Wikipedia:Reference desk archive/Science/2006 July 21

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[edit] DNA.... Magnetic?

I have stumbled upon some information that DNA is condusive of Electricity and therefore is effected by EMF's. The source claims the effect is either the cause or cure for cancer's and other cellular diseases. Is there any validity to this claim and has there been experiments as to the effects of EMF's on cellular DNA?

The cancer stuff sounds like quackery, but I guess DNA might conduct electricity in a sense. When you hydrate DNA at a reasonable pH, it's strongly negatively charged, so it attracts an atmosphere of positive counter-ions that's much more concentrated than in the rest of the solution. These might be reasonably free to move parallel to the molecule...? Melchoir 04:09, 21 July 2006 (UTC)
thats is quackery, and the idea that DNA is a conductor in the traditional sense is in doubt. for further info: http://physicsweb.org/articles/world/14/8/8 . there are plenty real causes of cancer to worry about rather than EMFs. Xcomradex 05:58, 21 July 2006 (UTC)
While there is some evidence that cells can respond to the presence of electromagnetic fields, the evidence linking EMFs to disease are tenuous and controversial at best. I'll note that it's virtually impossible to prove a negative, but the evidence available to date suggests that EMFs are responsible for very few – if any – illnesses. Your cellular phone is more likely to kill you by distracting you as you cross the street than by giving you brain cancer. TenOfAllTrades(talk) 15:01, 21 July 2006 (UTC)

[edit] basics of UAV

can any one give me the data/link about the basics of UAV(unmanned aerial vehicle)?

Some nice folks have written up some information at Unmanned aerial vehicle. Please try using the search box to search for an article before asking here. — Knowledge Seeker দ 07:26, 21 July 2006 (UTC)

[edit] History of crypsis

Hi - a question for history of science people - can anyone tell me if there were any observations made by scientists on the phenomenon of protective colouration/camouflage before Thayer in the 19th century? If so, could you point me towards any online texts? Thanks in advance Adambrowne666 07:27, 21 July 2006 (UTC)

There was an english naturalist named Henry Walter Bates (we have an uninformative stub on him) who apparently spent some time studying countershading in nature. [this] says Thayer was influenced by his work. He apparently also studied the related phenomenon of a species imitating a well-armed or poisonous species to gain the advantage of their reputation - it's called Bayesian mimicry. It does seem that Thayer was the first person to address the subject of camouflage comprehensively. --Bmk 14:45, 21 July 2006 (UTC)

That's great, Bmk, thanks - but I wonder if there are any even earlier examples of this observation being made, even if they're not entirely in the scientific context - in bestiaries, for example? Adambrowne666 22:29, 21 July 2006 (UTC)

I don't know for sure, but i would be surprised if some of the early pigmentation biologists didn't comment on camouflage. For example, in 1819 Sangiovanni published Descrizione di un particolare sistema di organi cromoforo espansivo-dermoideo e dei fenomeni che esso produce, scoperto nei molluschi cefaloso (G. Enciclopedico Napoli. 1819; 9:1-13) characterising cephalopod chromatophores. It would be odd, considering their mastery of pigmentation control, if there were not some mention of camouflage. I did, at one time, have a reproduction of his paper in Italian (which i can't read), so never bothered reading past what i was specifically interested in.
There is an extensive chapter in The Pigmentary System: Physiology and Pathophysiology [1] on the history of pigmentary science that may address the issue. Rockpocket 05:51, 22 July 2006 (UTC)

Great, thanks for that, very generous of you, Rocket Adambrowne666 21:51, 22 July 2006 (UTC)

[edit] height increase

why does height stop increasing after a certain age in human beings?i know one reason that is growth harmone production decreases gradually...but why does it decrease?or is there any other reason for the height to stop growing.....--203.109.89.130 12:41, 21 July 2006 (UTC)hima

Author Orson Scott Card apparently asked some experts this very question; his answer is at Anton's Key. Melchoir 19:22, 21 July 2006 (UTC)
It has to do with growth hormones and puberty, but a quick browse of the relevant articles doesn't reveal anything specific. If I recall from (you are going to hate me for this) an episode of "Doogie Howser, M.D.", the bones grow during stages of adolescence and eventually are stopped in a process that 'caps them off', additional hormones left in (or introduced to) the system have no effect on their length any more. edit- on second thought what was I thinking??? Just type in Human height and you will learn everything you wanted to know. --Jmeden2000 21:29, 21 July 2006 (UTC)
I may have some details wrong but... Bones grow "as cartilage" which eventually matures into bone, upon which growth ceases. One cause of bone maturation is estradiol, which in men is mainly produced by aromatization of testosterone (this is why steroid use in teenagers results in stunted growth). Something like that. Jack Daw 10:08, 22 July 2006 (UTC)


bones have plates called growth plates at their ends... a few years after puberty they literally " burn off" and hence no height increase is seen.it is mostly 18 for girls and 21 for boys..--219.91.134.238 14:24, 22 July 2006 (UTC)

[edit] Making Waxed Cards

At work, I'm often asked to make birthday cards for people. I print it on plain card stock. It doesn't look professional because it doesn't have a waxed coating like the Hallmark cards do. I can laminate them, but I would rather wax coat them. Does anyone know of a process for wax coating that I can do without the resources that Hallmark has? --Kainaw (talk) 14:10, 21 July 2006 (UTC)

Perhaps you can get more information from a printer's shop. --Ginkgo100 talk · contribs · e@ 02:36, 23 July 2006 (UTC)

[edit] Fast Help Please! Spain electricail suppy

OK, so I'm leaving for Spain in about 2 hours and I was wondering if you could tell me if it would be ok to plug in my ipod to recharge it with my AC Power Supply, which lets me plug my ipod into an American socket.

On the AC Power Supply thingy, it says on the back:

MODEL: 17B061001

INPUT: 100-240V~ 50-60Hz 0.2A

OUTPUT: 5.0V 500mA

FILE NO: E213987

DATE CODE: 1205

I.T.E. POWER SUPPLY

For I.T.E. use only

I've got the little converter thingy to switch it from American to European plug... but it doesn't convert the voltage...

I have the same converter thing as shown on this page at the top... http://wikitravel.org/en/Electrical_systems

I've already used this in the British Isles w/ my ipod and hair straitener and it worked fine... I just want to be really sure…

~Cathy T.~

I just found this: "Electricity supply is 220 volts throughout Spain with 2 pin wall sockets." Although I already knew that from wikipedia...

~Cathy T.~

This is standardised in the EU, afaik, so whatever worked in the UK should work in Spain. But the link you give shows that the whole of Europe (actually, most of the world) uses 220-240V/50Hz. So that's within the range of the adapter thingy. :) I'm not aware of any other possible issues. DirkvdM 15:20, 21 July 2006 (UTC)
Moved from double posting: (DirkvdM 15:22, 21 July 2006 (UTC))
Spain uses 220V / 50Hz power mains, and the plugs are the "Europlug" configuration. See an image of it here: Europlug. Your ipod will work fine with the proper convertor that mates to the Europlug (cool how most manufacturers are making their products ready to use world-wide, huh?)

Thanks for all the help... I thought it would be fine. I just wanted to be really sure... cause those ipods are expensive! It is nice that the world is going more universal. :)

~Cathy T.~

Well, it would be truly universal if they used the same values on Alpha Centauri. But I doubt that. :) DirkvdM 07:56, 22 July 2006 (UTC)
So it's a good thing that Jesse and Chester never tried to plug the Continuum Transfunctioner into a wall socket!

[edit] Why is diamond not anisotropic?

Why is diamond not anisotropic? —Masatran 15:38, 21 July 2006 (UTC)

Because it's isotropic? If this is a homework question you should do it yourself. If you know what the bond structure of diamond is, that should tell you. DJ Clayworth 17:57, 21 July 2006 (UTC)
It's because some bond angles, for example between carbon atoms as in diamond, minimize energy. Basically the bonds of an atom organize themselves so they have as large an angle from all other bonds to the same atom as possible, to minimize energy. In the case of diamond, there are four bonds per carbon atom, so they arrange themselves in a tetrahedral shape. When you put all those tetrahedrons together, they naturally form a regular, isotropic structure - the crystal structure. The crystal structure it forms is called face centered cubic. --Bmk 18:17, 21 July 2006 (UTC)
Diamond might be optically isotropic, but its crystal structure isn't isotropic. Like any crystal, it's got preferred directions all over the place. I imagine this distinction is the heart of Masatran's question. Melchoir 19:18, 21 July 2006 (UTC)
I was using isotropic in the sense that it has a crystal structure that is translation invariant. I'm not sure exactly what the question meant. --Bmk 19:26, 21 July 2006 (UTC)
Ah. My understanding is that isotropy means rotational invariance, while homogeneity means translation invariance. Melchoir 19:34, 21 July 2006 (UTC)

All crystals have anisotropic structure, so should not they all be optically anisotropic? —Masatran 05:17, 22 July 2006 (UTC)

Well, very short wavelengths of "light" on the scale of the crystal structure do respond to the anisotropies; that's why X-ray crystallography works. But the comparatively long optical wavelengths only see, in some sense, the first-order effects. In the specific case of diamond, there's too much symmetry, and the permittivity tensor is forced to have a single eigenvalue in all directions, making it a scalar. Melchoir 06:25, 22 July 2006 (UTC)

[edit] Price of small diamond

How much will a small diamond (0.1 or 0.2 carat) cost, when the other features are according to the table in Diamond? —Masatran 17:44, 21 July 2006 (UTC)

According to that same table, it looks like a 0.2 carat diamond would cost around $1500 per carat, or $300 in total. That's just a rough estimate. Hyenaste (tell) 22:09, 21 July 2006 (UTC)

[edit] Blood sugar and artificial sweeteners

I recently heard the statement, without any scientific attribution, that 'recent research' suggests that the body recognizes artificial sweeteners as sugars and reacts with the same responses in terms of excessive insulin production and insulin resistance at the cellular level in Type II diabetics. Does anyone know of any supporting evidence for this statement? --Mlbenson 17:45, 21 July 2006 (UTC)

I've not heard any evidence to supportsuch a statement, and since I know how insulin signaling works, I'm skeptical that there's much to it. Simply, pancreatic beta cells release insulin in response to increased blood sugar because that sugar is immediately piped into a metabolic channel, resulting in an increased ATP:ADP ratio. This activates potassium channels that depolarize the membrane, activating calcium channels leading to subsequent activation of exocytosis machinery. Fake sugars shouldn't increase blood glucose and would then be unable to induce insulin release via the classical pathway. More here.
Now, there are other mechanisms that can cause insulin release (such as adrenergic signaling), but I've seen no evidence that artificial sweetners have any effects on those systems, either. -- Scientizzle 00:47, 28 July 2006 (UTC)

[edit] virus infections

what are the different parts of a vrus? I'm confused....

Start with our Virus article, and then perhaps some more specific questions will occur to you. --LarryMac 18:39, 21 July 2006 (UTC)
If that confuses you ... a virus has so few parts it is questionable if it qualifies as a lifeform. DirkvdM 07:59, 22 July 2006 (UTC)

Because of the genetic material(DNA/RNA) found in a virus, it should' be considered as a lifeform... well, I think so(It's totally MY own opinion). I don't know of any such 'staff, which is both non-living, and having a genetic material at the same time;I will be really grateful IF ANYONE CAN PROVIDE ME SUCH AN EXAMPLE.Pupunwiki 12:44, 22 July 2006 (UTC)

Please don't experiment in ways to shout. DirkvdM 18:46, 22 July 2006 (UTC)
The original question had nothing to do with "life" or "non-life", but was simply asking for the constituent parts of a virus: a nucleic acid (RNA/DNA), a protein capsid, +/- an envelope and any viral enzymes. For those troubled about whether viruses are living or non-living: you'd be better off considering if that's a false dichotomy, and if it's a categorization at all useful when applied to viruses. How is it going to make any difference if you term a virus living? or non-living? What's non-living and contains DNA? A corpse. The dried scrapings from the inner cheek. A preserved surgical specimen. All kinds of things. - Nunh-huh 15:51, 22 July 2006 (UTC)
If viruses were alive, antibiotics would kill them. By definition. Since they don't, they ain't. Surely it can't be more complicated than that, right? Matt Deres 23:44, 25 July 2006 (UTC)
I can't believe you're serious, but in case you are: antibiotics don't kill you, yet you're alive. Go figure. - Nunh-huh 00:32, 26 July 2006 (UTC)
Nah, I just forgot my smiley, but in case you're serious, consider this: if you have a cold and decide to chug a dispensor jug of penicillin or other antibiotic - you'd be dead, but the little rhinoviruses wouldn't be (well, they'd be trapped in your corpse, but you know what I mean). Don't confuse "not harmful at prescribed doses" with "won't kill you". Two smileys to take care of the backorder :-) :-) Matt Deres 19:57, 26 July 2006 (UTC)

[edit] Lucozade

According to the small print on a bottle of Lucozade, "this product should not be used to replace fluids lost by diarrhoea". Why should this be, especially given that it is meant to help convalescence? smurrayinchester(User), (Talk) 19:34, 21 July 2006 (UTC)

I'd expect because it contains caffeine, which is a diuretic and it also doesn't replace any salts. —Bradley 19:54, 21 July 2006 (UTC)

[edit] designing a capacitor plate

Sir,

I am designing a capacitor plate to measure small variation in capacitance, for a pressure transducer. My base plate is of ceramic type and in have to coat some metal as electrode. My desire capacitance range is 10pF to 50pF with small variation of .001pF. I am using vacuum as dielectric between ceramic plate and deflection membrane (INCONEL).
Kindly provide my information’s regarding to designing parameters, material to be coated, and different shape in which material can be coated on ceramic plate. I shall be very thankful for these kind information’s.

Abawan

Email address removed

See Capacitor. All you need is the equation C \approx \frac{\epsilon A}{d}, where C is the capacitance, ε is the permittivity of the dielectric (in your case, ε0, the permittivity of free space), A is the area of the plates and d is the spacing between them. As for the coating material, I'll leave that question to a chemist, but the choice of material will have no effect on the capacitance. --Heron 09:26, 22 July 2006 (UTC)

[edit] Unknown plant?

I found patches of these plant on a hike in southern Michigan on the 4th of July weekend. I have no idea what it is. I thought it was a fungus but, on touching it, it didn't feel soft like fungus but oily and hard like a nutmeat. Anyone know what it is? Rmhermen 20:03, 21 July 2006 (UTC)

Looks like Conopholis americana to me. Choess 19:02, 24 July 2006 (UTC)

[edit] concrete

I was once taught that as cement,aggregate and water mixed, a chemical reaction occurs that forms molecules of concrete. These molecules have microscopic sized quills protruding like quills on a Porqupine egg. These quills interlace with surrounding molecules,thus locking them together. This interlocucution gives concrete it's strength. Furthermore,on a decreasing scale,these molecules continue to form for a very long time, and that is why very old concrete is so very hard. Is this true? I have read the Wikapedia article on concrete and it does not answer this question.

There isn't a "concrete molecule" as such, concrete is hydrated mineral. When it cures, it forms bonds with water molcules - that might be the 'spines' you're referring to. Concrete does continue curing for years, although it would be unlikely to contribute much additional strength. Peter Grey 19:45, 22 July 2006 (UTC)
There is something on concrete chemistry under Portland cement#Use. The particles are called grains. --Heron 19:52, 22 July 2006 (UTC)

[edit] mars encounter thisAug.

Is it true that mars will be so close to us next month that we will be able to clearly see it as large as a full moon?21:21, 21 July 2006 (UTC)(hobgoblin)

No. Weregerbil 21:30, 21 July 2006 (UTC)
Well if you are looking at it through a strong enough telescope. User:AlMac|(talk) 22:00, 21 July 2006 (UTC)
As you can see in this
Image:Inner Planets Image.PNG
The current state of the planets, viewed from above the ecliptic, generated in Celestia
picture of the current state of solar system (made using the excellent freeware celestia), Mars and Earth are nowhere near at their closest point. In fact, viewed from this position, the planets are orbiting counterclockwise, so they are currently getting farther apart. Essentially, Earth will have to "lap" mars around the sun before the two planets align at their closest approach of 0.5 AU, or around 75 million km. The angular diameter of astronomical bodies is quite easy to calculate. Basically, you form a right triangle with three points: Your eye, the center of the planet, and a point on the circumference of the planet. Find the actual radius of the planet, figure out how far away the planet is, divide, take the arctangent, multiply by two, and you have the angular width of the planet. Too lazy to do it myself :) --Bmk 00:24, 22 July 2006 (UTC)
Mars and Earth reached their closest distance last year, actually, around November 2005. Mars' apparent diameter from earth was 20.1" (according to the excellent program Celestia—no need to calculate arctangents); Jupiter's apparent diameter was still larger (around 32"). The Moon's apparent dimater was 32' (that's minutes, not seconds; perhaps that's where the confusion arose?). — Knowledge Seeker দ 03:26, 22 July 2006 (UTC)
Cool! How do you get celestia to tell you apparent diameter? --Bmk 06:01, 22 July 2006 (UTC)
Select anything, and it should appear in the top-left corner under the name. Sum0 15:54, 23 July 2006 (UTC)

[edit] Red patange

This article is currently running through AfD as being a possible hoax. I was curious if the knowledgeable people here could help with just knowing if this does in fact exist. Yanksox 22:07, 21 July 2006 (UTC)

The discussion is here. - Cybergoth 02:03, 22 July 2006 (UTC)

[edit] 1965 and 1967 chevy bel air station wagon windows

I really need to know if the rear passenger side windows in a 1965 and 1967 chevrolet bel air station wagon are the same? I don't have much money so I don't want to spend any money buying the wrong window for my car. Thanks. --72.20.69.12 23:34, 21 July 2006 (UTC)