I can specifically find all of the ADHD medication and dosages. I can not find which one is stronger than the other. Like Adderall XR is the slow relsease, but is Vyvanse more powerful? Adding a section to list ADHD medications ranking them from the smallest (such as Adderall) to a more powerful or longer lasting medication (such as Concerta and Adderall XR) would be very helpful in my opinion. Thank you for any knowledge on this subject. <small><span class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:IT Zach P|IT Zach P]] ([[User talk:IT Zach P|talk]] • [[Special:Contributions/IT Zach P|contribs]]) 21:55, 15 June 2011 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:Not sure re. US market. I would try Modafinil, if you can get a sympathetic doctor to prescribe it instead. See this [http://adhd-treatment-options.blogspot.com/2009/05/modafinil-alternative-treatment-for.html]--[[User:Phagopsych|Phagopsych]] ([[User talk:Phagopsych|talk]]) 22:08, 15 June 2011 (UTC)
== Monkey from Antalya, Turkey? ==
== Monkey from Antalya, Turkey? ==
Revision as of 22:36, 15 June 2011
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
So I'm having surgery in two months on my eyes. The surgery is to correct a rather villainous Strabismus that has become noticeable lately (both for myself, damn double vision, and those around me). Apparently my doctor is going to basically detach and reattach muscles attached near the front of the eye that control the ability to see inward. I'm curious, what muscle or muscles are those exactly? Sir William Matthew Flinders Petrie | Say Shalom! 01:26, 11 June 2011 (UTC)[reply]
I'm thinking of an object similar to this made of glass or metal, but more elongated, turn it upside-down, and putting holes or tabs on any of the surfaces so that they could be directly fingered or remotely adjusted (think trumpet valves), and using the entire device similar to a saxophone or like a pan flute. What's the timbre? ~AH1(discuss!) 14:45, 11 June 2011 (UTC)[reply]
Hi. What would a klein bottle sound like as a musical instrument, considering that a mouthpiece is attached to the open end, while holes on any part of the surface that can be fingered either directly or using valves adjust its pitch? Thanks. ~AH1(discuss!) 02:16, 11 June 2011 (UTC)[reply]
I don't see how you could use a klein bottle as a horn or similar instrument. There's nowhere for the air to go once you blow into it. I suppose you could use it like a jug though. In which case, it would depend on the interior dimensions of the bottle. More space = deeper tone. Dismas|(talk) 02:40, 11 June 2011 (UTC)[reply]
A Klein bottle is a topological entity. The musical characteristics of a container depend on its resonances, which are essentially independent of its topology. So, the question doesn't really have an answer. (Also it's impossible to embed a genuine Klein bottle in 3D Euclidean space, but that's another issue.) Looie496 (talk) 02:53, 11 June 2011 (UTC)[reply]
You don't have to be able to blow through something to use it as a musical instrument, you can blow across it, as a closed tube, eg a pan flute. Mitch Ames (talk) 03:09, 11 June 2011 (UTC)[reply]
I thought I said that. Dismas|(talk) 04:33, 11 June 2011 (UTC)[reply]
Can someone please direct me to an article that discusses how a space craft is navigated between planets, and between galaxies? I can find a number of Wikipedia entries on space travel, orbital dynamics, etc, but nothing that explains how a space craft can recognise where it is in relation to (say) Earth, what direction it is travelling, and what course corrections it needs to make in order to arrive at where it's destination will be when it gets there, be it another planet or another galaxy.58.174.69.136 (talk) 06:31, 11 June 2011 (UTC)[reply]
Also note that intergalactic travel is really not realistic because of the incredibly large distances. Dauto (talk) 06:59, 11 June 2011 (UTC)[reply]
Dawn sun tracker is the pink rectangle on top, seven others are on each other corner
All space crafts I know of use a Star tracker and a sun tracker. A light sensor looks for the sun which is very easy, for example the Dawn (spacecraft) has a sensor at every corner. The Camera system makes an image of the stars and compares the image with stored maps. With this information it is clear where you are and the where you go is easy to know, because you always go on a straight line (plus gravity) if you do nothing, which is the case most of the time. --Stone (talk) 11:10, 11 June 2011 (UTC)[reply]
How about interstellar travel, or when you lose sight of the sun? Plasmic Physics (talk) 12:57, 11 June 2011 (UTC)[reply]
Just for clarity - no human-built space probe built to date has ever needed a guidance system for interstellar travel. So far, only a couple of our space probes have ever left the vicinity of our Sun; and it's fair to say that they are unguided spacecraft at this time. For example, Voyager II is widely regarded to have transmitted the solar magnetopause and is by some definition now "interstellar" - but the craft has not made an orbital trajectory correction in something like a decade or two. Currently, we here on Earth know where Voyager II is because we track it from Earth using powerful, specialized RADAR (Deep Space Network) - but up there, Voyager II probably doesn't know exactly where it is. It's guidance systems aren't designed for this phase of its lifetime. Its limited computer programs and guidance were intended to control its planetary flyby stages, not post-heliopause navigation. All that the spacecraft is currently aware of are a few readings from a few still-functional scientific instruments. It may still have attitude awareness, but probably has essentially no positional awareness. Nimur (talk) 17:42, 11 June 2011 (UTC)[reply]
Note, everything mentioned so far is for working out what direction the spacecraft is pointing in. You also need to know where you are, but that isn't too difficult. You can just see what direction the radio signals from the spacecraft are coming from and how long they take to get to the Earth (or a relay craft if one is being used). --Tango (talk) 17:36, 11 June 2011 (UTC)[reply]
Your question is entirely hypothetical because an infinite mass does not exist, and an infinite force also does not exist. Science does not concern itself with things that are known not to exist.
It is often claimed that the universe has an infinite amount of mass. Hence, according to these claims, the mass of the universe is infinite.--Leptictidium (mt) 07:43, 11 June 2011 (UTC)[reply]
The universe may have infinite mass, but it's hardly a rigid object. Supposing you had a way of applying infinite force, where exactly would you hook it up to? --Trovatore (talk) 08:04, 11 June 2011 (UTC)[reply]
I was actually thinking of the Big Bang. If the universe indeed had an infinite mass, it would've taken an infinite force to initiate its expansion, wouldn't it?--Leptictidium (mt) 08:10, 11 June 2011 (UTC)[reply]
So I have to admit I don't understand the Big Bang in detail, but I don't think you can apply notions like "force" to it in exactly the same way you do in the current era. Those things get confusing when you start talking about things on the scale of universal expansion. At the time of the Big Bang, everything is on the scale of universal expansion. So for example I have only the vaguest notion of what might have caused inflation (cosmology); maybe there's more information at that article. --Trovatore (talk) 08:47, 11 June 2011 (UTC)[reply]
You say it is often claimed that the universe has an infinite amount of mass but you haven't commented on who makes that claim. It isn't a scientist or a mathematician. The mass of the universe is extremely large - so large that we have no way of assigning a number to it, or knowing exactly how large it is, but this does not make it infinite. Most of the universe is empty space and if the mass of the universe was to be infinite all that empty space, all of it, would have to be filled with mass and both the empty space and the mass would have to be increasing continuously. Clearly that isn't the situation so it is incorrect to apply the mathematical concept of infinite to the universe. Dolphin(t) 08:14, 11 June 2011 (UTC)[reply]
Hmm? No, that's not so. If the universe has infinite volume, then it can have arbitrarily small positive density and still have infinite mass. --Trovatore (talk) 08:36, 11 June 2011 (UTC)[reply]
Thanks for your answer, Dolphin. I actually knew everything you're telling me, but forum members at Physics Forums made me doubt by saying that the volume of the universe is simply more infinite than its mass. From what you're telling me, the forum members' claim is plain gibberish. Leptictidium (mt) 08:20, 11 June 2011 (UTC)[reply]
No, Dolphin is simply wrong. Whether the universe is finite or infinite is not known. --Trovatore (talk) 08:40, 11 June 2011 (UTC)[reply]
I apologize to Dolphin for my tone in the above. I allowed myself to get upset. --Trovatore (talk) 19:37, 11 June 2011 (UTC)[reply]
Physics Forums works by arguments from authority, don't trust a word they are saying on face value. I'm not saying that they are wrong, but they still managed to ban me indefinitely last year, simply because they could not stand that I would very, very occasionally contradict what the "mentors" were saying. What they do is very effective at keeping cranks out, but over time the forum has become similar to Libya under Gaddafi's rule. Count Iblis (talk) 16:51, 11 June 2011 (UTC)[reply]
Hmm, I think that article could use work. For example, we learn from it that [i]f there exists an irresistible force, it follows logically that there cannot be any such thing as an immovable object, and vice versa. But is that really so? Why can't there exist both an irresistible force and an immovable object, but for some reason the force cannot be applied to the object? For example, maybe the force is attached to an unstoppable object that happens to be moving away from the immovable object. The article doesn't seem to be well-sourced; I'm sure someone willing to put in the work could find a more in-depth analysis somewhere. --Trovatore (talk) 09:31, 11 June 2011 (UTC)[reply]
Better sources are always appreciated, but I believe the issue is one of definitions. What do you mean by "immovable object"? Usually you mean "an object that nothing (if it tried) could move". What do you mean by "irresistible force"? Usually "a force which will move anything (if it were applied to it)". So if the "irresistible force" is applied to the "immovable object", and the latter moves, it really wasn't an "immovable object". Conversely, if it *doesn't* move, then it really wasn't an "irresistible force". The only way around that is to alter the definitions (e.g. by dropping the implication of the parenthetical elements). But then you're talking about something different, and would need to be clear what exactly you meant by "irresistible" and "immovable". ("I once knew a dog which danced professional ballet" is surprising until you're told by "a dog", the person means their ex-boyfriend.)
Likewise, the original poster's question hinges on how they come by (the definition of) their infinities. In physics, "what happens when I combine two infinities" is usually referred to a "renormalization", which can yield sensible results, but which depends on where the infinities are from and how they're combined. For example, with a = F/m, we could have and , which would give one answer (no acceleration), or we could have and , which would give another (a finite, non-zero acceleration). -- 174.31.219.218 (talk) 16:03, 11 June 2011 (UTC)[reply]
Slight correction, the mass of the Observable universe is not infinite. The entire universe seems to be much larger and so could easily have an infinite extent, infinite mass and an infinite number of flame wars. Hcobb (talk) 16:59, 11 June 2011 (UTC)[reply]
Statements that we simply don't know the extent of the universe, and we don't know whether it is infinite or not, and therefore we should disregard the fact that the observable universe is not infinite, look to me to be a bit like saying We don't know whether Newton's Laws of Motion hold true at the farthest extremes of the universe and therefore we should not be claiming that Newton's Laws of Motion are true. Dolphin(t) 05:49, 12 June 2011 (UTC)[reply]
The theory of universal expansion predicts that the observable universe must be finite, whether the full universe is finite or infinite. Therefore the finiteness of the observable universe gives us no information about whether the full universe is finite or infinite.
On the other hand, if the curvature of space were reliably measured to be negative (it has not been, thus far; all accepted confidence intervals for the curvature include the value zero), then your very uniformitarian argument would be a point in favor of an infinite universe, for why should the curvature turn positive only far from us, to allow space to wrap back on itself?
I should note that negative curvature does not require an infinite universe; there has been some interesting research into what might be the topology of a compact universe with negative curvature. To my naive eyes, though, these seem rather forced, kind of epicycle-ish. --Trovatore (talk) 07:40, 12 June 2011 (UTC)[reply]
Well, no, we actually do have evidence of the existence of a very large finite mass in the universe, while there is neither any evidence for an infinite mass nor any way even of coherently connecting that idea to any real known observational truth. We simply don't take such ideas seriously, or try to refute them, any more that you would be expected to have to prove that you are not a murderer in response to someone who asserted the mere theoretical possibility of the accusation without bothering to specify who youd had killed or when you had killed them. μηδείς (talk) 21:46, 12 June 2011 (UTC)[reply]
For the first point, there is a very large finite mass for which we have direct evidence; that is not the same as direct evidence that it is finite.
As for "real known observational truth": what is known is subject to change. The error bars on the curvature of space currently include zero. Someday they may be tightened to the point that they do not, and they may lie on the negative side of the line. In that case, the simplest models of spacetime would coherently connect that idea to an infinite universe. Are you suggesting that we should not try to refute that idea by tightening the error bars? --Trovatore (talk) 22:04, 12 June 2011 (UTC)[reply]
So you yourself say that "there is a very large finite mass for which we have direct evidence" yet ask me for "direct evidence that it is finite." That reminds me of an Aristotle quote, something about the fool asking for the proof of the prior by means of the consequent. I will have to post that on the humanities board and get back to you. μηδείς (talk) 02:52, 13 June 2011 (UTC)[reply]
Perhaps my wording was not ideal. The referent of the last it is "all the mass in the universe". That is, we have direct evidence for the existence of a very large finite mass, for example all the mass in the observable universe. We do not have direct evidence, as yet, that the mass in the whole universe is finite.
I can see on rereading that it is possible to interpret the it as referring to the "very large finite mass", and that would indeed give a very strange pair of propositions to assert simultaneously, but that is not what I meant. --Trovatore (talk) 04:35, 13 June 2011 (UTC)[reply]
What nature is, then, and the meaning of the terms 'by nature' and 'according to nature', has been stated. That nature exists, it would be absurd to try to prove; for it is obvious that there are many things of this kind, and to prove what is obvious by what is not is the mark of a man who is unable to distinguish what is self-evident from what is not. (This state of mind is clearly possible. A man blind from birth might reason about colours.) Presumably therefore such persons must be talking about words without any thought to correspond.
Fine, that quote was relevant to what I wrote if you took the referent of the word it to mean the "very large finite mass", which admittedly by the rules of the English language it could be. Normally, however, I tend to count on the fact that, if I say something that, taken completely literally, makes no sense, my interlocutors will spend at least a little effort trying to figure out what I actually meant. --Trovatore (talk) 01:03, 14 June 2011 (UTC)[reply]
Low earth orbit
I'm studying physics on a very basic level with a book and without a teacher, and now there is a line of reasoning in my book that I don't understand. The book says, summarized:
"A projectile thrown horizontally will in the first second fall a vertical distance of 5 meters below the straight-line path it would have taken without gravity. The curvature of the Earth is such that its surface drops a vertical distance of nearly 5 meters for every 8000 meters tangent to its surface. Thus, a stone thrown fast enough to go a horizontal distance of 8000 meters during the 1 second it takes to fall 5 meters, will orbit Earth. So we see that the orbital speed for close orbit about Earth is 8000 m/s."
Now, I understand how this would work during the first second. But what happens with the acceleration of gravity??? Because during the 2nd second a projectile thrown horizontally will fall 15 meter. How come the projectile keeps orbiting and doesn't crash during the 2nd second??? Lova Falktalk 08:21, 11 June 2011 (UTC)[reply]
I'm too lazy to do the numbers, but from the principle, in the second second, the 8000m line segment has a slight angle with respect to the first. With respect to the second, the first one goes "upward" and the and gravity bends it down for the next segment to be tangential again. Note that in this picture the circular orbit is approximated by straight line segments. To get good results, the approximation would use ever more but shorter segments. 5BYv8cUJ (talk) 09:49, 11 June 2011 (UTC)[reply]
I did a quick sketch (at right, click to zoom) of the situation. The black curve is a segment of a circle and represents the surface of the earth. The gray line is a horizontal tangent at height equal to zero units. What one finds is that the surface of the circle locally approximates a parabolic curve; at time t=1 it has bent away from the horizontal tangent by 1 unit of vertical height; at time t=2 there is a separation of 4 units of height, at t=3 the distance between the tangent and the circle is roughly 9 units. In other words, the rate at which the surface of the earth moves away from the horizontal tangent increases with o distance from the starting point.
What this sketch doesn't account for is the fact that the direction of gravitational acceleration changes as our hypothetical orbiting object changes with time. (Having a constant direction for 'down' is fine when one deals with objects travelling well below orbital speed – a ball tossed in the air really does follow a parabolic path from start to finish – but it doesn't work at all for paths that approach the size of the planet.) From the sketch, it's plain to see that at later time points the gravitational force being exerted won't be straight towards the bottom of the picture. At each point in time, there is a new 'down'; this is what bends the path of the orbiting object into a circle instead of a parabola. TenOfAllTrades(talk) 14:22, 11 June 2011 (UTC)[reply]
(edit conflict) Picture the projectile being far above the Earth's surface, travelling fast enough to maintain a roughly circular orbit, rather than either crashing toward the Earth or flying off into space. At this velocity, the object will experience centripetalacceleration, such that the orbit will follow the curvature of Earth, where every 8 km of forward motion experiences 5 metres of motion toward the Earth's core. Assume also that a hypothetical straight-line velocity, ie. one tangential to a circular orbit with a given radius distance from Earth's core from the object's position, will experience no accelerational "tugging" effect toward the Earth. Conversely, such an object with no forward motion will fall toward the Earth in full gravitational acceleration (9.8 m/s2), given negligeable air resistance. Thus, in low earth orbit, the Earth's acceleration is largely applied unto the object's forward motion, keeping its trajectory the same distance to the Earth's core, which in fact does not accelerate the object, but keeps it at constant velocity. In other words, there are vector components of acceleration (down and forward), but along the projectile's velocity there is no +/- acceleration. Hope this helps. ~AH1(discuss!) 14:37, 11 June 2011 (UTC)[reply]
The key point here is that acceleration is a change in velocity, not just a change in speed. Velocity, and thus by extension acceleration, is a vector, not a scalar, so it has a direction as well as a magnitude. In a constant orbit, even though you're not experiencing a change in speed, you *are* experiencing a change in velocity, as the direction of movement changes. Gravity, acting as a centripetal force, causes an acceleration which rotates the velocity vector, but doesn't change its magnitude. -- 174.31.219.218 (talk) 15:21, 11 June 2011 (UTC)[reply]
Another way to explain this problem: the book is trying to explain a change in height for each second. But, as you intuitively know, the projectile isn't falling all that distance during one single instant - it's falling continously. To really describe the height, and velocity, of the projectile as it flies it's trajectory, we must use a little bit more sophisticated physics - that is, the mathematics must handle the height and velocity as continuous functions of time. Ultimately, this is the the most basic and fundamental application of simple calculus - and it is this problem that forced Isaac Newton to formulate the kinematics of falling objects using calculus. Basically, the book is describing a Riemann sum to approximate height at the end of each second, while in fact height changes continuously during each second. When we treat the function continuously, the math is actually easier to compute (even though a more complex process is being conceptually described). So we simply write that velocity is the first derivative of height, and (here is the most important contribution that Newton made to simple kinematics) ... Acceleration is the second derivative of height ... and acceleration is due to gravity only. You know this when we phrase it as "F = m a" but we are now going to write it as "the height at any time is equal to the integral of velocity, and the velocity is equal to the integral of the acceleration of gravity.". Now, because we're near Earth's surface, gravity is almost constant, so the height is a simple parabola. But in your more sophisticated "orbital cannon" case, the problem becomes more complicated - force due to gravity is changing with position - so we have to compute a more challenging integral! Saving you the complexity of that slightly more difficult Calculus problem, you can accept that the solution to that math problem is a conic section - it can be a parabola, a hyperbola, or an ellipse. If the trajectory intersects with the surface of the planet, the object falls back and hits the Earth. If not, the object becomes orbital, and either stays bound to the Earth or reaches escape velocity and never returns. Our article on orbit illustrates each of those cases. If you want to solve this math for yourself, you can - the simple two-body problem walks you through a standard solution. As you add more complicated effects, like perturbations in the gravity field due to the Moon, Sun, Jupiter, or the imperfect/not-quite-spherical Earth, you must solve a very difficult orbital dynamics math problem, usually with the help of a powerful computer. Nimur (talk) 17:27, 11 June 2011 (UTC)[reply]
I get it now. Thank you all so very much!! Lova Falktalk 17:55, 11 June 2011 (UTC)[reply]
Plasticisers and incineration
Some unscrupulous food producers in Taiwan have been adding plasticisers to food. Some of the plasticisers include Di-isodecyl phthalate, DIDP; Di-(2-ethylhexyl) phthalate, DEHP; Di-n-octyl phthalate, DNOP; Di-isononyl phthalate, DINP; Di-n-butyl phthalate, DBP; Butyl benzyl phthalate, BBP. The government responds by burning al the contaminated products in incinerators.[1] Is this a good way to destroy the products? Would the plasticisers escape in the air and pollute the environment? F (talk) 09:50, 11 June 2011 (UTC)[reply]
That depends on the temperature. But I think the main purpose is destroying the food, so no one will eat it. I don't think that low quantities of such stuff are dangerous unless you eat it. From the names they look like organic molecules (in the sense of organic chemistry) and will be decomposed by nature (UV-radiation, weathering, micro-organisms), just as the many toxins produced by a large number of poisonous plants. 5BYv8cUJ (talk) 10:37, 11 June 2011 (UTC)[reply]
Generally, temperatures high enough to incinerate the food would also be high enough to destroy most other organic substances, including phthalates. -- An American ultranationalist 67.169.177.176 (talk) 01:25, 12 June 2011 (UTC)[reply]
Plasticizers are organic compounds (in the chemical sense), just like plastics and most food components. They'll burn like all the rest, if subjected to sufficient temperature. The one concern is if they volatilize and escape before combustion. But typical garbage incineration not only handles such compounds regularly, but actually creates a large number of hazardous chemicals during the combustion process. All modern waste incinerators will be fitted with emission control systems and scrubbers which will ensure that what goes up the smokestack contains only a minimal amount fo dangerous compounds, if any. -- 174.31.219.218 (talk) 18:25, 12 June 2011 (UTC)[reply]
Principles of Quantum Mechanics
Wikipedia says ( Postulates of quantum mechanics) the Ket-Vectors were elements of some Hilbert space, wheras Dirac (The Principles of Quantum Mechanics, 4th edition, page 40) says "The space of bra and ket vectors when the vectors are restricted to be of finite length and to have finite scalar products is called by mathematicians a Hilbert space. The bra and ket vectors that we now use form a more general space than a Hilbert space."
To resolve that contradiction I assume that some later development has put all of Diracs intuitive integration and the need for infinity as a number (with all its ensuing troubles and inconsistencies) into a solidly defined mathematical framework that turned out to really be a proper Hilbert space. The question is now: where can I find this solid definition? 5BYv8cUJ (talk) 10:26, 11 June 2011 (UTC)[reply]
Not infinity as a number per se, but the theory of distributions had yet to be set up. One could then use that re-define the Hilbert space you need in quantum mechanics when you want to work in an infinite volume. You then get the Rigged Hilbert space. Note that you don't actually need to know about this to do computations in quantum mechanics. Count Iblis (talk) 15:12, 11 June 2011 (UTC)[reply]
I remember a talk long ago when someone stated that students of mathematics can't do computation. For example, they cannot compute the inverse of a matrix, whereas students of physics can. Someone answered, yes, that's true. But, on the other hand, students of physics can compute the inverse for any matrix.
Having told this anecdote I hope you understand what I have in mind if the following looks like nitpicking or trolling. Dirac thinks he needs vector lengths and scalar products to be allowed to be infinite, and vector lengths and scalar products should result to give numbers (elements of a commutative field), because otherwise all the theorems for vector spaces (and basic computation, too) would have to be prooven again. Every try to do computations with infinity leads to a hell of trouble, the least of which is me proving that zero equals one, using only the contradicting assumptions. Now your link to the rigged Hilbert space doesn't give me the mental breakthrough. Just for any one simple example from quantum mechanics, how exactly would that H and that really be defined? 5BYv8cUJ (talk) 16:15, 11 June 2011 (UTC)[reply]
While I have studied functional analysis, I don't know much about rigged Hilbet spaces. It is actually pretty useless in theoretical physics. You can avoid using this and still be rigorous, by putting systems in finite volumes (take the limit of V to infinity at the end of computations), avoid working in the ill-defined position basis (even if you can define it using rigged Hilbert spaces, physically it is not well-defined). Count Iblis (talk) 15:18, 12 June 2011 (UTC)[reply]
I have been rereading the book (up to page 40 where I throw a "NotANumberException"). I thought of a Schwartz space to fix it, which is not exactly what you are proposing but runs in the same lines. But I don't see how or even if either of those would cure the problem. For what I have seen, the only reason those infinity-values are needed is to fix problems that arise when he does what he calls "superposition" in the introduction and needs to do it on more than countably many kets, which in turn he believes to be necessary to represent any ket from the "complete sets" of eigenvectors of an observable. I am sure modern maths can give those intentions a solid base somehow, but I get crazy because I can't find such a thing anywhere. 5BYv8cUJ (talk) 15:51, 12 June 2011 (UTC)[reply]
You should look at the proof of completeness of bases of eigenfunctions in functional analysis textbooks. The case of discrete spectrum is rather simple, the case of the continuous spectrum is more complicated. But then, if you limit yourself to systems in a finite volume, you only have to deal with the discrete case. Also, physically, an infinite volume is in practice always a finite volume which is very large, so this is understood as the limit of V to infinity. Count Iblis (talk) 16:08, 12 June 2011 (UTC)[reply]
I have recovered that book yesterday and was shocked how much I have forgotten. I'll have a look at spectral theory and see if this gives me the hint I'm lacking now. 5BYv8cUJ (talk) 16:39, 12 June 2011 (UTC)[reply]
History of airline lavatories
Did the early airline aircraft (e.g. 1920s) have toilets/lavatories, at least on longer flights?--68.175.35.188 (talk) 18:45, 11 June 2011 (UTC)[reply]
I am in orbit round a planet and am a few hundred meters behind my command module at the same altitude. I need to dock with the command module. What combinstion of forward and reverse thrust should I use? (Not home work-- just interested).--78.150.233.171 (talk) 19:45, 11 June 2011 (UTC)[reply]
To quote Larry Niven, "Forward takes you out, out takes you back, back takes you in, and in takes you forward."[2] I don't know how literally true this is, but it seems to make sense... ;) Wnt (talk) 22:25, 11 June 2011 (UTC)[reply]
If you think about it, it would have to be a combination of first thrust TA (say) in direction DA (say) to introduce relative movement that decreases the distance between your module and the command module, followed by no thrust as the relative velocity between continues to decrease the distance, followed by reverse thrust TB (say) in directon DB (say) to bring the relative velocity back to zero. Hopefully exactly at the time the two are docking together. I would suspect that thrust TA = TB, and direction DA = - DB. I can't prove it though.--InverseSubstance (talk) 23:37, 11 June 2011 (UTC)[reply]
InverseSubstance is correct -- you need to use forward thrust to speed up and close the distance, followed by an equal amount of reverse thrust to bring the speed back down to the same level as before. You also need to apply a small amount of downward thrust (toward the planet) at the same time as the forward thrust, and upward thrust at the same time as the reverse thrust, in order to compensate for the small change in orbital radius that is caused by the change in speed. Or alternatively, you could use downward thrust alone to speed up and the upward thrust alone to slow down, which is essentially equivalent to doing a low yo-yo in a fighter plane to catch up to your target without overshooting it (though the latter admittedly looks a lot more dramatic). 67.169.177.176 (talk) 01:47, 12 June 2011 (UTC)[reply]
Using forward thrust won't work. It has the paradoxical effect of slowing you down because it will bring you to a higher orbit and for every unit of energy provided by the thrust, two units of energy get "stolen" by gravitational potential energy effectively removing one unit of energy from your kinetic energy and slowing you down. What you need to to is break! That will get the low yo-yo maneuver you described started. Dauto (talk) 05:33, 12 June 2011 (UTC)[reply]
"Flying a spacecraft is very different than flying a plane. There is no true up or down and the dynamics of orbital flight make maneuvering to dock, or rendezvous, two spaceships very complex. I focused my research on solving the problems of speed and centrifugal energy which lead to an ‘orbital paradox’ – a situation in which a pilot who speeds up to catch another craft in a higher orbit will end up in an even higher orbit, traveling at a slower speed and watching the second craft fly off into the distance. The solution to this paradox is counter intuitive, and required new orbital mechanics and procedures. Later, after joining the NASA astronaut corps, I spent time translating complex orbital mechanics into relatively simple flight plans for my colleagues – they thanked me (with a mixture of respect and sarcasm) with the nickname Dr. Rendezvous." Buzz Aldrin.
That is a very interesting aspect. What if the acceleration is done by gravitation? OK, you might not want to wait for this in a space ship, but I'm thinking about Theia_(planet). 5BYv8cUJ (talk) 06:54, 12 June 2011 (UTC)[reply]
Those kind of collisions happen by random chance. If you have hundreds of planetoids in similar orbits then, over millions of years, some of them are inevitably going to intersect. --Tango (talk) 13:00, 12 June 2011 (UTC)[reply]
I was thinking about if it was predictable that Theia hit earth from a slightly increased orbit thus accelerating earth's rotation instead of de-accelerating or reversing it. 5BYv8cUJ (talk) 16:33, 12 June 2011 (UTC)[reply]
Yes, Theia must have increased earth's rotation otherwise the moon wouldn't have a prograde motion. Dauto (talk) 03:32, 13 June 2011 (UTC)[reply]
(un-indent) The space shuttle faces this exact same problem when docking with the ISS. For the final part of the shuttle docking profile the shuttle starts a couple hundred meters ahead of the ISS at the same altitude, and the same velocity. To move towards the station the pilot maneuvers the shuttle radial out, that is away from the Earth. This temporarily moves the shuttle to a higher altitude where it has a slower velocity than the ISS, thus closing the distance between the two. The effect is that the final approach profile is a series of hops, as you can kind of see in this photo. In your situation the active vehicle is behind the passive vehicle, so you will need to move radial-in (towards the Earth), dropping into a lower, faster orbit to close the distance with the passive vehicle. anonymous6494 14:37, 13 June 2011 (UTC)[reply]
Yes, thank you Dauto and Anonymous, you are correct. I was thinking more as an airplane pilot (which I am) rather than an astronaut (which I'm not) when I first answered the question. So my first answer (forward thrust) was wrong, while the second one (the "low yo-yo") was indeed correct. I also assumed, from the way the OP phrased the question, that the spacecraft has provision for thrust straight up and straight down (I meant radial out and radial in -- see what I mean when I say that I can't stop thinking like an airplane pilot?) as well as forward/reverse. 67.169.177.176 (talk) 21:42, 13 June 2011 (UTC)[reply]
Is the Pythagorean scale universally pleasing?
Pythagoras said that musical strings of lengths in simple ratios (1 through 4) will produce "pleasing" sounds. Are only people in Western cultures (beginning with the Greeks) pleased by such sounds, or do all people people find the sounds pleasing? 82.31.133.165 (talk) 20:29, 11 June 2011 (UTC)[reply]
I don't know about what people find pleasing, but Musical scale#Non-Western scales will tell you a bit about what different cultures use in their music. It sounds like most do use harmonic scales (which is Pythagoras was talking about), but apparently Indonesia doesn't. It doesn't go into any detail, though. --Tango (talk) 23:59, 11 June 2011 (UTC)[reply]
From personal experience I would say the human ear / brain combination, adopts with time to new scales, as with languages. Newly heard music in an previously unknown scale or system may sound strange at the beginning, but eventually one finds it very pleasing. Take for example the music of Arnold Schoenberg or Free Jazz which are both in western scales, but may sound strange at first. Or Persian Music or Arabic Music or Greek Music which use different scales. Also note that the "western" scales (equal temperament) that we use today are quite different from the scales used a few hundred years ago, like the well temperament, kirnberger or werckmeister temperament. --helohe(talk) 00:07, 12 June 2011 (UTC)[reply]
Also note that not everyone likes Schoenberg or free jazz -- in fact, there are a lot of people who absolutely hate it. This has to do with personal and cultural preferences more than anything else. 67.169.177.176 (talk) 01:35, 12 June 2011 (UTC)[reply]
I'm afraid that includes me! Doesn't matter how long I listen. Alansplodge (talk) 18:02, 12 June 2011 (UTC)[reply]
Note that Schoenberg and free jazz (and other modern western composers inserting smaller dissonaces in their work) are intentionally trying to be jarring to their listeners by not using the "well-tempered" notes that everybody used in earlier works. 75.41.110.200 (talk) 14:33, 12 June 2011 (UTC)[reply]
Our inferior colliculus is hard-wired for the processing of low-order harmonics, which is why harmonic tone combinations are widely preferred in music.[3]Red Act (talk) 01:47, 12 June 2011 (UTC)[reply]
Simple pleasant harmonies not only appeal to humans but to most animals as proof of health. Dislike of dissonances compared to consonance has nothing to do with learning. Human preference for simple harmony, especially the octave, is universal. Helmholtz. μηδείς (talk) 22:46, 12 June 2011 (UTC)[reply]
How does the virtual particle exchange work for attraction? For example electromagnetic attraction between a proton and an electron. I mean, the virtual particle would need to have negative mass, or be emitted in the opposite direction (away from the centre of both particles). I couldn't find a good explanation anywhere. --helohe(talk) 23:09, 11 June 2011 (UTC)[reply]
Are you talking about gauge boson theory ? Yes, it's extremely non-intuitive, but then so is most of quantum dynamics. Even worse than what you mentioned is that a nearly infinite number of virtual particles would be required, especially in the case of gravitons, where a continuous stream of gravitons is needed from every atom to every other in the universe. That's a lot of gravitons. Myself, I think it might be a useful model, in some cases, but don't think it's literally correct (something like how the Dalton model of the atom was useful, but later needed many refinements). StuRat (talk) 23:46, 11 June 2011 (UTC)[reply]
Yes I meant gauge boson theory. I'm also wondering how the virtual particles "detect" the presence and the position of the involved particles. I would find it much more intuitive to understand if all virtual particles would be replaced with fields (or space-time "curvature" like in general relativity). --helohe(talk) 00:00, 12 June 2011 (UTC)[reply]
I think the idea is that there's so darned many virtual particles that those given off by each particle are bound to hit every other particle in the universe. Yes, this seems silly to me, too, and a field or wave does seem like a better approach. However, due to wave-particle duality, perhaps the bosons are sometimes particles and sometimes waves. StuRat (talk) 00:08, 12 June 2011 (UTC)[reply]
Virtual particles can have negative mass. Physicists refer to that by stating that virtual particles are not constrained to their mass shell. But note that any attempt to understand QM in terms of classical concepts is bound to fail at some point. Dauto (talk) 00:09, 12 June 2011 (UTC)[reply]
Compare with tunneling. In quantum mechanics an intitial state can evolve to some final state that classically would be impossible, because the system would have to evolve via an intermediary state which would have an inconsistent energy and momentum. In this case, the charged particles couple to photons, and the "forbidden" intermediary state is the virtual photon, which thus carries energy and momentum in a way that is unphysical. Count Iblis (talk) 15:29, 12 June 2011 (UTC)[reply]
The momentum is off-shell and unphysical whether the force is attractive or repulsive, so I don't think that was the question. Also, the off-shell momentum transfer is the same in classical electromagnetism, and loop-free Feynman diagrams can be used to describe classical electromagnetism, so I don't think there's anything essentially quantum about the question. -- BenRG (talk) 18:53, 12 June 2011 (UTC)[reply]
Not a spacetime diagram.Quantum field theory is a theory of fields, as the name suggests. Virtual particles show up in Feynman diagrams, which are a useful way of doing some calculations in quantum field theory, but don't work at all for others. I don't think it's very helpful to say that fields (like the electromagnetic field) are caused by virtual particles, because, for one thing, that picture doesn't even work in general.
Feynman diagrams look like spacetime diagrams, but they aren't. They are actually just graphs, that is, vertices connected by edges. The position of the vertices, and the orientation and length of the edges, don't mean anything. In a spacetime diagram, the momentum of a particle is always tangent/parallel to its worldline, but in a Feynman diagram you can assign any momentum to any edge as long as momentum is conserved at each vertex. So attractive forces don't present any difficulty. It's hard to explain why like charges repel and unlike charges attract, but it's easy to explain how Feynman diagrams can accommodate the attractive case: it's the same as the repulsive case because directions are meaningless. -- BenRG (talk) 18:53, 12 June 2011 (UTC)[reply]
I agree with every thing you said except that Feynman diagrams can be seen as abstract space-time diagrams. For instance, in that penguin picture to the right time is usually taken to flow to the right, in the sense that the lines on the left represent incoming particles while the lines on the right represent out-going particles, even though the intermediary vertices may happen at any point in time or space (even if that requires fast than light travel). Dauto (talk) 22:19, 12 June 2011 (UTC)[reply]
I think you are asking if it takes more energy to get a temperature change started than to keep it going in the same direction. In that case, the answer is "no, the first degree of temperature change takes about the same energy as the next". An exception would be if the first degree requires a phase change. StuRat (talk) 23:44, 11 June 2011 (UTC)[reply]
What about the time required to initiate the heating, assuming constant energy input into the fluid? Or is any "inertial" effect caused by the starting time required of the heating device itself? ~AH1(discuss!) 23:50, 11 June 2011 (UTC)[reply]
Yes, the heating time of the device itself, or whatever is in-between. In the case of a pot on an electric stove, for instance, first the burner must heat up, then it must radiate that heat to the bottom of the pot, then that heat must conduct to the inside of the pot. Only then will the liquid in the pot start to heat up. With a thick, cast-iron pot, that could take a while. With a thin, copper pot on a high flame, the heat should make it to the liquid quite quickly. A glass of liquid in a microwave should start to heat essentially instantaneously. StuRat (talk) 23:58, 11 June 2011 (UTC)[reply]
In the case of the microwave, this also has to do with the fact that the liquid is being heated directly by absorbing electromagnetic radiation, rather than by conduction. So essentially, you can think of it as the case where there's nothing in between at all. 67.169.177.176 (talk) 01:30, 12 June 2011 (UTC)[reply]
What biotech company is doing the study that replicates ccr4 immunity for people with hiv?
A few months ago I read a news article that a biotech company in South San Francisco or San Bruno is in the middle of human trials for a therapy where people with HIV are infused with t-cells that are adapted to not allow hiv to enter them similar to the ones that people with natural immunity have and that it was promising research because these t cells were replicating themselves in most people in the trial on their own. I want to find this article as some people I told don't believe me or want to know more and I want to look into the company, I also want to expand the article on the HIV timeline and Hiv treatment articles.Thisbites (talk) 00:32, 12 June 2011 (UTC)[reply]
I think this is [5]Irvin S. Y. Chen, head of the UCLA AIDS Institute. "He is currently engaged in a start-up company for HIV-1 genetic therapy involving collaborations with UCLA, Salk Institute, and Cal-Tech." Also [6], [7]. [8] says he formed the company with David Baltimore, former president of Caltech. There are various bits of flotsam [9] floating around that link Chen and Baltimore with Calimmune, a California company headquartered in Tucson, Arizona? - it isn't clear to me that this is the company. Wnt (talk) 02:40, 12 June 2011 (UTC)[reply]
Well, [10] ($20 million) makes it sound like Calimmune is doing just the right kind of study to match your criteria: "methods to transduce autologous hematopoietic progenitor stem cells (HPSC) with a viral vector delivering a specific interfering short hairpin RNA (shRNA) designed to block production of CCR5. In addition, since combination treatment strategies are often more effective than monotherapy, the applicant proposes to add a second inhibitory component to the vector, a gene encoding an inhibitor of virus-cell fusion." I should note however that there are considerable obstacles that come to mind right off. First, all sorts of gene therapy have been under the cloud of potential cancers when DNA goes into the wrong spot in the genome, and these immune cells will be undergoing rapid turnover in people prone to AIDS lymphoma already. Next, RNA interference isn't 100%. They say the cells may be protected anyway since the virus is less likely to bind, but is there really an excess of virus? If not, then the virus can just drift past a hundred missing receptors and bind the one that is there, without any delay. Finally, there's the matter of whether the gene therapy can be "rejected". Every once in a blue moon I've read the strangest claims about DNA being rejected by the immune system, or antibodies somehow getting into the cytosol of the cell. More recent publications include [11] and [12], a less radical claim that viruses bring antibodies into the cell with them that trigger special interfering factors inside the cell. But the point is this: we don't know how the body will respond to long term gene therapy. I can picture for example that the hairpin RNAs found together with the antibody-tagged HIV virus will be tagged somehow as foreign RNA, diced up, and the inserted genes end up being tagged as "spam" by methylation or chromatin changes. Wnt (talk) 18:23, 12 June 2011 (UTC)[reply]
Also that those links are for bone marrow/stem cell style treatments. What I read was not a bone marrow transplant. It was modified blood of the patients themselves to alter their t-cells so that they do not have ccr4 receptors. Furthermore there was mention that it was believed to cost 90-120 thousand dollars for the one-time treatment and that that was considered good since hiv medicines can cost upwards of 18k a month.Thisbites (talk) 05:09, 12 June 2011 (UTC)[reply]
I think you mean CCR5-Δ32. I heard some stories about a "healing" (remission below detectable levels) taking place after a bone-marrow transplantation of a donor with the CCR5-Δ32 mutation. Which makes sense as it replaces the T-cells with cells having some receptors missing. I also know of companies which offer genetic testing for the CCR5-Δ32 mutation. There is evidence that people with CCR5-Δ32 mutation are less likely to develop aids, and respond better to treatment. It may also be possible that people with CCR5-Δ32 are less likely to get infected, but this has not been researched properly at the moment and might be wrong. Introducing a CCR5-Δ32 mutation into someone's blood might be possible, but I guess a bone-marrow transplantation is a much easier, and already feasible way (even though much more risky). I don't know about recent research though --helohe(talk) 08:22, 12 June 2011 (UTC)[reply]
Also note that this treatment, even if successful, would make the person more susceptible to the West Nile virus. On the other hand, it would also give him/her better immunity against smallpox (and possibly black plague as well). -- An American ultranationalist 67.169.177.176 (talk) 02:21, 13 June 2011 (UTC)[reply]
Vulcan hearing
It is well known in the Trek universe that Vulcan's have superior hearing. For the most part, it seems people associate this with the shape of their ears. I know that animals can physically move their ears to hone in on a sound (e.g. deer listening for predetors). Since Vulcans cannot move their ears (like an animal, anyway), what affect (if any) does the shape of their ears have on their ability to hear? 99.250.117.26 (talk) 01:54, 12 June 2011 (UTC)[reply]
I'm not a Star Trek fan, so I can't tell you for sure, but generally larger ears (such as those of the elephant or the fennec fox) are better at capturing and focussing sound waves, which translates to better hearing. 67.169.177.176 (talk) 02:09, 12 June 2011 (UTC)[reply]
There are stores that sell "Vulcan ear" costumes to those Trekkies... they don't work as hearing aids. I think external ears in animals that enhance acuity are distinguished more by a concave shape, which allows them to concentrate sound to a single point. Wnt (talk) 02:14, 12 June 2011 (UTC)[reply]
I can't see the shape of their ears making any difference. I don't think it's ever been said on the show that they do (that they have superior hearing is stated, but not the cause). Vulcan's also have superior strength and longevity. I think they are made to be so superior physically so that it's all the more impressive when the emotional humans always better them. --Tango (talk) 13:13, 12 June 2011 (UTC)[reply]
This is, of course, what is called fiction, but do keep in mind that the Vulcan (Star Trek planet) atmosphere is less dense, and hence carries less sound energy. Presumably Vulcans have to have more sensitive hearing to have hearing as good as other species which live in thicker atmospheres. μηδείς (talk)
Interesting... Do they also have bigger lungs and better hemoglobin to prevent hypoxia in such a thin atmosphere? 67.169.177.176 (talk) 02:06, 13 June 2011 (UTC)[reply]
The "Vulcan equivalent of hemoglobin" is diagrammed here. Clarityfiend (talk) 02:27, 13 June 2011 (UTC)[reply]
The shape of the ear does have an effect on hearing. Sound pressure levels at the human eardrum are typically 7-18dB higher in the 1 kHz to 6 kHz frequency range (essential for good speech reception) than they would be without the pinna. Table 1 on this page gives a breakdown of this. Si1965 (talk) 12:11, 13 June 2011 (UTC)[reply]
I asked this question in the "Entertainment" section of the Reference Desk as well, but I feel that it pertains to both categories.
Hey everybody. I've been wondering something about some of the special effects in the newly-released movie Super 8, which came out in theaters on June 10th, 2011. In it, there is a horrible train crash that involves a mid-sized pickup truck (think mid-90's F-150) driving head-on at full speed into a diesel freight train travelling at well over 50 mph. The collision immediately results in an explosion and the locomotive grinds to a halt. But the filled freight cars behind it continue to shoot forward under their own momentum an end up flying everywhere. This continues to occur as the rear of the train continues moving forward. What makes me think that this is unlikely is the immense speed at which the rear of the train continues to move. I mean, of course the effects of inertia would cause the cars to continue moving, but would they really move at such speed? If you have not already seen the movie, here is a link to that particular scene on the Internet Movie Database: Clip 1, and here is another that is longer, but shows a more complete view of the crash: Clip 2. If anybody could help explain or describe this better to me, it would be much appreciated. Basically, all I want to know is, is this scene probable, or is it simply "movie magic" that looks realistic, but defies the laws of physics. Thanks! Stripey the crab (talk) 02:49, 12 June 2011 (UTC)[reply]
Perhaps you should have responded to and thought about my response on Wikipedia:Reference desk/Entertainment before posting here. The film is science fiction, not science. Putting the same question on two ref desks means that responses are dispersed. Not a good move. HiLo48 (talk) 03:00, 12 June 2011 (UTC)[reply]
Red Act, thanks, I forgot about that. :P And User:HiLo48, sorry about that. I posted it here, then went back to check at the Entertainment section. And despite the responses being dispersed, it's not that hard to navigate back and forth between two web pages, or easier still, two tabs. As for being a bad move, on the contrary - you expose the question to more people. I usually spend my time strictly on the Science section. I hadn't even visited the Entertainment section before today, and I'm sure I'm not the only one out there who behaves similarly. But thank you for your response, and for your time. It is much appreciated! :) Stripey the crab (talk) 03:12, 12 June 2011 (UTC)[reply]
It's clearly a CGI train, so of course it's not going to precisely do what a real train would do. However, I don't see anything in either clip that super obviously defies the laws of physics. Train crashes can indeed be immensely destructive, as a Google image search readily shows.[13]Red Act (talk) 04:05, 12 June 2011 (UTC)[reply]
What was less credible to me was that the truck's driver was still alive, the kids weren't harmed, and their camera and car survived. But it was sill a great movie. HiLo48 (talk) 04:47, 12 June 2011 (UTC)[reply]
IIRC, one of the wagons of the train was labeled "explosives". so I guess "theoretically" is is possible. but its unlikely, I have seen a few traincrashes/de-railings and usually I guess it just turns the wagons over squeezes them together etc (similar to what would happen if you do the same in a model-train at high speed)...
Also I don't think a pick up truck would be enough to do much to a train. There have been accidents where some car was in the middle of a crossing, when the train struck, and I guess it just "catapults" the car away, with minor damage to the train. --helohe(talk) 08:13, 12 June 2011 (UTC)[reply]
If a pickup truck crashes headon into a locomotive pulling a long freight train, the locomotive itself is so more massive than the pickup that the collision could not possibly bring the locomotive to a halt. The loco and the freight cars would continue at about the initial speed until the application of the train brakes brought the train to a halt. Train brakes are air operated and designed to bring the locomotive and cars to a smooth and safe stop, without the freight cars running over the magically stopped locomotive. The whole scenario sounds bogus. Standard Hollywood garbage, its physics about on a par with Roadrunner cartoons. If the lead locomotive somehow derailed, or it it hit a massive gravel truck or truck load of rolls of steel, the scene would be more plausible. It is still a great scene, cinematically, and I will make it a point to see the movie. Edison (talk) 00:50, 13 June 2011 (UTC)[reply]
Edison is exactly correct, the locomotive would not come to a dead stop given it outmassed the truck but the cars behind would have continued at the same speed they were being pulled by the locomotive. What really effs up a movie is when a falling object falls faster than gravity because Catwoman (film) jumped downward. μηδείς (talk) 01:20, 13 June 2011 (UTC)[reply]
The truck wouldn't need to itself bring the locomotive to a stop. If the locomotive is derailed by hitting the truck (which is conceivable) it's going to slow down pretty fast which could cause the subsequent cars to pile up. If the train happens to be packed full of explosives (which I have to assume it is by the way everything starts exploding) I guess it could be pretty catastrophic. Rckrone (talk) 04:35, 13 June 2011 (UTC)[reply]
I still don't buy it -- even if the engine is derailed and the other cars pile up behind it (pretty unlikely given the small size of the truck), modern high explosives are very stable and will not detonate simply from being jostled in this manner. In order to explode in this manner, the train would have to be carrying either some kind of high explosives with extremely high sensitivity to impact, such as nitroglycerin (implausible, since these types of explosives are no longer used as such, nor transported), or else live munitions with detonators fitted (TOTALLY implausible -- munitions are ALWAYS transported with detonators removed, precisely to avoid a disaster of this type). Or else the train would first have to catch on fire and the flames spread to the explosives (which is possible, but would take a while). But then again, most people don't know what REALLY happens when a train hits a pickup truck, much less what happens when a train derails. And all those peddlers of cheap thrills capitalize on this scientific ignorance to make big bucks... 67.169.177.176 (talk) 07:05, 13 June 2011 (UTC)[reply]
Modern explosives tend not to explode even if they catch fire -- it typically takes a combination of pressure and heat to get them to produce anything but an intense flame. --Carnildo (talk) 01:36, 16 June 2011 (UTC)[reply]
See what I mean? The train won't explode in this scenario, even if it jumps the tracks -- period! 67.169.177.176 (talk) 08:34, 16 June 2011 (UTC)[reply]
Cold fusion applicability
Reading cold fusion confuses me — I understand somewhat of what the proponents claim is happening, but I fail to see the applicability. Let's say that tomorrow someone shocks the scientific community and conclusively proves to everybody's satisfaction that cold fusion really is possible. What possible applications are there for it, aside from reducing the prices for manufacturers of helium balloons? As far as I know, all our uses for fusion rely on the significant amounts of energy that result, whether using the explosion as a powerful weapon, or (if we can figure it out) using a slower process to generate electricity with the very non-cold temperatures that result. Nyttend (talk) 12:17, 12 June 2011 (UTC)[reply]
The most common idea that I've seen is that you scale it up to the level of "personal reactors" that would power your household, heat your water, power your car, whatever. It's meant to be small-scale, personal, clean power. (This is part of the alleged conspiracy theory — it would destroy the need for centralized utility companies, oil companies, and so forth. So they've rallied against it, blah blah blah.) Obviously the prototypes don't really intend to do that, any more than Hahn and Meitner's experiments weren't a fission reactor (or bomb). If we could use hot fusion on that scale, we would, but hot fusion requires starting temperatures on the order of millions of degrees Fahrenheit, so getting back what you put into it requires liberating a huge amount of energy. --Mr.98 (talk) 12:49, 12 June 2011 (UTC)[reply]
Yes, you are right. Cold fusion would be useful as a source of energy. That's it. That is a extremely important applicability which makes me wonder why you say you fail to see the applicability. Dauto (talk) 18:42, 12 June 2011 (UTC)[reply]
I think the question is: if it is cold, then it doesn't generate energy that we can transform into electricity. So is the word cold in cold fusion misused? Or can we generate elecricity without heat or explosions? --Lgriot (talk) 10:25, 13 June 2011 (UTC)[reply]
Cold here is a relative term. Cold fusion still leads to temperatures high enough to produce electricity. Dauto (talk) 16:39, 13 June 2011 (UTC)[reply]
To put it in perspective, the temperature inside of a conventional coal based electric power plant is of the order of 1000 K while the temperature required for hot fusion is of the order of 100 000 000 K. There is plenty of space in between that would be hot enough to produce electric power but too cold to generate conventional fusion. If fusion is achieved in that range it would be considered cold fusion. Dauto (talk) 16:48, 13 June 2011 (UTC)[reply]
Just to clarify (perhaps): the "cold" and "hot" here refer to the temperatures necessary for ignition of the fusion reaction, not to the heat of the reactions themselves. --Mr.98 (talk) 14:10, 14 June 2011 (UTC)[reply]
Which, to clarify, is hot fusion. --Mr.98 (talk) 14:10, 14 June 2011 (UTC)[reply]
Diet by cold/hot air
Would it be an effective diet just to be outside our thermal comfort zone? This way our body would have to burn calories to keep us cool or warm. Which way would be more effective - hotter or colder? Quest09 (talk) 12:32, 12 June 2011 (UTC)[reply]
Cold. You don't really use energy to cool down, that would be counter-productive since using energy almost always converts it into heat (energy is never created or destroyed, remember). You cool down by sweating and redirecting blood to the skin. That doesn't really take energy. When you're cold, though, you need to use energy to generate heat (for example, by shivering). I don't think it would be a particularly good way to burn calories, though - you would need to be dangerously cold for it to have a significant effect. You would be better off going for a nice jog. --Tango (talk) 13:22, 12 June 2011 (UTC)[reply]
But, if you need 1Cal to heat one Kg of yourself 1 °C, and you put the A/C 3 °C below the comfort zone, you'll end up spending a lot of Calories each day (provided you don't get hungry in the cold), won't you? Quest09 (talk) 13:40, 12 June 2011 (UTC)[reply]
No, because food calories are a thousand times larger than the calories for heating water. (I'm not making this up, see calorie.) – b_jonas 08:50, 13 June 2011 (UTC)[reply]
He got it right. One food Calorie is one kg (1000 grams) of water for 1 °C. Thermodynamic calories are one gram of water for 1 °C. Hence by saying kilogram he already included the factor of 1000. Dragons flight (talk) 18:56, 13 June 2011 (UTC)[reply]
Hmm, okay. Sorry. – b_jonas 09:46, 15 June 2011 (UTC)[reply]
You'll gain weight when you attempt to change the energy balance like this, without drastically cutting back on your energy intake. This is because the body attempts to maintain a stable body weight on the long term. So, unless you go outside the range where the feedback mechanisms the body uses break down, you won't lose weight. Instead, the feedback mechanisms will lead to the opposite result, a modest weight gain, because it will take measures against a perceived threat to its long term energy reserves.
Incidentally, the article Mike Stroud (physician) says that Antarctic explorers can use over 10,000 calories a day (which I've seen described by a simple calorie count of the food consumed from some much earlier expedition). Wnt (talk) 17:59, 12 June 2011 (UTC)[reply]
Recent research has pointed to something else you can do to lose weight without dieting: Sleeping for longer. This is because during sleep the metabolic rate is slower. Naively, you may think that you'll gain weight if you sleeep better and longer. But what really happens is that the metabolic rate during sleep is regulated as part of all the feedback mechanisms to maintain a stable weight. Then, because the body will regulate the amount of energy reserves such that it can do without food for some given amount of time, a longer sleeping period means that you need less fat. You could say that the time you sleep counts as virtual fat, and the more virtual fat you have, the less real fat you'll have. The body apparently keeps track of how much you sleep on you get on the long term and uses that to regulate to what degree the fat cells are filled. Count Iblis (talk) 15:12, 12 June 2011 (UTC)[reply]
I personally find that it is much easier to lose weight when it is hot. Not because the heat is burning calories, but the heat makes me not feel like eating. Googlemeister (talk) 17:31, 13 June 2011 (UTC)[reply]
Electronic compass
I've just bought a GPS unit that includes an electronic compass, i.e. it supposedly doesn't rely on GPS data and functions when stationary, unlike cheaper GPS units which can only determine direction when moving. I was curious to know how the electronic compass worked, but there isn't a Wikipedia article, and the compass article refers readers to fibre optic gyrocompass, so I created a redirect to that article from electronic compass. However, reading the article on fibre optic gyroscope (to which fibre optic gyrocompass refers me) I am not sure I have done the right thing. Does my Oregon 450 GPS unit really contain a laser and lots of fibre optic cable? If not, how does the "electronic compass" work?--Shantavira|feed me 13:27, 12 June 2011 (UTC)[reply]
It probably does it with a magnetoresistance sensor like the Honeywell HMC6352 module described at www.cypress.com/?id=1128 -- Finlay McWalter ☻ Talk 13:43, 12 June 2011 (UTC)[reply]
A better link is this Philips note (the Philips parts are just the sensor, the Honeywell above implements much of what the Philips note discusses). -- Finlay McWalter ☻ Talk 13:46, 12 June 2011 (UTC)[reply]
There is a WK article about that: magnetometer (aka as digital compass). Quest09 (talk) 13:50, 12 June 2011 (UTC)[reply]
Thanks. Maybe someone more knowledgeable than me could tweak the various compass articles.--Shantavira|feed me 15:34, 12 June 2011 (UTC)[reply]
first magnet
Reading the question above, I wondered how the first magnet / compas needle was created. The only way I can think of to create a magnet is using an electromagnetic field applied to some iron or similar which would require electricity. then again to create electricity (besides using a chemical process like a battery) one needs a magnet to induce an changing electric field in a coil. --helohe(talk) 16:47, 12 June 2011 (UTC)[reply]
A lodestone is a natural magnet. You can take a non-magnetic piece of iron (like a needle) and magnetise it by rubbing it in one direction with a lodestone. -- Finlay McWalter ☻ Talk 16:50, 12 June 2011 (UTC)[reply]
The English scientist William Gilberd (1544 – 1603) was the first person to study magnetism in any scientific way. He found out how to manufacture magnets as Finlay describes - only natural lodestones were used previously. He also disproved the widely held belief that compasses could be demagnetised by contact with garlic! He was the first to suggest that the earth had magnetic poles - it had previously been thought that there was a big magnetic island in the Arctic that all compasses pointed to. He is credited with coining the word "electricity". He deserves to be better known, but few have heard of him outside of his home town of Colchester. Alansplodge (talk) 17:37, 12 June 2011 (UTC)[reply]
Whether by rubbing amber or by using an electrochemical reaction such as the Baghdad Battery, it is possible to make electricity without using magnets. Wnt (talk) 17:54, 12 June 2011 (UTC)[reply]
The Baghdad Battery is a likely hoax. Lodestones may have been created by lightning strikes in soil containing iron ore. Edison (talk) 00:43, 13 June 2011 (UTC)[reply]
wow, thanks. I haven't heard of lodestones before, very nice :) --helohe(talk) 19:26, 12 June 2011 (UTC)[reply]
Interchangeability of USB wall chargers
I have a Sandisk Sansa Clip+ which is charged over USB (mini-B) and doesn't come with a wall charger, and I have a Motorola mini-USB cell phone wall charger, model FMP5185B, input 100–240V, 50/60Hz, output 5.0V, 550mA. Can I safely charge the one with the other? This thread is full of people saying it's okay, but this thread makes me worry. If there's any doubt, I'd rather not do it. -- BenRG (talk) 19:02, 12 June 2011 (UTC)[reply]
I'm not an expert but those wall chargers just emulate a normal usb cable from a computer so they should be using the same specification. The USB article lists normal usb power as "500–900 mA @ 5 V" which is the same as yours AvrillirvA (talk) 22:41, 12 June 2011 (UTC)[reply]
As I remarked recently on the RDC, all wall AC/DC adapters for mobile phones or heck nearly everything I've seen in the past 4+ years or so have been SMPSs. There may be some traditional linear transformer only wall AC/DC adapters with fullsize/mini/micro USB sockets or plugs but I doubt they we were ever common. Definitely all image search results for the motorola razr v3 adapter I find seem to be SMPSs. Of course since you actually have the adapter you can probably tell by the size and weight. However since the specs for your device say it supports 100–240V, it obviously has some regulation and is almost definitely a SMPS.
Also if you overcharge li-ion batteries they may explode fairly violently. Since manufacturers find this undesirable, they tend to design devices to avoid this. If you supply too high a voltage you may kill the device or charging circuitry. You're far less likely to overcharge the batteries. (Li-ion batteries also should generally be charged with a CC-CV charging profile. And the CV stage should generally be 4.2V regulated to with +/- 0.05V or better [14], there are specialised chips for this which may be what most manufacturers use but in any case this isn't something you handle by simply dropping the voltage of a 5V USB supply where +/- 5% is within regulation.)
Finally if you're drawing a higher current then the AC adapter can supply and there's no safety or fuse, you risk damaging the adapter, perhaps even causing a fire. Alternatively the voltage may drop too low (as the poster sugggested) and the device and charging circuitry won't be able to function correctly. There's a slight chance this may result in an incomplete charge, more likely you're just get random problems or the device/charging won't work at all.
In other words, nearly all the claims of the person in the second link are questionable.
The power supply is small and light, not one of the big-and-heavy wall warts that were all the rage a decade ago, and I assume the Clip+ won't try to draw more than 500mA since that's all that USB guarantees, so I guess it's safe. I may still be too scared to try it, though. Thanks for the replies -- BenRG (talk) 06:36, 15 June 2011 (UTC)[reply]
Identifying small trilobites in Ordovician-age rock
Hi. I have some samples of Ordovician fossiliferous limestone. Some of those samples may contain fragments of trilobites, and I would like to identify them using specific features if possible. How do I identify the body fragments and distinguish them from other fossils, a partial list being bryozoans, gastropods, porifera, crinoids, brachiopods, and possibly others such as cephalopods and ostracods? Thanks. ~AH1(discuss!) 20:17, 12 June 2011 (UTC)[reply]
Take a course in invertebrate zoology. Look for a continuos closed chitinous exoskeleton. Contact Robert Loveland of Rutgers University. Look for a segmented body and jointed limbs. Publish any pictures yo have and ask for comments if you are not sure. μηδείς (talk) 22:35, 12 June 2011 (UTC)[reply]
Pain & C-Fibers
I'm having a hard time tracking down an answer for what I was assuming was a straightforward empirical question: People argue that pain is possible even without c-fiber stimulation. But are there cases on record of normal, psychologically healthy adults who complain of pains that cannot be correlated with any kind of c-fiber activity? I.e., cases where an otherwise normal (I say that to sort of weakly rule "hypochondriacs" or, generally, people we have reason to doubt make veracious claims about their physiological states) adults sought medical help for pains which subsequently could not be grounded to any neurological goings-on.
I think phantom pain, and neuropathic pain of the "central" type, are pretty clear examples. C-fibers contribute to phantom pain in some instances, but some of the worst pain comes in people for whom all the relevant C-fibers appear to have degenerated. Looie496 (talk) 00:31, 13 June 2011 (UTC)[reply]
I would say it's true, since a person is able to experience pain in a dream. Plasmic Physics (talk) 03:51, 13 June 2011 (UTC)[reply]
Really? In all my life I never have. Heck, when I had the gout I would sometimes avoid moving my legs for up to an hour after waking, simply to keep the sleep paralysis going so I wouldn't feel the pain. Wnt (talk) 05:14, 13 June 2011 (UTC)[reply]
It is actually a quite remarkable fact that people are not able to experience pain in dreams. You can dream that your legs are blown off by an explosion, but you will not feel any pain when it happens. Other forms of distress are common, such as a feeling of suffocation or overheating, or a need to urinate. Looie496 (talk) 06:38, 13 June 2011 (UTC)[reply]
That is wrong. I've felt pain in dreams, and I can't find any sources stating it's impossible to feel pain a dream. I understand that sometimes something which would cause pain in real life doesn't in a dream or the perception of pain is different in dreams, but that is very different from never being able to experience pain in dreams 82.43.90.27 (talk) 21:04, 13 June 2011 (UTC)[reply]
I speak from personal experience, I had my hand chewed on and I can tell you: it wasn't as painful as you'd think, but still very much (like a painfully firm handshake). Coincidentally, I realised that I was infact dreaming. As soon as I did, I managed to rationalise the pain away. You know what, dreaming is so much more fun when you know you are dreaming. The annoying thing is that as soon as you know that you are dreaming, one of two things can happen: either, your brain sabotages you and you wake up, or your state of mind lets you forget very easily that you are dreaming. Plasmic Physics (talk) 08:02, 13 June 2011 (UTC)[reply]
Rarely, I am able to maintain a rational state of mind to allow me to create my own dream. Plasmic Physics (talk) 08:08, 13 June 2011 (UTC)[reply]
I have to say that pain in a dream rarely matches the type, or severity of the injury, it hasn't so far for me. Plasmic Physics (talk) 08:43, 13 June 2011 (UTC)[reply]
I don't know about others but I can occassionally feel pain in dreams. I once went to sleep with a headache, and was aware of the headache in my dream. I then took some asprin in my dream and the headache went away. And it stayed away until I woke up whereupone the headache returned. This has also convinced me personally that the placebo effect is a real thing. Googlemeister (talk) 17:27, 13 June 2011 (UTC)[reply]
Here is another example: I dreamt I was on fire, you'd think it was agonising, but it wasn't, it felt like a bad sun burn. This makes me think that pain in dreams are sourced from personal experience, you can't feel a pain in a dream that you havn't experienced before in the real world. i.e. if you've never had a broken arm, you can't experience the pain of a broken arm, your brain just gives you the next closest pain that you have experienced.
Memory plays a central role in pain synthesis in dreams. I would really like to have a citation for 82.43.90.27's refutal. Plasmic Physics (talk) 23:23, 13 June 2011 (UTC)[reply]
I based my statement on an assertion in one of Alan Hobson's books, together with the fact that I myself don't recall ever experiencing pain in a dream. However, a check of the literature shows that the consensus view on this question has changed: more recent studies such as PMID7690981 and this paper report that although pain in dreams is rare, it does occur. Looie496 (talk) 23:39, 13 June 2011 (UTC)[reply]
I can possible explain why I have the ability, I have Asperger's - I am not an ideal test subject. My brain opperates differently to those that do not have Asperger's. Plasmic Physics (talk) 00:18, 14 June 2011 (UTC)[reply]
Oh, it actually was scientific consensus at some point that people didn't feel pain in dreams? I remember reading it in a pop-sci book as a young child, and discussing it with my older sister because we had both felt pain in our dreams: not awful pain, but pain. We briefly considered that maybe we simply dreamt that we had felt pain, without actually feeling pain, but (given that on one occasion she had been awoken by the shock of the pain) this seemed unlikely, and we decided that once we started defining pain as something other than 'a painful sensation', we were headed for trouble. So we assumed the book was simply wrong, as so many children's factbooks are. I'm not sure if I'm reassured or disturbed that this was actually an accepted theory quite recently: did nobody carry out even a broad survey? It's like the 'tongue maps' all over again. 86.164.30.215 (talk) 21:48, 14 June 2011 (UTC)[reply]
Fat
Why can body make fat easy from cabohyrat but you can eat lot of fat but no get fat? — Preceding unsigned comment added by 92.25.100.10 (talk) 20:49, 12 June 2011 (UTC)[reply]
That's not true. You get fat if you eat more calories than you burn in exercise, whether those calories come from carbohydrates or from fat. The moral is: eat, but don't eat too much. Simple, but not always simple to follow.Itsmejudith (talk) 21:26, 12 June 2011 (UTC)[reply]
(ec) Because the body also uses fat as a source of energy. (See Citric acid cycle for extensive details. Well, it's a bit complicated on the biochemistry level.) Fat is only synthesized from carbohydrates because fat has a higher energy density and thus can be stored more easily. 5BYv8cUJ (talk) 21:36, 12 June 2011 (UTC)[reply]
June 13
what are the health effects of chronic *low* blood sugar? (if there is such a thing)
Please note that nothing in this question is a request for medical advice, anyone who requires medical advice should seek the advice of a qualified doctor, rather than anonymous unqualified respondents from an online reference desk, who are liable to be completely mistaken in their understanding and assume no responsibility for anyone who kills or injures themselves or others by mistaking anything here as medical advice or relating to it in any way.
This is not a request for medical advice -- indeed, it does not relate to me or anyone I know -- but I was wondering what, if anything, the health effects of chronic *low* blood sugar are? For example if a diabetic using insulin were to be mistaken in the amounts of insulin given, but not to the point of an acute hypoglycemic attack, but, instead, consistently low (rather than high) blood sugars, so that it remains chronically below that of a healthy person by a significant amount, but not enough to cause an acute hypoglycemic ris... then is what are the health effects? thanks.
to give you an idea of my impression, it seems that unlike moderately high blood sugar, moderately low blood sugar is not something with chronic health effects - it can be an acute episode, but nothing chronic. This is my impression, since I'm having trouble digging anything up -- that's why I've come to the ref desk :)
Note: this is a question about blood sugar not blood pressure, which is a different question.
also please note that nothing in this question should be construed as requesting medical advice in any way. — Preceding unsigned comment added by 188.28.37.179 (talk) 01:01, 13 June 2011 (UTC)[reply]
See Hypoglycemia (low blood sugar) and Hyperglycemia (high blood sugar) for complete explanations. Both conditions can be chronic or acute; both are serious conditions if uncontrolled. Bielle (talk) 01:23, 13 June 2011 (UTC)[reply]
(EC)An answer more responsive to the question would cite the article Hypoglycemia, which says that low blood sugar produces the symptoms of shakiness, anxiety, nervousness, palpitations, tachycardia, sweating, pallor, coldness, numbness, hunger, nausea, vomiting, abdominal discomfort, headache, abnormal mentation, impaired judgment, fatigue, confusion, and a host of other symptoms. It can also be fatal, per the article. Edison (talk) 01:31, 13 June 2011 (UTC)[reply]
Did you need to chastise us, Edison? Does it help the OP in some way to have done so? Bielle (talk) 01:38, 13 June 2011 (UTC)[reply]
Note the (EC). The preceding response by Medeis was the one I considered less than ideally responsive to the question. You and I cited both cited Hypoglycemia. Chronic low blood sugar would not be much fun, with the symptoms listed in the article cited, as well as anger and depression listed as symptoms in some of the "alternative medicine" books about the claimed widespread hypoglycemia. Chronically reduced mental efficiency might be a problem. For a diabetic on insulin or oral sugar lowering meds, there would be the constant fear that it is about to drop from a low 70 mg/dL to a disastrous 40 mg/dL. It is rare for blood sugar to be really stable in a diabetic. There would be little margin for error between "low" and "so low as to cause convulsions and unconsciousness." "Chronic hypoglycemia" was a popular pseudodisease or fad disease of the 1970's and 1980's, [15] among gluconormal nondiabetic hypochondriacs, with popular books, [16] written about how to treat it. There are many true believers in chronic hypoglycemia as a cause of a variety of ailments not widely supported by the medical establishment, who claim that 10 to 25% of the general population suffers from hypoglycemia. Drugstores sell inexpensive glucose meters which can readily tell whether blood sugar is normal, low or high. Edison (talk) 03:12, 13 June 2011 (UTC)[reply]
I am sorry for having assumed that if the person were suffering from chronic low blood sugar he hadn't just died of starvation or accutehypoglycemic shock. The question seemed to imply voluntary dieting. Life extension by such means is a common topic of discussion. μηδείς (talk) 01:41, 13 June 2011 (UTC)[reply]
There was no implication in the question that hypoglycemia resulted from voluntary dieting. Edison (talk) 03:12, 13 June 2011 (UTC)[reply]
Let's hear from the poster, who did, I believe, use the word chronic. There certainly was no question of the acute effects which you referred to, while extreme caloric restriction, which I referred to, is posited as a method of life extension. Or did I get that wrong too? μηδείς (talk) 03:38, 13 June 2011 (UTC)[reply]
Any kind of suspected blood sugar imbalance, and any kind of dieting, should be dealt with by consulting a doctor. ←Baseball BugsWhat's up, Doc?carrots→ 02:13, 13 June 2011 (UTC)[reply]
Chronic hypoglycemia actually causes someone (well, at least some rat) to increase the amount of sugar transport past the blood-brain barrier. Thus some of the effects of acute hypoglycemia don't apply as the person's system adapts. Likewise, glucose transport decreases in diabetes, perhaps a bad thing for diabetics when insulin dose is too high.[17]Wnt (talk) 03:30, 13 June 2011 (UTC)[reply]
you guys don't really get the question. (op here). I mean, if you read about "diabetes complications" you can see that if someone has a blood sugar of 8 for 20 years (instead of the normal 5.5), or on the other scale 144 instead of the normal 100, then they can get complications. That is just slightly above normal. So, what about consistently slightly below normal? Like 4 (72 on the other scale) consistently day in day out for years? Are there complications that develop over time from chronic slightly below average blood sugar? (Note: all you guys have said about headache and vomiting and passing out etc are an acute attack of way lower blood sugar. Not my question). Thanks, and sorry I might not have been the clearest possible in originally asking. Nothing here relates to medical advice in any way, this is just more of a science quesiton. --188.28.126.160 (talk) 12:20, 13 June 2011 (UTC)[reply]
The article Hypoglycemia does "get the question, and answers it. Chronically low blood sugar has a host of possible symptoms that range widely both from person to person, and for any given person. Here, for example, from the linked article (boldface mine):
Determining the presence of both parts of this definition is not always straightforward, as hypoglycemic symptoms and effects are vague and can be produced by other conditions; people with recurrently low glucose levels can lose their threshold symptoms so that severe neuroglycopenic impairment can occur without much warning, and many measurement methods (especially glucose meters) are imprecise at low levels.
Reading the article will help you understand why a simple list of chronic symptoms is not going to be very accurate, although the list of possible symptoms and consequent damage is there. Bielle (talk) 17:09, 13 June 2011 (UTC)[reply]
Bed Bugs
I don't understand why people freak out about bed bugs. They are much more benign than other blood sucking insects, such as mosquitoes and ticks (for instance, they have not been proven to transmit diseases, and only a small percentage of people actually have a noticeable skin reaction to their bites. Most aren't even aware of it.). We get bitten by other insects all the time. So why all the fuss about bed bugs? Thanks. Quinn❀ BEAUTIFUL DAY 03:30, 13 June 2011 (UTC)[reply]
People are generally unpleased to be eaten by things, even if they are only being eaten in small bits at a time. There's a general revulsion against this, which is a Good Thing, since many other blood-sucking insects and other such parasites are known to transmit real disease. That bed bugs are comparatively less disease carrying isn't necessarily a factor in the level of revulsion people feel viscerally to being eaten. It's not an intellectual response. Furthermore, while bed bugs are pretty low on the "disease carrying vermin" ladder, the presence of any vermin is usually an indication of general uncleanliness; apartment buildings with bed bugs infestations can also have other pests (fleas, rats, etc.) which are not always so benign. Even if not true in every case, the presence of vermin of any sort is generally met with revulsion, for reasons described above. --Jayron32 05:22, 13 June 2011 (UTC)[reply]
Unlike mosquitoes or ticks, bed bugs infest homes, and particularly mattresses. Bed bug infestations are easily spread, and can be difficult to eradicate. Rckrone (talk) 05:30, 13 June 2011 (UTC)[reply]
Bed bugs are like head lice, not terribly dangerous, but very paranoia inducing. HiLo48 (talk) 06:03, 13 June 2011 (UTC)[reply]
I appreciate the answers, but I would point out that bed bugs have absolutely nothing to do with "un-cleanliness:". Bed bugs are generally brought in by the last person you allowed to sleep in your bed. Whether in luggage or other such transmitter.Quinn❀ BEAUTIFUL DAY 06:27, 13 June 2011 (UTC)[reply]
Inviting unclean people to sleep in your bed isn't itself a risky behavior? How is this different from inviting someone with fleas from sleeping in your bed? --Jayron32 17:49, 13 June 2011 (UTC)[reply]
Not terribly dangerous but they can be very irritating [18] on a whole lot of levels. I'm not sure people are paranoid about them; I think they are anxious which is rather different. Richard Avery (talk) 06:27, 13 June 2011 (UTC)[reply]
There is also what might be called the tautological response — people are disgusted by bedbugs because other people are disgusted by bedbugs. That is, it doesn't matter what I think, if all my friends will find me disgusting. Or, more to the point, if my property values are going to be affected, and so on. --Mr.98 (talk) 10:10, 13 June 2011 (UTC)[reply]
I'll also mention that many people are easily disturbed by bedbug behaviors, e.g. Traumatic_insemination. Granted, this has nothing to do with the risk/dangers they pose, but who said disgust was rational? SemanticMantis (talk) 13:32, 13 June 2011 (UTC)[reply]
Interesting premise but my guess is few people are sufficiently aware of such behaviours to be disgusted by them. Nil Einne (talk) 02:57, 14 June 2011 (UTC)[reply]
A sterile home were there are none of the insects that you find outdoors in Nature is a paradise for specialized bugs adapted to live in the home environment. Count Iblis (talk) 18:03, 13 June 2011 (UTC)[reply]
I'll take exception to your "small percentage of people". Our article on bed bug infestation puts the fraction of people with no visible skin response at between 20% and 70%. While that's a pretty broad range, if we assume that the non-responding fraction really is 70% (the 'best' case) then it's still better than even odds that at least one member of a two-person household will feel the bite. It turns out that it only takes one person waking up every day covered in spots to declare that the bugs are a 'problem' for the entire household.
The infestation article (and the main bed bug article, as well) talk about some other health and cosmetic issues. Rolling over on blood-engorged bed bugs leaves unsightly bloodstains on one's sheets and body. Bed bugs suck significantly more blood than mosquitoes; a full meal is on the order of 1 mL. While that's not a large amount by itself, ten bites per night for eight weeks is 560 mL of blood. That's as much as one donates when giving blood, at about the same frequency; severe or chronic infestation can push some people over into anemia. Some people also become sensitized to the bites through long exposure.
Finally, since transmission is relatively easy – and eradication can be rather difficult – they're the bane of multiple-unit dwellings. If one resident has them, eventually the bugs spread to everyone. Unless everyone treats them simultaneously, they'll tend to return and reinfest. Even if most people aren't bothered, some will suffer quite acutely. TenOfAllTrades(talk) 13:39, 14 June 2011 (UTC)[reply]
Need help identifying this ladybird-lookalike
Hi,
Was in my garden two days ago and noticed this colorful critter crawling around on an asparagus plant.
Colors and spots look like a ladybird. I am mostly familiar with the common seven-spotted ladybird, but I know there are other species of ladybirds. But this isn't a ladybird, is it? It is a bug trying to look like one, isn't it? The shape of the body just does not fit well with a ladybird. Any help on the id would be appreciated. Thanks,
Ok sorry about that link does not work; how ever if you type orange and black bug uk into google images you will find it there as a asparagus beetle.
Thanks for the hint. But I do not think it is a common asparagus beetle, rather a spotted asparagus beetle, Crioceris duodecimpunctata. --Slaunger (talk) 06:29, 13 June 2011 (UTC)[reply]
With the recent icelandic eruptions and now the chilean eruption pushing vast amounts of ash into the atmosphere, would this effect global temp or would this be an insignificant event? What scale of eruption at various points on the planet would significantly effect global temp? which could by all tense and purposes reverse global warming? — Preceding unsigned comment added by 109.224.25.11 (talk) 05:43, 13 June 2011 (UTC)[reply]
Pinatubo in 1991 had a significant effect, but it was on the same scale as natural variations on top of the warming trend
These are both fairly insignificant events on the global scale. In order to see significant global cooling you need to inject a vast amount of ash and sulfates into the stratosphere, which requires an extremely energetic eruption. The current eruptions of Puyehue in Chile and Grímsvötn in Iceland are 3 and 4 on the Volcanic Explosivity Index (VEI) respectively. To give you a sense of the scales involved: Mount Pinatubo's 1991 eruption had the effect of lowering the global temperature by about 0.4 °C; this about the same as the amount of warming seen in the past 20 years (see image). However, Pinatubo's eruption was a 6 on the VEI (i.e. about 100 times more material erupted than Grímsvötn and about 1000 times more material erupted than ), had an ash column up to 21 kilometres (13 mi) high, and occurred near the equator which facilitated the spread of cooling stratospheric aerosols across the entire globe. Even with this extreme event, its cooling effect only lasted about 2 years. The current eruptions have only had ash clouds up to 10 and 12 km respectively, which is just barely into the stratosphere (if it is at all; the height of the stratosphere actually changes from day to day with the weather).
Also, your idea that a volcanic eruption could somehow "reverse" global warming is quite unlikely; the residence times of sulfates and ash in the atmosphere are on the order of a few years, while CO2 has a residence time of about 400 years. Volcanoes also emit large amounts of carbon dioxide in addition to ash and sulfates, so I imagine in the long run the overall effect of a large volcanic eruption would be a net warming.-RunningOnBrains(talk) 06:25, 13 June 2011 (UTC)[reply]
I realize upon re-reading that I was unclear on a few things. Volcanic aerosols (mainly volcanic ash and sulfur dioxide) suspended in the atmosphere reflect sunlight back into space, thus if you inject a large amount of volcanic aerosols into the stratosphere you can lower the amount of sunlight that reaches the earth by several percent, leading to cooler temperatures. The reason you need the eruption to reach into the stratosphere is that there is very little in the way of weather-related processes such as rain which quickly remove volcanic aerosols from the atmosphere. Ash and sulfates in the troposphere will likely be washed out on the order of weeks; not nearly long enough to cause significant cooling.-RunningOnBrains(talk) 06:31, 13 June 2011 (UTC)[reply]
The volcanic winter article might be of interest, although it could do with some expansion. CS Miller (talk) 08:42, 13 June 2011 (UTC)[reply]
Being pedantic, but sulfur dioxide is a gas. It gets oxidized to a sulfate. -Atmoz (talk) 17:18, 15 June 2011 (UTC)[reply]
Note that the Mount Pinatubo eruption began in the early summer, while the Chilean eruption is occurring in early winter. μηδείς (talk) 18:56, 13 June 2011 (UTC)[reply]
I'm not sure that really matters, except that the tropopause (the bottom of the stratosphere) is typically a bit lower in the extratropical winter, though still around 10 km.-RunningOnBrains(talk) 20:44, 13 June 2011 (UTC)[reply]
It matters because there's a lot more sunlight to be blocked during summer, μηδείς (talk) 01:25, 14 June 2011 (UTC)[reply]
Well, the sun-reflecting effect of stratospheric aerosols is over the course of about two years, so it could have some effect, but the effects will be spanning several seasons anyway; thus, I doubt there will be much difference what season the eruption occurs in. However, a big difference here is the ash will be mostly confined to the hemisphere the eruption occurs in due to stratospheric wind patterns, unless, of course, like Pinatubo, the eruption occurs near the equator. Tropospheric volcanic aerosols are mostly washed out of the atmosphere by rain and other processes in a matter of days, so it is really only these long-lived stratospheric aerosols that matter. -RunningOnBrains(talk) 02:54, 14 June 2011 (UTC)[reply]
Yes, it's highly unlikely the the strongest sun blocking effects would actually occur during the time of the eruption rather than six to twelve (and eighteen to twenty-four) months after.
And what sort of magical numbers wizard could figure out what the chances are that the period starting one year to eigtheen months later will actually be during the same season as the first six months? What are we, fortune tellers? μηδείς (talk) 03:07, 14 June 2011 (UTC)[reply]
I was referring to the fact that the effect will last for more than one year, thus the dimming effect would be integrated over all seasons. Sure, maybe we'll have one more winter than summer, but unless we are talking arctic circle latitudes, this effect should be negligible. Additionally, the ash will spread to much of the hemisphere, and possibly the globe, over this time, further diminishing the seasonal impact. I'm not saying it won't matter, I'm saying it probably won't make a significant difference.-RunningOnBrains(talk) 22:32, 14 June 2011 (UTC)[reply]
Any effect that that lasts more than a year can be discounted, since after one year you are back to the same cycle of seasons. For example SUMMERWinterSUMMERWinter or the reverse. The same with the effect spreading over the entire hemisphere, since the entire hemisphere is in the same season at the same time. I cannot find a chart of seasonal insolation, but it is obvious from this temperature graph which can stand proxy for the effect at mid lattitudes that the effect is significant. Only if there is an extremely low rate of decrease in sun blocking from an eruption over many years or if there is a very fast mixing between the hemispheres will the seasonal effect be negligible. The Mount Pinatubo eruption caused a drop in temperature in the Northern hemisphere of about 1.0 degree F and about 0.4 degrees F in the Southern Hemisphere. This does not control for season, obviously, but it does show the significant hemispheric difference, and hence imply a seasonal effect. μηδείς (talk) 16:08, 15 June 2011 (UTC)[reply]
Triplet carbenes
why are triplet carbenes normally sp2 hybridised but become sp hybridised when bonded to oxygen ,nitrogen ,sulphur or halides ? Raky rough (talk) 12:05, 13 June 2011 (UTC)[reply]
The Carbene#Structure_and_bonding section shows two diagrams for triplet carbene .[[19]] now i can't understand how the presence of electonegative elements can change sp2 carbene to sp and in the process unhybridises one of the hybridised sp2 orbitals Raky rough (talk) 15:26, 14 June 2011 (UTC)— Preceding unsigned comment added by Raky rough (talk • contribs) 15:24, 14 June 2011 (UTC)[reply]
Does the attached group you are considering affect just the geometry/hybridization of the triplet, or also the relative stability of the singlet vs triplet? The article says the latter, you seem to be asking about the former. DMacks (talk) 15:33, 14 June 2011 (UTC)[reply]
well yes i was asking about the former . i was thinking about the case of trifluoromethyl radical where the strong -I effect of three fluorine atoms change hybridisation from sp2 to sp3 (hence s character of hybridised orbitals decreases). but the effect of the electronegative groups in case of triplet carbene is opposite (s character of hybridised orbitals increases) which puzzles me.Raky rough (talk) 16:52, 14 June 2011 (UTC)[reply]
pressing question
why is it that if you unplug a fridge for a while, even if you clean it fastidiously, it will smell really musky. no matter how long you air it out. but lo, when you plug it back in again, as soon as it finishes cooling again, that smell is gone! why does cold desmellify in this mysterious manner. thanks for any scientific insight you might have on this question. --188.28.126.160 (talk) 12:50, 13 June 2011 (UTC)[reply]
I've tracked down the musty smell in my refrigerator to the condenser and drain pan. So, cleaning the inside of the fridge won't help with that. A long time ago, when I lived in an apartment, my fridge really stank. That is how I learned about the drain pan because I tracked it down and found that the drain pan in that fridge was full of blood. -- kainaw™ 13:08, 13 June 2011 (UTC)[reply]
(edit conflict)Possibly, because there exists bacteria on the inside surface of your fridge that isn't removed by anything short of bleach. Low temperatures negatively impacts cellular metabolic rates, explaining why you only detect a smell when the fridge is above normal operating temperature. Bacteria give off gases as a waste product of metabolism, the lower the temperature, the lower the concentration in the air. Plasmic Physics (talk) 13:16, 13 June 2011 (UTC)[reply]
And that should be testable by storing said unplugged refrigerator in consistently cold conditions, say outside in locations where temperatures stay around freezing for several months at a time. Surely someone around here's done this? --jjron (talk) 14:28, 13 June 2011 (UTC)[reply]
It's not just a metabolic effect. The vapor pressure of the smelly compounds that produce the odor you're detecting also varies with temperature. Higher temperatures mean that the maximum concentration of stinky stuff in the air is also higher; higher temperatures will also tend to drive faster evaporation of these nasties. Your nose can detect some odiferous compounds at concentrations of parts per billion or even less, so it takes a very small reservoir of these compounds in the fridge (tucked into crevices, hidden in door seals, even just adsorbed on the plastic surfaces) to continue to release odor for a very long time. TenOfAllTrades(talk) 15:10, 13 June 2011 (UTC)[reply]
Which is more likely to be found in common household magnets? Or are they a mixture of both? --Chemicalinterest (talk) 16:11, 13 June 2011 (UTC)[reply]
I don't know but you could try an experiment, construct a rudamentary spectroscope using a prism, a gloss black backdrop, a candle, and a piece of cardboard with a narrow slit cut into it. Prepare a concentrated solution, by dissolving a few tens of miligrams into 5 ml of hydrochloric acid. Arrange the backdrop, prism and cardboard in such a way so that light from the lit candle is shining through the slit is reflected and refracted through the prism onto the backdrop. Once you have the experiment set up, dip a piece of iron wire in your solution. Hold the dipped end in the flame of the lit candle, and observe the spectrum on the backdrop, this works easier in the dark. Compare this spectrum to those of strontium and barium, I'm sure you know what to do with those. Plasmic Physics (talk) 14:53, 15 June 2011 (UTC)[reply]
body
what are the harmful effects of masturbating? — Preceding unsigned comment added by 117.224.212.237 (talk) 16:57, 13 June 2011 (UTC)[reply]
Do you consider sticky fingers harmful? Googlemeister (talk) 17:17, 13 June 2011 (UTC)[reply]
Depending on your social environment, there are taboos in some societies about masturbation, so you could suffer socially. There are lots of different cultures in the world, each with their own opinions on these things, and depending on which culture you find yourself in, you may experience various levels of social consequences from masturbation. --Jayron32 17:46, 13 June 2011 (UTC)[reply]
There are no known harmful health effects from masturbating. thx1138 (talk) 18:13, 13 June 2011 (UTC)[reply]
WebMD has some funny stuff up, that frequent masturbation is correlated with an increased risk of prostate cancer in men in their 20s and 30s, but a decreased risk in men in their 50s.[20]Wnt (talk) 18:23, 13 June 2011 (UTC)[reply]
Yes, but in that article the researchers say that the frequency only indicates the sex drive, which in turn is a function of the level of hormones. A man's prostate can't tell whether orgasms come from masturbation or intercourse - probably, how would it? Itsmejudith (talk) 21:23, 13 June 2011 (UTC)[reply]
Portnoy's Complaint _does_ highlight one disadvantage - the real thing is rather disappointing and difficult in comparison. I recall a story on Fark[21] some years ago (not the most reliable of sources, of course) about Japanese men who suffer from this problem, although I'm sure it's applicable across the world. Tevildo (talk) 20:20, 13 June 2011 (UTC)[reply]
Note to self: If I ever get engaged to marry, I've got to refrain from jacking off from that time onward. However, I've got to point out that even if this is true, 45 times a year translates to roughly once every 8 nights, which is not too bad -- in fact, AFAIK the world average for married couples is "only" once every 7 nights. 67.169.177.176 (talk) 23:22, 13 June 2011 (UTC)[reply]
Hmm the Durex surveys says 103 times a year is the average [22][23]. This includes all non-virgins surveyed, married or not. However my impression is despite some misconceptions, most surveys show married people usually have sex more often then unmarried. Of course surveys of that nature usually have a big question mark due to the likelihood of people lying. Also the 2007 one at least, uses the internet for many countries and which would likely lead to a bias towards those who are richer and may have more free time (and more likely to be living together if married or in a relationship).
But the Durex surveys are the ones that get reported, if others exist that have tried to study the frequency of sex over a range of countries I haven't seen them (not something I've really looked for). BTW an interesting thing I noticed, while frequency of sex has a strong impact on sexual satisfaction (well that's what the 2007 survey said), some countries like Nigeria have relatively high satisfaction despite relatively low frequency of sex.
To bring this mildy back on topic, it's worth remembering masturbation is not solely a solo practice. In fact our article says
Contrary to conventional wisdom, several studies actually reveal a positive correlation between the frequency of masturbation and the frequency of intercourse. One study reported a significantly higher rate of masturbation in gay men and women who were in a relationship.
Given that, while masturbation is safer then many other practices; if you do masturbate with a partner you should use safer sex practices and birth control where necessary. If you don't while arguably not a harmful effect of masturbation per se, there's a slight chance this could lead to pregnancy or a STI.
103 times a year? That's twice a week, which is very good indeed! 67.169.177.176 (talk) 21:42, 14 June 2011 (UTC)[reply]
Normalizing Associated Legendre Polynomials to get Spherical Harmonics
Hi all. I've been working on this problem for like weeks, and I can't seem to figure it out. I'm trying to normalize Associated Legendre polynomials to turn them into Spherical harmonics. The integral comes out to:
where is the normalization constant.
can be found in Spherical harmonics#Orthogonality and normalization. I know that it involves integrating by parts times, and that the boundary terms vanish in each case, but I'm not sure why they vanish. Can anyone point me to a (very detailed) discussion of how to actually do the integral, or maybe a better way than by parts? Thanks!--Dudemanfellabra (talk) 21:01, 13 June 2011 (UTC)[reply]
This question would probably be better on the Maths desk. Tevildo (talk) 23:57, 13 June 2011 (UTC)[reply]
It may be easier to use the definition of the states |l,m>, so you say that you get |l,m> by applying L^(-) l-m times to |l,l> And then you compare this |l,m> in the angular basis with the definition of P_l^m. Count Iblis (talk) 15:24, 14 June 2011 (UTC)[reply]
Cleaning styrofoam
I have a styrofoam cooler that I use all the time, just for ice and soda so it really doesn't get funky because no foodstuffs are in it ever. Anyway, after a lot of use, the inside is a bit yellowed and has a slightly musty odor, so I thought I'd put some water in it with some bleach (about one-half cup bleach to a half-gallon of water is what I usually use for such applications, I guess that's a 1:16 mixture). This works great for mildew and the like. However, my friend told me that bleach and styrofoam are a bad mix, that they give off deadly fumes. Of course, I am now terrified to do this, especially indoors. Is there validity to this? I guess I should be very precise: My household bleach doesn't say what's in it but does say that it
"CAUTION, CORROSIVE! contains sodium hydrochlorite". The styrofoam does not say exactly what it is but it is marked with a triangular recycle symbol with a 5 inside, and says just below that, "PS"--maybe PolyStyrene? Note that there's nothing on the bleach label's caution list to single out styrofoam, but of course it can't list every stupid thing anyone might try, so I'm not putting any store by that. Oh, and if anyone knows of an alternative method that works well with styrofoam, of course I'm all ears.--108.54.17.250 (talk) 23:03, 13 June 2011 (UTC)[reply]
My friend says I'm inhaling deadly fumes. Reference desk, can I continue or is he right? --188.28.126.160 (talk) 23:15, 13 June 2011 (UTC)[reply]
Are you the same identity as the the above IP? If you are not, what are the fumes originating from? Plasmic Physics (talk) 23:26, 13 June 2011 (UTC)[reply]
Polystyrene is pretty chemically inert (like most other plastics), so I don't think it will react with chlorine or sodium hypochlorite (at least, in the absence of a catalyst such as aluminum chloride), much less in a way that releases deadly fumes. At worst the plastic might become chlorinated and further discolored, but even this is rather unlikely. You don't need to worry about poisoning yourself. As for an alternative method: I don't have a clue. 67.169.177.176 (talk) 23:33, 13 June 2011 (UTC)[reply]
Well, whatever you do, don't clean it with acetone. Plasmic Physics (talk) 00:42, 14 June 2011 (UTC)[reply]
Bleach fumes are caustic, but I don't think the Styrofoam contributes a bit. I use bleach on them outside, so the fumes can dissipate. I just cleaned one that way last week, as a matter of fact. Make sure it's somewhere kids or pets won't get at the bleach, though, if you leave it out to soak in bleach, as I do. StuRat (talk) 00:50, 14 June 2011 (UTC)[reply]
Dear God. Styrofoam coolers are like $5.00 or so. If its so nasty it can't be cleaned, recycle the old cooler and buy a new one. This is a penny-wise-and-pound-foolish issue on two regards: 1) You are likely spending more money and effort on cleaning the cooler than the cost would be to just buy a new one 2) Harsh cleaning chemicals have a greater environmental cost than recycling an old cooler would, or probably even just throwing it away. You are seriously better off just buying a new one. If you can keep it for, say, 5 years, I don't think a dollar a year is too much of an investment for cold beer... --Jayron32 01:09, 14 June 2011 (UTC)[reply]
You seem to assume a cooler only needs cleaning once every 5 years. In my experience they need cleaning every time they are left closed up for a while. I get bleach for a dollar a gallon, so can do a lot of cleaning at that rate, before it would pay for a new cooler. And can you recycle Styrofoam ? The best I could manage was to reuse one as an (ugly) planter. StuRat (talk) 04:16, 14 June 2011 (UTC)[reply]
Of course you should clean it frequently, but at some point its important to know when to cut one's losses. When the cheap, disposable styrofoam cooler can't be cleaned by normal means and resists anything except exotic cleaning agents or requires an extensive committee discussion to arrive at a possible cleaning method, it's time to cut bait and start over. I'm quite a frugal person myself, and I quite support using items wisely, but even I have my limits; at some point you've just got to buckle down, and dip into those savings for that new styrofoam cooler... --Jayron32 04:25, 14 June 2011 (UTC)[reply]
You consider bleach to be exotic ? To me it's the most basic cleaning agent there is. :-) I doubt that it's as bad for the environment as detergents. Once fully diluted, the only harmful effect I could imagine is it making rivers and lakes less acidic, but that would take a massive quantity, and, due to acid rain, some movement in that direction might even be beneficial. StuRat (talk) 04:43, 14 June 2011 (UTC)[reply]
No, not really. I clean my cooler with it all the time... --Jayron32 04:44, 14 June 2011 (UTC)[reply]
Then I don't understand your previous posts. StuRat (talk) 04:47, 14 June 2011 (UTC)[reply]
Then we're both fooked, because I hoped that at least you could shed some light on them. I am quite baffled myself. --Jayron32 05:32, 14 June 2011 (UTC)[reply]
Diluted bleach solution shouldn't hurt the cooler, though depending on its precise composition you might get further yellowing. As Jayron says, you might consider the acquisition of a new cooler. Twenty bucks will get you one with a hard plastic shell and snug-fitting (possibly hinged) lid. They are better-insulated, so the beer stays cooler, longer. They're more durable and they won't chip off bits of unsightly styrofoam fluff if you bang them around a bit. (They'll also stay intact and closed if you pack them under all your luggage in the trunk of the car.) They have proper carrying handles, some have drain spigots to remove excess meltwater, and in a pinch you can sit on them. The interior hard plastic lining is non-porous, so it won't pick up odor quite as readily as exposed styrofoam, and can handle vigorous scrubbing. Yes, they're slightly heavier than the naked styrofoam coolers, but once you load them up with beer and ice the weight of the cooler is pretty negligible—and you may be glad of the carrying handle(s). For all coolers, you'll cut down a great deal on the mustiness if you leave them open (at least a little bit) after you clean them out, at least until the interior is completely dry. TenOfAllTrades(talk) 13:18, 14 June 2011 (UTC)[reply]
I have several large coolers of the type you describe; one I use a lot is a large cylindrical cooler, which I actually use when brining and/or marinating large roasts (whole turkeys, pork butts, stuff like that). Very convenient, and easy to drain off the brining fluid into the sink for disposal. I usually clean it with straight bleach afterwards, including cleaning out the drain spout with bleach and a small bottle brush. It probably cost me $30 dollars, and besides the meat preparation applications, I have used it for keeping beers and sodas cold as well. Much easier to work with than styrofoam... --Jayron32 15:11, 14 June 2011 (UTC)[reply]
(un-indent) "And can you recycle Styrofoam ?" -- Yes, polystyrene is fully recyclable, though for some reason (probably because it's so cheap and readily available) it doesn't get recycled to nearly the same extent as, say, PETE. There are AFAIK no particular technical obstacles to recycling styrofoam -- the only obstacles, if any, are economic and/or political.
"I doubt that it's as bad for the environment as detergents." -- Even if BOTH detergents AND chlorine bleach are used, the environmental impact from such small quantities of them will be negligible to nonexistent. All this "environmental impact" stuff has been deliberately hyped by Greenpeace and other likeminded eco-fascists eco-Luddites for at least the past thirty or forty years. 67.169.177.176 (talk) 21:55, 14 June 2011 (UTC)[reply]
I object to the malignment of Greenpeace (see article) as a fascist organization because Greenpeace does not accept funding from governments, corporations or political parties. Anionic detergents with branched alkyl groups were largely phased out in economically advanced societies because they are poorly biodegradable[1]Bleach is toxic to fish and invertebrates, in confined spaces. Cuddlyable3 (talk) 12:26, 15 June 2011 (UTC)[reply]
While I agree on second thought that fascist in the strict sense of the word is not really applicable to Greenpeace (they are more accurately described as marxist, third-worldist and eco-Luddite), I must point out that accepting funding from governments, corporations or political parties is not a criteria for being considered a fascist organization (or any other kind) -- this depends SOLELY on the ideology being advocated. Linear alkylbenzylsulfonates that are in universal use as detergents today (as opposed to the obsolete branched ones you're talking about) are biodegradable and nontoxic -- to claim that all detergents are environmentally harmful when in fact this is a property only of a specific subset that is no longer used is fallacious at best and deliberately misleading for political purposes at worst. Fish and invertebrates don't naturally occur in "confined spaces" as the latter term is commonly understood. 67.169.177.176 (talk) 16:58, 15 June 2011 (UTC)[reply]
Like you I read Wikipedia that says: The global organization [Greenpeace] does not accept funding from governments, corporations or political parties, relying on more than 2.8 million individual supporters and foundation grants.[2][3]. If you have verifiable information that should be in the article then add it. Cuddlyable3 (talk) 19:30, 15 June 2011 (UTC)[reply]
You can't always trust what Wikipedia says because it has a Marxist bias itself; as a matter of fact, I've been boycotting it for a year or so to protest against the actions of a certain commie scumbag re. the article Extermination through labor. In any case, you can't take documents written and published by the organization itself at face value without verifying this info with an independent, reliable, unsympathetic source (which Gilbert demonstrably isn't, as the title of her work clearly indicates her sympathies with the environmentalist movement). As for the matter of Greenpeace taking funding from corporations, there is the book The Hidden Face of Greenpeace by Olivier Vermont, where he alleges that Greenpeace has in fact been extorting racket money from various corporations. 67.169.177.176 (talk) 20:39, 15 June 2011 (UTC)[reply]
And even if in fact they do not take corporate money, that still doesn't prevent them from being third-worldist Luddites with Marxist political views -- this can be proved or disproved by their statements and actions alone. 67.169.177.176 (talk) 21:03, 15 June 2011 (UTC)[reply]
June 14
Does the planet Neptune contain water? If so, is it possible that there's a chance that maybe there's life?
Does the planet Neptune contain water? If so, is it possible that there's a chance that maybe there's life? If so, what kind of life? Neptunekh2 (talk) 03:23, 14 June 2011 (UTC)[reply]
Read Neptune. Basic summary: Neptune's mantle is mostly water and ammonia; one could call it an ocean many times the mass of Earth. It seems improbable that life as we know it could exist there, since temperatures are above 2000K, while DNA denatures at much lower temperatures.-RunningOnBrains(talk) 03:28, 14 June 2011 (UTC)[reply]
The problem with this retortreply is carbon chauvinism, DNA is unique to Earth. The same problem is with water, water is a good solvent, but it doesn't mean all life requires it. Plasmic Physics (talk) 04:23, 14 June 2011 (UTC)[reply]
It is incivil to call an another editor's considered and informative reply to the OP a "retort", even when you can give supplementary information. Cuddlyable3 (talk) 07:32, 14 June 2011 (UTC)[reply]
For the record, I didn't consider it incivil. Also for the record, I am not a carbon chauvinist, but it is completely pointless to speculate on alternative forms of life, because science knows of no possibilities for non-carbon-and-liquid-water-based life as of now. I never say impossible unless I mean impossible, thus I said "improbable".
I don't think many complex molecules are stable at 2000K, carbon or not. StuRat (talk) 05:00, 14 June 2011 (UTC)[reply]
Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching −218 °C (55 K). Temperatures at the planet's centre are approximately 5,400 K (5,000 °C). Cuddlyable3 (talk) 07:38, 14 June 2011 (UTC)[reply]
Yes, but water is only in a useable liquid(ish) form in the mantle, where there are extremely high pressures and temperatures.-RunningOnBrains(talk) 13:38, 14 June 2011 (UTC)[reply]
I think there are planets and moons in our solar system which are much better suited to life, carbon based or not. I would even go as far as saying that simple life forms are quite probable on Enceladus or Europa. --helohe(talk) 22:46, 14 June 2011 (UTC)[reply]
The problem is that the ambient conditions are either, incredibly high atm. pressure and very hot; or low atm. pressure and incredibly cold. There is no liquid water in Neptune, only crystal vapour and super critical water. Plasmic Physics (talk) 08:05, 14 June 2011 (UTC)[reply]
The answer to "is it possible...there's a chance..." regardless of what you fill in the blanks with is always "yes". There is always a very tiny possibility that there is a tiny chance that something may happen or exist. For example, it is possible that there is a chance that there is a flying spaghetti monster floating around the solar system. -- kainaw™ 12:57, 14 June 2011 (UTC)[reply]
This is a question about a drug I'm almost sure we have an article for, but I can't remember the exact name of it. The name is something like "Delidamide." It was pretty wide spread in the 50's and 60's for, what I think, was menstrual pains (or something along those lines.) It turned out to cause birth defects that caused shortened limbs among other things. JFK actually made a speech in which he encouraged women to stop using this drug and to "turn it in" to medical authorities. What was the name of this drug and any related articles about it on WP. Thanks! Quinn❀ BEAUTIFUL DAY 04:54, 14 June 2011 (UTC)[reply]
Actually, it is spelled "Thalidomide", but that's a minor issue. The drug itself was a sedative that was frequently prescribed for "morning sickness", which exacerbated the birth defect problem, for obvious reasons. The lesson of the drug shows up in organic chemistry classes when discussing the importance of knowing how stereochemistry works, in that one enantiomeric form of the compound cured morning sickness, and the other form gave your kids a third arm. the inability to give the correct answer at the reference desks. --Jayron32 05:05, 14 June 2011 (UTC)(edit: struck through wrong answer and corrected --Jayron32 12:58, 14 June 2011 (UTC))[reply]
3rd arm ? Not a side effect I'm aware of. StuRat (talk) 05:07, 14 June 2011 (UTC)[reply]
Right, so no third arm. StuRat (talk) 07:35, 14 June 2011 (UTC)[reply]
lunar eclipse
How full moon appers during lunar eclipse?'
' — Preceding unsigned comment added by 14.97.111.145 (talk) 08:46, 14 June 2011 (UTC)[reply]
See our articles lunar eclipse and full moon. I think they make sense, let us know if you have a specific question.--Lgriot (talk) 09:39, 14 June 2011 (UTC)[reply]
The requisite of a lunar eclipse is a completely shadow covered moon. You can't have a full moon concurrently occuring with a lunar eclipse. The moon is too big to have properties like a quantum superposition. Plasmic Physics (talk) 11:26, 14 June 2011 (UTC)[reply]
A lunar eclipse only happens at full moon. It usually has a reddish or brown tinge. Graeme Bartlett (talk) 12:51, 14 June 2011 (UTC)[reply]
No, really concurrently. Obviously, a lunar eclipse can only happen when the moon is on the exact opposite side of the Earth than the Sun. We call that a full moon. Just because most of the light is blocked doesn't change that - it's still considered a full moon. --Tango (talk) 22:00, 14 June 2011 (UTC)[reply]
I would argue that a lunar eclipse is the fullest possible full moon. 86.160.218.204 (talk) 13:54, 14 June 2011 (UTC)[reply]
It is not surprising that this question located to Hyderabad where they will experience the full glory of the June_2011_lunar_eclipse. Richard Avery (talk) 18:08, 14 June 2011 (UTC)[reply]
Lunar eclipses happen at Full Moon, and solar eclipses happen at New Moon. Furthermore, eclipses very often come in pairs, 2 weeks apart. ←Baseball BugsWhat's up, Doc?carrots→ 02:19, 15 June 2011 (UTC)[reply]
transduction, transformation, transfection and electroporation
Is there an umbrella term for transduction, transformation, transfection and electroporation? --129.215.47.59 (talk) 11:31, 14 June 2011 (UTC)[reply]
According to the article, each raspberry contains only a single seed, so why are there so many pips in raspberry jam and yoghurt? Aren't they all seeds? As far as I recall, when I eat fresh raspberries, there are no pips.--Shantavira|feed me 13:29, 14 June 2011 (UTC)[reply]
The article says "An individual raspberry weighs about 4 g, on average and is made up of around 100 drupelets, each of which consists of a juicy pulp and a single central seed. " So each raspberry contains about a hundred seeds. Whenever I eat fresh raspberries (which is as often as possible), I always get pips in my teeth. DuncanHill (talk) 13:34, 14 June 2011 (UTC)[reply]
This is something I've never understood. If sound moves fastest in solids, why are solids used for soundproofing? Metroman (talk) 13:43, 14 June 2011 (UTC)[reply]
Mostly, by intentionally designing a system to be poorly impedance matched to air. The key is that a large change in sound velocity means that the transfer of energy between two materials is poor. So, even if a material like solid steel conducts sound very well, at a high speed and with low attenuation, that sound doesn't transfer well from steel to air (and back). Most energy will be reflected at the surface. In addition, incoherency and diffusion are exploited by shaping the surface... a good sound barrier will be a rough surface (and a great sound barrier will be diffusive acoustic cones as you see in a studio booth). This way, you minimze the transmitted sound and the reflected sound. Nimur (talk) 14:15, 14 June 2011 (UTC)[reply]
The most common type of soundproofing I'm familiar with, like the kind used in recording studios is made of sponge. sponge is elastic so the little cells of air tend to absorb and dissipate sound energy rather then propagate it like a rigid solid. Vespine (talk) 00:16, 15 June 2011 (UTC)[reply]
Yes. Rubber or other elastomer has pronounced elastic hysteresis by which most received vibrational (sound) energy gets converted to heat. Cuddlyable3 (talk) 11:53, 15 June 2011 (UTC)[reply]
Unstable nuclei
Hi. Is there any qualitative difference between an atomic nucleus that is extremely unstable (arbitarily so) and one that simply can't exist at all? For example, suppose I took x protons and y neutrons, for some arbitrary x and y, and stuffed them together to make a nucleus, which then blew up effectively instantly but actually in some tiny amount of time like 10^-15 seconds, or whatever value it might be. Have I thus always created a nucleus with an extremely short half-life, or might I have tried to create one that simply can't ever exist, and can't meaningfully have a "half-life" assigned? 86.160.218.204 (talk) 13:51, 14 June 2011 (UTC)[reply]
How do you propose to stuff them together? You don't just pick out protons and neutrons from little trays, and apply some gluons and then let go and see if it sticks. You'd need a real possible procedure to create your proposed nuclei. Also, something with a half-life of 10^-15 seconds is still a real amount of time, several mesons (see List of mesons) have half-lives several orders of magnitude shorter than that before they disintegrate into their constituent particles, and they "exist". The answer is, if it exists, it exists and if it does not, it does not. The length of time is irrelevent, all that is relevent is if you can establish evidence of its existence in the first place. There's lots of ways to establish evidence of existing; and these don't always involve keeping a bunch of it in a jar long enough to do tests on it. To take two examples, the neutral pion has been positively confirmed to exist, despite having a halflife of 10^-21 seconds, see Pion#History. On the flipside, the Higgs boson has never been detected though many (not all, but many) models of particle physics predict, and rely upon, its existence. --Jayron32 15:05, 14 June 2011 (UTC)[reply]
The way in which they are stuffed together is not relevant to the question I want to ask. Just imagine that the requisite particles are in place in a putative nucleus and take it from there -- a kind of thought experiment, if you like. If the question can't be asked, even in principle, without knowing exactly how this state was achieved, then I guess my question makes no sense. As you can probably imagine, "if it exists, it exists and if it does not, it does not" is not the answer I was seeking. I have thought of another way to ask this which may be clearer: imagine you are compiling a table of all possible atoms -- that is, all values of my x and y -- in decreasing order of half-life. Is there some point at which you must stop and draw a line (that is, when there is a qualitative change from unstable atoms with a definable half-life, to "non-atoms" that simply aren't viable at all, even with no matter how short a half-life) -- or do you go on, in principle indefinitely, with the half-life just getting shorter and shorter? 86.179.117.174 (talk) 17:39, 14 June 2011 (UTC)[reply]
I believe what you are looking for can be answered in a few articles. There are ways to predict which nuclei should be stable enough to be considered to "exist" for a reasonable amount of time (reasonable as defined by Dauto below), one of the most common is the Nuclear shell model. The table of all possible atoms also exists. See Island of stability for a graph exactly like you want. --Jayron32 18:53, 14 June 2011 (UTC)[reply]
Yes. A viable nucleus must, at minimum, have positive nuclear binding energy. This means the strong nuclear forces holding the nucleus together have greater impact than the electrostatic repulsion trying to drive the protons apart. In principle, the binding energy can be modeled via quantum chromodynamics, though in practice it is often an impractically difficult computational problem for large atoms. Also, though this is a necessary condition, it isn't sufficient since some potential nuclei will fission without having been self-bound for any meaningful length of time (i.e. without even allowing binding forces to cross the whole nucleus). Dragons flight (talk) 19:12, 14 June 2011 (UTC)[reply]
That question shouldn't be dismissed so handedly. There are two aspects that should be taken into consideration. First, if the decaying object is a composite structure such as a nucleus, as opposed to a fundamental particle such as a quark or a gauge boson, than if its life time is too short there will not be enough time for light (or anything else) to cross its length before it decays and there is no meaningful reason to call it a particle. For the nucleus example the relevant length is 10^-15 m. Light takes about 10^-23 s to cross that length therefore no nuclei can exist with a lifetime shorter than that. The second point to take into consideration is that because of the uncertainty principle a particle with a very short lifetime will have a large uncertainty to its total energy. If that uncertainty is larger than the mass of the particle itself than we should more properly talk about a Resonance (particle physics) instead of a particle. Dauto (talk) 16:25, 14 June 2011 (UTC)[reply]
I read the article Fingerprint and even saw the use of the word "point" without clear definition. Nowhere did it explain what a "point" is in the context of fingerprints. On television, both in fiction and nonfiction, I've heard people speak of two fingerprints having X number of matching points, and sometimes they show a picture of a fingerprint with little squares or circles drawn on the fingerprint. Who decided to draw the points right where they are? If I draw a bunch of line curves, what's the objective method of deciding where any point is to be on any of those curves? 20.137.18.50 (talk) 18:03, 14 June 2011 (UTC)[reply]
A "point" is a common term which applies to an identifying characteristic of a particular print. In fingerprinting, these are often called "Minutiae" and applies to a set of "common" features which appear at specific locals in specific fingerprints. It isn't a simple problem, which is why a "positive" connection requires a sizable number of common "points" to call it a "match". What you have is an overall pattern of the print (a "whorl" or an "arch" or a "loop" are the three most common patterns) and within the main pattern are small features which are unique to the individual, like say you have a whorl-type print. Lets say on a line drawn at 12:00 from the center of the whorl, you have a gap on the third ridge, and there's a connecting bit between the fifth and sixth ridges, while on the line drawn at 3:00, there's gaps on the second and fourth ridge, etc. etc. This is in general how prints are identified; in reality the language used to describe the "points" and the manner in which they are connected between the sample print and the suspect print are much more precise than I have done here, but that should give you the idea. --Jayron32 18:47, 14 June 2011 (UTC)[reply]
diffrence
how can u distinguish between Allene and Alkyne? i know about bayers reagent test but both of them give it so there is no physical distinction((both discharge color of KMnO4).So my question is is there any other test which distinguish between Alkene and Alkyne physically. Can Ozonolysis be a authentic test for them? — Preceding unsigned comment added by 175.110.91.49 (talk) 21:13, 14 June 2011 (UTC)[reply]
There is distinction, an allene has an "sp" carbon bonded to two "sp2" carbons, while an alkyne has an two "sp" carbons bonded to each other and one other atom. However, you are correct in that allenes and alkynes are particularly tricky to identify via "wet chemistry" analytical techniques; this is because allenes and alkynes are frequently in equilibrium, see Propadiene, which exists normally as an equilibrium mixture with propyne (likewise, propyne will exist in the same equilibrium with propadiene) called MAPD. Any reaction which would react preferentially with the allene will simply, via Le Chatelier's principle, cause the equilibrium to shift to convert more alkyne to allene, and the same in reverse as well. There are likely ways to use technology to do the job for you, for example they may produce distinctly different peaks in IR spectroscopy or something like NMR or mass spectrometry may be very useful in this regard; however you may be correct in that it is almost impossible distinguish them via chemical reactivity. Ozonolysis may be an option, as you note, since ozonolysis of an alkyne should produce two carboxylic acids, while ozonolysis of an allene should produce carbon dioxide and two aldehydes. However, given the equilibrium situation I note, that may foil whichever ozonolysis reaction of the two is slower; the equilibrium situation would just cause the faster ozonolysis reaction to drive the reaction kinetics, and the other wouldn't happen. --Jayron32 23:24, 14 June 2011 (UTC)[reply]
Try infrared spectroscopic analysis, alkynes gives an absorption peak at a higher wave number. If you heat alkynes, they tend to polymerise easier. Plasmic Physics (talk) 23:26, 14 June 2011 (UTC)[reply]
Thank for the answer. my exams is on friday and i was a little confused.Can u suggest any links or articles.I am in 12 standard. — Preceding unsigned comment added by 175.110.91.49 (talk) 23:56, 14 June 2011 (UTC)[reply]
Physics and timetravel
I am interested in writing a short story about a scientist who creates a time machine. Instead of going to a certain year, he is accidentally catapulted to the very beginning of time billions of years ago. I know very little about physics. Was time as we know it created the very second that the big bang took place, or some other time? I'm just interested to learn if it is at least plausible for someone to go back to that exact moment (that is assuming time travel is possible in this scenario). --Ghostexorcist (talk) 22:30, 14 June 2011 (UTC)[reply]
At that instant the entire universe was smaller than an atomic nucleus. Looie496 (talk) 22:38, 14 June 2011 (UTC)[reply]
(edit conflict)Matter as we know it could not exist until the universe was about 380,000 years old, so the physicist would instantly transform into plasma, presuming time travel possible. See Timeline of the Big Bang.
If we assume that he somehow shields himself from the extreme energies at that time (this is science fiction after all), you have to consider that you can't go further back than the instant the universe began (my favorite analogy: going back before the big bang is like trying to go North from the North Pole), and at that instant, it was (practically) infinitely dense. At some point backwards, the universe itself would be smaller than the time-traveling scientist himself, so you can see why this would present a problem! There really is no practical way, even in the structure of a fictional time-travel book, to plausibly go back to the instant the universe was created. For this, you need to delve more into the "fiction" part of "science fiction".-RunningOnBrains(talk) 22:44, 14 June 2011 (UTC)[reply]
What is a good book that explains the most current research on the big bang that is dumbed down enough for the average joe interested in science? --Ghostexorcist (talk) 08:04, 15 June 2011 (UTC)[reply]
Thanks for the informative response. As for shielding, I was thinking that some strange quark of him physically traveling back through time (he doesn't travel in a machine) makes him immortal. His body is petrified into a rock like substance, in effect becoming a living statue. Going back to the beginning of the universe is just something I thought of a second ago. I originally conceived the idea of him going back to the earliest days of human civilization. He watches the rise and fall of various cultures over the course of thousands of years. Now that you have thoroughly answered my question, I would like to pose a related query. --Ghostexorcist (talk) 23:05, 14 June 2011 (UTC)[reply]
My favourite for unexpected time travel effects is the scientist who built a time travel machine to find out what caused the snowball earth. As it is impossible to send matter back, he sends information to rebuild the matter (himself and the time-ship). Unfortunately part of the matter uptake was in the form of heat energy so as a result, the whole earth got frozen. 5BYv8cUJ (talk) 09:39, 15 June 2011 (UTC) [reply]
Time travel and biology
What fictional process could effect the scientist's body in such a way that it would become living stone. I imagine that it would have to effect his body's natural atomic bond. Again, I know very little of physics. --Ghostexorcist (talk) 23:05, 14 June 2011 (UTC)[reply]
I don't know, you tell us, it is your work fiction after all. What is a human body's natural atomic bond? For that matter, what is an atomic bond? Plasmic Physics (talk) 23:20, 14 June 2011 (UTC)[reply]
That's why I said "Again, I know very little of physics" above. I guess his atomic bond would be the spacial density of his atoms. Then again, I have read that this density is fixed and cannot be change, so just consider that a bad word choice. I'm just interested in some type of real world explanation that can be greatly embellished. Like for instance, if you expose a certain element to a given energy source, does it effect its density in any way? If there is none, then I'll just shoot from the hip. --Ghostexorcist (talk) 23:27, 14 June 2011 (UTC)[reply]
An important clarification: what properties of stone do you want this living body to have? For instance, the hardness of stone is not (primarily) due to the density, but the crystal lattice structure of the mineral components. Once you have that hardness via the crystalline structure, malleability (e.g. the ability to move around) becomes a problem... SemanticMantis (talk) 23:43, 14 June 2011 (UTC)[reply]
I haven't the slightest clue to tell you the truth. I know living rock can move like toothpaste given enough pressure, but it's not like the guy is trapped between tectonic plates or anything. I guess I'll have to relegate this portion of the story to the fiction side of sci-fi. --Ghostexorcist (talk) 23:52, 14 June 2011 (UTC)[reply]
Thanks for reminding me of this. I'll look into it more. --Ghostexorcist (talk) 08:04, 15 June 2011 (UTC)[reply]
Since this is fiction your protagonist could meet up with the Gorgon. Insert obvious phallic joke here. You may find more scientific ideas in the article Fossil although your plot should allow plenty of time for this slow process. Note that fossilization will affect and not effect the body. Cuddlyable3 (talk) 11:37, 15 June 2011 (UTC)[reply]
phone tracing
Usually in movies it takes some time until the phone number of a caller can be traced. So they have to keep them on the line for a certain amount of time until they get the number. This sounds like BS to me, as the phone company certainly has the caller's number in real time. What are the technical reasons behind this? Is/was there at all any truth about this? --helohe(talk) 22:37, 14 June 2011 (UTC)[reply]
Technological capabilities at the present time may be superior to technological capabilities when the movie was made. Looie496 (talk) 22:39, 14 June 2011 (UTC)[reply]
No, they have pretty much always been bullshit, at least since the advent of relatively modern phone-switching systems (i.e. something better than women with headphones moving wires around a giant pegboard). Telephone_exchange#Digital_switches indicates that digital systems have been in place since the 1980's. Caller_ID#History indicates that the technology has existed, theoretically, since 1969, to instantly display a caller's phone number, though the first market-ready applications were in the mid 1980's. I'm sure at some point in the past this really was a major undertaking to "trace" a call, but given that for at least 20 years, my phone has been able to automatically tell me who is calling, and I am not the police, then any movie in the past 20 years where the police can't do so is bullshitting us. this article confirms that, during the days of manual switching it used to take upwards of 20 minutes to trace a call, and required the cooperation of the phone company. However, with the advent of electronic switching techniques, tracing calls went from "20 minutes for the phone company to track someone down" to "instantaneous". There was never a time when a call could be traced in an automated way, like you see in movies and cop shows, but did not return results essentially as soon as the connection was made. The whole "keep him talking while we trace the call" bit has always been an invention of scriptwriters. Either (pre-1980's) you had to get the phone company to figure out who called (and this didn't require the other person to be on the line; they could figure where it came from after they hung up) OR (modern systems) you can find out instantly as soon as the connection is made. --Jayron32 23:12, 14 June 2011 (UTC)[reply]
I've always had the suspicion that this is the result of not just the drama involved (to avoid making things too easy on the protagonists) but also script writers not wanting to give away the FBI's tricks. For instance even on shows where it would be great to have you never see them use portable cell towers for triangulation and to lock down a hostage taker's cell phone (by forcing it to connect to YOUR tower rather than the network at large) despite the fact the technology exists. HominidMachinae (talk) 00:54, 15 June 2011 (UTC)[reply]
I think some of the respondents above may be making a false analogy between the telephone network and the Internet. The Internet was designed to be stateless and is based on datagrams (i.e., postcards). You have to supply a legitimate return address if you want to get a reply, unfortunately for your privacy. The telephone network doesn't work that way. It is circuit switched, which means that every switch on the network behaves more or less like a NAT router. How do you find out which of the computers behind a NAT router was the source of an outgoing connection? You don't, unless the sender identifies itself or the router exposes an interface that can be used to query that information. I'm sure that mechanisms for fast call tracing have existed for a long time, because the spooks demand it, but it's not in the nature of the telephone network to expose the caller's identity, unlike the Internet. Caller ID works by sending the calling number over the circuit once it's made, encoded as pulses. The receiving phone displays whatever information is sent, even if it's wrong. It doesn't really know who's calling. -- BenRG (talk) 06:26, 15 June 2011 (UTC)[reply]
It should be noted that caller ID is completely unrelated to call tracing. A trick from the old days included tandem stacking, which would let one bounce a call back and forth across the US, and then connect to a given number (which would sometimes have the effect of the local telco's central office number showing up.) Similarly, using a calling card to place a call will often give the Caller ID for the calling card company, not the pay phone from where the call was originally placed. Related to this is ANI, which is included on all 800-numbers, as well as all law enforcement phone systems. One can block their caller ID, but they cannot block the ANI function. (although ANI information can also be spoofed by proper call routing.) None of this affects call tracing, but can affect the perceived origin of a call for your average citizen (or their Caller ID equipment.) Avicennasis @ 09:38, 13 Sivan 5771 / 15 June 2011 (UTC)
What is the measurement of malleability?Curb Chain (talk) 05:00, 15 June 2011 (UTC)[reply]
Malleability is the ability of a metal to be hammered into thin flat sheets, see the article Ductility. An example of a very malleable metal is gold. Malleability is an example of non-linear behaviour of a material that is stressed beyond its elastic limit (below which many materials obey a linear Hooke's law). There are approximate mathematical descriptions of material plasticity, see here, but I think there is no standard measurement unit and only empirical data on how materials behave beyond their yield point. Cuddlyable3 (talk) 11:14, 15 June 2011 (UTC)[reply]
Putting Humpty Dumpty back together again
In various medical dramas, I've seen doctors do everything from move intestines aside to get at something to basically scooping them out of the abdominal cavity and move them aside. Granted, these are works of fiction, so I don't think that they're always very accurate. What I'm wondering though is on the other end of things. When the patient has been saved and all their organs need to go back into their body, how much care needs to be taken to make sure the intestines aren't knotted up or laying incorrectly or something. Is there a process or procedure to putting them back in? Dismas|(talk) 06:19, 15 June 2011 (UTC)[reply]
My Dad had such a surgery, where his intestines were pulled out, then put back in, and they seemed to think they would just "find their way back" to the right spot. They didn't. From then on he was noticeably lopsided, with a bulge on one side of his abdomen. StuRat (talk) 07:07, 15 June 2011 (UTC)[reply]
I wonder if it was possible that your dad had a slight incisional hernia which weakened part of his abdominal wall and the pressure of the abdominal contents pushed out rather more on one side than the other, not uncommon in major abdominal surgery. Within the abdomen where the intestines are is a single cavity which would exert even pressure against the whole abdominal wall. I don't believe there is a right spot for removed and replaced intestines. The most important factors are that when they are replaced they should not have their blood supply compromised and the intestine should not be twisted, stretched or knotted in a way that peristalsis would not be able to correct. Richard Avery (talk) 14:39, 15 June 2011 (UTC)[reply]
The way the body packs the contents of the abdominal cavity can vary. An embryo is a different payload than the OP talks about, but its positioning is sometimes unlucky, see for example Breech birth and Umbilical cord prolapse. Cuddlyable3 (talk) 09:45, 15 June 2011 (UTC)[reply]
I am a mechanical engineer now i need a notes for the following topics
Specific requirements for automotive lubricants – Oxidation deterioration and degradation of lubricants – Additives and additive mechanism – Synthetic lubricants – Classification of lubricating oils – Properties of lubricating oils – Tests on lubricants – Grease – Classification – Properties – Test used in grease. — Preceding unsigned comment added by Vigneshvig88 (talk • contribs) 09:38, 15 June 2011 (UTC)[reply]
Our article on tribology (the science of friction and lubrication) may also be useful. Gandalf61 (talk) 10:53, 15 June 2011 (UTC)[reply]
Respondents: I've started a discussion of this question here. --Sean 19:56, 15 June 2011 (UTC)[reply]
Multiple biopsy
Do doctors perform biopsy on a cancer patient several times to discover how the cancer is developing? Or is it a one time shot? 2.139.12.164 (talk) 09:50, 15 June 2011 (UTC)[reply]
As with most questions like this one, it depends on the circumstances. There are some scenarios where several biopsies might be employed to assess for distant metastases of solid tumors, or serial bone marrow biopsies might be used to follow leukemia. --- Medical geneticist (talk) 10:18, 15 June 2011 (UTC)[reply]
Clearly more than one measurement at different times is needed to determine how anything is developing. Cuddlyable3 (talk) 11:17, 15 June 2011 (UTC)[reply]
True, but it need not be a biopsy, per se... often the cancer will be followed by less invasive imaging techniques such as positron emission tomography. Again, it is an "it depends" kind of answer. --- Medical geneticist (talk) 11:33, 15 June 2011 (UTC)[reply]
Medical geneticist's response is spot on; it really depends on the circumstances. For a specific example, a prostate biopsy will often be performed in the event of suspected prostate cancer. Because these tumors are often very slow-growing and the patients who develop them tend to be older, low-grade tumors – those with a low Gleason score – can sometimes be left in place untreated. The risk of disease progression during a period of watchful waiting may be less serious than the risk of negative side effects caused by more aggressive therapy. (Indeed, four out of five men over the age of 80 probably have prostate cancer. Most will never even know about it, because they'll die of something else long before the prostate cancer gets them.) If the patient's symptoms become more severe (or there are other signs of disease progression like an increasing PSA score) then another biopsy may be performed to determine if the cancer has become more aggressive. TenOfAllTrades(talk) 14:14, 15 June 2011 (UTC)[reply]
Because everything that is not deflected travels in a straight line. But even light does not always travel in a straight line. See lenses, prism and also gravitational lens. 5BYv8cUJ (talk) 11:34, 15 June 2011 (UTC)[reply]
Also relevent in this case is Geodesic (general relativity). One needs to define what it means to be a "straight line" before one can decide how and why light travels that way... --Jayron32 11:55, 15 June 2011 (UTC)[reply]
The Poynting vector is not a simple explanation why light, an electromagnetic radiation, travels in a straight line, but it serves to show how light's behaviour relates to its constituent electric and magnetic fields. Cuddlyable3 (talk) 13:09, 15 June 2011 (UTC)[reply]
Neutrino oscillations and CP violation
"Neutrino particle 'flips to all flavours'" (BBC News) says that the T2K experiment has announced provisional results that indicate that muon neutrinos can transform into electron neutrinos, and hence the θ13 component of the neutrino mixing matrix is non-zero. I follow all of that (after a hand-waving fashion). The article then goes on to say that this type of neutrino oscillation would be an example of CP violation. However, it doesn't really explain just how these particular neutrino oscillations violate CP symmetry. Can anyone explain the connection in more detail, please ? Gandalf61 (talk) 12:27, 15 June 2011 (UTC)[reply]
Neutrino mixing is governed by the Pontecorvo–Maki–Nakagawa–Sakata matrix. In principle, this involves 9 complex numbers. However, after requiring the total amplitudes to remain constant over time, assuming that all neutrinos always have the same chirality (which is true as far as we can tell), and assuming neutrinos are Dirac fermions (like all other known fermions, but the Majorana fermion model is not experimentally excluded), this reduces the 18 nominal degrees of freedom to only 4 real numbers. In particular, CP violation occurs if and only if the imaginary part of , where and are numbers to be determined experimentally. A non-zero imaginary part would imply that nuetrinos and antineutrinos have different mixing rates, or in other words, in a CP-inverted universe neutrino mixing rates wouldn't look the same (hence CP-violation). is known to be small, but the current report suggests it is non-zero. Incidentally, is also unknown and could be 0, so is a necessary but not sufficient condition to show where neutrinos oscillations violate CP-symmetry. Dragons flight (talk) 20:13, 15 June 2011 (UTC)[reply]
(ec) A non-real entry in the mixing matrix violates the C part of CP, which is complex conjugation. The standard parametrization consists of three Euler angles (θ12, θ23, θ13) and one complex phase (δ13). This article is about a new constraint on θ13. If you look at CKM matrix#"Standard" parameters you'll see that all of the terms with δ13 in them also have a factor of sin θ13. So, one could say that a nonzero value of θ13 "opens up the possibility" of CP violation, since the matrix is real if θ13 = 0 regardless of the value of δ13. But it's a stupid thing to say because (1) this parametrization is arbitrary and (2) there was never any reason to expect any of these parameters to be zero, and it would be very strange if they were, so the possibility has always been open and the only interesting result, in that connection, would be one that "closed it off". It's basically the same as saying "we have determined that we are not standing precisely at the North Pole, which opens up the possibility that we are not standing precisely on the Greenwich Meridian." -- BenRG (talk) 20:21, 15 June 2011 (UTC)[reply]
Problems topping up mobile
Does anyone know what a 'Error Code-91 System Error' means ? Because i have tried to topup my mobile (T-mobile) at three different stores today and the same thing happened in each case, on the recepts was:
'Transaction Failed'
'Error Code-91'
'System Error'
Does this mean my topup card, SIM card or both have been cancelled, which the staff in the stores believe it could be. Help!!!109.145.108.36 (talk) 12:41, 15 June 2011 (UTC)[reply]
It may help to note that the OP's IP is in the UK OK! OK! Enough abbreviations! so their mobile operator is T-Mobile (UK). Cuddlyable3 (talk) 12:56, 15 June 2011 (UTC)[reply]
Just doing a few obvious checks: have you taken the battery out and reseated it? Have you taken the SIM out and reseated it? Switched off and on again? --TammyMoet (talk) 14:49, 15 June 2011 (UTC)[reply]
Does T-mobile not have some sort of help line or email you can contact? Nil Einne (talk) 15:36, 15 June 2011 (UTC)[reply]
Try topping up your mobile via their website, or by text.--Shantavira|feed me 16:13, 15 June 2011 (UTC)[reply]
Horticulture Nurseries
What is a nursery?
What types of nurseries are there?
What are the opportunities and challenges of nurseries? — Preceding unsigned comment added by 62.24.111.249 (talk) 13:57, 15 June 2011 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. You may find the Wikipedia articles horticulture and plant nursery may help you, though your best option is to read through the text book that your teacher gave you and/or read the notes you wrote down during in-class lecture. --Jayron32 14:11, 15 June 2011 (UTC)[reply]
If the OP's homework was assigned not in a Biology class but in something related to Paediatrics or Pedagogy, then Nursery might be more relevant :-) . {The poster formerly known as 87.81.230.195} 90.197.66.241 (talk) 18:11, 15 June 2011 (UTC)[reply]
Directions near the Poles
Is there a standard way of giving direction at or near the North or South Pole? At lower latitudes, "the wind is from the south-west" means something.
But if someone set up a weather vane at the pole, how could they tell someone else which way the wind was blowing?
If you want the smartass answer... if you're at the North Pole, the wind is always from the south. Otherwise, see this page. -Atmoz (talk) 16:56, 15 June 2011 (UTC)[reply]
Nose to the Brain
Is there any truth to the idea of there being straight access from the nose to the brain or is that just a myth? — Preceding unsigned comment added by 71.143.240.229 (talk) 15:07, 15 June 2011 (UTC)[reply]
I don't know what you mean by "straight access", but consider the top diagrams at nasal cavity and human brain. The brain image also shows the nasal cavity, which appears to directly adjoin the brain at some points. SemanticMantis (talk) 15:34, 15 June 2011 (UTC)[reply]
What does "straight access" mean? direct unimpeded access? in that case, no. There is 1-2 mm layer of bone between the top of the nasal cavity and the base of the brain. Richard Avery (talk) 15:55, 15 June 2011 (UTC)[reply]
Is there also bone from the top of the ear to the brain, blocking access to the brain? — Preceding unsigned comment added by 70.136.157.251 (talk) 16:01, 15 June 2011 (UTC)[reply]
The olfactory receptor neurons connect to the olfactory nerve which connects to the olfactory bulb which connects to other parts of the brain via the olfactory tract - see olfactory system. Doesn't seem very much like "straight access" to me - not more so than the other sensory systems, anyway. Gandalf61 (talk) 16:11, 15 June 2011 (UTC)[reply]
How does cocaine get to the brain when sniffed if there is a bone between the nasal cavity and the base of the brain? — Preceding unsigned comment added by 70.136.157.251 (talk) 16:40, 15 June 2011 (UTC)[reply]
This one I know the answer to. For almost all of the classical sensory systems, the pathway from sensory organs to the cerebral cortex has a way-station in the thalamus. The olfactory system is the only one of the "five senses" for which signals can reach the cerebral cortex without passing through the thalamus -- olfactory receptors in the nasal epithelium project to the olfactory bulb, which projects to the olfactory cortex. Looie496 (talk) 18:19, 15 June 2011 (UTC)[reply]
I'm pretty sure the idea the OP is referring to is the one I described -- it is very commonly discussed in books or articles about the sense of smell. Looie496 (talk) 19:08, 15 June 2011 (UTC)[reply]
The sense of smell is so critical to the survival and brought such evolutionary advantage to early complex animals, that one could almost say that the brain is an extension of the olfactory bulbs rather than visa versa. http://www.sciencemag.org/content/332/6032/955 You can't get more direct than that. Later, part of this neural complex became light sensitive and became eyes. These developments happened independently in several different lifeforms. Someone may also be able to find reference to the sense of smell in humans, still over-riding all one's other senses. --Aspro (talk) 19:53, 15 June 2011 (UTC)[reply]
spin current
An electrical current is generally unpolarized (consisting of 50% spin-up and 50% spin-down electrons); a spin polarized current is one with more electrons of either spin. By passing a current through a thick magnetic layer, one can produce a spin-polarized current. http://en.wikipedia.org/wiki/Spin_transfer
how come current is composed of half spin up and half spin down?
is spin up magnetic north and spin down magnetic south? (apparently this is true is it correct Spin "up" would mean the electron is acting like a bar magnet whose north pole is pointing up; spin "down," the opposite.) — Preceding unsigned comment added by 82.38.96.241 (talk) 21:09, 15 June 2011 (UTC)[reply]
To be precise, half of them have the vertical component of the spin up while the other half has that component pointing down. The horizontal component being unknowable (which is not the same as unknown). Imporntant note: We talk about spin up and down by convention but we could just as well talk about spin left and spin right, or spin forward and spin backward if so we wished. Dauto (talk) 21:19, 15 June 2011 (UTC)[reply]
so is there only really 2 directions of spin and they happen to provide the effect for the north and south magnet — Preceding unsigned comment added by 82.38.96.241 (talk) 21:22, 15 June 2011 (UTC)[reply]
It is more understandable to say that for unpolarized electrons the spin points in a random direction in space; however, the nature of quantum mechanics is that we can only ever measure one component of it's direction per electron. So we pick an axis in space (call it vertical), and see how many of them have a positive vertical component (up spin) and how many have a negative vertical component (down spin). Another aspect of quantum mechanics is that we can only really get positive or negative (not a magnitude). If you have a consistently polarized spin current you can get more information about the spin orientation by measuring many electrons, but you are strongly limited about the information that can get from any single electron because the act of measuring it changes it. Dragons flight (talk) 22:03, 15 June 2011 (UTC)[reply]
(EC) It's not really that there are only two directions of spin. Rather, it's a matter of no matter which direction you arbitrarily choose, if you measure the spin of an electron along that direction, there are only two possible values that the spin can be measured to be. So if you measure the spin along the z direction, for example, the spin will either be in the +z direction or the -z direction (the magnitude of the spin will be the same either way). The amount of spin in each of the x, y and z directions are not independent; after you measure the spin along one axis, you can't know anything about what the spin is along the other two axes. The measurement process basically messes up the spin along any orthogonal direction. For example, if you measure the spin in the z direction and it's in the +z direction, and then measure the spin in the x direction, and then measure the spin in the z direction again, it's a 50/50 chance as to whether the spin will be measured to be in the +z or -z direction in that final measurement. Red Act (talk) 22:08, 15 June 2011 (UTC)[reply]
ADHD Medication Rankings
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, 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 Reference Desk's talk page.
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 Reference Desk's talk page. --~~~~
Monkey from Antalya, Turkey?
Sorry, if this is not the best place to ask this question. Can anyone tell me what kind of monkey this is? --Phagopsych (talk) 22:00, 15 June 2011 (UTC)[reply]
Please do your own homework.
![[19]](https://en.wikipedia.org/wiki/Image:Carbenes.png){kind=link}
