. APL (talk) 15:34, 1 November 2010 (UTC)
- Also, in the middle of the video one person asks the cameraman, "are you recording?" He goes on to say, "make sure this video doesn't leak; that wouldn't be good for us." I highly suspect that, even in China, what these people are doing is illegal. --99.237.232.254 (talk) 05:44, 1 November 2010 (UTC)
- Not necessarily. Farming animals is in many ways an unpleasant process. Anyone who's not a complete fool understands that it would be bad PR for the naive masses to be made to watch a heavily edited video of the most unpleasant aspects of your operation.
- I imagine someone working in an entirely legal slaughterhouse for entirely delicious beef would have a similar reaction to a video camera. APL (talk) 15:34, 1 November 2010 (UTC)
- Did you watch the entire video? If the animal was "out" after the first blow, how do you explain the squirming? Humans certainly don't move their limbs around frantically after being knocked out.
- Just watched the video. I have no idea how anyone could not have a problem with that. What exactly is the point of your "question", DRosenbach? Could you please clarify exactly what it is you would like to know? Thank you. WikiDao ☯ (talk) 02:27, 1 November 2010 (UTC)
- DRosenbach, your error is attempting to apply logic to what is intended as a shock video. APL (talk) 03:33, 1 November 2010 (UTC)
- This question is asking for opinion ("seems to me it's much ado about nothing - is it?") and should be removed. (Note that my response above is the only one that even makes an attempt to link to an article or source that might be relevant, and even still does not answer the "question" because there is no way to answer the question "encyclopedically"). WikiDao ☯ (talk) 10:11, 1 November 2010 (UTC)
- The question is clear and not opinion: "are the animals being either killed instantaneously or being knocked unconscious?" Yes or no? As illustration the OP refers to chickens. 92.24.189.164 (talk) 13:46, 1 November 2010 (UTC)
- WikiDao -- please cool your jets. What constitutes animal cruelty itself is an opinion, so there's certainly many ways to spin my question. But my intent was not to create a windstorm of emotion (as perhaps you are suggesting I intended to do)...assuming one ascribes to a normative view of animal cruelty -- in that the killing of an animal is not inherently uncruel -- does this video depict cruelty at all, because it sure seems a lot more sensational than anything else. I didn't watch the entire video either (only the first 2/3) but it was quite boring and I just couldn't finish. The head/neck-banging of the first 2/3 doesn't seem cruel at all. DRosenbach (Talk | Contribs) 01:15, 2 November 2010 (UTC)
- I'm fairly certain that the aim is to polarise opinion - ie those that are opposed will be appalled and some that were not opposed will become opposed, additionally, those that were blissfully ignorant may be appalled. It shouldn't come as a surprise that PETA characterise it as cruelty -since that's where they are coming from - so I doubt they post it for fun - but to attempt to bring what's happening into public view.
- WikiDao -- please cool your jets. What constitutes animal cruelty itself is an opinion, so there's certainly many ways to spin my question. But my intent was not to create a windstorm of emotion (as perhaps you are suggesting I intended to do)...assuming one ascribes to a normative view of animal cruelty -- in that the killing of an animal is not inherently uncruel -- does this video depict cruelty at all, because it sure seems a lot more sensational than anything else. I didn't watch the entire video either (only the first 2/3) but it was quite boring and I just couldn't finish. The head/neck-banging of the first 2/3 doesn't seem cruel at all. DRosenbach (Talk | Contribs) 01:15, 2 November 2010 (UTC)
- I won't comment on the cruelty or lack thereof, but will note that killing animals larger than birds is usually a two step process: first you stun them, then you kill them. Traditionally the stunning is done exactly as these Chinese guys are doing: you hit them on the head with something heavy. More modern techniques include the captive bolt pistol and electrocution. The killing is usually done be exsanguination, but these guys are doing it by inflicting massive head trauma. The style of blow they used in some cases, where they hold the animal upside down and whack it at the base of the skull, is often used in killing rabbits in one step. Having killed many things (in what I hope is a cruelty-minimizing way) I believe the animal has some brain function but nothing like its normal thoughts after a well-delivered first blow. --Sean 20:15, 1 November 2010 (UTC)
- See rabbit punch. Googlemeister (talk) 13:16, 2 November 2010 (UTC)
- In this case, as I noted above, there appeared to be five "first blows" right at the start of the video. Is this just evidence of incompetence? HiLo48 (talk) 20:53, 1 November 2010 (UTC)
- I figured apathy; suggestive, though, of such action not being cruel as a rule. DRosenbach (Talk | Contribs) 01:59, 2 November 2010 (UTC)
- I'm not sure if they have much choice - the first step, as noted above is to stun or knock out the animal - but because these animals are for fur, cutting the throat is not really an option (blood stains on fur, damage to the pelt etc) - so hitting it numerous times on the head seems a reasonable thing to do if selling pelts is something you do for a living. Probably less cruel than stunning it, then stripping the pelt and waiting for the animal to die of a massive stress related heart attack when it comes round and discovers it's got no skin anymore.. An unpleasent business alround - but I don't see that the killing of the animals was more cruel than any other obvious way of killing it. (Is there a better way?)
- actually according to http://features.peta.org/ChineseFurFarms/ some are still alive when being skinned - as the video shows. It's a different video, and is about 100x worse than the first video posted - even the strong of stomach may not want to watch it.Sf5xeplus (talk) 08:00, 2 November 2010 (UTC)
- I figure these guys just don't care, just like I don't care about a live oyster's opinion on sliding down my throat. I personally would care with these raccoon things, but Chinese slaughter operations are a rougher place, I suppose. --Sean 16:35, 2 November 2010 (UTC)
- Also, exsanguination is important for meat quality, which is (perhaps!) not an issue here. --Sean 16:35, 2 November 2010 (UTC)
- actually according to http://features.peta.org/ChineseFurFarms/ some are still alive when being skinned - as the video shows. It's a different video, and is about 100x worse than the first video posted - even the strong of stomach may not want to watch it.Sf5xeplus (talk) 08:00, 2 November 2010 (UTC)
- I'm not sure if they have much choice - the first step, as noted above is to stun or knock out the animal - but because these animals are for fur, cutting the throat is not really an option (blood stains on fur, damage to the pelt etc) - so hitting it numerous times on the head seems a reasonable thing to do if selling pelts is something you do for a living. Probably less cruel than stunning it, then stripping the pelt and waiting for the animal to die of a massive stress related heart attack when it comes round and discovers it's got no skin anymore.. An unpleasent business alround - but I don't see that the killing of the animals was more cruel than any other obvious way of killing it. (Is there a better way?)
- I figured apathy; suggestive, though, of such action not being cruel as a rule. DRosenbach (Talk | Contribs) 01:59, 2 November 2010 (UTC)
is HCl in 95% saturated salt solution still a strong acid?
I assume that a saturation limit exists for salt in water because at some point there aren't enough water molecules to separate the Na+ and Cl- ions, which are growing more acidic/basic for each other, respectively.
This makes me curious as to to acid-dissociation properties in highly saline water. Does the acidic species in solution change in highly salty water?
The pKa for HCl is given to be somewhere around -7, but hydronium is usually listed as -1.8 or something, but I assume the latter is for a dilute, distilled solution. I wonder if I can make a "more acidic hydronium species" by near-saturating the solution with neutral salts. So I have two questions:
1) Will Cl- be a stronger base in near-saturated salt solution 2) Will H3O+ be more acidic in near-saturated salt solution? Will Zundel cations and Eigen cations decompose in saturated salt solutions to form the more acidic "bare H3O+" species?
John Riemann Soong (talk) 02:09, 1 November 2010 (UTC)
- Generally, the common ion effect is only a major issue in equilibrium situations. The dissociation of hydrogen chloride in water is highly extensive process. To put it bluntly, the chloride ion has such a terrible affinity for the hydrogen ion, I would doubt that you could get any discrete HCl molecules in a water solution regardless of how much you pump it full of chloride ions. --Jayron32 02:22, 1 November 2010 (UTC)
- I still expect the HCl to dissolve more or less completely, but what I expect is for HCl's pKa to increase (to maybe -3) and for hydronium's pKa to decrease. Isn't hydronium pKa = HCl pKa in a solution of saturated 37% HCl? That's why as water evaporates, HCl gas evaporates from it as well right? So these are my hypotheses:
- As long as hydronium pKa > HCl pKa, you can dissolve more HCl in the water.
- If hydronium pKa < HCl pKa, then the protonated water will spontaneously reprotonate the chloride, forming HCl gas.
- I have noticed that concentrated HCl behaves a lot differently in reactions than dilute HCl, and not simply because the reaction rate increases, but because the acidic species seems to increase in strength.
- Dissolving NaCl (or perhaps some other neutral salt) in water decreases the pKa of hydronium because the hydronium has to compete with the salt for solvation stabilisation.
- At the same time the Cl- conjugate base is less-stabilised, and is so more basic.
- I guess for clarity I should state that this is not an attempt to use the common ion effect but actually solvation effects. We could dissolve something else, like lithium fluoride. I notice that HCl is a weaker acid than say, perchloric acid. There are some expensive (spectroscopic, crazy test compounds) way to test this, but I wonder if there are cheaper, more elegant ways of playing with the acid strengths of what are normally considered "strong acids". Perchloric acid forms stable solid hydrates because I suspect that hydronium is never a stronger acid than perchloric acid is. However in saturated conditions I quite suspect that at some point Cl- becomes a stronger base than water. This is not simply because there is more Cl- around (we could dissolve sodium nitrate, say) -- it's because the basicity strength of Cl- actually changes. John Riemann Soong (talk) 02:44, 1 November 2010 (UTC)
- I am unclear on what you are asking then; are you asking if you can create a solution which will have measurable quantities of discrete HCl molecules in a water-based solution? I suppose its possible, if you take enough water out of the solution through solvation effects with a highly soluble solute, you could do something like that. However, lithium fluoride wouldn't work as it would generate additional OH- which would throw everything off (the flouride ion is a weak base; since HF is a weak acid). --Jayron32 02:58, 1 November 2010 (UTC)
- Is there such a thing as solvated HCl -- the solubility of which I suppose is very low -- before it turns into gas? What I'm trying to ask is firstly whether I can create a stronger HCl solution even though I am far from having 38% HCl say. Let's say I have 3.8% HCl and I saturate the rest of the solution with something like lithium bromide or something. Will I have the strength of 38% HCl (in terms of the pKa of the dominant acidic species in solution), just 10 times more dilute?
- Because I note that 3.8% HCl (no salt) does not behave like 38% HCl that is ten times more diluted. Fischer esterification runs much more than 10 times more slowly with conc. HCl that has been 10X diluted. (Granted this is in the glacial carboxylic acid and not water, so we maybe talking about an RCOOH2+ species instead, but...) I believe 38% HCl will form carbocations (if the alkene is water-soluble -- take pyran maybe), but dilute HCl will not. I wonder if I can get the strength of concentrated HCl without needing concentrated HCl. The concentration will be much less of course, resulting in a slower reaction, but the strength will be comparable. John Riemann Soong (talk) 03:16, 1 November 2010 (UTC)
- AH. But it has nothing to do with the HCl per se in these reactions, its the hydronium ion (acidity) which does the relevent work. In other words, its not the pKa, it is the pH which makes a difference here! HCl tends to be used in these cases because other strong acids have their own problems, for example H2SO4 tends to cause unwanted deydration problems (if there are any hydroxides present in the target molecules) while HNO3 can both nitrate molecules AND oxidize them. HCl has the advantage that a) it is a strong acid, so can produce very low pH's, and b) the Cl- ion is pretty much inert, and is unlikely to cause unwanted side reactions, which can occur with other strong acids. It's even better than HBr or HI, which, due to the softer nature of the Br- and I- ions, tend to be better nucleophiles, so they have their own problems with side reactions. HCl is primarily used where you need a very low pH (high hydronium/H+/acid/whatever concentration) and you don't want side reactions. --Jayron32 03:23, 1 November 2010 (UTC)
- There is something more than a pH effect here I think. I read somewhere on another professor's page (confirming my suspicion) that the pH scale is really only effective down to pH=0. Lower than that, you can talk about a hydrogen ion concentration, but the H3O+ species involved becomes markedly different. At least that was what I perceived him to be saying. That is, between pKa 0 and 14, H3O+ has around the same strength (pKa = -1.8). At higher concentrations, the pKa of H3O+ seems to drop. However, no one has confirmed this for me -- in saturated HCl solution, does the pKa of molecular HCl equal the pKa of hydronium species? This would make sense to me, because if not, more molecular HCl would continue to dissociate.
- My other suspicion is that there is no way to add enough HCl until solution has a pH of -7. That would be asking for a concentration of 10^7 M, which seems impossible. Thus it seems logically necessary that either the pKa of HCl must rise or the H3O+ species to drop in pKa for HCl fumes to start appearing. John Riemann Soong (talk) 03:38, 1 November 2010 (UTC)
- Where did a pH of -7 come from - you dropped that in from nowhere? For HCl fumes see below about the solubility constant of HCl in water - it has practically nothing to do with pKa.Sf5xeplus (talk) 03:52, 1 November 2010 (UTC)
- It is common knowledge? You can find it at hydrogen chloride. As long as HCl can spontaneously protonate H2O, HCl reformation would seem to be minimal. In order for HCl species to start appearing, H3O+ would need to reprotonate Cl-. John Riemann Soong (talk) 04:03, 1 November 2010 (UTC)
- Please - note the difference between pKa and pH - conc. HCl does not have a pH of -7 , HCl has a pKa of -7 .
- If the pKa of hydronium did not change to match the pKa of HCl more closely, then hydronium would have a pretty hard time protonating Cl- to form HCl gas. Thus in the "no pKa change" situation, HCl gas would start bubbling out of solution at absurdly high H+ concentrations. I assume that as long as HCl is more acidic than effective acidity of hydronium, free HCl will dissociate. Fumes start appearing when free HCl starts appearing in solution. (How much of conc. HCl is dissolved free HCl? If you lower the temperature or increase the pressure of HCl above, I don't suppose more HCl dissociates, merely dissolves?) John Riemann Soong (talk) 04:40, 1 November 2010 (UTC)
- HCl gas would start bubbling out of solution at absurdly high H+ concentrations yes that's what happens
- When HCl solutions are saturated the vapour pressure
of HCl(g)above the solution is 1 atm (under standard conditions) you should be able to do the maths yourself (you've got pKa and the molar concentration of a conc. solution) - ask in another question if you get stuck.Sf5xeplus (talk) 04:54, 1 November 2010 (UTC) - I don't know the solubility of HCl(aq). What is the makeup of the HCl in 38% RT HCl -- 95% dissociated HCl, 5% free HCl? My question anyhow is that HCl gas would start bubbling out of solution way too late if H3O+ did not become more acidic. The pH of conc. HCl is low, but not that low. John Riemann Soong (talk) 05:04, 1 November 2010 (UTC)
- If the pKa of hydronium did not change to match the pKa of HCl more closely, then hydronium would have a pretty hard time protonating Cl- to form HCl gas. Thus in the "no pKa change" situation, HCl gas would start bubbling out of solution at absurdly high H+ concentrations. I assume that as long as HCl is more acidic than effective acidity of hydronium, free HCl will dissociate. Fumes start appearing when free HCl starts appearing in solution. (How much of conc. HCl is dissolved free HCl? If you lower the temperature or increase the pressure of HCl above, I don't suppose more HCl dissociates, merely dissolves?) John Riemann Soong (talk) 04:40, 1 November 2010 (UTC)
- Please - note the difference between pKa and pH - conc. HCl does not have a pH of -7 , HCl has a pKa of -7 .
- It is common knowledge? You can find it at hydrogen chloride. As long as HCl can spontaneously protonate H2O, HCl reformation would seem to be minimal. In order for HCl species to start appearing, H3O+ would need to reprotonate Cl-. John Riemann Soong (talk) 04:03, 1 November 2010 (UTC)
- Where did a pH of -7 come from - you dropped that in from nowhere? For HCl fumes see below about the solubility constant of HCl in water - it has practically nothing to do with pKa.Sf5xeplus (talk) 03:52, 1 November 2010 (UTC)
- (edit conflict) I think you need to start again. There's problem at point 1 : dissolution of HCl has little to do with pKa - you can dissolve gases in liquids and them not dissociate .. in a polar solvent like water polar gases dissolve well eg NH3 and HCl. Ionisation of the dissolved gas happens, much more so in HCl - but isn't required for dissolution. ie in conc. HCl(aq) there are free HCl molecules.
- The other but - if I've understood correctly is the suggestion of adding (saturated) NaCl to a HCl solution - this is a Buffer solution, and ignoring activity effects you can easily calculate the pH using the equations in the article.
- As for Cl- increasing water acidity - this isn't going to happen - Cl- is a base (weak).
- The meat of the question seems to be "does saturated NaCl" alter the proportion of different types of hydronium ions - in water "H3O+" doesn't really exist - all positive dipoles will be strongly solvated (H3O+ can exist in a compound as you know) - in water (H+).(H2O)(n) is a more "truthy" description where n is undefined, but greater than 1. see Hydronium#Solvation. 87.102.115.141 (talk) 03:10, 1 November 2010 (UTC)
- I believe Cl- can increase water acidity not because Cl- is acting as a base but because water has to form shells to hydrate the Cl- (granted the effect is stronger when hydrating Na+). We can ignore the common ion effect altogether as that was not my intention. NaCl is simply a cheap salt in the laboratory.
- But yes altering the strength of the H3O+ species is the meat of my question. As more salt is dissolved, H3O+ becomes destabilised. I suppose the Zundel and Eigen cations still exist, just more fleetingly -- and the extensive hydrogen bonding and "charge sharing" becomes more difficult. For ease of discussion I will simply talk about the "average H+ species" in water -- I am not talking about bare H3O+. But as more salt dissolves in water, I suppose the average H+ species approaches bare H3O+ that is increasingly less and less stabilised. (That is, lone pairs still solvate it, just not as well.)
- My assumption with HCl was that HCl gas isn't very soluble in water if it doesn't dissociate -- after all, that is the situation with carbon dioxide! (CO2 has a fair amount of charge separation -- but does the lack of a dipole moment hurt solvation?) I suppose what I should say that is when HCl species exist in concentrated HCl soln (either as a fuming gas or solvated species), hydronium pKa = HCl pKa, yes? In dilute solution, the pKa difference is large, but as you add more and more HCl, the pKa gap closes. John Riemann Soong (talk) 03:27, 1 November 2010 (UTC)
- HCl molecules are very soluble in water, just like NH3 and MeOH molecules.. Of course total lack of a dipole in CO2 affect solubility.
- I can't answer the rest - your talking gibberish. Or so it seems.
- The constants you want are the solubitity constant for HCl in water, and the dissociation constant for HCl. They're called constants for a reason - they're constant. For variations the concept of Activity (chemistry) is used to explain deviations. Sf5xeplus (talk) 03:37, 1 November 2010 (UTC)
- In class we always talk about dilute solutions, and dilute solutions is all that we ever analysed. I am intensely curious about the dynamics of saturated solutions, since they are easily achievable in practice and they seem to result in effects that go beyond mere concentration increases.
- I'm talking about the pKa gap between H3O+ (in all possible forms) and HCl. In dilute solution the difference is ~5, but in saturated HCl solution wouldn't this gap be zero?
- AFAIK the dissociation constant for HCl is not actually "constant" -- there are very large concentration effects. It is constant only if the free energy change is constant. This is true in dilute conditions, but not in near-saturated conditions, yes? John Riemann Soong (talk) 03:48, 1 November 2010 (UTC)
- No. pKa is a measure (-log) of the equilibrium constant which is constant - please read Activity (chemistry). It's the activity which is considered to change.
- The reactions are:
- HCl(g) <<<<>>>> HCl(aq) (solubility constant)
- HCl(aq) <<<<>>>> H+(aq) + Cl-(aq) (acid dissociation constant)
- The acid dissociation can aid the dissolution by reducing the amount of free HCl in solution.
- The amount of HCl that you can get in solution depends on both these equlibriums.Sf5xeplus (talk) 04:01, 1 November 2010 (UTC)
- I think you may be going wrong because you are considering Cl- ions in isolation - no such thing exists in a solution - there must be a Na+ ion for each Cl- ion when using NaCl - the counterpoint to your half of the argument is that Na+ will increase the basicity of the solution by stabilising OH- !! - does that make sense?Sf5xeplus (talk) 03:46, 1 November 2010 (UTC)
- I am not considering anything in isolation. I didn't even want to talk about the common ion effect... John Riemann Soong (talk) 03:48, 1 November 2010 (UTC)
- I don't really care about the identities of the specific counterions. All that matters is that it is a neutral salt, cannot form a buffer in dilute conditions, and that it requires lots of H3O+ molecules to solvate them. I am asking -- can I add lots of NaCl to a dilute HCl solution to decrease the pKa of the hydronium species? The pH will not change but will the solution become more acidic? John Riemann Soong (talk) 03:58, 1 November 2010 (UTC)
- No. It's the opposite - the Cl- will suppress the ionisation of HCl (as per common ion effect and as per Le Chatelier's principle) - even though Cl- is a weak base. You can actually calculate the magnitude of the effect because HCl/NaCl is a buffer solution - albeit a weak effect. The answer is no. absolutely no. it will not work.
- The pKa can vary - according to the solvent eg different pKas in different solvent... and adding NaCL changes the solvent.. but the effect is to make it less acid. If you add enough Cl- you can start to get HCl2- which doesn't help.Sf5xeplus (talk) 04:14, 1 November 2010 (UTC)
- I don't really care about the identities of the specific counterions. All that matters is that it is a neutral salt, cannot form a buffer in dilute conditions, and that it requires lots of H3O+ molecules to solvate them. I am asking -- can I add lots of NaCl to a dilute HCl solution to decrease the pKa of the hydronium species? The pH will not change but will the solution become more acidic? John Riemann Soong (talk) 03:58, 1 November 2010 (UTC)
(undent). Look, John, consider what you get when you dissolve HCl in water at any concentration. There are only a few possible species:
- Discrete HCl molecules
- The acid species (whether you consider this H+, hydronium, extra-solvated hydronium, etc.)
- The chloride ion
- The hydroxide ion (ignore this, its concentration is far too low to be useful)
- Water molecules
Forget the pKa stuff for a moment. What you need to know is which of these species are actually involved, either as reactants or as catalysts, in the chemical reaction you are trying to do. Once you know that, worry about how to tweak the relative concentration of those things. The entire pKa thing you seem to be on seems to be a completely unrelated tangent, and its steering you away from your potential solution to your problem. pKa may end up relevent later, but lets put first things first: What are you trying to do, and what species from the HCl solution participate in what you are trying to do? --Jayron32 03:56, 1 November 2010 (UTC)
- I need a reagent with a more potent Hammett acidity function, essentially. I need a stronger acidic species in terms of the acidity of the H+ species in water, and not merely H+ concentration (pH). Suppose the only starting acid I have is HCl, and other weak organic acids, if need be. If I am trying to form carbocations (or hell protonate an aromatic compound that has EDGs) it would seem not only to be pH-dependent, but dependent on the maximum acidity of the H3O+ species in water. In dilute conditions this is -1.8, yes? But in concentrated conditions this might be lower.
- I suppose my main interest is decreasing the pKa of H3O+ in water below -1.8. This is what my question resolves around. I believe this is quite reasonable. The harder thing to do I suppose is measure this pKa decrease.
- I suppose there is literature on this topic, but I don't know how this phenomenon would be searched for. John Riemann Soong (talk) 04:11, 1 November 2010 (UTC)
- If all you have is HCl, you are unlikely to make any significant changes to the Hammet acidity function with anything you can do in this way. The effects you note may actually happen, but will probably only make smallish changes to the aciditiy of HCl. What you need, if you want a stronger acid is a, um, stronger acid, like a superacid. If Conc. HCl isn't strong enough, there's really not much you can do to conc. HCl to "supe it up" enough for your purposes. --Jayron32 04:16, 1 November 2010 (UTC)
- No Conc. HCl is good enough. Actually what I want to do is increase the potency of the H3O+ species in dilute HCl solution to that resembling the situation with conc. HCl, that is, to simulate the H+ species in conc. HCl. The concentration will be less, of course. I don't believe it's just a change in activity -- the change in free energy changes too, changing K. John Riemann Soong (talk) 04:23, 1 November 2010 (UTC)
- If all you have is HCl, you are unlikely to make any significant changes to the Hammet acidity function with anything you can do in this way. The effects you note may actually happen, but will probably only make smallish changes to the aciditiy of HCl. What you need, if you want a stronger acid is a, um, stronger acid, like a superacid. If Conc. HCl isn't strong enough, there's really not much you can do to conc. HCl to "supe it up" enough for your purposes. --Jayron32 04:16, 1 November 2010 (UTC)
- (ec)You can't get the hammett acidity function significantly lower in water because if you try water acts as a base - if you add a very strong acid to water it just protonates the water (water acting as a base) and the acidity is limited by the actiity of the 'hydronium ion' - possibly you can get it a little more acidic using salts - but in general if you want to get greater protonating power you need to use a less basic solvent.
- however If you really want to increase the acidity of an aqueous solution so that it has greater protonating power you need to destabilise the oxonium ion - this is best done with a salt of a strong lewis acid, and very weak lewis base - eg LiBF4 , (but please bear in mind that the pKa does not change, only the activities change) - this is how pKa is defined - thus you want to increase the activity of H+ since pKa is by mathematical definition fixed. (NaCl will not do it)Sf5xeplus (talk) 04:25, 1 November 2010 (UTC)
- Won't a concentrated salt (say non-chloride) solution interfere a lot with water's stabilising basicity? It seems to me the effect is rather large as a significant stabilisation of the oxonium ion seems to come from intermolecular delocalisation of charge. AFAIK pKa is based on free energy change per mol, which tends to be constant in most situations but not always. John Riemann Soong (talk) 04:34, 1 November 2010 (UTC)
- Question - is it clear how adding LiBF4 to water will decrease its basicity ? Sf5xeplus (talk) 04:28, 1 November 2010 (UTC)
- Well Li+ is a weak Lewis acid (in the sense of vinegar weak). The BF4- anion is a weaker base/anion than Cl-, but I don't see how Li+ destabilises H3O+ any more than additional H+ ions might. John Riemann Soong (talk) 04:44, 1 November 2010 (UTC)
- You said you didn't want to add additional H+, but make do with a weak HCl solution .. :) Therefor I think you've got it.Sf5xeplus (talk) 04:47, 1 November 2010 (UTC)
- I understand BF4- is a weaker anion, and Na+ isn't as strong of a Lewis acid, but why wouldn't NaCl (or sodium nitrate, sodium perchlorate, etc.) achieve somewhat of the same effect? Wouldn't Na+ destabilise oxonium cations too? With conc. HCl, is the oxonium ion at its maximum destabilisation? Any further destabilisation would simply result in reprotonation of Cl-? John Riemann Soong (talk) 05:07, 1 November 2010 (UTC)
- You said you didn't want to add additional H+, but make do with a weak HCl solution .. :) Therefor I think you've got it.Sf5xeplus (talk) 04:47, 1 November 2010 (UTC)
- Well Li+ is a weak Lewis acid (in the sense of vinegar weak). The BF4- anion is a weaker base/anion than Cl-, but I don't see how Li+ destabilises H3O+ any more than additional H+ ions might. John Riemann Soong (talk) 04:44, 1 November 2010 (UTC)
Distinguishing H3O+ activity from H3O+ acid strength
I am not really convinced that these are the same. Activity is effective concentration, perhaps in this context effective pH. There are things that dilute H3O+ would not protonate but concentrated HCl would....to me, it's not simply because there's more H3O+ to go around such that the protonated reagent is favoured in the equilibrium. A kinetic barrier appears to be crossed that seems to be related to the free energy of the H3O+ species? If we take protonating a carbonyl in the Fischer esterification, there is a large surge in reaction rate that does not appear to be solely due to the increased activity of H+. (We could take methanol and formic acid say, and watch how much methyl formate we get at a reaction run at 34C.)
AFAIK an equilibrium constant is the ratio of all the relevant forward rate constants over the reverse rate constants. Isn't it possible that due to changes in solvation structure or the type of H3O+ species in solution that you get H3O+ species with different "eases" of protonation, i.e. different rate constants for protonating "tough to protonate" reagents and getting reprotonated? Activity AFAIK is effective concentration, perhaps affected by the other solutes "stealing solvent", but would not explain a different hydrogen bonding / solvation structures adopted by H3O+ species. That is, the H3O+ species in conc. HCl is different from the H3O+ in dilute HCl solution, and isn't merely the same species at a higher activity. John Riemann Soong (talk) 06:02, 1 November 2010 (UTC)
- For all that you need Activity coefficient which is the ratio of effective concentration to 'mass' concentration (ie activity:concentration)
- Changes in the Activity coefficient with concentration (ie a non linear relationship between activity and concentration) are usually taken to mean that the average chemical enviroment has changed.Sf5xeplus (talk) 06:13, 1 November 2010 (UTC)
- There's a table of activity coefficients of HCl(aq) here google books Corrosion of metals: physicochemical principles and current problems By Helmut Kaesche Sf5xeplus (talk) 06:30, 1 November 2010 (UTC)
- According to google books:Outlines of Theoretical Chemistry By Frederick H. Getman p.452 the high measured activity coefficient of conc. HCl might be due to HCl molecules.Sf5xeplus (talk) 06:32, 1 November 2010 (UTC)
- Hmm. Would there be an observable difference between hydronium pKa dropping 1 pKa unit versus the activity coefficient increasing tenfold? (Thanks so much for your effort in finding sources btw. Wikipedia chemistry articles usually do not have any concentration-dependent data...perhaps we should update them.) John Riemann Soong (talk) 07:38, 1 November 2010 (UTC)
- I only have ever taken two classes that mentioned real solutions, and they always tried to avoid the concentrated solution case. Why does the activity coefficient fall into a minimum for both univalent salts and HCl? This is not the same as the free energy minimum is it? Does the activity coefficient minimum occur at the same concentration as the azeotropic concentration? John Riemann Soong (talk) 07:49, 1 November 2010 (UTC)
- 1. possibly in some cases (more likely for low values of Ka)- because activity is not necessarily linear with the change in equilibrium constant , whereas it is linear with change in activity coefficient (for constant concentration)
- 2. read activity coefficient - the coefficient usually drops to 1 as concentration tends to 0 - because 1 represents the ideal solution case, and this is best got from very low concentrations - it's in the article.
- 2b and c No,no. Sf5xeplus (talk) 08:04, 1 November 2010 (UTC)
- The activity coefficient minimum for HCl soln is near 20% ....that's very far from zero if "saturated" is at 38%. It doesn't seem like a coincidence to me that it's near the eutectic and azeotropic compositions. John Riemann Soong (talk) 08:11, 1 November 2010 (UTC)
- Oops, my bad, I'm doing the conversions wrong. (Is ionic strength == N?) There is an activity coefficient minimum < 0.78 between an ionic strength of 0.1 and 1.0, whatever that means. John Riemann Soong (talk) 08:14, 1 November 2010 (UTC)
- Hmm upon examining the data at Hydrochloric acid, it seems to me that H3O+ Cl- is optimally solvated at around 20% or near the azeotropic concentration (interestingly this is near the eutectic point as well). Does the falling activity coefficient with increasing concentration (up to around 20% w/w HCl) this actually mean the average strength of the H3O+ species decreases with concentration until the azeotropic concentration is reached?
- Is this when the derivative of free energy of solvation with respect to concentration is lowest? This seems highly peculiar to me -- I would assume that maximum decrease in the free energy of solvation would be near a concentration of zero. None of this was ever mentioned in my chemistry classes. And it is also so very relevant! Why did they omit it? John Riemann Soong (talk) 08:04, 1 November 2010 (UTC)
- Is this wrong now? Can you slow down a bit, cos this is starting to read like random noise. Please double check the above because it looks nearly completely wrong.Sf5xeplus (talk) 08:19, 1 November 2010 (UTC)
- The relationship between free energy and activity is given at activity coefficient ie
- G=G0+RTln(acc) where ac is activity coefficient at concentration, and c is concentration
- differentiating with respect to concentration gives:
- dG/dc=RT/c + ( RT/ac x d(ac)/dc )
- I don't think that will have a minima.Sf5xeplus (talk) 08:37, 1 November 2010 (UTC)
- I only have ever taken two classes that mentioned real solutions, and they always tried to avoid the concentrated solution case. Why does the activity coefficient fall into a minimum for both univalent salts and HCl? This is not the same as the free energy minimum is it? Does the activity coefficient minimum occur at the same concentration as the azeotropic concentration? John Riemann Soong (talk) 07:49, 1 November 2010 (UTC)
- clarify the original question a long time ago - if another species starts to appear at high molality eg lets say H4O2+ then that has a separate pKa, (because it's a different acid) the pKa of H3O+ or whatever doesn't change.
- 1. If the pKa (or activities) look odd at high conc. then this could mean that a new compound is being former at high conc.
- 2. But in stuff like water it gets complex due to the dynamic nature of the liquid - it may be right to take a fuzzy approach since actually cations are hard to categorise or temporal - it's easier to just say that the average 'proton' energy increases, and map that onto the activity figure
- 3. And finally - this means that some experimental activity figures may not be theoretically correct - this is likely for the high activity coefficients in HCl that are found when HCl is very concentrated ie when they go to 4 or 8. High figures like this suggest option 1. 87.102.115.141 (talk) 09:47, 1 November 2010 (UTC)
- I note from the physical properties of concentrated HCl that the viscosity increases drastically after some threshold. But nonlinear viscosity behaviour with concentration appears to be consistent with perhaps saturated NaCl solution [9]. (This is not to even include the interesting nonlinear behaviours for viscosity, activities and K_w to be gotten at high temperatures.) Is K_w necessarily ~10^-14 at 20C in concentrated salt solution -- that is, is neutral pH for a saturated salt solution at RT necessarily 7? John Riemann Soong (talk) 19:47, 1 November 2010 (UTC)
- Kwater is really for pure water at standard conditions, so changes could be factored in using the changes in activitys, or activity coefficients (which are related to the changes in the free energy of the components)
- Really you should call it Kionisation of water in saturated salt, and yes it will be a bit different.Sf5xeplus (talk) 05:08, 2 November 2010 (UTC)
- As far as I can tell the physical properties of conc. HCl are fairly smooth with concentration. except vaporpressure - which is due to the HCl solution being saturated above 38% at 1 atm.Sf5xeplus (talk) 05:11, 2 November 2010 (UTC)
- I note from the physical properties of concentrated HCl that the viscosity increases drastically after some threshold. But nonlinear viscosity behaviour with concentration appears to be consistent with perhaps saturated NaCl solution [9]. (This is not to even include the interesting nonlinear behaviours for viscosity, activities and K_w to be gotten at high temperatures.) Is K_w necessarily ~10^-14 at 20C in concentrated salt solution -- that is, is neutral pH for a saturated salt solution at RT necessarily 7? John Riemann Soong (talk) 19:47, 1 November 2010 (UTC)
- By the way - in terms of chemical kinetics, the effects of ionic strength on reaction rate are described by the primary salt effect and secondary salt effect see google books Chemical kinetics and reaction dynamics Santosh K. Upadhyay pp.190-2 and 192-3 (or search - there are many examples on google).
- Note that the primary salt effect depends on all the reaction materials not just the H+ : so is complex
- These aren't really applicable when the reaction species changes. The secondary salt effect does cause increasing ionisation (of weak acids) as salt concentration increases .. due to increasing electrolytic strenght (dielectric strength of the solvent also increases)
- For the same reason increasing salt strength could stabilise different H+(aq) ions - but the key term here is stabilise - for that reason I wouldn't expect greater protonating power to result. Sf5xeplus (talk) 07:22, 2 November 2010 (UTC)
- But it occurs to me that whatever H+ protonates will be stabilised as well! ... thus, in concentrated salt solution would I see a greater favourability for SN2 reactions, or for anomeric reactions, or for acyl reactions, especially under neutral conditions? If I put methanol and acetone in concentrated salt solution for example would there be a lower barrier towards forming methyl formate (and vice versa -- a lower barrier to hydrolysis under neutral conditions)? The book says that primary salt effect doesn't appear to affect neutral reagents too much, but they seem to be talking about inorganic chemistry -- what about steps in organic chemistry that require separation of charge or where permanent dipoles already exist? So if I wanted to attack an alkyl chloride for example, in addition to the whole trick of adding potassium iodide, would adding more salt in general also help? John Riemann Soong (talk) 09:16, 2 November 2010 (UTC)
- Adding salt increases the dielectric constant - assuming that is the only effect then anything with charge, or a dipole should be stabilised - both reactants, products and intermediates. How that affects the rate of a particular reaction with depend on what exists at the rate limiting step primarily - eg for anionic nucleophilic attack on an (neutral) alkyl halide the intermediate and the anionic reactant will both be stabilised - this makes the nucleophile less nucleophilic, but the intermediate will be a little more stable.
- The best examples are probably when a neutral substance fissions into charged species eg SN1 nucleophilic substitution, or ionisation of a weak (non charged) acid eg acetic acid - both of these are helped by increasing dielectric constant.Sf5xeplus (talk) 09:44, 2 November 2010 (UTC)
- Something like the reaction of an alcohol ROH with an acyl chloride RCOCl would also probably be speeded up, since the intermediate is a zwitterion.Sf5xeplus (talk) 09:53, 2 November 2010 (UTC)
- I meant the value of the Dielectric constant when I was saying dielectric strength, not to be confused with this type of Dielectric strength.Sf5xeplus (talk) 09:59, 2 November 2010 (UTC)
- But it occurs to me that whatever H+ protonates will be stabilised as well! ... thus, in concentrated salt solution would I see a greater favourability for SN2 reactions, or for anomeric reactions, or for acyl reactions, especially under neutral conditions? If I put methanol and acetone in concentrated salt solution for example would there be a lower barrier towards forming methyl formate (and vice versa -- a lower barrier to hydrolysis under neutral conditions)? The book says that primary salt effect doesn't appear to affect neutral reagents too much, but they seem to be talking about inorganic chemistry -- what about steps in organic chemistry that require separation of charge or where permanent dipoles already exist? So if I wanted to attack an alkyl chloride for example, in addition to the whole trick of adding potassium iodide, would adding more salt in general also help? John Riemann Soong (talk) 09:16, 2 November 2010 (UTC)
Birefringence, redux
I suppose I should make my question clearer. I'm trying to write a lab report, and the article isn't at all helping identify which directions birefringence can be seen. In a uniaxial crystal, there is only two orientations (out of 6) in which birefringence can be seen, yes? (I had to guess from the hexagonal crystal structure of calcite -- the language isn't clear at all!) I couldn't figure out from the article
....if I laid the crystal shown in the images on its side and looked at the words, neither of the 4 faces would show birefringence, yes? John Riemann Soong (talk) 05:29, 1 November 2010 (UTC)
- You mean this image? with 4 opposed faces. As far as I can tell there are 3 faces of one type and 1 (hexagonal) face of another.
- If you pick one of the three faces, and look 'down' into it (offset from the perpendicular) you should see that as you rotate around the perpendicular the trigonal groups (CO32- carbonate) go from looking flat, to side on, to flat etc - this seems to be anisotropy and I would therefor expect double refraction based on what the Birefringence article says.
- The hexagonal face doesn't have such a strong effect (though there is some minor change every 120degrees) - I wouldn't expect birefringence as much. (or at all)
- This isn't my subject - if that doesn't sound right I'd wait for an expert opinion.Sf5xeplus (talk) 09:22, 1 November 2010 (UTC)
KNO3 + KI
What happens when potassium nitrate and potassium iodide are heated? Is iodine produced? --Chemicalinterest (talk) 12:45, 1 November 2010 (UTC)
- According to [10], the iodide is oxidized to the iodate. shoy (reactions) 13:16, 1 November 2010 (UTC)
Solar cells: Difference between dark current and diode current
Hello, I have noticed that some texts refer to diode current and dark current in PV cells interchangeably. Could someone kindly explain the difference, if there is one?
The most common rendition I have seen is:
Diode current = dark current . (exp(eV/kT) - 1)
However I have also seen basically the same equation to define dark current:
Dark current = Jo . (exp(eV/kT) - 1) where Jo is an unidentified constant.
Assuming they are *not* the same thing, what is the physical nature of how they differ? To my understanding both terms describe a forward current that flows the p-n diode under the influence of an externally applied voltage.
Many thanks. —Preceding unsigned comment added by 146.23.212.21 (talk) 13:51, 1 November 2010 (UTC)
- You are looking at two different cases of "loose terminology" describing the ideal diode equation. A photoelectric cell is a photodiode, and ideally behaves according to this equation that relates current and voltage. The term "dark current" is being used to refer to the current that would flow even if no light is shining on the cell. In actuality, that is a bit loose - what this really refers to is the saturation current and is a semiconductor physics parameter. In reality, diodes are very complicated: see our article on diode modelling for an introduction to some of the mathematical idealizations of them. In any case - the parameter J0 probably refers to the effective current density for a particular device, and depends on diffusion parameters of the semiconductor - i.e., its geometry, its chemical makeup (doping), and so on. Here is an extremely technical overview of the semiconductor physics that are relevant to this process in a P-N junction: Basic Device Behavior. (While this overview is horribly complicated, the underlying processes in a PN junction actually are complicated - so there's no sense sugar-coating it). You can accept the derivations at face-value, or you can work with idealized, empirical models of current/voltage relationships and light-intensity/power-generation measurements. Nimur (talk) 17:26, 1 November 2010 (UTC)
Thanks Nimur, glad that the problem is the complexity of the subject and not my stupidity :) (this time). Yes for my purposes it is sufficient to understand the dark current as being that which flows in the diffusion direction in a darkened cell, and balances out the drift current. As a (forward) external voltage is applied, the electric field in the space-charge region is reduced, allowing diffusion to increase, yet the drift current remains unaffected since there's still just as many electron-hole pairs being created, hence the overall diode current increases as described by the first equation given above. —Preceding unsigned comment added by 146.23.212.21 (talk) 08:21, 2 November 2010 (UTC)
knife
what kinda knife do the usa army use today? —Preceding unsigned comment added by Kj650 (talk • contribs) 22:01, 1 November 2010 (UTC)
- The United States Army issues the M9 bayonet. Some services and special operation groups may use other equipment, including the Aircrew Survival Egress Knife, the United States Marine Corps' standard OKC-3S bayonet, or older M7 or M6. Here is the official page for the Bayonet at the US Army website. See also, Bayonets, knives, bayonet-knife models for a more thorough list, including historical issues. KA-BAR, while popular amongst service members for historic reasons, is not standard issue, although in some cases it may be officially issued to active duty Army units. Nimur (talk) 22:32, 1 November 2010 (UTC)
- Reading M9 bayonet, I see that "some production runs of the M9 have a fuller and some do not". Blood groove redirects to Fuller (weapon), but that article currently makes no mention of that common term despite it being the title of two of its four references. Should Fuller (weapon) contain some explanation of "blood groove". -- 124.157.218.101 (talk) 01:23, 2 November 2010 (UTC)
- I don't think so. Our Fuller article explains the function quite well. If anything, the referring pages should be changed to fuller. "Blood groove" is based on a misconception-- that the groove somehow increases blade performance by letting blood escape through the groove. This is false. If anyone wants to include this terminology, it should be clear that it is a misnomer.SemanticMantis (talk) 16:36, 2 November 2010 (UTC)
- Reading M9 bayonet, I see that "some production runs of the M9 have a fuller and some do not". Blood groove redirects to Fuller (weapon), but that article currently makes no mention of that common term despite it being the title of two of its four references. Should Fuller (weapon) contain some explanation of "blood groove". -- 124.157.218.101 (talk) 01:23, 2 November 2010 (UTC)
recycling code
what plastic recycling code do vacuum cleaners have —Preceding unsigned comment added by Kj650 (talk • contribs) 22:37, 1 November 2010 (UTC)
- You asked this already, but I guess you got no answer. Ariel. (talk) 00:01, 2 November 2010 (UTC)
- (Edit Conflict) I doubt that there can be a simple answer to this since: (a) different makes and models will surely use different plastics; (b) the same model will almost certainly use different plastics for different components; and (c) any model will certainly include significant non-plastic components (for example, metals in the motor). If particular plastic components are recyclable, they may carry an applicable symbol (probably on their inside surface). Recycling a vacuum cleaner in order to salvage and reuse component materials could probably only be done by a professional outfit specialising in such work, since some components will likely contain substances requiring special handling or disposal - some junked electrically powered equipment is exported to third-world countries where such work is profitable.
- You might find the list of articles at Index of recycling topics useful. 87.81.230.195 (talk) 00:24, 2 November 2010 (UTC)
November 2
Technocracy
What country or countries today would be considered most like a technocracy? The article mentions China and Russia in passing, but I find that frankly ridiculous. 59.46.38.107 (talk) 00:54, 2 November 2010 (UTC)
- This was my question. I forgot to sign in. The Masked Booby (talk) 00:56, 2 November 2010 (UTC)
- Our article references this source for the Russia/China claim: The Technocratic Trend and Its Implication in China from Observa. I would hardly call that a notable or widely-read, well-respected expert publication in the domain(s) of technology, politics, or social commentary; so take the citation with a grain of salt. I think there are no current "technocracy governments", though there are elements of technocracy in many states and non-state actors (particularly, certain corporations and business structures). Nimur (talk) 00:59, 2 November 2010 (UTC)
- I agree with the summation. Now would you care to hazard a guess at which may be considered more technocratic than the norm? The Masked Booby (talk) 01:04, 2 November 2010 (UTC)
- To be fair I think this may be more a question for the Humanities reference desk. --jjron (talk) 01:58, 2 November 2010 (UTC)
- It might be more useful to compare, more generally, the way that expert decisions are made in different states. For example, in the United States, when you have a complicated scientific question that has to do with policy — say, concerns about global warming, or whether the US national labs can guarantee the reliability of its nuclear stockpile without testing, or whether GMO crops should be regulated differently than non-GMO crops — there are bodies that policymakers can consult for guidance (like the National Academy of Science, or the JASON group), and there are agencies that often have some regulatory role over those areas (e.g. EPA or DOE or FDA in the examples given). But in practice the question of regulatory authority and of which brand of technical expertise to go to often devolves into Congressional debates, since they control the purse strings and can pass the laws. So we get a particularly adversarial way of making technical decisions — instead of "what do the scientists say," it becomes, "what does my scientist say vs. what your scientist says." It would be hard to argue for this reason that there is much "rule by experts" in the United States — on anything even slightly controversial, experts become proxies for other political decisions.
- We might compare this to, say, France. When the French government wants to make a technical decision, it picks a few experts it trusts, asks them what to do, and does it. It doesn't open it up to public discussion most of the time, and it doesn't usually enter into the arena of party politics. (There are exceptions, I am sure.) This is one of the reasons that the French did not have anything like the American experience when it came to picking a nuclear waste repository, for example. It's experts said, "bury it here, this way," and that was that. In the United States, after some 50 years of trying to come up with such a plan, we find it endlessly scuttled by local and national politics, which deploy the experts in whatever way suits them best.
- I don't know the situation in China or Russia but my inclination is to think the Chinese use experts more like France and less like the United States. None of these countries are really "technocracies" in the standard sense, but they have pretty different roles for experts in the public domain. There is a lot of work in the field of Science and technology studies that is concerned with looking at this question. --Mr.98 (talk) 02:03, 2 November 2010 (UTC)
- For what it's worth both China and France are often described in the media as having decisions made by "Technocrats", as does the EU, and formely communist russia (I think that description is less commonly used for modern russia). Please use google to verify rather than asking me.
- Nevertheless none of these are true "technocracies" - decisions are still heavily informed by political matters (eg france) - perhaps China is the best example of a near technocracy. I think that the perception is mostly due to bias - all modern goverments use technical experts to make decisions. (Do 'anglo-saxon' counties tend to be more heavily influence by NIMBY concerns? maybe so [11]) Sf5xeplus (talk) 06:03, 2 November 2010 (UTC)
- I don't think it's really a NIMBY issue so much as it is an expectations of public participation issue. Everybody's NIMBY if you ask them if they want something big and toxic in their backyard. The trick about France and China is they don't ask them and people on the whole don't expect to be asked. In the US (and to a lesser extent in the UK), the form of deliberative government that has grown up there really sits on the idea that you always ask people what to do, which leads to the kinds of political and regulatory environments we are talking about. Germany is something of a separate case, if I recall. This table in a book that compares the US, UK, and German (and I also think Japanese and French) approaches to regulating biotechnology describes sort of the kind of analysis I am talking about. There are very different political "styles" in the countries we are talking about in respect to how they make expert decisions, and that leads to a lot of the difference in results that we see between them. I agree that none of them are "technocracies" in the strict definition, which I don't think has ever really existed. But some ways of using expert opinion are more "technocratic" than others. --Mr.98 (talk) 13:26, 2 November 2010 (UTC)
- Some countries like to give themselves the appearance of being a technocracy; Romania's Elena Ceauşescu liked to pretend that she was a world renowned chemist, despite leaving school with good grades in needlework followed by a brief job in a textile factory lab. Alansplodge (talk) 10:15, 2 November 2010 (UTC)
- Which country has the highest number of Nobel prizes per capita? Which country has made the most life-changing inventions and discoveries? Its the UK, of course. 92.29.115.229 (talk) 12:24, 2 November 2010 (UTC)
- Of your one factual statement and one opinion with a ton of unstated and unsourced assumptions, the former is not even true. According to data on the relevant WP pages (here and here), UK nobels-per-capita looks like 1/530K vs Switzerland at 1/300K and Sweden 1/335K. Those are just two of the only four I bothered to check (US is 1/952K and Germany 1/802K), so there may be others as well. Remember verifiability is a core wikipedia policy. DMacks (talk) 12:40, 2 November 2010 (UTC)
- I don't see a technocracy valuing a Nobel prize in literature or peace though, so you might want to consider that into your equation. Googlemeister (talk) 13:12, 2 November 2010 (UTC)
- Of your one factual statement and one opinion with a ton of unstated and unsourced assumptions, the former is not even true. According to data on the relevant WP pages (here and here), UK nobels-per-capita looks like 1/530K vs Switzerland at 1/300K and Sweden 1/335K. Those are just two of the only four I bothered to check (US is 1/952K and Germany 1/802K), so there may be others as well. Remember verifiability is a core wikipedia policy. DMacks (talk) 12:40, 2 November 2010 (UTC)
- Sorry should have typed England rather than the UK. 92.28.243.168 (talk) 15:38, 2 November 2010 (UTC)
- I don't see how that helps much... According to Demography of England the population is 49,138,831 in 2001 or according to Demography of the United Kingdom England's population 50,762,900 from a 2006 estimate. DMacks didn't give the number of Nobel prize winners for the UK and I'm lazy to work it out for myself but as the population of the UK is 58,789,194 in 2001 or 60,587,300 from the 2006 estimate we can guess the number of winners they estimated is probably 111 or 114 or perhaps 115 to be generous. So even if we assume all these winners are from England and we take the later figure yet use the 2001 population we still only end up with ~1/427k which is still less then Switzerland and Sweden. May be you're going to limit yourself to those living in certain areas in England now but can you at least ensure you have better then 1/300K this time? (We haven't of course established that is the highest nor does it make sense to start limiting to arbitary areas in one place but not the others but anyway...). Edit: Actually looking more closely at DMacks answer the UK number of winners is source to an article and is indeed 115 so lucky that I used that. Nil Einne (talk) 03:23, 3 November 2010 (UTC)
- Third in the world is not bad and I expect that if only the science-related Nobel prizes are included then it would be higher. Not forgetting all the famous English scientists. 92.29.117.88 (talk) 11:15, 3 November 2010 (UTC)
Clothes drying under clothes pegs
When I hang my clothes out to dry on a clothes line why is that the fabric underneath the pegs gets dry just as quickly as the rest of the cloth? Wouldn't it seem logical that that small patch covered by the peg would remain damp? (I can guess at the type of answer I would give here, but am interested to hear what others think). --jjron (talk) 03:24, 2 November 2010 (UTC)
- Gravity helps. If you hang a long-sleeved shirt out to dry, the top will be dry far sooner than the bottom of the arms and waist. The Masked Booby (talk) 03:27, 2 November 2010 (UTC)
- As the cloth near the pin dries, the water under the pin diffuses into the dry area. Ariel. (talk) 07:31, 2 November 2010 (UTC)
- And, at least in my experience, in many cases the assumption is wrong. The part under the pegs does dry slower that equivalent areas not under them. But the effect is small, and the overall amount of water is so small that usually nobody cares. --Stephan Schulz (talk) 07:37, 2 November 2010 (UTC)
- As the cloth near the pin dries, the water under the pin diffuses into the dry area. Ariel. (talk) 07:31, 2 November 2010 (UTC)
laminated wood
whats laminated wood
example
http://www.youtube.com/watch?v=pvZXqSn-mIs&feature=mfu_in_order&playnext=1&videos=H6X28Y6mdrU —Preceding unsigned comment added by Kj650 (talk • contribs) 05:03, 2 November 2010 (UTC)
- Laminated wood is pieces of wood glued together to make a bigger single piece. When the pieces are very thin and flat we call this Plywood.
- In the video the pieces (look closely at the end grain of the wood in the video) are about 1" thick - you should be able to see that 3 pieces - the grain of the wood doesn't match so there are 2 joins.
- A very thing flat piece of wood on top of something else is also a wood laminate and is called a veneer
- Usually the pieces of wood are joined longways, when they are joined longways, and shortways it's called Glued laminated timber Sf5xeplus (talk) 05:22, 2 November 2010 (UTC)
train deaths
The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.
does anybody think this
http://www.dreamindemon.com/2010/02/22/three-teen-girls-unable-to-outrun-train-struck-and-killed/
was likely a suicide like this
http://www.dreamindemon.com/2010/02/27/police-two-teen-girls-hit-by-train-were-part-of-suicide-pact/
and the guy was lying so he didnt get committed —Preceding unsigned comment added by Kj650 (talk • contribs) 05:34, 2 November 2010 (UTC)
- Please see the disclaimer at the top of the page The reference desk does not answer requests for opinions. Sorry.Sf5xeplus (talk) 05:40, 2 November 2010 (UTC)
Faster than Light
Lets assume i hold a lamp, and i travell in perfect vaccum at the the speed of ½c, will not the light from the lamp move faster then c? Daily motion of the Heavens was to hard to understand? But the moon goes around the earth, the earth goes around the sun, and the sun goes around the milky way, doesn't a light from the moon get a push, or is c independant to the course of the satellites of the universe? —Preceding unsigned comment added by 92.254.188.129 (talk) 12:36, 2 November 2010 (UTC)
- The light will move away from the lamp at the speed of light, and this is what you (travelling with the lamp) will observe. An outside observer will also see the light moving away from you at the speed of light. This is one of the fundamental postulates of Einstein's Special relativity. The Michelson–Morley experiment is a famous early (failed) experiment roughly along the lines of the concept you are suggesting. --jjron (talk) 13:56, 2 November 2010 (UTC)
- Basically the answer is that everyone will measure the speed of light (in a vacuum) as being c, no matter how fast they or the light emitter is traveling. It's extremely counterintuitive but has been verified by experiment pretty thoroughly. It is, as Jjron notes, the foundation of Special Relativity — SR is basically an exploration and elaboration of the implications from this fact. --Mr.98 (talk) 14:41, 2 November 2010 (UTC)
- Would the light be red-shifted or blue-shifted to the .5c speed observer? Googlemeister (talk) 16:26, 2 November 2010 (UTC)
- Neither, but it would be red-shifted to someone "stationary" behind him and blue-shifted to someone "stationary" in front. --Sean 16:40, 2 November 2010 (UTC)
- Would the light be red-shifted or blue-shifted to the .5c speed observer? Googlemeister (talk) 16:26, 2 November 2010 (UTC)
92.254.188.129, If light were a classical wave in the sense of being a vibration in an elastic medium, then the answer to your question would be 'no'. The light would always have a fixed speed relative to that medium, and if a light source were moving in that medium in the direction of propagation of the light, the speed of light relative to the source would actually be c-v, where v is the speed of the source relative to the medium. In order for an observer to observe light at a speed equal to c+v, they would have to either move into the light beam or else move with a light source which is moving backwards relative to the direction of propagation.
However, in recent times, the official belief is that light propagates in empty space and that it defies the normal rules of vector addition of velocities. Einstein postulated words to the extent that light will always be measured to have the speed c irrespective of the motion of the source or the receiver. This postulate is the cornerstone of the special theory of relativity. And so, based on either 20th century physics, or 19th century physics, the answer to your question is 'no'. You cannot push a light beam faster by pushing the source. Such a vector addition phenomenon is something which applies to particle projectiles and not to waves. David Tombe (talk) 22:44, 2 November 2010 (UTC)
Cheaper to turn off Compact fluorescent lamps briefly?
With old fashioned incandescant lightbulbs the consensus view was that it was cheaper to leave them on rather than turn them off for a few minutes, as the stress of being turned on or off wore them out more quickly. What is the best strategy regarding energy-saving lightbulbs in a domestic situation? Thanks. 92.29.115.229 (talk) 12:45, 2 November 2010 (UTC)
- It depends on the CFL. Some ballasts are more gentle, some less. But in general, CFLs are designed with a limit on the number of expected switches. That said, mine now seem to come with warranties of 10 or even 12 years, so the much greater financial risk seems to be losing the warranty slip. The design limit is large enough that manual (as opposed to, say, movement-triggered) switching is unlikely to be a problem. --Stephan Schulz (talk) 12:55, 2 November 2010 (UTC)
- In the UK they are often given away, or are available for a few pence each. 92.29.115.229 (talk) 13:06, 2 November 2010 (UTC)
- It's an interesting scenario. Given that CFLs typically use 20-30% the energy of an incandescent bulb for the same light output and are considerably more expensive to buy, it would seem to make a lot more sense to turn off the incandescent to save power and money as they're costing lots to run but are cheap to replace. Older CFLs had a warm up period where they started a bit dull and gradually brightened to full intensity, and as far as I know they still do, so that makes turning them on and off inefficient in terms of having a consistent light output. In Australia incandescent bulbs are being phased out and I was reading recently of people complaining that their new CFLs were having short lifespans, shorter they were claiming than their old incandescents (I believe it was generally the cheaper brands and seemed to be worse in certain locations). The reason suggested was that power fluctuations were causing high wear on the CFLs leading to the short lifespan. If correct, this would suggest they are quite susceptible to wear and tear and the answer to your question would be to leave them on. --jjron (talk) 13:27, 2 November 2010 (UTC)
- List_of_MythBusters_episodes#2006_season, Episode 69. shoy (reactions) 15:43, 2 November 2010 (UTC)
- Better link: MythBusters (2006 season)#Lights On/Off. --Anonymous, 07:27 UTC, November 3, 2010.
- List_of_MythBusters_episodes#2006_season, Episode 69. shoy (reactions) 15:43, 2 November 2010 (UTC)
- It's an interesting scenario. Given that CFLs typically use 20-30% the energy of an incandescent bulb for the same light output and are considerably more expensive to buy, it would seem to make a lot more sense to turn off the incandescent to save power and money as they're costing lots to run but are cheap to replace. Older CFLs had a warm up period where they started a bit dull and gradually brightened to full intensity, and as far as I know they still do, so that makes turning them on and off inefficient in terms of having a consistent light output. In Australia incandescent bulbs are being phased out and I was reading recently of people complaining that their new CFLs were having short lifespans, shorter they were claiming than their old incandescents (I believe it was generally the cheaper brands and seemed to be worse in certain locations). The reason suggested was that power fluctuations were causing high wear on the CFLs leading to the short lifespan. If correct, this would suggest they are quite susceptible to wear and tear and the answer to your question would be to leave them on. --jjron (talk) 13:27, 2 November 2010 (UTC)
- In the UK they are often given away, or are available for a few pence each. 92.29.115.229 (talk) 13:06, 2 November 2010 (UTC)
- I think this myth started in the days when fluorescent lamps were very expensive and electricity was very cheap. (Yes, I can remember them.) The claim had a better chance of being true then, but it was probably just a marketing lie even in the "old days". From a psychological viewpoint, the flickering and reduced light output for the first second or two after switchon might be a valid reason for leaving the light on rather than turning it off for a few minutes, but warm-up time is shorter if the lamp is still warm from recent use. Dbfirs 08:25, 3 November 2010 (UTC)
If man evolved from monkey, why are there still monkeys?
It might seem like a trivial question. We also evolved from bacteria, but they are still here. However, if the evolution was ape > primitive man (like the Austrolopitecus) > us, why did the middle species disappeared? Theoretically, the cave men should be better adapted than the original apes, shouldn't they then be here among us? Quest09 (talk) —Preceding undated comment added 13:10, 2 November 2010 (UTC).
- Simply because of the competition for the living space. Man and chimps separated, and used a different territory (men like the savanna better, chimps likes the forest better), and therefore they never eliminated each other. Well, that is until very recently, where we started to trim the tropical forest for our own use, which is killing the few thousands of chimps remaining.
- However the intermediates (that you call cave men) either used the same type as territory as Man (savanna) or the same type as apes (tropical forest) and therefore had a hard time to compete against either. They could have won the competition, of course, and eliminated us, but it just happen that they didn't, we and apes were better adapted to survive in our own type of territory, it seems. --Lgriot (talk) 13:37, 2 November 2010 (UTC)
- Sometimes, monkeys have attacked humans on their own territory. (http://news.bbc.co.uk/2/hi/1107970.stm)
- (Incidentally, monkeys are not chimpanzees.) -- Wavelength (talk) 20:02, 2 November 2010 (UTC)
- This is a classic question for which the internet has many nice succinct answers: [12]. Short story: chimps actually do occupy a different niche than man, and practically all of the middle species that occupied the same niche have disappeared. (Consider all of the extinct species in Genus Homo.) --Mr.98 (talk) 13:41, 2 November 2010 (UTC)
- e/c No. Organisms evolve to become better adapted to their current environment, but that does not mean they are 'better' than the organism they evolved from. Have a read also of Common descent, Evidence of common descent, and Human evolution as starting points. And for proof of concept, using a thought experiment, try living in the jungle with some chimpanzees/gorillas/orang-utans, etc to determine which species is better adapted to that environment. --jjron (talk) 13:44, 2 November 2010 (UTC)
- Remember the same argument could be made for bacteria. Why do single celled organisms still live if multicelled ones are better adapted? The simple answer as above answer have stated is better adapted doesn't mean better in every way. Organisms can co-exist if they fill different niches. Humans may be better adapted to live in some environments and conditions but in different ones other organisms are better adapted. (Given all our tech we can now comfortably live in many environments partly by changing our environment to suit us but it took us a while to get here.) If you're talking about such extreme comparisons as bacteria vs humans, humans can't live in another humans mouth or stomach, many bacteria can. Speciation is somewhat relevant here and to some extent so is Species problem. Nil Einne (talk) 13:59, 2 November 2010 (UTC)
- The most fundamental explanation, it seems to me, is that humans did not evolve from modern monkeys. Humans and monkeys both evolved from the same common ancestor, which is now extinct. The same goes for bacteria. Humans did not evolve from modern bacteria—rather, modern bacteria and humans are both descendants of a now-extinct common ancestor. —Bkell (talk) 14:08, 2 November 2010 (UTC)
- Mankind did not evolve from any modern-day apes. Both chimps and humans share a common, now-extinct, ancestor. Probably Nakalipithecus or something very similar to it.
- However, even if Nakalipithecus was still around, it wouldn't be a logical paradox. It's not as if every single one of them magically turned into either a chimp or a human. Populations probably got separated from the main group and began adapting to their new surroundings. Eventually they adapted so much that they were no longer the same species as the group they got separated from. If, hypothetically speaking, some of them had found some sort of isolated monkey-paradise, it's would not have been impossible that they would have remained mostly unchanged over all this time while other members of their species adapted and evolved. It's too bad that didn't happen, I'll bet biologists would love to get a blood sample from one. APL (talk) 14:34, 2 November 2010 (UTC)
- Apart from the actual substance of this question, humans are generally not considered to have evolved from Monkeys, but rather Apes (in fact, humans are considered a Great ape). The trouble is, apes are more closely related to Old World monkeys than Old World monkeys are to New World monkeys, making a good illustration of the inconsistencies in the traditional way in which we classify life. Buddy431 (talk) 15:10, 2 November 2010 (UTC)
- If we are the progeny of our grandparents, why do we have cousins? The answer is blindingly obvious: we are not the progeny of our cousins; we both evolved from common ancestors; and our existence does not invalidate the existence of our cousins. They share many traits with us, but have many different traits than us. As we pursue more distant ancestral relations, we see fewer common traits; and if we keep investigating farther up the ancestral tree, we gradually and eventually reach an ancestor who is quite unlike ourselves. If we count all the offspring of a very distant ancestor, we will clearly see a very broad group of individuals. Nimur (talk) 16:16, 2 November 2010 (UTC)
Plant respiration
Photosynthesis requires intake of Carbon dioxide and the plants release oxygen in the process. However, do plants breathe oxygen like animals? --117.204.87.227 (talk) 16:18, 2 November 2010 (UTC)
- Yes. They use carbon dioxide with water to make glucose. At night, plants burn this glucose by taking in oxygen. However, plants give off more oxygen than they take because to grow they need to join glucose together to make cellulose, so not all of the glucose is burned up. --The High Fin Sperm Whale 16:25, 2 November 2010 (UTC)
- Plants certainly take in oxygen for respiration, but "breathe" isn't really the word to use to describe it. --86.130.152.0 (talk) 16:57, 2 November 2010 (UTC)
- Yeah, the term breathing usually refers to respiration via lungs, which plants of course don't have. Something I just learned that surprised me is that plants respire not only through their leaves, but also through their roots; see soil gas. Our root article does mention "breathing pores" in reference to aerating roots, so apparently the word "breathing" is at least occasionally used when discussing plant respiration. Red Act (talk) 19:02, 2 November 2010 (UTC)
- Cooler than that, is this paper which discusses how Equisetum telmateia aerates its roots by taking air in through its leaves, allowing it to grow in waterlogged soil, which is about as close to breathing as a plant will get. The paper predicts that in the extinct Calamites from the Carboniferous, up to 70 litres of air could have been transported to its roots per minute! SmartSE (talk) 20:38, 2 November 2010 (UTC)
- Yeah, the term breathing usually refers to respiration via lungs, which plants of course don't have. Something I just learned that surprised me is that plants respire not only through their leaves, but also through their roots; see soil gas. Our root article does mention "breathing pores" in reference to aerating roots, so apparently the word "breathing" is at least occasionally used when discussing plant respiration. Red Act (talk) 19:02, 2 November 2010 (UTC)
Where are all the universes ?
I have read the Many-worlds interpretation article, but there is something I can't understand, no doubt due to my limited knowledge of physics. If there are many universes beyond our own, where are they ? Do they exist in the same sense that our universe exists, i.e. physically ? Wouldn't so many universes need a humungous amount of spacetime to contain them ? I guess I would intuitively think that Mother Nature would use her resources more sparingly. Regards, 62.241.87.223 (talk) 17:04, 2 November 2010 (UTC)
- "Beyond our own universe" means just that i.e. not having a location anywhere in this universe, and posessing each its own spacetime. On the presumption that there are infinitely many of them, encompassing every option of every alternative, there is someone very much like you wondering the same thing. The many-worlds theory is not proven but here are ideas in fiction about it. Cuddlyable3 (talk) 18:30, 2 November 2010 (UTC)
- These scientist will eventually figure out that the "universes" that they see in the formulas are just representations of other galaxies that have been completely separated by the emptiness of space. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:26, 2 November 2010 (UTC)
- This is certainly not what the MWI is about, at all. --Mr.98 (talk) 18:28, 2 November 2010 (UTC)
- Agree. 165.212.189.187's interpretation is completely incorrect and is unsupported by any reliable scientific literature. Here is one of the foundational papers of many-worlds interpretation, Quantum Mechanics and Reality (1970). The field has absolutely no connection to extragalactic astronomy. Nimur (talk) 18:53, 2 November 2010 (UTC)
- This is certainly not what the MWI is about, at all. --Mr.98 (talk) 18:28, 2 November 2010 (UTC)
- Sure and thats precisely how all the multiverse perpetuators want to keep it. Except extragalactic astronomy is part of our universe, helps us form theories about multiverse, and its relationship to the mulitverse is inseperable. —Preceding unsigned comment added by 165.212.189.187 (talk) 20:22, 2 November 2010 (UTC)
- See Multiverse for some discussion of this. Short answer: nobody is really sure. They might just be somewhere parallel to us in 3D space (what you mean by "physically" existing, I think), or they might be in some sort of weird quantum space, or something like that. In general this is one of those quantum things that once you've heard it ten times, you say, "oh yes, multiple universes, sure sure," but when you really try to make sense of what it would mean intuitively (e.g. not just with some equations), it becomes pretty clear that it falls outside of everyday human concepts and makes very little sense. That's a limitation of our brains, not to the concept. (I don't know whether the concept makes sense or not — I'm no physicist. But there are lots of quantum things that similarly make very little intuitive sense, yet appear pretty clearly true.)
- There is no reason to think that Mother Nature would be conservative with quantum things. It's not a good metaphor to use in this situation, if it ever is good. --Mr.98 (talk) 18:28, 2 November 2010 (UTC)
Other universes would obviously be outside this one, potentially with different rules. Unless someone developes a inter-universe traveling device, we'll probably never know. scientifically speaking, the other universes would probably have to physically exist though some could be figments of imagination too, and would be incorporeal. 70.241.22.82 (talk) 18:51, 2 November 2010 (UTC)
- A critical issue here is that "universe-splitting" is not an observable phenomenon in the formal definition of the many-worlds approach. So, philosophical pandering aside, "where are the other universes" is, by definition, an invalid question. There is no observable parameter for them - not an x-position, not a y-position, not a different time, place, or space, where the "other" universe is. "Other universe" represents an effort to use different plain natural language because "collapse" sounds catastrophic. All this boils down to is that the English language is a terrible medium for expressing quantum physics ideas. What we really mean by "many world interpretation" is
- , where refers to the system, and refers to the apparatus used to observe it [13].
- ... and that is a superposition of states. All this nonsense about "interpretation" is little more than philosophical rumination about whether random systems can be causal; and whether causal systems are truly random. If more philosophers would agree on the definition of "random" then there would be no debate about "interpretation." Nimur (talk) 19:10, 2 November 2010 (UTC)
- You also have to define what "universe" means; this is no trivial task as throughout history, what constitutes the universe, even in purely scientific terms, keeps changing. Remember that before Edwin Hubble, it was widely assumed, even within the astronomical world, that the Milky Way Galaxy was the entire universe. Consider how small the Milky Way is in comparison to the observable universe, and it becomes really clear what a revolutionary thing this was. If you define the universe as "the sum-total of all creation", then multiple universes makes no sense. What you end up doing instead is reclassifying the thing we call "the universe" as a different entity, and pushing the limits of what the universe is "outwards", much as what Hubble did. --Jayron32 21:02, 2 November 2010 (UTC)
Origin of a "love bite"
I cannot find any information on why animals and humans do this affectionate bite. Is it a way of communicating "Look, I could bite you hard, but instead I'm tenderly biting you?" AdbMonkey (talk) 17:16, 2 November 2010 (UTC)
- For humans (no idea about animals): because it feels good? Can also indicate (playful or not) dominance, which many people enjoy from one side or the other. → ROUX ₪ 17:17, 2 November 2010 (UTC)
- The OP is specifically asking for (presumably expert or at least reliable) information, not just personal speculation... --Mr.98 (talk) 18:18, 2 November 2010 (UTC)
- Male cats bite when mating, probably to immobilise and calm the female, and to balance the male. Cuddlyable3 (talk) 18:22, 2 November 2010 (UTC)
- The OP is specifically asking for (presumably expert or at least reliable) information, not just personal speculation... --Mr.98 (talk) 18:18, 2 November 2010 (UTC)
- All kinds of animals do play bites. Looie496 (talk) 18:37, 2 November 2010 (UTC)
- Please add any verifiable information you can find about this to our Love-bite article. DMacks (talk) 18:46, 2 November 2010 (UTC)
Cuddlyable, that was sort of what made me ask this question. My male cat does that to me sometimes when I pet him, and that got me thinking. Anyway, I know it exists among other animals too, but I could not find any info when I searched for it. The results only comes back with vampire literature, from what I've seen. AdbMonkey (talk) 20:13, 2 November 2010 (UTC)
- The hickey, or love bite, is just a variation of kiss. The Wikipedia article has a brief section at Kiss#Biology_and_evolution which discusess some of the anthropological research into the purposes of kisses. It's pretty weak, but if you do some off-wiki research into the kiss as a psychological, social, or anthropological phenomenon, you could apply most of what you find to something like the love bite. --Jayron32 20:54, 2 November 2010 (UTC)
what chemical gets released when you miss someone?
I know there must be some sort of biochemical that is released in a "flood" if I think the right thought or of the right person (that is no longer around) or hear the right song, the kind that pulls your heartstrings so. I suppose it might be "the nostalgia hormone" (or neurotransmitter) -- at least because there seems to be a strong physiological response. I know oxytocin and vasopressin seems to be involved in pair bonding, but is it these related hormones that get released or is it something else?
Are there any antagonists you can take to suppress this feeling? John Riemann Soong (talk) 18:56, 2 November 2010 (UTC)
- In my experience that's not a very useful antagonist and in fact often exacerbates it and upregulates all emotions (see short term effects of ethanol). John Riemann Soong (talk) 20:50, 2 November 2010 (UTC)
- You're meant to take it with company, not while editing Wikipedia. Physchim62 (talk) 22:05, 2 November 2010 (UTC)
- In my experience that's not a very useful antagonist and in fact often exacerbates it and upregulates all emotions (see short term effects of ethanol). John Riemann Soong (talk) 20:50, 2 November 2010 (UTC)
- I was making a serious scientific inquiry! But...I never drink by myself, seeing how as I am below 21 this usually means I have to rely on others to furnish drinkable EtOH for me. John Riemann Soong (talk) 22:41, 2 November 2010 (UTC)
- There are a number of other hormones that are involved in love, in addition to the two you've already mentioned: dopamine, phenylethylamine, adrenaline, and endorphin. I'm getting this from hubpages.com/hub/Hormones-and-love , which I apparently can't link to without triggering a spam trap filter. There's also a more technical article about the chemistry of love here. And at least some of those chemicals (e.g. dopamine) are addictive, so I suspect that missing someone you love might be at least partially due to withdrawal. Red Act (talk) 22:51, 2 November 2010 (UTC)
- Yes, but withdrawal is a chronic condition. How would I identify the chemical that gives you that "shiver down your spine" when you have a flood of memories? John Riemann Soong (talk) 23:15, 2 November 2010 (UTC)
- Missed one: prolactin, which is tied to dopamine. Red Act (talk) 23:18, 2 November 2010 (UTC)
- Chemical basis for love might help point in some right directions, too. Red Act (talk) 23:30, 2 November 2010 (UTC)
crabs
do crabs make sounds, analagous to our speech? how big do they get, and can they regenerate limbs? If so, how long does the latter take? 70.241.22.82 (talk) 19:00, 2 November 2010 (UTC)
- Did you try reading crab? (assuming you mean the oceangoing variety, and not the pubichairgoing variety). The section titled "Behaviour" discusses communication methods. Many crabs may regenerate limbs, see Florida stone crab for one famous example, likely most crabs can do this. As far as how big they can get, well, there are hundreds of different species of crabs, but the largest in terms of size and weight is the Japanese spider crab, which can reach up to 12 feet in size from claw tip to claw tip, and can weight up to 40 pounds. --Jayron32 20:50, 2 November 2010 (UTC)
- (edit conflict)Crabs can make sounds, but they are stridulations, rather than vocalisations. The abstract of this paper describes them in Trizopagurus and this does in Hemigrapsus oregonensis in more detail and there are many more examples in the literature. How big they get will depend on the species, but these guys can get up to 3.8 metres! Fiddler crabs can regenerate limbs e.g. but I can't find anything about how long, but it will certainly take at least one moult and maybe more for it to return to its full length. SmartSE (talk) 21:07, 2 November 2010 (UTC)
Microarray cost
How much does a typical microarray experiment cost, supposing you wanted to assess differences in gene expression between two/three/four samples? Are there cheaper versions which assses fewer genes (e.g. genes known or suspected to be involved in muscle growth, maintenance, differentiation etc)? --129.215.47.59 (talk) 20:46, 2 November 2010 (UTC)
Cartoon physics law break
Remember the classic cartoon where a character walks off the edge and "hangs" in the air before he falls down. My teacher wants me to answer what physics law does this cartoon breaks. Please help! Any clues or hints appreciated!!! --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 20:47, 2 November 2010 (UTC)
- When you step off the edge of a cliff yourself, what causes you to fall? Comet Tuttle (talk) 20:48, 2 November 2010 (UTC)
- You should learn, and go back to your teacher with, some of the stuff outlined at General Relativity and blow their mind... --Jayron32 20:56, 2 November 2010 (UTC)
- This is the actual cartoon: http://img213.imageshack.us/img213/2044/cartoonfall.png --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time! 21:03, 2 November 2010 (UTC)
- You should learn, and go back to your teacher with, some of the stuff outlined at General Relativity and blow their mind... --Jayron32 20:56, 2 November 2010 (UTC)
- As a hint which might help, the law was figured out by Isaac Newton. (Albert Einstein later figured out something that was more accurate.) Red Act (talk) 21:56, 2 November 2010 (UTC)
- The cartoon character has weight W which is a force acting on him continuously. When he walks off the cliff he hangs there for a short time. In physics we say his acceleration is zero. Then he suddenly starts falling downwards. In physics we say his acceleration is a and it is non-zero. So for a short time the cartoon character's acceleration is zero, even though the resultant force on him is greater than zero. Which of Newton's Laws of Motion does this violate? Dolphin (t) 21:58, 2 November 2010 (UTC)
- Wow, there are actually two different "laws" that Newton came up with, that could to be said to be violated by that cartoon. The "law" I was thinking of wasn't one of the laws of motion. I'm not actually sure which law is the answer the teacher is looking for. I think the answer I was thinking of would be more likely if Tyw7 is younger, and the answer you’re thinking of would be more likely if Tyw7 is older. I don't know what the cutoff age would be. Red Act (talk) 22:22, 2 November 2010 (UTC)
- The cartoon character is usually used to teach the laws of motion, and the character breaks two of them. So, the question is: "which ones and WHY?" Physchim62 (talk) 23:02, 2 November 2010 (UTC)
- Jeez, I'm just not seeing it. The character violates one of NLM in a very straight-forward way. If it violates another of NLM, it's in a less obvious way. The other law of Newton's that I was thinking of wasn't one of NLM.
- However, there is also at least a third valid answer, although I highly doubt it's the one the teacher's looking for. Namely, there's a law by Euler that's closely related to one of the two of Newton's being discussed. I guess this is another one of those cases where the "correct" answer is whatever you've covered in class recently. Red Act (talk) 01:06, 3 November 2010 (UTC)
- Try doing a vectorial analysis of the supposed trajectory, and you should see two separate NLM breaches (I can't be more clear because of our homework rules) Physchim62 (talk) 01:28, 3 November 2010 (UTC)
- The cartoon character is usually used to teach the laws of motion, and the character breaks two of them. So, the question is: "which ones and WHY?" Physchim62 (talk) 23:02, 2 November 2010 (UTC)
- Wow, there are actually two different "laws" that Newton came up with, that could to be said to be violated by that cartoon. The "law" I was thinking of wasn't one of the laws of motion. I'm not actually sure which law is the answer the teacher is looking for. I think the answer I was thinking of would be more likely if Tyw7 is younger, and the answer you’re thinking of would be more likely if Tyw7 is older. I don't know what the cutoff age would be. Red Act (talk) 22:22, 2 November 2010 (UTC)
- Look, there are two laws being violated. break it down into two steps:
- the character is moving forward at a steady forward pace, he takes what looks like 2 or 3 steps past the edge, stops, then falls straight down. how does he stop when he's moving forward and has nothing to push against to stop himself? what law is that?
- Again, the character is walking along on the ground without flying off into space on each step (think about how astronauts bounce on the moon). What force is it that holds him on the ground as he walks? When he walks off the edge of the cliff what happens to that force that was holding him to the ground, since the ground is no longer there to be held to?
- Think about it. --Ludwigs2 01:39, 3 November 2010 (UTC)
Quail genome?
Is there a publicly-available database of the genome sequence for the quail (ideally Coturnix japonica)? ----Seans Potato Business 21:48, 2 November 2010 (UTC)
- I was able to find this but it seems limited to Colinus virginianus at this point. The pubmed abstract (here) suggests that it will be "integrated with Japanese quail (Coturnix coturnix) data in future builds" so maybe there isn't such a thing as a publically-available Coturnix japonica genome yet. Good luck! --- Medical geneticist (talk) 23:19, 2 November 2010 (UTC)
Why does high temperature cause distant sights to "blur", and can this be replicated at room temperature?
Greetings.
For years, I've been fascinated by what I've seen at a local pizza place. The pizza oven is about 25 feet behind the counter, and (when I stand in front of the counter) the area surrounding the oven —and everything in it— appears "blurry" and very distorted to me.
What exactly causes this visual phenomenon? Are light particles excited (or even ionized) by high temperatures?
Also, can a similar visual effect be achieved AT ROOM TEMPERATURE through any known means?
--Thank You! Pine (talk) 22:44, 2 November 2010 (UTC)
- What you're seeing is a kind of mirage, caused by the hot air from the ovens. To explain it very quickly, the way that light travels through air depends on the temperature of the air: so when you have differences in air temperature over a short distance, you get strange effects.
- A similar effect can be created at room temperature, but not easily. You need a large amount of gas that's different from air within your visual field, and that is usually a sign to get the **** out of the place. You can see it sometimes when natural gas is released at a gas well. Physchim62 (talk) 23:13, 2 November 2010 (UTC)
To elaborate the explanation above, the hot air has a different refraction index than the cold air. Because of that light rays will bend a little bit when they move in and out of the hot air area. that causes the image distortions that you observed. 76.123.74.93 (talk) 02:40, 3 November 2010 (UTC)
- To attempt an answer to your "also" ... I can't think of any way to reproduce this in air all at room temperature, except by blowing a gas with a different refractive index in a way that produces turbulence in the mixing with air. (later) Sorry, I've just noticed that Physchim62 said that! The temperature effect in air can sometimes be seen on a small scale with domestic fires and radiators, and will be in evidence outside on Friday in some countries. Dbfirs 08:07, 3 November 2010 (UTC)
- Is it correct to say that hot air has a different refraction index than the cold air entirely because of the different densities, or does the temperature itself have anything directly to do with it (other than changing the density)? -- 58.147.58.203 (talk) 08:20, 3 November 2010 (UTC)
- Several websites claim that "Refractive index is proportional to the square roots of electrical permittivity and magnetic permeability. These factors may change with temperature, but not linearly, and therefore RI does not have a simple relationship with temperature." so I suspect that hot air at the same density (from greater pressure) will have a marginally different RI from cold air at the same density. This difference will be swamped by the difference in density at normal pressure. Dbfirs 08:35, 3 November 2010 (UTC)
Relationship between octane rating & emission levels
Consider two identical cars, one using low octane gasoline, the other high octane. Same driving conditions. Does one car create less emissions than the other? Thanks, CBHA (talk) 22:56, 2 November 2010 (UTC)
- Does not quite work like that. One could have a large megawatt, electrical generator, running on natural methane with a 14:1 compression ratio, producing a very clean CO2, water vapour, nitrogen exhaust. Or a high compression ratio, in WWII fighter aircraft, sports car, racing car, all with short stroke engines and the exhaust can be very, very dirty.--Aspro (talk) 23:28, 2 November 2010 (UTC)
- I've seen suggested (but do not have a source offhand) that using fuel with an octane rating higher than recommended can result in incomplete combustion. In either case, using incorrect fuel cannot improve your engine's performance or its emissions, and may be detrimental to both. — Lomn 01:42, 3 November 2010 (UTC)
Which animals are truely monogamous?
I've read that in nature, true monogamy is very rare and that even in species that tend to pair up for life, 'affairs' and side-pairings are common. Could you tell me some of the few species that are 100% monogamous? I think that the Peach-faced Lovebird is one of them. --95.148.105.15 (talk) 23:50, 2 November 2010 (UTC)
- Photocorynus spiniceps --Dr Dima (talk) 01:55, 3 November 2010 (UTC)
- Are humans truly monogamous? "Affairs" and side-pairings are very common in human societies too. --99.237.232.254 (talk) 02:11, 3 November 2010 (UTC)
- No one said they were. The Masked Booby (talk) 02:24, 3 November 2010 (UTC)
- I was wondering if, by the OP's criteria, humans would be considered truly monogamous. --99.237.232.254 (talk) 06:00, 3 November 2010 (UTC)
- Bald Eagles are monogamous, with the following caveats mentioned in their article: It is thought that Bald Eagles mate for life. However, if one member of a pair dies or disappears, the other will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates. Seems reasonable to me. The Masked Booby (talk) 02:24, 3 November 2010 (UTC)
- I don't know if that would rule out 'affairs'. Very often animals which appear to mate for life are found to mate with other partners on the sly (this can sometimes be difficult to observe but the recent advances in genetic analysis making paternity or parentage testing easy have shared a lot of light in this area including with the animal we discussed above), and this includes both sexes. However [14] found a high degree of fidelity in another species of eagle (by analysing DNA from feathers). On the other hand [15] claims recent research suggests that it may not be true but doesn't mention how so or what research nor even what it means by 'recent'. Prairie Vole are another common 'icon' of monogamy and studied for how they are adapted for it [16] but our article mentions they aren't always sexually faithful. Back to birds, [17] suggests low instances of extrapair copulation and extrapair parentage may be more common among isolated island populations where the genetic variation is low. Nil Einne (talk) 06:01, 3 November 2010 (UTC)
November 3
Time dilation? Time speeding?
The beginning of the section of {Time dilation and length contraction} under Special Relativity is confusing to me. Hope someone can help. It states:
- See also: Twin paradox
Writing the Lorentz transformation and its inverse in terms of coordinate differences, where for instance one event has coordinates (x1,t1) and (x'1,t'1), another event has coordinates (x2,t2) and (x'2,t'2), and the differences are defined as Δx = x2 − x1, Δt = t2 − t1, Δx' = x'2 − x'1, Δt' = t'2 − t'1 , we get
△t’=γ(△t-(v△x/c^2)) △x’=γ(△x-v△t) and △t=γ(△t’+(v△x’/c^2)) △x=γ(△x’+v△t’)
Suppose we have a clock at rest in the unprimed system S. Two consecutive ticks of this clock are then characterized by Δx = 0. If we want to know the relation between the times between these ticks as measured in both systems, we can use the first equation and find: △t’=γ△t (for events satisfying Δx = 0). This shows that the time Δt' between the two ticks as seen in the 'moving' frame S' is larger than the time Δt between these ticks as measured in the rest frame of the clock. This phenomenon is called time dilation.
- I am confused by the last two sentences. To explain △t’=γ△t in more detail, we can assume the unit time in S is Ut and in S' is Ut', then the time of the {two consecutive ticks event} measured in S is △t*Ut=(t2-t1)Ut, the t2-t1 can be 1; while measured in the S' is △t'*Ut'=(t'2-t'1)Ut', the t'2-t'1 may not be 1. Since they are for the same event, we have △t*Ut=△t'*Ut', then, put △t’=γ△t in it, we have Ut=γUt', that means the clock in S' is running quicker than the clock in S. This phenomenon should be called time speeding, isn't it?
When Einstein used x'=0 to derive t’=t/γ, so that △t’=△t/γ, we have time dilation; how can we call △t’=γ△t as time dilation too? Please help me to understand that paragraph. Thanks.
Regards, John HuangJh17710 (talk) 04:53, 3 November 2010 (UTC)
- Relativity of simultaneity actually has some nice, non-mathematical, explanations of the problem. If there are any two events, seperated by some arbitrary distance, which are perceived in one reference frame to occur at the same time, there will exist other reference frames which perceive them not to be simultaneous, some in which one event occurs first, and some in which the other event occurs first. This perception is dependent not only on the location of the reference frames but on their relative motion to each other. In other words, for your problem, lets assume that you and I are moving relative to one another. If we both start our stop watches at what we perceive at the same time, there will exist three different classes of reference frames relative to us:
- Some will perceive our clocks to run at the same speed.
- Some will perceive your clock to run faster than mine
- Some will perceive my clock to run faster than yours
- That's the key problem with Special Relativity, there is no reference frame which is "right". All are equally valid. By convention, we hold the reference frame of the designated observer to be "stationary" and measure time changes relative to that one; thus since everyone else is moving relative to THAT observer, everyone elses clock is running a little bit slower. But this convention holds regardless of who you choose as the observer. If two spaceships are moving away from each other at some fraction of c, but each is in communication with the other, each will perceive the other's clock to be slowed down. If they then, at some later time, change speeds to be stationary relative to each other, the perception of which clock slowed down will depend on which ship had to speed up or slow down to "match speeds". If the two ships performed identical, mirror image paths and speed changes, then the clocks will match when they reach the same relative motion. If one ship decelerated while the other maintained a constant speed, you will get different results. Special_relativity#Lack_of_an_absolute_reference_frame and Consequences of special relativity also discusses some of this. --Jayron32 05:34, 3 November 2010 (UTC)
if the moon and moon landings are real
why didn't they run around the moon to prove it is a sphere and not a disc like it looks? 85.181.145.78 (talk) 08:58, 3 November 2010 (UTC)
- We can observe 59% of the moon's surface, thus it is not a disk Tidal_locking#Earth.27s_Moon. Also there have been plenty of satellites (inclusing the moon landers themselves) that orbited the moon, observing it completely. See e.g. SELENE. Furthermore, the moon is simply too large to run around, especially with a limited oxygen supply. 157.193.175.207 (talk) 09:28, 3 November 2010 (UTC)
- To put it in context, the equatorial circumference of the moon is 10,921 kilometres (6,786 mi). Ghmyrtle (talk) 09:35, 3 November 2010 (UTC)
- The Apollo rover had a top-speed of 18 miles per hour (29 km/h), and a range of 57 miles (92 km). IIRC, NASA didn't want the rovers to go out of walking-distance of the lander, incase they broke down. CS Miller (talk) 09:52, 3 November 2010 (UTC)
- To put it in context, the equatorial circumference of the moon is 10,921 kilometres (6,786 mi). Ghmyrtle (talk) 09:35, 3 November 2010 (UTC)
if the moon is real
why didn't they run around it with a camera to prove it is a sphere and not a disc like it looks?
- It's rather a long way! They did fly round it - will that not suffice to convince you? (later) sorry edit conflict. The much better answer above wasn't there when I started to edit. Dbfirs 09:31, 3 November 2010 (UTC)
Heart muscles
- What property of the heart muscles are exploited in the heart transplant?
- In blood groups,why is it imposible for one individual to carry all 3 alleles?
- why is the oxygen dissociation curves of animals living at high altitudes located to the left of most of those of other animals?
— Preceding unsigned comment added by 196.0.7.4 (talk • contribs)
- Hmm, these look suspiciously like homework questions. Try reading "Heart", particularly the "Functioning" section. Axl ¤ [Talk] 10:41, 3 November 2010 (UTC)
- "ABO blood group system", section "Inheritance". Axl ¤ [Talk] 10:44, 3 November 2010 (UTC)
- "Oxygen-haemoglobin dissociation curve", section "Factors that affect the standard dissociation curve", will point you in the right direction, although it does not contain the answer that you seek. Axl ¤ [Talk] 10:50, 3 November 2010 (UTC)