Wikipedia:Reference desk/Archives/Science/2010 August 16

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August 16

Deutz gadget.

I have a gadget made by Deutz Germany in 1914 with a serial number GJ140740C. Can anyone please help me what it is and what is it used for 212.49.89.76 (talk) 11:33, 16 August 2010 (UTC)Kamen.

Deutz is a huge name in Germany. I'm sure they made thousands of different types of gadget. The serial number on your Deutz gadget is of no help in identifying it. I suggest you post a photograph of it here. Or at least a comprehensive description of its size and shape. That way the Science Reference Desk might be able to help. Dolphin (t) 11:39, 16 August 2010 (UTC)

If the data plate also has a model number, then we might be able to track down what the device is. However, as Dolphin said, a photograph would be better; you can upload it to wikipedia by following the Upload file link in the left-hand toolbar, but you need to be an autoconfirmed user to this; i.e. have an account for more than 4 days and make more than 10 edits. CS Miller (talk) 19:53, 16 August 2010 (UTC)

planet

Why planets revolve around the sun what force is responsible for elliptical path —Preceding unsigned comment added by 117.96.132.254 (talk) 13:36, 16 August 2010 (UTC)

You may be interested in our article on the formation and evolution of the Solar System. In a nutshell, angular momentum is conserved, and the initial momentum of the primordial molecular cloud is preserved today in part via the orbits of the planets. — Lomn 13:46, 16 August 2010 (UTC)

Why all planets revolve around the sun gravitational force does not force to follow elliptic path than what is responsible —Preceding unsigned comment added by 117.96.132.254 (talk) 13:54, 16 August 2010 (UTC)

The Sun is not the only gravitational force on the planets. They interact with one another as well. -- kainaw™ 14:03, 16 August 2010 (UTC)

Yes but the gravitational effect of other planets is relatively minor, and tends if anything to make the orbits not exactly elliptical. The short answer is that if a planet starts off moving in a certain range of speeds and directions, gravity will make it follow an elliptical orbit around the Sun. 20th Century physics (quantum theory) has modified the detail, but broadly the elliptical paths are almost exactly what Newton's law of gravity would predict. --rossb (talk) 14:14, 16 August 2010 (UTC)

General relativity is a far more significant correction that quantum theory for celestial mechanics. It's still fairly small for any planet other than Mercury, though. --Tango (talk) 14:28, 16 August 2010 (UTC)

OOPS - of course I meant to say general relativity! --rossb (talk) 17:05, 16 August 2010 (UTC)

I assumed the questioner was asking why the orbits are not exactly elliptical with the phrase "does not force to follow elliptical path". If the questioner would care to ask a question with a complete sentence, we can surely provide a good answer. -- kainaw™ 14:34, 16 August 2010 (UTC)

Articles like Kepler's laws of planetary motion, Kepler orbit, and just orbit may be helpful, though bits of insight are mixed in with a lot of complex mathematics. The discovery that orbits weren't circular shortly after 1600 did a lot to create (or spur the discovery of) such complex math. But the principle is really quite simple: the motion of an object (ignoring friction) in one dimension is completely unrelated to its motion in another. As shown beautifully in a Mythbusters episode, a bullet fired drops at the same rate as a bullet that is simply dropped. For a planet, what this means is that if it could fall straight through the sun, come out to the other side, and repeat, that straight-line pendulum-like motion is exactly the same as if the planet revolves in a perfect circle, from the point of view of that one dimension. Likewise the orbit of a planet will be an ellipse when it falls back and forth a greater distance in one direction than in another. (You may ask why it can't fall back and forth in the third dimension for some 3D orbit - answer is, if it does so, it works out that this is a 2D orbit in some other plane) This isn't perfectly true for a real planet however due to other factors - due to the precession as discovered by Newton and then the distortion calculated by Einstein in the two-body problem in general relativity. Wnt (talk) 15:21, 16 August 2010 (UTC)

Here is the answer that I think the OP is looking for: Isaac Newton proved mathematically that if the force of gravity drops off in proportion to the square of distance from an object, then orbits will be ellipses. So the answer is indeed gravity, although it takes a lot of work to see why that is the answer. Looie496 (talk) 19:51, 16 August 2010 (UTC)

PLACEBO

WHAT IS PLACEBO? —Preceding unsigned comment added by 124.253.228.118 (talk) 13:58, 16 August 2010 (UTC)

See placebo. -- kainaw™ 14:00, 16 August 2010 (UTC)

Can you make a "fire hose" that shoots solid ice?

I was looking at the phase diagram of water recently, and was quite surprised to notice a "horn" where water at just a certain pressure around 2 x 10⁸ Pa is liquid all the way down to 250 K. What strikes me about this is that water can't be heated with perfect uniformity, but its pressure can be released at the same rate throughout the liquid. This would seem to suggest to me that if you had a fire hose with a region of high pressure that gradually reduced, the water could be turned into a solid cylinder of ice as it came out! (Presumably friction applied to the side of the ice somewhere down the line would help maintain the high pressure at the base) Besides being just an odd-looking curiosity, I think such a device might be helpful in outer space, where liquid water is prone to evaporate, but well-cooled ice is a structural element practically as strong as steel. But could it work? Wnt (talk) 16:34, 16 August 2010 (UTC)

The ice would sublime when exposed to sunlight though. Not a good idea to have a space station made of the same material as a comet. John Riemann Soong (talk) 16:43, 16 August 2010 (UTC)

So you spray it with a visually reflective, IR-black paint as it emerges from the hose. I was just looking at black body - the Earth would be 250 K on its own, and halving its albedo from .3 to .15 would reduce that by 1/4th root of 2 = 16% to 210 K. I'd have to look at the Sun's fraction of IR output to see how low it possibly can go, but this seems good enough for sci-fi. ;) Wnt (talk) 17:19, 16 August 2010 (UTC)

Whether the radiation is IR or not makes no difference, all light will heat an object that absorbs it. IR is just the frequency range of light emitted by objects at every-day temperatures (basically, anything colder than red-hot (by definition) and warmer than liquid helium (roughly)) Ice, formed in the correct way, is already highly reflective (consider snow), so I doubt you'll be able to spray it anything better, just make sure the ice is white ice not clear ice (although, clear ice wouldn't be a problem as long as it isn't very thick, since the light would just go straight through it). You won't be able to make it a perfect reflector, though, so it will still sublime at some rate. I don't think you need high pressure, though, can't you just have the water in most of the hose at room temperature and then have the final, straight bit of hose immersed in liquid nitrogen? --Tango (talk) 17:25, 16 August 2010 (UTC)

I was actually thinking of a hose without a nozzle, perfectly smooth cylinder, using friction only on the fully cooled part of the ice to hold back the remainder. Wnt (talk) 17:52, 16 August 2010 (UTC)

So was I. If there were a nozzle, the ice would block it. --Tango (talk) 01:43, 17 August 2010 (UTC)

Hmmm... the more I think about this, the more I'm confused. Somehow I imagined that the crucial pressure gradient near the freezing point would be created by the acceleration of the water/ice as it spewed out, and the acceleration would be created by the pressure gradient. But I'm not sure whether such a description really makes any sense. Wnt (talk) 12:29, 17 August 2010 (UTC)

I am not convinced that the water will come out as a cylinder. Rarefaction waves and solidification fronts near the nozzle may turn it into a shrapnel of ice crystals and frozen droplets; you will need to put a lot of thought and effort into the nozzle design. Having the pressure drop gradually but preventing the water from freezing in the nozzle at the same time is an interesting challenge. This may turn out to be useful for future missions to the ice-rich bodies in the Solar System (Galilean satellites for example), although personally I have doubts. The thing is, on the ice-rich bodies you don't care about evaporation losses during the manufacturing process too much; and in the Earth orbit or on Mars the water is too expensive to spray it around, pressurized or not. Still, an interesting idea. Did you search the literature to see if people have tried this on Earth? May be more useful here than in space. After all, people have known for a very long time that pressure prevents water from freezing. --Dr Dima (talk) 17:26, 16 August 2010 (UTC)

It's not really my field, and it's hard for me to think of unique search terms (ice, pressure... no). I was envisioning a snazzy way to make a very large telescope quickly from a central pool of resources. ;) Wnt (talk) 17:52, 16 August 2010 (UTC)

How would lots of ice help you make a telescope? You need enormous mirrors and/or lenses for that, and while you could make a lens out of ice, I suppose, your method wouldn't do that (the precision required for a lens is very high). --Tango (talk) 01:43, 17 August 2010 (UTC)

Well, the mirror was pictured to be a very thin sheet of metal, suspended by "billions and billions" of nanotech tendons (I'm picturing something like two telescoped SWNTs and a basic control circuit - but it must be rigid enough to push as well as pull on the membrane, so a cable of such may be required). Some hard scaffold is needed for them to attach to, and to mediate reorientation of the telescope, which is what the ice was for. Wnt (talk) 12:29, 17 August 2010 (UTC)

Isn't this essentially what a snow cannon is doing? Admittedly, they intentionally form a fine mist, and also rely on evaporative cooling, but they do essentially convert water into ice via spraying it out of a nozzle at high pressure. --Stephan Schulz (talk) 15:44, 17 August 2010 (UTC)

As you can tell by the intolerable noise, snow guns are just giant fans with a bit of water added in. While perhaps they could add a bit more if they wanted chunks of ice rather than "snow", the limitation applies that you can't cool the liquid uniformly ... unless you mix it with a larger amount of uniformly cold material, here air. A snow gun that's all water and no air would simply pour out water. Wnt (talk) 03:59, 18 August 2010 (UTC)

EKG Analysis- practice Test

Last year I accessed a link for Wikepedia (EKG Analysis), a 129 quesiton practice test, multiple choiuce, true/false and fillins. An excellent study tool. Is to still available? —Preceding unsigned comment added by 168.28.203.185 (talk) 16:56, 16 August 2010 (UTC)

This sounds like the sort of thing Wikiversity or Wikibooks might handle. There's only a tiny page at Wikiversity, but maybe a related page is what you're looking for. Check your browser history for wikiversity, or see if any link at [1] looks familiar or is still colored from the last time you visited. Wnt (talk) 17:56, 16 August 2010 (UTC)

pH buffer of 1 or 1.5 (out of household/edible/supermarket ingredients)

I need a moderately acidic solution ... this solution would be mildly corrosive, right? I want a low pH but without so much H+ that acid-catalyzed side reactions become significantly active (hydrolysis, Fischer-style condensation). My goal is to supply a reaction that would steadily consume H+ (a lot of it!), but I want to avoid side reactions. It doesn't have to be a very precise buffer, as you can see. Btw, what's the pH of pure glacial acetic acid? Google seems to tell me 2.4, but this is surprising to me because my orgo prof told me that glacial acetic acid will prune your fingers almost immediately but vinegar takes a while to this. (I mean I spill vinegar on myself all the time while preparing meats.) John Riemann Soong (talk) 17:15, 16 August 2010 (UTC) If true edibility is desired, lime (fruit) juice (2.0) is the sourest I've ever heard of. For lower pH (truly strong acid) then a more chemical approach is needed - hydrochloric acid is not intrinsically poisonous, apart from its acidity ... I suppose there must be a food grade somewhere, as it's used extensively to adjust pH of pharmaceuticals. You should confirm your original question: pH 1 means a lot of H+ all at once by definition. If you want to supply a lot of H+ slowly, glacial acetic acid will provide an H+ from (almost) every molecule, without ever going to such low pH. Wnt (talk) 18:04, 16 August 2010 (UTC) Well I think it's a reaction that consumes H+ abundantly (it's a redox reaction), so unless I want a reaction that takes a million years to complete, so I need a fair bit of H+. But I don't want to catalyse something unwanted. Are there any organic acids whose conjugate bases are stabilised (or precipitated) by some other complex in solution? John Riemann Soong (talk) 18:15, 16 August 2010 (UTC) I think you'll have better luck searching for prior art for your specific reaction. Anything that can possibly be done by someone who's asked what the pH of acetic acid is, is already published somewhere in great detail. If you don't have good access to normal literature sources, try Patent Lens. Wnt (talk) 18:35, 16 August 2010 (UTC) I want to stabilise the intermediate Chromium(VI) peroxide before it decomposes, which I am told is fairly short-lived. I plan on using a dry-ice/acetone bath. Initially, the production of Chromium(VI) peroxide is more rapid than its decomposition. Both processes are acid-consuming processes, so I want there to be enough acid for the first reaction but insufficiently enough for the second one. Apparently decomposition of Cr(VI) peroxide requires more H+ than production ... (details in article) Btw, I expected the pH of glacial acetic acid to be quite different from an aqueous solution because the H+ species is not the same. One is solvated hydronium, and the other H+ species probably has a higher acidity function, what with the poor-stabilisation of protonated acetic acid and all. John Riemann Soong (talk) 20:35, 16 August 2010 (UTC)

I see what you mean about glacial acetic and the Hammett acidity function (e.g. [2]), if the solution is nearly free of water. But such a system won't run out of H+ after the first reaction and before the second. I don't know if you can do that effectively. Most of the information I'm seeing on a quick search has to do with stabilizing Cr0₅ in adducts as described in Chromium(VI) peroxide and Chromium, but I could be missing a lot here. Wnt (talk) 00:43, 17 August 2010 (UTC)

Well if a reaction consumes an abundant amount of acid, low levels of H+ at a time (despite a large amount of say, RCOOH) might slow the first reaction to unbearable levels. Although, is protonated acetic acid in ether a particularly good proton donor when "needed", i.e. when it arrives at the reaction site? John Riemann Soong (talk) 23:36, 19 August 2010 (UTC)

Gene Therapy/Hormones

Is it possible for gene therapy to increase or decrease the amount of certain hormones/chemicals in the body? —Preceding unsigned comment added by 71.156.3.118 (talk) 17:45, 16 August 2010 (UTC)

Certainly possible - difficulty depends on the hormone/chemical. See e.g. [3] about phenylketonuria, a disease that begs for an outside source of phenylalanine hydroxylase to reduce the amount of phenylalanine (and phenylpyruvate...) by converting it to tyrosine. Wnt (talk) 18:08, 16 August 2010 (UTC)

Our article on gene therapy doesn't mention hormones at the moment. Quite a few papers have been published discussing using gene therapy to introduce growth hormone into rats and mice, but I can't find anything about it being used in humans yet. Smartse (talk) 11:45, 17 August 2010 (UTC)

Take a look at the "Repoxygen" article. Also the "gene doping" article. —Preceding unsigned comment added by 76.169.33.234 (talk) 02:52, 18 August 2010 (UTC)

EPO

is epo Erythropoietin available as a pill or only a injection? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 18:03, 16 August 2010 (UTC)

Erythropoietin is a glycoprotein hormone so it's difficult to imagine the point of a pill other then perhaps if you need more protein in your diet but it's going to be a rather expensive protein source. Nil Einne (talk) 19:43, 16 August 2010 (UTC)

What he's trying to say is that if you ate it the protein would be digested, and it wouldn't be Erythropoietin anymore, but rather individual amino acids. Ariel. (talk) 19:51, 17 August 2010 (UTC)

Its injection only. Look up "Procrit" on wikipedia or another source.

People have been trying to get proteins into the bloodstream for something close to 90 years now. Every few years someone writes a hopeful review. Sooner or later they're bound to be right... Here's a patent application you might find interesting - no promises it works, and I doubt that it's safe.[4] Would be funny if the dope dealers beat the pharmaceutical companies to market after all that time... Wnt (talk) 20:09, 18 August 2010 (UTC)