Wikipedia:Reference desk/Archives/Science/2007 March 14

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March 14

Interested?

I've listed a reward for the creation of the article Interdental plate on the Reward board. It's an easy job & would help me & other articles in the long run. I didn't know where else to post this message, but I figured a bunch of master mind/science guys would be patrolling around this page, so I posted here. Hope you don't mind. Thanks for reading - Spawn Man 06:33, 14 March 2007 (UTC)

• I have created a decent stub with three references. I look forward to seeing what others can add. Johntex\^talk 06:40, 14 March 2007 (UTC)

Great work Johntex. The reward has been completed & your barnstar awaits you. The article looks great, but if anyone wants to expand it, go right ahead. I might post more reward notices here soon, so keep an eye out guys (& girls). Thanks again... :) Spawn Man 06:53, 14 March 2007 (UTC)

Its a struggle finding material for this, but I eventually found an important use for it in fossil cladistics! Rockpocket 07:42, 14 March 2007 (UTC)

Alcohol and Muscle loss

My trainer says that everytime I drink alcohol, I lose some muscle, is there any truth in this? —The preceding unsigned comment was added by 76.167.136.84 (talk) 06:52, 14 March 2007 (UTC).

I am not a professional trainer, but I guess that's complete nonsense. Some people say, however, that alcohol contains a lot of calories, what means that you will get more fat and, therefore, less defined. "Maybe" your trainer meant that. --Taraborn 12:51, 14 March 2007 (UTC)

Alcohol denaturates proteins. Since muscles do basicly consist of proteins they might be destroyed by alcohol. This is also true for brain cells and every other cell type. However, the effect depends on the dose. Falk Lieder 17:06, 14 March 2007 (UTC)

Rubbish. [Mαc Δαvιs] (How's my driving?) ❖ 19:15, 14 March 2007 (UTC)

As for the affects on "intelligence" caused by heavy drinking, it could be useful to note the case of the really heavy-drinker Alexandre Alekhine. --Taraborn 21:29, 14 March 2007 (UTC)

Yes, alcohol does denature protein, however, the idea that it would somehow leap out of your blood vessels, burst through the cell membrane and start going to town on your muscle cells is at best rather silly. Alcohol is high in 'empty' calories, but it woun't 'destroy' muscle tissue. Wintermut3 18:04, 15 March 2007 (UTC)

smd vs. through-hole (moved from Computing desk)

In the case of a varistor, how do its parameters such as maximum energy and maximum continuous voltage vary when you convert a through hole varistor to an SMD? thank you.Gfranz G 03:03, 14 March 2007 (UTC)Gfranz [--Ouro (blah blah) 07:13, 14 March 2007 (UTC)]

What do you mean by "convert"? Cut/bend the leads so it will surface-mount? Continuous voltage obviously wouldn't be affected. Power ratings might vary a bit but I'd imagine they'd vary just as much depending on the lay-up of the PCB; soldering the varistor leads into/onto massive ground or power planes would obviously have some positive benefit to the long-term power rating although the impulse rating probably wouldn't change noticeable.

Atlant 12:05, 14 March 2007 (UTC)

The RF characteristics more than anything else are prone to being affected by lead geometry. -- mattb @ 2007-03-14T17:10Z

Varistors have RF properties? Are you sure you're not thinking of varicaps (varactors) ;-) ?

Atlant 16:11, 16 March 2007 (UTC)

Thanks for taking the time in answering my question but I guess I didnt communicate my ideas well. What i meant by "converting" is to look for an SMD equivalent of a present through-hole varistor. In my case, the maximum continuous voltage of my through-hole varistor is 275Vdc and its maximum energy is 104J. I've looked up to the internet looking for SMD Varistors with the same or even almost equivalent parameters but the maximum contiuous vaoltage that I saw was around 56Vdc and worse for the maximum energy, the highest value that I got was 1.5J. that is why I was thinking that maybe some of the parameters of a varistor would be changed when it is "converted" from through-hole to SMD.

Gfranz G 00:40, 15 March 2007 (UTC)Gfranz

Varistors depend a lot on their physical size. For example, the pulse energy rating is directly proportional to the volume of "varistor material" that you're heating with each energy pulse. So small SMD devices can't possibly have the same pulse energy ratings as big, heavy devices.

Atlant 11:46, 16 March 2007 (UTC)

science behind the instrument triangle

Im doing a sound wave assignment in yr11 physics and i need to find out the science behind the instrument triangle but i can't find a thing on the internet. If anyone knows anything about it i would be very gratefull if they would share it with me.

Information after the 19/03/07 will be to late for my assignment

Thanks to anyone who helps —The preceding unsigned comment was added by 202.83.76.13 (talk) 09:40, 14 March 2007 (UTC).

I think you'll find that a triangle isn't so special; it's mostly just a compact form (of a cylindrical chime) that's cheap to manufacture. You might investigate this with a stroboscope. You might also consider tubular bell and mark tree.

Atlant 12:10, 14 March 2007 (UTC)

Resonance is my most favourite subject, but I can't find anything I really like with Triangle (instrument), and Bell (instrument). Link all of these with Standing waves, and you have a good paper. --Zeizmic 12:24, 14 March 2007 (UTC)

When you touch something, your atoms don't actually hit its atoms?

Hi all. I read somewhere that when you touch something, your atoms are not actually touching the atoms of the other object, but the electromagnetic force it exerts on your atoms, or something like that. Can someone please give me the specifics of that, as I found touch unhelpful. Or a wiki article referencing it would also be useful. Much help appreciated ! Xhin Give Back Our Membership! 09:56, 14 March 2007 (UTC)

Well, it really depends on how you definte touch. Everything is made of atoms, so practically, you're touching atoms. You're made of atoms, and the atoms on your hands are touching the atoms of whatever you're touching.

but if you want to get technical about it - then yeah, atoms don't actually "touch" atoms. It's like, the bits of one atom doesn't actually physically bump into the bits of another atom. The feeling of "solid"-ness is more to do with the energy field or repulsion around atoms. Atoms are mostly empty space anyway.

Then again, you can also say that the atoms on your hands aren't touching anything, because your hands aren't clean - they've covered in grim and dust and bacteria and all the rest. Our articles on atoms would probably help you more. And you may be interested to look at Cold welding too. --`/aksha 10:15, 14 March 2007 (UTC)

It's all true, in a way nothing ever touches anything else (or at least very rarely, where nuclear reactions aren't involved). Atoms are mostly empty space, and the 'contact' you feel in your fingers, the force that stops you falling through a chair when you sit on it, or stops a liquid seeping through the sides of a solid container, is the electrostatic force between the electrons in the atoms of one body and the electrons in the atoms of the other. Spiral Wave 11:54, 14 March 2007 (UTC)

As has been said it depends on how you define "touch". If you think about it as proton-on-proton action then no, you never "touch" in a very base kinetic sense. However once you realize that what we really mean by "touch" is not proton-on-proton action then it is not that weird. --24.147.86.187 00:08, 15 March 2007 (UTC)

'Solid on solid' doesn't exist, even in nuclear reactions. Every 'particle' is surrounded by force fields and the particles themselves have no 'solid' physical shape or size - the closer one examines a particle, the more insubstantial it appears. That doesn't mean that a force field isn't 'solid' - try jumping off a tall building to see the damage that force fields can do.... Paul venter 06:56, 15 March 2007 (UTC)

Yeah, 'particles' are pretty much just bundles of forces in the first place. More practically speaking, no, you're not floating above the ground or repelling off furniture, any more than you're mostly empty space. As long as you can't fly or walk through walls, atomic physics is academic. Black Carrot 06:56, 15 March 2007 (UTC)

Until someone drops an atom bomb on your city, sure it's academic. -GTBacchus^(talk) 07:00, 15 March 2007 (UTC)

Planet Fire

If you sent a space probe down into the atmosphere of a planet or moon made up of high levels of methane or any other flammable gas. Could the probe theoretically ignite the methane and set the whole atmosphere on fire? —The preceding unsigned comment was added by 212.219.119.130 (talk) 10:15, 14 March 2007 (UTC).

Not really. You need fuel+oxygen. If the atmosphere already consisted of fuel+oxygen then things like lightning or volcanoes would have set it off, in all probability. Pure methan can't burn unless there is an oxidant present. Greglocock 11:31, 14 March 2007 (UTC)

It's worth adding that, despite the massive abundance of oxygen in the universe, free (or molecular) oxygen is notoriously rare in planetary atmospheres, very rarely enough to fuel any sort of combustion. (Although ozone seems to crop up nearly everywhere.) Spiral Wave 13:02, 14 March 2007 (UTC)

The lack of free oxygen in planetary atmospheres - is precisely because if it existed, it would react with something and then it wouldn't be free oxygen anymore. The only reason we have it here on earth is because we have photosynthesis in plants continually pulling CO2 molecules apart and releasing free oxygen into the air. For this reason, if you did find a planet with abundant free oxygen, it would almost certainly be an indicator that there was life there. —The preceding unsigned comment was added by SteveBaker (talk • contribs) 16:59, 14 March 2007 (UTC).

The oxygen formed during photosynthesis comes from water molecules. The oxygen atoms from CO2 end up in organic compound such as sugars; see carbon fixation. --JWSchmidt 20:40, 14 March 2007 (UTC)

Jupiter, for example is mostly comprised of hydrogen which is highly flammable, but it cannot "burn", see Fire triangle. The vast majority of oxygen that is present is tied up in other chemical compounds, mostly water. Also, unless the oxygen concentration is large enough (beyond 5% or so) sustained fire is impossible, so any sort of "spark" will die. I'm not sure of the mechanism, but the Helium article gives the impression that the Helium mixed with natural gas (mostly methane) prevented combustion. Atropos235 23:58, 14 March 2007 (UTC)

c:) HS7 21:15, 14 March 2007 (UTC)

This also means that a lander could use a "jet engine" by supplying only the oxygen, and using methane from the atmosphere. This is the opposite of a jet engine in earth's atmosphere, where we carry the fuel and use oxygen from the atmosphere. -Arch dude 01:08, 15 March 2007 (UTC)

Magnetic strip

An easy way to check whether a magnetic strip is working or not? Another easy way of nullifying it? Thanks. --Taraborn 12:50, 14 March 2007 (UTC)

Per your first question: Dip it in Magnasee. Pass it through a skimmer.

Per your second question: Use a degausser. Run a rare-earth magnet along the stripe. Scrape the magnetic stripe entirely off.

Atlant 15:56, 14 March 2007 (UTC)

I had a magnets set when I was younger. It contained some sort of dull greenish "wax-paper" that could be laid on top of a permanent magnet. It would sort of glow brighter green indicating the field strength (I think I remember even seeing sharp green lines, which I always assumed were the division between north- and south- pole, but in retrospect, they are more likely transition regions between differently aligned magnetic areas). What in the world could that greenish paper be made of? Nimur 20:46, 14 March 2007 (UTC)

Apparently it is Magnet Viewing Film. Do we have an article? Nimur 20:48, 14 March 2007 (UTC)

Great answers! Thank you very much. --Taraborn 21:33, 14 March 2007 (UTC)

Acidity of oil

I read that the difference between extra virgin olive oil and regular olive oil is the acidity. Since oil and water don't mix, how can oil have acidity? --69.155.128.15 15:07, 14 March 2007 (UTC)

Fatty acids. See the Olive oil article for a starting point.

Atlant 15:53, 14 March 2007 (UTC)

How does taking breaks restore mental capacity?

I have read many suggestion on when and how long one should take breaks. However, I don't know any experiments on this subject. I also wonder how taking breaks restores mental capacity. Are there any neural correlates of mental capacity? If yes, do they change during demand and reverse during breaks? How well can blood sugar levels explain the effectiveness of breaks? Which effects do breaks have in addition to reducing monotony? I am looking for some information on research findings and references. Falk Lieder 16:56, 14 March 2007 (UTC)

Your subconscious mind often continues pondering things even while you're taking a break (or even sleeping). Unconstrained by the rigorous direction of your conscious thought processes, it often manages to look at your current problem from a new, unique, and useful point-of-view, thereby seeing a solution (or three).

Atlant 17:09, 14 March 2007 (UTC)

Breaks bother me. My mind works in turbo-charged mode, normal, or boring mode. I just do whatever each one tells me to do :) Boring mode, means sleep. Normal is normal, and turbo-charged means writing, reading, and talking. If I am like that I don't want to take a break and lose that, or my chain of thought. Lose the sense of discovery and learning. [Mαc Δαvιs] (How's my driving?) ❖ 19:14, 14 March 2007 (UTC)

I remember reading that a chemical in your brain is exhausted as you study/work/do whatever, and by taking a break, you allow the brain to recover its reserves of said chemical. I've been trying to remember the name of the thing for the last five years, though... Titoxd^{(?!? - cool stuff)} 19:59, 14 March 2007 (UTC)

Maybe you should take a break for a few minutes. [Mαc Δαvιs] (How's my driving?) ❖ 20:46, 14 March 2007 (UTC)

Improve hearing with training

Is it possible to improve your hearing by training yourself? Kind of like you can train your memory. Thanks in advance, Jack Daw 19:36, 14 March 2007 (UTC)

You can improve your listening skills by listening. You can practice identifying sounds, hearing a person speaking in a croud, identifying the direction a sound comes from. These will all involve the higher brain function rather than the brain stem nuclei improving. I dont know about improving your hearing however - cut down on the alcohol consumption and loud noise or music and clean the wax out of your ears! GB 20:54, 14 March 2007 (UTC)

Of course any ear doctor would recommend not sticking anything in (or even near) the ear canal without proper medical training. [Mαc Δαvιs] (How's my driving?) ❖ 21:02, 15 March 2007 (UTC)

Rumour

Is it true that you can get high off Earl Grey tea? I seriously doubt it is true, but people i know are convinced it is true, i cannot understand any scientific reason why you could get a 'high' off it.

Thanks a lot Dave 19:57, 14 March 2007 (UTC)

Bergamot orange says the oil has been linked to several negative side-effects such as photosensitivity (due to the chemical bergaptene) and the prevention of intestinal absorption of potassium. ST47Talk 20:49, 14 March 2007 (UTC)

If they are smoking the tea, they may be suffering from oxygen deprivation as the smoke displaces air in their lungs... Nimur 21:06, 14 March 2007 (UTC)

I have also heard this; the 'high' supposedly kicks in only upon smoking exceptional (although the numbers I do not have) amounts of the tea leaves. But I also suppose, if you'd be doing this with good Earl Grey, that it's a waste of perfectly excellent tea. --Ouro (blah blah) 21:41, 14 March 2007 (UTC)

I also seriously doubt it is true. BTW, how much does an ounce of "Earl" cost?  ;-) --hydnjo talk 00:19, 15 March 2007 (UTC)

What, are the banana peels not doing the trick? Never underestimate the ability for people to be willing to believe and re-tell utter nonsense. --24.147.86.187 03:45, 15 March 2007 (UTC)

I don't know about ounce, but a few months back I had bought really wonderful Earl Grey, selling for 8 Euro for half a kilo (=just a bit more than a British pound) in Germany. So, at rough count, it's equal to 16 ounces, so it's something round 50 cents for the ounce. The brand is Messmer, if I may. --Ouro (blah blah) 06:17, 15 March 2007 (UTC)

In Simon and Garfunkel's 1966 satirical song A Simple Desultory Phillipic, the amount prescribed is "a pint of tea a day". But maybe we were all just being Phil Spectored?

Atlant 11:53, 16 March 2007 (UTC)

S&G might be right, but I drink a lot more nonetheless. As noted here. --Ouro (blah blah) 18:47, 16 March 2007 (UTC)

base metals

I have searched for info regarding base metals, specifically gold, sodium, and magnesium. I'm certain that gold is a noble metal. I'm fairly sure that magnesium is a base metal, but sodium confuses me. Sodium is referred to as a alkali metal and magnesium is referred to as a akalne earth metal. Does that description answer my question or am I missing something? Thank you for your help.

Base metals are common, such as copper lead zinc or tin. Although sodium is common as an atom it is not often found as a metal. Magnesium is a marginal case as you noticed, I would not have counted it as a base metal as it is still slighly exotic. GB 21:06, 14 March 2007 (UTC)

There are articles on gold, sodium, magnesium, base metals, alkali metals and alkaline earth metals. Take a look and start from there. I'd answer myself, but chemistry was a looong time ago :) Cheers. --Ouro (blah blah) 21:38, 14 March 2007 (UTC)

According to the first, chemistry, definition of Base Metal given in the article Base metal, it looks like magnesium and , I'd say, sodium are base metals. According to the alchemical definition, they probably aren't, although they're not really precious metals either (in the alchemical sense) or noble (in the chemistry sense). Since it looks like you're looking for chemistry, I'd say they're both base, but I'm not sure how useful such description is. Oh, and I'm pretty sure the use of the word 'base' here is unconnected with acid/alkali, in case that was the problem! If you're looking for an alchemical answer, based on their value and such like, I don't think the alchemists had them. Skittle 00:35, 15 March 2007 (UTC)

PE at absolute zero

Hi all,

I have a physics simulation that I'm working on which models the movement of atoms. With this model, I can add or subtract heat from the system, and am able to move down to absolute zero where there is no motion. All the particles in the system are essentially frozen in place.

When I stop actively subtracting energy, the model slowly warms back up again. Looking in closer depth, I see that this is because the attractive forces between the atoms, however slightly, draw the atoms towards each other, which causes motion. That is, when the atoms in my model are at "absolute zero", they still have some potential energy.

Wouldn't this happen in the real-world (were it possible to reach absolute zero, which it isn't)? Or, if a system is at absolute zero, are all the atoms in the system at exactly the right distance such that their attractive forces and repulsive forces are absolutely balanced?

Thanks,
Michael 20:50, 14 March 2007 (UTC)

Of course this will depend on how you model your attractive forces. Can you shed some light on what attractive/repulsive system you are using? If you are using 1/r^2 (inverse square law forces), I think I recall that there are only stable equilibria for certain configurations. Also, be aware of numerical error (roundoff or quantization error) in any computational simulation - this error may accumulate depending on your method of computation. Also, it sounds like your "subtracting of energy" is done by decreasing the velocity - in that case, it is only affecting Kinetic Energy. In that case, you are not affecting Potential Energy at all. Can you describe your model a bit more? Nimur 21:01, 4 March 2007 (UTC)

In real life the collection of atoms will warm up by energy coming in from outside. If there is potential energy that can force an atom to move it is not at absolute zero. An isolated collection of atoms staying in the same position, that is not undergoing some transformation (eg chemical or radioactive) should stay at the same temperature. Nether-the-less there is still unextractable energy at absolute zero, due to the uncertainty principle. An atom in a fixed position cannot have its veolcity or energy known precisely, or coversely if you precisely know the energy of an atom, you will not know its position. Interesting things hapen when the uncertainty in the position becomes macroscopic. GB 21:02, 14 March 2007 (UTC)

1) Yes, the energy is "subtracted" by slowing down the atoms. Since temperature is the average KE, then slowing down the velocity to zero will make the temperature zero Kelvin. When I said there was still PE, what I meant was that there was still a force on the atoms from the other atoms which would incline them towards motion

2) If we were to suddenly make all atoms in the universe absolutely motionless for an instance, removing all their KE and momentum, would they not return to motion again because of the forces between them? This is the situation my model seems to be in.

3) Am I right in thinking that, at real absolute zero, the atoms ought to be in some stable configuration around each other?

Thanks --Michael 01:25, 15 March 2007 (UTC)

Regarding your first point, I want to add that there's a bit more to absolute zero than the stopping the motion of whole atoms. Absolute zero implies the total cessation of thermal motion: no vibrational motion in the nucleus, no orbital motion of the electrons, nothing. And if you could "stop" the electrons, then all sorts of funny stuff would happen (and very little of it stable). (Edit: 2 am and back from the pub, this was meant to be read as tongue-in-cheek, but it doesn't come across as such. My apologies again.) So asking what happens when everything gets - if I may paraphrase - "slowed to a stop" is probably not going to properly answer your question. Instead, you would do better to try and model what happens when you get arbitrarily close to zero, a more physically realistic getup. Spiral Wave 01:58, 15 March 2007 (UTC)

No, I'm sorry, that's just not accurate; absolute zero does not imply anything of the kind. It doesn't even imply that the individual atoms are not moving. In fact, they are moving, even at absolute zero.

You have an overly simplistic notion of what "absolute zero" means. It can't be characterized completely in terms of motion. What it means is that the first derivative of entropy with respect to internal energy is infinite. --Trovatore 02:40, 15 March 2007 (UTC)

While I would agree that I have an overly simplistic view of A.Z., the point that it can't be completely characterized in terms of motion is exactly what I was trying to get across. I wasn't concerned with being overly accurate; just to show how bizarre things become (although I plainly pushed it way too far; my apologies to our questioner). That mathematical description of entropy is of course far better; but it's not going to help this person with their physical model, which is why I linked the appropriate subsection. Spiral Wave 02:55, 15 March 2007 (UTC)

Correct if I'm wrong, but I understood that AZ had no Latent heat in the system. This implies a solid and an equilibrium such that bonds of the solid have any potential energy transfer due to vibration and attractive forces are balanced by the forces of the solid. --Tbeatty 03:07, 15 March 2007 (UTC)

Helium is not a solid at absolute zero (at atmospheric pressure). --Trovatore 03:15, 15 March 2007 (UTC)

It's a meaningless question - the Third law of thermodynamics says that no real world system can ever reach absolute zero. It's similarly meaningless to say what happens to Helium at a temperature that it simply can never reach. SteveBaker 06:32, 15 March 2007 (UTC)

Not at all. As I recall, the superfluid phase of Helium II is at absolute zero. Liquid helium below the lambda point is a mixture of Helium I and Helium II, so the system as a whole has positive temperature, but if you restrict attention to just the Helium II, it's actually at absolute zero.

Neither is it impossible in principle for a body to reach absolute zero. You can't get it there mechanistically, but if all the phonons radiate away just by chance, it can get there on its own. Entropy reversals can happen, if you wait long enough.

The point is that the zero-point energy of helium is sufficient to overcome the interatomic attraction. While you can't (at least on purpose) get its internal energy down that low, you can get very close indeed, close enough to tell that the little bit you have left to go is not enough to allow interatomic attraction to cause the helium to freeze. This, if you like, is the real-world meaning of the statement, without waiting for all the energy to radiate away by chance. --Trovatore 06:57, 15 March 2007 (UTC)

Indeed, you can get arbitrarily close, which is why I think our questioner would be better off trying to describe a superfluid (or a supersolid) rather than worry about what happens at zero itself.

The helium II is a good case, but it depends on the complexity of his model; a thermodynamic description of one component of a 2-fluid mixture may or may not be of any use. (Is it, Michael? I'm curious myself, now!) Spiral Wave 10:10, 15 March 2007 (UTC)

Individual atoms (or, I guess, very small groups) could happen to get to a zero energy state - but temperature is a bulk property and the laws of thermodynamics most certainly apply. SteveBaker 14:58, 15 March 2007 (UTC)

The laws of thermodynamics are probabilistic, and apply only probabilistically. That means they can be violated just by chance. The chance is extremely small, of course, but if you're arguing that something is meaningless because it can't happen, well that's wrong. --Trovatore 17:30, 15 March 2007 (UTC)

The short answer is Simulations with classical mechanics can't reproduce 0 Kelvin - you need Quantum Mechanics. WilyD 15:21, 15 March 2007 (UTC)

Fine fine, let's call it "arbitrarily close to absolute zero". It doesn't really change my question. If I suddenly slowed all the atoms in, say, a liquid, so that their KE was arbitrarily close to zero, but they remained in the same general location as before I slowed them down, they would still have attractive and repulsive forces between them, right? So in this bizzare simulation, I'd expect the atoms to start speeding up again, right? Or not? --Michael, 16:46, 15 March 2007 (UTC)

You can't just stop the atoms in place where they happen to be, they have to moved to the position where they have no potential energy, as you have already observed they will start moving again. You need to take out all the available energy to get to AZero. GB 00:40, 16 March 2007 (UTC)

what is the difference between denaturing and melting?

ditto.

HS7 21:17, 14 March 2007 (UTC)

Depends on context, of course, but Denaturation (biochemistry) and Melting may help. If you are talking about these in terms of DNA, then "melt" is just a term often used to descibe the denaturation of a double strand into two single strands. Its not technically an example of true melting. Rockpocket 21:22, 14 March 2007 (UTC)

They both seem the same to me, things falling apart because of the particles they are made from moving more :( HS7 19:08, 15 March 2007 (UTC)

Yeah, they both involve the same molecular process, but the difference is the change in state. Melting requires a change from s solid to a liquid, denaturation doesn't. Rockpocket 19:19, 15 March 2007 (UTC)

What is rescued virus?

Hi all, Can anybody please tell me what is rescued virus as they are making in all of the experiments and why we need to make them in the experiments? I am referring about the virology and molecular biotechnology stuff. Thanks! --Nirajrm ^{talk ||| sign plz!} 22:37, 14 March 2007 (UTC)

I'm not 100% sure, but I think a "rescued" virus is a virus that is missing in its genome a key component for viral replication, but when infected into a cell line expressing that key component, allows replication. As to why that strategy is used, there could be several reasons (control of replication, protein/gene of interest is what's "rescued", other things I don't know about since I'm not a virologist...). Hope that's sorta right, and it helps. -- Scientizzle 03:01, 15 March 2007 (UTC)

In molecular biology the term "rescue" is typically used in the sense "recover". Plasmids, genes and other entities can be rescued from cells containing them. In the context of viruses the term is most often used to mean recovery of infectious virus particles from a cell line that has been transformed with one or more pieces of viral DNA. This way the researcher can first manipulate the viral sequence using standard molecular biology techniques (e.g., pcr) and subsequently obtain virus particles containing the manipulated viral genome. This is useful for vaccine construction for instance. [1] -- Gorm 12:12, 15 March 2007 (UTC)

Thanks a lot and I think I got the answer. Thank you Scientizzle and Gorm! --Nirajrm ^{talk ||| sign plz!} 21:39, 15 March 2007 (UTC)