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Can you move your eye so that your iris and pupil are not visible to reasonably sizeably open eyelids? The reason I ask is that you quite often see in tv/movies etc folk with just the white of their eyes visible, but I just tried to do this both up and down in my webcam and it didn't work, and then I asked a girl friend of mine with a very different build to try it on webcam and it didn't work, so it isn't a male/female thing and probably isn't a build thing. Doesn't work with left/rights either with me at least, I just realised that when typing this. Indeed, I can't even move my eyes to the extent that I can't see anything (although she says she can). If it isn't possible and we're not freaks, is this a physical or a mental limitation? Egg Centri c 02:49, 19 May 2012 (UTC)
Just watching trainspotting at the moment (which is actually where my eye question inspriation came from!), and Renton is going through all the drugs he and his fellow junkies enjoy aquiring illicitly. As an opioid addict myself, which I've mentioned before (although never one who has ever stolen things or manipulated people or in any way whatsoever behaved like a twat to get drugs, and in fact I resent that stereotype for a million reasons - but primarily cause it means that a lot of so called medical "professionals" treat me like shit - oops rant detected... in my view it comes about because twats are far more likely to use drugs, rather than drugs make you a twat, I've even met highly functional crack and meth addicts, I know a head of a desk at a bulge bracket bank who's one... but I digress...) I've never heard of this drug, unlike the others, and looking it up... ok, it's a sedative and a hypnotic. That usually means it may have some recreational potential. But is that the only reason they would want it, and does anyone know of it actually being abused? Is it a potentiater (sp?) for something? One suspects there was another reason for including it in the list. Egg Centri c 03:19, 19 May 2012 (UTC)
In the artile ( http://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain_reaction), the third paragraph reads:
“In the Sun, deuterium-producing events are so rare (diprotons being the much more common result of nuclear reactions within the star) that a complete conversion of the star's hydrogen would take more than [ten billion] years at the prevailing conditions of its core.”
I am confused by this, as well as the next sentence, which states
“The fact that the Sun is still shining is due to the slow nature of this reaction; if it went more quickly, the Sun would have exhausted its hydrogen long ago.”
Regarding the first sentence; I find several problems for me to conclude that the article is accurate. First of all it claims that ‘deuterium-producing events are so rare in our sun, that it would take 10 billion years to convert all the sun’s hydrogen into helium’ - yet this IS what the sun’s lifetime is predicted to be.
Secondly; the article goes on to explain this very deuterium process (one proton, one neutron) in the subtitle: The proton-proton chain reaction - opposed to the “much more common” nuclear reactions the author proposes is taking place in our sun.
Thirdly; the sentence, in parenthesis, infers that the sun’s main fusions product is “diproton” - or, helium-2. The article for helium-2 ( http://en.wikipedia.org/wiki/Diproton#Helium-2_.28diproton.29) explains that diproton is only a “HYPOTHETICAL” helium isotope. It appears to me that helium-2 not only defies the Pauli exclusion principle, if even possible, it would convert the sun’s hydrogen into helium exponentially faster than 10 billion years!
As for the second sentence; it could be accurate IF it unambiguously defined WHICH “reaction” (deuterium or diproton) is responsible for the “slow nature” of the sun’s actual proton-proton fusion process.
To me, it seems the contributor may have cut-and-pasted information from another stellar nucleosynthesis web-page, without making the necessary changes to the wording to fit the context of the actual article. — Preceding unsigned comment added by 64.180.243.107 ( talk) 03:50, 19 May 2012 (UTC)
My textbook asked me to prove that a system with scleronomic constraints is in equilibrium if and only if for all generalized coordinates qj, assuming that all non-constraint forces are conservative. (V is the system's potential energy).
I was able to prove this, but as far as I can tell this proof holds for all holonomic systems, not just scleronomic ones. But because it was stressed that the constraints are scleronomic, I suspect that I'm making a mistake somewhere.
Proof of above statement: System is in equilibrium iff , where is the total force on the ith particle. , where Qj is the generalized force associated with the jth generalized coordinate. So, if , then Qj = 0. But , so is a necessary condition for equilibrium.
Now we prove that it is a sufficient condition. To do this, we find the 's as a function of the Qj's by making virtual displacements to the generalized coordinates. The the virtual work is . Writing (we've tacitly expressed the generalized coordinates as functions of the ri's; stands for ).
From this, it follows that , implying that . Therefore, if Q_j = 0, system is in equilibrium. QED.
Now, as far as I can tell I haven't used the assumption that the constraints are scleronomic, but maybe the assumption sneaked in there somewhere.
This is a pretty pedantic question, but it's been bugging me for a little while now, and I'd appreciate anyone's help in alleviating this confusion. 65.92.6.118 ( talk) 06:26, 19 May 2012 (UTC)
http://rt.com/usa/news/donna-summer-cancer-singer-627/
Donna Summer believed that it was the September 11 deadly smokes that gave her cancer.
During the WW2, the U.S. and Nazi Germany destroyed many cities by carpet bombing: Dresden, Coventry just to name a few. These WW2 cities certainly did not have much polymers and advanced man-made materials. People could live in the ruins. The cities were rebuilt within years after the end of the wars.
What will happen if a today's city is destroyed by a major earthquake or a meteor impact? Will they become too toxic for anyone after the fire? -- Toytoy ( talk) 07:02, 19 May 2012 (UTC)
Actually, the Royal Air Force destroyed Dresden before the yanks even got there. 1.124.213.85 ( talk) 18:12, 20 May 2012 (UTC)
Could I have help identifying this flower species ( 1, 2) and this monkey species? — Crisco 1492 ( talk) 09:13, 19 May 2012 (UTC)
Could anyone help identify this houseplant please? I suspect it of being some sort of geranium. DuncanHill ( talk) 09:21, 19 May 2012 (UTC)
Find the potential difference between the tube and the wire in a Geiger tube. Variables are ; you can guess what they stand for. Doing these integrals is prone to mistakes all the time. This is what I have tried so far. We must find the potential difference between a ring segment of the tube and the corresponding segment of the wire, each of width . This makes the ring segment carry charge and the little wire segment carry charge . To find this, we must find the potential difference between a point on this ring segment and the little wire segment. By Gauss's law, the electric field due to the little wire segment a displacement away from the wire is if and zero otherwise. This potential difference is therefore . I am wondering if you have to do lots more integrals; is there an easier way perhaps? The version of Gauss's law I have been given is: the electric field in the tube is solely contributed by the wire, and the field outside the wire is the same as though the wire were infinitely thin; the outer tube does not contribute as long as we are not near the ends of the tube. -- 150.203.114.37 ( talk) 10:59, 19 May 2012 (UTC)
For comparable tasks, I mean. Suppose a 1400kw microwave versus an ordinary GE electric stove (I have no idea what it's kw rating is, but it plugs into a standard 220v outlet). I wonder if anyone can make a reasonable calculation of energy required in two cases:
Am I truly saving energy by using the microwave for these tasks, or not? A plain-English answer, please. Textorus ( talk) 15:05, 19 May 2012 (UTC)
Thanks for these observations, Stu, but I'm not concerned with the cost (convenience is paramount in these situations), and I'm not going to buy an outlet monitor that I would never use again for anything. It's an academic question - I was thinking that someone who knows what must surely be a very simple equation or two could quickly calculate the amount of energy used in each case (e.g., 1 min. @ 1400kw/hr. = 23.33 kw, no? But how much for five minutes on a stove burner?). Textorus ( talk) 15:39, 19 May 2012 (UTC)
There is a label of some kind inside the oven door, but it's long since become illegible from heat and cooking stains. I don't need a precise, down-to-the-last ion answer, just a general comparison between the two heating methods. Using standard ratings, such as in the link Nimur provided, would be sufficient. And no, I'm not going to go stand in the yard and guestimate how fast the little wheel in the electric meter is turning; that would be highly inexact for anyone but the meter reader, perhaps, and not worth the trouble. Textorus ( talk) 17:03, 19 May 2012 (UTC)
I made some experiments on a Electrolux cf 502(stove), and Melissa AG820CQM (microwave).
In both cases I thrid to heat 2.1 dl (aprox. 7 oz.) from around 22 C to boiling.
To heat the water 2.1*100*4.2*(100-22)/3600/1000 kWh=0.019 kWh is needed.
The stove used about 1640 W for 3 minutes, approx. 0.08 kWh, 23% efficency.
The microwave used about 1220 W for 2 min, approx. 0.04 kWh, 46% efficensy.
If the claimed 800 W microwave power are correct 0.027 kWh, 66% become microwaves.
The losses in the stove are mostly due to the heat remaining in the stove when the water starts to boil. The stove could be used more effeciently by turning it of before the water strts boiling and use some of the after heat.
The electriciy consumption was mesured by counting impulses on the meeter and clocking them and substracting background consumption.(1000 imp/kWh)
The stove will be more efficient when boiling larger volumes. I expect the microwave oven to be much more effecient than a conventional oven but i have not tested. Gr8xoz ( talk) 18:50, 20 May 2012 (UTC)
Is it possible to express specific entropy in terms of the gas constants cv, cp and pressures p1 and p2 only? I can't derive anything close to this without using v1 and v2. The closest I've got is s2-s1=cvln(p2/p1)+cpln(v2/v1) but i don't want the vs in there. This is an is isentropic process so were saying PV^n is constant. 94.116.0.41 ( talk) 15:17, 19 May 2012 (UTC)
Since dinitrogen, the acetylide dianion, and the nitrosonium cation are isoelectronic with carbon monoxide and the cyanide ion, why aren't they as deadly poisonous as carbon monoxide and the cyanide anion? Whoop whoop pull up Bitching Betty | Averted crashes 16:24, 19 May 2012 (UTC)
Since Dasyuromorphia are carnivores, why there are ranked as separate order and not suborder of Carnivora? Also, what hinders thylacine from being placed in Canidae or Caniformia?-- 176.241.247.17 ( talk) 22:27, 19 May 2012 (UTC)
Didn't the xenic acid article say that there is no such thing as a completely de-protonated xenate salt?-- Jasper Deng (talk) 23:22, 19 May 2012 (UTC)
Science desk | ||
---|---|---|
< May 18 | << Apr | May | Jun >> | May 20 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
Can you move your eye so that your iris and pupil are not visible to reasonably sizeably open eyelids? The reason I ask is that you quite often see in tv/movies etc folk with just the white of their eyes visible, but I just tried to do this both up and down in my webcam and it didn't work, and then I asked a girl friend of mine with a very different build to try it on webcam and it didn't work, so it isn't a male/female thing and probably isn't a build thing. Doesn't work with left/rights either with me at least, I just realised that when typing this. Indeed, I can't even move my eyes to the extent that I can't see anything (although she says she can). If it isn't possible and we're not freaks, is this a physical or a mental limitation? Egg Centri c 02:49, 19 May 2012 (UTC)
Just watching trainspotting at the moment (which is actually where my eye question inspriation came from!), and Renton is going through all the drugs he and his fellow junkies enjoy aquiring illicitly. As an opioid addict myself, which I've mentioned before (although never one who has ever stolen things or manipulated people or in any way whatsoever behaved like a twat to get drugs, and in fact I resent that stereotype for a million reasons - but primarily cause it means that a lot of so called medical "professionals" treat me like shit - oops rant detected... in my view it comes about because twats are far more likely to use drugs, rather than drugs make you a twat, I've even met highly functional crack and meth addicts, I know a head of a desk at a bulge bracket bank who's one... but I digress...) I've never heard of this drug, unlike the others, and looking it up... ok, it's a sedative and a hypnotic. That usually means it may have some recreational potential. But is that the only reason they would want it, and does anyone know of it actually being abused? Is it a potentiater (sp?) for something? One suspects there was another reason for including it in the list. Egg Centri c 03:19, 19 May 2012 (UTC)
In the artile ( http://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain_reaction), the third paragraph reads:
“In the Sun, deuterium-producing events are so rare (diprotons being the much more common result of nuclear reactions within the star) that a complete conversion of the star's hydrogen would take more than [ten billion] years at the prevailing conditions of its core.”
I am confused by this, as well as the next sentence, which states
“The fact that the Sun is still shining is due to the slow nature of this reaction; if it went more quickly, the Sun would have exhausted its hydrogen long ago.”
Regarding the first sentence; I find several problems for me to conclude that the article is accurate. First of all it claims that ‘deuterium-producing events are so rare in our sun, that it would take 10 billion years to convert all the sun’s hydrogen into helium’ - yet this IS what the sun’s lifetime is predicted to be.
Secondly; the article goes on to explain this very deuterium process (one proton, one neutron) in the subtitle: The proton-proton chain reaction - opposed to the “much more common” nuclear reactions the author proposes is taking place in our sun.
Thirdly; the sentence, in parenthesis, infers that the sun’s main fusions product is “diproton” - or, helium-2. The article for helium-2 ( http://en.wikipedia.org/wiki/Diproton#Helium-2_.28diproton.29) explains that diproton is only a “HYPOTHETICAL” helium isotope. It appears to me that helium-2 not only defies the Pauli exclusion principle, if even possible, it would convert the sun’s hydrogen into helium exponentially faster than 10 billion years!
As for the second sentence; it could be accurate IF it unambiguously defined WHICH “reaction” (deuterium or diproton) is responsible for the “slow nature” of the sun’s actual proton-proton fusion process.
To me, it seems the contributor may have cut-and-pasted information from another stellar nucleosynthesis web-page, without making the necessary changes to the wording to fit the context of the actual article. — Preceding unsigned comment added by 64.180.243.107 ( talk) 03:50, 19 May 2012 (UTC)
My textbook asked me to prove that a system with scleronomic constraints is in equilibrium if and only if for all generalized coordinates qj, assuming that all non-constraint forces are conservative. (V is the system's potential energy).
I was able to prove this, but as far as I can tell this proof holds for all holonomic systems, not just scleronomic ones. But because it was stressed that the constraints are scleronomic, I suspect that I'm making a mistake somewhere.
Proof of above statement: System is in equilibrium iff , where is the total force on the ith particle. , where Qj is the generalized force associated with the jth generalized coordinate. So, if , then Qj = 0. But , so is a necessary condition for equilibrium.
Now we prove that it is a sufficient condition. To do this, we find the 's as a function of the Qj's by making virtual displacements to the generalized coordinates. The the virtual work is . Writing (we've tacitly expressed the generalized coordinates as functions of the ri's; stands for ).
From this, it follows that , implying that . Therefore, if Q_j = 0, system is in equilibrium. QED.
Now, as far as I can tell I haven't used the assumption that the constraints are scleronomic, but maybe the assumption sneaked in there somewhere.
This is a pretty pedantic question, but it's been bugging me for a little while now, and I'd appreciate anyone's help in alleviating this confusion. 65.92.6.118 ( talk) 06:26, 19 May 2012 (UTC)
http://rt.com/usa/news/donna-summer-cancer-singer-627/
Donna Summer believed that it was the September 11 deadly smokes that gave her cancer.
During the WW2, the U.S. and Nazi Germany destroyed many cities by carpet bombing: Dresden, Coventry just to name a few. These WW2 cities certainly did not have much polymers and advanced man-made materials. People could live in the ruins. The cities were rebuilt within years after the end of the wars.
What will happen if a today's city is destroyed by a major earthquake or a meteor impact? Will they become too toxic for anyone after the fire? -- Toytoy ( talk) 07:02, 19 May 2012 (UTC)
Actually, the Royal Air Force destroyed Dresden before the yanks even got there. 1.124.213.85 ( talk) 18:12, 20 May 2012 (UTC)
Could I have help identifying this flower species ( 1, 2) and this monkey species? — Crisco 1492 ( talk) 09:13, 19 May 2012 (UTC)
Could anyone help identify this houseplant please? I suspect it of being some sort of geranium. DuncanHill ( talk) 09:21, 19 May 2012 (UTC)
Find the potential difference between the tube and the wire in a Geiger tube. Variables are ; you can guess what they stand for. Doing these integrals is prone to mistakes all the time. This is what I have tried so far. We must find the potential difference between a ring segment of the tube and the corresponding segment of the wire, each of width . This makes the ring segment carry charge and the little wire segment carry charge . To find this, we must find the potential difference between a point on this ring segment and the little wire segment. By Gauss's law, the electric field due to the little wire segment a displacement away from the wire is if and zero otherwise. This potential difference is therefore . I am wondering if you have to do lots more integrals; is there an easier way perhaps? The version of Gauss's law I have been given is: the electric field in the tube is solely contributed by the wire, and the field outside the wire is the same as though the wire were infinitely thin; the outer tube does not contribute as long as we are not near the ends of the tube. -- 150.203.114.37 ( talk) 10:59, 19 May 2012 (UTC)
For comparable tasks, I mean. Suppose a 1400kw microwave versus an ordinary GE electric stove (I have no idea what it's kw rating is, but it plugs into a standard 220v outlet). I wonder if anyone can make a reasonable calculation of energy required in two cases:
Am I truly saving energy by using the microwave for these tasks, or not? A plain-English answer, please. Textorus ( talk) 15:05, 19 May 2012 (UTC)
Thanks for these observations, Stu, but I'm not concerned with the cost (convenience is paramount in these situations), and I'm not going to buy an outlet monitor that I would never use again for anything. It's an academic question - I was thinking that someone who knows what must surely be a very simple equation or two could quickly calculate the amount of energy used in each case (e.g., 1 min. @ 1400kw/hr. = 23.33 kw, no? But how much for five minutes on a stove burner?). Textorus ( talk) 15:39, 19 May 2012 (UTC)
There is a label of some kind inside the oven door, but it's long since become illegible from heat and cooking stains. I don't need a precise, down-to-the-last ion answer, just a general comparison between the two heating methods. Using standard ratings, such as in the link Nimur provided, would be sufficient. And no, I'm not going to go stand in the yard and guestimate how fast the little wheel in the electric meter is turning; that would be highly inexact for anyone but the meter reader, perhaps, and not worth the trouble. Textorus ( talk) 17:03, 19 May 2012 (UTC)
I made some experiments on a Electrolux cf 502(stove), and Melissa AG820CQM (microwave).
In both cases I thrid to heat 2.1 dl (aprox. 7 oz.) from around 22 C to boiling.
To heat the water 2.1*100*4.2*(100-22)/3600/1000 kWh=0.019 kWh is needed.
The stove used about 1640 W for 3 minutes, approx. 0.08 kWh, 23% efficency.
The microwave used about 1220 W for 2 min, approx. 0.04 kWh, 46% efficensy.
If the claimed 800 W microwave power are correct 0.027 kWh, 66% become microwaves.
The losses in the stove are mostly due to the heat remaining in the stove when the water starts to boil. The stove could be used more effeciently by turning it of before the water strts boiling and use some of the after heat.
The electriciy consumption was mesured by counting impulses on the meeter and clocking them and substracting background consumption.(1000 imp/kWh)
The stove will be more efficient when boiling larger volumes. I expect the microwave oven to be much more effecient than a conventional oven but i have not tested. Gr8xoz ( talk) 18:50, 20 May 2012 (UTC)
Is it possible to express specific entropy in terms of the gas constants cv, cp and pressures p1 and p2 only? I can't derive anything close to this without using v1 and v2. The closest I've got is s2-s1=cvln(p2/p1)+cpln(v2/v1) but i don't want the vs in there. This is an is isentropic process so were saying PV^n is constant. 94.116.0.41 ( talk) 15:17, 19 May 2012 (UTC)
Since dinitrogen, the acetylide dianion, and the nitrosonium cation are isoelectronic with carbon monoxide and the cyanide ion, why aren't they as deadly poisonous as carbon monoxide and the cyanide anion? Whoop whoop pull up Bitching Betty | Averted crashes 16:24, 19 May 2012 (UTC)
Since Dasyuromorphia are carnivores, why there are ranked as separate order and not suborder of Carnivora? Also, what hinders thylacine from being placed in Canidae or Caniformia?-- 176.241.247.17 ( talk) 22:27, 19 May 2012 (UTC)
Didn't the xenic acid article say that there is no such thing as a completely de-protonated xenate salt?-- Jasper Deng (talk) 23:22, 19 May 2012 (UTC)