Wikipedia:Reference desk/Archives/Science/2007 August 5

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[edit] August 5

[edit] P -type conductor

Any idea if the use of metallic conductor causes loss due to resistance, then if we were to use a p-type conductor, would it reduce the loss, as only the imbalance of holes would cause propagation of current??~~ —Preceding unsigned comment added by 59.92.134.100 (talk • contribs) 02:20, 5 August 2007

You mean P-type semiconductor? --Spoon! 03:29, 5 August 2007 (UTC)

Semi-conductors are inherently "lossy". That means they have "some" leakaage. Modern ones are less lossy. But they still "leak" a very tiny amount. For example the zener diode ideally would only allow current to pass when a breakdown voltage is reached.. but the reality is they are not ideal and actually leak more and more as the bv is approached. Fantastic efforts are made in industry to limit leakage with pretty nice results (but with more intricate parts). So its a compromise; how much do you want to spend vs how much leakage can you stand for. In a battery operated device you will need less leakage to save the batteries. One voltage regulator for example uses only nano watts (~0) in the monitoring mode. Nice! But it costs ($1) and all those parts add up to increase the total device cost.

All materials have some resistance, so yes metallic conductors have resistance. But most metals have less resistance (ie copper, alum, steel, silver, gold, etc) so if you are replacing a non-metal with a metal "probably" the overall R will be less. TripleBatteryLife 13:39, 5 August 2007 (UTC)

What I actually meant was that is it possible to use a somewhat heavily doped p-type semiconductor as a efficient electrical conductor...~~

[edit] Messages and/or Words in Microwave Oven Heated Liquid

I was at a gathering the other day, and we were talking about many many different things. Someone brought up a very interesting topic just as I was leaving. I stayed long enough to hear some details, and I would like to know more or at least find out where I can learn more about it. It was about some sort of scientist who I think I remember has an Asian name. This scientist was talking about writing words or something on glasses or cups with whatever liquid you are heating up in a microwave oven. I think it alo has to do with crysals of some sort. Anyway, by doing this, after microwaving, there is a message or symbol. I am sorry I don't have much to go on, and what I do have sounds pretty strange I must admit. But, if anyone knows at all what I am referring to I would really like some clarification! Thanks, and have a great night! Genjianne

Perhaps you're referring to Advanced Multiple Organized Experimental Basin (AMOEBA)? Clarityfiend 06:09, 5 August 2007 (UTC)


I finally found what I was looking for! Here is a link in case I sparked any one else's interest:


http://www.cygnus-books.co.uk/mind_body_spirit_books/hidden-messages-water.htm

That looks like and ORDER FORM for a BOOK? Be leery of these types of things which promise pie in the sky. TripleBatteryLife 13:16, 5 August 2007 (UTC)

We do have an article on Masaru Emoto. I've seen this before, and it looks like junk science (to me anyway). There is a huge lack of experimental controls, as the article mentions. --Bennybp 19:32, 5 August 2007 (UTC)
Then again, now that I think about it, that is pretty tame compared to some of the stuff on this page. Water seems to be a magnet for pure and absolute junk science and hoaxes (compounds purporting to change the bond angles of water, etc). --Bennybp 19:43, 5 August 2007 (UTC)
of course, everybody knows that when you heat water and sit there thinking "hurry up and boil, dammit" at it, it keeps it from boiling. Gzuckier 15:01, 6 August 2007 (UTC)

[edit] Glare Circles

What are these things called, and how do they happen? Why are they always either circles or hexagons, and why is there always a lot of them? --CodellTalk 06:48, 5 August 2007 (UTC)

Lens flare, the shape is the shape of the aperture which is commonly hexagonal on many low-end camera, and rounded edged polygons for higher-end lenses. You can use a hood (or your hand) to reduce the effect of them. --antilivedT | C | G 06:54, 5 August 2007 (UTC)

Thank you.--CodellTalk 07:33, 5 August 2007 (UTC)

Some people call these things "orbs" and attach some supernatural meaning to them. My opinion is that these so called "orbs" are really just a refraction of light around a very tiny speck of dust on the lens. The more dust, combined with a specific sun (or other light source) angles, makes more "orbs". The hood reduces the intensity of the light and eliminates direct light on the lens which can refract around the specks of dust. (clean the lens more often and avoid direct light on the lens. ) TripleBatteryLife 13:11, 5 August 2007 (UTC)

[edit] shaver

Anyone know what sort of lubricant to use on a remington type electric shaver - for the head/foil? My intructions recommend own brand lubricant - but of course it's not sold in any shop - what about silicone oil -would that be ok?83.100.183.144 19:12, 5 August 2007 (UTC)

There are several companies that sell such oil. My Remington electric shaver came with "Braun" oil. If you search the internet for "remington electric shaver oil braun" you can get more information. I have no idea what type of oil is commonly used as electric shaver "blade oil". --JWSchmidt 02:28, 6 August 2007 (UTC)

ok I'll try that (thanks)
If anyone knows what type of oil is commonly used as electric shaver "blade oil" please say. Thanks.87.102.34.140 08:24, 6 August 2007 (UTC)

[edit] Homework question

No, not this kind of homework, the heading is just an eye catcher. Some cleansing agents contain abrasive materials like quartz or marble dust. Is it save to use them on enamel? Mohs hardness doesn't give any clue. 84.160.204.218 19:42, 5 August 2007 (UTC)

What, oh what, are you planning to brush your teeth with? Someguy1221 19:48, 5 August 2007 (UTC)
To be on the save side, I'd perfer Marshmellows. But the question was concerning my bath tube. 84.160.204.218 20:23, 5 August 2007 (UTC)

It depends what you mean by enamel, there are enamel (teeth) - use toothpaste obviously, enamel paint (not safe - will scratch it), enamel bathrooms (meaning glazed porcelain) - may be safe with marble dust, probably not with quartz (will scratch) - again use a propietary cleaner.

What sort of cleaning agent were you thinking of? (If in doubt only use cleaning agents on the materials they are recommended for..)83.100.183.144 20:07, 5 August 2007 (UTC)

It contains marble dust and would be used for the enamel on my bath tube. I hope the natural enamel of my teeth is even a bit harder. Another agent contains quartz and is recommended for steel, but I doubt this wouldn't scratch the material. Thanks so far. 84.160.204.218 20:23, 5 August 2007 (UTC)
Answer seems to be yes then - it's safe.. Was there anything else?
I think the only question which remains unanswered is what on earth is a bath tube?? ;) Vespine 02:08, 6 August 2007 (UTC)
It's the thing an astronaut uses to take a shower in zero-gravity :-) --Carnildo 23:20, 6 August 2007 (UTC)

[edit] aircraft cabin pressurization

The Cabin pressurization article suggests that cabin pressure is gradually increased as the aircraft reaches high altitudes. Why can't the cabin pressure just be kept at the same pressure experienced on the ground throughout the flight including landing and take-off? Why does the cabin pressure need to be increased?86.139.49.201 19:50, 5 August 2007 (UTC)

As far as I know, the objective is exactly what you say: to keep the cabin pressure stable at sea-level pressure (which is what humans are used to). What the article probably means is that the difference between cabin pressure and exterior pressure increases, which creates stress on the cabin structure. --Waldsen 20:12, 5 August 2007 (UTC)
If that is the case, then why is it that you can experience ear discomfort during take off and landing and some people can even develop the bends.86.139.49.201 20:34, 5 August 2007 (UTC)
The cabin pressure drops until a predetermined point (8,000 feet IIRC), then remains constant until coming back down through the same pressure altitude. They don't hold sea level pressure, but a lower pressure. anonymous6494 20:37, 5 August 2007 (UTC)
Can anyone explain why the pressure is dropped to below sea level. No websites explain this very well.86.139.49.201 21:02, 5 August 2007 (UTC)
First of all the pressure is that of 8000 ft above sealevel, it is the pressure that is lower. The reason this is done is a tradeoff between comfort for the passengers and forces on the aircraft. Ideal for the passengers is keeping the pressure the same as they had on sealevel, ideal for the aircraft would be an unpressurised cabin. - Dammit 21:09, 5 August 2007 (UTC)
Im so confused. Is the cabin presssure lower or higher than at sea level above 8000ft and what is it below 8000ft? Also is the change in pressure a gradual one or a rapid one? The Cabin pressurization article needs alot of work.86.139.49.201 21:21, 5 August 2007 (UTC)
You may be confused because as the altitude increases, the pressure decreases.
Or you may be confused because as the altitude increases and the pressure in the pressurized cabin stays the same, the difference between the cabin pressure and the outside pressure increases.
Between 0 ft and 8000 ft, as the aircraft ascends, the pressure decreases. The pressure inside the aircraft is the same as the pressure outside the aircraft. (The cabin is basically not pressurized.) The pressure drops gradually as the plane ascends.
Above 8,000 ft, the cabin is pressurized. Enough artificial pressure is applied so as to make the pressure inside the cabin equivalent to the the pressure at an altitude of 8,000 ft. When the plane is at (say) 9,000 ft, the difference in air pressure between the inside and outside of the plane is not very high (we could say that it's "not pressurized very much"). But at a cruising altitude of 25,000 or 30,000 ft, there's quite a pressure difference.
As the plane ascends past 8,000 ft., the pressure inside the plane does not change (it stays at the equivalent of 8,000 ft). But as the plane ascends past 8,000 ft., the difference between the cabin pressure and the ambient pressure increases. —Steve Summit (talk) 21:46, 5 August 2007 (UTC)
Is the decrease in cabin pressure at 8000ft gradual or rapid? Also if the pressure was made the same as sea levekl which would be better for passengers would that cause the aircarft to explode? Can you provide a reliable reference that could explain all this so that I dont have to keep asking? Thanks86.139.49.201 22:00, 5 August 2007 (UTC)
There is no decrease in cabin pressure at 8,000 feet.
Between 0 ft and 8,000 ft the cabin pressure decreases gradually. Above 8,000 ft the cabin pressure (as experienced by the passengers) does not change at all; it stays the same as it was at 8,000 ft.
What happens at 8,000 ft is that the pressure stops decreasing. (If you wanted to get analytical about it you could say there's a spike in the second derivative of the pressure at that point, but I don't think this is what you were asking.)
Yes, it would theoretically be possible to keep a plane's cabin pressurized equivalently to sea level at all times. However, the plane would either (a) have to be built more strongly (and hence be more heavy and more expensive to operate), or (b) have its lifetime reduced. (It wouldn't "explode" under normal circumstances, but it might experience catastrophic failure after too many pressurization/depressurization cycles, as a certain number of airplanes, such as the Comet 1 and Aloha Airlines Flight 243, have tragically done.)
I can't help you out with any reliable references, I'm afraid. My sources for what I've written here are my own knowledge, and some tidbits I just now read in the same cabin pressurization article you've been looking at. —Steve Summit (talk) 22:14, 5 August 2007 (UTC)

Drive up a mountain. Your ears pop because the pressure decreases as you go up. Imagine your car kpet the inside pressurized so that anything above 8000 ft wasn't felt. That's what a plane does. Mostly because of oxygen requirements. --Tbeatty 22:30, 5 August 2007 (UTC)

I think the following source looks reasonably reliable: [1]. Although I'm not sure at exactly which pressure the cabin is kept, the physics we've discussed is correct (i.e. the cabin pressure is higher than the exterior pressure, and the cabin structure resists the expansion force created by the air inside). --Waldsen 11:07, 6 August 2007 (UTC)
The air pressure in the cabin is not kept to normal 1 atmosphere. it is lower than this for two reasons: 1. The plane would have to be built like a gas tank so it doesn't explode. 2. The plane becomes lighter as the air is let out.--Dacium 04:57, 9 August 2007 (UTC)

[edit] What happens to it?

When someone gets a blowjob, what hapens to the semen that is swallowed and what effect will it have?(Wildweasal 20:05, 5 August 2007 (UTC))

See Blowjob#Ingestion_of_semen.

Does it have any graphic pictures? cause I'm willing to click it only if its only text(words).(by graphic I mean disgusting)(Wildweasal 20:28, 5 August 2007 (UTC))

(pointless rhetorical question)
If you're so disgusted by the act, how come you're so incessantly asking so many questions about it all of a sudden? —Steve Summit (talk) 21:26, 5 August 2007 (UTC)
no pictures, promise - it's on wikipedia which is pretty much porn free.83.100.183.144 21:19, 5 August 2007 (UTC)
The article has a cartoon of the act, but that particular section is free of images. Click in the link, but don't scroll up! Rockpocket 21:19, 5 August 2007 (UTC)
"while other factors may improve its flavor"??! Good God, it sounds like an article from Cosmo or something.... SGGH speak! 21:53, 5 August 2007 (UTC)
While I'm here I've got to say that I've had a variety of diets and the semen (mine) always tastes/tasted the same (spot single guy) - in fact I believe it's a common phrase or saying to say "that tasted like wank" when refering to something that didn't taste very good - I would change the article but don't really want to get involved in an edit war over this..83.100.183.144 22:01, 5 August 2007 (UTC)
Would it be indelicate to ask why you would choose to taste your own semen in such an experimental manner?
Would it be indelicate to point out that the first kiss after a blowjob can be a sharing experience? —Steve Summit (talk) 23:12, 5 August 2007 (UTC)
He appeared, to me, to make the point ("spot single guy") that it was a solo exerience. Rockpocket 23:30, 5 August 2007 (UTC)
Well, there is that. And you've been around Wikipedia long enough that I bet you're thinking of the same notoriously contentious image I am... —Steve Summit (talk) 23:46, 5 August 2007 (UTC)
Who me? I couldn't possibly comment ;) Rockpocket 03:41, 6 August 2007 (UTC)
See also Snowballing (sexual practice). DMacks 03:28, 6 August 2007 (UTC)
For the record, diet can effect the constituent make up of seminal plasmsa (see for example, these papers) Therefore one would expect diet could effect taste also, though one may have to follow some extreme diets for the taste to be noticibly different to the average person. Rockpocket 22:27, 5 August 2007 (UTC)

To answer the original question: The same thing happens to swallowed semen that would happen to swallowed food. Notwithstanding any special medical conditions, it goes into your stomach and is digested. The acid in the stomach kills the semen. Nutrients (not much by the way) are then extracted the same way they are from food.Mrdeath5493 16:36, 6 August 2007 (UTC)

[edit] Comfrey- visual recognition of bocking 14 variety

I have a number of comfrey plants in a garden plot and would like to know if there is a visual way of determining if they are the sterile bocking 14 variety or not. I could wait and see if the plants self seed but am concerned about too much of a good thing...

many thanks BillAnderson deas 20:20, 5 August 2007 (UTC)

I can 't answer your question, but my comfrey has multiplied greatly due to roots breaking off and sprouting again. So be carefull not to ever move the plant — if you don't want two plants, and if you dig up the ground around a plant and break off roots, you will probably have more plants sprouting up. And the way to get the most plants is to reloacate the soil where a plant was growing without removing every single pice of root. Plants pop up everywhere! A bobcat can do this for you. GB 00:33, 6 August 2007 (UTC)

[edit] Burnt edges of bread

When you burn the edges of bread for example, what is the black stuff (chemically speaking), and what exactly happens (chemically speaking)? Weird question I know, but an answer would be most appreciated. Jack Daw 20:28, 5 August 2007 (UTC)

Charring, the black stuff is mostly carbon. Rockpocket 21:17, 5 August 2007 (UTC)
Note that the charring can occur without any combustion (not entirely what the charring page says) - the alternative reaction is dehydration eg starch/cellulose > carbon + water.83.100.183.144 21:23, 5 August 2007 (UTC)
The carbon will be mostly impure amorphous carbon and the process is known as pyrolysis83.100.183.144 21:25, 5 August 2007 (UTC)
Maillard reaction may be of interest to you too. Aaadddaaammm 21:30, 5 August 2007 (UTC)

[edit] things that burn

This reminds me of something I heard that i've never known if is true. I heard that the only solid thing known to man that cannot be 'burnt' is ash. Now it sounds very made up but anybody know? ny156uk 22:55, 5 August 2007 (UTC)
Since "burnt" (or "burned", or the verb "to burn" or whatever) isn't well-defined here, it could be as true as one wants. Same for the word "ash". DMacks 23:48, 5 August 2007 (UTC)
Helium definitely isn't ash, and I'd love to see someone burn helium. —Keenan Pepper 01:21, 6 August 2007 (UTC)
Keenan, my friend, I'd love to see you supply some helium in a solid state! —Steve Summit (talk) 03:02, 6 August 2007 (UTC)
Helium can be burnt to Carbon or Oxygen by fusion at high enough pressures and temperatures, such as could be found in the cores of large stars! GB 03:24, 6 August 2007 (UTC)
I think it's just a simple sort of riddle - everything that can be burnt leaves ash (if it leaves anything).
In general it's not true - granite for instance (and most other rocks) cannot be burnt - they're not ash.87.102.34.140 08:30, 6 August 2007 (UTC)
I want to see the originator of this nonsense try to set light to an icecube! This is clearly untrue - and 10 seconds of thought reveals why. Suppose (hypothetically) that this was true. Ask yourself this: Is 'ash' a pure substance or a mixture? It's a mixture - we know there isn't one pure 'ash' molecule. So - if you were to separate out the ingredients of ash - you'd end up with a variety of solid materials that also won't burn. Now, suppose you find some of that material in nature that didn't come from ash - would it burn? No - of course it wouldn't. This is a typical 'folk-science' idea - and it's just wildly incorrect. Even if you extend the concept of "burning" to include addition of oxygen by any means, you always end up with a substance that won't "burn". So, rust won't burn - it's already "burned" iron. SteveBaker 11:41, 6 August 2007 (UTC)
If ash cannot be burned, then what pray tell is Charcoal --Jmeden2000 17:28, 6 August 2007 (UTC)
See answer to previous question about burned toast. Charcoal is what you get from heating wood WITHOUT letting it burn. The result is mostly carbon...which burns quite nicely. Ash is the residue after everything that's likely to burn at reasonable temperatures has burned away - so it's mostly metal salts and oxides. SteveBaker 19:03, 6 August 2007 (UTC)

[edit] Kittiwakes

Why are Kittiwakes called 'Kittiwakes' as opposed to Kittiwake Gulls? --Kurt Shaped Box 23:52, 5 August 2007 (UTC)

Looking at the names of gulls, the others require "gull" to know what they are talking about. For example, it would sound silly to say "Did you see that Iceland fly by?" However, the Kittiwake is rather unique to the gull. If you refer to it as a "kittiwake", it can be safely assumed you are referring to a gull. -- Kainaw(what?) 23:57, 5 August 2007 (UTC)
According to my nearest etymological dictionary, the word kittiwake is (like many other bird names) imitative of the cry, so as Kainaw suggests it doesn't apply to anything else and gull would be redundant, like whippoorwill bird or katydid bug. —Tamfang 18:04, 6 August 2007 (UTC)