Wikipedia:Reference desk/Archives/Science/2006 November 2

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November 2

Having wet dreams about drinking breastmilk

Posting anonymously for obvious reasons. I keep having dreams about being breastfed by some of my favourite large breasted female celebrities. Really vivid ones too, I can taste their sweet milk, feel its warmth and I get really turned on by it. Sometimes I have sex with them whilst nursing from them. I often wake up having ejaculated in my sleep. When I'm awake, this feels creepy and wrong but still there's a part of me that wants to find a woman with milk in her breasts and do it for real. Am I really fucked up for thinking this? I don't know anyone I can talk to about this.

So...is this actually causing you some sort of problem? or are you just boasting 8-)--Light current 00:12, 2 November 2006 (UTC)

It just feels "sick" to me. Like I subconsciously want to have sex with my mother, or get involved with all that weird adult baby stuff. It's like the idea of drinking breastmilk really turns me on but the implications of why I want to do it scare me, if you know what I mean. My dreams usally involve MILF age women too, which makes the connection with my own mother seem more apparent. For the record, I don't fancy my mother but I'm scared what my head is trying to tell me. --194.164.208.87 00:33, 2 November 2006 (UTC)

Why not take it at face value? --jpgordon^∇∆∇∆ 00:46, 2 November 2006 (UTC)

Meh, lactophilia isn't the most bizarre or disturbing fetish you could have. Just take a look at some of the entries on Template:Paraphilia for some reassurance if you're worried about appearing weird. GeeJo ^(t)⁄_(c) • 01:08, 2 November 2006 (UTC)

LOL! I just found out that I have a smoking fetish. I love the taste of cigarettes in a woman's mouth when I kiss her, the smell of smoke on her hair and clothes, etc. and I do tend to seek out women that smoke. I didn't even realize that it was a 'fetish' as such, or that there was a particular name for it. Knowing that, do I feel any different about it? Hell no. ;) --Kurt Shaped Box 01:17, 2 November 2006 (UTC)

Then you'd love Morticia Addams..."Do you mind if I smoke ?". :-) StuRat 03:38, 2 November 2006 (UTC)

There's nothing to worry about. The female breast is an erogenous zone; according to the erotic lactation article, this fantasy is more common than we might think. The sex-positive movement suggests liberating ourselves from the repression and shame associated with many consensual sexual activities and fantasies that has been foisted upon us by puritanical prudery. If no one is harmed, how are such activities and fantasies to be regarded as wrong? Sexual Puritanism is responsible for shame over the human body, shame over human sexuality, etc, which it justifies with nothing more than bizarre claims of a "war" between the flesh and the spirit, the body as an instrumentality of the devil, and other such nonsense. To hell with that :) Personally, I found the description of sucking the milk from a woman's breasts to be highly erotic -- quite an appropriate word since the ancient Greeks regarded Eros as a divine experience. 75.26.10.224 01:10, 2 November 2006 (UTC)

Doesn't sound like anything to worry about. IMO, breasts are the best part of a woman's body - the bigger the better (as long as they're natural and about the same size on each side) as far as I'm concerned. You can rub them, squeeze them, grope them, squidge them together, use them as a pillow, suck them, bury your face in them, nibble them, lick them, kiss them, hump them, etc. etc. etc. I will never get bored of breasts. ;) If they have milk in them, they'll be bigger still - which is a Good Thing in my book. You're not actually having sexual thoughts about your own mother, so what's the problem? --Kurt Shaped Box 01:29, 2 November 2006 (UTC)

HEY! Don't say that! You'll give the guy who was having wet dreams about his mother a complex ;).. There's nothing "wrong" with having a sexual dream about your mother.. I definitely agree about the comments above about puritanism, I find personally find it disgusting and perplexing that war and death are more socially acceptable on the media and in the news then two people loving each other. Vespine 02:01, 2 November 2006 (UTC)

Heh, sorry. :) I do know what you mean though - gratuitous violence on TV is fine but sex is taboo. The act of destruction is more acceptable than the act of creation. Bringing life to an end is superior, morally-speaking than bringing about new life. That's *really* fucked up. --Kurt Shaped Box 02:10, 2 November 2006 (UTC)

The weirdest example in the US was the editing of Conan the Barbarian (film) (Arnold's first big movie) for TV. The scene where a person is beheaded is kept in, while a scene showing a bare-breasted woman was censored for being "obscene". StuRat 02:54, 2 November 2006 (UTC)

So god damned it people!? HOW do we affect change?? Issues like this make my skin crawl, I can feel it in the deepest part of my being! Let's EVOLVE! There seem to be SO many like minded people yet so much of our lives are led by these evil crypto fascist ultra conservatives. Is it strange to sometimes think you understand why people start cults?? ;) Vespine 04:55, 2 November 2006 (UTC)

WWCD? (What Would Che Do?) ;) --Kurt Shaped Box 06:45, 2 November 2006 (UTC)

Che would execute anyone who disagreed with him. StuRat 01:14, 3 November 2006 (UTC)

If you've been around usenet for any length of time (ten years and counting...) and met all the trolls, kooks, drama queens, stalkers, and pedants, you'd soon start to come around to his way of thinking. First up against the wall when the revolution comes will be the people who use 'we' instead of 'I' in their postings to imply that their opinions have some sort of support outside of their own heads... ;) --Kurt Shaped Box 02:12, 3 November 2006 (UTC)

Yeah, we hate those guys here. GeeJo ^(t)⁄_(c) • 11:16, 3 November 2006 (UTC)

Electrons

Which electrons are most responsible for the properties of an atom?

Bob and Sue ? :-) StuRat 06:58, 3 November 2006 (UTC)

The ones orbiting it. Would you like a more specific answer? GeeJo ^(t)⁄_(c) • 00:56, 2 November 2006 (UTC)

THe outer most ones. The ones in the valence shell--Light current 01:16, 2 November 2006 (UTC)

Which properties? Optical properties (photon energies of several electron-volts and lower) - the outermost one; that's why an electron in the outermost orbit is called an "optical electron". Chemical - several outermost ones, see previous answer. Interaction with X-rays - depends on the X-rays energy and atomic number. Interaction with gamma radiation - the innermost ones. Nuclear reactions and interactions involving atomic electrons - the innermost ones. And so on. By the way, technically the electrons are indistinguishable, so a better way to ask the question might have been "Electrons in which orbitals are most responsible..."; but those are really technicalities. Dr_Dima

You forgot to mention the kind of properties handled by the real estate agent electrons --froth^{T C} 23:15, 4 November 2006 (UTC)

Conservation of momentum

Hi, I have question about the conservation of momentum and energy consumption using the kenetic energy formula, m*v^2/2. It seems to me that, if we had a row boat with a frictionless hull and a man rowing, every time he pulled on the oars he would expend energy and one could estimate the energy consumed by looking at the mass and velocity of the water he was moving. Say that he could accelorate 100 kg of water to 1 meter per second every stroke producing a force of 100 newtons. If he and his frictionless hull massed 100 kg as well, then he would be accelorating 1 meter per second every stroke, using 50 joules each stroke. After 100 strokes he would have used 5000 joules of energy, and would be traveling at 100 meters per second. However this can't be right because the kenetic energy formula for a 100 kg object at 100 meters per second says that we need 500000 joules. What have I done wrong? Thanks 71.7.199.126 01:08, 2 November 2006 (UTC)

So he's accelerating the water and himself? (in opposite directions)--Light current 01:23, 2 November 2006 (UTC)

The "50 joules" part is wrong. Energy = force x distance, so in order to exert a constant 100 newtons against the water, you need 100 joules of energy for each meter you travel relative to the water. So you have to stroke more energetically as you speed up, and need higher power (= energy/time) to keep accelerating while moving at a higher speed. --Anonymous, 01:45 UTC, November 2.

I haven't checked your math, but two points to remember: First, Newton's law is F = ma, not F = mv. Second, and I suspect this is more important, the energy required to cause a given constant change in the velocity of an object depends on the initial velocity of the object. Even if you stay in the rower's frame of reference, it costs an increasing amount of energy to push on the water as it starts going by faster. Melchoir 01:47, 2 November 2006 (UTC)

Yo, the math makes it equal to 500,000 too. K.E. = ½(m)(v²)= ½(100)(100²)= 500,000. --AstoVidatu 02:09, 2 November 2006 (UTC)

Thanks a lot, so on the second stroke the energy required is 50 newtons times 2 meters since the boat is moving at 1 meter per second? --71.7.199.126 02:07, 2 November 2006 (UTC)

If the rower exerts exactly 50 newtons of force during the time it takes the boat to move exactly 2 meters, then yes. However, I wouldn't count on that being the case, since the boat is accelerating during the stroke. Given simple starting assumptions about how much momentum the boat gains after each stroke, it is much easier to just calculate its kinetic energy before and after, and subtract. And remember, this is just the energy required to move the boat; you'd have to do a more sophisticated analysis to add in the additional energy that gets wasted in the water. Melchoir 16:13, 2 November 2006 (UTC)

boiling water and conserving energy

this question stems from a running (amicable) disagreement with my girlfriend. she, when boiling water (e.g. a teakettle), prefers to use a medium or low flame, believing that it conserves natural gas. i prefer to use the highest possible flame: i think one needs X amount of heat energy to raise the temperature of Y amount of water Z degrees, and one has to burn the same amount of gas to produce that much heat whether one burns it quickly or slowly. which one of us is correct? 67.68.215.151 01:31, 2 November 2006 (UTC)

Both. At low flame, heat energy is lost due to cooling basically as a function of time and ambient temperature. At high flame, heat is lost simply because the pot can't capture it all and it's wasted. So there is an opimal point. Personally, however, my time is more valuable than the natural gas and I will put it on the largest flame that the pot can cover. That's the quickest boil.--Tbeatty 01:37, 2 November 2006 (UTC)

You need the optimum energy transfer rate from the flame into the water. This means that you should use an electric kettle! 8-)--Light current 01:41, 2 November 2006 (UTC)

It should be rather easy to tell if you are wasting heat. Since it isn't being absorbed by the kettle, it must escape around the kettle. You will be able to feel a draft blowing out from underneath it. The optimal temperature will be at a point where very little heat rushes out from under the kettle. --Kainaw ^(talk) 01:43, 2 November 2006 (UTC)

thanks! i'll keep these answers in mind next time this comes up. 67.68.243.140 02:02, 2 November 2006 (UTC)

The flame should be almost completely blue. Yellow and orange indicate inefficient combustion. -THB 02:17, 2 November 2006 (UTC)

Also note that whether it is winter or summer makes a major difference (assuming you're in a temperate zone):

• In summer, the escaped heat must be countered by increased air conditioning, at a high energy cost.

• In winter, the escaped heat warms the house, reducing the amount of heat needed. If it's a gas stove and you have gas force-air heat, it's even more efficient to heat your home with gas burners than with the furnace, as they don't suffer from the inefficiency due to the venting of the combustion products. Of course, those fumes are toxic in large quantity, so completely heating your home in this manner would be unwise.

One final thought, covering the pot also makes a huge difference in how quickly it boils and how much energy is used. StuRat 03:32, 2 November 2006 (UTC)

Orbital maintainance as a function of orbital velocity

If the gravity of a body in space increases (say from the accommodation of material coming from outer space) and the orbiting bodies would have to increase their orbital velocity in order to maintain their orbit and there is no limit on the size of a neutron star except the total amount of mater in the Universe is there a neutron star size at which its gravity is so great that no particle, not even one orbiting at the speed of light would have sufficient velocity to maintain its orbit? Adaptron 01:53, 2 November 2006 (UTC)

I'm gonna think and write at the same time, so go with me here. Centripital Acceleration has to be equal to gravity in order for the object not to fall into the star. C.A. = (v²)/r. The speed of light is equal to 299,792,458 m/s. And gravity is equal to (G(m))/r² (assuming that the particle speeding around the star has inconsequential mass). Thus if (6.67 x 10^(-11))(mass of neutron star)/(r²) > (299,792,458)²/r; or if (5.99 x 10^28)(radius) < mass, then even stuff travelling the speed of light should be sucked in. I think we call them black holes (?). Note that r is measured in meters, and mass in kg. --AstoVidatu 02:04, 2 November 2006 (UTC)

IIRC a Neutron star is one that lacked sufficient mass to become a Black Hole. Therefore there is a maximum/critical size where a neutron star will collapse. See also Chandrasekhar limit--Tbeatty 02:12, 2 November 2006 (UTC)

See also Schwarzschild radius. --Tardis 02:23, 2 November 2006 (UTC)

Would this point of collapse of a Neutron star into the formation of a Black Hole then be the point at which no particle, not even with an orbital velocity of the speed of light, be able to maintain its orbit and if so what size would the Black Hole have to be so that no particle in the Universe could maintain an orbit? Adaptron 02:24, 2 November 2006 (UTC)

Yes. As for your second question, "size" isn't the proper term, since the radius of the event horizon depends on the density mass of the object in question - like Tardis suggested, Schwarzchild radius describes that better. The dependence of the Schwarzchild radius on mass ultimately means that a sufficiently large object of any density can become a black hole. And black holes have a large range in sizes.

For a little bit of extra fun, there has been at least one documented instance of a white dwarf which exceeded the Chandrasekhar limit, for reasons which have yet to be documented fully.

Locusts as food for humans

Just been reading a few recipes for locust on the web and I'm now wondering why people who live in areas affected by plagues of locusts don't just go out and gather these fat, tasty, nutritious insects by the sackful and use them as a food source to replace the crops consumed by the swarm. AFAIK, locusts can be ground into flour and used to make bread, can be eaten as meat and also keep for a long time if dried. Why the big panic about them? --84.69.57.172 02:02, 2 November 2006 (UTC)

I don't know about you, but if I had spent two months plowing, planting, growing, and watering my crops, I wouldn't want them to be eaten. Also, one must consider that not everyone shares your interest in eating insects. I know they have lots of protein, but a lot of people, for some reason, don't find the idea of eating locusts appealing. ;) --AstoVidatu 02:06, 2 November 2006 (UTC)

A much better idea is "Locusts as Bait for Food for Humans." Teach cows/pigs/sheep/fish/chicken to eat them. --Tbeatty 02:08, 2 November 2006 (UTC)

God told the seagulls to eat locusts. --Kurt Shaped Box 02:14, 2 November 2006 (UTC)

That's just squeamishness. If people actually tried them, they'd probably like them. They had a rat problem in Vietnam not so long back. In order to counteract this, the government started a campaign urging people to eat more rat meat - it worked. Just about everything that crawls or walks is food. If the human race is going to survive, we'd better start realizing this. --84.69.57.172 02:18, 2 November 2006 (UTC)

What about the Galah? Those things are apparently almost completely inedible, no matter how you cook them. --Kurt Shaped Box 02:23, 2 November 2006 (UTC)

Agreed. There's nothing about insects that makes them inherently less appealing as food than carcasses of dead animals. If appearance is the problem, you can always process them into something that doesn't look like insect bodies. --71.244.111.101 03:15, 2 November 2006 (UTC)

It's an interesting point. There is no real reason why the majority of species that we consider to be pests cannot be used as food, if we drop the 'I don't like it - even though I've never tried it' thing. I'm sure that even rats and street pigeons can be made palatable and safe to eat if prepared in the correct manner. Same with starlings and house sparrows in the US - and obviously Australian rabbits. It's a simple solution and the Vietnamese had it spot on - "if there's too many of them, dine on them exclusively for a time to 'thin the herd'". --Kurt Shaped Box 06:43, 2 November 2006 (UTC)

There is a practical reason to avoid eating small animals. The amount of work to "gut" them becomes greater relative to the amount of meat produced. Thus, most small animals aren't eaten at all or are a rather expensive treat. For insects, however, people eat them whole, assuming that the bacteria in their gut won't be a problem. I'm not quite sure why that's the case. StuRat 18:35, 2 November 2006 (UTC)

Also note that there would be considerable difficulty in gathering the locusts once they've taken to flight. They could, however, be gathered while still on the ground. Since they all move in one direction, on the ground, I would think collection trenches could be constructed for this purpose. If people don't like eating them, they could be ground up (the locusts, that is) and used as protein supplements for livestock or as fertilizer for crops. StuRat 02:30, 2 November 2006 (UTC)

I wish I could find it but there are communities that eat locusts. I saw a video clip of a village in Africa with a huge pile of locusts that the locals had gathered using long "net fences", the women of the village were coming up to the pile and scooping up bowlfulls to take back home.Vespine 04:45, 2 November 2006 (UTC)

There are many societies that eat insects - grasshoppers are apparerntly common in rural cuisine in Mexico with some fancy restaurants in Mexico City serving insects as well. The Yemeni Jews are said to be the only Jewish group to retain the knowledge of which locusts are "kosher" which is mentioned in the very short "Locusts as food" section of our locust article. I think that they would be rather easy to collect by nets in the air. In the U.S. Midwest we sometimes have cicada barbeques during the largest brood emergences (just google "cicada recipe") Rmhermen 15:25, 2 November 2006 (UTC)

Locusts are supposed to go well with wild honey. Edison 18:16, 2 November 2006 (UTC)

What causes Electromagnetic radiation ?

I have been searching through the Electromagnetic Radiation article. It lists properties but I am not sure where to identify the origins of electromagnetic radiation 69.150.209.13 02:12, 2 November 2006 (UTC)

accelerating charged particles. --Tbeatty 02:17, 2 November 2006 (UTC)

There are many sources, depending on the frequency. Stars are one source of certain frequencies, as the radiation is given off by atoms undergoing fusion or decay. Neutron stars, supernovae, and black hole accretion disks given off other frequencies of EM radiation. There are also man-made EMs and some "background radiation" remains from the Big Bang. StuRat 02:18, 2 November 2006 (UTC)

But if this is for school you fill in the blank with "accelerating charged particles." :) You know light counts as EM radiation? Photons are often created in subatomic reactions, symbolized by gamma X [Mac Davis] (SUPERDESK|Help me improve) 05:46, 2 November 2006 (UTC)

Accelerating charged particles aren’t the only source, though, right? Particle-antiparticle annihilation will create EM radiation. So will switching from a high-energy to a low-energy orbital. Anyway, if you’re looking for specific examples: humans, TVs, mobile telephones, light bulbs, and fire are some of the obvious ones that come to mind as I glance around the room. — Knowledge Seeker দ 07:57, 2 November 2006 (UTC)

The simpliest answer: highly energetic objects. You won't get much radiation leaking out of a nuclear core, if you dropped it down a glacial crevasse. Surround it with high explosive, detonate that, and you've got a rather different scenario. -- Chris 16:53, 2 November 2006 (UTC)

Electromagnetic radiation is one of the four fundamental fources of the universe. To get into what causes there to be four fources and not five and what gives each force its properties is something that can't be answered with surety. superstring theory has an answer to this but is, at the moment, an untestable theory. Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 19:57, 2 November 2006 (UTC)

By the use of wikipedia I have analyzed that the sun is the main source for electromagnetic radiation, it is mostly composed of hydrogen and helium, which seems to give its nuclear fusion reaction. So does nuclear fusion also cause electrons jumping orbitals, hence releasing electromagnetic radiation? 69.150.209.15 21:11, 2 November 2006 (UTC)

I don't think "jumping orbitals" is the right term, as both hydrogen and helium posses a single S orbital, with a single electron in that orbital in the case of hydrogen and two sharing the orbital in the case of helium. StuRat 16:54, 3 November 2006 (UTC)

Organization of the periodic table

Please help because I am stumped. Strontium, SR(Number 38) is especially dangerous to humans because it tends to accumulate in calcium-dependent bone marrow tissues, CA(#20). HOW does this fact relate to what you know about the organization of the periodic table? I missed this on a test and he will not give us the right answer, so I would just like to know why I was wrong because I have no clue. Thanks!!!!

It's answered on the Strontium article.--Tbeatty 02:46, 2 November 2006 (UTC)

As for your teacher being unwilling to tell you what the correct answer is, that is rather unacceptable, in my opinion, both because it's counter to the overall purpose of education and because students have a right to double-check the grading process, as teachers often make mistakes. I suggest you discuss this with your parents, and have them complain to the teacher and school administration. You might, however, wish to have them wait until the end of the school year, after grades are all in, so he can't retaliate against you. StuRat 03:23, 2 November 2006 (UTC)

odd isn't it. given that school-level chemistry these days is often taught by non-chemists, kind of makes me think the teacher is unsure of their own answer. 132.181.173.233 04:20, 2 November 2006 (UTC)

Bad teachers are universal. You never forget them. I used to be good at Chemistry at school - then I had a crap teacher in my final year who screwed everything up for me, completely turned me off from the subject and didn't get around to teaching us everything we were supposed to know for our exams (he also hit me with his car one time - but that was unrelated). I failed miserably. --Kurt Shaped Box 07:48, 2 November 2006 (UTC)

I, too, am surprised that your teacher could not just admit to the phrase "They're both in Group 2". G N Frykman 07:43, 2 November 2006 (UTC)

• Abbreviations of elements in the periodic table are only written with a capital first letter. The second one is never capitalized. (so it's Sr and Ca instead of SR and CA) - 131.211.210.17 10:01, 2 November 2006 (UTC)

An experiment made to separate oil from Coconut milk.

Dear Sirs,

                       CENTRIFUGE TO SEPARATE COCONUT OIL FROM COCONUT MILK.

I wanted to do above with a motor of RPM 23000, and 1500 W mounted on a Cylinder of 2 ft. heigh and 6" in diameter.In this case Cylinder (bowl) is stationary and it is the roter which revolves the coconut milk with in the Cylinder. I made small holes on the shaft of the roter to bring down the oil if separated from Coconut milk.I used racers and water seals at the top lid of the cylinder and at the bottom of the cylinder, in the mechenism,in order to do this experiment. Also made two ports on upper level of the cylinder and outer (at loverlevel) edge to expell the water and heavy particles respectfully. How ever much I adjusted the shape the size and vertical level of the roter (FAN) I did not get any liquid (expected oil) through the hollow roter shaft with which provided holes to enter oil in to it.I expected to drain out oil through the rotor shaft down wards. The Coconut milk sent to the cylinder moves up to the discharge port provided on the cylinder [to expell only the denser liquid (Water)] without doing any separation . In other wards no liquid touched the roter shaft after passing the upper or lower level of the roter. My question is - What steps and adjustments should I do in order to keep the coconut milk rotation in the cylinder as a whole in order to get the separated oil without being liquid taking a parabolic shape at the middle ?. (Coconut milk which has 30 % oil is a juice extracted by pressing fresh coconut.

--Ishitha777 04:43, 2 November 2006 (UTC) Thank You. K.Samarasinghe.

I'm not an engineer, but I am pretty familiar with machinery, pumps and blue prints, that kind of stuff; I don't think I'm being unreasonable by saying your description is really, really hard to understand, you lost me on "small holes on the shaft of the roter"... I am not particularly familiar with centrifugal separation techniques so someone that is may be able to make more sense. Otherwise, maybe draw a diagram. Vespine 04:40, 2 November 2006 (UTC)

Would it be possible for you to post a link to a drawing of this contraption? Here's a link to a coconut milk centrifuge: X but it doesn't show the actual mechanism. I don't think you can avoid the parabolic shape--my blender makes the shape unless the liquid is too viscous. My thought is that cold pressing would be easier. -THB 04:48, 2 November 2006 (UTC)

Okay, here you go: [1] and [2] have the info you need. -THB 05:06, 2 November 2006 (UTC)

Ear clapping?

What would be the effects of someone jumping from behind you and clapping their hands against your auricles? I hope you know what I mean. X [Mac Davis] (SUPERDESK|Help me improve) 05:44, 2 November 2006 (UTC)

It'd hurt and there's a chance that it might burst your eardrums? We used to do that all the time at school - we called it "Tangoing" (after the UK fizzy drink - one of the ads for Tango had a fat guy running up to people and ear-clapping them). AFAIK, the kids are still "Tangoing" each other. There was a rumour that someone had once been "Tangoed" to death that everyone seemed to have heard but I think it was just an urban legend. The ad got pulled because everyone was copying it (video here). --Kurt Shaped Box 06:27, 2 November 2006 (UTC)

I'd have thought WP would have an article on boxing ears (which is an older term for it), but apparently it doesn't (at least not that I can find). In addition to causing pain, ear boxing can cause some disruption of the eardrum(?) or inner ear, which can disturb the balance of the person being hit. In rare cases, it can also burst the eardrum, leading to permanent deafening - this is unlikely, though. Some of the (nonfictional) devices in the sonic weaponry article may have descriptions of similar effects.

The Tango advert got pulled after a child had his ear-drums perfurated. So, I wouldn't suggest trying it out! Englishnerd 16:33, 2 November 2006 (UTC). Also if you are jumping out at the person, there is every chance they could get some, albeit mild, whiplash. Englishnerd 16:34, 2 November 2006 (UTC)

Pain, anger, retribution, ad infinitum. -- Chris 16:50, 2 November 2006 (UTC)

Fully N-type MOSFETs

I'm doing some research into MOSFET oxides, but the samples I have have phosphorus doped source and drain, on a very lightly phosphorus doped silicon substrate.

I was wondering what effects having all N-type regions will have on the threshold voltage. In the threshold voltage page the definition is the voltage required to push all the majority carriers away from the gate creating a depletion layer (at higher voltages the inversion layer forms). But I don't really have an inversion layer do I? And my majority carriers aren't pushed away. My results do show a threshold voltage at about 0.3 volts, and yes the thing works.

One more question, often one finds references saying that the inversion layer comes from minority carriers in the substrate, but this feels wrong to me? Does the 2DEG come from the source and drain or the substrate? In my case it may be both right?

Thanks very much, Frontier

Depletion mode mosfet. Tbeatty 06:20, 2 November 2006 (UTC)

But it's not always on. There's still a potential barrier when no gate voltage is applied and no current flows. I did a Hall analysis on it and found 0 carrier density at positive 0.2 volts on the gate.

What's the gate material? And then look at the work function difference.--Tbeatty 06:50, 2 November 2006 (UTC)

They're all silicon dioxide. Some are thermally oxidised (dry, wet, dry). Others use other oxidation texhniques. The base is very lightly doped. It's almost intrinsic.

Gate material is usually polysilicon and there is a work function difference between the bulk and the gate due to doping differences. This is MOS, there is no base. --Tbeatty 08:16, 2 November 2006 (UTC)

Oh, sorry I answered a different question. I oxidised a lightly phosphorus doped crystalline silicon substrate in an oxidation furnace; that was the field oxide. Then etched holes for the source and drain with HF, indiffused phosphorus, etched the gate region again with HF, reoxidised in a furnace the gate oxide, then evaporated aluminium for the gate contact. There's more to it than that, but yeah.

AIDS after death

Ok, I watch too much CSI but how long can HIV remain viable after the hosts' death? And, do different viruses have different within-host postmortem survival rates?? --Cody.Pope 06:45, 2 November 2006 (UTC)

Considering that people got HIV from blood in blood banks, probably a good long time.--Tbeatty 08:16, 2 November 2006 (UTC)

Different situation, because donated blood is processed and refrigerated to keep it fresh and 'alive'. Anchoress 08:18, 2 November 2006 (UTC)

I agree. There's a preservative and anti-coagulant added to blood. Not sure what else is done to whole blood. I'm not sure it's any more "alive" than uncoagulated blood in dead people though. --Tbeatty 08:23, 2 November 2006 (UTC)

As far as I know, HIV can't survive in coagulated blood. So it probably won't survive very long in a cadaver. WB Frontier 09:38, 2 November 2006 (UTC)

I wonder: would you get AIDS from eating steak from a poz corpse? I reckon it wouldn't do much good for your immune system, at any rate. -- Chris 16:49, 2 November 2006 (UTC)

Before you break out the Chianti and fava beans, let me advise against this idea. A virus isn't really "alive" in the sense that it actively does anything, it just "exists". It's existence tends to cause copies of itself to be produced, however, in the right environment (a primate's body, in the case of HIV). So, the question is, how long before it would degrade to a point where it couldn't cause copies of itself to be produced. I would expect the body would need to be in an advanced state of decomposition for this to be true. I believe, however, that the virus is damaged by oxidation if exposed to atmospheric oxygen. So, drops of blood which have dried out are probably not potential sources of AIDS (although they may contain other contagions). StuRat 17:55, 2 November 2006 (UTC)

Any virus is guaranteed to be destroyed by enough heat, and the heat of a frying pan is almost certainly enough to destroy HIV. So the answer would probably be "no" as long as the thing is cooked properly. Somebody out there probably knows the exact temperature at which HIV denaturates irreversibly, but I'm pretty sure it's less than 100 C - even the most hardy of RNAs and DNAs melt at less than that. That said, drying is not necessarily enough to denaturate viruses. It's not unreasonable that a drop of dried blood could still be infectuous, at least for perhaps a day or two. --BluePlatypus 19:10, 2 November 2006 (UTC)

Drying does imply oxidisation and HIV is vulnerable to oxygen, so my 'guess' would be that HIV would not survive drying. As for the eating, assuming you are having HIV tataki (very rare) I believe the oral contract rate is quite low. The mucus membranes of the mouth and following tract can absorb the virus but I believe the chance of that happening is relatively low. After that the stomach acids are definitely too much for the virus. I say 'low' but it is still something I wouldn't be willing to personally test! Vespine 21:52, 2 November 2006 (UTC)

No, drying does not imply oxidation. Whatever gave you that idea? Drying implies the loss of water. And for a virus, it doesn't even imply that, in the short term. If you go read the HIV article, you'll see that the virus is contained within a lipid envelope, which does a good job of keeping it from dehydrating (in the short term). And there's no reason to "guess" because there's plenty of experimental evidence on the fact that HIV can remain infectuous for days after being dried. See, for instance van Bueren, et al (J Clin Microbiol. 1994 February; 32(2): 571–574) --BluePlatypus 22:52, 2 November 2006 (UTC)

Tides

why is the tides vigrous during no moon day —The preceding unsigned comment was added by 61.11.77.8 (talk • contribs) .

A new moon is when the moon is directly in line with the sun, thus only the dark side of the moon is visible from earth. Since the moon and sun are in a line (called Syzygy), their gravitational attractions both work together to make a stronger tide, called a spring tide. --TeaDrinker 07:49, 2 November 2006 (UTC)

Just 'cuz you don't see the moon, it don't mean it ain't there. -- Chris 16:48, 2 November 2006 (UTC)

The gravitational attraction of the Moon pulls on the water regardless of the position of the Moon. The gravitational force travels right through the Earth, so the pull exists even when the Moon is on the far side of the planet. The only difference in the pull (other than the direction) would be because the Moon is slightly farther away (the diameter of the Earth) when on the far side. Compared to the orbital distance of the Moon, however, the diameter of the Earth is small. Also note that the Sun has an effect on tides, as well (although less than the Moon, due to it's much greater distance). StuRat 17:47, 2 November 2006 (UTC)

Boiling_water_and_conserving_energy Part 2

This has something to do with Wikipedia:Reference_desk/Science#boiling_water_and_conserving_energy. I wonder if it is more effecient to boil water in a microwave oven than on a stove with optimal flame ?--Wikicheng 13:01, 2 November 2006 (UTC)

What is an "optimal flame"? —Bromskloss 15:57, 2 November 2006 (UTC)

Check the power output of your microwave, compare it to the joules released through the combustion of gas.

Yes, it is more efficient, as microwaves specifically heat only water molecules (well, they also heat metals, but hopefully you don't have any of those inside), whereas the stove also heats the pot and air. However, using the stove may still be less expensive, because natural gas typically costs less per unit of energy than electricity. StuRat 17:41, 2 November 2006 (UTC)

Oops - an editing conflict. For you to use a microwave oven there must be a power station somewhere nearby which burns that same gas you are trying to save, to produce electricity that your microwave oven consumes. What you are asking is whether the power plant is more efficient than your gas stove in bringing a given amount of water to a boil. The ansewr is: I don't know, but it's easy to check. Follow these steps:

1. Find out how much gas it takes to boil the kettle. To do so, take your montly gas bill. Divide the total quantity of gas consumed (per month) by the estimated time (per month) your stove is lit, and multiply by the time it takes to bring the kettle to a boil.

2. Find out how much electricity it takes to boil the same amount of water in a microwave oven. To do so, multiply the power rating of your microvawe oven (in watts) by the time in seconds it takes to bring the water to the boil. The result is in Joules.

3. Burning a cubic meter of natural gas yields approximately 39 megajoules. Efficiency of a typical fossil-fuel power station is approximately 40%, so that's about 16 megajoules of electricity per cubic meter of gas. (see "energy content" section of Wiki natural gas article, and "Super critical steam plants" section of Wiki Fossil fuel power plant article for these data and much more).

4. You do the math :)

Let us know what you've got. Dr_Dima

Note that electricity is typically produced by some method other than burning natural gas (since natural gas is quite useful as is). Those methods include burning coal, nuclear reactors, hydroelectric plants, etc. Also, the monthly natural gas usage is likely to include their oven, furnace, water heater, and possibly clothes dryer. Pilot lights for those devices may also burn gas, even when the devices are not in use. StuRat 18:22, 2 November 2006 (UTC)

Year without a Summer

I have seen some references to weather records dating back to 1816 (the 'Year Without a Summer'), but I've been unable to find them. I am looking for day-by-day temperatures in New England that year, because I want to determine just how anomalous it really was, and do some analysis of the weather pattern. Any way to find weather data back to 1816 would be greatly appreciated.

-[User: Nightvid]

The wiki article is here. I can't help you otherwise, what you are asking is pretty specific. It might be best to ring the New England meteorological group to see if they have it in their archives. Thanks. --liquidGhoul 13:22, 2 November 2006 (UTC)

Although NASA is usually the best place for this, it seems in the New England region it only goes back to 1880. I don't have any data, but I'll advise you that a day-by-day temperature record, of a single year, and of that time is

• highly inaccurate
• fairly useless

Brian Fagan's book could help? Good luck. X [Mac Davis] (SUPERDESK|Help me improve) 20:28, 2 November 2006 (UTC)

What is a "Lewis conjugate" substance?

Hi, wise guys. I have read something about "Lewis acids", etc. but found nothing like "Lewis conjugate" which Señores Hernando et al. chemisorbed on gold in this article: PRB 74 052403. Thanks for your time. 193.232.124.163 13:07, 2 November 2006 (UTC)

You probably want Conjugate acid, except that the article mostly deals with the Brønsted-Lowry definition. Still, a redirect shouldn't hurt. (There are also conjugated Lewis structures, but I don't think that's what is meant here.) —Ilmari Karonen (talk) 15:30, 2 November 2006 (UTC)

Actually, I chased down the cited article, and they seem to mean a conjugated system after all. Now I'm getting confused. I think I'll turn that redirect into a disambiguation page for now. —Ilmari Karonen (talk) 15:38, 2 November 2006 (UTC)

Thanks, Ilmari. I'll try to figure out. 193.232.124.163 15:57, 2 November 2006 (UTC)

SCR's

My question is concerned wthh silicon controlled rectifiers. I don't seem to understand the theory of SCR's too well - but that I can get over, I will study a bit more. As a side question, are there any specific pages which explain the theory and working of SCR from the basics ? The wp page is more like a reference than a step by step explanation (which is how it should be)

My question has more to do with the application of SCR - What are the advantages of SCR over an equivalent diode only rectifier ? In fact, the way we were taught in school, seems to suggest that the output voltage of SCR is "clipped" in the beginning by "alpha" degrees, where alpha is the delay after which a triggering voltage is applied to the gate terminal. Would that not lead to decrease in the output voltage ? Why then, is it said, are SCR's more useful than normal diode-only rectifiers ?

Thanks. --RohanDhruva 13:21, 2 November 2006 (UTC)

The clue is in the name: Silicon Controlled Rectifier. More useful because they are controllable as to the part of the cycle at which they start to conduct and therefore they can be used to vary the amount of power delivered to an electrical load. Ordinary diodes cannot do this. (they always turn with about 0.6 volts forward across them)

The average power delivered to a load depends upon the (square of the) average voltage supplied (See RMS). If you can vary the 'time on' to 'time off' ratio, you alter the time average of the voltage applied to the load and hence the average power.8-)--Light current 17:53, 2 November 2006 (UTC)

For an in-depth discussion, see http://www.allaboutcircuits.com/vol_3/chpt_7/5.html or our article at Silicon-controlled rectifier. --Jmeden2000 18:06, 2 November 2006 (UTC)

Thank you very much for the response, that explains it ! :) --RohanDhruva 02:06, 3 November 2006 (UTC)

KENTUCKY'S SOIL

WHAT IS WRONG WITH KENTUCKY'S SOIL 208.61.241.196 14:40, 2 November 2006 (UTC)

First, do not type in all caps - it is very rude.

Second, the answer to your question is mu. --Kainaw ^(talk) 14:46, 2 November 2006 (UTC)

You do realize you've linked to a monster of a disambiguation page, right? Presumably the one you meant was mu (negative). —Ilmari Karonen (talk) 16:10, 2 November 2006 (UTC)

Nothing's wrong with Kentucky soil. Leave the land how it is for twenty years, and you'll see all sorts of wonderful things sprouting up. Perhaps, not things that you would fancy eating, but I'd wager that there'd be plenty of pretty vegetation. At worst, you could burn that, then your soil will be good again for a few years. -- Chris 16:45, 2 November 2006 (UTC)

I was unable to find any specific info on soil deficiencies common in the US state of Kentucky. However, if you contact the Kentucky Department of Agriculture, they should have info on potential problems and solutions: [3]. StuRat 17:35, 2 November 2006 (UTC)

NOT A DAMN THING. Some people have good luck growing bluegrass, which at least looks nice. Some grow Tobacco, some grow Cannabis (drug), or hay. Farmers grow tomatos and other veggies, corn, & soybeans . Except for the floodplains of major riversand, much of the soils lacks the deep black humus seen in, say Minnesota, and there is a lot of clay soil. But it generally has abundant water and a long, warm growing season. Acid soils are supposed to be good for growing popcorn.

Chemical bonding in the nitric oxide

How does the oxygen bond to the nytrogen? I´ve learned the oxygen can only have two covalent bonds, and the nytrogen, three. If two electrons from each are in the bond, the nytrogen doesn´t have its octet complete. What happens, then? A.Z. 14:54, 2 November 2006 (UTC)

Well, that unpaired electron is what the article means when calling the molecule a free radical. Melchoir 15:52, 2 November 2006 (UTC)

Nitric oxide is a somewhat unusual molecule in that it has an unpaired electron, making it technically a free radical, but an unusually stable one. It structure is best analysed using molecular orbital theory. Effectively, NO has three filled bonding orbitals and one half-filled antibonding orbital (see f.ex. page 8 of this PDF), meaning that there are, in effect, 2.5 bonds between the atoms. For a more in-depth study, see for example this article. —Ilmari Karonen (talk) 16:07, 2 November 2006 (UTC)

Oh, now that last paper is interesting. To me anyway. (Although it's a bit old and the theory is low-level) Unfortunately it doesn't give a population analysis (although this is much more advanced stuff than what the original question was about). But FWIW, the picture in the Nitric Oxide article, with the dashed third bond is misleading. A better one would be *N=O, because (and the article makes the point) it's not significantly contributing to the bonding; The unpaired spin population is highly concentrated to the nitrogen atom and the (Mulliken) bond order is 1.9 and not 2.5. --BluePlatypus 22:31, 2 November 2006 (UTC)

The two normail bonds are shared, and you can also have dative donding, where only one atom contributes electrons in this case, they share an electron from the oxygens now complete outer shell, in order to also complete the nitrogens outer shell. Philc _T^E_C^I 21:35, 2 November 2006 (UTC)

The information that the molecule is not stable is good enough for me. The other things you said are a little bit harder for me to understand and, even though I would really like to study those advanced matters, I have no time to do it right now. Thank you very much! A.Z. 16:34, 3 November 2006 (UTC)

Density and space

Makes sense that an area of space with more matter has a greater density. Does this mean that absolute density is matter without space and if so what would matter then occupy? Adaptron 14:58, 2 November 2006 (UTC)

could you please elaborate? Dr_Dima

Remember the old comedy routine where someone pushes down on a bed spring and another spring pops up? Absolute values tend to do the same thing. For instance: can you reach absolute zero without also having absolutely no heat? If you think of increasing density as simply the process of removing space then at some point you are faced with the dilemma of having to remove absolutely ALL space - in order to achieve absolute density. 16:01, 2 November 2006 (UTC)

Dare I say your question exhibits absolute density. -- Chris 16:43, 2 November 2006 (UTC)

and your response absolute space. Adaptron 17:03, 2 November 2006 (UTC)

I think you mean vacuity (Dictionary.com: 2. absence of thought or intelligence; inanity; blankness: a mind of undeniable vacuity). -- Chris 18:19, 2 November 2006 (UTC)

Isn't the gravitational singularity in a black hole an example of "absolute density" ? That is, as far as we know, the singularity is a geometric point, with absolutely no volume, but a finite mass, thus infinite density of matter. Of course, there is a finite volume within the event horizon, so a black hole does not have an infinite matter density if measured in that manner. StuRat 17:17, 2 November 2006 (UTC) StuRat 17:15, 2 November 2006 (UTC)

However, as you approach the singularity, the density rises asymptotically towrd infinity (the last time I looked). The orig Q, however does not make sense. The Q should have been: Is there a theoretical maximum density? A: No (not as far as we know) 8-)--Light current 17:39, 2 November 2006 (UTC)

Why, unless the black hole was actively "feeding", would there be any mass outside the singularity ? StuRat 18:18, 2 November 2006 (UTC)

THe average density of the sphere formed by the singularity at the centre and you on its surface. Sorry wasnt clear

--Light current 18:21, 2 November 2006 (UTC)

Black holes aren't actually infinitesimally small with infinite gravitational force, the best we can do with mathematics for now is to arrive at that conclusion. X [Mac Davis] (SUPERDESK|Help me improve) 18:41, 2 November 2006 (UTC)

I would say it the other way, that, as far as we know, the gravitational singularity is a point of infinite density (as our article claims). We could be wrong, if there is some yet undetected force that prevents the infinite collapse, but I wouldn't assume that to be the case. The only argument for making such an assumption is that it would make things more like those we are familiar with. This isn't a good way to do things, however, as we already know that things behave in bizarre ways at such different scales, as demonstrated by quantum mechanics, etc. StuRat 18:53, 2 November 2006 (UTC)

Speaking of StuRat standing on the surface of a singularity, wouldn't someone who lives in infinity regard us as living in infinity? In other words, is infinity reversible? (Did I just introduce cultural relativism into Kosmology?) DirkvdM 08:27, 3 November 2006 (UTC)

protocol

can u please provide me a micropropagation protocol for citrus limon? i need it for my tissue culture work... please.. i tried to search it on thenet but was not able to find the apprpriate results.. please help me!!

Flea eggs

Can flea eggs survive and hatch if they are 'squeezed out' of a flea rather than laid by the female? When either my cat or dog has fleas I go for a 2 pronged attack - a good flea collar and regular grooming with a fine-toothed comb (the sort used for head lice is good). the fleas are picked up between the teeth of the comb and then I can pick them up between my finger and thumb to kill them. But, as it's impossible(?) to kill a flea by squeezing between the soft flesh of fingers, I squeeze it between my fingernails instead (I was taught a little rhyme which goes "break their back, they don't come back"). this works well (although is a little messy if you kill a flea which has just fed). However, if you get a pregnant female, squeezing the flea will cause flea eggs to burst from the flea - sometimes quite violently. I'm sure that some must fall back onto the animal. I understand that flea eggs which have been laid conventionally can lay dormant before hatching.

(also, if I might, a related question. Is there any evidence to suggest that fleas know where they're jumping to?)

thanks and sorry for the long question!

simon

• I always found a lighter to be a useful tool in one-by-one flea killing. Roast the ones you catch on the comb. --jpgordon^∇∆∇∆ 16:52, 2 November 2006 (UTC)

If the egg is ready to be laid, then yes, it may well be viable. I suggest you drown the fleas, instead. Keep a bowl of water next to you and stick them in that. Don't just drop them in, as the surface tension may allow them to stay on the surface, then they could escape when they float to the edge of the bowl. On the other hand, if they are under the surface, it becomes a barrier to their escape. Then flush them down the toilet once done grooming the dog. StuRat 17:11, 2 November 2006 (UTC)

I wondered abotu vaccuuming the up then spraying insecticide into the vaccuum?

I suspect they may be able to jump out of the way of the vacuum cleaner if still alive. Try powdering the carpet with a flea pesticide first, then wait until they are dead, then vacuum the floor. Keep the kids and pets out of the room while the powder is on the carpet to minimize their exposure. You might want to wear a breathing mask when vacuuming, to limit the amount of flea powder you inhale. ("Vacuuming" = "Hoovering", for you Brits.) StuRat 18:11, 2 November 2006 (UTC)

Re: vacuuming, water and insecticide: a) a drop of dishsoap will remove enough of the surface tension to allow the fleas so sink; b) rather than insecticide in the vacuum, use a couple of moth balls; and c) borax is a good (and healthy, and environmentally-sound) alternative to pesticide. Just sprinkle it on your floor (and actually fleas prefer floor cracks to carpets), leave it for a bit (don't recall how long offhand, but that's what google is for), then vacuum it up. Anchoress 19:17, 2 November 2006 (UTC)

I always say take a page out of nature's book: Make like a chimp and eat the fleas, no mess, no fuss, no chance of eggs getting anywhere.. Ok, but really, an ex-housemate of mine once had a cat and he didn't look after it, the thing got so flea bitten I could no longer stand it. I'm not a cat person, but it got a bit hard not to notice when you could see fleas in its FACE when you gave it a pat. Anyway, to get to the point, all I did was get those liquid flea drops that you drip on the back of your animal's neck, after about 3 applications (which were all in the one packet), the cat was flea free. i can't remember the specific one I got but it was something like advantage Vespine 21:37, 2 November 2006 (UTC)

Simon,I wash my dogs in Dawn dish detergent,this works well.After I wash them ,I have a cup of hot water with a drop of dawn in it.I pick the fleas off, and put them in the cup this kills them.I find this method works.I hope this helps.Andrea216.218.118.90 01:53, 3 November 2006 (UTC)216.218.118.90 01:24, 3 November 2006 (UTC)

Dogs have less layers of skin than humans, therefore it might be harmful to use dish soap to wash pets. --Wirbelwindヴィルヴェルヴィント (talk) 05:22, 3 November 2006 (UTC)

What is the collective term for a group of Jellyfish?

By this, I mean the kinda thing like a group of fish is called a school, what's a group of Jellyfish called?

According to List of collective nouns by subject I-Z, a "smack of jellyfish" is conventional, with a "fluther of jellyfish" as a slightly uncertain alternative GeeJo ^(t)⁄_(c) • 18:06, 2 November 2006 (UTC)

Booorrriiinnnggg. That should be changed to a "belly" or even a "peanut butter sandwich" of jellyfish. Clarityfiend 18:48, 2 November 2006 (UTC)

Someone needs to come up with one for Reference Desk contributors... Vitriol 19:31, 2 November 2006 (UTC)

Hmmm....how about a "straitjacket"? Clarityfiend 20:45, 2 November 2006 (UTC)

How about a "group"? That's certainly the most common one when we're talking about jellyfish. --Bowlhover 21:41, 2 November 2006 (UTC)

I thought this indentation was about Reference Desk contributors. For some, 'pack' might be appropriate. DirkvdM 08:30, 3 November 2006 (UTC)

A "fester" of contributors? Philc _T^E_C^I 18:54, 3 November 2006 (UTC)

How about a "gaggle" of contributors, similar to geese? A "parliament", similar to owls, sounds far to civilized for us. ;o) EWS23 (Leave me a message!) 06:28, 5 November 2006 (UTC)

What is the collective term for a group of Reference Desk contributors

How about 'consensus'? OK maybe a 'disruption' or possibly a 'catastrophe'--Light current 02:17, 3 November 2006 (UTC)

This question should be moved somewhere--Light current 02:22, 3 November 2006 (UTC)

Could have an 'addiction' of RD contribs I suppose--Light current 03:56, 3 November 2006 (UTC)

amniocentesis

Does anyone know who developed the technique amniocentesis. The article doesn't say so.

Christopher

I don't know who developed it. Dr. David Brock is well known as the pioneer of the test for checking on the welfare of the fetus. --Kainaw ^(talk) 18:53, 2 November 2006 (UTC)

Well, I am asking because one of my biology lecturers, Dr Roger Sutcliffe said something along the lines of him developing it, and I am wondernig if he said that HE had co-developed it.

Christopher

Four different groups of researchers are credited with the dis­covery in 1955 that the sex of human fetuses could be predicted through analysis of fetal cells in amniotic fluid: one each in New York, Minneapolis, Copenhagen, and Haifa (Shettles, 1956; Makowski, 1956; Fuchs & Riis, 1956; Serr, Sachs, & Danon, 1955). A short while later the Copenhagen group became the first to report that they had performed an abortion in order to prevent the birth of a fetus, diagnosed as being male, whose mother was a carrier of hemophilia (Riis & Fuchs, 1960). Pre­natal diagnosis through amniocentesis was, if you will excuse the pun, born; the year was 1960. [4] --jpgordon^∇∆∇∆ 00:23, 3 November 2006 (UTC)

Thermal Energy loss of a person

Is their a way of estimating the amount of thermal energy a person gives out in different circumstnaces, specifically:

1. When doing a sport? 2. When sitting down?

Also how does this amount change depending on the temperature at which this 'act' is being carried out in? i should add for an average person (whatever that is). A general answer will suffice.

Thanks

Me22ac 19:37, 2 November 2006 (UTC)

All energy that your body used ultimatively ends up as heat. So you can safely use the usual table about how many calories you burn when doing what kind of excercise. For the energy needs withou exercisew, see basal metabolic rate. Simon A. 20:56, 2 November 2006 (UTC)

As for the effect of the ambient temperature, I would model it as three independent events:

• Basal metabolic rate, which is energy used to beat your heart, breathe, etc., and which ultimately becomes heat. This is a constant.

• Exercise related energy, which is used by the voluntary muscles, along with an increase in heart rate and breathing rate, all of which also ends up as heat.

• Energy used to maintain body temperature (this only applies to warm-blooded animals). The rate of thermal loss is proportional to the difference in the temperature from the skin to the environment. Wind, humidity, and clothing, of course, also effect the rate of thermal loss.

StuRat 23:07, 2 November 2006 (UTC)

I think it's relevant to point out that if your energy used to maintain body temperature varies much from the "standard" values associated with room temperature, you notice by, well, feeling hot or cold. So if you're out jogging in winter, dressed more warmly than you would be in summer, but feeling about the same thermally (on average), you should be able to re-use the "normal temperature" jogging statistic. --Tardis 23:41, 2 November 2006 (UTC)

gas turbine

what is a gas turbine engin good for—Preceding unsigned comment added by 69.132.236.116 (talk • contribs)

Chrysler experimented with gas turbine engines in cars for a while. See the link for other uses. StuRat 23:12, 2 November 2006 (UTC)

High power, light weight, pretty good reliability owing to mechanical simplicity, pretty good efficiency. This makes them widely used in aircraft in the form of turboshaft engines.

Atlant 19:09, 3 November 2006 (UTC)

How many fish are in the sea?

Was the caption for the Finding Nemo trailers right that there are 3,000,000,000,000 fish in the sea? If thats right, thats overwhelming! If it is true, are most of them in the Pacific, the largest ocean?—Preceding unsigned comment added by 82.36.182.217 (talk • contribs)

Stuff like this is impossible to prove or disprove. It can be an estimateif they're considering how much of Earth is covered by water (about 70%), and how deep fish can live, and a lot of other factors. --Wirbelwindヴィルヴェルヴィント (talk) 05:17, 3 November 2006 (UTC)

News item: "World's Fish Supply Running Out, Researchers Warn" By Juliet Eilperin Washington Post Staff Writer Friday, November 3, 2006; Page A01

"An international group of ecologists and economists warned yesterday that the world will run out of seafood by 2048 if steep declines in marine species continue at current rates, based on a four-year study of catch data and the effects of fisheries collapses.The paper, published in the journal Science, concludes that overfishing, pollution and other environmental factors are wiping out important species around the globe, hampering the ocean's ability to produce seafood, filter nutrients and resist the spread of disease." [5] --GangofOne 06:31, 3 November 2006 (UTC)

That's only 500 times as many as there are humans. And humans are just one (sub)species. If your average fish weighs 200 grams (given that whales aren't fish, there will be many more littluns than bigguns and humans are growing ever fatter) then the total biomass of all species of fish is the same as that of humans. That's frighteningly little if they are a major food source for us. DirkvdM 08:43, 3 November 2006 (UTC)

protein molecular weight

Which technique gives better resolution of proteins by molecular weight, SDS-PAGE or size exclusion (or gel filtration) chromatography? I realize this depends on many factors, but in general which would choose if you wanted good resolution by size? If it makes any difference, I am interested in peptides smaller than 3 kDa. ike9898 23:25, 2 November 2006 (UTC)

Well, no wonder you're confused: Do you want them by weight or by size? That distinction is quite relevant to which method you should choose. --BluePlatypus 23:46, 2 November 2006 (UTC)