Wikipedia:Reference desk/Archives/Science/2008 May 16

From Wikipedia, the free encyclopedia

Science desk
< May 15 << Apr | May | Jun >> May 17 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.


Contents


[edit] May 16

[edit] Transformer configurations.

I work for an electric company. I quote distribution transformers on different configurations but since I am not an engineer there are some things I dont fully understand. I do understand the basics of transformers and electricity but I cant seem to understand the difference between a Y and a GY. I mean I do recognize the physical differences but I dont really understand why you would ground the neutral or why WHY! you would put both neutrals together in a Y-Y transformer. How come that doesnt create a short circuit or something like that?. I also dont understand why Deltas are ungrounded, is it not necessary? When and why is it necessary? Thanks a lot in advance, guys. —Preceding unsigned comment added by 200.56.210.20 (talk) 01:12, 17 May 2008 (UTC)

All electricity supply systems need to be grounded for safety. It is also the law that they must be grounded. :[1]. Continuity of the neutral conductor is :mandatory in law.
A Y (or star) connected transformer sometimes needs the star point connected to earth. This I imagine :would be achieved using the GY type (ie the star point is brought out for connection to earth). The normal Y :transformer may not have the star point connection brought out. If you connect one Y transformer to another :Y transformer via some overhead lines, it is my understanding that the star point of one of the transformers :should be earthed (you dont need to connect the other one to earth to achieve adequate system grounding).
Delta transformers may be connected to Y transformers via lines and therefore dont need grounding because the Y :transformer is grounded at its star point. In the case of delta to delta connection, since there is no neutral :connection available, I believe earthing transformers are used between each line and earth to ground the system. —Preceding unsigned comment added by 79.76.158.222 (talk) 06:45, 17 May 2008 (UTC)
Protective relaying engineers in power systems natter on about "zero sequence currents" as part of "symmetrical components." It may have something to do with that, and the ability to detect ground faults. Edison (talk) 01:15, 19 May 2008 (UTC)

[edit] I was reading FANCD2 article.

They used word monoubiquinated. What dose it mean? "This protein is monoubiquinated" That is apparently taken from NCBI web site. I could have requested it in Wiktionary, but afraid it could take years before someone will create article there. Vitall (talk) 01:40, 16 May 2008 (UTC)

The protein had one ubiquinone unit attached to it. DMacks (talk) 01:52, 16 May 2008 (UTC)
Thank you! That's perfectly answered my question! Vitall (talk) 02:15, 16 May 2008 (UTC)
Be careful when reading, as proteins can also be ubiquitinated, which is something altogether different. -- 128.104.112.147 (talk) 15:57, 16 May 2008 (UTC)
Actually, I'm pretty sure that "ubiquinated" is simply an alternative spelling of "ubiquitinated". I don't think ubiquinone ever gets attached to proteins, but ubiquitin does that for a living. --169.230.94.28 (talk) 02:18, 17 May 2008 (UTC)

[edit] Higher frequency mean more bandwidth

Shorter wavelength mean more bandwidth. Like data could be transfered at higher speed, more bits per second. There should be a law/axiom or something clearly stating this. And I do remember I read about that here, in Wikipedia. Could someone point me to an article, preferably here, but anywhere in the internet would also be good enough. I did tried to Google for like 20 min but fail:( Vitall (talk) 01:49, 16 May 2008 (UTC)

Something like frequency modulation might have the info you want.--Fangz (talk) 03:18, 16 May 2008 (UTC)
I think you're looking for the Shannon–Hartley theorem. — Lomn 04:02, 16 May 2008 (UTC)
Shannon–Hartley theorem state, that the more bandwidth we got, more data(actual bits and bytes) we can transfer in a given time. That is excellent point, but it don't reflect wavelength bandwidth relation. Or am I missing something? Is it actually safe to say, that if we use ten times shorter wavelength we can reliably transfer 10 times more data using same amount of power in a given time(same signal to noise ratio)? Sorry if I making question even more complicated, but this whole thing is confusing. Vitall (talk) 05:09, 16 May 2008 (UTC)
Um as far as I'm aware there is no direct dependency between wavelength and bandwidth, however the shorter the wavelength, the higher the frequency and at a higher frequency you can have more bandwidth. For example, if your device works between 100-200mhz you only have 100 mhz of bandwidth. If your device works between 11-12ghz, you have 1ghz of bandwidth a 10 fold difference Nil Einne (talk) 06:37, 16 May 2008 (UTC)
From the article-Surprisingly, bandwidth limitations alone do not impose a cap on maximum information rate. This is because it is still possible for the signal to take on an indefinitely large number of different voltage levels on each symbol pulse, with each slightly different level being assigned a different meaning or bit sequence. If we combine both noise and bandwidth limitations, however, we do find there is a limit to the amount of information that can be transferred by a signal of a bounded power, even when clever multi-level encoding techniques are used. Em3ryguy (talk) 14:25, 16 May 2008 (UTC)

It's important to distinguish the two different meanings of the word "bandwidth". See respectively bandwidth (computing) and bandwidth (signal processing). The first is a measure of the data rate. The second is a measure of the spectral extent of the signal. Speaking slightly loosely, all else being equal, a higher data rate bandwidth requires a higher spectral bandwidth to transmit it, essentially because of the Shannon-Hartley theorem (assuming you don't change the signal-to-noise ratio and a bunch of other assumptions). I think what you are thinking of is the point-of-view of a data source. The data rate that comes out of that is related to how quickly it can turn something on-and-off - how quickly it can produce 1's and 0's. The higher the frequency that can be done at (the shorter the wavelength of the resulting signal), the higher the data rate it produces. So in general, you can produce a much higher data rate with a laser (ie at optical frequencies) than by having computer change the voltage on a modem (ie at electrical frequencies). In that sense, the data would have a higher bandwidth (computing). What that means in terms of spectral bandwidth depends on what you are comparing. Splash - tk 19:34, 19 May 2008 (UTC)

[edit] Endangered Species- Polar Bear

How can we save the polar bears from becoming endangered? —Preceding unsigned comment added by 75.108.103.100 (talk) 02:00, 16 May 2008 (UTC)

Reverse the effects of global warming (which unfortunately deflects a nearly impossible question with another nearly impossible question). The main threat to the polar bear is loss of habitat due to melting of sea ice. --Bmk (talk) 02:17, 16 May 2008 (UTC)
If we pray hard enough the Divine Intervention might save them. Vitall (talk) 02:36, 16 May 2008 (UTC)
I can't think of any course of action less likely to work. That kind of "wish things turn out" attitude is precisely the problem. Matt Deres (talk) 02:48, 16 May 2008 (UTC)
Well... Making sure all of the sea ice melts as quickly as possible might be even less likely to work than prayer, but apart from that... -- Captain Disdain (talk) 08:52, 16 May 2008 (UTC)
One radical solution might be to introduce polar bears to Antarctica, which will likely contain ice and snow long after it has all melted at the North Pole. This is because there is so much more ice in Antarctica to start with. Of course, this may have disastrous implications for other species in Antarctica now, such as penguins. StuRat (talk) 10:38, 16 May 2008 (UTC)
give em clubs to help with the seal hunt --Shaggorama (talk) 07:34, 19 May 2008 (UTC)

[edit] PAUA OPALS

WHAT ARE PAUA OPALS? —Preceding unsigned comment added by 66.191.157.101 (talk) 04:14, 16 May 2008 (UTC)

It's probably cut pieces of Paua or abalone shell. Graeme Bartlett (talk) 05:14, 16 May 2008 (UTC)
Cut and polished to resemble the iridescent disk of an opal though hardly like it, the name is linked with a desirable and more notable material to expand the market for what is as GB says, NZ abalone shell jewellery. In the business world the practice is called "tailgating" – a tactic to gain an advantage from something already established in a market – linking it in your mind, but not in reality. Julia Rossi (talk) 08:55, 17 May 2008 (UTC)

[edit] flame test

colour of tap water in a flame test

Did you read flame test? It will be coloured by the dominating metal, most likely sodium as it gives a much stronger emission than calcium or potassium. Graeme Bartlett (talk) 07:02, 16 May 2008 (UTC)

[edit] Airport X-rays

Do I need to protect electronics (computer, camera, …) from being irradiated by X-rays at the baggage inspection at an airport? Mabye it's necessary to differentiate between two cases: hand luggage and checked-in luggage. —130.237.2.72 (talk) 09:55, 16 May 2008 (UTC)

Consumer electronics are almost invariably not bothered by airport X-rays (I say almost because I'm sure as soon as I throw in an absolute, someone posts the counterexample). If some affected device exists, it will certainly be well-noted in the instructions. As previous similar topics have noted, the equipment used for carry-ons is less powerful than that used on checked luggage, so when in doubt, carry. Note also that the security of carry-on luggage is superior, and that some items (lithium ion batteries, for one) may be prohibited from checked luggage anyway. If something is really delicate, it's probably worth checking with your local post office to see if they x-ray shipments -- surely some non-x-ray transportation arrangement exists, though you're not going to find it at the airport. — Lomn 13:03, 16 May 2008 (UTC)
The airport's website will probably have a list of items that you shouldn't put in your baggage - I would expect that to include things that will be damaged in addition to the obvious security rules. --Tango (talk) 13:39, 16 May 2008 (UTC)
The electronocs of your camera will not be affected. If you are using film, however, you could be a little more cautious. Generally, x-rays are safe for film speeds up to 800 asa. For 800 and above they generally allow you to request screening by hand (though, in my experience, they do not always honor such requests). Even for film below 800 asa, however, you should try an avoid having un-processed film go through the machines several times. — Sam 14:16, 16 May 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

[edit] Bush Stone Curlew

Hi What colour do the eyes of a bush stone curlew turn when it dies? —Preceding unsigned comment added by 121.217.227.24 (talk) 10:27, 16 May 2008 (UTC)

I don't see anything about the eyes of a Bush Stone-Curlew that's different from any other bird, so I would say they probably get cloudy dark gray or black, and somewhat sunken and dehydrated, just like any other bird after it dies. ~Amatulić (talk) 21:09, 19 May 2008 (UTC)

[edit] Exercise pill

After exercising, muscles which were flexed repeatedly, grow, of course. I believe this happens because the muscle cells reproduce. I would think this would require some chemical messengers, whether RNA, hormones, or other catalysts or proteins, to tell the muscle cells in the area to reproduce. Do we know what these chemical messengers are ? It doesn't seem to be testosterone or steroids, since increasing those levels alone doesn't cause muscles to grow, the exercise is still needed. I also suspect that the chemical messengers in question don't travel via the circulatory system, since exercising the right arm has no effect on the muscles of the left arm. Are they completely contained within the muscle cells, or do these chemicals diffuse through the cell walls to adjacent cells ? In any case, it would seem to be theoretically possible to provide those chemical messengers to the muscle cells, possibly using a modified virus to deliver them, in order ot get muscle growth without exercise. This would have several benefits:

1) Patients who are unable to exercise, due to a coma, spinal injury, etc., could maintain their muscles until healed.

2) Astronauts could maintain their muscles, which otherwise would atrophy due to weightlessness.

3) People with degenerative muscular diseases, like muscular dystrophy, could possibly be helped.

4) People too lazy to exercise could take a pill to get muscles.

So, does this sound theoretically possible ? StuRat (talk) 10:31, 16 May 2008 (UTC)

I *think* (or at least someone at the gym told me) that muscle growth occurs as a result of mechanical tearing to the muscle tissue (and the healing thereof) following exercise. I'm not sure as to how much influence chemicals have on the process, beyond those secreted as part of the body's natural healing response. Artificially stimulating cell growth sounds like a 'very bad idea' to me, considering that the heart is also a muscle (one which doesn't need, or like to be messed with) and that not all cell growth is strictly desirable. --Kurt Shaped Box (talk) 12:44, 16 May 2008 (UTC)
Agreed. Reading around in the following Skeletal muscle Sarcomere Myofibril Satellite cells Muscle contraction Muscle hypertrophy Muscle atrophy will help clarify what we know of the picture to date. Muscular dystrophy is distinct from atrophy because it affects the Sarcolemma. Muscle growth is guided by neuronal signals. They are location inherent. With a pill or virus you'd have no way of guiding the desired effect. Lisa4edit (talk) 19:14, 16 May 2008 (UTC)
And what causes the "neuronal signals" ? StuRat (talk) 23:11, 16 May 2008 (UTC)
Sorry a bit out of time right now Action potential has some info. The thing is that unless you know what causes the atrophy, just adding one of the factors that make muscles grow in a healthy system may/does not work. You can use electro-stimulation or hormones or exercise to grow muscles. (And those methods are used in your examples 1 and 2 to some degree.) But if there's some underlying disease/cause that interferes with the process you may be pouring water into a leaking bucket. 71.236.23.111 (talk) 00:37, 17 May 2008 (UTC)
Ah, but you can fill a leaky bucket if you pour water in faster than it can leak out. I can think of several scenarios where adding "substance A" might help:
1) Their production of "substance A" is low.
2) Their production is normal, but their cells are less receptive to it than normal.
3) Their production would be normal, if they could exercise normally, but they can't (due to illness, lack of gravity, or plain laziness). StuRat (talk) 19:16, 19 May 2008 (UTC)
ALthough the above authors are correct about the nature of exercise, you all seem to be forgetting something. The general theory behind the original quesiton has been put into practice for years, the problem is that these chemicals often have unwanted side effects, and still need to be used in tandem with exercise regimens. See Anabolic steroid, Growth hormone, and Doping (sport).

[edit] Rolling

I asked this question a little while back, and when I did I suspected that the answer would be no, and that seemed to be the consensus amongst those answering. The question was whether a ball placed on a frictionless inclined plane would roll. I though that it wouldn't roll because it is the force of friction causing the torque, and so without friction there cannot be torque. However, I came across another method of dealing with the problem which has instilled some doubts. In this case, we will treat the axis of rotation not as the center of the object but as the point of contact between the inclined plane and the ball. The idea is that the ball will try to rotate about this axis, but would be unable to because of the normal force, which would redirect it to roll down the inclined plane. In this scenario, the friction force will not add torque because it is applying a force on the axis of rotation, so radius is zero. In fact, it would be gravity which causes the torque. Both methods predict the same acceleration of the ball. So, can a ball rotate on a frictionless inclined plane? —Preceding unsigned comment added by 74.15.138.130 (talk) 12:38, 16 May 2008 (UTC)

I think the answer we came up with before is correct. When you think of the ball as rotating about the point of contact that's because that point is stationary. There is no reason for it to be stationary if there is no friction to make it so. The ball can rotate if you start it rotating before you let go, but it won't actually roll (since the ball is accelerating down the slope it would need to rotate ever faster to roll, so you can't even start it rotating just the right amount for it to "roll" by coincidence - although you could if you gave it a push on a level plane). --Tango (talk) 13:45, 16 May 2008 (UTC)
If you move the origin of the coordinates to anywhere except the center of mass of the ball, you lose the nice symmetry and you should deal very carefully to make sure you have calculated all torques. The answer should be the same regardless of where you place the origin, but the natural (simplest equations) are obtained with the standard origin at the center. Nimur (talk) 15:00, 16 May 2008 (UTC)
Raise your ramp until it is vertical. The normal force is now zero since it is perpendicular to the direction of weight, and friction is zero whether the ramp is "frictionless" or not. In fact, this situation is equivalent to there being no ramp at all. But what happened to your sum of torques around the point of contact? Your logic would have the ball rotating about any point we choose on the ball (except for any point along the line between the top and bottom points). Obviously that cannot be. So what's the problem? ;-) --Prestidigitator (talk) 16:18, 16 May 2008 (UTC)
Where you set your pivot point is arbitrary. The ball does "rotate" with respect to the new pivot, but that rotation is actually a linear motion with respect to the center. Summing torques only tells you about rotation, or non-radial motion, with respect to the pivot that you select. If you want to know if the ball "rolls", you must take the pivot at the center of the ball, because that is what defines "rolling". SamuelRiv (talk) 16:51, 16 May 2008 (UTC)
Right. I may have worded my hint a little poorly, but that's the idea. Also many problems dealing with ramps and balls/cylinders assume the point of contact will remain stationary because of friction, which gives you a little more of a basis for dealing with "rolling", but only as long as the assumption holds. Of course, it is often a pretty safe assumption until the word "frictionless" is thrown in. --Prestidigitator (talk) 17:41, 16 May 2008 (UTC)
You can better imagine this with a slightly soft object like maybe a beanbag (I'm thinking of a roughly spherical cloth bag, stuffed with beans or sand or something so it's slightly 'squishy'). Place it on a ramp and if the friction is high enough, it'll roll like a ball - if the friction is not so high, it'll slide without rolling. If you have trouble imagining this, try imagining an even softer beanbag. Now, in the case of a rigid object, the rotational inertia of the object causes it to resist rolling - so if there is no frictional force to overcome that inertia - it'll just slide. In the case of the beanbag, some of the frictional force is consumed in moving the beans around to deform the bag enough to allow it to roll. Also it's not a perfect sphere, so in order to roll, the center of gravity may have to move upwards a little bit - and that takes energy too. So imagine a steel cube - it would "definitely" slide down your smooth ramp without rolling. Now imagine a dodecahedron - 12 pentagonal faces...well, it MIGHT roll - but it's not hard to imagine that it would just sit on one face and slide down a really gentle, smooth slope. Now think about an icosahedron, that's much more like a ball. But still - it has little flat, triangular faces and we could probably get it to slide down a sheet of wet ice or teflon or something. As you add more facets and make the object more and more ball-like, it seems more and more likely that it would roll instead of sliding. So if you have no problem imagining how and why my beanbag ball slides instead of rolling, or that a dodecahedron would either slide or roll depending on the amount of friction...then consider that in the real world - at the microscopic level - all balls are SLIGHTLY squishy and SLIGHTLY lumpy. In the real world, there is no such thing as a perfectly stiff, perfectly spherical ball so it's probably possible to get any ball to slide instead of rolling if you had a sufficiently low friction surface. In the case of a zero friction surface (such a thing is impossible of course) then even a perfectly stiff, perfectly spherical ball would fail to roll. In the real world, it's a contest between the friction between ball and ramp and the degree of imperfection of the ball. 66.137.234.217 (talk) 13:41, 17 May 2008 (UTC)

[edit] Eating freshly harvested grains

Generally we boil dried rice and cook food made from dried wheat flour. Are there any people who eat freshly harvested rice, wheat or rye? How do the "wet" rice and wheat taste?

I wonder if I can put fresh raw fish on freshly harvested raw rice. I may start a revolution in Japanese cuisine! -- Toytoy (talk) 12:39, 16 May 2008 (UTC)

From rice: 'Raw wild or brown rice may also be consumed by raw foodist or fruitarians if soaked and sprouted (usually 1 week to 30 days).' Algebraist 12:41, 16 May 2008 (UTC)
"Freshly harvested" would not be good for you. Grains should at least be either soaked or sprouted. Original Muesli recipes called for the grain (oat) to be soaked overnight. Grains contain many substances that make food preparation a good idea. Just a few I've come across : phytic acid Enzymes Glycosides. Prepared grain is "predigested" so the body can use the starch and nutrients inside. Also see Ruminant. --Lisa4edit (talk) 22:40, 16 May 2008 (UTC)
I dispute this logic. I don't think phytic acid or glycosides are destroyed by cooking. Enzymes would be denatured, but so what? Which enzyme would you be concerned about ingesting? What does ruminant have to do with this question? I think this is an interesting question that deserves a more complete answer. ike9898 (talk) 12:17, 17 May 2008 (UTC)
I presume she's referring to the fact that ruminants are capable of fairly fully digesting complex carbohydrates such as those found in uncooked rice and other grains (as well as cellulose of course which even cooking won't help you use much). Humans, not so much... You could try eating your shit (Cecotrope) like some rodents do, but this probably still won't work very well, plus being fairly unappealing to most people... Nil Einne (talk) 20:13, 17 May 2008 (UTC)
I somewhat doubt you'd start a revolution in Japanese cuisine. While the Japanese do some crazy stuff, most of the stuff they do eat at least tastes somewhat okay or has sometimes special about it. There is nothing special about uncooked rice. It's just hard, without much taste. You can't make sushi, or anything of that sort from it since it won't stick to itself. Raw foodists and stuff aside, there is a reason why we cook a lot of our food, and it isn't just to aide digestion or to kill harmful pathogens or to remove harmful compounds like cyanogens (ala tapioca, cashew nuts etc). It's because it often tastes better too. If you don't believe me, try actually eating some raw rice (or other grains) or raw potatoes or raw whatever you think is going to taste good Nil Einne (talk) 20:43, 17 May 2008 (UTC)

[edit] What if the Ice Age never happened?

What would the earth be like? Most importantly, how would human beings be like? --Vincebosma (talk) 13:43, 16 May 2008 (UTC)

There have been many ice ages in Earth's history. Do you want to cancel all of them, or just the most recent? Algebraist 13:48, 16 May 2008 (UTC)


cancel all of them --Vincebosma (talk) 13:48, 16 May 2008 (UTC)

(edit conflict) It's worth pointing out that there is no "the ice age", there have, in fact, been several (see ice age#Major ice ages). The first difference to spring to mind would be the lack of any U-shaped valleys. I'm not sure what differences it would have on life, but there would certainly be some - various species have been forced to migrate or evolve (or both) in order to survive an ice age, or have simply died out. --Tango (talk) 13:52, 16 May 2008 (UTC)
If you cancel all ice ages, then the history of life on earth would be radically different for at least the last few hundreds of millions of years. I doubt anything sensible can be said about what humans would be like in such a circumstance; it's not clear that there would be anything even vaguely humanlike around at all. Algebraist 14:10, 16 May 2008 (UTC)


OK, how about just cancelling the most recent one? --Vincebosma (talk) 14:24, 16 May 2008 (UTC)

Well here's one observation: Native Americans came to North American via the Bering Land Bridge created by low sea levels during the last glaciation. Remove that and North American history certainly changes. In addition, if the overkill hypothesis for the Pleistocene extinction of North American animals is correct, you'd also substantially change the distribution of animals in North America. Dragons flight (talk) 14:33, 16 May 2008 (UTC)
You'd also destroy environments created by glacial activity. For example, the entire environment of the Ozarks region of Missouri exists as the result of glacial activity. Without glaciers, the mineral deposits that were pushed southward wouldn't be on the north side of the ozarks, most of the lakes wouldn't be there, and the mountains would be more mountainy and less hilly. That would affect the wildlife that lives there. Do that on a global scale and you affect all wildlife pretty much everywhere. -- kainaw™ 15:41, 16 May 2008 (UTC)
There is steadily mounting evidence that the Bering Land Bridge migration had a much smaller influence in populating the Americas than previously believed. One of the most recent [[2]]. But since the age of sites still falls within the last glacial, the ice sheet might have helped quite a bit. Comparing [[3]] and [[4]] may be useful in seeing how the mineral deposits Kainaw mentioned help agriculture. Lisa4edit (talk) 16:48, 16 May 2008 (UTC)

[edit] Indefinite Viral Carriers

I have been reading about common contagious viruses in humans. Some are commonly transmitted through fecal contact (ie: Coxsackie A virus). Is there a classification of viruses that are indefinitely reproduced in the intestines of humans? I'm looking into reading about treatments to try and eradicate indefinite viral infections in the intestines. If the virus dies out on its own, there obviously won't be a treatment. That is why I'm interested in finding the classes of viruses that don't die out. -- kainaw™ 15:37, 16 May 2008 (UTC)

Don't all viruses replicate indefinately? Otherwise they would die out? Fribbler (talk) 16:32, 16 May 2008 (UTC)
Yes. They replicate indefinitely, but the body fights off the virus and eventually wins out, eradicating it from the body. Some viruses are not beaten - just beaten into submission. I'm interested in viruses located in the human intestines that remain there throughout life but cause contagious diseases. Specifically, I am looking for classification names to help me in searching medical publications. -- kainaw™ 17:29, 16 May 2008 (UTC)
You could search for "virus carrier" and "carrier state virus" or ("name of virus" + "chronic carrier state") - though I don't know that you'll find much involving intestinal viruses, which tend to be evanescent. Viruses that persist in the body, and so induce a carrier status, tend to infect cells elsewhere - HIV, hepatitis B & C, herpesviruses, etc. (HIV -> lymphocytes; hepatitis -> liver; HVZ -> ganglia; mumps -> conjunctiva, etc.) Unfortunately you'll get a lot of "noise" when searching, because cell cultures are also called "carriers", and you're not interested in them. - Nunh-huh 20:22, 16 May 2008 (UTC)
I know about the noise. That is why I was hoping there was some weird Latin term for "chronic carrier of an intestinal virus" that I could use to narrow down the noise. Thanks though. It is nice to know that my difficulty in finding research on this isn't "just me." -- kainaw™ 20:31, 16 May 2008 (UTC)

[edit] CO2

What is the weight ratio of CO2 released to fuel burned? LLOTAAMI (talk) 16:11, 16 May 2008 (UTC)

Depends on the fuel. DMacks (talk) 16:19, 16 May 2008 (UTC)
You get 3.7 kg of CO2 per kg of C in the fuel. A fuel like gasoline is about 85% C by mass. Dragons flight (talk) 16:22, 16 May 2008 (UTC)
(Edit conflict) I believe the best-case scenario would be complete combustion of pure hydrocarbons, which would produce a number of CO2 molecules equal to the number of carbons in the fuel combusted. So you might want to start by trying to find out the typical composition (and probably density since we usually measure fuel in terms of volume not mass) of the fuel you are interested in. If combustion is not complete (which you can bet on) you'll get less CO2 but lots of stuff that is worse. So in any case you should be able to come up with a decent upper-bound, best case figure. --Prestidigitator (talk) 16:40, 16 May 2008 (UTC)
Dragons flight is completely correct - and here is why: Weight of one mole of Carbon is 12 grams - weight of one mole of Oxygen is 16 grams. If combustion is complete then for every atom of carbon you started with, you end up with one atom of carbon and two atoms of oxygen. So for every mole of carbon, you added two moles of oxygen. So if you completely burn 12 grams of carbon to form CO2 then you have 12+16+16=44 grams of CO2 at the end. For every kilogram of carbon you burn, you end up with 44/12 = 3.7 kilograms of CO2. In reality, complete combustion is rare - you'll always end up with some carbon monoxide and various other byproducts that depends on the nature of the fuel you started with. Since carbon monoxide is lighter than carbon dioxide, you get less weight of CO - but because it reacts to form Methane - it's a much nastier greenhouse gas. 66.137.234.217 (talk) 12:50, 17 May 2008 (UTC)
Well, Dragons flight would be correct in a perfect world. Carburetors were not perfectly stoichiometric in their burning of fuel. (Reference: Fuel injector#Supersession of carburetors) However, stoichiometric burning is not always feasible or desirable. (References: Fuel injector#Functional description, Air-fuel ratio#Synopsis) Gasoline:air ratios may range from 1:10 to 1:18. Many real fuels have additives that change the stoichiometric air-fuel ratio by as much as a few percent. (Reference: Air-fuel ratio) —Preceding unsigned comment added by Fuzzyeric (talk • contribs) 00:27, 18 May 2008 (UTC)

[edit] Effect of salt on blood ADH concentration

Why would an injection of salt solution into a vein or eating large amounts of salt result in the production of Anti diuretic hormone by the pituitary gland? I've often heard it said that salt dehydrates the body. Any help would be great. —Preceding unsigned comment added by 92.21.248.149 (talk) 16:20, 16 May 2008 (UTC)

To retain water thus attempting to maintain an osmotic balance. Less urine is produced but it is more concentrated, eliminating salt. see Vasopressin. Fribbler (talk) 16:26, 16 May 2008 (UTC)
ADH secretion is stimulated by osmoreceptors in the hypothalamus, which respond, as the name suggests, to changes in plasma osmolarity which would change if blood volume decreased/increased or sodium chloride concentration were elevated or depleted. (well the ions). Wisdom89 (T / C) 18:15, 16 May 2008 (UTC)

[edit] Speed of Thought

I was thinking (pardon the pun) the other day, and I wondered, what is the speed of thought? How long does it take, once you have enough information, to make a decision? Are all areas of the brain involved or is there a sort of "thinking center" where this takes place? Thank you. Jen17op (talk) 16:24, 16 May 2008 (UTC)

There are whole branches of science devoted to studying such things. Have you tried starting at the thought article? I'm sure there are lots of artificial intelligence related articles that will provide useful information as well. --Prestidigitator (talk) 16:47, 16 May 2008 (UTC)
I haven't read it (yet), but I would expect that Malcolm Gladwell's recent book Blink would be relevant to your question. -- Coneslayer (talk) 16:51, 16 May 2008 (UTC)
Another way to go is start at Brain and have a look at Electroencephalography Functional magnetic resonance imaging Neuron. Don't have the time now to dig up pages, but there have been quite a number of studies correlating increased brain activity in certain areas to corresponding induced thoughts. Having a scout around in the science magazine archives should get you some more information. Lisa4edit (talk) 17:17, 16 May 2008 (UTC)
It can take days or even years to make a decision even after the brain is in posession of all the information needed. Or it can take as little as 300 milliseconds if a simple decision must be made and a response given, including time for the stimulus to go from the ear or eye to the brain and the response to cause a physical movement, as when you must press one of two buttons depending on which of two tones you hear. A simple reaction time can be much shorter, if no decision is required (as when you know to press a button when a buzzer sounds). Edison (talk) 22:19, 16 May 2008 (UTC)
Surely it would be the same as the speed of electricity, although it would be slower when going accross synapses? --h2g2bob (talk) 22:53, 16 May 2008 (UTC)
200ft/second Ziggy Sawdust 23:21, 16 May 2008 (UTC)
It is way slower than the speed of electricity, which is like the speed of light. Nerve impulses travel by a chemical process along nerve fibers and across synapses. The decision part is what can be time consuming. Edison (talk) 03:38, 17 May 2008 (UTC)
The problem is that the speed of transmission from one neuron to another is not a measure of the time it takes to form a thought. The brain is a massively parallel computing machine and many parts are working on the problem at the same time. Most disturbing to me is that there have been some fairly robust studies showing that our conscious mind isn't really what's doing the work. Thoughts and even decision making happens at an entirely subconscious level and all that our conscious mind does is to retroactively justify those results. But certainly the speed of nerve impulses is positively sluggish compared to the speed of light and the speed of electricity. Studies that measure 'reaction time' are not really measuring the time it takes to make a decision because you've already decided that when the buzzer sounds or the light flashes, you're going to press the button. What those experiments measure is the time to ACT on a decision you've already made. Even something like the time it takes for you to stand on the brakes of your car if a kid runs out in front of you is only the time to act on something you already decided on. The fastest reactions of all (eg pulling your hand away when you touch something hot) don't even go as far as the brain. There is enough processing power in the spinal cord to deal with those kinds of low level emergency. The message that you touched something hot and moved your hand away does eventually reach the brain - and your conscious mind then carefully 'edits' your train of thought to make you THINK that you made the decision at a conscious level. 66.137.234.217 (talk) 13:19, 17 May 2008 (UTC)
I distinguished between simple reaction time, such as you describe, where the decision of what action to take is already made, and choice reaction time, where a decision has to be made before the response is initiated. The decision could be red versus green versus yellow light, word versus nonword, animal versus non-animal picture, match versus nonmatch of multiple stimuli, target list versus nontarget item, etc. Physiologist F.C. Donders in the 1860's introduced the method of subtracting simple reaction time from choice reaction time to determine the time required for the decision to be made. Much research was done in the 1960's and since along these lines, although a simple subtractive method has largely been discredited. As for there being physiological processes operating below and in advance of your mental life, I tend to agree. It is common to start, then realize it is because someone in a crowd spoke your name. Edison (talk) 19:44, 17 May 2008 (UTC)
I don't tend to have that problem (but I don't have people calling me in crowds much) but I do have the problem when I asked 'what?' or something of that sort then a few seconds later realise I actually understand what that person said... Nil Einne (talk) 20:03, 17 May 2008 (UTC)
Would the conscious mind perform said edit if one is fully aware of the process you describe? Zain Ebrahim (talk) 15:38, 17 May 2008 (UTC)
According to Benjamin Libet, the conscious mind doesn't really make "decisions," it has the power to veto decisions made pre-concsciously. Weird, right? As you can guess, though the experiment is compelling, the interpretation of the results is contentious. See Readiness potential and Benjamin Libet, although the topic isn't covered very deeply on wikipedia. --Shaggorama (talk) 06:07, 21 May 2008 (UTC)
It's becoming increasingly clear that the conscious mind may only be there to post-justify things that the subconscious mind already decided to do. That's certainly the best interpretation of Libets' work. Even the power to veto may be an illusion. In the experiment described in our Benjamin Libet article, it may well be that the conscious mind says something like "OK, subconscious, we have to decide to push that button at some time during the next 10 seconds." - the subconscious waits six seconds then makes the decision to actually to it. Eventually - sometime after the six seconds is over - the conscious mind notices that the button was actually pushed and fixes things up such that our EXPERIENCE is that we actually consciously decided when to push it. This editing of memory to make it seem as if we're making all of the decisions consciously when in fact the subconscious is doing all of the work is consistent with the idea that we first evolved as non-self-conscious creatures who were perfectly able to make decisions and survive in the world - and that consciousness is just a layer that evolved afterwards for some as-yet-unknown benefit. 71.155.164.147 (talk) 21:03, 21 May 2008 (UTC)

[edit] biology

what are prions??? what are the possible mechanisms through which they cause diseases??and what are the current techniques being employed to understand them and cure them??? —Preceding unsigned comment added by 220.226.30.96 (talk) 18:18, 16 May 2008 (UTC)

Have you read prion? --Tango (talk) 18:21, 16 May 2008 (UTC)
Prions are malformed/misfolded proteins (that you can ingest say from meat) that have the capability of inducing the misfolding of other crucial native proteins important in the brain. This leads to aggregation of the proteins and eventually plaques. Extremely long incubation time. That's it in a nutshell. Wisdom89 (T / C) 18:32, 16 May 2008 (UTC)
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. -mattbuck (Talk) 19:09, 16 May 2008 (UTC)
Prions are similar to viruses. Prions are rampant proteins that make other proteins rampant. Mac Davis (talk) 22:09, 17 May 2008 (UTC)
They're like zombie proteins! --Bmk (talk) 02:48, 18 May 2008 (UTC)

[edit] Twaron subject to UV degradation?

I was reading the Kevlar article, and link hopped to the Twaron article, and I was wondering if Twaron shares Kevlar's vulnerability to UV radiation. Aradraugfea (talk) 22:44, 16 May 2008 (UTC)

Sailcloth#Twaron should answer your question pretty well :) Regards, CycloneNimrodTalk? 22:54, 16 May 2008 (UTC)
That it did. Thank you very much. Aradraugfea (talk) 23:09, 16 May 2008 (UTC)