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June 24

Impact of dissolved hydrogen on electrical resistivity of iron

A sample of essentially pure solid iron, in an atmosphere of hydrogen, will absorb some of the hydrogen. The amount absorbed rises with temperature. I've been looking without success for quantitative data on the impact on the resistivity of the iron as fuction of temperature and pressure. Since hydrogen diffuses into between Fe atoms in the iron crystals, it is expected that the electrical resistivity will rise, but I would like to know by how much. By Googling and libray search, I could only find a paper on the resistivity increase that occurs when hydrogen precipitates out between the Fe crystals as a result of rapid cooling - but that's not what I'm after. I'm after the steady state situation. Is there a way of calculating or roughly estimating the resistivity change? 203.54.115.168 (talk) 15:22, 24 June 2014 (UTC)[reply]

You may want to take a look at papers on Palladium hydride resistivity. Palladium resistivity depends on the fraction of dissolved hydrogen. This effect is used in some hydrogen sensors, so it should be rather well known. Metallic Iron hydride is an alloy of hydrogen and iron, the same way as palladium hydride is an alloy of hydrogen and palladium; the difference being only that hydrogen dissolves in iron much less readily than in palladium. My suggestion, therefore, is to find how the Palladium hydride resistivity dependence is modelled theoretically, and apply the same method to Iron hydride. To do this you have to be comfortable with a grad-level solid state physics, though, so caveat emptor. --Dr Dima (talk) 18:31, 24 June 2014 (UTC)[reply]

Quark Induction

Can quark induction be possible? For example- can +ve quark inside the proton attract -ve quark inside the neutron ? — Preceding unsigned comment added by 106.212.120.46 (talk) 17:22, 24 June 2014 (UTC)[reply]

The force that binds protons and nucleons together in a nucleus (the nuclear force or residual strong force) is very much like that. It comes from the underlying strong force (QCD) in much the same way that van der Waals force comes from electromagnetism. A proton or neutron has no net color charge: it is neutral relative to the strong force. However, each proton or neutron is made up of quarks that do have a color charge, and the attractive and repulsive forces between the individual quarks within the two nucleons don't quite cancel out. There's a small net attractive force left over. Of course, in reality the interactions between quarks are not described by classical forces but by a quantum field theory in which it is notoriously difficult to calculate such things. It has not been possible so far to derive the nuclear forces between protons and neutrons from the first principles of QCD. --Amble (talk) 02:50, 25 June 2014 (UTC)[reply]

Sweat, insects, and sunlight

Is there a substance (either natural or artificial) with the properties of (a) a deodorant, (b) an insect repellent, and (c) a sunscreen?
—Wavelength (talk) 21:55, 24 June 2014 (UTC) and 22:32, 24 June 2014 (UTC)[reply]

(b) Natural pyrethrins from chrysanthemums are potent insect repellents. 24.5.122.13 (talk) 23:28, 24 June 2014 (UTC)[reply]

Does it also have to be clear ? Because sunblocks that are not clear are easier to come by, like zinc oxide. Then the next issue is if it can be a mixture of substances with those properties. Also, since armpits are likely to need deodorant but not so much insect repellent or sunscreen, you might want to keep the deodorant separate. StuRat (talk) 02:27, 25 June 2014 (UTC)[reply]

Let us begin by including opaque substances and mixtures of substances. One challenge with mixtures of substances is avoiding mutual counterproductivity.

—Wavelength (talk) 02:39, 25 June 2014 (UTC)[reply]

OK, how about if we mix citronella oil, which is both a perfume and insect repellent, with zinc oxide. Do you also want to add in an antiperspirant, like aluminum zirconium octachlorohydrex GLY ? (Note that it's dangerous to cover large portions of your body with antiperspirant, as the inability to sweat may make you overheat.) StuRat (talk) 02:54, 25 June 2014 (UTC)[reply]

No, I do not want to add in an antiperspirant, now that you have alerted me to that danger. Besides opacity, is there any disadvantage with a mixture of citronella oil and zinc oxide?

—Wavelength (talk) 03:09, 25 June 2014 (UTC)[reply]

None that I'm aware of, but that combo may not have been tested before. StuRat (talk) 03:12, 25 June 2014 (UTC)[reply]

I wouldn't recommend using citronella as a deodorant, i.e. on underams, since it can irritate the skin especially in sensitive areas. For natural deodorant you might try baking soda + cornstarch, though this mixture is not super-effective nor long-lasting.. El duderino ^(abides) 05:34, 25 June 2014 (UTC)[reply]

Try a MOPP suit. Sunlight and insects can't get in and odors can't get out.--Wikimedes (talk) 08:31, 25 June 2014 (UTC)[reply]

Thinking laterally, see pictures at incense. When you have enough of it in a small area, it acts as all three... SemanticMantis (talk) 15:16, 25 June 2014 (UTC)[reply]

Not quite a new idea, Mantis. During my childhood years in the Far East, these were frequently deployed. {The Poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:19, 26 June 2014 (UTC)[reply]

The Australian "RID" range of insect repellents (not the American "RID" product, which is an insecticide for body mites) includes one version with Vitamin E and an SPF30 sunblock, and has emollients and a scented base. Not exactly a deodorant, but it's meant to be worn on the body, which citronella isn't. http://www.rid.com.au/plussunscreen.htm for details on purchase through the company's Web site. loupgarous (talk) 06:30, 26 June 2014 (UTC)[reply]