Wikipedia:Reference desk/Archives/Science/2006 October 31

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October 31[edit]

Sense of humour[edit]

Does a persons sense of humour depend upon the serotonin levels in the brain? If so, should these mentally affected people be criticised for making jokes that others may not find very funny? (not just on WP but verbally too)--Light current 01:41, 31 October 2006 (UTC)

Serotonin has nothing to do with humour. However, it is something that is not controlled - you do not choose what you find funny and not funny. It is based on many things (listed in humour. Being criticized for making offensive jokes has nothing to do with homour either. It has to do with etiquette, maturity, sympathy, and compassion - among many other things. --Kainaw (talk) 01:54, 31 October 2006 (UTC)

Are you really sure about that?

In the central nervous system, serotonin is believed to play an important role in the regulation of mood, sleep, emesis (vomiting), sexuality and appetite. Low levels of Serotonin have been associated with several disorders, notably depression, migraine, bipolar disorder and anxiety.

my links/ bolding. And do you know what mania is? --Light current 01:59, 31 October 2006 (UTC)

Are you trying to claim that mood and depression equate to a sense of humour? A sense of humour is what your brain identifies as being humorous. You can be angry and laugh at a fart. You can be happy and laugh at a fart. You can be suicidal and laugh at a fart. Your mood or state of depression may change how much you laugh, but it doesn't change how your brain reacts to a fart. --Kainaw (talk) 03:13, 31 October 2006 (UTC)
They dont equate to it but obviously affect it. Which is what I indicated in the question. Do you laugh more at silly things after a few drinks?--Light current 03:36, 31 October 2006 (UTC)
Also in answer to Kainaws last post:

You can be pissed as a fart and laugh at your brain.

Now is that funny in this context or not?--Light current 11:54, 31 October 2006 (UTC)

Actually, I believe a sign of depression is a lack of ability to laugh at things. So, there is a link between depression and (lack of) humor. StuRat 05:44, 31 October 2006 (UTC)
What I was trying to point out is that a "sense of humour" is not based on how much a person laughs. It is called "sense" because it is a "sense". Regardless of your emotion, an anchovy will taste salty because your "sense of saltiness" still functions to tell you if it is salty or not. The same with humour. Your sense of humour tells you is something is funny or not. It is up to other parts of your brain to control the reaction to that sense. Now, if Light Current asked something along the lines of "Do serotonin levels control how much a person laughs at things they find funny?" I would have had a completely different response. --Kainaw (talk) 13:51, 31 October 2006 (UTC)
Yes OK. But I still think I am inclined to find certain things funnier than others do when Im a bit high. When Im low even very funny things may not elicit a response from me. Also the amount I laugh is proportional to how funny i find things at the time. Its funny isnt it? So therefore my sense of humor does get more or less acute with mood. Or am I missing something?--Light current 14:02, 31 October 2006 (UTC)
It is well known that THC affects a person's sense of humour. With enough THC, everything is perceived as "funny", as in "Man, I just broke my leg. That is so funny!" You can chemically override the brain's functions in many ways. Also, it is getting a bit semantic when you say that your mood affects how funny you find things. My opinion is that your sense of humour decides "funny/not funny". A completely different part of the brain decides "how much do I laugh". Assuming you are not chemically influenced, something you do not find funny will not make you laugh regardless of your mood. However, I feel you've missed the point that I was half supporting your apparent opinion and half disagreeing with it. In support, a person's sense of humor is a sense that is not controlled (without chemicals). So, if my brain tells me that watching nuns fall off a cliff is funny, I can't turn off my sense of humour. I'm stuck with it. In disagreement with you, I do not feel that making offensive jokes is beyond a person's control. To switch topics slightly (making a clearer point), my father-in-law talks about boobs nonstop. We take him out to Outback and the conversation goes,
Waitress: "Hi, I'm Kathy and I'll be your waitress."
Father-in-Law: "Are your boobs real?"
Control over what you say (or type) is expected. Blaming everyone else for your inability to socialize is not a solution. You can find things funny, but you are not required to vocalize everything that goes through your brain. As much as I'm disgusted by humans, I would have been banned from Wikipedia long ago if I said everything that I thought. --Kainaw (talk) 14:33, 31 October 2006 (UTC)
Well you aint seen it with the filter removed! (be thankful). Whats THC BTW? OK found it. I may be a dope , but I dont smoke it!--Light current 14:44, 31 October 2006 (UTC)
I think the key word of your question is should. Science generally can answer questions about what is, but what we should bame people for (what should be) are not answerable in science. So says, at least, David Hume and the Naturalistic fallacy. We have no answer to what we should blame people for, since normative questions are not in the realm of science. --TeaDrinker 04:10, 31 October 2006 (UTC)
There's a difference between the emotional intensity one gets when receiving a joke and the inability to come up with jokes that are humorous. If your jokes get no laughter it's not due to anyone's seratonin, you're just not funny. Ƶ§œš¹ [aɪm ˈfɻɛ̃ⁿdˡi] 06:21, 31 October 2006 (UTC)
Ah well. Humor is in the mind of the audience I suppose.--Light current 11:23, 31 October 2006 (UTC)
Check your serotonin level: Wikipedia:Reference_desk/Science#Of_mice_and_lab_rats . Worked for me, but I'm on SSRI --GangofOne 07:10, 31 October 2006 (UTC)
I think maybe this should now be moved to Talk:Humour as it has become more of a discussion. Any objections?--Light current 14:54, 31 October 2006 (UTC)

Burnt Stock Pot[edit]

I have an Aluminum (might be stainless steel) stock pot which, in a moment of stupidity, I left on high heat with nothing in it for at least 5 minutes (before I removed it, I heard several large BANG noises). A patch of the bottom appears to have burnt and changed color to blue. It's a relatively small patch.

Basically, can I keep using this pot safely? These things are quite expensive and I'd rather not have to buy a new one....

--Wedgeoli 04:39, 31 October 2006 (UTC)
I would say no, from your description it sounds ruined to me, but it's up to you to judge. StuRat 05:39, 31 October 2006 (UTC)

Almost certainly stainless steel rather than aluminum. Stainless steel contains chromium and nickel both of which are transition metals which have coloured oxides. Theresa Knott | Taste the Korn 06:03, 31 October 2006 (UTC)

As long as its only your outside bottom thats burnt, and the inside is still clean, I see no reason why you cant still use it. THe loud bangs will have been the bottom expanding and maybe buckling slightly. If on examination you find no crack in the bottom, then I think youll be ok. OTOH if you have permanently bent your bottom, then it may no longer sit comfortably on the stove. 8-|--Light current 10:27, 31 October 2006 (UTC)

I agree that it was probably stainless steel. Rainbow-like changes of colo[u]r would be charateristic of overheated steel whereas melting would be more characteristic of alumin[i]um ;-). I've never heard that the color changes were hazardous in any way, though, and they can sometimes be completely or partially polished out with a mildly-abbrasive cleaner (in the United States, Bon Ami, Comet/Ajax, or Zud, in roughly increasing abbrasiveness). If it was a multi-layer pot (stainless steel clad aluminum), the bangings might have been ruptures in the bonds between the layers. If this occurred, the pot might no longer heat as uniformly as before. And I agree that if the pot shows any cracks, discard it; you don't want it to fully fail while loaded with hot liquids!

Atlant 18:24, 31 October 2006 (UTC)

I've had experience with metal discoloration if you over heat while cutting or grinding and from experience, it is only the very surface that discolours, I'm guessing it's an oxidisation. I personally think you have nothing to worry about. Unless there is actual plastic deformation to either the top or bottom surface then I think you have absolutely nothing to worry about, even if the "layers" have slightly seperated. Vespine 22:07, 31 October 2006 (UTC)
I second the oxidation idea. Aluminum only has one oxidation state (3), which means that it won't change color when you heat it (it'll melt, but it won't turn blue like you described). Steel, however, is composed of chromium and nickel which certainly could have oxidized. This will not, I am thinking, be toxic or such. However, I *would* wash that pot out well first in case something reacted and got in your pot (unless you like REALLY crunchy beef stew) :) 22:32, 31 October 2006 (UTC)
I've had a similar experience with a small pot. It was/is stainless steel and I'm still alive Nil Einne 18:25, 1 November 2006 (UTC)


Do you think it would be possible, given the right environmental pressure, for, in a long time (i.e. few billion years), a population of bacteria-like "simple" organisms to be the descendants of a human population?

No, humans have evolved to the point were they can themselves solve any problems much faster than waiting for evolution to do it for them. Given the pressure to do such a thing, we would just manipulate our enviroment until it suited us the way we are. Philc TECI 10:25, 31 October 2006 (UTC)
You missed the questioner's point. I had to re-read it also. He is asking if a billion years of evolutionary pressure could result in simplification of an complex organism back to a form of protista that could reproduce asexually by mitosis. It sounds like the poor guy has had an even worse experience than J Alfred Prufrock, who only wanted to be a "pair of ragged claws" etc. I never thought about this, but there certainly have been examples of size reduction, of chromosome reduction, of abandonment of organs and body parts. I am doubtful if it could happen, but I think it sounds like a good senior thesis project, don't you? I would suggest some eukaryotic organism with a quick maturation time and simple breeding conditions, like a fruit fly. See if you can manipulate the environment to eliminate one feature after another... alteripse 12:25, 31 October 2006 (UTC)
Ok, maybe humans weren't the best example, as we do buck just about every trend. :) Philc TECI 17:02, 31 October 2006 (UTC)

That's exactly what I was asking. Wether there was a principle in our theory of evolution that would maybe prevent the "simplification" of organisms over time (is the process reversable). And i forgot to sign Keria 12:50, 31 October 2006 (UTC)

The common misconception is that evolution always leads to larger, more complex organisms. Evolution doesn't care, it goes with whatever works. A classic example is a retrovirus, where "retro" means "backwards from the typical evolutionary direction". A retrovirus is so simple, some are almost nothing but chunks of RNA (similar to DNA). Since they can't eat, grow, or reproduce on their own, they couldn't possible have existed before there were more complex cells around that they could use to reproduce. Think of them like a chain letter that says "copy me", they don't actually do anything, but their existence tends to cause copies of themselves to be produced. StuRat 13:08, 31 October 2006 (UTC)
I don't know if the concencus on retro viruses is that they evolved from more complex organisms. The reason they are called "retro" is they use reverse transcriptase, and undergo the reverse process for protein synthesis than all other life forms. The best example of evolutionary "simplifications" are internal parasites. Once they are within a body, the environment is constant, and therefore easier to survive. Their mouth parts generally become more complex, as they need to hang on, and their defence against the host's defences will also become more complex. But, they will lose all limbs, as well as many internal organs neccesary for terrestrial or marine life. --liquidGhoul 13:21, 31 October 2006 (UTC)
My name is TenOfAllTrades, and I approve this nitpick. Retroviruses are named for their use of reverse transcriptase to transcribe their RNA back into DNA—the reverse of the usual process.
Meanwhile, check out our article on viruses for at least a brief discussion of their possible organisms; note that at least one possible model is based on the same type of simplifications that LiquidGhoul describes above for multicellular parasites. Alternate explanations suggest that viruses developed from short stretches of genetic material and other macromolecules that escaped from existing cells and evolved from there. A third explanation is that viruses evolved in parallel with conventional cells in the RNA world. (It's possible that any or all of those three things could have happened at various times.) TenOfAllTrades(talk) 14:44, 31 October 2006 (UTC)
Thanks for the correction (my equating the "retro" in retro-virus with the "retro" in retro-evolution). I still subscribe to the theory that they are an example of retro-evolution, however. StuRat 18:46, 31 October 2006 (UTC)
Although I do agree with your theory, I wouldn't call it retro-evolution. This suggests evolution is supposed to be increasing complexity. It's not. There is no retro-evolution, just evolution Nil Einne 18:17, 1 November 2006 (UTC)

If environmental conditions changed, it is more likely that the existing simpler organisms just take over. This has happened many times in the fossil record. --Zeizmic 13:15, 31 October 2006 (UTC)

OK I take it that the answer to the original question is "yes". Keria 14:57, 31 October 2006 (UTC)

Probably, yes. There are examples of evolutionary simplification, though none as radical as suggested in the original question. Loss of tail in Hominidae, loss of limbs in snakes and some lizards, loss of gills, and loss of parietal eye seem to be valid examples. So is also the loss of a number of body segments and simplification of respiratory system along the evolutionary path of terrestrial arthropods. Neoteny can probably be considered as a rather general class of evolutionary simplification, too. There are also simplifications resulting from transition to parasitism (as in scale insect or many endoparasites) or transition to attached (immobile) lifestyle (as in barnacles). Please note though that in last two cases the larvae are not respectively "simplified". Keep in mind also that I am a physicist, not a biologist, so my perception of "simplified" may differ from that in the mainstream biological science. It would be very nice indeed to hear from an expert in the field. As for the reason why there are no extreme examples of evolutionary "simplification" - I think Zeizmic got it right. It would take far longer time for a slow-reproducing mammal to simplify itself back to basics than for a pre-existent bacteria to mutate. Thus, mutant bacteria will likely occupy the vacant ecological niche way before your "Homo trivialis" Dr_Dima.
It would strike me as rather unlikely though obviously not "impossible". Complex organisms, like complex societies, usually end up with a lot of distribution of labor. To attempt to scale that back down a point where fewer cells did more tasks seems unlikely to occur. But I'm going with the original question you asked in particular, not the additional ways it has been elaborated. I don't know if losing an eye or a limb makes one biologically more "simple". I would consider "simple" to mean "less complex", which biologically would seem to mean (to me at least, a non-biologist) a lot less specialization among cells. I don't want to say it's impossible (I would just be showing the limits of my imagination) but it does seem quite unlikely to have that occur on an organism-wide level. --Fastfission 15:25, 31 October 2006 (UTC)
Why does it have to be unlikely? The conditions on the Earth can change a lot in a billion years, going "backwards" might be the most favorable thing to do. X [Mac Davis] (SUPERDESK|Help me improve) 15:57, 31 October 2006 (UTC)

Wrong, the answer is "No."

We, and every living thing you see about you are at the current endpoints of long evolutionary lineages that have moved in the direction of more complexity from bacteria-like beginnings. While evolutionary changes are random, successful changes are heavily weighted toward increased complexity. The "goal," of course, is best fit with the environment. While it is true that some modifications are toward simplification — the reduction in modern horses' toes from five to three to one with a pair of functionless side splints, or the non-functionality of the human appendix — these are minor matters relating to the availabilty and variety of foods in the niche.

What is being suggested in the question is impossible for three reasons.
  1. All of the thousands of necesary modifications would have to fall in the less-likely direction of simplification.
  2. The modified descendent individuals would have to complete with their unmodified cousins during the billion-year interim. Loss of sense organs, manipulative organs, and brains would hardly give them an advantage.
  3. Even should the inconceivable happen, these neo-bacteria would then be in the same ecological niche as the real bacteria that already occupy it. These bacteria are the product of billions of years of descent with modification which has honed them to fit in perfectly in their environment. They would have a massive headstart on filling any posited neighboring niche that would open up in the next billion years.
So the answer is "no" because the choices are "up" or "out," and "down" is already out.
B00P 16:38, 31 October 2006 (UTC)
What tends to happen is when these pressures arise, instead of retro-evolution or whatever, the complex organisms that cannot cope just die out, leaving the simpler, faster reproducing organisms, which have less requirements, and also reproduce faster. Philc TECI 17:04, 31 October 2006 (UTC)
I agree with your point. I don't personally believe complex organisms like humans are likely to evolve in to bacteria like organisms. Not because they can't but because it's never likely to happen that way since there will always be other simpler organisms which will evolve in to these bacteria like organisms Nil Einne 18:20, 1 November 2006 (UTC)

Another example is cave-dwelling animals which lose their eyes. StuRat 18:48, 31 October 2006 (UTC)

Thanks! Good arguments.

I still can't find where it doesn't work. Leaving the theoretical principles to go back to an example: could we imagine a scenario where a mamalian population ends up as a microorganism? (ok I stretched it a bit with humans because we have such a control over our environment that we make our own niche).

Say: One species of mammals. Their environment gets warmer, they migrate towards the edge of the sea, warmer they spend half their time in the water, still warmer they become predominently aquatic (limbs become fins, lung turn "back" into gill-like system), surface acidity forces them to the bottom (lose eyes, pigmentation), more acid, less and less oxygen(gills aren't good enough anymore) etc... I haven't got enough knowledge to do the whole evolution backwards but it doesn't seem too difficult.

Of course here we follow the winners in the end, all the other species that branched off (modified or unmodified cousins) along the way are not taken into account.

The argument of the ecological niche of the microorganism being already taken is a good one but it doesn't seem to work that way to me. The taken position is only part of a system. The niche is in constant interaction with all the other "niches". So I don't see a problem with having the two populations (our heroes and the preexisting microorganism) cohabitting in the same environment, like they've always done. Especially as we come from more complexity the existing microorganisms seem like an interesting source of food or even like potentials for a symbiotic relationship.

When BOOP you say that the line of evolution has gone along more complexity, I would say that more complexity has been allowed by the environment and the constant interaction of organisms (I guess the biggest step was from mono- to multicellular). I'm not sure how we can make of "complexification" a general unbreakable rule of evolution. Can an organism go back to being a colony of cells? I'm not sure why it couldn't.

The idea of the possibility of the reduction (almost to the absurd I confess) is seducing because it really place mankind as a carrier of a principle (life) rather than as the pinnacle achievement of that same principle.

Thank you for all your thoughts (although I'm still ready to hear more).

Keria 17:37, 31 October 2006 (UTC)

Actually I'm going to vote "yes" (except for the prokaryote part). We already have human-derived cell-lines, so to go from a lab-hosted cell-line to a unicellular organism doesn't strike me as all that difficult. Guettarda 18:42, 31 October 2006 (UTC)

I would say yes, with one provision: the organisms currently occupying the next biological niche must first be removed, to make room for the new, devolved, organism. That is because those organisms already in the niche will be well-adapted to it, and thus able to out-compete any new entry into the niche, which will still need lots of "fine-tuning" to become competitive. StuRat 18:51, 31 October 2006 (UTC)
Actually that depends. Niches are probably overrated. Anyway, is "lab bench" an acceptable ecological niche?  ;) Guettarda 21:44, 31 October 2006 (UTC)
Again I agree with your points. But I also don't like the term devolution anymore then I like retro-evolution Nil Einne 18:22, 1 November 2006 (UTC)
I know what you mean, because phases like devolution and retro-evolution imply that there is something abnormal, or at least unusual, about organisms evolving into simpler forms. Still, I think the terms are useful shorthand for "evolution counter to the direction that people generally expect". StuRat 20:36, 1 November 2006 (UTC)

  1. Humans make machines with artificial intelligences.
  2. Humans become genetically engineered "pets" of the intelligent machines.
  3. Humans are engineered to be totally microbe-free.
  4. The intelligent machines take a trip to another star system, thaw some human germ cells out of a liquid hydrogen storage tank, and recreate a colony of their "pets" on a planet with no endogenous life. The only culture that the humans have is to be clean, happy pets; they know nothing about technology.
  5. After terraforming the planet by planting kelp and a few land plants, the artificial intelligences all merge into a giant MMORPG, leaving the humans to evolve as the only non-plant organism on the planet.
  6. Due to several problems with the terraforming including poor control of the composition of the atmosphere and inability of the atmosphere to control the high radiation output from the planet's star, the human population suffers a high mutation rate, never establishes a technological society, and over the course of a couple billion years, has descendants that fill many of the available niches of the planet's ecosystem, including a population of bacteria-like, single-celled organisms.
    --JWSchmidt 02:12, 1 November 2006 (UTC)

Too many assumptions. Microorganisms are necessary for the plants. Also there are the plants themselves. I think in the most cogent answers, the simpler life forms will adapt to changes more quickly (i.e. the system prefers making simpler organisms more complex). It is more likely that the other life will simply outperform the humans in your example and push them out. Think of mammals that returned to the sea. We already know that fish survive very well. They don't even need to surface for air for example. But mammals didn't retroevolve back to fish. They adapted their existing systems into more complex one. The other choice would be extinction. Nature would seem to prefer starting from a simpler canvas. Tbeatty 06:06, 1 November 2006 (UTC)

dry cell[edit]

how dry cell works? what gives rise the currentin a circuit? what is a current? what is direct current? what is alternating current? 11:41, 31 October 2006 (UTC)

See dry cell , electric current, direct current , alternating current--Light current 11:45, 31 October 2006 (UTC)

There's a kind of cool poetry to that answer+signature that wouldn't be there if anyone else had answered the question.

mysteries of mirrors[edit]

I'm short-sighted (I believe the correct term is myopic). without my glasses, objects far away are out of focus. when I look at a mirror - close enough for it's frame to be in focus, why are reflected distant objects out of focus?

thanks Spiggy.

Myopic is correct. The virtual image formed in a plane mirror is as far behind the mirror as the object is in front of the mirror (The article Mirror_image does not seem to mention this !). Imagine the mirror to be a window, which just shows the objects behind you but maintaining all the distances. So when you look at the reflection of a distant object (say at 10 metres in front of the mirror), you are looking at the image of the object which is 10 meters behind the mirror. -- Wikicheng 13:49, 31 October 2006 (UTC)

thanks - now I'm (more) confused. I thought that we see light reflected off objects, and in this case it's reflected off glass (aka mirror) a few inches from my face. (sound of brain melting). how can light be reflected off something in a 'negative' way? spiggy

There are two different types of reflection - see reflection (physics). You see an image of an object when light reflects off it in diffuse reflection. However, a (well polished) mirror reflects light in a different sense called specular reflection, which preserves the relative directions of light rays, and gives the illusion that you are looking at objects beyond/behind the plane of the mirror. You can't normally see the surface of the mirror itself - unless you make a mark on it, when you can see the mark because of diffuse reflection. Try making a mark on a mirror and looking at it close up - you should find the mark is in focus for you whereas the reflected images of more distant objects are not. Gandalf61 14:27, 31 October 2006 (UTC)

Some thing are easier explained with a drawing. Have a look at the following sketch I made for you. Observe that the important property that your eye has to accomodate for the focussing is how much the rays diverge. Rays from a nearby point diverge much and from a point far away diverge so little that they are nearly parallel. A mirror does not change this.


Simon A. 16:43, 31 October 2006 (UTC)

The mirror doesn't change anything to do with focusing, it merely "redirects" the light. If the object is 20 feet from the mirror and the mirror is 2 feet from your face, the light from the object has to travel 22 feet to reach your eyes and your eyes would have to focus exactly the same as if the object were 22 feet away from you in a straight-line path.

Atlant 18:46, 31 October 2006 (UTC)

Expense of PCR[edit]

Why is a PCR machine so expensive, if all it does is cool down and warm up at the programmed times and temperatures. I don't understand what could be so expensive about its construction to justify its price. --Username132 (talk) 14:59, 31 October 2006 (UTC)

There's a certain argument to be made that the instrument has to be very precise in its heating and cooling cycles; that it's a specialized tool sold in limited quantities, so there are fewer purchasers over which to spread design costs and other overhead; that it needs to be extremely reliable and trustworthy, and subject to extensive testing during manufacture—but mostly, it's VWR, Fisher Scientific and all the others just charging whatever obscene price the market will bear. If you're selling a tool to drug companies and well-funded institutions, there may be a bit of a tendency to mark up your prices a bit. Take what I say with a grain of salt, of course—I'm just a bitter grad student. TenOfAllTrades(talk) 15:16, 31 October 2006 (UTC)
see Make magazine, vol 07. instructions to build your own PCR thermal cycler. and other interesting biotech stuff. --GangofOne 19:19, 31 October 2006 (UTC)
'Specialist' equipment always costs more, regardless if it's actually technically more sophisticated or not. So yes, anything labelled with the 'biotech equipment' label is subject to a massive price markup. I've spent some time hanging out with a friend who works in a biotech lab, and it's something I've cracked more than one joke about. Know what they pay for the aluminum foil squares they use to cover those standard 96-well microplates? About $0.50 a piece! Sure, it's slightly thicker than the household variant, and it's free of any bacterial or DNA contamination, but it's still ridiculously expensive. --BluePlatypus 21:28, 31 October 2006 (UTC)

you all miss the key point: PCR machine manufacturers pay a license fee to the owners of the PCR and Taq polymerase patents. when you buy Taq, you only buy a license to use it in authorised PCR machines. Your machine only gets authorised if as a manufacturer you give a cut to the patent holders. and we all know where that money comes from. to quote:


A license under U.S. Patents 4.683.202, 4.683.195 and 4.965.188 or their foreign counterparts, owned by Hoffmann-La Roche Inc. and F. Hoffmann-La Roche Ltd ("Roche"), has an up-front fee component and a running-royalty component. The purchase price of this product includes limited, nontransferable rights under the running-royalty component to use only this amount of the product to practice the Polymerase Chain Reaction ("PCR") and related processes described in said patents solely for the research and development activities of the purchaser when this product is used in conjunction with a thermal cycler whose use is covered by the up-front fee component. Rights to the up-front fee component must be obtained by the end user in order to have a complete license. These rights under the up-front fee component may be purchased from Perkin- Elmer or obtained by purchasing an Authorized Thermal Cycler. No right to perform or offer commercial services of any kind using PCR, including without limitation reporting the results of purchaser's activities for a fee or other commercial consideration, is hereby granted by implication or estoppel. Further information on purchasing licenses to practice the PCR Process may be obtained by contacting the Director of Licensing at The Perkin-Elmer Corporation, 850 Lincoln Center Drive, Foster City,

California 94404 or at Roche Molecular Systems, Inc., 1145 Atlantic Avenue, Alameda, California 94501.

So you pay twice. business genius huh? Xcomradex 22:37, 31 October 2006 (UTC)

And the guy who first thought of a way to make PCR practical got $10,000 for his effort. --JWSchmidt 01:21, 1 November 2006 (UTC)
the joy of commercial research i guess. but the nobel prize means a job for life, so you take the good with the bad. Xcomradex 04:08, 1 November 2006 (UTC)
Although you can make Taq yourself. It's unlikely to be as good quality and you could get in trouble in anyone finds out but I have heard people talking about having done it before (in a large lab I believe in the US). Of course, it may not be worth your effort. In any case, aren't tha patents expiring soon? BTW, I believe you can obtain PCR machines without licenses if you have an existing agreement with the patent owners (and could probably produce Taq yourself legally). And by the by, what's going on with all the legal battles anyway? Nil Einne
Also, having worked in a lab myself and a knowing few people who've had some knowledge of the purchasing I think it will surprise a lot of people (but hopefully not too many people actually working in labs) how expensive your work can be. I sometimes used to wonder how much I'd wasted today... Nil Einne 18:14, 1 November 2006 (UTC)

THe PCR patents HAVE expired. --GangofOne 22:24, 1 November 2006 (UTC)


1. If we arrange the substituents from highest to lowest priority (CIP system) which of the following arrangements is correct?

A) –N(CH3)2 > -OCH3 > -CN > -COOH

B) -OCH3 > –N(CH3)2 > -COOH > -CN

C) -CN > -COOH > –N(CH3)2 > -OCH3

D) -COOH > -CN > -OCH3 > –N(CH3)2

Which do you think? Why? Does looking in Wikipedia for information on likely topics such as "CIP" provide any useful infomation about how to do your homework? DMacks 17:53, 31 October 2006 (UTC)
But mistah, thinkin makes me brane hurt.. Eyez gots no idea watta do yo. Ize gots no ideez wherez to lookz for this teyep of thing. Maybe if I clickz this link??? -_- --AstoVidatu 22:50, 31 October 2006 (UTC)

why human beings can not fly like birds?[edit]

Birds use wings to fly which they move in such a way that make them fly in air. Why human can not do same using somthing similer to wings and use of their muscles to put them in motion. If weight is a probelm then electric motor could be use to move the wings in air. could it make man to fly? Is it already tried like this or if yes then do you know what was the result?


What you describe is called an ornithopter. They do work, but might be rather unpleasant for a person to ride in as all that flapping motion will likely make them sick. They are also less efficient than an ultralight or other type of conventional airplane. StuRat 18:15, 31 October 2006 (UTC)
As for why human powered wing-flapping flight can't work, it's due to the basic design of people. We have relatively little muscle in our arms, with most of the muscle being in our legs and torso. Thus, even a body-builder wouldn't have enough strength in their arms to support the rest of their body by flapping wings. Total size is also an issue, as people are a bit heavier than the heaviest birds. The larger an animal is, the less able it is to get off the ground, as lift, which is proportional to surface area (I think), only increases with the square of the length, while mass increases with the cube of the length. Thus, the larger an animal is, the higher it's mass-to-lift ratio. Birds also have light weight, sponge-like bones, to reduce their weight further, and are streamlined, to reduce drag. StuRat 18:28, 31 October 2006 (UTC)
Birds have incredibly strong chest muscles, light bones, and special sternums. Humans don't have any of these. Maybe if we wore masks? AMP'd 18:20, 31 October 2006 (UTC)
Birds are also designed to be very light in weight. Hollow bones, big air sacs filling much of their bodies, etc. You might want to look at our Gossamer Albatross article to get an idea of just how hard it is for a human to overcome our natural disadvantages in this area.
Atlant 18:28, 31 October 2006 (UTC)

Thanks everyone. I got more than expected info about this thought.

Don't forget about Feathers! -THB 20:52, 31 October 2006 (UTC)
I think birds are also completely designed around flying. Their are muscles in every part of the body that twist the bird so that it can maneuver and move its side and tail wings. You can't just replace human arms with wings and flap them, flying is an entire system. It is similar to walking on 2 feet, making a robot that can do it well takes more that a few joints and motors. Ed Dehm 21:27, 31 October 2006 (UTC)
Birds also have much more efficent respiratory and circulatory systems than our own. They have a higher metabolism too. A bird's body temperature is about 5 degrees higher than our own. I'm pretty sure that they have a 6 chambered heart too. -- 21:53, 31 October 2006 (UTC)
Number one reason: humans are fat bastards in comparison to birds. We're built around walking/running/storing up fat for winter, and that calls for an entirely different skeletal, muscle, and tissue system than our avians friends. -- Chris 23:53, 31 October 2006 (UTC)
Well, penguins are fat, too. Of course, the only way they're going to get airborne is if you fire one out of a cannon. :-) StuRat 00:20, 1 November 2006 (UTC)
Oh there are other ways DMacks 02:17, 1 November 2006 (UTC)

V8 Engines[edit]

Are V8 engines very powerful? What type of cars are they used in?—Preceding unsigned comment added by (talkcontribs)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see V8 engine. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. .--Shantavira 18:21, 31 October 2006 (UTC)

Yes, V8 engines tend to be powerful. The same power can also be achieved in smaller engines by using high compression ratios, turbo-chargers, or superchargers. These methods tend to shorten the life of the engine, however. StuRat 18:33, 31 October 2006 (UTC)

OK whats so special about the V formation?--Light current 23:09, 31 October 2006 (UTC)
Power is due to general engine size (number of cylinders, displacement, compression ratio, etc). I don't know of an advantage in that department specifically due to the V formation. OTOH, the V formation gives a more compact overall engine than having all the cylinders adjacent in a single row, meaning one can have a larger cylinder or stroke for a given overall engine-block size. To quote the V8 engine page, Instead of going to a straight-6 like its competitors when something larger than a straight-4 was needed, Ford designed a modern V8 [...] After World War II, greater vehicle size meant that the straight-6 became increasingly underpowered, while lower hoods and more aerodynamic styling meant that the straight-8 was simply too large. DMacks 23:33, 31 October 2006 (UTC)
W formations are usually more powerful, but just because they're two Vs. See also: W18. V and W formations are used I believe due to their symmetry. I heard that from some old guy. X [Mac Davis] (SUPERDESK|Help me improve) 23:45, 31 October 2006 (UTC)

Car top[edit]

If a car has a black vinyl top, underneath it does it still have the same metal as the rest of the body? So could you take it off and it look like it never had one? If you could would you have to take to a mechanic or could you just rip it off? —The preceding unsigned comment was added by (talkcontribs) .

Assuming you're not speaking of a convertible (cabriolet, drop-head, etc.), yes, you could theoretically remove the vinyl. But the paint underneath might be in tough shape and there might be a lot of adhesive residue to contend with.
Atlant 18:41, 31 October 2006 (UTC)
The metal also is not designed to be in contact with the elements, so may be likely to rust, unless properly treated. StuRat 19:07, 31 October 2006 (UTC)

Mating/pairing off behaviour in seagulls[edit]

Amongst other birds, when spring comes around, I see them performing all sorts of different mating calls and displays in order to attract a partner. Just about all the other birds except the seagulls that is. They don't seem to show any interest in other members of their own species except for the desire to fight with them or steal their food. Then a bit later on, I notice that some of them have just paired up and that there are now two gulls stood closer to each other than gulls normally allow other gulls to get, pretty much just ignoring each other. I never see any affection between them at all. So, what is the gull 'mating ritual'? I've never seen it? Is there even one? Or is it a case of 'you'll do, let's screw'? -- 21:37, 31 October 2006 (UTC)

Kurt shaped box its over to you! You moment of fame has arrived!--Light current 23:11, 31 October 2006 (UTC)
It's probably comprised more of eye contact and body language, which is of course harder for us to pick up on. Or perhaps gulls are simply more discreet, and prefer not to get it on when humans are watching. -- Chris 23:51, 31 October 2006 (UTC)
There's a video of gull courting/mating here . I've never actually seen them 'at it' myself but it doesn't really look like there's much to it in terms of an elaborate display. Apparently, many gulls pair up for life. --Kurt Shaped Box 23:55, 31 October 2006 (UTC)

hollow head[edit]

Ok, this is going to sound a bit weird.

My right ear is messed up. Whenever I gently tap my hand against my skull, my head sounds "hollow" almost, with a basis around the right ear. My hearing is slightly worse in that ear too. What's wrong with me? Don't tell me to see a doctor, because I don't have the money. All I have is ya'lls help.

Sounds like earwax. Try pouring some olive oil in nightly for a few weeks to see if it dissolves the wax!. olive oil is perfectly safe to use in the ears.--Light current 23:13, 31 October 2006 (UTC)
If you think there is something wrong with you, you should see a healthare professional. Since you have access to a computer and the internet, you hopefully are in or can get to a place where you can obtain healthcare without needing to pay (US, UK, Canada...) (notice I make no promises about how easy that might be...). That said, it is not reasonable to assume that you can adequately auscultate structures in your own head, especially close to the ear itself. Another individual, however, trained in auscultation, may be able to distinguish tympanic resonation by tapping over the sinuses, particularly the frontal sinus and (though much less likely) the sphenoid sinus, using a stethoscope. Since these sinuses are hollow, this would be normal. I can't personally think of any pathologies which would present as periauricular typanic resonation first ( that is to say, you would be unconscious or dead long before you would have or notice a hollow sound in your skull, e.g. with a very large air embolus or after a hemispherectomy). Tuckerekcut 23:16, 31 October 2006 (UTC)
Yeah good! But do you think he's going to understand all that? I dont! Or are you trying to make a point?--Light current 23:19, 31 October 2006 (UTC)
Yea, that advice, while excellent, likely went over his head. Let me try a simpler version:
There are hollow areas in your head, such as the sinuses. However, they should not extend to the area you described. A smaller hollow area is the eustachian tube, but that isn't normally large enough to create the audible resonance you described. I suspect that it's not an extra hollow space in your head, but rather something wrong with the hearing in one ear, that's causing your brain to hear it slightly later than the other ear. This would cause an inability to locate the source of sounds, and possible nausea and dizziness. I agree that you need to have this looked at by doctors, it sounds potentially serious. Go to a free clinic or emergency room. I also agree that you should try cleaning out the ear first, but think a Q-tip (cotton swab) will do the job nicely, assuming you know how to use one properly. StuRat 00:09, 1 November 2006 (UTC)
This is the person who asked the question again. Whenever I talk, I hear something that sounds like a resonance in my voice. Almost like a slight echo. Would that mean anything?
Have you tried going to the pharmacy to get some decongestant etc?--Light current 23:29, 31 October 2006 (UTC)
The cheapest and best way to clear sinuses is to get plenty of fresh air. I know, I used to hate it when my parents badgered me on this point. But it's completely true. If you never want to get congested sinuses, sore throats, wierd ear conditions, pinkeye, and the like, get plenty of fresh air.
Of course the problem with this is the cold: most people can't stand it, so they stay indoors all day. There's only one remedy for this: improve your diet. When your metabolism is running smoothly you'll feel the cold a lot less, so you can spend more time ourdoors, keep your windows open a little, turn the heating down, and so on. All these measures will reduce cold symptoms, including 'hollow head' syndrome.
That said, the very best time to be breathing outdoor air is the winter. It just feels so clean and refreshing! -- Chris 23:48, 31 October 2006 (UTC)
This question is spiraling out of control! I thought I had an ear problem! Thanks everyone though 00:04, 1 November 2006 (UTC)
I'm sorry if I used some jargon in my explanation. However this is an encyclopedia, and just about every word or phrase can be investigated (though I was sad to see that 3 red links popped up. For posterity: auscultate means to listen, tympanic resonation is when something sounds hollow, and periauricular means near the ear.) I would not recommend putting anything in your ear; neither a cotton swab nor olive oil are likely to help you, and both could certainly do damage. Cotton swabs are stiff enough to damage the delicate membranes of the ear, and even if they don't they tend to push ear wax back into a ball when it should be spread out. And if there is any sort of rupture or fistula in the eardrum (which happens all the time even in people without symptoms), the oil can foster the growth of anaerobic bacteria in places where you definitely don't want them, such as the eustachian tubes, which incidentally are potential spaces, and definitely do not participate in resonation. As for the "improve your diet" advice: it may improve your overall health, and is certainly never bad advice, but it won't alleviate your symptoms specifically, and the connection with metabolism is teleological and frankly false.
One question does pop into my head though: what is the incidence of post-surgical lacunar amnesia in hemispherectomy patients? Hey... is that a zebra outside?... Tuckerekcut 03:07, 1 November 2006 (UTC)
No, it's a swan (unless you're looking out a different window). Ignoring the fact that this is an encyclopedia, without looking anything up, let me guess what what you said means. 'How often do people forget about emptiness after they have had half their brain removed'. How close did I get? DirkvdM 17:39, 1 November 2006 (UTC)
On the off-chance you missed the reference entirely (and for any others that do, even if you didnt), Tucker was (I believe) referring to a Zebra (medical) :) GeeJo (t)(c) • 23:38, 1 November 2006 (UTC)

Digital MULTIMETERs[edit]

Hi, I would like to know what is the accuracy of a typical digital multimeter that has auto range detection. (for example: +/- 5%) 00:46, 1 November 2006 (UTC)

Basic dc voltage accuracy of 1% is no problem these days. But you get what you pay for. If you want 0.1% DCV acc be prepared to pay a few hundred £. Mine (without auto ranging) cost about £35 a few years a go and has dc voltage acc of 0.5% of rdg +/- 1 digit. All other ranges will of course have worse accuracy figures.--Light current 01:11, 1 November 2006 (UTC)
Actually I think all accuracy is rated at full scale, not the reading if I recall correctly. For example, on the 5 volt scale, the accuracy is +/- 1% of 5 volts regardless of whether the reading is 1 volt or 4 volts. that's why you always want it on the lowest range setting for the highest reading. This is in memory though. --Tbeatty 05:51, 1 November 2006 (UTC)
Most high-end digital voltmeters are rated as a certain % of full scale + a certain percentage of reading. This occurs because there are multiple error sources within the DVM and they gave varying effects.
Atlant 18:42, 3 November 2006 (UTC)
No, I was just quoting from the handbook of my cheapo DMM!--Light current 12:29, 1 November 2006 (UTC)
Cheap digital multimeters are more accurate for DC than AC. Unless a meter says "True RMS" it reads the average AC but is calibrated to display the equivalent RMS value. It will be inaccurate for other than DC or pure sine waves. Such meters get fooled by distorted waveforms, such as result from the current going to electronic power supplies, or such as result from unbalanced 3 phase loads, or harmonics.I do not see this discussed in Wikipedia, but it is discussed at [1] and [2]. The problem is not a trivial one, since wiring or transformer overloads may be missed when a cheap ammeter shows low current but an RMS meter shows the actual current producing heating effects in equipment. Edison 18:05, 1 November 2006 (UTC)