Wikipedia:Reference desk/Archives/Science/2007 June 22

= June 22 =

Amino acid analysis: Asn and Gln always missing
In every nutritional amino acid analysis I've seen so far, asparagine and glutamine are missing. They are not nutritionally important, but the same applies to other amino acids which aren't missing. Why are Asn and Gln missing? Icek 01:06, 22 June 2007 (UTC)

It has probably something to do with the fact that they are the only (biochemically relevant) amide-containing amino acids. Maybe the chemical process used to dissolution of the peptide bonds for analysis destroys these amides and converts them to aspartate and glutamate? Icek 01:30, 22 June 2007 (UTC)


 * Hit the nail on the head there, if only everyone answered their own questions! :) Aaadddaaammm 01:34, 22 June 2007 (UTC)


 * My fav nutrition site: lists aspartic acid and glutamic acid. StuRat 06:57, 22 June 2007 (UTC)


 * Yes, but you don't know how much of the aspartic acid was originally asparagine and how much of the glutamic acid was originally glutamine. Icek 13:43, 23 June 2007 (UTC)

Bugs
I'm wondering what type of bug this is. Can anyone help me identify it?

http://tinypic.com/view.php?pic=6fz9ufa

is the picture of it. My girlfriend took a picture of it since she is wondering as well. It is stuck between her window and screen. It can fly obviously. My girlfriend has woods in her backyard and it has lots of bugs, trust me. Any help would be appreciated. Thank you.


 * It looks a bit like an ant or wasp to me, GB 03:28, 22 June 2007 (UTC)
 * Maybe a black wasp, like this.. Vespine 03:34, 22 June 2007 (UTC)


 * It's definitely Order Hymenoptera, most likely a wasp of some sort, you can tell by the thorax. There aren't enough details in the image to be sure, but you could probably look up what wasps are common in your area. --  JSBillings  12:23, 22 June 2007 (UTC)

thermodynamics:
Woul you pliz explain to me the following:

1.)A professor parked his car for eight hours in a shed, checked the pressure and found it to be normal for his car/ He the drove for thirty(30)minutes to a supermarket and then discovered that the pressure had slightly increased. In his wisdom, he decided to let some air out to reduce its original level.Comment on this action.

2.)A container has 2500moles of air. Find the change in internal energy if its cooled from 30 degees celcius to 20 degrees celcius at constant pressure of 1atm. Treat the gas as an ideal gas.
 * Definately looks like homework to me. -- JSBillings  13:27, 22 June 2007 (UTC)
 * Maybe even yesterday's homework? 213.48.15.234 13:33, 22 June 2007 (UTC)
 * How strange? :). In any case, why don't you ask your teacher for help?--GTPoompt (talk) 14:35, 22 June 2007 (UTC)
 * Read ideal gas law, and good luck with your homework! TomTheHand 15:19, 22 June 2007 (UTC)


 * I even answered yesterday's homework! To the original poster: Pliz put a little effort in, we're assuming good faith.  Nimur 18:24, 22 June 2007 (UTC)


 * Well at least he/she fixed the spelling error from the last post. Although I don't quite get why he/she bothered to remove the religious studies part. Or perhaps we're both wrong and it's not the same person just another idiot person from the same class who's liable to fail it. Nil Einne 22:17, 23 June 2007 (UTC)

Definition of temperature units
The Wikipedia articles on kelvin and degree Celsius both define the respective units in terms of two fixed points: absolute zero and the triple point of specially formulated water. However, neither of them makes any reference to the thermometer (or equivalently, the procedure for extrapolating the scale). The mid-point between the two fixed points as measured by one type of thermometer is not necessarily the mid-point as measured by another type of thermometer.

My question is: Is there an implied thermometer or physical phenomenon that is used to extrapolate the Kelvin and Celsius scales (beyond the two fixed points)? If so, what is the thermometer/phenomenon?

(I seem to recall from many years ago that my physics teacher said that constant-volume gas thermometer is used for the purpose, but I'm not sure.)


 * It seems to me that the problem here can be sorted out by knowing what temperature is. Once we know that, we can define $$T_0$$ to be the temperature of said triple point. The kelvin is then defined as $$1\,\mathrm{K}=T_0/273.16$$. —Bromskloss 16:41, 22 June 2007 (UTC)


 * As my professor once said, temperature is that thing that thermometers measure. An ideal thermometer is linear so that the change in temperature is proportional to the input in thermal energy.  An ideal gas themometer is a reasonable approximation of this at modest temperatures and far from phase transitions.  In practice though there are a whole host of different thermometers and techniques used to extrapolate over different ranges of temperature.  I've seen a list before, but don't have it handy.  Inventing a truly precise absolute themometer that works over a large dynamic range is an engineering challenge that has yet to be solved.  Dragons flight 16:52, 22 June 2007 (UTC)

The answer is that the SI standard defines the kelvin specifically as being the unit of thermodynamic temperature, which as you can see at that page, means the average kinetic energy of the translational motions of the particles making up the substance. This is the "physical phenomenon" that thermometers attempt to measure. --Anonymous, June 23, 2007, 08:58 (UTC).

Insulation
I have always been wondering....does the insulation coating of a conducting wire have anything to do with its current conducting capacity?I mean does the plastic insulation coating on the top affect the resistance of the wire or something? I have heard somewhere that without the coating a simple wire carries upto 200 amperes but with the coating it can carry only upto 40 amperes max..(hypothetical figures)... is it really posible? and if so...how does it affect? i mean does the thickness of the plastic coatin affect it or is it something else....and is this a well known fact used in the manufacturing of wires or its just a trifle thing?


 * What sets the limit for how much current a wire can carry is that it gets hotter and hotter the more current you run through it. Too much and it will burn off. If what you've heard is true, it's probably because the coating prevents the heat from escaping into the air and therefore makes the temperature in the wire higher. —Bromskloss 16:34, 22 June 2007 (UTC)


 * Correct. Standard insulation on a wire can melt and start a fire.  If there is no coating on the wire and it isn't touching anything, it can get much hotter than it could if it was coated - assuming your goal is to prevent melting the coating.  You can think of a filament in a light bulb.  Without the coating, it is allowed to get so hot it glows.  If you coated it, you would have to cut the current down a lot to prevent the insulation from melting. -- (¿ʇɐɥʍ) ʍɐuıɐʞ 16:37, 22 June 2007 (UTC)


 * Oh, apparently I was not entirely correct, then, but not too far from. And you were polite who didn't stab me for it. :-) —Bromskloss 16:45, 22 June 2007 (UTC)


 * At extremely high frequencies, such as fiber optics, total internal reflection can be described as a form of insulation. The relative index of refraction of the outer ("insulating") layer determines the signal integrity and loss rate.  For normal electrical applications, I think the limiting factor is heat, as mentioned above.  Plastic or rubber insulation will melt at lower temperature than copper or metal wire.  ɹnɯıu 17:36, 22 June 2007 (UTC)


 * A few years ago, I recall some electronics engineers in my group specified Gore-Tex-coated wires for their superior ability to reduce crosstalk between adjacent wires with high speed digital traffic going across them - so I suspect there is more to it than simply preventing the wires from touching each other or other metal surfaces. SteveBaker 17:54, 22 June 2007 (UTC)


 * Of course! If you are talking about signals, that is completely different than current capacity.  I was discussing simple current - shoving little electrons down the wire.  Insulation is used to keep the electrons on the wire.  In signal wires, you also have to worry about bleed, interference, signal loss... a completely different topic. -- (¿ʇɐɥʍ) ʍɐuıɐʞ 18:07, 22 June 2007 (UTC)

I am very sorry, but when i asked the question, what i meant was actually this- how does the insulation coating affect the amount of current passing through the wire. Like...will there be more current passing without insulation than with insulation? and if so...what is it that exactly determines the amount of current passing?


 * The insulation makes no difference to the current, assuming that the insulation is functioning correctly. The above replies are correct: the insulation only affects the current-carrying capacity of the wire by reducing heat loss.  Judging by the wording of your question, you are not talking about advanced applications like radio frequencies or high-precision measurements. --Heron 20:39, 22 June 2007 (UTC)


 * As in, those who are shoving electrons down the wire could run it at, for instance, 200 amp, but that will melt the coating and be rather bad. So they are limited to use 40 amp, to not melt it, despite the wiring being able to carry much more. 81.93.102.185 21:46, 22 June 2007 (UTC)
 * Assuming the melting/flash point of the insulation is below that of the conductor - yes. But some kinds of insulation (such as the ceramics and other bizarre stuff they use in very high voltage work) might not melt until after the metal inside has melted - in which case the insulation isn't the limiting factor.  But for 'normal' stuff - yeah - the limiting factor is that the plastic/rubber/paper insulation melts or catches fire long before the conductor would have given out. SteveBaker 14:02, 23 June 2007 (UTC)


 * Insulation retains heat, making an insulated copper conductor hotter than a bare one, making it have higher resistance, thereby producing still more heat. It is not a trivial effect, since a conductor might heat up appreciably under normal design loadings. See Electrical wiring and Ampacity. Edison 15:19, 23 June 2007 (UTC)

accessory fruit, false fruit, spurious fruit
I was looking up the german word "Scheinfrucht" in german-speaking Wikipedia when I realized that no english interwiki was there. In english-speaking WP I found an article on accessory fruits and via dictionary I found the terms false fruit or spurious fruit; to add to the confusion I found pericarps and epigynous berries. After a quick discussion with native speakers on IRC I guess it's all the same, so I linked "Scheinfrucht" to accessory fruit and mentioned false fruit and spurious fruit and even epigynous fruit as alternative terms there and created redirects. Now because I'm not 100 % sure about all that I put up this "question" to have somebody check that and change things if my guessing was wrong...

Thanks! --Speck-Made 19:29, 22 June 2007 (UTC)


 * Looks right Bendž|Ť 07:20, 23 June 2007 (UTC)

can we have non functional Mc1r on purpose
i recently read that non-functional Mc1r makes people have red hair, but how is this caused, can it be done on purpose?


 * The Mc1r article describes this gene. This paper is fairly incomprehensible to me, but it looks like preliminary investigation into the effect you describe.  Perhaps you should try Google Scholar ? Nimur 01:10, 23 June 2007 (UTC)


 * It'd be easier to give a person with red hair the functional MC1R gene, giving them brown/black hair than to replace a functional gene with a non functional gene (give a black/brown haired person red hair). This is generally the case with recessive characteristics such as red hair. See gene therapy. Bendž|Ť 07:35, 23 June 2007 (UTC)


 * It is not currently technically feasible to "change genes" in humans. In mice, however, it is relatively simple to swap the functional Mc1r for a non-functional Mc1r. Infact, I have done it myself - my lab replaced the mouse gene with a human non-functional Mc1r to see what colour of mouse you get - by a process called trangenesis.
 * The reason a non-functional Mc1r causes red hair is because it acts as a molecular switch on the surface of melanocytes (the cells that produce pigment). A functional Mc1R receives a signal from outside the cell in the form of melanocyte stimulating hormone and transduces it into the cell. The signal tells the cell to produce eumelanin, which is a black or brown type of melanin. When Mc1r is mutated, it cannot transduce this signal properly and, by a mechanism not yet fully understood, it instead "switches" production to make phaeomelanin, which is red in humans (and yellow in mice). Rockpock  e  t  18:37, 23 June 2007 (UTC)

Budgerigar/sparrow hybrid?
I just removed the following unlikely-sounding paragraph from the budgerigar article, on account of being unable to find any reference to it using Google.

"Although highly unusual, in some rare cases a female domensticated budgerigar is known to be capable of mating with a male North American sparrow (particularly the ones in Canada), thus creating mixed sparerigar juveniles. However, it is still currently unsure if the sparerigars are anywhere capable of reproducing other cheeks."

It sounds like BS to me (surely budgies and sparrows are far too distantly related to crossbreed?). Is it BS? Can anyone confirm/deny? Thanks. --Kurt Shaped Box 23:12, 22 June 2007 (UTC)


 * Attribution is necessary for inclusion; it also contains a neologism; as a whole, the paragraph does not make a strong case for inclusion. I can't comment on the factual accuracy, but even if true, it needs sources.  Nimur 00:41, 23 June 2007 (UTC)


 * On the subject of strange animals, the necrolemur article is in need of a biology/zoology expert. Nimur 00:42, 23 June 2007 (UTC)


 * Necrolemur is legit, but, sadly, pining for the fjords . As for budgerigar x sparrow, well, that doesn't seem biologically possible; however, I can see how someone watching too much "Pirates of the Caribbean" can get inspired ;). Cheers, Dr_Dima.


 * sparerigar produces not one single Google hit - it's not even a neologism.  Extraordinary claims require extraordinary evidence.  You can say '2+2=4' without attribution - you can say 'the MINI Cooper requires 91 octane gasoline' (but we'd prefer to see some kind of a reference to prove it please) but if you want to claim that BigFoot is standing for the Republican party in the next presidential election (not a bad idea actually!) then we're going to need to see some proof in the form of exceedingly solid, credible, references.  Without references of any kind, you were 100% correct to remove that paragraph. A mere  tag isn't enough for such outrageous claims. SteveBaker 13:52, 23 June 2007 (UTC)


 * Agreed, there can be little doubt this is total BS. These birds aren't just different species, not just different genera, not just different families, but different orders for crying out loud. They evolved on entirely separate continents. A human successfully mating with a tamarin would probably be more likely. About the only way you'd get a cross between these would be to cut them up and sew the bits together. BTW, the number of spelling mistakes in that paragraph would hardly inspire confidence to start with; oh to see a sparerigar cheek [sic]. --jjron 16:36, 23 June 2007 (UTC)